US3268094A

US3268094A - Apparatus for transferring workpieces and the like

Info

Publication number: US3268094A
Application number: US373740A
Authority: US
Inventors: Fischer Heinrich; Kriegl Max
Original assignee: Carl Hurth Maschinen und Zahnradfabrik GmbH and Co
Current assignee: Gleason Hurth Tooling GmbH
Priority date: 1962-07-25
Filing date: 1964-06-09
Publication date: 1966-08-23
Anticipated expiration: 1983-08-23
Also published as: GB1039225A; FR1382943A

Description

1966 H. FISCHER ETAL 3,268,094

APPARATUS FOR TRANSFERRING WORKPIECES AND THE LIKE FiledJune 9, 1964 5 Sheets-Sheet 1 7nvenfors;

' 23, 1966 I H. FISCHER ETAL 3,268,094

APPARATUS FOR TRANSFERRING WORKPIECES AND THE LIKE Filed June 9, 1964 5 Sheets-Sheet 2 F/g. 5 Fig. 5 MM KEIEGL Aug. 23, 1966 H. FISCHER ETAL 3,268,094

APPARATUS FOR TRANSFERRING WORKPIECES AND THE LIKE Filed June 9, 1964 5 Sheets-Sheet 5 i176 e T 4071 53 7nvenfons;

m/M fink Mar Airmen/s7 Aug. 23, 1966 H. FISCHER ETAL 3,268,094

APPARATUS FOR TRANSFERHING WORKPIECES AND THE LIKE Filed June 9, 1964 5 Sheets-Sheet 4 Aug. 23, 19 66 Filed June 9. 1964 H. FISCHER ETAL APPARATUS FOR TRANSFERRING WORKPIECES AND THE LIKE 5 Sheets-Sheet 5 United States Patent 3 268,094 APPARATUS FOR TRANSFERRING WORKPHECES AND THE LlKE Heinrich Fischer and Max Kriegl, both of Munich,

Germany, assignors to Carl Hurth Maschinenund Zahnrafii'a'erilr, Munich, Germany Filed June 9, 1%4, Ser. No. 373,740 16 illaims. (Cl. 214-1) The present invention relates to material handling apparatus, and more particularly, to an apparatus for transferring blanks, semifinished workpieces, finished workpieces and similar articles.

It is an important object of the invention to provide an apparatus which insures planned, continuous and automatic or semiautomatic progression of workpieces or similar discrete products through a manufacturing plant.

Another object of the invention is to provide an apparatus, also called automatic or semiautomatic transfer machine, which is especially suited for delivering workpieces from one or more conveyors to one or more machine tools or vice versa.

A further object of the invention is to provide an apparatus of the above outlined characteristics which may be rapidly and conveniently converted for handling of differently configurated and/or dimensioned workpieces and which is readily convertible to move such workpieces along a shorter, longer, arcuate, straight or composite pathway.

An additional object of the invention is to provide an apparatus wherein the workpieces or similar articles may be conveyed between different levels and without any appreciable danger of damage, contamination or breakage.

Still another object of the instant invention is to provide an improved transfer unit which may be utilized in an apparatus of the above outlined characteristics and which is capable of manipulating two or more workpieces in a simultaneous operation.

A concomitant object of the invention is to provide improved lifting, shock absorbing, actuating, spacing, conveying and other devices which may be used with advantage in an apparatus of the above outlined characteristics.

A further object of the invention is to provide an apparatus for transferring gear blanks, finished gears, gear clusters and many other types of discrete products to and from one or more gear shaving, burnishing, lapping and similar machines.

Another object of the invention is to provide a readily transportable apparatus which may be assembled for temporary or permanent use in connection with a single lathe, milling machine or another machine tool, or with a battery of such machines.

Still another object of the invention is to provide an apparatus for controlled advance of discrete workpieces along an assembly line with a control system which enables the component parts of the apparatus to perform their functions in a fully automatic way, at required intervals, with requisite force, through desired distances and with utmost accuracy so that the number of supervisory person nel may be reduced to a minimum even when the associated machine tool or tools will operate at full capacity.

An additional object of the invention is to provide an apparatus for transferring workpieces or similar articles in orderly and planned fashion so that such articles may be received on conveyors and/ or at the working stations of cooperating machine tools, and to construct the apparatus in such a way that it occupies little room as well as that it occupies room which is readily available in manufacturing plants without blocking access to the working stations.

See

Another very important object of the invention is to provide a highly versatile apparatus of the above outlined characteristics which may be used with equal advantage in connection with many different types of machine tools, which can be adjusted to be useful in a large variety of work schedules, which can be used in connection with many types of conventional conveyors, which may be adjusted to take workpieces from a first conveyor to a working station and from such working station to a second conveyor, and which may be used in connection with different sizes or makes of a given machine tool as well as in connection with totally unrelated machines such as lathes, spline milling tools, gear shaving machines and the like.

A further object of the invention is to provide an apparatus for transporting workpieces directly between the working stations of two or more machine tools.

With the above objects in view, one feature of the present invention resides in the provision of an apparatus for transferring workpieces and similar discrete articles to and from the working stations of machine tools and the like so that such articles may be removed from one or more conveyors to be delivered to a working station and vice versa. In its simplest form, the apparatus comprises a guide which is preferably mounted on a separate groundcontacting stand so as to be transferrable from one machine to another and which defines an elongated preferably horizontal pathway one end of which is adjacent to a working station, a transfer unit which is mounted on the guide to reciprocate along the pathway between a first position at which it is adjacent to the working station and one or more additional positions adjacent to one or more conveyors or to a lifting device which may deliver or receive articles from the transfer unit, and means for reciprocating the transfer unit along the pathway so that the transfer unit may pick up articles at the working station for delivery to the conveyor or conveyors, or vice versa. The .transfer unit comprises two or more preferably symmetrically disposed horizontal or inclined arms arranged to orbit (swivel) about a fixed vertical axis which is perpendicular to the pathway, and each arm is provided with a specially configurated gripper or hand distant from the axis about which the .arms revolve back and forth and which is provided with article-engaging fingers capable of grasping the articles and of releasing them when necessary.

In accordance with a preferred embodiment of the invention, each gripper comprises at least two fingers at least one of which is movable with reference to the other thereof, and at least one finger may comprise several articulately connected levers which are movable with reference to each other and with reference to the other fingers, preferably in response to automatic impulses and at such intervals as are necessary for a given operation. The fingers are connected to a back portion of the respective gripper which back portion is articulately secured to the respective arm, and each arm is preferably mounted on a spindle of the transfer unit in such a way that it may revolve about its own axis, either in response to operation of a special motor or in response to orbiting about the aforementioned fixed vertical axis.

The novel features which .are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawings, in which:

FIG. 1 is a front elevational view of an apparatus for transferring gear-shaped workpieces to and from a q gear shaving machine which is shown by phantom lines;

FIG. 2 is a top plan view of the structure shown in FIG. 1;

FIG. 3 is a similar top plan view of a slightly modified apparatus which serves to feed work-pieces from a first convey-or to a gear shaving machine and to deliver them from the shaving machine to a second conveyor;

FIG. 4 is a larger-scale vertical section through the transfer unit of the apparatus which is shown in FIG. 3;

FIG. 5 is a horizontal section through a fluid-operated motor of the transfer unit as seen in the direction of arrows from the line VV of FIG. 4;

FIG. 6 is a section as seen in the direction of arrows from the line V-IVI of FIG. 4 and illustrates a stop device of the transfer unit;

FIG. 7 is a greatly enlarged horizontal section through one arm of the transfer unit shown in FIG. 4;

FIG. 8 is a similar horizontal section through the arm subsequent to rotation through 90 degrees;

FIG. 9 is a horizontal section through a portion of a slightly modified arm;

FIG. 10 is an enlarged top plan view of a carriage for the transfer unit of FIG. 4;

FIG. 11 is a section as seen in the direction of arrows from the line XI-X-I of FIG. 10 and illustrates a cushioning or shock-absorbing device for the transfer unit;

FIG. 12 is a fragmentary top plan View of the structure shown in the left-hand part of FIG. 10 .and illustrates a modified cushioning device;

FIG. 13 is a section as seen in the direction of arrows from the line XI'IIXIII of FIG. 12;

FIG. 14 is a top plan view of a spacer device which moves the workpieces into the range of the transfer unit;

FIG. 15 is a vertical section through a lifting device which serves to deliver or to receive workpieces from the transfer unit; and

FIG. 16 is a transverse section through a conveyor which may feed or receive workpieces from the lifting device of FIG. 15.

Referring to the drawings, FIGS. 1 and 2 illustrate schematically an apparatus which is utilized for transfer- :ring workpieces to and from a machine tool 20, for example, a gear shaving machine. The workpieces 21 travel along the upper stringers of an endless chain conveyor 22 to reach the platform of a lifting device 23 which moves them to a higher level and into the range of a novel transfer unit 24. This transfer unit is reciprocable in a horizontal plane along a guide 25 including a series of horizontal tie rods, and is arranged to transfer workpieces seria-tim to a shaving (working) station 26 of the machine 20. A workpiew 21a is shown in FIG. 1 in the gap between a pair of work clamping members in the form of tailstocks 2'7, 28 which may engage its ends after the workpiece has been turned through 90 degrees to take the position shown in FIG. 2. Just before the workpiece 21a has been moved to the position of FIG. 1, the transfer unit 24 has withdrawn a finished worbkpiece 211) from the space between the tailstocks 27, 28 and thereupon returns such finished workpiece onto the platform of the lifting device 23. The latter lowers the finished workpiece 21b to the level of the upper stringers of the conveyor 22 so that the workpiece may advance in a direction to the left, as viewed in FIG. 1 or 2, and to a next treating or processing station. A single file of finished (i.e., shaved) workpieces 21b is shown at the left-hand end of the conveyor 22. Such workpieces may be fed to a precision finishing machine tool, for example, to a burnishing or lapping machine,-not shown. In the embodiment of FIGS. 1 and 2, each workpiece 21, 21a or 211) comprises a shaft and a plurality of coaxial gears having different diameters.

The conveyor 22 is supported by

legs

29, 30 and its width may be adjusted in a manner to be described in connection with FIG. 16. The

legs

29, 30 are adjustthat its stroke may be selected at the will of the operator.

The guide 25 for the transfer unit 24 is preferably mounted on a separate stand 32 which is placed on the floor close to the working station 26 so that the tie rods of the guide 25 may lead the gripping elements of the transfer unit between the lifting device 23 and the tailstocks 27, 23. Of course, the stand 32 'may be replaced by a different supporting structure, for example, by a bracket or arm which is suspended from a side wall or from the ceiling of a factory hall, depending on the availability of space and on certain other factors. It is often advisable to construct the stand 32 as a separate part, i.e., not to connect the stand with the base or with another component of the machine too-l, or to provide for a readily detachable connection between the stand and the machine. FIG. 1 shows that the stand 32 is adjustable vertically, again for the purpose of making the apparatus more versatile and to render it useful in connection with a great number of different machine tools or other mass-producing or mass-treating automatic or semiautomatic machines.

In FIGS. 1 and 2, the forward or outward stroke of the transfer unit24 along the guide 25 is limited by a fixed but readily adjustable stop 33 which may cooperate with a cushioning device to be described in connection with FIGS. 10 and 11. The range of the transfer unit 24 (i.e., the range of its arms and gripping elements) may be adjusted in a number of ways, all as will be described later. As a rule, the transfer unit 24 will operate automatically, and its movements are preferably synchronized with the operation of the machine tool. However, it is advisable to provide a control panel 34 having a series of knobs or analogous control elements which serve to change the operating cycle of the apparatus at the will of the supervisor. The control elements on the panel 34 also serve to set the apparatus for a given operation. The electrical components of the apparatus are preferably assembled in a box 35.

FIG. 3 illustrates a portion of a slightly different apparatus which comprises two

chain conveyors

22, 222. The transfer unit 24 removes untreated workpieces from the conveyor 22 and returns treated workpieces or finished products to the conveyor 222, or vice versa. The stand 32a for the guide of the transfer unit 24 in FIG. 3 is located to the left of the transfer unit. Also, FIG. 3 shows that the machine tool 20 is positioned mirror symmetrically with reference to the machine tool of FIGS. 1 and 2. This was done to indicate that the improved apparatus may be used in connection with many types of machines and with differently mounted machines. In other words, not only are the parts of the improved apparatus adjustable, interchangeable, shiftable and otherwise adaptable to a given type of machine tool, but the position of the entire apparatus with respect to a machine tool (or vice versa) may be selected in a way which is best suited in a given manufacturing plant.

FIG. 4 illustrates the transfer unit 24 and a portion of the guide 25. The guide 25 comprises two parallel horizontal tie rods 4%, 49 (see also FIG. 10) which support a reciprocable carriage 41. The carriage 41 constitutes a component part of the transfer unit 24 and is provided with a vertical sleeve or neck 42 which guides a vertical spindle 43. The spindle is adjustable axially in the neck 42 and is held in a selected axial position by a pair of

lock nuts

44, 45 which are respectively located at the lower and upper ends of the neck. Of course, a portion of the spindle 43 is provided with external threads so that it may mesh with the

lock nuts

44, 45. Such vertical adjustability of the spindle 4-3 enables the operator to select an optimum position for the gripping elements with reference to the guide 25. Furthermore, the neck 42- is preferably secured to the carriage 4-1 in such a way that it may pivot about a horizontal axis so that the axis 244: of the spindle i?) and the plane of the

tie rods

40, 49a may make an angle other than 90 degrees. The spindle 43 does not rotate with reference to the neck 42 or carriage 41.

At a point close to its lower end, the spindle 43 carries two vertically spaced

bevel gears

46, 47, see also FIG. 7, which constitute two sun gears of a planetary transmission. The lower end portion of the spindle 43 extends to a level below the bevel gear 47 and carries the casing 51 of a hydraulic motor 48 and an abutment or stop device 49. The bevel gears 46, 47 are surrounded by a transmission housing 5t? which is rotatable on the spindle 43 but cannot move axially with reference thereto. The lower portion of the transmission housing 50 is rigid with the casing 51. in addition, the transmission housing carries a series of horizontal collars; in the embodiment of FIG. 4-, the housing 5b is provided with two collars 52, 52a which are located diametrically opposite each other, and each of these collars accommodates a rotary arm 53. One of these arms is illustrated on a larger scale in FIGS. 7 and 8, and it will be noted that each arm 53 carries at its inner end a bevel gear 54 which constitutes a planet pinion and which meshes with the bevel gears 46 and 47. In FIG. 4, the bevel gear 54 of the lefthand arm 53 is shown in mesh with the upper bevel gear 46. At its outer end, each arm 53 carries a bifurcated holder 55 for the back portion 56 of a gripper or hand 57. The hand 57 shown in FIG. 7 is rockable about a pivot axis 57a which is perpendicular to the horizontal axis of the respective arm 53. The extent to which a hand 57 may rock about the corresponding axis 57a is determined by the position of an adjusting screw 59 (see FIG. 8) which is disposed at one side of the axis 57a. A helical expansion spring 58 acts between the holder 55 and the back portion 56 and serves as a means for biasing the hand 57 in abutment with the tip of the corresponding adjusting screw 59. If desired, the spring 58 may be replaced by a second adjusting screw so that the hand 57 may be rockably or non-movably fixed in any desired angular position with reference to the axis 57a.

It is to be noted that the drawings show simple journal bearings for all such parts which are mounted for rotation or for axial movement. Of course, in actual construction of my apparatus, at least some of the movable parts are mounted in suitable ball hearings or roller bearings to reduce friction and wear on such moving parts.

The outer end of each hand 57 carries a cylinder 60 which defines a cylinder chamber 61 for a reciprocable piston 62, see FIGS. 7 and 8. One end of the cylinder 69 is sealed by a removable cover 63 which is engaged by one end of a helical expansion spring 64. This spring 64 serves as a means for biasing the piston 62 toward the other end of the respective cylinder. Each cylinder 62 further supports a detachable gripping element 65 which is analogous to one or more fingers on a human or animal hand and which may be configurated with a View to come in actual engagement with a portion of a workpiece 2-1. In FIGS. 7 and 8, the gripping element 65 comprises two sector-shaped portions each of which may engage a gear at the respective end of the workpiece 21. The apparatus may be furnished with a spare set of gripping elements 65 each of which is useful in connection with a different type of workpieces. The gripping elements 65 are secured to the cylinders 64) by screws, bolts or by other readily detachable fasteners.

The cylinders 60 carry laterally extending inclined supporting, brackets 66 for pivot pins 67. Each of these pivot pins supports a second gripping element or finger 68 which resembles a two-armed lever with one of its arms articulately coupled to the outer end of a piston rod 69. The piston rods 69 are fixed to the respective pistons 62 and may reciprocate in response to admission or evacuation of a fluid pressure medium from the lower cylinder chamber of the respective cylinder 60. Each finger 68 carries at its outer end a bell crank lever '70 which is articulately fixed thereto by a pivot pin 71 and which is biased against the workpiece 21 by a helical expansion spring 72. This spring bears against a plunger which is received in a blind bore of the respective finger 68 and whose position is adjustable by a nut 73. An adjustable stop pin 74 serves to limit the extent to which the lever 71') may be rocked by the spring 72. On removal of the pin 67, the lever 7t) may be replaced by a differently configurated or dimensioned lever. This will be necessary when the apparatus is utilized for transferring a different make of workpieces or a series of differently dimensioned workpieces. FIG. 7 shows that the lever 70 engages the shaft of the workpiece 21 midway between its ends. It is obvious that the gripping element 65 may be replaced by an element which will engage the shaft of the workpiece 21 and that the lever 70 may be replaced by a differently configurated lever which will engage the gears at both ends of the workpiece. The

levers

68, 69 together form a jointed digit whose parts are movable with reference to each other (about the axis of the pin 71) and which is movable with reference to the grip ing element 65 (about the axis of the pin 67). If desired, the

digit

68, 70 may be replaced with one having a single link or three or more links, depending on the nature of workpieces and on the type of transferring operation.

Each of the

springs

58 and 72 may be replaced by different biasing means, for example, by hydraulic or pneumatic biasing device or by weights. FIG. 9 illustrates a portion of a slightly modified arm 53 wherein the spring 58 is replaced by a fluid operated single-acting cylinder 75. This cylinder is rigidly connected to or integral with the arm 53 and defines a chamber 76 for a piston 77 which may be reciprocated by a gaseous or liquid pressure medium. A return spring 7 8 serves to bias the piston 77 to a starting position, and the rod 79 of the piston comprises a head which is received in a slot 79:: of the back portion 56. A pin secures the head of the piston rod 79 to the lower part of the back portion 56, as viewed in FIG. 9, so that the hand 57 will rock in a clockwise direction about the vertical axis 570 whenever the cylinder chamber 76 receives a supply of pressure medium.

The spring 72 of FIG. 8 may be replaced by a singleacting cylinder similar to or identical with the cylinder of FIG. 9. Of course, and if it is desired to simplify the transfer unit, the parts 66453 and 69 of FIG. 9 may be replaced by a spring (similar to the spring 58) which will serve to bias the finger 68 in order to keep the bell crank lever 70 in engagement with the workpiece 21. It is further obvious that the position of the spring 72 and of the cooperating plunger with the nut 73 may be reversed. The same applies for the mounting of the cylinder 75 in FIG. 9 and for the mounting of the cylinder 6t in FIG. 8, i.e., the piston rod 69 may be coupled to the back portion 56 if the cylinder 60 is mounted on the finger 68, and the piston rod 79 may be coupled to the arm 53 if the cylinder 75 is mounted on the back portion 56.

In FIG. 4, the gripping elements on the left-hand arm 53 are turned through 90 degrees with reference to the gripping elements on the right-hand arm. Thus, one of these arms may remove a horizontal workpiece from the working station 26 while the other arm may remove a vertical workpiece from the lifting device 23. If needed the transfer unit may comprise three or more arms 53 which may but need not be equidistant from each other and which may be mounted at different levels.

That portion (numbered 80) of the spindle 43 which extends through the casing 51 of the hydraulic motor 48 is fixedly but detachably connected with a piston or stator 81, see particularly FIGS. and 7. The casing 51 is rigidly connected to a partition 82 which cooperates with the piston 81 to define two

cylinder chambers

83, 84 communicating with fluid-conveying

ducts

85, 86 in the casing 51. The lower end portion of the spindle 43 carries an annulus 87 with two adjustable stop screws 88, 89. These screws may come in abutment with a stop block 90 which is fixed to the housing 51. The parts 87-90 together constitute the stop device 49.

The hydraulic motor 48 serves to rotate the arms 53 between two end positions about the axis 24a of the neck 42 and through an angle determined by the block 90 and stop screws 88, 89 of the stop device 49. Of course, the block 90 may be readily detached from the casing 51 to be replaced by a differently dimensioned block in order to change the angle through which the arms 53 may rotate in response to operation of the motor 48. Also, the block 90 may be replaced by an adjustable block and the transfer unit 24 then comprises suitable elements which may adjust the position of the block by remote control. For example, the configuration and the mounting of the block 90 may be selected in such a way that the arms 53 will be rotatable between three, four or more preselected angular positions. Such construction is of considerable advantage when the transfer unit is utilized for moving workpieces or other articles between three or more stations, for example, between a treating (shaving) station and two conveyors corresponding to the

conveyors

22, 222 of FIG. 3. Analogously, such transfer units may be used for transferring articles between a single conveyor and two or more machine tools.

The chamber 83 of the motor 48 receives or discharges pressure medium from a source (not shown) through a flexible conduit 91 and through

conduits

92, 93, 94, shown in FIG. 4. The conduit 94 communicates with the duct 85. The chamber 84 may be filled or evacuated through a similar system of conduits (not shown) and duct 86. When the motor 48 is in operation, the housing 50 rotates about the axis 24a shown in FIG. 7. The valves which regulate the flow of pressure medium into and from the

chambers

83, 84 are not shown in the drawings. The housing 50 rotates in response to rotation of the casing 51 and acts as a planet carrier to swing the arms 53 about the axis 24a. Consequently the bevel gears 54 are caused to rotate, because they mesh with the bevel gears 46, 47, and thereby cause each of the arms 53 to rotate about its own axis. Of course, it is not always necessary that the arms 53 rotate about their axes in response to rotation of housing 50 about the axis 2411; it is often advisable to provide a separate motor for each of the arms 53 so that such arms may be rotated independently of the spindle. Also, both arms 53 may be rotated by a common motor, similar to the motor 48, and such common motor then cooperates with a stop device similar to the device 49 to select the angle through which the arms rotate about their axes at a predetermined stage of a transfer operation.

In order to move the fingers 68 toward or away from the gripping elements 65 (i.e., to move the bell crank levers 70 about the pins 67), the cylinders 60 will receive a pressure medium through a system of conduits shown in FIGS. 4, 7 and 8. FIG. 4 shows a flexible conduit 95 for the left-hand finger 68 which is connected to the upper portion of the spindle 43 and which communicates with an axially extending conduit 96 in the spindle. The conduit 96 communicates with

conduits

97, 98, 99, 100 and 101. The finger 68 for the right-hand arm 53 is movable in response to admission of pressure medium through a flexible conduit 102 and additional conduits 103, 104 shown in FIG. 4. FIG. 9 shows an arrow 105 which indicates the flow of pressure medium through conduits 106a, 107a and into the cylinder chamber 76 to shift the piston 77 in order to rock the back portion 56. The valves for regulating the flow of pressure medi- 8 um through the

conduits

91, 95, 102 and 106a are not shown in the drawings because the exact construction of the remaining parts of the hydraulic of pneumatic actuating system forms no part of the present invention.

As mentioned above, the carriage 41 is slidable along a pair of

horizontal tie rods

40, 49a best shown in FIG. 10. The

tie rods

40, 49a, are shown as being of circular cross section, and the carriage 41 is reciprocable by a reversible electric motor 106 through an endless flexible element here shown as a chain 107. The chain 107, shown in FIGS. 4 and 13, engages a motion transmitting pin 108 on the carriage 41. The operative connection between the driving sprocket (shown in FIG. 13) for the chain 107 and the output shaft of the motor 106 comprises a suitable slip clutch of any known design, not shown. The direction in which the carriage 41 may travel along the

tie rods

40, 49a is determined by the motor 106 which is of the reversible polarity type. If the nature of the operation requires that the carriage 41 should change the direction of its movement with no delay whatever, the operative connection between the motor 106 and chain 107 preferably comprises a worm drive with an elastically deformable worm. Furthermore, it is obvious that the electric motor 106 may be replaced by a hydraulic or pneumatic motor.

The stroke of the carriage 41 is determined by the stop 33 which comprises a threaded portion 123 extending through a crosshead of the guide 25 and meshing with a lock nut 124. The arrangement is such that the stop 33 may be adjusted axially of the

tie rods

40, 49a in order to change the stroke of the carriage 41 and transfer unit 24.

In order to reduce the impact when the carriage 41 reaches the one or the other end of its stroke, the apparatus preferably comprises suitable cushioning or shock absorbing devices one of which is illustrated in FIG. 11. This cushioning device is mounted on the carriage 41 and may come in abutment with the stop 33, It wil be noted that the cushioning device resembles a dash-pot which includes a piston rod 109 secured to a piston 110, the latter being reciprocable in a cylinder 111. The piston 110 is biased by an expansion spring 112 which is accommodated in the chamber of the cylinder 111 and which tends to push the piston rod 109 outwardly, i.e., in a direction to the left, as viewed in FIG. 10 or 11. The right-hand end portion of the piston 110 is of reduced outer diameter, as at 113, so that the piston and the wall of the cylinder 111 cooperate to define an annular gap which may communicate with a radial port 114 bounded by a smooth surface and leading to a storage tank 115 for a compressible fluid. The width of the gap between the cylinder 111 and the piston portion 113 exceeds the normal clearance between these parts. A second communicative connection between the chamber of the cylinder 111 and the tank 115 may be established through a suitable one-way valve, here shown as a ball valve 116. This valve is provided with a small spring and also includes an adjusting screw which enables the operator to regulate the pressure at which the ball moves away from its seat in order to allow fluid to flow from the tank 115 to the chamber of the cylinder 111. If desired, the port 114 may be replaced by a suitable nozzle with an adjustable orifice so that the operator may control the rate at which fluid can flow through the gap between the end portion 113 of the piston 110 and the wall of the cylinder 111. The free end of the piston rod 109 carries a laterally extending beam 117 whose free end carries an adjustable screw 118 which acts as a trip and is arranged to come in abutment with a switch 119 fixed to the carriage 41, see FIG. 10, and connected in circuit with the motor 106.

The cushioning device of FIG. 11 operates as follows:

When the mot-or 106 rotates in a sense to drive the carriage 41 in the direction indicated by an arrow 120 (see FIG. 10), the tip of the piston rod 109 will strike against the right-hand end portion of the stop 33 whereby the piston rod yields and causes the piston 110 to move in a direction to the right, as viewed in FIG. 11, so as to compress the spring 112 and to expel some of the fluid from the chamber of the cylinder 111, through the gap around the end portion 113 and via port 114 into the tank 115. Initially, the flow of fluid from the cylinder 111 to the tank 115 takes place with little resistance, as long as the fluid is permitted to flow through the gap around the end portion 113; however, the resistance to such flow increases markedly when the piston 110 moves to a position in which the end portion 113 is located to the right of the port 114 so that any fiuid which can escape through the port 114 and into the tank 115 must fiow through the minimal clearance between the internal surface of the cylinder 111 and the left-hand portion of the piston 110.

When the piston rod 109 has performed a stroke of predetermined length, selected by the axial position of the trip 118, the latters tip engages and opens the switch 119 to arrest the motor 106 so that the carriage 41 comes to a halt and the transfer unit 24 is in a position to perform a given operation. For example, the

parts

65, 70 of FIG. 8 may deposit a finished workpiece 21b on the conveyor 22 of FIGS. 1 and 2.

When the motor 105 causes the carriage 41 to travel in the opposite direction (see the arrow 121 in FIG. 10), the spring 112 is free to expand whereby the fluid contained in the tank 115 opens the valve 116 and flows back into the chamber of the cylinder 111. A second cushioning device 122 (see FIG. 10) becomes active when the carriage 41 approaches the right-hand end of its stroke.

The spring 112 and the fluid in the chamber of the cylinder 111 will brake the carriage 41 so that the transfer unit 24 travels at reduced speed just before the screw 118 strikes against the switch 119 to insure that the carriage comes to a gradual stop. In other words, the carriage 41 may be driven at full speed at the start of a movement in a given direction, and at reduced speed when it approaches the end of its stroke. This can be achieved in a different way by replacing the motor 106 with a variable-speed motor.

Though the nut 124 allows for axial adjustments of the stop 33 in order to regulate the stroke of the carriage 41, such arrangement is normally used only in an apparatus which removes or deposits workpieces on a single conveyor, such as the conveyor 22 of FIGS. 1 and 2. When the transfer unit 24 cooperates with two conveyors, such as the

conveyors

22, 222 of FIG. 3, the apparatus preferably comprises a different stop device shown in FIGS. 12 and 13 and including two stops which operate alternatively. One of these stops takes the form of an externally threaded stop pin 125 which may be adjusted axially upon loosening of a lock nut shown in FIG. 12. The other stop includes an assembly 126, best shown in FIG. 13, comprising a slide 127 which is pivotable at its upper end and which is also reciprocable in a suitable supporting bracket 127a shown in FIG. 12. The direction of such reciprocatory movement is horizontal, as viewed in FIG. 12, and the upper end portion of the slide 127 is biased by a spring 128 which tends to move this slide in a direction to the right. The slide carries two adjustable screws 129, 130 which serve to select the first position of the carriage 41. The means for pivoting the slide 127 about an axis which is perpendicular to the plane of FIG. 13 comprises a double-acting horizontal cylinder 131 and a piston 132 which is reciprocable in this cylinder and comprises a piston rod 133 whose free end is articulately secured to an intermediate portion of the slide. Conduits 131a and 13119 serve to admit or evacuate a pressure medium from the cylinder chambers at the opposite ends of the piston 132. It goes without saying that this fluidoperated cylinder 131 may be replaced by an electrically or electromagnetically operated pivoting device.

When the transfer unit 24 is to move to a position adjacent to the conveyor 22 of FIG. 3, the conduit 131a admits pressure fluid to the left-hand chamber of the cylinder 131, as viewed in FIG. 13, so that the slide 127 pivots to the position of FIGS. 12 and 13. The carriage 41 is then free to advance in the direction indicated in FIG. 10 by the arrow and strikes against the screw 130. The slide 127 now begins to move in a direction to the left, as viewed in FIG. 12, and compresses the spring 128 which cushions the impact when the screw 129 reaches the tip of the pin 125. The transfer unit 24 is in proper position with respect to the coveyor 22 and the trip 118 may open the switch 119 to arrest the motor 106. When the carriage 41 is to per-form a different stroke, the slide 127 is pivoted downwardly in response to admission of a pressure medium through the conduit 131b so that the piston rod 109 of FIG. 10 may reach the tip of the pin because the screw 129 is not aligned with the pin 125. The transfer unit 24 is then in proper position with respect to the conveyor 222.

Referring again to FIG. 10, the framework of the guide 25 supports a series of

electric switches

133, 134 which are located in the path of a trip mounted on the carriage 41. Each of the

switches

133, 134 is adjustable in the longitudinal direction of the

tie rods

40, 49a and their purpose is to control movements of the carriage and transfer unit 24. In the position of FIG. 10, the switch 133 will be ineffective because it cannot be reached by the trip 135; however, the switch 134 may be used to reverse the motor 106 in response to movement of the carriage 41 in the direction indicated by the arrow 121, or the switch 134 may serve to change the speed of the motor 106 so that the speed of the carriage 41 is reduced before the piston rod 109 strikes against the stop 33. This presupposes that the motor 106 is of the variable-speed type.

It is preferred to provide the apparatus with a spacer device which moves the workpieces individually into the range of the transfer unit 24. One form of such spacer device is illustrated in FIG. 14 and this spacer device is intended to move the workpieces 21 with reference to the conveyor 22 so that the transfer unit 24 may take the workpieces seriatim and without interference on the part of the next-following workpiece or workpieces. The spacer device of FIG. 14 is equally useful to insure that the transfer unit 24 may deposit articles on the conveyor 22 without being obstructed by workpieces which were deposited in preceding operations. The upper stringers of the conveyor 22 travel in the direction indicated by an arrow 135a and this conveyor comprises two narrower endless flexible chains 22a, 22b. The spacer device in cludes a first or main arresting member in the form of a pusher 136, a second arresting member in the form of a two-armed lever 137 which arrests a workpiece that has been allowed to advance past the arresting member 136, and a third arresting member 138 which also resembles a pusher and which is sort of a braking device to slow down the articles before one thereof can reach the arresting member 136. The arresting

members

136, 138 are provided with pins which respectively extend into

guide slots

139, 140 of a V-shaped control lever 141 arranged to pivot about the axis of a fixed pin 142 located at a point close to the junction of its legs. The pin 142 is rigidly connected to one terminal portion of a link train including a link 143 which is located behind the plane of FIG. 14. The arresting member 137 is rockable about the axis of a fixed pivot pin 144. One (the lower, as viewed in FIG. 14) arm of the arresting member 137 extends into the space between the chains 22a, 22b to come in actual abutment with the foremost workpiece 21 The other arm of the arresting member 137 is provided with a guide slot 145 and receives a pin of the aforementioned link train. This link train includes a second link 148 which is articulately connected with the link 143 and with a push rod 146. The connection between the link 148 and the push rod 146 includes that pin which extends into the guide slot 145 of the arresting member 137. The push rod 146 may be reciprocated by mechanical, hydraulic,

pneumatic or electrical means. In the illustrated embodiment, the push rod 146 constitutes the core of an electromagnet and is surrounded by a winding 147.

Electric switches

149, 150, 151 are distributed along the path of the workpieces and in the path of movable parts of the spacer device to initiate or terminate certain steps of the transfer operation. For example, the switch 149 may initiate the release of a workpiece by the arresting member 137 so that such workpiece may travel between the chains 22a, 22b (arrow 135a) and to a next machine.

The spacer device operates as follows:

A single file of workpieces 21 (numbered 21c, 21d, 216) is supported by the chains 22a, 22b and the foremost workpiece 210 is in abutment with the arresting member 138 so that it cannot advance toward the arresting member 136. A treated workpiece 21 has been deposited by the transfer unit 24 and is in abutment with the arresting member 137. The shafts of the workpieces are accommodated in the space between the chains 22a, 22b so that, as soon as the workpieces meet an obstruction (in this case, the arresting members 138 and 137), the workpieces located upstream of such obstruction or obstructions are brought to a halt but the chains 22a, 22b and the workpieces located to the left of the arresting member 137 are free to continue their advance in the direction indicated by the arrow 135a.

When the circuit of the winding 147 is completed, the push rod 146 is caused to move in a direction to the right to rock the arresting member 137 in a clockwise direction and to release the finished workpiece 21 At the same time, the main arresting member 136 is caused to extend into the path of the workpieces 21c21e and the arresting member 138 is withdrawn so that the workpieces 21c21e advance by a step and the foremost workpiece 210 comes in abutment with the arresting member 136. This workpiece is now in the phantom-line position 21'c. The workpiece 21 (which was held by the arresting member 137 after it has been transferred from a machine tool by the unit 24) is free to advance in a direction to the left and actuates the switch 154) (see the position 21 which deenergizes the electromagnet by opening the circuit of the winding 147 so that the push rod 146 moves to the left and the lever 137 moves in the path of the workpieces between the chains 22a, 22b to arrest the next finished workpiece which is to be transferred by the unit 24. The unit 24 also removes the workpiece 21's and transfers it to the working station. Th arresting member 133 abuts against the workpiece 21d.

The operative connection between the chains 22a, 22b and the transfer unit 24 is established by the lifting device 23. As shown in FIG. 15, the lifting device may comprise a jack having an upright cylinder 150 which is vertically adjustably mounted on the support member 31. The chamber of the cylinder 150 accommodates a piston 151 whose rod 152 extends upwardly into the space between the chains 22a, 2212. At its upper end, the piston rod 152 carries a detachable platform 153 (see also FIG. 14) which is in registry with the workpiece 21f, i.e., with that workpiece which abuts against the arresting member 137.

Two electric switches 154, 155 are adjacent to the path of the piston 151 and are actuated when the piston respectively reaches the lower and the upper end of its stroke. The switches 154, 155 also form part of the automatic control system for the transfer unit and for the remaining parts of the improved apparatus. The conduits which regulate the fl-ow of a hydraulic or pneumatic pressure medium into and out of the chambers of the cylinder 150 are not shown in FIG. 15.

When the piston 151 performs the next upward stroke, the workpiece 21 is lifted by the platform 153 and is raised to a position in which it may be engaged by gripping elements on one arm 53 of the transfer unit 24. For example, the switch 155 may control a suitable solenoid 12 valve (not shown) which then admits pressure medium into the chamber of the cylinder 60 shown in FIG. 8 so that the lever 71) may engage the workpiece 21) during subsequent transfer to the working or shaving station 26.

The lifting device 23 can be considered to constitute a part of the conveyor system. Of course, the assembly of FIG. 3 will comprise two lifting devices.

The distance between the chains 22a, 22b of the conveyor 22 may be changed so that the space between these chains may accommodate workpieces and other articles of different width, height and/or length. Each of the chains 22a, 22b is trained around pairs of suitable sprocket wheels (not shown) which are mounted in a frame 155, see FIG. 16. One sprocket wheel of each pair drives the respective chain and the other sprocket wheel is adjustable in a manner know per se to keep the chain under necessary tension. The chain 22a is adjustable in directions toward and away from the chain 22b (not shown in FIG. 16) by means of a series of distancing members 156 (only one shown) which extend between the upper and lower stringers of the chain 22a.

The distancing members 156 carry upper and lower rails 159 which extend between the links of the respective stringers of the chain 22a. Exchangeable sleeves 158 keep the distancing members 156 at a desired distance from the frame 155, and the latter supports bolts 157 which mesh with central portions of the distancing members. The rails 159 may consist of wear resistant metallic or synthetic plastic material, for example, of sintered metal. The lower stringer of the chain 22a rests on a rail 160 carried by a mounting member 161 which is held in position by bolts 162 secured to the frame 155 and extending through exchangeable spacer sleeves 163.

Lateral stops 164 provided on top of the frame 155 abut against the sides of the workpieces 21 to keep them accurately centered between the chains 22a, 22b. Each lateral stop 164 is adjustably secured to a bracket 165 which is bolted to the frame 155. The other frame (not shown) for the chain 22b carries similar lateral stops. Each lateral stop 164 may consist of a single strip of material extending along the upper stringer of the respective chain or, alternatively, each such stop may comprise a series of aligned sections.

It is often advisable to prevent direct sliding contact between the workpieces 21 and the links of the chains 22a, 22b. FIG. 16 shows one of several L-shape-d holders 166 which are secured to the links of the chain 22a and come in direct supporting engagement with the workpieces 21.

It will be seen that the apparatus of the present invention is preferably provided or combined with conveyors in the form of chains which are not positively coupled to conveyed articles. Thus, the upper stringers of the chains 22a, 22b shown in FIG. 14 are free to travel with reference to the workpieces 21c, 21d, 21c, 21 to make sure that the chains can build up stacks or files of such articles. This is important in the event that one of the machine tools happens to be out of order while the other machine tools continue to operate. For example, and referring to FIGS. 1 and 2, if the machine tool 20 happens to break down, the machine which delivers workpieces 21 onto the right-hand portion of the conveyor 22 can continue to deliver such workpieces, and the workpieces will merely accumulate in front of the spacer device without being able to travel past the platform 153 of the lifting device 23. Also, the conveyor 22 need not be arrested during such breakdown because its chains 22a, 22b are free to travel with reference to the workpieces. Of course, the length of the conveyor 22 may be much greater than shown in FIG. 1 or 2 so that this conveyor may accommodate a very large number of treated and/or untreated workpieces.

When the apparatus of the present invention is provided with a spacer device of the type or analogous to the one shown in FIG. 14, the speed of the chains 22a, 22b preferably exceeds the speed at which the machine tool 2%) treats the workpieces so that there will be relative movement between the chains 22a, 22b and the workpieces, and a certain number of workpieces (ready for treatment) will always be ready at the right-hand side of the arresting member 133.

The spacer device of FIG. 14 is particularly suited for use in an apparatus of the type shown in FIGS. 1 and 2 wherein the gripping elements on the arms of the transfer unit 24 receive and deliver workpieces to a single conveyor 22. Thus, the workpiece 21 shown in FIG. 14 is in a position in which (after lifting by the device 23) it may be grasped by the transfer unit 24 or in which it has been deposited by the transfer unit on the platform 153.

Referring again to FIG. 4, the switches 170 on the spindle 43 cooperate with cam shaped trips 171 on the housing 50 to control certain operations of the apparatus. These switches (and the aforementioned switches such as 154, 155, 133, 134, 149, 150, 151 and others) constitute elements of the control system which enables the apparatus to operate in a fully automatic or in a semiautomatic way.

The loading process is as follows: First, an empty hand is above the lifting device 211 (FIG. 14). The piston rod 152 (FIG. 15) then lifts a blank into the gripper. The latter rocks about its axis through an angle of 180 degrees, pivoting at the same time the blank horizontal position and moving it into between the tailstocks 27, 28 (FIG. 1), returns and takes up the next blank, and remains in this position until the first blank has been machined. Then, the empty arm enters the machine and takes up the finished workpiece. The gripper rocks about its axis, removing the workpiece from the machine and moving the next blank between tailstocks 27, 28. Then, it moves back to position 211 and deposits the workpiece onto the platform 153. The latter returns the workpiece to the conveyor, lifts a new blank into the gripper which takes up this blank and remains in this position until the workpiece has been machined. The cycle is then repeated as described above.

A similar operation can be carried out with a device comprising only one arm; however, in this case, working time is prolonged by the fact that the machine remains idle during the entire loading cycle.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to Letters Patent is:

1. In an apparatus for transferring workpieces and similar discrete articles to and from the working stations of machine tools and the like, in combination, guide means defining an elongated pathway having an end adjacent to a working station; a transfer unit mounted on said guide means to reciprocate along said pathway between a plurality of spaced positions, said unit comprising a plurality of article-engaging arms arranged to orbit about an axis of rotation which is substantially perpendicular to said pathway; stop means for arresting said unit in each of said positions; shock absorber means provided on said unit and arranged to cooperate with said stop means so as to cushion the impact on engagement between said unit and said stop means; means for reciprocating said unit along said pathway at different speeds; and control means arranged to reduce the speed of said unit prior to engagement between said stop means and the respective shock absorber means.

be secured by 2. A structure of the character described comprising a machine arranged to treat consecutive workpieces and similar discrete articles and comprising a working station at which the articles are located during treatment; conveyor means arranged to feed unfinished articles for treatment at said station; and an apparatus for transferring workpieces between said working station and said conveyor means, said apparatus comprising a guide defining an elongated pathway extending in a direction from said working station toward said conveyor means, a transfer unit mounted on said guide to reciprocate along said pathway, said unit comprising a plurality of article-engaging arms arranged to orbit about an axis which is substantially perpendicular to said pathway, and means for reciprocating said unit along said pathway so that said arms may engage articles at said working station for transfer of such articles toward said conveyor means or vice versa.

3. A structure as set forth in claim 2, wherein said conveyor means is arranged to advance the articles at a speed exceeding the rate at which the articles are treated at said working station so that a supply of articles accumulates on said conveyor means for transfer by said arms.

4. A structure as set forth in claim 3, further comprising spacer means adjacent to said conveyor means and arranged to maintain articles in positions necessary for engagement by said arms.

5. A structure as set forth in claim 3, wherein said conveyor means comprises a pair of endless flexible elements defining between themselves a space accommodating portions of conveyed articles, and wherein said spacer means comprises arresting members extendable into said space to arrest the articles, said flexible elements being movable with reference to such articles which are held against movement by said arresting members.

6. A structure as set forth in claim 4, wherein said spacer means comprises a pair of cooperating arresting members including a main arresting member movable into and out of the path of articles on said conveyor means and a second arresting member located past said main arresting member as seen in the direction of movement of said conveyor means, and means for selectively moving said arresting members into and out of the path of articles on said conveyor means.

7. A structure as set forth in claim 6, wherein said spacer means further comprises a third arresting member located ahead of said main arresting member and arranged to extend into the path of articles on said conveyor means when said main arresting member is withdrawn from said path.

8. A structure as set forth in claim 7, further comprising actuating means for moving said arresting members at predetermined intervals so that said second arresting member receives consecutive articles at intervals required for transfer of such articles to said working station.

9. A structure of the character described, comprising a machine arranged to treat consecutive workpieces and similar discrete articles and comprising a working station at which the articles are located during treatment; a first conveyor arranged to feed unfinished articles for treatment at said station; a second conveyor arranged to receive articles subsequent to treatment of such articles at said working station; and an apparatus for transferring workpieces between said working station and said conveyors, said apparatus comprising a guide defining an elongated pathway extending in a direction from said working station toward said conveyors, a transfer unit mounted on said guide to reciprocate along said pathway, said unit comprising a plurality of article-engaging arms arranged to orbit about an axis which is substantially perpendicular to said pathway, and means for reciprocating said unit along said pathway so that said arms may engage articles at said working station for transfer of such articles toward said second conveyor and that said '15 arms may also transfer articles from said first conveyor to said working station.

10. A structure of the character described, comprising a machine arranged to treat consecutive workpieces and similar discrete articles and comprising a working station at which the articles are located during treatment; conveyor means arranged to feed unfinished articles for treatment at said working station and to receive finished articles subsequent to such treatment, said conveyor means being located at a level which is different from the level of said working station; and an apparatus for transferring articles between said working station and said conveyor means, said apparatus comprising a lifting device arranged to receive and to deliver articles seriatim to said conveyor means, means for actuating said lifting device at intervals corresponding to the rate at which the machine treats workpieces at said working station, a guide defining a horizontal pathway extending between said working station and the path of movement of said lifting device, a transfer unit mounted on said guide to reciprocate along said pathway, said unit comprising a plurality of article-engaging arms arranged to orbit about a common vertical axis, and means for reciprocating said unit along said pathway so that said arms may receive articles seriatim from said lifting device for delivery to said working station or vice versa.

11. In an apparatus for transferring work-pieces and similar discrete articles to and from the working stations of machine tools and the like, in combination, a conveyor comprising a pair of endless flexible elements having spaced parallel upper stringer-s arranged to advance a file of articles; guide means defining an elongated pathway extending substantially from said conveyor to a working station; a transfer unit mounted on said guide means to reciprocate along said pathway and comprising a plurality of article-engaging arms arranged to orbit about a common axis which is substantially perpendicular to said pathway; and means for reciprocating said unit along said pathway so that said arms may receive articles from the working station for transfer of such articles toward said conveyor or vice versa.

12. A structure as set forth in claim 11, wherein said conveyor comprises means for regulating the distance between said flexible elements so that said elements may convey differently configurated and differently dimensioned articles.

13. A structure of the character described, comprising a machine arranged to treat consecutive workpieces and similar discrete articles and comprising a working station at which the articles are located during treatment; conveyor means arranged to feed unfinished articles for treatment at said station; and an apparatus for transferring workpieces between said working station and said conveyor means, said apparatus comprising a guide defining an elongated pathway extending in a direction from said working station toward said conveyor means, a transfer unit mounted on said guide to reciprocate along said pathway, said unit comprising a plurality of articleengaging arms arranged to orbit about an axis which is substantially perpendicular to said pathway, means for reciprocating said unit along said pathway so that said arms may engage articles at said working station for transfer of such articles toward said conveyor means or vice versa, said conveyor means being arranged to advance the articles at a speed exceeding the rate at which the articles are treated at said working station so that a supply of articles accumulates on said conveyor means for transfer by said arms, and spacer means adjacent to said conveyor means and arranged to maintain articles in positions necessary for engagement by said arms, said spacer means comprising a pair of cooperating arresting members including a main arresting member movable into and out of the path of articles on said conveyor means and a second arresting member located past said main arrest-ing member as seen in the direction of movement of said conveyor means, and means for selectively moving said arresting members into and out of the path of articles on said conveyor means, said second arresting member being arranged to arrest the articles seriatim in a position of registry with one of said arms when the transfer unit is moved to an end position distant from said working station.

14. A structure of the character described, comprising a machine arranged to treat consecutive workpieces and similar discrete articles and comprising a working station at which the articles are located .during treatment; conveyor means arranged to advance articles past said working station at a speed exceeding the rate at which the articles are treated at said working station; transfer means for transferring articles seriatim between said working station and said conveyor means; and spacer means for regulating the movement of articles with said conveyor means, comprising first arresting means movable into and from the path of articles on said conveyor means to intermittently interrupt the advance of consecutive articles whereby the conveyor means travels with reference to the articles located upstream of said first arresting means, and second arresting means located downstream of said first arresting means and movable into and from the path of articles on said conveyor means to arrest an article which has bypassed said first arresting means in a position for engagement by said transfer means.

15. A structure as set forth in claim 14, wherein said spacer means further comprises third arresting means located upstream of said first arresting means and movable into and from the path of articles on said conveyor means for holding against movement with said conveyor means all such articles which are located upstream of said first arresting means while said first arresting means is outside of said path.

16. A structure as set forth in claim 15, further comprising an operative connection between said first and third arresting mean-s for moving said first arresting means into said path when said third arresting means is withdrawn from said path and vice versa.

References Cited by the Examiner UNITED STATES PATENTS 1,839,438 1/1932 Prussing. 2,224,975 12/ 1940 McNamara. 2,253,155 8/ 1941 Wadman. 2,359,432 10/ 1944 McNamara. 2,771,177 11/1956 Cutter 198-34 2,943,724 7/ 1960 McCoy 198-34 2,950,805 8/ 1960 Heimlicher. 2,974,811 3/1961 Dammert. 2,998,887 9/1961 Sommer. 3,007,097 10/ 1961 Shelley. 3,010,587 11/1961 H-ollinger. 3,095,982 7/1963 Weiser.

FOREIGN PATENTS 1,161,336 3/1958 France.

MARVIN A. CHAMPION, Primary Examiner.