US3384930A - Injection-molding machine and unthreading means therefor - Google Patents

Description

May 28, 1968 H. REES 3,334,930

INJECTIONMOLDING MACHINE AND UNTHREADING MEANS THEREFOR Filed April 20, 1966 7 Sheets-Sheet l Herberf Rees IN VEN TOR.

Attorney May 28, 1968 H. REES 3,

INJECTION-MOLDING MACHINE AND UNTHREADING MEANS THEREFOR Filed April 20, 1966 7 Sheets-Sheet 2 Herbert Rees INVENTOR.

BY 6 W M Attorney May 28, 1968 H. REES 3,384,930

INJECTION-MOLDING MACHINE AND UNTHREADING MEANS THEREFOR Filed April 20, 1966 7 Sheets-Sheet 3 26 f E, I

Fig.3 INVENTOR:

Herberf Rees out Attorney May 28, 1968 H. REES 3,384,930

INJECTION-MOLDING MACHINE AND UNTHREADING MEANS THEREFOR Filed April 20, 1966 7 Sheets-Sheet 4 Herberf Rees INVENTOR.

BY 1 p53 Attorney May 28, 1968 H. REES 3,384,930

INJECTION-MOLDING MACHINE AND UNTHREADING MEANS THEREFOR Filed April 20, 1966 v 7 Sheets-Sheet 5 Herberf Rees INVENTOR.

BY (B955 Attorney May 28, 1968 3,384,930

INJECTION-MOLDING MACHINE AND UNTHREADING MEANS THEREFOR H. REES Filed April 20, 1966 Sheets-Sheet 6 Herbert Rees INVENTOR.

Attorney May 28, 1968 H. REES 3,384,930

INJECTION-MOLDING MACHINE AND UNTHREADING MEANS THEREFOR Filed April 20, 1966 7 Sheets-Sheet 7 L4 I 7 0 A S J 18 41; \L 55 P31 W B m M l e w W P -r E Mold- ConTrol 3 F CivcuiT 1 G? i I 1 l l as L 5 T 1 L5 g C 5 c I e I I C y cl e I F a o b c d a F 5 h L M (as) reverse I Forward Mold PM": U L m YGVBTSQ I J lhjnthon m FL} Tlsfon nurse L He d Forward. MW a) reverse. E

OPE" 5V1 closed H OPE"! I 8V2 {closed. I n L n I Mold Swims; J T on E g r F1 F1 INVENTOR. Fl 9- Herberf Rees BY R059 Attome y 3,384,930 INJECTION-MQLDIlIG MACHlNE AND UNTHREADHNG MEANS THEREFQR Herbert Rees, Willowdale, Ontario, Qanada, assignor to Husky Manufacturing and Tool Works Ltd, Toronto,

Ontario, Canada, a corporation of Canada Continuation-impart of application Ser. No. 4lld,il23,

Oct. 23, 1964, now Patent No. 3,328,844. This application Apr. 20, 1966, Ser. No. 543,971

5 Claims. (til. 18-30) This application is a continuation-in-part of my pending application Ser. No. 406,023 filed Oct. 23, 1964, now Patent No. 3,328,844. My present invention relates to injection-molding machines of the general type described in my US. Patent No. 3,117,348 and my pending application Ser. No. 321,218, filed Nov. 1, 1963, now Patent No. 3,254,371. More particularly, this invention relates to an unthreading attachment for use with such machines.

Many articles molded today have formations such as threads requiring that the article be removed from its mold by rotation about an axis. Up to now, however, various difficulties have been encountered in providing automatic apparatus for the unthreading of these articles. In general, several types of unthreading systems are used. The most common system provides automatic devices within one of the mold members which rotate and withdraw the articles during the opening movement of the mold. Not only is such a system complicated by virtue of its incorporation in the mold structure but additionally this arrangement is of limited value when a multiplicity of mold cavities are provided in the common mold plate; the latter difliculty arises from the fact that the gearing and transmission systems required to drive the rotating elements necessitates many parts and is so complex that the cost of multicavity molds becomes prohibitive. To avoid the disadvantages of high cost and complexity, some installations still accomplish removal by manual unthreading of the articles or with the aid of motor-driven but hand-operated appliances.

It is a principal object of this invention to provide a device of the general character described which enables the automatic removal of a threaded article from a mold member and yet is free from the complexities and cost problems affecting earlier systems.

A more specific object of this invention is to provide a mechanism for the unthreading of injection-mold articles which permits the simultaneous withdrawal of a plurelity of articles from the mold and thereby expedites the production of the articles.

in particular, my invention aims at the provision of means for unthreading even relatively delicate articles which must not be subjected to excessive impacts.

These objects and others which will become apparent hereinafter are attained, in accordance with the present invention, by the provision of a mechanism or a screw machine of the character described which oscillatingly displaces a mold member threadedly engaging one or more articles out of the injection-molding station and into an unthreading station wherein the article is engageable by gripper means rotatively withdrawing it from the mold member. An important feature of the present invention resides in the oscillating movement of the mold member between the two stations, thereby eliminating a continuous displacement of a mold plate or the like, and enabling a conventional mold member with associated cooling means (eg. water inlet and outlet lines) to be used without requiring complex connectors or the like.

According to another feature of the present invention, the mold consists of at least two members provided with guide rails, aligning bars or the like permitting the relative displacement of the members, the swingable mold memher being pivoted on one of these members for movement from the molding station to the unthreading station. Thus, a system according to the present invention can be constituted as an attachment for a conventional injectionmolding machine and may be provided with a support upon which a mold portion (cg. the central portion of a tripartite mold) is swingable in a transverse plane out of alignment with the other mold portions and into the unthreading station; at the unthreading station, a holder is movable generally perpendicularly to this plane and is provided with engaging means (eg. the gripper means mentioned above) and with drive means whereby the lOlClGf is advanced toward the swung-out mold portion, the latter having the unthreading portion for engagement of the molded article by the gripper means. The system also comprises a mechanism operable upon such engagement for rotating the gripper means jointly with the molded articles relatively to the swung-out mold portion at the unthrcading station.

According to an important feature of this invention, the holder is provided with a multiplicity of friction cups, rotatably journaled thereon, through the centers of which fixedly positioned ejector pins extend to dislodge the molded articles when the holder plate is retracted from the mold portion disposed at the unthreaded station. Each of the friction cups is, advantageously, keyed to a respective spindle of a multispindle gear head of the fixedly disposed drive mechanism and is axially displaceable relatively thereto so that the holder plate can be shifted along these fixed spindles while they rotate to extract the molded articles. In practice, the ejector pins can be extensions of the respective spindles.

In order to permit the gripping means to remove the threaded articles without disengagement therefrom in the course of unthreading, the mechanism further includes leadscrew means in step with the spindle rotation for retracting the holder upon engagement of the friction cups with the molded articles. Additionally, fluid-responsive means must be provided to displace the holder when the related movement of the spindle and the holder is not required, i.e. after the article has been withdrawn from the mold or prior to engagement of the friction cups with the articles.

Still another feature of this invention resides in the provision of a pair of mold plates interchangeably positionable opposite another portion of the mold and disposed at diametrically opposite locations with respect to their axis of oscillation on a common carrier. Thus one of the plates of the mold can be in position at the mold ing station enabling the molding of additional articles, while the other mold plate is disposed at the unthreading station at which the articles are removed. It has been found that this oscillating movement of the mold-plate carrier eliminates complex arrangements for the supply of the cooling liquid to these plates and is a vast improvement over earlier proposals according to which a mold carrier performed continuous rotation about an axis. It has, moreover, been found that the present system can be highly eiiicient without a propensity to breakdown due to misalignment and shock resulting from sudden stops when the angular oscillation of the mold-plate carrier is a harmonic motion. This can be accomplished, in accordance with the invention, by journaling the carrier on one of the stay or guide bars of the bed of the machine and providing it with a tubular shaft to which is fixed a pinion gear in mesh with a rack. A crank drive is then arranged to reciprocate the rack with harmonic motion. The control arrangements for the unthreading system can be integrated with the control systems for the various other parts of the injection-molding machine without difiiculty.

When the workpiece and its friction cup are provided with mating peripheral formations, such as ribs and as s grooves or complementary teeth, the unthreading motion should start at slow speed in order to allow these formations to interfit properly whereupon unscrewing may proceed at a more rapid rate. The leadscrew may be coupled, for this purpose, with its drive motor by way of a speed changer suitably controlled to bring about the desired slowdown in an initial phase of an uuthreading stroke, to be followed after, say, one or two spindle revolutions by a speedup so that the remainder of such stroke may be carried out at the same fast rate as the next forward stroke. The unthreading devices together with their holder and drive means may be selectively positionable on either of two platforms on opposite sides of the swung-out mold part to permit unscrewing in one or the other axial direction.

The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a plan view of an injection-molding machine using a tripartite mold and provided with an unthreoding device according to the present invention;

FIG. 2 is a cross-sectional view, drawn to an enlarged scale, of a portion of the machine of FIG. 1, taken along the line II-II thereof and showing the mold-plate-swinging mechanism;

FIG. 3 is a vertical cross-sectional view, taken along the line IIL-III of FIG. 1, illustrating the mold-plate holder in elevation;

FIG. 4 is an enlarged cross-sectional view, taken along the line IV-IV through the unthreading device of FIG. 1 with the motor shown in elevation;

FIG. 5 is a further cross-sectional view, taken along the line VV of FIG. 4, diagrammatically illustrating the control means and head assembly of the unthrcading device;

FIG. 6 is a cross-sectional View, drawn to an enlarged scale, taken alon the line VIVI of FIG. 1, showing the tripartite mold in one operating condition;

FIG. 7 is a circuit diagram of a suitable control system for the unthreading device; and

FIG. 8 is a timing diagram showing the correlated movements of the various mechanisms during two molding cycles.

General description of apparatus While an injection-molding system of the type illustrated in FIGS. 1-6 makes use of a tripartite mold, it will be understood that the principles herein disclosed are equally applicable to two-part molds, in which case the longitudinally fixed mold member can be swingable, and multipart molds having more than the three members described in detail hereunder. The principles of the invention are a plicable to all mold types in which one of two co-operating mold members is swingable transversely to the direction of mold closure.

In the system of FIGS. 1-6, the injection-molding machine has a bed 10 upon which is mounted a mold assembly 11, an injection assembly 12, a mold-opening-andclosing mechanism 13 and an unthrcading device 14 offset from the path of the mold. As disclosed in my copending application Ser. No. 321,218 and described in my US Patent No. 3,117,348, the mold-displacing mechanism 13 can include a crank-and-toggle drive or, alternatively, a conventional piston-and-cylinder arrangement adapted to displace the movable mold holder 15' along a pair of diagonally opposite tie bars or rails 16, 17 extending parallel to the direction of displacement of the mold holder 15 and passing through apertures in diagonal 1y opposite corners of the latter. The guide rails 16, 17 are anchored at the mold-displacing mechanism 13 to the housing 18 thereof via nuts 19 and, at their opposite extremities, to an upstanding support plate 29 via nuts 21. Support plate 20 is rigidly fixed to the bed 16 of the machine. A connecting rod 22 couples the movable mold carrier 15 with the mold-displacing mechanism The injection mechanism can be identical with that described in my aforementioned patent and thus can include a housing 23 containing the injection plunger which is received in a cylinder 24 whose discharge port communicates via duct 25 with suitable passages in the fixed mold plate 26 and thus also with the cavity of the mold 27, removably mounted upon the fixed carrier 26. The movable member 28 of the mold is disposed upon the movable carrier 15. A plasticizing screw 29 feeds the injection-moldable thermoplastic synthetic resin to the injec tion cylinder 24 from which it is injected into the mold by the customary lunger.

Mold-plate assembly As previously indicated, the mold assembly 11 is of the tripartite type including the fixed mold carrier 26 with its mold member 27, the longitudinally displaceable mold carrier 15 with its mold member 28, and a swing able assembly generally designated by the reference numeral 30. The swingablc assembly (FIG. 3) includes a pair of diametrically oppositely disposed mold plates 33a, 31b adapted to retain the synthetic-resin, injectionrnolded articles 32 by their threaded portions. When the caps or other articles to be made are internally threaded, the mold plates will include at each mold aperture 33 a centrally positoned threaded core; in the present case, howeve, it can be assumed that the threaded articles 32 are to be externally threaded so that no core is required. While in practice a considerable number of articles may made during each molding cycle, e.g. 24 plastic cups per mold plate, only four such articles and apertures have been shown herein for the sake of simplicity. The articles can conveniently be clustered in groups of, say, four, for reasons to become apparent hereinafter. The mold plates 31a, which correspond to the conventional so-called B plates of the usual tripartite molds, are bolted between respective arms 34a, 35a and 34!), 35b of a rotary holder 36, reinforced by webs 37. The arms 34a, 35a and 34b, 3512 are providedwith water-circulating channels (not shown) supplied with liquid from a fitting 38 by a flexible hose 3), a similar fitting 40 and hose 41 returning the cooling liquid to a reservoir 42 (FIG. 1), heat exchanger or waste collector; a pump 43 circulates the liquid via line 3? and fitting 38 through the arms of the swingable holder 36. The metallic arms are in surface contact along two sides of each mold plate 31a, 311) while being afiixed to them by the metallic bolts 44, thereby insuring excellent thermal conductivity from the mold plate: to the cooled holder. As also apparent from 165. 3 and 6, the holder 35 is formed with a hub 45 provided with cooling channels 46 and is rotatably entrained by a tubular shaft 47 surrounding the upper tie bar 17 via a key 48 longitudinally slidable in a slot or keyway 49 of the tubular shaft 47. A lost-motion linkage is formed between the movable mold carrier 15 and the holder 36 by means of a plurality of rods 59, 51 angularly spaced about the tubular shaft 47 and threadedly fixed in a bearing 52 rotatable within the hub 45. The rods 5t), 51 are provided with adjustably positionable nuts 53, 54 engageable with the mold carrier 15 when it is drawn to the left (FlG. 6) by the rod 22. A retaining ring 55 insures that the holder 36 will be axially entrained by the rods 5%), 51. Another set of rods 55 can extend to the right from a similar bearing 57 journaled in the hub 45 and held therein by a retaining ring 53, the rods 56 passing through the fixed. mold carrier 26.

It will thus be evident that forward displacement of the mold carrier 15 (i.e. in the direction of arrow 59) will proceed while the plate holder 36 remains stationary until the mold member 28 abuts the mold plate 31b and entrains it together with the holder 36- to the right (arrow 59) along the tubular shaft 47 until the plate 31b abuts the stationary mold member 27. Pins 60, 61 on the movable and stationary mold members 28, 27 are receivable in pilot bores Za, 6211 of the mold plates Bin, 3i!) to insure the proper registry upon closure of the mold. When the mold opens, the movable member is drawn to the left (FIG. 6) while the mold 31b remains in contact with stationary mold member 27 until the mold carrier 15 engages the adjustable abutment nuts 53, 54 and draws the rods 5t), 51 to the left. The holder 36 is then withdrawn from contact with the stationary mold member 27 and restored to its original, left-hand position.

Mold-plaie-swinging assembly The mold holder 36 carrying the diametrically opposite mold plates 31a and 31b is swingable oscillatingly through an angle of about 180 to alternately dispose the plates at the molding station and at the unthreading or article-removing station at the upper right-hand position (as viewed in FIG. 3). The swinging mechanism includes the tubular shaft 47 which is rotatable upon the tie bar 17 to displace the holder 36. As best seen in FIGS. 1 and 2, the mechanism, generally designated 65, includes a unidirectional electric motor mounted on a pedestal 67 of the bed ll) of the machine and. provided with a worm 68 which is in continuous mesh with a worm wheel 69 upon a trunnion 70. The worm wheel is keyed to a shaft 71 upon which is mounted an eccentric wheel 72 whose pin 73 serves as a pivot for a rack 74, the teeth 75 of which mesh with the teeth 76 of a pinion gear formed rigid or integral with the tubular shaft 37 or mounted thereon and keyed thereto. A bracket 77, swingable about the axis of shaft 47 and the tie bar 17, forms a guide for the rack 74 and prevents its withdrawal from engagement with the pinion 76. It will be immediately apparent that rotation of the worm 63 by motor 65 will drive the eccentric disk 72 which constitutes a crank mechanism imparting longitudinal motion to the rack 74, this oscillating longitudinal motion being, in turn, converted to an angular oscillation of the tubular shaft 47 via its pinion 76 and the holder 36. The transferred movement is the harmonic motion of a crank so that the angular velocity of the holder as it is moved out of one extreme position and brought into the other is substantially less than its velocity between these positions. The energizing circuit for the motor 66 includes, as will be apparent: hereinafter, a pair of sensitive limit switches L and 1. which are operated by the cam portion 78 of the disk 72; and terminate its rotation after the holder has been angularly oscillated through an angle of about 180.

Unrhreading device The unthreading device 14 of the system is disposed at the discharge station in line with the upper mold plate (e.g. 31a) and can be removably disposed on either one of a pair of pedestals St} (only one seen in FIG. 1) on opposite sides of the swingable mold-plate assembly 30, depending upon the direction in which the articles must be unthre-aded. 1n the embodiment shown, the articles are unscrewed from the left-hand side of the mold plates. From FIGS. 4 and 5 it will be seen that the unthreading device, generally designated by the reference numeral 14, includes a head 81 displaceable toward and away from the mold-plate assembly 3%} at the discharge station. The head 81 consists essentially of a plate 82 carried by a pair of bars 83, 84 slidably mounted in the gear housing 85 and a plurality of gripper members 86 each aligned with a respective molded article and adapted to engage it frictionally for unthreading same from the mold plate. The gripper members are advantageously constituted as rubber cups axially shiftable upon the splined spindles $7 against the force of springs 83 normally urging the cups in the direction of the confronting mold plate. The springs 38 are seated against axially fixed abutments 3% on the spindles 87, which are journaled in respective bearings 9% of the support plate 82. The cups 86 are thus rotatably entrained by the spindles 87 but have limited freedom of spring-cushioned axial movement with respect thereto.

By more specifical reference to the system of FIG. 4

it will be seen that the spindles 87 are rotatably driven by a splined shaft 91 which permits axial displacement of the spindles to dislodge the articles from the cups upon retraction of the unthreading device. Each of the splined shafts 91 is received within and pinned to a respective stub shaft 93, the latter being journaled in clusters within a support plate 94 mounted by bolts 95 onto the housing 35. The shafts d3 are integral with respective pinions 96 clustered about and in mesh with a common drive gear 97 disposed within the transmission compartment 98.

When a multiplicity of clusters of articles are to be provided on a single mold plate, it is desirous that the axis of the articles of each cluster be spaced by the same distance from a common axis; in this case a drive gear such as that shown at 97 can be axially aligned with the axis of the cluster, while the axes of pinions 96 will be in line with the respective axes of the molded articles. Similarly, the clusters can be disposed equidistantly from a common axis at which a main drive gear is disposed for meshing with and displacing the secondary drive gears vhich, in turn, mesh with the pinions 96. In a device as shown, wherein four friction cups constitute the single cluster, the main drive gear is shown at 99 and meshes with a gear 16%} fixed to the shaft 101 carrying the secondary drive gear 97. Gear 99 is fixed to a large double gear 162, 1G2 in a speed-reducing train driven by a double pinion 103, N3 slidably mounted on the shaft 1G4 of an electric motor 105 bolted at 106 to the housing 85. The latter also contains a bearing block 107 rotatably supporting a leadscrew shaft 198 whose gear 10? meshes with a further gear 116, also driven by the large gear 102 of the speed-reducing train. The axial shifting of pinions 183, 193 on shaft 1594 is controlled, in a manner more fully described hereinafter, by a solenoid S for alternately engaging gear 162 with pinion 103 (slow drive) or gear 192 with pinion 1&3 (fast drive), the latter being the normal position of the speed changer generally designated SC.

A leadscrew 111 is interchangeably joined to the shaft 1% by a pin 199 and co-operates with a removable nut 113, held in place by a screw 114, of a body 1155 connected with the bars 33, 34 (FIG. 5) via a cylinder memher 116. As will be apparent from FIG. 4, a plurality 0 of compression springs, one of which is shown at 117,

urge the members 115, 116 apart until the member 116 abuts against the head 118 of a screw 119 threaded into the body and having an unthreaded shank surrounded by the compression spring 117. It is evident, therefore, that the rotation by motor of pinion 103 is transmitted to the cups 86 which are driven in, say, the clockwise direction in step with the rate of advance of the plate 82, carrying the cup spindles S7, determined by the leadscrew 111. Upon reversal of the motor 1 .35, the cups 86 are rotated in counterclockwise direction (as viewed in FIG. 3) as the cups are withdrawn from the plate. The pitch of the leadscrew is so chosen with respect to the rotation speed of the friction cups 86 that they threadedly withdraw the articles from their respective cavities in the mold plate while moving with the pitch determined by the threads on the articles, thereby preventing damage to these threads. Frequently, the molded articles will have radial teeth or other laterally projecting formations engageable by corresponding formations on the cups 862.

a If the cups started their reverse rotation at high speed,

her 115 of the leadscrew assembly is provided with a pair of pistons 120, 121 slidably received in respective cylinders 122, 123, while passages 124 connect the cylinder bores in front of the pistons with a duct 125. A solenoid valve 8V is interposed between an air compressor 126 and the duct 125 while a similar, normally closed solenoid valve 5V is disposed between this duct 125 and the atmosphere. When solenoid valve 5V is energized, compressed air flows into the cylinders 122, 123 to urge the members 115, 116 toward one another and displace the plate 82 carrying the spindles 87 and the cups 85 to the right (FIGS. 1, 4 and 5), simultaneously, the springs 117 (FIG. 4) are loaded. Since the solenoid valves both are normally closed in the absence of energization, the springs 117 remain in their compressed state. When, however, solenoid valve 8V is energized, the cylinders 122 and 123 are vented to the atmosphere so that springs 117 shift the members 115, 116 apart and draw the plate 82 to the left (FIG. 4) whereby ejector plungers 92 dislodge the articles retained in the cups 86.

Control circuit In FIG. 7, I show a control circuit for the injectionmolding machine which insures the sequential operation to be described hereinafter. This circuit can comprise, for example, a source of electric current (e.g. a battery B) whose ungrounded terminal is connected in series with a main or safety switch P13 which, when closed, renders the circuit operative. The Wiper of a selector switch S5, whose three operative modes are off automatic (A) and semi-automatic (S), is connected in series with the switch PR A further, manual mode of operations can, of course, be provided in place of the off mode. The selector switch is designed to energize, in position A, a mold-control circuit M similar to that of my U.S. Patent No. 3,117,348, to effect opening and closing of the mold with a predetermined operating sequence.

Additionally, a normally open limit switch L (FIG. 6) is carried by the movable mold holder 15 and is actuated when this carrier picks up for displacement the holder 36 to energize a relay R whose contacts close to drive the motor 105 (FIG. 4) in the forward direction and advance the unthreading head 81 via the leadscrew 111. A limit switch L having a set of normally closed contacts in series with relay R and a set of normally open contacts in series with the solenoid valve SV can be disposed upon the plate 115, as shown in FIG. 5, for engaging an adjustable abutment 130. As previously indicated, the operation of solenoid valve SV causes the adjustable abutment 131 to close a limit switch L carried by the plate 115 as plates 115 and 116 draw together. This switch L energizes a relay R whose contacts reverse the direction of drive of motor 105 and simultaneously deenergize the relay R This reversal takes place in three steps, i.e. a momentary tie-activation of the motor as relay R releases, an initial unscrewing motion at reduced rate and the main unscrewing stroke at relatively high speed. Relay R energizes a timer T, which actuates the solenoid S to shift the speed changer SC into its low-speed position, and closes an energizing circuit for a slow-operating relay R, which after a certain delay applies reverse volt age to motor 105. Timer T thereafter restores the speed changer SC to its high-speed position while motor 165 continues its operation. When the head 81 has been withdrawn sufficiently, another adjustable abutment 132 releases the limit switch L (FIG. Whose hitherto closed contact deenergizes relays R and R and whose erstwhile open-contact energizes solenoid valve 8V to release the pressure within cylinders 122 and 123 and eject the cups. During the mold-opening operation, the movable mold member closes the limit switch L (FIG. 6) to operate a holding relay R whose back contact is connected in series with the limit switches L and L previously mentioned (FIG. 2). Limit switch L is of the momentary-actuation type and closes for a period only sufficient to allow the front contact of relay R to energize the motor 66 and advance the eccentric and cam disk 72 so that the protuberance 78 closes the switch L or L, which it previously held open. Relay R is then locked in the on condition until the protuberance 78 opens the other switch. A pushbutton PE, is provided for the manual operation of the unthreading unit, should a control by the mold assembly be undesirable, while a pushbutton P13 serves the same function for the mold-plate swinging mechanism. A further pushbutton switch PB enables manual operation of the mold-control circuit independently of the unthreading device.

Operation Reference will now be made, additionally, to FIG. 8 whence it will be seen that, at the start of a cycle, the movable mold plate 28 closes limit switch L to operate relay R for swinging the mold holder 36 through an angle of about 180 to position the mold plate 31b, laden with the injection-molded articles 32, into alignment with the cups 86 of the unthreading apparatus. The moldcontrol circuit M then begins (point a) to advance the mold in the forward direction and, at a time corresponding to point b on the graph 1 of FIG. 8, the lost-motion connection brings the movable mold portion 28 on carrier 15 into contact with the mold plate 31a, newly positioned in the mold assembly 11. From point b to point e, the mold plate 28 (graph 11) is entrained by the movable carrier. Switch L is simultaneously closed to energize the relay R and drive the unthreading motor in the forward direction by the leadscrew, as indicated in the graph IV. At point 0, however, the mold is fully closed and injection can begin (period c to period I of graph III) with the injection piston or plunger being retracted in the usual manner. The forward drive of the unthread ing head terminates after the mold has been closed (graph IV) and, as the injection plunger is retracted, the limit switch L tripped by the forward motion to inactivate the motor 105 and open solenoid valve SV (graph V). The opening of this valve draws the plate 116 to the right to bring the friction cups 86 into engagement with the molded articles 32 and firmly seat them in these cups. The limit switch L is closed by the relative motion of plates 115, and 116 at the beginning of the pneumatic forward stroke of head 81, which insures that the cups 86 at contact with the articles are no longer positively driven but rotate only by inertia for the interfitting of their inner peripheral formations, if any, with those on the outside of the articles. The operating delay of relay R is suflicient to allow the articles to be firmly engaged by the cups 86 under pressure of their biasing springs 88. Relay R is then energized and the two-step reverse movement of the lead screw (graph IV) withdraws the articles threadedly from their apertures upon entrainment by the rotating cups 86. The newly injected articles concurrently formed in the other mold plate (e.g. 311)) are allowed to cool during this period whereupon the mold circuit commences the reverse movementof the mold carrier 15 (graph 1) and at time h effects entrainment of the mold-plate holder 36 in the reverse direction (graph II). Meanwhile, the reverse movement of the leadscrew (graph IV) has terminated upon actuation of limit switch L which simultaneously opens solenoid valve 8V (graph VI). Thus, the articles are ejected by plungers 92 from the friction cups 86 and the unthreaded assembly has been returned to its original position. Continued movement of the mold again brings it into contact with limit switch L to trigger the reverse mold swing (graph VII) as previously indicated. Manual operation of the various elements can be etfected by the use of the pushbuttons PB through PB with the selector switch SS in its semiautomatic or manual position.

It will be understood that the invention as described and illustrated admits of many modifications and variations within the ken of persons skilled in the art. Thus, the mold need not be tripartite as indicated earlier nor need the swinging portion of the mold be a longitudinally movable member. In fact, when a two-part mold is employed, it is desirable that the swinging member be the one that is longitudinally stationary. Furthermore, the circuit and control arrangement can make use of timing devices or programming systems of any convenient type. It should be noted that the friction cups 86, which are readily interchangeable to accommodate the contours and dimensions of the molded articles, can be replaced, if desired, by other gripping means, including suction devices. Interchangeable friction cups are desirable because various materials might require gripper elements having different degrees of resiliency. While the limit switches controlling the unthreading head and drive have been shown with screw-type adjustable abutments, it is equally possible that the limit switches themselves may be movable and that time-delay relays to servo-mechanisms are employed. It should also be noted that, whereas it has been found to be advantageous to use an upper tie bar to support the swingable mold holder, some axis can be provided, offset from the mold path as required. The oscillating movement of mold holder, which reverses direction for each of its swings, insures that the watersupply tubes 38, 40 etc. will not be broken and complex rotary distributors will not be required. The springs 38 bearing against the gripper cups '86 force these cups onto the articles with the cushioned thrust required when the pneumatic advance of the head 81 is effected, while the exchangeability of the leadscrew and nut assembly 111 through 114 insures that the unscrewing head will be capable of accommodating articles of various pitch.

The system described and illustrated may be modified in various ways within the framework of the present invention. Thus, the output shaft 104 of motor 105 may be reversed and arrested by the interposition of a suitable coupling between this shaft and the motor, rather than by reversible and intermittent energization of the motor as specifically disclosed by way of example. Such modifications, readily apparent to persons skilled in the art, are intended to be embraced in the spirit and scope of my invention as defined in the appended claims.

I claim:

1. In an injection-molding machine, in combination, "a bed; a pair of relatively displacea'ble mold members mounted on said bed, one of said members being provided with at least one screw-threaded mold cavity adapted to form a molded article thrcadedly seated the-rein; means for injecting a solidifiable plastic mass into said cavity in a closed position of said mold members; drive means for swingab-ly oscillating said one of said members about an axis parallel to the direction of relative displacement of said members out of registry with the other member and into an unthreading location; a holder at said unthreading location displaceable toward and away from said one of said members upon the latter occupying said unthreading location; gripper means on said holder engageable with said article for rotatively entraining same out of said cavity, said gripper means including a mating cup rotatable about the axis of the screw threads of the confronting cavity; and drive means for rotating said cup about the last-mentioned axis at relatively high speed while advancing said cup toward said cavity for engagement with a molded article seated therein and for rotating said cup in the opposite direction at a relatively low speed during withdrawal of said cup from said cavity whereby said article is unscrewed from said one of said mold members.

2. The combination defined in claim 1 wherein said drive means includes speed-changing means and control means for switching said speed-changing means into a low-speed position at the beginning of a withdrawal stroke and returning said speed-changing means to a high-speed position during a later stage of said withdrawal stroke.

3. The combination defined in claim 2 wherein said drive means includes a motor having an output shaft coupled with said cup by way of said speed-changing means, and circuit means for reversibly rotating said output shaft from said motor.

4. The combination defined in claim 3 wherein said drive means further includes a leadscrew and a spindle jointly driven by said output shaft for imparting concurrent rotation and axial motion to said cup, and a fluidpressure-responsive actuator for axially displacing said cup independently of said leadscrew and spindle during a terminal part of its forward stroke, said circuit means including cont-acts for arresting said output shaft during said terminal part.

5. The combination defined in claim 4 wherein said gripper means includes a biasing spring for resiliently urging said cup into contact with said article during said terminal part.

References Cited UNITED STATES PATENTS 2,317,823 4/ 1943 Strauss. 2,513,216 6/1950 Sullivan et al. 2,744,288 5/1956 Fienberg et al 2,808,620 10/ 1957 Schmid et al. 2,894,284 7/1959 Allison et al. 3,328,844 7/1967 Rees.

I. HONARD FLINT, JR., Primary Examiner.

Claims (1)

1. IN AN INJECTION-MOLDING MACHINE, IN COMBINATION, A BED; A PAIR OF RELATIVELY DISPLACEABLE MAOLD MEMBERS MOUNTED ON SAID BED, ONE OF SAID MEMBERS BEING PROVIDED WITH AT LEAST ONE SCREW-THREADED MOLD CAVITY ADAPTED TO FORM A MOLDED ARTICLE THREADEDLY SEATED THEREIN; MEANS FOR INJECTING A SOLIDIFIABLE PLASTIC MASS INTO SAID CAVITY IN A CLOSED POSITION OF SAID MOLD MEMBERS; DRIVE MEANS FOR SWINGABLY OSCILLATING SAID ONE OF SAID MEMBERS ABOUT AN AXIS PARALLEL TO THE DIRECTIO OF RELATIVE DISPLACEMENT OF SAID MEMBERS OUT OF REGISTRY WITH THE OTHER MEMBER AND INTO AN UNTHREADING LOCATION; A HOLDER AT SAID UNTHREADING LOCATION DISPLACEABLE TOWARD AND AWAY FROM SAID ONE OF SAID MEMBERS UPON THE LATER OCCUPYING SAID UNTHREADING LOCATION; GRIPPER MEANS ON SAID HOLDER ENGAGEABLE WITH SAID ARTICLE FOR ROTATIVELY ENTRAINING SAME OUT OF SAID CAVITY, SAID GRIPPER MEANS INCLUDING A MATING CUP ROTATABLE ABOUT THE AXIS OF THE SCREW THREADS OF THE CONFRONTING CAVITY; AND DRIVE MEANS FOR ROTATING SAID CUP ABOUT THE LAST-MENTIONED AXIS AT RELATIVELY HIGH SPEED WHILE ADVANCING SAID CUP TOWARD SAID CAVITY FOR ENGAGE-ENT MENT WITH A MOLDED ARTICLE SEATED THEREIN AND FOR ROTATING SAID CUP IN THE OPPOSITE DIRECTION AT A RELATIVELY LOW SPEED DURING WITHDRAWAL OF SAID CUP FROM SAID CAVITY WHEREBY SAID ARTICLE IN UNSCREWED FROM SAID ONE OF SAID MOLD MEMBERS.

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