US2796633A - Powder presses - Google Patents

Description

J1me 1957 c. G. CARLSON El'AL 6,

POWDER PRESSES Filed March 6, 1955 2 Sheets-Sheet 1 Fig.

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POWDER PRESSES Filed March e, 1953 2 Sheds-Sheet 2 C G. Cap 66 am Z;.TH.6pJzwLz ,9

United States rear POWDER PRESSES Carl Gustav Carlson and Hermann Theodor Walter Schulz, Huskvarna, Sweden, assignors to Husqvarna Vapenfabriks Akfiebolag, Huskvarna, Sweden, a corporation of Sweden Application March 6, 1953, Serial No. 340,818

Claims priority, application Sweden March 7, 1952 3 Claims. (Cl. 18-1fi.5)

This invention relates to mechanical presses for the compaction or molding of powder, particularly metal powder. Such presses are preferably arranged for applying pressure both from top and from bottom which is essential for the production of compacts of fairly uniform density. This may be accomplished by means of the conventional friction-actuated floating die. In a more advanced die construction the movement of the die body is mechanically controlled, the die body being lowered from a filling position into a pressing position and further into an ejecting position. Such construction allows for proper coordination of punch and die move ments and a more efiective control of the density distribution, particularly in parts of complex shape.

The invention has for its object to provide simple and etficient means whereby such die constructions may be successfully incorporated in mechanical presses having a compression motion from above only, such as a singleaction eccentric press, such presses having the advantages of high-speed production rates, simplicity and economy in operation, and low maintenance costs. Another object of the invention is to provide a mechanical powder metallurgy press of high flexibility in accommodating different jobs.

With the above and other objects in view, as will hereinafter appear, the invention comprises the novel combinations and arrangements of parts hereinafter set forth and illustrated in the accompanying drawings, and the advantages attained thereby will be readily understood by those skilled in the art.

In the accompanying drawings Fig. 1 is a schematic side view and Fig. 2 a similar front view, both partly in section, of a mechanical press with a molding die assembly operated by a cam and lever arrangement. Figures 3 and 4 are enlarged, vertical sectional views of the die assembly in different working positions. Fig. 5 is an enlarged, more detailed front view and Fig. 6 a similar end view, partly in section on line VIVI in Fig. 5, of the die operating cam. Figs. 7 and 8 are vertical cross sectional views of another molding die assembly and a coining die assembly, respectively, which are both adapted for use in connection wth the invention. Fig. 9 is a rather schematic side view of a toggle or knuckle-joint press embodying the invention.

The press shown in Figs. 1 and 2 comprises a frame 1 with a pair of uprights 2 and a stationary press table 3 provided with a central opening 4 above which a die assembly may in known manner be clamped to the table. A horizontal drive shaft 7 journaled in the uprights 2 is preferably driven by means of a flywheel 6, possibly adapted to serve as a belt or rope pulley. In the space between the uprights the shaft is provided with an eccentric 51, by means of an eccentric rod 52 connected in known manner to a vertically movable press head 5 which is slidably mounted on the uprights and to which an upper punch 37 may be secured opposite the opening in the table 3. The press head may be driven discontinuously, for instance by providing that the shaft 7 ice is connectible with the wheel 6 by means of a clutch operated by a pedal 56 and of the well-known type automatically disconnecting after each revolution, the press head being each time caused to perform a downward pressure-stroke and thereupon return to its upper position shown in Figs. 1 and 2. So far described the press may be a conventional eccentric press, for instance for sheet metal working.

In the embodiment shown in Figs. 1 and 2 a singleacting cam disk, comprising a cylindrical disk 55 and a cam 9 mounted thereon, is secured to one end 8 of the drive shaft projecting laterally from the frame, which can disk is engaged by a roll 10 on a vertical rod 11 which is slidable in its longitudinal direction in guide pieces 12 mounted on the frame. At its lower end the rod is connected by a pair of links 13 to one arm 14 of a lever mounted to swing on a pin 15 in the frame and the other arm 16 of which is coupled by means of a pair of links 17 to the lower end of a vertical draw bar 18 which, in known manner, may be divided into two and adjustable as to its length by means of a screw bushing 19. The draw bar is preferably positioned in a bearing 53 opposite the press head 5 and movable in the vertical plane through the drive shaft 7 together with the parts 11 and 16. The roll 10 should normally engage the cam disk 9, 55 under a yielding pressure, such as the pressure of a compression spring confined on the bar 11 and denoted by dotted lines in Fig. 2, or, better, a pneumatic pressure. To the latter end the lever 14, 16 may, by means of a pair of links 20, be connected to a piston 21 movable in a cylinder 22 mounted on the frame and having an air inlet at each end, the upper one preferably connected with some source of compressed air of substantially constant pressure.

The draw bar 18 is provided with an upper, threaded end portion 54 or other means for attachment to a vertically movable part of a die assembly mounted on the press table 3. In the embodiment shown in Figs. 1-4 this die assembly comprises a press platen 3t clamped to the table, a sleeve-shaped lower punch 31 secured to the table but, if desired, vertically adjustable, and a vertically movable die body 32 which in known manner may be provided with a hard metal insert. By means of a number of, preferably four, bolts or guide posts 33 vertically slidable in the platen 30, the die body is rigidly connected to a cross-piece 34 provided under the platen and attached to the draw bar 18. A cylindrical core rod 35 fixedly mounted on the cross-piece extends through the platen and the lower punch and is situated with its upper end surface in flush with the top side of the die body. The latter is movable between the powder filling position shown to the left in Fig. 3 and the ejecting position shown in Fig. 4. In the filling position the parts 31, 32 and form together a ring-shaped die cavity 36 suiting an upper punch 37 mounted on the press head 5.

For the purpose of feeding metal powder into the die cavity a plane, horizontal and, preferably, vertically adjustable support 4%) for a feed shoe 41 may be mounted between the uprights 2 in flush with the top side of the die body when in its filling position. The shoe is movable back and forth between a receiving position shown in Fig. 1, under a substantially funnel-shaped powder container or hopper 43, and a delivery position above the die cavity 36, the shoe being guided, for instance, by rails 42 on the support and the die. When the shoe is not in the receiving position, the bottom of the container may be automatically closed, for instance by a plate 44 secured to the shoe. The feed shoe may be driven mechanically from the drive shaft 7 for instance. It may also be driven pneumatically, being connected to a piston rod 45 of a double-acting piston in a cylinder 46 mounted on the frame and having two inlets 47 con- 7 3 nected with a source of compressed air over some valve mechanism well-known in the art and therefore not shown in the drawings. The valve mechanism is preferably by mechanical or electrical transmission means operated from the shaft 7, or some part driven thereby, in such a way that the feed shoe performs a stroke forth and. back when the die has resumed its filling position.

' By the movement of the feed shoe over the die cavity 36 the latter is each time .filled with substantially the same quantity of powder. By actuating the above-mentioned clutch the upper punch is lowered to the position shown to the right in Fig. 3, the pressing position, whereby the powder is compressed into a compact 50 of predetermined dimensions. The shape of the cam 9 should be such that the die is lowered after the upper punch has entered the same, and obtains substantially equal amounts of moveinent relative to; both punches 31 and 37 during the pressin'g operation whereby the compact will obtain a possibly even density. .The latter may easily be varied by an adjustment of the mutual height positions of the pressing tools in the pressing position, the end positions of the upper punch being adjustable in known manner. The compact is removed from the die by stripping, the die being lowered by the cam 9 into the ejecting position shown in Fig. 4 wherein the top side of the die is in flush with or somewhat below the press surface of the punch 31.. The cam may be shaped to lower the die continuously, but the lowering may also be interrupted in the pressing position shown to the right in Fig. 3, in order to continue as soon as the upper punch has started moving upward. From the ejecting position the die is rapidly moved back into the filling position, preferably before the upper punch has reached its upper position. In so doing the die brings with it the compact which, by the subsequent movement of the feed shoe, is pushed away, for instance to a slooping chute not shown in the drawing, whereupon the operations described are repeated, if desired automatically, the driving shaft being in such case caused to rotate continuously.

By changing the cam disk the press may readily be adapted for the production of compacts of difierent shapes. In the embodiment particularly shown in Figs. 5 and 6 the cam 9 is provided with a side flange 70 secured to one side of the cylindrical part 55 by means of easily accessible bolts 71. The filling position of the die body is determined by the radius of the part 55 and its ejecting position by the top 79 of cam 9. Somewhat in advance of its top 79 the cam is provided with a part 78 of constant radius corresponding to the final compression position of the die body and causing the same to make 'a dwell in this position (the cam disk being assumed to rotate in a clockwise direction in Fig. 5). Having been passed by'the cam 9 the roll 10 generally makes contact again with the cylindrical part 55, the connecting rod 11 being urged downwards as above described. In order to ensure an immediate return of the die body into the correct filling position it may, however, sometimes be advisable to provide a counter cam 75 in the path of the roll, said cam being secured by means of bolts 76 to one side of a disk 73 preferably having a circumferential backing flange 74 for such cams and if desired, formed integral with the cylindrical part 55. Such counter cams may be used whenever it is desired to ensure an upward movement of the draw-bar 18. At its periphery the cam disk is preferably provided with a plurality of equidistant, alternative cam fastening means, such as bolt holes 72, 77.

"A metal powder compact located in a die cavity may transmit or give rise to heavy frictional forces in the axial direction. It is possible that, during the last stage of the compression stroke, the compacted powder can, by friction against the walls of the members 32 and 35, transmit heavy forces from the upper punch 37 to the member 32 and cross-piece 34 whereby the cam and/or the guideposts 33 could easily be damaged. However, as the draw-bar can yield downwardly during the compres- 4 sion stroke, there is no danger of the parts being damaged.

The invention may be used to advantage also in the production of compacts of a more complicated shape, also compacts having sections of different heights in the pressing direction, such as a flanged bushing, the lower punch being subdivided in corresponding, mutually movable sec tions. The die assembly particularly shown in Figs. 3 and 4 may'thus be substituted by a die assembly in substantial accordance with Fig. 7 which, too, comprises a press platen 86 to be fixed on the table 3, a movable die body 81, a cross-piece 82 to be attached to the drawbar 18, and guide posts 83 rigidly connecting the parts 81, 82 and slidably mounted in the press platen. The lower punch is composed of a central section 84 corresponding to the highest section of the compact and fixedly mounted on platen 80, and two individually movable side sections 85, 86 mounted on vertical bolts 87, 88, respectively, slidably mounted in platen 8t). Cams 90 secured to the guide posts 33, for instance, are adapted to cooperate with rolls 93 on stop members 91, 92 mounted on the press platen St and horizontally movable out of the path of punch sections 85, 86, respectively, against the action of springs 94. In the filling position shown the punch sections 85, 86 rest on the cross-piece 82 with the heads 89 of their bolts 87, 88, the composite lower punch and the die body 81 defining a fill volume 95. During compression the side sections move individually downwards until, in the final pressing position of the die body,

piece 82 whereby alsothe punch sections 85, 86 will berestored into filling position.

Particularly in case the lower punch is subdivided into mutually movable sections, it may be suitable in known manner to provide for a limited yielding movement of the upper punch so that the latter rests against the compact under the action of a spring or the like during the ejecting operation or an initial stage thereof. In the embodiment shown in Fig. 7 a number of springs 98 are thus interposed between the upper punch 96 and a part 97 secured to the press head 5, the punch being provided with a number of guide pins 99 slidably mounted in the part 97 and surrounded by the springs.

A press according to the invention may readily be changed also to perform an upwardly directed ejecting movement of a lower punch in a molding die assembly having a die body yielding in the pressing direction, or in a coining die assembly having a stationary die. To the latter end the draw-bar 18 may be attached to a horizontal yoke 57, Fig. 8, at each end connected by links 58 to one end of a lever 59 swingably mounted on a lug 69 depending from a die adaptor or holder 64 to be clamped to the table 3. The opposite ends of the levers 59 engage a head 61 on the lower end of an ejector pin 62 slidably mounted in the adaptor and operated in a downward direct-ion by a spring 66. At its upper end the ejector pin is attached to a lower coining punch 63 situated in the stationary die 65 and cooperating with an upper punch, not shown in Fig. 8, to coin or size a sintered compact 67 supported by the punch 63, in its turn supported by the adaptor 64 during coining. After coining the draw-bar 18 is lowered by the means previously described whereby the punch 63 is raised so as to eject the compact from the die 65.

Naturally, also other embodiments are possible within the scope of the invention which may be applied also to mechanical presses, available or specially built, of the types wherein the pressure is created by means of a cam disk, a crank and/ or a toggle lever. Fig. 9 illustrates an application of the invention to a toggle press comprising a frame 100, a stationary die table 104 and an upper, vertically reciprocating press head 103 operated by a toggle lever 102, connected by means of a rod 115 to a crank disk 116 on a rotary driving shaft 101. Mounted on a laterally projecting end of this shaft is a cam disk 105 engaged by a cam follower 106 on one arm 107 of a two-armed, vertically swingable lever fulcrumed at 114. By link means 109 the opposite lever arm 108 is connected to the upper end of a vertical connecting rod 110 slidable in guide pieces 111 on the frame and connected at its lower end by link means 112 to one end of a lever 113. For the rest, the arrangement may be similar to that shown in Figs. 1 and 2.

What we claim is:

l. A mechanical powder compacting press of the character described comprising a frame, a stationary table carried by the frame and having an opening therein, a press head mounted on the frame for vertical reciprocation above the table, a horizontal driving shaft for the press head mounted in the upper part of the frame and having one end thereof projecting laterally from the frame, an upper punch secured to the press head, a press platen fixedly mounted on the table above the opening therein, a lower punch mounted on the platen opposite the upper punch, a vertically movable die body above the press platen, a vertically movable cross piece below the platen, guide posts rigidly connecting the die body and the cross piece and mounted to slide vertically in the press platen, a vertically movable draw-bar below the table, means connecting one end of the draw-bar to the cross piece, a radially acting cam secured to the projecting end of the drive shaft, a vertical connecting rod slidably mounted laterally of the frame, a cam follower associated with one end of the connecting rod and engaging the cam at a point above the cam, a two armed lever swingably mounted on a horizontal pivot on the frame, a positive connection between one arm of the lever and the lower end of the connecting rod and a further positive connection between the other arm of the lever and the lower end of the draw-bar, the profile of the cam imparting a downward movement to the die body from an upper powder filling position into a lower compact ejecting position, and means operatively associated with the connecting rod urging the follower into a yielding engagement with the cam and allowing the draw-bar to move freely downwardly during the compression stroke of the upper punch.

2. A press according to claim 1, comprising a counter cam extending along a part of the circumference of said cam and adapted to ensure an upward movement of said draw-bar and die body.

3. A mechanical powder compacting press according to claim 1 wherein said means operatively associated with the connecting rod urging the follower into a yielding engagement with the cam is defined by a fluid pressure operated assembly including a cylinder carried by the frame, a piston movable in the cylinder, a piston rod connected to the piston, and connecting means between the piston rod and the arm of the lever remote from the positive connection between the lower end of the drawbar and the two armed lever.

References Cited in the file of this patent UNITED STATES PATENTS 1,607,389 Claus Nov. 16, 1926 1,766,265 Smith June 24, 1930 1,820,235 Lemming et al. Aug. 25, 1931 2,122,874 Whipple July 5, 1938 2,127,994 Davis et al. Aug. 23, 1938 2,325,687 Kux Aug. 3, 1943 2,338,491 Cutler Ian. 4, 1944 2,358,765 Stadlin Sept. 19, 1944 2,393,130 Toulmin Jan. 15, 1946 2,398,227 Hubbert Apr. 9, 1946 2,457,127 Richardson Mar. 2, 1948 2,499,980 Stokes et al. Mar. 7, 1950 2,570,989 Seelig Oct. 9, 1951 FOREIGN PATENTS 663,040 Great Britain Dec. 12, 1951

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