US2960952A - Workholding press - Google Patents

Description

Nov. 22, 1960 c. F. KRAUSS WORKHOLDING PRESS Original Filed April 13, 1954 5 sheets Shee't l IN V EN TOR.

Nov. 22, 1960 Original Filed April 13, 1954 c. F. KRAUSS 2,960,952

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Original Filed April 15, 1954.

Nov. 22, 1960 c. F. KRAUSS WORKHOLDING PRESS 5 Sheets-Sheet 5 Original Filed April 13, 1954 OoOOO INVENTOR CARL F. KRAUSS ATTORNEY 2,960,952 Patented Nov. 22, 1960 wonanornmo PRESS Sari F. Krauss, Salem, Qhio, assignor to E. W. Bliss Company, Qanton, Cvhio, a corporation of Delaware Continuation of application Ser. No. 422,814, Apr. 13, 2954. This application Nov. 4, 1957, Ser. No. 694,324

Qlaims. (Cl. 113-99) This application is a continuation of my co-pending application Serial No. 422,814, filed April 13, 1954 (now abandoned) and entitled Workholding Press.

The invention relates in general to cam driven presses and more particularly to presses of this type adapted to hold work-piece firmly together while welding operations are being performed thereon.

In mechanically driven presses, either an eccentric or a crank is commonly used to move the platen or ram toward and away from the bolster. The circular motion of the crank or eccentric is converted to linear motion by means of suitable connecting rods or links secured to the platen. The stroke of the press is determined by the throw of the crank together with the connecting rod mechanism linking the platen to this crank motion. Once this motion has been determined, the characteristics of the platen movement are fixed, that is to say, the rate of acceleration or deceleration of the platen as it progresses through a cycle always remains the same. With this type of apparatus, as the platen reaches the top or bottom of its stroke, it momentarily stops due to the passing of the connecting links through their dead centers.

it is frequently desirable to provide a somewhat extended dwell at some stage in the operating cycle, and, in order to provide this dwell, toggle link constructions have been developed in which a substantial period of socalled dwell is obtained by arranging the toggles to pass through dead center in consecutive order. This is not a true dwell, however, but is rather the reduction of the platen motion to a very small amount without ever actually stopping its motion, except at the precise instant dead .center of a particular toggle is reached. In welding operations, it is preferable that the upper and lower welding dies remain in constant and absolutely fixed positions during the welding operation and it has been found that the so-called dwell obtainable by toggle link mechanisms does not yield the results required for the best welding.

Accordingly, it is ,a general object of the present in-' vention to provide an improved press drive in which any desired acceleration and deceleration may be imparted to the platen and an absolutely constant dwell of desired duration may be obtained during any portion of the cycle of operation. Other objects of my invention include the provision of a press drive in which a longer and more constant dwell may be obtained than with toggle type presses without slowing down the time of the operating cycle; the provision of a press drive having a minimum of joints, toggles, links, etc.; the provision of a press drive in which substantially all of the load is applied at the end of the stroke only; the provision of a press in which air cylinders carry the major portion of the press load and cam driven platen links assist in carrying this load but act primarily as a timing mechanism to give the desired characteristics to the operating cycle; and the provision of a press bed arrangement which gives greater access to the work, during loading and unloading operations, than conventional bed shapes.

To the attainment of these and other new and useful objects as will appear hereinafter, the invention consists in the features of novelty more fully described, claimed and shown in the accompanying drawings which illustrate a preferred embodiment of invention and in which Figure l is a somewhat schematic perspective View of the welding press showing the platen in the lower posi-' tion, the bolster being omitted for clearness of illustration;

Figure 2 is a diagrammatic perspective view illustrating my improved apparatus for vertically reciprocating the platen;

Figure 3 is a side elevation of one embodiment of the invention, partly in vertical cross-section taken substantially on line 33 of Figure 5, and with portions of the frame broken away to show the operating mechanism including the cam and its shuttle beam follower;

Figure 4 is a vertical cross-sectional view of the crown of the press and drive mechanism, generally similar to Figure 3 but showing the cam revolved 180 from platen down position as shown in Figure 3 to platen up position;

Figure 5 is a horizontal cross-sectional view of the rockshaft driving mechanism taken substantially on line 55 of Figure 4;

Figure 6 is an enlarged fragmentary elevation of the driving mechanism of the press, partially sectioned as indicated substantially along line 66 of Figure 5 to show certain of the component parts;

Figure 7 is an enlarged vertical cross-sectional view of the cam mechanism employed in the press, partially sectioned and taken substantially on line 7-7 of Figure 5;

Figure 8 is an enlarged vertical cross-sectional view of the center portion of one of the rockshafts and its cooperating rock mechanism taken substantially on line 38 of Figure 5; and,

Figure 9 is a top plan view of the press showing the relationship of the driving means to the shuttle beam mechanism, and the location of the surge tank employed to counter-balance the weight of the press platen.

In general, a press built according to the present invention employs a cam drive mechanism in the crown in place of the usual eccentric or crank and, through suitable links, the cam acts to reciprocate the platen or ram in the frame toward and away from the bolster, as set forth more fully hereinbelow. As illustrated, the drive includes a cam and follower, the cam being driven and the follower being connected to move the platen. The cam is so formed that a portion of its circumference lies at a uniform radius from its axis of rotation and this circumferential portion is disposed to provide a constant-prolonged dwell on either side of dead center at the end of the work stroke of the press. Other portions of the cam are formed to give the desired acceleration or deceleration characteristics on either side of the dwell.

Although the invention is not limited to such construction, in the present embodiment the bolster is carried by the crown and faces downwardly while the platen is supported beneath it and by suitable mechanism, hereafter described, is caused to move upwardly toward the bolster during the work stroke and down away from welding dies carried by the platen and bolster respectively are held together. A fluid pressure counterbalance mechanism is provided to carry the major part of the weight of the platen and its associated parts.

Referring now to the drawings in greater detail, one embodiment of a welding press incorporating my invention is illustrated in Figure l at 10, resting on a suitable base B. The frame of the press comprises four stanchions or side members 12, 14, 16 and 18 rectangularly arranged for supporting a crown portion 20 at their upper ends. The crown 20 carries most of the working portion of the drive as will be hereafter described. Beneath the crown and between the side members of the press is located a cruciform platen 22 which is supported forvertical movement beneath the bolster. The platen 22 is provided with end portions 24, 26, 28 and 30 (Figure 2) adapted to engage and be guided by the side members of the press frame, end portions 24 and 26 sliding between side members 12 and 14 and end portions 28 and 30 sliding between side members 16 and 18.

By making the platen of cruciform configuration, it is possible to provide greater access to the work during loading and unloading operations than is possible with conventional rectangular shapes. A protective apron 23 (Figures 1 and 3) encases the sides of the platen 22, and serves to guard both the workmen and the press from harm. With the protective apron 23, foreign objects or portions of a workmans body, such as a foot, are prevented from being accidentally placed beneath the platen 22 during its down stroke. While the form of platen shown and described is to be preferred, it is to be understood that the invention is not limited to any particular construction of platen.

- The platen 22 is raised and lowered with respect to the bolster 31 (Figure 3) by a cam mechanism (to be later described) in the crown 20 and receives an upward thrust from the piston cylinders 32, which, as shown in Figures 2 and 3, are disposed adjacent each platen end portion 24, 26, 28 and 30 and are supported at their lower ends on the base B. The upper die supporting bolster 31 is secured to the crown 20 and side members 12, 14, 16 and 18 by means well understood by those skilled in the art. Accordingly, the bolster securing means are-not discussed in further detail.

The upper ends 36 of cylinders 32 are provided with openings for piston rods 42 which have pistons 40 at their lower ends and are pivotally connected by pins 43 at their upper ends to brackets 38. These brackets in turn are secured to the platen 22 as seen at 39 in Figure 2 and include pivotal connections 41 with the links to be described.

A pair of rockshafts 44 and 46 are journaled within the crown 20 adjacent the opposite end walls 48 and 50 and extend from the front wall 52 to the rear wall 54 thereof (see Figures 4 and 9). Rockshaft pinions 56 and 58 are keyed to the center portions of their respective rockshafts 44 and 46 and are driven by a shuttle beam mechanism 82 hereafter described. Eccentric means in the form of a pair of rock arms or cranks 60 and 62 are secured to opposite ends of rockshaft 44 and like eccentric means comprising a pair of rock arms or cranks 64 and 66 are correspondingly secured to the opposite ends of rockshaft 46.

It will be noted that these pairs of rock arms are opposed in that, as shown in Figure 2, rock arms 60 and 62 extend outwardly to the left, whereas rock arms 64 and 66 extend outwardly to the right. The purpose of this is to provide a balanced mechanism such that the horizontal component of the thrust imparted by the rock arms on one side of the press is balanced by a corresponding component on the other side, eliminating undue stress in the parts.

Platen links 68, 70, 72 and 74 are pivotally secured at'their lower ends to brackets 38 and attheir upper ends to rock arms 60, 66, 62 and 64 respectively, whereby they are reciprocated substantially vertically as the rock arms describe semi-circular paths from bottom dead center to top dead center and back.

The aforesaid rock arms are rotated upwardly at a rapid rate to top dead center where a prolonged dwell occurs and thereafter the rock arms are rotated downwardly at a rapid rate to bottom dead center for an instant prior to commencing another cycle. The means for providing this movement, as shown in the drawings, include the circular cam discs 78 and 80 (Figures 4 and 5) which are keyed to a cam shaft 76 which is journaled in the crown of the press intermediate the rockshafts 44 and 46 parallel thereto. The cam discs are spaced apart to straddle a shuttle beam 82, the opposite ends of which are provided with racks 90 and 92 adapted to engage adjacent pinions 56 and 58 keyed to their respective rockshafts 44 and 46. The teeth of rack 90 are on the upper side thereof and engage pinion 56 on the underside of rockshaft 44. A taper block 94 (see Figures 4 and 8) is adjustably secured to a web 96 of the crown 20 for sliding contact with the bottom face of the rack thereby providing support for the end of shuttle beam 82 and proper contact between the rack 90 and the pinion 56. On the opposite side of the beam, rack 92 has teeth on its lower face for engagement with pinion 58 above the rockshaft 46. A taper block 98, similar to block 94, is secured to web 100 for adjustable sliding contact with the top face of the end of shuttle beam 82 which carries rack 92 so as to guide the shuttle beam and hold the rack in proper contact with pinion 58 (see Figure 4).

A pair'of identical opposed cam grooves 106 and 108 (Figures 4 and 7) are machined on the inside surfaces 110 and 112 of the cam discs 78 and 80 respectively. Cam follower 114 is carried by the beam 82 adjacent one end of the elongated slot 116 and is fitted with cam groove contacting rollers 118 on its opposite end portions to ride in grooves 106 and 108. Slot 116 is aligned with the longitudinal axis of shuttle beam 82 enabling the beam to straddle camshaft 76 and to reciprocate from one side of the press to the other as the cams 78 and 80 are rotated. The cam grooves 106 and 108 are so contoured as to accelerate the shuttle beam 82 rapidly toward one end of the crown 20 following which there is a prolonged dwell during the passage of a large segment of the cam grooves past the cam follower 114, all points of said segment being equidistant from its center of rotation. The remainder of the cam groove then acts on the cam follower 114 to return the beam 82 rapidly to the starting position. As illustrated, the dwell portion of the cam grooves is midway between the accelerating and decelerating portions thereof. Thus constant uniform rotary movement to the cam discs 78 and 80 is translated into intermittent generally horizontal reciprocal movement of the shuttle beam 82 and, through rockshafts 44 and 46, rock arms 60, 62, 64 and 66, and platen links 68, 70, 72 and 74, into intermittent vertical movement of the platen 22. 7

As aforesaid, the welding press shown in the drawings includes centrally located cam means employed to actuate rockshafts on opposite sides of the press. The rock shafts are driven by a shuttle beam which is reciprocatingly driven bythe cam means, It is recognized, however, that other embodiments will occur to those skilled in the art from a study of the invention in its illustrated form. For instance, by placing the cam discs on opposite ends of a camshaft equal in length to the rockshafts, a pair of shuttle beams might be employed to engage pairs of rockshaft pinions whereby the rockshafts would be subject to less torsional strain under certain conditions. With a similar arrangement, cranks, eccentrics or rock arms could be placed in the centers of the rockshafts, rather than on the ends as now situated, to provide center lifting of the platen. In still another embodiment, the cam drive means may be offset, with a platen centrallylocated between but two operating links, thereby eliminating the other. two operating links as presently shown. With a two link lift, either one or two shuttle beams could be employed, depending on the job requirements. Furthermore, although the invention is shown in. the form of an overdriven press, it is recognized that in certain applications an underdriven press would be more satisfactory, in which case the mechanisms would be reversed with the drive in the base rather than in the crown, and with the links extending upwardly to draw a platen down toward a bolster secured to the bed of the press.

The driving means for the cam discs 78 and 80 comprises an electric motor 120 (Figure 9) secured to the base 122 of the crown 20 and connected by V-belt means 124 to a flywheel 126 idly rotatably mounted on the flywheel shaft 128. The flywheel shaft 128 (Figure 6) is journaled for rotation on one end to a bearing stanchion 130 and on the other end in a roller bearing block 132 mounted in wall 134 of the shuttle beam housing 136. The shaft is also provided with intermediate hearing support 138 in wall 140 of the shuttle beam housing 136. A pinion 142 is keyed to the flywheel shaft 128 midway between bearings 132 and 138 for meshed engagement with intermediate gear 144 which is keyed to a rotatable shaft 146. The shaft 146 is also journaled for rotation in walls 134 and 140 of the shuttle beam housing 136 and carries a pair of pinions 148 and 150 on opposite sides of intermediate gear 144 for meshed engagement with the ring gears 152 and 154 (Figures 2 and 7) of cam discs 78 and 80.

A clutch and brake unit 156 is integrally fastened to the flywheel shaft 128 between the bearing stanchion 130 and the flywheel 126 for alternate clutching engagement with the flywheel and braking relative to the frame of the press. A flywheel brake shoe 157 is carried adjacent the rim of the flywheel 126 by a brake unit 159 which is integrally bolted to the lower portion of wall 140 of the shuttle beam housing 136. Brake shoe 157 is used to stop the flywheel from idly rotating on the shaft 128 when it is desired to shut down the press completely for any reason. Also mounted in the crown 20 is a surge tank 158 (Figure 9), between wall 134 of the shuttle beam housing 136 and wall 52 of the crown 20, having appropriate connections and valves 162 to maintain sufiicient air pressure in air cylinders 32 to carry the major portion of the load encountered in lifting the platen 22. The operation and function of surge tanks and counter-balancing cylinders on presses and the like is well understood by those skilled in the art and, as it does not constitute a part of the present invention, is not deemed to require further discussion.

From Figures 4 and 5 it may be seen that rotation of the cam discs 78 and 80 will cause the grooves 106 and 108 to bear against the cam follower 114 thereby exerting a longitudinal thrust against the cam follower 114 to exert a longitudinal thrust against the beam 82, causing the beam to shift to its farthest right position. In the position of the beam shown in Figure 4, the follower is at the center of the constant radius portion of the groove, all points of which are equidistant the center of rotation 76 and accordingly no movement is being experienced by the beam at this time. As the cam continues to rotate, the dwell portion of the groove passes by the cam follower 114 until the portion of the groove is reached which begins the move of the beam 82 to the right.

Thus, as the cams rotate at uniform angular speed, from the position of Figure 3 through a single revolution, the shape of the cam grooves is such that the beam 82 is caused to move rapidly from right to left into the position seen in Figure 4, dwell in this position for a predetermined period, and then return rapidly back to its initial position of Figure 3. In this embodiment of the invention, the cam grooves have been adapted to provide a period of dwell approximately 120 of the 360 cycle of rotation of the cam discs, but it will be understood that modifications of this cycle may be resorted to, if necessary, to serve various work holding requirements.

While the beam 82 is reciprocating to the left from the initial or starting position seen in Figure 3, the position of the racks and 92 with relation to the pinions 56 and 58 is such that pinion 56 will rotate in a clockwise direction and pinion 58 will rotate in a counter-clockwise direction. On the return stroke of beam 82 the direction of rotation of the pinions 56 and 58 will be reversed. It follows therefore that rock arms 60 and 62 will rock in a direction opposite to that of rock arms 64 and 66, and, starting from the positions of Figure 3, the rock arms will rotate from their lowermost positions outwardly and upwardly into their uppermost positions (Figure 4). Then after the dwell period imposed by the constant radius portions of the cam grooves has passed, the rock arms are lowered by being r rotated outwardly and downwardly to their original starting positions (seen in Figure 3). While this is taking place, platen links 68, 70, 72 and 74 will first be drawn upwardly and will carry with them the platen 22 which is integrally secured to the lower ends of these links. This lifting of the platen is substantially assisted by the pneumatic cylinders 32 which carry a substantial portion of the load required to lift the platen, but the rate of acceleration of the platen is controlled by the vertical movement of the links as regulated by the grooves in the cam discs. After reaching its highest position and dwelling therefor the time established by the constant radius portions of the cams, the platen links and the platen are lowered rapidly back to the initial or starting position seen in Figure 3. The clutch and brake 156 are preferably so operated that the cams make a single revolution from the position of Figure 3 and then stop until again actuated by the operator.

By making the platen 22 of cruciform configuration (Figures 1 and 2), it is possible for a team of workmen to stand beneath the crown of the press so as to be equally close to the work to be inserted in the press and removed after a welding operation. Since only the center portion or" the platen is usually used in pressing the work against the bolster, this shape of platen further tends to lighten the load which must be overcome in order to lift the platen during each cycle of operation.

From the foregoing, it is evident that I have provided a press which is particularly adapted for use in welding operations and is provided with a platen which, after bringing the upper and lower dies into contact under pressure, maintains constant pressure for any desired period of the cycle, whereinafter the dies are quickly separated and ready for a second operation.

I claim:

1. A press comprising: a quadrant of upstanding, rectangularly arrayed stanchions; a crown supported on the top ends of said stanchions; a vertically movable platen adapted to be guided by and slide between diagonally opposed stanchions; an operating link adjacent each stanchion and pivotally secured at its lower end to an adjacent side of said platen; a pair of rookshafts journaled in said crown and adapted to rock in opposite directions; rock arms secured to the end portions of said rockshafts; a pinion secured to each rockshaft intermediate its end portions; a cam shaft journaled in said crown to lie in the same plane as said rockshafts and positioned an equal distance from each rockshaft; a shuttle beam mounted on said cam shaft for movement transversely of the axis of said cam shaft, said shuttle beam having rack portions in driving engagement with said pinions; a cam member mounted for rotation on said cam shaft and having a cam face a segment of which has its periphery radially equidistant from its axis of rotation; a cam follower secured to said shuttle beam and adapted to maintain following contact with said cam face; and said operating links pivotally secured at their upper ends to adjacent rock arms, whereby said cam, shuttle beam, and link system cooperate to reciprocate said platen and to impart to said platen a dwell determined by the length of said cam segment.

. 7 v 2. In a workholding press having a crown, crown supporting side members, and a movable platen, the improvement comprising: a fixed platen secured to the underside of said crown; movable platen drive mechanism adapted to shift said movable platen to and from said fixed platen and including a pair of rock shafts mounted on opposite sides of said crown; rock arms secured to the end portions of said rock shafts; a cam shaft lying between'and parallel to said rock shafts; a shuttle beam supported for movement transversely of the axis of said cam shaft, driving connecting means between said shuttle beam and said pair of rock shafts to drive said rock shafts in equal and opposite directions of rotation; a cam secured to said cam shaft; means to drivingly engage said cam with said shuttle beam for imparting a reciprocal movement thereto; and operating link means between said rock arms and said movable platen; said cam having a segment of its face radially equidistant from its axis of rotation and oriented so that said segment imparts a prolonged continuous dwell to said movable platen when said platen is adjacent said fixed platen.

3.111 a workholding press having a crown, crown sup porting side members, and a movable platen, the improvement comprising: a fixed platen secured to the underside of said crown; movable platen drive mechanism 7 adapted to shift said movable platen to and from said fixed platen and including a pair of rock shafts mounted on opposite sides of said crown; rock arms secured to the end portions of said rock shafts; a cam shaft lying between and parallel to said rock shafts; a shuttle beam supported for movement transversely of the axis of said cam shaft; driving connecting means between said shuttle beam and said pair of rock shafts to drive said rock shafts in equal and opposite directions of rotation; a pair of cam discs mounted on said cam shaft to straddle said shuttle beam, each of said cam discs having a matched closed cam groove on its inside face, a cam follower secured to said shuttle beam and adapted to have its opposite end portions engage and run in said grooves; and operating link means pivotally secured to and extending between said rock arms and said movable platen, said cam grooves having aligned segments radially equidistant from their common axis of rotation and oriented southat said s'egmentsimpart a prolonged continuous dwell ,to said movable platen whenrsaid platen is adjacent said fixed platen. a a

4. The workholding press settforth in.claim'8, wherein the peripheries of said cam discs are provided with gear teeth; drive gear means engaging said gear teeth;tsaid shuttle beam being slotted and adapted to straddle said cam shaft, and said cam follower being secured to said shuttle beam adjacent one end of said, slotted portion.

5. A workholdingpress comprising a quadrant of up standing rectangularly arrayed stanchions; a crown supported on said stanchions; afixed platen secured to the underside of said crown; a vertically movable platen adapted to be guided by and to slide between diagonally opposed stanchions; movable platen drive mechanism adapted to slide said movable platen to and from said fixed platen and including a pair of rock shafts mounted on opposite sides of said crown; rock arms secured to the end portions of said rock shaft; a cam shaft lying between and parallel to said rock shafts; a shuttle beam supported for movement transversely of the axis of said cam shaft; driving connecting means between said shuttle beam and said pair of rock shafts to drive said rock shafts in equal and opposite directions of rotation; a cam secured to said cam shaft; means to drivingly engage said cam with said shuttle beam for imparting a reciprocal movement thereto, an operating link adjacent each stanchion and pivotally secured to an adjacent side of said movable platen, and to one of said rock arms; fluid pressure means associated with the lower end of each operating link adapted to urge said movable platen toward said fixed platen; and said cam having a segment of its face radially equidistant from its axis of rotation and oriented to provide a prolonged continuous dwell to said movable platen when adjacent said fixed platen.

References Cited in the file of this patent UNITED STATES PATENTS Hotfmann Mar. 5, 1957

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