US2808736A - Counterbalancing means for punch press - Google Patents

Description

5 Shets-Sheet 1 NWN I Oct. 8, 1957 P. s. JACKSON COUNTERBALANCING MEANS FOR PUNCH PRESS Filed Feb. 7, 952

INVEN TOR. ad 5. JQCk-SOJZ; M

0c; 8, 1957 P. s. JACKSON 2,808,736

COUNTERBALANCINGMEANS FOR PUNCH PRESS Filed Feb. 7, 1952 5 Sheets-Sheet 2 Y BY 1957 I P. s. JACKSON 2,808,736

COUNTERBALANCING MEANS FOR PUNCH PRESS Filed Feb. '7, 1952 5 Sheets-Sheet 4 I INVEQTORVU 1957 P. s. JACKSON 2,808,736

I COUNTERBALANCING MEANS FOR PUNCHPRESS I Filed Feb. 7, 1952 5 Sheets-Sheet 5 INVENTOR.

4 ml \9. dc zciaom COUNTERBALANCENG MEANS FOR PUNCH PRESS Paul S. Jackson, Rockford, 111., assignor to Jackson Hydraulic Machine Co. Inc, a corporation of Eiliuois Application February 7, 1952, Serial No. 270,377

Claims. (Cl. 74604) This invention relates to a method and apparatus for counterbalancing a reciprocating force and to a punch press incorporating such counterbalancing means together with means for adjusting the die of the press toward and away from the ram and for feeding a workpiece between the ram and the die.

It is the general object of this invention to produce new and improved apparatus and methods as described in the preceding paragraph.

It is well known that a reciprocating mass produces a primary unbalance in the plane of reciprocation of the mass. In a vertical punch press for example, maximum upward unbalance is manifested as the crankshaft passes over top dead center and maximum downward unbalance occurs when the crankshaft passes over bottom dead center. With a reciprocating mass two neutral points exist, which points are approximately 90 between top and bottom dead centers.

It is possible to counterbalance a portion 'of the primary unbalance by counterweights. A common procedure which has been followed is to counterbalance half the weight of the reciprocating mass by attaching a weight to the crankshaft opposite to the crankpin with the weight having an inertia equal to half the inertia of the reciproeating parts. Rotation of the counterbalance weight serves to offset or diminish the primary unbalance of the reciprocating mass by about fifty percent inasmuch as the counterbalance is maintained oppositely to the mass and hence passes over top dead center as the mass passes over bottom dead center. Because of the fact that in such systems the counterbalance weight is rotating rather than reciprocating, transverse unbalance forces are introduced into the system at points approximately 90 from dead center. As just noted, maximum reduction of vibration is attained in such systems by constructing the counterbalance Weight so that it has an inertia equal to onehalf of the inertia of the reciprocating parts, that is, the Weight of the counterbalance weight multiplied by its distance from its axis of rotation should be equal to approximately one-half of the mass of the reciprocating parts multiplied by the throw of the crank to which it is connected. With the counterbalance weight so constructed it Offsets approximately 50% of the primary unbalance but, as noted, introduces transverse unbalance of approximately equal intensity. If the counterbalance weight is constructed to counterbalance more'than half of the primary unbalance, then the transverse unbalance becomes greater than the primary unbalance and little benefit is achieved. The transverse unbalance is of course exerted in a plane substantially normal to the plane of reciprocation of the reciprocating mass and thus .in a vertical punch press, for example, the transverse unbalance is exerted in a horizontal plane.

It is one of the features of the present invention to provide a method and an apparatus whereby the total amount of primary unbalance may effectually be canceled out by using a plurality of rotating counterbalance weights 2,808,73fi Patented Oct. 8, 1957 but which are so constructed as to also eliminate transverse unbalance. To this end there is provided a plurality of counterbalance weights which are rotated in unison with the reciprocation of the mass so as to pass over top dead center when the mass passes over bottom dead center with the sum of the inertias of the counterbalance weights being equal to the inertia of the reciprocating mass. Thus, the counterbalancing weights cancel out substantially all of the primary unbalance of the system. The counterbalance weights themselves are so rotated as to be in spaced relationship to each other in a plane normal to the plane of reciprocation of the mass so that the transverse unbalance of each weight opposes a transverse unbalance of another weight so that such transverse unbalance forces are canceled out. A simple form of construction would include a pair of counterbalance weights which are rotated in unison with the rewhich serve not only to eliminate primary unbalance, i

ciprocation of the reciprocating mass and so arranged that the weights pass over top dead center as the mass passes over bottom dead center and with the weights rotating in opposite directions and in the same plane so that at the'points from dead center the transverse unbalance force of one weight is exerted in one direction while an equal transverse unbalance force created by the other weight is exerted in the opposite direction, thus permitting the two equal but opposed transverse unbalance forces to cancel each other out.

Where a reciprocating mass, such as the ram of a punch press, is reciprocated by a crankshaft and connecting rod arrangement, a further unbalance'fac'tor arises because of the fact that when a crankshaft with its connected reciprocated weight and connecting rod passes over bottom dead center position (where the weight is below the crankshaft), the crank throw length is added to the connecting rod length in calculating the inertia force or the massmoment, while on the other hand in passing over top'dead center position the crank throw length is subtracted from the connecting rod length resulting in a lesser unbalanced force. This form of unbalance is known as secondary unbalance.

In order to eliminate secondary unbalance, I prefer to dispense with a connecting rod and in its place use a slotted crosshead (or scotch yoke principle). This method of drive produces a simple harmonic motion of the reciprocating parts with the result that. the massmoments of the reciprocating mass are equal both in the top dead center position and in the bottom dead center position. The use of the slotted crosshead gives the same results as if using a connecting rod having a length of infinity. Thus, the length of the crank throw does not vary the inertia forces between top and bottom dead centers.

In the event that the counterbalancing method and apparatus herein disclosed is employed on a punch press which is equipped with a ram whose weight may vary depending upon the type and number of punches secured thereto, as a further feature of the invention I provide counterweights which are readily removable and replaceable by other counterweights of different mass so that a ready correlation between the mass of the counterweights and that of the reciprocating ram can be effected. As a further feature of the invention I may provide counterweights which are adjustable so that it is not necessary to remove the weights but merely to shift their position rela- 3 weight of the counterbalance weight itself may be reduced while achieving the same inertia forces for the counterbalancing system.

.It is usually required in a punch press to provide some means of adjusting the position of the punches in the ram relative to the die mounted on the bolster or press frame below. This adjustment normally requires the use of one or more heavy adjusting screws and a locking device mounted on the ram. Inasmuch as the punch press disclosed herein is designed for heavy duty, high speed operation, it is desirable to reduce the weight of the ram as much as possible so as to reduce the over-all required weight of the press including the counterbalance system. As an additional feature of the invention, I provide a movable die holder on the frame of the press which is adapted to be moved by the adjusting screws and. to be held in adjusted position by locking devices. Thus, the necessary adjustment of the relationship between the ram and the die is achieved not by means mounted on the ram, as has heretofore been the practice,vbut. rather by means mounted on the frame apart from the ram.

Another feature of the invention is the provision in a die adjusting mechanism of the type mentioned in the preceding paragraph of a plurality of adjusting screws which may be motor driven so as rapidly to effect the raising and lowering of the die relative .to .the ram together With an easily operated locking mechanism which serves to lock the screws in adjusted position.

Yet another feature of the invention is the provision of a novel feed means for feeding a workpiece between the die and ram of a punch press which is operable either to move a workpiece at a feed rate orat a rapid rate so that a series of punches may be formed on a workpiece, with each series being spaced a predetermined amount. 'During the formation of each series of punches, the workpiece is moved at a feed rate to space the punch holes a predetermined amount, while the workpiece is moved at a rapid rate between each series of punches so as to space the series from one another along the length of the workpiece. Thus, the spacing can be achieved Without slowing the ram or press.

Another feature of the invention is to mount the feed rolls which serve as a part of the feed mechanism just described on the movable die holder so that adjustment of the die holder relative to the ram does not affect the relationship between the feed rollers and the die.

Yet another feature of the invention is the provision of a feed means connected directly to one of the crossheads in a punch press or other machine of that general type so that the sliding movement of the crosshead produces oscillation of the feed mechanism. Thus, a feed can be achieved without the use of independently rotated cams and the like.

Other and further features and objects of the invention will be readily apparent from the following description and drawings, in which: a

Fig. 1 is a top plan View of a punch press embodying the feature of the invention;

Fig. 2 is a side elevation of the upper portion of the press, partially broken away for clarity of illustration, taken on line 2-2 of Fig. 1;

Fig. 3 is a front elevational view of the lower portion of the press showing a part of the feed mechanism and the means for adjusting the die;

Fig. 4 is a vertical sectional view of the press taken along line 4-4 of Figs. 2 and 3; and

Fig. 5 is a horizontal sectional view through the upper portion of the press taken along line 5--5 of Fig. .2.

While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail one specific embodiment, with the understanding that the present disclosure is to be considered as an exemplifieation of the principles of the invention and is not intended to limit theinvention to the embodiment illustrated. Thescope of the invention will be pointed out in the appended claims.

Referring now to Fig. 4, the apparatus of this inven-..

tion is shown as incorporated. in a punch press including a frame A which supports at its top a driving mechanism B for driving the crankshaft system C of the press. The crankshaft system is connected to a ram D for reciprocating the same toward and away from the die E of the press, with the die being supported on an adjusting system F.

The frame includes a pair of vertical steel panels or side plates 10 and 11 which carries the mechanism of the press and which are provided with aligned openings 12 and 13 through which a workpiece is passed through and beneath the ram of the press. Supported at the top of the side plates is a pair of spaced horizontal top plates 1414a which carry an electric motor 15 for driving the press through the medium of a pulley 16 secured to the drive shaft of the motor which carries a plurality of V-belts 17 engaging a second pulley 18 secured to one of the drive shafts 19 of the press. As best shown in Fig. 1, the top of the ram carries a plurality of oil lines 20' which serve to lubricate various portions of the press, as will hereinafter be described. A transparent plastic cover 14b is secured to the top plates and extends over the space therebetween to prevent oil from splashing upwardly as the ram is reciprocated.

Referring now to Fig. 5, parallel to and horizontally spaced from the crankshaft 19 is a second crankshaft 21, with both crankshafts being rotatably mounted on relatively massive, anti-friction bearings 22 carried by the side plates of the frame. Each of the bearings is mounted on a. conical-shaped removable sleeve 23 machined properly to fit the outer surface of the crankshaft and the inside of the inner bearing race of each of the bearings 22. Fixed to the crankshaft 19 adjacent the ends thereof is a pair of gears 24 and 25 which mesh with a similar pair of gears 26 and 27 secured to the crankshaft 21. The gears are in a 1 to 1 ratio so that rotation of the shaft 19 in one direction throughthe medium of the driving pulley 18 rotates the shaft 21 at the same speed but in the opposite direction. The gears are each mounted on removal sleeves 28 and spaced from the bearings 22 by spacers 30a. The removal sleeves 28 are held in position by nuts 29 which, after being tightened in position, are held against slippage by keyed lockwashers 30.

Integrally formed on each of the cranksh afts 19 and 21 is tapered eccentrics 31 and 32. The eccentrics are oppositely positioned so as both to be facing toward the center line of the press in one position and horizontally outward from the center line when rotated 180, with the eccentrics being in aligned relationship in vertical planes so as to achieve the reciprocation of the ram.

As previously noted, the eccentrics ,31 and 32 are tapered toward each end with the oppositely facing tapers on each eccentric being separated by integral rings 33 and 34 which act as spacers for pairs of anti-friction bearings 35 and 35a and 36 and 36a carried by the eccentrics 31 and 32 respectively. It will be noted that the inner surface of the bearing races of each of the anti-friction bearings in said pairs is tapered to facilitate press-fitting the pairs of hearings on the eccentrics. To provide for easy removal of the bearings when their replacement becomes necessary, each crankshaft is drilled as indicated at 37 to form an oil passage communicating with an annular oil groove 38 formed on each taper of each eccentric. Introduction of oil under pressure into the passages 37 and thence to the passages 38 spreads the inner side of the bearing races slightly but sufliciently to permit the bearings to be removed with ease.

Inasmuch as the drive shafts 19 and 21 are not symmetrical but rather are provided with off-center eccentrics, the drive shafts themselves would produce unbalrance forces when rotated. To elf-set the unbalance of the crankshafts which is equal both at top and bottom dead center, each of the gears 2427 is provided with drilled openings 40 positioned on the same side of the nuts 49 to maintain the frame in place.

crankshaft as the eccentricity of the eccentrics and serves to off-set any unbalance produced by such eccentrics. The holes 40 may, if desired, be of a size suflicient only to counterbalance the eccentrics. If desired, the holes may be larger than necessary to counterbalance the eccentrics to further reduce the weight of the counterbalancing mechanism for the entire press. For counterbalancing the ram which is reciprocated by the crankshafts, each of the gears 2427 is provided with counterbalance weights 4144 positioned oppositely from the holes 40 with the weights being removably held in a groove formed in the gear by the screw device illustrated. Counterbalance weight of diiferent mass may be required depending upon the weight of the ram and punch assembly; and as punches are changed, which naturally results in a change in the weight of the ram, the counterbalance weights may also be changed. As previously mentioned, the weights may be adjustably fixed on the gears, such as by mounting them on eccentric shafts, so that the weights may be moved inwardly toward or outwardly away from the axis of rotation of the crankshafts to increase or decrease the inertia of the weights and thus to adjust for varying ram weights.

From the foregoing it will be evident that the gears 2427 serve not only as driving members to drive the crankshaft 21 at the same speed but in the opposite direction to the rotation of the shaft 19, but also serve as counterbalance weights not only for the eccentrics, as has just been described, but also for the reciprocating parts hereinafter to be described. It will be further noted that the counterbalance weights on the gears are oppositely positioned in a plane normal to the plane of reciprocation of the ram. Thus, when the gears are in the position shown in Fig. 5, the counterbalance weights 41 and 42 exert an outward force (to the left as shown in that figure) while the counterbalance weights 43 land 44, being equal in mass to the weights 41 and 42, exert an equal but opposite outward force (to the right as seen in Fig. 5). When the crankshafts have been rotated 90 from the position shown in Fig. 5, all of the counterweights will be exerting an accumulative force in a vertical plane, that is in the plane of reciprocation of the ram, and when the crankshafts have further been rotated an additional 90, the counterweights will be exerting opposite but equal inward forces. By so positioning and rotating the counterweights on the two parallel crankshafts, transverse unbalance created by any one counterweight is oifset by an equal and opposite transverse unbalance of another counterweight. Thus, the counterweights are mounted so as to be in opposing relationship, that is opposed to another counterweight in planes normal to the plane of reciprocation of the ram but are mounted to be in accumulative relationship in the plane of reciprocation of the ram. Inasmuch as the counterweights pass over top dead center as the ram passes over bottom dead center, the accumulative force of the counterweights is opposite to the unbalance force exerted by the ram and with proper proportioning of the counterweights may be made equal to the unbalance force of the ram. The counterweights, by their accumulative effect, therefore, quite effectively counterbalance the primary unbalance forces of the ram.

As previously mentioned, slotted crossheads or scotch yokes are employed for translating the rotary movement of the eccentrics into reciprocal movement of the ram. To this end each pair of bearings 35 and 35a and 36 and 36a is mounted in a crosshead slidable in suitable ways formed in a crosshead way frame. The crosshead way frame includes an upper plate in the form of a channel member 45 and a lower member 46. The members are maintained in spaced parallel relationship by aluminum spacer blocks 47a, 47b and 47c. Bolts 48 pass through the members and blocks and are provided with suitable I Upper and lower bronze bearing plates 50 and 51 are secured to the inner sides of the members 45 and 46 to provide slide bearings for a pair of crossheads 52 and 53 which in turn are carried by the bearings 35 and 35a, and 36 and 36a. Thus, movement of the eccentrics in a horizontal plane produces merely sliding movement between the crossheads and their ways while movement in vertical planes causes vertical movement of the crossheads and ways. The actual movement of the crossheads is circular but relative to the ways is a horizontal movement back and forth.

Secured to the center spacer block 4712 is a pair of V-gibs 56 which extends vertically from top to bottom of .the crosshead way frame and are slidable in suitably formed bearing surfaces 57 which are secured to the frame and extend vertically therealong. End gibs 58a and 580 are secured to the end spacer blocks 47a and 470 and are slidable on suitable bearing surfaces 59a and 59c also secured to the framework soas to provide a guided support means for the reciprocating parts of the press. 'The V construction of the center gibs makes an accurate center guide for the ram and still permits it to expand equally toboth ends from the center.

Lubrication of the crossheads in their ways is supplied through the lubricating conduits 20 previously noted. For the purpose of circulating the lubricating fluid, each of the spacer'blocks 47a47c is provided with a lube oil passages 60a-60c. Oil is introduced into suitable interconnected lubricating grooves formed in the bearing sur faces 50 and 51 through a lube oil connection 61 in turn connected to one of the oil lines 20. Lubricating oil in the grooves on the bearing surfaces passes outwardly from the connectionof the line 61 thereto and circulates, by means of the spacer block passages 60a-60c, through similar lube oil grooves formed in the lower crosshead bearing surface. A suitable drain connection is provided for the lower bearing surface 51 to produce a continuous circulation of lubricating oil for, the crosshead way system.

The ram D comprises a welded steel arm 62 secured at its upper end to the lower crosshead way frame member I 46 and provided at its lower end with means for securing thereto a punch holder 63, a punch liner 64 and upper and lower wedges 65. The punch holder, punch liner and upper and lower wedges are held in position on the arm 62 by clamps 66. A stripper plate 67 is carried by upper clamps 68 secured to side rails 69 fixed in the frame.

It will be noted that the ram assembly does not include the usual adjusting screws for adjusting the punches mounted on the punch holder relative to the die of the press. Thus, the weight of the ram is reduced to a minimum without in any manner detracting from, and in fact adding to, its strength.

The reciprocating ram of the press and its attendant accessories is substantially completely counterbalanced by the counterbalance weights attached to the gears hereinbefore described. It will be noted that the weights are located symmetrically about the center line of the reciprocating mass, that is are positioned equidistantly on both sides of such center line and symmetrically front and rear. Because of this symmetrical relationship of the counterbalance weight, no rocking couple is introduced in the system and the weights, when acting in accumulative relationship, counterbalance the primary unbalance of the reciprocating ram and are in opposed relationship from between top and bottom dead center of the ram (where the ram creates no primary unbalance) effectively to cancel out the transverse unbalance of the rotating weights. In the specific embodiment shown, the press is a one hundred ton punch press, the ram weighs about nine hundred pounds and the eccentrics have a quarter inch throw and thus impart a half inch stroke to the ram. Thus, the ram develops an inertia of two hundred twenty-five inch pounds. The counterbalance weights are aboutfive and a half inches from their axes of rotation and, as four are provided, each balances one fourth themass-moment of the ram, thus each weighs about ten pounds. With the' press so counterbalanced, speeds up to five hundred strokes per minute have been achieved without creating vibrations suificient to tip a coin balanced on edge on'the press frame.

The die assembly E comprises a die holder 70 having a suitable groovein which there is located a die shoe 71 which carries a suitably formed die 72. Positioned on either side of the die are lower guides 73. The die holder 70 is clamped toa bottom plate 74 by a die clamp 75 and the bottom plate is bolted to a base plate or platen '76 movably mounted in the frame A. As previously noted, the die assembly E is providedwith an adjusting means F for adjusting the die relative to the punches in the punch holder with the adjusting means being mounted on the frame rather than carried by the ram.

Theadjusting means F are so designed as to facilitate vertical movement of the die on the frame properly to position it relative to the ram and also to permit rapid replacement of broken punches and the like. The adjusting mea'ns F is provided with a plurality of screws 80 having external threads engaging the threads of an internally threaded collar 81 fixed to a lower cross brace 82 in the frame. A housing '83 is fixed to the lower side of the platen 76 and encloses a transversely extending drive shaft 84 carrying a plurality of worms 85 each engaging a worm rear 86 fixed to the leadjscrews 80. Thus, each of the screws 80'is provided with a worm gear 86 affixed thereto so that rotation of the screws and hence vertical movement of the platen may be achieved by rotating the shaft 84. If desired, a motor may be attached to the shaft 85, which motor may be operated by a suitable manual or pedal control to achieve rotation in either direction of the shaft 84 and hence to raise'or lower the platen, and thus the die, toward'and away from the ram. It will be noted that the upper face of the worm gear 86 bears against a face portion 87 of the housing 83 and by movement thereagainst with rotation of the screw accomplishes vertical movement of the platen.

It is necessary after making an adjustment of the die relative to the ram, that is after rotating the adjusting screws 80, that the screws belocked in adjusted position to prevent creeping during the operation of the'press. To this end one or more of the lead screws are hollow and provided with locking means to prevent such creeping movement. In the exemplary embodiment of the invention shown, three of the screws 80 are so constructed,

thus as seen in Fig. 4, wherein one of such hollow screws is illustrated, there is provided a locking rod 90 secured by means of the key 91 in a hollow 92 formed in the lead screw 80. The keyed connection between the screw and the locking rod is such as to prevent relative rotation between the screw and the rod but to permit sliding longitudinal movement between the rod and the screw. The lower end of the locking rod is threaded at 93 with the threads having the same pitch as the threads formed on the exterior surface of the lead screws 80 and with the threads 93 engaging threads formed in the interior of a worm gear 94. A worm 95 fixed to a rotatable shaft 96 engages the teeth of the gear 94 so that rotation of the shaft 96 causes rotation of the worm gear 94. The upper end 97 of the rod is provided with a collar 98 to' hold the rod in position with the lower face of the collar being adapted to bear against the upper portion of the bottom plate 74. A foot treadle 99 (Fig. 3) is provided for rotating the shaft 96 and hence to rotate all of the worm gears 94. Inasmuch as the threads formed at the lower end of the locking rod have the same pitch as the threads on the lead screw and as the key-way 91 causes the screw and rod to rotate together, vertical adjustment of the platen may be achieved through rotation of the shaft 84.

The similar pitch of the threads in the rod and screw permits such rotational movement Without'corresponding as... rotation of the worm gear 94. When the platen has been moved to the desired position, it is merely necessary for the operator to step on the treadle99 to cause rotation of the shaft 96 and hence of the worm gears 94, Such movement serves to move the rod 93 downwardly to bring the lower face of the collar against the upper face of the b ottom plate and thus to apply sufficient tension on the lead screw and'rod as to prevent their rotating with operation of the press. To release the adjusting means for further adjustment, it is merely necessary to rotate the shaft 96 in the opposite direction, thus releasing the locking means.

Means are provided on the press for feeding a workpiece in predetermined increments to the ram and die during the. reciprocation of the ram. For this purpose there is mounted on the platen.7.6 twopairs-of feed rolls 193-101 and 100a 101a with the rolls in each pair being vertically arranged and with the pairs being located on opposite sides of the die., The rolls are rotatably mounted on the platen, for example as shown in Fig. '3 the lower rolls 100100a and upper rolls 101-101a are suitably journaled in bearings 102-102a and 103 103a at each end. Secured to the shaft carrying each of the rolls is an upperdrive gear 104 and a lower drive gear 105. Thefrolls are pressed together by pneumatic piston and cylinder devices 106 mounted at each end of the upper roll and means are provided for operating such devices to separate the rolls slightly to permit insertion of a workpiece in the nip between the rolls. The teeth on the gears 104 and are made extra long so that they remain in mesh in all positions of the upper roll relative to the lower roll. If desired, a lubricant may be supplied to the workpiece by the upper T011 101 and to this end it may be provided with a hollow shaft connected to a suitable lube line 108 which feeds lubricant into the interior of the .upper roll from which it is extruded through small openings 109 in the surface of the roll and onto the surface of the workpiece The lower roll 100 rotates in a pan 110 of lubricant to supply its surface with oil. 7

A friction clutch, such as the clutch 111, is provided for the lower roll of each pair and is-so designed as to prevent rotation of the rolls except through the positive action of feed means hereinafter to be described. Thus, when the rolls arestationary, the workpiece held therein is maintained in fixed relationship relative to the ram and die and backlash or slippage of the rolls and hence of the workpiece is prevented.

The feed rollers 100 and 101 are located at the entering side of the workpiece while the opposite pair of feed rolls 100a and 101a is at the exit side. The upper roll 101:: of the exit feed rolls may also be provided with pneumatic devices 112 for raising and lowering the upper roll relative to the lower roll 100a for the purpose of permitting the initial insertion of a workpiece.

Means are provided for rotating both pairs of feed rolls in unison and by predetermined increments to feed a workpiece through the press. To provide for such intermittent movement of the feed rolls there is provided a rod (Fig. 2) threaded into the crosshead 5 2 and pivotally connected to a second rod 121in turn connected by a link 122 to a shaft 123' rotatably mounted in the frame. The shaft carries a block 124 provided with a dovetailed groove 125 in which is slidably mounted a block 126 rotatably carrying anactuating rod 127. With operation of the press the rotary movement (relative to the fixed frame) of the crosshead 52 is imparted to the rod 120 and translated by the link 122 into oscillatory movement of the shaft 123 and hence pivotal rocking movement of the block 124. The slide block 126 may be secured in the groove 125 at any desired position away from the axis of rotation of the block so as to impart to the actuating rod 127 whatever degree of vertical reciprocation is desired, ranging from zero, when its pivotal connectionto the slide block coincides with the axis of movement of the block 24, to maximum when the block is adjacent the end of the dovetailed groove,

The actuating rod 127 is connected at its lower end to a vertically reciprocable member 128 having rack teeth thereon engaging teeth 129 on a gear 130 fixed to a clutch shaft 131 having one end journaled in a pillow block 132 fixed to the platen, and having its other end supported in a free-wheeling indexing type clutch 133. The clutch 133 is of well known construction adapted to impart to the drive gear 105 motion in one direction only in response to the oscillatory movement. of the shaft 131.

The gears 104 and 105 are connected through a gear train (not shown) to similar gears connected to the top and bottom rollers of the other pair of feed rollers so that both pairs of feed rollers are simultaneously driven. The gear corresponding to the gear 105 secured to the roll 100a is connected through a second freewheeling indexing type clutch, clutch shaft, gear and rack to the piston of an air cylinder 134 which is adapted, when air under pressure is introduced into the cylinder, to rotate both pairs of feed rollers rapidly to advance a workpiece through the press.

The gear 130 may be shifted along the shaft 131 t disengage its teeth from those of the rack 129. To this end there is provided a hand lever 135 provided at 136 to the frame and secured to a pair of vertically spaced arms 137 and 137a each carrying detents 138 and 138a which ride in an annular groove 139 formed in the gear 130. Movement of the handle 135 slides the gear teeth out of mesh with the rack teeth to disconnect the feed mechanism.

If a series of perforations are to be made in a workpiece, for example the perforations in the back panel of a radio or television set, a long workpiece may be inserted in the rolls and the press started. Each stroke of the ram punches one row of holes in the workpiece and on each stroke the feed mechanism serves to rotate both pairs of feed rolls and advance the workpice slightly to determine the spacing between perforations. When the required number of rows of perforations has been punched in the workpiece, the air cylinder 134 is operated, either manually or by suitable automatic controls, rapidly to rotate both pairs of feed rollers a distance greater than their rotation during the feed operation and thus to provide a space between the first series of perforations and a succeeding series. Both feed and rapid speed mechanism operate while the punches are out of contact with the workpiece, that is they ,operate when the ram is moving upwardly toward top dead center and during only a portion of the rams movement downwardly toward the die and workpiece. To prevent operation of the air cylinder when the punches are in contact with the workpiece, a suitable limit switch may be incorporated in the electrical energizing means for the air cylinder valve to permit such energization only when the ram is near top dead center.

It will be noted that the feed rolls and most of the feed mechanism is carried by the platen and thus adjustments of the platen upwardly or downwardly do not misalign the feed rolls. If desired, the feed rolls may be provided with an individual adjustment to lower the position of the lower rolls as the dies are reground, thus making it a simple matter to keep the top of the lower roll of each pair in the same plane as the reground die. A similar adjustment is not necessary for the upper rolls inasmuch as the air cylinders with which each of the upper rolls is provided serves to move those rolls down wardly against its associated lower roll.

The die holder 70 is provided with openings at the location of the die so that the small portions of the workpiece which are punched out by the punches drop therethrough onto a waste conveyor belt 140 suitably mounted on rollers 141, one of which 141a is driven by a motor 142. The belt is driven in the direction indicated by the arrow so that the waste slugs are carried on the were uppensurface of the belt toward a chute 143 positioned at theleft-hand side of the press (as seen in Fig. 3) and as the belt passes around the first roller 141, such slugs drop off into the waste chute.

I claim:

1. Apparatus of the character described comprising a support, a pair of spaced parallel crankshafts rotatably mounted on the support, a mass mounted for reciprocation on the support along a path lying between said crankshafts and approximately normal to a plane' passing through the axes of said crankshafts, means connecting the mass to the crankshafts, means for rotating the crankshafts to reciprocate the mass, a first pair of counterbalance weights of equal mass mounted for rotation in parallel planes substantially parallel to the path of reciprocation of the mass at the opposite ends of one crankshaft, a second pair of counterbalance weights of equal mass mounted for rotation in said planes at the opposite ends of the other crankshaft, each pair of weights being arranged to .be in oppose relationship to the other pair in a plane normal to said path and to be in accumulative relationship and opposed to the mass in a plane paralleling said path.

2. Apparatus of the character described comprising a support, a pair of spaced parallel crankshafts rotatably mounted on the support, a mass mounted for reciprocation on the support along a path lying between said crankshafts and approximately normal to a plane passing through the axes of said crankshafts, means connecting the mass to the crankshafts, a first pair of gears mounted in spaced relationship on one of the crankshafts, each meshing with one of a similar pair of gears mounted on the other crankshaft whereby said crankshafts are connected together for rotation in opposite directions to reciprocate the mass, a counterbalance Weight mounted on each gear, said weights being of equal mass and the weights on the first pair of gears being ararnged to be in opposed relationship to the weights on the other pair of gears in a plane substantially normal to the path of reciprocation of the mass and to be in accumulative relationship with the weights on the other pair of gears and opposed to the mass in a plane paralleling said path.

3. Apparatus of the character described comprising a support, a pair of spaced parallel crankshafts rotatably mounted on the'support along a path lying between said crankshafts and approximately normal to a plane passing through the axes of said crankshafts, a mass mounted for reciprocation on the support, an eccentric on each crankshaft, crosshead ways secured to the mass, a pair of crossheads slidable in the ways each carried by a different one of the eccentrics, a first pair of gears mounted in spaced relationship on one of the crankshafts, each meshing with one of a similar pair of gears mounted on the other crankshaft whereby said crankshafts are connected together for rotation in opposite directions to reciprocate the mass, a counterbalance weight mounted on each gear, said weights being of equal mass and the weights on the first pair of gears being arranged to be in opposed relationship to the Weights on the other pair of gears in a plane substantially normal to the path of reciprocation of the mass and to be in accumulative relationship with the weights on the other pair of gears and opposed to the mass in a plane paralleling said path.

4. A punch press comprising a frame, a pair of spaced parallel crankshafts rotatably mounted in the frame, a ram mounted for reciprocation on the frame along a path lying between said crankshafts and approximately normal to a plane passing through the axes of said crankshafts, an eccentric on each crankshaft, crosshead ways secured to the ram, a pair of crossheads slidable in the ways each carried by a different one of the'eccentrics, a first pair of gears mounted in spaced relationship on one of the crankshafts, each meshing with one of a similar pair of gears mounted on the other crankshaft whereby 11 i said crankshafts are connected together for" rotation in opposite directions to reciprocate the ram, each of said gears having a lightened portion on the same side .of the crankshaft as the eccentric to counterbalance the eccentrics and the crossheads, a counterbalance weight adjustably mounted on each gear, said weights being of equal mass and the weights on the first pair of gears being arranged to be in opposed relationship to the weights on the other pair of gears in a plane substantially normal to the path of reciprocation of the ram and to be in accumulative relationship with the weights on the other pair of gears and oposed to the ram in a plane paralleling said path. 1

5. Apparatus for counterbalancing. a reciprocating mass comprising a support for the reciprocating mass, a pair of spaced parallel crankshafts rotatably mounted on the support and connected to-the rnass for reciprocating the same along a path lying between said crankshafts and approximately normal to a plane passing through the axes of said crankshafts, a plurality of counterbalance weights mounted on the support for rotation about axes substantially normal to and positioned on opposite sides of the path of reciprocation of the mass and substantially equidistant therefrom, said weights being distributed symmetrically about a line coincident with the path of movement of approximately the center of the reciprocating mass, and means for rotating said weights at a speed equal to the rate of rotation of the gen . References Cited in the file of this patent v UNITED STATES PATENTS Re. 23,373

Oschwald June 5, 1951 630,229 Hoyt Aug. 1, 1899 1,205,895 Hoyt Nov. 21, 1916 1,349,283 Kollack Aug. 10, 1920 1,494,547 Hubbard May 20, 1934 1,945,992 Boblett Feb. 6, 1934 1,959,602 Stanbon May 22, 1934 2,009,660 Irmis July 30, 1935 2,094,349 Carlson Sept. 28, 1937 2,268,242 Candee Dec. 30, 1941 2,280,384 Dickson Apr. 21, 1942 2,283,504 Johnson May 19, 1942 2,284,515 Criswell May 26, 1942 2,306,777 Buzonik Dec. 29, 1942 2,595,464 Kaufmann May 6, 1952 2,610,524 Maussnest Sept. 16, 1952 2,639,737 Forsberg May 26, 1953

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