US2676799A

US2676799A - Strip feeding mechanism

Info

Publication number: US2676799A
Application number: US125223A
Authority: US
Inventors: William A Fletcher
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1949-11-03
Filing date: 1949-11-03
Publication date: 1954-04-27
Anticipated expiration: 1971-04-27

Description

April 1954 w. A. FLETCHER I 2,676,799

STRIP FEEDING MECHANISM Filed Nov 3, 1949 8 Sheets-Sfieet 1 INVENTUR NIH/AH A. flfTCf/[R 1W6 ATM/M015 April 27, 1954 W. A. FLETCHER 2,676,799

STRIP FEEDING MECHANISM Filed Nov. .3, 1949 8 Sheets-Sheet 2 l/Wf TUB "Ill/AH A. flfTC/fffi Y I Mun-a4 April 27, 1954 w. A. FLETCHER 2,676,799

STRIP FEEDING MECHANISM Filed Nov. 3, 1949 8 Sheets-Sheet 3 )mrvroa Mil/AN A. run/1m BYW WM r 2 4 ///5 ATM/Mm April 27, 1954 w. A. FLETCHER 2,676,799

STRI-P FEEDING MECHANISM Filed Nov. 5, 1949 sheets-sheet 4 fi w w J 8 Sheets-Sheet 5 W, A. FLETCHER STRIP FEEDING MECHANISM April 27, 1954 Filed Nov 5, 194

April 27, 1954 w. A. FLETCHER 2,676,799

STRIP FEEDING MECHANISM Filed Nov. 5, 4949 8 Sheets-Sheet 6 I I INVM'M/l [WU/A A. Hilly/[B 5 7 4 HIS ATM/M076 April 1954 w. A. FLETCHER 2,676,799-

STRIi FEEDING MECHANISM Filed Nov. 3. 1949 8 Sheets-Sheet 7 Patented Apr. 27, 1954 UNITED STATES PATENT OFFICE General Motors Corp corporation of Delaw are oration, Detroit, Mich., a

Application November 3, 1949, Serial No. 125,223

3 Claims.

This invention relates to feeding a strip of sheet metal in punch presses. It has been the practice to feed sheet metal by means of rolls which are driven by the crank shaft of the press through a one-way drive such as a one-Way clutch. A sheet feeder of this type requires about one-half revolution of the press shaft for the feeding operation leaving the other half for die closing and opening to the extent required to permit feeding; and such feeder starts and stops its action relatively abruptly and requires the use of a brake to prevent over-travel, the maintenance of which is expensive.

An object of the invention is to provide a sheet metal feeding device which requires substantially less thanone-half revolution of the press shaft to operate it so that greater die closing and opening time can be permitted and which will gradually accelerate the sheet from rest and which will gradually decelerate it to rest at the end of the feeding operation.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a front view of the feeding apparatus.

Fig. 2 is a side View looking in the direction of arrow 2 of Fig. 1.

Figs. 3 and 4 together form a plan view on a larger scale than Figs. 1 and 2 of the apparatus, the part in section at the left of Fig. 3 being on the line 3-3 of Fig. 1, and a fragmentary plan view of an attachment to the punch press crank shaft from which power is taken off for driving the feeding apparatus.

Fig. 5, drawn to the same scale as Figs. 3 and 4, is a fragmentary sectional view on line 5-5 of Fig. 1.

Fig. 6, drawn to the same scale as Figs. 1 and 2, is a fragmentary sectional view on line 66 of Fig. 5.

Fig. 7, drawn to the same scale as Figs. 3 and 4, is a fragmentary sectional view on line 7-4 of Fig. 2.

Fig. 8, drawn to the same scale as Fig. 7, is a fragmentary sectional view on line 8-8 of Fig. 2.

Fig. 9, drawn to the same scale as Fig. 1, is a view in the direction ofarrow 9 of Fig. 1.

Fig. 10, drawn to the same scale as Fig. 9, is a sub-assembly of fixed and movable frame parts, the part in section being on line l+l 0 of Fig. 11.

Fig. 11 is a view in the direction of arrow H of Fig. 10.

Fig. 12 is a sectional view on line 12-42 of Fig. 11.

Fig. 13 is a chart used in explaining the mode of operation of the feeding device.

The punch press is equipped with two similar feeding devices embodying the invention, one being used to push the sheet metal into the press and the other to pull it out. The feeding devices operate in synchronism. The drawings show the feeding mechanism which pulls the sheet metal out from the press.

Referring to Figs. 3 and 4, 20 indicates a part of the frame of the press as viewed from above it. The frame 20 provides vertically disposed machined surfaces 2| and 22 and supports vertical bars 23 which guide for vertical movement of frame 24 which can be vertically adjusted by means to be described.

Frame 24 provides vertically disposed

machined surfaces

25, 26, 21, 28, 29 and 29a and supports vertically disposed plates 30 in order to guide for vertical movement a frame (not shown) which carries a movable shear blade 3| (Fig. 5) cooperating with a shear blade 32 which is secured by clamp bar 33 and screws 34 to a plate 35 which is supported by and movable with the frame 24. The function of blades 3|, 32 is to cut into small pieces the scrap or what is left of the strip S (Fig. 5) after the punches and dies of the press have punched out the required pieces which, for example, may be laminations for armature cores of dynamo electric machines. As shown in Fig. 1, the plate 35 is received by grooves 25a in frame 24 and is secured by screws 25b. As shown in Figs. 2 and 9, the frame 213 has frontwardly extending portions of cylindrical shape it and AI which are tied together by a rod 42 (Fig. 1) passing through a tube 43 and having threaded ends receiving nuts 44.

Sub-assembly A of the feeding device comprises a frame 50 secured to extension 43 by screws 5| (Fig. 3). Frame 53 provides a gear housing which is closed by

caps

52 and 53 which support needle bearings 54 and 55 for a shaft 56 supported also by a needle bearing 57 carried by a bracket 58 attached to a bracket 59 (Fig. 2) which is attached to frame 50.

On shaft 56 there is loosely journaled a sprocket 69 connected by a chain 6! (Fig. 3) with a sprocket 62 attached to a support 63 attached to a flange 64 which is provided by the crank shaft 65 of the punch press. It will be understood that parts 62-65 are located in the upper part of the punch press. v

The sprocket is connected with shaft 56 by a one-turn clutch comprising a drum In connected with shaft 56 by a key II and carrying a do I2 adapted to be received by a notch "I3 of the sprocket 60. The dog is urged into this notch by a spring I4 retained by a ring I5 which screws I6 secure to the drum II).

To the drum is screws I'I secure a brake drum 18 adapted to be frictionally engaged by a brake band liner I9 (Fig. 8) secured to brake shoes 8b which are connected by a pin El and which are urged together by a spring 82 surrounding a screw 83 threaded into one of the brake shoes and passing through a plain hole in the other and carrying a washer 84, the spring 82 being confined between this washer and the adjacent brake shoe. The right brake shoe 80 (Fig. 8) is supported by a screw 85 threaded into the extension 48 of frame 24.

Referring to Figs. 2 and 8, the clutch do I2 can be retracted from the notch l3 by the inter position of a wedge 90 provided by a clutch throwout lever 9I pivoted on a pin 92 supported by the bracket 59 and carrying a pin 93 received by a slot 94 in a yoke 95 provided by a piston rod 96 connected with a piston in a cylinder er. While the punch press is operating, pressure fluid is being admitted continuously to the left end of cylinder 91 so that lever 3! is disengaged from the dog I2 so that the press will continuously drive the shaft 56. When the strip material being fed through the punch press is used up, the press is caused to stop; and, through the medium of the cylinder 91, the lever 9i is caused to move to clutch throwout position so that the feed mechanism will stop at the end of its cycle. The brake functions only to stop the shaft 5% (Fig. 3) when the clutch is disengaged. It has no particular function with respect to the feeding operation.

The sub-assembly unit B (Fig. 7) of the mechanism comprises a frame Iilil with screws WI attached to the extension ii! of frame M. Frame I supports needle bearings I52 for a shaft Hi3 which extends through a seal IM and a thrust bearing I and which with a bevel gear III'I meshing with a bevel gear I08 (Fig. 3) connected by a key HQ with shaft 56. Gear IGI is retained by a washer III (Fig. 6) which a screw I I2 attaches to the shaf I83.

Shaft IE3 has a head portion II3 (Fig. 7) having a hole II I receiving needle bearings H5 for a shaft I I6 having an integral pinion II'I meshing with a fixed ring gear H8 (Fig. 5) fixed to frame IOII by dowel pins I I9 and screws IN. The pitch radius of the gear I It is indicated by c and the pitch radius of the pinion III by a. For reasons to be described, radius 0 is four times radius a. Shaft IIE has an integral crank portion I2I whose axis is represented by line I2Ia (Fig. 6). The eccentricity of axis IZIa relative to the axis IIIia of shaft III: is represented by the letter b in Fig. 7. A cover I22 is secured by screws I23 to frame I00.

Referring to Figs. -12, sub-assembly C of the mechanism comprises brackets Ice and I3I which are attached to frame 24 as shown in Figs. 2 and 9 respectively. These brackets support arod I32 which passes through spacing washers I33 and which has threaded ends receivin nuts I34 which on being tightened clamp the washers against shoulders I35 of the rod. That portion of the rod I32 between the shoulders I35 provides for reception of bearings I36 which are press fitted into frame members I40 and MI and a connecting tube I42 which is welded thereto.

is connected by keys I36 Referring to Fig. 12, members MI] and I iI, together, with bosses IM- and I45 welded thereto, support bearings M6 and It: respectively for a rod Its which supports a yoke I49 integral with a pitrnan I58 which, as shown in larger scale in Fig. '7, receives a needle bearing IEI journaled on crank IZI. Referring to Fig. 12, the yoke I49 of pitman I59 receives a bushing I52 shown on a larger scale in Fig. 5. This bushin guides for slidin movement a rod I53 providing a. spherical seat IE I for the spherical end IE5 or a link I58 connected by a pin I5? with a jaw I58 or clamp adapted to cooperate with a jaw I58 for gripping the strip of sheet metal S as shown in Fig. 5. Jaw I58 is guided for vertical movement by bars use secured by screws Itia to plate Itl. Springs IE2 tend to urge the jaw I58 downwardly and such downward movement relativ to plate Isl is limited by the flanges Itta of plates I50. Jaw IE9 is attached by screws I53 to a bracket IES I attached to frame members lit and I I! and providing a channel I65 through which the strip 8 can pass. To exclude dirt from the spherical surfaces 15s and I55, a flexible member I66 is retained by a spring Iiil against the bushin I52 and by a spring Ifle against a shoulder I58 of the link I56. The lower clamp IE8 is urged toward the upper clamp I59 as shown in Fig. 5 by a spring VII confined in a tube I?! attached by screws I72 to the yoke IE9 and connected by screws I'IS with a plate II I threadedly receiving a screw H5 retained in adjusted position by a nut IIB. Screw IIE has an integral disc III which confines spring He in a state of compression between said disc and the lower end of the rod I53.

As shown in Fig. 5, the pitman its is in an upper position causing the strip S to be gripped by the clamps I58 and I59. When the pitman its is caused to move counterclockwise about the pivot its in a manner to be described, the bushing I52 engages the shoulder Itta of the rod I53 and causes it to move downwardly against the action of spring 5T6. Pressure of the rod I53 on the link I being relieved, springs I82 effect separation of clamp I58 from the clamp I59 to the extent permitted by engagement of clamp I53 with the flanges IBM of plates IEII. Further counterclockwise movement of pitman I53 causes separation of rod I53 from link I56.

Referring to Fig. 13, a circle lisp represents the pitch circle of the ring gear I I8 whose center i represented by point H3301. which represents the axis IIiSa (Fig. 5') of shaft I83 (Fig. '7). Circle IIIp represents the pitch circle of the pinion II'I. As stated before the radius of circle I581: is represented by a small letter 0 and the radius of circle IIlp by the small letter a. The dot new represents the center line IIEa of shaft IIG. Considering circle I I'Ip as a disc rolling on the circle H812, points at or within the boundary of this disc will generate what are known as prolate hypotrocoids. The polar equation for the prolate hypotrocoid shown in Fig. 13 in which a: is the distance along a straight line from the center lilta' to the generating point, it is the angle in radians of that line with respect to a 45 diagonal through point M3311 and b is the distance from the center I Ita of the disc I I'Ip to the generating point. Obviously, if 1? equals zero the center IIfia will generate a circle I regardless of the relation between 0 and a. When c equals 4a and b equals a, which means that the generated point lies on circle II'Ip, the symmetrical figure II will be generated. Obviously, other forms of prolate hypotrocoids will be generated depending upon the relation of values 11 to a, it being understood that b is less than a because, if greater than a, a curtate hypotrocoid would be generated.

For purpose of the present invention, it is desirable to obtain vertical upward movement of the clamp I58 (Fig. 5) to grip the strip S followed by horizontal movement for feeding purposes followed by downward vertical movement to retract the clamp I58 and followed by horizontal movement in the reverse direction to return the mechanism to initial position. I have found that when value b is substantially .3611, during one revolution of shaft I03 the axis of crank I2I represented by point IZIa' in Figs. 5 and 3 will describe the prolate hypotrocoid figure, curve 111, which is substantially a square having rounded corners. The mechanism is so arranged that when the clamps I58 and I59 are at mid-feeding stroke position, as shown in Fig. 5, the generating point or the end of axis I2Ia' will have moved on curve III to a position vertically above the axis above a point I 03a representing the end of the axis 33a of shaft I03 (Fig. '7). In other words, the axis I 2Ia' of the crank I2! is so located as to be intersected in one position by a vertical line intersecting the axis ItISa' of shaft I03 and the axis IIBd of pinion I I I and at right angles to the path of movement of the sheet S. Therefore the locus of the positions of the axis I 2Ia' are on the prolate hypotrocoid, curve III, two of whose parallel sides are parallel to the sheet S and two of whose sides are at right angles thereto.

Sprockets 6B and 52 (Fig. 3) have the same pitch diameter and gears I08 and I01 have the same pitch diameter. Therefore the center I ifia' of shaft H6 will rotate once during each rotation of the punch press crank shaft. Point I IEd' moves counterclockwise and describes circle I which can be used to represent one rotation of the punch press crank shaft. Horizontal position of the pitman is represented by line mn. When point I 2 Ia is at P on curve III, the clamp I 58 begins to press the strip S against the clamp I59. At Q the gripping action is sufficient for the starting of movement of the strip S to the left (Fig. 5). At Q the point I 2Ia' starts moving horizontally as well as upwardly and the feeding of the strip begins slowly, the feeding speed increasing relatively slowly as the gripping action increases more rapidly. When point I2 Ia has reached R, the gripping action has reached such value as to permit more rapid increase of feeding speed. At point S the gripping pressure is at the maximum and the strip is being fed rapidly. At T deceleration of the strip begins. Feeding speed decreases as the crank axis I2I a rounds the corner to U, and then more rapidly between U and V, At V the gripping pressure begins to be relieved and at W the strip is entirely free.

The feed time is about one-third of a press shaft revolution and the die opening and closing time is about two-thirds. In the conventional stock feeding mechanisms, feed time is about onehalf of a press shaft revolution. It is desirable to reduce feeding time especially for presses operating a plurality of punches which clear the dies at different elevations. By the present invention feeding time has been reduced and jerking of the stock has been eliminated.

The foregoing is a description of the stock feeder at the exit of the punch press. At the entrance to the punch press, there may be located a stock feeder which is constructed like the one described with the exception that its supporting frame does not provide for guidance of a scrap cutter. It would have a shaft 56' (Fig. 3) corresponding to shaft 56 and connected therewith by coupling members 200 and 2!. The two feeding mechanisms operate in synchronism.

The frames which support the two feeding mechanisms are vertically adjustable because, when the dies are ground to sharpen them, the elevations of the upper surfaces of the dies are lowered. Therefore, it is necessary to lower the frames which support the feeding mechanisms. Frame 24 is lowered by the turning of screws I99 (Fig. 5) threaded through bosses I9I provided by the press frame and receiving flat surfaces I92 provided by the extensions 40 and M of frame 24.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A mechanism for use with a shaft operated punch press for moving a metal sheet in a substantially straight path, said mechanism comprising a shaft adapted to be connected with the press shaft as to rotate at the same speed and having its axis parallel to the sheet and at right angles to its path of movement, a fixed internal ring gear concentric with the mechanism shaft, a pinion having a pitch radius of one-fourth the pitch radius of the ring gear supported by the shaft for orbital movement about the axis ther of while meshing with the ring gear, a crank carried by the pinion and having its axis parallel to the pinion axis spaced from it a distance of about .36 the radius of the pinion and so located that, in a position of the pinion when its axis lies in a plane containing the center of the ring gear and located at right angles to the path of movement of the sheet material, said plane will contain the axis of the crank whereby, during a revolution of the shaft, the axis of the crank describes a prolate hypotrocoid figure which is substantially a square with rounded corners, two straight sides of the figure being parallel to said path of movement and two straight sides being at right angles to said path of movement, grippers located adjacent opposite sides of the metal sheet, one gripper being movable relative to the other, a frame supporting the grippers for movement in said path, a link connecting the crank with the frame, a spring normally ineffective to cause the movable gripper to advance toward the other gripper, and means operated by the link during movement of the crank in the parallel path defined by one of the first mentioned sides of the figure for conditioning the spring for urging the movable gripper toward the other gripper.

2. A mechanism for use with a shaft operated punch press for moving a metal sheet in a substantially straight path, said mechanism comprising a shaft adapted to be connected with the press shaft as to rotate at the same speed and having its axis parallel to the sheet and at right angles to its path of movement, a, fixed internal ring gear concentric with the mechanism shaft, a pinion having a pitch radius of one-fourth the pitch radius of the ring gear supported by the shaft for orbital movement about the axis thereof while meshing with the ring gear, a crank carried by the pinion and having its axis parallel to the pinion axis spaced from it a distance of about .36 the radius of the pinion and so located that, in a position of the pinion when its axis lies in a plane containing the center of the ring gear and located at right angles to of the sheet material, said plane will contain the axis of the crank whereby, during a revolution of the shaft, the axis of the crank describes a prolate hypotrocoid figure which is substantially a square with rounded corners, two straight sides of the figure being parallel to said path of movement and two straight sides being at right angles to said path of movement, grippers located adjacent opposite sides of the metal sheet, one gripper being movable relative to the other, a frame supporting the grippers for movement in said path, a spring normally effective to separate the grippers, a compressible spring normally inefiective to advance the movable gripper toward the other gripper in opposition to the first spring, two abutment members between which the second spring is located, means transmitting motion from one abutment member to the movable gripper and a link which connects the crank with the frame and which supports the other abutment member, said second spring being compressed sufficiently to cause the movable gripper to move toward the other gripper during movement of the crank in the parallel path defined by one of the first mentioned sides of the figure.

3. A mechanism for use with a shaft operated punch press for moving a metal sheet in a substantially straight path, said mechanism comprising a shaft adapted to be connected with the press shaft as to rotate at the same speed and having its axis parallel to the sheet and at right angles to its path of movement, a fixed internal ring gear concentric with the mechanism shaft, a pinion having a pitch radius of one-fourth the pitch radius of the ring gear supported by the shaft for orbital movement about the axis thereof while meshing with the ring gear, a crank carricd by the pinion and having its axis parallel to the pinion axis spaced from it a distance of about .36 the radius of the pinion and so located that, in a position of the pinion when its axis lies in the path of movement a plane containing the center of the ring gear and located at right angles to the path of movement of the sheet material, said plane will contain the axis of the crank whereby, during a, revolution of the shaft, the axis of the crank describes a prolate hypotrocoid figure which is substantially a square with rounded corners, two straight sides of the figure being parallel to said path of movement and two straight sides being at right angles to said path of movement, a frame which extends generally at right angles to the plane of the sheet, a sheet gripper fixed at one end of the frame on one side of the sheet and a gripper on the other side of the sheet and supported by the frame for movement toward the fixed gripper, spring means for urging the movable gripper away from the fixed gripper, a pivot support for the frame at the end thereof remote from the grippers, a link pivotally connected With the crank and the frame, and means for transmitting motion yieldingly from the link to the movable gripper to move it against the sheet as the link swings toward the sheet.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 812,333 Doran et a1 Feb. 20, 1906 1252,1 10 Morrison Jan. 1, 1913 1,297,587 Nordstrom Mar. 18, 1919 1,850,411 Mitchell Mar. 22, 1932 1,936,680 Lindgren Nov. 28, 1933 2,223,100 Foster Nov. 26, 19%0 2,250,584: Kreuger et al. July 29, 1941 2,263,721 Le Lorme Nov. 25, 1941 2,360,762 Conrad Oct. 17, 1944 2,506,736 Oschwald May 9, 1950 FOREIGN PATENTS Number Country Date 210,087 Great Britain May 21, 1925 364,436 France May 30, 1906