US2576295A

US2576295A - Knockout device for punch presses

Info

Publication number: US2576295A
Application number: US84231A
Authority: US
Inventors: Alonzo C Good
Original assignee: NCR Corp
Current assignee: NCR Voyix Corp; National Cash Register Co
Priority date: 1949-03-29
Filing date: 1949-03-29
Publication date: 1951-11-27
Anticipated expiration: 1968-11-27

Description

Nov; 27, 1951 c. GOOD 2,576,295

KNOCKOUTDEVICE FOR PUNCH PRESSES Filed March 29, 1949 3 Sheets-Sheet l INVENTOR ONZO 0. GOOD igww HIS ATTORNEY Nov. 27, 1951 c, GOOD 2,576,295

KNOCKOUT DEVICE FOR PUNCH PRESSES Filed March 29, 1949 3 Sheets Sheet 2 \l. I 29 3 130 I? T l7 YINVENTOR ALONZO 0. 6000 HIS ATTORNEY Nov. 27, 1951 A. c. GOOD 2,57 ,295

KNOCKOUT DEVICE FOR PUNCH PRESSES Filed March 29, 1949 I5 Sheets-Sheet 3 INVENTOR ALONZO 0. e000 HIS ATTORNEY Patented Nov. 27, 1951 UNITED STATES PATENT OFFICE 7 2,576,295 KNOCKOUT DEVICE FOR- PUNCH PREssEs Alonzo 0. Good, Dayton, Ohio, assignor to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland Application March 29, 1949, Serial No. 84,231

the length of the stroke of the die results in less of the punch and the die necessary less frequently. In actual operation of conventional punch press or dieing machines, it was found necessary to regrind the punch and the die after a run of between 50,000 and 60,000 pieces, whereas with the improvement no regrinding was found necessary until after a run of 250,000 pieces. The conventional stroke, heretofore considered necessary in a machine of the type disclosed, for blanking small pieces and shedding them from the die, was one and one-half inches. With the novel construction provided herein, the length of stroke required is reduced to approximately one-half inch. The shorter stroke of the cross head results in the blanks being shed into a more concentrated air blast, which ejects the blank from between the die set faster. The shorter stroke of the die also makes it possible to operate the machine at a higher rate of speed. In said conventional machines, the limit of speed was 180 R. P. M., while the same machine with the improvement attached makes it possible to run the machine at a speed of 600 R. P. M. when one piece at a time is blanked.

It is therefore an object of the invention to provide a means for shedding the blanks from the die of a compound, or inverted, die at the beginning of the upstroke of the die.

Another object of the invention is to provide a means for shedding the blanks from the die of a conventional compound, or inverted, die quickly to reduce the length of the stroke necessary for the proper operation of such machines to 3 Claims. (01. 164110) ferred form or embodimentof which is hereinafter described with reference to the drawings which accompany and form a part of this specification.

Of said drawings:

Fig. 1 is a cross-sectional view of the machine, taken on lines l-l of Figs. 2 and 3, and looking in the direction of the arrow.

Fig. 2' is a cross-sectional view of the machine, taken on lines 22 of Fig. 3, and looking in the direction of the arrow.

Fig. 3 is a plan view of the machine.

General description The invention is disclosed as applied to a machine disclosed in the United States patent to Daniel M. Wright, No. 1,270,913, issued on July 2, 1918, and is particularly useful when such machines are equipped to use compound dies, in which case an overhead knockout is provided to shed the blank from the die. The overhead knockouts heretofore provided in the machine disclosed in said patent were stationary, being supported in an overhead framework and located in such position that the knockout plunger carried by a reciprocating frame engaged the overhead knockout when the reciprocating frame approached its upper limit of travel. In actual practice, it was found that such constructions required a comparatively long travel of the upper die to properly shed the blanks and to eject them from the die set. Also comparatively slow speed is required to get these results.

Applicants novel construction comprises a moving means to replace the stationary knockout, which means includes a cam and a cam follower arm to operate the knockout plunger immediately as the die begins to rise or at any point between, thus providing a means to shed the blank quickly, making the stroke of the die shorter by as much as one-third. For example, in a dieing machine which ordinarily required a one-and-one-half-inch stroke, the stroke was reduced to one-half inch when the novel construction is used. The shorter stroke results in many advantages, which in the machine of the above example are as follows:

1. The operating speed of the machine can be increased from R. P. M. to 600 R. P. M.

2. The number of pieces which can be run before regrinding of the die set becomes necessary is increased from 50,000 to 250,000, when one piece is punched out per stroke of the machine.

3. The blanks are ejected from between the die set more efiiciently because the air stream for ejecting them is more concentrated in the narrow space between the die set. In the machines having the one-and-one-half-inch stroke and equipped with a conventional knockout, the air stream is so dispersed that the blank sometimes falls on the lower die before being ejected, thus causing damage to the'die.

4. The shorter travel of the die permits the machine to be operated at a higher number of strokes per minute without increasing the cutting speed of the die set. The higher operating speed causes blanks to be snapped from the stock without the cutting edges of thepun'ch and the die coming into actual contact with 'each other, which results in increased life of the die set.

5. The shorter travel of the die results in less wear on the guide rods of both the machine and the die set, which maintains a closer fit and better alignment of the die set and also reduces heat and friction to a minimum.

6. The shorter and faster stroke also results in a smoother operation of the machine, the machine developing little vibration.

7. The invention also has theadvantage of being usable to press the blank back into the stock strip, when such an operation is desirable, by a simple adjustment of the cam for operating the' knockout plunger. In this adjustment of the cam, the knockout plunger is operated quickly at the beginning of the upstroke of the cross head.

Detailed description The machine to which the invention is shown applied by way of illustration is provided with a stationary frame 10 (Figs. 1 and 2) to support a bolster plate H and a punch 'shoe l2. The punch l3 of a'die set is mounted on the shoe I2. A stripper plate It coacts with the punch 13 and pressure pins in'the'usual manner.

A reciprocating ram it, in the form of a square plate, is mounted to slide up and down on four guide rods I! in the usual manner, by means fully described in the aforesaid patent. A subplate 8, a die holder I9, and a sub-block 20 are mounted beneath the ram l6 so as to be reciprocated therewith. A'die 2| of the die set is carried by the sub-block 20.

A plurality of guide rods 22 for the die set maintain the punch and the die of the dieset in proper alignment when they are assembled in the machine and while the machine is operated. The guide rods may be secured in the shoe l2 and enter guide openings in the die holder 19 as shown.

When the ram I6 is lowered, the die 2|, contacting the stock 23 and forcing the latter over thepunch |3,"cutsa blank out'of the stock, which blank is forced into the opening in the'die 2|. 'Also, as the stock 23 is forced downwardly, the stripper moves therewith, andywhen the die 2| is again raised, the pressure. pins force the stripper upwardly to strip the'stock from the punch l3. The pressure pins l5 are operated in the usual manner, well known in the art.

As is well known, it is necessary to shed the blank from the die 2| after the blank has been out from the stock. To accomplish this, a shedder 25, loosely mounted in the die 2|, is provided. The shedder is provided'with a head 25, located in an opening 27 in the sub-block 20, which head limits the downward movement of the shedder '25. A shedder pin 28 is slidably mounted in the punch holder |9 and the sub-block 28,- and its lower end r'ests r on the head 26 of :the shedder.

4 A knockout plunger 29 is slidably mounted in a sleeve 30, carried by the ram l6, and the plunger is provided with a head 3|, resting on the top side of the punch holder l9. The knockout plunger 29 is provided with a pin 32 passing therethrough, and the pin 32 rests in the bottom of a yoke connector 33 (Fig. 2). The pin 32 is locked' against-lateral movement'by a block 34, notched to receive the ends of the pin 32, which block is brazed to the yoke connector. The flanges :of the yoke connector 33 rest on springs 35 surrounding guide bolts 36, on which bolts, nuts can be locked in any desired position.

-The-framework of :the machine supports two posts 40, at the top of which a cross bar 4| is mounted. A cam 42 is adiustably mounted near the center of the cross bar 4|, the upper end of which is threaded. The threaded end of the cam is locked in any desired position of adjustment by nuts 43. During the machine operation, the cam 42 is stationary.

Two frames 44 are mounted on the ram I6, so as to be reciprocated therewith during machine operations. A pin 45 is carried between the frames to pivotally support a cam follower arm 46, the upper end of which is bifurcated to receive a roller 41, carried on a bolt 48 mounted in the two ears of the bifurcated end of the cam follower arm 46. The roller 41 is always in engagement with the face-of the cam 42. The cam follower arm lliisalso provided with an adjustablev screw 49, adjusted to 'engagethe upper end of the knockoutplunger 29. The screw 48 is locked in an'adjusted position by lock nut 50, which position is such thatwhen the lower end of the screw 49 is'in contact with the plunger 29, the roller 4'! is incontact with the face of the cam 32-to maintain a snug fit between the parts.

Two rollers 5|, mounted in boltsv 52 carried between the two frames 44, provide a backing for the cam 42 during the machine operations. The frames 44 are held in spaced alignment by a cross bar 53 extending therebetween.

Operation In the'operation of the-machine, the stock 23 is fed between thedies l t-and 2| by any-wellknown means; for example, by a means shown in the United States Patent No. 2,231,325, issued to Sherman et al. on June 8, 1943. The ram I6 is then lowered to cutthe blank from the stock, and, as is known in the'art, the blank enters the die 2|, pushing the shedder 25 up'at the same time. As the" ram l6 movesqdownwardly (Fig. 1),-the

' roller dlmoves off the-high section 55 of the face of the cam 42 and'into a position adjacentthe low section 56-01 the cam 'faoe, thus allowing the cam arm 46 to rock clockwise, and the shedder 25, the shedder pin 28, and the knockout plunger 29am permitted to rise asthe'blank enters the die 2|. When the ram thereafter rises, the roller 47, coacting with the high section'55 of the cam 42, rocks the'cam arm-counter-clockwise (Fig. 1), to thrust the knockout-plunger 29, the knockout pin 28, and the shedder 25-downward-ly to push the blank out of the die. The cam 42 is set to shed the blank immediately the ram l6 starts to move upwardly, thus shedding the blank before the punch |3=andthe-die 2|are separated a. great extent. This provides for ejecting the blank from betweenthe punch and the die, while a stream of air, suppliedthrough-anair nozzle 60, is concentrated between the die-set. The concentratedair stream quickly ejects-the blank and makes a long stroke of-the ram unnecessary. In conventional regrinding the die set.

machines, to which the present invention is shown applied, the knockout plunger is lowered when it comes into contact with a stationary stop, which takes place at the terminus of the upstroke of the ram and while the die set is separated the full extent; This reduces the effectiveness of the air stream and therefore causes the blank to move more slowly, and sometimes the blank drops on the punch before being ejected from between the die set. This makes it necessary to allow sufiicient time to eject the blanks, which time has been made available in the past by a longer and slower stroke of the ram. By the improvement disclosed herein, a shorter and faster stroke of the ram is made possible. The faster operation of the ram makes it possible to adjust the die set in such a way that the punch [3 need not enter the die 21 any great extent, since a c1eancut blank can be had by the quicker operation. This results in the die sets remaining in good condition for a longer period, making it possible to obtain many more blanks without In actual operation, the number of blanks obtained, when one at a time is blanked, without regrinding has been increased from 50,000 to 250,000. The number of blanks successfully out per minute, when one blank at a time is blanked, has been increased from 180 to 600. When the die is constructed to obtain four blanks per stroke, an output of 1,600 per minute has been attained.

While the form of mechanism shown and described herein is admirably adapted to fulfill the objects primarily stated, it is to be understood that it is not intended to confine the invention to the one form or embodiment disclosed herein, for it is susceptible of embodiment in various other forms.

What is claimed is:

1. In a punch press or dieing machine having a compound die set consisting of a punch and a die, a reciprocating ram, and a knockout means in said ram to shed a blank from the die of the die set, the combination of a stationary frame, a cam adjustably mounted on said stationary frame, and a cam follower arm pivotally mounted on said ram coacting with the cam and the knockout means to operate the knockout means to shed the blank from the said die, said cam adjusted to actuate the cam follower and the knockout means immediately the ram begins to recede from its punching stroke, and before its receding stroke is completed.

2. In a punch press or dieing machine provided with a compound die set consisting of a punch and a die, a ram on which the die of said set is mounted, a main framework for the machine, and a knockout means carried by the ram, the combination of a cam carried by the main framework of the machine, and a cam follower pivotally supported on the ram and in engagement with the cam and the knockout means, whereby the knockout means is actuated immediately the ram starts its upward movement.

3. In a punch press or dieing machine provided with a compound die set consisting of a punch and a die, a ram on which one die of said set of dies is mounted, a knockout means carried by the ram and projecting into the die of the die set, said ram movable in one direction to cause the die set to cut a blank from stock and movable in a reverse direction to permit the shedding of the blank from the die and the ejecting of the blank from between the die set, a means to direct an air blast between the punch and the die of the die set when the die set is separated, and a main framework of the machine, in combination with a cam carried by the main framework, a means pivotally mounted on the ram and engaging the cam and the knockout means, said means operated by said cam when the ram initially starts to move in the reverse direction to move the means relatively to the cam to thereby move the knockout means in said one direction to shed the blank from the die while the punch and the die are still in close proximity to each other and the blast of air is concentrated, whereby the blank is ejected quickly from between the dies.

ALONZO 0. GOOD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 368,133 Cowles Aug. 9, 1887 369,970 Stiles Sept. 13, 1887 735,119 Leauitt Aug. 4, 1903 736,167 Stimpson Aug. 11, 1903 754,704 Rehfuss Mar. 15, 1904 1,007,103 Heine Oct. 31, 1911 1,208,019 Roney Dec. 12, 1916 1,503,829 Heald Aug. 5, 1924