US2408379A - Press - Google Patents

Description

oct. 1', 1946. F, DAY 2,408,379

' K vPRESS Filed Aug. 7, 1944 3 Sheets-Sheet 2 unlllllllllllnllllllllllnllllllllnllnll, I

2; zg v INVENTOR.

l y Y L. F. DAY

Oct'. 1, 1946.

PRES S Filed Aug,` '7, 1944 3 Sheets-Sheet Z @il Y INVENTOR Luiher FDay BY v 2f Patented Oct. 1, 1946 S l PATENT oFFlcE PRESS p Luther F. Day, Hawthorne, Calif., vassignor to North American Aviation, Inc.

' 'Application August '1, 1944, serial No. 548,383

This invention relates to improvements inA pneumatic presses and has asits general object toiprovide a press of relatively simple and in-r expensive construction which is capable of delivering a rapid succession of strokes having ex-V treme accuracy of stroke limit. A further object of the invention is to provide a press which elimi- Vnates the wear and tear lupon the clutch used in `the conventional flywheel and crank-type press.v A further object is to provide vapress adapted to deliver a stroke of maximum terminal power with' a minimum expenditure of energy in the lover-al1 operation o f the press. lA further object is to provide a press which permits of rapid variation in the'speed of operation thereof without wasting power and without straining the mechanism. y'

rThe invention contemplates a lm eumatically powered, toggle stroke delivery mechanism type of press and aims particularly to provide a press of this type whichiscapable of delivering twice as many working strokes per rcycle of motor op-v eration, and which provides for greater accuracy of stroke and correspondingly more uniform accuracyin the workpiece, than has been possible inyprior presses of this' general type. To this end', the inventioniprovides for'through-center operation ofthe toggle'mechanism by the pneumatic servo motor, so that the working stroke of f the ram terminates inthe middle rather than at the end of` a movement of the servo motor.

This arrangement produces the double advantage of improving the accuracy and uniformityk of the length of the ramstroke and'also ldoubles the` number of ram strokesper cycle of servo motor operation. A further object of the invention is to provide novel and improved control mechanism for a double acting 'servomotoL wherein Vautomatic control is derived from thedevice actuated by the servo motor.

Another object is to provide a kpress which may be converted from single stroke to continuous operation lsimplyfby turning a valve handle.

Another object of the invention is'to provide a pneumatically-powered press 'which can readily be synchronized with a cooperating machine such as, for example, an automatic feeding. device.4

Like` reference characters designate similar parts in the several which: f

Fig. 1 is a front elevation of the press; Fig. 2 is a section taken on the line Fis. 1;

l 1 claim." (c1. Y10o-'10) Fig. 3 illustrates diagrammatically the operating circuit; Y.

Fig.`4 is a detail oi the valve arrangement taken on line 4-\-4 of Figs. 1 and 5; and

Fig. 5 is a side elevation partially in section of the valve shown in Fig. 4.

shaft 6 is Secured to Y in the frame As an example of one form in which theinvention maybe embodied, I have shown in the drawings a light punch press comprising a frame I having parallel side members provided with slide Ways 3*--3 in which is mounted, for vertical reciprocation, a ram 2. Movement is transmitted to the ram 2 by toggle mechanism comprising pairs, of toggle arms 4.' andV 5-5 pivotally joined together by a shaft 8 and pivoted respectively at-their remote ends to the ram 2 by trunnions and to the frame I by a shaft 6. The the arms 4 and journaled A tool 'la may be supported in the ramr2 and adapted to cooperate with a suitable mating tool mounted on the bed 1b of the press.

Vertical reciprocating movement of the ram 2 is produced by alternately moving the pivotal joint between the toggle arms rst to one side and then to theother side of the axis of ram movement, and for this purpose-I provide a pneumatic servo motor comprising a cylinder pivoted at |2 to the frame and havingva double acting piston 3| (Fig. 3) to which is fixed a piston rod l0 linked to the shaft 8 by a cross head 9. It may be noted at this point that the stroke of the tool 1a is deliveredr when the piston 3| is intermediate the ends of its stroke. In the single stroke type of operation that has previously characterized toggle presses of this type, it has been impossible to terminate the piston stroke with suicient accuracy at the exact point of on-center alignment of the toggle arms so as to attain uniformityv of ram stroke. By .moving the toggle through center Yand delivering the ram kstroke greater accuracy andstriking powerin the ram views of the drawings, in V stroke and at the same time provide for double the number of ram strokes per cycle ofV servo motor operation.

Retracting ymovement of the piston 3| is'effected by introducingV air through a feed line 29Y intovthe chamber 30 formed between the one side of the piston 3| and the cylinder -Extending movement of the piston 3| is effected by introducing air under pressure through a line 33 into the chamber 32 delined between the opposite side of the piston 3| and the cylinder When air is being introduced through the line 2,9 into the 3 chamber 3i), air from the chamber 32 is exhausted through the feed line 33, and vice versa.

For reversing the flow through the lines 25 and 33, I provide a slide valve including a casing 25 having ports 28 and 34 with which the lines 29 and 33 communicate, having -an inlet 25 communicating with a. source of air under pressure, and having discharge vents 35 and 42 respectively, the former adapted to vent air from the line 33 while the inlet 26 is delivering air to the other line 29 and the latter adapted to vent air v from the line 29 when the inlet 26 is delivering air to the line 33, Slidably mounted in a bore 50 in the casing 25 is a valve plunger 38` having spaced valve ports 21 and 35 respectively (each enlarged at the surface of the plunger so as to bridge the space between the inlet 26 and the ports 23, 34 respectively) the port 21 being adapted at one limit of plunger movement to establish communication between the inlet 26 and the line 29 while the port 35 establishes communication between the line 33 and the vent 35, and the port 35 being adapted .at the other limit of plunger movement to establish communication between the inlet 2G and the line 33 while the port '2l establishes communication between the line 29 and the vent 42.

On the respective ends of the plunger 38 are pistons 31 andl which operate respectively in cylinders 45 and 43 formed in the respective ends of the casing 25. For moving the slide valve toward the right as viewed in the drawings, air is introduced from a line 22 into the cylinder 43 to act against the piston 39 while air behind the piston 39 is bled through a vent 44. Simultaneously, air in the cylinder 45 is vented through the line 2I in response to movement of the piston 31; and air enters the cylinder 45 through a vent 4I to ll the space behind the piston 31. In the movement of the plunger in the opposite direction, the flow is reversed.

The flow through the lines 2i and 22 is ccntrolled by a pilot valve comprising a cylindrical casing I mounted on the frame I and encircling one end of the shaft 6 which is oscillated by the upper toggle arms 4. The air lines 2| and 22 connect respectively with ports I9 and 28 circumferentially spaced in the casing I5. The shaft 6 has a central bore I6 which is connected toa source of vair under pressure by a fitting I1 threaded into the end of the shaft 6, a. rotatable coupling I'Ia, and a feed linellb. A passage I8 in the shaft 5 delivers air from the bore I6 to the port IS when the arms 4 are at one limit of their movement and to the port 24 when the arms 4 are at the other limit of their movement."v When the passage I8 is thus delivering lair to the line 2-I the line 22 is vented through a Vent I8b in the periphery of the shaft 5, registering with the port 20. Vand opening into the end of the shaft 6. When the passage I8 is delivering air to the line 22, the line 2i is vented through av vent lila,

4 its function until the next half cycle of operation of the servo motor has taken place, and the slide valve continues to function until that half cycle of operation is completed, the pilot valve being the while shifted for the next half cycle of operation.

The invention lends itself readily to synchronization with a cooperating machine without .change in the above-described mechanism. All that is necessary in 'order to achieve such synchronization is to control the pilot valve feed line I1b from the cooperating machine. For example, where it is desired to synchronize the `press with a feeding device such as that shown in Fig. 3, including a slide 41 operated by any 'suitable source of reciprocating movement (such as the crank shaft 48 driven by a motor 49 and similar tothe Vent i811 but located in the shaft 6 on 'the opposite shown.

The pilot valve operates to shift the plunger 38 from one limit of its movement to the other limit thereof prior to any substantial movement of the servo motor piston 3|. With the slide valve thus shifted, the pilot valve has completed side Vof the passage VI8 as connected to the slide 41 by a pitman 56) it is only necessary to provide a control valve operated by the slide 41 when the latter has completed its cycle of operation, and for rthe purpose of illustrating such a valve, .I have shown a valve including a casing 5I having an oscillatory valve element 52 therein voperated by an arm 53 which in turn is moved in one direction by the slide 41 and in the other direction by a spring 54. By connecting the line I1b and a feed line v55 in properly spaced relationship to the casing 5|, the valve may be made to cut olf the flow of air under pressure to the pilot valve except for a short interval at the limit of retracting movement of the slide 41, during which interval the air may be supplied to the pilot valve for a suicient length of time to reverse the slide valve. While I have shown a power-driven source of movement for the slide -41 it is to be understood that the slide 41 could, if desired, be operated manually and the press .would automatically operate in respense to the manual operation of the slide. It is also to be understood that while the movement of thev cooperating machinehas been described, for illustrative purposes, as a`reciprocating movement, that it need not necessarily be that type of movement but could be any other type, such r as, vfor example., rotary movement.

The foregoing may be taken as illustrative of one form in which the invention may be embodied, it being 'my intention to cover in my claim the use of any equivalent arrangement or apparatus.

I claim as my invention:

In a press, a frame, a ram adapted 'to have linear reciprocating movement with reference to said frame, a toggle comprising a pair of arms -pivotally joined to each other, the remote ends of one of said "arms being attached to a trunnion member which is journaled in said frame., the remote end of the other arm being vpivoted to said ram, a double acting pneumatic 'servo motor linked to the pivotal joint between sai-d 'armsjair circulating means for delivering air 'under pressure to one end of said servo motor while eX-y hausting air from the opposite end thereof, and means for reversing the ilow in saidV circulating means Vat predetermined limits of reciprocating movement of said servo motor, comprising a valve having an oscillating valve element comprising an extension of saidv trunnion 'and receiving movement therefromj v LUTHER DAY.

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