US2606610A - Control means for hydraulic presses - Google Patents

Description

Aug. 12, 1952 I R. COLLIER 2,606,610

CONTROL MEANS FOR HYDRAULIC PBESSES Filed March 21, 1950 3 Sheets-Sheet 1 Aug. 12, 1952 R COL P 2,606,610

CONTROL MEANS FOR HYDRAULIC PRESSES Filed March 21, 1950 3 Sheets-Sheet 2 //vz/E/v Toe E/CH/IRD COLL/5Q 57 mag Aug. 12, 1952 R. COLLIER 2,606,610

CONTROL MEANS FOR HYDRAULIC PRESSES Filed, March 21, 1950 s Sheets-Sheet a Patented Aug. 12, 1952 CONTROL MEAN S FOR HYDRAULIC PRES-SE Richard Collier, Esher, England Application March 21, 1950, Serial No. 150,916 In Great Britain August 25, 1949 6 Claims.

This invention relates to control means for hydraulic presses for producing plastic mouldings from materials such as synthetic resins and particularly those known by the registered trademark Bakelite.

During the cycle of a moulding operation it is usually necessary to control the sequences of opening and closing of the dies with different timing to suit the nature of the moulding being produced. For example, with Bakelite, after an operator has charged adie with moulding powder and metal inserts, it is necessary to operate the press so that it commences to close, then closes, and at a predetermined time after closing opens slightly momentarily to eiiect "breathing to allow the escape of gas to avoid blemishing the moulding. The dies are then allowed to remain closed for a predetermined time to effect curing and are then opened and, when approaching the fully open position the movable die, which is usually the lower die, moves relatively to an ejector pin device which acts to raise the moulding slightly from the movable die to enable an operatorto remove the moulding by means of a hand stripper. This means therefore that before the movable die can again be charged with moulding powder, the die must again be moved slightly in relation to the ejector pin device to raise it clear of the ejector pins and then retained in this charging position.

These operations with a'hydraulic moulding press have up to now generally been efiected by an operator manually actuating two levers for controlling the inlet and exhaust of the hydraulic medium to and from the press and, in practice, an operator cannot handle more than two presses at one time and keep them working constantly and efliciently.

It is the object of the present invention to provide a simple and reliable control mechanism which will enable all the operations (which need not necessarily be those referred to above) to be eiiected automatically in the correct sequence and with requisite timing between stages so that all an operator has to do is to charge a moulding press and put the press into action, when the desired cycle of operations is efiected automatically. During this time the operator can attend to other presses. By fittin hydraulic moulding presses with the control means of this invention it is estimated that'a single operator can attend to six presses and keep all of them constantly in action.

It has been found impracticable to secure efficiently the automatic operation by simple continuously rotating cam mechanisms, operating the inlet and exhaust valves of the hydraulic press in predetermined sequence and times, owing to variables which cannot conveniently be excluded, such as variation in the pressure fluid supply to the press which causes fluctuations in the time occupied. in the closing and opening strokes This is very pronounced when a plurality of presses are fed from a main hydraulic system with the possibility of an indeterminate number of the presses working simultaneously or standing idle.

According to this invention, there is provided control means for a hydraulic press for producing plastic mouldings which comprises, in combination, a rotary element, an electric motor for intermittently driving the rotary element, a first series of relatively fixed cams carried by the r0- tary element, inlet and exhaust valves through which the pressure medium passes to and from the press, which are actuated mechanically in a predetermined sequence by the first series of cams, a second series of cams carried by-the rotary element which are co-related with the said valve-actuating cams and movable simultaneously therewith, switch means actuated by the second series of cams including some for opening the motor circuit to bring the rotary element to rest at predetermined positions in its cycle of movement, and one or more switches operated independently of the cams fo closing the motor circuit to re-start the rotary element in accordance with a cycle of press operations.

In order that the invention may be clearly understood and readily carried into eifect, reference will now be made to the accompanying drawings which illustrate an embodiment of the invention by way of example as applied to the control means adapted, in addition to controlling the opening and closing of the dies, to permit a breathing operation of the dies to take place after the initial closing together of the dies and also an inching movement of the dies when fully open as hereinafter explained. Referring to the drawings:

Figure 1 is a diagrammatic perspective view showing the control means disposed alongside a hydraulic moulding press,

Figure 2 is a side view of the control means with the adjacent side of a casing, in which the means is located, removed,

Figure 3 is a plan View of the control means with the roof of the casing removed, 7

Figure 4 is an elevation of the control means looking in the direction of arrow A of Figure 2,

press P and the main control member comprises a disc 2 which is suitably supported for rotation and driven intermittently by an electric motor 3 through the intermediary of reduction gearing 4.

Fitted to this rotary disc 2, in predetermined spaced apart relation, are five cams or the equivalent lever lifting and lowering abutments 5, 6, I, 8 and 9, three of which, i. e. 5, 6 and 'I are located on one side of the disc 2 (and alone are visible in Figure 2) and coact with a roller or the equivalent anti-friction device It provided at the lower end of an arm II secured to a hand lever IE or the like loaded by a spring I2a and controlling a valve I3 fitted in an inlet pipe I}! through which hydraulic medium passesto the press P so as to allow pressure to act on the movable d-ie I5. The remaining two cams 8 and 9 are located on the other side of the disc 2 and co-act with a roller Ia at the lower end of arm 51? fitted to a hand lever or the like I6 loaded by a spring Ito and which controls a valve I! in an outlet or exhaust pipe'IB for the pressure medium. These cams 5 to 9 inclusive are referred to herein as the first series of cams. A pipe I9, connected to the hydraulic chamber of the press is common to both the inletand outlet pipes I4 and I8, for delivering and exhausting the pressure medium. These five cams 5 to 9 are adjustably mounted respectively in a groove or slot provided in each side of the disc 2 and are locked in position by bolts 2I so that they can be preset to suit requirements for treatment in producing difierent forms of mouldings from various materials.

The side of the disc 2 having the pressure cams 5, 6 and I is fitted with a second series of five cams or trip rollers 22, 23, 24, 25, and which may conveniently comprise rollers mounted on the outer ends of rods 21 which are fitted at their inner ends to blocks adjustable in a second and inner groove 28 in this latter side of the disc 2 and these cams 22 to 25 co-act with three rockable switches 29, and 3I supported adjacent the periphery of the disc 2 and this second series of cams 22 to 26, which will-hereinafter be referred to as roller cams to distinguish them from the first series of pressure and exhaust valve-operating cams 5 to 9, are co-related with the cams 5 to 9 ina manner described hereinafter. The, switches 29 and 30 control the supply of current to the electric motor 3, and switch 3| controls a circuit energising a time-switch 34 also for controlling the supply of current to the motor 3. V

The circuit arrangement as seen in Figure 11 includes an electromagnetic relay 32a associated with the push-button 32, and a timing switch 34 which is adapted to open its contacts 34a for a predetermined time interval on excitation of its winding 3%. The switches 20, 30 and 3| are shown in their normal positions in Figure 11, i. e. the positions they assume when not acted upon by the cams 22 to 26. It willbe observed that in these positions of the switches, the motor circuit is closed from the supply terminal Z through the motor 3, switches 30 and 29, and normal closed contacts 34a of timing switch 34 to the supply terminal n.

To enable a full cycle or operations to be described, it must here be explained that at the end of a moulding operation, the movable die I5, at its extreme lowermost position, has moved downwardly over ejector pins which act to push the moulding upwardly away from the die to facilitate removal of the moulding by a hand strippen, Thus, when commencing a new operation, ,a preliminary inching movement of the die has a first to be efiected in an upward direction so as to clear the die of the ejector pins before the die can be recharged with moulding powder and metal inserts (if the nature of the moulding includes same).

Figure 5 shows the positions of the members of the control mechanism'at this stage with the exhaust cam 8 operative and the exhaust valve [1 open, and with the pressure cams 5, 6 and 'I.

inoperative and the inlet valve I3 closed.

The movable die I5 is then inched or raised a short distance (see Figure 6), so as to clear the ejector pins, by pressing the push button 32 (Figures 1 and 11) mounted on the front wall of the casing I which operates the relay 32a. The relay 32a momentarily closes the circuit to the electric motor 3 to drive the disc 2 sufficiently to allow the roller cam 22 (which acted on the switch 30 at the end of-the previous cycle of operations to break the motor circuit to the motor end stop the disc) to move out of engagement with the change over switch 30 to allow the switch to close the circuit to the motor 3' to render the latter operative. During this movement of the disc 2 the exhaust cam 8 leaves the arm I612 as in Figure 6 and permits the exhaust valve I! to close, and the pressure cam 5 then comes into action to open the inlet valve I3 to effect slight upward movement'of the die I5.

The next step in the cycle of operations consists in stopping the die when it has cleared the ejector pins and the condition of the parts shown in Figure '7 is arrived at in which both the inlet and exhaust valves l3 and H are closed so that the die remains stationary in its slightly raised position. At this stage the exhaust cams moment the roller cam 26 engages with the switch 29 to open the entire circuit to the motor which can then only be closed by way of a switch 43 actuated by a guard which has to be moved into a protecting position before the press can again be operated.

The die I5 is then charged with moulding pow der and inserts and the guard moved into position to screen the operator from the dies and the push button 32' is again pressed to close the circuit to the electric motor 3 momentarily to move the disc sufficiently to clear the roller cam 23 off the switch 30 whereupon the latter is rocked and closes the circuit to the motor to drive the disc 2. With the continued movement of the disc the pressure cam 6 see (Figure 8) acts to open the inlet valve l3 and simultaneously the roller cam 24 moves into engagement with the switch 30 to open the switch 30 and stop the motor. The inlet valve I3 is now held open by'the cam 6 while pressure builds up to the desired force and the press is completely closed.

To ensure that the required pressure is built up to effect complete closure of the press before the cycle continues, irrespective of the time occupied between the positions of Figures '7 and 8, a switching device 33 is provided for re-starting the motor and disc 2, this device being adapted to operate only when the dies have actually come together with full pressure. This switch 33 may be operated by the pressure of the fluid which operates the press (as illustrated in Figure 2) or instead of the switch 33 being actuated by a predetermined pressure in the fluid feed line, it may be mechanicall actuated by the movable press element [5 when the same has reached its com plete closure position.

When required pressure has been built up, the switch 33 which, with the exhaust valve I! closed, is included in the pressure inlet system by a pipe line 33a, becomes operative to close the motor circuit to cause the disc 2 to run on to effect a breathing operation in which the exhaust cam 9 then opens the exhaust valve ll momentarily as shown in Figure 9 and as the disc 2 in this instance is not stopped by any roller cam of the second series the breather cam 9 moves quickly out of engagement with the exhaust lever arm 16b to close the exhaust I! and the momentary lowering of the die away from the fixed top die I5a enables breathing of the moulding to take place and allows gases to escape from between the dies which would otherwise blemish the moulding. As the breather cam 9 moves out of engagement with the arm of the exhaust lever Ifib of the machine the remaining pressure cam I, engages the pressure lever arm ll (Figure 10) to cause the dies to close and at the same time the roller cam 25, associated with pressure cam 1 engages with the switch 3| and energises a process timing switch 34 (Figures 13 and 11) on the machine and this timing switch 34, which is of any suitable design, opens the electric motor circuit at its contacts 34a and causes the disc 2 to stop. The dies I 5 and l5a are now held closed, to enable the moulding to be cured. This curing time is pre-set on the switch 34 and can be varied according to the characteristics of the moulding but for the purpose of general understanding of the invention can be said to be about a minute. The breathing time effected by the rapid opening and closing of the dies takes about one second.

At the end of the curing time, the timing switch 34 on the machine automatically closes the circuit to the electric motor 3 (at its contacts 34a) and the disc 2 again starts to rotate and the exhaust cam 8 engages the arm IBa of the exhaust lever l6 and the hydraulic medium is exhausted to allow the die l5 to travel downwards away from the upper die 1501.. At this exhaust cam 8 engages the arm [6a of the exhaust lever [6, the roller cam 22 associated with the exhaust cam 8 actuates the switch and stops the motor 3 so that the exhaust cam 8 remains in engagement with the arm Ilia. of the exhaust lever IB to enable a complete exhaust action to take place and the die to return to its lowest position as shown in Figure 5 in which ejector pins raise the moulding away from the bottom die.

The press is now open ready for the operator to remove the moulding and this is effected by the operator raising the guard and inserting the hand stripper underneath the moulding, the operator thereafter again pushing the push button switch 32 on the press as already explained which closes the circuit to the motor 3 (by means of the relay 32a) and the pressure cam 5 again engages the arm H of the pressure lever [2 to allow the die 15 to rise about one inch to clear the ejector pins. The press then comes to rest ready for a subsequent operation, the roller cam 23 acting on the switch 30 and cutting out the motor 3 after the bottom die l5 of the press has risen the required distance and thepressure cam 5 has moved out of engagement with the lever.

The purpose of the relay 32a associated with the push-button switch 32 is to maintain the circuit to the motor 3 closed a suificient time, say five seconds, so as to keep the motor '3 running and the disc 2 in action to enable the roller cams 23 and 26 to clear the switch 30 and allow the latter to make contact and close the motor circuit again. I

The foregoing embodiment has only been described by way of example and various modifications are possible within the scope ofv the invention. For instance, the invention has been described with reference to the adaptation of an existing press and the pressureor exhaust cams can be made to actuate means other than levers l2 and I6 associated with the pressure and exhaust valves l3 and I! of the press. Also, while it is convenient and preferable to arrange both the pressure cams, exhaust cams and the roller cams on a single revolvingdisc 2 theselcams may be provided respectively .onseparate discs if so desired. r

The relay 32a may if desired be dispensed with by constructing the switch 32 so that it will remain closed for a predetermined period after the push-button has been pressed (say five seconds) and will thus hold the motor circuit closed while the cam roller 23 or 25 is running off its associated switch.

What I claim is:

1. Control means for a hydraulic press for producing plastic mouldings comprising, in combination, a rotary element, an electric motor for intermittently driving the rotary element, a, first series of relatively fixed cams carried by the rotary element, inlet and exhaust valves through which the pressure medium passes to and from the press, which are actuated mechanically in a predetermined sequence by the first series of cams, a second series of cams carried by the rotary element which are co-related with the said valve-actuating cams and movable simultaneously therewith, switch means actuated by the second series of cams including some for opening the motor circuit to bring the rotary element to rest at predetermined positions in its cycle of movement, and one or more switches operated independently of the cams for closing the motor circuit to re-start the rotary element in accordance with a cycle of press operations.

2. Control means according to claim 1, including an additional switch, also operated by a cam of the second series, for the purpose of energizing a, time switch for closing the motor circuit and restarting the rotary element after a predetermined time interval following the closure of the press at an appropriate point in the cycle of operations.

3. Control means for a hydraulic press for producing plastic mouldings comprising in combination a rotary element, an electric motor for intermittently driving the rotaryelement, a first series of relatively fixed camscarried by the rotary element, inlet and exhaust valves through which the pressure medium passes to and from the press, which are actuated mechanically in a predetermined sequence by the first series of cams, a second series of cams carried by the. rotary element which are co-related with the said valve-actuating cams and movable simultaneously therewith, switch means actuated bythe second series of cams includingsome for opening'the motor circuit to bring the rotary element to rest at predetermined positions in its cycle of movement, afirst independent switch under control of the operator for the purpose of starting the motor to drive the rotary element until the switch-operating cams of said rotary element are clear of the switch means controlled thereby, and a second independent switch comprising a time switch for keepingthe motor circuit open until a predetermined time interval elapses from the closing of the press through the first series of cams, said timing switch being set in operation automatically at a selected point in the cycle of operations so asvto cause a dwell in the cycle equivalent to-the said time interval substantially as described.

4. Control means according to claim 3, including a third independently operated switch and means for automatically operating this third switch on closure of the press to close the motor circuit and recommence movement of the rotary element for acontinuance of the cycle.

5. Control means for a hydraulic press for producing plastic mouldings comprising, in combination, a rotatable disc, an electric motor for intermittently driving the rotatable disc, a first series of relatively adjustable cams carried by the rotatable disc, means for locking said cams in desired positions, inlet and exhaust valves through which the pressure medium passes to and from the press, which are actuated mechanically in a, predetermined sequence by the first series of cams, a second series of cams carried by the rotatable disc which are co-related with the said valve-actuating cams and movable simultaneously therewith, switch means actuated by the second series of cams including some for opening the motor circuit to bring the rotary element to rest at;predetermined positions in its cycle of movement, and one or more switches operated independently of the cams for closing the motor circuit to re-start the rotary element in accordance with a cycle of press operations, and and a pressure switch in the hydraulic feed to the press which is responsive to the pressure of hydraulic medium passing to the press when the dies are first closed and which acts to close the motor circuit to commence a breathing operationonly after the desired pressure has been built up.

6. Control means for a hydraulic, press for producing plastic mouldings comprising, in combination, a rotatable disc, an electric motor for intermittently driving the rotatable disc, at first series of relatively fixed cams carried by the rotatable disc, means for presetting and fixing said cams in required relative positions on said rotatable disc, inlet and exhaust valves controlling flow of pressure medium to and from the press, actuating levers connected with said valves and actuated mechanically in a predetermined sequence by the first series of cams, a second series of cams carried by the rotatable disc which are corelated with the said valve-actuating cams and movable simultaneously therewith, means for adjustably fixing said second series of cams to the rotatable disc, the switch means actuated by the second series of cams including same for opening the motor circuit to bring the rotatable disc to rest at predetermined positions in its cycle of movement, and one or more switches ope erated independentlyof the cams for closing the motor circuit to restart the rotatable disc in accordance with a cycle of press operations.

RICHARD COLLIER.

REFERENQES CETED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,111,857 Jefiery Mar. 22, 1938 2,128,417 Kerr Aug. 30, 1938 2,375,252 Sayre May 8, 1945 2,454,362 Whitmore et al Nov, 23, 1948

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