US2271656A - Press - Google Patents

Description

Feb. 3, 1942. l s. E. McLAuGHLlN 2,271,656

PRESS Filed May ,27, 1940 3 sheets-sheet 2 Feb. A3, 1942. G. E. MCLAUGHLIN l PRE'vss Filed May 27, 1940 3 Sheets-Sheet 3 Patented Feb. 3, 1942 PRESS George E. McLaughlin, Brookline, Mass., assignor to The Turner Tanning Machinery Company, Portland; Maine, a corporation of Maine Application May 27, 1940,`Serial No. 337,501 l 54 Claims.

This inventoin is embodiedvin a press wherein mechanical means is employed to move one of the platens into co-operative relation to another platen,`the latter being hydraulically operated during pressure applying operations upon given pieces of work, and in which electrical controlling means is provided to secure operation of the mechanical means and of the hydraulic means in properly timed relation each other. In certain kinds of work, for example, where the work pieces are tanned hides or skins, one of the platens will be heated, preferably the upper platen, since application of heat to the surface of theleather is commonly advantageous both in plating and embossing operations upon leather.

It is an important feature ofthe invention that electrical controlling means is provided to operate the mechanical operating means for one of the platens and also the hydraulic means for the other platen in such manner that initiation of a pressure applying operation is followed by operations of the press in the full automatic cycle during .which the press operates repeatedly at regular short intervals to apply light pressure to the hide or skin, the latter being shifted between successive pressure applying operations tov This treatment of a When it is desired to employ a more substlantial pressure iny kiss-plating operations upon light leathers, provision is made for introducing a low range pressure governor. in both the hydraulic and electrical circuits of the press so'that pressure may be 'built u p to a point regulatable by adjustment of the pressuregovernor.' The electrical circuit also includes a repeating relay for control of the mechanical means operating one a manual control member may be so manipulated as to initiate repeated operations of the press in the full ,automatic cycle, thereby expeditlng treatment of the skins since the operator readily accommodates himself to the periodic opening and closing ofthe press to shift the lwork piece, thereby to secure treatment of all parts thereof and to remove and introduce successive pieces of work.

Preferably, and as shown, the press embodies a high range pressure governor as well as a low range pressure governor with means to select one or the other according to the type of work to be done. The arrangement of the electrical means, however, is such that cutting-in of the high range pressure governor results in making the repeating vrelay ineffective so that the press operates semi-automatically, that is, it opens automatically at the end of the cycle under control of the pressure governor but each cycle must be initiated by proper manipulation of the manual control member in the electrical circuit. 'It is to be understood, however, that by proper manipulation of a manual control member a pressing operation may be terminated at any time in the judgment of the operator without waiting for the termination of the operation under control of the pressure governor.

Conveniently, the electrical circuit may be made to include two time relays which may be cut in or out of the circuit by the use of selector switches. By the use of one of the time relays it is possible to secure a dwell for a predetermined period while the work piece is subjected to a heated platen at low pressure, the purpose being to heat the surface of the leather as a preliminary to either a plating or an embossing operation at higher pressures. The arrangement of the electrical means is such that cutting-in of the time delay rela-y for a dwell at low pressure automatically eliminatesthe repeating relay, with the result that the press can no longer operate in the full automatic cycle. Through the use of the proper selector switch, a time relay may be cut into the electrical circuit to secure the application of maximum pressure, as determined by a high range pressure'.

governor, for a dwell of regulatable lengthl suitable to secure the best results in embossing operations upon light or heavy leathers.

It is also an important feature of this press,

vfrom the standpoint of safety, vthat it may be y caused to open at any time through the operation kof the regular manual control or by the operaof the p latens, the arrangement being such that "tion of en emergency button. The arrangement is such that the press may be caused not only to reverse the movement of the platens at any time during the closing operation but also to open again instantly at any time after it has closed. In order that an operator working under piece work rates may not misuse his power to open the press, for example, by interrupting the building up of rpressure to the desired maximum, thereby to speed up the operations of the press, there is provided a gong which will sound if the press be opened .while it is still under control of the pressure governor. Where it is de,- sired, however, to leave to the judgment of the operator the amount of pressure and the length of time during which it is applied to the pieces of a given batch of work, the gong may be disconnected by a switch which is normally under lock and key. The press may then be operated by the usual manual control memberisuch as a foot treadle) to initiate and also to terminate each pressure applying operation.

It is to be understood that various important features of the invention are applicable to a pressv of the type wherein mechanical means 'operates one of the platens to close the gap. between it and a stationary platen, hydraulic means being also provided in connection with the same movable platen to effect a pressure applying operation. Other features of the invention are also applicable to a press wherein hydraulic means associated with one of the platens operates the latter both to closethe gap between the platens and to effect a pressure treatment of a work piece placed between the platens.

In the light of the foregoing brief description of the invention, it will be evident that this press is characterized by marked flexibility since it may be readily adjusted to operate in any one ofl a number of ways to secure various results on different classesvof work. In the full automatic cycle, wherein the press operates repeatedly following a single depression of a treadle or other controlling member, the operator is freed from constant foot operation of the controlling treadle and may give his attention to proper manipulation of' work pieces suitable for treatment by regularly recurring pressing operations of short duration, this arrangement being especially advantageous in that the capacity of the press 'and of the operator are greatly increased. Through control of a switch or of a valve in the hydraulic means, the operator may instantly change the press to one which operates semi-automatically, wherein a manual control member initiates each operation of the press which perform in a predetermined manner and comes to rest automatically. This manner of operating the press assures thev operator of greater safety and permits him to take whatever time is required to present the work pieces for each pressure operation. By-the operation of a switch, thepress may be made to dwell while the work piece is undergoing treatment by a heated platen at low pressure, while another switch may be used to insure a dwell while the work piece is undergoing treatment at maximum pressure. Furthermore, the time that it takes to build up pressure under control of either a low range pressure governor or a high' range pressure governor may be readily adjusted through proper manipulation of a control memlarly for .embossing and for the general run of smooth plating, while the full automatic cycleis especially suitable for kiss-plating of light skins after boarding.

These and other important features of the invention-and novel combinations of parte will now b e described in detail in the specification and then pointed out more particularly in the appended^claims.

In the drawings:A l

Fig. 1 is a view in side elevation ofa press showing one embodiment of the invention;

Fig. 2 is a front view, partly in section, of the press shown in Fig. 1; i A j Y Fig. 3 is a detail of a check valve:

Fig. 4 is a detail of a valve arrangement;

Fig. 5 is a detail of the pump;

Fig. 6 is a diagram showing `relative time operation of three limit switches;

Figs. 7 and 8 are sectional views of a three-way valve showing a movable valve member in two valve showing a movable valve member in different positions;

Fig. 11 shows in side elevation a rotary radial piston-pump provided to furnish a pressure medium for the pres's operations;

Fig. 12 is a more or less diagrammatic view of the pump, the press cylinders, and the hydraulic circuit;

Fig. 13 is a sectional view of a regulating valve shown in the line in Fig. l2;

' Fig. 14 is a sectionalview of a and clutch;

Fig. 15 is a sectional view of a valve for cutting a low range pressure governor into or out of the hydraulic circuit; and

Fig. 16 is a diagrammatic representation of electrical circuits for operating the press.

In th illustrated embodiment of the invention, which s designed particularly for smooth plating magnetic 'brake and embossing operations upon hidesv and skins,

there is provided an'upper platen 10 carried at the forward end of a heavy lever member 1| movable about a pivot at 12 to carry the platen 10 into and out of co-operative relation with respect to a lower platen 13. Preferably and as power, a clutch 'I6 and a brake 11 (Fig. 14) being provided under electrical control respectively to connect and disconnect the pulley with respect to a shaft 18. l

As shown, a pinion 18 fast von the shaft 18 is in mesh with a large gear secured to a shaft 82 which includes a crank to operate a link 83-'pivotally connectedto a toggle 84, 84a to operate the lever member 1i, it being understood that straightening of the toggle 84, 84a moves the upper platen 10 into co-operative relation with the lower platen 13, while breaking of the toggle 84, 84a effects separating movement of the two platens. Movement of the platen 10 by the described mechanical means has the effect ofopening and closing a gap between the platens, suitable for the introduction and removal of work pieces between pressure applying operations.

As shown, the lower platen 13 'is carried by two rams or pistons 85 (Figs. 1 and 2). It will be readily understood, however, that either a large or a small hydraulic -press may make use of only one hydraulic ram or piston for operating the lower platen'. Each piston is movable in a well fitting cylinder 86, the usual U-packing'such as that shown at 81 being provided to minimize the escape of the pressure medium under the this press. Preferably each piston 85 is supported yieldingly by a spring 88 (Fig. 2), it being one of the purposes of the spring to insure good coni-V tact of both upper and lower platens with a work piece placed on the lower platen, the arrangement being such as to accommodate the press to work pieces within a relatively wide range of thicknesses, sumcient, for instance, for all thicknesses of leather. Preferably, and as shown, the

lower platen yields downwardly to a slight extent, when the upper platen engages the work piece on the lower platen. When the press is open, the

served that, when the movable valve piston |30 hydraulic circuit `may be so adjusted -that the' I pressure medium may be under pressure just sufiicient to "oat the pistons or rams 8 5, one purpose being to speed up the pressure applying operation.

. The pressure medium (preferably a suitable oil) is supplied to the cylinders 88 by a constantly running pump shown in side elevation at .90 in Fig. 11. This pump is of the type known-Las a rotary radial piston pump and capable of iurnishing about four gallons per minute. Since the pump is commercially well known, full tietails thereof are not shown in the drawings. For

carrying a tight and a loose pulley 94, 88, respectively, adapted to be driven from any suitable source of power, a vcoupling being provided at 98 whereby the pump shaft |00 may-be driven from the shaft 92, the speed of the shaft being tion of these valves being shown in detail in Figs. 7 to 10, inclusive. Conveniently, the valve pistons of the valves and |28 are solenoid-operated,V as indicated at |21, |28, respectively, in Figs. 12

anu 16.

Upon reference to Figs. 'land 8. it will .be obin the valve |25 is in its lowered position (Fig. '1), the ilow of oil is from the pump discharge pipe |20 to the pipe |2| and thence to the cylinders 88, whereas when the valve piston' |30 is in its raised position (Fig. 8), the ow of the oil is from the pump discharge |20 intoa pipe |3| which opens into a return pipe |32 leading'back to the tank 80.'

Upon inspectionof Figs. 9 and 10, it will be observed thatthe construction of the valve 28 is substantially the same as that ofthe threeway valve |25, the three-way valve shown in Figs. 7 and 8 having been conveniently converted into a two-way valve. |28 simply by plugging one of the outlets by a screw plug |33. When the valve -driving the pump there is provided a shaft 82 of the type shown in United States Letters Patent No. 1,250,170 granted December 18, 1917, upon application of Hele-Shaw and Martineaux. After adjustment of the wheel |02 the latter may be locked in place by a lock member |04 (Fig. 5).

Located below the pump 00 there is shown a fifteen gallon tank |08 (Fig. 11) for the lubricating oil which conveniently serves as the pressure medium in this case, the quantity being large enough to insure that there is no overheating of the oil. At one end of the tank |08 there is a suction screen |08 covering the inner end of a pipe |50 (Figs. 11 and 12) which conducts the oil to the pump 90, a return discharge pipe being in dicated at ||2 (Fig. 12). Conveniently the tank E08 is provided with two baille plates |4 and with anoil level gage ||5. that the pump 90 is a constantly running pump with one direction of discharge. Furthermore, control through the wheel member |02 provides for adjustment of the stroke of the pump piston and hence determines the oil capacity of -the pump and therefore the time it willtake to build up pressure in the piston cylinders 88, there being also an indicator (not shown) which affords anindication to the operator of the stroke setting of the pistons. With this pump, the pressure in the medium under the press pistons 85 may be as high as 3000 pounds per square inch.

Upon reference to Fig. 12 of the drawings, it will be observed that oil from the pump 90 passes throughthe discharge pipe |20, |2| to both .ofv

It is to be understood piston |34 in valve |28 is ln'its lower position (Fig. 9), oil entering from the pipe |2| passes through the valve |28 and out through a pipe |35 to the pipe |32 which returns the oilto, the tank |08, in which case there is little or no pressure in the cylinders 88. On the contrary, when the valve piston |34 is in its raised position in the valve |28 (Fig. 10) oil entering the valve |26 from the pipe |2| is checked or blocked, with the result that pressure within the pipe |2| and hence in the cylinders 88 may be built upto the maximum pressure for which the press vis set.

1n order that oil may occupy the space below the piston 85 in each cylinder 88, when the press is open, there is provided a regulating valve |31 (Figs. 2, 4, 12 and 13) operative to oier resistance to the ow of oil from pipe |35 to pipe |32 sufficient to cause and maintain pressure in pipe |2| and pipes |23, during the continued operation o'f the pump 80, so that not only are vthe said spaces below the pistons 85 occupied by oil but the pressure may be so adjusted as just to iloat the pistons 85 in the cylinders 88.

When putting the press in commission, or 'when reiilling after having drained the oil from the press to make repairs, it is necessary to provide for escape of air from the hydraulic circuit, For this purpose an air relief cock |38 is conveniently provided on one of the cylinders 62 asindicated in Figs. 2 and l2.

A check valve |39 is provided between the three-way valve |25 and vthe pipe |23 leading to the first press cylinder 88, the check valve bethe cylinders 88 through branch pipes |23, a pres- I ing so constructed that oil may readily pass toward the cylinders but not in the reverse direction, thus insuring, as far as possible, maintenance of the pressure being built up within the pipe |2|. While very high pressure is being maintained in the pipe |2| and in the valves |25 and |25, there is bound to be some leakage with a corresponding drop in the pressure.` Such drop in pressure is overcome by pump action operating through the valve |25, the check valve |39 having served toA maintain the pressure in the f pipe |2| even though oil was being by-passed through the pipes |3| and |32 back to. the tank |08. Hence when the dropped pressure is to be restored, the pump has only to bring the pressure up the requiredl amount in the short portion of the pipe |20 between the pump and the check valve |39 in order to build it up to (and beyond) the pressure maintained in the pipe |2| by said |25 and also a two-way valve |28, the construccheck valve |39. By vthis arrangement, there is no drop in the pressure in the pipe I2 I. and press cylinders 86 except that' caused by some slight leakage, whereas if there were no check valve |39, there might be quite a drop in pressurein the cylinders 86 at the time of thestarting of the pressure buildup to replace leakage'loss.

There is shown at |40 (Figs. 2 and 12) a relief valve having a chain connection (Fig. 2) to the lower platen 13. When the press is open, `the chain1is. slack, so that the lower platen would have to 'rise a predetermined distance beyond the normal before the relief valve would become operative. This prevents lifting of the lower platen to an extent such that damage might result to the press through premature contact of the lower platen with the descending -upper platen, which is mechanically operated .to a pree determined low position. In case the relief valve |40 is operated, liquid is discharged through pipe |4| to an outside container (not shown). For further details of this valve mechanism reference should be had to Patent No. 1,115,013., granted upon application of F. Perkins.

In the operation of the press in embossing hides or skins, there is, during the rst stage, a relatively small pressure on the piece of leather being treated, this being due to the fact that, at the time the upper platen descends into contact with the workpiece, there is a certain denite pressure in the pressure medium to float the pistons in their cylinders. At this'stage, the piston valve |30 of valve |25 is in lower position (Fig. '7), whereby the pressure medium' is passing through valve 25 by way of pipes |20, |2|, and through valve |26 and by way of pipe |35 to the pipe |32 to return to tank |06. As stated above, pressure in the hydraulic circuit at this stage is due to the regulating valve |31, which is a well-known commercial unit commonlydesignated a back-pressure valve. This will be clear upon inspection of Fig. 13, wherein the valve |31 is shown to comprise a valve piston |31 having a head |31b which may be seated in a countersunk opening at |4| to close the valve against movement of oil from pipe |35 to pipe |32. However, by means of a small pipe |43, the pressure medium enters the bottom of the regulating valve |31 and, because of the large area of a flexible wall or diaphragm |45, thepressure (which is the same as in the pipe |35) lifts the valvehead I31b, against the pressure of a regulatable'spring |41, from the seat |4| and thus permits restricted flow of the pressure medium from pipe |35 to pipe |32', whereby a back pressure is produced in the cylinders 86, just suiiicient to lift the pistons 85 with the aid of the springs 88 and to maintain the latter in floating condition. The weight of the lower platen and pistons is suiiicient to compress the springs 88 (1i'ig.`2).l On the other hand, the back pressure in the hydraulic medium, due to the valve I 31, counterbalances a definite (but regulatable) part of such weight so thatthe springs 88 are enabled to lift these parts to a deflnite position, for instance, to a position such that the lower platen is contacted and forced downwardly by the upper platen as the latter reaches its lowest position. This resuits in jumping the pressure on the work piece at the very beginning of a pressure applysubstituted therefor;

lowering of the upper platen 10 into contact with the leather on the lower platen 13, fthe upper platen moving to a predetermined position and thus forcing downwardly the lower platen against oil in the cylinders86. It is to -be understood, however, that back pressure in'the pipe |35 (and hence in the piston cylinders 86) may be eliminated by adjusting a manually operable stop |49 upwardly to a. position Where it lifts the diaphragm |45 and the piston |31 upwardly to a position'where the head |31b is lifted to oer-no obstruction to the flow of oil from pipe |35 to pipe |32. In that case, there will be no back pressure in the pipe |35 and in the cylinders 86.

In the second stage, pressure is being built up in the hydraulic circuit, including the piston cylinders 86. During this stage the piston |30 in valve |25 is in lowered position (Fig, '1) so that oil passes from the pipe |20 through the check valve |39 (Figs. 3 and 12) to the pipe |2|, while at the same time the valve piston |34 in the valve |26 is in raised position (Fig. 10) thereby blocking the flow of oil to pine |35. Hence, pressure is built up in the pipes |2| and |23 and the cylinders 86 to a point predetermined beforehand (for example, by the use of a pressure governor), although it is also under the control of the operator, as will hereinafter be pointed out. In this stage, during which pressure is built up, the length of time involved in arriving at maximum pressure maybe predetermined (as indicated above) `by manual adjustment of the member |02 (Figs. 5 and 11) which controls |25 is moved to and maintained in its raised position (Fig. 8) so that the oil is by-passed through the pipes |3| and |32 back to the tank |06, while pressure is held in the pipes |2| and |23 by the check valve |39 and by the valve |26 in which the piston' |34 is in its raised position (Fig. 10) thus blocking the escape of oil to the pipe |35. After a period of time which may be predetermined (although it may be terminated at the will of the operator), the valve piston |3| 'in valve |26 moves to its lowered position (Fig. 9) thereby connecting pipe |2| with pipe |35 whereby the pressure instantly drops substantially to zero and the oil may return through the pipe |32 to the tank |06. This movement of valve piston |26 terminates stage 3 and initiates stage 4. j

It will be noted that, in this stage 4, both valves |25, 26 have their valve pistons so pol sitioned that oil may iiow freely through them and through pipes |2| and |35 to the return pipe |32 back to the tank- |06. which comes at the end of the pressure applying operation corresponds also to stage 1, except that the pressure inthe press cylinders is approximately at zero. Another difference is that, in stage 4 after the release of pressure in the hydraulic circuit, the upper platen' 10 is moved upwardly so that the treatedpiece of work may be readily removed and another piece On the otherhand, stage 1 begins with the lowering of the platen 18 to engage a piece of work on the lower platen 13,

afterwhich pressure is built up back of the lower platen to treat the work piece to a pressure operation.

This stage 4 result that the shaft 18 is frictionally locked There are `provided in the hydraulic circuit, through suitable connections to a pipe |16, which is a branch from the pipe |2I, two pressure governors P and Q. Conveniently. governor P may have a working range between 63 and `470 tons pressure at the platens of the press or from about 410 lbs. to about 3000 lbs. per square inch. Governor Q has a minimum cut-in of about 110 lbs. per square inch and a maximum of about 400 lbs. per square inch. the range being from about 17 tons to about 611/2 tons at the platens. The figures given above may be reconciled when it is understood that the pistons in the illustrated press are 14 inches in diameter and the platens are 26 by 54 inches. Since governor Q operates to terminate pressing operations at a lowerrange than governor P, both governors may be con- .nected to the pipe |18, and hence to pipe |2|,

With reference to Fig. 14 it will be observed that the clutch 16 comprises annular clutch plates 200 keyed to the hub of thev driving pulley rotatably mounted on the shaft 18. Keyed to the shaft 18 is a sleeve member 202 having integral therewith an annular flange 204. Surrounding the sleeve member 202 inside the ange 204 is an annular armature member 206 having a screw threaded periphery `for engagement with a screw threaded surface at 208 on an enclosing annular cup member 2|0, the latter being constructed and arranged to enclose the flange 204 to which it is splined and to enclose the clutch plates or rings 200 and also other annular clutch plates 2|2 which are keyed to the inside of the cup member 2|0. These clutch -plates 2|2 are shown as made of ber, although they may be of metal with fiber faces, which present frictional surfaces for engagement with the clutch plates 200. Upon energizing the clutch coils one of which is indicated at 2|4 (in magnet bodyl 2|5 keyed to the sleeve 202) the armature member 206' is pulled to the left in Fig. 14 with the result that the clutch plates 200, 2|2 are firmly engaged with each other to clutch thepulley 15to the shaft through the' sleeve 202. Upon deenergizing thecoils, the clutch is released by reason of the movement of the armature 206 and parts attached thereto to the right in Fig. 14 through expansion of a number of light springs one of which is'shown at 2|6.

The brake 11 comprises a member 220 which is attached to the machine frame, the member 220 having keyed thereto a plurality of annular friction plates 222, these friction plates being shown as made of fiber throughout, although they may be of metal having ber faces. In between the members 222, are lannular plates 224 which are .keyed to a sleeve 226 in turn keyed to the sleeve the springs 230, an annular armature member 232 is pressed toward the leftfin Fig. 14 thereby I `compressing all" of. the platesl 2212. 224 with the against movement by the brake members in the brake device 11. Upon energizing the brake coils one of which is shown at 234 with a coil shield 235 between it and the armature 232, the latter is drawn to the right in Fig. 14, thus releasing the pressure on the brake plates 222, 224, whereby the brake is disengaged from the shaft. At 238 are shown collector rings of the electrical mechanism, the rings being insulated from the magnet body 2|5 which carries the clutch and brake coils. Incidentally, brake and clutch adjustment may 'be secured through proper setting of the threaded members 228 and 206, respectively.

It will be clear that, upon energizing the brake coils the brake is disengaged with respect to the shaft 1 8 while, upon energizing the clutch coils,

the clutch is caused to engage to hold the pulley 15 in. driving engagement with respect to the shaft 18. This isthe normal operation of the clutch and brake since, in most press operations, the clutch will be engaged and the brake disengaged while a platen is being moved mechanically toward the other platen. On the contrary, the clutch is disengaged and the brake engaged when the platen is in its open position or when it is in pressing relation with respect to the other platen during building up of pressure in a pressing operation. Sometimes, however, both clutch and brake are disengaged thereby permitting the upper platen in the illustrated machine to swing -to open position without any driving action on tions of the clutch and brake devices will be described more in detail later in this specification.

Control of the press is exercised through a` number of manually operable members having electrical connections to the` power means for causing relative movement between the upper and lower platens of the press, means being also provided for exercising automatic control of valves in the hydraulic circuit whereby the lengths of time that the leather -is subjected to heating at substantially zero pressure and subsequently at maximum pressure may be predetermined. The control referred to is exercised through electrical circuits including various relay switches, time relays, clutch and brake contactors, solenoid contactors, and pressure governors, all obtainable in the open market as well-known electrical units. These latter are shown in Fig. 16 enclosed in rectangular spaces deflned by dash lines. Upon energized by completing circuits to the otherv side of the supply line.

In order to prepare the press for operation, a

. main switch |40 (Fig. 16) is closed. At this time a limit switch X is operative by reason of the. fact that a cam |56 4on the shaft 82 of the press was left in a positionl to close contacts XI and X2 in limit switch X, at the end of the preceding cycle of operations. Closing of the main switch |40, therefore, results in energizing the coil of a non-repeat relay A whereby contacts A2, A3 and A4 in relay A are closed and contact Al opened. 'I'he current energizing relay A may be traced lthrough thecoil in relay A, through normally closed contact W3 in a foot switch W, adapted to be operated by treadle |51 TFig. 1), thence through contact X2 and normally closed contact V| in an emergency button V. It will be'noted that the closing of contact A4 establishes an electric interlock (through A4 and normally closed contact H3 ina relay'I-I to be described later) i. e.. a shunt circuit around contact W3 in the foot switch W. Hence, depressing the treadle |51 and opening contact W3 does not break` the Acurrent energizing the relay A.

In order to initiate the closing of the press, the foot switch W (Fig. 16) is closed by means of the treadle |51 whereby contacts W2 and W4 in switch W close while WI and W3 open. Closing of contact W4 establishes a current through the coil of master relay D (thence through W4, A3, XI and VI) and thus energizes master. relay D whose contacts D| and D2 close simultaneously. The closing of contact D2 in turn energiZes the coil in a brake contactor B, whose contacts BI, B2 and B3 are thus closed, while through the closed contacts DI and Bl the coil in a clutch contacter C is energized, closing contacts CI and C2. Thus, the coils of clutch and brake are simultaneously energized whereby the brake is disengaged and the clutch engaged, the crank shaft 82 of the press begins to rotate and the press arms begin to close. Inasmuch as the current energizing the clutch contactor C is dependent on the closing of switch Bi it can be Vseen that the clutch cannot be energized, i. e.,

,through the clutch and brake magnets.

Shortly after the upper platen of the press has begun its downward motion, a contact Z2 in a second limit switch Z opens while contact ZI- closes. This is due to the rotation of a cam |64 mounted on shaft 82. A timing diagram (Fig. 6) shows the open positions in dotted circles and closed positions in heavy lines of the contacts of the various cam-operated limitl switches. The vertical center line in Fig. 6 represents the crank shaft dead center positions for the fully open and fully closed press platen. During almost the full downward motion of the press platen (as seen in Fig. 6) contact ZI remains closed and is eiective to hold the brake contacter B energized, i. e., theY brake disconnected independently of masterrelay- D. It is to be understood that the operator is required to hold the foot switch. |51 depressed until the closing of the press has been completed. Should the foot switch be prematurely` released, the current through W4 energizing the master relay D would be interrupted and the clutch disengaged. However, the brake coil would be held energized, with the brake disen- .gaged through theaction of contact ZI, and the crank shaft would be free to rotate. The rocker arms 1| of the press are unbalanced, that is, so weighted as to return the upper platen of the press to'open position, if there is no driving or breaking power on the crank shaft. Thus the operator is able, in an emergency, not only to stop the closing of the press immediately but also to obtain opening of the press by the simple expedient of removing his foot from the treadle |51.

- limit switch Y are closed by the action of a cam |53 also mounted on shaft 82.l The closing of -contact Y2 is immediately effective to energize thecoil in a timing relay N and to start a synis returned to normal with contact ZI open and Z2 closed. At exactly dead center, contact XI and X2 in limit switch X open whereby relays A and D are deenergized, theA opening of contacts DI and D2, of course, drops out relays C and B,

. through E3, F5, M4 and Y2.

chronous motor N5 therein running. A tap 'on 75 deenergi'zing clutch and brake coils. The clutch is released, the brake becomes effective through spring pressure, and the press stops in closed position. The foot treadle |51 may now be released, returning all contacts in foot switch W to normal, as shown in Fig. 16.

Contact A| having returned to closed position upon deenergizing the'coil in relay A, contact WI, which closes when the foot switch is released, .becomes effective to energize the `coil in a repeating relay H which causes contacts HI, H2, H4l and H5 to close and contact H3 to open. With the closing of contact HI an interlock or shunt circuit around Al and W| is established holding the coil in relay H energized, regardless of a possible redepression of foot treadle |51, that is, opening of contact WI. Current may be traced through coil in H thence either through A| and WI in sequence or through HI, thence The purpose of establishing this current through repeating relay H will be described later.

The time relay N, of course, has remained energized and after the timing' motor N5 has counted of! the time period for which the relay had been set contact Nl' opens, stopping motor N5 and contact N3 closes, energizing solenoid contactor K by current through the coil of contacter K, and thence' through N3, GI, E3, F5, M4 and Y2. This causes the contacts KI and K2 in the 'contactorK to close, energizing the solenoid |23 which in turn raises piston |34 in the valve |25 thus closing the latter and causing the building up of pressure in the system, as heretofore explained.

In addition to being ame to adjust the amountv of time required for operation of time relay N, it is possible to eliminate the time dwell altogether by manual closing of the contacts RI and R2 in a selector switch R. Fig. 16 shows clearly that contact RI of the selector switch-R provides a shunt circuit around the delayed contact N3 of the time relay N, thus allowing the coil in contactor K and the solenoid |23 to become energized immediately uponcl'osing of the contacts in the limit switch Y. Thus, valve |26 closes before the press platen4 reaches the full extent of its downward motion, .thus permitting the Jumping of pressure, as previously explained'in connection lwith the lregulating valve |31. As heretofore stated, the closing of valve |26 (either previous to the completed closing of the press or after a period of dwell) causes the pressure to rise in the press cylinders 86 and the rate of building up such pressure is deternined by the manual stroke adjustment ofthe pumpli (assuming a constant speed of the pump) and not by any element of the electrical circuit. When the hydraulic pressure-being built u P3 will make contact with a' high contact Hi (as to maintain the valve |25 inthe by-passing position oi Fig. 8. s

Should pressure in the press cylinders 36 fall very substantially, due to the said leakage, the

Lo contact (shown in full lines) within the presaround the coil of the pressure governor. De-Iv shown in dotted lines), which is adjustable to determine the pressure (withinethe range oi! ,pressures givenl above) at which the pressure governor cuts in to allow current to flow through the relay coil of the pressure governo sure governor P will be established, in which case the coil of the pressure governor is deenergized,

since the circuit established by the new position of the contact member P3 is a shortcircuit energizing of the coil in the pressure governor P `opens all oi the contacts therein and alsoin the control relay F and in the solenoid contacter L. y

vthe result being that the solenoid operated valve l5 piston |30 drops to its `lower or rest position) (Fig.

This current may be traced through the resist-V ance member P4 and through the coil of pressure governor P, thence through contact member P3, contacting point Hi and contact YI in limit switch Y. Upon energizing the coil in P, contaets Pl' and P2 cibse, Pl forming an interlock.

through establishing a shunt circuit aroundl member P3, thereby to hold the pressure governor energized whether or not the contact member P3 maintains contact at Hi. Closing of contact P2 results in energizing the coil in a control relay F, thus closing contacts FI, F2, F3 and F4 and at the'same time opening'contact F5. At this .time only two of the contacts will be described, viz., Fi. and F4. Closingof contact F4 energizes the coil in a second solenoid contactor L. (current through coil of contacter L, GI, E3, M4, Y2), whereby contacts L| and L2 in the contactor L are closed, energizing the solenoid-coil 7) and once more operates to direct the pressure medium into the pipes |2| and |23 to build up the pressure therin and in the cylinders 53. 'I'his cycle of pressure loss and rebuilding may or may not take place one or more times. The

Lo contact is manually adjustable as is the Hi contact, and the two may be brought close enough together to provide a differential oi about 70 pounds per square inch on the pistons, thereby providing fora drop of about ten tons in the pressure on the work piece before pressure be- A gins tobuild up again. Whenvthe maximum pressure has been reestablished, the pivoted switch member P3 reaches Hi position in Athe ,30 pressure governor P which again operates determine the period during which maximum |21. Energizing of this coil results in lifting the ing up and maintaining the maximum pressure.

This time relay M is energized and its timing motor started running through the contact FI in control relay F. As in the mst-mentioned time relay N, here again a tap is provided on the coil oi' relay M to provide, through a normally closed contact MI, current for timing motor M5; from there and from the coil in relay M the circuit continues through contact FI in control relayF and YI in limit switch Y. Immediately upon en-` 65 -pressure shall be applied to the leather.

When the timing motor M5 in the time relay 40 M3 closes and M4 opens. The opening of contact M4 causes solenoid contactors K and L to be deenergized, thereby allowing'the valve pistons in both valves |25 and |26 to drop, thus instantly releasing the built-up pressure in the cyla inders 86 and reestablishing the normal iiowof thepressure medium through pipes |20, |2| and back through pipes |35 and |32 (Fig. 12). Closing ofv contact M3 establishes-a circuit through the coil of `master relay D through said contact 5 Ma and through contact Y2 1n limit switch Y,

ergizing the 'coil in time relay M, an interlock 'contact M2 closes providing a shunt circuit around Fl' and thus `holding relay M energized until the current supplied to it is broken by the opening of Y| in the limit switch Y. The delayed In case there should be leakage of pressure medium past valve piston |34 in -valve |28 (Fig. 12) during the time dwell of time relay M, while Y the maximum pressure is being -held in the press contacts Mi, M3 and M4 will operate after the timing motor M5 has completed its preset cycle.

at PI in the pressure governor is still effective to energize the coil therein. whereby the pressure governor through its contact P2 remains eil'ective thus energizing the master relay D and, in the manner previously described, making the brake inoperative and the clutch operative whereby rotation of the crank shaft to open the press arms is effected. The opening of contact M4 at the same timecauses the previously mentioned repeating relay H to become deenergized when the press begins to open. Near the end of the movement of the upper platen to its uppermost posicomeenergized because W3 will then be in open position, and the press cannot be started again until after W3 has been closed again through releasing the foot switch to establish the described l current through relay coil A.

At the end of the upward movement' of the tion, the cam |56 again closes limit switch X.,

upperplaten the camy |63 opens the limitswitch Y, thus deenergizing the coil in master relay D,

'l5 .hence dropping out clutch and'brake contactors C and B with the result that the brake is on, the clutchofi', the presses stopped in open position and ready for another cycle.

The time dwell at maximum pressure, controlled by timing motor in relay M is adjustable within the range of the instrument. It is to be understood that both time relays N and M can be commercially procured having a rangeV of from 4 to 40 seconds in two-second intervals. be understood also that instruments of a different range may be substituted therefor, for instance, one commercial timer being operated by a vacuum tube rather than by a synchronous timing motor and having a range of from .6 to 12 seconds, in a stepless adjustment.

I have provided means to eliminate :either or both time dwells at the choice of the operator, the time dwell at substantially zero pressure being eliminated, as previously described, through closing of .selector switch R. Another selector switch T has been provided having two contacts TI and T2 which are open when the time dwell is desired and a third contact T3 which is closed in this case. If these three contacts are reversedr they will make effective the three contacts F2, F3.

and F5, respectively, in control relay F. In this case the operation of the press will be .as described heretofore up to the point where the maximum pressure has been reached and the contact member P3v and pressure governor P makes contact at the Hi point energizing relay P, whereupon contact P2 serves to energize the coil in relay F. The contact TI in the selector switch T being closed, it forms together with contact F2 in the control relay F an interlock for the latter through ,the establishment of a shunt circuit around contact P2 thus making control relay Fr independent of the pressure governor and holding it energized until the press has opened at which point opening of contact Yi disconnects coil of relay F. The relay F which, in this case is used to control the opening of the press and also to relieve lthe pressure in the hydraulic system, thus replaces contacts M3 and M4 in the maximum pressure time relay M which performed these functions as previously described when a time dwell was warranted. To effect the opening of the press, the master relay D is energized by a current flowing through the coil of this relay,

through contact T2 in the selector switch T and.-

at .maximum pressure.

In kiss-plating operations, the press is organiz'ed to apply a heated platen for a short time and under low pressure to the grain surface of relatively low grade skins and to boarded skins of various grades. In such operations, the skins are treated to a heated platen .during the time that it takes to build up the pressure to 25 or 30 tons, for. instance, (the`range being up-to about 60 tons) whereas embossing operations normally involve pressures at about 400 tons and even higher, i. e., at about 2500 lbs. or more per square inch, while s'rnooth plating might bedone at pres- Itis tof For kiss-plating, therefore, it is desirable to'operate the press rapidly and this may be conveniently accomplished by arranging the power` control mechanism in such manner that the press continues to operate cycle after cycle once the operation has been initiated. Besides a pressure governor P, operative in a range of about 63 to 470 tons, there is provided a low pressure gov'- errior Q operative at pressures in a range of about 17 to 62 tons. As indicated in Fig. 12, a threeway valve |88 is provided to connect or disconnect pressure governor Q with respect to the main line |2| of the hydraulic circuit.

vus

It will be noted that for-operating the press in the kiss-plating treatment of skins, the selector switch R is set so as to eliminate the time dwell at' substantially zero pressure. However,

the selector switch .T- may remain set at either of its' two positions since the time delay at maximum pressure is automatically eliminated by the use of the low pressure governor Q, it being obvious that, with both pressure governors connected to the pipe |2l, pressure in the said pipe |2| will never rise above the maximum of the low pressure governor Q.

The operation of the press organized for kissplating operations begins in the same manner as explained above for the usual smooth plating operation. Upon depressing the -treaclle |51 by which switch W4 in foot switch W is closed, the upper platen begins to close, and Shortly before it has reached fully closedV` position the limit switch Y will close, energizing the solenoid contactor K with the result that the valve |26 (Fig.

l2) closes and pressure begins t0 build up in the pipe |2| and in the piston cylinders 86. This pressure will act on both pressure governors P and Q. However, since pressure governor Q has a lower operating range than the pressure govemor P, a pivoted contact member Q3 (Fig. 16) in the pressure governor Q will reach its Hi contact before the corresponding contact Amember in pressure governor P becomes effective. When contact member Q3 reaches Hi position, the coil in the pressure governor-Q will become energized vwith the result that both contacts QI and Q2 are moved to closed position.

causing the coil therein to remain energized even after the pivoted contact member Q3 leaves the Hi contact. 'I'he other switch Q2 allows the coil in a second control relay G tobecome ener.- gized. 'I'he control relay G has, for the kissplating cycle, the same function as the control relay F in the press organized to provide instantaneous opening of the press at maximum pressure, as before described. An electric interlock for holding control relay G energized during the opening stroke of the press has been provided by removing from the pressure governor Q the connecting wire between the upper end of the coil and the Lo contact. This connecting wire is normally furnished in commercial instrument, as shown in pressure governor P. In the absence of such connecting wire in the pressure governor Q there is no short circuiting around its coil when the pressure drops low enough in the pressure governor to allow contact device Q3 to make consures ranging from about to perhaps 300 tons. 75

tact at Lo. Hence, the coil in Q remains enernormally op'en contact G2 which, upon closing, establishes'current through the coi1 of master relay D, through contact .G2 and limit switch contact Y2 to energize the clutch and brake coils and thereby effect the opening of the press. At the same time normally closed contacts Gl and G3 open. The function of the latter will be described later. The function of the opening or GI is to deenergize the solenoid contactor K whereby valve |28 is opened and the built-up pressure in the hydraulic system immediately released through pipes |35 and |32 (FigflZ).

It will be noted that this same function was performed in the smooth plating or embossing operation of the press by either contact F5 in the control relay F or contact M4 and time relay M. However, either oi the last-named contacts performed the additional function of interrupting the current through the coil of repeating relay H. While in the kiss-plating operation, GI serves to relieve the hydraulic pressure, it is so positioned that it will not interrupt the current which holds repeating relay H energized, and which, irrespective of the operation oi Gl, may

lstill be traced through coil of relay H, contacts HI, E3, F5, M4, and limit switch contact Y2. Re-

peating relay H has been energized, as previously described, through the release ofthe foot treadle |51 by which contact WI of the foot switch was closed. If the foot switch now remains released relay H will remain energized until the press has fully opened. Shortly before the opening of the press is completed, limit switch contacts XI and Y2 close again and X2 energizes the coil of relay A through the closed foot switch contact W3, ,A through limit switch contact X2 and contact V| in the emergency switch V. ContactXl of the limit switch at the same time serves to hold the repeating relay H energized by current which ows through the coil of relay H, relay contacts `H4 and- A2 (the latter closed when relay A was energized) selector switch contact R2 and during the press will open and stop in its openingposition. After this a new cycle of continuous operations may be initiated by holding the treadle depressed for one closing stroke of the press as described above, and then releasing it.

In kiss-plating operations the depression of the foot treadle to terminate the operation would probably. take place during the opening stroke. It will be remembered that repeatingrelay H remained energized while the press was opening and also during the closing stroke and hence that. al contact H2 in said relay Hremains closed. If, during the opening stroke, the foot treadle is depressed, closing the contact W2 in the foot switch W, a current will beffestablished energizing the coil ofan emergency relay E and l flowing successively through W2, H2, F5, M4

- and Y2.

through contacts XI and Vl. Thus it can be seen y that the repeating relay H will remain energized not only during the opening stroke of the press but also during the immediately following closing stroke, that is, until limit switch X opens again.

The closing of the press-follows immediately upon its opening without even `releasing the clutch or energizing the brake because a contact H5 in repeating relay H has become closed and serves to hold the master relay D energized even after limit switch Y2 has opened upon reaching Fig-.16 that contact H5 is arranged in parallel with contact W4 of the foot switch which latter serves to operate the master relay D in the smooth plating or embossing operation. In these previously described operations, however, repeating relay H had been dropped out previously through the opening of either contact F5 or M4,

while in the kiss-plating operation relay H has remained energized 'during the opening stroke of the pressand remains so again during the closing stroke.

- limit switch Z, thus allowing the press arms to l From this point on, the press'will continue cycle `after cycle, closing, building up the pressure to. the high point Hi on the pressure governor Q, opening and immediately closing again, and so on, until the operator stops it by a second depression' of the foot treadle. This redepres-v sion of the foot treadle |51 may take place at any time, that is, during the down stroke of the press, during the building up of pressure, or

The relay E, in addition to an emergency function t be described later, serves to stop the continuous operation of the press by the opening of its contact E3 vwhich interrupts the current owing through the coil of repeating relay` H. It should be mentioned that an interlock is provided for relay E by means of a current owing through the coil of relay E, a contact E2 therein, and through limit switch contact YI. Thus even if the footswitch is only` momentarily depressed the relay Ewill remain energized until the press has opened completely and the l now open contactA E3 will prevent the repeating relay H from becoming energizedagain. Upon closing of limit'switch X `near the high position of the upper press platen, the current through relay H does not become reestablished since the contact H4 in said relay H has opened with the deenergizing of relay H and will not close unless relay H is energized by means of contacts AI and WI. This means then th'at the press will stop in its fully open position since contact H4 (used to energize master relayvD) remains open anda new cycle of operations would have to be started again in the manner described above.

Should the depression of the foot switch, in-

I tended to stop the continuous operation of the press, occur after the press h as opened and immediatelystarted on its down stroke, then the relay E -will not become effective but even then the press/operation will be interrupted immediately. This is due to thev opening of switch contact W3 when the foot, treadle is depressed.

At this time the function of contact, H3 in thel leased while, as has been shown previously, the e brake coil is held energized (thatis, with the brake on) by the action of contact ZI in the swing back to their openl position by means of gravity. In consequence of .deenergizing relay A, contact A2 has also opened, interruptingthe current through repeating relay H so that the press will not start again after it has been returned to open position, as described, or after the the opening of the press, and in each case of the press, the foot switch is depressed while the press is closed andthe pressure being built,

up, the coil of relay E is energized, as described above. In this case,l in 'addition to contact El opening, whereby the repeating relay H is dropped out, the relay A effects immediate opening of the press, but this is an emergency Operation and will be considered later.

If the manually operable selector switch R.V

should be set to the open position, as shown'in Fig. 15, thereby providing the time dwell at subncras the usual cycle of the press organized for smooth plating or embossing wherein the foot switch phas to be released and then again depressed in order to secure successive operations l .of the press.

It -is believed that for certain types of leather or small size skins kiss-plating may be accomplished satisfactorily with pressures no higher than, perhaps, about v15 tons which may be securedrfor instance, by the so-called jumping of pressure, that is, by the depression of the floating vpress pistons li due to the action of the downwardly moving upper platen. If this is so. then noA building up of ,pressure beyond that reachedby jumping" is necessary and for this type of leather the crank shaft may be kept ro- `tating continuously, the clutch never becoming deenergized, that is, released, either in the open or closed position of the press. As has been pointed out previously,v the amount of jump" pressure reached may be manually adjusted by regulating the pressure of spring |41 (Fig. 1l) in back pressure'valve |31-(Flgs. 11 and 12). 'I his methodof operation may be secured by the manual clomng of a selector switch S. As will be seen from Fig. 16, this'switch S is so arranged as to allow control relay. G to become energized .Y the first time, that. is, the pressure rises to the upon/the closing of a contact Z2 in limit switch z which, by reference to mfc, sin be round to occur practically at fully closed position of the prs but having a very slight overlap with the blosedposition of limit switch X This enables the control relay Gato become energized just before the clutch would be released and the brake applied in the press closed position and without waiting for pressure to bebuilt up in the pressure governor Q; Control relay G, of course,

energizes master relay D as in the previously described kiss-plating cycle, (where the pressure was built up in the pressure governor Q) [with the. result thatbrake and clutch coils remain energized, that is, the clutch is never released nor the brake applied, and the crank shaft continues right through its dead center position to effect the immediate opening of the press. Reference to Fig; 6 shows'that Y2 closed enough ahead or the crank shaft reaching itstottom.

dead center to allowthe valve\piston l in valve 26toclose atapointwhere the pressarms would still have a small amount of travel be; fore reaching their lowest position so that, due

to the action of the press arms on the floating rams, a dennite pressure (jump." pressure) will be produced' before valve, |26 again opens under the influence of opening contact GI of thev control relay; this latter, of course, takes place at 7 6 means 'are applied to crank shaft, un-

the point where contact Z2 closes. At the same moment G2 also closes and since this occursjust before Xl opens, the coil of master relay D is never allowed to become deenergized, thus holding the clutch on and the brake oif' continuously. In all other respects this kiss-plating opez-, ation with jump pressure functions exactly like the before-described kiss-plating operation with built-up pressure, the repeating relay H being energized and remaining energized through the opening and closing strokes of the press as closing the preadjusted pressure buildup with or without time dwells takes place and then the press opens and stops in position. To initiate a second cycle the treadle must first be released and then depressed again.

A second mode of operation may be chosen by reverse setting of yvalve |88 to cut in pressure governor Q, in which case the pressure range will be from zero to 62 tons, whereof a' range o f from about Q to about 15 tons may be obtained by the previously described jump" pressure while the remainder of the range from about 16 to 62 tons is determined by the setting of pressure governor Q. In the last-mentioned pressure ranges, it is impossible to obtain a time dwell at maximum pressure. The operation of the press in this case is what is commonly termed full automatic after the press has been closed for predetermined point, the press opens and-immediately begins closing again without interruption,.the operator being allowed just enough time to shift'askin to a new pressing Position between the platens or to remove it preparatory to introducing a new skin. Of course. the operator has control over this immediate reclosing of the press since to stop the press all that is required is a depression of foot treadle |61 at any time during the full automatic cycle. It is believed that in the lower pressure rangesa I time dwell at substantially zero pressure is not required. However, provision has been made for obtaining it by means of selector switch R. The choice of this time dwell atl substantially zero pressure automatically precludes full automatic operation of the press and changes the cycle to a semi-automatic one the same as is obtained when `working in the high pressure range above 63 tons.

.certain safety features for the Aprotection ofv the operatonas well as for the protection of the press itself or the leather to be treated, are in corporated inthe illustrated embodiment of the invention. f For the protection of the operator, means 'is provided for interrupting the lclosing stroke of the press platen at any time, at the same vtime-returning the upper movable .Platen to its fully open position. It is to be understood that, in theillustrated press construction, the

arrangementis such that, if no or brak- .may be operiited at balance of the prese arms will swing them into fully open vposition from a closed position -or from one approaching closed position. This constructinal feature is made use of in the electrical safety controls herein provided. At any point during the semi-automatic closing stroke of the press arms, i. e. when working in the high pressure range, or during the initial closing in the pressure range up to 62 tons, the operator has twoindividual means for interrupting this closing stroke. He may release the foot switch by withdrawing his foot from the treadle |51 ,and thus :interrupt the current through the master relay D because of the opening of contact W4 in footswitch W. Alternatively, he may depress the emergency button V which interrupts the same current by opening contact VI in said button V. Opening of the master relay D, of course, deenergized the clutch while the brake is held energized (disengaged) by means of con-4 tact ZI in limit switch Z, as previously described, allowing the press arms to be returned to their open position by gravity. As said just above, this emergency opening is accomplished by depression of the emergency button as well as by release of the foot switch. In either case, the press will remain in'its open position until theA foot switch has been yreleased and then redepressed to initiate a repetition of the normal cycle.

In connection with thepperation of the press within the low pressure range up to 62 tons and performing the full automatic continuous cycle, it has been explained that depressing the foot treadle while the press is running continuously will terminate the'operation of the press and if this occurs during the down stroke of the upper platen, the current through master relay D will be interrupted through the opening of contact A3,`nonrepeat relay A having been dropped out opening of emergency button contact VI whichk at the same time interruptsv the .current supply to master relay D as well as repeating relay H. Thus, depression of the emergency button V during the full automatic closing of the press arms has the same eiect as operation of foot ,switch W by means of depressing treadle |51, namely,

to interrupt the closing of theC press and permitV` thepress arms to return to open position by gravity and stop there until a new cycle is initiated in the usual manner.

In addition, another safety feature is provided making it possible to cause instant opening of the press at any time after its closing has been completed, for instance, during the building up 0f pressure or during the' time dwells. It has been shown previously that after the press arms stopped in their closed position relay A was deenergized, closing contact AI thereof; and, if now the foot switch |51 were released, repeating relay H became energized through the closing of foot switch contact WI, whereafter H remained energized by means of the interlocking contact H| Energizing relay H closed a contact H2 and the operator can now, in case of emergency, by depressing foot treadle |5l, and consequently closing foot switch W2, establish a current through the coil of emergency relay A, thence through W2, H2, F5, M4 and Y2. This is, of course, true for either the semi-automatic orthe full automatic cycleof operation because in either cycle repeatingl relay H becomes energized by the release of the foot switch after the press is closed. As has been previously pointed out, in the fullautomatic cycle, this relay H usually remains energized while in the semi- .automatic cycle (that ls, within the high pressure range) it is dropped out again by the opening of to the emergency depression of the foot treadle,

is immediately released bythe opening of valve |26 (Fig. 12)'. Contact E4 of the emergency relay at the same time establishes a current through master relaycoil D by way of E4 and Y2, thus starting the immediate opening of the press in a manner exactly like the action of either contacts M3 on the time relay M, G2 in control relay G or F3 in control relay F (together with switch contact T2), had the press been. allowed to continue its normal cycle.

If the treadle |51 is held depressed until after the completed opening of the press arms, the non-repeat relay A will not again become `energized upon closing of limit switch F2, thus making it impossible for the crank shaft to continue its rotation after the press is open. The foot treadle must rst be released (allowing relay A to be- Fig. 16 shows that a contact- V2 `in the emer gency button V is arranged in parallel with the combined contacts W2 and H2, by the closing.

of both of which the emergency relay E became energized. Thus not only the foot switch but also the emergency button may be used to energize emergency relay E by means of a current through the coil'of E through-V2, F5, M4 and Y2. It is clear then. that after the press has completed the closing stroke and at any time thereafter until it again begins to open, the action of the press may be immediately interrupted, the pressure of the hydraulic medium relieved, and the press armsv opened either by'a depression of the emergency button or by a new depression of the treadle which had been released subsequently to the closing of the press'.

In order to prevent an operator from shortening the time of dwellat maximum pressure .or from working the leather at insuilicient pressure by means of the above-described emergency devices, provision has beenmade to sound a gong |92 or other indicating device every time the press is opened before completing its normal cycle, so that any repetition of this emergency opening will be called to the attention of the supervisor. Current is supplied to this gong |92 througha small transformer J which, in turn, is energized upon operation of the emergency relayE by a current which passes through the /primary transformer coil, thence through contact vEl and normally closed contact G3 in control relay G and thence through a selector switch U t 'It will vbe noted that when operating in the through the coil of relay E, which is normally established by closing of emergency contact V2 or'foot switch contact W2, is then interrupted either at the contact F5 or contact M4 of the control relay F or time relay M, respectively,

either of which has been operated to start theL opening of the press. Thus, the emergency relay E has been rendered inoperative when opening of the press arms started, and'hence if the emergency button is operated after that time the gong will not ring. In other words, the emergency relay E can become ener-gized and cause the gong or signaling devices 192 to sound only if the emergency button is operated after the press has closed and before the press begins its opening stroke. `This of course is the period yiuring which the` operator could shorten the 'time of operation at the expense of the quality of the work if he were not inhibited by the ringas new and desire to secure by Letters Patent controlled by control relay G and if theemergency relay E is operated (either by means of foot treadle or emergency button) after the press has started to open, that is, after relay G has become operative, the normally closed contact G3 has opened (and remains open until the press has stopped in the open position) thus interrupting the current supply to the primary coil of transformer J. Therefore, in full automatic operation also the gong will only sound if theemergency b-utton (or foot switch) is used during the time of building up pressure and not after the predetermined maximum pressure` has been reached and the press begun to open.

It has been possible to use presses, as heretofore constructed, in a manner which allowed the operator to vary the pressure built up during each pressing operation, according to his judgment. Such Ian operation of the Apress described in this specification is possible because the press can (as described in connection with an emergency operation) be opened at the will of the operator at any time during the building up of pressure. It is, of course, understood that the amount of pressure acting onk the upper platen at each instant may be read'from the pressure gage |24 incorporated into the pressure governor .P. When it is desired to have the operator use his own judgment as to the amount of pressure to be used in each pressing operation,

when plating or embossing hides or skins, the t0 sounding of the gong may be prevented by opening the manually adjustable selector switch U in the line supplying current to the transformer J. Ordinarily the switch U, along with both time relays M and N, as well as selector switches` R, S, and T, will be in a box which may be locked so that the foreman or supervisor may decide the type of operation tobe performed by the press. The enclosing cases housing the adjustment members of the two. pressure governors are also provided with locks. Of course, the treadle |51 controlling foot switch W and the emergency button V are always accessible to the operator.

Having descr-ibed my invention, what I claim -one of said platens being movable relatively to the other` and one of the platens having a heated work contactingsurface, mechanical means operative to cause relative movement of the `platens, hydraulic means comprising a piston cylinder and a piston to move the movable platen toward the other platen, a low range pressure governor in the hydraulic circuit, a pump arranged to be continuously operated to circulate a pressure medium through said circuit whereby a work piece engaged by both platensvis subjected to heat at a lowA pressure built up to a selected point under control of said low range pressure governor, and electrical means including'said pressure governor and comprising a manually operable member for securing operation of both the mechanical and hydraulic means in timed relation to each other to effect rapidly repeated operations of the press in the full automatic cycle.

2. In a press, an upper and 'a lower platen one of which is movable with respect to the other to exert a pressure applying operation on a work piece, mechanical means for moving one of the platens toward and from the other platen to open and close a gap between the platens, hydraulic means including a valve for operating one of said platens in a pressure applying operation, electrical means for controlling the operation of both the mechanical means and the hydraulic means in timed relation to each other, and la manually operable member having connections in said electrical means to initiate operationl of rboth the mechanical and the `hydraulic means, said electrical means comprising an electrical power unit for said valve in the hydraulic?,

means and electrical controls for said mechanical means so arranged that, upon initiation of pressure applying operations by a single operation of the manually operable member the' press andl a manually operable member having conl nections in said electrical means to initiate operation of both the mechanical and the hydraulic means, said electrical m'ans lcomprising a solenoid contactor for said valve inthe hydraulic means and controlling relays for said mechanical means so arranged that, upon initiation of pressure applying operations by a single sustained operation of the manually operable mem'- ber for a predetermined'period in the ilrst pressure applying operation, the press continues in I full automatic cycle with repeated operations of the press until control of the latter by the electrical means 'is interrupted. y

4. In a press, a lower platen and an'upper platen movable toward and from each other, mechanical means for eiecting movement of one of said platens toward the other platen to close the gap between the platens, hydraulicmeans ens to effect a pressure applying operation, a

pressure governor connected to said hydraulic means, electrical means including said pressure governor for opening said valve to terminate the building up of pressure in the hydraulic means, said electrical means serving also to control said mechanical means, and a manually operable member having connections in said electrical means to initiate operation of both the mechanical means and the hydraulic means whereby said mechanical, means is 'caused to move one platentoward and from theother platen and said hydraulic means is rendered operative to effect a building up of pressure between said upper and lower platens in timed relation to ,the mechanical movement of one ofthem, and said electrical means including a repeating relay so connected as to secure repeated operation of the press in a full automatic cycle when said manuvally operable member is operated to initiate pressure applying operation.

5. In a press, an upper and a lower platen, me chanical means for moving one platen toward and from the other platen alternately to close and to open a gap between -the platens, said means comprising a power shaft, clutch and brake devices for controlling operations of the shaft, hydraulic means including a valve for operating one of the platens to eiect a pressure applying operation, a pressure governor connected to said hydraulic ing a clutch contactor and a brake contactor respectively for saidclutch and brake device, and a manually operable member having connections to said electrical means to initiate operation o'f the press through both the mechanical means and the hydraulic means in timed relation to each other such that one platen moves toward the other platen to cause both platens to engage a work piece resting on the lower platen, prior to the operation of said hydraulic means to eiect a pressure applying operation during which pressure is built up in said hydraulic means under control of said pressure governor, said electrical means comprising a repeating relay operative in said-electrical means .to maintain current in the clutch and brake contactors whereby the clutch remains on and the brake off to secure repeated operation of the press in the full automatic cycle following a single movement of said manually means, electrical means including said pressure governor for opening said valve to terminate the building up of pressure in the hydraulic means, said electrical means having connections to effect operation of the valve to cause building up of pressure in the hydraulic means and said electrical means including controlling means for said clutch and brake devices, and a manually operable member having connections to said electrical means'to initiate operation of the press through both the mechanical means and the hydraulic means in timed relation to each other such that one platen moves toward the other'platen to cause engage'- following a single movement of said manually operable member for a predetermined period in the rst pressure applying operation of thel press. 6. A press according to claim 5 in which a limit switch operating in timed relation. to said power operable member to initiate a pressure applying operation of the press.

8. A press according to claim 7 in which a limit switch operating in timed relation to said power shaft maintained said repeating relay continuously operative to holdA a master relay in control of the clutch and brake contactors for full automatic operation of the press.

9. In a press, an upper platen, a lower platen, one of said platens being movable 'relatively to theother and -one of the platens having a heated Work contacting surface, mechanical means operative to cause relative movement of the platens,

hydraulic means comprising a piston cylinder and a piston 4to move the movable platen toward the other pl n in timed relation to the operation of said me hanical means, a low range pressureL governor in said circuit, a pump arranged to be r continuously operated to circulate a pressure medium through said circuit, whereby a work piece engaged by both platens is subjected toheat at a low pressure which is built up to a selected low pressure under control of said low range pres' sure governor, electrical means including said pressure governor and comprising a manually. operable member for vsecuring rapidly repeated operatlons of the press in the full automatic cycle, and means including 'a regulating valve in the hydraulic circuit to maintain a predetermined vminimum pressure against the piston associated shaft controls a solenoid contactor for said valve in the hydraulic means to start the building up of pressure therein.

'7. In a press, an upper and a lower platen, mechanical mea-ns for moving one of said platens toward and from the other platen, said means ing a solenoid contactor to effect operation of the valve to cause building up of pressure in the hydraulic means and said electrical means includwith the movable platen, whereby a work piece engaged by both platens is-rst subjected to heat at a minimum pressure and also to` heat at a low pressure built up under control of the low range pressure governor.v

10. In a press, 'an upper platen, a lower platen movable in an upward direction toward the upper platen, one of the platens having a heated work contacting surface, hydraulic means comprising a piston cylinder and a piston to move said lower platen in an upward direction, mechanical means operable in timed relation to said hydraulic means to move one of the platens to close the gap beltween tbe platens whereby a work piece on the lower platen is engaged by both platens, a pump arranged to be continuously operated `to-circulate a-'pressure medium through said circuit, means including a regulating valve in said hydraulic circuit operative to maintain in the piston cylinder a predetermined lminimum pressure such as will just float the piston and the lower platen,

' whereby the lower platen will yield against said pressure in the piston cylinder when the work piece is engaged by both platens, the eiect being also to produce an instantaneous or jump pressure of low degree-on the work piece, and means comrapidly repeated operations of the press in the Y* full automatic cycle.

:,built up to a predetermined degree substantially above the instantaneous or jump pressure produced by the upper platen in pressing against the lower floating platen.

,12.'In' a press, an upper and a lower platen movable v with respect to each other to exert a pressure 'applying operation upon a work piece, one of said platens having a heated work contacting surface, mechanical means for moving one of the platens toward the other platen to causev both platens to engage a work piece on the lower platen,l hydraulic means including a regulating valveand an electrically controlled valve for operating the lower platen, a pump for supplying a pressure medium to' said hydraulic means, saidV regulating valve operating to raise the pressure in the hydraulic means sufficiently to oat the lower platen, a pressure governor in said hydraulic means, electrical means for controlling said mechanical means and said hydraulic means including the electrically controlled valve in timed relation such that the last-mentioned valve is closed before the platens engage the work piece on the lower platen whereby the' pressure is jumped inthe hydraulic circuit and then built up to apoint determined by the presprising amanually operable member for securing a heated platen at small pressure for a predetermined period of dwell to be followed by the building up of pressure toa point satisfactory to thel operator who then trips the press to terminateV the pressure applying operation.

17. In a press, an upper and a lower platen I movable with respect to each other to exert a sure governor, a repeating relay in the said electrical controlling means, land a manually operable member in said electrical means and operable to initiate a pressure applying operation of thel press and thereafter repeated operations of the press in the full automatic cycle.

13. A press according to claim 12 in which a time relay is included in the electrical means to delay the operation of a valve in the hydraulic means thereby to provide a predetermined dwell at substantially zero pressure, during which pressure is not built up in the hydraulic means, cutting-in of the time 'delay relay being accompanied by elimination of the repeating relay from the said electrical means, whereby a work piece may be subjected to treatment by a heated platen at minimum pressure for a predetermined time or dwell and then to a built-up pressure under control of the pressure governor, in a press conpressure' applying operation on a work piece, mechanical means for moving one platen toward and from the other platen, said means comprising a. power shaft and clutch and brakedevices for controlling the shaft, hydraulic means including a` valve for operating onev of the platens for a pressure applying operation, electrical means for controlling the operation of both the mechanicallmeans and the hydraulic means in timed relation to eachother, a manually operable member having connections in said electrical means to initiate operation of both the mechanical and the hydraulic means, said electrical means comprising an electrical power unit for operating said valve in the hydraulic means and also clutch and brake contaotors for the clutch and brake devices, respectively, together with a controlling relay for the last-mentioned contactors, and a repeating relay in said electrical means, all so arranged that, uponinitiation of pressure applying operations by appropriate movement of the manually operable member, the press continues in full automatic cycle with repeated operationsof` the press until control of the latter by the electrical means is interrupted.

18. A press according to claim 17 in which a time relay ls included`in the electrical means to delay the operation of a valve vin the hydraulic means thereby to provide a predetermined dwell at substantially zero pressure, during which pressure is not built up in the hydraulic means, cutting-in of the time delay relay being accompanied by elimination of the repeating relay from the said electrical means whereby .a work piece may be subjected 'to treatment by a heated platen at little or no pressure in a press conditioned for the semi-automatic cycle following each operation ofsaid manually operable member.

' 19. A press according to claim 17 in which a selector switch is included in the electrical means to provide, if desired, a shunt circuit around the ditioned ,for the semi-automatic cycle following each operation of said manually operable member.

14. A press according to claim 12 in which a selector switch is included in the electrical means to provide, if desired, a shunt circuit around the time relay thereby to eliminate the dwell at substantially zero pressureand concomitantly therewith to restore the said repeating relay and the full automatic cycle, the latter being secured through proper manipulation of said manually operable member.

15. A press according to claim 12 in which a pressure governor is included in both the hydraulic and electrical means and a second time relay included in the electrical means to give adwell for a predetermined period at a pressure maximum determined by said pressure governor, in a pressv selector switch is included in the electrical means to eliminate, if desired, the' second time relay and therewith the time dwell at maximum pressure, whereby a work piece may be treated t0 time relay thereby to eliminate the 'dwell at substanti'ally zero pressure and concomitantly therewith to restore the said repeating relay and the full automatic cycle, the latter being secured throughfproper manipulation of said. manually operable member. f

20. A press according to claim 17 in which a pressure governor is included in both the hydraulic and electrical means anda second time relay `included in the electrical means to give a dwell for. a predetermined period at a pressure maximum determined by said pressure governor, in a press conditioned for the semi-automatic cycle. `21. A press according to claim 17 in which a selector switch is included in the electrical means to eliminate, if desired, the second time relay and therewith the time dwell at maximum pressure, whereby a work piece may be treated to termined period of dwell to be` followed by the building up of pressure to a point satisfactory to the operator who then ltrips the press by suitablel manipulation of the manually operable member to terminate the pressure applying operation.

2,2. In -a press, an upper and a lower platen, one of said platens being movable with respect a piston cylinder and a piston therein for supf porting the lower platen in a floating condition, said hydraulic means including a regulating valve and a valve operative to check the flow of'the pressure medium through a part of said hydraulic means whereby pressure will instantaneously develop in said part of the hydraulic circuit and in thelpiston cylinder when the work piece is first engaged by both platens, this instantaneous or jump pressure between the platens being regulatable by adjustment of said regulating valve electrical means for controlling both the mechanical means and the hydraulic means in timed relation to each other such that operation of the hydraulic means precedes engagement of the work piece by both platens, and a manually operable member to control said electrical' means so arranged that operation of the manually operable member is followed by operation of the press in the full automatic cycle during which thepress performs repeated pressure applying operations upon a work piece or work pieces introduced by the operator between said platens. i Y

23. A machine according to claim 22 in which the mechanical means for moving one of the platenscomprises a power shaft together with electrically operated clutch and brake devicesa associated with the shaft, and in which a con-v trol relay energizes a master relay which keeps the clutch engaged and, the brake released throughout repeated operations of the press in full automaticcycle.

24. In a press, an upper and a lower platen movable withrespect to each other to exert a pressure applying operation upon a workpiece supported on the lower platen, mechanical means including a power shaft for moving the upper platen toward the lower platen to engage a work piece on the latter, a clutch device and a brake device for controlling said shaft, combinedl mechanical and hydraulic means including a piston cylinder and a piston therein for supporting the lower platen in a floating condition, said hydraulicA means including a valve operative to check momentarily the flow of the" pressure medium through a part of said hydraulic means whereby pressure will develop in said part of the hydraulic circuit and in the piston cylinder when the upper'platen presses thework piece against thevlower platen, whereby the work piece be' tween the platens is subjected toa jump pressure, electrical means for controlling the operation of both the clutch and brake devices and the valve in the hydraulic means in timed relation to each other such that operation of the hydraulic means immediately precedes movement of the upper platen to its lowest position inrelationto the lower platen, and a manually operable member to control said electrical means, said electrical control means for the clutch and brake devices including also a control relayall so arranged that operation of themanually operable memberis followed byoperation of the press in the full-. automaticcycle during which the clutch device is constantly engaged with respect to said shaft and the brakedevice disengaged, y whereby the press performs repeated pressure applying operations upon a work piece or work' pieces introduced by the operator between said platens.

25. In a press, an upper and a lower platen movable with respect to each other to exert al pressure applying operation upon a work piece supported on the lower platen, mechanical means including a power shaft for moving the upper platen toward the lower platen to engage a work piece on the latter, a clutch device and a brake device for controlling said shaft, hydraulic means including a piston cylinder and a piston therein for supporting the lower platen in a floating condition, said hydraulic means including a regulating valve and a valve operative to check the flow of the pressure medium through a part of said hydraulic means whereby pressure vwill develop in said part of the hydraulic circuit and in the piston cylinder when the upper platen presses the work piece against the lower platen, electrical means for controlling both the mechanical means and the hydraulic means in timed relation to each other such that operation of the hydraulic means immediately precedes movement of the upperplaten to its lowest position in relation to the lower platen, and a manually operable member to control said electrical means, said electrical means including a clutch contact, a-brake contactor and a control Vrelay all so arranged that operation of the manually operablemember isfollowed by rotation of said power shaft with the clutch device constantr ly engaged and the brake device disengaged,

whereby operation of the press in the full auto-l matic cycle 4takes place, during which the press performs repeated pressure applying operations upon a work piece or work pieces introduced by the operator between said platens.

26. In a press, an upper and a lower platen relatively movable with respect tof-each other to exert a pressure applying operation upon a work piece supported by the lower platen, hydraulic means including valves for operating one of the platens with respect to the other to effect a pressure applying operation, said hydraulic means comprising a regulating valve to secure a minimum pressure approaching zero in the hydraulic circuit, a pressure governor connected to said hydraulic means, electrical means including said pressure governor for controlling said hydraulic means, and a manually operable control member having connections to said electrical means for initiating a pressure applying operaf, tion through control of said hydraulic means,

one of said platens being movable with respect i to the other platen and one of the platens having a heated work contacting surface, a hydraulic circuit comprising a piston cylinder and a piston to move the movable platen into pressing relation to the other, means to circulate -a pressure medium through said circuit, means including a y regulating valve in said hydraulic circuit to vmaintain a predetermined minimum pressure against the piston associated withv the movable platen whereby a work piece engaged by both platens u is subjected to heat at a` minimum pressure, a

second valve to effect building up of pressure in the piston cylinder to a predetermined maximum,

.a solenoid for operating the second valve, and

the application of heavy pressure at a predetermined regulatable point.

29. In a press, an upper platen, a lower platen movable in an upward direction toward the upper platen, one of said platens having a heated work contacting face, a hydraulic circuit comprising a piston cylinder and a piston to move said lower platenin an upward direction, a mechanical device to exert an upward pressure on said piston, a pump operating continuously to force a pressure medium into said circuit, said hydraulic circuit comprising a valve operative to maintain in the piston cylinder a predetermined minimum pressure such that the pressure medium in co- 'operation with said mechanical device operates to float the piston and the lower platen, whereby pressure in a smooth plating or embossing operation.

31. In a press, a heated upper platen, a lower platen movable in an upward direction toward the upper platen, a hydraulic circuit comprising a piston cylinder and a piston to move said lower platen in an upward direction, a spring arranged to press upwardly upon said piston, said hydraulic .circuit comprising a valve constructed to maintain in the piston cylinder a predetermined minimum pressure such that the pressure medium in co-operation with said spring operates toi iloat laying the operation of the last-mentioned valve the lower platen will yield when a work piece is engaged vby both platens to effect treatment of the work piece by heat at a minimum pressure, a second valve in the hydraulic circuit operable to stop the ow of pressure medium at a, point beyond the piston cylinder whereby pressure'is built up in said cylinder to a predetermined maximum, andelectrical means comprising a time delay relay to delay the operation of the second valve fora predetermined period whereby the work piece is subjected to heat `treatment at fminimum pressure for a desired period of time as a preliminary to the application of heavy pressure in a vsmooth plating operation. i

30. In a press, a lower platen, a'hydraulic circuit comprising apiston cylinder and'a piston to operate said lower platen in an upward direction, a spring arranged to exert a yielding upward pressure on said piston and platen, means to circulate a pressure medium through said circuit, a regulating valve in the hydraulic circuit 'operative to provide in the piston cylinder a predetermined mnimum pressure4 of the pressure medium therein, whereby said .pressure medium co-operates with the spring to float the piston and lower platen, an upper platen movable downfor delaying the operation of the last-mentioned valve for a regulatable period of `time, thereby securing heat treatment of the work piece at minimum pressure for a predetermined period E as a preliminary to the application of heavy -wardly a predetermined distance-such that a for a'period of time which may be predetermined by the loperator thereby securing a preliminary heat treatment of the work piece fora predeter-A mined period before the application of heavy pressure in a smooth plating or embossing operation. I

32. A machine accordingto claim 31, in which a high range pressure governor is included in both the hydraulic circuit and in the electrical means and is operative to terminate heavy pres- `sure on Athe work pieceat a predetermined regulatable point.

33. In a. press, an upper and a lower platen relatively movable with respect to each other to exert a pressure applying operation upon a work piece supported on the lower platen, hydraulic means including valves foroperating one of said platens toward the other, a high range pressure governor connected to said hydraulic means, a

low range' pressure governor adapted to be connected to said hydraulic means. electrical means including said pressure governors for controlling said hydraulic means, and a manually operable member connected to said electrical means for initiating operation of said hydraulic means, said electrical means comprising time delay relays and selector switches therefor whereby a time delay may' be provided for at substantially zero pressure at the beginning of the building up of pressure in said hydraulic means or for a time dwell at substantially maximum pressure in the operation of the press on a given piece of, work.

34. In a press, an upper and a lower platen one of which is movable with respect to the other, a hydraulic circuit comprising a piston cylinder and a piston therein for moving the movable platen into pressing relation to the other platen, a valve and Ia pressure governor both in the hydraulic circuit to control the building up of pressure in the piston cylinderwhereby the piston and the platen moved thereby are operated to produce a predetermined maximum pressure on a work piece backed by the other vplaten, and electrical connections comprising said pressure governor anda time delay relay for controlling said valve to maintain said maximum pressure for a predetermined period of time and then to cause operation of the valve to terminate the period of maximum pressure.

` 35. In a press, an upper and a lower of which is movable with respect to the other, a

`hydraulic circuit comprising a piston cylinder;

and a piston thereins-for moving the, movable-11s,.

platen one platen into pressing relation vto the other platen, a pump adapted to be continuously operable to force a pressure medium through said circuit, a valve located in the hydraulic circuit beyond the piston cylinder on the side away from said pump and operable to stop the flow of the pressure medium, thereby to build up pressure in said piston cylinder whereby the piston and the platen moved thereby operate to produce a predetermined maximum pressure on a work piece backed by the other platen, a second valve operative to admit the pressure medium to the piston cylinder and to by-pass the pressure medium as soon as the maximum pressure has been built up in the piston cylinder, and electrical means including a time delay relay for controlling said valves to determine the period of operation of the iirst-mentioned valve in stopping the ilow of the pressure medium through the piston cylinder thereby to maintain said maximum pressure for a predetermined period of time and then to cause operation of the valves to terminate the period of maximum pressure and to restore circulation of the pressure medium through said circuit.

36. In a machine according to 'claim 35, in which a pressure governor is connected in both the hydraulic circuit and in the electrical means and is operative to condition the said second valve to oy-pass the pressure medium at a predemined maximum, a second valve in the hydraulic circuit operable to pass the pressure mediu-m to the piston cylinder and alternatively to by-pass the pressure medium back' to a reservoir, a pressure governor to control the operation of the second valve to terminate the building up of pressure in the piston cylinder at a predetermined point, and an electrical circuit including said pressuregovernor and electrical power units in connection with the first-mentioned valve and the second valve and also .a time delay relay in 'the circuit of the electrical unit associated with thrst-mentioned valve, tov control the operations of these two valves, whereby pressure may be built up in the hydraulic circuit to a predetermined maximum and then that maximum retained for a predetermined period.

38. In a press, an upper and a lower platen at least one of which is movable with respect tothe other, a hydraulic circuit including a piston cylinder and a pistonl for moving the movable platen toward thxeifother platen, a pump adapted to be',operated continuously to force a pressure medium through said circuit, a valve in the hydraulic circuit operable to stop the ow of pressure medium in the hydraulic circuit to build up pressure in the piston cylinder to a predetermined maximum, a pressure governor adapted to vary the capacity of the pump thereby to predetermine the time required tobuild up the pressure to maximum in said circuit, and an electrical circuit comprising electrical power units in con` nection With'the mst-mentioned valve and the third valve and also an adjustable time delay relay inthe circuit of the electrical unit associated with the first-mentioned valve to control the operations of these two valves, whereby pressure may be built up in the hydraulic circuit to a predetermined maximum and then that maximum retained for a predetermined period, the result being that a work piece may be treated to pressure built up either rapidly or lrelatively slowly and to maximum pressure for a period of time in a relatively wide range.

39. In a press, an upper and a lower platen at least one of which is movable with respect to the other, one of said platens having a heated face, a hydraulic circuit including a piston cylin` der and a piston for moving the movable platen towards the other platen, means to circulate a pressure medium through said ,circuit at a very low or minimum pressure, means to cause both platens to engage a work piece placed between them at'said minimum pressure, a valve in theJ hydraulic circuit operable to stop the ow of pressure medium in the hydraulic -circuit to build up pressurev in the piston cylinder to a predetermined maximum, a check valve to maintain pressure in that part of the hydraulic circuit which includes the piston cylinder, a third valve in the hydraulic circuit operable to pass the pressure medium to the piston cylinder and alternatively to by-pass the pressure medium back to a reservoir, and an electrical circuit comprising electrical power units associated with said rst-mentioned and third-mentioned valves to control the latter, said electrical circuit comprising also two time delay relays one of which determines a delay in the operation `of the mst-mentioned valve thereby to secure heat treatment of the work piece at minimum pressure for a predetermined period, the other time delay relay being operative to control the first-mentioned valve to cause it to maintain maximum pressure in the hydraulic circuit for a predetermined period, whereby a work piece lsv treated to heat at minimum pressure for a predetermined period and subsequently to heat at maximum pressure for another' predetermined period.

40. In a press, an upper and a lower platen at l least one of which is movable with respect to the other, a hydraulic circuit including a piston cylinder and a piston for moving the movable platen toward the other platen, a valve in the hydraulic circuit operable to stop the flow of pressure medium in the hydraulic circuit to build `up pressure in the piston cylinder to a predetermined maximum, a check Valve to' maintain pressure in that part of thehydraulic circuit which includes the piston cylinder, a third valve' in the hydraulic circuit operable to pass the pressure medium to the piston cylinder and al- ;iredetermine 'the pressure in the piston cylinder and adjustable throughout a wide range of pressures, a check valve co-operating with the rstmentioned valve to maintain pressurel in that v ternatively to by-pass the pressure medium back to a reservoir, a pressure governor to control thelby-passing operation of said third valve, and an electrical circuit comprising solenoids asso-I ciated with said first-mentioned andthird-men-` part ofthe hydraulic circuit which includes the.

- piston cylinder, a third valve in the hydraulic circuit operable to pass the pressure medium to the piston cylinder and alternatively to by-pass the Pressure medium back to a reservoir, means to tioned valves to control the latter, said electrical circuit comprising also two time delay relays one of which determines a delay in the operation of the first-mentioned valve thereby to secure heat treatment of the work piece at minimum pressure for a predetermined period, the other'time

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