US2790305A - Control valves for hydraulic presses - Google Patents

Description

April -"30, 1957 Fil ed Jan. 11-, 1954 J. M. TOWLER ET .AL

CONTROL VALVES FOR HYDRAULIC PRESSES 4 Sheet-Sheet 1 JOHN MAURICE TOv/LER FRANK HATHORN FOWLER av swam, 02% ,'W/V ZL ATTQENEYS April 30, 1957 J. M. TOWLER ET AL 2,790,305

CONTROL VALVES FOR HYDRAULIC PRESSES 4 Sheets-Sheet 2 Filed Jan. Ll, 1954 II I m 2 TR w mm Wm 7 H L\. vv M mm 5 M u W m ,m w 0. 0 w J Y \J E A 0 m x M Q a IA/ I QHU II V w In: l m a M H L? A 0 V 4 ATTORNEYS April 1957 J. M. TOWLER ET AL CONTROL VALVES FOR HYDRAULIC PRESSES 4 Sheets-Sheet 3 Filed Jan. 11, 1954 .v12 Q -I I2 di INVENTORS JOHN MAURlCE TOVLCR FRANK HATHoRN Towl-ER BY Guam, 65?, MM

ATTOEN EYS April 30, 1957 J. M. i'OWLER ET AL 2,790,305

- CONTROL VALVES FOR HYDRAULIC PRESSES Filed Jan. 11, 1954 4 Sheets-Sheet 4 ACC UMUL ATOE PRO/W 710 N K VWWv-ll PILOT PUMP Index-21291.5

Hafiz Haj/e014 jaw 1&7 3 m, Egu Ws W @iZa ree/ s United States Patent'f) CONTROL VALVES FOR HYDRAULIC PRESSES John Maurice Towler, Mayfair, London, and Frank Hathorn Towler, Dob Park, Otley, England, assignors to Electraulic Presses Limited, Rodley, near Leeds, England, a limited liability company of Great Britain Application January 11, 1954, Serial No. 403,354

Claims priority, application Great Britain January 20, 1953 3 Claims. (CI. 60-52) This invention relates to apparatus for controlling the operation of hydraulic presses and it is an improvement in ormodification of the invention according to our copending United States application Serial No. 288,796, filed'May 20, 1952.

The invention according to the said co-pending application consists in control means for a hydraulic press whereby by the manual manipulation of a single operating lever a hydraulic press can be caused to operate so that its ram is enabled to make a series of short forging or planishing strokes of predetermined length under auto matic control and with the operating lever held in a selected position in addition to normal forging strokes which are made as a result of corresponding and proportional movements of the operating lever.

The control means according to one embodiment of the invention according to our above mentioned co-pending application comprises a pressure fiuid operated piston control valve, a manually operated valve adapted to control the movement of the piston of the main control valve by controllnig the flow of pressure fluid which actuates the said valve piston, and an automatically operating reversing valve which comes into operation in one selected' position of the manually operated valve to cause the piston of the main control valve to reciprocate automatically to produce corresponding movement of the press ram in the performance of the short forging or planishing strokes.

In an installation embodying the above control means pressure fluid for operating the press ram is pumped directly into the press cylinder by one or more continuously running pumps, and such fluid is enabled to build up pressure on the ram when making a forging'stroke or to escape freely to a supply tank under the control of a combinedprefill-exhaust valve on the press cylinder. The operation of the combined prefill-exhaust valve is effected by a further supply of pressure fluid and this in turn is under the control of the main control valve.

The return stroke of the press ram is effected by pressure fluid from one or more pumps additional to the pump or pumps operating to supply pressure fluid-direct to the press cylinder.

An object of the present invention is to enable one or more additional pumps to be used to increase the normal pumping capacity available for moving the press ram when it is desired to provide both a high pressing speed and a high return speed and to utilise this additional pumping capacity in such manner that only a part of the total pump capacity passes through the main control valve, whereby only a comparatively-small control valve will be required to control the movement of the press ram.

A further object of the invention is to improve the construction of control valves of the type shown and described in our co-pending application whereby the valves requiring large bore high pressure piping may be mounted on or near the press cylinder and the pilot pressure valves which require only small, borepiping to be mounted in a control panel conveniently located. to suit thepress operator.

2,790,305 Patented Apr. 30;, 1957 Other. objects and advantages of the invention will be come apparent from the following description of the preferred embodiment illustrated in the accompanying drawings, in which:

Figures 1, 2 and 3' are diagrams of related sections of a hydrauliopress system, embodying the features of the invention, the figures being laid out for arrangement in side-by-side relation with the lines representing pipes positioned to register throughout the three figures.

Fig. 4 is a small scale diagram showing the manner in which the circuit elements shown in the preceding figures are connected to the pressure fluid sources.

The improvement in or modification of the control meansof our co-pending application which forms the invention of the present application consists in the inclusion of at leastone auxiliary pump which normally delivers direct into the press cylinder. to augment the capacity of the one or more direct pumps during each forging stroke of the press ram in combination with a valve which functions automatically to divert the delivery of said auxiliary pump from the press cylinder to the return cylinders. to assist in effecting a rapid return stroke of' the press ram.

Ina preferred embodiment of the present invention the aforesaid valve for diverting the delivery of the auxiliary pump has a valve member which on. one side is springloaded and is permanently open tothe delivery from a control pump and on the opposite side. is permanently open to the delivery from the auxiliary pump, the arrangementbeing such that during the down or forging stroke of the press ram the valve member is held open by the pressure of the liquid delivered by the auxiliary pump and permits such delivery to pass to the, press cylinder and at a point in the return stroke of the-press'ram the delivery pressure of the auxiliary pump is overcome andtlie valve will close when theauxiliary pump will discharge into the return, cylinders with the delivery from the one or more control pumps.

The present invention also consists of hydraulic control means as above wherein the primary. pressure control valves and the pilot pressure control valves form separate structures whereby the primary pressure, control valves may be mounted on or closely adjacent to the press so :as to save piping and'the pilot pressure control valves may be grouped in a control panel and this panel may be located to suit the press operator.

To enable the invention to be clearly understood and carried into effect a hydraulic installationembodying the improvements in and modifications of the installation de scribed in the specification of "our co-pending application, above mentioned,- will now be described by the aid of the accompanying drawing.

The installation illustrated in the drawing comprises a hydraulic down-stroking press on the upper end of the cylinder 1 (Figs. 1 and 4) on which is mounted a prefillexhaust valve V for controlling the ingress of liquid from a supply tank 2 into the press cylinderv 1 during the down stroke of the press ram 3 and its exhaust back into the supply tank during the return stroke of the press ram.

The press ram 3 can either be allowed to fall by gravity orit may be pumped down. ,Theup or reutrn stroke is effected by pumping pressure liquid. into a pair of return cylinders 4.

In accordance with the invention the hydraulic press has associated with itcontrolgear such that by-manual manipulation of a single operatinglever an operator can cause the press ram to give the following sequence of operations, starting with the press ram'at the bottom of its stroke:

(a) To moverapidly upwardsor away from the work,

(b Toibeaarrestedi at any part of its stroke,

(c) To be pumped towards the work at full forging speed,

(d) To apply a series of short forging or planis-hing strokes of predetermined length and with an intensity or force that will be directly proportional to the force that is applied to the operating lever by the operator.

Pressure liquid for operating the press and the control gear in the example illustrated in Fig. 4 is supplied by four pumping units A, B, C, and D. The unit A comprises two pumps which deliver directly into the press cylinder 1 by way of the pipe P in which is interposed a check valve V4C. The unit B is made up of a single pump hereafter referred to as the control pump and this delivers pressure liquid to the return cylinders 4 by way of pipe P and check valves V4D, V4B and V4E. Alternatively the delivery of the control pump B can be directed by the control valve V either to the press cylinder by way of a pipe 116 or to the control cylinder 87 of the prefill-exhanst valve V by way of a pipe 110.

The pump unit C also consists of a single pump which is hereafter referred to as the auxiliary pump. This auxiliary pump delivers directly into the return cylinders 4 by way of pipe Q, check valve V4A and pipe P or to the press cylinder 1 under the control of a spring loaded valve V and by way of pipes 113 and P When the valve V is open the auxiliary pump is free to deliver to both the return cylinders 4 and the press cylinder 1, and when the valve VT is closed it also closes the path to the press cylinder.

The valve V will operate under each of the following four conditions;

(:1) During the down stroke, whether forging or automatic, the control pump B is coupled through the valve V to the main cylinder, and therefore, the pressure on top of the valve V (applied via pipe P is substantially equal to the main cylinder pressure and consequently the oil from the auxiliary pump C can pass through valve V into the main cylinder with a pressure loss of little more than that due to the spring on top of the valve V'.

(b) With the spindle of the directional control valve V in the neutral position, the condition of valve V' will be substantially the same as in (a) above and consequently the auxiliary pump C will be unloaded through the main cylinder when the prefill valve V is opened.

At the beginning of the return stroke before the prefill valve V is fully opened, the control pump pressure falls to a pressure determined by the relief valve R incorporated in the prefill exhaust valve V As this pressure will normally be less than that in the main cylinder, the valve V will remain fully open until the cylinder pressure falls below the relief valve pressure, when the valve V will consequently close under the influence of its spring. When the valve V' is closed the delivery of pressure liquid from auxiliary pump C is directed along pipe Q through check valve V4A and. pipe P to the return cylinders 4 thereby augmenting the delivery of control pump B to effect the rapid return stroke of the press ram.

(d) During the return stroke the valve V will be in hydraulic balance and will remain closed due to the force of its spring.

N0te.The valve V is shown as a seated type valve in the accompanying drawing, but a piston type valve serving the same function may be employed without departing from this invention.

The remaining pump unit D supplies pilot pressure liquid direct to an accumulator by Way of pipe line P The reversing valve V is identical with reversing valve of our co-pending application. The valve V corresponds to the left-hand portion of the directional control valve of our co-pending application, the porting of the two valves being identical with that of the valve of said application except that in the valve V a choke and port are omitted. The function of the said. choke and port is combined in a valve V together with that of a relief valve. The valve V has three main positions as follows:

(1) A central neutral position to which the spindle is spring returned.

(2) A right hand position corresponding to either forge or automatic, which is secured by admitting pilot pressure to the left hand end of the spindle via the pipe 97;

(3) A left hand return position which is secured either by exhausting pilot pressure from the left hand end of the spindle and admitting it to the right hand end via a pipe 54 by means of a hand operated pilot control valve V (Fig. 3), or by admitting pilot pressure from the reversing valve V via a pipe 122 to a piston S of larger area than the spindle at the right-hand end, Whilst pilot pressure is still maintained on the left-hand end of the spindle from the pilot valve V Note, with reference to the terms left hand and right hand, this is looking at the drawing of the valve.

The function of the valve V is to determine whether the press table is to be pumped down for the forging cycle or falls freely for the automatic cycle. During the forging cycle the valve acts as a relief valve similar to the relief valve shown in our co-pending application, but during the automatic cycle pressure is admitted under the piston at the top of the valve via the pipe 122 so as to open it an amount determined by an adjustable stop, oil under pilot pressure being supplied for this purpose from the end of the manually operated pilot valve V When in its automatic position (as drawn). The non-return valve V4A renders the valve V inoperative during the return stroke of the press ram. The remainder of the valves marked V4B, C, D, and E are check valves and their function will be obvious to those skilled in the art. The valves VSA, B, C and D are safety relief valves.

The normal control valve V comprises three elements. The left hand element X, looking at the drawing, is an open centre directional control valve for the pilot pressure and controls the three positions of the primary control valve V The extreme right hand element Z corresponds to and serves the same function as the needle valve shown in our co-pending application. The intermediate element Y shown as part of this needle valve, serves as a bye-pass valve to make the automatic reversing of valve V and the piston T valve V inoperative.

The relief valve V determines the maximum pressure exerted by the press when the needle valve is held hard closed, in which case the valve V blows and trips the reversing valve V The valve V is a tappet-operated bye-pass valve to direct pilot pressure to trip the reversing valve V at a given point in the forging stroke, determined by tappets associated with the press ram, so as to be able to control the thickness of the forging if desired.

It will be seen that the valves V V and V shown on the accompanying drawings together serve broadly the same function as the main control valve and the refluxrelief valve shown in our co-pe-nding application. The spindle of the directional control valve V moves at the command of the lever L of the valve V which has four operating positions. In the position as drawn, the v alve V in cooperation with the valve V effects the automatic planishing strokes of the press ram as described in our copending application. Alternatively, the other three positions of the lever L will cause the spindle of V to take up the corresponding three positions of forge, neutral and return. There is however, no continuous follow-up movement between the control valve spindle of V and the control lever L. It will be seen that the valve V which has no counterpart in the system disclosed in'our co-pending application, performs the new and useful function of combining the delivery of the auxiliary pump C either with the delivery of pumps Aand B to elfect a down stroke of the press or with the control pump B alone to effect the return stroke of the press. More particularly, in the first instance, the valve V acts to direct pressure liquid from the auxiliary pump C to the main cylinder of the press and it is so actuated by the pressure of the control pump B, that the auxiliary pump C augments the delivery of pumps A and B to effect the rapid forging stroke of the press ram; all the primary pressure pumps A, B and C are then delivering to the press cylinder and consequently they will be unloaded when the prefill valve is opened and the directional control valve V is moved to the neutral position. On the return stroke, the delivery of both pumps B and C is directed to the return cylinders 4.

In a typical operation of a press equipped with the improved controls, assuming that the press ram is in its upper or retracted position, a pressing cycle is initiated by the operator manipulating lever L to shift the control valve V to the position shown in Fig. 3. In that position of the valve pilot pressure fluid is directed by way of the pipe 97 to the left end of the directional valve V The plunger of the directional valve is shifted to the right hand position and pressure fluid is permitted to exhaust from the right end of the valve by Way of the pipe 122 and valve V The latter is operated to the down position by pressure fluid supplied through the valve V The valve V also closes by reason of the connection of pipe 122 to exhaust.

With valve V in the operated position, the push back cylinders 4 are permitted to exhaust through the pipe P and thus into the press ram cylinders 1. The press ram descends by gravity opening the prefill valve in the usual way to augment the supply of pressure fluid delivered by the pump A and the push back cylinders. At the same time pressure on the ends of the valve V' is equalized so that pressure fluid from the pump C is also delivered to the ram cylinder.

When the ram contacts the work the prefill valve closes in the usual manner due to the buildup of pressure in the ram cylinder from the fluid delivered by the pumps A and C. This pressure also builds up in the chamber at the right end of the valve V When the pressure in the chamber reaches a predetermined figure it will overcome the pressure applied by the operator through the hand lever L and move the valve plunger Z back to open the outlet from the chamber. The pressure surge result ing from the suddenly released pressure will create a back-pressure within the space in the left end of the reversing valve V sufiicient to displace the valve plunger into the pressure position and cause the piston of the directional valve V to be moved to the return position.

With the directional valve in return position the con: trol pump B will deliver pressure fluid through pipes and 116 to both chambers of the prefill valve V opening the prefill valve in the usual manner. This will permit the fluid from the press ram to return directly to the supply tank. At the same time pressure from the control pump B combined with fluid from the pump C will be directed to the push-back cylinders 4 to effect the return stroke of the ram. The switching of the output of the pump C from the ram cylinder to the push-back cylinder is effected jointly by the closing of the valve V and the opening of the valve V Accordingly the return is eiiected at a high rate of speed. 0n the return stroke, the delivery of both pumps B and C is directed to the return cylinders 4.

What is claimed is:

1. In the hydraulic system of a press having a main press cylinder and a return cylinder, in combination, a main pump connected to deliver fluid under pressure directly to the press cylinder in the working stroke of the press, an auxiliary pump, a control pump adapted to deliver fluid under pressure either to the main cylinder or to the return cylinder, and two-position valve means oper- Iative in one position to direct fluid from the auxiliary pump to the press cylinder to augment the delivery of said main and control pumps, and means for operating said valve means to its alternate position to direct fluid from said auxiliary pump to the press return cylinder to augment the delivery of said control pump.

2. A hydraulic system as defined in claim 1 in which said valve means is connected in the system so that it is retained in position to combine the delivery of the main and auxiliary pumps by the pressure of the fluid delivered by the control pump.

3. A hydraulic system as defined in claim 1 having a main valve controlling delivery of the high pressure fluid from the main, auxiliary and control pumps, which valve is operated by low pressure pilot fluid, a pump supplying pilot fluid, and a valve controlling the delivery of pilot fluid to said main valve, said valves being separately construoted to permit mounting of the main valve closely adjacent the press cylinder while the control valve is located remotely from the press cylinder for convenient access by an attendant.

References Cited in the file of this patent UNITED STATES PATENTS 2,615,302 Camerota Oct. 28, 1952 2,636,346 Hofimann Apr. 28, 1953

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