US1468605A - Means for controlling hydraulic presses - Google Patents

Description

Sept. 18 1923. 11,468,6(115 w. F. MAYER MEANS FOR CONTROLLING HYDRAULIC PRESSES Filed Nov. 12, 1919 2 Sheets-Sheet 1 INVENTOR.

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Sept. 18, 1923.. nmww W. F. MAYER MEANS FOR CONTROLLING HYDRAULIC PRESSES Filed Nov. 12 1919 2 Shaefics-Sheet 2 ffg4 Gm: ucq

Patented Sept. 18, 11923..

UNHTED STATES earner oeieiee.

WALDEMAR F. MAYER, 0F PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO TAYLOR- WHARTON IRON AND STEEL COMPANY, OF HIGH BRIDGE, NEW JERSEY, A COR- PORATION OF NEW JERSEY.

MEANS FOR CONTROLLING HYDRAULIC PRESSES.

Application filed November 12, 1919.

To all whom it may concern Be it known that I, VALDEMAR F. MAYER, a citizen of Switzerland, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Means for Controlling Hydraulic Presses, of which the following is a specification.

This invention relates to a controlling means for hydraulic presses wherein the dead weight or additional live weight has a tendency to vary the set position of the press due to leakage loss of the motive fluid.

In presses of this type, the moving parts have a certain weight and friction-resistance, and in raising the ram the fluid pressure has to be increased to overcome these counter-pressures, while in lowering the ram the fluid pressure has to be decreased as a compensation. If, however, there is the slightest lakage in the motive fluid a corresponding-decrease of operating pressure results, an a movement of the ram is had in correspondence with such pressure loss. It has been proposed to utilize the movement of the ram, incident to such pressure losses. to automatically start the pressure pump to restore the pressure the return of the ram to set position automatically cutting out the pump. This means of control is objectionable, in that an actual movement of the ram is necessary to start the pump, arid this movement will loosen the grip on the work-piece, and in the case of a horizontal ram permit the work piece to fall out.

It is therefore highly desirable to provide means to take care of the pressure reduction due to leakage losses, without permitting any movement of the ram from set position, and in the present invention, such means is directed toan auxiliary pressure pump to maintain a constant pressure in the press cylinder, say equivalent to the suspension pressure of the ram. so that any loss due to leakage following the zero delivery position of the main pump, would be corrected as it occurred by the auxiliary pump pressure. and no possible movement of the ram could occur.

In the drawings Fig. 1 is a view in elevation, partly in Serial No. 337,427.

section. showing the improved control means applied to a hydraulic press.

Ifig. 2 is an enlarged side elevation of the main and auxiliary pumps and connected parts.

Fig. 3 is an enlarged sectional view of the control valve.

F g. 4 is an enlarged sectional view, illustrating a conventional form of the main pump.

The invention is here Shown as applied to a hydraulic press, including a platen 1, guided by uprights 2, and operated by a ram 3, drlvcn by the motive fluid in a cylinder 4. The motive fluid is delivered from a storage tank 5, through a pump 6, hereinafter termed the mam pump, and from the pump to the cylinder 4, through a. pipe 7. The main pump is preferably of the reversible flow, variable delivery type, a lever 8, controlling the pump, such, for example as illustrated conventionally in Fig. 4. This particular type of pump is well known in the art. and no claim is made herein as to any particular construction thereof. The lever 8, in the position shown. controls the main pump to maintain the pump at zerodelivery point, the extreme opposite positions of the lever, as indicated. setting the pump for maximum flow in reverse directions. that is to raise the'ram, or to lower the same.

lVith the main pump at zero delivery, any leakage loss. correspondingly reduces the pressure in the ram cylinder 4, and a corresponding movement of the ram results. To avoid this loss of pressure, notwithstanding a leakage loss in the main pump.

as here shown is positively and continuously operated from the pump shaft 10, which is in turn driven from a prime motor 11. The pump 9 is of ordinary single delivery rotary type. and being well known in the art requires no particular description or illustrar tion herein.

The auxiliary pump, which is continuously driven, takes the motive fluid from the tank 5, through a connection 12, and delivers the same through a pipe 13 to the pipe 7 beyond the main pump. A check there is provided an auxiliary pump 9, which valve 14 is arranged in the pipe connection 13, and set to open under pressure from the auxiliary pump, but of course held closed when the pressure from the main pump in pipe 7 exceeds the auxiliary pump pressure. A by-pass pipe connection 15 leads from the pipe 13 beyond the auxiliary pump to the tank 5, and in this by-pass is arranged a control valve 16. The valve 16 includes a casing 17, formed with a valve seat for a valve 18, opening toward the tank. A. spring 19, hearing between the valve 18 and a washer 20 on the valve stem 21, is arranged for manual tension adjustment through a plug 22, bearing on the washer 20 and threaded into the casing 17 A hand wheel 23, or other means is provided 'for adjusting the plug, and thereby varying the tension on the valve.

If the pressure of spring 19 is set for the suspension pressure of the ram, it will require such pressure to open the by-pass from the auxiliary pump to the tank 5, and

' through this control the desired result is obtained. When the main pump is operating the pressure in pipe 7 will exceed the pressure in pipe 13 from the auxiliary pump, and the fluid from such auxiliary pump will by-pass to the tank. \Vith the main pump in zero delivery position, the motive fluid is held under the set pressure in the pipe 7 and ram cylinder. As neither of these parts, including the main pump, can be absolutely fluid tight, pressure loss due to leakage is certain to occur. But, if such leakage loss reduces the suspension pressure of the ram, or would tend to such reduction, the pressure of the auxiliary provides a constant source of fluid pressure to the ram cylinder at suspension pressure. Excess fluid from the auxiliary pump will by-pass to the tank, but the control valve will constantly maintain the delivery from the auxiliary pump of the suspension pressure, providing the control valve is set for such pressure, as is contemplated.

The control means described provides, therefore, a constant pressure, always available, to maintain the active pressure at a predetermined limit, to thereby automatically take care of leakage losses and consequent otherwise loss of pressure. This sustained pressure will therefore absolutely prevent any movement of the ram, and will maintain the set position irrespective of leakage losses.

Having thus described the invention, what is claimed as new, is

1. A control means for hydraulic presses, comprising a constant auxiliary pressure means including an adjustable valve to maintain the main set pressure constant against leakage losses.

2. A control means for hydraulic presses to avoid variation in the main pressure in the set position of the press under leakage losses, comprising a constant auxiliary pres sure for the press equal to the set pressure, and means for controlling the pressure limit of such auxiliary pressure.

A control means for hydraulic presses for maintaining main set pressure constant against leakage losses, comprising an auxiliary pressure means, and an adjustable'valve for holding such auxiliary pressure at any predetermined set pressure limit for press control.

4. A control means for hydraulic presses for maintaining the main set pressure constant against leakage losses, comprising an auxiliary pump for delivering a fluid under pressure to the press, and a valve for main- ,taining the auxiliary pump pressure delivered to the press constant.

5. A hydraulic press, a main pressure pump therefor, means for setting the pump at zero delivery to maintain the press under a set pressure, and auxiliary means for maintaining the set pressure of the pump constant against leakage losses.

6. A hydraulic press, a main pressure pump adapted when set at zero delivery to maintain the press at set pressure, an auxiliary pump to maintain the set pressure of the press constant under leakage losses, and a valve for controlling the pressure limit of the auxiliary pump in its eflect on the set pressure.

7 A hydraulic press, a main pump therefor, a storage tank for the main pump, means for controlling the pump to maintain a set pressure on the press, an auxiliary pump for delivering a constant pressure from the tank to the press, a by-pa'ss from between the auxiliary pump and tank, and a manually adjustable valve for controlling the by-pass, whereby any pressure of the auxiliary pump to the limit of the valve-set will be delivered to the press.

In testimony whereof I afiix my signature.

WALDEMAR F. MAYER.

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