US2077894A - Surge control valve for hydraulic presses - Google Patents

Description

April 20, 1937. PATRICK SURGE CONTROL VALVE FOR HYDRAULIC PRES SES 2 Sheets-Sheet 1 Filed Aug. 13, 1934 Ftl 5&

MOW

April 1937- 1.. PATRICK 2,077,894

SURGE CONTROL VALVE FOR HYDRAULIC PRESSES Filed Aug. 15, 1934 2 Sheets-Sheet 2 13440 Pufr/c/r shim M4301 Patented A r. 20, 1937 .UNlTED STATES suaon CONTROL VALVE FOR mnaouo" Pnnssns.

Isaac Patrick, Salem, ,ohiaa s i uur to E. w.

'- Bliss Companygfroledo,"

hi0, a icorporation of Appli ant-law an. ass-serial at. 39,531 r c a ms-j 11a s+ f This invention relates to hydraulic presses, and

is more particularly directed to the surge control valve mechanism of such a press. T

The primary objeot'of the invention is the. provision or means to facilitate rapid pre-fllling of' in the main cylinder at the lowermost point of the working stroke so that the liquid contained in the cylinder may be forced out into a reservoir on the return stroke of the press.

A further object of the invention is the provision of means to accomplish these ends rapidly and with a minimum of shock to the workin parts of the press.

Other objects and advantages of the invention will become apparent as the description proceeds, reference being'had to the accompanying drawings which disclose a preferred embodiment of the mechanism and in which- I Figure 1 is a, diagrammatical view, parts in section, of a hydraulic press embodying the invention, with the ram in raised position and the surge valve closed; Fig. 2 is an enlarged section of the surge valve unit similar to that shown in Fig. 1; Fig. 3 is a cross-section on the line 3-3 in Fig. 2, and Fig. 4 is an enlarged perspective of a portion of the stem'of the relief valve of the surge valve unit.

Referring to the drawings, the present invention is shown as embodied in a hydraulic press having a slide I adapted to be forced downwardly by a main ram 2 working in a -main pressure cylinder 3. The return of the slide, after its working stroke, is accomplished by pistons l working in push-back cylinders 5 in a manner well known in the art.

The press operating hydraulic circuit forms no part of the present invention and hence will be but briefly described. A surge tank In is mounted on the top of the press, so as to be closely adjacent the main cylinder 3. A pump I I motivates the fluid in the circuit and has its intake side connected to the surge tank by a. conduit I2. The output side of the pump-is-een:

nected by a pipe I3 with an operating valve I4, which latter has communication with and controls the flow in leads l5 and I6 to the main cyl- 5oinder 3 and push-back cylinders 5, respectively. A relief conduit I'I connects the branch I6 with the surge tank so that fluid may be passed to the latter if the pressure in the push-back cylinders' rises excessively. A suitable outwardly 5 opening relief valve I8 is interposed in this sub-circuit. A relief conduit I 9 connects the conduit I5 through the valve l4 with the tank 1 III. A fluid return conduit 20 is provided for the push-back cylinders so that during the working stroke of the press the fluid may be forced out of 5 thepush -back cylinders into the surge tank.

Aby-pass conduit 3|! connects the pump out-, put passage I3, through a suitable control valve 3|, to the surge control'or pre-flll valve with which the present invention is particularly con- 10 cerned. When the valve 3| is in closed position, as shown, the conduit 30 at the pre-fill valve side thereof is in communication through the conduit I1 with the surge tank. It is apparent that when I the valve I4 is in the closing position indicated 15 in Fig. 1, the pump II is in communication with the cylinder 3 and the push-back cylinders are in relief communication through the conduit 2|II with the relief line H. When the valve I4 is'in I the opening position, the above communica- 20 -that the fluid may be rapidly transferred to and from the latter. Before the working stroke of 30 the press reaches the point of contact of the slide with, the work, the slide travels down of its own weight and fluid is allowed to run in from the surge tank to the main cylinder.

This operation is known as pre-fllling and must be rapidly ac- 35 complished so as to prevent any air from entering the main cylinder. It will be seen that the area of the valve controlling the passage between the main cylinder and surge tank must be relatively large. After the working stroke of the 40 press, this valve must be opened to allow the return of fluid to the surge tank. Obviously, the force required to open a valve of considerable area against the existing pressure in the'cylinder at the end of the working stroke is very great 45 and is the source of considerable trouble in presses of this character. One' of the purposes of the present invention is to provide a means whereby the pressure in the main cylinder is relieved before any attempt is made to open the main valve.

The communication between the surge tank III and the main cylinder 3 includes an axial central passage 35 and smaller side passages 35 leading into the central passage A main valve 31 is adapted to cooperate with a seat 38 to close the main passage and such seat is disposed at the outer side of the passages 36, relative to the cylinder 3, and preferably adjacent thereto.

The valve 3'! is provided with a'stem 39 extending from the head portion on each side thereof,

which is adapted to cooperate with stationary guides 40 and 4|] to control the path of movement of the valve. Guide webs 4| are provided on the valve body to cooperate with the wall of the passage 35 to further prevent any side movement of the valve. A spring 42 placed between the lower guide 40 and the head of the valve biases the latter to closed position, but is only of suificient strength to place a very light upward force on the valve which can be very easily overcome by a reduction of pressure in the main cylinder from that existing in the surge tank.

The stem 39 of the main valve may be made as a unit with the valve body, but is preferably built up by the addition of an elongated tubular insert 45 held in the valve stem by any suitable means such as a nut 46 which draws the insert against a shoulder 41. The insert has a central longitudinal bore 50 formed therein and surrounded at its lower end by a valve seat 5|. The upper end of the insert 45 projects up through the guide 40. The passage 50 communicates with the space above the valve head 31 by small bores 52 and 53 formed in the body of the valve and insert 45, respectively. A relieving valve 55 is adapted to close the central passage by cooperation with the valve seat 5|, and includes a stem 56 of smaller diameter than the passage 50.- Collars 51 are fixed on the stem to guide its movement and, as shown in Fig. 4, are formed with a series of spaced longitudinal peripheral grooves 58 so that fluid may pass freely within the bore 50 when the relieving valve 55 is opened.

At the top of the stem 56 and cooperating with a stationary cylinder 59, carried by the guide 40 is a piston 60, carried by the stem. A spring 6| urges the piston upwardly from the valve body and hence urges the relieving valve 55 to its seating position. In its upper or normal position the piston 60 stands spaced from the uppermost end of the main valve stem insert 45. It will thus be seen that movement of the piston downwardly from such position will bring it into contact with this stem. The purpose of this will presently become apparent.

In the operation of the press, the slide moves down of its own weight as soon as the pressure in the push-back cylinders 5 is relieved, which takes place at the beginning of a working stroke and when the operating valve 4 is in its closing position. The timing and press control valves may be manual or automatic, as these devices are well known in the art. The downward movement of the slide causes the ram 2 to move out of the main cylinder 3. Thus, the pressure in the main cylinder becomes less than that in the surge tank, so that the main valve 31 is opened against the slight tension of the spring 42, permitting'fluid from the tank In to pre-fill the main cylinder. During this time, with the control valve in the position in which it is shown in Fig. 1, fluid from pump flows through the valve.and pipe l5 into chamber 3, but the downward movement of ram 2 is so rapid that the fluid entering through pipe I 5 is negligible in comparison'to that entering through valve 31. Of course, the fluid from cylinder 5 escapes through pipe l6 and the valve to pipes 20, I1 and tank l0.

When slide contacts the work, chamber 3 is full and valve 31 closes. Thereafter the pressure in the main cylinder 3 is raised by the pump H through the pipes l3 and I5 and interposed operating valve 4 to carry out the pressing operation in the usual manner. When the pressure has risen to a predetermined extent, the bypass control valve 3| opens. The pump pressure is then exerted through conduit 30 on the piston 60 and from it through the stem 56 to the small pressure relief valve 55. The first downward movement of the piston 60 moves the valve 55 oil its seat, allowing a small quantity of oil to flow through the central passage 50 and passages 52 and 53 into the surge tank. The pressure in the main cylinder is relieved by the removal of this small quantity of fluid. As long as the operating valve remains in the position in which it is shown in Fig. 1, this reduction of pressure in chamber 3 immediately results in relief of pressure in pipes l5, l3 and 30, resulting in descent of plunger 3| and closing of valve 55. Thereupon pressure is built up in chamber 3 and pipe 30 so as to repeat the process. However, when the operating valve is shifted to the left, as viewed in Fig. 1, pipe I3 is connected to pipe Hi. When pressure in cylinder 5 rises sufiiciently, pressure in connected pipes I3 and 30 raises plunger 3| and opens valve 55. Pressure in cylinder 5 remains sufficiently high to maintain communication through pipe 30 against piston 60, although pressure in the much larger chamber 3 is so far reduced as toallow piston 60 to continue its downward movement and open the main valve 31 by contacting the upper end of the main stem insert 45. Obviously, the liquid in the main cylinder can now flow rapidly past the main valve into the surge tank so that the push-back cylinders can be brought into operation to raise the ram. The pressure from the output side of the pump, which is needed to operate the push-back rams to cause the return of the slide, acts through the conduit 30 and valve 3| to hold the main valve 31 open.

When slide reaches its upper limit; relief valve l8 prevents excessive pressure in pipe I6 and connecting passages, while maintaining sufficient pressure to keep the parts in the position they have assumed until the operating valve is again shifted to the right.

It will be appreciated that the present invention may be used with any type of press in which rapid operation is desired. I Wish it expressly understood, therefore. that my invention is not limited to the particular arrangement shown, as

various changes may be made in the form and disi position of the parts without departing from the spirit of the appended claims.

Having thus described my invention, what I claim as new, and desire to secure by United States Letters Patent, is:

1. In combination, a main cylinder, an opposing push-back cylinder, plunger means having parts-operable in said cylinders, a surge tank in communication with said main cylinder, a main surge valve and an associated relief valve normally closing said communication, fluid pressure actuated means operable to open said relief and main valves in predetermined sequence, and controlled means operable to supply fluid pressure to said valve opening means whenever pressure admitted to either the main or push-back cylinder exceeds a predetermined amount.

2. In a press of the class described, main and push-back cylinders, a surge tank in communication with said main cylinder, plunger means 2,077,894 hating parts operating in opposed relation in.

said main and push-back cylinders, a surge valve and an associated relief valve normally closing said communication, means including a piston in connection with said valves, a liquid control means operating on said pistons to open the relief valve when pressure in the main cylinder exceeds a predetermined amount and to open both the relief and surge valves upon the pressure in said push-back cylinder exceeding said amount.

3. In a hydraulic press, a main cylinder arranged vertically and having a piston therein moved downwardly on its working stroke, a; pressure supply connectible with said cylinder, a surge tank above and communicating with the upperend of said cylinder, a main surge valve and a relatively small relief valve governing communication between the surge tank and cylinder, said valves being of the poppet type and opening by downward movement, springs normally holding said valves upward in closed position, the spring normally closing the main surge valve yielding to the pressure in the surge tank and allowing the valve to open when the main piston is lowered; a valve cylinder having a piston therein connected to said valves to open first the relief valve upon admission of pressure fluid to said valve cylinder and then to open the main surge valve upon continued admission of pressure fluid to said valve cylinder, and connections between,

the valve cylinder and said pressure supply.

4. In a hydraulic press, a main cylinder and a push-back cylinder having alternate working strokes, a surge tank communicating with the main cylinder, a main surge valve and a relief valve normally closing said communication, a valve operating cylinder having a piston connected to open the relief valve and main valve in succession, and connections providing communication through a pressure-openable valve to said valve cylinder from that one of the main and push-back cylinders that is on its working stroke, whereby the relief valve, but not the main valve, is opened upon the pressure in the main cylinder exceeding the limit of said pressureopened valve during the working stroke of the main cylinder, whereas both relief and main valves are opened upon pressure in the push-back cylinder exceeding the limit of the pressureopened valve during the working stroke of the push-back cylinder.

5. In a hydraulic press, a main cylinder, a

push-back cylinder, a surge tank communicating with the main cylinder, a main and a relief valve normally closing said communication, both valves being of the poppet type and opening towards the main cylinder, a valve cylinder with a piston therein connected to said valves to open first the relief and then the main valve upon admission of fluid pressure to said valve cylinder, and fluid connections to the valve cylinder admitting fluid thereto to open the relief valve, and not the main valve, upon pressure in the main cylinder rising to a predetermined amount and to open both relief and main valves when pressure in said pushback cylinder rises to a predetermined amount.

6. In a hydraulic press, a main cylinder and a push-back cylinder having alternate working strokes, a surge tank communicating with the main cylinder, a main surge valve and a relief valve normally closing said communication, said valves being of the poppet type and openable towards the main cylinder, a valve cylinder having a piston connected to open first the relief valve and then the main valve, and fiuid pressure connections to said valve cylinder operating the piston to open the relief valve, but not the main push-back cylinder, a surge tank communicating with the main cylinder, a main and a relief valve normally closing said communication, both valves being of the poppet type and opening towards the main cylinder, a valve cylinder with a piston therein connected to said valves to open first the relief and then the main valve upon admission of fluid pressure to said valve cylinder, a source of fluid under pressure, control means for directing fluid from said source first to the. main cylinder and then to the push-back cylinder, and connections between the main and push-back cylinders and the valve cylinder through a pressure-openable valve, whereby the relief valve operates as a pressure limit while pressure is directed to the main cylinder, and as preliminary relief to opening of said main valve when pressure is: directed to the push-back cylinder.

ISAAC PATRICK.

Images