US3134398A

US3134398A - Hydraulic prop valve

Info

Publication number: US3134398A
Application number: US117978A
Authority: US
Inventors: Reynolds Reginald; Stammers Peter Haig
Original assignee: Acrow Engineers Ltd
Current assignee: Acrow Engineers Ltd
Priority date: 1960-06-17
Filing date: 1961-06-19
Publication date: 1964-05-26
Anticipated expiration: 1981-05-26

Description

May 26, 1964 R. REYNOLDS ETAL 3,134,398

HYDRAULIC PROP VALVE Filed June 19, 1961 z'sneets-sheet 1 uae enfoui( 555% A ttornQS May 26, 1964 R. REYNOLDS ETAL 3,134,398

HYDRAULIC PROP VALVE Filed June 19, 1961 Sheets-Sheet 2 United States Patent O 3,134,398 HYDRAULIC PROP VALVE Reginald Reynolds and Peter Haig Stamina-rs, Saffron Walden, England, assignors to Acrow (Engineers) Limited, London, England Filed June 19, 1961, Ser. No. 117,978 Claims priority, application Great Britain .lune 17, 196i) 2 Claims. (Cl. 137-4935) This invention relates to valves for hydraulic props, jacks and the like.

Hydraulic props normally include a hollow cylindrical ram working within a cylinder. The cylindrical body of the ram constitutes a reservoir for oil or other working fluid which, when the prop is to be extended, is pumped from the reservoir through the head of the ram into a pressure chamber formed between the head ofthe ram and the bottom of the cylinder in which it works, so as to extend the ram out from the cylinder. Whilst the ram is being moved from the cylinder and oil is being pumped from the reservoir it is necessary to allow air to ow into the reservoir to take the place of the oil. Conversely when the ram is being collapsed back into the cylinder and oil is owing back into the reservoir from the pressure chamber it is necessary to allow air to escape from the reservoir. The reservoir must, therefore, be appropriately vented. Hereafter such a chamber or reservoir will be referred to as a vented chamber.

It is usually an essential condition of such props that there be substantially no loss of operating hydraulic uid, c g., oil, either during operation or, where the device is portable as is the case with pit props, during transportation or during idle periods where it may be resting in a position other than that which it is designed to occupy when being used. Furthermore props such as pit props are liable to be treated fairly roughly for instance the prop may be dropped, from a height of several feet and it is necessary that the valve be sucientlyrrobust to stand up to this treatment without leaking.

A valve for a vented chamber of a hydraulic prop or jack in accordance with this invention has at least one passage passing through it, each passage being normally closed by a valve element which is biased to a position closing the passage, a ilexible diaphragm or bellows being arranged so as to be able to iiex in response to pressure changes in the vented chamber either above a certain maximum or below a certain minimum, movement of the diaphragm or the like in either direction from its normal position causing the valve element(s) to be unseated to open the passage (s) through the Valve.

Preferably separate inlet and outlet passages are provided in the valve each being closed by a separate valve element, movement of the diaphragm in one direction when pressure in the vented chamber falls below a predetermined minimum causing the valve element in the inlet passage to be unseated to allow air to flow into the chamber and movement of the diaphragm in the other direction resulting from the pressure in the vented chamber rising above a predetermined maximum, causing the valve element in the outlet passage to be unseated to allow air to flow out from the vented chamber.

A diaphragm having a fairly large area say in the order of 5 or 6 square inches can be utilized so that a cornparatively small pressure change in the vented chamber say of the order of 2 pounds per square inch can be translated into a force on the valve elements of about to 12 pounds. Thus fairly strong springs can be used to bias the valve elements into the closed position so that the valve elements will not normally be accidentally unseated even if the prop is subjected to rough treatment. The springs also act to close the valve elements and to Mlce return the diaphragm toits normal position when the pres- Sure in the vented chamber returns to normal. Thus when the chamber is not being either contracted or expanded the valve elements close the passages and iluid is prevented from leaking out from the chamber through the valve.

One very suitable arrangement of valve elements is to have one of them attached to the diaphragm and constructed in the form of a tube having an outwardly extending lip which seats against a seating to close one passage. The bore of the tube provides the other passage which is closed by a second element mounted within the bore of the rst element.

The invention will now be described by way of example with reference to the accompanying drawing in which;

FIGURE 1 is a diagrammatic cross sectional elevation showing a hydraulic pit prop incorporating a valve in accordance with the invention; and

FIGURE 2 is a cross section of the valve in the closed position to an enlarged scale.

The pit prop comprises essentially a hollow cylindrical ram 1 slidably mounted in a cylinder 2. The body of the ram constitutes a reservoir 3 for oil or other working fluid which, when the prop is to be extended is pumped by a pump diagrammatically shown at 4 through a check valve 5 in the head of the ram to a pressure chamber 6 between the ram head and the bottom of the cylinder so that the ram is moved out from the cylinder and the prop extended. The ram is extended by pumping liquid from the reservoir 3 of the prop through valve 5 in the base of the ram to the pressure chamber 6 below the ram. The prop is contracted by opening the valve 5 by any conventional means to allow iiuid to be transferred back from the pressure chamber 6 to the reservoir 3. The valve in the piston head 4 and the Valve 5 in the ram head are conventional check valves. Whilst the ram is being moved from the cylinder and oil is being pumped from the reservoir it is necessary to allow air to flow into the reservoir 3 to take the place of the oil. When the ram 1 is being collapsed back into the cylinder 3 oil iiows back through the ram head from the pressure chamber 6 to the reservoir 3 past a release valve (not shown) in the ram head which can be opened in a conventional fashion from outside the prop through for example a push rod or the like. Alternatively the valve 5 can be arranged so that it can be deliberately opened by any conventional means such as a push rod (not shown in the drawings). In each case it is necessary to allow air to escape from the reservoir. The reservoir is, thterefore, appropriately vented by a valve generally indicated at 7 and positioned as a unit in a hole through the top closure plate 8 of the reservoir across the ram 1.

The valve 7 comprises a main body portion 9 having a central passage through it in which a valve element 16 in the form of a tubular plunger is slidably mounted. 'I'he valve element 10 has at its top, a projecting lip 12 arranged to seat on an O-ring 14 to close a passage 16, between its bore and the atmosphere.

The lower portion of the plunger 10 extends downwardly from the body 8 through a central hole in a ilexible diaphragm 1S. The diaphragm is mounted at the bottom of plunger element 10 between a plate 2i) extending over the diaphragm and a nut 22 screw rthreadedly engaged on the valve plunger. The outer edge of the diaphragm is fixed to the closure plate 2 so that the only passage through the diaphragm is that provided by the bore of the tubular plunger element 10.

The plate 20 is biased downwardly by a spring 23 acting between a shoulder 24 on the main body portion by the valve and the face of the plate 20 so that the lip 12 of the plunger is held against its seat 14.

The bore of the plunger valve element 10 is normally closed near the top of the plunger by a second valve element 25 seating on a ilexible seat ring 26 which is held er and it is biased to a closed position by a spring 30,'

acting between it and a shoulder 32 on the interior of the plunger 10. A rod 34 projects downwardly within the bore of the plunger from the second valve element and the lower end of this rod projects out from the plunger 10 and passes through a hole in a downwardly projecting part 36 of a plate 38 extending over the major portion of the under side of the diaphragm. A nut 4@ is provided on the lower portion of the rod 34 so that downward movement of the plate 38 causes a corresponding downward movement of the plunger 34 and valve element 2S against the bias of spring 30 to unseat the valve element 25.

The drawing shows the'valve in its normal closed position with no open passage between the reservoir chamber 3 and the atmosphere, above the Valve. lf the prop is extended and the pressure in the reservoir chamber drops the pressure on the under side of the diaphragm also drops as compared with the pressure on the upper sikle thereof which is at normal atmospheric pressure due to the air vent 44. The diaphragm thus flexes downwardly causing a downward displacement ofthe plate 38 and rod 34. As the shoulder or lip 12 of the plungerlll is engaged on its seat 14 the plunger 10'cannot move downwardly and the plate and inner edge of the diaphragm remain in the position shown in the drawing. The upper side of the diaphragm thus separates from the underside of plate 20. The downward movement of the rod 34 and valve element against the pressure of the spring 30, opens the passage or bore through the plunger 10 to atmosphere and air can flow down the bore of the plunger 10 around the element 25 and rod 34 which thus constitutes an inlet passage, to the upper side of the portion 36 of the plate 38 from whence it can flow through an Y aperture 46 in this plate to the reservoir. When the pressure in the reservoir rises to about atmospheric the diaphragm is no longer subjected to a negative pressure and the spring returns the valve 25 on to its seating to close the inlet passage and to'bring the diaphragm back to its normal horizontal position with Vboth passages closed.

When the pressure in the reservoir 3 rises due to contraction of the prop, the central portion of the diaphragm exes upwardly causing an upward movement of the plate 20 and valve plunger element 10 within the main body portion of the valve and against the bias of the spring 23. This upward movement of the plunger unseats its lip 12 from thek seating 14 to open communication between the bore of the plunger and the atmosphere through outlets 16. Thus air can flow from the reservoir chamber 3 through the opening 46 in the lower plate 38 up the bore of the plunger around the rod 34 and out through openings 16 past the seating ring 14 to atmosphere. This passage constitutes the outlet passage. The second valve element 25 moves up with the irst valve plunger element '10 and remains seated to close part of the inlet passage a minimum force of 5 pounds eort may be required to open them. in this case the spring force tending to keep the valve elements on their seatings to close the inlet and outlet passages and to prevent fluid from flowingout from the vented chamber, may be so strong that the valve elements will not become unseated during any normal rough usage to which the prop would be likely to be subjected. For example it has been found that when a 60 pound prop incorporating such a Valve is dropped repeatedly from a height of f our feet, that the valve has rremained sealed and no uid has'escaped from the reservoir. This is because the use of weak springs',pwhich are necessary it only a small operating area is acted upon by the pressure in the vented chamber, are obviated without the use of any very heavy valve part.

It will be appreciated that a single valve elem,nt can be provided, movement in either direction from a normal position due to tlexing of the diaphragm being designed to open a passage through the valve. Furthermore a bellows device may be used instead of the diaphragm illustrated in the drawing.

We claim:

l. A valve for a vented chamber of a hydraulic: prop or jack having at least one passage passing through it comprising valve elements biassed normally to close said passage, a exible diaphragm having two side faces, said diaphragm being so mounted that it may ex in either direction perpendicular to said faces from a mid-position in response to a difference in the pressure acting on said facm, said diaphragm being connected to said valve elements so that the liexure of said diaphragm in either direction from the mid-position causes. one of said valve elements to be unseated to open the passage through the valve; said valve having separate inlet and outlet pas-V sages passingthrough it, and a valve element being provided for each of said passages, movement of the diament of the diaphragm in the other direction from the midposition causing the valve element in the other passage to be unseated, the valve element in said one passage being formed by a tube which is attached to the diaphragm, said tube having an outwardly extending lip which closes said one passage, the bore of said tube providing a portion of the other passage which is closed by the valve element in said other passage which is positioned within the tube. i

2. A valve according to claim 1 in which the valve element in said other passage has a stem projecting out from the bore of the tube and a plate is provided eX- tending across one of the faces of the diaphragm and connected to the stern of the latter valve element.

References Cited in the file of this patent UNITED STATESv PATENTS 1,229,885 Chadwick June 12, 1917 1,344,919 Marr June 29, 1920 1,644,101 Anderson Oct. 4, 1927 1,656,430 Dybens Jan. 17, 1928V 1,745,024 Malone Jan. 28, 1930 2,619,106 Wilkerson Nov. 25, 1952 '2,621,631 Dowty Dec. 16, 1952 2,690,757 Orchowski Oct. 5, 1954 2,844,165 Morse July 22, 1958 2,954,740 Wilkenloh et al Oct. 4, 1960 FOREIGN PATENTS 6,690 Great Britain Mar. 19,1902

Claims

1. A VALVE FOR A VENTED CHAMBER OF A HYDRAULIC PROP OR JACK HAVING AT LEAST ONE PASSAGE PASSING THROUGH IT COMPRISING VALVE ELEMENTS BIASSED NORMALLY TO CLOSE SAID PASSAGE, A FLEXIBLE DIAPHRAGM HAVING TWO SIDE FACES, SAID DIAPHRAGM BEING SO MOUNTED THAT IT MAY FLEX IN EITHER DIRECTION PERPENDICULAR TO SAID FACES FROM A MID-POSITION IN RESPONSE TO A DIFFERENCE IN THE PRESSURE ACTING ON SAID FACES, SAID DIAPHRAGM BEING CONNECTED TO SAID VALVE ELEMENTS SO THAT THE FLEXURE OF SAID DIAPHRAGM IN EITHER DIRECTION FROM THE MID-POSITION CAUSES ONE OF SAID VALVE ELEMENTS TO BE UNSEATED TO OPEN THE PASSAGE THROUGH THE VALVE; SAID VALVE HAVING SEPARATE INLET AND OUTLET PASSAGES PASSING THROUGH IT, AND A VALVE ELEMENT BEING PROVIDED FOR EACH OF SAID PASSAGES, MOVEMENT OF THE DIAPHRAGM IN ONE DIRECTION FROM THE MID-POSITION CAUSING THE VALVE ELEMENT IN ONE PASSAGE TO BE UNSEATED AND MOVEMENT OF THE DIAPHRAGM IN THE OTHER DIRECTION FROM THE MIDPOSITION CAUSING THE VALVE ELEMENT IN THE OTHER PASSAGE TO BE UNSEATED, THE VALVE ELEMENT IN SAID ONE PASSAGE BEING FORMED BY A TUBE WHICH IS ATTACHED TO THE DIAPHRAGM, SAID TUBE HAVING AN OUTWARDLY EXTENDING LIP WHICH CLOSES SAID ONE PASSAGE, THE BORE OF SAID TUBE PROVIDING A PORTION OF THE OTHER PASSAGE WHICH IS CLOSED BY THE VALVE ELEMENT IN SAID OTHER PASSAGE WHICH IS POSITIONED WITHIN THE TUBE.