GB1569854A

GB1569854A - Combined relief valve and non-return valve

Info

Publication number: GB1569854A
Application number: GB29781/77A
Authority: GB
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 1976-07-15
Filing date: 1977-07-15
Publication date: 1980-06-25
Also published as: JPS5310133A; FR2358604B1; PL198838A1; BR7703340A; FR2358604A1; YU141477A; IT1085842B; PL118171B1; DE2631922A1

Description

(54) A COMBINED RELIEF VALVE AND NON-RETURN VALVE (71) We, LINDE AKTIENGESELLSCHAFT, a German Company, of Abraham-Lincoln Strasse 21, D162 Wiesbaden, Federal Republic of Germany, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement:- This invention relates to a combined relief valve and non-return valve.

A so-called servo relief valve, in which the space behind the spring-loaded slide element is connected across a throttling point to the connection leading to the pressure which may have to be restricted and in which a pressure limiting valve is connected to this space, is known from 'Olhydraulik and Pneumatik", 1957, No. 1, page 22, figure 35.

In another known valve arranged for two directions of operation two slide elements are provided, each of which has a throttling point, the two slide elements being disposed co-axially one behind the other and the connection between the two channels being produced by the opening of the springloaded main slide element. In the case of loading in the one direction only the front face of the main slide element is affected, with loading in the other direction the second slide element is moved and exerts a force upon the main slide element which leads to this opening. In this case also a pre-setting valve is disposed behind the main slide element (United States Patent Specification No. 3,090,398). With this valve also under pressure loading there is a continuous fluid seepage at the periphery of the main slide element.

It is the principal object of the present invention to create a valve with which energy losses and heating of the oil with a closed valve are avoided at least significantly reduced and which ensures a certain rapid response.

Accordingly, the present invention consists in a hydraulic valve operable both as a safety relief valve and as a non-return valve, said valve comprising a hollow body having a longitudinal axis and first and second access means by way of which pressurised fluid can reach the interior of said body, said first access means being arranged coaxially with said body and said second access means being arranged transversely of said axis, a main slide element being spring-urged at all times towards a valve seat associated with said first access means, a chamber at that end of said element which is remote from said valve seat, passage means in said element establishing communication at all times between said chamber and said second access means, and a spring-loaded valve element of which a first portion extends into said passage means and provides throttled fluid communication between said second access means and said chamber, said valve element being operable by fluid pressure to regulate the exhaust of said chamber to a fluid reservoir, said second access means being intended for connection to the source of the fluid pressure whose maximum level is to be controlled and said first access means being intended for connection to the source of fluid pressure in relation to which the valve may be needed to act as a non-return valve, the outside diameter of that portion of said main slide element is in sliding contact with said hollow body being greater than the diameter of said valve seat, whereby an annular differential area is formed which is loadable by way of said second access means by the fluid pressure whose maximum level is to be controlled.

Preferably, said spring-loaded valve element includes a second portion which is urged at all times by a spring to close a passageway which, when open, places said chamber in communication with said fluid reservoir, said first portion of the valve element comprising an enlarged free end which is remote from said second portion and which is accommodated within said passage means and which therewith creates an annular restriction which provides said throttled fluid communication, the arrangement being such that the face of said free end is always subjected to the fluid pressure prevailing at said second access means. In one embodiment, said enlarged free end and the passage means in which said enlarged free end is accommodated are of rightcylindrical form. In one alternative embodiment, said enlarged free end and the passage means in which said enlarged free end is accommodated are of frusto-conical form, the respective parts of said enlarged free end and said passage means which are of least diameter being nearer to said second portion of the spring-loaded valve that the respective parts thereof which are of greatest diameter.

Said passage means may consist of a first passage which extends axially but not completely through the main slide element, and a second passage which is in fluid communication with the first passage and which extends transversely of said main slide element. The second passage opens into an area which lies behind the annular zone of the main slide element which butts against the valve seat when the valve is in its closed position.

The present invention will now be more particularly described with reference to the accompanying diagrammatic drawing which illustrates one exemplary embodiment of valve according to the invention. In fact, two valves constructed, arranged and operable in accordance with the present invention are illustrated in the drawing, one in the opened condition thereof and one in the closed condition thereof, the two valves being disposed in a circuit of a closed-circuit hydrostatic transmission. A pump 1 is connected in a closed circuit to a hydro-motor 4 through the two lines 2 and 3. The shaft of the pump 1 carries a feed pump 5, which delivers hydraulic fluid (oil) into a line 6 which is protected by a low-pressure relief valve 7. The line 6 is connected with a line 8 which, in turn, is connected across a first valve 9 with a line 10 and across a second valve 11 with a line 12.

The duty of the valves 9 and 11 is as follows :- if the line 2 is the delivery line and if the line 3 is the return line of the transmission, then the valve 11 has to protect the line 2 against unacceptable pressure. The flow provided from the supply pump 5 has to pass across the valve 9, acting in this case as a non-return valve and thence through the line 10 into the low-pressure line 3. Since in this postulated flow direction the valve 9 functions as a non-return valve and with the opening of the valve 11 as a result of too high a pressure in the line 2, the oil flowing away across the valve 11 likewise flows into the line 8 and from there will be led away across the valve 9 into the lowpressure line 3.

Conversely, if the line 3 is carrying the high pressure and if the line 2 is the return flow line, then the valve 11 acts as a nonreturn valve across which the oil delivered from the supply pump 5 is fed into the low-pressure line 2 and where appropriate also the oil flowing away across the valve 9 is fed into the line 2, the valve 9 being connected to the line 3 as a pressure relief valve which protects the line 3 against unaccpetable excessive pressure.

The frame line 13 drawn in broken line indicates that the valves 9 and 11 and also the feed pump 5 are disposed in the casing of the pump 1. Each of the two valves 9 and 11 is in the form of a cartridge element 14 which is screwed into a threaded bore in a part 15 of the pump casing. For assembly reasons, an inner insert 16 is screwed into the appropriately threaded cartridge element 14, which insert is provided in its lower part (as seen in the drawing) with an annular edge seat 17 against which the corresponding seating face of a main slide element 18 can bear.

A central drilled aperture 19 in the inner insert 16 communicates with an aperture 20 with which the line 8 is also in com.

munication.

Within the inner insert 16 the main slide element 18 is movable away from the seat 17 against the force of a spring 21 and said element 18 is provided on its periphery with circumferential grooves 22 whose function is not only to accommodate the oil which passes between the radially inner surface of the insert 16 and the radially outer surface of the element 18 in a uniformly distributed manner but also to improve lubrication and reduce the leakage current. The diameter of the element 18 in its cylindrical zone, which zone has sliding contact with the inner insert 16, is greater than the diameter of the seat 17, so that in this way, a differential area is constituted on the main slide element 18. Pressure can reach this differential area through the passageway 23 in the inner insert 16 and the drilling 24 in the casing part 15. The line 10 is connected to a passageway 24 which is associated with the valve 9 and the line 12 is connected to a corresponding passageway 24 which is associated with the valve 11. In the element 18 there is a transverse passageway 25 which at one end opens into a zone on the periphery of the element 18 which is always in communication with the drilling 23. At substantially its mid-length point, the passageway 25 opens into an axial passageway 26 by way of which the passageway 25 is placed in communication with a space or chamber 27 which is definel by surfaces of said element 18 on the one hand and by a sealing plate 28 on the other hand. The inner insert 16 is screwed so firmly into the element 14 up against the sealing plate 28, which in turn is forced firmly against a shoulder which forms part of the cartridge element 14, that these parts are tightly joined together. In the sealing plate 28 there is a passageway 29 which can be closed by a servo valve element 30 which contacts a plate 31. Said plate 31 supports one end of a spring 32 whose other end is supported against a further spring plate 33, the location of which (axially of the element 14) is adjustable by means of a screw-threaded shank 34 which is integral with said plate 33 and which meshes with a locking nut 35. The element 30 is provided with an extension 36 which penetrates into the passageway 26 and which terminates in an enlarged free end, the outside diameter of said free end being such in relation to the inside diameter of the passageway as to form an annular flow-restrictor.

In the drawing, the valve 19 is illustrated in its opened position as a non-return valve, that is, in the position thereof in which the element 18 is pushed back against the force of the spring 21, whereas the valve 11 is illustrated in its closed position, that is, in the position thereof in which the element 18 bears firmly against the seat 17.

The manner of functioning is as follows:- if the fluid pressure in the passageway 19 is higher than that in the passageway 24, then this pressure acts upon the domed lowermost face of the element 18 in the immediate vicinity of the seat 17. In view of the fact that, at the rear of the element 18 and by way of the passageways 25, 26, the same pressure exists as in the passageway 24, the element 18 is pushed back against the force of the compression spring 21 through the action of the pressure in the passageway 19 and thus establishes communication between the passageway 19 and the passageway 24. When the pressure in the passageway 24 rises above the pressure in the passageway 19, the spring 21 moves the element 18 back into the closed position thereof.

If there is a high pressure in the passageway 24 which lies below the highest permissible fluid pressure, then this pressure communicates through the passageways 25 and 26 with the chamber 27 behind the element 18. Thus, the same fluid pressure prevails at the two ends of the clearance around the periphery of the main slide plunger 18 and consequently, no seepage losses occur by way of this clearance. If the pressure in the passageways 24, 25 reaches the highest permissible limit value, then this pressure also acts upon the enlarged end of the extension 36 of the valve element 30, thereby opening said element 30. This allows the pressurised fluid to flow out of the chamber 27 to a discharge channel 38 and thus to an unpressurised storage container 39. Between the cylindrical wall of the passageway 26 and the cylindrical periphery of the extension 36 an annular restriction is constituted which has the effect that, with the discharge of pressurised fluid past the element 30, the pressure in the chamber 27 falls very rapidly because less fluid is able to pass through said restriction than is able to be discharged by way of said element 30. This very rapid drop of the fluid pressure in the space 27 has the effect that, as a result of the area differential between parts of the element 18, said element 18 is moved against the force of the spring 21, thereby once again establishing communication between the passageway 24 and the passageway 19, so that oil can flow out of the passageway 24.

If the increased production cost is acceptable, the passageway 26 can be given a taper such that the portion of greatest diameter is farthest away from the chamber 27 and the enlarged end of the extension 36 can be given a complementary taper, this having the result that when the valve element 30 starts to open against the force of the spring 32, the annular restriction between said wall of the passageway 26 and the periphery of the enlarged end of the extension 36 is at first narrowed until theelement 18 has, in turn. moved sufficiently.

Such complementary tapers therefore have the effect of ensuring, in a very positive manner, that the necessary very rapid drop in fluid pressure is obtained.

Thus, it will be appreciated that, with the valve described above, no flow losses occur. The servo valve element 30 opens very rapidly because the enlarged end of the extension 36 thereof is exposed to pressure prevailing in the passageway 25. Moreover, said element 30 consists of relatively few simple parts. The adustment of the preloading force of the spring 32 and thus the response point of the servo valve 29, 30 can be effected very simply. The annular restriction between the wall of the passageway 26 and the periphery of the enlarged end of the extension 36 is easier to produce and to keep clear than a fine drilled passageway.

WHAT WE CLAIM IS: 1. A hydraulic valve operable both as a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. opens into a zone on the periphery of the element 18 which is always in communication with the drilling 23. At substantially its mid-length point, the passageway 25 opens into an axial passageway 26 by way of which the passageway 25 is placed in communication with a space or chamber 27 which is definel by surfaces of said element 18 on the one hand and by a sealing plate 28 on the other hand. The inner insert 16 is screwed so firmly into the element 14 up against the sealing plate 28, which in turn is forced firmly against a shoulder which forms part of the cartridge element 14, that these parts are tightly joined together. In the sealing plate 28 there is a passageway 29 which can be closed by a servo valve element 30 which contacts a plate 31. Said plate 31 supports one end of a spring 32 whose other end is supported against a further spring plate 33, the location of which (axially of the element 14) is adjustable by means of a screw-threaded shank 34 which is integral with said plate 33 and which meshes with a locking nut 35. The element 30 is provided with an extension 36 which penetrates into the passageway 26 and which terminates in an enlarged free end, the outside diameter of said free end being such in relation to the inside diameter of the passageway as to form an annular flow-restrictor. In the drawing, the valve 19 is illustrated in its opened position as a non-return valve, that is, in the position thereof in which the element 18 is pushed back against the force of the spring 21, whereas the valve 11 is illustrated in its closed position, that is, in the position thereof in which the element 18 bears firmly against the seat 17. The manner of functioning is as follows:- if the fluid pressure in the passageway 19 is higher than that in the passageway 24, then this pressure acts upon the domed lowermost face of the element 18 in the immediate vicinity of the seat 17. In view of the fact that, at the rear of the element 18 and by way of the passageways 25, 26, the same pressure exists as in the passageway 24, the element 18 is pushed back against the force of the compression spring 21 through the action of the pressure in the passageway 19 and thus establishes communication between the passageway 19 and the passageway 24. When the pressure in the passageway 24 rises above the pressure in the passageway 19, the spring 21 moves the element 18 back into the closed position thereof. If there is a high pressure in the passageway 24 which lies below the highest permissible fluid pressure, then this pressure communicates through the passageways 25 and 26 with the chamber 27 behind the element 18. Thus, the same fluid pressure prevails at the two ends of the clearance around the periphery of the main slide plunger 18 and consequently, no seepage losses occur by way of this clearance. If the pressure in the passageways 24, 25 reaches the highest permissible limit value, then this pressure also acts upon the enlarged end of the extension 36 of the valve element 30, thereby opening said element 30. This allows the pressurised fluid to flow out of the chamber 27 to a discharge channel 38 and thus to an unpressurised storage container 39. Between the cylindrical wall of the passageway 26 and the cylindrical periphery of the extension 36 an annular restriction is constituted which has the effect that, with the discharge of pressurised fluid past the element 30, the pressure in the chamber 27 falls very rapidly because less fluid is able to pass through said restriction than is able to be discharged by way of said element 30. This very rapid drop of the fluid pressure in the space 27 has the effect that, as a result of the area differential between parts of the element 18, said element 18 is moved against the force of the spring 21, thereby once again establishing communication between the passageway 24 and the passageway 19, so that oil can flow out of the passageway 24. If the increased production cost is acceptable, the passageway 26 can be given a taper such that the portion of greatest diameter is farthest away from the chamber 27 and the enlarged end of the extension 36 can be given a complementary taper, this having the result that when the valve element 30 starts to open against the force of the spring 32, the annular restriction between said wall of the passageway 26 and the periphery of the enlarged end of the extension 36 is at first narrowed until theelement 18 has, in turn. moved sufficiently. Such complementary tapers therefore have the effect of ensuring, in a very positive manner, that the necessary very rapid drop in fluid pressure is obtained. Thus, it will be appreciated that, with the valve described above, no flow losses occur. The servo valve element 30 opens very rapidly because the enlarged end of the extension 36 thereof is exposed to pressure prevailing in the passageway 25. Moreover, said element 30 consists of relatively few simple parts. The adustment of the preloading force of the spring 32 and thus the response point of the servo valve 29, 30 can be effected very simply. The annular restriction between the wall of the passageway 26 and the periphery of the enlarged end of the extension 36 is easier to produce and to keep clear than a fine drilled passageway. WHAT WE CLAIM IS:

1. A hydraulic valve operable both as a

safety relief valve and as a non-return valve, said valve comprising a hollow body having a longitudinal axis and first and second access means by way of which pressurised fluid can reach the interior of said body, said first access means being arranged coaxially with said body and said second access means being arranged transversely of said axis, a main slide element being springurged at all times towards a valve seat associated with said first access means, a chamber at that end of said element which is remote from said valve seat, passage means in said element establishing communication at all times between said chamber and said second access means, and a spring-loaded valve element of which a first portion extends into said passage means and provides throttled fluid communication between said second access means and said chamber, said valve element being operable by fluid pressure to regulate the exhaust of said chamber to a fluid reservoir, said second access means being intended for connection to the source of the fluid pressure whose maximum level is to be controlled and said first access means being intended for connection to the source of fluid pressure in relation to which the valve may be needed to act as a non-return valve, the outside diameter of that portion of said main slide element which is in sliding contact with said hollow body being greater that the diameter of said valve seat, whereby an annular differential area is formed which is loadable by way of said second access means by the fluid pressure whose maximum level is to be controlled.

2. A hydraulic valve as claimed in Claim 1, wherein said spring-loaded valve element includes a second portion which is urged at all times by a spring to close a passageway which, when open, places said chamber in communication with said fluid reservoir, said first portion of the valve element comprising an enlarged free end which is remote from said second portion and which is accommodated within said passage means and which therewith creates an annular restriction which provides said throttled fluid communication, the arrangement being such that the face of said free end is always subjected to the fluid pressure prevailing at said second access means.

3. A hydraulic valve as claimed in Claim 2, wherein said enlarged free end and the passage means in which said enlarged free end is accommodated are of right-cylindrical form.

4. A hydraulic valve as claimed in Claim 2, wherein said enlarged free end and the passage means in which said enlarged free end is accommodated are of frusto-conical form, the respective parts of said enlarged free end and said passage means which are of least diameter being nearer to said second portion of the spring-loaded valve than the respective parts thereof which are of greater diameter.

5. A hydraulic valve as claimed in any one of the preceding Claims, wherein said passage means consists of a first passage which extends axially of but not completely through the main slide element, and a second passage which is in fluid communication with the first passage and which extends transversely of said main slide element

6. A hydraulic valve as claimed in Claim 5, wherein the second passage opens into an area which lies behind the annular zone of the main slide element which butts against the valve seat when the valve is in its closed position.

7. A hydraulic valve constructed, arranged and operable substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.