GB1583450A

GB1583450A - Valve for a pressurised fluid system

Info

Publication number: GB1583450A
Application number: GB3097677A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-07-22
Filing date: 1977-07-22
Publication date: 1981-01-28

Description

(54) A VALVE FOR A PRESSURIZED FLUID SYSTEM (71) - I INGVARD FASTH, of Swedish nationality, of Vretvägen 22, S-352 47 Växjö Sweden, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a valve for a pressurized fluid system. In use the valve is intended to close in response to pressure in the system falling below a certain level. The valve may be used in a hydraulic system in a hoisting crane, a contract machine or other machines with a hydraulically operated member or tool. For-example the valve may be used in a hydraulic system for operating the jib or boom of an excavator.

In a machine operated by pressurized fluid, breakage of a fluid line causes loss of pressure and can result in the operating member or tool falling causing serious personal injury and damage to property.

Therefore in a machine having a pressurized fluid system which is under pressure when the machine is working it would be desirable to include in the fluid system a valve which closes when a fluid line breaks causing loss of pressure. The valve would serve to isolate the portion of the system in which the breakage occurs from the portion connected to the first-mentioned portion through the valve. Thus the consequences of the breakage could be reduced. This is of particular importance in contract machines which have hydraulic systems which operate under high pressures and contain large quantities of hydraulic fluid. Such a machine is an excavator where the valve could be effective in preventing the jib or boom falling if breakage of a hydraulic-line occured.

A known valve for a pressurized fluid system and which is intended to close when a line breakage occurs is actuated by the flow rate of the fluid. Such a valve is quite satisfactory for a machine such as a crane where the fluid operated part is driven at a constant speed but is unsatisfactory where the flow rate of the fluid varies during normal operation e.g. in an excavator where the fluid system serves to raise and lower the jib or boom. Large fluctuations in pressure in the system may also adversely affect the operation of such a valve.

Also the response of the valve when a tube breakage occurs tends to be slow, allowing the falling operating member or tool to attain an excessive speedy An object of the present invention is to provide a valve for a pressurized fluid system, the valve remaining open even when large pressure fluctuations occur in the system provided that the pressure does not fall below a certain level and closing rapidly, but preferably not abruptly, when the pressure does fall below said certain level.

In accordance with the present invention, there is provided a valve for installation in a pressurized fluid system, the valve being adapted to stay open when the pressure in the system remains relatively high and to close when the pressure in the system is substantially reduced, the valve comprising: a valve body having an opening for communication with a portion of the pressurized fluid system, a pressure chamber being defined in the valve body; a sleeve accommodated in the valve body and movable between a first position in which the opening is in communication with the pressure chamber whereby the valve - is open, and a second position in which the opening is out of communication with the pressure chamber whereby the valve is closed; a piston or plunger within the valve body and coaxial with the sleeve, the piston or plunger being movable between a first position and a second position, the piston or plunger being arranged to be acted upon by the pressure of pressurized fluid in the pressure chamber to be urged towards its first position; and locking means for locking the sleeve in its first position; wherein when movement of the piston or plunger to its second position in response to a substantial reduction of pressure in the pressure chamber occurs, the locking means releases the sleeve and the sleeve moves to its second position.

A valve embodying the invention is described below by way of example with reference to the accompanying drawings, wherein: Figure 1 shows in side view and partly in section the valve in an open condition; Figure 2 shows in side view and partly in section the valve in a closed condition.

Referring to Figure 1, the valve shown in the drawings comprises a cylindrical body 1 and end members 2 and 3. The end member 2 has an external screw thread engaging an internal screw thread in one end of the body 1. The end member 3 has an internal screw thread engaging an external screw thread on the other end of the body 1. A pressure chamber 4 is defined with the valve body 1. When the valve is in an open condition the pressure chamber 4 communicates, through an opening 5, in the wall of the valve body 1, with a socket 6 on the outside of the valve body. The pressure chamber 4 also communicates through an opening 7 in the end member 2 with a socket 8 on the outside of the end member. The sockets 6 and 8 may be screw threaded for connections to be made thereto.

A valve sleeve member 9 is accommodated within the valve body 1 and a plunger or piston 10 is accommodated within the valve sleeve member 9 and is coaxial therewith.

The wall of the sleeve member 9 has at least one through hole 11 formed therein, the or eacll hole 11 receiving a ball 12 constituting a locking member. A groove 13 is formed in the internal surface of the valve body 1. When the valve is in an open condition, the ball or balls 12 are held engaged in the groove 13 by the plunger 10.

The plunger 10 comprises a portion 16 adjaccnt the pressure chamber 4 and a portion 20. The portion 16 has a peripheral surface 17 which is a close fit in the valve sleeve member 9. The peripheral surface of the portion 20 may also be a close fit in the valve sleeve member 9. Between the portions 16 and 20 of the plunger 10 is an annular groove 18 receiving a sealing ring 19, preferably on O-ring. The distance measured radially of the valve body 1, between the peripheral surface of the portion 20 of the plunger 10 and the bottom of the groove 13 is substantially equal to the diameter of the or each ball 12. The plunger 10 also comprises a portion 21 of reduced cross section relative to the portions 16 and 20.The distance, measured radially of the valve body 1, between the inner surface of the valve body 1 and the surface of the portion 21 is equal to or greater than the diameter of the or each ball 12.

Referring to Figure 2, a spring 14 is disposed between the valve sleeve member 9 and the end wall 3 and serves to bias the valve sleeve member towards the end wall 2. An insert 15 is held against the body 1 by the end wall 3, the spring 14 acting between the insert 15 and the valve sleeve member 9.

A spring 22 is disposed between the plunger 10 and an adjusting screw 25 iocated in the insert 15 and serves to bias the plunger 10 towards the end wall 2.

One end of the spring 22 is received in a recess 22 in the plunger 10 and the other end of the spring is received in a sleeve forming part of the insert 15.

The valve is used in a hydraulic system in for example a crane, an industrial lift truck, a loading truck or an excavator between a hydraulic pump serving as a source of fluid pressure and a hydraulic sleeve cylinder of a load-bearing operating member or tool for example a jib of an excavator.

The socket 6 is connected to the hydraulic sleeve cylinder. the connection between the socket and the hydraulic cylinder being short in length. The socket 8 is connected to the hydraulic pump via a controller or hand-operable valves. The connection between the socket 8 and the pump may be relatively long.

The valve is normally held in its open condition (as shown in Figure 1) by the hydraulic pressure in the pressure chamber 4 acting on the plunger 10, the pressure chamber thus being in direct communication with the hydraulic cylinder, the sleeve 9 and the plunger 10 being in respective first positions. The plunger 10 is held in its first position in spite of pressure fluctuations in the hydraulic system provided that the pressure does not fall below a predetermined level.

When the pressure in the system suddenly drops, because of for example a breakage in a hydraulic line of the hydraulic system and falls below a predetermined level, the plunger 10 is displaced towards the end wall 2 by the spring 23. When the plunger reaches its second position, the portion 21 of the plunger is in alignment with the ball or balls 12 and the sleeve 9, which is acted on by the spring 14, causes the ball or balls 12 to be displaced from the groove 13 allowing axial movement of the valve sleeve member 9. The ball or balls 12 remain engaged with the valve sleeve member 9 and engage with the reduced diameter portion 21 of the plunger 10. The valve sleeve member 9 and the plunger 10 are then displaced by the spring towards the end member 2 to close the opening 5. The valve is then in its closed condition (as shown in Figure 2), the valve sleeve member 9 being in its second position.

In the manner described above, a fast and an effective closure of communication between the part of the hydraulic system between the valve and the pump and the part of the hydraulic system between the valve and the hydraulic cylinder is achieved whereby the pressure in the hydraulic cylinder can be maintained if the breakage was between the valve and the pump.

The drop in pressure in the hydraulic system causes the load-bearing member or tool to start to fall and the closure of the valve (assuming the breakage is between the valve and the pump) caused the fall to be arrested. However, the valve is constructed such that the load-bearing operating mem ber does not stop suddenly, a certain damp ing being achieved.

The damping occurs because hydraulic fluid has to be expelled from the pressure chamber 4 as the valve sleeve member 9 and the plunger 10 move to their second positions and the valve sleeve member closed the opening 5. The degree of damping can be controlled by selection of the dimensions and the strength of the spring 14 and by selection of the insert 15. It may be desirable that the spring 14 is substantially fully èxtended when the valve sleeve member 9 reaches its second position. The degree of damping is also dependent on the dimensions of the pressure chamber 4 and can be adjusted by altering the radius of the pressure chamber.

The predetermined pressure level, below which the valve closes, can be adjusted by means of the adjusting screw 25.

A valve such as described above and shown in the drawings was used in an experiment. The hydraulic pressure fluctuated up to 145 kilograms (319.73 Ibs.). The predetermined pressure level was varied between 2 kilograms (4.41 lbs.) and 9 kilograms (19.85 lbs.). The valve remained open despite the pressure fluctuations provided that the pressure did not fall below the predetermined level. When a hydraulic line breakage was induced the valve assumed its closed condition.

The end wall 2 may be of size and shape as indicated by reference numeral 26, the end wall 2 having like the end member 3, an internal screw thread engaging an external screw thread on the body 1.

The valve sleeve member 9 is a close sliding fit in the valve body 1 and may have a peripheral groove (as shown in the draw ings) to receive a sealing ring, preferably an O-ring to prevent hydraulic fluid leak ing into the part of the valve body contain ing the ball or balls 12 and the springs 14 and 23.

The valve may be used in pneumatic and hydraulic installations having fluid in pres sure operated members or tools. The valve may also be used in dish washing and washing machines for preventing water damage.

WHAT I CLAIM IS: 1. A valve for installation in a pres surized fluid system, the valve being adapted to stay open when the pressure in the system remains relatively high and to close when the pressure in the system is substantially reduced, the valve comprising: a valve body having an opening for commuication with a portion of the pressurized fluid system, a pressure chamber being defined in the valve body; a sleeve accommodated - in the valve body and movable between a first position in which the opening is in cqkh- munication with the pressure chamber whereby the valve is open, and a second position in which the opening is out of communication with the pressure chamber whereby the valve is closed; a piston or plunger within the valve body and coaxial with the sleeve, the piston or plunger being movable between a first position and a second position, the piston or plunger being arranged to be acted upon by the pressure of pressurized fluid in the pressure chamber to be urged towards its first position; and locking means for locking the sleeve in its first position; wherein when movement of the piston or plunger to its second position in response to a substantial reduction of pressure in the pressure chamber occurs, the locking means releases the sleeve and the sleeve moves to its second position.

2. A valve according to claim 1, wherein the locking means is received within the sleeve and engages with the valve body when the sleeve is in its first position.

3. A valve according to claim 2, wherein the locking means is kept in engagement with the valve body by means of the piston or plunger when the piston or plunger and the sleeve are in their first positions.

4. A valve according to any preceding claim, wherein the sleeve has one or more holes which receive the locking means and the valve body has a groove which receives the locking means when the sleeve is locked in its first position, the combined radial dimension of the hole or any one of the holes and the groove being substantially equal to the radial extent of the locking means.

5. A valve according to any preceding claim, wherein the piston or plunger is a close fit within the sleeve.

6. A valve according to any preceding claim, wherein the piston or plunger in duds a portion which has a radially outer surface such that the radial distance between said radially outer surface and the valve body is equal to at least the radial extent of the locking means, said portion being in radial alignment with the locking means when the piston or plunger is in its second position.

7. A valve according to any preceding claim, wherein the locking means comprises at least one ball.

8. A valve according to any preceding claim, wherein the locking means comprises

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Claims

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cylinder can be maintained if the breakage was between the valve and the pump.

The drop in pressure in the hydraulic system causes the load-bearing member or tool to start to fall and the closure of the valve (assuming the breakage is between the valve and the pump) caused the fall to be arrested. However, the valve is constructed such that the load-bearing operating mem ber does not stop suddenly, a certain damp ing being achieved.

The damping occurs because hydraulic fluid has to be expelled from the pressure chamber 4 as the valve sleeve member 9 and the plunger 10 move to their second positions and the valve sleeve member closed the opening 5. The degree of damping can be controlled by selection of the dimensions and the strength of the spring

14 and by selection of the insert 15. It may be desirable that the spring 14 is substantially fully èxtended when the valve sleeve member 9 reaches its second position. The degree of damping is also dependent on the dimensions of the pressure chamber 4 and can be adjusted by altering the radius of the pressure chamber.

The predetermined pressure level, below which the valve closes, can be adjusted by means of the adjusting screw 25.

A valve such as described above and shown in the drawings was used in an experiment. The hydraulic pressure fluctuated up to 145 kilograms (319.73 Ibs.). The predetermined pressure level was varied between 2 kilograms (4.41 lbs.) and 9 kilograms (19.85 lbs.). The valve remained open despite the pressure fluctuations provided that the pressure did not fall below the predetermined level. When a hydraulic line breakage was induced the valve assumed its closed condition.

The end wall 2 may be of size and shape as indicated by reference numeral 26, the end wall 2 having like the end member 3, an internal screw thread engaging an external screw thread on the body 1.

The valve sleeve member 9 is a close sliding fit in the valve body 1 and may have a peripheral groove (as shown in the draw ings) to receive a sealing ring, preferably an O-ring to prevent hydraulic fluid leak ing into the part of the valve body contain ing the ball or balls 12 and the springs 14 and 23.

The valve may be used in pneumatic and hydraulic installations having fluid in pres sure operated members or tools. The valve may also be used in dish washing and washing machines for preventing water damage.

WHAT I CLAIM IS: 1. A valve for installation in a pres surized fluid system, the valve being adapted to stay open when the pressure in the system remains relatively high and to close when the pressure in the system is substantially reduced, the valve comprising: a valve body having an opening for commuication with a portion of the pressurized fluid system, a pressure chamber being defined in the valve body; a sleeve accommodated - in the valve body and movable between a first position in which the opening is in cqkh- munication with the pressure chamber whereby the valve is open, and a second position in which the opening is out of communication with the pressure chamber whereby the valve is closed; a piston or plunger within the valve body and coaxial with the sleeve, the piston or plunger being movable between a first position and a second position, the piston or plunger being arranged to be acted upon by the pressure of pressurized fluid in the pressure chamber to be urged towards its first position; and locking means for locking the sleeve in its first position; wherein when movement of the piston or plunger to its second position in response to a substantial reduction of pressure in the pressure chamber occurs, the locking means releases the sleeve and the sleeve moves to its second position.
2. A valve according to claim 1, wherein the locking means is received within the sleeve and engages with the valve body when the sleeve is in its first position.
3. A valve according to claim 2, wherein the locking means is kept in engagement with the valve body by means of the piston or plunger when the piston or plunger and the sleeve are in their first positions.
4. A valve according to any preceding claim, wherein the sleeve has one or more holes which receive the locking means and the valve body has a groove which receives the locking means when the sleeve is locked in its first position, the combined radial dimension of the hole or any one of the holes and the groove being substantially equal to the radial extent of the locking means.
5. A valve according to any preceding claim, wherein the piston or plunger is a close fit within the sleeve.
6. A valve according to any preceding claim, wherein the piston or plunger in duds a portion which has a radially outer surface such that the radial distance between said radially outer surface and the valve body is equal to at least the radial extent of the locking means, said portion being in radial alignment with the locking means when the piston or plunger is in its second position.
7. A valve according to any preceding claim, wherein the locking means comprises at least one ball.
8. A valve according to any preceding claim, wherein the locking means comprises

at least two locking members.
9. A valve according to any preceding claim, further comprising a spring urging the sleeve towards its second position.
10. A valve according to claim 9, wherein the spring is arranged between the sleeve and an end wall of the valve body.
11. A valve according to any preceding claim, further comprising a spring urging the piston or plunger towards its second position, the spring acting on one end of the piston or plunger, the other end of the piston or plunger facing the pressure chamber.
12. A valve according to claim 11, wherein the spring, specified in claim 11, does not displace the piston or plunger from its first position to its second position when pressure variations expereinced in normal operation occur in the pressure chamber.
13. A valve according to claim 11 or claims 11 and 12, further comprising means for adjusting the force exerted by the spring on the piston or plunger.
14. A valve according to any preceding claim, wherein the valve body has a further opening which is in communication with the pressure chamber whether or not the valve is open or closed.
15. A valve according to any preceding claim, wherein the opening, specified in claim 1, of the valve body communicates with a hydraulic cylinder.
16. A valve according to any preceding claim, constructed such that movement of the valve sleeve from its first to its second position is damped.
17. A valve substantially as described herem with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings.