GB2142123A

GB2142123A - Pressure limiting valve

Info

Publication number: GB2142123A
Application number: GB08415690A
Authority: GB
Inventors: Ludwig Budecker; Juergen Schonlau
Original assignee: Alfred Teves GmbH
Current assignee: Continental Teves AG and Co oHG
Priority date: 1983-06-24
Filing date: 1984-06-20
Publication date: 1985-01-09
Also published as: JPS6014671A; IT1196166B; SE8403089L; GB8415690D0; IT8421587A0; DE3322771A1; SE8403089D0; FR2549166A1

Abstract

A valve (5) for limiting pressure in a system comprises a ball closing member (14) resiliently biased against a valve seat (13) and removable from valve seat (13) by fluid at a predetermined pressure thereby providing a path of flow to a point of relief (24) via passages (25). With valve (13,14) opened, an additional opening force is exerted upon closing member (14), which force is generated in that the closing member (14) is arranged in the path of flow to the point of relief (24) such that the fluid flow is constricted. Moreover with the valve open fluid pressure is also applied to element (15) having a shaft portion (16) with a conical depression (17) receiving the closing member (14). <IMAGE>

Description

SPECIFICATION Pressure limiting valve The present invention is concerned with a pressure limiting valve for limiting the pressure in a pressurised system, wherein system pressure is applied to a closing member resiliently biased against a valve seat and removable from the valve seat at a predetermined pressure thereby providing a path of flow to a point of relief, and wherein means are provided which, with the valve opened, exert an additional opening force upon the closing member.

Avalve arrangement having the afore-described features is disclosed by United States Patent Specifi cation number4,046,163.lnthispriorartvalve arrangement, the closing member is provided on an essentially cylindrical valve body which in turn is guided in a cylindrical bore of a housing. A force is applied to the valve body by way of a compression spring such that the closing member is biased against a valve seat. If the pressure of the system to be monitored exceeds a predetermined value, the force acting upon the closing member is sufficient to dislodge the closing member from the valve seat against the force of the compression spring in the opening direction to thereby provide within the valve arrangement a valve passage thus establishing a connection between the pressurised system and a point of relief.With the valve passage opened, pressure fluid escapes from the pressurised system to the point of relief, with a fluid pressure building up in the direction of flow behind the valve arrangement dislodging a constricting member in the opening direction of the valve passage thereby exerting an additional force in the opening direction of the valve passage on the closing member resulting in the pressure prevailing in the pressurised system dropping below the opening pressure in the valve passage before the valve passage of the valve arrangement returns to a closed position.

The relatively complex construction involved with the prior art valve arrangement is disadvantageous and is due in particular to the fact that special means are required for enhancing the opening force of the valve passage.

The present invention seeks to substantially reduce the complexity of a valve arrangement of the afore-described type.

According to the invention there is provided a valve arrangement for limiting the pressure in a pressurised system, wherein system pressure is applied to a closing member resiliently biased against a valve seat and removable from the valve seat at a predetermined pressure thereby providing a path of flow to a point of relief, and wherein means are provided which, with the valve opened, exert an additional opening force upon the closing member, characterised in that the closing member is arranged in the path of flow to the point of relief such that the fluid flow is constricted. Owing to the constrictive effect of the closing member in the path of flow to the point of relief pressure increase is provided on the closing member that has an additional effect in the opening direction of the valve passage of the valve arrangement.It is achieved thereby that the system pressure required for opening the valve passage is higher than the pressure maintaining the valve arrangement in an opened position. Such a way of operation is especially advantageous with pressurised systems in which the system pressure is generated by a fluid pressure pump. As is well known in the art, such pumps deliver pressure pulses in dependence upon the operating speed. The pressure prevailing at the output of the fluid pump accordingly, varies between two limit values.

The valve arrangement can be so designed as to permit the opening pressure of the valve arrangemenu to be reached art a pressure peak of the fluid pump. Owing to the pulsation of the pressurised fluid flow, the pressure will drop at the pressure side of the pressurised fluid pump by a predetermined amount, in which the opening pressure of the valve arrangement, admittedly, has fallen below although the valve arrangement due to the constricting effect of the closing member, is held in an open position, resulting in that the valve arrangement performs fewer indexing operations, causing, on the one hand, reduced noise and, on the other hand, reduced wear. Moreover, the pressurised fluid pump has to deliver against a generally lower pressure so that the energy consumption of the pump drive is reduced.

This results in a reduction of heat generation in the pump and the pump drive.

In a preferred embodiment of the invention, the end of a substantially cylindrical shaft acts on the closing member and is guided with a low radial clearance in a housing bore. The shaft forms a constricting gap with the wall of the housing bore through which the pressurised fluid flowing to the point of relief is constricted so as to exert an additional force on the shaft in the opening direction of the valve arrangement such that the opening pressure of the valve arrangement is in excess of the holding pressure. Moreover, it is of advantage and especially simple for a ball to be used as a closing member to which force is applied through the end of the shaft in a direction toward the valve seat. In such an embodiment it is not necessaryforthe shaft to have a precisely dimensioned diameter.By employing standard element such as a ball as the closing member a defined constricting gap in the path of flow to the point of relief is achieved at low cost.

In a refinement of the invention the front surface of the shaft facing the ball is provided with a substantially conical depression such that the ball is guided in a defined position relative to the wall of the housing bore. Moreover, owing to the conical depression in the shaft end, the ball is adjustable in a defined position relative to the valve seat. In this connection it is of advantage for the diameter of the shaft to be smallerthan the diameter of the ball.

In order that the invention and its various other preferred features may be understood more easily, an embodiment thereof will now be described, by way of example only, with reference to the drawing, the single Figure of which is a sectional view.

In the drawing a pressurised fluid pump 1 is drivable by an electromotor 2. The pressure side of the fluid pressure pump 1 is in communication with a hydropneumatic pressure tank 3. Connected to the pressure tank 3 via a pressure line 4 is at least one hydraulic user. Moreover, the pressure tank 3 and the pressure side of the pump 1 are both in hydraulic communication with a valve arrangement 5 having a housing 6 in which there is provided a stepped bore 7. Stepped bore 7 includes three bore sections 8, 9, 10, with an insert member 11 provided in bore section 10, which insert member 11 is provided with a central bore 12 formed as a valve seat 13 at its end facing bore section 9.

In the rest position of the valve arrangement as shown in the drawing, closing member formed by a ball 14, is in abutment with valve seat 13, which ball is end-supported on a closure element 15. The end of closure element 15 which, in the drawing, is the bottom end, is formed as a cylindrical shaft 16, with the end of shaft 16 facing ball 14 being provided with a substantially conical depression 17 so as to centrally guide ball 14 in bore section 9 of step-bore 7. The diameter of ball 14 is so dimensioned as to be guided with a low radial clearance in bore section 9.

The shaft 16 is preferably of diameter smaller than that of the ball 14.

The part of closure element 15 contained in bore section 8 is formed as a spring plate 17 supported on which is a compression spring 18. Compression spring 18 is end-supported on an insert sleeve 19 provided with a central bore 20 receiving the end of the closure element 15 remote from valve ball 14.

Insert member 19 is hexagonal in cross section such that six passages 25 are formed along the outer periphery. To permit a precise adjustment of compression spring 18 insert member 19 is loaded, for example, with a weight corresponding to the compressive load. Insert member 19 is then clinched in housing 6 at point 22, preferably at three positions around the periphery.

In the hydraulic system as shown, during operation of electric motor 2 the pressurised fluid pump 1 extracts pressure fluid from the feed tank 24 at atmospheric pressure, feeding it at an increased pressure to both pressure tank 3 and user line 4. The pressure on the pressure side of the fluid pump 1 is also fed to valve arrangement 5, becoming operative in bore 12 of insert member 11. Accordingly, a hydraulic force is exerted upon ball 14 that is determined by the pressure prevailing in bore 12 and by the diameter of the valve seat 13.

At a predetermined pressure in the hydropneumatic pressure tank 3 the force exerted upon the ball is sufficient to lift ball 14 off its seat 13 and to dislodge closure element 15 against the force of compression spring 18 so that pressure fluid can now escape via the opened valve 13,14, valve chamber 23 and passages 25 to feed tank 24 at atmospheric pressure.

The pressure fluid flowing through opened valve 13, 14 as a result of the restricting effect of ball 14 in the bore section 9 of the step bore 7 generates a hydraulic pressure which is additionally applied to the element 15 in the opening direction so that the pressure prevailing in bore 12 is required to drop by a predetermined amount below the opening pressure of valve 13, 14 before ball 14 can return into abutment with valve seat 13.

Claims

1. A valve arrangement for limiting the pressure in a pressurised system, wherein system pressure is applied to a closing member resiliently biased against a valve seat and removable from the valve seat at a predetermined pressure thereby providing a path of flow a point of relief, and wherein means are provided which, with the valve opened, exert an additional opening force upon the closing member, characterised in that the closing member (14) is arranged in the path of flow to the point of relief (24) such that the fluid flow is constricted.

2. Avalve arrangement as claimed in claim 1, characterised in that the end of a substantially cylindrical shaft (16) acts on the closing member (14), which shaft is guided in a housing bore (9) with low radial clearance.

3. A valve arrangement as claimed in claim 2, characterised in that the closing member is a ball (14) to which force is applied by the end of the shaft (16) toward the valve seat (13).

4. A valve arrangement as claimed in claim 3, characterised in that the front face of shaft (16) facing ball (14) is provided with a substantially conical depression (17).

5. A valve arrangement as claimed in any one of claims 2 to 4, characterised in that the diameter of shaft (16) is smaller than the diameter of ball (14).

6. A valve arrangement substantially as described herein with reference to the drawing.