GB2031117A

GB2031117A - Pressure limiting valve

Info

Publication number: GB2031117A
Application number: GB7921099A
Authority: GB
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1978-06-19
Filing date: 1979-06-18
Publication date: 1980-04-16
Also published as: JPS6145109B2; GB2031117B; BR7903818A; FR2429362B1; DE2826643B1; DE2826643C2; JPS5527572A; FR2429362A1

Abstract

The valve comprises an elongate valve housing 1 having an inlet 2 and an outlet 3 for a pressure medium. A valve member in the form of a ball 4 is biassed against a seat 6 by a compression spring 5 guided by a hollow pin 7 disposed co-axially with the inlet 2. Between the ball 4 and the adjacent end face of the pin 7 there are arranged at least three balls 8 of equal diameter. The balls 8 fill, with slight clearance, the interior of the valve housing 1 and are located in a plane extending at right-angles to the opening direction of the valve, whereby they serve to centralise the ball 4 and frictionally dampen any vibrations thereof. <IMAGE>

Description

SPECIFICATION Pressure limiting valve This invention relates to a directly controlled pressure limiting valve with a spring-loaded ball as the valve member, in a valve housing having a valve seat, and a spring guide pin which urges the ball on to the valve seat.

Such pressure limiting valves are used in hydraulic or pneumatic systems. The function of such valves is to prevent a predetermined selected pressure being exceeded.

In German Patent Specification 11 88 961, for example, a pressure limiting valve is described which is used for the oil circuit of a steering device which is servo-assisted. In this case, a ball which is prestressed by spring force, seals off a bore in which the pressure of the system is present. If, then, a preselected pressure is exceeded, the valve ball lifts off the bore and the pressurised medium can escape into a space disposed behind the ball.

However, a disadvantage of such arrangement is that the pressure limiting valve can be caused to vibrate. These vibrations are brought about by axial overswing and by radial swing-out of the valve member. The valve ball does in fact not lift exactly in the axial direction, i.e. along the direction of opening but jumps about or vibrates over the exposed aperture so that a considerable amount of noise is generated. In addition to the considerable generation of noise, this also results in damage to the edges of the bore and thus to destruction of the pressure limiting valve.

For this reason, the pressure limiting valves are either constructed as so-called pre-control valves or alternatively, one seeks to achieve damping by complicated and thus expensive constructions. This is achieved either by extremely accurate guiding of the valve member or by particular hydraulic damping members.

Also friction members in the form of O-rings are used, although these were subject to considerable wear and tear.

Therefore, the present invention is based on the problem of providing a directly controlled pressure limiting valve with which it is possible to avoid vibrations of the valve member by simple and economical means.

Accordingly, the present invention consists in a pressure limiting valve comprising a valve housing having a valve seat formed therein, a valve member constructed as a ball, a springloaded guide pinlocated in said housing and urging the ball on to the valve seat, and at least three damping balls of equal diameter arranged between the guide pin and the ball, said damping balls filling with a slight clearance the interior of the valve housing and being located in a plane extending at rightangles to the opeing direction of the valve. By means of these damping balls, it is possible easily to prevent an axial overswing and a radial swing-out of the ball when this is used as a valve member. On the one hand, the three damping balls provide a centring effect on the valve member and on the other hand, by virtue of the wall friction, a damping effect is achieved.Namely, a radial component of the compressive force occurs in the three damping balls and this is supported on the valve housing. The friction which occurs thereby leads to a corresponding damping of the movement of the ball which functions as a valve member.

By virtue of three balls being used, a selfcentring effect is achieved. It goes without saying, however, that it is also possible to use more than three damping balls.

There is negligible wear and tear on the damping balls if, in a further development of the invention, it is envisaged that the damping balls consist of roller bearing steel.

In order that the invention may be more readily understood, reference is made to the accompanying drawing which illustrates diagrammatically and by way of example one embodiment of a pressure limiting valve in axial section.

The pressure limiting valve illustrated is built into a part of the housing (not shown) of a pressure system to be monitored and comprises a valve housing 1 which has at one end a bore 2, at which the pressure to be monitored is available, and which has at the oppositely disposed end a bore 3 for carrying away the pressurised medium released.

In the interior of the valve housing 1 is located a ball 4 which serves as a valve member, being urged by a spring 5 by way of a spring guide pin 7 on to a valve seat 6. The guide pin 7 is provided with a through bore 9. Between the spring guide pin 7 and the ball 4, in a plane at right-angles to the direction of valve opening, there are arranged three damping balls 8. These three damping balls 8 are of equal diameter and lie in a common plane with a slight clearance in the interior of the valve housing 1.

The pressure limiting valve operates in the following manner: So long as a predetermined pressure is not exceeded in the system which is to be monitored, i.e. so long as a definite compressive force is not exceeded in the aperture 2, the ball 4, serving as valve member, remains urged on the valve seat by the force of spring 5 acting upon it. If, now, the pre-selected pressure is exceeded, the compressive force in the aperture 2 on the ball 4 becomes greater than the force of the spring 5, so that the ball 4 is lifted off the valve seat 6 and pressurised medium can escape through the bore 9 in the valve guide pin 7 and through the aperture 3.

The three damping balls 8 act thereby both in a damping manner and also in a centring manner on the ball 4. On the one hand, because they maintain the ball 4 in the axis of symmetry of the valve and on the other hand because friction occurs between the damping balls 8 and the inner wall of the valve housing 1 during the opening movement of the valve.

The three damping balls (only two damping balls are completely visible in the longitudinal section) are thereby symmetrically disposed in the interior of the valve housing 1. An expedient material for the damping ball 8 is roller bearing steel.

Claims

1. A pressure limiting valve comprising a valve housing having a valve seat formed therein, a valve member constructed as a ball, a spring-loaded guide pin located in said housing and urging the ball on to the valve seat, and at least three damping balls of equal diameter arranged between the guide pin and the ball, said damping balls filling with a slight clearance the interior of the valve housing and being located in a plane extending at right-angles to the opening direction of the valve.

2. A pressure limiting valve as claimed in claim 1, wherein the damping balls are made from roller bearing steel.

3. A pressure limiting valve, substantially as herein described with reference to and as shown in the accompanying drawings.