GB2134224A

GB2134224A - Pressure relief valve

Info

Publication number: GB2134224A
Application number: GB08401453A
Authority: GB
Inventors: Hermann Lang
Original assignee: PFEIFFER VAKUUMTECHNIK; Arthur Pfeiffer Vakuumtechnik Wetzlar GmbH
Current assignee: PFEIFFER VAKUUMTECHNIK; Arthur Pfeiffer Vakuumtechnik Wetzlar GmbH
Priority date: 1983-01-28
Filing date: 1984-01-19
Publication date: 1984-08-08
Also published as: FR2540218A1; GB8401453D0; GB2134224B; JPS59144872A; FR2540218B1; DE3302784A1; IT8419109A0; IT1173002B

Abstract

A relief valve has a valve poppet 4 at the inlet 7 which is guided in a cylinder 3, the space 8 above the poppet being connected with the inlet 7 either by a bore 5 through the poppet or by a separate pipe 10, and the diameter D1 of the cylinder being less than the diameter D2 of the inlet so that the valve operates on the differential area between diameters D1 and D2. <IMAGE>

Description

SPECIFICATION Pressure relief valve The invention concerns a relief valve especially for vacuum-tight rotary pumps.

During the operation of rotary or rolling plunger pumps, a pressure difference builds up between the suction side and the pressure side. To protect the pump from mechanical and thermal overloads, which are caused by the pressure difference, relief valves are inserted between the inlet and discharge sides.

A criterion for the opening and closing of a relief valve is the permitted pressure difference between inlet and discharge sides of the pump. The necessary pressure differences in the valve can be produced both by loading the valve poppet or cone with weights as well as by resilient loading of the valve poppet.

However, in order to maintain the same pressure difference at each opening stroke, the weight-loaded construction is preferred. A relief valve which is arranged on a rolling plunger pump at an angle of 45" to the direction of conveying, is described, for example, in German Offenlegungsschrift 28 44 019.

Such arrangements have, however, the following disadvantage: With large pressure differences large weights are also necessary. The pressure differences are often so large, that the necessary weights assume such dimensions that the size of the valve is determined more by these than by the flow cross section. Upon sudden alterations in pressure the large weights also lead to loud knocks in the connection system. The use of springs is no better solution from a constructional point of view. The same applies to a valve controlled by means of a lever transmission.

The present invention seeks to provide a relief valve, which in its dimensions is essentially determined by the necessary flow crosssections. The valve is preferably controlled by a weight-loaded valve poppet and the operation of the valve should occur without an external energy source.

According to a first aspect of the present invention there is provided a relief valve having a valve poppet which faces the inlet and is guided in a cylinder, wherein the space over the valve poppet is connected through a pressure equalisation bore to the inlet, the dia meter (D1) of the cylinder differing from the diameter (D2) of the valve inlet.

According to a second aspect of the present invention there is provided a relief valve having a valve poppet which faces the inlet and is guided in a cylinder, wherein the space over the valve poppet is connected through a pipe to the inlet, the diameter (D1) of the cylinder differing from the diameter (D2) of the valve inlet.

Thus there operates on the valve poppet only a pressure which is determined by the difference of the annular surfaces.

A preferred embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawing which shows a schematic cross-sectional view of a relief valve.

The valve housing designated 1. On the valve cover 2 there is provided a hollow cylinder 3, of which the interior has been machined smooth and which is closed at the top (valve cover) and open at the bottom. The control of the valve occurs through the valve poppet or cone 4 which at the bottom sits on the valve seating and at the top slides easily in the cylinder 3. In the valve poppet 4 there is situated a bore 5 which connects the space 7 underneath the valve poppet 4 with the space 8 above the same and maintains pressure equality. The weight necessary for a particular pressure difference results from a corresponding selection of the diameters D1 and D2, D1 being the diameter of the cylinder and D2 being the diameter of the valve seating (or inlet).Instead of the bore 5 the space 7 can be connected to the space 8 by means of a pipe 10. In order to keep low the reverse flow losses through the cylinder with a closed valve, piston rings 6 are provided. They act moreover as damping elements upon sudden pressure fluctuations. Also by selection of the diameter D3 of the bore 5 in the valve poppet the damping of the valve can be influenced.

The above-mentioned arrangements have the advantage that, by corresponding selection of the diameter D2 with reference to the diameter D1 the weight of the valve poppet can be varied at will and can match the constructional requirements. This means a small light construction and simple mounting without auxiliary means.

The pressure equalisation bore 5 or the pipe 10 is preferably so dimensioned in crosssection between the upper side and lower side of the valve poppet, that pressure equalisation only occurs after several seconds.

1. A relief valve having a valve poppet which faces the inlet and is guided in a cylinder, wherein the space over the valve poppet is connected through a pressure equalisation bore to the inlet, the diameter (D1) of the cylinder differing from the diameter (D2) of the valve inlet.

2. A relief valve according to claim 1, wherein the pressure equalisation bore is so dimensioned in cross-section between the upper side and lower side of the valve poppet, that pressure equalisation only occurs after several seconds.

3. A relief valve having a valve poppet which faces the inlet and is guided in a cylinder, wherein the space over the valve poppet is connected through'a pipe to the

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Pressure relief valve The invention concerns a relief valve especially for vacuum-tight rotary pumps. During the operation of rotary or rolling plunger pumps, a pressure difference builds up between the suction side and the pressure side. To protect the pump from mechanical and thermal overloads, which are caused by the pressure difference, relief valves are inserted between the inlet and discharge sides. A criterion for the opening and closing of a relief valve is the permitted pressure difference between inlet and discharge sides of the pump. The necessary pressure differences in the valve can be produced both by loading the valve poppet or cone with weights as well as by resilient loading of the valve poppet. However, in order to maintain the same pressure difference at each opening stroke, the weight-loaded construction is preferred. A relief valve which is arranged on a rolling plunger pump at an angle of 45" to the direction of conveying, is described, for example, in German Offenlegungsschrift 28 44 019. Such arrangements have, however, the following disadvantage: With large pressure differences large weights are also necessary. The pressure differences are often so large, that the necessary weights assume such dimensions that the size of the valve is determined more by these than by the flow cross section. Upon sudden alterations in pressure the large weights also lead to loud knocks in the connection system. The use of springs is no better solution from a constructional point of view. The same applies to a valve controlled by means of a lever transmission. The present invention seeks to provide a relief valve, which in its dimensions is essentially determined by the necessary flow crosssections. The valve is preferably controlled by a weight-loaded valve poppet and the operation of the valve should occur without an external energy source. According to a first aspect of the present invention there is provided a relief valve having a valve poppet which faces the inlet and is guided in a cylinder, wherein the space over the valve poppet is connected through a pressure equalisation bore to the inlet, the dia meter (D1) of the cylinder differing from the diameter (D2) of the valve inlet. According to a second aspect of the present invention there is provided a relief valve having a valve poppet which faces the inlet and is guided in a cylinder, wherein the space over the valve poppet is connected through a pipe to the inlet, the diameter (D1) of the cylinder differing from the diameter (D2) of the valve inlet. Thus there operates on the valve poppet only a pressure which is determined by the difference of the annular surfaces. A preferred embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawing which shows a schematic cross-sectional view of a relief valve. The valve housing designated 1. On the valve cover 2 there is provided a hollow cylinder 3, of which the interior has been machined smooth and which is closed at the top (valve cover) and open at the bottom. The control of the valve occurs through the valve poppet or cone 4 which at the bottom sits on the valve seating and at the top slides easily in the cylinder 3. In the valve poppet 4 there is situated a bore 5 which connects the space 7 underneath the valve poppet 4 with the space 8 above the same and maintains pressure equality. The weight necessary for a particular pressure difference results from a corresponding selection of the diameters D1 and D2, D1 being the diameter of the cylinder and D2 being the diameter of the valve seating (or inlet).Instead of the bore 5 the space 7 can be connected to the space 8 by means of a pipe 10. In order to keep low the reverse flow losses through the cylinder with a closed valve, piston rings 6 are provided. They act moreover as damping elements upon sudden pressure fluctuations. Also by selection of the diameter D3 of the bore 5 in the valve poppet the damping of the valve can be influenced. The above-mentioned arrangements have the advantage that, by corresponding selection of the diameter D2 with reference to the diameter D1 the weight of the valve poppet can be varied at will and can match the constructional requirements. This means a small light construction and simple mounting without auxiliary means. The pressure equalisation bore 5 or the pipe 10 is preferably so dimensioned in crosssection between the upper side and lower side of the valve poppet, that pressure equalisation only occurs after several seconds. CLAIMS

3. A relief valve having a valve poppet which faces the inlet and is guided in a cylinder, wherein the space over the valve poppet is connected through'a pipe to the inlet, the dianieter (D1) of the cylinder differing from the diameter (D2) of the valve inlet.

4. A relief valve according to claim 3, wherein the pipe is so dimensioned in crosssection between the upper and lower side of the valve poppet, that pressure equalisation only occurs after several seconds.

5. A relief valve according to any preceding claim, wherein the guiding between the valve poppet shaft and the guiding cylinder is sealed with piston rings.

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