GB2065239A

GB2065239A - Cylinder/cylinder head assembly for a compressor

Info

Publication number: GB2065239A
Application number: GB8033475A
Authority: GB
Original assignee: Wabco Fahrzeugbremsen GmbH
Current assignee: Wabco Fahrzeugbremsen GmbH
Priority date: 1979-10-19
Filing date: 1980-10-16
Publication date: 1981-06-24
Also published as: IT1129325B; IT8068595A0; GB2065239B; DE2942299A1

Abstract

A cylinder/cylinder head assembly for a piston compressor comprises a valve plate 2 arranged between the cylinder casing 1 and cylinder head 3. The valve plate 2 carries valve members 11, 14 of suction and pressure valves which, to achieve efficiency, are plate valves. With a view to simplifying the sealing of the various chambers within the cylinder head 3, the plate valve members 11, 14 are arranged on one face 5 (facing the cylinder head) of the valve plate whereby a simple flat seal can be used between the valve plate and cylinder head. <IMAGE>

Description

SPECIFICATION Piston cylinder for compressors The invention relates to a piston cylinder for a compressor.

Conventionally, a piston cylinder for a compressor comprises a cylinder casing, a cylinder head and a valve plate arranged between the casing and the head. The valve plate carries valve members for a suction valve and a pressure valve which, when open, connect the compression space in the cylinder casing (i.e. the space between the piston and the valve plate) with, respectively, a suction chamber and a pressure chamber formed in the cylinder head.

The cylinder casing may be smooth-walled or it may be provided with cooling ribs. In constructions using smooth-walled tubes it is not readily possible to use plate suction valves because there is a lack of support surface of the plate valve members. For this reason it is customary to install disk valves which are considerably more expensive and with which the compressor will have a lesser degree of efficiency.

Furthermore, disk valves are suitable only for compressors having low to medium speeds.

In a known compressor piston cylinder the problem of lack of support for the valve member of a plate suction valve is overcome by casting the cylinder casing, valve plate and a cylinder head member in one piece. In this method of construction, the cylinder head member must be open at the top to enable the valve member to be mounted and it is necessary, to complete the head, to provide a cylinder head lid which is constructed in the form of a valve seat for the suction valve member and a valve stop for the pressure valve member and is provided with an inlet connection.This cylinder head lid is provided with ribs and hollow spaces which form the suction chamber, the pressure chamber and cooling spaces, and it is necessary to provide seals between the chambers and the cooling spaces and the exterior of the cylinder: however, in view of the construction, these seals must lie on several planes of the cylinder head so that sealing problems may arise.

The problem with which the present invention is concerned is that of providing a piston cylinder for a compressor of which the cylinder casing is smooth-walled and the suction and pressure valves are plate valves but in which it is possible, in a trouble free manner, to use simple flat sealing material.

The present invention provides a piston cylinder for a compressor, comprising a smooth-walled cylinder casing, a cylinder head, and a valve plate which is arranged between the cylinder casing and the cylinder head and which carries at least one suction valve member and at least one pressure valve member, the valve members being plate valve members and being arranged on one face, facing the cylinder head, of the valve plate.

By way of example, a compressor cylinder constructed in accordance with the invention will now be described with reference to the accompanying drawings in which: Fig. 1 shows a longitudinal section through the compressor cylinder, and Fig. 2 shows a top view of the valve plate of the cylinder shown in Fig. 1.

The piston cylinder shown in Figs. 1 and 2 consists of a smooth-walled cylinder casing 1, a valve plate 2 and a cylinder head 3, of which the sealing faces are indicated by the reference numerals 4 and 5. Tension rods (not shown) secure the three components 1, 2 and 3 to the crank housing (also not shown) of the compressor.

A valve stop 6 is incorporated into the upper face of the valve plate 2 in the form of a recess and lateral slots 7 arranged around this valve stop 6 form a connection between the cylinder compression space 8 (below the valve plate 2) and a suction space 9 located above the valve plate 2, the suction space 9 being connected to the atmosphere by way of an opening 10. A plate valve member 11 arranged above the valve stop 6 forms, together with a seat 12 of the cylinder head 3, a suction valve 11, 12 which is opened during the air suction phase of the compressor and forms a connection between the suction space 9 and the compression space 8. A control bore 13, which does not appear in Fig. 1, penetrates the valve plate 2, being arranged between the lateral slots 7 for a purpose to be described below.

The upper face of the valve plate 2 carries two plate valve members 14 and 15, which, together with the seats 1 6 and 1 7 respectively of the valve plate 2, form respectively a pressure valve 14, 16 and a pressure control valve 15, 1 7. When the pressure valve 14, 1 6 is open, a bore 1 8 in the valve plate 2 makes a connection between the cylinder compression space 8 and a pressure space 1 9 in the cylinder head 3, while when the pressure control valve 15, 1 7 is open, a bore 20 in the valve plate 2 makes a connection between the compression space 8 and a pressure control space 21 which is also arranged in the cylinder head 3.

Above the pressure control valve 15, 17 there is arranged a switching piston 22 which is guided in the cylinder head 3 and is pressed against the plate valve member 1 5 by a spring 23, so that, as a result, the pressure control space 21 is closed in the direction of the compression space 8, if there is no counterpressure present in this compression space 8. An annular face 24 formed by a tapered portion on the piston 22 forms the pressurereceiving face of an annular chamber 25 which is connected, by way of a bore 26 and a connection 27 of the cylinder head 3 and by way of a line (not shown), to a regulating valve (also not shown) controlling the operating pressure of the system.

An opening 28 assigned to the pressure space 1 9 serves for the connection of a pressure line leading to a consumer component or to a storage container, while an opening 29 assigned to the pressure control space 21 is provided to release air from the pressure control space 21 under circumstances to be described below.

The operating procedure is as follows: On a downward stroke of the piston (which does not appear in the drawings) a low pressure is produced in the compression space 8, so that the suction valve member 11 is lifted off its seat 12.

External air is sucked into the compression space 8 by way of the opening 10, the suction space 9, the open suction valve 11, 12 and the lateral slots 7. During this operating phase the valves 14, 16 and 15, 17 seal off the spaces 19 and 21.When the upward stroke of the piston produces excess pressure in the compression space 8, the suction valve member 11 is pressed against its seat 12 and seals off the compression space 8 from the atmosphere. When a certain excess pressure has been reached the pressure valve member 14 lifts off its seat 16, the length of opening stroke of the valve member 14 being limited by a formation of the cylinder head 3 that serves as a valve stop 30, and compressed air flows into the pressure chamber 19 and, via the opening 28, into the consumer or storage container.

At a certain pressure level set at the abovementioned regulating valve of the system (not shown), the regulating valve switches over and passes the compressed air into the annular chamber 25 by way of the connection 27 and bore 26 of the cylinder 1 head 3. As a result of pressure acting on the annular surface 24, the switching piston 22 is lifted against the tension of the spring 23 and frees the pressure control valve 1 5, 17 which now assumes the function of the pressure valve 14, 16 (the latter being closed by the counter-pressure in the consumer system). The compressed air now escapes into the open air through the pressure control space 21 and the opening 29.If the operating pressure in the container subsequently decays to a pressure level set at the regulating valve, this switches back into the flow direction of the storage container, the pressure in the annular chamber 25 decays and the force of the spring 23 effects a downward stroke of the switching piston 1 3, so that the pressure control valve 1 5, 1 7 closes and the pressure valve 14, 1 6 assumes its old function.

In the described compressor cylinder, the use of a smooth cylinder casing and plate valves for all the valves of the compressor is combined with a comparatively simple sealing system. More especially, the sealing faces 4, 5 of the cylinder each lie in one respective plane so that, in each case, only a simple one-piece paper or flat seal is required for sealing and, in the case of the sealing face 5, this serves for sealing the suction and pressure spaces 9, 1 9 and 21 from each other as well as from the exterior. The plate valve members 11, 14 and 1 5 are all arranged on the larger face (that facing the cylinder head) of the valve plate 2 and can be mounted from one side.

Although, in the described arrangement, the cylinder casing 1, the valve plate 2 and the cylinder head 3 are each formed by a single component, it is also possible to imagine a solution in which the cylinder casing and the valve plate form one component, so that in this case only the seal between the valve plate and the cylinder head is necessary.

The control bore 13, arranged in the valve plate 2 between the lateral suction slots 7 of the suction valve, accelerates the closure of the suction valve as a result of the excess pressure produced on the upward (pressure) stroke of the piston. Although, even without this control bore 13, the plate valve member 11 of the suction valve will, as a result of its inherent tension, move back onto the valve seat 12 when the downward (suction) stroke of the piston has been completed, this movement is subject to a certain delay because of the inertia of the valve member material. This delay can be prevented, to a large extent, by the provision of the described control bore 13: the effect of the bore 1 3 can, accordingly, be regarded, in an advantageous manner, as equivalent to a reduction in the cylinder clearance, since the closure behaviour of the suction valve member is improved (there being a reduction in closing time).

Claims

1. A piston cylinder for a compressor, comprising a smooth-walled cylinder casing, a cylinder head, and a valve plate which is arranged between the cylinder casing and the cylinder head and which carries at least one suction valve member and at least one pressure valve member, the valve members being plate valve members and being arranged on one face, facing the cylinder head, of the valve plate.

2. A piston cylinder according to claim 1, in which a recess in the valve plate is provided as a valve stop for the suction valve member.

3. A piston cylinder according to claim 2, in which there are arranged, on the periphery of the recess, a plurality of inlet channels forming a connection, via the suction valve, between the compression space in the cylinder and a suction space in the cylinder head.

4. A piston cylinder according to claims 3, in which the valve plate contains a control bore, arranged between the inlet channels and forming a connection between the compressin space and one side of the suction valve member.

5. A piston cylinder according to any one of the preceding claims, in which a pressure control space which is connected to the atmosphere is provided in the cylinder head, and a pressure control valve is provided to connect the cylinder compression space and the pressure control space; the pressure control valve including a plate valve member lamella which is carried by the said one face of the valve plate, and the cylinder head including a pneumatically-controlled switching piston movable between one position in which the switching piston holds the pressure control valve member in a closed position and another position in which the control valve member is freed for operation.

6. A piston cylinder according to claim 5, in which a single planar seal between the valve plate and the cylinder head also seals the pressure control space from a suction space in the cylinder head and from the outside.

7. A piston cylinder according to any one of the preceding claims, in which the cylinder casing and the valve plate are separate components and a single, planar, seal is provided between the casing and the valve plate.

8. A piston cylinder according to any one of claims to 6, in which the cylinder casing and the valve plate are constructed in one piece.

9. A piston cylinder according to one of the preceding claims, in which the cylinder head is shaped to provide a valve stop for the pressure valve member.

10. A piston cylinder according to claim 1, having a planar seal between the valve plate and the cylinder head.

11. A piston cylinder for a compressor, the cylinder being substantially as described herein with reference to, and as shown in, the accompanying drawings.