PRESSURE CONTROL VALVE

Abstract: In a refrigerating system and heat-pump system, refrigerant is delivered to a condenser at high pressure through the action of a compressor. A pressure control valve is connected to the high pressure side, for the purpose of controlling the pressure of the refrigerant. The valve is constructed so that it will not open to allow gaseous refrigerant to flow through until the pressure of the refrigerant has reached a given level. By providing the valve with a throughflow passage (9) which is connected to a servocylinder device (6) mounted in the valve, a servopiston (7) connected to the valve body (3) of the valve is able to cause the valve to open for the flow of refrigerant therethrough. Mounted between the cylinder (6) and the valve body (3) is a spring (5), such that the valve will close immediately in response to a drop in system pressure.

Description: PRESSURE CONTROL VALVE Technical Field The present invention relates to a pressure control valve for controlling refrigerant pressure in a re¬ frigerating system or a heat-pump system. The pressure control valve is intended to be connected to the high pressure side of the system and functions to counteract the throughflow of refrigerant until a sufficiently high pressure has been obtained in the system. Background Art In refrigerating systems and heat-pump systems in which gaseous refrigerant is compressed in a compressor which lacks an oil pump, the oil is circulated with the aid of the pressure difference that prevails between the oil separator on the outlet side of the compressor, i.e. the compressor outlet pressure, and the inter¬ mediate pressure in the compressor compression chamber, to which the oil is recycled. In the case of certain operating conditions in which the pressure differences are small, for example booster operation, an external oil pump is coupled to the system in order to ensure a sufficient flow of oil. When starting-up the re¬ frigerating system, there is no pressure difference and therewith no oil transport. When the compressor is started-up, the compressor will successively build-up pressure until the requisite pressure difference is reached. In the case of large systems, the time taken to reach the requisite pressure difference may be too long for the compressor to work without supplying lubricating oil to the system, resulting in possible damage to compressor bearings. The same problem is also encountered when pressure falls-off rapidly, for in¬ stance when defrosting. Disclosure of the Invention A pressure control valve, or pressure holding valve, has been connected to the high pressure side of a refrigerating system or a heat-pump system, for the purpose of controlling the pressure level of a re¬ frigerant on said high pressure side. This pressure control valve includes a valve housing which houses a valve body and a valve seat, and the valve is essen¬ tially and primarily spring balanced and will not open to allow gaseous refrigerant to pass therethrough until the pressure of said gaseous refrigerant has reached a determined level. When the valve opens, the through- flowing gaseous refrigerant is able to act on one side of a servopiston in a servocylinder, via a throughflow passage in the pressure control valve. The piston rod of the piston is connected to the valve body of the valve. The other side of the piston is influenced by an intermediate pressure or low pressure from the refri¬ gerating system or heat-pump system. Depending on the pressure difference across the piston, this will have a secondary influence on the valve body of said pressure control valve, such as to hold the valve body in its valve open position. In a refrigerating system or heat-pump system, the pressure control valve will open subsequent to starting the compressor and will subsequently deliver gaseous refrigerant of sufficiently high pressure to the sys¬ tem. The valve then remains open for as long as the gaseous refrigerant on the high pressure side of the system has the aforesaid high pressure. When the pres¬ sure drops, for example when shutting down the re¬ frigerating compressor, the valve will close immediate¬ ly and therewith interrupt the supply of gaseous re¬ frigerant, due to the spring action on the valve body and due also to an insufficient pressure difference across the piston of the servodevice. Brief Description of the Drawings Figure 1 illustrates a closed pressure control valve constructed in accordance with the invention; and Figure 2 illustrates the valve when open. Description of an Exemplifying Embodiment The drawings illustrate the construction of an inven¬ tive pressure control valve. The valve comprises a valve housing 1 which houses a valve seat 2 and a valve body 3. The valve seat 2 has a substantially circular shape and is connected to a vertical connector part 4 through which gaseous refrigerant enters from a high pressure side/refrigerating compressor in a refrigerat¬ ing system or heat-pump system. The valve body 3 has the form of a substantially circular disc which is vertically moveable in relation to the valve set 2. A spring 5 is mounted between the valve body 3 and a servocylinder device 6 in the valve housing 1 and acts in a valve closing direction. The cylinder 6 has moun- ted therein a piston 7 and a piston rod 8, or some like device, which may be detaσhably connected to the valve body 3. The spring 5 may surround the piston rod 8. The working direction of the piston 7/piston rod 8 coin¬ cides with the valve-body action line. A throughflow passage 9 connects the internal throughflow space 10 of the valve housing 1 with one internal part-chamber 11 in the servocylinder, this part-chamber being defined by the inner wall of the cylinder 6 and one end surface and the end surface of the piston 7, discounting the cross-section surface of the piston rod 8. The other part-chamber 12 of the cylinder is defined by the inner wall of the cylinder 6 and one end surface and the end surface of the piston 7. The second part-chamber 12 is connected to a passage 13 which extends to a connector part 14 in a cylinder closure member 15. Arranged in the closure member 15 is a screw 16 which functions to positively or forcibly close the valve. Subsequent to removing a protective part 17 or the like, the screw 16 can be screwed down into or up out of the cylinder 6, with the aid of a spanner or like tool. When the screw is screwed down, the piston is forced downwards in the cylinder 6, wherewith the valve body 3 connected to the piston rod 8 can be forced down against the valve seat 2 therewith to close and shut-off the pressure control valve. The valve opening pressure can be varied, by using springs of different spring characteristics and/or different spring forces. When using the valve in a refrigerating system or heat- pump system, the valve is fitted in a connection line on the high pressure side of the system, between, for example, a refrigerating compressor and a condenser function incorporated in the system. When starting the refrigerating compressor, the pressure will rise in the connection line upstream of the control valve. The valve body 3 is held in its valve closed position, see Figure 1, until the spring force and the possibly occurrent resultant force across the servopiston are together greater than the pressure prevailing in the connector part 4. The spring 5 constantly urges the valve body 3 in its valve closing direction, such as to shut-off through¬ flow 18. The pressure difference across the piston 7 counteracts the force exerted by the spring 5. The pressure control valve is closed when a given first lowest pressure difference prevails across the piston 7. When a given second lowest pressure-difference is reached between the pressure area of the valve body 3 and the control-pressure area of the piston 7 which is greater than the spring pressure and results in an upwardly acting force on the valve body, the valve will begin to open. The valve is held fully open when there is reached a given third lowest pressure-difference which is greater than said second lowest pressure- difference. Thus, the valve will open at a given predetermined pressure and allow gaseous refrigerant to flow there¬ through, wherein the pressure exerted by the re- frigerant also acts on the undersurface of the piston 7, via the throughflow opening 9. The other side of the piston is constantly under the influence of an inter¬ mediate pressure or a low pressure. The pressure difference across the piston 7 will be capable of lifting and holding the piston with the piston rod counteracted by the spring force, in spite of the area difference, and therewith of holding the valve body, which is connected to the piston rod, in a raised position and away from the valve seat, thereby enabling the flow of gaseous refrigerant through the valve to be maintained. If the pressure should fall beneath a given predetermined level, the pressure control valve will therewith close immediately and prevent the throughflow of refrigerant.

Claims: CLAIMS 1. A pressure control valve for controlling re¬ frigerant pressure in a refrigerating system or heat- pump system, for example on the high pressure side, wherein the valve is intended to open to allow the throughflow of refrigerant subsequent to a given pres¬ sure level having been reached, and to remain open until the pressure falls beneath said given pressure level, c h a r a c t e r i z e d in that a spring- influenced valve body (3) is intended to act against a valve seat (2) in a manner to cut-off the throughflow of refrigerant; in that a servopiston (7) mounted in a servocylinder device (6) is connected with said valve body (3) for activation of said body; and in that the cylinder (6) has provided therein a connecting passage (9) which extends to the throughflow space (10) of said valve, and a further, opposed connecting passage (13) which extends to an outer source, for instance, an intermediate pressure or low pressure from the system. 2. A valve according to Claim 1, c h a r a c ¬ t e r i z e d in that the piston (7) is connected to the valve body (3) by means of a piston rod (8) ; and in that a spring (5) is arranged to act between the servo cylinder (6) mounted in the valve and the valve body (3) , and surrounds said piston rod (8). 3. A valve according to Claim 1, c h a r a c - t e r i z e d in that a positive closure part (16) is arranged in connection with the servocylinder, said positive closure part (16) having the form of a screw means which can be screwed into the cylinder (6) for action against the piston (7) such as to move said piston, and therewith move the valve body (3) connected thereto towards and into contact with the valve seat (2). 4. A valve according to Claims 1-3, wherein the action lines of the positive closure part (16), the servopis- ton (7) , the piston rod (8) and the valve body (3) mutually coincide.

Inventors: JOHANSSON ALF, LINDHOLM PETER, JOHANSSON, ALF, LINDHOLM, PETER
Applicants: STAL REFRIGERATION AB
Application year: 1991
Main classification: F16K31
IPC codes: F16K17, F25B41