Fluid handling – Systems – Dividing into parallel flow paths with recombining
Reexamination Certificate
2000-07-24
2001-09-18
Hepperle, Stephen M. (Department: 3753)
Fluid handling
Systems
Dividing into parallel flow paths with recombining
C137S601180, C137S601210
Reexamination Certificate
active
06289930
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to refrigeration and cooling systems which include a piston orifice expansion device.
BACKGROUND OF THE INVENTION
Air conditioning and refrigeration systems typically operate in a cycle which employs a series of functions, including a compression step wherein low-pressure refrigerant gas is compressed to a high-pressure state and a condensation step in which the gas is converted to a liquid, accompanied by a release of heat.. The condensed liquid is then forced under pressure through an expansion device, partially converting the liquid to a gaseous state, after which the refrigerant is passed through a second heat exchanger or evaporator stage where heat from the surrounding air is transferred to the refrigerant, resulting in cooling of the air. Low pressure gas produced by evaporation is then recycled to the compressor.
Air conditioning systems generally use one of three different types of expansion devices; a thermostatic expansion valve, a capillary tube or tubes with a precise diameter or length or a fixed orifice piston check valve having a cylindrical chamber in which a piston with an axial bore is mounted for movement responsive to the direction of fluid flow. This invention is concerned with the third type, that is, expanders using a piston orifice check valve. Orifice pistons in these devices move from a position at the rearward end of the chamber to a position at the opposite or forward end, where the periphery of the piston is sealed by fluid-tight engagement of mating surface of the piston and chamber so that forward flow of the refrigerant is restricted to the central orifice of the piston. The orifice is sized according to system specifications to provide a selected pressure drop within the refrigerant flow stream. Flow in the reverse direction toward the rearward end of the chamber would cause the piston to move out of sealing engagement with the chamber, allowing unrestricted movement of the fluid through flutes or grooves around the periphery of the piston. Reverse flow would thus be provided as would be required for systems using a heat pump cycle. Piston orifice expansion devices of this type are exemplified by U.S. Pat. No. 5,894,741, issued Apr. 20, 1999, to Durham, et al.
A problem associated with piston orifice check-valve expansion devices is that the pressure which builds up across the piston when the system is operating is allowed to bleed down through the orifice when the system cuts off, which occurs periodically. This results in a requirement for use of additional energy to bring the system back to operating pressure upon start up. Providing a means for maintaining operating pressure differential across the piston during the off cycle would result in higher system efficiency and a consequent saving of energy costs.
Solenoid valves have been incorporated into the same valve body for certain types of expansion devices, as is disclosed in U.S. Pat. No. 5,588,590, issued Dec. 31, 1996, to Sakakibara, et al. The expansion valve of this device is a capillary type device, and the patent is concerned with eliminating impact noise resulting from “water hammer” by placing a solenoid valve between primary and secondary ports. The solenoid valve is not used to maintain a pressure different across the expander upon shutdown, the combined valve instead having an equalizer hole to reduce pressure differential. This patent makes reference to a prior Japanese patent publication disclosing use of a solenoid valve provided to the evaporator to shut off refrigerant flow to evaporators of a multi-stage system which are not in use, thus resulting in a saving of energy. The cited patent, however, does not disclose a combined device having a piston orifice valve and a solenoid valve disposed in a single integrated housing and functioning as a unit. Further improvements directed to prevention of migration of refrigerant between areas of different pressures would be desirable.
SUMMARY OF THE INVENTION
The present invention is directed to a refrigerant expansion device for an air conditioning or cooling system combined with a solenoid-actuated shut-off valve and incorporated in a common housing. The expansion device may comprise a conventional piston orifice check valve in which a piston having an axial throughbore orifice is disposed in a first, cylindrical chamber portion of a housing for sliding movement between the rearward and forward ends of the chamber. Forward ends of the chamber and piston have cooperating surfaces around their peripheries, which form a fluid-tight seal when the piston is exposed to high-pressure fluid from the rearward end of the chamber. This causes all of the refrigerant flow to be forced forward through the piston orifice, where it is subjected to controlled expansion.
A solenoid-actuated plunger of a shut-off valve is situated in a second portion of the housing in a position such as to make sealing contact with the rearward end of the piston orifice or with a sealable surface of the housing proximate the piston. The plunger serves to close off flow through the device during shut-off and to stop loss of pressure differential across the piston.
An arm of the housing is provided for support of the solenoid plunger in a desired alignment, which may be in an axial or radial direction with respect to the piston chamber. In addition, the plunger housing arm may provide support for a magnetic coil and biasing spring as required for actuation of the plunger. Suitable electronic controls are coupled to the solenoid to enable opening and closing movements of the plunger at necessary intervals in the operating cycle of the system.
The combined piston orifice expansion valve and solenoid valve closure of the invention is also suitable for use in “heat pump” systems wherein the direction of fluid flow through a pair of heat exchangers is reversible.
The combined expansion device and shut-off valve provides for positive control over movement of refrigerant fluid and the consequent loss of pressure differential which would otherwise occur during normal “off” portions of a cooling system cycle. As a result energy consumption is reduced and system efficiency is increased.
It is therefore, the object of this invention to provide a means for preventing loss of pressure differential due to bleeding down of pressure through a piston orifice during “off” portions of an air conditioning system operating cycle.
Another object is to provide a positive closure mechanism for shutting off refrigerant flow across such a piston.
Yet another object is to provide a common housing for containment of both an orifice-piston check valve and a solenoid-actuated shutoff valve in operating position.
Other objects and advantages of the invention will be apparent from the following detailed description and the claims appended hereto.
REFERENCES:
patent: 2863473 (1958-12-01), Gantz
patent: 3477466 (1969-11-01), Sturm
patent: 4147180 (1979-04-01), Steele
patent: 4624282 (1986-11-01), Fargo
patent: 5588590 (1996-12-01), Sakakibara et al.
patent: 5894741 (1999-04-01), Durham et al.
Beumer Joseph H.
Hepperle Stephen M.
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