Expansion valve

Details Expansion valve Expansion valve

2000-01-10

2001-10-02

Tapolcal, William E. (Department: 3744)

Automatic temperature and humidity regulation

Thermostatic

With pressure control

C236S09200D

Reexamination Certificate

active

06296194

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention refrigerant by controlling the flow rate of the refrigerant supplied to an evaporator in a refrigerating cycle, and according to the preamble part of claims
1
and
11
.
In known expansion valves a valve body is arranged opposite to a valve seat formed by a thin contraction in the high-pressure refrigerant duct. Said valve body is moved in relation to said valve seat to open and close said valve seat corresponding to the temperature and the pressure of low-pressure refrigerant exiting the evaporator. The valve body is moved by an axially retractable rod which is guided along its shaft line in a penetration bore of the valve casing. Said rod is actuated by a power element operating corresponding to the temperature and the pressure of low-pressure refrigerant. In operation it may occur that due to some reasons the pressure of the high-pressure refrigerant supplied into the expansion valve significantly varies at the upstream side of the valve body. Said pressure variations are transmitted to the expansion valve body by means of the refrigerant medium. In case the pressure raises upstream the valve body due to a pressure variation, a pressure depending force acts on the valve body in its closing direction and consequently pushes said rod repeatedly. As a result, due to the closing or increasing throttling effect of the valve body the pressure of the refrigerants on the upstream side also is increasing and the occurring pressure variation even is multiplied. This might lead to an extremely unstable operation of the expansion valve.
2. Description of the Related Art
As disclosed in JP H 9-222 268 the operation of a known expansion valve was made stable by applying energy in lateral direction to the rod axially retractably disposed between the power element and the valve body, e.g. by a spring or the like. As a result, the valve body cannot respond as sensitively anymore to a variation of the pressure. However, the spring laterally pressing against the rod had to be made passive during a stable operation of the expansion valve and only should be set into action to stabilise the operation behaviour in case of pressure variations of the high-pressure refrigerant. As a result, the structure of the expansion valve became complicated as well as the assembling work, and the costs for manufacturing and assembling the expansion valve were high.
It is an object of the invention to provide an expansion valve performing a stabilised operation even in case of variations of the pressure of the high-pressure refrigerant and having an extremely simple and low cost design.
OBJECTS AND SUMMARY OF THE INVENTION
Said object is achieved by the features of claim
1
and an independent claim
11
. Since the forces originating from the power element and applied to the rod held between the power element and valve body as well as for the valve body closing spring and even forces resulting from a pressure rise upstream of the valve body now are applied as couple forces, as a result, said forces applied to the rod from both its ends act to rotate or to bend the rod. Thus, a large frictional resistance occurs when the rod tends to slide axially. The valve body is disabled to respond too sensitively to a pressure change of the high-pressure refrigerant. Furthermore, it is possible to achieve said stable operational behaviour of the expansion valve by an extremely simple and cheap structure. During normal and stable operation of the expansion valve said couple forces may not gain significant influence. In other words, only in case that both ends of the rod are loaded by oppositely directed, significant forces said couple forces increase the sliding resistance of the rod temporarily in order to stabilise the operation. This is the consequential effect of the couple forces tending to rotate or bend or displace the rod sidewardly in firmer contact with the wall of said penetrating bore guiding the rod. The structure is simple and cheap, because the structural measures for the generation of the couple forces can easily be realised in the design of the expansion valve without complicating its design or the work necessary to assemble the expansion valve.
Preferred embodiments are disclosed in the depending claims.


REFERENCES:
patent: 5303864 (1994-04-01), Hirota
patent: 5924299 (1999-07-01), Karl
patent: 5961038 (1999-10-01), Okada
patent: 09-222268 (1997-08-01), None

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