Patent Publication Number: US-2012036885-A1

Title: Expansion valve comprising biasing means

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is entitled to the benefit of and incorporates by reference essential subject matter disclosed in International Patent Application No. PCT/DK2009/000234 filed on Nov. 11, 2009 and Danish Patent Application No. PA  2008   01568  filed Nov. 12, 2008. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an expansion valve, in particular for use in a refrigeration system, e.g. an air condition system. The expansion valve of the present invention is adapted to distribute fluid medium to at least two parallel flow paths, e.g. in the form of at least two parallel evaporators or evaporator tubes. 
     BACKGROUND OF THE INVENTION 
     In a fluid circuit, such as a refrigerant circuit of a refrigeration system, it is sometimes desirable to split the flow path into two or more parallel flow paths along part of the fluid circuit. This is, e.g., the case in refrigeration systems comprising two or more evaporators arranged in parallel. It may further be desirable to be able to control the fluid flow to each of the parallel flow paths, e.g. in such a manner that a substantially equal fluid distribution is obtained, or in such a manner that the system is operated in an optimum manner, e.g. in terms of energy consumption or efficiency. 
     In some previous attempts to control distribution of refrigerant between two or more parallel flow paths in a refrigeration system, a distributor is arranged downstream relative to an expansion valve in the refrigerant flow path. Thus, the refrigerant is distributed after expansion of the refrigerant, i.e. the refrigerant is mainly gaseous. This has the disadvantage that it is very difficult to control the flow of refrigerant to obtain a substantially equal distribution between the parallel flow paths. 
     SUMMARY OF THE INVENTION 
     It is an object of embodiments of the invention to provide an expansion valve which is capable of controlling distribution of fluid to two or more parallel flow paths. 
     It is a further object of embodiments of the invention to provide an expansion valve which is adapted to manage distribution of fluid to two or more parallel flow paths in an easy manner. 
     According to a first aspect the present invention provides an expansion valve comprising:
         an inlet opening adapted to receive fluid medium in a liquid state,   at least two outlet openings, each being adapted to deliver fluid medium in an at least partly gaseous state,   a first valve part having at least two valve seats formed therein, each of the valve seats being fluidly connected to one of the outlet openings,   a second valve part, the first valve part and the second valve part being arranged movably relative to each other,   at least two valve elements, each valve element being arranged in such a manner that the valve seats and the valve elements pair-wise form at least two valves, and   biasing means arranged to bias the valve elements and the valve seats towards a position defining a minimum opening degree of the valves, or towards a position defining a maximum opening degree of the valves,
 
wherein the second valve part and the valve elements are connected in such a manner that the mutual position of the first valve part and the second valve part determines an opening degree of each of the valves.
       

     The expansion valve of the invention defines flow paths between the inlet opening and the at least two outlet openings. Fluid medium in a liquid state is received at the inlet opening and fluid medium in an at least partly gaseous state is delivered at the outlet openings. In the present context the term ‘liquid state’ should be interpreted to mean that the fluid medium entering the expansion valve via the inlet opening is substantially in a liquid phase. Similarly, in the present context the term ‘at least partly gaseous state’ should be interpreted to mean that the fluid medium leaving the expansion valve via the outlet openings is completely in a gaseous phase, or at least a part, e.g. a substantial part, of the volume of the fluid medium leaving the expansion valve is in a gaseous phase. Accordingly, at least a part of the fluid medium entering the expansion valve undergoes a phase transition from the liquid phase to the gaseous phase when passing through the expansion valve. 
     The inlet opening and the outlet openings may preferably be fluidly connected to one or more other components, such as other components of a refrigeration system. The expansion valve may advantageously form part of a flow system, such as a flow circuit. 
     The expansion valve comprises a first valve part and a second valve part arranged movably relative to each other. This may be achieved by mounting the first and/or the second valve part in a manner which allows it/them to move relative to the remaining parts of the expansion valve. Thus, the first valve part may be movable while the second valve part is mounted in a fixed manner. As an alternative, the second valve part may be movable while the first valve part is mounted in a fixed manner. Finally, both of the valve parts may be movably mounted. In all of the situations described above a relative movement between the first valve part and the second valve part is possible, thereby defining a mutual position of the first valve part and the second valve part. 
     The first valve part has at least two valve seats formed therein, and each of the valve seats is fluidly connected to one of the outlet openings. At least two valve elements are arranged in such a manner that the valve seats and the valve elements pair-wise form at least two valves. The valve elements are further connected to the second valve part in such a manner that the mutual position of the first valve part and the second valve part determines an opening degree of the valves. Accordingly, the valve elements preferably performs movements relative to the valve seats when the first valve part and the second valve part perform relative movements. Thus, the opening degrees of the valves, and thereby the amount of fluid medium supplied to each of the outlet openings, can be adjusted by adjusting the mutual position of the first valve part and the second valve part. Since the opening degrees of the valves are defined by the mutual position of the first valve part and the second valve part, the opening degrees are adjusted synchronously, thereby at least substantially maintaining a distribution key among the outlet openings. 
     The expansion valve further comprises biasing means arranged to bias the valve elements and the valve seats towards a position defining a minimum opening degree of the valves, or towards a position defining a maximum opening degree of the valves. In the case that the biasing means is arranged to bias the valve elements and the valve seats towards a position defining a minimum opening degree of the valves, the biasing means will attempt to close the valves, and when the expansion valve is operated to cause the valves to be opened, work must be performed against the biasing force provided by the biasing means. On the other hand, in the case that the biasing means is arranged to bias the valve elements and the valve seats towards a position defining a maximum opening degree of the valves, the biasing means will attempt to keep the valves open, and when the expansion valve is operated to cause the valves to be closed, work must be performed against the biasing force provided by the biasing means. 
     In any event, the biasing force provided by the biasing means defines a point of equilibrium for the relative movements of the valve seats and the valve elements. Designing and positioning the biasing means carefully thereby allows a correspondence between a movement force applied for providing relative movement between the valve parts and opening degree of the valves to be designed. For instance, the biasing force may be selected in such a manner that a ‘soft’ closing of the valve is obtained, and/or in such a manner that a specific applied moving force results in a specific opening degree. 
     The valve elements may form part of the second valve part. According to this embodiment, relative movements between the first valve part and the second valve directly results in corresponding relative movements between the valves seats and the valve elements. For instance, the relative movements between the first valve part and the second valve part may be substantially linear movements causing each of the valve elements to simultaneously move towards or away from the corresponding valve seat. The valve parts may each, e.g., be or comprise a substantially disk shaped part having the valve seats and the valve elements, respectively, formed on surface parts thereof. In this case the valve seats may be in the form of through-going bores of the disk forming the first valve part, and the valve elements may be in the form of protruding parts formed on a surface of the disk forming the second valve part which is facing the first valve part. 
     As an alternative, the valve elements may form separate parts being operatively connected to the second valve part. According to this embodiment the valve elements and the second valve part may be arranged on opposing sides of the first valve part, and moving the first valve part and the second valve part towards each other may cause the second valve part to simultaneously push the valve elements in a direction away from the valve seats, thereby increasing the opening degrees of the valves defined by the valve elements and valve seats. In this case the biasing means may advantageously be arranged to push the valve elements in a direction towards the valve seats. Thereby, when moving the first valve part and the second valve part away from each other, the biasing means will ensure that the valve elements are moved towards the valve seats, thereby decreasing the opening degree of the valves. 
     The biasing means may be or comprise at least one spring, such as a compressible spring. The spring may be in a compressed state, in which case the spring force acts to push two parts, e.g. the first and second valve parts or the first valve part and one or more valve elements, away from each other. Alternatively, the spring may be in a stretched state, in which case the spring force acts to pull two parts, e.g. the first and second valve parts or the first valve part and one or more valve elements, towards each other. 
     The valve elements may be of a needle type, or they may be of a ball type. Alternatively, the valve elements may be of any other suitable kind. 
     The expansion valve may further comprise a thermostatic element, and the first valve part and/or the second valve part may be operatively connected to the thermostatic element, relative movements of the first valve part and the second valve part thereby being caused by the thermostatic element. According to this embodiment, the thermostatic element determines the opening degrees of each of the valves defined by the valve seats and the valve elements, i.e. the thermostatic element simultaneously determines the mass flow to each of the outlet openings. 
     The biasing means may, in this case, be arranged to counteract movements caused by the thermostatic element in response to an increase in pressure. According to this embodiment, biasing force provided by the biasing means and the moving force originating from the thermostatic element in response to changes in pressure, in combination define an equilibrium which determines the opening degrees of the valves. 
     As an alternative, the relative movements between the valve parts, and thereby the opening degrees of the valves defined by the valve seats and the valve elements, may be controlled by means of other suitable kinds of actuators. 
     According to a second aspect the present invention provides a refrigeration system comprising:
         at least one compressor,   at least one condenser,   at least two evaporators arranged in parallel along a refrigerant flow path of the refrigeration system, and   an expansion valve according to any of the preceding claims, said expansion valve being arranged in such a manner that each of the valves is arranged to deliver refrigerant to one of the evaporators.       

     Thus, the expansion valve according to the first aspect of the invention may advantageously be arranged in a refrigeration path of a refrigeration system, e.g. a refrigeration system used in a cooling arrangement or an air condition system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described in further detail with reference to the accompanying drawings in which 
         FIG. 1  is a cross sectional view of an expansion valve according to a first embodiment of the invention, and 
         FIG. 2  is a cross sectional view of an expansion valve according to a second embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a cross sectional view of an expansion valve  1  according to a first embodiment of the invention. The expansion valve  1  comprises a first valve part  2  having a number of valve seats  3 , two of which are visible, formed therein. The expansion valve  1  further comprises a second valve part  4  having a number of valve elements  5  of a needle type, two of which are visible, forming part thereof. The valve seats  3  and the valve elements  5  are arranged relative to each other in such a manner that a number of valves are defined by pairs of valve seats  3  and valve elements  5 . 
     The first valve part  2  and the second valve part  4  are movable relative to each other along a substantially vertical direction of the Figure, i.e. in such a manner that the valve elements  5  are movable towards and away from the valve seats  3 . Thereby the relative position of the first valve part  2  and the second valve part  4  determines the relative position of the valve seats  3  and the valve elements  5 . Due to the substantially conical shape of the valve elements  5 , the relative position of the first valve part  2  and the second valve part  4  determines the size of a passage through each valve seat  3 , and thereby the opening degree of each of the valves defined by the pairs of valve seats  3  and valve elements  5 . 
     The expansion valve  1  further comprises biasing means in the form of a compressible spring  6 . The spring  6  is arranged between the first valve part  2  and the second valve part  4 . It may be in a compressed state, in which case it pushes the first valve part  2  and the second valve part  4  in a direction away from each other. Since the valve seats  3  form part of the first valve part  2  and the valve elements  5  form part of the second valve part  4 , the spring  6  also pushes the valve seats  3  and the valve elements  5  in a direction away from each other, i.e. towards a position defining a maximum opening degree of the valves. 
     Alternatively, the spring  6  may be in a stretched state, in which case it pulls the first valve part  2  and the second valve part  4 , and thereby the valve seats  3  and the valve elements  5 , in a direction towards each other, i.e. towards a position defining a minimum opening degree of the valves. 
     The second valve part  4  is operatively connected to a thermostatic element (not shown), and the relative position of the first valve part  2  and the second valve part  4  is thereby determined by the thermostatic element. 
     The expansion valve  1  of  FIG. 1  may operate in the following manner. Fluid medium in a substantially liquid state enters the expansion valve  1  via an inlet opening as illustrated by arrow  7 . The fluid medium is led through the expansion valve  1  towards the valve seats  3 , and further on towards outlet openings  8 , eventually leaving the expansion valve  1  via the outlet openings  8 . During this the fluid medium is expanded, and the fluid medium leaving the expansion valve  1  via the outlet openings  8  is therefore in an at least partly gaseous state. 
       FIG. 2  is a cross sectional view of an expansion valve  1  according to a second embodiment of the invention. Similarly to the embodiment shown in  FIG. 1 , the expansion valve  1  of  FIG. 2  comprises a first valve part  2  having a number of valve seats  3  formed therein, and a second valve part  4 . The first valve part  2  and the second valve part  4  are movable relative to each other along a substantially vertical direction of the Figure. 
     The expansion valve  1  further comprises a number of valve elements  5 , two of which are visible, in the form of separate elements arranged movably with respect to the valve seats  3  and in such a manner that a number of valves are defined by pairs of valve seats  3  and valve elements  5 . 
     The valve elements  5  are arranged in such a manner that they are allowed to extend through the openings defined by the valve seats  3  and in abutment with the second valve part  4 . Biasing means in the form of compressible springs  6  are arranged between the valve elements  5  and a base part  9  of the expansion valve  1 . The springs  6  are in a compressed state, thereby pushing the valve elements  5  towards the valve seats  3  and into abutment with the second valve part  4 . Thus, the springs  6  push the valve elements  5  towards a position defining a minimum opening degree of the valves. 
     Since the valve elements  5  are arranged in abutment with the second valve part  4 , and since the springs  6  ensure a firm abutment between the valve elements  5  and the second valve part  4 , the valve elements  5  perform movements corresponding to the movements of the second valve part  4 . Thus, when the first valve part  2  and the second valve part  4  are moved relative to each other in a direction away from each other, the valve elements  5  and the valve seats  3  are moved in a direction towards each other, thereby decreasing the opening degrees of the valves defined by the valve seats  3  and the valve elements  5 . Similarly, when the first valve part  2  and the second valve part  4  are moved relative to each other in a direction towards each other, the valve seats  3  and the valve elements  5  are pushed away from each other, thereby increasing the opening degrees of the valves defined by the valve seats  3  and the valve elements  5 . Due to the substantially conical shape of the valve elements  5 , the relative position of the first valve part  2  and the second valve part  4  thus determines the size of a passage through each valve seat  3 , and thereby the opening degrees of the valves. 
     The second valve part  4  is operatively connected to a thermostatic element (not shown), and the relative position of the first valve part  2  and the second valve part  4  is thereby determined by the thermostatic element. 
     The expansion valve  1  of  FIG. 2  may operate in the following manner. Fluid medium in a substantially liquid state enters the expansion valve  1  via an inlet opening as illustrated by arrow  7 . The fluid medium is led through the expansion valve  1  towards the valve seats  3 , and further on towards outlet openings  8  formed in the base part  9  and fluidly connected to the valve seats  3 . The fluid medium leaves the expansion valve  1  via the outlet openings  8 . During this the fluid medium is expanded, and the fluid medium leaving the expansion valve  1  via the outlet openings  8  is therefore in an at least partly gaseous state. 
     While the present invention has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this invention may be made without departing from the spirit and scope of the present.