Abstract:
A metal diaphragm is provided which acts as a spring while defining a flow path. A restraint limits upward movement of the diaphragm during transient motion. Downward movement is resisted by a Belleville spring.

Description:
BACKGROUND OF THE INVENTION 
     Rigid connections between members in a mechanical system can be a path of vibrational propagation between members. One arrangement in which this can occur is in a refrigeration system chiller where a compressor is mounted on a heat exchanger by a rigid connection through which fluid is transferred. 
     Screw compressors, especially high speed geared compressors, generate high levels of structure borne energy in a frequency range where components of the systems in which they are typically applied are very responsive. This often leads to unacceptably high radiated sound levels from both the compressors and the rigidly attached system components. The problem is particularly acute with compressors designed to be directly mounted on a heat exchanger shell such that the compressor is fully supported by a flange extending directly from the shell. This is because this joint tends to transmit energy very efficiently from the compressor to the heat exchanger shell. Reducing this transmission by conventional means such as elastomeric or helical springs is very difficult due to the conflicting requirements placed on the joint. Specifically, the joint must hermetically contain the refrigerant, withstand the operating pressure in the system, and be structurally robust, especially if the joint represents the sole support for the compressor. Additionally, space requirements are often very restrictive since minimizing package size is critical. 
     Several designs have been formulated to address the radiation of structurebome noise. They involve structurally decoupling the compressor from the heat exchanger. When transient events occur, however, the flexibility of the isolator may allow too much compressor motion. Additionally, during pressure testing in the factory, stress levels in the isolator may induce yielding, which would have a potential negative impact on performance and reliability. 
     SUMMARY OF THE INVENTION 
     The present invention is essentially a stand alone insertion installed between a compressor and a heat exchanger which supports the compressor and provides a fluid path between the compressor and heat exchanger. A flexible metal diaphragm acts as a spring to isolate vibration while defining a portion of the fluid path thereby fully containing the refrigerant. Hence, it can be incorporated without requiring any major design changes. The metal diaphragm is of an appropriate thickness and geometry to have the needed spring constant. Because the diaphragm member is thin and horizontal, space demands in the critical vertical direction are minimized. Since the design is 100% metallic, except for the seal structure, the diaphragm can be machined to the proper configuration or, if assembled, welding can be used to guarantee hermeticity. Additionally, no material compatibility problems with refrigerant and oil are raised, as would be the case with elastomeric materials. 
     The present invention includes a restraint that prevents the motion of the vibration isolator during large amplitude transient events or while the chiller undergoes a pressure test in the factory. Under normal compressor operation, the restraint is not in contact with the compressor side of the isolation system/diaphragm in order to prevent acoustic short circuiting of the isolator. When the system is pressure tested, however, the diaphragm deflects until the restraint is reached, much like a valve&#39;s opening movement being limited by a valve stop. At this point, further motion of the diaphragm is limited and the restraint becomes the primary load bearing member of the assembly. During a transient event, the isolator also can deflect until the diaphragm contacts the restraint and the load is again borne by the restraint. 
     It is an object of this invention to reduce heat exchanger vibration due to compressor excitation in a refrigeration or air conditioning system. 
     It is an additional object of this invention to use a metal diaphragm as a spring and to limit movement of the diaphragm during transient motion. 
     It is another object of this invention to reduce structure borne sound resulting from compressor operation. 
     It is an additional object of this invention to reduce overall sound radiation from a chiller. 
     It is a further object of this invention to provide an axially compact vibration isolator. These objects, and others as will become apparent hereinafter, are accomplished by the present invention. 
     Basically, a metal diaphragm is provided which acts as a spring while defining a flow path. A restraint limits upward movement of the diaphragm during transient motion. Downward movement is resisted by a Belleville spring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the present invention, reference should now be made to the following detailed description thereof taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a sectional view of the present invention taken along line corresponding to  1 — 1  of FIG. 4 providing vibration isolation and a fluid connection between a compressor and a heat exchanger; 
     FIG. 2 is a view of the heat exchanger side of the mounting plate; 
     FIG. 3 is a view of the heat exchanger side of the diaphragm; and 
     FIG. 4 is a view of the heat exchanger side of the restraint. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIG. 1 the numeral  10  generally designates a refrigerant compressor, such as a screw compressor, and the numeral  12  designates a cooler or evaporator of a refrigeration or air conditioning system. Compressor  10  has an annular groove  10 - 1  which receives o-ring  11 . Diaphragm  30  is secured to compressor  10  by circumferentially spaced bolts  16  which extend through bores  30 - 7  in diaphragm  30  and are threaded into threaded bores  10 - 2  in compressor  10 . Crush washers  18 , or the like, underlie the heads of bolts  16  to provide a seal. If necessary, or desired, an annular groove can be formed in diaphragm  30  in place of annular groove  10 - 1 . Flange  12 - 1  is overlain by annular mounting plate  20  which is illustrated in FIG. 3. A fluid seal is provided between mounting plate  20  and flange  12 - 1  by o-ring  21  which is located in an annular groove in either flange  12 - 1  or plate  20  with groove  20 - 1  in plate  20  being illustrated. 
     Diaphragm  30  which is illustrated in FIG. 2, overlies plate  20  and peripherally engages, and is supported by, plate  20 . An o-ring  22  provides a fluid seal between mounting plate  20  and diaphragm  30  and is located in an annular groove in either diaphragm  30  or plate  20  with groove  20 - 4  in mounting plate  20  being illustrated. As noted, diaphragm  30  peripherally engages plate  20  and this is due to the fact that the outer portion  30 - 1  of diaphragm  30  is the portion with the greatest axial thickness. Immediately, radially inward of portion  30 - 1  is thinnest portion  30 - 2  which is capable of flexure responsive to compressor induced vibrations, etc. Radially inward of thinnest portion  30 - 2  is portion  30 - 3  which is of intermediate thickness such that it is rigid and, in use, supports the weight of compressor  10  but is separated from plate  20 . Annular extension  30 - 4  is normally spaced from mounting plate  20  and forms a portion of bore  30 - 5  which is generally coaxial with bore  20 - 2  in plate  20  and bore  12 - 2  in evaporator  12 . The engagement of annular extension  30 - 4  with plate  20  is one extreme position of diaphragm  30 . Belleville spring or washer  40  surrounds annular extension  30 - 4  and engages portion  30 - 3  of diaphragm  30  and plate  20  and tends to keep them separated while supporting the weight of compressor  10 . Belleville spring  40  is much stiffer than thinnest portion  30 - 2  and has a spring constant that is on the order of five times higher than that of thinnest portion  30 - 2 . 
     Annular restraint  50  is secured to plate  20  and diaphragm  30  by circumferentially spaced bolts  60  which serially extend through bore  20 - 3  in plate  20 , bores  30 - 6  in diaphragm  30  and are threaded into threaded bores  50 - 1  in restraint  50 . Restraint  50  has a radially inwardly extending portion  50 - 2  which is normally separated from portion  30 - 2  of diaphragm  30  by a small distance which is on the order of 0.004 inches. Accordingly, the other extreme position of diaphragm  30  is when portion  30 - 2  engages portion  50 - 2  of restraint  50 . Portion  50 - 2  acts in the manner of a valve stop in that it limits the movement/flexure of diaphragm  30  upon engagement of portion  50 - 2  by diaphragm  30 . Mounting plate  20  is secured to the flange  12 - 1  by bolts  24  which extend through bore  20 - 4  and are threaded into threaded bore  20 - 4  of mounting plate  20 . 
     In operation, diaphragm  30  will be separated from portion  50 - 2  of restraint  50 . The resilience of diaphragm  30  coupled with the biasing force of Belleville spring  40  normally keeps annular extension  30 - 4  of diaphragm  30  separated from mounting plate  20 . Accordingly, while there is a metal-to-metal contact of the compressor  10  with other members it is through the resilient coupling provided by Belleville spring  40  and thin portion  30 - 2  of diaphragm  30 . Transient movement of diaphragm  30  is limited by portion  50 - 2  of restraint  50  and by contact between annular extension  30 - 4  with mounting plate  20 . However, such contact is out of the range of movement during normal operation. 
     Although a preferred embodiment of the present invention has been specifically illustrated and described, other changes will occur to those skilled in the art. For example, the description has been specific to a chiller but is applicable to other fluid connections. Also, gaskets may be used in place of the o-rings and other suitable springs or biasing structure can be used in place of the Belleville spring. It is therefore intended that the scope of the present invention is to be limited only by the scope of the appended claims.