Abstract:
The base pan of a refrigeration, air conditioning or heat pump is overlain by a series of assemblies each serially including a grommet, a compressor foot or base and, optionally, a washer or the like. A stud or bolt extending through each assembly secures the respective assembly to the base pan. The grommets are each received in recesses defined by a lip or rim formed on a compressor foot such that the grommets are exteriorly, peripherally or circumferentially engaged by the lip or rim so as to resist transverse motion of the compressor. The grommets are preferably located entirely between the compressor foot or base and the base pan. The grommets have different wall thicknesses at different axial and/or circumferential locations.

Description:
BACKGROUND OF THE INVENTION 
     Compressors used in refrigeration, air conditioning and heat pump systems are normally mounted to the associated base pan through a vibration isolating mounting assembly. Specifically, compressors are commonly mounted to the base pan of the condensing or outdoor unit. In such an installation, it is desirable to damp vibrations and the resultant noise caused by operation of the compressor. A common arrangement is to locate elastomeric grommets between the base or feet of the compressor and the base pan upon which it is mounted. The grommets have lips and necks which permit their insertion into openings in the base or feet of the compressor which generally correspond to the neck dimensions. The compressor, with attached grommets, is set on the base pan which has a plurality of threaded studs secured thereto. The threaded studs are then pushed through the grommets as the compressor is set on the base pan. Nuts are threaded to the studs to secure the connection. 
     The grommets support the weight of the compressor and are radially spaced from the center of gravity of the compressor to prevent it from tipping. While the spaced supports provide stability, they also increase the torsional restoring forces due to their distance from the axis of rotation. The grommets serve to vibrationally and acoustically isolate the compressor from its support. The resonance frequencies of the compressor torsional and rocking modes are inherently high in such a mounting arrangement, tending to fall into the proximity of the compressor speed and to cause vibration and noise problems. To alleviate these problems, the grommets are normally made very soft in the transverse directions which may result in excessive movement during shipping causing damage to the piping and/or coils in the system. Because movement of the compressor base or feet is a shearing or cutting movement relative to the necks of the grommets, their weakest point, damage may occur to the grommets. Besides being vulnerable to damage, installation is difficult due to the grommet lips, and the neck represents a small clearance between the compressor foot and the studs such that a short circuit for vibration can be created upon the cutting of the neck. 
     In addition to vibrationally and acoustically isolating the compressor from its support during operation, they also cushion the compressor during shipping. Tipping, dropping and the like can subject the compressor to forces and magnitudes of forces not encountered in normal operation. Upon severe tipping, or the like, the lip, or a portion thereof, may be pulled through the compressor base or foot such that the isolator will be subsequently damaged and/or ineffective. 
     SUMMARY OF THE INVENTION 
     The grommets of the compressor mounting assembly are preferably made without necks but, if present, can be made larger and with a clearance around the necks since the grommets are received and engaged, at the location of their greatest radial extent, in annular recesses in the compressor feet or base. With the elimination of the lips or heads due to the elimination of the necks, rubber washers, or the like, may be optionally located between the compressor feet or base and the nuts on the studs holding the assembly in place during shipping. If rubber washers, or the like, are not used, the spacing between the compressor feet and the nuts must be less than the depth of the annular recesses such that the grommets will not be withdrawn from the recesses as when tipping occurs. 
     It is an object of this invention to facilitate grommet installation. 
     It is another object of this invention to reduce isolator failure due to cutting of the grommets. 
     It is a further object of this invention to reduce forces transmitted to the base pan from a compressor. 
     It is another object of this invention to attenuate compressor generated sound. 
     It is a further object of this invention to provide improved vibration isolation of a compressor. These objects, and others as will become apparent hereinafter, are accomplished by the present invention. 
     Basically, the base pan of a refrigeration, air conditioning or heat pump system is overlain by a series of assemblies each serially including a grommet, a compressor foot or base and, optionally, a washer or the like. The compressor foot or base defines a plurality of recesses for receiving one end of each grommet and are of such a depth as to retain the grommets when the compressor is subject to tipping or the like. A stud or bolt extending through each assembly, and coacting with a nut, secures the respective assembly to the base pan. 
    
    
     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 pictorial view of a compressor mounted to a base pan according to the teachings of the present invention; 
     FIG. 2 is a sectional view of a PRIOR ART compressor mounting assembly; 
     FIG. 3 is a sectional view of a compressor mounting assembly according to the teachings of the present invention; 
     FIG. 4 is an exploded view of the compressor mounting assembly of FIG. 3; 
     FIG. 5 is a vertical sectional view of a first modified grommet; 
     FIG. 6 is a vertical sectional view of a second modified grommet taken along line  6 — 6  of FIG. 7; 
     FIG. 7 is a top view of the grommet of FIG. 6; 
     FIG. 8 is a partial, vertical sectional view of the details of a modification that can be made in the grommets of FIGS.  1  and  3 - 7 ; and 
     FIG. 9 is a sectional view of a compressor mounting assembly in which a PRIOR ART grommet is employed in combination with a compressor foot or base of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIG. 1, the numeral  10  generally designates a vertical hermetic compressor having a plurality of feet  10 - 1 . Compressor  10  is secured to base pan  12  via a plurality of compressor mountings  20  which vibrationally isolate compressor  10  from base pan  12  during operation and cushion compressor  10  during shipping. The vibrational isolation is due to the fact that compressor feet  10 - 1  are not in metal-to-metal contact with any other structure. 
     FIG. 2 illustrates a PRIOR ART compressor mounting  120 . Grommet  122  is made of a resilient material, such as rubber, and has a bore  122 - 1 , a neck portion  122 - 2  and a lip portion  122 - 3 . Lip portion  122 - 3  is forced through opening  10 - 1   a  of compressor foot  10 - 1  such that neck portion  122 - 2  is located in opening  10 - 1   a  when the grommet  122  is in place relative to compressor foot  10 - 1 . With grommets  122  in place in the feet  10 - 1  of a compressor, the grommets  122  are placed such that threaded studs  14  extend through bores  122 - 1 . A washer  130  is placed over stud  14  followed by nut  40  which is treaded onto stud  14  such that it engages washer  130  which, in turn engages the lip  122 - 3  of grommet  122  such that compressor feet  10 - 1  are secured to base pan  12 . Because neck portion  122 - 2  is the smallest diameter portion of grommet  122  and is received in opening  10 - 1   a , the weakest structure is located in a location where it is most easily cut. 
     Referring specifically to FIGS. 3 and 4, threaded stud  14  is welded or otherwise suitably secured to base pan  12 . Grommet  22  is made of a resilient material, such as rubber, and has a first bore  22 - 1  and a second bore  22 - 3  with shoulder  22 - 2  therebetween. Bore  22 - 1  receives stud  14  and the bottom  22 - 4  of grommet  22  rests on base pan  12  when compressor mounting  20  is assembled. Compressor foot  10 - 1  has an opening  10 - 2  for loosely receiving stud  14  and a downwardly extending annular lip or rim  10 - 3  defining bore or recess  10 - 4  for snugly receiving and circumferentially securing the top portion  22 - 5  of grommet  22  when compressor mounting  20  is assembled. Rubber washer  30  and metal washer  34 , if present, overlie compressor foot  10 - 1  and receive threaded stud  14 . Nut  40  threadedly receives threaded stud  14  and secures grommet  22  in engagement with base pan  12  and with top portion  22 - 5  received in the bore or recess  10 - 4  defined by annular lip or rim  10 - 3 . The grommets  22  support the weight of compressor  10 . It will be noted that there is an annular space  50  between stud  14  and bore  22 - 3 . The size and shape of annular space  50  is dictated by corresponding dimensional/thickness factors which dictate the lateral and vertical stiffness of grommet  22  and therefore of compressor mounting  20 . Additionally, or if desired, the outer surface of grommets  22  may be modified by providing circumferential relieved portions, axial grooves, etc. to modify the lateral and vertical stiffness. 
     In comparing PRIOR ART compressor mounting  120  of FIG. 2 with compressor mounting  20  of FIG. 3, a number of differences are readily apparent. First, grommet  122  extends through foot  10 - 1  and engages the perimeter of opening  10 - 1   a  at its least external radial extent whereas grommet  22  is entirely located between base pan  12  and compressor foot  10 - 1  and is engaged at its greatest external peripheral extent. If a neck and lip is formed on grommet  22  there would be a clearance with opening  10 - 2  and bore or recess  10 - 4 , rather than opening  10 - 2 , would be the structure preventing transverse movement. Second, because grommet  122  is circumferentially engaged/restrained by compressor foot  10 - 1  at neck  122 - 2 , the smallest diameter portion of grommet  122 , it is subject to a cutting motion by compressor foot  10 - 1 , whereas grommet  22  is circumferentially and uniformly engaged by lip or rim  10 - 3 , defining recess  10 - 4 , at the fullest peripheral or circumferential extent of grommet  22 . These differences make grommet  22  less likely to be damaged, more easily installed, and the length and diameter of bore  22 - 3  and external surface of grommet  22  can be varied to permit changes in the lateral and vertical stiffness of grommet  22 . 
     FIG. 5 illustrates a first modified grommet  222 . Grommet  222  differs from grommet  22  in the addition of radially extending annular lip  222 - 1  which defines the outermost portion of grommet  222 . Lip  222 - 1  is received in bore or recess  10 - 4  of lip or rim  10 - 3  of compressor foot  10 - 1  and would be the only portion of grommet  222  circumferentially engaged by rim  10 - 3 . Lip  222 - 1  will nominally have an unstressed diameter the same as that of the bore or recess  10 - 4  and may, accordingly, be flexed in being located in bore or recess  10 - 4 . The addition of lip  222 - 1  permits the independent adjustment of the radial stiffness of grommet  222  to a desired value. 
     FIGS. 6 and 7 illustrate a second modified grommet  322  which is a further modification of grommet  222 . Like grommet  222 , grommet  322  has a radially extending annular lip  322 - 1  which functions the same as lip  222 - 1 . Additionally, grommet  322  has a plurality of axially extending grooves  322 - 2  which are formed in the bore  322 - 3  and/or bore  322 - 4 . The function of grooves  322 - 2  is to change the lateral and vertical stiffness of grommet  322 . 
     FIG. 8 illustrates a grommet  422  having a modified annular lip  422 - 1 . Lip  422 - 1  is of a C-shape or semi-circle in radial section. The free end  422 - 1   a  of lip  422 - 1  is radially spaced from the main body portion of grommet  422 . Lip  422 - 1  can flex or be circumferentially compressed with a varying resistance. The resistance will increase when lip  422 - 1  engages the main body portion of grommet  422 . The lower initial resistance to deformation is desired for vibration isolation under normal operating conditions and high resistance is desired to limit compressor motions during shipping. 
     Grommet  22  of FIGS. 3 and 4 may be modified by providing it with a lip  222 - 1  or  422 - 1  as illustrated in FIGS. 5 and 8, respectively. Additionally, or alternatively, the cross section of grommet  22  may be modified as by providing grooves  322 - 2 , as illustrated in FIGS. 6 and 7. 
     Referring now to FIG. 9, the PRIOR ART grommet  122  may be used in combination with a compressor foot  10 - 1  having a lip or rim  10 - 3  defining bore or recess  10 - 4 . Basically, FIG. 9 differs from FIG. 3 in the replacement of grommet  22  with grommet  122  and the elimination of washers  30  and  34 . Because opening  102  is much larger than opening  10 - 1   a , lip  122 - 3  and neck  122 - 2  have no significant coaction with foot  10 - 1  or opening  10 - 2 . In the absence of washers  30  and  34 , nut  40  is threshold to the extent permitted by the threads on stud  14  but nut  40  would be spaced from foot  10 - 1  a distance less than the axial extent or depth of bore or recess  10 - 4 . Accordingly if the compressor is tipped, or the like, during shipping grommet  122  would remain in recess  10 - 4 . Normal compressor operation would not cause contact between foot  10 - 1  and nut  40 , even in the absence of washer  30  and  34 . 
     Although preferred embodiments of the present invention have been described and illustrated, other changes will occur to those skilled in the art. For example, the description has been specific for a vertical compressor, but the present invention is applicable to a horizontal compressor. Also, while a round/cylindrical shape has been illustrated, the grommets may have other shapes. It is therefore intended that the scope of the present invention is to be limited only by the scope of the appended claims.