US2028584A - Refrigerating machine - Google Patents

Description

Jan. 21, 1,936. H,` H. B IXLERY k 2,028,584

REFRIGERATING MACHINE Filed Jan. 11, 1935 Figa.

Inventor: Harley HBbder:

77/ by Hi/*Zttorf hey.

Patented Jan. 21, 1936 UNITED STATES n 2,038,584 meneame MACHINE n Harley H. Bixler, Schenectady, N.

Y., signor to General Electric Company, a corporation, oi'

New York Application January 11, 193s, serial No. 1,838 14 (c1. zzo- 235) My invention relates to refrigerating machines.

In many refrigerating machines, and particularly in those designed for domestic use, a cabinet is provided having a cooling compartment therein for the preservation of foods or the like. 'Ihe machine also includes a compressor for compressing gaseous refrigerant and an electric motor or ,the like for driving the compressor. 'Ihe compressed refrigerant is liquefied by a suitable condenser and is supplied to an expansion type cooling unit within the cooling compartment. It is desirable that the compressor, motor and c011- denser all be mounted on the cabinet in order that a portable self-contained machine may be had. It will be understood that the motor driven compressor unit may be mounted either on. top of the cabinet, in a machinery compartment in the lower part thereof, or in any other` suitable location therein. The mounting oi' the motor and compressor on the cabinet presents special difficulties inconnection with the minimizing of vibrations produced thereby. `The parts of the motor and compressor moving at relatively high speeds set up vibrations therein and it is necessary that the cabinet should not be similarly vibrated both because of the undesirable noise entailed and because of possible damage to the cabinet and its contents. Since the cabinet is ordinarily quite heavy, as well as comparatively rigid in a vertical direction, vertical forces applied thereto due to the vibration ofthe motor and compressor are of little or no consequence but special precautions must be taken to avoid the application of horizontal vibrational forces to the cabinet. The transmission of horizontal forces is particularly undesirable since the cabinet is usually mounted on a smooth or even slippery floor surface and lateral vibration of the cabinet might cause it to walk about the floor.

It is frequently desirable to combine the motor and compressor into a unitary structure in order to simplify the connections therebetween and to otherwise reduce the number of parts required for their construction. Such a unitary structural arrangement introduces peculiar difficulties, however, in the matter of transmission of vibrations since there are several reciprocatory, as well as rotary, parts contained in the same structure and the weight distribution is also usually unsymmetrical.

It is an object of my invention to provide ay refrigerating machine of the type described having a motor and a compressor mounted as a unitary structure thereon in such a manner that a minimum amount of horizontal vibration is transmitted therefrom to the remainder of the, machine. A

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a. part of this specication.

For a better understanding of my invention, ,reference may be had to the accompanying drawing in which Fig. 1 is a front elevation of a refrigerating .machine embodying my invention; Fig. 2l is a sectional view of a portion of the re-l. frigerating machine shown in Fig. 1;l Fig. 3 is a schematic representation of the unitary compressor and motor and the mounting therefor, included in the refrigerating machine shown in Fig. 2; Fig. 4 is a. fragmentary View, partly in section, of one of the resilient supports included in the refrigerating machine shown in Fig. 2, and 20.

Fig. 5 is a plan view of the resilient support shown in Fig. 4.

Referring to the drawing, in Fig. 1 I have shown a refrigerating machine having a cabinet III provided with a cooling compartment II, the cabinet I D being supported on legs I2 and I3. The cabinet I0 is preferably provided with an outer steel shell and an inner steel shell lining for the cooling compartment II, the inner and outer shells being separated by heat insulating material in the usual manner. A comparatively heavy structure is thus provided which is rigid in a vertical direction. The comparatively light legs I2 and I3 cause it to be less rigid in a horizontal direction. The cooling compartment I I is cooled by an evaporator I 4 which is supplied with liquid refrigerant from a condenser I5 through a conduit I6 and a flow controlling float valve I-'I. 'I'he liquid refrigerant supplied to the evaporator I4 is vapori'zed therein by the absorption of heat from articles contained in the compartment II a and the vaporized refrigerant is returned therefrom through a suction conduit I8 to the interior of an yhennetically sealed casing I0. The gaseous refrigerant in the casing I9 is compressed by a compressor 20 of the Scotch yoke type which is driven by an electric motor 2 I. Although a compressor of this type has many advantages adapting it for use in refrigerating machines, the inherent unbalance of its moving parts makes it 50 particularly difcult to mount in such a manner that undesirable vibrations will not be transmit# ted therefrom. The compressed gaseous refrigerant passes from the compressor 2li through a conduit 22 to theair-cooled condenser I5. The 55 described in de .here since it forms no part of my present in ntion.

I have provided an'arrangement for supporting the compressor 2l and motor 2l in such manner that a'minimum amount of average horizontal force will be transmitted vtherefrom to the cabinet I0. In the preferred form of my invention, the compressor 2lis mounted on-top of the-`motox 2l being secured thereto as aunitary structure by bolts 23 and 24. Since the cabinet I0 forms a heavy base for the motor 2l and compressor 2t which is relatively rigid in a vertical direction, we may neglect the effect of any vertical forces which may be transmitted to the cabinet l0 as they will have relatively little effect thereon in .any case. The mounting for the unitary compressor and motor structure must be so arranged, however, that a minimum amount of horizontal force will be transmitted therefrom to the cabinet l0.

Any` body which is capable of unrestrained,y

movement in all directions, whether the body be symmetrical or unsymmetrical, has `six normal modes of vibration. By mode of vibration is meant a pattern or path of movement through which the body vibrates at a natural frequency,

there being a natural frequency for eachhmode.-

The frequency for each mode is dependent upon the distribution of mass ln the body and upon the characteristics of its mounting as is the mode of vibration itself. Each of these modes of vibration is independent of every other mode of vibration in that the body will vibrate freely in any one particular mode, the exactly appropriate initial displacing force having been applied thereto to initiate such vibration, and while so vibrating will have no tendency to vibrate in any of the other modes. For purposes of analysis, these modes of vibration may conveniently be referred to a series of coordinates illustrated in Fig. 3. As will be seen from an inspection of Fig. 3, these coordinates include the three axes X, Y and Z, each of which is located at right angles with respect to the others at an arbitrary point of origin o which in the present instance is at approximately the center of gravity of the unitary structure. The other three coordinates are the arrows A, B and C which indicate rotary movement about the axes X, Y and Z, respectively. Any movement of the motor and compressor shown' in Fig. 3 can be analyzed in terms of rectilinear movement along the axes X, Y and Z and in an angular movement about the same axes, the six coordinates thus entailed being the minimum number of coordinates to which any general movement of the compressor and motor can be reduced. Consequently, the six normal modes of vibration of the compressor and motor can be expressed in terms of the coordinates shown in Fig. 3.

' In thev case ofa symmetrical bodyv each normal mode of vibration thereof is either a rotational movement, in a plane about some single axis (not necessarily onev of thelarbitrary reference axes chosen, of course) or reciprocatory movement along some straight line axis. In thecase of an unsymmetrical body, however, the normal modes of vibration are more complicated in that each one consists of simultaneous rotary movement about, as well as rectilinear movement along, some fixed axis, that is, a screw motion along an axis.

In the case of the motor 2l and compressor 2l! l aoaasu i operation of the refrigerating system need not be modes of vibrationare indicated byR, S,T,U and Z, respectively, the reference axis Z having been chosen coincident with the axis of one mode of vibration. The vibratory screw motion of the unitary compressor and motor structure in ijive` of its modes of vibration about the axes R, B, T.

U and Z, is indicated by the arrows u1, uz, as, 4.

and as, respectively. The axis of the sixth mode of vibration of the unitary structure illustrated is approximately in the plane of the axis R and vis in part determined by the point or points at which the resilient mounting acts on the body and the elastic characteristics of the mounting itself. The modes of vibration which are illus- I trated in Fig. 3 are the modes of vibration of the unitary structure which are in part determined by the resilientmounting therefor which is illustrated, the terms being so used hereinafter. I'he natural frequency of vibration of the unitary structure about the axes R, S, T, U, Z, and a remote sixth axis may be designated as f1, fz, f3, f4, f5, and fe, respectively. For the particular machine illustrated. ,f1 and f2 are approxi- I mately equal and are of about four cycles per second; f3 and f4 are approximately equal and are about twelve cycles per second; f5 is about eight cycles per second and fe is about nine cycles per second.

It is important to consider the normal modes of vibration of a body in determining its movement when subjected to forced vibration due to some applied exciting force since its movement as a result of such forced vibration will be in all of the normal modes simultaneously in the general case. The excitation of the body in any particular mode may, however, be modied by varying the relation of the exciting force and the axis of the mode. That is, if the force is applied at the axis it will create no couple about it and hence induce no vibration about it. In the machine illustrated the frequency of the applied force is approximately 30 cycles per second.

In order to determine the proper arrangement of the compressor 2li and motor 2| and its resilient mounting and thus to minimize the horizontal forces transmitted to the cabinet I0, consideration must be given to the ratio of the forces applied to the unitary motor and compressor structure to the forces transmitted to the base. In the case of anyresiliently mounted body the ratio of the force transmitted to the base on which the body is mounted to the forces applied thereto may be expressed by the equation:

In the above equation F1 is the forcetr nsmitted to the base and F2 is the forceapplied to the body; fo is the frequency 'of theapplied force and fs is the natural frequency of the mode considered. It will be apparent from an examination of this equation that for any given applied force having a fixed frequency that as the natural frequency of the mode which it excites is despaanse creased the amount of force transmitted to the base is also decreased. Although the natural frequency of the mode of the body may, to some extent, be decreased by changing the resilient characteristic of the mounting, definite limitations are imposed onthis method by the resulting lack of stability of the machine if too light a spring is used. A second method. and the one which I prefer, is to design the bodyand mounting in such manner that the couples causing vibration of the body in the modes having the highestnatural frequency are minimized.

'I'he motor 2| and compressor 20 are each subjected to vibratory or periodic displacing forces during their normal operation. That is, the movement of the moving parts of the compressor subject it to certain vibrational forces while the rotation of the rotor and the magnetic forces in the electric circuit of the motor subject it to certain other vibratory forces. Since the'compressor 20 and motor 2l are combined in a unitary structure all of these forces act simultaneously on this unitary structure and cause it to vibrate to a greater or lesser degree in all of its six modes simultaneously, that is, to move in all of six paths or patterns of movement'at the same time. Since this unitary structure is subjected to such a variety of .forces and is so unsymmetrical insofar as weight distribution is concerned, it should be apparent that great care must be exercised in analyzing the-complicated resultant vibratory movement of the unitary structure as a whole.

As pointed out above, the use of a relatively heavy and rigid cabinet l0 which forms the base of the unitary motor and compressor structure makes it unnecessary to design the mounting to minimize vertical vibratory forces. Since the motor 2| is arranged with its driving shaft extending in a. vertical direction, if its rotor is properly balanced by makingit symmetrical the motor will impart very small, if any, horizontal vibratory forces to the structure about the axis Z. The principal sources of horizontal force occurring during the operation of the machine are the reciprocatory piston which moves in the cylinder 25-of the compressor 20 and the counterweight 26 which rotates with the crank shaft 21 of the compressor 20. The crank shaft 21 is driven by the motor 2| and reciprocates the slide 28 in the yoke 29 of the compressor 20. Such l compressors of the Scotch yok\\type` are well known in the art and need not be described here in further detail. In accordance with my invention I position the resilient mounting at a sufficient vertical distance from the moving parts oi! the compressor 20 that the axes of the normal modes of vibration of said unitary structure on said resilient mounting having relatively high natural frequencies lie in the region of the displacing forces exerted by said moving parts. That is, the points or region of attachment of the vertical helical compression springs 30, 3| and 32 are positioned at such a distance from the piston and counterweight of the compressor 20 that the axes T and U are in the region of the lines of movement of piston andcounterweight. Also, in the preferred form of my invention the resilient mounting for the unitary compressor and motor structure is so positioned with respect to the latter that the axes'R and S will be approximately in the planeA of attachment of the resilient mounting, this plane being below the moving parts of compressor 20 in the illustrative form of my invention. It will be understood that as the points or region of attachment of the springs 30, 3| and 32 are varied the axes` of the several modes of vibration will also be displaced in different directions. The advantages of the mounting, which I have provided, which causes the axes of the several modes of vibration to fall in the positions noted will be apparent from an analysis of the effects of the forces caused by the various moving parts of the machine during its normaloperation, particularly the piston and counterweight.

Since the piston in the cylinder 20 and the counterweight 26 are "closely adjacent to the axes T and U, the forces set up by the piston and counterweight will cause very small, if any, couples to be set up about these axes, the lever arms between the forces and the axes being small. As

`the forces transmitted to the base I0, due to the vibration of the unitary structure will also be minimized. Although the forces set up by the movement of the piston in the cylinder 20 and the counterweight 26 will set up couples about the axes R and S causing the unitary structure to vibrate at the modes w1 and wz, the latter modes are of relatively low frequency and hence only a small proportion of the force applied will be transmitted to the cabinet I0 due to vibration of the unitary structure in these modes. Also since the springs 30, 3| and 32 are attached to the periphery of the motor 2| in approximately the plane of the axes R and S, the amplitude of horizontal vibration yof the unitary'structure inLthis plane will bea minimum invso far as the modes @Rand oz are concerned and thus the horizontal force exerted on the mounting due to vibration in the modes w1 and wz will also be a minimum.

The detalls of the construction by means of which the vertical helical compression spring 30 is attached'to'the side of the frame of a motor 2| are best shown in Figs. 4 and 5. A V-shaped foot 33 is welded along the surface 34 and 35 to the side of the motor 2|.v A bridging'piece 36 extends across the'top of foot 33 and a bolt 31 passing downwardly through an aperture in the bridging piece 36 is in threaded engagement with a block 38. The spring 30 is secured to the block 38 by a helical groove 38a formed in the surface of the block 38. 'I'he block 36 is of a greater diameter than the width of the opening in the foot 33, and as a consequence when the bolt 31 is screwed tightly into the threaded aperture 39 in the block 38, the top of the spring 30 is held rmly against the bottom of the foot 33, The lower end of the springl 30 is placed in a helical groove 40 formed in the surface of alower supporting block 4|, the block 4| beingA welded to the casing I9 as indicated at points 42 and 43.

`The supporting springs 3| and 32 are similarly a notch 41 cut in the outer end of the foot 33. The ring 46 is snapped -into similar notches provided in the outer sides of the feet 44 and 45. A series of stops 48 are provided in the casing I9, which are welded to the inner side wall of the casing I9. As shown in Fig. it, a notch 49 is cut in the lower side of each of the stops 48. These stops 48 serve to limit the vertical movement of the unitary compressor and motor structure beyond a predetermined limit. This arrangement is also" particularly useful in limiting the movement of the motor 2| and compressor 20 within the casing I9 when the machine is being shipped from one place to another.

While I have shown a particular embodiment of my invention in connection with a compression refrigerating machine, I do not desire my invention to be limited to the particular construction shown and described, and I intend in the appended claims to cover al1 modications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A refrigerating. machine comprising a heavy, rigid base which is relatively unresponsive to vertical forces tending to move said base in a vertical direction, a motor and a compressor assembled as a unitary structure, said unitary structure including a plurality of moving parts exerting horizontal displacing forces thereon during the normal operation of said machine, and resilient means attached to said unitary structure for supporting the same on said base, the region of attachment of said resilient means to said unitary structure being positioned at a sufcient vertical distance below said moving parts and said resilient means having such elastic characteristics that the horizontal axes of the normal modes of vibration of said unitary structure on said resilient means having relatively high natural frequencies lie in the region of said displacing forces in order to minimize the horizontal force transmitted to said base.

2. A refrigerating machine comprising a heavy,

rigid base which is relatively unresponsive to vertical forces tending to move said base in a vertical direction, a motor and a compressor assembled as a unitary structure, said unitary structure including a plurality of moving parts exerting horizontal displacing forces thereon during the normal operation of said machine, and resilient means attached tosaid unitary structure for supporting the same on said base, said unitary structure having aplurality of normal modes of vibration on said resilient means about a plurality of horizontal axes, the region of attachment of said resilient means to said unitary structure being located in the region of the horizontal axes of the normal modes of vibration having relatively low natural frequencies and at a suiiicient vertical distance below said moving parts and said resilient means having such elastic characteristics that the horizontal axes of the modes of vibration having relatively high natural frequencies lie in the region of said displacing forces.

3. A refrigerating machine comprising a heavy, rigid base which is relatively unresponsive to vertical forces tending ,to move said base in a vertical direction, a motor and a compressor assembled as a unitary structure, said unitary structure including a plurality of moving parts exerting horizontal displacing forces thereon during the normal operation of said machine, and resilient means including aplurality of compression springs attached to said unitary structure for supporting the same on said base, the region of attachment of said resilient means to said unitary structure being positioned at a suiilcient vertical distance below said moving parts and said resilient means having such elastic characteristics that the horizontal axes of the normal modes of vibration of said unitary structure on said resilient Ameans having relatively high natural frequencies lie in the region of said displacing forces in order to minimize the horizontal force transmitted to said base.

4. A refrigerating machine comprising a heavy, rigid base which is relatively unresponsive to vertical forces tending to move said base in a. vertical direction, a motor and a compressor assembled as a unitary structure, said unitary structure including a plurality of moving parts exerting horizontal displacing forces thereon during the normal operation of said machine, and resilient means including three helical compression springs attached at spaced intervals to said unitary structure for supporting the same on said base, said unitary structure having a plurality of modes of vibration on said resilient means about a plurality of horizontal axes, said resilient means being attached to said unitary structure in the region of the horizontal axes oi.' the normal modes of vibration having relatively low natural frequencies and at a sufiicient vertical distance below said moving parts and said compression springs having such elastic characteristics that the horizontal axes of the modes of vibration having relatively high natural frequencies lie in the region of said displacing forces.

5. A refrigerating machine comprising a heavy, rigid base which is relatively unresponsive to vertical forces tending to move said base in a vertical direction, a compressor, a motor for driving saidcompressor, said compressor being mounted on the top of said motor as a unitary structure,

and resilient means attached to said unitary structure for supporting the same on said base, the region of attachment of said resilient means .to said unitary structure being positioned at a suiiicient vertical distance from said moving parts and said resilient means having such elastic characteristics that the horizontal axes of the normal modes of vibration of said unitary structure 'on said resilient means having relatively high natural frequencies lie in the region of said displacing forces in order to minimize the horizontal force transmitted to said base. i

6. A refrigerating machine comprising a heavy, rigid base which is relatively unresponsive to vertical forces tending to move said base in a vertical direction, a motor having a vertically extending shaft, a compressor of the Scotch yoke type mounted on the top of said motor as a unitary structure and driven by said shaft, said compressor including a plurality of moving parts exerting horizontal displacing forces in said unitary structure during the normal operation of said machine, and resilient means attached to said unitary structure for supporting the same on said base, the region of attachment of said resilient means to said unitary structure being positioned at a suilicient vertical distance below said moving *parts` and said resilient means having such elastic characteristics that the horizontal axes of the normal modes of vibration of said unitary structure on said resilient means having relatively high natural frequencies lie in the region of said displacing forces in order to minimize the horizontal force transmitted to said base.

'1. A refrigerating machine comprising a heavy,

rigid base which is relatively unresponsive to vertical forces tending to move said base in a vertical direction, a motor 'having a vertically ex- .y tending shaft, a compressor of the Scotch yoke type mounted on the top of said motor as a unitary structure and driven by said shaft, said compressor including a plurality of movingparts exerting horizontal displacing forces on said unitary structure during the normal operation of said machine, and resilient means including three helical compression springs attached to said unitary structure for supporting the same on said base, said unitary structure having a plurality oi' modes of vibration on said resilient means about a plurality of horizontal axes, the points of attachment of said resilient means to said unitary structure being positioned in the region of the horizontal axes of the normal modes of vibration having relatively low natural frequencies and at a sufficient vertical distance below said moving parts and said compression springs having such elastic characteristics that the horizontal axes of the modes of vibration having relatively high natural frequencies lie in the region of said displacing forces.

8. A refrigerating machine comprising a heavy, rigid base which is relatively unresponsive to vertical forces tending to move said base in a vertical direction, a motor having a vertically extending shaft, a compressor mounted as a unitary structure on the top of said motor, said compressor being provided with a horizontally reciprocating piston and a counterweight rotating about a vertical axis, said piston and said counterweight being driven by said shaft, said piston and said counterweight exerting horizontal displacing forces on said unitary structure during normal operation of said machine, and resilient means attached to said unitary structure for supporting the same on said base, the region of attachment of said resilient means to said unitary structure being positioned at a suilicient vertical distance below said piston and counterweight and said resilient means having such elastic characteristics that the horizontal axes of the normal modes of vibration of said unitary structure on said resilient means having relatively high natural frequencies lie in the region of said displacing forces in order to minimize the horizontal force transmitted to said base.

9. A refrigerating machine comprising a heavy, rigid base which is relatively unresponsive to vertical forces tending to move said base in a vertical direction, a motor having a vertically extending shaft, a'compressor mounted as a unitary structure on the top of said motor, said compressor being provided with a horizontally reciprocating piston and a counterweight rotating about a vertical axis, said piston and s aid counterweight being driven by said shaft, said piston and counterweight exerting horizontal displacing forces on said unitary structure during the normal operation of said machine, and resilient means attached to said unitary structure for supporting the same on said base, said unitary structure having a plurality of -modes of vibration on said resilient means about a plurality of horizontal frequencies and at a sumcient vertical distance l below said piston and counterweight and said resilient means having such elastic characteristics that the horizontal axes of the modes of vl- 5 bration having relatively high natural frequencies lie in the region of said displacing forces.

10. A refrigerating machine comprising a heavy, rigid cabinet containing. a cooling compartment, said cabinet being relatively unresponsive to vertical forces tending to move said cabinet in a vertical direction, a motor and a compressor assembled as a unitary structure, said unitary structure including a plurality of moving parts exerting horizontal displacing forces thereon during the normal operation of said machine, and resilient means attached to said unitary structure for supporting the same on said cabinet, Asaid unitary structure having a plurality of' modes of vibration on said resilient. means about a plurality of horizontal axes, the region of attachment of said resilient means to said unitary vstructure being positioned in the region of the horizontal axes of the normal modes .of vibration having relatively low natural frequencies and at a sufficient vertical distance below said moving parts and said'resilient means having such elastic characteristics that the horizontal axes of the modes of vibration having relatively high natural frequencies lie in the region of said displacing forces.

11. A refrigerating machine comprising a heavy, rigid cabinet containing a cooling compartment, said cabinet being relatively unresponsiveA to vertical forces tending to move said cabinet in a vertical direction, a motor having a vertically extending shaft, a compressor mountedas a unitary structure on the top of said motor, said compressor being provided with a horizontally reciprocating piston and a countercient vertical distance (from said piston and counterweight and said compression springs having such elastic characteristics that the horizontal axes of the normal modes of vibration of said unitary structure on said resilient means having relatively high natural frequencies lie in the region of said displacingv forces in order to minimize the horizontal force transmitted to said cabinet.

12. AA refrigerating machine comprising a heavy, rigid base which is relatively unresponsive to vertical forces tending to move said base in a vertical direction, a m'otor having a vertically extending shaft, a compressor mounted as a unitary structure on the top of said motor, said compressor including a plurality of moving parts exerting horizontal displacing forces on said unitary structure during the normal operation of said machine, and means including a plurality of vertical compression springs secured at spaced intervals to the periphery of said motor for supporting said unitary structure on said base, the tops of said springs lying in a plane slightly below the center of gravity of said unitary structure 13. A refrigerating machine comprising a motorv the inner side 'waliiiI of'said casing for engaging said bumper ring to limit the vertical ,movement of said unitary structure in said casing. to the side of said frame and a bolt passing down- 14. A motor having a vertically ectending wardly through the open portion of said foot and 5 frame, a vertical helical compression spring, a engaging said block. y

block secured to the top of said spring, and

means for mounting said motor on said spring. said means including a V-shapedv foot aecurcd HARLEYH..

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