US2425404A - Electric terminal for hermetic compressors - Google Patents

Description

Aug. 12, 1947. J. TOUBORG ELECTRIC TERMINAL FOR HERMETIC COMPRESSORS Filed June 10, 1946 INVENTOR Jena Toadory ATTORNEY Patented Aug. 12, 1947 UNITED STATES PATENT OFFICE ELECTRIC TERMINAL FOR HERMETIC COMPRESSORS Claims.

This invention relates to mechanical refrigeration, and it has particular reference to the provision of an electrical terminal or binding post for the wires leading to the refrigeration motor, which will be durable and secure against leakage, such as tends to occur in a refrigeration compressor of the hermetic type.

Hermetic type compressors consist of a casing which is sealed to the atmosphere, and which contains the pump or compressor for handling the refrigerant, and the electric motor which drives the compressor. As the refrigerant is highly volatile, it is essential that the enclosing casing be sealed at every point, including the joint between the parts of the casing, around the tubes through which the refrigerant flows, and at the place where the electric wires pass through to supply current to the motor. At present, a problem still exists with respect to the terminals for the electric wires. Such types of terminals or binding posts as have heretofore been available have a tendency to open up, or become leaky, even when they are initially installed with care. The difficulty has been augmented by the accepted procedure in assembling a hermetic compressor, which requires that the unit be heated to expel all moisture before the refrigerant is introduced.

The warming up and cooling of the casing causes, of course, an appreciable expansion of the metal, thereby loosening what might have initially been a tight joint. Accordingly, moist air can seep back into the casing after the drying operation has been completed, or refrigerant can leak out, if the loose joint is not discovered, corrected, and the defective unit re-processed. The factors producing these poor joints also come into play, in the same manner or in different ways, with satisfactorily tested compressors sent out into service. It has been found that the jarring of the units during shipment, and the temperature changes to which the refrigerator is subjected in service, also cause failures at the electric terminal.

The present invention provides a simple and inexpensive terminal or connector, adapted to be installed in a hermetic compressor, which will remain tight at all times. A typical embodiment of the invention is illustrated in the accompanying drawings, wherein:

Fig. l is a schematic elevation of a hermetic compressor with a portion of the shell broken away to show the electric terminal;

Fig. 2 is a section of the terminal taken on the line 2-2 of Fig. 1;

Fig. 3 is a section taken on the line 3-3 of Fig.

Fig. 4 is a view similar to Fig. 2, showing a modified form of construction prior to tightening of the assembly;

Fig. 5 is a perspective of a compressible conical washer adapted to be incorporated in the assembly; and,

Fig. 6 is a fragmentary section of the parts shown in Fig. 4 after tightening.

The apparatus shown in Fig. 1 comprises a two-part outer casing or shell ll, sealed at the junction line l2 by welding or other means, within which the moving parts of the compressor assembly are mounted. These include an electric motor l3 whose rotor I4 is coupled to the crankshaft of a pump I5, the compressor in turn being mounted in the casing by supporting lugs I6. As the details of these parts are not material to an understanding of the present invention, and their general purposes are well understood, they need not be further illustrated or described.

The electric current for operating the motor I3 is supplied through a terminal ll, mounted at some suitable point in the casing, and passing through the wall thereof in order to make a connection with the external power source. A cable 18 leads from the terminal I! at the inner side thereof to the motor proper. While only one wire and terminal are illustrated, it will, of course, be understood that as many may be used as the nature of the circuit requires. It is essential, however, that each terminal be of such nature that leakage cannot occur around or through it.

As best shown in Fig. 2, the terminal I! passes through aligned apertures formed in the wall of the casing H and bosses 2| secured on either side thereof. These bosses serve as spacers for the wires and exposed electric conducting parts on either side of the shell, and, also provide a sleeve supporting other elements of the structure. They are secured to the shell wall by the operation known as projection welding, and while this kind of welding will give good mechanical strength, it is not entirely safe to rely upon it for gas tightness. Although the bosses are welded in place, leakage of the refrigerant may nevertheless occur between the abutting surfaces of the bosses and the casing wall. The concentric apertures in the bosses and wall provide a sleeve in which are mounted a somewhat soft or plastic bushing 22 and two insulating bushings 23.

As of the date of making this description, the usual soft plastic material-natural rubber-is not readily available, and accordingly recourse has been made to the synthetic plastic called neoprene. The material is electrically non-conductive, resistant to deterioration by the atmosphere, refrigerant, or lubricating oil, and is sufficiently plastic to serve the intended purposes. The bushings 23 are electrically non-conductive but are not plastic in the sense of being deformed readily by the stresses encountered.

It will be seen, from Fig. 2, that the plastic bushing 22 fits snugly in the apertures and is of such length as to overlie the inner portions of each boss 2|. The bushings 23 abut the bushing 22 within the sleeve portion, and extend at each side beyond the outer face of each boss.

The three bushings are in turn provided with aligned bores in which is snugly disposed a stud 24 formed with a head 25 at the inner end and with a threaded stem 26 on the outer end. An insulating washer '21, of greater diameter than the adjacent boss 2| and bushing 23, and formed with a recessed portion 28, is positioned over the exposed end of the inner bushing 23, to be drawn up tight against it when the stud is drawn up. A connector 29, to which the cable |8 is attached, is interposed between the washer 27 and the head 2'5, thus providing an electrical and mechanical connection within the casing The threaded stem 26, which extends beyond the outer boss 2| and associated bushing 23, similarly receives an insulating washer 3| provided with a concentric recess 32 to fit over the protruding end of the bushing 23. Like the washer 2 the washer 3| is electrically non-conductive, and is sufficiently rigid to resist deformation or shearing stresses when in service. The stem 25 also receives a pair of ordinary fiat steel washers 33 between which is disposed a steel spring or cupped washer 34 These are pressed against the insulating washer 3| by a lock nut 35, and an additional nut 36 provides a means for securing an electrical wire leading to the external source of current.

It will be seen that the stud 24, through which the current must pass, is insulated and spaced from the wall of the shell H and the metallic bosses, 2|, thus iorestalling short-circuiting. When the nut is drawn up, a compressive force is applied, through the washers 2"! and 3|, to the two relatively rigid bushings 23. These in turn compress the plastic bushing 22, forcing the composition into all the minute crevices which may be present, and thereby forming a gas-tight joint along the stud 24 and around the bosses 2|. It was previously pointed out that the bushing 22 was longer than the thickness of the wall of the shell II, the purpose being to seal around the welded area to safeguard against the defect described. It will also be understood that the movement of the bushings 23 normally does not eliminate all of their extension beyond the bosses. However, if this should occur, the insulating Washers 21 and 3| will still provide against shortcircuiting.

When the terminal is first installed, which normally is before the compressor is placed in the drying oven, the resilient washer 34 may be compressed until it is flat. The expansion by heat of the neoprene, or such other plastic as might be used, will accordingly tend to extend the assembly, permitting the washer 34 to regain some of its original curvature. -Ioweve1, this is beneficial, as the continuing pressure exerted by the washer prevents any opening up of the joint when the unit cools, or is subjected to temperature changes in service.

It should additionally be noted that the present invention avoids a difficulty which has heretofore been experienced with some of the commercially available terminals. The stresses imposed are axial of the stud 24, and shearing around the washers or bushings, causing total failure, will not occur under the normal forces applied by the workmen or encountered during use.

In the form of the invention shown in Figs. 4, 5, and 6, the parts just described have also been incorporated and have been designated with the same reference numerals, and therefore it will be unnecessary to explain them again. The form shown in these figures diifers from the described embodiment in that a pair of conical and collapsible washers 4| have been interposed between the ends of the plastic bushing 22 and the adjoining relatively rigid bushings 23. As shown in Fig. 5, the washers 4| are of frusto-conical formation, and they may be made of any suitable material, such as insulating fiber. They have, in the conical shape, an external diameter about the same as that of the bore through the sleeve portion of the shell I i, and a central aperture about the same in diameter as that of the stud 24.

When the parts are first assembled, as shown in Fig. l, these conical washers 4| slightly space the rigid bushings 23 from the plastic bushing 22. However, when the assembly is drawn up, the washers 4| are compressed and they collapse into plane form, as near as may be, as shown in Fig. 6. In so doing, the bore or inner diameter becomes thus causing the washer to hug the stud 24 very tightly. The outer diameter tends to increase, and accordingly contact the sleeve wall with a tight fit. Joints are therefore provided at either side of the plastic bushing 22 which preclude axial flow of the material and restrain it to tight engagement with the bore of the sleeve.

In the form of the invention shown in Fig. 2, satisfactory joints can be obtained provided the bushings and stud are made with fairly close tolerances, so that no excessive gaps or cracks are provided through which the plastic material can ilow. However, in assembling these terminals on a mass production basis, it is practically impossible to eliminate occasional misfits which permit hairline cracks to remain through which the plastic may fiow axially. By providing the conical washers 1|, however, end seals for the plastic are provided which prevent such flow, even when the dimensions of the parts in the assembly depart from normal manufacturing tolerances. By providing this means, it has also been discovered that gas-tight joints may be obtained even when the cup-shaped washer 34 is omitted, although for most purposes it is advantageous to retain this part.

While the invention has been described with reference to a. preferred embodiment and a single modification thereof, and to one field of use wherein it has been found valuable, it is to be understood that the invention is not limited to the specific disclosure made, but that its scope is to be deemed commensurate with the following claims.

This application is a continuation in part of my application Serial No. 549,724, filed August 16, 19-14:, now abandoned in favor of the instant case.

I claim:

1. An electrical terminal assembly comprising a wall member having bosses on either side thereof, said wall and bosses being formed with aligned apertures defining a straight sleeve, a plastic non-conductive bushing positioned in the sleeve adjacent the wall, relatively rigid non-conducting bushings positioned in the sleeve on each side of the plastic bushing, said rigid bushings being of such length as to extend beyond its adjacent boss when unstressed, a stud passing through all of said bushings and projecting beyond the bosses on each side of the wall, relatively rigid insulating washers positioned around the stud and abutting the rigid bushings at their exposed ends, a head on one end of the stud adapted to retain an electrical conductor on the stud against one of the insulating washers, and a nut and spring washer on the opposite end of the stud adapted to retain an electrical conductor and to exert compressive force against the plastic bushing through the other of said insulating washers.

2. An electrical terminal assembly comprising a wall member having bosses on either side thereof, said wall and bosses being formed with continuous and substantially uninterrupted aligned apertures forming a straight sleeve, a plastic nonconductive bushing positioned in the sleeve adjacent the wall, the length of the bushing being such that its ends overlie portions of said bosses, relatively rigid non-conducting bushings positioned in said sleeve at each end of the plastic bushing and abutting said bushing, said relatively rigid bushings extending from the sleeve beyond said bosses, a stud extending through all of said bushings and extending at its ends beyond said bosses, relatively rigid insulating washers positioned around the stud and abutting the outer ends of the relatively rigid bushings, said washers having a greater diameter than said bushing and bosses, a head on one end of the stud adapted to retain an electrical conductor against one of said washers, and a nut and cupshaped washer on the opposite end of the stud.

3. An electrical terminal assembly comprising a wall having bosses on either side thereof, said wall and bosses being formed with aligned apertures defining a straight sleeve, a plastic nonconductive bushing positioned in the sleeve adjacent the wall, relatively rigid non-conducting bushings positioned in the sleeve on each side of the plastic bushing, said rigid bushings being of such length as to extend beyond its adjacent boss when unstressed, normally frusto-conical nonconducting washers interposed between said rigid bushings and the adjacent end of the plastic bushing, a stud passing through all of said bushings and said washers and projectin beyond the bosses on each side of the wall, relatively rigid insulating washers positioned around the stud and abutting the rigid bushings at their exposed ends, a head on one end of the stud adapted to retain an electrical conductor on the stud against ne of the insulating washers, and a nut and spring washer on the opposite end of the stud adapted to retain an electrical conductor and to exert compressive force against the plastic bushing and said frusto-conical washers through the other of said insulating washers, said frusto-conical Washers being adapted to collapse under such force and thereby form end seals for said plastic bushing.

4. An electrical terminal assembly comprising a wall having bosses on either side thereof, said wall and bosses being formed with aligned apertures defining a straight sleeve, a plastic nonconductive bushing positioned in the sleeve adjacent the wall, relatively rigid non-conductive bushings positioned in the sleeve on each side of the plastic bushing and extending at one end beyond the adjacent boss, a normally frusto-conical non-conductin washer interposed between the inner end of each rigid bushing and the adjacent end of the plastic bushing, a stud passing through all of said bushings and said washers and projecting beyond the bosses on each side of the wall, relatively rigid insulating washers positioned around the stud and abutting the rigid bushings at their exposed ends, a head on one end of the stud adapted to retain an electrical conductor on the stud against one of said insulating washers, and a nut on the opposite end of the stud adapted to retain an electrical conductor and to exert a compressive force against the plastic bushing and said frustc-conical washers, said frusto-conical washers being adapted to collapse under such force and to assume plane Configurations whereby the inner and outer peripheries thereof respectively engage said stud and said sleeve and form end seals for the plastic bushing.

5. An electrical terminal assembly comprising a wall member having bosses on either side thereof, said wall and bosses being formed with aligned apertures defining a straight sleeve, a plastic non-conducting bushing positioned in the sleeve at the central part thereof, relatively rigid non-conducting bushings positioned in the sleeve on each side of the plastic bushing, a normally frusto-conical Washer interposed between the inner end of each rigid bushing and the adjacent end of the plastic bushing, a stud passing through all of said bushings and said washers, means at each end of the stud adapted to engage the outer ends of the rigid bushings to exert compressive force thereon, means at each end of the stud adapted to receive and retain an electrical connector in spaced relation to said rigid bushings and said sleeve, said frusto-conical washers upon application of said compressive force means being adapted to collapse into plane configuration and thereby circumferentially engage said stud and said sleeve and form end seals for the plastic bushing.

JENS TOU'BORG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,904,805 Selling Apr. 18, 1933 1,941,397 Grier Dec. 26, 1933 2,028,942 Money Jan. 28, 1936 2,278,974 Christensen Apr. 7, 1942 2,235,429 Henry Mar. 18, 1941

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