US3504147A - Refrigerating device having improved switch - Google Patents

Description

March 31, 1970 fK E. CHRISTMAN ETAL 3,504,147

REFRIGERATING DEVICE HAVING IMPROVED SWITCH Filed Jan. 22, 1968 FIG.2

WITNESSES 56.4.. 997. M

mwm I United States Patent 3,504,147 REFRIGERATING DEVICE HAVING IMPROVED SWITCH Karen E. Christman and Ralph E. Christman Columbus,

Ohio, assignors to Westinghouse Electric orporatiou,

Pittsburgh, Pa., a corporation of Pennsylvania Filed Jan. 22, 1968, Ser. No. 699,592 Int. Cl. H01h 9/02 US. Cl. 200-168 2 Claims ABSTRACT OF THE DISCLOSURE Refrigerating device cabinet of the type constructed with expanded, foamed-in-place thermal insulation in the cabinet hollow wall spaces, and using a switch of low cost having an unsealed casing portion immersed in the expanded foam space, a plastisol film sealing the unsealed casing portion of the switch against intrusion of the foam into the switch.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to the art of manufacture of expanded foam insulated refrigerator device cabinets and the provision of protection for electrical switch means exposed to contact with the foam.

Description of the prior art In the highly competitive field of domestic refrigerators and freezers, it is distinctly advantageous to employ low cost commercially available components to the extent possible. However, the low cost parts sometimes cause their own problems. For example, the manufacture of foam insulated cabinets, the low cost door operated switch, usually mounted on a thermal breaker strip with a portion of the switch in the hollow wall space into which the foam insulation is expanded, has been subjected to internal fouling by the foam if not protected. Various techniques have been used to isolate that portion of the switch from the expanding foam. One way of accomplishing this is to provide a mold in the space in which the switch is to be located, then foam against the mold, and subsequently install the switches after the foaming operation. In other cases, protection for the mounted switch has been afforded to varying degrees by the use of plastic :bags, tape, latex, or wax coatings to isolate the buried portion of the switch from the expanding foam. These methods have not been reliable to a satisfactory degree, or alternatively have been found to be unduly expensive.

In the manufacture of a refrigerator cabinet according to Simmonds US. patent application Ser. No.

508,221 now US. Patent 3,373,478, it is preferred that substantially all of the electrical devices which are buried in the hollow wall foam space be connected and testable prior to the foaming operation. Accordingly, it is desirable that the door operated switch, which has its rear portion in the hollow wall space and is electrically connected by wires extending through the hollow wall foam space, be in position and connected prior to the foaming operation. However, the typical low cost push button switch used as a door switch has'a portion which projects into the foam space and is not sealed to a degree sufficient to insure against the entrance of foam into the switch. Foam entering one of these inexpensive switches causes it to jam and be inoperable.

SUMMARY OF THE INVENTION In accordance with the invention, in a refrigerator cabinet environment of the type described, the low cost door operated switch is improved by providing a plastisol film sealing the rear terminal portion against the intrusion of the foam into the switch during the expansion of the foam in the holow wall space. A satisfactory plastisol is a polyvinyl chloride in powder form dispersed in a suitable plasticizenThe switches are preheated and then dipped in the plastisol which sets before it can enter the switch by capillary action. A postheat operation then sets the outer surface of the plastisol compound. While the plastisol film formed on the casing and adjacent electrical terminal portion temporarily covers the electrical terminals, the plastisol on the terminals is easily stripped off by slipping the mating terminals onto the switch terminals.

DRAWING DESCRIPTION FIGURE 1 is a horizontal sectional view through a fragmentary portion of the front edge of a cabinet having a switch according to the invention installed therein;

FIG. 2 is a perspective view of one type of low cost push button switch suitable for use in the invention; and

FIG. 3 is a side view of the rear fragmentary portion of the electrical switch after being sealed with the plastisol according to the invention.

PREFERRED EMBODIMENT The front edge portion of a side wall of a refrigerator cabinet shown in FIG. 1 includes an outer shell 10, an inner liner side wall 12, a thermal breaker strip 14, and a door operated switch 16. The liner 12 as a whole has the general form of an open front, rectangular box which generally defines the storage space of the refrigerator. The outer shell 10 also has the form of a forwardly open, rectangular box of slightly larger dimension than the liner, which is nested therewithin. The breaker strip 14 closes the gap between the forward edges of the liner and shell. The plane in which a portion of the refrigerator door lies when closed, to depress the switch plunger, is shown by the broken line 17. In the hollow wall space defined between the liner and the shell, thermal insulation is provided in the form of a plastic foam 18 which is introduced into the hollow wall space and undergoes an expansion phase to completely fill the hollow wall space.

In accordance with this invention it is proposed that the technique taught in the noted Simmonds patent application be followed. This calls for the foaming operation to occur after those electrical components of the refrigerator cabinet located in hollow wall space are installed, and the wiring connected so that the devices may be tested in place before foaming. Hence, the switch 16 is installed and the electrical wires 20 connected to the switch 16 before the foaming step.

Reference should be had to the noted Simmonds patent application for a fuller exposition of the technique of foaming-in-place with the components to be buried in the foam in place. Reference should also be had to Kessler US. patent application 508,223, filed Nov. 17, 1965, now US. Patent 3,380,615, regarding the relationship of the specifically illustrated thermal breaker strip 14 and the specifically illustrated flange arrangement on the liner and shell by which foam tight joints are provided.

Turning now to the specific switch 16 shown in FIG. 2 it is of a conventional, low cost, push button type illustrated in its conventional off-the-shelf form as typically received by the manufacturer from the switch supplier. As such, it includes a plastic casing 22 having a forward, integrally-molded face flange 24 upon which friction detents 26 are provided, the center of the flange 24 having a hole therein in which the plunger 28 is slidably situated. The rear end of the casing is substantially open to permit the insertion of the various parts within the casing of the switch from the rear end before a fiberboard end cap 30 is snapped in place. This end cap is held by outwardly-projecting ears 32 received in retaining apertures molded in the casing lugs 34. The rearwardlyprojecting terminals 36 of the switch are also held in place by the end cap 30. Such a switch construction is relatively simple and permits low cost manufacture and thus is desirable for use by the refrigerator manufacturer. However, the nature of the switch is such that the fiberboard end cap and terminal arrangement does not provide a seal of the rear portion of the switch lyingin the hollow wall space into which foam is introduced. Accordingly, use of the switch without projection will result in the intrusion of foam into the switch casing in many instances and the jamming of the switch.

Thus in accordance with the invention the unsealed portion of the switch which is located in the hollow wall space is sealed against the intrusion of foam by the application of a plastisol film on the unsealed portion, This plastisol film 38 is shown as broken in part on one of the terminals in FIGURE 3 and with the cross-sectional dimension of the section enlarged for the sake of clarity, The film is not shown at all in FIGS. 1 and 2 so that the switch construction will be more readily apparent, but it will be understood that the switch as installed in FIG. 1 has its rear end portion covered to the extent shown in FIG. 3.

One satisfactory plastisol compound which may be used is commercially available as Uniseal SP-129 obtainable from Uniseal, Incorporated. This material is essentially a polyvinyl chloride in powder form dispersed in a plasticizer such as dioctylphthalate. The preferred method of applying a plastisol is to pre-heat the switch to, say, 300 F. for ten minutes and then dip its rear end to a depth as shown in FIG. 3 into a pool of the liquid, unheated plastisol compound. The heated switch causes the inner layer of the plastisol to set quickly as it comes in contact with the heated switch so that the plastisol does not enter the interior of the switch by capillary action. Then the switch is removed after the momentary dip and placed in an oven for the continued application of heat for, say, 10 minutes at 300 F. to set the remainder of the plastisol. A convenient fixture for holding a large number of switches for the heating, dipping, and post heat operations can take the form of a fiat sheet having a number of holes, one for each switch.

It will be noted in FIGURE 3 that the terminals 36 are shown as having a film of the plastisol compound 38 thereon. This plastisol film is automatically stripped from the terminals when the mating sleeve terminals of the electric wire 20 are slipped on. t

It will be appreciated that in accordance with the invention the low cost conventional door operated switch may be used in a refrigerator cabinet Of the foamed-inplace type in which the foam is expanded into direct contact with the portion of the switch lying within the hollow wall space.

What is claimed is:

1. In a refrigerating device cabinet of the foamed-inplace thermally insulated type in which foaming insulation is expanded into place:

an outer shell and a nested inner liner defining a hollow wall space therebetween into which said thermal insulation is foamed-in-place, said shell and said liner each having front edges spaced from each other to define a gap therebetween;

thermal breaker strip means bridging said gap defined between said front edges of said shell and liner;

a. door operated switch of the type having a casing with an unsealed rear terminal portion, said switch being disposed in said breaker strip means so that said rear terminal portion is exposed to said insulation during its expansion into contact therewith in said hollow Wall space, said switch including a plastisol film sealing said rear terminal portion only against intrusion of said foam into said switch during said foam expansion.

2. In combination with a refrigerating device including a cabinet made up of an outer shell, a nested inner liner, hollow wall space with a gap defined between forward edges of said liner and shell, a thermal strip, a door, and being of the type having foamed-in-place expanded thermal insulation in said hollow wall space defined between said cabinet outer shell and said nested inner liner, an improved door operated switch installed in said thermal strip closing said gap between said forward edges of said cabinet and said liner, said switch comprising:

an outer casing having a plunger projecting forwardly through an unsealed forward end of said casing into the path of movement of a part of said door, and electrical terminal means projecting rearwardly through an unsealed rear portion of the casing, said electrical terminal means being adapted to be connected to the electrical wiring extending through said hollow wall space, said switch including a plastisol film sealing said rear terminal portion only against intrusion of said foam into said switch when said switch is installed in a position exposing said rear terminal portion to said expanding foam.

References Cited UNITED STATES PATENTS 3,305,658 2/1967 Heyhal. 3,373,478 3/1968 Simmonds 29-407 3,376,246 4/ 1968 Valentine et al 260-313 3,380,615 4/1968 Kessler s12. 214

OTHER REFERENCES Penn, W. 8., PVC Technology, July 2, 1963, p. 332.

HERMAN O. JONES, Primary Examiner

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