Structural Support for Hermetic Terminal Assembly Heater Apparatus

The present invention relates to a heater apparatus for heating fluid medium confined in a hermetically sealed chamber and more particularly to an apparatus which includes a heating element that extends directly into the sealed chamber.

In the refrigerant compressor art, it is generally known to heat the fluid medium confined in a crankcase of a refrigerant compressor by means of a PTC thermistor device confined in an insulating ceramic case such as disclosed in U.S. Pat. No. 4,236,065, issued to M.A. Yashin et al. on Nov. 25, 1980 and U.S. Pat. No. 4,544,316 issued to M. Takeuchi et al. on Feb. 17, 1987. An appropriately sized, heat conductive metallic sleeve member which is closed at one end and open at the other, has its opened end sealed to the wall of the crankcase with its closed end projecting into the crankcase chamber. A ceramic encased PTC heater is inserted into the sleeve opening and connected to an electrical source to heat fluid medium in the crankcase chamber through the surrounding heat conductive metallic sleeve member projecting into the crankcase.

The present invention recognizing that such past apparatus presents problems in heat loss through the insulating ceramic sleeve, the surrounding metallic sleeve and the housing to which it is attached and that the wattage required to apply the required heat is not directly responsive to the fluid medium confined by the crankcase housing and surrounding ambient conditions, provides a novel crankcase heater arrangement which avoids these past difficulties by eliminating the comparatively costly and difficult to manufacture and assemble heat conductive sleeve and by inserting a heating member electrically connected to a conventionally mounted terminal assembly to heat the fluid medium in a more direct manner without the aforedescribed concomitant heating losses through a heat dissipating sleeve and the crankcase housing to which it is mounted. Further, the crankcase heater arrangement of the present invention is more directly responsive to confined fluid medium and ambient temperature conditions so as to minimize wattage consumption and thus optimize overall heating efficiency.

Further the present invention of this continuation-in-part application includes a novel heater element electrical connection and support structure which is not only light in weight and economical to manufacture and assemble but which also provides stable electrical contact and insulation in those areas where such is required and which, at the same time, minimizes undesirable vibrational effects.

Various other features of the present invention will become obvious to one skilled in the art upon reading the disclosure set forth herein.

More particularly, the present invention provides a novel heating apparatus to be mounted in a fluid medium containing chamber defined by a wall of a hermetically sealed housing comprising: a terminal assembly including a body member sealed to the housing wall, the body member having terminal pin means embedded in a seal extending between the terminal pin means and an aperture in the body member with an outer pin segment of the terminal pin means extending outwardly from the outer face of the wall to be electrically connected to an electric power source and an inner pin segment of the terminal pin means extending inwardly from the inner face of the wall into the fluid medium chamber; and, a heating element electrically connected to the inner pin segment of the terminal pin means to be disposed in the chamber to transmit heat to the fluid medium. In addition, the present invention provides a unique arrangement of combining and positioning a PTC thermistor disc with the terminal pins of a terminal assembly for heating a fluid medium in a more direct and efficient manner than heater elements of past arrangements. Further, the present invention provides for an insulating sleeve surrounding the inner pin segment extending into the fluid chamber with one end of the sleeve embedded in the seal between the pin and body member. Even further, the present invention of this continuation-in-part application provides for a support means for the heating element to firmly support such heating element independently of a unique partial loop arrangement of an electrically conductive wire assembly for the heating element to minimize vibration and to insure a stable electrical connection of the heating element to the inner pin segment.

It is to be understood that various changes can be made in one or more of the several parts of the apparatus disclosed herein without departing from the scope or spirit of the present invention. For example, other types and configurations of PTC thermistor heating units beside that disclosed can be utilized with the internal pin segments of the terminal assembly and the terminal assembly itself can be any one of a number of terminal assemblies known in the art, including those known to include a fuse-like area either on or adjacent to the terminal pin means.

Referring to the drawing which discloses one advantageous embodiment of the present invention:

FIG. 1 is a side view of a hermetically sealed heater housing assembly in the general form of a refrigeration compressor crankcase heater which heater incorporates the novel terminal assembly heater of the present invention;

FIG. 2 is an enlarged, partially broken away isometric view of the novel terminal assembly heater arrangement incorporated in the heater housing of FIG. 1;

FIG. 3 is an enlarged, partially broken view of the terminal assembly heater and housing assembly taken in a plane through line 3--3 of FIG. 1;

FIG. 4 is an exploded isometric view of a still further novel terminal assembly heater arrangement incorporating a novel modified electrical connection between the heater element and pin segments and a novel support for the heater element;

FIG. 5 is a side view of the heater element and support in assembled relation; and

FIG. 6 is an isometric view of the assembled parts of FIGS. 4 and 5.

Referring to FIG. 1 of the drawing a hermetically sealed crankcase housing 2 of a configuration generally known in the refrigeration art is disclosed incorporating the novel heater apparatus 3 located directly within the hermetically sealed housing 2 and advantageously at the bottom of housing 2. Suitable electrical wires 4, leading from an electrical power source (not shown) are provided to connect to the outer pin segments of heater 3 disclosed in detail in FIG. 2 of the drawing.

As can be seen in FIG. 2, the heater apparatus 3 to be mounted in the wall confining electrically non-conductive refrigerating fluid medium in housing 2 is in the form of a terminal assembly including a cup-shaped body member 6 have a bottom or base 7 and a peripheral rim 8. The base 7, as is known in the art of terminal assemblies and therefore not shown in detail herein, is provided with a pair of spaced apertures therein through which a pair of spaced electrically conductive terminal pins 9 extend. As also is known in the art and shown at the broken away portion of FIG. 2, each of pins 9 is embedded in an appropriate seal 5 which is usually of glass and which extends between the outer periphery of the pin and a lip 10 integral with the aperture periphery so that pin 9 is in sealed relation with base or bottom 7. A suitable arc preventing insulating sleeve 11 of ceramic, glass or a composition of both surrounds each inner pin segment 12 with one end of the insulating sleeve 11 being embedded in the seal 5 and the other end of the sleeve being appropriately recessed to minimize the possibilities of arcing between inner pin segment 12 and cup-shaped body member 6. In this regard, an appropriate insulating silicone rubber coating 13 can be provided at the base of each outer pin segment 14 with the extremities of each outer pin segment having an electrical connector 16 fastened thereto to receive one of the lead wire ends of wires 4 (FIG. 1).

Electrically fastened to each extremity of each inner pin segment 12 of terminal pin 9 by some suitable means such as spot welding is one leg of a pair of mirror-image right angle support members 17 (only one of which can be seen in the drawing) the other leg of these support members is so arranged that these opposed legs face each other in spaced relation and serve to receive and conductively support therebetween by some suitable means such as spot welding, the opposite faces of an appropriate PTC thermistor disc 18 with the wider opposed face portions of such heater disc 18 extending in a longitudinal fashion proximate the longitudinally extending center line of the fluid chamber to enhance fluid medium heating capabilities of the heater. The thermistor disc 18 can be formed from any ore of a number known PTC thermistor discs which are formed from elements similar to those described in the aforementioned U.S Pat. Nos. 4,236,065 and 4,644,316.

Although, in accordance with the present invention, it is possible to locate the heating element at any one of a number of suitable location within hermetically sealed housing 2, it has been recognized to be advantageous that the heating element, in the form of the PTC thermistor disc 18, which can be covered with a suitable insulating material, such as epoxy coating, be located as shown in the lower portion of housing 2 to be more responsive to the electrically non-conductive fluid medium temperature and the surrounding ambient conditions, to optimize the power requirements as existing occasions require.

Referring to FIGS. 4-6 of the drawings, a still further novel terminal assembly heater arrangement is disclosed in the form of a terminal assembly including a cup-shaped body member 26 having a bottom or base 27 and a peripheral rim 28. Cup-shaped body member 26 is in many respects similar to that described in FIG. 2 of the drawings with base 27 being provided with a pair of spaced electrically conductive terminal pins 29 extending therethrough, as known in the art. As also is known in the art, each pin 29 is embedded in an appropriate seal 25, which is usually of glass and which extends between the outer periphery of the pin and a lip 30 integral with the aperture periphery so that pin 29 is in sealed relation with the base or bottom 27. A suitable arc preventing insulating sleeve 31, like insulating sleeve 11 of FIG. 2, also of ceramic, glass are composition of both surrounds each inner pin segment 32 of pin 29 with one end of insulating sleeve 31 being embedded in seal 25 and the other end of sleeve 31 being appropriately recessed to minimize the possibilities of arcing between inner pin segment 32 of pin 29 and cup-shaped body member 26. Here too, an appropriate insulating silicone rubber coating 33 can be provided at the base of each outer pin segment 34 and, if the occasion warrants, the extremities of each outer pin segment can be provided with an electrical connector (not shown) such as connector 16 of FIG. 2 or can be bare to nestingly engage with the female portion of some other suitable type of electrical connector having lead wires appropriately connected to an electrical power source.

In accordance with the modified embodiment of the invention as disclosed in FIG. 4 of the drawings, an electrically insulated PTC thermistor heater disc 38 is provided which can be of a disc shape similar to the thermistor heater disc 18 of FIG. 2 with the wider, opposed face portions of such heater disc 38 extending in a longitudinal fashion proximate the longitudinally extending center line of a fluid chamber to be heated to enhance fluid medium heating capabilities of the heater. A commercially available thermistor disc such as a Model ECB-1363A sold by Thermo Disc Company can be employed, such disc having a break point of 105.degree..+-.5.degree. C. with a resistance in a range of 500-3000 ohms at 25.degree. C., a diameter of 0.575.+-.0.025 inches and a thickness of 0.160.+-..010 inches before coating. The disc is rated at approximately twenty-two (22) watts at 0.degree. C. The opposed faces of the disc, which are of different polarity, can be treated with a suitable coating of at least 0.007 inches thickness to meet U.L. requirements of 0.005 inches. Any one of a number of suitable epoxy resin insulator coatings can be employed, as can a suitable polymer insulator coating such as Teflon.TM.. Before a coating is applied to the thermistor disc 38 a pair of suitable electrically conductive lead wires 39 which can be of flexible nickel clad or copper alloy wire material of 0.040 inch thickness are soft soldered at corresponding extremities thereof to opposite polar faces of the thermistor disc 38 in offset relation to engage on opposed sides of the pair of inner pin segments 32 to which the other corresponding extremities of the lead wires 39 are eventually fused or welded. Advantageously, the major cantilevered portion of each of the lead wires 39 is in the form of a rounded loop for strain relief and, as shown in FIGS. 4 to 6 of the drawings, lead wire 39 extend substantially at opposed right angles in offset mirror-image, "Mickey-Mouse" ear-like fashion from the PTC thermistor heater disc 38 as offset, opposite partial loops of rectangular-like shape, each including three softly curved corners so that the opposite extremities can be fused to opposed sides of inner pin segments 32. It is to be noted that the ends of the extremities to be fused to inner pin segments 32 are each spaced from an adjacent polar face of PTC heater disc 38 a distance less than the cross-sectional distance or thickness of a conductive wire 39 so as to minimize possible wire interlocking of several heater assemblies during storage and shipment of such assemblies.

As can be seen in FIG. 4-6 of the drawings, a substantially flat, electrically non-conductive platform disc 41 is provided to firmly and stably support PTC thermistor heater disc 38 in position with offset ears formed by wires 39 appropriately fused or welded in electrically conductive position against inner pin segments 32. Platform heater disc 41 can be made from any one of a number of suitable insulative materials and advantageously can be formed from a suitable plastic insulative material such as "Valox".TM. 310 sold by the General Electric Company. This material is suitable for use in hermetic compressor environments and meets U.L. minimum temperature requirements of 105.degree. C. Platform disc 41 is provided with four (4) integral, spaced support feet 42 extending from the lower face thereof as shown in the drawings. These feet 42, which can vary in number and contour, are preselectively positioned and sized to engage against the upper surface of insulating sleeves 31, which surround inner pin segments 32, so as to hold and support the flat disc surface of platform disc 41 in spaced relation from the insulating sleeves 31--thus insuring that coated PTC thermistor heater disc 38 avoids undesirable abrasive, coating damaging contact therewith. Platform disc 41 is slotted along the periphery thereof with spaced, opposed, mirror-image peripheral slots 43 sized to snugly engage with spaced inner pin segments 32 to be in nesting and aligned, supportive engagement therewith. A longitudinally ex&:ending through slot 44 is provided in disc 41 with its longitudinal axis advantageously extending substantially normal to the lonqitudinal axis of opposed peripheral slots 43 so that through slot 44 extends between spaced, opposed peripheral slots 43. Through slot 44 is preselectively sized in length and width to allow snug and limited passage therethrough of a preselected portion of PTC thermistor heater disc 38, the heater disc 38 thus being firmly supported by insulated platform disc 41. In this regard, it is to be noted that through slot 44 is provided with opposed pairs of integral, flexible feathered edges 46 and 47 along the peripheral walls of the slot 44 to snugly engage against opposed polar wall and side faces of that portion of PTC thermistor heater disc 38 extending therethrough. It further is to be noted that support disc 41 is provided with an integral stirrup 48 which extends from the lower face of disc 41 between spaced integral legs 42 and transverse the longitudinal axis of slot 44 to further restrict movement of that portion of PTC thermistor disc 38 which extends through slot 44 so as to be firmly supported by supporting platform disc 41 free of abrasive, coating damaging contact with the several parts of cup-shaped body member 26 and, at the same time, insuring first fused contact of PTC thermistor heater disc 38 through projecting offset mirror-image ears 39 with inner pin segments 32, minimizing the effects of any undesirable, solder damaging vibrations which might occur during operations.