Grounding Clip For Plug-in Surface Heating Unit

Abstract

A plug-in electric surface heating unit for use in the cooktop of an electric range. The heating unit is a metal sheathed electrical resistance heating element in spiral form with radial, outwardly directed terminal portions in close side-by-side relation. The invention relates to a four-sided grounding clip of spring material that is fastened to the sheath at the terminal portions of the heating element so as to make a reliable grounding connection with the grounding arms of a terminal block mounting bracket as well as permit relative movement between the terminal end portions due to thermal expansion and contraction.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to application Ser. No. 311,630 filed Dec. 4, 1972, entitled PLUG-IN SURFACE HEATING UNIT TERMINAL BLOCK MOUNTING of Richard V. Prucha and Teamus Bowling, which is being filed concurrently herewith.

BACKGROUND OF THE INVENTION

The repeated use of electric surface heating units formed of metal sheathed electrical resistance heating elements in open spiral form occasions the gradual accumulation of grease spatter and food spillage that passes down between the spiral coils and eventually comes to rest either on the underlying reflector pan or a bottommost pan or insulation guard that is designed to contain the soils and protect the thermal insulation that is wrapped around the baking and broiling oven located beneath the cooktop. These accumulated soils should be cleaned up periodically so that they do not become a safety hazard or begin to contaminate the kitchen. In order to clean beneath the heating unit it is first necessary to raise the unit.

In the prior art there are two main categories of movable heating units. The first category comprises hinged heating units which may be raised up at an angle so that the reflector pan beneath the unit may be removed and the underlying pan wiped clean of soil. The second category of movable heating units comprises plug-in heating units having a separate terminal block mounted beneath the cooktop. The heating unit is provided with plug-in terminal portions which are insertable into sockets in the terminal block, such that a person may unplug the heating unit from the terminal block almost in the same manner as unplugging an attachment plug of an electrical cord set from a convenience outlet mounted in the wall of a room. One important advantage in a plug-in surface heating unit is that it is easy for the average user to replace the unit without the need of an appliance serviceman to rewire the heating unit into the cooktop. One criteria is that the design must be simple in operation so that anyone of ordinary intelligence may plug in the heating unit in a foolproof action so that lengthy installation instructions are not necessary. A second criteria is one of safety in providing an automatic grounding means for the heating element by grounding the outer sheath to harmlessly drain off any electrical current which may leak to the sheath. This grounding action must be effected automatically as the plug-in heating unit is being plugged into the terminal block. This grounding connection must be made prior to the time the electrical connection is made. The reverse action is also true. This grounding connection must not be broken until the electrical connection is first broken.

The principal object of the present invention is to provide a grounding clip for a plug-in electric surface heating unit where the clip is adapted to be mounted on the sheath of the terminal end portions of the heating unit and is capable of making a strong grounding connection with the mounting bracket of the terminal block and at the same time is resilient enough to permit relative movement in all directions between the terminal end portions due to thermal expansion and contraction of the heating element.

A further object of the present invention is to provide a grounding clip of the class described of four-sided configuration which is resilient in side compression and while mounted on the sheath of the terminal end portions is capable of universal movement between the terminal end portions.

SUMMARY OF THE INVENTION

The present invention, in accordance with one form thereof, relates to a grounding clip that is adapted to be mounted on the sheath of the terminal end portions of a metal sheathed electrical resistance heating element of a plug-in surface heating unit. This clip is of spring strip material that is formed edgewise into a four-sided figure where the first side is of split configuration while the second and third sides are generally parallel to each other and the fourth side is generally parallel to the first side and is provided with a special resilient section. The clip has two apertures in the first side and two similarly aligned apertures in the fourth side so that the terminal end portions of the heating element may be inserted therethrough. The clip includes gripping means for engaging the sheath of the terminal end portions.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention will be better understood from the following description taken in conjunction with the accompanying drawings and its scope will be pointed out in the appended claims.

FIG. 1 is a top plan view of a plug-in electric surface heating unit mounted in a cooktop and plugged into a separate terminal block and mounting bracket combination, and showing a four-sided grounding clip mounted on the sheath of the terminal end portions of the heating element that comprises the present invention, there being a part of the cooktop broken away in the area over the grounding clip and terminal block.

FIG. 2 is a fragmentary, cross-sectional elevational view taken on the line 2--2 of FIG. 1 and showing a side view of the spiral heating element with its two terminal end portions having mounted on the sheath thereof the grounding clip of the present invention.

FIG. 3 is an isometric, fragmentary view of the terminal end portions of the heating element with the grounding clip fastened thereon.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning now to a consideration of the drawings and in particular to the plan view of FIG. 1, there is shown a plug-in surface heating unit 10. This heating unit comprises a metal sheathed electrical resistance heating element 12 that is of open spiral configuration of rather standard design. Notice this heating element has two terminal end portions 14 and 16 which are arranged in close side-by-side relation and extend in a radial, outward direction. The first terminal end portion 14 extends horizontally inward nearly to the center of the heating unit, and then rises vertically as at 18 to the plane of the spiral configuration. It is then wound into the first small diameter coil 20 and then spirals in a gradually increasing radius until it finishes the largest diameter coil 22 where it is then turned down vertically as at 24, and then extends outward as terminal 16 in a side-by-side relationship with the first terminal 14, as is best seen in FIG. 1.

These spiral coils of the heating element 12 are relatively flexible in a vertical direction. Hence, these coils are rested on a triangular framework or spider 28 of vertically arranged metal strips, which spider has three oppositely directed arms 30, 32 and 34. The arm 30 has two upward tabs 38 which grip the outer coil 22, as well as two similar tabs 40 which grip the inner coil 20. The remaining coils are unattached to the spider 28 so as to allow the heating element to have a certain amount of freedom of movement due to thermal expansion and contraction of the heating element 12 during the heating up and cooling down of the heating element.

As is conventional in this art, a decorative trim ring 44 is supported by the tips of the radial arms 30, 32 and 34 of the spider 28 so as to be joined with the heating element 12 by means of the spider. This trim ring 44 serves both as a support means with the cooktop 48 and a transition piece to generally bridge or close the gap between the outer coil 22 of the heating element 12 and the downward peripheral flange 103 defining a circular opening 46 that is formed in the cooktop 48 of an electric range. Positioned beneath the heating unit 10 is a removable reflector pan 52 which is of dished-shape having a large central opening 54, and an outer horizontal flange 56 that is adapted to rest upon a recessed ledge 58 that is formed within the opening 46 at the bottom of the flange 103. A suitable cut-out or notch 62 is formed in the reflector pan 52 for accommodating the terminal end portions 14 and 16 therethrough, as is best seen in FIGS. 1 and 2. Missing from FIG. 1 is a center medallion that is a small circular plate that fits within the center of the spider 28 and is supported therefrom so as to close some of the opening within the smallest coil 20 and prevent large objects from falling down through the spider.

As is best seen in the fragmentary view of FIG. 3, the two terminals 14 and 16 of the heating element 12 are each provided with an outer metal sheath 60 and an innermost cold terminal 14' and 16' which is insulated from the sheath by an end seal 62. The tips of these terminals 14' and 16' are each supplied with folded blade 64 that is welded thereto and serves to make electrical connection with spring contacts (not shown) within an insulating terminal block 70 that is of generally hollow configuration formed of molded ceramic insulating material and for containing the spring contacts within separate sockets, as is well known in this art. The terminal block 70 is supported by a mounting bracket 72 and this particular terminal block 70 and mounting bracket 72 combination is not fully described here in all its detail because it comprises an invention which is described and claimed in a copending patent application of R. V. Prucha and T. Bowling Ser. No. 311,630 which is being filed concurrently herewith, as was mentioned above.

The mounting bracket 72 is of folded sheet metal construction which has a top wall 74 overlying the front portion of the top wall of the terminal block 70. The opposite side edges of this top wall are folded down to form side walls 76, 76 which substantially overlie the front portion of the side walls of the terminal block in close side-by-side relation. The front edge of the top wall 74 of the bracket is formed with an upwardly turned tab 78 which is a mounting tab that has a hole for receiving a sheet metal fastening screw 80 that extends through the hole in the tab and is threaded into an opening in the downturned flange 103 that defines the periphery of the opening 46 in the cooktop 48. This is a simple, single screw fastening means 80 for supporting not only the mounting bracket 72, but in turn the terminal block 70.

Notice in FIG. 2 that the front wall 84 of the terminal block 70 stops short of the front of the mounting bracket 72. Only the front portion of the side walls 76, 76 of the mounting bracket that is in front of the front wall 84 of the terminal block is folded under as at 86, and the ends are butted together to form a downwardly inclined ramp 88 which leads from the entrance to the two sockets of the terminal block that contain the spring contacts for mating with the spring blades 64, 64. Moreover, the two side walls 76, 76 of the mounting bracket are extended forwardly to form two grounding arms 90, 90 as is seen in both FIGS. 1 and 2. These grounding arms 90, 90 serve to make engagement with a grounding clip 95 that is mounted on the sheath 60 at the terminal end portions of the heating element as will be explained with relation to the detailed view of FIG. 3.

The grounding clip 95 is formed of a strip of thin spring material such as stainless steel that is formed edgewise into a four-sided figure having a first side 97 of split configuration and second and third sides 99 and 101 which are generally parallel to each other, and a fourth side 105 that is provided with a special resilient section 107. The first side 97 of the grounding clip 95 has a split 109 where the butt ends are folded over to form small flanges 111. When these flanges butt they serve as stop means to limit the movement of the two terminal end portions 14 and 16 toward each other. This first side 97 of the grounding clip is provided with a pair of apertures 113 that are provided with extruded collars 115. The fourth side 105 of the grounding clip is provided with a pair of larger apertures 117 which are generally aligned with the apertures 113 so that the terminal end portions 14 and 16 of the heating element 12 may be inserted therethrough. The two collars 115, 115 are crimped down onto the sheath 60 of the terminal end portions 14 and 16 for making a permanent connection of the grounding clip 95 to the sheath. It was mentioned earlier that the second and third sides 99 and 101 of the grounding clip are generally parallel to each other. Actually these two side portions diverge slightly from each other as they extend from the first side 97 to the fourth side 105. The reason that this is advantageous is that the grounding clip is thereby tapered slightly so as to exert a strong outward pressure against the two grounding arms 90, 90 of the mounting bracket 72 as is best seen in FIG. 1. In other words, in the disassembled condition of the heating unit away from the terminal block 70, the second and third sides 99 and 101 of the grounding clip are slightly diverging and it is only when the heating unit 10 is plugged into the terminal block 70 that the grounding arms 90, 90 compress the grounding clip and force the two sides 99 and 101 to be generally parallel to each other, as is seen in the assembled view of FIG. 1.

The special resilient section 107 of the fourth side 105 is represented by a central elongated internal loop with a deep horizontal notch 120 which further weakens the loop and renders it more resilient in all directions. Thus it will be seen that the grounding clip 95 is permanently fastened to the sheath of the terminals of the heating element and the clip is so designed that it is resilient in all directions to permit relative freedom of movement of the two terminals due to thermal expansion and contraction of the heating element.

Modifications of this invention will occur to those skilled in this art, therefore it is to be understood that this invention is not limited to the particular embodiments disclosed but that it is intended to cover all modifications and their equivalents which are within the true spirit and scope of this invention as claimed.

Claims

What is claimed as new and desired to secure by Letters Patent of the United States is:

1. A metal grounding clip adapted for mounting on the sheath of the terminal end portions of a metal sheathed electrical resistance heating element of a plug-in surface heating unit, said clip being a strip of thin spring material that is formed edgewise into a four-sided figure, a first side having a split adjacent the center and formed by the two ends of the strip being adapted to have a close butting relationship, the second and third sides being generally parallel to each other, and the fourth side closing the back of the clip, this fourth side including a resilient compression section, the said first side having a pair of apertures adapted to receive terminal end portions therethrough with a forced fit engagement with the sheath, the said fourth side also including a pair of larger apertures that are adapted to loosely receive the terminal end portions therethrough, whereby the clip permits relative movement between the terminal end portions.

2. A grounding clip as recited in claim 1 wherein the apertures of the said first side are provided with extruded collars which are each adapted to be crimped onto the sheath of the terminal end portions of the heating element.

3. A grounding clip that is adapted to be mounted on the sheath of the terminal end portions of a metal sheathed electrical resistance heating element of a plug-in surface heating unit, said clip being of a strip of spring material that is formed edgewise into a four-sided figure, the first side being of split configuration, while the second and third sides are generally parallel to each other, and the fourth side is generally parallel to the said first side and is provided with a special resilient section, the clip has two apertures in the first side and two similary aligned apertures in the fourth side so that the terminal end portions of the heating element may be inserted therethrough, and gripping means on the clip adapted for making a firm connection with the sheath of the heating element whereby the clip will not prevent relative movement between the terminal end portions due to thermal expansion and contraction of the heating element.

4. A grounding clip as recited in claim 3 wherein the said special resilient section is a central, elongated internal loop with a deep horizontal notch formed therein to render it more resilient in all directions.

5. A grounding clip as recited in claim 3 wherein said gripping means is represented by extruded collars originating from the two apertures in the first side of the clip, said collars being adapted to be crimped tightly onto the sheath of the terminal end portions of the heating element.

6. A grounding clip as recited in claim 4 wherein the said gripping means is represented by extruded collars originating from the two apertures in the first side of the clip, said collars being adapted to be crimped tightly onto the sheath of the terminal end portions of the heating element.

7. A grounding clip as recited in claim 6 wherein the second and third sides of the clip are slightly diverging from the first to the fourth sides whereby the clip member is adapted to be compressed due to opposing side forces adapted to be exerted by a generally parallel pair of grounding arms of a terminal block mounting bracket.