US3437774A - Terminal structure for thermostats and the like - Google Patents

Description

April 8, 1969 H. F. SNIDER 7 3,437,774

TERMINAL STRUCTURE FOR THERMOSTATS AND THE LIKE Filed Oct. 27, 1967 INVENTOR.

BY M V A/A/KFAPIQ/A/CTGM 1 54,04: ,rcopmv United States Patent US. Cl. 200166 9 Claims ABSTRACT OF THE DISCLOSURE A terminal structure for thermostats or the like is described including an electrical terminal connector which is substantially immune to damage caused by vibration or end loading of a lead wire. The lead wire is welded to a U-shaped strap imbedded in the body of the terminal structure. The ends of the U-shaped strap mechanically grip the lead wire ahead of the weld to prevent vibration or end loads from reaching the weld. The strap is also provided with an opening through which the end of the wire projects to prevent spreading of the wire during welding. The structure is arranged to provide a low profile to minimize the space requirement of the terminal.

Background of invention This invention relates generally to an electrical terminal connector for thermostats and the like and more particularly to a novel and improved terminal connector which is substantially immune to damage resulting from vibration and end loading of the terminal lead.

Prior art Thermostatic switching devices or the like are often provided with quick disconnect push-on type terminals to connect the lead wires to the switch. However, such terminals cannot be used when the leads may be subjected to tension loads and/or severe vibration loads. When the leads of such devices are likely to be subjected to tension or substantial vibration loads, it has been the practice in the past to use terminal connectors which employ some form of threaded fastener to clamp the lead and/ or attach a terminal secured to the end of the lead. Such terminals, with threaded fasteners, are expensive to manufacture since they require several part which must be manufactured and assembled, usually by hand. Also they require substantial space and often result in an increase in the overall size of the device.

Summary of invention The present invention provides a permanent terminal connection for thermostatic switching devices, or the like, which is capable of withstanding substantial tension loads on the lead wires and which can withstand substantial vibration loads without damage. Further the structure is arranged so that the terminal lays flat on the body of the device and does not materially increase the overall dimensions thereof.

The illustrated embodiment includes a U-shaped strap which is imbedded in the body of a switching device such as a thermostat. The two legs of the strap project out of the terminal surface of the body at spaced points. A first leg extends substantially parallel to the terminal surface a distance substantially equal to the spacing between the legs and is provided with an aperture adjacent to the terminal surface. The end of the lead wire extends through the aperture and the lead wire is welded or otherwise metallically bonded to the under surface of the first leg at a point approximately midway between the aperture and the end of the leg.

3,437,774 Patented Apr. 8, 1969 The second leg is formed with a central notch and spaced projections extending along both sides of the notch. The first leg is bent so that it extends along the terminal surface of the body and its end is located adjacent to the side of the second leg. The notch on the second leg and the end of the first leg enclose and tightly grip the lead wire at a point spaced from the weld to provide a strong mechanical connection which prevents vibration movement from reaching the weld. The two projections are clinched over the end of the first leg to insure that tight mechanical gripping is provided.

With this terminal connection the metallic bond at the weld provides a reliable low resistance electrical connection that is substantially immune to deterioration. The tight mechanical connection ahead of the weld prevents any substantial force from being applied to the weld. This mechanical connection also prevents vibration induced movement from reaching the weld and prevents breaking of the wire strands at the weld which would otherwise occur if the strands were repeatedly bent adjacent to the weld. The aperture confines the ends of the lead wire so that it does not spread when the weld is made.

The illustrated embodiment of this invention, therefore, provides a strong permanent terminal connection which is substantially immune to damage by end or vibration loading of the terminal lead. Still further the terminal itself is firmly anchored in the body and provides a mounting for the switch elements of the device. The cost of manufacture is low since the number of parts is minimized and since the procedures for assembly lend themselves to automation.

Objects 09 invention It is an important object of this invention to provide a novel and improved terminal structure which employs a minimum number of parts and which provides safe and "reliable service.

It is another important object of this invention to provide a novel and improved terminal structure including a metal to metal bond between the terminal and a lead wire and which provides mechanical gripping of the lead wire ahead of the bond to isolate the bond from vibration or end loads applied to the lead wire.

Further objects and advantages will appear from the following description and drawings wherein:

FIGURE 1 is a perspective view of an assembled thermostat incorporating a terminal connection according to this invention;

FIGURE 2 is an enlarged fragmentary perspective view of the thermostat of FIGURE 1 shown with the terminal cap removed to illustrate the structural arrangement of the terminals with the lead wires attached;

FIGURE 3 is a fragmentary perspective view of one terminal before the lead wire is attached; and,

FIGURE 4 is a fragmentary perspective view similar to FIGURE 3 illustrating the terminal after the lead wire is welded thereto and before the legs are bent down to provide mechanical gripping of the lead wire.

FIGURES l and 2 illustrate a typical thermostat incorporating a terminal structure in accordance with this invention. This thermostat includes a body 10 with a disc retaining case 11 mounted thereon. In the illustrated embodiment the case -11 is provided with a mounting flange 12 and a terminal cap 13 is provided to cover and enclose the terminal assemblies 14 and 16. A spring wire 17 extends over the cap 13 and is provided with opposed hooks 18 which extend into recesses 19 in the body 10 to removably secure the terminal cap to the body. Switch means are provided which operate by temperature responsive means to electrically connect and disconnect the terminals 14 and 16.

The particular switch structure and the structure of the temperature responsive means are not illustrated since any suitable structure may be used. For example, the patent to Bolesky et al. No. 2,954,447 illustrates one type of switch and temperature responsive means which may be employed. It should be understood that a terminal structure incorporating this invention may be used on other types of devices and it is shown as applied to a thermostat only to illustrate a particular use to which it is well suited.

Reference should now be made to FIGURES 2 through 4 for a clear understanding of the structure of the terminal 14. It should be understood that the structure of the terminal 16 is the same as the terminal 14 so the following detailed description applies equally well to both terminals.

The terminal 14 includes a U-shaped strap member 24 providing spaced legs 26 and 27 which extend through the body 10 and project beyond the terminal surface 23 thereof. The two legs 26 and 27 are jointed by a lateral connecting portion 28. The terminal strap 24 may be embedded in the body 10 at the time the body is molded or may be inserted through appropriate openings molded into the body after the body is formed. In the illustrated embodiment the strap member 24 is inserted into mating openings molded in the body and is staked at 32, as illustrated in FIGURES 2 and 4, so that it is permanently mounted in position.

The leg 27 provides a projecting portion 29 extending beyond the terminal surface 23 which is formed with an aperture 31 adjacent to the location where it emerges from the body. The portion of the leg 27 within the body is wider than the projecting portion 29 to provide shoulders 32a which cooperate with the aperture 31 to reduce the cross section of the leg and provide a bend line adjacent to the terminal surface 23. The shoulders also provide material for the staking of the strap.

The leg 26 is formed with a central notch 33 extending along the projecting portion thereof to a gripping surface 34 substantially coplanar with the terminal surface 23. Extending upwardly along each side of the notch 33 are similar but opposite projections 36. Here again shoulders 32a are provided adjacent to the terminal surface 23.

When the lead wire 21 is to be connected to the terminal, its end 38 is pushed through the aperture 31 from the side adjacent to the leg 26. The lead wire is then positioned along the adjacent side of the projecting portion 29 and is welded thereto at 39. It should be understood that other forms of metal to metal bond may be employed at 39. For example, the lead wire can be soldered, brazed, or otherwise suitably metallically bonded to the projecting portion of the leg. The bond or weld, however, should be arranged so that it is spaced from the end 41 of the leg 27 for reasons discussed in detail below.

After the lead wire 21 is welded to the leg the projecting portion 29 is bent along a bend line 42 adjacent to the shoulders 32 until it extends substantially parallel to the terminal surface 23. This positions the lead wire in the notch 33 adjacent to the gripping surface 34. The various elements are proportioned so that the end 41 is positioned immediately adjacent to the leg 26 as best illustr-ated in FIGURE 2. The projections 36 are then clinched over the top of the adjacent end of the projecting portion 29 to cause the wire to be tightly mechanically gripped between the gripping surface 34 and the adjacent underside of the leg 27.

With this structure a tight mechanical gripping of the wire is provided ahead of the weld 39 and the end of the wire projects through the aperture 31 so that it does not spread during the formation of the weld. The mechanical gripping prevents vibration or end loads from being transmitted to the weld so fatiguing of the Wire does not occur at the weld and the terminal connection is not damaged even when vibration or end loads are applied. The terminal structure, because it lays substantially adjacent to the 4 terminal surface 23, provides a low profile. In fact th maximum spacing between the terminal structure and the terminal surface 23 is substantially equal to twice the thickness of the legs 26 and 27 plus the thickness of the wire. This maximum spacing is provided at the clinched projections 36.

The terminal provides considerable strength since two spaced le-gs project through the body to firmly anchor the terminal with respect to the body. In most installations the lateral connecting portion 28 is used to connect and support the adjacent switch element 43. Therefore, in most instances the lateral portion 28 is arranged to be exposed at the inner surface of the body 10.

Although a preferred embodiment of this invention is illustrated, it is to be understood that various modifications and rearrangements of parts may be resorted to without departing from the scope of the invention disclosed and claimed herein.

I claim:

1. A terminal structure for a thermostatic switching device or the like comprising a body provided with a terminal surface, a pair of spaced terminal legsmounted on said body and extending from said surface, a portion of a first of said legs extending substantially parallel to said surface to an end adjacent to a portion of a second of said legs, a lead wire extending along said portion of said first leg substantially parallel to said terminal surface, a metallic bond connecting said lead wire and the portion of said first leg, the end of said first leg and said second leg cooperating to provide a mechanical connection to tightly grip said lead wire at a point spaced from said bond preventing relative movement between said lead wire and said pair of legs from reaching said bond.

2. A terminal structure as set forth in claim 1 wherein said second leg is formed with a gripping surface adjacent to said end of said first leg cooperating therewith to encircle said wire and providing said mechanical connection, and a projection on said second leg extending over said'end of said first leg urging said end toward said gripping surface.

3. A terminal structure as set forth in claim 2 wherein the end of said second leg is formed with an axially extending notch, the bottom of which provides said gripping surface, said second leg providing a pair of spaced projections extending along opposite sides of said notch each of which extends over said end of said first leg to urge it toward said gripping surface.

4. A terminal structure as set forth in claim 1 wherein I said bond is a weld, said lead wire is stranded, and said first leg is formed with an aperture remote from said mechanical connection, and the ends of said lead wire extend through said aperture.

5. A terminal structure as set forth in claim 4 wherein said pair of legs are provided by a U-shaped terminal member having a lateral leg connecting portion within iaid body at a location spaced from said terminal surace.

6. A terminal structure as set forth in claim 5 wherein switch 'means are provided in said body, said switch means including a switch element supported on said leg con necting portion.

7. A terminal structure as set forth in claim 1 wherein said first leg extends through said body substantially perpendicular to said terminal surface to a bend located adjacent to said terminal surface, said first leg having a cross section at said bend which is substantially less than the cross section of said first leg adjacent to said bend within said body.

8. A terminal structure as set forth in claim 7 wherein the maximum spacing between said terminal surface of said body and said pair of legs is approximately equal to twice the thickness of said pair of legs plus the thickness of said lead wire.

9. A terminal structure as set forth in claim 8 wherein said body is provided with a cylindrical outer surface, a cap member is mounted on said body to enclose said 5 6 terminal, said cap member providing a cylindrical skirt 2,887,670 5/1959 Lowell. extending around and along the outer surface of said body, 2,947,968 8/ 1960 Mapelsden et a1 339-276 and a clip wire removabiy secures said cap member to 3,114,818 12/1963 Renaud et a1 339-275 said body. 3,215,027 11/1965 Modrey et a1 339275 References Cited 5 3,376,540 4/1968 Turban 339-275 UNITED STATES PATENTS ROBERT K. SCHAEFER, Primary Examiner.

2,183,109 12/1939 51% H. o. JONES, Assistant Examiner. 2,371,494 3/1945 Benander.

2,462,867 3/1949 Hubbell; us. 01. X.R. 2,794,176 5/1957 Barnes. 337-343; 339*275

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