US2717940A - High pressure contact - Google Patents

Description

Sept. 13, 1955 T. FJELLSTEDT HIGH PRESSURE CONTACT Filed Dec. 5, 1951 INVENTOR. Tfior-szen {7&2 cit BY I Zl'orniy United States Patent HIGH PRESSURE CONTACT Thorsten Fjellstedt, Iugleside, Ill., assignor to McGraw Electric Company, Milwaukee, Wis., a corporation of Delaware Application December 5, 1951, Serial No. 259,971

3 Claims. (Cl. 200-166) This invention relates to an improvement in a high pressure cont-act for use in electrical apparatus.

The inherent ability of metals to be conductors of electricity is a vital part of the electrical industry. The generation of heat that accompanies the flow of current in conductive elements is one of the greatest problems of the industry. Various means have been used to dissipate this heat. However, the contact points of the engaging elements are still vulnerable spots where heat accumulation occurs on switches and frequently makes them highly resistant to How of current at the joints.

Switches used for making and breaking conductive connection between current carrying conductors, lines, or bus bars are often used outdoors and must therefore be adapted to withstand varying weather conditions.

Weathering causes corrosion and it has been found that where corrosion occurs at contact points, the contact points rise to higher temperatures than normally.

In other electrical apparatus, the current is sometimes conducted from a metal of great mass to a metal of lesser mass. The lesser mass may be in the form of a springlike contact means or a resilient clamp where a thin metal would probably be used. A thin metal carrying as much current as a heavier metal is apt to become destructively hot if the heat is not dissipated.

Even when the current flows between two metals of similar weight, the contact point is always inclined to become hot. If dust, dirt, or corrosion accumulates at the contact point the increase in temperature is even greater. When this heat becomes intense it may distort the metal and destroy the resiliency of the contact. Or the heat may fuse the two metals at their contact point and make it extremely diificult to break the joint when it is desired to open the circuit.

It is to counteract these dangers that I developed this novel method of protecting a contact point in an electrical apparatus.

The object of this invention is to provide a means of dissipating the heat which intensifies around a contact point.

Another object of this invention is to protect a resilient contact means from overheating and resultant distortion.

I illustrate several ways of using my invention in the accompanying drawing, in which:

Fig. l is an end view of a stationary terminal contact and switch blade, partly in section, incorporating my heat dissipator.

Fig. 2 is a fragmentary view, partly in section, of another form of switching device incorporating my heat dissipator.

Like reference characters designate like parts throughout the specification.

In order to keep contact points cool, I devised this novel method of placing a heat difiuser behind the contact points in the form of metal protrusions. The heat that intensifies at the contact point spreads throughout the metal diffuser as quickly as it accumulates. As it spreads it becomes less intense until it finally dissipates ice into the surrounding atmosphere. The large metal mass quickly conducts the heat away from a concentrated point and thus is an effective means for holding down the temperature of the contact points.

Fig. 1 illustrates a switch which embodies my novel means for dissipating heat. The general construction of the switch is substantially the same as disclosed in the patent to Cornell et al. 2,316,844 and for that reason is not illustrated in such great detail. I show a transverse view similar to Fig. 3 of that patent illustrating the stationary contact assembly on a stationary insulating stack 1. Mounted on the stack 1 in fixed relation is a carrier or frame 2 having mountings formed by two rearwardly extending arms 3 and 4. These arms are shown broken away so as not to obstruct the view of other details. Attached to these mountings are contact bars (not shown) which terminate in angularly slotted structures forming the contact springs 5 and 6. Each of these springs is curved, its convex side 5a and 6a facing the switch blade 7 for high pressure engagement therewith. Each spring 5 and 6 is also shaped so as to flare outwardly and upwardly as indicated at 5b and 6b. Secured to the mountings on the side walls of the frame 2 are also sets of counterpressure springs 8, each set consisting of two leaves. These sets coact with the contact springs 5 and 6. Interposed between each set of counterpressure springs 8 and the corresponding contact spring is a spacer 9. Each spacer 9 is provided with studs 10 on each side which project through apertures in the associated springs.

This switch is shown in closed position. The outer contact end of the polygonal switch blade 7 is in high pres sure contact engagement with the convex faces of the contact springs 5 and 6 at the corners 11 and 12. This high pressure contact engagement is reinforced and safeguarded by the counterpressure springs coacting with the contact springs.

Within the polygonal switch blade 7 at the corner near the Contact 11 is a metal diliuser piece 13 which dissipates the heat from the contact point 11 and at the opposite corner within the switch blade 7 near the contact point 12 is a metal diffuser piece 14 which dissipates the heat away from the cont-act point 12. Heat radiating diffusers 13 and 14 may be extruded integrally with blade 7 or sweated, brazed or soldered thereto. However, merely holding the diffusers in place by mechanical pressure does not comply with the teaching of this invention because perfect metal to metal contact throughout the surfaces to be joined is unattainable by ordinary pressure means without polishing or lapping the abutting pieces.

Fig. 2 illustrates a preferred modified form in which is provided a switch blade 15 with flattened end 16 fitting in tight contact at 17 with a pair of contact springs 18. A metal diffuser 19 is placed on the outer side of the contact springs 18 from the contact point 17. Another metal diiiuser 20 is placed on the inner side of the switch blades flattened end 16 opposite the contact point 17. It can be seen from Fig. 2 that these metal protrusions more or less fan out from the contact point 17 so as to dissipate the heat.

Fig. 3 is a section through Fig. 2 taken on the line 3-3 of Fig. 2. This view shows the metal diffusers 19 and 20 as separate pieces attached by some tight soldering means to the contact springs 18 and to the switch blade 16.

Fig. 4 is a similar view but in this case the metal diffusers are formed integral with the contact members. The dilfuser 24 is formed in one with a switch blade 21 and the diffuser 22 is formed in one with the contact springs 23.

Either the method of Fig. 3 or 4 can be used to dissipate heat away from the contact points. When the diffuser is an added piece as in Fig. 3, it is necessary to have a tight fit between the two pieces so that no air gaps occur to interrupt the conductive properties of the metals.

Using metal protrusions in close proximity to the contact point has many advantages over using heavier metal throughout the conductor members. Heavier metal would add to the cost of manufacture and also to the weight of the product. It is much simpler and more effecitve to concentrate the diffusing means around the contact points. This permits the use of switch blades and contact elements with a minimum of metal contents.

Comparative tests have been made on the conventional type contact and my improved type diffuser contact under identical ambient conditions, each being subject to identical current flow of different amperages and for different durations. places 011 the conductors and on the diffusers and in all the tests it was found that where my diffuser was used the temperature at the contact point was approximately 3 C. lower than on conventional type contact. When higher amperage was used for a longer duration, the temperature differential was approximately 4 C.

Thus, it can be seen and tests have proved that by placing a metal diffuser behind the contact points the temperature at the contact points is lowered. This is especially significant on switches where corrosion is apt to form, such as switches exposed to varied weather conditions. The corrosion ordinarily would add several degrees to the temperature of the contact points but with the metal diffuser behind the contact points the temperature at the contact points was held considerably lower.

With this means of conducting heat away from a vital point critical situations can be prevented. Consequently, my novel method of dissipating heat should be a great value in innumerable forms of electrical apparatus.

I claim:

1. In a high tension switch including separable conductors each having a heat generating surface in current conducting joint contact relationship to the heat generating surface of the other conductor and each having a heat radiating surface in opposed relationship to its corresponding heat generating surface, a heat diffusing means on at least one of said conductors intermediate Thermocouples were attached to various said heat generating and heat radiating surfaces, said means comprising a heat conductive metallic section of uninterrupted continuity between said surfaces, whereby heat generated at the joint of contact between said heat generating surfaces may be conducted through an uninterrupted metallic path for radiation from a heat radiating surface.

2. In a high tension switch including separable conductors each having a heat generating surface in current conducting joint contact relationship to the heat generating surface of the other conductor and each having a heat radiating surface in opposed relationship to its corresponding heat generating surface, a heat diffusing means on at least one of said conductors intermediate said heat generating and heat radiating surfaces, said means comprising a heat conductive metallic section metallically fused to said conductor and extending longitudinally of said joint of contact, whereby heat generated at said joint of contact between said heat generating surfaces may be conducted through an uninterrupted metallic path for radiation from a radiating surface.

3. In a high tension switch including separable conductors each having a heat generating surface in current conducting joint contact relationship to the heat generating surface of the other conductor and each having a heat radiating surface in opposed relationship to its corresponding heat generating surface, a heat diffusing means on at least one of said conductors intermediate said heat generating and heat radiating surfaces, said means comprising a heat conductive metallic unitary protuberance projecting from said conductor and defined by said radiating surface, whereby heat generated between said generating surfaces may be conducted through an uninterrupted metallic path of radiation from a radiating surface.

References Cited in the file of this patent UNITED STATES PATENTS 2,231,992 Fjellstedt Feb. 18, 1941 2,265,667 Mekelburg et al. Dec. 9, 1941 2,316,844 Cornell et a1 Apr. 20, 1943

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