Dec. 15, 1959 F. E. CHABOT 2,917,612

PLUG IN DISCONNECTS Filed Nov. 25, 1957 United States PLUG IN DISCONNECTS Application November 25, 1957, Serial No. 698,832 4 Claims. (Cl. 200-166) This invention relates to a novel disconnect jaw for making connection to a cooperating current carrying member, and more specifically relates to a disconnect jaw having a plurality of fingers having different lengths whereby current paths from the cooperating member to the contacting fingers are non-coincident and the current density and thermal flow pattern are distributed over a relatively large area at the contacting area,

Disconnect jaws as used in blade switches or plug-in disconnection means for panel-board circuit breakers are well known in the art and are usually comprised of a flat bus or blade which cooperates with a jaw of a single sheet of conductive material or a plurality of fingers each having the same length. Because of this construction, the contact area alongthe full length of the disconnect jaw is at substantially the same transverse position whereby current flow across the contact area from the switch blade to the jaw is concentrated at this transverse section of the jaw. Thus, there will be a high concentration of current density at this relatively thin area of contact engagement between the jaw and the blade which leads to a distorted thermal fiow pattern with subsequent generation of heat and higher electrical resistance at the contact. At the same time, a relatively high plug-in force is required since the blade is simultaneously connected to the current carrying portions of the jaw, which portions are biased into engagement with the blade so as to achieve good electrical contact.

The object of my invention is to provide a novel disconnect jaw in which there is a broad distribution of current density and hence a better thermal flow pattern at the point between the connection between a blade and a disconnect jaw.

Another object of my invention is to provide a novel disconnect jaw which has a relatively low contact resistance.

Another object of the invention is to provide a novel disconnect jaw which includes contacting fingers which are staggered.

A further object of my invention is to provide a novel disconnect jaw having a plurality of fingers of different lengths for engaging a cooperating conductor in a staggered manner to thereby improve the thermal flow pattern at the contact area.

These and other objects of my invention will become apparent from the following description when taken in connection with the drawings, in which:

Figure 1 shows a disconnect switch having a disconnect jaw constructed in accordance with my invention.

Figure 2 is a top view of the disconnect switch of Figure 1.

Figure 3 is a perspective view of my novel disconnect aw.

Figure 4 is an enlarged view of the disconnect jaw portion of Figure 1.

Figure 5 is a sectional view of Figure 4 taken across the lines 5-5.

Referring now to Figure 1, the disconnect switch shown atent therein is comprised of a base 10 which supports insulator members 12 and 14. Insulator members 12 and 14 then support terminal cars 16 and 18 respectively which are fastened thereto in any desired manner as by bolt means 13 and 15.

Terminal 18 has a pair of upwardly protruding arms 20 and 22 (Figure 2) which pivotally support switch blade 24 by means of the pivot pin 25 which extends through cooperating apertures in arms 20 and 22. It is to be noted that a current connection is completed from switch blade 24 through arms 20 and 22 to the end of terminal member 18 in any conventional desired manner.

The left-hand end of blade 24 is then seen in Figure 1 as being in engagement with my novel disconnect jaw 26 which is fastened to terminal car 16 by bolt means 28 and 30, or in any desired manner, and blade 24 may be moved into and out of engagement with disconnect jaw 26 by a force applied to pull-ring 32 which is fastened to blade 24. Thus, when the blade 24 engages disconnect jaw 26 a current path is completed from terminal 16, disconnect jaw 26, blade 24, arms 20 and 22, and terminal 18.

In order to open this current path, it is only necessary to apply a force to pull-ring 32 which will rotate blade 24 in a clockwise direction about pivot pin 25,whereby blade 24 moves out of engagement with jaw 26.

My novel disconnect jaw 26 is best seen inFigure 3 as comprising a first plurality of fingers 34, 36, 38 and 40, and a second plurality of fingers 42, 44, 46 and 48 which may be formed of a unitary sheet of conductive material bent into a U-shape, as shown in Figure 3.

Each of fingers 34 through 48 are tied to a common member formed by the bottom portion 50 of the U-shaped material in Figure 3. However, it is to be noted that in accordance with my invention, it is only necessary that a plurality of fingers having different lengths be provided and that they may be formed of physically separate members which are only ultimately fastened at some current connecting point.

Each of fingers 34 through 40 of the first plurality of contacting fingers are seen in Figure 3 to be progressively longer, while the contact fingers 42 through 48 which are aligned with fingers 34 through 40 are progressively shorter. gered in a first direction, while fingers 42 through 48 are staggered in a second direction.

It is to be further noted that the upper contacting portions of each of the fingers of Figure 3 are bent inwardly so as to afford an area of high pressure contact with respect to an interposed blade.

Figures 4 and 5 show the use of the disconnect jaw 26 of Figure 3 in the embodiment of Figure 1 in an enlarged view to specifically show the manner in which current distribution at the contacting area is spread over a large area. In the normal type of disconnect jaw, the contacting portion of each of fingers 34 through 48 will be longitudinally aligned whereby current flowing through blade 24 will be concentrated along that line and thus cause an increased current density and a distorted thermal distribution. In the case of Figure 3, however, the current flow in blade 24 is comprised of distinct paths to each respective finger, these paths being non-overlapping.

That is to say, there will be a first current path to finger 34 from the lower portion of blade 24; a second current path will be formed from a lower intermediate portion of blade 24 to finger 36; a third current path will be from the higher intermediate portion of blade 24 to finger 38, while a fourth path will be in the upper portion of blade 24 to the finger 40.

Thus, since the fingers are of different transverse dimensions, the blade 24 will carry longitudinally displaced currents to the individual fingers whereby the current That is to say,- fingers 34 through 40 are stag;

density of the blade is spread out throughout the complete blade and thermal distribution will be substantially the same as for normal current flow through the blade. Because of this, the area will run cooler and contact resistance will be lower.

In order to further stagger the current path, the fingers 42 through 48 on the other side of blade 24 are staggered in an opposite direction, as shown in Figures 3, 4 and 5. This causes'a still further improvement in thermal characteristics of the blade since the fingers which oppose one another, such as fingers 4t) and 4? will contact the blade at longitudinally displaced portions and thus avoid a concentration of heating at any one point along the blade.

While the embodiment set forth herein has been specifically directed to the use of my novel disconnect jaw in a disconnect switch, it is to be clearly noted that the disconnect jaw is not limited to this application.

By way of example, in a plug-in type of circuit breaker or panel-board circuit breaker, the circuit breaker terminals may be adapted to; be of the blade type and coopcrate with a jaw terminal of the type set forth in Figure 3 which is'fastened to the panel-board.

Although I have described preferred embodiments of my novel invention, many variations and modifications will now be obvious to those skilled in the art, and I prefer therefore to be limited not by the specific disclosure herein but only by the appended claims.

I claim:

1. A disconnect jaw for making a current connection to a cooperating conductor; said disconnect jaw having a first plurality of contacting fingers extending from a common member and being adapted to be biased into engagement with one side of said cooperating conductor and a second plurality of contacting fingers extending from a common member and being adapted to be biased into engagement with another side of said coopfrom a common member and being adapted to be biased into engagement with another side of said cooperating conductor; the fingers of said first plurality of fingers having different lengths to be staggered in a first direction; the fingers of said second plurality of fingers having different heights to be staggered in an opposite direction; each of said fingers of said first and second plurality of fingers forming non-coincident current paths from said cooperating conductor to said fingers.

3. In a disconnect jaw for electrically cooperatingwith a movable blade; said disconnect jaw comprising a first and second plurality of extending fingers adapted to engage opposite sides of said movable blade in longitudinal alignment with one another when said movable lade is moved in a first plane'into engagement with said disconnect jaw; the engaging portion of each finger of each of said first and second plurality of fingers W respectively being transversely displaced when measured in said first plane, with respect to said fingers of the corresponding plurality of fingers; the engaging portions of the fingers aligned opposite one another in each of said first and second plurality of fingers being transversely misaligned with respect to one another.

4. In a disconnect jaw.for electrically cooperating with a movable blade; said disconnect jaw comprising a first and 'second plurality of extending fingers adapted to engage opposite sides of said movable blade in longitudinal alignment with one another when said movable blade is moved in a first plane into engagement with said disconnect jaw; the engaging portion of each finger of each of said first and second plurality of fingers respectively being transversely displaced when measured in said first plane, with respect to said fingers of the crating conductor; the fingers of said first plurality cooperating conductor; the fingers of said first plurality of fingers having difierent lengths to be staggered in a first direction; the fingers of said second plurality of fingers having different heights to be staggered in an opposite direction.

2. A disconnect jaw for making a current connection to a cooperating conductor; said disconnect jaw having a first plurality of contacting fingers extending from a common member and being adapted to be biased into engagement with one side of said cooperating conductor and a second plurality of contacting'fingers extending corresponding plurality of fingers; the engaging por-,

tions of the fingers aligned opposite one another in each of said first and second plurality of fingers being transversely misaligned with respect to one another; said plurality of fingers engaging said blade in a staggering.

' relationship thereby equally distributing current density and thermal flow at the junction portion between said blade and said disconnect jaw.

References Cited in the file of this patent UNlTED STATES PATENTS 1,477,527 Raettig Dec. 11, 1923 1,957,213 Hobson May l, 1934 2,765,380 Graybill Oct. 2, 1956 2,789,189 Graybill et al. Apr. 16, I957