US2439084A - Insulated reinforced circuit breaker contact bar - Google Patents

Description

April 6, 1948. 2,439,084

INSULA iED REINFORCED CIRCUIT BREAKER conmcw BAR' H. c. GRAVES, JR 7 2 Sheets-Sheet 1 Filed Dec. 28, 1944 III] PLAST/CMAT'k/AL IIIIl/IIIII/ III/I [III/1111111 iIIII/IIIIII I III/IIIIIIIIII IIIII/IIIIIIIIIII/I,

IN VEN TOR. HERBERT C GRA m JR Arron/var April 5, 1948- H. c. GRAVES, JR 2,439,084

INSULATED REINFORCED CIRCUIT BREAKER CONTACT BAR Filed Dec. 28, 1944 2 Sheets-Sheet 2 I N V EN TOR. HERBEP T 6: 624 via" JR. /z BY Ar-mmrsy Patented Apr. 6, 1948 BREAKER CONTACT BAR Herbert C. Graves, J r., West Chester, Pa., assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania I Application December 28, 1944, Serial No. 570,095 3 Claims. (Cl. 200166) My present invention relates to contact bars for circuit interrupter-s and more particularly to a novel reinforced insulated contact bar for carrying the movable contact arm of circuit breakers, switches and the like.

More specifically, my invention contemplates a novel contact bar and method of producing the same wherein said contact bar has a number of reinforcingv metal inserts, preferably of steel, where the inserts extend longitudinally through the bar and are spaced from each other by in-.

sulating plugs which prevent any accidental conduction of currentthrough the contact bar. Such contact bars may be of various length depending lem existed, no method for solution thereof has been obtained. My invention provides a novel method for manufacturing such insulated contact bars in long lengths which may be cut apart,

while nevertheless retaining the steel inserts with on the number of poles which the circuit breaker or switch is intended to control and may be designed to carry one or a plurality of movable contact arms.

My invention also contemplates a construction of such an insulated steel reinforced contact bar and method of making the same whereby said contact bars maybe made in relatively long lengths and cut off as desired to predetermined lengths while nevertheless maintaining the full insulation between metal inserts and the full insulation of the contact bar itself.

Essentially in the manufacture of my novel contact bar, the insulating plugs are threaded or forced into steel inserts in order to furnish a mandrel oi sufiicient length to fit a wrapping machine and to take advantage of the full operative width thereof. After the wrapping operation, the mandrels are processed and cut off to proper length, care being taken that the cuts fall in the center of the insulating plug. The wrapping is, of course, done with suitable insulating material such as uncured plastic products. After the processing and before the mandrels are cut apart to desired lengths, the cured plastic exterior becomes firmly bonded to the metallic insert and the material of the insulating plug, during the curing process. The metallic reinforcing insert, by reason of the knurling or scoring or other formation of the metallic insert, provides a suitable anchor for the plastic covering.

It has been customary previously to make these contact bars individually and insert the insulating plugs at a subsequent operation. This is a slow, tedious and unsatisfactory method since machine capacity is adequate for multiple use. Inasmuch as it was necessary to have a completely insulated bar yet to retain the steel insert for strength, it was necessary to devise satisfactory means for including the plugs in the original processing. However, although this probthe insulating plugs between them in order to increase the creepage distance between the metal inserts.

A primary object of my invention therefore is the formation of an insulated contact bar reinforced by metallic inserts separated by insulating plugs.

Another object of my invention is a novelprocess for manufacturing long lengths of insulated contact bars which may readily be cut apart into desired lengths and which may have steel inserts properly located and imbedded in. plastic.

These and many other objects of my invention will become apparent from the following description and drawings in which:

Figure 1 is a longitudinal view in section of my novel steel reinforced contact bar.

Figure 2 is a fragmentary view in perspective partially broken away showing a portion of the novel insulated contact bar of Figure 1.,

Figure 3 is an expanded view showing the relationship between the insulating plug and the metal reinforcing insert of the contact bar of Figure 1.

Figure 4 is a cross-sectional view showing an alternative shape for the metal reinforcing insert of the contact bar of Figure 1.

Figure 5 is a fragmentary view in perspective partially broken away showing an alternative shape for the exterior of my novel contact bar.

Figure 6 is a fragmentary view in perspective partially broken away showing another slight modification which the shape of the metal insert of my novel contact bar may take.

Figure 7 is an expanded view in perspective showing the ends of a pair of adjacent steel inserts of my novel contact bar and insulation plug having tapered ends which may be forced into drilled holes in the end of the steel insert. Figure 7 shows the preferred form which the steel insert and insulating plugs of my invention should take.

Figure 8 is a view in perspective showing my novel contact bar in use carrying contact arms in a circuit interrupter.

Figure 9 is a schematic view in perspective showing a step inthe process of manufacturing my novel contact bar.

Referring now to Figure 1, I have here shown in longitudinal section 'a simplified view of my aesaoee novel insulated contact bar which illustrates not only the construction thereof but suggests a method of manufacture therefor. The exterior II of my novel insulated contact bar I is of plastic material. The insulated contact bar It is rigidified and strengthened by a number of longitudinal metallic inserts H2, H2 separated by the insulating plugs I3, i 3. 1

Each end of each metallic insert i2 is provided with a threaded opening I5 to receive the threaded end iii of the insulating plugs I3. The main body of each insulating plug it has a diameter the same as that of the metal insert I2. Consequently when the threaded end I6 of the insulating plug I3 is screwed into the threaded opening I5 of the metallic insert i2, the outer surface of the metallic insert I2 and the insulating plug I3 are continuous.

As the metallic inserts I2 and the insulating plugs I3 are threaded together as shown in Figure 1, a continuous outer cylindrical surface is formed by the adjacent members l2, I3, 2, I3, i2 which are screwed together. The insulation material for the entire contact bar may then be readily wound about the entire length of the mandrel formed by the combination of the metallic inserts I2 and it until the desired thickness of insulation material is obtained. The entire contact bar may then be fused and shaped to form.

After it is thus formed, the bar may be cut to appropriate length by cutting across the center of any insulated plug it as indicated at of Figure 1. This will produce the result shown in Figure 2, which shows the end of a contact bar which has been completed and is ready for use.

Figure 2 emphasizes the fact that the principal circumference of the insulating plug l3 matches that of the metallic insert i2 to produce a continuous mandrel on which the insulation II may be wound and formed. In Figure 2 it will be seen that although the insulation material is originally circularly wound around the mandrel l2, it may be shaped to a rectangular form by the fusing processes (which are well known in the art). The resins in the plastic sheet material which is wound around the man-' drel (consisting of metallic inserts i2 and plugs I3) are suflicient when the plastic is cured and shaped to cause the plastic to adhere very closely to the material of the insulating plugs I3. The surface of the metallic inserts 82 are knurled, scored or otherwise shaped or indented to provide a suitable anchor for the plastic.

The relationship of adjacent metallic inserts l2 to the insulation plugs I3 between them is also more readily seen in the expanded view of Figure 3 which shows an insulating plug I3 about to be inserted by threading an end I8 thereof into the tapped hole I5 of one of the inserts I2. The other insert I2 may then be threaded over the other threaded extension I8 of the insulating pl g.

The steel inserts I2 and the insulating plugs I3 may have any suitable cross-sectional shape and the exterior of the insulated contact bar may also have any suitable shape as may be required for the particular apparatus in which the same is to be incorporated. Thus, as shown in Figure 4, the insulating plug H3 is shown with a hexagonal cross-section, while the insulation coating III on the steel insert and insulating plug 3 is of square cross-section.

As seen in Figure 5, the steel insert II2 is of hexagonal cross-section while the insulating plug it is of the shape previously described in con- ,nection with Figures 1 to 3. The exterior Bakelite coating 2H is. however, also of hexagonal cross-section. The shape of the forming apparatus in which the entire unit is fused predetermines the outside shape of the contact bar.

As shown in Figure 6, the steel insert 3l2 may be of square cross-section, while the exterior 3!! of insulation material may also be of square cross-section with the insulating plugs it having the same cylindrical shape as that shown in Figure 3.

The preferred construction for the metallic insert is the square cross-sectional form of the insert 3I2 of Figure 6. This provides an insert with greater strength and there is alsoless tendency for the insulating material to be torn away from a square steel insert than a round one. This tendency of the insulation to separate from the metallic insert is due'to the high torque to which the insulated contact bar may be subjected. However, as shown in Figure 6, where an insert plug I3 is used having the shape of the insert plug I3 of Figure 3, the square crosssection metallic inserts are spaced from each other by round plug sections. Where the plug ends I6 are to be threaded into tapped recesses at the ends of the metallic insert, then the main body of the plugs l3 must be round in order to avoid dificulties in alignment.

Since, however, the very best construction would include steel inserts of square cross-section connected together by plugs also of square cross section, this result is achieved by the construction shown in the expanded view of, Figure 7, which shows steel reinforcing inserts M2, M2 ofsquare cross-section, and an insulating reinforcing plug 3 also of square cross-section. The corners of the square metallic insert may be rounded to avoid dielectric stress which may otherwise occur at sharp corners. The insulating plug M3 is provided at each end with the tapered projections M6, M6 which may be forced into the cylindrical non-tapered drilled holes M5, M5 in each end of the metal insert 2.

Neither the projections 6 nor the drilled holes 6 are threaded. The projection M6 tapers from a diameter slightly less than the diameter of the drilled hole M5 to a diameter just slightly greater than the diameter of the drilled hole 585.

The material of the insulating plug H3 and its projections tilt is, however, while stiff and rigid, nevertheless suficiently compressible under suflicient force so that the tapered projection e I 6 may be forced into the drilled opening M5 so that the end surface of the insulating plug M3 from which the tapered projection 6 projects is in surface to surface relation with the end surface of the steel insert which has the recess or opening M5.

By avoiding the necessity for using threads, perfect alignment may be obtained between the surfaces of the body of the insulating plugs M3 and the surfaces of the metal inserts 4I2 so that a continuous supporting insert structure of square cross-section may be formed. This insert structure, when formed,'may then be coated with an insulating material in the same manner as that previously described in connection with Figures l to 6. This continuous square insert with square metal inserts of square metal plugs is, as has above been mentioned, preferred over the knurled round one because ofits greater strength, also for the reason that the insulation material will i not be readily torn away owing to the torque. similarly, a continuous square cross-section supporting structure for the interior of the insulated contact bar is preferred over a series of square metal inserts with round plugs, because it provides a continuous unit with continuous surfaces which may readily be covered with insulation, and which is almostsubstantially continuous and strong.

In Figure 8, I have shown the manner in which an insulated contact bar of the type shown in any one of Figures 1 to 7 may be used'in an ordinary circuit interrupter. The contact bar it has been cut oif from a longer length so that the surface of the insulating plug l3 at either end The contact arm 5! carries pivotally mounted thereon around the pivot 503 appropriate contact structures 504 to which appropriate connections may be made through the pigtail 505.

One of the contact arms 5M, preferably the center one, is connected to suitable operating mechanism by means of which that contact arm and hence the insulated contact bar It) and the other contact arms may be rotated in either direction to open or close the circuit.-

It is obvious that if a contact bar of a length necessary for only a one pole circuit breaker were needed, then the metal insert would have to be reduced in length to accommodate this smaller size circuit breaker and a new register, for cutting oif the bars, would be needed. It would be necessary to redesign the metal inserts for any variation in the size of the circuit breaker.

By means of the present invention, the entire operating width of a winding machine may be used to construct a long length of insulated contact bar which may then be cut up into appropriate lengths. Thus, as shown schematically in Figure 9, a mandrel structure 600 comprising metallic insert pieces l2, l2 and insulating plugs I3, I 3 may be screwed together into a long length substantially equal to the width or capacity of the winding machine so that the insert structure will have the form of the insert structure shown in Figure 1. The entire mandrel 600 thus formed may be mounted between the chuck 6M and tailstock 602 of the winding machine, and the plastic treated material 605 may be wound thereon.

When the winding of the insulation is completed to the required thickness, the insulating contact bar thus formed may be cured by molding to the desired shape so that the plastic windings will become homogeneous with each other and be secured to the insulation plugs and to the metallic inserts and so that an appropriate shape may be formed. Thereafter, the completed long length of insulated contact bar may be cut apart, as previously described in connection with Figure 1, by cutting through the center of the insulating plugs l3.

Further, in the assembly shown in Figure 8,

the steel bar should not extend to the end of the phenolic or other plastic coating, since it would be too close to the contact arm 50!; thus a continuous steel bar cannot be raised and cut off because then the steelwould extend to the end of the bar.

Previously. it has been customary to use a circular steel-bar and to insert an insulating plug that would extend some distance in from the end of the bar. Efforts to glue such a plug inposition after the entire bar had been made were not satisfactory. Also, various insulating compounds were used to fill up the end of the phenolic bar as additional insulation. This material often softened under the temperatures to which the circuit breaker was subjected and thus ran out and interfered with the operation of the breaker. Further, it did not form a complete insulation. Since the steel insert had to extend fairly close to the ends of the bar so as to be included in the clamping action of the two outside pole parts, the recess [for the insulating plug was relatively shallow. Also, after a steel piece had been inserted into the phenolic tube, it was difiicult thereafter to insert a plug which would be tight and sealed in to prevent a breakdownon dielectric tests. I

My novel process and the construction produced thereby avoids all of these difilculties, The plug can be short because it is tightly sealed in the wrapping. Further, the insulating plugs may be uncured when wrapped and cured during the curing process of the wrapping.

Further. it should be understood that in present molding thickness, it is practically impossible to properly locate inserts completely embedded in a plastic for reinforcing purposes without having-them float during the molding operation. My novel process overcomes this diihculty, and the reinforcing insert of my invention may be located and maintained in its exact location during the molding operation without having some portion of the metal extend outside the molding after the operation is completed.

This method further permits the construction of insulated pull rods for solenoids. In the case of solenoids, the steel parts would project beyond the tubing at both ends for a pull operation. The spacing plugs separate and insulate from each other the projecting pieces of steel. These projecting pieces of steel may be threaded. In

such case, the steel rods may be reduced in diameter at the end, threaded and screwed into the plug. Such pull rods for solenoids may, of course, be made round or square or of any suitable cross section.

It will be obvious that in all of the constructions above shown, the plugs of insulating material maybe provided with openings; and the metal members may have the extensions for insertion in the openings of the plugs.

By means of my novel construction and methad, I have devised a novel and simplified insulating contact bar having a plurality of spaced metailic inserts separated by insulating plugs whereby the insulated contact bar is completely reinforced while no continuous current path through the insulated contact bar is provided. My invention is adapted to the making of long or continuous lengths of such insulated contact bars which may thereafter be readily cut apart to desired separate lengths, while retaining allof the initial characteristics.

In the foregoing, I have described my inven tion only in connection with preferred embodiments thereof. Many modifications and variatlons will now be obvious to those skilled in the art; accordingly, I prefer to be bound not by the specific disclosures herein but only by the appended claims.

I'claim:

1. The method or manufacturing contact bars which comprises the screwing of threaded insulating plugs into steel inserts to form a mandrel of predetermined length to fit a wrapping machine, wrapping and molding-insulation material on the mandrel and cutting the mandrel with the insulation wrapping into predetermined lengths,

- the cuts falling in the center of the insulating plugs and bonding the plugs to the steel inserts.

2. The method or making insulated contact bars with reinforcing metal inserts which comprises securing the reinforcing metal inserts to the insulating plugs using the assembly of metal reinforcements and insulating plugs as a man drel for applying longitudinal insulation and molding the insulation thereto.

3. A contact bar for a circuit interrupter consisting of an elongated metallic reinforcing member attached to an aligned insulating member at each end, said reinforcing member having a socket at each end internally threaded,

each or said insulating members having threaded extensions engaging the associated internal threads of said reinforcing members and having I enclose the reinforcing member.

mam c. GRAVES, .111.

REFERENCES cr'rm The following references are of record in the file oi. this patent:

UNITED STATES PATENTS Number Name Date 798,160 Carichofl A118. 29, 1905 1,510,119 Wahlberg' Sept. 30, 1924 1,603,231 Bayne Sept. 4, 1928 2,197,465 Brunetti Apr. 16, 1940 2,203,297 Cvranberg June 4, 1940 2,250,967 Riddle July 29, 1941 2,261,633 Spooner Nov. 4, 1941 2,285,577 Gary June 9, 1942 2,318,080 maelstrom May 4, 1943 Glogau May 18, 1943

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