US2732468A

US2732468A - Electric switch

Info

Publication number: US2732468A
Authority: US
Publication date: 1956-01-24
Anticipated expiration: 1973-01-24

Description

United States Patent ELECTRIC SWITCH Thomas E. Curtis, Hampton, Ga., and George N. Lemmon, Birmingham, Ala., assignors to Southern States Equipment Corporation, a corporation of Georgia Application September 4, 1952, Serial No. 307,894

13 Claims. (Cl. 200-170) This invention relates to electric switches and particularly to a stationary contact and blade assembly for high capacity switches and has for an object the provision of a device of the character designated in which the electric current conducted through the switch, whether due to normal loads or occasional overloads, shall be utilized to increase the pressure between the contact portions of the blade and the stationary contacts.

A further object of our invention is the provision of an electric switch which shall include rigid stationary contacts and a rigid blade, together with resilient contact members secured to the blade and cooperating with the jaw contacts.

A still further object of our invention is the provision of an electric switch embodying rigid jaw contacts and a rigid blade together with resilient contact members cooperating between theblade and the contacts and so disposed that the electric current flowing through the switch creates electro-magnetic forces which act to press the resilient contact members into tighter engagement with the jaw contacts.

Another object of our invention is the provision of an electric switch in which there shall be heavy pressure between the blade and its stationary contacts, which pressures shall be increased by reason of the electromagnetic forces developed when overloads are imposed on the switch.

A still further object of our invention is to provide an electric-switch which shall be simple and rugged of construction, economical of manufacture, and reliable in operation.

As is well known in the art, current flowing in a conductor produces electro-magnetic stresses surrounding the conductor. Where the electric current is flowing through a continuous straight conductor there are an infinite number of curved lines of force which encircle the conductor as long as current flows therethrough, These forces are greatest close to the conductor, and the greater the electric current, the more intense are the electro-magnetic forces. Where there is a sharp angle in the conductor the forces are compressed by the angle into a much smaller space. The mechanical effect is a violent tendency to straighten the conductor or, if this can not be done, to break the conductor apart at the angle. The stresses are most severe close to the angle.

Two parallel conductors, both transmitting currents of electricity, are either mutually attractive or repellent, depending on the relative directions of their currents. If the currents are flowing in the same direction in both conductors, the lines of force tend to surround both conductors and contract, thus causing the conductors to attract each other. If, ho'wever, the currents are flowing in opposite directions, the lines of force lying between the conductors-have the same direction, 'and therefore the conductors repel each other. The present invention relates to apparatus for counteracting the harmful etfects of such forces especially those produced by overloads and has for a prime object to provide a switch in which such 2,732,468 latented Jan. 24, 1956 forces are utilized to obtain better electrical contact between the switch members.

A switch embodying features of our invention is illustrated in the accompanying drawings, forming a part of this application, in which:

Fig. l is an elevational view of the switch;

Fig. 2 is a detail plan view of the jaw contact end of the switch;

Fig. 3 is a detail elevation partially in section taken along the line III-III of Fig. 2;

Fig. 4 is a sectional plan of the hinge contact end of the switch taken along the line IVIV of Fig. '1; and,

Fig. 5 is a diagrammatic plan view illustrating the utilization of the electro-rnagnetic forces developed in the switch to increase the pressure between its contacting elements.

Referring now to the drawings for a better understanding of our invention, we show two spaced insulators 10 and 11, which, as is well understood, would be mounted upon a base, not shown. Mounted on the insulator 10 is a hinge contact base member 12 which is secured to the insulator by means of bolts 13 and which carries the stationary hinge contact 14. Forming apart of the base 12 is a pad 16 to which the incoming line 17 is connected.

Mounted on the insulator 11 is a jaw contact base 18 which is secured to the insulator by means of bolts 19. The stationary jaw contact 21 is mounted on the base 18. Forming a part of the base 18 is a pad 22 to which the outgoing line 23 is connected. Hingedly connected to the hinge contact 14, by means of a hinge bolt 24'is a switch blade 26, which, as will be seen from Fig. 1, spans the two

stationary contacts

14 and 21 with its ends extending beyond both of said contacts. The switch may be opened and closed by means of the usual ring 25 provided on the blade 26.

As may be seen from Fig. 4, the stationary hinge contact 14 embodies two

rigid jaw members

27 and 28 which are spaced apart a considerable distance greater than the thickness of the switch blade 26. It will also be seen that the hinge bolt 24 passes through an opening 29 in the switch blade 26 which is larger in diameter than the hinge bolt 24 whereby there is no electrical contact between the hinge bolt and the blade.

The stationary jaw contact 21 likewise comprises two

rigid jaw members

31 and 32 which are spaced apart a considerable distance greater than the thickness of the' blade 26 so as to afford a substantial space between the blade proper and the said jaw members. The

jaw members

31 and 32 are bowed outwardly at their lower ends, as shown at 31a and 32a so that current flowing from the blade 26 into the

jaw members

31 and 32 does not at this point in its travel make an abrupt downward turn but follows a path that is partially horizontal. It is also contemplated that the

jaw members

27 and 28 of the hinge. contact 14 may be similarly outwardly bowed at their lower ends.

of the jaw members, shown at 33and 34 on the

jaw contact members

31 and 32 and at 36 and 37 on the jaw two separate members as shown in Fig. 5, maybe used instead of the U-shaped

member

39, 41; The hinge bolt 24 passes through openings 42 and 43 in the contact the

contact elements

39 and 41 are bowed outwardly to

members

39 and 41 with a bearing fit which holds the Another feature which is common to boththe jaw and the hinge contacts is a contact rib on eachthe hinge bolt.. Preferably,

provide ridges 44 and 46 which bear against the ridges 36 V The

contact elements

39 and 41 are pres'tressed'- to assume a normal position outside ofthat shown in Fig. 4 where they are in contact with the jaw contactmembers whereby to provide the required, initialcontact press-urea To aid in assemblying' the switch, detents 47 and 48 are providedon thesides' of the blade 26 to limitthe outward movement of the contact elements 39 and 41- when otherwise not restrained;

Secured to the jaw contact end of the switch blade 25 by means of a suitable fastening" such as rivet's'49 is" a resilient contact member having ontwardy flaring arr'ns SI and 52 which extend trackwardsfrcm the end of the blade 26 to engage with the

contact ribs

33 and 34. As shown in Fig. 2, the space between the

jaw members

31 and 32, the thickness of the blade 26, and the thicknes'sof the contact elements 51 and 52, are so proportioned as" to provide a spacebetween the contactelements 51 and 52v and the blade 26', opposite the

ribs

33 and 34 where they engage the jaw members. The contact member is prestressed so that normally, the" members 51 and 52'would' assume a position corresponding to the-dotted line position of 51. This affords the requisite pressure between the contact element and the stationary contacts. In order that'- the elements 51 and 52 will not move outwardly when the switch is opened and they are disengaged from their associated jaw'contacts, so that the switch will not again close, we provide

detents

53 and 54 on the sides of the blade 26' which engage the" ends-of the contact elements 51 and 52 when the switch is open to limit the outward movement of the elements 51- and 52. Stop

members

56 and 57 are provided on the jaws 31 and 32' to limit the closing movement of the blade 26 and prevent overtravel, If desired these-stop members may be continuous, instead of separate, as shownb'y' dotted lines 56.

From the foregoing it will be seen that in our improyed switch, the only electrical contacts between the blade 26 and thesta'ti'onary contact members is through the

flexible contact elements

39, 41,'and 51', 52. Also, it will be seen by reference to Fig. 3, that the current flowing from the blade to the jaws or from the jaws to the blade flows in a curved path without any abrupt turns between vertical and horizontal travel so that there is a lessened building up of electromagnetic forces due to the change of direction. p

In-Fi-g. we show diagrammatically the electromagnetic forces which are developedinour improved switch due to'the how of electric current therethro'ugh. In this figure of the drawing, which represents the flow of current at the jaw contact end at a switch, it will be seenthat the current in the blade 26:: flows to the end of the blade andthen backwardly'through'the resilient contact elements 51d and 52a to the jaws 31 a and 32a, the current through the elements 51a and SZa'flbwing in a direction opposite to that through the blade 26th This brings about the development of electromagnetic forces indicated by the large arrows 60 and 61-which tendto'spread theelements SIa'and 52kt apart and awvayrrent the blade 26a and into tighterengagement with the jaws 31a and 3211. Upon overload, these e-lectro-magnetic forces are increased, and the pressure between the contact elements is accordingly proportionately increased. If we assume the diagram in Fig; 5 as representing the hinge end of the switch, the current flow would be opposite to that shown, that is, the current now would be from the jaw contact members 31a and 32:2 thencethrough the resilient contact elements 5-1a' and 52a to the blade/26d and backwards along'the blade; The" electi'ii-r'nagnetic' force's' 'develope'cl by" this new at cur rent would be the same as that illustrated by the heavy arrows 60 and 61.

Fromthe foregoing-it will be apparent that we have devisedan electric switch'which is'simple of design, rugged and economical of construction, reliable in operation, and one in which the electromagnetic forces developed as a result of the flow of excessive current therethrough is utilized to increase the contact pressures in the switch.

While we have shown our invention in but one form, it will be obvious to those skilled in the art that his not so limited, but is susceptible'of various changes and modifications without departing from-thespir-it thereof, and we desire, therefore-,that only such limitations shall be placedthe'reupon as are specifically set forth in the appended claims.

What we claim is: W

1. In an electric switch, a pivotally mounted switch blade movable into and out of engagment with a pair of stationary jaw contacts positioned inwardly with respect to the end of the blade, two resilient contact members secured to the swing end of the blade and extending backwards adjacent to but spaced from the blade to engage, respectively, with the two jaw contact members only away from the end of the blade when the switch is in closed position,whereby'all thecurrent flowingthrough the switch travelsin' one directionthrou'g'hthe blade andin'theopp o site direction through the two adjacent resilient contact members, to the" stationary jaw contact member's.-

ln an electric switch,- a switch blade movable into and out of contact with stationary contact member, a resilient contact member secured to the end of the blade" and extending; backwards adjacent to but spaced from] the blade to make engagement with the saidstationary .blade extending beyond the pivotal mounting, a pair' of resilient contact member's secured to the end of the blade and extending back to the pivotal mountingadjac'ent' to but spaced from the blade, the blade itself being out of direct electrical contact with said pivotal mounting, whereby all the current flowing between the blade and the hinge jaw travels in one direction through theblarle and travels in the opposite direction through thesaid adjacent resilienf Contact members.

4. In an: electric s'rwitch, two bifurcated stationary: in sulated contacts, and a switch blade movable toclose the circuit there-between; the blade comprising a main member with the ends extending beyond the said stationary' contacts, and: are pairs of resilient cont-act members, one pair secured to eachend of the blade and with their r'ee end portions extending backwards adjacent to but spaced from the said main blade member andinto con tact, respectively, with the said stationary contacts,

whereby all the current flowing between the s'aid'main' member and each of the said stationary members travels in one direction through the main member and in the opposite direction" through the adjacent resilient contact members. V

5. In an electric switch, two Bifurcated rigid stationary contacts, aswitch blade spanning and extending beyond both of said contacts and'in laterallyspaced relanon therewith and a U-shaped resilient contact member fitted about each end ofthe blade, each with its free ends extending backward along the blade and in spaced rela tion thereto and in electrical contact with its adjacent stationary contact.

6. In an eiectr ic switch ave biiurcated'rigid station ar gt sea-taste, a s'witchblade" mangand extending lac-- yond both" at said 'c'ontacts andin laterally speedin sea uiereeini and a o-shaped prestre'ss'ed' (inwardly pressing resilient cbhtic t member fitted about each end of the blade,- each' with its free ends in electrical contact in a reduced area only with its associated rigid contact and in spaced relation with the blade.

7. In an electric switch a jaw contact and blade assembly comprising a prestressed leaf spring secured to one end of the blade and extending back alongside the blade in spaced relation thereto, a raised contact rib on said spring and a jaw member having a corresponding contact rib in position to engage the rib on the spring when the switch is closed.

8. In an electric switch, a stationary contact and blade assembly wherein the blade extends beyond the stationmy contact, comprising rigid bifurcated stationary contact members spaced apart a distance greater than the thickness of the blade, and two resilient prestressed leaf spring contact members secured to the end of the blade with their free ends extending backward alongside the blade in spaced relation thereto and in electrical contact with the stationary contact members only at locations away from the end of the blade.

9. An electric switch as defined in claim 8 in which a hinge bolt passes through the stationary contact members, both free ends of the resilient contact member and through the blade out of electrical contact with the blade.

10. An electric switch as defined in claim 8 in which contact ribs are provided on the stationary contact members and coacting contact ribs on the resilient contact member.

11. An electric switch as defined in claim 8 in which the bifurcated stationary members are spaced much further apart at their portions which are just below the leaf spring contact members than is the spacing at their places of contact with said spring contact members.

12. In an electric switch, rigid stationary contact members, a rigid blade, and resilient contact members se cured to the blade and cooperating with the stationary contact members, constructed and arranged for all the current to flow through the blade and through the resilient contact members in parallel paths in opposite directions.

13. In an electric switch, rigid stationary contact members, a rigid blade, and resilient contact members secured to the sides of the blade and with their free ends extending alongside the blade in spaced relation thereto, said contact members being so disposed that all the current flows therethrough in a direction opposite to that flowing in the blade.

References Cited in the file of this patent UNITED STATES PATENTS 1,828,281 Crabbs Oct. 20, 1931 2,695,350 Schultz Nov. 23, 1954 2,707,220 Hollander Apr. 26, 1955 FOREIGN PATENTS 17,479 Great Britain Nov. 30, 1888 560,368 Germany Oct. 1, 1932