US1935512A - Electric switch - Google Patents

Description

H. B. MASSEY ELECTRIC SWITCH Nov. 14, 1933.

Filed July 17, 1931 2 Sheets-Sheet l H. B. MASSEY ELECTRIC SWITCH Nov. 14, 1933.

Filed July 17, 1931 2 Sheets-Sheet 2 Patented Nov. 14, 1933 PATENT OFFICE ELECTRIC SWITCH Hemsley B. Massey, Greensburg, Pa., assignor to Railway and Industrial Engineering Company, Greensburg, Pa., a corporation of Pennsylvania I Application July 17, 1931. Serial No. 551,456 '13 Claims. (01. 200-166) This invention relates to switches and particuv larly to switches of the high contact pressure type.

One of the cbjectsof the invention is to provide a switch of the high contact pressure type 5 which is simple and rugged in construction and emcient in operation. Another object of the invention is to provide a switch in which the contacts have a self-cleaning action, thus removing oxides of the'metal, old lubricant and foreign l matter which tend to reduce the electrical efficiency of a switch after long periods of service.

Another object of the invention is to provide a switch of the high contact pressure type, wherein the contact areas are formed integrally with 1 the switch members.

Other objects of the invention will appear from the following description taken in connection with the appended drawings, wherein:

Figs. 1 and 2 are side elevational and plan views respectively showing one formof the invention,

Figs. 3and 4 are views showing sections taken along lines 3-3 and 4-4 respectively of Fig. 1.

Fig. 5 is a side elevational view showing a modifled form of the switch,

Figs. 6 and 7 are views showing sections taken along lines 66 and '1--7 of Fig. 5, and Fig. 8 is a fragmentary view showing a detail. The invention is herein illustrated as applied to the two common types of knife switches, that is, the tongue type and clip type. In. the "tongue type of switch, the stationary contact member takes the form of a single upstanding member which is engaged by a pair of parallel blades when the switch is in closed position.

In the "clip type of switch, the stationary contact member comprises a pair of jaws arranged to engage a single blade.

In Figs. 1 to 4. is shown a switch of the tongue type, constructed according to the invention. A base 1 of-insulating material supports a pivot terminal 2 to which is pivoted a pair of spaced parallel blades 3 connected at their free ends for simultaneous rotation about their common pivot. A contact terminal 4 is mounted on the base 1 in a position in the path of movement of the blades 3, whereby it is engaged by the blades 3 when they are rotated into the closed position of the switch, as shown in Fig. 1.

Referring to Fig. 4, registering perforations 5, 6 are provided in the pivot terminal 2 and in the adjacent portions of the blades 3, through which perforations a hollow rivet '7 extends. The

ends of the rivet '7 are spun over against spring washers-8 whereby the blades 3 are forced tightly but resiliently against the pivot terminal 2. Formed on each face of the pivot terminal 3 and concentric with the perforation 5 is an annular ridge 9 having an arcuate contour. The annular ridges 9 provide an area of contact between the pivot terminal 2 and the blades 3 of the order of line contact. As shown in detail in Fig. 3, the free ends of the blades 3 are connected by a hollow rivet 10 which extends through registering perforations 11, in the blades 3 and is spun over against spring washers 12 to resiliently limit the separation of the blades 3. The contact terminal 1 is pro-- vided with a slot 13 to accommodate the rivet 10 when the. switch is in closed position.

Formed on each face of the contact terminal 1 adjacent the slot 13, is a pair of raised contact surfaces or buttons 14 which, when the switch is in closed position, bear against inwardly projecting alined bosses 15 formed on the blades 8. The contact buttons 14 have a substantially spherical contour whereby the area of contact between each button 14 and its corresponding boss 15 is so small that it may be considered to be of theorder of point contact. V

The desired pressure on the contact buttons 14 is obtained by spinning over the rivet 10 against the spring washers 12 until the blades 3 are drawn togetherto leave a space between the inner surfaces of the blades 3 slightly smaller than the thickness of the terminal fat the contact buttons 14. When the blades 3 are in closed position and engage the contact terminal 1, the blades 3 are spread against the force of the spring washers 12 by the contact terminal 1 and press against the contact terminal 1 with the proper pressure. The proper pressure at the pivot is obtained by spinning over the rivet against the spring washers 8 untila predetermined frictional resistance is offered to the rotation of the blades 3.

Although the total pressure may be, for example, from 25 to 75 pounds, the unit pressure is very high since the area of contact is of the order of one one-hundredths of a square inch. It has been'found that where such a high contact pressure is obtained, the switch will satisfactorily carry currents of the order of a thousand amperes, the current density being of the'order of 25,090 amperes per square inch. The contact areas at the pivot being of the same order of size as the principal contact areas'and the pressure thereon being substantially the same as that on the principal contact areas, hence the current carrying capacity is substantially the same as that of the'principal contact areas. no

A latch pin 16 is fitted snugly in the hollow rivet 10 and extends beyond the ends thereof. Pivoted in the contact terminal 1 is a pair of latch hooks 17 positioned to engage the projecting ends of the pin 16 when the switch is in closed position. 'An operating member 18 pivoted to the ends of the blades 3, has a pull ring 19 and a pair of bell-crank levers 20, one arm 21 of each lever bearing against an inclined surface 22 on its respective latch hook 17, the other lever arm 23 hearing on a shoulder 24 formed integral with the contact terminal 1. Springs 25 are provided for forcing the latch hooks 17 into engagement .with the latch pin 16 and set screws 26 are threaded through the shoulder 24 for adjusting the normal position of the latch hooks 17.

The operation of the latch should be readily apparent. The switch being in the position shown in Fig. 1, a clockwise movement of the pull ring 19 will cause the first lever arms 21 of the bell-crank 20 to force the latch hooks -17 out of engagement with the latch pin 16. Simultaneously the second lever arms 23 bear against the shoulder 24 to force the ends of the blades 3 upwardly out of engagement with the contact terminal 1.

The annular ridge 9 on the pivot terminal 2 and the contact buttons 14 on the contact terminal 1 preferably are formed by casting these portions of the terminals of slightly greater thickness than the adjacent portions of the terminal and then pressing the contact areas in dies which operation imparts to the areas the proper thickness and shape and also serves to harden the material. Other methods of forming the areas may be practised, such as pressing or spinning the material of the blade to raise a portion to form the contact areas (as described in the copending application of Arthur T. Musgrave, Ser. No; 444,579, filed April 15, 1930) or the areas may be die cast when the entire terminals are formed in this manner.

Perforations 27 are provided in the terminals for the reception of members (not shown) for connecting conductors (not shown) to the terminals; Surrounding each perforation is an annular boss 28, formed integrally with the terminal. The boss 28 is formed by casting oversize, the'portion of the terminal corresponding to the boss and then pressing the material to the desired shape and size to form the boss. After the boss 28 is formed, the perforation 27 is drilled through the boss. This method of forming the boss provides a-hard smooth surface for contact with the conductor whereby a good electrical connection readily may be made between the conductor and the terminal.

The bosses 15 on the blades 3 preferably are formed by pressing out of the principal plane of the blade a portion of the blade having the desired size and shape. This method is generally practised for the reason that the blades are formed of rolled material. If the blades are formed by casting, the bosses may be formed in any of the methods set out for the formation ofthe contact buttons.

The invention as applied to a switch of the clip type is shown in Figs. 3 to 8. A base 30 of insulating material supports a pivot terminal 31 having a substantially U-shaped upstanding portion 32 in which is pivoted a single blade 33. A contact terminal or clip 34 is mounted on the base 30 in a position in the path of rotation of the blade 33 whereby it is adapted to engage the blade 33 when the latter is moved into the position shown in Fig. 5.

Referring to Fig. 7, registering perforations 35, 36 are provided in the blade 33 and the two arms 3 of the pivot terminal 32 through which perforations 35, 36 a hollow rivet 37 extends. The ends of the rivet 37 are spun over against spring washers 38 to press the arms of the terminal 32 against the blade 33. Two oppositely directed concentric annular ridges 39, 40 of different diameters are formed on the blade 33 surrounding the perforation 35 to thereby provide two concentric contact areas. As will be obvious, the areas of contact between the blade and the terminal arm are of the order of lines.

Formed on the free end of the blade 33 is a pair of alined contact buttons 41 which are arranged to cooperate with a pair of inwardly directed bosses 42 formed on the arms of the clip 34 to provide the desired restricted area of contact between the blade 33 and the terminal 34.

The contact rings 39, 40 on the blade 33 and the contact bosses 42 on the clip 34 are formed by pressing operations. The contact buttons 41 on the blade 33 are formed by pressing or spinning as above set out.

The desired pressure at the pivot contact surfaces is obtained in a manner similar to that employed for the first-described form of the invention. The pressure atthe principal contacts is determined by the spacing of the clip arms 34. It is possible to provide an arrangement for spacing the arms similar to that employed above in spacing the two blades, of the tongue switch but s uch an arrangement is generally not deemed necessary.

Claims to the described methods of forming a swiitch and switch elements are presented in my copending application, Ser. No. 580,140, filed Dec. 1.0, 1931. The copending application of Carl G. Koppitz and Hemsley B. Massey, Ser. No. 532,293, filed April 23, 1931, discloses and claims high contact pressure switches of the pivoted blade itype in which the blade and cooperating membe rs are each provided with raised contact surface s, and my copending application Ser. No. 478,181,. filed Aug. 27, 1930, discloses and claims a knife switch in which the contact area of the blade and its pivotal support annular contact rib.

I claii r1:

is restricted by an 1. In :a high contact pressure switch, a tongue,

a bifurcateblade element, means on said blade element gyieldingly urging the branches of said bifurcate: blade element towards each other, means mlounting said blade element for rotation into engagement with said tongue, and cooperating, raised contact means on said blade element and said tongue for providing contact areas beg1 ie being provided with raised contact sur- .1

faces; disposed to restrict the contact area of said blades and tongue when the switch is closed.

3. In a high contact pressure switch, a pair of s ipaced blades, means mounting said blades for rotation about an axis, means connecting said 'blades for simultaneous movement, a tongue disposed in the path of said blades for engagement therewith, said tongue and said blades being provided with raised contact surfaces disposed to restrict the contact area of said blades and tongue when the switch is closed, and spring means on said blades for resiliently pressing the blades towards each other.

4. A switch comprising a hinge member, a blade member pivoted thereon; one of said members being bifurcated to provide portions at the opposite faces of the other member, and raised annular portions on the faces of said hinge member restricting the contact area of said members.

5. The invention as set forth in claim 4, wherein said raised portions have rounded surfaces engaging the said blade member, thus restricting the contact area to the order of line contacts.

6. A switch comprising a hinge member, a blade member pivoted thereon; one of said members being bifurcated to provide portions at the opposite faces of the other member, and raised annular portions on the faces of and integral with one of said members restricting the contact area of said members. 7

7. The invention as set forth in claim 6, wherein said raised annular portions are constituted by material pressed out of the planes of the opposite faces of the said member.

8. A contact member for an electric switch of the high contact pressure type, said contact member comprising. a flattened member having substantially parallel faces, and an annular ring integral with said member and projecting beyond one face thereof.

9. A'contact member for an electric switch of the high contact pressure type, comprising a flattened member having substantially parallel faces and two concentric annular ridges on opposite faces respectively.

10. A contact member for an electric switch of the high contact pressure type, comprising a flattened member having substantially parallel faces, an annular portion offset from the principal plane of the member toward one face and a second annular portion offset toward the plane of the second face and concentric with said first annular portion.

11. A high contact pressure switch comprising a pair of fiat contact members, means mounting said members in substantially parallel planes for relative movement into mutual engagement, said members being provided on their engaging surfaces, with raised contact areas arranged, when said members are in engagement, to lie in a line perpendicular to the planes of said members.

12. In a knife switch, a pair of spaced blade members, a hinge contact, a tongue contact, means pivotally mounting said blade members on said hinge member, spring means pressing said blades towards each other, and cooperating raised contact surfaces on said blade members and said tongue contact to restrict the contact area and to increase the unit pressure between said blade members and tongue contact when the switch is closed.

13. The invention as set forth in claim 12, in combination with means restricting the contact area of said blade members and hinge contact.

HEMSLEY B. MASSEY.

DISCLAIMER 1,935,512.Hemgl'y B. Massey, Greensburg Pa ELECTRIC S I P tent dated November 14 1933. Disclaimenfil d 20 193-7 {f i Railway (fa Industrial Engineering Oo y f y 1 y the assigne Hereby enters thisdisclaimer of claim 11 of said [Ofliaial Gazette Jane 15, 1937.]

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