US2526062A

US2526062A - Rheostat switch

Info

Publication number: US2526062A
Application number: US45703A
Authority: US
Inventors: Earl C Booth
Original assignee: Arvin Industries Inc
Current assignee: Meritor Inc
Priority date: 1948-08-23
Filing date: 1948-08-23
Publication date: 1950-10-17
Anticipated expiration: 1967-10-17

Description

Patented Oct. 17, 1950 EHEOSTAT SWITCH Earl C. Booth, Columbus, Ind., assignor to Arvin Industries, Inc., a corporation of Indiana Application August 23, 1948, Serial No. 45,703

3 Claims.

This invention relates tc a combined switch and rheostat of the type suitable for controlling the operation and speed of small electric motors. It is the object of the invention to produce a switch which can be simply and economically manufactured and which will be compact and adaptable for installations where a small amount of space is available.

In carrying out the invention, the body of the switch is formed as a sheet-metal stamping having a base, opposed side walls, and an end wall. A plate of insulating material about which a resistance element is wrapped overlies the edges of the side walls and is secured thereto. Such plate also bears a stationary switch contact to which a terminal and one end of the resistance element are connected. The body of the switch constitutes the other terminal, and its end wall is provided with an exteriorly threaded sleeve serving both as a mounting means for the switch and as a guide for a longitudinally slidable operating rod having secured to its end a U-shaped member of resilient material one lef.r of which bears against the body-base and the other leg of which is positioned to engage the stationary contact and the successive turns of the resistance element as the rod is moved longitudinally of itself.

In the accompanying drawing, which illustrates the invention, Fig. 1 is an elevation of the switch; Fig. 2 is a section on the line 2-2 of Fig. 1'; Fig. 3 is a section on the line 3-3 of Fig. 2; and Fig. 4 is a section on the line 4 4 of Fig. l.

The switch shown in the drawing comprises a body formed as a sheet-metal stamping to have a base I Il, side walls II, and an end wall I2. The end wall is provided with an opening which receives an end portion of reduced diameter on an exteriorly threaded sleeve I3, the reduced-diameter end portion of the sleeve I3 being riveted over as indicated at I4 to secure the sleeve rigidly to the end wall I2. Nuts I5 on the sleeve complete a means for mounting the switch.

Overlying the edges of the side walls Il is a rectangular plate I'I of insulating material having in its opposite edges a series of notches which receive and locate successive turns of an electrical resistance wire I8. One end of the resistance wire I8 is formed into an eye I9 which limits the extent to which the wire can be drawn through a hole located in the plate I'I between the side walls II of the body. From such hole, the wire is wound about the body for several turns and is anchored at its opposite end beneath the outer head of a rivet 20, which also serves to secure to the plate Il a terminal 2l adapted for connection to an electrical conductor 22. Desirably, the notches in the edges of the plate I'I are so located and the wire so disposed in them that those stretches of wire on the inner face of the plate I1 will extend in a direction normal to the edges of such plate.

The plate II is desirably located on the switch body by having in its side edges notches which receive fingers 24 on the side walls II of the switch body. After the plate is in place on the switch body, the fingers 24 are bent over the plate as indicated in Figs. 1 and 4 to hold the plate securely in place. Over the region occupied by the inner stretches of the resistance wire I8, the side walls II of the switch body are notched, as shown at 25 to prevent electrical contact between the resistance wire and the switch-body. Additional notches 26 are desirably provided in the side wal-ls I I adjacent the end wall I2. The

notches

25 and 26 and the open end of the switch-body opposite the end wall I2 permit free access of air to the interior of the switch-body and hence are of value in providing for cooling of the resistance wire I8 when the switch is mounted in close quarters.

The switch is operated by a rod 30 longitudinally slidable in the sleeve I3 and provided at its outer end with an operating knob 3|. To the inner end of the rod 30 there is secured the intermediate leg of a U-shaped strip of resilient material 32, which serves as a means for electrically connecting the switch-body with the rivet 20 or with any of the turns of the resistance wire I8. For this purpose, the outer leg of the strip 32 is provided with an outwardly offset portion or contact 33 which, by movement ofthe rod 3U, can be shifted from a position beyond the rivet 20 into engagement successively with the inner head of such rivet and with the Several turns of the resistance wire I8.

Desirably, the contact 33 is so dimensioned that it can enter for a short distance into spaces between adjacent turns of the resistancewire I8 in order that it will act as a detent releasably holding the rod 30 in any of a series of definite longitudinal positions. To locate the contact 33 in engagement with the inner head of the rivet 20 and also to locate it in the off position beyond such rivet-head, the inner leg of the strip 32 is provided with offsets 35 releasably engageable with depressions 36 formed in the base II) of the switch-body.

The terminal 2l is shown in the drawing as of Lshape, but it may have other forms. It includes a portion which lies against the outer face of the plate i7 and is provided with an inwardly bent nger 3S adapted to be received in an opening 39 in the plate l to prevent the terminal from rotating about the axis of the rivet 2Q. Conveniently, the opening 39 is formed by a punching operation which is not carried to completion, with the result that the slug EB is left in the openinff 39 and projects inwardly of the switch-body to receive and support the mov-v able contact 33 when the switch is in the ofi position and to prevent such contact from engaging the finger 3S.

When the switch is used in an automobile, as for the purpose of controlling the operation and speed of an electric motor associated with an automobile heater', it is conveniently mounted in a ange #i9 such as is commonly provided along the lower edge of a metal instrument panel To mount the switch, the nange "i5 is provided with an opening large enough to roccive the sleeve I3, the outer nut l5 is removed from the sleeve, the sleeve is inserted through the opening from above, and the lower nut is replaced and tightened to clamp the switch firmly in position. A s the switch-body is grounded through engagement of the sleeve i3 with the grounded instrument panel i, he switch controls the connection of the conductor to ground either directly or through one or more turns of the resistance wire I3. The two legs of the strip 32 bear oopositely and withsubstantially equal force inst the body-baie El? and the elements carried by the plate I7 with the result that no lateral forces of any appreciable magnitude are applied to the inner end or" the rod which is therefore free to slide without binding in the sleeve i3.

I claim as my invention:

1. A combined switch and rheostat, comprising a unitary metal body having a base, opposed side walls, and an end wall, a plate of insulating material secured to said side walls in spaced relation to the base, a fixed contact secured to said plate, a resistance wire wrapped about said plate with its turns in spaced relation and one of its ends connected to said fixed Contact, a terminal secured to said iixed contact, a rod supported from said end wall for sliding movement between the base and plate, and a generally U-shaped strip of resilient material having its intermediate portion secured to said rod with one of its ends bearing against the base and the other in position to engage the fixed Contact and successive turns of the resistance wire as the strip is shifted in movement of the rod, said strip being formed of electrically conducting material to provide a direct path for electric current between the point at which one of its ends engages said base and the point at which its other end engages a turn of said resistance wire.

2. A device as set forth in claim 1 with the addition of a sleeve secured to said end wall and projecting outwardly therefrom, said rod being slidable in said sleeve, said sleeve being exteriorly screw-threaded, and nuts on said sleeve for clamping the switch to a mounting member.

3. A device as set forth in claim 1 with the addition that the side walls of the switch-body are provided with notches between the end wall and the adjacent end of the plate and with additional notches ccextensive with that portion of the plate about which the resistance wire is wrapped.

EARL C. BOOTH.

cnFE-ENCES CXTED The following references are of record in the le of this patent:

UNITED STATES PATENTS