US3123792A

US3123792A - Switch-rheostat

Info

Publication number: US3123792A
Authority: US
Publication date: 1964-03-03
Anticipated expiration: 1981-03-03

Description

March 3, 1964 J. R. KLEMM I 3,123,792

' swTcH-RHEOSTAT Filed March 18, 1955 j )fl 7a I? y 2@ A Z A 7 Y ala/'MAS muy( United States Patent O 3,123,792 SWITCH-RHEOSTAT Julius R. Klemm, Wilmette, Ill., assignor to Dowst Manufacturing Company, a corporation of Illinois Filed Mar. 18, 1963, Ser. No. 265,973 6 Claims. (Cl. 338-100) This invention relates to a switch-rheostat assembly and, particularly, to a pressure sensitive device in which initial operation thereof will close the switch, and the continued application of pressure will vary the resistance of the device.

A switch-rheostat of the type that will respond to slight changes in pressure is particularly useful with games in which a variation in electrical current is desirable for varying the speed of such toys as electric trains or model racing cars. To be acceptable, such a device must have a long life and oe capable of hard usage since it is to be handled by youngsters. The switch-rheostat to be marketable must at the same time be inexpensive to manufacture and suiciently sensitive so that it will respond to slight changes in pressure. This sensitivity will minimize, if not eliminate, finger fatigue. While it is particularly adaptable to racing games in which reasonably accurate speed control is a factor, it is not limited to such a use.

It remains to note that the device is designed so that it will automatically be returned to the open position when the finger pressure is released to prevent the switch from remaining in the on position.

In accordance with the present invention, there is provided a housing assembly within which are disposed a pair of spaced contacts. To complete the circuit, there are interposed between the contacts a switch member and an electrically conductive material, the resistance of which will vary in accordance with the pressure applied there- An increase in pressure imposed on the electrically conductive material acts to lower the resistance and thereby increase the current flow to the article being controlled thereby, and conversely a decrease in pressure increases the resistance and decreases the current flow. In the case of a toy racing car, the speed will be varied depending on the pressure applied by the operator.

In the instant case, one of the contacts is resiliently biased out of engagement with the switch member whereby when the switch is not operated it will remain in the open position. When the spaced contact is moved into engagement with the switch member, the circuit is closed between the contacts wherein current Hows from the one contact through the ball switch and electrically conductive material to the other contact. The application of additional pressure compresses the electrically conductive material to reduce the resistance thereof and correspondingly increase the current flow through the switch-rheostat. When the pressure is released from the device, the contact previously retained in engagement with the switch member is moved away therefrom to open the switch and the pressure imposed by the switch member on the electrically conductive material is released with a corresponding increase in resistance. When carbon granules are used as the electrically conductive material, a resilient compressible member is disposed within the recess containing the granules. When the granules are compacted, this member will compress and when the pressure on the granules is released the compressible member expands to return the granules to their uncompacted condition.

The structure by which the above and other advantages of the invention are attained will be described in the following specification, taken in conjunction with the accompanying drawings illustrating a preferred structural embodiment of the invention, in which:

FIGURE l is a perspective view of a switch-rheostat assembly incorporating the present invention;

Patented Mar. 3, 1964 ICC FIGURE 2 is a cross-section of the device illustrated in the switch open position;

FIGURE 3 is a cross-sectional view similar to FIGURE 2, but showing the switch closed and the electrically conductive material in a compacted condition; and b FIGURE 4 is a plan View of one of the contact memers.

As illustrated in FIGURE 2, the novel switch-rheostat embodying the present invention is made up of a plastic housing 1 consisting of readily

separable sections

2, 3. The housing is of a molded construction in which the upper section 2 is formed with an inwardly extending annular lip 4, and the lower section 3 is formed with an outwardly extending lip 5. The inner diameter of the inwardly extending lip 4 is less than `the outer diameter of the outwardly extending lip 5 to prevent the halves from separating once the device is assembled. The housing is sufficiently resilient to permit enough relative movement therebetween to assemble the two housing sections. However, once the device is assembled, the interengaging lip portions act to prevent separation of the housing sections during normal usage.

The

housing sections

2, 3 are each provided with slits 2a, 3a, respectively, to receive contact members 7, 8. The other ends of the contacts 7, 8 are soldered or otherwise secured to leads 10, 11, respectively. The ends of each of the contacts extending into the housing sections are formed with a punched

tongue portion

7a, 8a that is adapted to engage with the

inner wall

2b, 3b of

housing sections

2, 3, respectively. The tongue prevents removal of the contact from its respective housing once it is assembled in position (see FIGURES 2 and 4).

The

sections

2, 3 of the housing l are maintained in the spaced position shown in FIGURE 2 by a sleeve 13 made of an elastomeric non-conductive material. The sleeve 13 is fitted into the upstanding tubular portion 14 of the lower housing 3 and extends above the top thereof wherein it engages an inner wall 2c of housing section 2. The resilient sleeve 13 denes a substantially spherical cavity in which is located a ball or switch member 16. The upper portion of the sleeve extends above the ball and biases the housing section 2, and contact member 7 out of engagement with the ball 16. Thus, when the switchrheostat is in the position shown in FIGURE 2, i.e., the inoperative position, the circuit between the contact members 7, 8 is open.

The lower portions of the sleeve 13 and ball 16 form with the lower housing 3 a cavity or recess 18 in which is located an electrically conductive material, such as a plurality of carbon granules 2l). The granules 20 are sealed in the recess by the sleeve 13 and ball 16 which thus gives the device a long life since the carbon granules will be positively retained in the recess at all times. The granules may be of any suitable size and shape, and commercially available configurations are usable in this device. The quantity of granules located in the recess is such as to substantially iill the recess when in a loose or uncompacted condition.

When the switch-rheostat is operated, pressure is applied as shown in FIGURE 3 against the upper housing section 2. During the movement from the position shown in FIGURE 2 to that shown in FIGURE 3, the downward movement of the upper housing section moves the contact 7 into engagement with the switch member 16 to close the circuit between the leads 10, 11. The application of additional downward pressure against the upper housing section urges the ball 16 downwardly to compress the lower portion of the sleeve 13 and compact the carbon granules 20 located in the recess. The resistance variation in the carbon granules is obtained by varying the contact resistance therebetween so it can be seen that the application of pressure to compact the granules through the application of pressure against the ball and sleeve will reduce the resistance of the carbon granules. The built-in resiliency of the sleeve 13 will return the ball to the position shown in FIGURE 2 when the finger pressure is released from the housing. The pressure against the granules is thus released to allow them to return to their uncornpacted condition. The interface relationship between the carbonV granules will tend to return them to the uncompacted state when the switch returns to the off position.

To facilitate the return of the carbon granules to the uncompacted condition, a resilient compressible ball member 21 may be located in the recess 18 containing the carbon granules. When the granules are compacted by the compressing action exerted by the ball and sleeve, the granules 20 distort the compressible ball 21 as shown in FIGURE 3. This action sets up a reaction force tending to expand the ball when the pressure thereon is released. When the pressure applied to the upper housing section is reduced or eliminated completely, the compaction force acting on the granules is correspondingly changed, thus allowing the compressible member to return to its normal conguration. During this latter movement, the granules in the recess are loosened up, which increases, the resistance thereof. For example, the resistance can be set to vary between 500 and 5 ohms, Vdepending on the quantity of carbon granules and the pressure applied thereto.

Another advantage of this device is that the switch will be turned off if it is accidentally held in the normally closed position for an inordinate length of time. While the theory upon which this is based is not completely understood, the continued application of heat to the unit, due to current iiow, results in expansion of internal parts, which breaks the contact between the switch member 16 and the upper contact 7.

While a particular embodiment has been described and illustrated, it is to be understood that the invention is not so limited. For example, the switch member and rubber seal supporting the same could be of any suitable design, and other equivalent means could be` employed for resiliently supporting the switch member in place in the device. Other modifications could include the replacing of the compressible ball in the recess with a springbiased plunger, or other mechanism which would yield in response to the pressure of the compacted granulesand would expand upon release of said pressure to return the granules to the uncompacted condition. Similarly, the switch-rheostat could employ other electrically conductive materials that would vary in resistance according to the pressure applied thereto, such as foam plastic or rubber impregnated with carbon.

It is, of course, intended to cover by the appended claims all such modications and embodiments that fall within the true spirit and scope of the invention.

I claim:

1. A switch-rheostat comprising a pair of telescopically and slidably arranged housing sections, means on each of said sections cooperating to prevent inadvertent separation thereof, the first of said sections dening a recess, particulate electrically conductive material in said recess, a lirst contact member in said first section in electrical contact with said material, a conductor member in said 2. The switch-rheostat of claim l in which said housing sections are cylindrical in configuration and said means comprises an external annular bead on said first housing section and an internal annular bead on said second housing section.

3. The switch-rheostat of claim 1 in which said conductor member comprises a metal ball.

4. The switch-rheostat of claim 3 in which said sleeve is open-ended and disposed coaxially of said iirst housing section, said sleeve snugly encasing said ball and extending beyond the extremitiesV thereof. Y

5. vThe switch-rheostat of claim l in which resilient compressible means is positioned Within said material for decompressing said material upon release of said second housing section.

6. A switch-rheostat comprising a pair of opposed Vtelescopically and slidably arranged cylindrical housing sections, an annular external bead on the bottom section, an annular internal bead on the top section, said beads cooperating to prevent inadvertent'V separation of said sections, said bottom section dening a recess, a plurality of carbon granules in said recess, arst contact member in said bottom section adjacent the bottom edge thereof and in electrical Contact with said carbon granules, an open-ended tubular elastomeric sleeve positioned in said bottom section above said carbon granules, a metal ball encased in said sleeve so that the top andl bottom edges of said sleeve extend beyond said ball, said ball and the bottom portions of said sleeve cooperating tov afford a seal for retaining said granules in said recess, a second contact member in said top section adjacent the top edge thereof, the top edges of said sleeve normally retaining said second contact member in spaced relation with said metal ball, said top section being downwardly movable whereby said second contact member rst contacts said metal ball to close the circuit between said contact members and further movement thereof causes said metal ball to compress said carbon granules to vary the resistance thereof, and a compressible ball positioned in said carbon granules for decompressing said granules upon release of said top section.

References Cited in the le of this patent UNITED STATES PATENTS 740,787 Vetter Oct. 6, 1903 1,159,674 Honold Nov. 9, 1915 2,333,814 Perkins Nov. 9, 1943 2,367,441 Schwinn Jan. 16, 1945 2,394,271 Taylor Feb. 5, 1946 2,475,696 Cornish July 12, 1949 2,856,492 Heyhal Oct. 14, 1958

Claims

1. A SWITCH-RHEOSTAT COMPRISING A PAIR OF TELESCOPICALLY AND SLIDABLY ARRANGED HOUSING SECTIONS, MEANS ON EACH OF SAID SECTIONS COOPERATING TO PREVENT INADVERTENT SEPARATION THEREOF, THE FIRST OF SAID SECTIONS DEFINING A RECESS, A FIRST CONTACT MEMBER IN SAID FIRST SECTION IN ELECTRICAL CONTACT WITH SAID MATERIAL, A CONDUCTOR MEMBER IN SAID FIRST SECTION ADJACENT SAID MATERIAL, A SECOND CONTACT MEMBER IN THE SECOND HOUSING SECTION, AND A RESILIENT SLEEVE IN SAID FIRST HOUSING SECTION AND SUPPORTING SAID CONDUCTOR MEMBER RELATIVE TO SAID MATERIAL AND SAID SECOND CONTACT MEMBER IN SPACED RELATIONSHIP WITH SAID CONDUCTOR MEMBER, SAID SECOND HOUSING SECTION BEING SLIDABLE AXIALLY WHEREBY SAID SECOND CONTACT MEMBER FIRST WILL ENGAGE SAID CONDUCTOR MEMBER TO CLOSE THE CIRCUIT BETWEEN THE CONTACT MEMBERS AND FURTHER MOVEMENT THEREOF WILL COMPRESS SAID MATERIAL TO DECREASE THE RESISTANCE THEREOF.