US3451020A - Switch assembly for use in oxygen environment - Google Patents

Description

W. T. DOWNS .Fume 17, 169

SWITCH ASSEMBLY FOR USEy IN OXYGEN ENVIRONMENT N Sheet Filed Dec. 5, 1966 l/I/ilvsll..

June 17, 1969 W. T. DOWNS 3,451,020

SWITCH ASSEMBLY FOR USE IN OXYGEN-ENVIRONMENT Filed Dec. 5, 196e sheet 2 ggg KZ @Vim l m u) I sllllll INVENTOR.

W. T. DOWNS lFume l?, 1969 SWITCH ASSEMBLY FOR USE IN OXYGEN ENVIRONMENT Sheet Filed Dec. 5, 1966 INVENTOR.

United States Patent Office 3,451,020 Patented June 17, 1969 U.S. Cl. 335-206 16 Claims ABSTRACT OF THE DISCLOSUIE A switch assembly including a board 'with a plurality of reed switches and a printed circuit associatedtherewith disposed on a first side of the board. A potting material is disposed on the first side of the board for surrounding the switches, the printed circuit and electrical leads extending from the printed circuit. A plurality of bar magnets are disposed on the second side of the board where one of the magnets is rotatable to actuate one of three radially arranged switches on the opposite side of the board. There are two other bar magnets which are movable into position by push buttons for actuating other reed switches.

The instant invention relates to an electrical switch assembly which is particularly adapted for use in inflammable and/ or explosive environments and, more specifically, to an electrical switch including means responsive to a magnetic force for movement from a non-current transmitting position to a current transmitting position with potting material surrounding the means and including magnetic means for selectively moving the means to the current transmitting position.

As will become clear upon a full understanding of the invention, the invention may be used to advantage in various enviroments where a spark may cause combustion or an explosion. However, since the switch assembly of the instant invention is particularly adaptable for use in a power actuated hopsital bed which may have an oxygen tent associated therewith, it will thus be described.

At present, there are many hospital beds being utilized which include adjustable components. That is to say, numerous hospital beds have a head portion which may be adjusted, a seat portion which may be adjusted,\and a foot portion which may be adjusted. Various other hospital beds include one or more of these adjustable portions as well as other adjustable components. Normally, the adjustments of the bed are accomplished by use of an electrically operated motor which serves as a drive means to position a portion or component of the bed. One or more motors may be utilized, and when one motor is utilized, electrically operated clutching devices are frequently utilized. An example of one such hopsital bed is set forth in U.S. Patent 3,081,463, which issued Mar. 19, 1963. The hospital bed disclosed in the abovementioned patent has head, seat and foot portions which may be independently adjusted by actuation of a series of clutches and a single electric motor.

A serious problem associated with such power actuated hospital beds results from the disposition of the switching assembly on the bed adjacent a patient when an oxygen tent is being utilized with the bed. There are known instances where a patient in an oxygen tent has created sufficient static electricity to cause a fire by merely combining his hair. Thus, there is a need for an electrical switch which may be utilized to actuate the motor or motors for adjusting the bed without the possibility of shorting or creating a spark when being used within an oxygen tent. In the past, this problem has not been satisfactorily solved. For instance, in many prior art assemblies, the switch for controlling the motor which adjusts the bed is disposed outside of the oxygen tent and is, in fact, padlocked to a portion of the bed so that it cannot be moved within the oxygen tent. Attempts have been made to fabricate switching assemblies utilizing extremely low voltage so that there is no possibility of a short occurring while the switch is disposed within an oxygen atmosphere. Also, attempts have been made to provide mechanical switches. However, to date no switch which may be satisfactory and safely used within an oxygen tent has been developed.

Accordingly, it is an object and feature of this invention to provide an electrical switch assembly which may be satisfactorily and safely utilized in highly combustible or explosive environments, such as within an oxygen tent of a hospital bed.

In general, these and other objects and features of this invention may be attained in a switch assembly including one or more switches with each of the switch having a pair of normally spaced metal strips disposed in overlapping relationship and a glass enclosure surrounding the strips for hermetically sealing the strips. Each of the strips extends through the glass enclosure and current carrying leads are in contact with the strips exteriorly of the enclosure. A potting material surrounds the enclosure and the current carrying leads. There is also included a magnetic means comprising a permanent bar magnet and actuation means for moving the bar magnet into and out of a position adjacent the enclosure for moving the strips together so that current may be transmitted from one strip to the other. The potting material is preferably resilient so that in the event the switch is dropped, the potting material absorbs shocks and prevents breakage. In addition, the potting material prevents liquids from contacting the switch and the electrical leads, thus preventing shorts. This is a very important feature because switches used in hospital beds are very susceptible to becoming wet. In a preferred embodiment of the instant invention, a plurality of the switches are associated together in a manner to provide a switch assembly which is particularly suited for adjusting the head, seat and foot portions of a hospital bed, as for example the hospital bed disclosed in the aforementioned patent.

Other objects and attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIGURE 1 is a front elevational view partially broken away of a preferred embodiment of the instant invention;

FIGURE 2 is a rear elevational view partly broken away of the embodiment of the instant invention disclosed in FIGURE 1;

FIGURE 3 is a fragmentary cross-sectional view taken substantially along line 3 3 of FIGURE 1;

FIGURE 4 is a fragmentary cross-sectional view taken substantially along line 4-4 of FIGURE l;

FIGURE 5 is a fragmentary cross-sectional view similar to FIGURE 1 showing a moved position;

FIGURE 6 is an enlarged fragmentary view of the upper portion as shown in FIGURE l;

FIGURE 7 is a cross-sectional view taken substantially along line 7-*7 of FIGURE 6;

FIGURE 8 is a cross-sectional view taken substantially along line 8 8 of FIGURE 6;

FIGURE 9 is a view similar to FIGURE 6 but showing a moved position;

FIGURE l0 is a plan view of a preferred embodiment of the switch component used in the instant invention;

FIGURE 11 is an enlarged fragmentary cross-sectional view taken substantially along line 11-11 of FIGURE FIGURE 12 is a perspective view of the preferred embodiment of the switch assembly disclosed and described herein; and

FIGURE 13 is a schematic view of the circuitry utilized in the preferred embodiment of the invention disclosed and described herein.

Referring now to the drawings, wherein like numerals indicate like or corresponding parts throughout the several views, a preferred embodiment of the switch assembly of the instant invention is generally shown at 10. Referring more particularly to FIGURES 10 and 11, the switch assembly 10 utilizes one 0r more means, generally indicated at 12, responsive to a magnetic force for movement from a non-current transmitting position to a current transmitting position, the current transmitting position being illustrated in FIGURE l1, and a potting material 14 surrounding the means 12, and magnetic means, generally indicated at 16, for selectively moving the means 12 to the current transmitting position. More specifically,

the means 12 includes a pair of normally spaced metal strips 18 which are disposed in overlapping relationship to one another and an enclosure which surrounds the strips 18 for hermetically sealing the strips 18. The strips 1'8 extend through the enclosure and include terminals 22. The potting material 14 surrounds the enclosure 20 and the terminals 22. The magnetic means 16 comprises a permanent bar magnet which is moved into and out of close parallel relationship with the enclosure 20 for selectively moving the strips 18 together so that current may be transmitted therethrough. The enclosure 20` is disposed on one side of a board 24 and the bar magnet 16 is disposed on the other side of the board 24. Preferably, the board 24 has a printed circuit thereon, which will become more clear hereinafter. The potting material 14 is preferably resilient to absorb shocks and in addition prevents liquid from coming into contact with the terminals 22 or the printed circuits, thus preventing shorts.

The switch assembly 10 is particularly adapted for use with a hospital bed having one motor for selectively adjusting the head, seat or foot, either up or down. As disclosed in FIGURE 12, there is included a housing, generally indicated at 26, a selector knob 28, which may be moved to one of three positions for actuating either the head, seat or foot, and up and down push buttons 30 and 32. The housing 26 includes two components which are held together by the screws 25. Once the selector knob 28 is positioned in one of the head, seat or foot positions, one of the push buttons 30 or 32 is pushed into the housing to move the selected portion of the bed either up or down.

As best illustrated in FIGURE 4, the assembly includes a board 24 and a plurality of switches 40, 41, 42, 43, 44, 45 and 46, all of which are disposed on a first side or face of the board 24. Each of the switches 40 through 46 includes a pair of normally spaced metal strips disposed in overlapping relationship with an enclosure surrounding each pair of strips in spaced relation to the strips for hermetically sealing the strips and each pair of strips extends through the associated enclosure. There is also included current carrying means comprising the electrical cable 50, which includes a plurality of leads, and the circuits printed on the first side of the board 24, which are described more specifically hereinafter. As best illustrated in FIGURES 3 and 4, the potting material 14 is disposed on the first side of the board 24 and surrounds the glass enclosures, the leads and the printed circuits. As best illustrated in FIGURE l, the assembly also includes magnetic means, generally indicated at 16', disposed on the second side of the board 24 for selectively moving the strips of each switch together so that current may flow therethrough. The housing 26 surrounds the potting ma terial 14, the board 24, and the magnetic means 16.

Referring now more particularly to FIGURES 2 and 13, one of the strips of each of the first and second switches 40 and 41 is connected to a first lead 52. More specifically, one of the strips of each of the switches 40 and '41 is connected to the printed circuit 54 which is in turn connected to the lead 52. This first lead 52 is adapted to supply a current to the switches 40 and 41. The other strips of each of the first and second switches 40 and 41 are connected to the respective second and third leads 56 and 58. Thus, upon actuation of the first switch 40, current may be applied to the second lead 56 and upon actuation of the second switch 41, current may be applied to the third lead 58.

In addition, one of the strips of third and fourth switches 42 and 43 are connected respectively to a fourth lead 60 by way of the printed circuit 62. The fourth lead 60 is also adapted to supply a current. One of the strips of each of the fifth, sixth and seventh switches 44, 45 and 46 is connected to the other strips of the third and fourth switches 42 and 43 by way of the printed circuit 64. The other strips of the fifth, sixth and seventh switches 44, 45 and 46 are connected respectively to the fifth, sixth and seventh leads 66, 68 and 70 respectively, such connections being by way of the printed circuits 72, 74 and 76 respectively. Thus, upon actuation of either of the third and fourth switches 42 and 43, current may be supplied to one of the fifth, sixth and seventh leads 66, 68 and 70, depending upon which one of the fifth, sixth and seventh switches 44, 45 and 46 is actuated.

The first switch 40 and the third switch 42 are disposed in side-by-side parallel relationship. A first permanent bar magnet 78 is moved into and out of close parallel relationship to the rst and third switches 40 and 42 to move the respective strips thereof together. The magnet 78 is moved by a first actuation means which is generally indicated at `80. In addition, the second and fourth switches 41 and 43 are also disposed in side-by-side parallel relationship and a second permanent bar magnet 82 is moved into and out of close parallel relationship to the second and fourth switches 41 and 43 by a second actuation means, generally indicated at 84. The bar magnet 82 moves the strips of the second and fourth switches 41 and 43 together when moved into close relationship thereto by the actuation means 84. Thus, the magnet means 16' includes the first and second magnets 78 and 82 and the first and second actuation means and y84.

Each of the first and second actuation means 80 and 84 includes a magnet support member 92 which is rotatably attached to the second side of the board 24 by the pin 94. That is to say, the support members 92 are Idisposed on the board 24 for rotation about a common axis. The first magnet 78 is secured to one of the support members 92 and the second magnet 82 is secured to the other support member 92. Each of the actuation means 80 and 84 also includes a push button, the push buttons being shown at 30 and 32. Each of the push buttons 30 and 32 is slidably supported in the housing 26 for movement toward and away from the board 24. There is also included a motion transmitting means operatively interconnecting each support member 92 and each of the push buttons 30 and 32 for rotating the support members 92 upon movement of the associated push button in a first direction into the housing. When the member 92 of the first actuation means 80 is moved to the position illustrated in full lines in FIGURE 5, the first bar magnet 78 is in the close parallel relationship with the first and third switches 40 and 42. Likewise, when the support member 92 of the second actuation means 84 is moved to the position shown in phantom in FIGURE l, the bar magnet 82 is in the close parallel relationship with the second and fourth switches 41 and 43.

It will be noted that the support members 92 include projecting portions 96 and one of the support members 92 includes a stop member 98 secured thereto and in the plane of the other support member 92, thus providing a stop means for preventing rotation of either of the support members 92 to the central position, i.e., the position illustrated in phantom in FIGURE 1 or the position illustrated in full lines in FIGURE 5, when the other support member 92 is in such a position. There is also included a biasing means comprising the springs 100 which urge each of the support members 92 to rotate away from the positions illust-rated in phantom in FIGURE 1 and in full lines in FIGURE 5.

The motion transmitting means interconnecting the push buttons and the respective support members 92 comprises a spiral surface 102 presented by each support member 92 and a coacting spiral surface 104 presented by each push button. The spiral surface 104 of each push button slides along the spiral surface 102 of the associated support member 92 to rotate `the Iassociated support member 92 toward the central position (i.e., the position illustrated in phantom in FIGURE 1 and the position illustrated in full lines in FIGURE 5) as the associated push button is moved into the housing 26. Each button has a cylindrical projection 105 which extends through the board 24 and is slidably disposed in a cavity 107 in the potting material 14. The projections 105 aid in guiding the movement of the respective buttons 30 and 32.

The fifth, sixth and seventh switches 44, 45 and 46 are disposed on spaced radials extending from a iirst axis 86, the axis 86 being perpendicular to the board 24. The magnet means 16 also includes a third permanent bar magnet 88 and a third actuation means, generally indicated at 90. The actuation means 90 moves the -third magnet 88 between rst, second and third positions. More specically, the third magnet 88 is in close parallel relationship to the fth switch 44 to move the strips thereof together when in the rst position, which is illustrated in FIGURE 9. The third magnet 88 is in close parallel relationship to the sixth switch 45 to move the strips thereof together when in the second position, as illustrated in FIGURES 1 and 6y through 8. The third magnet 88 is in close parallel relationship to the seventh switch 46 to move the strips thereof together when in the third position which is evident but not illustrated.

The third lactuation means 90 comprises a rot-ary selector secured to the second side of the board 24. The selector includes a rotatable shaft 106 which extends through the housing 26 for receiving the selector knob 28. The shaft 106 is coaxial with the first axis 86 about which the switches 44, 45 and 46 are radi-ally disposed. A brace 108 supports the rotary selector on the board 24. Preferably, the brace 108 and related support components, such as the screws 110, are made of non-magnetic material. A member 112 is attached to the shaft 106 for rotation therewith. The third magnet 88 is secured to the member 112 with the longitudinal -axis of the magnet 88 being disposed on a radial of the axis 86. The rotary selector is preferably of the detent type so that when moved to a particular position a detent, or the like, maintains the switch in `the selected rotary position. Thus, the shaft 106 is rotatable to move the third magnet 88 from the first position as illustrated in FIGURE 9, to the second position as illustrated in FIGURES l and 6 through 8, to the third position which is not illustrated, and vice versa.

As mentioned herenbefore, the embodiment of the switch assembly specically described herein is particularly suitable for use with a hospital bed of the type disclosed in the aforementioned Patent 3,081,463. The hospital bed disclosed in Patent 3,081,463 has a head portion which moves up or down, a seat portion which moves up or down, and a foot portion which moves up or down. A single reversible AC current operated motor is utilized in conjunction with three DC power actuated clutches. A DC current is supplied through the lead 60. The AC current for the motor is supplied through the lead 52. It will be noted that the tirst and second switches 40 and 41 are larger than the remaining switches. This is because the rst and second switches 40 and 41 carry a relatively high AC current to the motor and are, therefore, required to be larger than the remaining switches 42 through 46 which carry a relatively lower DC current to the clutches.

The selector knob 28 is in either the head, seat or foot position so that at all times one of the fth, sixth o1 seventh switches 44, 45 and 46 is closed whereby current may pass therethrough. Assuming that the selector switch is in the seat position as illustrated in FIGURE 12, the operator may push either the up button 30 or the down button 32 to raise or lower the seat portion of the bed. Assuming that the up button 30 is pressed, the rst bar magnet 78 is moved into close parallel relationship with the first and third switches 40 and 42, although the bar magnet 78 is on the opposite side of the board 24 from the first and third switches 40 and 42. Thus, the strips in the respective switches 40 and 42 are moved together to allow current to pass therethrough. While the button 30 is depressed, the projections 96 on the support members 92 prevent the down button from being depressed to actuate the second and fourth switches 41 and 43. Once the up button is depressed, AC current flows from the lead 52 through the rst switch 40 to the lead 56 which rotates the AC motor in one direction. If the down button is depressed, AC current flows through the switch 41 and to the lead 58 to rotate the AC motor in the opposite direction.

When the up button is depressed, the iirst switch 40 is closed and the fourth switch 42 is closed. The fourth switch 42 is disposed in side-by-side parallel relationship with the switch 40 so that the switch 42 is closed momentarily before the switch 40. Likewise, the switch 43 is closed momentarily before the switch 44 when the down button 32 is pushed. Thus, the appropriate clutch is actuated momentarily before the AC motor begins to rotate, thus providing a smooth operation.

When the switch 42 is closed and the selector 28 is in the seat position, DC current passes through the sixth switch 45 and to the lead 68 to a clutch which transmits rotary motion from the AC motor to the mechanism to raise the seat portion of the bed. When the down button 32 is depressed, current passes through the switch 43, and through the sixth switch 45, and to the lead 68 to engage the clutch which transmits rotary motion from the AC motor to the mechanism connected with the seat portion of the bed to lower the seat portion. In a similar manner, the selector knob 28 may be positioned in either the head or foot position so that either the head or foot may be raised or lowered by depressing either the up push button 30 or the down push button 32.

'I'he instant invention, therefore, provides a switching assembly which is suitable for use in inflammable or explosive environments because of the possibility of electrical shorts or sparks occurring is negated.

The invention has been described in an illustrative man- -ner and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation.

Obviously, many modications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A switch assembly comprising; a. pair of normally spaced metal strips disposed in overlapping relationship, an enclosure surrounding said strips for hermetically sealing said strips, each of said strips extending through said enclosure, a board supporting said enclosure on a rst side thereof, a printed circuit on said rst side of said board and in electrical contact with said strips, current carrying means in contact with said printed circuit exteriorly of said enclosure, a potting material disposed on said first side of said board and surrounding said enclosure, said printed circuit and said current carrying means, a permanent bar magnet and actuation means for moving said magnet into and out of close relationship with said enclosure for selectively moving said strips together, said magnet and said actuation means being disposed on the second side of said board, and a housing surrounding said potting material and said board, said actuation means including a magnet support member rotatably attached to said second side of said board, said magnet being secured to said support member, a push button slidably supported in said housing for movement toward and away from said board, and motion transmitting means operatively interconnecting said support member and said push button for rotating said member to a first position where said magnet is in said close relationship with said enclosure upon movement of said push button in a first direction.

2. A switch assembly as set forth in claim 1 wherein said actuation means rotates said magnet into and out of said close parallel relationship to said enclosure.

3. A switch assembly as set forth in claim 2 wherein said enclosure is made of glass and said potting material is resilient to absorb shocks and prevent breakage of said glass.

4. A switch assembly as set forth in claim 1 wherein said actuation means includes a rotary selector secured to said second side of said board with a shaft extending through said housing, said rotary selector having a member attached to said shaft for rotation therewith, said magnet being secured to said member with the longitudinal axis thereof disposed on a radial from said shaft, said rotary selector having one position in which said magnet is disposed in said close relationship with said enclosure.

5. A switch assembly as set forth in claim 1 including biasing means urging said support member to rotate away from said first position and to urge said push button to move in a direction opposite to said first direction.

6. A switch assembly as set forth in claim 5 wherein said motion transmitting means comprises a spiral surface presented by said support member and a coacting spiral surface presented by said push button so that one surface slides along the other to rotate said support member toward said first position as said push button is moved in said first direction.

7. A switch assembly comprising; a board, first and second groups of switches disposed on a first side of said board, each of said groups including a plurality of switches, each of said switches including a pair of normally spaced metal strips disposed in overlapping relationship and an enclosure surrounding said strips in spaced relation thereto for hermetically sealing said strips, said strips extending through said enclosure, a printed circuit on said first side of said board and in electrical contact with said strips, current carrying means in Contact with said printed circuit exteriorly of said enclosures, a potting material disposed on said first side of said board and surrounding said enclosures, said printed circuit and said current carrying means, magnetic means disposed on the second side of said board for selectively moving said strips of each pair together so that current may ow therethrough, and a housing surrounding said potting material, said board, and said magnetic means, said current carrying means including an electrical cable comprising a number of leads extending through said housing and in electrical contact with said strips of said switches through said printed circuit, said first group of said switches being electrically connected by said printed circuit to a first of said leads which supplies current, each of said first group of switches being connected to one of a first plurality of said leads whereby current may be selectively supplied to any one of said first plurality of leads, said second group of said switches being electrically connected by said printed circuit to a second of said leads which supplies current, each of said second group of switches being connected to one of a second plurality of said leads whereby current may be selectively supplied to any one of said second plurality of leads, at least one switch of said first group disposed adjacent a switch of said second group whereby said magnetic means actuates both switches substantially simultaneously.

S. A switch assembly as set forth in claim 7 wherein said first group includes first and second switches, one of said strips of each of the first and second switches being connected to said first of said leads, the other strips of each of said first and second switches being connected to respective third and fourth leads of said rst plurality of leads so that upon actuation of said first switch current may be applied to said third lead and upon actuation of said second switch current may be applied to said fourth lead.

9. A switch assembly as set forth in claim 8 wherein said second group includes third, fourth, fifth, sixth and seventh switches, one of said strips of said third and fourth switches being connected to said second lead, one of said strips of said fifth, sixth and seventh switches being connected to the other strips of said third and fourth switches, the other strips of each of said fi-fth, sixth and seventh switches being connected respectively to fifth, sixth and seventh leads of said second plurality of leads so that upon actuation of either of said third and fourth switches current may be supplied to one of said fifth, sixth and seventh leads upon actuation of one of said fth, sixth and seventh switches.

10. A switch assembly as set forth in claim 9 wherein said first and third switches are disposed in side-by-side parallel relationship and said magnetic means includes a first permanent bar magnet and first actuation means for moving said first magnet into close parallel relationship to said first and third switches to move the respective strips thereof together, and wherein said second and fourth switches are disposed in side-by-side parallel relationship and said magnetic means includes a second permanent bar magnet and second actuation means for moving said second magnet into close parallel relationship to said second and fourth switches to move the respective strips thereof together.

11. A switch assembly as set `forth in claim 10 wherein said fifth, sixth and seventh switches are disposed on spaced radials extending from a first axis which is perpendicular to said board, and said magnetic means includes a third permanent bar magnet and third actuation means to move said third magnet between first, second and third positions, said third magnet being in close parallel relationship to said fifth switch to move the strips thereof together when in said first position, said third magnet being in close parallel relationship to said sixth switch to move the strips thereof together when in said second position, said third magnet being in close parallel relationship to said seventh switch to move the strips thereof together when in said third position.

12. A switch assembly as set forth in claim 11 wherein each of said first and second actuation means includes a magnet support member rotatably attached to said second side of said board, said first magnet being secured to the support member of said first actuation means and said second magnet being secured to the support member of said second actuation means, each of said first and second actuation means further includes a push button slidably supported in said housing for movement toward and away from said board and motion transmitting means operatively interconnecting the support member and the push button for rotating the support member to a first position upon movement of the push button in a first direction into said housing, said first magnet being in said close parallel relationship with said first and third switches when said support member of said first actuation means is in said first position, said second magnet being in said close parallel relationship to said second and fourth switches when said support member of said second actuation means is in said first position.

13. A switch assembly as set forth in claim 12 wherein said support members are disposed on said board for rotation about a common axis, said support members including stop means for preventing rotation of one of said support members to its first position when the other support member is in its irst position, and including biasing means urging each of said support members to rotate away from the respective first positions.

14. A switch assembly as set forth in claim 13 wherein said motion transmitting means comprises a spiral surface presented by each support member and a coating spiral surface presented by each push button so that the spiral surface of each push button slides along the spiral surface of the associated support member to rotate the associated support member toward its rst position as the push button is moved into said housing in said first direction.

15. A switch assembly as set forth in claim 14 wherein said third actuation means comprises a rotary selector secured to said second side of said board with a rotatable shaft extending through said housing and coaxial with said irst axis, said selector including a member attached to said shaft ifor rotation therewith, said third magnet being secured to said member with the longitudinal axis thereof disposed on a radial of said first axis, said shaft rbeing rotatable to move said third magnet -between said first, second and third positions thereof.

16. A switch assembly as set forth in claim 15 wherein said enclosure is made of glass and said potting material is resilient to absorb shocks and prevent breakage of said glass.

References Cited UNITED STATES PATENTS 3,161,742 12/ 1964 Bagno 335-202 X 3,260,820 7/ 1966 OBrien 335-153 3,281,734 10/1966y Ansley 335-152 3,364,318 1/ 1968- Bulliet.

BERNARD A. GILHEANY, Primary Examiner. R. N. ENVALL, JR., Assistant Examiner.

U.S. Cl. X.R. ZOO-168; 317-112

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