Sphere-actuated float switch

Abstract

A sphere-actuated float switch is provided including (i) a cage defining a longitudinal raceway, (ii) a yoke pivotally mounted externally to the cage and having a first and second legs which extend into the raceway, (iii) an electrical switching means which is electrically open when the yoke is in a first position and electrical closed when the yoke is in a second position, (iii) an over-center spring capable of biasing the yoke into the appropriate electrically open and the electrically closed positions once the yoke is urged past a transition point, and (iv) a sphere within the raceway for urging the yoke between the electrically open and the electrically closed positions.

Description

FIELD OF THE INVENTION

Broadly, the invention relates to float switches. Specifically, the invention relates to float switches which open and close an electrical circuit in response to the repositioning of a sphere within a raceway caused by a change in the attitude of the switch.

BACKGROUND

Many different types of float switches have been developed for opening and closing an electrical circuit in response to the level of a liquid within a reservoir. Generically, float switches includes a floating buoy and a means, responsive to the vertical position of the buoy, for alternately closing an electrical circuit when the float achieves a predetermined maximum height and opening the electrical circuit when the float achieves a predefined minimum height (normally open) or visa versa (normally closed).

One type of available float switch is known as a mercury-actuated switch. Referring to FIGS. 1a and 1b, a typical, normally open, mercury-actuated float switch includes an electrode 10a", 10b" which extend into a sealed tube 11" containing mercury 12". The mercury 12" resides at a second end of the tube 11" and electrically closes the electrode 10a", 10b" after the float switch has attained a predefined upward vertical angle caused by a high liquid level within the reservoir (FIG. 1a). Conversely, the mercury 12" resides at a first end of the tube 11" and leaves the electrode 10a", 10b" electrically open after the float switch has attained a predefined downward vertical angle caused by a low liquid level within the reservoir (FIG. 1b).

Mercury-actuated float switches provide superior switching performance. However, because of environmental concerns relating to the use of mercury, alternatives to the mercury-actuated switch are being explored.

One type of mercury-free float switch is what is known as a sphere-actuated float switch. Generally, sphere-actuated float switches utilize movement of a sphere within a raceway caused by changes in the attitude of the raceway to effectuate opening and closing of an electrical circuit.

Examples of sphere-actuated float switches are provided in U.S. Pat. Nos. 4,644,117 (Grimes et al.) and 4,629,841 (Riback et al.). Referring to FIGS. 2a and 2b, the sphere-actuated float switch of Grimes et al. includes (i) a pair of positionable electrical contacts 63" attached to a shuttle 55" which is slidably retained within a raceway 33" defined by housing 25" and (ii) a corresponding pair of stationary electrical contacts 53" which are connected to the housing 25" and extend into the raceway 33". The shuttle 55" resides at a second end of the raceway 33" and provides contact between the electrical connections 53" and 63" after the float switch has attained a predefined upward vertical angle caused by a high liquid level within the reservoir (FIG. 2a). Conversely, the shuttle 55" resides at a first end of the raceway 33" and prevents contact between the electrical connections 53" and 63" after the float switch has attained a predefined downward vertical angle caused by a low liquid level within the reservoir (FIG. 2b). Movement of the shuttle 55" within the raceway 33" is effected by a sphere 75" which rolls within the shuttle 55" based upon the attitude of the shuttle 55". The float switch of Grimes et al. addresses the environmental concerns associated with the utilization of mercury-actuated float switches. However, the switch lacks the reliability associated with mercury-actuated float switches. Various factors contribute to this lack of reliability including specifically, but not exclusively, excessive friction between the shuttle 55" and the housing 25" resulting in failure of the sphere 75" to reposition the shuttle 55", wedging of the shuttle 55" within the raceway 33" again resulting in failure of the sphere 75" to reposition the shuttle 55", and generation of deposits upon the electrical contacts 53" and/or 63" resulting in poor electrical flow between the electrical contacts 53" and 63".

Referring to FIGS. 3a, 3b and 3c, the sphere-actuated float switch of Riback et al. includes (i) a longitudinally extended raceway 51" having a first longitudinal end 50" and a second longitudinal end 52" within which a sphere 54" is free to roll based upon the attitude of the raceway 51". A pivotally mounted cage 56" is positioned proximate the raceway 51" with legs 64" and 65" of the cage 56" alternately extending into the raceway 51". An actuator extension 60" extends from the cage 56" in a direction opposite the legs 64" and 65" for actuating a microswitch 62" based upon the pivoted position of the cage 56". The cage 56" resides in a first pivoted position with the sphere 54" at the second end 52" of the raceway 51", the actuator extension 60" detached from the microswitch 62", and the microswitch 62" in an electrically open mode after the raceway 51" has attained a predefined downward vertical angle caused by a low liquid level within the reservoir (FIG. 3c). Conversely, the cage 56" resides in a second pivoted position with the sphere 54" at the first end 50" of the raceway 51" and the actuator extension 60" in contact with the microswitch 62" so as to place the microswitch 62" in an electrically closed mode after the raceway 51" has attained a predefined upward vertical angle caused by a high liquid level within the reservoir (FIG. 3a). Pivoting of the cage 56" is effected by movement of sphere 54" between the first 50" and second 52" ends of the raceway 51". A locking mechanism (not shown) is employed to lock the cage 56" into the first and second pivoted positions in an effort to maintain synchronization between pivoting of the cage 56" and movement of the sphere 54". The locking mechanism releases the cage 56" to pivot between the first and second positions only when the sphere 54" depresses a pressure plate 86" which extends into the raceway 51".

The float switch of Riback et al., as with the float switch of Grimes et al., addresses the environmental concerns associated with mercury-actuated switches but lacks the reliability associated with mercury-actuated float switches. Various factors contribute to the lack of reliability including specifically, but not exclusively, insufficient momentum to effect a clean repositioning of the cage 56" and loss of synchronization between movement of the cage 56" and the sphere 54". In addition, the float switch of Riback et al. utilizes a microswitch to effectuate opening and closing of the electrical circuit based upon movement of the cage 56" rather than direct electrical contact.

Accordingly, a substantial need exists for a reliable, mercury-free float switch which can directly provide effective opening and closing of an electrical circuit under heavy electrical load conditions.

SUMMARY OF THE INVENTION

The invention is directed to a reliable float switch which includes (i) a cage defining a longitudinal raceway, (ii) a yoke which is pivotally mounted externally to the cage and having first and second legs which extend into the raceway, (iii) a biasing means capable of biasing the yoke in a first direction when the yoke is in a first longitudinal position and biasing the yoke in a second longitudinal direction, which is substantially diametrically opposed to the first direction, when the yoke is in a second position, (iv) an electrical switching means which is electrically open when the yoke is in the first position and electrically closed when the yoke is in the second position, and (v) a means for urging the yoke between the first and second positions against the bias of the biasing means based upon the longitudinal angle of the raceway.

The float switch may optionally include a second electrical switching means which is electrically closed when the yoke is in the first position and electrically opened when the yoke is in the second position.

The float switch operates to control the flow of electricity through a circuit by cycling through the steps of (i) urging an electrically open pair of electrical contacts toward an electrically closed position, (ii) biasing the pair of electrical contacts toward an electrically closed position once urging of the electrical contacts towards the electrically closed position proceeds past a transitional position, (iii) electrically closing the electrical contacts, (iv) urging the electrically closed pair of electrical contacts towards an electrically open position, (v) biasing the pair of electrical contacts toward an electrically open position once urging of one of the electrical contacts towards the electrically open position proceeds past the transitional position, and (vi) electrically opening the electrical contacts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a depicts a prior art mercury-actuated float switch in an electrically closed position.

FIG. 1b depicts the prior art mercury-actuated float switch of FIG. 1a in an electrically open position.

FIG. 2a depicts the prior art sphere-actuated float switch disclosed in U.S. Pat. No. 4,644,117 (Grimes et al.) in an electrically closed position.

FIG. 2b depicts the prior art sphere-actuated float switch of FIG. 2a in an electrically open position.

FIG. 3a depicts the prior art sphere-actuated float switch disclosed in U.S. Pat. No. 4,629,841 (Riback et al.) in an electrically closed position.

FIG. 3b depicts the prior art sphere-actuated float switch of FIG. 3a in a transitional position.

FIG. 3c depicts the prior art sphere-actuated float switch of FIG. 3a in an electrically open position.

FIG. 4 is a schematic view of a float switch controlled pumping system.

FIG. 5a is an elevational side view of one embodiment of the invention in an electrically closed position with a portion thereof broken away to facilitate viewing of the switch.

FIG. 5b depicts the invention embodiment depicted in FIG. 5a in an electrically open position.

FIG. 6 is a top view of the switch depicted in FIGS. 5a and 5b.

FIG. 7 is a side view of the switch depicted in FIG. 6.

FIG. 8 is a front view of the switch depicted in FIG. 7.

FIG. 9a is a cross-sectional view of the switch depicted in FIG. 8 taken along line 9--9 depicting the switch in an electrically open position.

FIG. 9b depicts the switch of FIG. 9a in an electrically closed position.

FIG. 10 is a top view of a second embodiment of the invention.

FIG. 11a is a cross-sectional view of the switch depicted in FIG. 10 taken along line 11--11 with the switch in a first position.

FIG. 11b depicts the switch of FIG. 11a in a second electrical position.

DETAILED DESCRIPTION OF AN INVENTION EMBODIMENT INCLUDING A BEST MODE

Nomenclature

100 switch 110 switch housing 111 top of switch housing 112 base of switch housing 113 sidewall of switch housing 114 chamber defined by switch housing 115 orifice through switch housing 120 cage 121 top of cage 122 bottom of cage 123 front of cage 124 back of cage 125 right side of cage 126 left side of cage 127 inner surface of cage 127a front planar portion of cage inner surface 127b front inclined portion of cage inner surface 127c central planar portion of cage inner surface 127d rear inclined portion of cage inner surface 127e rear planar portion of cage inner surface 128 lateral channel across top of cage 129 longitudinal slit through top of cage 130 longitudinal raceway through cage 130a front retention portion of longitudinal raceway 130c central transitory portion of longitudinal raceway 130e rear retention portion of longitudinal raceway 143 front cover plate 144 rear cover plate 150 yoke 153 front leg of yoke 154 rear leg of yoke 155 central projection on yoke 156 lateral extension bar 160 J-shaped brackets 160a long leg of J-shaped brackets 160b short leg of J-shaped brackets 161 center pin/pivot point 170a right side yoke spring 170b left side yoke spring 171a right side post 171b left side post 172 connector pin 180a front right stationary electrical contact 180b front left stationary electrical contact 181a front right positionable electrical contact 181b front left positionable electrical contact 182a front right electrical contact mounting bracket 182b front left electrical contact mounting bracket 183 front electrical contact extension shaft 184 contact spring 185a rear right stationary electrical contact 185b rear left stationary electrical contact 186a rear right positionable electrical contact 186b rear left positionable electrical contact 187a rear right electrical contact mounting bracket 187b rear left electrical contact mounting bracket 188 rear electrical contact extension shaft 190 sphere 210 source of electricity 220 first electrical cord 221 piggy-back plug 230 second electrical cord 240 stand pipe 250 pump 300 pumping range 301 top of pumping range 302 bottom of pumping range

Construction

Referring to FIGS. 6, 7, 8, 9a and 9b, the core of the switch 100 is a cage 120 which defines a substantially cylindrical longitudinal raceway 130 extending from the front 123 to the back 124 of the cage 120. The inner surface 127 of the cage 120 defining the raceway 130 includes (i) substantially identical front 127a and rear 127e portions which define substantially identical front 130a and rear 130e cylindrical retention portions, (ii) a central portion 127c between the front 127a and rear 127e retention portions which defines a central transitional portion 130c, (iii) a front inclined portion 127b between the front 127a and central 127c portions, and (iv) a rear inclined portion 127d between the rear 127e and central 127c portions.

The inclined portions 127b and 127d of the inner surface 127 provide a barrier which retards movement of the sphere 190 out of the front 130a and rear 130e retention portions of the raceway 130. The inclined portions 127b,127d of the inner surface 127 generates potential energy within the sphere 190 as the longitudinal angle of the raceway 130 changes and begins to urge the sphere 190 towards the other end 123,124 of the cage 120. Once the longitudinal angle is sufficient to permit the sphere 190 to roll past the inclined portion 127b or 127d which is retarding movement of the sphere 190, the sphere 190 readily proceeds through the central portion 130c of the raceway 130 and into the retention portion 130a or 130e of the raceway 130 at the other end 123, of the cage 120.

Front 143 and rear 144 cover plates are respectively coupled to the front 123 and rear 124 of the cage 120 over the raceway 130 in order to prevent continued longitudinal movement of the sphere 190 out of the longitudinal raceway 130.

A U-shaped yoke 150 is pivotally mounted above the top 121 of the cage 120 by means of a pair of J-shaped brackets 160. The long leg 160a of one bracket 160 is connected to the right side 125 of the cage 120 while the long leg 160a of the other bracket 160 is connected to the left side 126 of the cage 120. The brackets 160 extend upwardly from the sides 125,126 of the cage 120 with the short legs 160b of the brackets 160 facing one another above the cage 120. The center of the yoke 150 is sandwiched between and pivotally connected to the short legs 160b of the brackets 160 by means of a center pin 161.

The front 153 and rear 154 legs of the yoke 150 extend into the longitudinal raceway 130 through a longitudinal slit 129 in the top 121 of the cage 120. The legs 153,154 extend a sufficient distance into the longitudinal raceway 130 to insure that the sphere 190 remains between the legs 153,154 at all times.

Longitudinal movement of the sphere 190 within the raceway 130 between the front 130a and rear 130e portions of the raceway 130 causes the sphere 190 to strike the legs 153,154 of the yoke 150 and pivot of the yoke 150 between a first pivot position and a second pivot position depicted in FIGS. 9a and 9b.

A front pair of right and left stationary electrical contacts 180a,180b are separately mounted upon the top 121 of the cage 120 by a pair of L-shaped mounting brackets 182a,182b. The front pair of electrical contacts 180a,180b face the rear 124 of the cage 120 and extend over a lateral channel 128 in the top 121 of the cage 120.

A front pair of right and left positionable electrical contacts 181a,181b are mounted upon opposite ends of a lateral extension bar 156 which is connected to a central projection 155 on the yoke 150. The central projection 155 extends between the legs 153,154 of the yoke 150 into the lateral channel 128 in the top 121 of the cage 120. The front pair of positionable electrical contacts 181a,181b are configured in conjunction with the front pair of stationary electrical contacts 180a,180b so as to provide an electrical connection of the corresponding right 180a,181a and left 180b,181b electrical contacts when the yoke is in one pivoted position and prevent electrical connection of the corresponding right 180a,181a and left 180b,181b electrical contacts when the yoke is in the other pivoted position.

The laterally extending channel 128 on the top 121 of the cage 120 is provided with sloped front and rear walls (unnumbered) to permit arcuate movement of the front positionable electrical contacts 181a,181b between the electrically open and electrically closed positions.

The lateral extension bar 156 is reciprocally mounted onto the center projection 155 of the yoke 150 by means of an extension shaft 183. A spring 184 is provided around the extension shaft 183 and retained between the lateral extension bar 156 and the center projection 155 for biasing the front positionable electrical contacts 181a,181b towards the front stationary electrical contacts 180a,180b. Biasing of the front positionable electrical contacts 181a,181b towards the front stationary electrical contacts 180a,180b, assists in assuring effective contact between the positionable 181a,181b and stationary 180a,180b contacts when the yoke 150 is in the first pivotable position.

The first electrical cord 220 connected to the float switch 100 includes a live wire (unnumbered) and a return wire (unnumbered) with the live wires coupled to the front right stationary electrical contact 180a and the return wire connected to the front left stationary electrical contact 180a. Flow of electricity is provided from the live wire to the return wire so as to complete the electrical circuit by simultaneously coupling the front right stationary electrical contact 180a to the right positionable electrical contact 181a and the front left stationary electrical contact 180b to the left positionable electrical contact 181b. Such coupling of the front electrical contacts 180a,180b,181a,181b permits electricity to sequentially flow from the live wire to the return wire through (i) the front right stationary electrical contact 180a, (ii) the front right positionable electrical contact 181a, (iii) the lateral extension bar 156, (iv) the front left positionable electrical contact 181b, and (v) the front left stationary electrical contact 180b.

Biasing of the yoke 150 towards the appropriate first or second pivotable positions is provided by a pair of longitudinal springs 170a,170b which are coupled at a first end (unnumbered) to the cage 120 proximate the back 124 of the cage 120 and at a second end (unnumbered) to the yoke 150 between the pivot point 161 and the front 123 of the cage 120. The springs 170a,170b are connected to the cage 120 by means of a pair of vertical posts 171a,171b and connected to the yoke 150 by means of a laterally extending connector pin 172. The springs 170a,170b are vertically positioned with respect to the pivot point 161 so as to provide biasing of the yoke 150 to remain in the first pivotable position when the yoke 150 is in the first pivotable position and biasing of the yoke 150 to remain in the second pivotable position when the yoke 150 is in the second pivotable position. Such a dual biasing effect is obtained by vertically positioning the springs 170a,170b so that the springs 170a,170b pass through the axis of the pivot point 161 as the yoke 150 moves between the first and second pivotable positions. Referring to FIGS. 9a and 9b, the springs 170a,170b bias the yoke 150 towards the front 123 of the cage 120 when the yoke 150 is in a first pivoted position (springs 170a,170b above pivot point 161) and bias the yoke 150 towards the back 124 of the cage 120 when the yoke 150 is in a second pivoted position (springs 170a,170b below pivot point 161).

The cage 120, cover plates 143,144, yoke 150, and brackets 160 may be constructed from substantially any structural material possessing sufficient structural integrity regardless of electrical conductivity including specifically, but not exclusively, plastics such as polyester and polyvinylchloride and metals such as aluminum and steel.

Proper functioning of the switch 100 requires that the force exerted upon the yoke 150 by the sphere 190 in the longitudinal direction when the sphere 190 strikes one of the legs 153,154 will always be sufficient to overcome a combination of the longitudinal biasing force applied to the yoke 150 by the springs 170a,170b and the frictional forces acting upon the yoke 150.

The longitudinal force applied to the yoke 150 by the sphere 190 is attributable to a combination of the longitudinal momentum of the sphere 190 when the sphere 190 strikes the yoke 150 and the linear distance between the point at which the sphere 190 contacts the yoke 150 and the pivot point 161 of the yoke 150. The momentum of the sphere 190 when the sphere 190 strikes the yoke 150 is dictated by the mass of the sphere 190 and the velocity of the sphere 190 when the sphere 190 strikes the yoke 150. Because movement of the sphere is based upon gravity, the velocity of the sphere 190 when the sphere 190 strikes the yoke 150 is dictated by the vertical distance traveled by the sphere 190 prior to striking the yoke 150. The vertical distance traveled by the sphere 190 prior to striking the yoke 150 is the vertical distance between the restraining inclined surface 127b or 127d and the point at which the sphere 190 contacts the yoke 150. The vertical distance between the restraining inclined surface 127b,127d and the point at which the sphere 190 contacts the yoke 150 is a function of the linear distance between these two points and the vertical angle achieved by the raceway 130 prior to release of the sphere 190. The vertical angle achieved by the raceway 130 prior to release of the sphere 190 is dictated by the angle of the restraining inclined surface 127b or 127d.

Accordingly, in the final analysis, the longitudinal force applied to the yoke 150 by the sphere 190 depends upon a combination of (i) the linear distance between the point at which the sphere 190 contacts the yoke 150 and the pivot point 161 of the yoke 150, (ii) the linear distance between the restraining inclined surface 127b,127d and the point at which the sphere 190 contacts the yoke 150, (iii) the angle of the restraining inclined surface 127b,127d, and (iv) the mass [size and density] of the sphere 190,.

The yoke 150 should be constructed with a linear distance of at least about 2 cm and most preferably about 3 to about 6 cm between the point at which the sphere 190 contacts the yoke 150 and the pivot point 161 of the yoke 150 in order to provide effective repositioning force to the yoke 150 without constructing an unwieldy switch.

Likewise, the raceway 130 should be constructed to retain the sphere 190 and the yoke 150 at a linear distance of at least about 1 cm and most preferably about 2 to about 5 cm until the sphere 190 is released in order to provide effective repositioning force to the yoke 150 without constructing an unwieldy switch.

The inclined surfaces 127b,127d are preferably angled such that the raceway 130 must achieve a vertical angle of at least about 10.degree. most preferably about 30.degree. to about 65.degree., before releasing the sphere 190. Angles of less than about 10.degree. are difficult to consistently obtain under normal operation conditions and can result in failure of the switch 100.

The sphere 190 should be constructed from a fairly dense material in order to maximize the momentum available to reposition the yoke 150 against the bias of the springs 170a,170b. Accordingly, the sphere 190 is preferentially constructed from such materials as steel or iron.

Referring to FIGS. 10, 11a and 11b, an alternative embodiment of the float switch 100 further includes a rear pair 185a,185b of stationary electrical contacts and a corresponding rear pair of positionable electrical contacts 186a,186b which are simply mirror images of the front set 180a,180b,181a,181b. The rear set of electrical contacts 185a,185b,186a,186b are electrically opened and closed in direct opposition to the front set 180a,180b,181a,181b such that when one set is electrically closed the other set will be electrically open.

The pumping range 300 is dictated by a combination of the angle of the inclined surface portions 127b,127d and the length of cord 220 provided between the stand pipe 240 and the float switch 100.

Referring to FIGS. 5a and 5b, the switch 100 is sealed within a chamber 114 defined by a substantially cylindrical housing 110. The switch 100 is configured within the housing 110 so that the raceway 130 longitudinally extends from the top 111 to the bottom 112 of the housing 110 and the sphere 190 will roll between the front portion 130a and the rear portion 130e of the raceway 130 based upon the relative heights of the top 111 and bottom 112 of the housing 110. A dual wire electrical cord 220 extends into the housing 110 and into contact with the front stationary electrical contacts 180a,180b through an orifice 115 in the base 112 of the housing 110.

The switch 100 may be employed to control various electrical equipment based upon the level of a liquid within a reservoir. FIG. 4 depicts use of the switch 100 to control a submersible pump 250. The switch 100 is connected to a source of electricity 210 by a first electrical cord 220 with a piggy back plug 221. The pump 250 is connected to the source of electricity 210 by a second electrical cord 230 which is plugged into the piggy back plug 221. Flow through the piggy back plug 221 to the second cord 230 is controlled by the float switch 100 which is electrically open to prevent the flow of electricity to the pump 250 after the float switch 100 reaches the lowest point 302 of the pumping range 300 and is electrically closed to permit the flow of electricity to the pump 250 after the float switch 100 reaches the highest point 301 of the pumping range 300.

Operation

A liquid level within the reservoir which is at or below the bottom 302 of the pumping range 300 causes switch 100 to occupy a downward position such as depicted in FIG. 5b. In the downward position, (i) the switch 100 is electrically open, (ii) the sphere 190 is retained within the rear retention portion 130e of the raceway 130, (iii) the yoke 150 is in the second pivotable position towards the rear 124 of the cage 120, and (iv) the springs 170a,170b bias the yoke towards the rear 124 of the cage 120. As the liquid level increases, the raceway 130 angles upward past horizontal until the sphere 190 rolls toward the front 121 of the cage and into contact with the rear inclined surface 127d. Further increases in the liquid level causes the switch 100 to reach the top 301 of the pumping range 300 at which time the sphere 190 rolls over the rear inclined surface 127d, through the central transitory portion 130c of the raceway 130, into contact with the front leg 153 of the yoke 150 so as to pivot the yoke 150 past a transitional pivot position, and into the front retention portion 130a of the raceway 130. Once the yoke has been pivoted past the transitional pivot position, the springs 170a,170b complete repositioning of the yoke 150 into the first pivotable position as they are then positioned to bias the yoke towards the front 121 of the cage 120 and into the first pivotable position. In the first pivotable position the switch 100 is electrically closed with the front positionable electrical contacts 181a,181b coupled to the front stationary electrical contacts 180a,180b and retained in the closed position by the springs 170a,170b.

Movement of the switch 100 from electrically closed to electrically opened is simply a reverse of the described sequence with the sphere 190 moving from the front retention portion 130a of the raceway 130 to the rear retention portion 130e and the yoke pivoting from the first pivotable position proximate the front 123 of the cage 120 to the second pivotable position proximate the rear 124 of the cage 120.

The specification is intended to aid in a complete non-limiting understanding of the invention. Since many variations and embodiments of the invention may be created without departing from the spirit and scope of the invention, the scope of the invention resides in the claims hereinafter appended.

Claims

1. A switch used in a float switch system, the switch comprising:

a cage defining a longitudinal raceway:

a yoke pivotally mounted to an exterior of the cage and having first and second legs which extend into the raceway;

biasing means capable of biasing the yoke in a first direction when the yoke is in a first position and biasing the yoke in a second direction, which is substantially diametrically opposed to the first direction, when the yoke is in a second position;

electrical switching means which is electrically open when the yoke is in the first position and electrically closed when the yoke is in the second position, wherein the electrical switching means includes first and second electrical contacts, the first electrical contact mounted to the cage, the second electrical contact mounted to the yoke, the second electrical contact movable with the yoke as the yoke is pivoted between the first position and the second position, the second electrical contact being in electrical contact with the first electrical contact when the yoke is in the second position, and the second electrical contact being spaced apart from the first electrical contact when the yoke is in the first position; and

means for urging the yoke between the first and second positions against the bias of the biasing means based upon the longitudinal angle of the raceway.

2. The switch of claim 1, further comprising third and fourth electrical contacts, and an electrical connector member, the third electrical contact mounted to the cage, the fourth electrical contact mounted to the yoke, the second and fourth electrical contacts connected by the electrical connector member, the first and third electrical contacts connectable to an external electrical power supply.

3. The switch of claim 1, wherein the yoke is pivotally mounted about a pivot axis and the biasing means is a spring which passes through the pivot axis as the yoke pivots between the first and second positions.

4. The switch of claim 1, further comprising contact biasing means for biasing at least one of the electrical contacts towards the other.

5. The switch of claim 1, further comprising second electrical switching means which is electrically closed when the yoke is in the first position and electrically open when the yoke is in the second position, wherein the second electrical switching means includes first and second electrical contacts, the first electrical contact mounted to the cage, the second electrical contact mounted to the yoke.

6. The switch of claim 1, wherein the means for urging the yoke between the first and second positions is a sphere and the raceway has a substantially circular longitudinal cross-section and defines a longitudinal axis.

7. The switch of claim 6, wherein one of the first and second legs of the yoke at least partially supports the sphere when the yoke is in the second position in all orientations of the raceway about the longitudinal axis.

8. The switch of claim 6, wherein the sphere contacts one of the first and second legs of the yoke to apply a closing force to the yoke during movement of the yoke from the first position to the second position, the closing force acting to rotate the yoke about a pivot axis of the yoke against the biasing means, the closing force transmitted through the yoke to apply a contact force to the first and second electrical contacts as the yoke moves to electrically close the contacts, the contact force influenced by the weight of the sphere.

9. The switch of claim 6, wherein the sphere contacts one of the first and second legs of the yoke to apply an opening force to the yoke during movement of the yoke from the second position to the first position, the opening force acting to rotate the yoke about the pivot axis of the yoke against the biasing means, the opening force transmitted through the yoke to apply a separating force to separate the contacts as the yoke moves to electrically open the contacts, the separating force influenced by the weight of the sphere.

10. The switch of claim 1, wherein the first and second yoke legs project continuously into the raceway.

11. A switch used in a float switch system, the switch comprising:

a cage defining a longitudinal raceway having a longitudinal axis;

a yoke pivotally mounted to an exterior of the cage about a pivot axis, the yoke having first and second legs which project continuously into the raceway the legs of the yoke each extending into the raceway in a non-parallel direction to the longitudinal axis of the raceway at all times during operation of the switch;

biasing means capable of biasing the yoke in a first direction when the yoke is in a first position and biasing the yoke in a second direction, which is substantially diametrically opposed to the first direction, when the yoke is in a second position;

electrical switching means which is electrically open when the yoke is in the first position and electrically closed when the yoke is in the second position; and

a sphere positioned within the raceway between the first and second legs of the yoke at all times during operation of the switch, the sphere urging the yoke between the first and second positions against the biasing of the biasing means based upon the longitudinal angle of the raceway.

12. The switch of claim 11, wherein the electrical switching means includes first and second electrical contacts, the first electrical contact mounted to the cage, the second electrical contact mounted to the yoke, the second electrical contact movable with the yoke as the yoke is pivoted between the first position and the second position, the sphere applying a force to the yoke as the yoke is moved by the sphere between the first and second positions, the force applied by the sphere to the yoke being transmitted through the yoke to the first and second electrical contacts to make electrical contact between the electrical contacts or break electrical contact between the electrical contacts during pivoting movement of the yoke between the first and second positions, the force applied to the contacts to make or break electrical contact influenced by the weight of the sphere.