Float switch assembly for submersible pump
BACKGROUND OF THE INVENTION 
     1. Field Of The Invention 
     This invention relates to the general art of float switch assemblies and more particularly to magnetically actuatable float switches intended for use with pumps. Although the float switch assembly can be used with submersible and non-submersible pumps as well, it is described herein with specific reference to the operation of submersible pumps as the preferred use of the invention. The switch in its most preferred embodiment is characterized by providing it in a hermetically sealed compartment along with a permanent magnetic body and twin armatures adapted to sequentially &#34;make&#34; or &#34;break&#34; electrical contacts in an electrical circuit, and a contact-actuating mechanism. 
     2. Description Of The Related Art 
     Sump pumps and the like generally use two types of switching mechanisms. One type is a tethered cord float switch. A drawback of this type of switch is that to increase the pumping differential, the length of the cord must be increased. This can be problematic if the pump is to be operated in smaller diameter sumps, for example, as the tethered cord switch would not have enough room to operate adequately and could possibly cause the float to hang up. To overcome this problem, some sump pump manufacturers rigidly attach a rod mounted vertically along the outer pump housing. A float with a hollow center rides up along the rod and at a certain height will actuate a switch, turning on the pump. As long as the pump can fit in the sump, there should be no interference. Examples of this type of pump and switch arrangement are found in U.S. Pat. No. 1,170,377 to Weed and U.S. Pat. No. 1,838,135 to Derby. 
     Float switches having a magnetic arrangement of sorts at the upper end of the rod for actuating a contact switch have been described in U.S. Pat. No. 2,726,296 to Hanson, U.S. Pat. No. 4,647,740 to Hanson III, and U.S. Pat. No. 4,865,073 to Kocher. 
     Operation with a sump pump requires equipment that will assure certainty of operation over long periods of time. This invention fulfills a need which has developed for an improved magnetically actuatable float switch assembly for use with sump pumps, and the like. In its most preferred form it also provides a hermetically sealed environment for the electrical contacts and the contact-actuating mechanism, thereby assuring a longer operating life, greater reliability and less wear and tear on parts of the switch assembly. 
     SUMMARY OF THE INVENTION 
     The invention in its most preferred embodiment is directed to a magnetically actuatable float switch for use with sump pumps and the like, the switch assembly comprising a float rod with two spaced, adjustable stops between which a float carried by the rod moves in response to fluid level in the sump. A reciprocating magnetic body is carried at the upper end of the rod, which is mounted in a vertical oriented position for movement upwardly and downwardly in response to float movement against the two spaced stops. A generally U-shaped magnetic follower element or armature with two vertically spaced, magnetically responsive arms, is rotatably mounted such that the arms are situated horizontally, one above the other, and may move upwardly and downwardly in a vertical plane, the arms and magnetic body being positioned relative to each other so as to dispose the magnetic body for movement from arm to thereby allow proximity actuation of the follower by magnetic attraction between the arms and the magnetic body. Preferably, a dual set of such arms is provided as is described further hereinbelow. As the follower element arms move upwardly and downwardly, respectively, in response to proximity actuation by the magnetic body as controlled by float movement against the stops on the rods, an electrical contact means carried by the follower element makes and breaks with a fixed electrical contact means, thereby switching the pump on and off. In an even more preferred form, the follower element includes dual, U-shaped arms, each of which are laterally spaced on opposite sides of the magnetic body and operate in unison. The invention further provides an embodiment in which a hermetically sealed environment is provided for the magnetic body and its follower element, the electrical contacts and the contact-actuating mechanism. Also, a filtered float chamber may be provided. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS. 
     The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may be best understood by reference to the following description taken in conjunction with the accompanying drawings, wherein like reference numerals identify like elements, throughout and in which: 
     FIG. 1 is a vertical sectional view through a magnetically controlled float switch according to the invention, showing the contact points open and the fluid level low; 
     FIG. 2 is a vertical sectional view as in FIG. 1, showing the contact points closed and the fluid level high; and 
     FIG. 3 is a perspective view of the sealed housing with the cap removed to show the parts as disposed therein. 
     FIG. 4 is a perspective view of an alternative embodiment of the sealed housing with the cap removed to show the parts as disposed therein. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2, a magnetically controlled float switch, generally indicated at 10 comprises a float mechanism, generally indicated at 14, optionally covered by a casing or screen 12, further comprising a float rod 16 and two spaced stops, an upper limit stop 18 and a lower limit stop 20, secured by upper and lower set screws 22,24, and a moveable float 26 carried by rod 16 positioned between stops 18,20 and moveable therebetween in response to the fluid level. Float mechanism 14 is joined with an essentially flat base support 28 by means of a bushing 30. A metal mount 32 for securing float switch 10 to a pump or the like is disposed between bushing 30 and base support 28. 
     A relatively thin upright housing element 34 stands on the surface of base support 28. This may be a block of plastic, or other non-magnetic material. An opening extends upwardly through base support 28 in communication with a receiving cavity 36 formed in housing element 34 for upward and downward movement of a reciprocating element 38 received therein. Float rod 16 is attached to reciprocating element 38, which moves with the rod up and down in response to movement of float 26 between upper and lower limit stops 18,20. Rod 16 and reciprocating element 38 may also be of one piece as of molded plastic. A magnetic body 40 is carried by reciprocating element 38 for movement with rod 16. A generally U-shaped magnetic follower element 42 having two spaced magnetically responsive arms, an upper arm 44 and a lower arm 46, is mounted on housing 34 by means of a pivot 48. Alternatively, follower element 42 may be made of a magnetic material, in which case item 40 would be a magnetic attracting body made of a magnetic attractable metal. 
     In a preferred embodiment of the invention, as shown in FIG. 3 of the drawings, follower element 42 is disposed alongside of housing 34 and includes dual laterally spaced and generally U-shaped members 44a, 44b, 46a, 46b, each of which is disposed along opposite sides of housing element 34, to provide a dual U-shaped armature arrangement. Arms 44a, 44b, 46a, 46b and magnetic body 40 are positioned relative to each other so as to dispose magnetic body 40 therebetween for movement between upper arms and lower arms, thereby allowing proximity actuation of follower element 42 by magnetic attraction between arms 44a and 46a and magnetic body 40 or between arms 44b and 46b and magnetic body 40. 
     A pair of fixed electrical contacts 52 is carried by housing 34 transverse of the upright edge of housing 34 and attached above pivot point 48 of follower element 42 with one contact disposed to each side of housing 34 and follower arms 44a,44b,46a,46b. A moveable contact support 53, including a transverse bar 54 which carries a pair of spaced electrical contacts 56 arranged for mating with fixed contacts 52 is carried by follower element 42 above pivot point 48 thereof and extending across the upright edge of housing element 34. Electrical contact is effected through lateral movement of transverse bar 54, in response to movement of follower element 42. In a preferred embodiment transverse bar 54 is carried by moveable contact support 53 and includes a biasing spring 62. Biasing spring 62 is used for biasing contacts 56 toward fixed contacts 52 to ensure that electrical contact is made when follower element 42 is in the closed position, as shown in FIG. 2, and also to take up contact bounce. Base 28 is further equipped with an opening 66 for electrical contact wires 68, which attaches to fixed contact means 52 located on housing element 34. 
     Referring now to FIG. 4, in which like numbers are used to designate like elements referred to in FIG. 3 above, an alternative embodiment of the invention is shown in which fixed electrical contacts 52 are attached to base 28 by means of fixed contact supports 51 disposed to either side of moveable contact block 53 which is carried below pivot point 48 of follower element 42. In this embodiment, transverse bar 54 carrying spaced electrical contacts 56 is horizontal to base 28, and moves vertically to effect electrical contact. 
     A unique feature of the invention is the manner in which the assembly is enclosed for protection. Referring to FIG. 1, the switch assembly is shown protected by a cap 70 which fits in a groove 72 formed around the outer edge of base 28. The entire switch assembly is hermetically sealed as follows: where base 28 meets cap 70; where base 28 meets element 34; and at opening 66 for electrical wire 68, to ensure that the switch assembly is water and vapor tight. Housing element 34 is preferably molded to the surface of base support 28, or housing element 34 may be sealingly attached, as by plastic sealant, adhesive or the like, to the surface of base support 28 thereby sealing off the switch assembly from receiving cavity 36 formed in housing element 34 which communicates with float mechanism 14. Most preferably, base 28 and housing 34 will be a single unitary molded plastic part. Also, as an option, casing or screen 12 shown in FIGS. 1 and 2 can be attached to protect float 26 from debris or foreign material that might enter float mechanism 14, impairing the float&#39;s function. In a preferred embodiment, float casing 12 is equipped with slits 13 designed to filter the liquid entering float mechanism 14. 
     In operation, float 26 is allowed to travel freely up and down rod 16 due to rising and falling liquid levels. Set points or stops 18,20 for pump &#34;on&#34; and pump &#34;off&#34; are adjustable and are positioned above and below float 26. When the liquid level rises, float 26 travels vertically along rod 16 until reaching upper limit stop 18 at which point float 26 will lift rod 16. Connected to rod 16 is a structure or reciprocating element 38 that holds magnetic body 40 so if rod 16 is rising, magnetic body 40 will also rise. Magnetic body 40 rises and at a certain point the magnetic field attracts upper metal arm 44 of follower element 42 causing it to rotate downwardly thereby &#34;closing&#34; switch contacts 52,56 and starting the pump. As the water level falls, float 26 travels down rod 16 but rod 16 remains motionless because of the magnetic attraction between magnetic body 40 and arm 44 of follower element 42. This phenomena is desirable to create a pumping differential. When float 26 reaches lower limit stop or set point 20 on rod 16, the water continues to fall so that the downward force exerted at lower set point 20 increases. The increase in downward force causes magnetic body 40 to start moving downwardly. While magnetic body 40 is moving down, the magnetic field attracts and pulls upper metal arm 44 of follower element 42 and increases the contact pressure. At a certain point in time, the weight at lower limit stop 20 becomes greater than the magnetic force between magnetic body 40 and upper metal arm 44 of follower element 42 and causes the magnetic force to be broken. At this time rod 16 and magnetic body 40 travel rapidly in the downward direction and at a faster rate than the downward travel of float 26. As magnetic body 40 is traveling downward there is a point at which there becomes a magnetic attraction between magnetic body 40 and lower metal arm 46 of follower element 42 thereby causing arm 46 to rotate upwardly and open contacts 52,56 stopping the pump. The position of stops 18,20 on rod 16 may be adjusted so that different pumping ranges can be achieved. 
     This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.