US2116415A - Packless float switch - Google Patents

Description

y 3, 1938. F. SHENTON 2,116,415

PACKLES S FLOAT SWITCH Filed April 30, 1935 2 Sheets-Sheet l IN V TOR Lu .7 M Q 26 ATTORNEY May 3, 1938. SHENTO'N 2,116,415

PACKLESS FLOAT SWITCH Filed April 30, 1935 2 Sheets-Sheet 2 Patented May 3, 1938 PATENT OFFICE PACKLESS FLOAT SWITCH Francis Shenton, Waynesboro, Pa., assignor to Frick Company, Waynesboro, Pa., a' corporation of Pennsylvania Application April 30, 1935, Serial No. 19,081

4 Claims.

more particularly to float-operated switches embodying a float within a fluid-tight casing containing fluid under pressure other than atmospheric.

The invention is particularly applicable where the fluid under pressure is of a volatile character such, for example, as a refrigerant and is adapted for use particularly in steam plants 10 and chemical plants as well as in refrigerating systems.

Heretofore switches of this general character have been made which employed a shaft or rod which extended through the wall of a float chaml6 ber wherein it was necessary to seal the joint around such rod or shaft against pressure or leakage either. by packing or by constructing the same to operate. through a flexible diaphragm or bellows. In other switches of this character, the electrical switch mechanism has been located directly within the sealed casing.

Obviously constructions of the above character possess certain disadvantages or objectionable characteristics. For example, the packing around 5 the shaft or stems is subjected to wear and resulting leakage and introduces an objectionable uncertainly due to friction. between packing and the movable shaft or stem. Such friction impairs the reliability and operation of the device and re- 0 strains the free movement of the float. Further the flexible disc and bellows type sealing elements require considerable force to operate, are aifected by the pressure in the casing and subject to early failure.

casing there is involved considerable hazard on account of the likelihood of explosionof the volatile substance in case of a short-circuit or the like, or even as a result of arcing at the contacts 40 of the switch.

It is an object of the invention to overcome the objections above enumerated by providing a floatoperated switch which requires no packing and in which the hazards are removed due to location of the circuit-controlling contacts exteriorly of the casing providing the chamber in which the float is located.

It is a further object of the invention to pro- 50 vide a simple, inexpensive, commercially feasible,

durable and reliable device.

Referring to the accompanying drawings, which are made a part hereof and in which similar reference characters indicate similar parts.

55 Fig. 1 is a vertical longitudinal section through Where the switches have 35 been located in the interior of the pressure-type This invention relates to electric switches and a float switch illustrating one application of the invention;

Fig. 2, a top plan view of the casing of Fig. 1;

Fig. 3, a vertical transverse section taken at right angles to Fig. 1;

Fig. 4, a diagrammatic view. of a refrigerating system embodying the invention;

Fig. 5, a vertical longitudinal section of a modifled type of float switch;

Fig. 6 is a horizontal section of a second modi- 10 fled form of float switch;

Fig. 7, a vertical longitudinal section of the switch of Fig. 5 and Fig. 8, a detail illustrating the relationship of the magnetic plugs of the valve shown in Figs. 6 and '7. I

Referring to Figs. 1, 2 and 3 of the drawings a two-part casing 10 provides a suitable container for float mechanism. The casing ill is preferably provided with a horizontal division ii to permit assembly and to afford access to the interior of the casing. The joint I I is made pressure tight in any desired manner, for example, by means of a gasket or other sealing element. Within the casing III is located a float 12 mounted upon an arm or beam I3 pivotally supported on a pin or shaft I4. If the float I! when used with certain liquids whose level is to be controlled is not sufliciently buoyant, a counterweight l5 may be provided on the end of the beam opposite the float l2, such counterweight being adjustable on the beam and being secured in a fixed relation by lock nuts Ii.

In the preferred form of the invention as illustrated in Figs. 1, 2 and 3, a horse-shoe magnet I l is rigidly mounted upon the beam I! in a manner to swing with the beam around the pivot H, the arc described by the magnet when it is swung being dependent upon the amount of raising and lowering of the float [2. The horseshoe magnet I! is clamped in place by a clamping block il' rigidly fastened to the beam l3 by screws ii. For cooperation with the poles of the horse-shoe magnet H at each extremity of its swing, two pairs of plugs iii of low reluctance and negligible residual magnetism are provided by means of which a pendulum switch element pivoted at 20 is oscillated for making and breaking contacts at each extremity of its swing. .This pendulum switch element comprises a body of nonmagnetic material formed with a relatively large flat base and a narrow upstanding neck located centrally at the base. At each side of the pivot 20 the base is provided at its underside with magnetic keeper strips 22 so that when one set of plugs is magnetized by the horse-shoe magnet engaging the same the adjacent keeper strip 22 is attracted, swinging the pendulum in one direction and when the magnet ermages the opposite set 01' plugs the pendulum is swung in the opposite direction. On the upper end of the pendulum is carried a bracket with contacts 23 which close a circuit through two pairs of spaced contacts 24 from which extend conductors 24.

The switch mechanism is enclosed within a housing or casing 25 located exteriorly of the housing or casing l0 and provided with a cover glass 26 and is held in place by jam nut 21. The casing 25 has interposed between it and the easing ill, a nonmagnetic member 31 in which the plugs l8 are mounted, the casings 25 and I0 being fastened together by means of bolts or other fastening elements 38 which extend through the nonmagnetic member 31. The above-described construction is susceptible to use in varied relationships as for example, in a refrigerating system in whicha valve or other element is operated in accordance with liquid level within a chamber such for example, as an accumulator, such chamber being in communication with the casing II) bymeans of passages 28 and 29 to permit free flow of fluid into and from the casing 10. v

In the operation of the switch it will be noted that as magnet I'l approaches plugs l8, as on an increase in fluid level, the magnet will reacha certain point and then snap into engagement with the plugs which is caused by the magnetic attraction, which is due to the fact that the magnet is carried in a balanced state by the float members and the magnetic attraction causes a slight unbalancing thereof as will be apparent. When the poles of the magnet so engage the plugs the keeper strip 22 is attracted in the same manner so that the switch contacts areclosed with a snap action. Again when the fluid level lowers the magnetic attraction tends to maintain the magnet in engagement with these plugs so that the switch will remain closed until the fluid level has lowered sufficiently so that the weight of the float members in the unbalanced state is suflicient to separate the magnet from the plugs. At this time the magnetic attraction transmitted through the plugs to the keeper of the switch is removed and the switch member'is free to open its contacts. In the arrangement shown in Figs. 1 to 3, when the fluid level decreases magnet I? will cooperate with the other magneic keeper throughthe other set of plugs l8 in a similar manner.

It will thus be seen that this retarded action permitted by the float is such that a positive closing action and maintenance of engagement of the switch contacts is afforded which may be relied upon for the operation of the control circuits afiected thereby.

A system of this character is shown in Fig. 4 wherein a compressor 10 is arranged to supply refrigerant to an evaporator H from which liquid and gaseous refrigerant flow to an accumulator or separator 12. The float switch I0 is arranged to be responsive to the liquid level in the accumulator l2 and may be connected to electro-responsive valve 13 in the supply line adjacent expansion valve 14 for shutting oiT the supply of refrigerant from the compressor or condenser to the evaporator I l.

Referring to Fig. a two part float casing 40 similar to the casing of the preceding figures is provided with fluid inlet and outlet openings 4i and 42. .Within the casing 40 is a float l2 mounted upon the beam l3 pivoted at M, said beam being provided with a counter-weight 55 held between lock nuts It as previously described. A horse-shoe magnet I1 is mounted upon the beam l3 by means of a pin and slot connection, the pin l3 being carried by the beam and the slot 44 being formed in a plate 45 carried by a rod 48 which connects the plate with the horse-shoe magnet Il. With this construction the horseshoe magnet is caused to reciprocate vertically and is adapted to contact two magnetic plugs ll when the magnet is'in its uppermost position. The plugs l8 are mounted in a nonmagnetic member 41 upon which is mounted a keeper beam 30 which is attracted by the magnet to oscillate a switch element 48 pivoted at 49 against the action of a spring 50 which tends to hold the switch element on the free end of the switch arm in its .lowermost position. The switch element engages contacts 5| and 52 from which extend conductors 53 and 54 through one of which and the conductor 55 extending to the switch arm 49, the circuit is completed. The pin and slot connection provides a connection to permit variations in the float operation due to difference in liquid levels.

In Figs. 6 and 7 is illustrated a construction similarto that shown in Fig. 5 except that instead of the horse-shoe magnet being reciprocal vertically or endwise it is rotated to bring its extremities into engagement with plugs it which causes a keeper bar to be attracted to oscillate the switch arm as in Fig. 5. In this embodiment of the invention a casing 60 is provided in which the float I2 is mounted upon a beam l3 pivoted upon a supporting member 6| accessible through an opening in the casing closed by a plug 62 pressing against a spring 63 by means of which the member 6| is held against the end of the magnet H. The magnet is provided with a pin 54 which extends into an opening in the beam 13 so that when the beam raises or lowers the magnet will be oscillated about the member 6|. The magnet is supported in a bearing member 66 of nonmagnetic material. The housing or casing of the float is provided with openings 61 and 68 for the inlet and discharge of fluid as previously described.

In eachof the embodiments of the invention it will be readily apparent that the magnetic attraction of the movable switch element will cause it to operate with a snap action.

In operation the horse-shoe magnet I1 is rotated by the float l2 and when the ends of the magnet are in contiguous relation to the magnetic plugs Hi, the magnetic circuit is completed through the plugs and the keeper is drawn towards the plugs and the switch is snapped into one position. When rotated away from such a position the switch is snapped to the opposite position by means of the spring.

It will be obvious to those skilled in the art that various changes may be made without departing from the spirit of the invention and the invention is therefore not limited to what is shown in the drawings and described in the specification but only as indicated in the appended claims.

I claim:-

1. In a float operated switch for use with an electrically operated valve, means for controlling the flow of a fluid in response to liquid level, said means comprising a float chamber, a float in said chamber, a horse-shoe magnet movable by said float within said casing, two pairs of magnetic low reluctance plugs extending through said casing as stops between which the polesof said horse-shoe magnet reciprocate and with which they cooperate, said plugs also limiting both the up and down movements of the float, and movable switch elements without said casing operating through said plugs by the magnetic field created 5 by the horse-shoe magnet when in a predetermined pofltion.

2. For use with an electrically operated valve, a float-operated switch for controlling the operation of said valve, said float-operated switch comprising a casing, a float within said casing, a sensitized magnetic member in said casing operated by said float, spaced elements of low magnetic reluctance extending through the casing as stops limiting the movement of the magnetic member within the casing, and both the up and down movement of the float, and a magnetic member without said casing operated by said sensitized magnetic member through the last said element.

3. A float switch and operating means therefor comprising a casing, a float within said casing, magnetic means moved by said float, a switch located exteriorly oi said casing, said switch having spaced magnetic elements adapted to be alternately attracted by said magnetic means for shifting the switch, and spaced elements of low reluctance extending through said casing and projecting inwardly thereof as stops adapted to be alternately engaged by said magnetic means, limiting both up and down movement of the float, and correspondingly cooperating with said magnetic elements for eflecting positive operations of the switch.

4. In an electric float switch, an operating means therefor comprising a fluid chamber, a float in said chamber and an electric switch located exteriorly of said chamber and comprising a fixed contact, a movable contact pivotally mounted and swingable into and out of engagement with the fixed contact for making and breaking an electrical circuit, said movable contact being arranged to be normally influenced by gravity to open circuit position or closed circuit position, and a magnet for operating said movable contact in accordance with the level of the liquid.

FRANCIS SHENTON.

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