US2500704A - Switch mechanism with wire armature - Google Patents

Description

C. C. RENNECAMP SWITCH MECHANISM WITH WIRE ARMATURE March 14, 1950 Filed Dec. 4, 1946 T f 6 Z 9 M a Z 3 mm 5 a, 5 w a Patented Mar. 14, 1950 SWITCH MECHANISM WITH WIRE ARMATURE Clarence C. Itennecamp, St. Louis, Mo., assignor, by mesne assignments, to Missouri Automatic Control Corporation, a corporation of Missouri Application December 4, 1946, Serial No. 713,957

2 Claims.

This invention relates to switch mechanisms and more particularly to switch mechanisms actuated by temperature or pressure responsive devices and including magnetic means which acts to provide a snap action in both closing and opening movements of the switch.

In mechanisms of this character the relationship of the armature to the magnet when in an attracted position is extremely critical because it determines the minimum difl'erential in a condition which will cause the switch to be moved from an open to a closed position and vice versa.

In the usual construction of armatures of'this type in which flat surfaces of extended area are presented to a flat surface of the magnet, any slight non-parallelism or irregularity of the surfaces occurring in manufacture, assembly or in adjustment will alter the magnetic pull an therefore the differential.

Because any variables due to such surface irregularities or non-parallelism are greatly multiplied as the distance between armature and magnet are decreased, it is customary to provide stops for definitely spacing the armature from the magnet when in its attracted position.

'It is an object of the present invention to provide a new and improved switch mechanism adapted to economical and uniform manufacture.

A further object is to provide a switch mechanism incorporating an improved two direction magnetic snap action device having substantially point contact between magnet and armature.

A further object is to provide a novel and imspherical contacting surfaces spaced from the rial and has mounted thereon switch terminal connectors 4 and I5. The connectors have riveted thereto flexible switch blades l5 and I1 respectively, which in turn carry contacts l8 and i9 respectively. A cover fits over the frame Ill, its open side resting against the front plate members [i and I2.

Pivoted on a pin 2| which is supported in the side walls of frame member III are a differential lever 22 and a primary lever 23. Lever 22 has a forked outer end 24 extending between a fixed stop 25 and the adjustable collar 26 on the threaded member 21. Lever 22 is further provided with a right angularly formed portion 28.

center of mass of the armature and arranged to alternately contact the magnet.

the following description and accompanying drawing referring to which:

Fig. 1 is a front view of a switch mechanism constructed in accordance with the present invention.

Fig. 2 is a longitudinal section taken on line 2-2 of Fig. l.

Fig. 3 is a transverse section taken on line 33 of Fig. 1.

Figs. 4, 5 and 6 are enlarged detail views of the armature.

In the drawing reference numeral ill indicates a channel shaped frame member having attached thereto front plate members i l and I2.

The front plate members are attached to the channel frame by the four peened over projections l3. Plate member ii is of insulating mate- The lever 23 also has a right angularly formed portion 29 at its outer end. Lever 23 is urged in a clockwise direction by actuation spring 30.

A secondary lever generally indicated at 3| is provided at one end with right angularly formed portions 32 and 33 parallel to the formed portions 28 and 29 of levers 22 and 23. Lever 3| is connected to levers 22 and 23 by thin flexible strips 34 and 35. These strips 34 and 35 perform the function of pivoted links and have the advantage of eliminating any lost motion incident to the necessary tolerance in fitting and journaling link pivots. Lever 3| includes an intermediate portion 35 of insulating material and a flexible free end portio 36a.

Lever 3| carries at its free end, an armature generally indicated at 31, preferably formed of round wire of magnetic material and having the general shapepf a block letter S. A loop 38 formed at the end of the upper horizontal leg facilitates suitable attachment to the outer end of lever 3| by a bolt 39. A bar magnet 40 supported in an insulator block 4| has one end pro- .jecting betweenthe intermediate and lower horizontal legs 42 and 43 of the armature. The magnet supporting block 4| is attached to the base of frame l0 by inserted rivets 44.

In order to space the main mass of legs 42 and 43 from the magnet when either are in the attracted position, and in order to provide a flux path between the main mass of the armature legs and the magnet, a pair of inwardly formed V- shaped projections 45 and 46 are provided. The points of the V's, 45 and 46 are rounded with a radius approximately equal to the diameter of the wire, resultin in a substantially spherical point.

Lever 3| also carries at the outer end of its insulator section 35 a screw 41 which under certain conditions bears against the outer end of switch blade ll thereby to open the contacts I I and II.

There is a stud ll extending thru an opening II in lever 22, an opening 50 in lever 22, and an opening ii in the base of frame ll. Stud 4| threadedly engages an adjusting nut |2 at one end and at its opposite end abuts the displaceable wall or diaphragm 52 of a solid charge type condition responsive element generally indicated at N. Element 54 further includes a rigid cup shaped member 5| having a flange H and a capillary tube 51 which communicates with a bulb (not shown) located in the conditioned area. Element 54 is securely fastened to the base of frame In by screws 58. Cover member 2| and a mounting bracket 59 (shown in part) are also secured to the base of frame III by screws ll.

Adjusting nut 52 is guided for free axial and rotary movement in a washer H which i mounted in front plate l2, The outer end of nut 52 has an indicator dial 50 attached thereto and a spring 6i having one end bearing against the end of stud 0 and its other end bearing against the nut 52 thru an intermediate washer 62 provides increased friction for retaining adjusted positions. The opposite or inner end of nut 52 engages a pair of projections 62 on the primary lever 2|.

A return spring it having one end bearing against the base of frame In and its other end against a collar 65 on stud I! normally urges the stud and nut 52 toward the left (in the drawing) and therefore urges lever 22 in a counterclockwise direction. Spring 64 is sufllciently stronger than spring 30 to readily overcome. it.

Operation The switch mechanism shown in the drawings operates upon an increase in temperature or expansion of the solid liquid charge in the element 54 to close a circuit, as would be required in refrigeration service wherein the closing of contacts Ill and I9 would complete an energizing circuit for a compressor or the like. It will be noted however, that by simply switching the connections of the levers so that angularly formed portion 33 of lever 3| is connected to lever 22 at 29 and portion 32 is connected to lever 22 at 2| instead of the way shown, the mechanism would then operate to open a circuit upon an increase of temperature as would be required for a space heating control.

As shown in the drawings the mechanism is in a circuit closing position, to which it is moved under the urging of spring 30 upon sufficient expansion of element 54. The outer end of arm 3| is in its leftwardmost position, Fig. 2, screw 41 having been moved leftward sufficiently to permit the closing of contacts I8 and I! by the spring action of switch blade IT. The outer end of lever 22 bears against the collar 26 of differential adjusting screw 21 and horizontal leg 42 of the armature 31 is in contact with magnet 40 thereby holding the outer end of arm Si by magnetic force.

Upon a decrease in temperature resulting in a contraction of the solid liquid charge, return spring 64 will act to cause stud l8 and nut '52 to move leftward following the movement of diaphragm 53. This movement will cause a counterclockwise rotation of lever 23 about its pivot 2i, and it will carry with it the connected end of lever 3| and therefore the outer end of lever 22 until the outer end of lever 22 abuts the fixed 4 stop 2| which is the limit of the adjustable lostmotion differential.

During this first phase of the switch opening movement, that Ls until the outer end of lever 22 abuts the stop 2|, the lever 21 pivots about the ball point of armature leg 42. Continued decrease in temperature and therefore further counterclockwise rotation of lever 22 after contact has been made with stop 2| will'cause the connector strip 2| to flex, and as a result the outer free end of lever II, to swing toward the right. During this latter phase of the opening movement, however, and until a critical point is reached wherein the magnetic attraction of leg 42 of the armature is overcome. it will be seen that energy is stored in the flexible outer end portion Ila of lever II. This energy initiates a snap action of the outer end of arm II in a rightwardly direction and provides a carry over to the point where leg 43 of the armature is moved into a sumciently strong magnetic field to complete the opening movement.

It is desirable in many types of service that the mechanism operate from a switch open to switch closed position upon a very slight change in temperature, often as slight a differential as 2 F. In the mechanism shown the resulting movement of stud 2| due to volume change of the solid liquid charge for a temperature change of 2 F., would be between one and two thousandths (.001 and .002) of an inch. With this in view it will be readily appreciated that even slight variations in the magnet and armature relationship from unit to unit will appreciably affect the uniformity of manufacture with respect to minimum operating differential.

In the armature construction shown, slight lateral or longitudinal tilting with respect to the face of the magnet is not reflected in any measurable variation of operating differential. In this construction there is provided a rounded point contact between armature and magnet and a means for spacing the main mass of the magnet from the main mass of the armature which lends itself admirably to uniform and economical manufacture. This spacing means being of magnetic material provides a flux path between the main mass of the armature and the magnet.

()bviously, numerous modifications of the principles of this invention will occur to those skilled in the art. For example, the magnet itself may be provided with projections having ends with reduced area for contact with flat surfaces of an armature.

The exclusive use of all such modifications within the scope of the appended claims is contemplated.

I claim:

1. For use in a device of the class described, a movable armature constructed of round wire and having a portion thereof formed in a general U shape a bar magnet disposed between the parallel legs of said U-shaped portion, each of said parallel legs havingan inwardly formed V- shaped projection adapted to contact said magnet as said armature legs are alternately moved toward it, whereby the main mass of said armature portions are spaced from said magnet and whereby substantially point contact is made.

2. For use in a device of the class described, a movable armature constructed of round wire having the general form of a block letter 8, a bar magnet disposed between the lower horizontal legs of said armature, the upper horizontal leg of said armature having an attaching eye formed at its open end, and each of said lower horizontal UNITED STATES PATENTS legs having a. portion formed in a 'generalV- shape with its apex toward said magnet, whereby Number Name Date substantially point contact is made between said 649,102 Flechtenmacher y 8, 1 0 magnet and said armature'as the lower horizontal 5 1,725,255 Claytor 1929 legs thereof are alternately moved toward said 1,946,261 Zupa 6, 1934 magnet. 2,145,950 Persons Feb. 7, 1939 CLARENCE c, RENNECAMR 2,29 ,502 Persons July 28, 1942 2,353,075 Rennecamp July 4, 1944 REFERENCES CITED 1

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