US2315960A - Circuit controller - Google Patents

Description

April 6; 1943.

F. w. HOTTENROTH, JR

CIRCUIT CONTROLLER Filed Oct. v51. 1941 I Inventor FredetiCkW. Hottehroth J11,

WW/ 612M His Attorney.

Patented Apr. 6, 1943 UNITED STATES" PATENT OFFICE I Frederick N. Y.,

assignor to GeneralElectric Company, a corporation of N ew York application October 31, 1941, Serial No. 417,286

, 9 Claims. (Cl. 2 83)- My invention relates to circuit controllers and particularly to electric switches having contacts operable with a snap action.

It is common practice in the control of small In carrying out my invention I provide a movable switch member comprising a 'pivotally mounted rigid base portion and a relatively long and substantially rigid contact arm flexibly atactuating bellows of the type commonly used motors, suchas refrigerator motors and the like, 5 tached thereto. To obtain the desired weld to provide control switch contacts which open and shearing action the contact arm is so arranged close with a snap action. It is also .known to that in its contact closing position it is angulararrange such contacts to open and close with a ly disposed with respect to a line between the piv-' sliding or wiping action for the purpose of 0t and the fixed contact. The free end of the breaking any weld which may occur at the concontact arm carries a magnetizable armature and tacts upon the closing thereof. In such arrangeamovable contact member positioned closely adments, the actionoi' the movable contact in the jacent to each other. A snap action magnet opening direction is usually the same as its action is disposed near the contacts for cooperation with in the closing direction with the order of operathe armature. When the .rigld base portion 01' tion simply reversed; that is, if wiping action is such a switch member is positively rotated in the present in opening it is also present in closing. switch opening directionpas by an expansible However, it has been found that l! electric cirthermostatic me be t e armature and magnet cuit controlling contacts are closed with a simulwill prevent disenga ement ithe nta s dur ng taneous closing and sliding movement, the slidin initial rotation of the rigid member, and the conmovement causes bouncing oi" the movable co tact arm and movable contact will be constrained tact upon the stationary contact. Such bouncing to slide longitudinally without bowing or other results in recurring arcing and ultimate welding lateral movement, the flexible connection being as the contacts come to rest in pools or molten deformed during this movement. When summetaL' A gentle closure with minimum slide or cient force to overcome the magnetic attraction no slide generally produces good results, ior, while v h s e n built p by deformation 01' the flexible it does not necessarily avoid welding, it does minconnection, the armature will be released and the imize contact bouncing and prolonged arcing.- switch arm rotated suddenly about the flexible Upon opening of the contacts,however, an enconnection to disengage the contacts. Upon retirely diilerent action is necessary in order to turn movement of the rigid base member and the ensure the breaking of any weld which may have flexibly connected switch arm toward the conoccurred upon the closing of the contacts. In I tact closing p si i n, 8 p n W l. be r h d opening it is desirable that a strong transverse where the force or ma n attr cti n l e force be available for positively sliding the con suflicient to draw the contacts into engagement tacts relative to each other prior to their separawith a snap action, the contact arm pivoting tion in order to shear a weld. 5 about the flexible connection so that the contacts Accordingly, it is one object of my invention to are engaged without sliding movement. provide an electric switch which shall have a dif- For a more complete understanding of my in- Xerent contact action in closing than in opening, vention and a further appreciation of its objects each action being specifically adapted to thelparand advantages, reference should now behad to ticular condition of operation. I 4 the following detailed specification taken in con- It is a 'i'urther object of my invention to pro- Ju c io with the o panyin drawin i vide an electric switch having a strong wiping or which Fig. 1 is a side view of a thermostatic weld shearing action at the contacts prior to the switch embodying my invention in one form; .Flg. separation thereof. 2 is a sectional view taken along the line 2-4 of It is a still further object of. my invention to .45 Fig- 1; Fig. 3 is 9- sectlon l v ew taken 1 8 the provide an electric switch contact which shall :be line 33 of Fig. 1; Fig. 4 is a detailed View of my separated with a snap .action preceded by a strong switchmembel' in 8 circuit Opening P o an wipin action, 1 Fig. 5 is a multiple diagrammatic view of my It is a further object of my invention to proswitch member illustrating sequentially the opvide an electric switch contact which shall have 5 crating positions of the switch member in circuit no wiping action upon engagement of the conopening and circuit closing operation. tacts,.but which shall have a strong wiping ac- Referring now to the drawing, I have illustion upon disengagement thereof to shear any trated my invention as applied to a temperature weld which may have been formed upon engage- 4 responsive control device having an expansible ment. 66

for the control of the domestic and other mechanical refrigeration systems. The control device comprises a housing III of suitable insulating material, such as a molded plastic compound, forming a support for mounting a movable switch member II and an expansible thermo-responsive actuating bellows i2. The expansible bellows I2 is filled with an expansible fluid and is connected by means of a conduit i3 to a fluid-filled bulb (not shown) which may be disposed as desired in a space to be cooled. Preferably the expansible fluid system including the bellows I2 is of the partial vapor type in which the charge is gaseous at normal room temperature and is condensed to a greater or less degree in accordance with the temperature maintained in the refrigerator, thereby to reduce the pressure within the bellows i2. Methyl chloride is a suitable fluid for such a system. Mounted in opposing relation to the thermostatic bellows I2 is an adjustable compression spring I3 having one end seated against a pivotally mounted switch actuating lever l3 and having its other end seated in a cup I 3 which is adjustably mounted upon a manually operable threaded shaft l1. The shaft l1 extends through the front wall of the casing i3 and is secured against longitudinal movement relative thereto. A control knob i3 is provided at the outer end of the shaft IT. The actuating lever i3 is pivotally mounted upon a fixed pivot l3 and carries an annular cup or washer 23 formed of suitable insulating material such as a phenolic condensation product. The cup 23 is shaped to provide a fulcrum for the movable end of the expansible bellows i2, as described and claimed in Patent 2,050,883, issued to John 18. Ford on August 11, 1936. The opposite end of the expansible bellows I2 is fixedly mounted within a dome-like casing 23 which is firmly attached to the casing 3. The pivoted actuating lever l3 includes 8. depending lip 23 arranged for engagement with a boss 21 formed on one side of the casing l3 thereby to provide stop means for limiting the expansion of the bellows l2.

Fixedly mounted upon one side of the casing closely adjacent each other I also provide a stationary contact 23 and a snap actionmagnet 23. For convenience these elements are shown attached to a block 23a of insulating material which is in turn attached to the casing l3. The contact 23 is mounted upon a short cantipositioned by means of a bolt 33 passing through the casing l3 and block 230 and having its head portion positioned to be accessible from the outside of the casing. V

In order to obtain a strong coercive force while limiting the physical proportions of the magnet 23, I prefer to use for the magnet an alloy comprising six to fifteen per cent aluminum, twelve to thirty per cent nickel, five per cent copper if desired, and the remainder of iron, such as described and claimed in Patents 1,947,274 and 1,968,569, issued on February 13 and July 31, respectively, 1934, to William E. Ruder.

The movable switch member comprises a rigid base portion 3| pivotally mounted upon a fixed pivot 32 and flexibly connected to a, substantially rigid contact arm'33, 33. The contact arm comprises a leaf spring 33 and a substantially rigid magnetizable armature 33. The

spring 33 is connected at one end to the rigid base portion 3| of the switch member and carries at its other end a movable contact 33 arranged to engage and disengage the fixed contact 4 lever spring strip 29 which may be adjustably The contact 33 is mounted upon a pin 34a. The armature 35 of magnetic material extends for nearly the full length of the contact arm, and is attached to the spring 33, as by a rivet 33, at a point close to the rigid base member 3|. The armature 35 is apertured at its lower end and the pin 33a passes loosely therethrough so that the lower end of the armature is loosely embraced between the spring arm 33 and the contact head 33. With this construction the spring arm 33 is maintained relatively inflexible between the rivet 33 and the contact 33, and this portion oi the spring acts only as a follow-up spring for the contact. The small length of spring between the rivet 33 and the rigid base member 3| serves as a flexible connection 31 between the rigid base member and the contact arm assembly.

It will be observed that the contact arm 33, 33 is connected to the rigid base member 3| in such a manner that the contact arm in its contact closing position is disposed in non-parallel relation with respect to a line drawn between the fixed contact 23 and the fixed pivot-32. In the particular form illustrated the contact arm 33, 33 is relatively long and, when in contact closing position, lies in a plane substantially perpendicular to a line normal to the contact surfaces at their point of engagement, while the distance from the pivot pin 32 to the point of attachment of the spring 33 to the member 3| is relatively short, the contact arm being substantially perpendicular to a line from the pivot pin to the point of attachment. With this disposition of parts the initial movement of that portion of the rigid base member 3| to which the contact arm 33, 33 is attached is in a direction perpendicular to the normal through the contact surfaces at this point of engagement. By this means in combination with th magnet and armature a strong and positive sliding movement of the contacts is insured prior to their disengagement. By the term substantially rigid" when used in connection with the contact arm 33, 33 I mean an arm which is sufficiently rigid to prevent bowing before it is released by the snap action magnet 23. Thus, since the armature 33 will not bow away from the magnet 23 during the initial opening movement, a predetermined air gap and hence the desired snap action may be maintained despite a slight bowing of the follow-up portion of the spring 33. While the portion of the spring 33 between the rivet 33 and the contact 33 may, if desired, be sufficiently strong to break a weld without the assistance of the more rigid armature 33, its bowing action is strictly limited by the pin connection 340 even if the spring itself does not resist bowing. Furthermore any bowing of the spring 33 does not aflect the air gap between the armature 33, and the magnet 23. The principal function of the follow-up spring is to preclude reduction of the contact pressure to zero at any time even though opposing forces on the armature 33 be exactly balanced. With such an arrangement, fluttering of the contacts and arcing during opening are prevented. The armature 33 is so arranged "that it never engages the magnet 23.

The rigid base portion 3| of the switch member i also includes a rigid arm 33 which extends toward the control knob I3 and has a depending portion (not shown) arranged to engage a stop formed integrally with the knob l3, thereby to limit the rotation of the knob to one complete revolution and to provide means for positively separating the contacts N and 34 in one position of the control knob.

The movable switchmember H is shown at Fig. l and at position a of Fig. in the .completely relaxed position which it assumes when there is no weld formed at the contacts 24, I4 and when the actuating lever i5 is moved en tirely out of engagement with the rigid base portion 31 of the switch member, as by full expansion oi the bellows it until the lip 26 engages the stop 21. The biasing force exerted by the magnet "8 upon its armature 35 is sumcient to bring the switch member to this position whenever the lever i5 becomes disengaged therefrom. Since the contacts are engaged in this position, the refrigerating system to which the controller is connected will be operating to cool the fluid in the bellows l2. Cooling and contraction oi the fluid will permit the spring ll to rotate the actuating lever II in a clockwise direction, as viewedin the drawing, until its end engages the rigid base portion 3| of the switch member. Further contraction of the bellows will produce rotation of the rigid base portion II of the switch member about the pivot pin 32. Due to the arrangement of parts as previously described, the

respect to a line drawn between the flxed pivot 32 and the flxed contact 24, the initial movement of that portion of the rigid base member II to which the contact arm 88, 35 is attached is in a direction substantially transverse to the contact surfaces, so that the contact arm 33, 35 and the movable contact 84 are initially moved longitudinally and downward as viewed in the drawing. During this initial movement, as between the positions a and b of Fig. 5, the attraccontact arm 83 being angularly disposed with g the force oi magnetic attraction during such movement. For the purpose of illustration, it may be assumed that when the rigid member 3| reaches position b of Fig. 5 suflicient force has built up by deformation of the flexible connection 31 to overcome the magnetic attraction between the permanent magnet 28 and its armature 35. At this instant the magnet will release its. armature and the contact arm ll, 85 will spring suddenly from position b of Fig. 5 to position 0 oi Fig. 5. During this snapping movement the rigid portion ll of the switch member experiences no substantial change in position, so that the contact arm 33, 35 pivots about a'point in the region of the flexible connection 81. Since the flexible connection 31 is substantially in a asviewed in Fig. 1. The magnetic biasing force exerted upon the switch member ll constrains the switch member to clockwise following movement while engaging the lever ID. If such clockwise rotation is begun from the position 0 of Fig. 5, the switch member II will move as a unit to a predetermined position such as position it of Fig. 5. Let it now be assumed that when the switch member reaches the position d of Fig. 5 the attractive force between the snap action magnet 28 and the armature 35 is suflicient to attract the armature and contact arm despite the bias of the flexible connection 31. Thus by mag netic attraction the armature I5 and spring 31 will be moved almost instantaneously from the position d to the position e of Fig. 5 while the rigid base portion ll of the switch member experiences no substantial change in position. It will now be observed that the contact engaging movement of the switch arm is carried out by rotation of the switch arm about the flexible connection I1 and consequent deformation oi the flexible connection. Since the connection 81 lies substantially in the plane of the switch arm, the contacts are engaged without sliding movement.

If no weld is formed at the contacts at the instant of closure indicated at position 6 oi Fig. 5-, continued clockwise rotation of the rigid base member Si by the magnet 25 will cause the movable contact to slide longitudinally upward as viewed in the drawing to position a of Fig. 5. For the purpose of illustration, however, let it be assumed that as soon as the movable contact 34 arrives at position e oi. Fig. 5 a weld is formed between the contacts. Such a weld will hold the movable switch member II in position e c! Fig. 5 even though the bellows i2 continues to expand and disengages the rigid portion ll of the switch member because the attractive iorce of themagnet is ordinarily insufllcient to break a weld. Since the contacts are now engaged, however, the reirigerating system will be in operation to cool the conditioned space and the bellows I! will eventually contract until the actuating lever I! again enga'ges the rigid base portion ll oithe switch member.

Cohtinued contraction of the bellows will permit the spring to move the lever II and to rotate the rigid base portion 3! of the switch member about the fixed pivot 32. As previously described in connectionwith an initial switch opening operation, the rigid member 3| will be rotated to the position b oIFig. 5 before the force exerted by the flexible connection 31 is suflicient to overplane drawn perpendicular to the normal to the contact surfaces at their point of engagement,

the contacts are disengaged by movement of the movable contact substantially along the normal. thereby to avoid sliding movement in the actual contact disengaging motion.

With the contacts 24 and N disengaged the refrigerating system will be out of operation and the temperature of the conditioned space will increase. The resulting increase in the temperature of the fluid'contained in the bellows l2 will cause the bellows to expand and rotate the actuating lever II in a counter-clockwise direction come the attraction between the magnet 20 for its armature 35. Comparison of positions b and e of Fig. 5 will show that in position b the rigid base member is displaced in a counterclock wise direction with respect to its position e and the movable contact 34 is displaced downwardly with respect to its location at position c. This difierence between the contact engaging and contact disengaging positions of the movable switch member results from the fact that the holding force of magnetic attraction in the armature 35 is considerably greater when the contact arm is in its circuit closing position and the I position e to position b prior to their separation is insured even though the contacts may have welded upon closure and prevented complete relaxation of the flexible connection 31 by the magnet.

While I have shown and described but one preferred embodiment of my invention by way of illustration many other modifications will occur to those skilled in the art, and I therefore wish to have it understood that I-intend by the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure Letters Patent of the United States is:

1. A circuit controller comprising a fixed contact, a switch member having a rigid base portion rotatably mounted upon a fixed pivot and movable between circuit opening and circuit closing positions, a substantially rigid contact arm carrying at one end a movable contact and having its other end flexibly connected to said rigid base portion, said contact arm in the circuit closing position of said switch member being disposed in non-parallel relation with respect to a line passing through said fixed pivot and said fixed contact, means for rotating said rigid base portion of said switch member to said circuit opening position, and snap action means for releasably retaining said contacts in engagement during a predetermined initial rotation of said rigid base portion and for re-engaging said contacts with a snap action, whereby disengagement of said contacts is necessarily preceded by relative sliding movement and said contacts are re-engaged without substantial wiping action.

2. A circuit controller comprising a fixed contact, a switch member having a rigid base portion rotatably mounted upon a fixed pivot and movable between circuit opening and circuit closing positions. a substantially rigid contact arm carrying at one end a movable contact and having its other end resiliently connected to said rigid base portion, said contact arm in thecircuit closing position of said switch member being disposed in non-parallel relation with respect to a line passing through said fixed pivot and said ,fixed contact, means for rotating said rigid base portion of said switch member to said circuit opening position, and snap actionmeans for releasably retaining said contacts in engagement during a predetermined initial rotation of said switch member to ensure relative sliding movement of said contacts prior to disengagement and for re-engaging said contacts without substantial wiping action.

3. A circuit controller comprising a fixed contact and a movable contact having engaging surfaces, a movable switch member comprising a rigid base portion and a substantially rigid contact arm flexibly connected at one end to said rigid base portion, said contact arm carrying at its other end said movable contact and being so disposed when said contacts are engaged that it lies in a plane substantially perpendicular to the normal to said surfaces at their point of engagement, said rigid base portion being pivotally mounted upon an axis substantially parallel to and displaced from said plane, means for rotating said rigid base portion to disengage said contacts, and magnetic means for releasably retaining said contacts in engagement during a predetermined initial rotation of said rigid base portion and for reengaging said contacts with a snap action, whereby disengagement of said contacts is necessarily preceded by relative sliding movement along a line parallel to said plane and said contacts are reengaged without sliding movement.

4. A circuit controller comprising a fixed contact and a movable contact having engaging sur- 15 faces, a movable switch member comprising a rigid base member and a substantially rigid contact arm carrying said movable contact at one end thereof, said contact arm being so disposed when said contacts are in engagement that it lies in a plane substantially perpendicular to the normal to said surfaces at their point of engagement, said rigid base member being rotatably mounted upon a fixed pivot and having a portion movable in a direction substantially parallel to said plane, flexible means for connecting said contact arm to said portion of said rigid base member, magnetic means operable in conjunction with said contact arm to bias said contacts into engagement, and actuating means arranged to move said rigid base member to engage and disengage said contacts, whereby rotation of said rigid base member to disengage said contacts will slide said movable contact relative to said fixed contact and deform said fiexible means until said as magnetic means releases said contact arm with a snap action thereby to disengage said contacts by rotation of said movable contact about said fiexible means and rotation of said rigid base member to reengage said contacts will permit said magnetic means to attract said contact arm with a snap action and reengsge said contacts without sliding movement.

5. A circuit contrbller comprising a support, a fixed contact mounted upon said support, a permanent magnet mounted upon said support ad- Jacent said fixed contact, a movable switch member comprising a rigid base portion rotatably mounted upon a fixed pivot and a substantially rigid contactarm carrying at one end a movso able contact arranged to engage said fixed cmtact, spring means for connecting the other end of said contact arm to said rigid base portion of said switch member. said contact arm being disposed in nonparallei relation with respect to a line passing through said fixed pivot and said fixed contact when said contacts are in engagement, an armature of magnetic material mounted upon said contact arm adJacent said movable contact and operable in conjunction with said permanent magnet to bias said contacts into engagement, and actuating means for rotating said rigid base portion in a direction to place said rigid contact arm under longitudinal compression and to disengage said contacts.

.6. A pressure responsive switch comprising a support, a fixed contact mounted upon said support, a permanent magnet mounted upon said support adjacent said fixed contact. a movable switch member comprising a rigid base rotatably mounted upon a fixed pivot, a substantially rigid contact arm carrying at one end a movable contact having a contact surface arranged to engage and disengage said fixed contact, said contact arm being so disposed when said contacts are in engagement that it lies in a plane substantially perpendicular to the normal to said surface at its int of engagement with said fixed contact, said r gid base having a portion lying substantially within said plane and said fixed pivot being disposed substantially parallel to and displaced from said plane, deformable spring means for connecting said contact arm to said portion of said rigid base, an armature of magnetic material mounted upon said contact arm adjacent said movable contact and arranged in combination with said permanent magnet to bias said contacts into engagement, an actuating element arranged to engage said rigid base, adjustable spring means for mov ing said actuating member to rotate said rigid base in a direction to disengage said contacts thereby to move said contact arm longitudinally in said plane while said magnet prevents disengagement of said contacts and simultaneously to deformsaid spring means, said magnet being arranged to release said armature after a. predetermined deformation of said spring means thereby to disengage said contacts by rotational movement of said contact arm about said spring means, and pressure responsive means opposing the action of said adjustable spring and arranged upon increase in pressure to disengage said actuating element from said rigid base member.

7. A circuit controller comprising a pivoted operating arm, an elongated rigid member including an armature, a flexible spring member connecting one end of said rigid member to said arm so that said rigid member extends substantially at right angles to said arm, a movable contact operated by the other end of said rigid member, a

stationary contact, a magnet cooperating with said armature so as to snap said movable contact into and out of engagement with said stationary contact, said spring member being flexed by the force of said magnet to provide for engagement of member having one end connected to said sprin member at a point adjacent said arm so as to provide a portion of said spring member between said point and said arm, a magnet cooperating with said armature so as to snap said movable contact into and out of engagement with said stationary contact, said portion of said spring member being flexed by the force of the magnet to provide for engagement of said contacts without substantial wiping action between them and upon opening movement of ,said operating arm said portion of said spring memberflexing to provide for a wiping action between said contacts prior to separation of said contacts.

9. A circuit controller comprising a pivoted operating arm, a flexible spring member connected at one end to said arm at a point spaced from the pivot of said arm so as to extend substantially at right angles to said arm, a movable contact on the other end of said spring member, a stationary contact, an armature member extending in lengthwise engagement with said spring member having one end connected to said spring member at a point adjacent said arm so as to provide a portion of said spring member between said point and said arm, a loose connection between the end ing flexed by the force of said magnet to provide o for engagement of said contacts without substantial wiping action between them and upon opening movement of said operating arm said portion of said spring member flexing to provide for a wiping action between said contacts prior to separation of said contacts.

FREDERICK W. HOTI'ENROTH, J R.

Images