US2295240A - Control switch - Google Patents

Description

B. E. SHAW 2,295,240

CONTROL SWITCH Filed May 13, 1940 2 Sheets-Sheet 1 Sept. 8, 1942.

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Sept. 8, 1942. B. E. SHAW 2,295,240

CONTROL SWITCH Filed May 15, 1940 2 sheets-sheet 2 3.9 89 f6 T j www/g i l f7 Patented Sept. 8, 1942 2,295,240 CONTROL SWITCH Buruma. shaw, Bram, ma., signor o Penn Goshen, Ind., a corpora- Electric Switch Co.,

tion of Iowa Application May 13, 1940, Serial No. `334,871 8 Claims. (Cl. 2011-83) My present invention relates to a control switch particularly adapted for controlling refrigerant compressor motors in response to changes in pressure, such as those produced by temperature.

One object of the invention is to providel a comparatively simple and efficient switch structure which can be manufactured at low cost and which includes a rugged contact structure and actuating means therefor operable to provide desired snap action for the contacts and at the same time effect their response to the pressure responsive means throughout a comparatively narrow diil'erential of movement thereof.

Another object is to provide a switch structure wherein magnet and armature means effect snap action of a switch arm, the switch arm itself being so connected with a pressure operated acmating armthat the switch contacts are moved slowly toward closed position until the magnet and armature means become effective to quickly snap them the rest of the way to their closed position, operation in the reverse direction, however, permitting the contacts to remain engaged under constraint of at least the magnet and armature means until the toggle spring passes dead center, and thereupon snap action is eifected throughout the entire movement of the switch arm from closed to open circuit position.

Another object is to provide a manual control means which is effective to move the switch to oi position, regardless of the position of the pressure responsive means and the manual control member being very simple and yet efficient in construction.

A further object is to provide a switch structure so designed that ready access to the switch contacts for making the circuit connections is had, and the contacts are so located that they may be readily cleaned or replaced when neces-i Sal'y.

'sun a further object is to provide a switch structure in which a simple bracket arrangement permits ready mounting oi' the various parts of the switch structure thereon and the sub-assembly thus provided is readily mounted within a switch casing. i

With these and other objects in view, my invention with respect to its features which I believe to' be novel and patentable will be pointed out in the claims appended hereto. For a better detailed understanding oi' the invention, and further objects relating to details of economy of my invention, reference is made to the following description and to the accompanying drawings wherein such further objects will deiinitely appear, and inwhich Figure i is a front elevation of a switch structure embodying my invention, the cover part of the casing being shown in section and the switch being shown in open circuit position; l

Figure 2 is a vertical sectional viewjthereof showing the switch about to be closed;

Figure 3 is a similar sectional view showingthe switch -in its closed circuit position;

Figure 4 is an end elevation from the left end of Figure 1 showing the cover part of the casing in section;

Figure 5 is a similar end elevation of the right hand end of Figure 1;

Figure 6 is a plan view of my control switch, with a cover plate removed and certain parts shown in section, as taken on the line 6--6 of Figure 2;

Figure 'l is a horizontal sectional view on the line i-l of Figure 2;

Figure 2a is a diagrammatic view of the pivot point relations in Figure 2, and

Figure 3 is a diagrammatic view of the pivot point relations in Figure 3. y.

On the accompanying drawings I havev used the reference character C to indicate generally a casing consisting oi back, bottom and top walls IB, I2 and il, respectively, forming part of the switch casing. A cover portion of the casing has a front wall i5 and end walls I6 and I1. The walls i6 and I1 are held in position by screws i8 entering threaded ears i8 of the back wall i0. The walls is and i2 are provided with knockout discs 20 for the purpose of making circuit connections to the switch within the casing C, Within the casing C, I provide a bracket B having a front vertical portion 2i, a horizontal shelf 22 and a back vertical portion 23. The lower edge of the portion 2i terminates in a pair .of feet 24 secured to the casing bottom I2 by screws 25. 'I'he portion 23 rests against a boss 26 extending from the back wall III and a screw 21 extends from the boss and is threaded into the bracket portion 23. 'I'he bracket B further includes an upstanding ange 2l terminating in a ange 29 provided with a pivot opening 30. Complementary to the flange 29 is an yextension 2| from the bracket portion 22 'having a similar pivot opening 32.

An L-shaped actuating arm A is provided having a horizontal arm 32 and a vertical arm 2l. Perforated ears 25 extend from theactuating arm A and are pivoted to a pin 36. The pin 28 is supported by the back wall i0 of the casing C and by the front portion 2| of the bracket B, the

pin being held in position by a retainer clip 31. rihe right hand end of the arm I3 is bifurcated to coact with stop shoulders 38 and 39 of a stop bracket 4D. A pair of washers 4I and 42 are arranged on opposite sides ofthe arm 33 and are provided with pointed ears 4I and 44, respectively. The ears 43 and 44 are seated in slight depressions in the arm 33 and the washers 4I and 42 are backed by an actuating pin 45 and a range adjusting spring 44, respectively.

The actuating pin 4l, as shown in Figure 2, is connected to the head 41 of a bellows 4l. The bellows 48 is located ina bellows chamber 44 from which a. capillary tube 5l extends to a capillary bulb or coil ll. The bellows and capillary tube and bulb system may be suitably charged in the usual manner for varying the pressure within the bellows chamber 49 against the head 41 of the bellows 48, in response to temperature changes in the temperature range ior which the switch is designed.

The range adjusting spring 4l has its upper end engaging with an adjusting washer 52 into which is threaded an adjusting rod 53. The washer 52 has an extension 54 into a slot 55 of the bracket B to prevent rotation of the washer but permit axial movement thereof relative to the adjusting rod. The adjusting rod is rotatable in the shelf 22 of the bracket and in the top wall I4 of the casing C. A control knob is secured to the outer end of the adjusting rod and may coact with suitable indicia on a cover plate B1 indicating the temperature settings in the usual manner.

A switch arm S is provided having a pair of pivot extensions 58 and 59 entering the pivot openings 30 and 32, respectively, of the bracket B. For operating the switch arm S from the actuating arm A, I provide a pair of spring cups 64 and 6| pivotally engaging an extension I2 of the switch arm S and the upper end of the vertical arm 34 of the actuating arm A. A toggle or overcenter spring 8l 1s interposed between the spring cups i4 and 6I. Y

The arm 34 of the actuating arm A has secured thereto a leaf spring $4 which may be adjusted relative to the arm 34 by a set screw 45. The spring 64 is adapted at times to engage an extension BS from the shelf 22 of the bracket B.

The switch armS"has a downward extension 61 terminating in a finger B8 located under the spring cup 8i. An armature 69 is carried by the switch arm S and is adjustable relative thereto by reason of being secured to` a rod 1,0 threaded in the switch arm.

The switch arm S carries a bridging contact member 1| having a pair of opstanding ends 12. The ends 12 are freely slidable through openings 13 in an insulating member 14 of the switch arm S. The bridging member 1| is urged'downward- 1y by a leaf spring 15 arranged below the switch arm member 14 and having its ends located in slots 14 of the upstanding member 12. A retainer clip 11 limits the bridging member 1| in its downward movement relative to the arm 14.

The bridging member 1I carries a pair of contacts 18 adapted to bridge a pair of stationary terminals 19. 'I'he terminals 19 are mounted in a block 80 vof insulating material and are provided with terminal screws 8| for making circuit connections. The block 4U is secured to the shelf 22 of the bracket B as by a screw 42.

A permanent horseshoe magnet Il is mounte on the block 8l by means ofl a screw 44. The

magnet 83 coacts with the armature 49 for securing snap action, as will hereinafter appear.

In the top I4 of the casing C below the cover plate l1, an elongated depression Il is provided. A slide bar 86 is slidable therein and is retained therein by the cover plate. 'Ihe slide bar 34 has one end downtumed as at l1, which end passes through a slot 88 in the top wall I4 of the casing. The other end is upturned as at Il and passes through a slot 90 in the cover plate l1. The downturned end 41 enters a slot ll of the switch arm S, while the upturned end 89 is provided for convenience in manual manipulation of the slide bar Il.

A spring wire catch 92 is provided to retain the slide bar I8 in one of two adjusted positions. The spring 82 coacts with either a pair of notches or a pair of notches 94 in the bar 44, asshown in Figure 6. for this purpose. The spring catch is retained in its proper position in the depression 45 by the cover plate 51 and is retained against longitudinal sliding movement with the bar I4 by certain portions thereof projecting into a slot 3l of the casing C, as shown in Figure 2.

Practical operation In the operation of my switch structure in response to pressure changes in the bellows chamber 49, a relatively low pressure condition in the chamber will permit the parts to assume ,open circuit position, as illustrated in Figure 1. Upon a rise of pressure, the arm I4 of the actuating arm A will move from the position of Figure l (with the pivot points 34 and 42 aligned indicated by the center line a and such center line falling to the right of the pivot point B4) toward the position of Figure 3. When the pivot points at the upper end of the arm 34 reach a position substantially in alignment with the pivot pointsof the elements Il and I9, taken with relation to the pivot point of the element l2, the switch arm S will start moving in synchronism with the arm A until approximately the position of Figures 2 and 2a is reached. The pivot points of the elements I4, B4, 59 and C2 are still substantially in alignment, as indicated by the center line I4. The armature 63 is now sufficiently close to the magnet 43 for the magnet to exert enough pull on the armature to swing the toggle spring 43 on past dead center, so that the switch closes to the position of Figures 3 and 3a with snap action and the actuating arm A may move on from the position of Figures 2 and 2a (dotted position of Figures 3 and 3a) to the full line position of Figures 3 and 3a (on center line 31,), as a result of overrun causing further pressure increase in the bellows chamber 49.

Slow movement of the' switch to position with the contacts adjacent each other, as in Figures 2 and 2a, insures the elimination of any bouncing of the contacts when the switch closes. 'I'he remaining distance is so short and since the pull of the magnet on the armature increases in proportion to the square ofthe distance of travel, that movement from the Figures 2 and 2a position to the Figures 3 and 3a position produces a positive closing of the contacts without bouncing. Thus I eliminate the undesirable arcing experienced with some switches upon closure.

When the pressure in the bellows chamber 49 recedes, the range spring 4l will cause the bellows to expand and the actuating arm to move reversely from the full line position of Figures 3 and 3a to the dotted line position. The respective center lines are indicated at 91 and 94, and

when the centerlune se is reached the toggle spring connection passes dead center, so that it immediately urges the switch arm S toward open circuit position. When the parts are in the full line position of Figures 3` and 3a, the switch contacts are held in engagement by the action of the magnet and armature in addition to the tensionin the toggle spring. The toggle spring tension reduces to zero at center line 96, but the contacts are still held firmly in engagement with each other by the action of the magnet and armature. After the dead center position, the contacts are quickly separated and it is evident from such an arrangement as above described that there is no gradual reduction of contact pressure to zero, as in usual toggle spring connections of switch structures. There is always a minimum contact pressure produced by the magnet and armature, and this pressure is instantly relieved when the toggle spring passes dead center and acts in conjunction with the amature and magnet to effect quick movement of the switch arm from closed circuit to open circuit position throughout its entire travel.

When the slide bar 86 is in the position of Figures 2 and 3, `the switch will operate automatically in the normal manner. If the slide bar 86 is moved to the left, so that the spring'catch 92 coacts with the notches 94, then the projection 81 of the Aslide bar swings the switch arm clockwise to the open circuit position of Figure 1, even though the pressure responsive means is calling for a closed circuit condition.

The particular arrangement of armature and magnet cooperating with the toggle spring as I have disclosed produces the desired contact action above described,v and does so with a minimum of parts for the manufacture of the switch. The terminals 'i9 are conveniently located for ready access for wiring purposes and for renewal and cleaning of the contacts of the switch when art to which this invention appertains to embody or adapt my improvements as maybe desired.

Having thus described my invention, I now claim and desire to secure by Letters Patent:

i. In a control switch, pressure responsive means, an actuating arm movable in response thereto, a pivoted switch arm, switch contacts controlled thereby, an armature carried by said switch arm, a stationary magnet cooperating with said armature to impart snap action to said switch arm, an operative connection between said switch arm and said actuating arm comprising a toggle spring having its ends pivoted to said switch arm and actuating arm with the main pivot of the switch arm located intermediate the pivots of said toggle spring to said arms, said toggle spring thereby effecting slow movement of said switch arm toward closed position until said contacts are closely spaced and said armature and magnet means have approached a point permitting said magnet to attract said armature and thereby finish the contact closing operation with snap action and said toggle spring, in response to reverse action of said pressure responsive means, effecting build-up of tension therein to a point where, when the toggle spring passes dead center, it will overcomethe pull of the magnet on the armature and effect snap action throughout the complete movement of said switch arm from closed tc open position.

2. In a control switch, pressure responsive` means, an actuating arm movable in response thereto, a switch arm, switch contacts controlled thereby, an 'armature carried by said switch arm, a stationary magnet cooperating with said armature to impart Snap action to said switch arm, an operative connection between said switch arm and said actuating arm comprising an overcenter spring, said switch arm being pivoted at a point intermediate the ends oi' said spring to effect slow movement of said switch arm toward closed position until said contacts are closely spaced, said magnet thereafter attracting said amature to finish the contact closing operation with snap action of said spring as it passes over center in njunction with said magnet and armature, and said spring, upon passing dead center in response to reverse action of said pressure responsive means, overcoming the pull of said magnet on .said armature and snapping said switch arm from closed to open position.

3. In a switch of the character described, pressure responsive means, a pivoted switch arm, switch contacts controlled thereby, an armature carried by said switch arm, a stationary magnet cooperating therewith to impart snap action to said switch arm, and an operative connection between said switch arm and said pressure respon- 4sive means including -a toggle spring having subvsaid mounting means, an armature carried by said switch arm to provide snap action for the operation of the switch arm, a toggle spring inlterposed between said actuating and switch arms,

and a leaf spring secured to said actuating arm and engageable with said bracket in the closed circuit position of said actuating arm, said leaf spring being adjustable relative to said actuating arm.

5. In a control switch, a housing, a bracket therein, actuating and switch arms pivoted to said bracket, a contact carried by said switch arm, a stationary contact for cooperation therewith, mounting means for said stationary contact and mounted on said bracket, a. magnet, an armature carried by said switch arm and cooperatng with said magnet to provide snap action for the operation of the switch arm, a toggle spring interposed between said actuating and switch arms, and a leaf spring secured to said actuating4 arm and engageable with said bracket in the closed circuit position of said actuating arm.

6. In a control switch, a casing, pressure responsive means, an actuating arm movable in response thereto, a switch arm, switch contacts 'controlled thereby, amature and magnet means to impart snap action to said switch arm, an operative connection between said switch arm andsaid actuating arm comprising a toggle spring, and a manual control for said switch arm comprising a member movable to move said switch arm to open circuit position against the constraint of said toggle spring and magnet and armature means in one position of the member, and to permit free action oi the switch arm in the other position of the member, said casing being provided with an elongated depression in which said member is slidable, and a cover for said depression and eiTective to retain said member therein.

7. In a control switch, pressure responsive means, an actuating arm movable in response thereto, a switch arm. switch contacts controlled thereby, armature 'and magnet means to impart snap action to said switch arm, an operative connection between said switch varm and said actuating arm comprising a toggle spring, and a manual control for said switch arm comprising a member movable to move said switch arm to open circuit position against the constraint of said toggle spring and magnet and armature means in one position of the member, said member having a pair of notches therein, and a latch wire engageable selectively with said notches to retain said member in either of its positions.

8. In a control switch, a casing, pressure .responsive means, a switch arm, switch contacts controlled thereby, amature and magnet means to impart snap action to said switch arm, an operative connection between said pressure responsive means vand said switch arm comprising a toggle spring. and a manual control for said switch arm comprising a member movable to move said switch arm to open circuit position against the constraint oi said toggle spring and magnet and amature means in one position of the member, and to permit free action of the switch arm in the other position oi the member, said casing being provided with an elongated depression in which said member is slidable, said member having a pair of notches therein, a latch wire engageable selectively with said notches tc retain said member in either of its positions, and a cover platefor said casing and retaining said member in said depression.

BURTON E. SHAW.

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