US2094473A

US2094473A - Thermal switch

Info

Publication number: US2094473A
Application number: US733005A
Authority: US
Inventors: Richard H Schmitt
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1934-06-29
Filing date: 1934-06-29
Publication date: 1937-09-28
Anticipated expiration: 1954-09-28

Description

Sept'. j28,

r il l@ l l I R. H. SCHMITT THERMAL SWITCH Filed June 29, 1934 Inventor:

Ric/Hamel H. Schmitt www ' Hi Attorney.

rammed sept. 21s, 1957 UNITED STATES PATENT OFFICE to General Electric New York Application June 29,

9 Claims.

lMy invention relates to thermal switches, more particularly to switches arranged to control vthe starting of motors, and has for an object the provision of a simple, inexpensive and reliable switch of this character.

In carrying out my invention in one form there.

. erating handle is operated'from the .on to the olf position.

For a more complete understanding of my invention, reference should now be had to the accompanying drawing wherein I have shown in Fig. 1 a plan view `of switch'embodying my invention; Fig. 2 is a sectional elevation taken on the line 2--2 of Fig. l; Fig. 3 is a perspective view of` the switch, while Fig. 4 is a plan view showing the relation of the thermal overload devices with a portion of the tripping mechanism located on the lower or left-hand side of the insulating base.

Referring to the drawing, I have shown my invention in one form as applied to a three-pole switch III provided with a base II formed of insulating material. The base is 4secured within a metal switch box I2 by means of brackets I3 and I4 which cooperate lwith ledges I5 and I6 formed integrally with the base member II, and by screws I8 and I9, which screws extend through vthe insulating base member and into screwthreaded engagement with the switch box I2.

A switch member 22, formed of insulating material and pivotally mounted on a pivot pin 23 extending vthrough the respective sides vof a U-shaped metallic frame 24, supports the movable bridging contacts v25, 26 and 21. The frame 24 is mountedbn the right hand side or upper side ot the base II as viewed in Fig. 2. The member 22 and the movable contacts are normally biased to an open circuit position by means of a spring 28 wound about the pivot pin 23, one end of the spring bearing against the cross member of the frame and its other end bearing against a pin 30 5u carried by the switch member. The switch mem` ber 22 is operatively connected to an operating handle 3i by means of a toggle link 32 connected by the pin 30 tothe switch member and a toggle link 33 connected at one end by a pivot pin 34 Vmi to the handle 3i, the two links being connected Company, a corporation of 13934, serial No. 733,005

(ci. l20o-116) together by a knee pivot pin 31. The collapsible driving connection or toggle formed by the

links

32 and 33 is normally maintained in a straightened and slightly overset position, as shown in the drawing, by a coil spring 38 wound about the knee pivot pin 31. A cross portion 33a of the link 33 forms a stop for the toggle in the overset position, i. e. the position when the knee pivot pin 31 is located slightly below a line taken through the centers of the

pins

30 and 34 of Fig. 2. Consequently, the force of the spring 28 does not tend to collapse the toggle.

When the handle 3i is in the fully closed position, shown in Fig. 2, the bias of the spring 28 is applied directly by the toggle to the handle in a direction to hold the handle in its on or fully closed position. Thus the bias of the spring 28 is applied to the handle in the direction oi a line extending from the center of the pin 30 through the center of pin 34. This line of the applied force passes below the pivot pin 3Ia of the handle and thereby tends to rotate the handle in a counter-clockwise direction as viewed in Fig. 2. The on position of the switch, however, is determined by the engagement of the projection 39 on the handle with a pin 4U extending between opposite sides of the frame 24. The compression springs 4I', 42 and 43 associated with the respective

movable bridging contacts

25, 26 and 21 and resiliently securing the contacts on the switch member 22 are 4compressed as the movable con-v tacts are operated into engagement with their associated pairs of stationary contacts only one pair of which, the contacts 46 and 41, being shown. Besides insuring a strong contact pressure and permitting automatic adjustment for irregularities in the contact surfaces, the compression springs 4I-43, inclusive, assist in accelerating the switch member 22 during its operation to its open circuit position. By rotatingl the switch handle 3i in a clockwise direction, as viewed in Fig. 2, the pivot pin 34 is rotated to the opposite side ofthe pivot pin 3Ia so that the springs 28, 4I ,'42 and 43, quickly open the switch.

The three-pole switch I0 is particularly applicable to the control of a three-phase motor and in order to insure the automatic operation of the switch to its open circuit position in the event of an overload on any one of the phases, two thermal overload devices 50 and 5I are connected in spaced relation with a'stationary bushing 54, both the coil and bushing being mounted on the right hand or upper side of the base. A shaft 55, normally rigidly secured to the bushing 54 by means of a solder lm, extends through the base and rigidly supports at one end a releasing gear 56, shown in Fig. 4. The'thermal overload device 5| provided with a releasing gear 51 is of identical construction with the device 50.

The .tripping or release mechanism operated in respnse' to there'lease of either one, or both, of the

gears

56 and 51 consists of a bifurcated tripping lever 60 pivoted on the pin 40. One arm 6| fof this lever, located on the upper side, as viewed in the drawing, of a resetting extension 62 formed integrally with the switch member 22, is arranged for movement into engagement with the knee portion of the toggle. The other arm 63 located on the opposite or lower side of the resetting extension 62 extends throughan aperture Ila provided in the base and through a slot 64 provided in a floating latch 'member 65 to which are secured

t'wo latching pawls

66 and 61. The pawl 66 is pivoted at 10 to one end of the latch member, the opposite end 1| of the pawl engaging the gear 56. Similarly, the pawl 61 is pivoted at 12 to the latch member 65 while its opposite end 13 engages the gear 51. A tension spring 15 connected between a stationary supporting plate 16 and the end 63a of the arm 63 of the tripping lever serves to bias the tripping member 60 for movement of its other arm 6|` to break the toggle.

leasing gears

56 and 51 by a leaf spring 80 carried by the plate 16. This plate 16, secured to the bottom of the base by a screw 8|; (Fig. 2) has tripping mechanism on opposite sides of the base Furthermore; since the overload tripping mechanism is concealed in its position below the base, there is less likelihood that the operation of the switch will be impaired due to tampering by the unskilled.

Continuing with the description of my inven` tion, it will be assumed that a predetermined overload current flows through the heating coil 53 f tocause the release of the gear 56 forrotation.A

The tension spring 15 thereupon rotates the latch member `65 and the arm'66 in a counter-clockwise direction about the pivot pin 12, as viewed in Fig.l

4, the arm 61 being held stationary by its associated gear 51. The arm 63 of the tripping lever 60 extending through the slotted latch member 65 and rotating with it, moves the other arm 6| against the knee of the toggle and thereby moves the knee pivotpin 31 upward, as viewed in the drawing, to bre kfoncollapse the toggle. A very small movemei is required since the toggle is'but slightly overse the opening of the switch occurring very quickly due to the combined action of the springs28 and 4|-43, inclusive.

As the opening movement of the switch member 22 begins, its resetting extension 62 engages the arm 63 to return the tripping member 60 to its original position, against the force applied by the spring 15,'the switch opening springs being many times stronger than the spring 15. The return movement of the arm 63 rotates the latch member 65 and the pawl 66 about the pivot pin 12 to their original positions completing .the automatic resetting of the tripping mechanism.

The pawls' 66 and 61 are biased towards the respective re-l It will be observed that coil spring 38 encircling the knee pivot pin 31 biases the

toggle links

32 and 33 to their straightened positions. This spring 38 functions to straighten the toggle, after the' switch has tripped open, and in so doing rotates the handle 3| rfrom its on position to its oi position. Consequently to reclose the switch it is only necessary to move the handle 3| to its thereby prevent the closing of the switch.

Since the toggle or collapsible driving connection is located between the handle 3| and the switch member 22the switchis trip free; that is, the overload` opening of the switch occurs irrespective of the position of the handle 3|. Similarly, the automatic resetting of the thermal tripping mechanism isindependent ofthe position of the handle 3|. f

In case of an overload which frees the gear 51, it will be understood that the latching member 65 and the paWl 61 rotate about the pivot pin 16 to operate the tripping member 60 to trip the switch. In case of an overload which frees both

gears

56 and 51, the latching member 65,

pawls

66 and 61 and the tripping member 60 move longitudinally to trip they switch to the open circuit position. In each case therigid engagement of the resetting extension 62 withthe arm 63 vof the tripping'member 60 resets the thermal tripping mechanism.

While I have shown a particular embodiment of my invention, it will be understood, ofl course,

that I do not Wish to be limited thereto since many modifications may be made, and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention. f

What I claim asnew and desire to secure by Letters Patent of the United States, is:-`

l. A switch comprising a base formed of insulating material provided with an aperture, a switch member, means mounting said switch member for movement between open and closed circuit positions, an opening spring for biasing said switch member to said open circuit position,

an operatinghandle, pivot means mounting said handle for rotation between on and oi positions, a collapsible toggle pivotally connecting said handle and saidswitch member and normally forming an operating connection therebetween, said handle when rotated from its off to its on position operating said switch member to said closed circuit position against the bias of said opening spring, a trip member biased for 'movement from one position to a second position to collapse said toggle, said trip member extending through said aperture, a thermal responsive device on the opposite side of said base from said switch member restraining said trip member against movement from said one position but Operable on overload to free said trip member to operate said switch member to said open circuit position, and means operable withv said switch member as said switch member moves to its open circuit position to return said trip member to said one position.

2. A switch comprising a switch member, pivot; means pivotally mounting said switch member for movement between open and closed circuit positions, said switch member being provided with an extension adjacent said pivot means, a spring normally biasing said switch member to said open circuit position, an operating handle for said switch, toggle means between said handle and said yswitch member normally forming an operating connection between them and operable to hold said switch member in said closed circuit position against the bias of said spring, a trip member for breaking said toggle means to permit the opening movement of said switch member by said spring, said extension engaging said trip member to return said trip member to its normal position as said switch member moves to its open circuit position.

3. A multipole switch comprising a plurality of stationary contacts, a plurality of movable contacts, a switch member Vformed of insulating material, means mounting said movable contacts on said switch member, pivot means pivotally mounting said switch member for movement between .open and closed circuit positions, said switch member being provided with'an upturned extension adjacent said pivot means, a spring normally biasing said switch member to said open circuit position, toggle means for holding said switch member in said closed position, a trip member for said toggle means, pivot means mounting said trip member'adjacent said extension, a spring biasing said trip member from a normal position to release said toggle means, a thermal device for restraining said trip member in a normal position against movement by its associated spring, said thermal device being responsive to overload current andoperable thereby to free said trip member to open said switch. said extension during the opening of said switch engaging said trip member to return the same to its normal position.

4. In combination, a multi-pole switch com` prising a switch member formed of insulating material, pivot means pivotally mounting said switch member for movement between open and closed circuit positions, an operating handle movable between on and oi positions, a normally rigid l operating connection between said handle and said switch member, a trip member provided with an extension normally maintained in a normal position and out oi engagement with said operating connection, a spring biasing said trip memstraining memberprovided with two arms, gear wheels normally maintaining said arms in ilxed position, solder films for ,said wheels normally,

maintaining them stationary and responsive, to overload current to free said gears for rotation, the resulting movement of said restraining memberinto engagement with said trip member efi'ecting the opening of said switch, and means forming a connection between said switch member and said trip membereil'ective during thel opening of said switch to reset said thermal device.

5. A thermal switch comprising aiswitch member operable between open and closed circuit positions, pivot means for said switch member, an extension provided on said switch member adjacent said pivot means, a biiurc'ated trip member having its respective arms located on oppo- .f

site sides of said extension,1 means biasing said switch member to said open `circuit position, toggle means for holding said switch member in saidclosed circuit position, one arm of said trip member being operable into engagement with said toggle means to cause the operation of said switch member to its open circuit position, a pair of .solder lm overload devices, a restraining member provided with a pair of arms respectively engaging said solder film devices, said restraining member being provided with a slot into which said other arm of said trip member extends, biasing means for biasing said trip member to trip said latching means, said restraining member and said arms preventing movement of said trip member except during the occurrence of an overload on one or the other of ,said solder' l illm devices.

6. A thermal switch comprising a base formed of insulating material; a switch member, means pivotally mounting said switch member on one sidev of said base for movement between openA and closed circuit positions, biasing means for biasing said switch member to said open circuit position, a resetting extension provided on said switch member adjacent said pivot means, a bifurcated trip member having its respective arms located on opposite sides of said extension, toggle means for holding said switch member in said closed circuit position, means biasing said trip member for movement of one arm into engagev ment with` said toggle means to cause the opera- "said trip member in a normal position, said rsetting extension` rigidly. engaging said second arm of said trip member to resetsaid trip member after rthe release 'of said' trip member by said thermal overload means upon movement of the switch member to said open circuit position.

'7. A switch comprising a base formed of insulating material, a contact supporting switch member, means mounting said switch member on one side of s'aidbase for movement between open and closedcircuit position, an opening spring normaljly biasing said switch member to said open circuit position, a switch operating handle movable be- -tween on and oi positions, a double link. toggle connected between said handle and said switch member for holding said switch member'in said closed position against the bias of said opening spring, a resetting extension secured to said switch member adjacentsaid pivot means, a bifurcated trip member pivoted at one end adjacent said hant ment froma normal position to break said toggle, a pair of solder-film overload devices located on oppositesides of said second arm of said trip member, and latching means mounted on said opposite side of said base and normally engaging said second arm of said trip member and said overload devicesfor holding said trip member in said normal positio'n, said resetting extension rigidly enmember for biasing said trip member for movegaglng said second'arm as said switch member moves to its open circuit position to return said,

trip member and said latching means to their nor- ,mal positions against the bias oi said 'tripping 8. Aiswitch comprising a switch arm, means' pivotally mounting said switch arm at one end, a resetting extension on said switch arm adjacent said pivot extending substantially at right angles with respectl tosaid switch arm, switch contacts carried on the other end of said arm, means biasing said switch arm from a closed to an open circuit position, an operating handle, a releasable operating connection between said handle and said switch arm for maintaining said switch arm in said closed position, a trip member biased for movement to release said connection, an overload responsive device normally holding said trip member against its bias, said trip member having a portion arranged to be engaged by said resetting extension upon movement of said switch member to its open circuit position after release ing substantially at right angles 4with respect td toggle being normally overset to hold said switch arm in said closed position, a trip member biased for movement against said togglel to thereby release-said operating connection, thermal overload responsive means Afor holding s'aid trip member against its bias, said trip member having a portion arranged to be engaged by said resetting extension when said switch arm moves to said open circuit position whereby said trip member is returned to its original position for engagement by said thermal overloadvmeans.

RICHARD H. SCHMI'I'I.