US2237262A - Safety switch - Google Patents

Description

April 1941 E. M. MILLER 2,237,262

SAFETY SWITCH Original Filed May 4, 1936 INVENTOR Ernesi M- Miller BY fli ht ATTORNEY Patented Apr. 1, 1941 @rlglnal application May 4, 3936, Serial No,

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W558. Divided and this application @ctohe 25, 193i, aerial No. l'ZllfiiEt 18 Claims. ((U1- Wil -122) Another object of the invention is to provide a time switch comprising a bimetallic element which is actuated by a heater to trip a latch to cause the switch to open.

Another object is to provide a switch of the above type wherein the bimetallic element is compensated for variations in .ambient temperature.

Another object is to provide a switch which will open automatically at the end of a given time interval, and means for adjusting the length of this time interval.

Still another object is to provide an automatic switch which will open after a predetermined time interval and wherein a means is provided for manually resetting the device.

A further object of the invention is to provide a switch which will automatically trip to open position upon the occurrence of a predetermined condition by means of a thermostatic latch, and which cannot be closed by the manual reset mechanism until the thermostatic latch is in a position to hold the switch closed.

A further object of the invention is to provide a switch of the above type wherein the switch will not close until the latch has been reset and the manual means released.

A still further object is to provide a safety switch requiring a manual resetwhereinthe main stress exerted on the spring contact arms is exerted thereon by the manual reset lever which has a very limited motion whereby said spring contact arms are saved from undue stress and strain.

Other objects will become apparent to those skilled in the art as the specification is considered having reference to the accompanying drawing in which:

Figure 1 is a side elevational view of the switch, parts of the supporting structure being shown in section;

Figure l and looking in the direction of the arrows;

Figure 3 is a perspective view of certain portions of the structure shown in Figure 2 in a different operating position; and

Figure 4 is a detail view showing the thermostatic latch. and electric heater therefor and taken on the line 3-6 of Figure 2.

This application is a division of my co-pending application serial number 77,758, filed May 4, 936, now Patent 2,175,720.

The switch mechanism is all mounted upon an insulating panel it and supported bya mounting bracket M which has at one extremity a downwardly depending portion 62 and at the other extremity a second downwardly depending portion 113. As better shown in Figure 3, portion l3 has an aperture 84 therethrough. A pair of spring leaf contact members l5 and it is carried by bracket ill and secured thereto by screws ll, which pass through an insulating panel it and relatively large apertures in flange 12 into panel i0, and thus serve not only to support contact members l5 and it but also to maintain bracket M in related assembly with panel ill through the frictional engagement of panel it and panel it with opposite sides oi flange ii. The, enlarged apertures which may if desired be filled with suitable insulating washers are to preclude any electrical contact between flange l2 and screws ill which, it will be seen, are in electrical engagement with members it and to. Members 65 and it bear on their adjacent surfaces opposed contacts l9 and 20, the separation of which serves to break a circuit for a purpose to be hereinafter described. Adjacent the extremities of contact members 55 and i6 and supported by bracket ii is a pivot pin 29, which has mounted thereon a manually operable lever 22, comprised of insulating material to preclude interference with a circuit through arms l5 and i6. Lever 22 has an arcuate portion 23 at an extremity thereof, adapted, under certain circumstances, to abut an upwardly extending portion 24 of contact member l6. Also carried by pin it is a bracket member 25, which has a lateral extension 26 and a vertically extending portion 2! (see Figure 3). Extension 21 is adapted to be engaged, under certain circumstances, by a projection 28 of member 22. Bracket member 25 also has rigidly associated therewith a circular portion 29 also comprised of insulating material. A mounting member 30 is connected to bracket H, as by a screw 30 and a screw I Figure 2 is a. view taken along the line 2-2 of 32 in a slot 33 which latter permits adjustment of the assembly with respect to extension 26. Two bimetallic strips 35 and 35, secured together as by a stud 36, are suitably secured to mounting member 30. Mounted adjacent member 35 is a resistance element comprised of a coil 37 having wires 38 leading thereto from suitable terminals 3d carried by a depending insulating panel 60, secured in any desired manner to bracket ii. Rigidly secured to the free end of bimetal strip 35 and on the opposite side of coil 3? is a third bimetal element Lil, which has, as better shown in Figures 3 and 4, an upwardly extending portion :32 adapted, under certain circumstances to be set forth hereinafter, to engage extension 25. v 1

The disposition of the component metals of strips 34 and 351s opposite in order that a change in temperature value applied equally to both will cause a balancing movement of the two strips.

in opposite directions. In other words, the positioning of strips so and 85 is designed to overcome the efiect of ambient temperature changes on the assembly. Resistance M is positioned, as above stated, adjacent strip 35 and heat therefrom accordingly aflects strip 35 more strongly than strip as to overcome the compensating effect. Element (ii is so arranged that temperature change will occasion movement thereof corresponding to the movement of strip 35 and since heat from resistance 31! is supplied to both strips 35 and All, such temperature rise will by the multiplication of energy occasioned by the two elements readily overcome any resistance offered by element 36.

In operation, when a circuit passes through coil 31 the bimetal assembly comprised of elements 36, 35, and 6! tends to expand and the arrangement, as above stated, is such that such expansion causes the assembly to move in a direction away from contact carrying members 85 and It. Upon such motion, portion 62 will move beyond the end of extension 26, which, due to the spring pressure exerted on portion 29 by spring contact carrying member is, will immediately drop into the position shown in Figure 3, which permits contacts i9 and 20 to separate and due to the pressures of arcuate portion 23 against extending portion 26 oil spring contact arm' I 6, contact 20 will be precluded. from moving with contact it as the latter moves away. Extension 26 also serves to hold the bimetal assembly in the position shown in Figure 3 until such time as lever 22 is moved manually to the left, as seen in Figure 2. Upon such motion, projection 28 engages extension 21 and lifts extension as out of engagement with projecting portion 32. Since the breaking of contacts 59 and 2e serves to break the circuit through coil 37! the bimetal assembly will cool substantially immediately after the cessation of heat in coil 37 and upon the raising of extension 26 by movement of manual clearance upon movement of lever 22 to the left, curved portion 23 will first engage extension i l to move it to the right. After the clearance above mentioned has been closed, projection 28 will engage extension 21, which will in turn move circular member 29 a short distance to the right until such time as extension as clears projection 42. Then upon release of lever 22, the spring pressure, as above described, will permit the parts to return to normal position and the contacts i9 and 20 to close.

From the foregoing it will be seen that all stress on the movable parts of the device, such as projection 26 and contact bearing arms l5 and I6 is transmitted directly thereto from lever 22 and that no strain other than normal spring pressure is placed upon contact bearing arms I5 and I 6. In other words, movement of lever 22 causes projection 28 to move extensions 2? and 2e and circular member 29 to move contact arm l5, and pressure of arcuate portion 23 against extension 26 causes movement of contact arm it.

By this means, the resilience of arms l5 and it is less apt to be impaired, the life of the switch is lengthened, and more emcient operation assured.

Many modifications of this invention may occur to those skilled in the art, and it is therefore to' be distinctly understood that I am not to be limited to the particular embodiment disclosed but rather by the scope of the appended claims.

I claim. as my invention:

1. A 'switch comprising a pair of resiliently mounted contacts, a pair of pivoted levers one end of each engaging one of the contacts to move it against the resilience of its mounting, a oneway driving connection between one of said levers and the other, means for rotating said one lever and hence said other lever through the one-way driving connection, a thermostaticlatch for preventing return of said other lever upon release oi said first lever, and means for heating said thermostat to cause it to trip the latch.

reset lever 22 returns to its normal or closed.

position. Contacts l9 and at close and the device will be ready to repeat the previously described cycle of operation.

It may here be pointed out that due to the configuration of lever 22, contacts 89 and so will not close until lever 22' has been manually moved to the left and released whereupon pressure of spring arm i8 and extension 241 against circular member 29 and curved member 23, re-

.spectively, will return the switch to its normal 2. A switch comprising a pair of resiliently mounted contacts, a pair of pivoted levers one end of each engaging one of the contacts to move it against the resilience of its mounting,

a one-way driving connection between one of said levers and the other, means for rotating said one lever and hence said other lever through the one-way driving connection, a thermostatic latch for preventing return of said other lever upon release of said one lever thus causing switch 010-- and hence said other lever through the one-way driving connection, a bimetallic blade having an and engaging said other lever under normal temmounted contacts, a pair of pivoted levers one end of each engaging one of the contacts to move a generally U-shaped member, the other end of acstgecc the first thermostatic element being connected to a support and the other end of the second thermostatic element engaging said second lever, and heating meansdisposed between the two thermostats to heat them both and cause them to bend in the same direction to cause the second element to release the second lever to cause switch opening.

5. A switch comprising a pair of resiliently mounted contacts, a pair of pivoted levers one end of each engaging one of the contacts to move it against the resilience of its mounting, a one-way driving connection between one of said levers and the other, means for rotating said one lever and hence said other lever through the oneway driving connection, a thermostaticlatch for preventing return of said other lever upon release of said first lever thus causing switch closure, said latch comprising two bimetallic thermostats connected together at one end to form a generally U-shaped member and being arranged to flex in the same direction on temperature change, one end of the first thermostat being connected to one end of a third bimetallic thermostat mounted on a support at its other end and arranged to flex in the opposite direction from the other two and of a size to just compensate them for changes in ambient temperature, the other end of said second thermostat engaging said second lever, and heating means disposed between the first and second thermostats to heat them and cause them to bend in a direction to cause the second thermostat to release the second lever and cause switch opening.

6. A switch comprising a pair of resiliently mounted contacts, a pair of pivoted levers one endoi each engaging one of the contacts to move it against the resilience or its mounting, a-oneway driving connection between one of said levers and the other, means for rotating said one lever and hence said other lever through the one-way driving connection, a thermostatic latch for preventing return of said other lever upon release of said first lever thus causing switch closure, said latch comprising two bimetallic thermostats connected together at one end to form a generally U-shaped member and being arranged to fiex in the same direction on temperature change, one end of the first thermostat being connected to one end of a third bimetallic thermostat mounted on a support at its other end and arranged to flex in the opposite direction from the other two and of a size to just compensate them for changes in ambient temperature, the other end of said second thermostat engaging uaid second lever, and heating means disposed between the first and second thermostats to heat them and cause them to bend in a direction to cause the second thermostat to release the second lever and cause switch opening, the support or said 70 third thermostat comprising a plate mounted for. rotation about a pivot so that the thermostatic latch assembly may be adjusted relatively to the two levers.

7. A switch comprising a pair of resiliently 75 mounted contacts, a pair of pivoted levers one end 01 each engaging one of the contacts to move it against the resilience of its mounting, a oneway driving connection between one of said levers and the other, means for rotating said one lever and hence said other lever through the one-way driving connection, a first thermostat mounted at one end on a support and connected at its other end to one end of a second thermostat the other end of which engages said other lever for preventing its return upon the release of said first lever, said first thermostat being arranged to respond oppositely to said second thermostat in order to compensate it for changes in ambient temperature, and means for heating said second thermostat to cause it to disengage said other lever.

8. A switch comprising a pair of resiliently mounted contacts, a pair of pivoted levers one end of each engaging one oi! the contacts to move it against the resilience of its mounting, a oneway driving connection between one of said levers and the other, means for rotating said one lever and hence said other lever through the one-way driving connection, aflrst bimetallic thermostat having one end cooperating with said other lever under normal temperatures thus preventing its return upon release of said first lever thus causing switch closure, a second bimetallic thermostat connected at one end to the other end of said first thermostat and adapted to flex in the opposite direction therefrom on temperature change, said second thermostat being mounted on an adjustable plate, and means for heating said first thermostat to cause it to flex from engagement with said other lever to permit it to rotate and open the switch.

9. A switch comprising a pair of leaf springs each carrying an electrical contact, said contacts being in spaced relation when the leaf springs are in their normal position, a first lever having one end adjacent one of the leaf springs, a second lever having a one-way drive connection with the first lever and having one end adjacent the other leaf spring, manual means for rotating the second lever and hence the first lever through the one-way drive connection causing both leaf springs to move in unison and maintain the contacts spaced apart, latch means for preventing reverse movement of said first lever after a predetermined rotation thereof, said other leaf spring causing said second lever to reverse upon release thereof which causes the electrical contacts to engage, and means for tripping the latch to cause said contacts to open.

10. A switch comprising a pair of leaf springs each carrying an electrical contact, said contacts being in spaced relation for normal positions 01 said leaf springs, a first lever having an extension on one of its arms, its other arm lying in contact with one of the leaf springs, a second lever having a projection lying adjacent said extension and having one end lying in contact with the other of the leaf springs, a handle on said second lever forming a manual means for rotating it and the first lever through the projection and extension, said levers causing said leaf springs to bend in unison in the same direction maintaining the contacts in spaced relation, latch means tensioned to move into the path of said first lever after a predetermined rotation thereof, the other or said leaf springs causing reversal of said second lever upon release thereof, reversal of said first lever being prevented by said latch thereby causing said switch contacts to close, means to trip said latch, and stop means for limiting the manual rotation of said second lever in one direction and the rotation oi said second lever by said other leaf spring in the other direction.

11. A switch operating mechanism comprising,

thermostat, a pivoted lever one end of which engages said thermostat and the other end of which engages the first of said contacts to hold it in switch closing position against the resilience of its mounting, means for heating said thermostat to cause it to flex in a direction to release said lever thus permitting the switch contact to move to open contact position and to' rotate said lever about'its pivot, a second lever having a portion adapted to engage the second switch contact and another. portion adapted to contact the first lever, and means for rotating said second lever to cause rotation of the first lever and hence cause movement of both switch contacts simultaneously in the same direction, release of said second lever permitting said second switch contact to reverse its rotation and to cause two resiliently mounted electrical contacts, a

switch closure providing the thermostat has cooled enough to engage the first lever and prevent its reversal.

12. A switch comprising a pair of resiliently mounted contacts, a pair of pivoted levers one end of each engaging one of the contacts to move it against the resilience of its mounting, a oneway driving connection between one of said levers and the other, means for rotating said one lever and hence said otherlever through the one-way driving connection, a thermostatic latch for preventing return of said other lever upon release of said one lever thus causing switch closure,

means for heating said thermostat causing it to expand and release the other lever and permit switch opening, and means for adjusting the amount of heat necessary to cause the thermostat to trip the latch.

. to form a generally U-shaped member, the other,

end of the first thermostatic element being connected to a support and the other end of the second thermostatic element engagingsaid second lever, heating means disposed between the two thermostatic elements to heat them both and cause them to bend in the same direction to cause the second element to releasethe second lever to cause switch opening, means for mounting said thermostatic elements on the same support and means for adjusting said support.

14. A switch comprising a pair of resiliently mounted contacts, a pair of pivoted levers one end of each engaging one of the contacts to move it against the resilience of its mounting, a

one-way driving'connection between one of said levers and the other, means for rotating said one lever and hence said other lever through the one-way driving connection, "a thermostatic latch for preventing return of said other lever upon release of said first lever .thus causing switch.

aaaaeae 1 closure, said latch comprising two bimetallic thermostats connected together at one end to form a generally U-shaped member and being arranged to flex in the same direction on temperature change, one end. of the first thermostat being connected to one end of a third bimetallic thermostat mounted on a support at-its other end and arranged to flex in the opposite direction than the other two and of a size to just compensate them for changes in ambient temperature, the other end of said second thermostat engaging said second lever, heating means disposed between the first and second thermostats to heat them and cause them to bendin a direction to cause the second thermostat to release the second lever and cause switch opening, and means for adjusting the amount of heat necessary to cause the second thermostat to-reiease the second lever.

15. A switch comprising a'pair of leaf springs each carrying an electrical contact, said contacts being in spaced relation when the'leaf springs are in their normal position, a first lever having one end adjacent one of the leaf springs, a second lever having a one-way drive connection withthe first lever and having one end adjacent the other leaf spring, manual means for rotating the second lever and hence the first lever through the one-way drive connection causing both leaf springs to move in unison and maintain the contacts spaced apart, latch means preventing reverse movement of said first lever after a predetermined rotation thereof by said second lever, said other leaf spring causing said second lever to reverse upon release thereof which causes the electrical contacts to engage, means for automatically tripping the latch after a predetermined time to cause said contacts to open, and

means for adjusting the time necessary for tripping the latch.

16. A thermal cut-out comprising a. pair of leaf springs, a contact carried by each, a retainer for biasing one of said leaf springs to position with its contact engaging the other contact, a bimetal latch for said retainer, said latch upon releasing said 1retainer permitting one of said leaf springs to move to position with the contact carried thereby out of engagement with the other contact, a heating element for so unlatching said latch upon predetermined current flow through said heating element and manual means for relatching said retainer, said means being engageable with said retainer to move it to latched position and simultaneously engageable with said other leaf spring to move it in a direction separating the contact carried thereby from the contact carried by one of said leaf springs.

17. A thermally operated current responsive switch of the class described, comprising, in combination, a support, a first spring contact blade having one of,its ends fixedly secured thereto, a second spring contact blade also having one of its ends fixedly securedto said support near the fixed end of said first spring contact blade and extending substantially parallel to said first blade, said spring contact blades being normally blades to locking position after they have been released, said manual means maintaining said contact blades in open circuit relation during the locking operation.

18. A thermally operated current responsive switch of the class described comprising a pair of electrical contact carrying blades each anchored at one end and biased away from each other to normally open the contacts, a bimetal strip thermal element and means for operatively associating the thermal bimetal strip element with the contacts to normally afford endwise resistance by the bimetal strip to opening movement of the contacts, warpin movement of the bimetal strip under influence of heat shifting the end of said bimetal strip to permit the contacts to open under their normal bias, the parts being so arranged that upon removal or breakage of the himetal strip the contacts will separate, and means for resetting said contacts to closed position comprising a movable member separately moving each of said contact blades to retain them separated until the thermal bimetal strip has been endwise engaged to retain one of said contact blades in its reset position before the other contact blade is permitted to engagetherewith.

ERNEST M. MILLER.

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