US1838944A - Switch - Google Patents

Description

C. E. IVES f swI'rrcH iled Nov, 28. 1927 fn sulafiorz barrier fs] /6) L34 L-:Jg 3

v :1FL Clifford E. l/e

'CLOSE PUSH 'Patented 29, 1,93l

- Unirse arras Application flletl Hover@ lcs?.

lli/ly invention relates in general to electrical switches.

lt relates more in particular to a so called limit switch which has as its principal funcn tion, limiting the travel ol such mechanisms as lioists, elevators, electrically controlled. gate-valves, electrically controlled vault lor other doors and the lilre.

@ne oi the principal diliiculties in designn m ing a switch of this type is the obtaining ol a sturdy, simple, construction which at the Sametime will pass the rigid tests required by the lire insurance underwriters. Since these switches are generally in out of the way 1f, positions, as for instance, oetween partitions and the like, they cannot readily be subjected to the same daily inspections and tests which are possible when dealing with mechanisms which are at all times in plain View.

As an example of the purely structural features which must be incorporated in such a switch, it might he noted that where tell volt current is employed (and this is a standard industrialcurrent for power machinery) there must be at least a half inch gap from .a pole to ground through the air; where the path to the ground is across the surface ol a dielectric, this must be increased to one inch. Between contacts oi opposite polarity with no intervening dielectric but a straight air path, the space must he one inch; and where a dielectric. intervenes the space between these parts having opposite polarity must be a minimum of twoinches. l

A switch conforming to these requirements and structurally of sufficiently sturdy design to stand up under daily use, is in existence but this switch is quite expensive and is objectionable for this reason.A lt is not as simple 40 in its operation as can be desired and leaves somthing to be wished for in the matter of ru gedness and positive action.,

ne of *he diiliculties in constructing limit switches is that they serve to regulate the movement of relatively large slow moving objects, such as vault doors for example, The usual type oi small snap switch would be inelicient 'for 'this purpose they size of the object manner of use requires sturdiness, and the incident slow moi/ement is not suited to the function and. method oli operation ci? such switches. The

snap movements ol these switches alc also ineilectual, even il an attempt were made simply construct themen a larger scalea litith these premises in mind, is appar ent that the principal object of my iiivenw tion is 'the production ol an improved limit type ci switch., f.

Another object is the production oi a limit switch of sturdy design.

Another object is the production ol a limit switch of relatively low initial cost and economical from the standpoint ol uri-heen.

Another object is the provision of af cheap electrical switch conforming to the present specifications oi the underwriterls labora tories. i

Another object is to produce a cheap limit switchv of sturdy construction, and adapted to be operated by a slow moving objectu ln carrying out the invention, a rectangular housing is provided toward one end oiwhich two pairs oi spring type electrical contacts are imbedded in a suitable dielectric. At the opposite end of the housing, a U-shaped switch arm is pivoted midway between the planes of the two pairs ol contacts. .At the end ot the switch arm adjacent the contacts a bridging member is provided to interconnect either of the pairs ol contacts depending) upon whether the switch arm is above or elow its pivot point. A suitable mechanism is provided operated by a lever on the outside of the housing, this mechanism including a spring so that as the contact arm is moved it will have an over center lever snap action causing it to snap from a point above its pivot to a point below thev saine or vice versa, and thus snap out of mi 1i."

il 'orovided 'with screw holes .1.2

contact with one pair of terminals and into contact with the other pair. The s eine arrangement of arts is of considerati e irnportance and Wild he a parent from the tot lowing description talen with the accom panying drawings, wherein U hig. i is a. plan vieiv ci" the switch with the housing cover removed; v

Fig. 2 is a, sectional view taken along the line 2-11 oit lig. l;

3 is a sectional vievv similar to 1' shown in 2 hut vvith the parte in ei terent position;

""g. d shovvs schematically the manner in which, the terminals are interconnected by the svvitch har, and

Wig.. 5 shows a circuit illustrative ofi er in which the switch may he use@ neterring n-oiv to the dravvine*c lit-e reference chorecters are en designate sirniiar members throughout severai viewsa the switch. inciuccs o hou l0 'which the innjor portion the. o.

adapted to contain-ed this housing the switch on suitahle su rihe switch `night he mounted o course -o i- Zontally? f or in any other position depending upon eciiic manner f lich o is used..

enclose the housin. l v means of screw Toward one end of the ifiousing, die; tric bloch: Iii is secured to 'the bottom thereof hy machine screvvs 1li/it this bloclr connected oniy tothe bottom oi the housing and spaced trom the sides ther-ect as shovvn Within the hloclr are secured terminal lugs l8-l8 and lid-i9 having at one end thereo't conductor receiving siots We and 19o 'respectively, screvvs Ql-Ql vbeing provided in each instance to secure the conductor to the terminal block. Adjacert these ositions, the end of the housing is provide with an opening 22 through which a cable (not shown) is adapted to entend, its separate conductors bein tanned out on the inside oi the housing tor connection to the proper terminal lugs.

The terminal lugs lS--JlB and 19-19 have secured thereto in ciamping relation or in any other suitable manner7 spring contacts 23-23 and .Q4-24, respectively, to Which are secured contact points 26-26 and 27-27, respectively. These Contact points may be formed integral with the springs, in which case. they would simply comprise thickened portions thereof, or they may be fastened in any other Way. It is obvious of course, that contact may be formed with the springs directly if it were considered desirable.

The terminal lugs are firmly imbedded in the insulating block 16 but on each side thereof the block has a cut away portion of circular cross section in which short tubular insecuring Losanna;

sorts 28-28 of dielectric material are placed to act as an insulation barrier and assist in adhering to the underwriters speciiications described above. v

Toward the opposite end ci the housing, a itshaped svvitch .arm 29 is secured' on pivots 23h-31 `which ere in the torm oi screvvs threaded into the side ci' the housing and with their heads extending on the outside thereof.. Narrowed portions of the shanlr engage in suitably provided apertures in the closed end ot the switch arm.

hit the open end of the svvitch arm, a rod 32 is secured surrounded hy an insulating 'tube 33 surrnounted hy a cross har 341 'tor ininterconnecting svi/'itch 'terminals carried hy the Toloclr The contact har 34 is ot tuhuiar cross section und has on each side thereof, insulation harrier in the form ot dielectric LWashers these 'nnshcrs extending 'to the insuT tube B3 and having tno i here f, opposite the cross har, spacers apparent the 'tree end oi" e may hy's suitahie mechanism he 'forced u 'Werdly or downwardly `to interect ect, with the inmeans resu in a quick d breaking o'l" contact to prevent ci ercing. ivo opposite on the switch arm intermedi trie ends thereot., slots 38m-38 L vided into which entend the narrowed ends a rod 39 which carries at its mid point, a roiier ll rtree to revolve thereon and secured in place hy the arms of a biiiurcated guide d2 which is pinned to the rod 39 and has the end et its shank` 42a extending through a slot in the bovv portion ci the svvitch arm 29. linterinediate the bifurcations and the hovv end ot the svvitch arm, compression spring d3 is mounted upon the shanlr oit the biturcated guide member.

Near the bottom oit -the housing, an operatin shaft 44 is provided havingat its midpoint a roller engaging rocking arm 46 and on its end on the outside of the housing, an o erating lever 47 to the unconnected en of which, is secured a roller 48. The roller is adapted to he engaged by any moving object to move the lever 47, and the movementoi the lever operates to move the roller engaging rocking arm 46 as Well. This arm is at apted to incline either to the left as shown in Fig. 2, or to the right as shown in Fig. 3. The spring 43 being under-compression, the roller at all times tends to ride on the incline or cam surface so as to move the switch arm about its pivots either upwardly or downwardly. it does this by building up a cornpression in the spring until the rocking arm reaches a. dead center position at which time Contact is still maintained between the cross bar and terminals. the switch arm being lili) maintained in osition by the tension of the spring, or just foreit trips, by its own inertia.

As-soon as the inclination of the rocking arm is slightly beyond that from which it is changing, however, the roller, impelled .by the spring, starts to ride downl the oppositely inclined surface. When this action takes place, it occurs with a snap, the roller in its movement of course carrying with it the entire mechanism of. which it is a part, namely the entire switch arm assembly. This movement results in the quick breaking of the contact between the cross bar and one pair of terminals and a correspondingly quick snap engagement being effected between the cross bar and the other pair of terminals. i

As an instance of the manner in which a switch of this type may be used, reference may be had to Fig. 5 showing a simplified circuit in which a pair of such switches may be incorporated. The same reference characters are employed as near as possible, as those used in the description of the apparatus itself. In this circuit, a source of power 51 is employed to drive suitable apparatus (not shown), put in motion by a solenoid controlledby coils 52 and'. There are many ways in which this arrangement is carried out. -As for example, on a door opening device, one solenoid may set the door opening mechanism in operation to open the door, while the other solenoid. may function to cause the mechanism to move Vin an opposite direction to move the door to a closed position. The circuit will be described in connection with this arrangement.

Assume that the door is closed, then switch 54 may be pressed to establish a circuit through the terminalsQ-Q and 2323 of the two switches indicated by the terms limit closes and limit open. This energizes the solenoid 52 and operates the mechanism for opening the door. As the door starts to open, the limit close switch is actuated because the lever 4i? which has been held by the closed door, is released. The switch bar 34 then shifts to the position indicated by the dotted lines. The door continues to open, the circuit being established through the limit open switch until it reaches substantially the desired end of its travel. Here its actuating arm i engaged by the door to move the cross har 34 and so open the circuit and stop the movement of the door.

yhe door is open and the circuit is in the position shown with the switch bars contacting with the opposite pairs of terminals, their position being shown in dotted lines. dassume that it is now desired to close the door, 'the switch 54 is closed. This establishes a circuit through the terminals 24-24 and 24-24 of the limit switches and energizes the solenoid 53. As the door begins to close, however, the cross bar 34 1s moved out of engagement with the terminals 24 and the circuit is then throu h the other limit switch. When, however, t ie door approaches the final closed position, the lever 47 is moved by the door engaging the roller 48 and the circuit including the `solenoid 53 is broken.l

This stops the movement of the door closing mechanism and leaves the circuit as shown in full lines, ready for the button 54 to be pushed to again open the door. Thence the operation is repeated each time the door must be leither opened or closed.

There are many other manners in which a switch ot this type may be used but it is not necessary to refer to them. The switch accomplishes everything that complicated, very expensive switches were required to do in the past, and in addition it is sturdy, positive in its action, and effects a quick throw.

Mecnanically, electrically and structurally it is an improvement over the prior art and writers;

Although specific details of one embodiment ofthe invention have been described to .passes the tests required by the lire underof electrical contacts disposed. at one end of the housing, a switch arm pivoted at a point midway of the planes of the two pairs of contacts, a cross bar carried by the switch arm and adapted to interconnect either pair of contacts, a guide reciprocable with respect to the arm, a spring for normally holding the guide in a posltion toward the contacts, a roller on the guide, a rocking operating arm in contact with the roller, and means pro'ecting from and operable outside of the housing for incliningy the operating arm in either direction to move the switch arm quickly from one position to another to snap the cross bar out of engagement with one pair of contacts and into engagement with the other pair.

2. The switch defined in claim 1 wherein said guide is T-shaped, with two of its legs extending into longitudinal slots in the switch arm, with the other leg thereof extending through and axially reciprocable in the pivoted end of said arm.

3. The switch defined in claim 1 wherein said guide is T-shaped and is secured on the switch arml in longitudinally reciprocable relation, the spring being mounted on one of the legs of the T, and compressed by having its ends engaging a portion of the switch arm and the 'other legs of the T respectively.

4. In a limit switch, a housing, an insulating block at one end of the housing, a plurality of contacts secured in the block, a U- lli) shaped switch arm-pivoted at its bow end to the housing, a cross bar secured across the open end of the switch arm and insulated therefrom a T-shaped uide assembly having two of its legs extending into slots in the sides of the switch arm and its remaining leg extendin through a slot in the bow end of said switc arm, a roller mounted on said guide, sprin means normally forcing said guide and said roller in the direction toward the contacts, an operating shaft in the bottom of the housmg, a rocker arm pivoted to the shaft and engaging said roller, and an operating lever on' the outside of the housing and secured to said shat for changing the angle of inclination of said. rocker arm to move said switch arm with an over center snap action about its pivots and so snap said cross bar out of engagement with one pair of contacts and into engagement with the 5. The combination defined in claim 4 wherein the means of insulating said cross bar from the switch arm includes a pair of relatively large dielectric washers forming an insulation barrier between said bar and other conducting portions of the switch. j u

6. A swltch as defined in claim 4 where-1n 4 said spring is mounted on the longitudinal 7. A switch as defined in claim 4 wherein the roller engages said rocker arm always at the same side of said operating shaft, so that the switch arm will remain in one position without holding the operating lever, but when said operating lever is released the switch armimpelled by said spring returns to its normal position.

8. In a limit switch, a housing, an insulating block secured at one end of the housing, two pairs of terminal lugs secured in said block with terminal connecting means projecting into the smaller end of the housing, said housing provided with an opening adjacent said terminal lugs for leading a conductor therethrough, contacts of resilient material secured to said lugs and projecting from the insulating block to the large end of the housing, a U-shaped switch arm pivoted to the housing at aA point midway between the planes of the contacts, a cross bar secured across the open end of the switch arm and adapted to engage the terminals to interconnect either pair thereof, a T-shaped guide reciprocable on said switch bar, a .spring no1'- mally holding said T toward the terminals, a rocker arm interposed between said T and said terminals, and means partly on the outside of the housing for moving said rocker arm to cause the T-shaped guide to ride on the inclined face of the rocker arm to move said switch arm and disconnect one pair of terminals and connect the other pair with a. snap motion.

9. In a limit switch, a housing, an insulating block secured at one end of the housin two pairs of terminal lugs secured in said block with terminal connecting means projecting into the smaller end of the housin said housing provided with an opening a jacent said terminal lugs for leading a conductor therethrough, contacts of resilient material secured to said lugs and projectin from the insulating block to the large end o the housing, a U-shaped switch arm pivoted to the housing at a point midway between the planes of the contacts, a cross barsecured across the open end of the switch arm and adapted to engage the terminals to interconnect either pair thereof, a T-shaped guide reciprocable on said switch bar, a roller secured) on said guide, a spring mounted on one leg of said T with its ends engaging` the closed end of the U-shaped switch arm, and the cross piece of the T, respectively, said roller being in line, with the end of said spring, a rocker arm engaging said roller and disposed between said roller and said cross bar, a shaft supporting said rocker arm and extending to the outside o the housing, and an operating lever mounted on the projecting end of the shaft for moving said rocker arm` to cause the roller driven by the spring to be moved on the inclined surface of said rocker :zrm to snap said switch arm in either direction.

10. The switch defined in claim 9 wherein I said roller engages said rocker arm at all times on the same side of the rocker arm shaft, so that when said operating lever is disengaged the switch arm assembly will be returned to normal position by sai d spring.

11. A 4limit switch for controlling the movement of relatively slow moving objects, said switch including an over center snap mechanism, a single compression spring operating said mechanism, and av roller arm. adapt-. ed to be engaged by the object to control the over center snap mechanism to snap the switch in one direction and means, including said spring for returning the mechanism and roller arm to normal position when said object is moved in the opposite direction, the roller arm being returned gradually, and the over center snap mechanism moved with a snap action when the arm has been moved through a portion of its distance.

12. ln a limit switch, a pair of fixed, spaced contacts, a switch arm carrying a contact movable with respect to said fixed contacts and pivoted at its `opposite end, a roller carried by said arm, a spring for urging said roller radially from the pivot point of said arm, an operating arm pivoted at one end and engaging the roller whereby the spring urges said operating arm always in the same direcarm against the pressure ofthe spring.

1,sss,944

13. In a' limit switch, a movable contact member, a switch arm `supporting said contact member at one end, and being pivotally mounted at the other end, a roller carried by said switch arm, un operating arm pivoted at one end, a spring for urging the roller against the operating arm, said spring urging the operating arm always in one direction, and means moving the operating arm against the force of the spring. v

In witness whereof I hereunto subscribemy name this 24th day of October, 1927.

v CLIFFORD E. IVES.

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