US1579255A - Automatic switch - Google Patents

Description

' ,April6,1926. V

" R. D. SMITH AUTOMATIC swmcu Filed June 21. 1922 Inventor" :noncll? k" Patented Apr. 6 1926.

warren sures rarer eerie RAYMOND 1). SMITH, or sal sman new YORK, assre'i on, BY Assren MENTS, T0 rnnMoNrjrn-onnors CORPORATION, or season, MASSACHUSETTS. A

CORPORATION OF MASSACHUSETTS.

AUTOMATIC swircn.

Application filed June 21, 1922. serial in). 569,856.

To all whom it may concern:

Be it known that I, RAYMOND D. SMIT a citizen of the United States, and aresident of Scarsdale, in the county of Vestchester and State of New York, have invented an Improvement in Automatic Switches, of

which the following description, in connection with the accompanying drawings, is a specification, like characters on the draw ings representing like parts.

This invention relates to electric switches and more particularly to automatic switches, wherein an automatic control, such as a thermo-electric control, is relied upon to control in whole or in part the action of the switch. I

While the invention may have useful application to thermo-electrically controlled switches of widely different types and employed for various purposes, or to automatic switches other than those thermo-electrically controlled, herein for the purposes of illustration it is shown as applied to a lamp socket switch of the pull-chain type, where in the thermoelectric control is such as to delay the breaking of the lamp circuit and to maintain the light for a substantial interval after the switch has been manually actuated for the purpose of extinguishing the lamp. I p

The invention will be best understood by reference to the following description when taken in connection with the accoi'npanying illustration of one specific embodiment thereof, While its scope will be more particularly pointed out in the appended claims.

In the drawings,

Fig. 1 is an inverted plan View partly in section of a lamp socket switch embody,- ing one form of my invention, the switch parts being shown in open circuit position and the electrical connections being inclicated diagrammatically; v

Fig. 2 is a similar view showing the switch parts in closed position; t

Fig. 3 is a similar View showing the switch in the incomplete 01f position and before the circuit has been automatically broken;

shown one form of the invention embodied in a lamp socket switch of the pull-chain type, such as is illustrated in my co-pending application Serial No. 428,100, filed Decemher 3, 1920, such parts as are necessary for an understandingof the invention being shown in Figs, 1, 2 and 3 in an inverted sectional view taken between the upper and lower' porcelain buttons, the upper one of which i is represented at 1 1. The two porcelain buttons, the lower one of which does not appear in the drawing, are secured in spaced relation by a main contact carrying bracket 13, an auxiliary contact carrying bracket 15, a thermostpt bracket 17 and a center bracket 19. The electrical connections to the lamp socket are herein represented only diagrammatically, one side of the circuit, represented at 21, being connected to one terminal of the lamp 23 and the other side of the circuit 25 being connected to the remaining lamp terminal through the switch contacts about to be described. It will be understood that in the-actual structure these connections are had to the lamp through the usual central contact tongue and theshell of the lamp sockctrespectively and various intermediate structural parts of the lamp socket itself. The conductor 25 is connected through the bracket 13 with the spring leaf contact 27, which latter is supported by the bracket, there being provided a second resilient contact member 29, the free end of which is adapted to be forced into or out of electrical engagement w'th the contact 27 when the lamp is thrown on or off. The opposite end of the contact 29 is supported by an arm or extension 31 from thebracket 17.

To force the contact 29 into engagement with the contact 27, the bracket 17 has a portion 33 extending toward the center of the socket controlling switch which provides a 1 to the on position shown in pivotal support 35 for an oscillatory contact-controlling member 87. The latter is provided with two down-turned ear portions 89 and ll (which in cross section are bent into two right angled parts), and one of these portions in operative relation to the leaf contact 29, so that when the switch 37 is turned in a clockwise direction from the position shown in Fig. 1 to that shown in 2, the pressure of the switch portion 39 springs the contact 29 into the position shown in Fig. 52, where its outer edge is brought into wiping contact with the curved edge of the leaf contact 2'? and there maintained until the switch 37 is turned back to its original position.

Vhen the oscillatory switch member is moved from the off position shown in Fig. 1 9 tie:

remaining ear portion il is placed in electrical contact with the auxiliary contact bracket 15, and thereby with the lamp terminal 23, by engagement with a contact member 13 carried by the f ee end of the auxiliary sprin lost contact as, the opposite end of which is fixed y secured to ti ol'n'aclret 1.5. The contact piece 43 is herein in the form of an eyelet or rivet head which secures the end of the contact to an insulating facing i? so arrai' V d that when the switch member 11 moves item the on position (Fig. into the off position (Fig. 1), it moves out of contact with the eye-let and into contact with the insulating plate H which is thus pressed resiliently against the switch member 41 and provides a restoring action tendingto restore the switch to its off position it ii is given a movement insufiicient to carry it to its full on position, shown in Fig. 2.

The two switch memben 39 and 41 and the connecting plate 3'? being of conductive material a complete circuit is established therethrough from the contacts 27 and 29 to the contact 15 in the on position of the switch shown in Fig. 2, while, in the cit position of the switch, contact is broken both at the contacts 537 and 29 and at the contacts il and 13.

The oscillatory switch member 37 may be operated in any desired manner, but herein it is secured to a fibre segment 4:9, the move ment of which is limited in one direction (Figs. 1 and 3) by engagement with the auxiliary contact bracket 15, and in the opposite direction by engagement with the main contact bracket 13 2). This segment may be provided with any desired form of manual actuator, such as the pair of pull-chains 51 and 53 (indicated in Fig. 1), secured to opposite ends of the segment and passing through any suitable guiding opening in the side of the socket casing. lVhen one chain is pulled, the switch is moved from the OE to the on position against the restoring'eil ect of the leaf spring contact 15, the shape oi. the two switch members 39 and 11 tending to locate and retain the switch in its on position when novement is fully completed. When the remaining chain is pulled the switch member returns to its oil position shown in Fig. 1, leaving, as will now be described, the contact parts, as represented in Fig. 3. I v

YVhen switch is manually turned to the of position, the switch contact 11 separates from the contact and the switch contact from the leaf contact 29, but the latter, for a substantial interval of time, is maintained inelectrical contact with the main contact 2'? and the lamp remains lighted a substantial interval, the current passing through a resistance winding which therino-dynamically controls the leak Contact For this purpose the bracket l7 carries what is commonly termed a bimetallic thermostat con'iposed of two nietals, having unequal coefficients t expansion, such as steel and brass, the strip having curvilinear shape. This is covered with suitable insulating material 59, such as asbestos, and provided with the resistance winding '3, the free end said. thermostat being bent in at 61 to serve as-a hitch or detent for the spring contact 29. The latter is o'l such a shape that, when forced outwardly by the switch contact it rubs yieldingly over the end 01 the thermostatic member and is forced into wiping engagement with the resilient end of the mat contact 27, as represented in Fig. 2. Vdhen released from its sprung position by the return of the switch member 39 to its initial position, the contact member 29, on its return movement and before disengagement from the lea-l contact 27, is caught by the projecting end of the thermostatic member and is there held until the rise in ten perat'ure, due to the heating current through the winding 57, deforms the thermostatic strip and the end of the latter moves radially outward, whereupon the spring contact 29 is released by the withdrawal oi the titer-most strip from the edgc'thcrcot.

The resistance winding 5? has one end in metallic contact with the bimetallic thermostat by means of the small staple 63, the opposite end being secured to a thin metallic strip 65 mounted on the insulating covering and connected in turn with the bracket 15 through the conductor 6?. l fhen the switch is manually turned to the off position represented in Fig. 3, the current then passes from the main contact 27 to the contact 29, thence to the thermostatic strip 55 and through the resistance winding 57 to the auxiliary contact bracket 15, and

thence through the lamp and back througl'i the conductor 21 as before, it being seen that the resistance wire is thrown in series with the lamp and thereby heated. This in turn heats the thermostatic strip tending to straighten the latter and move its end 61 outward and from under the contact 29, releasing the latter and permitting it to snap away from the Contact 2. and into its initially off position represented in Fig. 1. In this position the circuit through the socket has been broken and the switch parts have been restored to their initial positions ready for subsequent manual operation to turn on the light.

An interval of delay is thus interposed between the act of manually moving the switching member to its off position and the actual breaking of the lighting circuit,

' iermitting the lamp to give out its light fora substantial intervalof time after the manual actuation of the switch and then to be automatically extinguished.

The parts employed in a switch of this type are subject to considerable variation in their characteristics. It is difficult to construct a thermostatic strip so as to give (ex-- act predetermined control over the contact 29 and it is ditlicult to manufacture these parts in quantities with such uniformity in respect to physical characteristics as to have them function with the same time interval. It is also difficult after such a switch has been assembled to adjust the thermostatic member by reshaping or otherwise so as to give the required interval in the automatic operation of the lamp. For this and other reasons it is frequently desirable to have some means whereby the automatic action of the switch may be accurately adjusted and particularly after assemblage, and also adjusted in such manner that in the ordinary usage of the lamp the adjustment Will remain without substantial change. For this purpose I have provided the free end 61 of the thermostatic member, which temporarily prevents the return movement of the contact 29, with an abutment plate through which engagement with the contact takes place, such plate being adjustably mounted on the said free end and so arranged that it may be accurately set at different angular positions of adjustment toprovide varying amounts of ovcerhang with which the tip of the contact piece 29 may contact.

The abutment plate 69 is preferably of some form of rustless steel, such as the soealled Invar steel, or steel with a nickel content which will not rust under common conditions of use and should be harder than the contact 29, which latter should ordinarily be of copper or brass. The abutment plate is herein secured to the thermostatic member by means of the rivet 71 which is set up sutliciently tight to hold the plate frictionally against displacement in any position of adjustment to which it may be moved but which permits adjustment when engaged by a small special tool or key member such as the sheet metal wrench 73, the head of the lamp will leave it undisturbed and it can not be tampered with or ordinarily readjusted without the use of some tool similar to thewrench 73.

It will be observed that the edge of the abutment plate presented for contact with the contact member 29 is curved and has an increasing peripheral distance from its pivotal center so that, when turned contraclozkwise with relation to the position shown in Fig. t, a greater bearing surface is presented 7 to the edge of the contact member 29 and the time interval of the switch thereby a justably increased. The position of the abutment plate 69 in its extreme position of adjustment, or that of greatest overlap, is shown by dotted lines in Fig. i. It will be observed that the portion of the abutment plate which extends furthest beneath thev contactmember, or the portion of greatest overhang, lies very close to the center line of the contact member in all adjustable positions with the abutment plate so that the tendency to turn or twist the contact member at or just prior to its release by the abut ment plate is at all times reduced to a min imum. It is frequently desirable to have some indication of the adjusted position of the plate, and in Fig. f there is shown for this purpose a series of graduations 77 on the free end 61 in visible relation to a reference mark 7 9 on the plate.

WVhile I have herein shown for purposes of illustration one specific form of the invention, it is to be understood that the same is not limited to the specific details herein shown or to the specific application herein made thereof, but that extensive deviations may be made both with respect to the em bodiment of the invention and its mode of application without departing from the spirit thereof.

Claims:

1. In an electric switch, the combination with a bimetallic thermostatic control member curvilinear in shape, a. winding for electrically heating the same, a detent plate overhanging the free end of said thermostatic member and disposed in a plane transverse to the plane of fieXural movement of said thermostatic member, a switch member with means for moving the same, said detent plate lying normally in the path. of movement of said switch member, and means to adjust said detent plate on the control member to vary the extent to which it normally engages with said switch member.

2. in an electric switch, the combination *ith a bimetallic thermostatic control member curvilinear in. shape, a winding for electrically heating the same, a cam plate overhanging the free end of said thermostatic member and disposed in aplane transverse to the plane of fiexural movementof said thermostatic member, switch member with means for moving the same, said cam plate lying normally in the path of movement of said switch member, and means rendering said cam plate adjustable comprisa pivotal and frictional mounting for a .a plate wher by the extent to which it engages with said switch member may be varied at will.

In an automatically controlled electric switch, the combination with a bimetallic thermostat device, electric heating means therefor, and an adjustable con rol member on said device comprising a. plate having a varying radius overhanging the end of said thermostat and pivotally and friction-ally mountcd'thereon.

ln an automatically ontrolled electric sr cch, the combination with a bimetallic thermostat device, electric heating means therefor, an adjustable control member on said device comprising a plate having a varying radius overhanging the end of said thermostat and pivotally and l'rictionally mounted thereon, and a key member for adjusting said plate.

In an electric switch, the combination with a spring contact, a rotatable controlling member adapted to force the contact into sprung position, and a thermo-dynamic control device to retain the contact in its sprung position, including an adjustable cam plate suoject to thrust of said contact against its face and permitting esca iement of said contact from its edge.

6. ln an electric switch, the combination with a spring contact, a rotatable controlling member adapted to force the contact into sprung position, a bimetallic thermostatic strip to control the contact in its sprung position, an adjustable cam plate pivotally mounted on the strip with its edge overhanging same in detent relation to the contact, and means for electrically heating the strip to move said camplate.

7. An electric switch having a controlled member and an electrically heated, thermally actuated controlling member provided with an adjustable portion comprising a cam plate pivotally mounted thereon and rotatively adjustable to present differentamounts of overhan of its Jeri )her relatire to the controlled member.

8. An electric switch having a. switching member and a device to automatically control the movement of said member, the same having a projecting cam plate interposed within the path of the switching member, said plate having a periphery of varying radius and being pivotally mounted to per mit rotative adjustn'ient whereby a detent suriace of greater or lesser extent may be pr sented for engagement with the switching member.

9. 111 a thermostatic switch mechanism a mounting support, a bowed thermostatic strip secured at one end to said support, a spring-actuated contact mounted at one end to an adjacent portion of said support and chordally disposed in re ation to said then mostat, the free ones oi said thermostat and said contact co-operating as a detent latch for the control of said Contact by said thermostat, together with means to adjust the operative relation of the free ends of said thermostat and contact without re-shaping either thereof after being secured to said support.

10. A unitary detent and controlled contact structure including common mountino; means to which both said detent and said contact are secured, said detent being moved by a thermostat to retain and release said contact, and establishable in variable relation to said thermostat for determining its manner of controlling said contact.

In testimony whereof I have signed my name to this specification.

RAYMOND D. SMITH.

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