US1794000A - Call switch for signal systems - Google Patents

Description

Feb. 24, 1931. w. P. CROCKETT CALL SWITCH FOR SIGNAL SYSTEMS Filed April 29, 1929 3 Sheets-Sheet 1 Feb. 24, .1931. w. P. CROCKETT 1,794,000

CALL SWITCH FOR SIGNAL SYSTEMS I Filed April 29, 1929 s Sheets-Sheet 2 llllllllllll Feb. 24, 1931. ,w CROCKETT 1,794,000

CALL SWITCH FOR SIGNAL SYSTEMS Filed April 29, 1929 3 Sheets-Sheet 3 4 9 1/69 J5 Wine 50 66 1' Patented Feb. 24, 193i UhlE EED STATES PATENT OFFICE WILLIAM P. CROCKETT, OF CHICAGO, ILLINOIS CALL SWITCH FOR SIGNAL SYSTEMS Application filed April 29, 1929. Serial No. 358,848,

The invention relates to a call switch for have tried to alleviate and dispose of the difsignal systems, and is for improvements ficulties in various ways. One of the ways which have been made over those shown is by placing the call switches in certain poand described in my Patent Number sitions relatively to the bed of the patient so 1,620,951, issued March 15, 1927, and those that the difliculties would be overcome, but shown and described in my application for this has not been sufiicient to overcome the United States Letters Patent, Serial Numdifficulties that have been found in practice. ber 317,807, filed November 7, 1928. By use of the call switch of the present in- The particular adaptation of my invenvention, visual signals and audible signals 10 tion as well as the cases mentioned, is for a have been readily made by the patient from call switch which ay b us d i v hogpracticallyany position regardless of Where pitals, or other places, to be operated the call switch is placed with respect to the by a patient, or other person, to call ed of the patlent V a nurse or other attendant, who after 're- A primary obJect of the invention is to 15 spending to the call resets the call switch employ mechanism in the call switch, parso that it will be in order for the next ticularly as to the portion thereof which is operation by the patient. operated by the patient, or other person, in

In my Patent Number 1,620,951, referred which the pull cord of the switch is entirely to, the greatest burden of operation of the outside of the cover plate of the switch and 90 switch is upon the patient, who is required does not at any time pass therethrough to operate the switch against the tension of A further object of the invention is to a spring and a certain amount of friction, employ and embody a back mounting plate whereas the nurse, or other attendant, has associated with the various parts of the ap the more simple operation of merely pressparatus in order to enable the finished call ing the slidable latch against the action of switch to be set in the wall in plumb and a much weaker spring and a lesser amount straight lines irrespective of the position of of friction. the wall boxinto which the call switch is to In the present invention, as is also the case be adjusted and fitted no matter how much in the application referred to,the greatestbur out of plumb the wall box may be.

3 den of operation of the device is placed upon In the present application it is an object 30 the nurse, or other attendant, who is usually of the invention to employ a relatively weak in good health, and away from the patient, spiral or coiled spring in connection with the who may be in a very weak condition. In the plunger which. is operated by the patient, or present case the nurse, or other attendant, other person, to signal the attendant.

compelled to operate the sliding plate of It is a further object of the invention to hie switch against the spring contained imbed certain contact posts in the insulated therein having the greatest tension and the or bakelite base of the switch. largest amountof resistance and friction, Another object of the invention is to emwhile the patient, in whatever weakened conploy a combined plunger guard and contact 40 dition, may readily and quite easily operate mechanism for the switchf the call switch and signal the nurse, or The invention will be further understood other attendant, by pulling the chain or cord by reference to the accompanying drawings t the action of relatively weaker illustrating one embodiment thereof, al-

-: and with much less friction involved though it will be understood that changes whole operation. and modifications therefrom may be made In many forms of call switches for hoswithout departing from the spirit of the inpital signal systems which have heretofore vention as set forth in the appended claims. been put izno operation, the burden upon In the drawings:

the patient has been so heavy and onerous Figure 1 is a front elevation of the call in many cases, that engineers and architects switch and shows the front plate thereof with 7 the pull cord or chain to be operated by the patient, this cord or chain being shown in various positions.

Figure 2 1s a front elevatlonal view showing the wall box and also illustrating the slide bar and movable switch element, and is on the line 22 of Figure 4. v

Figure 3 is a rear view of the call switch mounted on the front plate and is shown on the line 3-3 of Figure 4, looking in the direction of the arrows andin a direction opposite to that of the line 2-2 of Figure 4.

Figure 4 is a vertical cross sectional view .of the call switch on the line of Figure 3. I

Figure his a front view of the slide bar and contact mechanism of the call switch with the cover plate removed.

Figure 6 is a transverse sectional view of the insulated or bakelite base and several contacts on the line 6-'6 of Figure 5.

Figure 7 is a longitudinal view through the base and the contacts shown in Figures and6, on the line 7- 'Z ofFigureh.

Figure 8 is a front elevational View of the slide bar of the switch and omitting the movable switch element and contacts Figure 9 is an enlarged view of the assemled parts of the outer end of the plunger, the inner end of the pull cord or chain and the manner of encasement. I

Figure 10is an enlarged View showing the parts illustrated in Figure 9, prior to assembly in operative position.

Figure 11 is a diagrammatic View showing the various electric light and buzzer circuits operated by the call switch.

Figure 12 is a longitudinal central sectional view of thecall switch showing the condition thereof after having been reset and with the lights out and the buzzer not in operation, on the line 12-12 of Figure 15. Figure 13 is a longitudinal central sectional view, of the call switch showing the condition of the parts thereof with the lamps illuminated and the buzzer not in operation, on the line 13-13 of Figure 16. V

, Figure 14. is a' longitudinal central sectional view of the call switch showing the condition of the parts thereof with the lamps illuminated and the buzzer in operation, 5n the line 14-14of Figure 17. Y I

Figure 15 is a transverse sectional view on the line 15 15 of Figure 12.

Figure 16 is atransverse sectional view on the line 1616 of Fi ure 13, and v Figure 17 is a transverse sectionalvicw on the line 14 14 of Figure 17.

, By referring to F igure 11, which shows the circuit which is preferably used in connection with the call switch of the inventiomthe pur-' pose of the invention maybe more readily,

understood, 7

- A source of current supply, such as the battery 20, is connected between the main lines 21 and 22. The signalling devices for the removed into connection therewith, it will also contact with fixed contacts 29, and 31.

Contact 29 may control a door lamp 32 arranged in a connection 33 from said contact to the main wire 21,- and also a call lamp 34 arranged in a parallel connection 35. Either or both of these visual signals may be moved for indication at the door of the sending station, or at some nurses station in the hospital, or other place, and of'course, other parallel connections from this contact to other; signal devices may be employed if desired.

The contact 31 may be connected through a common wire 36 with like contacts of other signal-initiating stations, and this wire 36 may be connected as at 37, through the lamp 38 to the main wire 21, so that the lamp 38 may serve as a pilot common to a plurailty of signal-initiating stations. The contact 30 may be connected through a commonwire 39 with like contacts of other signal-initiating stations, and this wire 39 may be connected through a lamp 40 to the common wire 21, so that the lamp 40 may serve asa pilot common to a plurality of signal-initiating stations.

Provision of another auxiliary contact 41, with a contact 81 is made through conductor 43 connected tothe movable switch element 23, and connected on the other side through the wire 44 with an audible signal means, such as a buzzer 45, to the other main wire 21. The audible signalling means may be located in any place desired, preferably within hearing distance; of the transmitting station so that the patient, or other person, initiating the signal, may be self-assured that the audible signal is given. 7 o r In the embodiment of the call switch illustrated in the drawings, the switch is shown as being fitted in a wall box 46 in an aperture 47 in the wall 48, or other support. It will. he

understood, however, that the call switch may be attached to the wall, or other support, in any suitable manner, or it may be placed in a container and suitably supported;

The call switch is secured to. the back mounting plate 49, the call switch with the mounting plate is secured to theturned in upper and lower ears 50 and 51, respectively, of the wall box 46 by means of the screws 52 and 53 at the upper and lower ends, respectively.

Themounting plate 49 is spaced from the wall and from the wall box by the spacers 54 and 55.

The outer cover plate 56 is secured to the mounting plate and held in position against the wall by the plurality of screws 57, passing through the cover plate and the back mounting plate. The cover plate 56 is large enough to entirely conceal the wall box and the back mounting plate 49.

To the rear face or under side of the back mounting plate 49, an insulating base or block 58 is secured, as by screws 59, the other face of this block being channeled,'as at 60, in a vertical direction for reception of the movable or sliding switch and its associated parts. The slide bar 61 has suitably secured to it, by riveting, the four pronged movable contact plate or switch 23, and to the upper end of the slide bar 61, and suitably insulated therefrom, is secured a slide stud with a knurled operating handle, generally designated 62.

The slide bar 61 is provided with the slots 63, 64 and 65, the slots 63 and 64 are rectangular, while the slot 65 has its lower portion rectangular and its upper portion 66 circular. Guiding screws 67 and 68 are screwed in the base or block 58 and pass through the slide bar 61 and guide the latters vertical movement.

The movable switch element 23 and the slide bar 61 being secured together coact at all times. The four extensions or prongs of the switch element 23 and numbered 24, 25, 26 and 27 are brought into connection with the respective fixed or stationary contacts 28, 29, 30 and 31.

The stationary contact posts 28, 29, 80 and 31 are permanently secured in the insulating block or base 58. As shown more particularly in Figures 6 and 7 of the drawings, they are embedded or molded into the bakelite which is preferably used for the insulating block 58. The lower ends of the contacts 28, 29, 30 and 31 project beyond the surface of the channel portions 60 of the block 58 and contact with these ends is made by the prongs or arms 24, 25, 26 and 27, respectively, of the movable switch element 23 as more particualrly shown in Figures 5 and 11.

Each of the contact posts 28, 29, 30 and 31 extend through the insulating block 08 so that the surface thereof opposite the contact faces, are flush with the opposite face of the block. Each contact is provided with a screw threaded aperture designated 69, into which is screwed a screw designated 70. Each of the apertured contacts and their respective screws 70 serve as binding posts.

The relatively strong coiled spring 71 is located in the recess 7 2 in the base or block 58. A boss 73 formedby turning in a portion of the slide bar 61, extends from the slide bar 61 into the recess 7 2. The top of the spring 71 is in constant engagement with the bottom face of the boss 73 and through the instrumentality of the boss 7 3 exerts a constant upward force on the slide bar 61.

A latch or plunger 74 having enlarged head portions 75 and 76 of two different diameters is placed in and extends through an aperture 77 in the lower end of the base or block 58. The latch or plunger 74 is provided at its rear end with screw threads adapted to receive the nut 78, which is preferably round.

A metallic sleeve 0r thimble 79, having its rear end provided with an annular ledge 80 is fitted into the aperture in the lower portion of the insulating block 58. A contact plate 81 is secured to the rear face of the insulating block 58 by means of the bolt 68. The lower end of the contact plate 81 is provided with an aperture through which the sleeve or thimble 79 surrounding the latch or plunger 74 extends. The contact plate 81 rest-s against the ledge 80 of the sleeve or thimble. A relatively weak coiled spring 83 is mounted on the latch or plunger 74 and is interposed between the nut 78 and the rear end of the thimble or sleeve 79, in contact with the contact plate 81.

The rear end of the latch or plunger 74 with the nut 78 is protected and guarded by the housing 84 which is open at its top and bottom.

The housing 84 is provided with the inwardly extending wall portions 85 and 86 and the laterally extending foot portions 87 and 88, the foot portions being held against the rear surface of the insulatin block 58 by bolts and nuts 89 and 90. The wall 86 is apertured at 91 to permit the insertion therein of one end of the buzzer contact strip 41, the other end of the strip 41 being held in place by the bolt and nut 90.

The relatively weak spring 83 which is coiled about the rear end of the plunger 74 has one end in contact with the reduced annular rear end of the thimble or bushing 79 and has its other end engaging the front face of the round nut 78. The coiled spring 83 always presses rearwardly against the round nut 78 to keep the plunger 74 in its normal and inoperative position.

It is important that proper adjustment between the rear end of the thimble or bushing 79, the spring 83 and the nut 79 be maintained and accordingly the nut '78 should be firmly secured to the rear end of the plunger or latch 74, as by soldering.

The contact 41 extends from a position adjacent the rear end of the latch or plunger 74 and between the contactbar or plate 81 and the round nut 78, secured to the end of the latch or plunger 74. The other end of the contact 41 is secured by the bolt and'nut to the-laterally extending leg 88 of the latch guard 84. The bolt and nut 90 serves as a binding post for th contact 41 which is connected through the conductor 44 to the buzzer 45.

i The metallic protector or guard 84 extends across the rear of the base orblock 58 from the binding post 90 to the bolt or nut 89, also serving as a binding post and thus furnishes a connection for an additional signal, such as another buzzer. V

'The construction of the head 76 of the latch or plunger 74 is best shown in the enlarged detail views of Figures 9 and 10. A metallic ball pull chain 92, or other suitable means, such as a cord, is used tooperate the plunger 7-;- against the action of the coil spring'83. The head of the enlargedportion 7 6 of the plunger comprises the enlarged outer end portion 93 0t thelatch or plunger 7 l, the fiber post 94, which is'bored and provided with the central aperture 95, the fiber disc 96 andthe outer casing 97. The method of assembling the parts of the enlarged head portion of the plunger is shown in Figure 10.

The plunger 7 l is inserted into the outer casing 97 through the aperture 98 in one end of the casing. The vfiber post 94 is then set upon the enlarged end93 o'frthe plunger. Theend of the metallic pull chain is inserted into the fiber disc 96 by forcing the end of the chain through the radial slot 99 of the disc. This radial slot is merely a narrow cut in the disc where a relatively small hole100 has been bored large'enough to receive the link connecting the two end balls of the chain. lVhen the posts 94: and the disc 96 with the end of the metallic pull chain 92 have been placed against the enlarged portion 93, the end 101 of the casing is pressed or flanged inwardly against the disc 96 as shown at 102. The enlarged head as thus assembled is shown in Figure 9.

The enlarged heads and 93 of the plunger 7 i, the fiber post or filler9 and the disc 96 are of such dimensions that the end of the metallic ball chain is always outside of t'heouter line oi the outer plate of thecall switch. This is the situation even though the latch or plunger is in itsinnermost position as shown in Figures12 and 15 of the drawings. I 1

It will further be seen that by means ofthe associated.'-parts as shown particular-L in Figures 9 and 10 the metallic ballpull chain is enabled to operate the latch or plunger 7 i and is insulated therefrom by being held in the fiber disc 96 and the fiber post 94 from contact with the metallic latch or plunger 7% and the metallic casing-97. The cover plate 56 is apertured opposite the plunger 7 1 to permit the plunger head 76 to extend through and beyond the outer face thereof. A metallic housino' 103 for the end of the plunger head is inserted in the aperture in the outer plate 56 and suitably held in the cover plate as by outwardly turned flanges on the inside surface thereof. The housing is provided Wltll the aperture .04: to

% permit the pull chain 92, connected with the The mounting plate l9 and the outer 1ne-.

tallic cover plate 56 have apertures 105 and 106 respectively registering w1th each other, to permit the upward and downward 1novemen-t or the insulated stud secured in the upper end of the slide bar 61 and which is provided with the knurled handle 62. The aperture 106 is wide enough to enablethe cover plate 56 to be placed on the call switch mounted on the plate 4:9 and permit the lrnurled head 62 to readily pass therethrough. The aperture 106 must, of course, be of sufficient length to permitthe head to be operated upwardly and downwardly a sutlicient distance for proper operation of the slide bar 61.

, The mounting plate 1-9 isprovided with two elongated slots 107 and 108' placed respectively at the top and bottom portions of the plate in order to compensate for any Vd-l'lil? tion there may be from the correct upright position of the box and thus permit the call switch, the plate upon which it is mounted and the cover plate 56, to he placed in straight and upright positions. 7 r

The operation of the call switch is as follows, and in this connection particular'reterence may be had to'Figures 12 to 17 in elusive:

In Figures 12 and 15 the call switch is shown with the lights oil or unilluminated.

In Figures 13 and16 the call switch is shown with the lights on and illuminated but the buzzer or audible signal in an inoperative position. In Figures 14 and 17 the call switch is shown with the lights on and illuminated and with the buzzer or audible signal in operative position.

In Figures 12 and 15 in which no visual or audible signals are'being given at the receiving stations, it will be observed that the handle62 with its associated stud secured in the slide bar 61 is in the lower partof he slots 105 and 106, the'handle having been depressed. The slide bar 6l also been dc pressed to its lowermost position carrying with it the boss 73 extending into the recess 72 causing the spring 71 to become pressed.

At this timethe latch or plunger 7 4t is in its innermost position with the enlarged head portion 75 of smallest diameter in the circular recess 66 of the slide'bar 61.. The latch or plunger 7 has been broughtto this position previously by the action of the coiled spring 83 against the nut 78, the nut being soldered to the plunger 7 4. I i V It will also be seen by reference-to Figure 15 that the contact 41 is not in contact with the nut 78 of the plunger 74.

By reference to Figure 5, it will be seen that when the slide bar 61 carrying the movable switch element 23, is in its depressed position as shown in Figures 12 and 15, the prongs or laterally extending contacts 24, 25, 26 and 27 are not in contact with the respective contact posts 28, 29, 30 and 31, and therefore the visual signals or lamps are unilluminated.

In case the patient, or other person, desires to cause the visual signals or lamps to be operated the patient pulls the metallic pull chain or cord 92, which in turn pulls the latch or plunger 74, with its enlarged head 76 from the position shown in Figures 12 and 15, to that shown in Figures 13 and 16. As the plunger is pulled, as stated, the enlarged por tion 75 is pulled out of the enlarged slot 66, thereby readily releasing the slide bar 61 so that it snaps and moves upwardly through the action of the spring 71 against the iuturned boss 73.

At this time the stem portion of the plunger 74 is in the slot in the lower portion of the slide bar 61. The slide bar has also been permitted to move upwardly be-,

cause of the slots 63 and 64 through which the guiding screws 67 and 68 pass. The handle or button 62 with its stud connected to the sliding plate 61, though insulated therefrom,

is now in its uppermost position in the slots 105 and 106, respectively, and the laterally extending prongs or contacts 24, 25, 26 and 27 are in contact with the respective contact posts 28, 29, 30 and 31 causing current to flow in the various circuits and illuminating the various visual signals or lights.

It will be noted, however, at this time, as shown in Figures 13 and 16, the nut 78 is brought forward a slight distance and compresses the spring 83 interposed between the nut 78 and the reduced annular head of the bushing 79. The nut 78 is not pulled forward the entire distance it may travel, nor is the spring 83 entirely compressed and therefore the nut 78 remains out of contact with the strip contact 41, and consequently, since no current flows through the nut 78 and the contact 41, the audible signal or buzzer is not operated.

In order to cause the audible signal to operate or ring the buzzer for the nurse, or other attendant, the patient may pull on the metallic pull chain or cord 92 slightly more than was done to cause the illumination of the visual signals or lamps, as is shown in F igures '13 and 16. This signalling by means ofthe buzzer is shown in Figures 14 and 17. Itwill also be seen from an inspection of Figures 14 and 17 that the call switch is shown as continuing to operate the visual signals orlamps.

The pull on the chain or cord 92 pulls the latch or plunger 74 a little further outwardly than wasthe case in Figures 13 and 16. This causes the nut 78 to make contact with the strip contact 41 causing the audible signal or buzzer to operate. It will thus be seen that while the buzzer is operating the lamps remain illuminated. The buzzer will operate, however, only while the patient is pulling the plunger 74 and causing the nut 78 to contact with the strip contact 41. On release of the chain or cord 92 by the patient, the buzzer will cease operating but the lamps will remain illuminated. It is only by the downward sliding or depression of the handle or button 62 causing the slide bar 61 to travel downwardly and break the circuits at the contacts 24, 25, 26, 27 and 28, 29, 30, 31 respectively, that the lamps will be extinguished.

It will be seen from the foregoing statement of the operation of the call switch, that when the chain or cord 92 is pulled the slide bar 61 with its slide button 62 is operated only in an upward direction but is never operated in a downward direction or a set position. The only way in which the call switch may be reset to extinguish the lights or illuminating signals is for the nurse, or other attendant, to push down on the slide button 62, which in turn pushes the slide bar 61 clownwardly and compresses the spring 71 through the medium of the boss 73. The action of the coiled spring 83 between the nut 78 and the bushing 79 causes the plunger 74 to be forced rearwardly into position in the slot 66,

Where it is held against the slide bar 61.

Having thus described theinvention what I claim and desire to secure by Letters Patent is:

1. Electrical switch means of the character described comprising in combination, a

cover plate, a wall box, said wall box having inwardly turned apertured ears, a mounting plate, said mounting plate having elongated apertures at its top and bottom adapted to register with the apertures in the wall box ears and permitting adjustment of said switch means with relation to said Wall box, spacers between said wall box and said mounting plate, an insulating base, a sliding bar on said base, a contact member secured to and coacting with said sliding bar, Contact posts in said base adapted for inclusion in signaling circuits, said Contact member and said contact posts coacting to make and break the signaling circuits, a spring acting on said sliding bar to elevate it to circuit closing position, manual means for depressing said. sliding bar to circuit opening position, a plunger associated with said sliding bar, a pull chain entirely outside of and beyond the outer face of said cover plate, said pull chain being connected to said plunger whereby said plunger ing circuits.

2. Electrical switch means of the character described comprising in combination, a

cover plate, an insulating base, a sliding bar on said base, a contact member secured to and coacting with said sliding bar, contact posts of said cover plate, a contact bar on the rear face of said insulating base electrically connected with said sliding bar,an enlargement at the rear end of said plunger, a second spring coiled about said plunger between said last mentioned contact and said enlargement, saidpull chain being connected to said plunger whereby said plunger may be operated to aid in closing said signaling circuits. 7

3. Electrical switch means of the character described comprising in combination, a cover plate, a wall box, said Wall box having inturned apertured ears, a mounting plate -intermediatesaid cover plate and ears, said mounting plate and said wall box being connected together with spacers in between, an insulating base, saidbase being carried by said mounting plate, a bar slidably mounted on said insulating base, a contact member secured to and coacting with said sliding bar, contact posts in said base for inclusion in signaling circuits, said contact member and said posts coacting to make and break signaling circuits, both visual and audible, a relatively strong coiled spring in said base operatively associated with said sliding bar, said spring acting on said sliding bar contact member to elevate it to circuit closing position, manual means for depressing said contact member to circuit opening position, a plunger extending through an aperture in said insulating base, a pull chain entirely outside of and beyond-the outer face of said cover plate, a bushing in the aperture through which the plunger extends, a contact on the rear face of said base connected to said bushing and. electricallyconnected to said sliding bar, an enlargement on the rear end of said plunger, a relatively short coiled reset spring on said plunger between said enlargement and the rear end of said bushing, said pull chain being connected to said plunger and whereby said plunger may form contacts to operate said signaling circuits.

4. Electrical switch means of the character described comprising in combination, a cover plate, an insulating base, a sliding bar on said base, 'a contact member secured to and coacting with said sliding bar, contact posts in said base adapted for inclusion in signaling circuits, said contact member. and said contact posts coactingto inake and break the; signaling circuits, each of said contact posts being embedded or molded in said insulating base with one end thereof protruding beyond the surface of said insulating base, each of said posts having a screw threaded aperture for the reception of a screw, a spring acting on said sliding bar to elevate it to circuitclosing position, manual means for depressing said sliding bar to circuit opening position, a plunger associated pull chain entirely outside of and beyond the outer face of said cover plate, said pull coacting with said sliding bar, Contact posts in said base adapted for inclusion in-signaling circuits, said contact member and said.

contact posts coacting to make and break the signaling circuits, a spring acting on said sliding bar'to elevate it to circuit closing position,=manual means for depressing said sliding bar to circuit opening position, a

plunger associated with said sliding bar, a

pull chain entirely outside of andbeyond the cute f face of said cover plate, said pull chain being fastened to said plunger to pull said plunger in a direction transverse to the move ment of said sliding bar, a contact strip on therear face of said insulating base, a bushing surrounding said plunger, an enlargement on the rear end of said plunger, a relatively weak coiled sprlng free upon'and surrounding said plunger between said enlargement and the rear end of said'bushing, and a contact withits free end intermediate said bushing and said enlargement, adapted to be brought into contact with said enlargement to cause an additional signal to be made upon the pulling of said pull chain. 1

6. Electrical switch means of the character described comprising in combination, a cover plate, an insulating base, a sliding bar on said base, a contact member secured to and coacting with said sliding bar, contact posts in said base adapted for inclusion in signaling circuits, said contact member and said contact posts coacting to make and break the signaling circuits, a spring acting on said sliding bar to elevate it to circuit closing po-. sition, manual means for depressing said sliding bar to circuit opening position, a plunger associated with said sliding bar, apull chain entirely outside of and beyond the outer face of said cover plate, said pull chain being fastened to said plunger to pull said plunger in a direction transverse to the movement of said sliding bar, a contact strip on-the'r'ear face of said insulating base,'abushing sur rounding "said plunger," an enlargement on V i with said sliding bar, a:

the rear end of said plunger, a relatively Weak coiled spring free upon and surrounding said plunger between said enlargement and the rear end of said bushing, and a guard for the rear end of said plunger, its enlargement and said second spring, the said guard being provided With an aperture through which the free end of said last named contact strip extends.

7. Electrical switch means of the character described comprising in combination, a cover plate, a mounting plate adapted to be secured to a Wall box, an insulating base secured to said mounting plate, a sliding bar mounted on said insulating base, a contact member secured to and coacting with said slide bar, contact posts embedded in said base for inclusion in signaling circuits, said contact member and fixed contact posts coacting to make and break signaling circuits, a relative ly strong spring acting on said sliding bar to elevate it to circuit closing position, manual means including a handle protruding from said slide bar through said mounting and cover plates for depressing said sliding contact member to circuit opening position, a plunger extending through an aperture in said insulating base, and also through an aperture in said cover, a. pull chain secured to said plunger, said plunger having heads of difierent diameters at its front end and an enlargement at its rear end, a second or relatively Weak coiled spring upon said plunger adjacent the rear end of said plunger, the head of said plunger of greatest diameter comprising an apertured extension post of non-metallic material seated on said head, a disk of insulated material upon said post, said disk being provided with a radial slot adapted to receive the end of said pull chain, said pull chain being thereby insulated from said plunger, a housing secured in said cover plate, said housing extending beyond said cover plate sufliciently to permit said pull chain to be entirely outside of and be yond the outer face of said cover plate and said housing being provided with an annular curved opening to permit ready movement of the pull chain in any desired direction.

In Witness whereof, I hereunto subscribe my name this 12th day of April, A. D. 1929.

WVILLIAM P. CROCKETT.

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