US2079003A - Electric switch device - Google Patents

Description

May 4, 1937'. s. B, DICK ELECTRIC SWITCH DEVICE Filed July 8, 1936 INVENTOR.

ATTORNEYS 1' -2- F27 ll 2 FE/J.

A 24ml! Patented May 4, 1937 UNITED STATES PATENT OFFICE ELECTRIC SWITCH DEVICE Application July 8, 1936, Serial No. 89,492

8 Claims.

This invention relates to improvements in electric switch devices.

The principal object of the invention is to provide an electric switch device which can be safely employed for opening and closing electric circuits at places where combustible or explosive vapors or gases are present. A further object is to provide a device of the above-mentioned type which will be durable and yet may be readily manufactured in quantities at a relatively low price.

With the above objects in view, as well as some others that will be obvious to those skilled in the art, from the description hereinafter, the invention consists of an electric switch device, which, while permitting a liberal amount of distance between the circuit terminals, is relatively compact and, therefore, can be accommodated in a small space entirely closed from the outside atmosphere by a casing formed from molded fireproof and corrosion resistant material set from a. plastic condition, in which material the conductive material forming the terminals of the circuits may be solidly embedded so as to avoid leakage from the space inside the casing to the atmosphere outside it or vice versa.

The invention will be described in detail in connection with the accompanying drawing, illustrating the best embodiment of the invention.

In the drawing:

Fig. l is a side elevation of one side of a switch device embodying the invention.

Fig. 2 a similar View of the opposite side of the switch device.

Fig. 3 an end elevation.

Fig. 4 a top plan or front view.

Fig. 5 a bottom plan view or elevation, enlarged, of the casing member of the device, with the cap plate and packing device removed.

Fig. 6 a bottom plan view of the completed device.

Fig. 7 a central longitudinal sectional view taken on the line (-1, Fig. 5.

Fig. 8 is a central transverse sectional View, enlarged, on the line &8, Fig. 1.

Fig. 9 is a detail view illustrating a. modified form of the invention in which binding screws are employed for connecting the circuit wires.

Fig. 10 is a front elevation showing the switch device secured to a vertical wall plate, broken away.

Fig. 11 a side elevation. of the same, the wall plate being in section.

Figs. 12 and 13 are detail views hereinafter referred to.

Referring to the drawing, A is a receptacle comprising a casing member It, a cover or lid H and a packing device or gasket i2, located between the casing member [0 and the cover H. The casing member ID is a recessed block of fireresistant, electrical-insulating material, this block being formed of molded solidified plastic material most advantageously of the type termed phenolic resin such as bakelite, or other composition which is fire-resistant and capable of being molded and set or hardened. The cover is 10 advantageously of the same type of material as the casing member ill, but could be made of any other fire-resistant material.

The packing device or gasket I2, is fire-resistant and somewhat compressible. In practice this packing device is formed of fish paper.

The cover H is held to the casing member by suitable means which will resist any internal pressure that might be developed accidentally within the receptacle; which will allow the cover to be removed readily; and which will serve to force the cover toward the casing member Ill to compress the packing device or gasket l2, to insure a substantially air-tight joint. In the present example, the holding means comprises a plurality of internally screw-threaded sockets I3, embedded in the wall of the casing member while the latter is in its plastic condition, each socket having its exterior arranged to be properly gripped or engaged by the material of the 9 wall, as for example, by providing projections on the outside surface of the socket, which can be done by knurling it. The holding means also comprises suitable screws l4, passing through holes in the cover II and screwed into the sockets, the screws most advantageously having their 5 heads countersunk into the cover.

The casing member is recessed to provide a chamber for the circuit-making and breaking elements, this chamber, when viewed as in Fig. 5, being contracted at the center and arc-shaped at each end. On the front or outer face of the casing member there is provided a hub portion l5 formed integral with the body of the casing member, and projecting an appreciable distance from the face of the casing member. At the center of the chamber there is provided a metallic cylindrical bearing member or bushing l6, Figs. '7 and 8, which extends through the hub portion I5. A switch spindle I! having an enlarged head l8 at its outer end, extends through the bore of the bearing member l6, projecting a short distance into the chamber of the casing member l0. Its innermost end I!) is reduced and made polygonal in cross-section, for example,

square, as shown, to enter a correspondingly shaped hole in a resilient contact arm or plate 25), whose central portion lies fiat on the shoulder formed by the said reduced end and is held to the spindle in any suitable way, as for example, by swaging or riveting the end of the square portion. Between the head I8 of the spindle and the face of the bushing it, there is a packing washer 2i carried by the spindle. The packing washer 2i is made of material softer than the spindle and of such a nature that during use, the spindle head It will tend to produce a lapping action on the eoacting face of the washer 2|, due to continuous pressure of the spindle head 18 against the said face of the washer 2|. As a result of this lapping action the packing effect of the washer 2| against leakage of air is improved with use. One material suitable for use as a packing washer and having the properties stated, is a good grade of vulcanized fibre.

The contact arm or plate 29 has its ends bent downward toward the bottom of the recess, where suitable contact devices are located. The number and location of these will, of course, depend upon the number of circuits to be controlled by the switch. In the present example three contact devices 22, 23 and 24 are shown, for use with two circuits. In the present embodiment of the invention, the contact device 22 is a strip of conductive material of such a length and width that the corresponding end of the contact arm or plate 28 will remain in engagement with the strip at all times through the entire angular movement of the arm 25. Furthermore, this strip is also long enough to extend outside the casing memher it! and is provided at each end with an end portion 22 extending at right angles to the main portion of the strip forming the contact device 22, and embedded in the external casing wall.

The contact devices 23 and 24 may also be in the form of strips, their inner ends being separated to a suitable extent, these strips extending in opposite directions to the outside of the casing member ill, where the respective ends are provided with end portions 23 and 24=-, respectively, each extending at right angles to the length of the corresponding strip and being embedded in the casing wall. It is an important feature of the present invention that although the contact devices 22, 23 and 24 are embedded in the material forming the casing wall so as to make a sealing contact therewith, yet their operative faces, over which the ends of the contact arm 26 ride, are above the level of the bottom oi the recess, in order to insure a good contact with the respective ends of the contact arm, and also to prevent the molded material in its semiplastic state under heat and pressure from flowing over and adhering to said operative surfaces, which otherwise would occur and thereby necessitate an extra mechanical cleaning operation to remove such overflow material.

In order to positively lock the contact-devices in the material of the casing wall, against longitudinal forces, the contact device, 22, is provided with a hole as indicated at 22 and each of the contact devices 23 and 24 with a hole, as indicated at 23 and 24 respectively, into which holes the material of the casing wall may flow to a limited extent and when set will firmly hold its contact devices. The holes in the contact devices are in line with corresponding holes in the wall of the casing member ID, as indicated at w Fig. 5. It will be noted that these holes are close to the upturned outer ends of the contact devices,

so that if the said upturned ends are drilled and tapped for binding screws, 25, the ends of the screws may project into the corresponding hole, as shown in Fig. 9.

The holes W are formed in the wall of the casing member, at the time of molding it, by pins (not shown) which are a part of the mold, and these pins serve to enter, but not entirely fill, the holes in the respective contact devices and thereby hold the latter during the molding operation.

One end of the resilient contact arm 20 rides on the contact device 22 and at all times presses firmly against it. The other end of the contact arm 23 may ride on and press firmly against the contact device 23, or pass from it and ride on and press firmly against the contact device 24, or vice versa, according to the direction of movement of the spindle ll.

1* will be noted that the contact arm 20 may any one of three operative positions, as follows: it may electrically connect contact de vice 23 with contact device 22, or contact device "ith contact device 22, or it may occupy an mediate position in which one end of the co...tact arm 23 rests in the space between the o contact devices 23 and 24, so that both cirsuits are broken. For the purpose of retaining the contact arm 20 in any of the three positions to which it is adjusted, each end of the contact arm may be provided on its under side with 1 protuberance, or detent, 2B, which may be or struck up from the metal of which the 20 is made, and each contact device 22, 23, and 24, may be provided with a recess 2'! to receive the respective protuberance. As the pro tuborances are rounded and the recesses have sloping walls, the respective protuberances will readily ride into and out of the corresponding recesses when the spindle is rotated, yet at the same time, a protuberance, when in its recess will hold the spindle H, and contact arm 20, sufiiciently to prevent them. from moving accidentally by ordinary jarring or vibration. Also the protuberances, as they ride into the respective reesses, provide an audible click denoting the proper positioning of the contact arm. .t is to be observed that as the recesses are usually stamped or pressed into the respective stationary contact devices, a bulge or projection of the metal is provided on each of said contact devices, opposite its respective recesses. These bulges or projections are embedded in the material of the wall of the casing member and thus aid in look- 'ng the contact devices in place.

i will be noted that, as the contact arm 2i! is formed of resilient material, and is what might termed arched, that although at its ter has its ends bent down toward the con- J devices, it acts as a plate spring to maintight contact between the ends of the contact arm and the respective contact devices, and also reacts to pull the head N3 of the spindle topacking washer 2i so as to prevent access the outside atmosphere to the interior of the casing, and also takes up any slack due to wear 1 the parts.

Suitable means is provid spindle to an angular said hole, so that it will be held firmly therein. While this is satisfactory for light voltages, it is advisable with higher voltages to provide an insulating knob of molded plastic material, instead of the lever handle, as indicated at 29, Fig. 13. In this case the molded material when plastic will enter the transverse hole and when hardened will be firmly secured to the spindle.

The completed switch device may be secured to a wall or support in any suitably way. However, the device is particularly suitable for use in conditions where it is to be secured to the back of a vertical wall, or plate, with its hub portion projecting through and fitting snugly in a hole in said wall, or plate, as illustrated in Fig. 11, the wall, or plate, being indicated in crosssection at 30. In this case the wall, or plate, has a thickness about equal to the thickness of the hub portion.

The completed switch device may be secured to the wall or plate by screws indicated at 3|, which have their heads at the front of the said wall. The screw-threaded end of each screw is arranged to enter an internally screw-threaded socket device 32, embedded in the cover plate H, Fig. 6. As the screws 3| are located on a line at right angles to that which passes through the two screws I 4, and serve to pull the casing member toward its cover plate, there is obtained a substantially uniform distribution of the pressure clamping the casing member In to its cover plate H, whereby the packing device or gasket is properly compressed to prevent leakage of air. Although, as heretofore explained, the contact devices 22, 23 and 24 are partly embedded in the material which forms the wall of the receptacle but have their operative surfaces above the inner face of the bottom of the chamber, it is advantageous to have the space between the inner ends of the contact devices 23 and 24 completely filled with the same material as the wall, up to the level, or practically the level, of the said operative surfaces of the contact devices, so that the respective end of the contact arm 2! which rides along the operative surfaces of the contact devices 23 and 24, will stay at the same level in passing from one of said contact devices to the other, and not have to ride down into a depression and then up again, as is the case where the 2 space between the said inner ends of said contact devices 23 and 24 is not filled up even with the operative surfaces of said contacts.

The respective terminals of the electric conductors of the circuits in which the switch mechanism is to be included are connected to the outer ends of the corresponding contact devices in any suitable way, for example, by placing the respective terminals in close contact with the corresponding upturned ends 22 23 and 24*, Fig. 5,

and soldering them in such positions. When the contact devices have their outer upturned ends tapped and provided with screws, as indicated at 25 in Fig. 9, the terminal of the respective circuit conductor may be wrapped or bent around the screw, which is then screwed down tight to clamp the said terminal. In this case, it is advisable to put a drop of solder on each screw to solder it to the respective contact end. This'makes certain that there cannot be any sparking outsidethe switch, due to a loose binding screw.

From the description hereinbefore given it will be seen that the switch device of the present invention has its contact devices for making and breaking the respective electric circuits located in a relatively small chamber or recess enclosed by relatively thick walls of the receptacle so that the chamber is air and gas tight, the conductive connections which extend through the walls of the receptacle being so embedded in the walls as to form an adhesive union with the said walls, thereby preventing leakage of air or gas along the electric conductive connections from' the outside of the receptacle to the chamber inside or vice versa. Thus it is not possible for air charged with explosive vapors, or for explosive gases themselves, to enter the switch chamber in the receptacle directly. Even if, however, the explosive gas or vapor should gain access to the switch chamber, the amount is so small that, if ignited, it would not develop pressure enough to burst the relatively thick walls of the receptacle even though this is of hardened plastic material. Furthermore, as the pressure will act on the end of the spindle l9 it will press this outward against the action of the resilient contact arm 20, thus allowing the gas to escape around the spindle H, in the joint or clearance between the spindle and the cylindrical bearing 16, and then radially outward along the inner face of the packing washer 2|, which, of course, is not then under compression by the spring action of the contact arm, because of the opposing pressure of the exploded gases acting on the inner end of the spindle. It will be observed that owing to the length of the annular passage between the spindle and the bearing through which the gas must pass on its way from the interior chamber to the outside, as well as the cooling effect of the metal of the spindle and of the cylindrical bearing, any gas which finally exits from the receptacle will be cooled down and extinguished so that it cannot ignite the explosive gases, if any, in the surrounding air.

While the electric switch of the present invention is particularly suitable for use in an environment containing explosive gases and vapors, it also is advantageous when used in an environment having corrosive vapors or gases which might corrode the metallic contact devices if brought in contact therewith. Owing to the fact that these contact devices are enclosed in an air or gas tight receptacle, they will be protected against corrosion.

What is claimed is:

1. An electric switch device comprising an air tight receptacle having a relatively small chamber, a spindle extending from the outside through one wall of the receptacle and having one end projecting into the chamber, a resilient contact arm within the chamber and attached to the inner end of the spindle, said arm having ends bent toward the bottom of the chamber, a plurality of contact devices located at the bottom of said chamber and arranged to coast with the respective bent ends of the contact arm, each contact device having a portion extending through a wall of the receptacle to the outside and arranged to be there connected to an exterior circuit conductor, an enlargement on the spindle outside the receptacle, a packing washer mounted on the spindle between said enlargement and the recap-- tacle and arranged to be pressed against said receptacle by the elastic reaction of the contact arm against the respective contact devices, and means outside the receptacle for giving the spin dle a rotary motion in either direction.

2. An electric switch device comprising 2. casmember having a relatively small chamber, a spindle extending from the outside through one wall of the casing member and having one end Cal projecting into the chamber, a resilient contact arm within the chamber and attached to the inner end of the spindle, said arm having ends bent toward the bottom of the chamber, a plurality of contact devices located at the bottom of said chamber and arranged to coact with the respective bent ends of the contact arm, each contact device having a portion extending through a wall of the casing to the outside and arranged to be connected there to an exterior circuit conductor, an enlargement on the spindle outside the casing, a packing washer mounted on the spindle between said enlargement and the face of the hub portion and arranged to be pressed against the hub by the elastic reaction of the contact arm against the respective contact devices, means outside the casing member for giving the spindle a rotary motion in either direction, a cover, a packing device located between the cover and the casing member, and means for holding the cover and easing member together and compressing the packing device.

3. An electric switch device comprising a casing member of hardened molded plastic material having a relatively small chamber, a plurality of contact devices located at the bottom of the chamber, each contact device having a portion extending to the outside of the casing member through a wall of said casing member and embedded air tight therein, the outer ends of the contact devices being arranged to be connected there to an electric circuit, the respective portions of said contact devices which extend with in the chamber being only partly embedded in the bottom wall of the chamber and having their operative faces raised above the bottom of the chamber, a spindle extending from the outside through one wall of the casing and having one end projecting into the chamber, a resilient contact arm within the chamber and attached to the inner end of the spindle, said arm having ends arranged to coact with the operative faces of the respective contact devices, and means outside the casing for operating the spindle.

4. An electric switch device comprising a casing member of hardened molded plastic material having a relatively small chamber, a plurality of contact devices located at the bottom of the chamber, each contact device having a portion extending to the outside of the casing member through a wall of said casing member and embedded air tight therein, the outer ends of the contact devices being arranged to be there connected to an electric circuit, the respective portions of said contact devices which extend within the chamber being only partly embedded in the bottom wall of the chamber and having their operative faces raised above the bottom of the chamber, a spindle extending from the outside through one wall of the casing and having one end projecting into the chamber, a resilient contact arm within the chamber and attached to the inner end of the spindle, said arm having ends arranged to coact with the operative faces of the respective contact devices, means outside the casing member for giving the spindle a rotary motion in either direction, a cover, a packing device located between the cover and the casing member, and means for holding the cover and casing member together and compressing the packing device.

5. An electric switch device comprising a receptacle of hardened molded plastic material having a relatively small chamber, a plurality of contact devices located at the bottom of the chamber, each contact device having a. portion extending to the outside of the casing member through a wall of said casing member and embedded air tight therein, the outer ends of the contact devices being arranged to be there connected to an electric circuit, the respective portions of said contact devices which extend within the chamber being only partly embedded in the bottom wall of the chamber and having their operative faces raised above the bottom of the chamber, each of said portions having a recess in its operative face and a protuberance on the opposite face, a spindle extending from the outside through one wall of the casing and having one end projecting into the chamber, a resilient contact arm within the chamber and attached to the inner end of the spindle, said arm having ends arranged to coact with the operative faces of the respective contact devices, each of said ends having a protuberance arranged to ride into and out of the respective recesses in the contact devices, and means outside the receptacle for giving the spindle a rotary movement in either direction.

6. An electric switch device comprising a casing member having a relatively small chamber and provided with an integral hub member, a tubular bushing embedded in the wall of the casing member and hub member to provide a spindle bearing, a spindle extending from the outside, through the bushing and having one end projecting into the chamber receptacle and having one end projecting into the chamber, a resilient contact arm within the chamber and attached to the inner end of the spindle, said arm having ends bent toward the bottom of the chamber, a plurality of contact devices located at the bottom of said chamber and arranged to coact with the respective bent ends of the contact arm, each contact device having a portion extending through a wall of the receptacle to the outside and arranged to be there connected to an exterior circuit conductor, an enlargement on the spindle outside the receptacle, a packing washer mounted on the spindle between said enlargement and the receptacle and arranged to be pressed against said receptacle by the elastic reaction of the contact arm against the respective contact devices, and means outside the receptacle for giving the spindle a rotary motion in either direction.

'7. An electric switch comprising a casing member of hardened molded plastic material having a chamber, a plurality of contact devices located at the bottom of the chamber, each contact device having a portion extending outside the casing member through a wall of said casing and embedded air tight therein, the outer ends of the contact devices being provided with terminal ends embedded in the casing member, the casing member being provided with holes adjacent to the respective terminal ends, binding screws threaded into the respective terminal ends, and projecting into the respective adjacent holes in the casing member, a spindle extending from the outside through one wall of the casing and having one end projecting into the chamber, a resilient contact arm within the chamber and attached to the inner end of the spindle, said arm having ends arranged to coact with the operative faces of the respective contact devices, and means outside the casing for operating the spindle.

8. An electric switch device comprising a casing member having a chamber and provided with an integral hub member, a plurality of contact devices located at the bottom of the chamber, each contact device having a portion extending to the outside of the casing member and arranged to be there connected to an electric circuit, a spindle extending from the outside of the casing through the hub member and easing wall and having one end projecting into the chamber, a resilient contact arm within the chamber and attached to the inner end of the spindle, said arm having ends arranged to coact with the operative faces of the respective contact devices, a cover, a packing device located between the cover and the casing member, screws passing through the cover and packing and threaded into sockets embedded in the wall of the casing member, the heads of the screws bearing against the cover, a wall plate having an opening into which the hub member fits, screws extending through the wall plate and threaded into bushings embedded in the cover plate, the heads of said screws bearing against the wall plate, said screws being in a plane; substantially at right angles to the plane through the other screws whose heads bear against the cover plate, and means connected to the spindle outside the casing for operating it.

STEWART B. DICK.

Images