US2771521A - Remote control key switch - Google Patents

Description

Nov. 20, 1956 R. c. CRESSMAN ET AL 2,771,521

REMOTE CONTROL KEY swncn Filed Nov. 30. 1954 [h vent: 02 8: Robert C. Cr'essman, far/ F Re/fiman, by W 4. AW 77-: 9/) A t L, orn gy United States Patent Ofiice 2,771,521 REMOTE CONTROL KEY SWITCH Robert C. Cressman and Earl F. Reihman, Warwick, R. I.,

assignors to General Electric Company, a corporation of New York Application November 30, 1954, Serial No. 471,976 2 Claims. (Cl. 200-42) This invention relates to improvements in electrical switches and in particular to a single-pole, double-throw, momentary-contact, normally-open switch which is actuated by a separate key member of special design. It is possible to utilize the key member as part of the electrical circuit since this switch is for use in low-voltage control circuits as for the operation of on-off relays for the remote control of residential lighting circuits and the like.

In ordinary residential installations now in use it is customary to wire the lighting system from the lighting fixtures to the controlling wall-mounted switches with suitable high-voltage cable such as armored or non-metallic sheathed cable, which is adapted to operate under the full voltage with which the system is supplied, for example, 110 volts. Within recent years remote control wiring systems have been gaining popularity since they enable the use of an increased number of controlling switches at only a small additional cost over the conventional wiring systems.

The switch of the present invention has been primarily designed to operate in a low-voltage remote control wiring system operating at 24 volts. In such a system a relay which is actually a small two-coil solenoidoperated switch is mounted in one of the knock-out openings in a standard outlet box which supports a lighting fixture to be remotely controlled. This means that it is unnecessary to run high-voltage cable from the relay to the several control points or switches. Consequently, a great deal of expense is saved in wiring the lighting fixture inasmuch as low-voltage conductors, for example bell wire, may be run from the relay to the controlling switches. The average residence requires only one transformer to furnish the 24 volt power necessary to operate the remote-control relays regardless of the number of relays installed. An alternate arrangement would be to mount the transformer and a group of the relays in a single gang box near the service entrance switch. One of the early type of momentary-contact switches for use in a remote control wiring system is shown in the Smith Patent No. 2,587,399, while an earl, remote control relay is shown in the Hutt Patent No. 2,324,844 both of which are assigned to the same assignee as is the present invention.

In order to effect the wide acceptance of a remote control wiring system, it is understandable that a complete wiring system must be made available in order to accommodate the particular wiring problems and desired conveniences of the consumer. Consequently, it has been found necessary to produce a tamper-proof switch which must be operated by a special key for use in public places such as auditoriums, theaters, churches, as well as in outdoor lighting and outlet circuits, and power tool and other electrical equipment circuits in home workshops. This key switch makes it possible .to lock selected circuits in a remote-control wiring system, thereby making the switches safe from small children and practical jokers.

The principal object of this invention is to provide a key operated low-voltage switch for use in a remote control wiring system.

A further object of this invention is to provide a lowvoltage momentary-contact key switch with a centering 2,771,521 Patented Nov. 2t), 1956 spring that will act as a guide means during the insertion of the key in the switch housing.

A still further object of this invention is to provide a low-voltage momentary-contact key switch with a centering spring that exerts a force against the cover of the switch housing to press it against the mounting strap in order to correct any loose fitting conditions between the mating parts.

Our invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Figure 1 is an exploded view of a low-voltage momentary-contact key switch embodying our invention, showing also the special design of the key.

Figure 2 is a cross-sectional elevational view taken transversely through the center of the key switchof Figure 1.

Figure 3 is a simplified wiring diagram of a remote control lighting system in which is incorporated the subject key switch.

Figure 4 is a partial cross-sectional bottom plan view of a key switch embodying our invention taken on the lines 44 of Figure 2 showing in particular the cooperation between the centering spring and the key with relation to the cover of the switch housing.

Referring in detail to the drawing, Figure 1 shows in detail the parts which make up the key switch 10 that embodies our invention. First, there is a recessed base 11 molded of a suitable insulating material and having a'bottom wall 12 and opposite side walls 13 and end walls 14. The side walls 13 are provided with upwardly extending notches 15 and 16 of dissimilar size, while the adjacent end walls 14 have their upper edges arranged below the upper edges of walls 13 so that the cover 20 of the switch housing is supported in the notches 15 and 16 as well as on the upper edges of the end walls 14, as will be better understood hereinafter. A center contact 17 is mounted by means of a hollow rivet its on the raised shelf 19 formed onthe bottom wall 12 of the base. Side contacts 21 and 22 are mounted in openings formed through the bottom wall 12 to be symmetrically spaced from the longitudinal axis of the center contact 17 as well as around the inner end of said center contact. In actual practice a 4-inch color-coded pigtail lead is secured to each of the contacts 17, 21 and 22 in a manner which is well known in this art. 23 is threaded into the hollow rivet 18 and soldered therein while the remaining two leads 24 are joined to flush-type recessed terminals of contacts 21 and 22 formed on the bottom of the base 11.

The cover 20 is also a box-like part molded from a suitable insulating material and it is of a size to enclose the top opening in the base 11 so as to form a hollow switch housing. The outer appearance of the cover 20 is made to conform to a standard remote control pushbutton switch although it should be appreciated that this does not form a part of the present invention and that modifications may be made in this detail without aifecting the invention claimed herein. Trunnion-like members 26 and 27 are located on the sides of the cover 20 to mate with the notches 15 and 16 respectively. It should be understood that the mating parts 15, 26 and 16, 27 are made of diiferent sizes so that it is not possible to assemble the cover 20 in an incorrect manner. If by chance the cover 20 were reversed from the position shown in Figure 2 then it would not be possible to apply the mount- For instance, the lead wireing strap 3%) over the cover so that the strap could be staked. to the base 11 to form an assembled switch. A keyhole 31 is formed through the top face of the cover 29 to communicate with the interiorof the cover 2%. A generally C-shaped boss 32 is formed from the inner'surface of the top Wall of the cover 20 to-straddle the enlarged rounded end 33 of the keyhole 31.

The mounting strap as seen in Figure l is. generally of rectangular sheet metal construction having downwardly extending end members. 28 with corner stakes 29. When the cover 20 is properly seated on the basell and the strap 30 is installed the stakes29 are bent under the abutments 45 on the end walls 14 of the base to form a completely assembled switch.

Turning now to a consideration of the key 35 best shown in Figures 1 and 2, the key is formed at one end with a handle portion 36 and at its opposite end with bifurcations 37 and 38 of difierent widths. The smallest leg or bifurcation 37. is of a size to project through an opening 34 located in the inner end of the center contact 17. A notch 39 is cut in one edge of the stem or shank of the key adjacent the handle 36. I Consequently, the key cannot be inserted into the switch housing incorrectly for then the bifurcation 38 would be seated on top of the center contact 17 and the notch '39 would be outside of the cover 20 so that the key could not turnand close the circuit between the center contact 17 and either one of the side contacts 21 and 22. Therefore, it should be appreciated that only a special key offthe nature of key 35 could be used to operate the subject switch.

In the wiring diagramof Figure 3, 50 is a conventional step-down transformer with the primary connected to the 110 volt power supply, and the secondary delivering 24 volts to the control circuit. The control circuit comprises a parallel arrangement of two momentary contact push-button switches 51 and a key switch 10 which embodies the invention disclosed herein. Each switch is capable of actuating either the On or the Off coil of the relay 52 so as to open or close the lighting circuit which is directly connected across the 110 volt power supply and shown as comprising the lamp load 53.

In actual practice a remote control switch is mounted in a switch strap (not shown) which in turn is fastened by a suitable screw means to .a recessed switch box embedded in a wall structure or as. an alternative special brackets (not shown) are available for supporting the switches in a wall since it is not necessary to mount the switches in a closed box because of'the low voltage that is being used in the relay circuits. Remote control switches may either be arranged vertically or horizontally. This fact presents a problem in the design of key switches of the type disclosed herein foriif the switch were mounted vertically and the key were left in the switch it will be appreciated that the key will naturally pivot in the switch housing due to its own weight and thereby close the switch and hold it closed. Only a momentary contact is necessary between the switching parts in order to actuate the relay to switch the power circuit for the particular lighting fixture. If the switch is held closed by leaving the key therein, the coils of the relay will tend to overheat and after a period of time the relay is likely to fail due to the excessive heat. For this reason, a thin metal centering spring 40 generally of rectangular shape encompasses the boss 32 in the cover 20 and is' provided with a pair of spaced fingers 41 arranged at the sides of thekeyhole 31. The ends 42 of the fingers 41 adjacent the keyhole 31 diverge outwardly to form wedge surfaces that permit the key 35 to enlarge the spring as shown in Figure 4 so that there is no looseness between the key and the fingers 41 of the centering spring. An anchoring leg 43 is formed integral with the spring 40 and it is bent at an obtuse angle away from the main portion of the spring to be seated on the ledge 44 of the shelf 19 in the base of the switch housing. The anchoring-leg 43 is of such a length that when the cover-20 is seated *on the base 11 the leg 43 will be placed under compression so that in the assembled switch the springing effect of the leg 43 tends to hold the cover 20 against the mounting strap 30 of the switch to remove any looseness between these parts.

Accordingly, it will be appreciated that when the key 35 is inserted in the keyhole 31 of the switch housing the key will spread the fingers 41 of the centering spring apart and the bifurcation 37 will extend throughthe opening 34 in the center contact 17 0f the switch. As the key 35 is turned in the switch, the centering spring 40 will be deformed so that the key will close the circuit to operate either the On or the Off coil of the relay to operate the lighting circuit. When the turning force is removed from the handle of the key, the centering spring 40 will naturally return the key to the neutral position with the bifurcation 38 centered between the sidccontacts Ziand 22. Another advantage of the centering spring is to provide a slight resistance to the turning movement of the'kcy in the switch so as to improve the feel of the key to correspond to the action of a conventional lock and key.

Consequently, having described our invention of a lowvoltage key switch fora remote control wiring system, it will be readily apparent to those skilled in this art that this switch has a minimum number of parts which are simple in construction and easy to assemble by mass production methods. This switch is also reliable in operation and made to withstand a great deal of use and abuse as well as being attractive in appearance and low in cost. While we have chosen to illustrate our present invention in a flush mounted switch, it should be readily apparent that this invention is not limited to such a switch and that the claims of invention found hereinafter are intended to cover all modifications which are within the true spirit and scope of this invention.

What we claim as new, and desire to secure by Letters Patent of the UnitedStates is:

l. A low voltage momentary-contact key switch comprising a hollow housing with a center contact and one or more side contacts mounted therein, the center contact having an aperture to receive a portion of a key member -so that the key maypiv-ot therein to make contact with one or the other of the side contacts, and a centering spring supported in the housing and adapted to hold a key member in a neutral open circuit position when the key 15 left in the switch, the said centering spring being supported by an anchoring leg from the bottom portion of the housing, while the main portion of the spring encompasses a boss formed as an integral part of the top portion of the housing to provide a pairof spring fingers adapted to engage and resist any turning movement of the key.

2. A low voltage momcntar3-contact key switch comprising a hollow housingwith a common contact and one or more side COIlitiCtSiTlOlll'llCd in the bottom portion thereof, the common contact having an aperture to receive a portion of a key member so that the key may pivot therein to make contact with one or the other of the side contacts. a keyhole formed through ire top surface of the switch housing and an inner hoss integral with the top portion of the switch housing and located adjacent one end of the said keyhole, and a centering spring with an anchoring leg supported in the bottom of the housing. while the main portion of the centering spring encompasses the said inner boss, one side of the main portion of the said spring being split and formed with spring fingers adapted to engage the sides of a kcyinscrtcd into the switch housing.

References Cited in the file of this patent UNITED STATES PATENTS 970,410 Wilson Sept. 13, 1910 1,143,676 Williams June 22, 1915 1,291,722 Barnes Jan. 21, 1919 1,977,887 Murray Oct. 23, 1934

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