GB2194395A

GB2194395A - Mounting electric accessories

Info

Publication number: GB2194395A
Application number: GB08620494A
Authority: GB
Inventors: Norman Edward Bruce Reynolds
Original assignee: MK Electric Ltd
Current assignee: Novar ED&S Ltd
Priority date: 1986-08-22
Filing date: 1986-08-22
Publication date: 1988-03-02
Anticipated expiration: 2006-08-22
Also published as: IN168039B; GB8620494D0; GB2194395B

Abstract

An electric accessory assembly comprises a plate (1) having an aperture (3) to receive one or more switches, fuse holders or other accessories, the aperture having inwardly extending projections (5) to abut the rear surface of the accessory and the accessory having rearwardly extending resilient prongs with out- turned flanges (21) to snap fit in the aperture and engage the rear of the plate to hold the accessory in place. The width of the aperture and of the accessories may be multiples of a standard modular width to allow a selection of accessories to be fitted in a single aperture. The aperture may be polarized to allow insertion of an accessory in only one orientation and the plate may be formed with a socket outlet. <IMAGE>

Description

SPECIFICATION Mounting electric accessories This invention relates to mounting electric accessories in a support plate.

Electric accessories such as switches and plug sockets for household and commercial use commonly comprise plates of metal or plastics material which are attached to a wall or other supporting structure and which support the circuit elements of the accessory. A wide variety of accessories including switches and sockets, fixed connection units, fuse units and circuit breakers are wall-mounted in this way, the circuit elements being attached to the back of the plate and being accommodated in either a box or an aperture in the wall behind the plate. As different accessories are generally of different shapes and sizes, each accessory requires a specific design of plate to support it. The elements of the accessory accommodating the working parts behind the plate may be integral with the plate or attached to the plate by screws.

The present invention is intended to provide means whereby a single supporting plate may support a variety of interchangeable electrical accessories of different types, so that the type of accessory installed may be varied at wili, but once installed in the plate the accessory cannct readily be removed from the plate without removing the plate from a box or surface on which it is mounted.

According to one aspect of the invention there is provided an assembly comprising a support plate provided with an aperture and at least one electrical accessory to fit within the aperture, the plate comprising projections extending into the aperture and abutting a rear surface of the accessory when the accessory is fitted in the aperture, and the rear surface of the accessory comprising rearwardly extending resilient prongs having outwardly directed flanges to engage a rear surface of the plate, so that the accessory may be inserted in the aperture while a force is exerted on the prongs to deform them inwardly, and after release of said force the accessory is held in place by abutment of said projections with the accessory and by abutment of said flanges with the plate.

In one arrangement according to the invention the accessory comprises a generally rectangular front plate, the prongs are located on opposite sides (the ends) of the rectangular plate, and the projections extend from opposite sides (walls) of the aperture to engage the ends of the front plate bearing the prongs.

The accessory is then held in the aperture at two opposite sides. Depending on the dimensions of the accessory, the opposite sides bearing the prongs may be longer or shorter sides of the rectangle.

The aperture may be dimensioned to receive only one accessory, the shape and dimensions of the aperture then corresponding to those of a single accessory, or the aperture may be dimensioned to receive two, three or more similar accessories side-by-side, all the accessories being held in the aperture by the same method. When more than one accessory is held in a single plate aperture, the accessories may be the same or functionally different. The width of the aperture may be a whole multiple of a single modular width and the or each electrical accessory may have a width equal to said modular width or a whole multiple thereof.

The accessories to be fitted in the plate may be of various kinds such as one and two-way switches, sockets, indicator lights, circuit-breakers, fuse units and other devices used in electric circuitry.

The plate itself may be provided with circuit elements which operate in conjunction with the accessories mounted in the plate aperture.

For example, the plate may be provided with holes forming a socket to receive the pins of a plug, the rear of the plate may support the terminals and other socket components for establishing electric contact with the plug pins to connect the plug in a circuit, and an aperture in the plate adjacent the holes may accommodate a switch in the manner described above to open and close the circuit.

The support plate may be provided with holes to receive screws for attaching the plate to a box or a wall in known manner.

Support plates and accessories to be mounted on them according to an embodiment of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a front view of a support plate; Figure 2 is a cross-section of the plate of Fig. 1 along Il-Il; Figure 3 is a front view of a switch for use with the plate of Fig. 1; Figures 4 and 5 are side views of the switch of Fig.

3; Figure 6 is a cross-section similar to Fig. 2 showing the switch of Fig. 3 mounted in the plate of Fig. 1; Figure 7 is a front view of the switch of Fig. 3 mounted in the plate of Fig. 1; Figure 8 shows a switch socket according to another embodiment of the invention.

The switch plate shown in Figure 1 comprises a generally rectangular plate 1 moulded from a plastics material having holes 2 for receiving screws for attaching the plate to a wall on which the switch plate is to be mounted. The plate has a central rectangular aperture 3 in which switches or other accessories may be held. When the plate is mounted on a wall the wall is provided with a recess, corresponding to aperture 3, to accommodate the bodies of switches held in aperture 3 which projects outwardly behind plate 1.

As shown in Figs. 1 and 2 the upper and lower edges of aperture 3 are defined by surfaces 4 which extend through the thickness of the plate. Surfaces 4 are provided with projections 5 extending into the aperture, distributed at regular intervals along the surfaces 4 and separated by gaps 6. In the direction of the thickness of the plate, the projections extend from the rear of the plate to a distance short of the front surface of the plate, each projection thus defining a shoulder 7 as shown in Fig. 2.

Figures 3, 4 and 5 show a two-way switch for use with the plate of Figs. 1 and 2. The switch operates in a conventional manner and comprises a rectangular front plate 11 having an aperture in which pivots a switch rocker 12. The rocker actuates a switching mechanism within the switch body 13 integral with the rear of plate 11. The switch comprises a centre screw terminal 14 and end screw terminals 15 to be connected to wires behind the plate. All these terminals are accessible from one side of the switch body, as shown in Fig. 4, to receive wires connected to the switch but on the other side of the switch body, as shown in Fig. 5, the end terminals 15 are shielded by the wall 17 of the switch body.

The plate 11 of the switch comprises a rearwardly facing shoulder 18 at both its ends, providing an end part 21 of reduced thickness at the front surface of the plate, and each end part is provided with a pair of rearwardly projecting resilient prongs 19, of plastics material and integral with the switch plate.

Each prong is provided at its end with a flange 20 extending in the direction away from the switch body and, as shown in Fig. 3 of the drawings, when the prongs 19 are undeformed the flanges 20 extend beyond the ends of the switch plate 11.

The manner in which the switch of Fig. 3 may be fitted into the plate of Fig. 1 is shown in Figs. 6 and 7. The prongs 19 of the switches may be deformed inwardly against their resilient bias by manual pressure so that the flanges 20 are moved inwardly and do not extend beyond the length cf switch plate 11.

The switch may then be inserted into the aperture of the support plate, from the front of the support plate, as shown in Figs. 6 and 7, and the pressure exerted on the prongs is released, so that the prongs may spring outwardly. The thickness of the end parts 21 is such that, when the switch is mounted in position in the plate, the rear surfaces of end parts 21 abut the projections 5 and the front surface of the switch is substantially flush with the front surface of the plate 1. The prongs 19 are positioned so that, when the switch is positioned as shown in Fig. 7, the prongs pass through the gaps 6 while the portions of end parts 21 between or on either side of the prongs abut projections 5.The length of the prongs is such that in this position the flanges 20 can engage the rear surface of plate 1 when pressure on the prongs is released, thus holding the switch in position in plate 1 and preventing its removal from the direction of the front of plate 1. The switch can then only be removed if access is gained to the rear of the switch/plate assembly, and this is not normally possible when the plate 1 is mounted on a wall without removing the plate from the wall.

As shown in Fig. 7, when the switch is mounted in plate 1 its respective end parts each abut two projections 5, in the middle of the end part 21 and at its corners, spaces 6 being provided to allow passage of prongs 19. As shown in Figs. 1 and 4, the projections on one surface 4 only of the plate are such that there is no projection 5, to engage the middle of end part 21, and the middle part of one end only of the switch is provided with an outwardly projecting step 23. When the switch is mounted in plate 1 the absence of the middle projection 5 allows passage of step 23, so that the switch can be mounted in place as shown in Figs. 6 and 7, but if the switch is inverted it cannot be inserted because step 23 abuts middle projection 5 on the other surface 4. This feature prevents the switch being mounted in place upside down.

Aperture 3 in the plate of Fig. 1 is sufficiently wide to allow two switches or similar accessories of the kind shown in Fig. 3 to be mounted in plate 1 side-by-side in identical manner, the width of aperture 3 being twice the width of the switch so that aperture 3 is completely closed by the two switches. Aiternatively the aperture 3 may be made sufficiently wide to accommodate 3, 4 or even more switches in this manner, or narrower to accommodate only one switch. In all cases the width of aperture 3 is an integral multiple of the width of the switch and projections 5 are arranged so that each switch, mounted in plate 1, abuts projections 5 at each end in the manner shown in Figures 6 and 7.

The arrangement described above allows a large number of combinations of wall plate and switches or other accessories to be assembled at will. The switch described is a two-way single pole switch having a typical rating of 5 amps at 240 V A.C. but other accessories such as one-way switches, double pole switches, circuit-breakers, fuse units, indicator sockets, lamp holders and other types of accessory may be mounted in the wall plate in the same way, each accessory comprising a front plate with prongs of the kind shown in the drawings so that it may be mounted in the wall plate in the same way.

An accessory of greater width than the switch shown in the drawings may be provided with a front plate of increased width which is dou ble or treble the width of the switch shown so that it may be fitted in a wall plate having an aperture of width which is an integral multiple of the width of the switch.

If the number of accessories to be mounted in the plate is less than that maximum number which the aperture can accommodate, so that the aperture is not completely filled by the accessories, a blank plate of the appropriate dimensions, fitted with prongs in the same way as the accessories, may be fitted to close the gap.

When a number of switches of the kind shown in the drawings are mounted in a wall plate side-by-side the end terminals 15 of the respective switches are separated by wall 17 on one side of each switch body, which prevents electrical contact between the terminals 15 of adjacent switches. On the other hand, as no wall 17 separates centre terminals 14 of adjacent switches these terminals 14 may be easily wired together, or connected by a common bus-bar passing through them, so that one side of the circuits controlled by the switches is fed from a common source. The switches may be provided in known manner with neon indicator lights (not shown in the drawings).

Figure 8 shows a switch socket to be fitted with a switch as shown in Figs. 3 to 5. The front plate 31 of the switch socket, to be mounted on a wall using holes 2, is of similar constructicn to the plate of Fig. 1 except that the aperture 32 is dimensioned to receive only one switch and the plate is provided with holes 33 for receiving the pins of a three-pin electric plug of known type. The rear of the plate behind the holes is provided with a shutter and terminals for establishing electrical contact with the plug pins in conventional manner. When the switch has been inserted in the aperture its terminals may be wired to the terminals behind holes 3 in known manner.

The aperture 32 is provided with projections 34 similar to projectipns 5 in the plate of Fig.

1 and the switch fits into the aperture in the same manner. The unit shown in Fig. 8 allows different kinds switch to be fitted at will to a standard plug socket.

In a further embcdiment of switch socket, not shown in the drawings, the aperture 32 is of a width to receive two accessories and a switch and a fuse unit may be fitted in the aperture side-by-side to provide a fused switch socket.

Figures 9 to 11 of the drawings show a fuse unit to be mounted in the wall plate. The fuse unit comprises a rectangular shroud 40 of plastics material having rearwardly projecting prongs 41 similar to those of the switch of Figure 3 and the shroud 40 is fitted in the aperture of a plate of the kind shown in Figure- 1 in the same way. The front of the shroud has a central rectangular aperture to receive a rewirable fuse holder 42 of plastics material which contains a ceramic element 43 to which fuse wire of the appropriate rating is fixed by screw terminals in known manner.

The fuse holder comprises a pair of metal tabs 44, shown in Figure 11, connected in known manner to the screw terminals, and the shroud carries on its rear surface a pair of screw terminals 45 electrically connected inside the shroud to contact surfaces (not shown) which engage the tabs 44 when the fuse holder is inserted in the aperture of the shroud as shown in Figure 11. The shroud and fuse holder are dimensioned such that when the fuse holder is inserted in the aperture its front surface 46 is substantially flush with the front surface 47 of the shroud and it is held in place by friction beween the tabs 44 and the contact surfaces. The length of front surface 46 is slightly less than that of the aperture so that a screwdriver blade or like implement may be inserted from the front of the unit into the gap 48 between the edge of the fuse holder and that of the aperture.

The fuse holder may then be levered out of the aperture to allow replacement of the fuse wire.

The fuse unit described may be fitted in a plate in the same manner as the switch of Figure 3 and the fuse unit may then be removed from the front without need to remove the shroud from the plate. Terminals 45 may be wired to other circuit elements mounted in the plate in the usual manner.

Figure 12 shows a support plate 51 having an aperture containing a switch 52, a fuse unit 53 and a 3-pin socket 54. The interior surfaces of the aperture are again provided with projections 5 as in the plates shown in Figures 1 and 7. Switch 52 is of the type shown in Figures 3-5 and the fuse unit is as shown in Figures 9-11 and the switch and fuse unit are fitted within the aperture of the plate in the same way. The aperture in the plate is also occupied by a 3-pin plug socket 54. The socket comprises a front plate which is dimensioned to fit into the aperture, in the same way as the front plates of the switch and the fuse unit, and when so fitted the front plate of the socket is substantially flush with plate 51.The upper and lower edges of the socket front plate are provided with prongs of the same type as the switch and fuse unit described above and these prongs engage the inside surface of the aperture in the same way to retain the socket in the aperture.

In this instance it is desirable for the socket always to be mounted in the left-hand side of the aperture and in order to ensure that the socket cannot be mounted in any other position one of the projections 5 on the upper side of the aperture is omitted at location 5' and the socket body is provided with a corresponding outwardly projecting step, similar to step 23 on the switch of Figure 5, to occupy the space at 5' which would otherwise be occupied by a projection 5. This feature ensures that the socket may be mounted in the aperture only in the position shown in Figure 12.

It will be appreciated that with the arrangements described above accessories of varying width may be mounted in a standard type of plate, the width of each accessory being a whole multiple of a single standard width which in this case is the width of the switch.

Thus each switch and fuse unit may have the standard single width, a 5-amp plug unit may be of double this width, and a 15-amp plug unit may be of 3 times this width. Other accessories of greater width, such as dimmers, may be mounted in the same way.

The number of accessories which may be mounted in a single plate is limited only by the width of the aperture and a single plate may be provided with more than one aperture.

For example a plate intended to accommodate accessories having a total width of 24 times the standard single width may have 4 similar apertures each having a width of 6 times the standard single width.

The plate and/or the accessories to be mounted on it may be provided with neon lamps to provide a visual indication of the on/off condition of the circuits containing the accessories in known manner. A neon lamp for this purpose may be mounted in a lamp unit having a front plate which is fitted within the aperture in the same way as the switch and fuse units mentioned above The plate and the accessory bodies may be formed of plastics material but metal clad accessories and plates can also be used if desired.

Claims

1. An assembly comprising a support plate provided with-an aperture and at least one electrical accessory to fit within the aperture, the plate comprising projections extending into the aperture and abutting a rear surface of the accessory when the accessory is fitted in the aperture, and the rear surface of the accessory comprising rearwardly extending resilient prongs having outwardly directed flanges to engage a rear surface of the plate, so that the accessory may be inserted in the aperture while a force is exerted on the prongs to deform them inwardly, and after release of said force the accessory is held in place by abutment of said projections with the accessory and by abutment of said flanges with the plate.

2. An assembly according to claim 1, in which the accessory comprises a rectangular front plate, the prongs are attached to both of opposite sides of the front plate, and the projections extend from opposite interior surfaces of the aperture to engage the ends of the front plate bearing the prongs.

3. An assembly according to claim 2, in which the accessory comprises an accessory body behind the front plate, the body has an outwardly projecting step at one of said opposite sides located to occupy a space between projections on the respective interior surface of the aperture when the accessory is fitted in the aperture and the opposite interior surface of the aperture has a projection to abut said step and prevent the accessory being fitted in the aperture in an inverted position.

4. An assembly according to claim 1, 2 or 3 in which the aperture and the accessory are dimensioned so that a plurality of similar accessories may be fitted side-by-side within the aperture.

5. An assembly according to claim 4, in which the width of the aperture is a whole multiple of a single modular width and the or each electrical accessory has a width equal to said modular width or a whole multiple thereof.

6. An assembly according to claim 5, in which a plurality of switches are fitted sideby-side in the aperture.

7. An assembly according to claim 5, in which a switch and a socket are fitted sideby-side in the aperture.

8. An assembly according to claim 5 in which a switch, socket and fuse unit are fitted side-by-side in the aperture.

9. An assembly according to any one of claims 1 to 6, in which the support plate is provided with holes to receive the pins of an electric plug and terminals are provided at the rear of the support plate to make electric contact with the pins cf an inserted plug.

10. An assembly according to any preceding claim, in which the front surface of the accessory is substantially flush with the front surface of the support plate when the accessory is fitted in the aperture.

11. An assembly comprising a support plate and an electrical accessory, substantially as hereinbefore described with reference to Figures 1 to 7 or 8 or 9 to 11 or 12 of the accompanying drawings.