GB1571093A

GB1571093A - Electrical time switch

Info

Publication number: GB1571093A
Application number: GB4866176A
Authority: GB
Original assignee: Westdeutsche Elektrogeraetebau GmbH
Current assignee: Westdeutsche Elektrogeraetebau GmbH
Priority date: 1976-01-07
Filing date: 1976-11-22
Publication date: 1980-07-09
Also published as: TR19660A; FR2337932A1; AT369189B; CH615291A5; DE2600409C2; IE44856B1; ATA960976A; NL7700105A; DE2600409A1; IT1070525B; DK6677A; FR2337932B1; IE44856L; LU76512A1; BE850176A; ES454829A1

Abstract

In the electrical switching device, e.g. a staircase light time-delay switch, clock timer or the like, electrical and/or mechanical subassemblies are installed in a multi-part housing (112, 213). One of the subassemblies (106) is adapted in a positively-locking manner to another subassembly and/or to a housing part and is thereby necessarily designed to be self-adjusting and retaining in the other assembly (115) or in the corresponding housing part (112 or 213). The subassemblies must include a switch device (120), a device (115) for its actuation, and also connection devices (123) and, in any given number or combination, an electromechanical drive assembly (101) and a unit (inhibiting mechanism 106 to 108) to control the device or its drive in time-dependent fashion. Further improvements can include: integrally formed single-piece spacers etc. for the plug-in connection of sub-assemblies or parts thereof, in particular the switch device (120) and its parts, a rocking lever (135) to block the switch device, an electromechanical drive assembly (102 to 104) and parts thereof, an inhibiting mechanism of mechanical, in particular pneumatic, or electronic design, and finally the base part (213) which can be mounted on a carrier rail. A switching device of this type, particularly in its final assembly, requires little working time, and the workers concerned require little specialist knowledge. <IMAGE>

Description

(54) AN ELECTRICAL TIME SWITCH (71) We, WESTDEUTSCHE ELEK TROGERATEBAU GMBH, a German Com- pany, of Windmühlenweg 27, 4770 Soest, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be par ticularly described in. and by the following statement: This invention relates to an electrical time switch.

Conventionally, most electrical time switches, and particularly staircase light time switches, have relatively large casings which, depending upon whether they are required to be mounted on a switchboard or to be surface mounted, either have to be of completely different construction or have to have different assembly parts, e.g. at their bottom end.

Following developments requiring such devices to be fitted in a very small casing of similar shape to modern narrow automatic cutouts in accordance with a standard grid or raster (e.g.

with 17.5 mm width) or switchboard mounting, casings have grown smaller and smaller, so that the limitations on a relatively obvious construction have become more and more restrictive.

A problem arising from this requirement is that either an optimal association of components in such a switching device, and, where applicable, the possibility of adjustment have not been possible or it has not been possible to subdivide the casing in a manner giving suitable access to the components. The trend towards smaller casings based on standardised grid or raster construction has conferred great significance on a convenient subdivision of the casing into a substantially dome-shaped part and into another part, great importance also attaching to the nature of the assembly aid provided.

In known time switches, the various components are either assembled individually in the casing, e.g. with the aids of screws, or just placed in the casing without any special location. Production of such known switches therefore requires a considerable labour time and the operatives must have special skills since they must make sure in assembly that fitting and adjustment are accurate, as otherwise the relability of operation may be impaired. These points become of decisive importance when the time switch is required to be received in a relatively small casing.

It is an object of the present invention so to devise the various components of an electrical time switch that their introduction into the casing automatically locates them relatively to one another and so that tolerances of the discrete geometric dimensions can either be compensated for automatically or at least do not disturb the operation of the device. The assembly work is correspondingly simplified, and because of this simplification and also because of other individual features-i.e., because of simplifications of the components themselves, production costs are reduced.

According to the present invention, there is provided an electrical time switch comprising a switching unit having a contact set for operation in dependence upon time, an actuating unit engaging with the switching unit to operate the contact set, an electrically powered drive unit for driving the actuating unit to operate the contact set, and a timing unit coupled to the drive unit for governing the action of the drive unit in dependence upon time, the said units being received in a casing consisting of at least two parts, the said units constituting a plurality of sub-assemblies which are geometrically adapted to one another and to the casing so that the units are self-locating as regards their mutual positions in the casing.

In order that the invention may be readily understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which: FIGURE la is a circuit diagram of a time switch having an electronic time delay device and a bistable a.c. relay; FIGURE Ib is a circuit diagram of a time switch having an electronic time delay device and a sticking relay; FIGURE ic is a circuit diagram of a fourwire time switch having a mechanical or pneumatic time delay device; FIGURE id is a circuit diagram similar to FIGURE ic but for a three-wire switch; FIGURE 2a is a cross-section through a time switch embodying the invention and having a pneumatic time delay device, the switch having provision for continuous operation and for timed operation and being shown in the continuous-operation condition; FIGURE 2b is a fragmentary cross-section corresponding to FIGURE 2a, showing the time switch in an operative condition as regares both continuous operation and timed operation; FIGURE 2c is a cross-section on the line A-A of FIGURE 2d, showing a top part of the casing of the switch; FIGURE 2d is a cross-section on the line B-B of FIGURE 2c; FIGURE 3a shows the switch in the in operative condition of FIGURE 2b; FIGURE 3b shows the switch in an inter mediate condition during its actuation from the inoperative condition to a timed-operation condition.

FIGURE 3c shows the switch in its timedoperation condition; FIGURE 4a shows in side elevation the configuration of an actuating lever arrangement of the switch in the condition of the switch shown in FIGURE 3b; FIGURE 4b shows the configuration of the actuating lever arrangement in the inoperative condition of the timed-operation condition of the switch; FIGURE 4e is a plan view of the actuating lever arrangement; FIGURE 5a is a cross-section on the line A-A of FIGURE 5b, showing the top casing part of the switch; FIGURE 5b is a cross-section on the line B-B of FIGURE 5a; FIGURE Sc is a cross-section in the line C-C of FIGURE 5b; FIGURE 6a is a cross-section on the line A-A of FIGURE 6c, showing the top casing part of the switch; FIGURE 6b is a cross-section on the line A-A of FIGURE 6c, showing a bottom casing part of the switch; FIGURE 6c, is a plan view of the bottom casing part of the switch; FIGURE 7a is a cross-section through the time switch, showing a support-bar mounting of known form; FIGURE 7b is a cross-section through the bottom casing part of the switch, showing a novel support-bar mounting; FIGURE 8a is a cross-section on the line B-B of FIGURE 8b, showing a mounting element as used in FIGURE 7b; and FIGURE 8b is a plan view of the mounting element.

FIGURES la to id are circuit diagrams of four typical time switches. FIGURES la and ib relate to time switches having an elec tronic time delayed means and FIGURES 1 C and ld relates to time switches having a mechanical or pneumatic time delay.

Referring to FIGURE la, an a.c. power supply is connected to a phase line 1 and a neutral line 2 across which is connected a load circuit comprising a lamp 3 in series with a normally open contact set 4. Contact set 4 is operated by a relay having a winding 5 which is connected across the supply lines 1 and 2 in series with a conventional protective contact set 6 and a press-button switch 8. The relay 5 takes the form of a changeover relay having two windings 5 and 16 and an additional pulse contact 7 whose operation is coupled to that of contact 4 as indicated by chain-dotted line 18. Connected in parallel with the relay operating winding 5 are a non-linear resistance 9, serving to limit the current in the event of prolonged operation of switch 8, and a telltale lamp 10.

Operation of switch 8 causes contact set 4 to be closed so that junction 11 becomes energised, with the result that a capacitor 15 is charged by way of a fixed resistor 12, an adjustable resistor 13 and a rectifier 14, the rate at which capacitor 15 is charged depending upon the setting of resistor 13. When the striking voltage of a switching diode 17, connected in parallel with capacitor 15 and in series with the second opposition winding 16 of relay, is reached, diode 17 becomes conductive and capacitor 15 discharges through the winding 16; relay 5 therefore reverts back to its initial condition, i.e., it returns contact 4 to its normally open state. To ensure that the RC charging circuit composed of the capacitor 15 and resistors 12, 13 always has the same initial state of charge, each energisation of the relay 5 causes the capacitor 15 to discharge by way of the pulse contact 7 and a resistance 7a down to the extinction voltage of diode 17.

As compared with FIGURE la, the circuit arrangement shown in FIGURE ib is much cheaper, for in FIGURE ib the expensive relay S with its two windings and pulse contact is replaced by a simple remanence relay 19 which is equivalent in function to the relay 5 and which is e.g. a bistable relay. In other respects the underlying principle is very simi lar to FIGURE la. The load, in the form of a lamp 20, is connected across a.c. supply lines 23 and 24 in series with a normally open contact set 21 which is relay of 19 as indicated by chain-dotted line 22. Upon operation of a press-button switch 25, with which an indicating tell-tale (not shown) can be connected in parallel, a capacitor 31 is charged up by the phase voltage on line 23, by way of rectifier 26, adjustable resistor 27, the winding of relay 19, resistors 28, 29 connected in parallel with the latter winding (the resistor 29 being a nonlinear current-limiting resistor) and rectifier 30. As in the case of FIGURE la, when the striking voltage of a switching diode 32 is reached, the capacitor 31 discharges there through and through the winding of relay 19.

Since current now flows through the winding in the opposite direction, relay 19 returns to its initial position and opens the contact set 21. The delay time is adjusted by means of the adjustable resistor 27.

As is clearly evident, in the circuits shown in FIGURES la and 1b the circuit elements associated with the RC arrangements 33, 33' are the actual electronic delay devices. As will be apparent, these time-dependent partly electromechanical delay devices can be replaced by purely electronic time delay devices, e.g.

using pulse-counting circuits.

In FIGURE lc, circuits comprising lamps 34 and 35 are connected by way of terminal 1, a normally open contact set 36 and a terminal 2 to a phase line 37 of a.c. mains having a neutral line 38. Contact set 36 is mechanically connected by a rod 40 to a part of a simple relay having a coil 39, such as a solenoid, as is indicated by a rod 40.

As indicated by chain line 41 rod 40 also operates an auxiliary contact set 42 which, in cooperation with a mechanical coupling to be described hereinafter, prevents overloading of the winding of relay coil 39 in the event of prolonged operation of either of press-button switches 43 and 44 via which the coil of winding 39 of relay 39 is connected across the a.c. supply lines 37 and 38. The "four-wire circuit" of FIGURE ic differs from the threewire circuit of FIGURE Id only in having an additional circuit, comprising a switch 45 and a lamp 46 which are connected in series across the lines 37 and 38 and are therefore independent of the relay 39, 36.

The same reference numerals are used in FIGURES lc and 1d to denote the same elements.

The circuit arrangements of FIGURES lc and 1d have no electronic parts producing a "delay" in the return of the normally open contact 36 to its normal position, so that the desired delay must be produced by an addi tional mechanical or pneumatic device. Some of the features to be described hereinafter with reference to an embodiment of a time switch according to the invention relate to these delay features which can of course be transferred to "delay" mechanisms operating on some other principle.

The time switch illustrated in FIGURES 2a to 2d has an electromagnet-and-armature unit 101 comprising a winding former 102, a winding 103, a plunger 104 and a biasing spring 105. The unit 101 is disposed at the bottom and on the right-hand side of a twopart casing comprising a dome-like top part 112 and a bottom part 113. A pneumatic time delay unit 106 of the time switch comprises a cylinder 107, a piston 108, an air cushion 109, a sealing disc or gasket 110 serving as a valve, and an adjustable air vent 111. The time delay unit 106 is disposed at the top of the casing on the right-hand side. The time delay unit 106 and the unit 101 are so adapted geometrically to the top and bottom parts of the casing respectively as to form subassemblies which are geometrically adapted to one another and to the casing so that they are self-locating as regards their mutual positions in the casing.

FIGURES 2a to 2d also show that one of the sub-assemblies, in this case the time delay unit 106, comprises a component, namely the cylinder 107, which is rigidly secured to the casing and receives an associated movable part, namely the piston 108. In fact, the cylinder 107 is integral with the casing part 112 materially and structurally. As a result, there is no need for accurate assembly of a separate cylinder in the casing. In addition, the piston 108 is connected by piston rod 114 to plunger 104 and serves as an abutment for an actuating lever 115 of an actuating unit for operating a switching unit 120, the lever 115 having a guide end 116 disposed between a bottom surface 117 of the piston 108 and an end plate 118 of the plunger 104. The plate 118 also serves as an abutment for the upper end of the biasing spring 105.

The switching unit 120 comprises a contact set 121 for the current to be time switched, a switch block 122 and electrical connectors 123. The switching unit constitutes a sub-assembly disposed in geometrically adapted form, in the left-hand part 119 of the casing. The block 122 forms a moulding or shaped element for another component, i.e.

the block 122 has an abutment projection 124 for engaging the winding former 102.

The adjustable air vent 111 of the time delay unit 106 comprises a hollow valve housing 125 formed integrally with an end wall 128 of the cylinder 107, the end wall 128 itself being integral with a cover part 129 of the top part 112 of the switch casing. The housing 125 receives a spindle 127 having a screwthreaded end portion 126 which is accessible from the outside of the switch casing to enable adjustment of the depth of penetration of the spindle 127 in housing 125.

A resilient damping disc 132 made of rub ber or rubber-like plastics material is received in a circular recess 133 within an annular bead 134 on a baseplate 130 of the switch casing. The winding former 102 fits on top of the disc 132 and is centred by the recess 133 and bead 134 so that the disc 132 closes the adjacent end of a bore 131 of the former 102.

A rocker 135 is provided to enable the contact set 121 to be held closed to select a continuous-operation condition of the switch which overrides timed-operation of the switch.

FIGURE 2a shows the rocker 135 in the posi tion in which it selects such continuous operation of the switch and FIGURE 2b shows the rocker 135 in an operative position which permits timed-operation of the switch.

The rocker 135 has an arm 136 for engaging an insulating moulding 138 pushed onto the end of one contact blade 137 of contact set 121 The moulding 138 is formed with a groove 139 to guide rocker arm 136. A top portion 140 of the moulding 138 forms a transverse boundary wall at the upper end of the groove serving as an abutment for the rocker 135.

Rocker 135 has a slot 141 formed with a half-cylindrical bearing shell 147 which cooperates with a pivot 142 to mount the rocker, the rocker being introduced into the casing from outside and, when mounted, projecting through the cover 129 of the casing top part 112 between two parallel walls 143 and 144 only one of which is visible. In addition to the guidance provided by arm 136, the rocker 135 is guided by means of a U-section projection 145 on a wall 146 formed on the inside of cover 129. Pivot 142 interconnects the walls 143 and 144.

A U-shaped spring 148 presses rocker 135 on to pivot 142 and provides bistable biasing of rocker 135. Spring 148 engages a groove 151 in rocker 135 and a slot 150 in a retaining element 149 which is inserted into the top part of the casing from below. In the inoperative position of the rocker 135 shown in FIGURE 2b, a projection 152 on the rocker bears on the cylinder 107.

FIGURES 2c and 2d shows the casing top part 112 of the switch with components of the switch omitted in order to illustrate clearly the integral construction of the cylinder 107 and the casing part 112. As can be seen, parts of the cylindrical wall 153 of cylinder 107 are integrally combined with portions of the side walls of the casing part 112 and the end wall 128 of the cylinder is co-extensive with part of the cover 129 of the casing part 112. The hollow valve housing 125 formed on end wall 128 has a bore 154 provided at one end with screwthreading 155 for the spindle (not shown). The bore 154 is also provided at its other end with a recess 156 for a screw or the like which projects from the surface of the piston (not shown). Bottom edge 157 of cylinder 107 serves as an abutment for the switching lever 115 of FIGURE 2a.

FIGURES 2c and 2d also show clearly the U-section guide projection 145, internal wall 146, pivot 142 and the retaining element 149 which is formed with slot 150 and is pushfitted in the casing part 112 from below.

It is desirable to make at least one component of the switch, preferably a part of the casing such as the top part 112, of a transparent material. Conveniently, other components, such as those serving as a mounting or guide element or as retaining element, are also made of transparent material.

The operation of the switching unit 120 for timed operation of the switch will now be described with reference to FIGURES 3a to 3c. Since the main interest in this connection centres on the various operation conditions of the switch, the same are shown separately, the normal or inoperative condition being shown in FIGURE 3a, a condition intermediate the inoperative condition being shown in FIGURE 3b and the operative condition being shown in FIGURE 3c. Components which have been described previously have the same references as in FIGURES 2a and 2d.

Pivot 235 of lever 115 is supported in a mounting comprising a top part 236 and, shown in chain lines, a bottom part 237. In addition to a longer arm 238 having the guide end 116, the lever 115 has a shorter arm 239 having a curved engagement surface 240. A cam 241 is also mounted on pivot 235, together with a third lever arm 242. The contact blades of a contact set 243 are in series with the winding 103 of electromagnet-andarmature unit 101, a press-button switch (not shown), connectors and the electrical mains.

The contact springs of contact set 121 are connected by way of connectors 123 to the load and to the mains.

When the circuit of winding 103 closes in response to operation of press-button switch, plunger 104 is attracted into winding former 102, the biasing spring 105 being compressed and the piston 108 being pulled down in cylinder 107, the disc 110 allowing the air cushion 109 to fill up. Escape of the air cushion is initially prevented because of the valve effect of disc 110 and of the smallness of air vent 111 (FIGURE 3b). During this movement of the plunger 104 and piston 108, the piston surface 117 and end plate 118 act on the end 116 of switching lever 115 so that the shorter lever arm 239 pivots clockwise around pivot 235 and the curved surface 240 of the arm 239 engages moulding 245 to press contact blade 244 against the other contact blade 246 and thus close the circuit for the load.

When the lever arm 239 has deflected the contact spring 244 sufficiently, cam 241 is free and makes an abrupt clockwise movement under the influence of a spring 248 (FIGURE 3b) until an abutment 249 on the cam abuts arm 239 (FIGURE 3c) and arm 242 opens contact set. With the coil 103 the deenergised piston 108 urged by spring 105 subsequently expels air cushion 109 through the adjustable orifice 111 at a rate depending upon the open cross section thereof, cam 241 slides anticlockwise back along the moulding 245 and piston 108 and lever 115 slowly return to their initial position (FIGURE 3a). Only when top edge 250 of the cam 241 reaches the botom edge 251 of moulding 245 does contact spring 244 return abruptly to its normal position (FIGURE 3c).

When the third lever arm 242 of lever 115 is in an operative position at the maximum stroke of piston 108, the arm 242 opens a normally closed contact set 243, thereby open ing the energising circuit for winding 103 of unit 101 (if the same is still in the closed state because of the press-button switch being operated), so that the winding 103 cannot be overloaded even though the press-button switch may remain depressed for a long time.

Operation of the contact set 243 can occur in some other manner than as a protective circuit arrangement and, as will be apparent, lasts for only a relatively short time during a part of the stroke of piston 108-i.e. long enough to exclude any possibility of subsequent switching.

The actuating unit sub assembly is shown separately in FIGURES 4a to 4c, FIGURE 4a showing the configuration of the assembly in the intermediate switch condition of FIGURE 3b, and FIGURE 4b showing the configuration of the assembly (except for the absolute angular position) in the inoperative or operative conditions of FIGURES 3a and 3c.

The pivot 235 has a portion 253 of relatively large diameter and a portion 254 of relatively small diameter. Lever 115 is mounted on pivot portion 253 and cam 241, with its integral spring 248 which bears on a pin 255 carried by lever 115, is mounted on the pivot portion 254 (FIGURE 4c). The fact that the two portions of the pivot 235 are of different diameters facilitates assembly be excluding the risk of assembly the wrong way round. In the inoperative or operative condition of the switch, cam 241 is pressed by spring 248 against the shorter arm 239 and during the return movement of lever 115 is moved by the arm 239. The third lever arm 242 is integral with cam 241 and therefore accompanies the same in its initial delayed movement and subsequently in the slow return of the lever 115.

As will be readily apparent, the switching unit 120 with the lever 115 and the contact set 121 or normally closed contact set 243 in the switch block 252, provides, in timed operation, abrupt operation of the switch which can be adjusted and maintained sufficiently accurately as regards timing. Two subassemblies are located and adjusted automatically merely by their introduction into the casing and tolerances in the various geometric dimensions are either compensated for automatically or at least cannot upset the operation of the complete device.

The positive positioning and location of the sub-assemblies is clearly apparent from FIGURE 5, where switch block 252 is so devised from two mouldings 257, 258 formed with apertures 259-262 for the contact springs (not shown) as to be adapted to be plugged-in in an assembled state and engaged positively between two parallel walls 263, 264 with guide grooves 265, 266 or corresponding guide projections of the switch block (of.

FIGURE 5c). The two mouldings 257, 258 are automatically associated with one another in irreversible manner by pins 267, 268 engaging in blind bores 269, 270 and are associated with the casing top part 112 by way of abutment strips or ridges or the like 271, 272, which are integral with the walls of part 112.

The moulding 257 of the switch block 252 is integrally combined with the bottom part 237 of the mounting for the actuating-lever pivot, the part 237 having a bearing shell 273.

In addition, the block 252 is integrally formed with abutment projection 274 for the winding former of the electromagnet-and-armature unit. These features provide automatic and positive location and adjustment relatively to the switching lever and to the plunger. The bottom part 237 of the mounting for the pivot 235, and with it therefore the switch block 252, are engaged with positive centering in a corresponding slot with the top half hub shell 275 of the top part 236-i.e., between the webs 276, 277-and so the switch block, switching lever, casing and electromagnet-andarmature unit are further located relative to one another.

The same purpose is served by projection 278 on switch block 252 which is also used to produce a fit between the side walls and projections in the other part (not shown) of the casing. Also, abutments 279, 280 for the contact spring, strengthening walls 281, 282 for projection 274 and the bottom part 237 of the mounting are devised integrally, and also in laterally symmetrical relationship, on the two mouldings 257, 258, another feature contributing towards accurate layout of the subunits of the complete time switch.

A detailed description of further features of the switch will now be given of the embodiment in FIGURES 6 to 8. The reference numerals of parts already mentioned are the same as in FIGURES 2 to 5.

FIGURE 6a shows the dome-like top part 112 of the casing of the switch, the part 112 having snap connections 302, 303 for engaging the base part of FIGURE 6b. On the underside of the casing part 112 a projecting lug or the like 304 (the corresponding laterally symmetrical lug cannot be seen) is integrally formed on the bottom edge of the major side wall and serves for lateral guidance of the base part by means of a stepped shoulder or the like similar to the one 305, 306 on the longitudinal ends; the element 307, 308 can be seen in plan in FIGURE 6c. The snap elements 302, 303 of the dome-like top part 112 engage in corresponding stepped cutaway parts 309, 310 in the integral walls 311, 312.

Connecting terminals (not shown) are also located correctly relatively to one another and secured just by a plug-in retention laterally of the walls 311, 312, through the agency of base part webs 313, 314, the walls 315, 316, covering elements 317, 318 of the top part 112 and bottom elements 319, 320 of the base part. Clamping screws for connecting wiring extend either through tapped sleeves or through plain bores 321, 322. Other guide projections 323, 324 (325, 326) provide guidance and retention of switch block 327, which is plugged in to top part 112 and which has projections 328, and therefore provide positive location purely on the basis of plugging-in. Contrived integrally in the inside 330 of base 329 is a circular recess 331 and peripheral annular web 332 for centering and retaining the magnet (not shown) of the electromagnet-and-armature unit. Like the guide projections hereinbefore described, the integers 331, 332 provide positive location of a unit relative to another unit or to the casing with automatic compensation for tolerances- not least of all because the relatively thin and not particularly rigid walls are fairly resilient.

In FIGURE 6b a plug-in lug or strip 333 formed with a slot 334 for surface mounting is so engaged in its plug-in aperture that it is retained in position positively by abutment 335 and a unitary tongue 336 on both sides of web 337 on the underside remote from the casing top part 112. The particular features of integer 333 will be described hereinafter with reference to FIGURE 8.

In FIGURE 7a, the dome-like top part 112 containing the units 101 and 106, the actuating lever 115 with its pivot 235 mounted in the top part 236 of the mounting, the switch block 122 and the electrical connecting parts 123 is adapted to be connected to and located relative to a base part 361 by snap connecting elements 358, 359 and partitions or projections, only one, 360, of which can be seen.

Disposed in a matching plug-in mounting aperture in part 361 is a member 363 resiliently biased by means of a helical compression spring 362. The member 363 snaps into engagement behind a support (not shown) on which the switch is mounted.

FIGURE 7b shows the same base part as in FIGURE 6b for this bar mounting corresponding to the top part of FIGURE 7a, except that as compared with the previous case the lug 364 is plugged in at an offset of 180 . The helical compression spring 365 is now clamped between abutment 366 of lug 364 and a resilient tongue 367, at one end, and abutme

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

112 and bottom elements 319, 320 of the base part. Clamping screws for connecting wiring extend either through tapped sleeves or through plain bores 321, 322. Other guide projections 323, 324 (325, 326) provide guidance and retention of switch block 327, which is plugged in to top part 112 and which has projections 328, and therefore provide positive location purely on the basis of plugging-in. Contrived integrally in the inside 330 of base 329 is a circular recess 331 and peripheral annular web 332 for centering and retaining the magnet (not shown) of the electromagnet-and-armature unit. Like the guide projections hereinbefore described, the integers 331, 332 provide positive location of a unit relative to another unit or to the casing with automatic compensation for tolerances- not least of all because the relatively thin and not particularly rigid walls are fairly resilient.

In FIGURE 6b a plug-in lug or strip 333 formed with a slot 334 for surface mounting is so engaged in its plug-in aperture that it is retained in position positively by abutment 335 and a unitary tongue 336 on both sides of web 337 on the underside remote from the casing top part 112. The particular features of integer 333 will be described hereinafter with reference to FIGURE 8.

In FIGURE 7a, the dome-like top part 112 containing the units 101 and 106, the actuating lever 115 with its pivot 235 mounted in the top part 236 of the mounting, the switch block 122 and the electrical connecting parts 123 is adapted to be connected to and located relative to a base part 361 by snap connecting elements 358, 359 and partitions or projections, only one, 360, of which can be seen.

Disposed in a matching plug-in mounting aperture in part 361 is a member 363 resiliently biased by means of a helical compression spring 362. The member 363 snaps into engagement behind a support (not shown) on which the switch is mounted.

FIGURE 7b shows the same base part as in FIGURE 6b for this bar mounting corresponding to the top part of FIGURE 7a, except that as compared with the previous case the lug 364 is plugged in at an offset of 180 . The helical compression spring 365 is now clamped between abutment 366 of lug 364 and a resilient tongue 367, at one end, and abutment wall 368 of base part 369-i.e., on projection 370 thereof on the underside remote from the dome-like top part 112-at the other end and is pressed inwards towards the support or mounting or carrying bar (not shown).

FIGURE 8 is a view on an enlarged scale of the plug-in lugs 364. The sectional view in FIGURE 8a shows the unitary resilient tongue 371 and the abutment 372 between which one end of the helical compression spring (not shown here) is retained, the spring being pushed on to projecting fingers 373, 374. Slot 375 serves to receive a screw for screw fixing in the case of surface mounting of the switch or in the case of bar mounting as an aperture for a tool to pull the lug 364 outwardly and thus separate the base part from the mounting bar.

WHAT WE CLAIM IS:- 1. An electrical time switch comprising a switching unit having a contact set for operation in dependence upon time, an actuating unit engaging with the switching unit to operate the contact set, an electrically powered drive unit for driving the actuating unit to operate the contact set, and a timing unit coupled to the drive unit for governing the action of the drive unit in dependence upon time, the said units being received in a casing consisting of at least two parts, the said units constituting a plurality of sub-assemblies which are geometrically adapted to one another and to the casing so that the units are selflocating as regards their mutual positions in the casing.
2. A switch according to claim 1, wherein the sub-assemblies and casing have integral mouldings providing the said geometrical adaptation.
3. A switch according to claim 1 or 2, wherein one of said units comprises a fixed component which is integral with one of the casing parts and an associated movable part coupled to another unit is movably received in the fixed component.
4. A switch according to any one of claims 1 to 3, wherein one sub-assembly is formed with an abutment for spacing it apart from another sub-assembly.
5. A switch according to any preceding claim, wherein the switching unit is formed with a mounting portion for a pivot spindle of an actuating lever of the actuating unit.
6. A switch according to claim 5, wherein the switching unit and the casing have integral locating elements by which the switching unit is located and retained in the casing.
7. A switch according to claim 6, wherein the switching unit comprises a switch block formed by spacing mouldings for contact blades of the contact set, which switch block engages between two parallel walls of the casing formed with guide grooves and/or guide projections.
8. A switch according to any of claims 5 to 7, wherein the casing is also formed with a mounting portion for the pivot spindle of the actuating lever.
9. A switch according to claim 8, wherein the mounting portions for the pivot spindle on the switching unit and on the casing constitute half-hubs between which the actuating lever pivot is received.
10. A switch according to any one of claims 5 to 9, wherein a contact blade of the. switching

unit has a free end provided with a moulding having a shaped actuating surface for engagement by the actuating lever.
11. A switch according to any one of claims S to 10, wherein the switching unit has two contact sets which the actuating unit actuates in succession.
12. A switch according to claim 11, wherein another lever is mounted on the actuating lever for actuating the second contact set, such other lever being mounted on a pivot parallel to the actuating lever pivot and being biased by a spring onto an abutment in one direction.
13. A switch according to claim 12, wherein the pivot of the said other lever is the actuating lever pivot.
14. A switch according to any one of claims 11 to 13, wherein the actuating lever pivot has two portions of different diameters.
15. A switch according to any one of claims 5 to 10, including a rocker for holding the contact set of the switching unit in an operative position irrespective of the condition of the actuating unit, which rocker is mounted on a spindle formed on and interconnecting two parallel walls of the casing and is bistably biased by a spring extending between a groove in the rocker and a retaining slot in a retaining element disposed in the casing between the said parallel casing walls.
16. A switch according to claim 15, wherein the retaining element is integrally formed in the casing.
17. A switch according to claim 15 or 16, wherein an end member of a contact blade of the contact set forms one abutment for the rocker and an edge of a component rigidly secured to the casing forms another abutment for the rocker.
18. A switch according to claim 17, wherein the end member of the contact blade comprises a moulding received on the free end of the contact blade and formed with a groove to guide the rocker, such groove having to wards the free end of the contact blade a transverse boundary wall serving as the said one abutment.
19. A switch according to any one of claims

5 to 10, wherein the drive unit comprises a solenoid having a winding and a plunger, the actuating lever being coupled to the plunger.
20. A switch according to claim 19, wherein a winding former of the solenoid is adapted to plug into the casing.
21. A switch according to claim 19 or 20, wherein the timing unit comprises a pneu matic time delay in the form of a piston and cylinder unit having an air cushicn, a sealing valve and an adjustable air vent, the cylinder being formed integrally with the casing and the piston being coupled to the plunger of the solenoid.
22. A switch according to claim 21, wherein the adjustable air vent takes the form of a valve housing which is formed integrally in the end wall of the cylinder and receives a screwthreaded spindle which is adjustable through the casing.
23. A switch according to claim 22, wherein the valve housing is in the form of a hollow cone.
24. A switch according to any preceding claim, wherein the casing is composed of a dome-shaped part fitted on a base part which is formed with a mounting aperture for receiving a resiliently biased mounting member for mounting on a support bar.
25. A switch according to claim 24, wherein the base part of the casing is also formed for the selective attachment of a mounting member having a fixing aperture for the surface mounting of the switch.
26. A switch according to claim 25, wherein the mounting member is a plug-in part having a rearward lug for the support bar and adapted to be plugged in at different positions and in one position being retained by an abutment and a spring strip in a rigid positive latching engagement and, in the other posi tion which is for mounting on the support bar, being retained resiliently in a free fit, for example by means of a compression helical spring between two abutments.
27. A switch according to claim 26, wherein the base part has on one side of the mounting aperture a preferably unitary web around which the plug-in part is clamped on both sides, when in the latched or engaged position, by the abutment and the spring strip.
28. A switch according to claim 26 or 27, wherein the mounting aperture in the base part of the casing is formed with grooves in whose cross-section a spring strip of the mounting member fit without jamming in its resiliently retained position.
29. A switch according to claim 28, wherein the mounting member can be plugged into the same mounting aperture in two positions at a 1800 offset from one another, and the abut ment and web on one side of such aperture, for example the side remote from the dome like casing part, and on the opposite side, respectively, are formed with grooves through which the spring strip can extend freely.
30. A switch according to any one of claims

24 to 29, having so received in the dome-like casing part as to abut the inside of the base part which is formed with grooves and/or projections for locating the sub-assembly.
31. A switch according to claim 30, having an electromagnet-and-armature unit, wherein the inside of the base part is formed with a circular recess and an annular web for locating a winding former of the said unit.
32. A switch according to claim 30 or 31 wherein the contact set is retained in a switch block, the switch having a lug block enabling a switch block of the switching unit to be engaged in, and positively guided by, parallel webs on at least one of two parallel walls.
33. A time switch substantially as hereinbefore described with reference to the accompanying drawings.