A conventional contactor (also known as a relay) comprises at least one set of terminals, a coil with an armature, means for energizing the coil, and connecting means for connecting the terminals to allow a current flow therebetween, which connecting means are arranged to be operated by the armature. Said connecting means may be"normally on"or"normally off", and on energizing the coil, the armature will operate the connecting means to switch the connecting means to the opposite state.

Typically, the connecting means comprise an electrically conductive, movable bridging element that is mounted on a push rod arranged to be driven by the armature. The bridging element can be moved between a connected position in which it extends between and contacts both terminals, and a disconnected position in which it is removed from at least one of the

terminals. Biasing means are provided for biasing the bridging element into the connected position or disconnected position, according to whether the contactor is"normally on"or"normally off" respectively. A contactor comprising a single set of terminals is known in the art as a"single pole single throw"contactor. A"double throw"or"changeover" contactor comprises two sets of terminals and two corresponding bridging elements, usually mounted on a single push rod. The bridging elements are arranged such that when one bridging element is"on", the other element is"off".

It is an object of the present invention to provide an improved contactor.

In particular, it is an object of the invention to provide a contactor that can be used on a PCB.

More particularly, an object of the invention is to provide a high current contactor that can be used on a PCB.

Further objects of the invention will be apparent from the following description.

According to one aspect of the present invention therefore there is provided a high current contactor that is characterised in that each high current terminal comprises a plurality of conductive fingers for connection to a PCB.

Each high current terminal may comprise two or more fingers, typically three fingers. The contactor of the invention may be used for AC and DC applications, although contactors of this kind are most commonly used for DC currents. Each terminal may be adapted to carry a current in excess of 30amps, and in some embodiments, each terminal may be suitable for conveying an electrical current in excess of 50amps, for example 60 or 80amps. Each finger of a high current terminal in accordance with the invention is sufficiently slender that it can be conveniently soldered to a cooperating track on a PCB, but collectively the fingers of the terminal provide sufficient conductivity to conduct a high current. A further advantage of the invention is that whilst each finger presents a small cross sectional area for ease of soldering as mentioned above, collectively, the fingers are capable of efficiently conducting heat associated with high currents.

Preferably, each high current terminal comprises a unitary terminal member having a plurality of fingers for connection to a PCB, and a contact portion adapted to contact suitable, selectively operable connecting means. Said terminal member may comprise a pressed, wrought or extruded body. Said contact portion may comprise an integral contact element. By way of example, said contact element may comprise a disk or button rivetted, soldered or brazed to the body. Each terminal member may be conveniently removable from the contactor as a single part.

Alternatively, said contactor may comprise a unitary mounting base comprising at least one set of high current terminals, wherein each terminal comprises a plurality of fingers adapted for permanent connection to a PCB; and a removable portion incorporating the coil and armature, the connecting means and at least one set of fixed contacts associated with the connecting means; wherein each fixed contact on the removable portion is adapted for detachable connection to a respective terminal on the base portion of the contactor. Typically, each fixed contact on the removable portion may comprise a plug portion adapted to engage in a socket portion on the respective

terminal. Equivalently, the terminal may be provided with a plug portion adapted to engage in a corresponding socket on the respective fixed contact.

Each plug portion may comprises a single pin or, alternatively, may comprise a plurality of fingers adapted to engage in a corresponding number of recesses. The removable portion can thus be conveniently be removed from the base portion for servicing or replacement.

According to another aspect of the present invention there is provided a high current contactor for a PCB, characterised by at least one set of primary high current terminals and a set of auxiliary low current terminals, first connecting means associated with the high current terminals and second connecting means associated with the low current terminals; wherein said first and second connecting means are arranged to be operated together by the armature.

Said first connecting means may comprise a movable bridging member comprising a set of movable contacts. Said bridging member may be carried by a push rod that is driven by the armature.

Said second connecting means may comprise a snap- action or microswitch. Said microswitch may be operated by said push rod or a part operably connected thereto.

Said auxiliary low current terminals and said microswitch may be accommodated in an integral unit which can be detached from the contactor. Said integral unit may be provided with engaging means for releasably engaging cooperating means on the contactor for attaching the unit to the contactor. Said push rod or part connected thereto may protrude from the contactor to engage the microswitch when the integral unit is attached for operating the microswitch.

Typically, the contactor will be accommodated within a housing. In some embodiments, the housing may be sealed against water ingress for use in wet or damp environments.

The contactor may be further equipped with magnetic blow-out means of the kind known to those skilled in the art, such that the contactor of the invention can be used in high voltage DC applications, for example voltages in excess of 48volts.

As a further option, magnetic latching means may be provided for latching the armature in the"energized" position, such that the armature remains in the "energized"position when the coil is de-energized.

Magnetic latching means of this kind are well known to those skilled in the art, and suitable means may be provided for ensuring that on each successive occasion, the coil is energized with a polarity that is opposite to the polarity employed on the immediately preceding occasion.

Following is a description by way of example only with reference to the accompanying informal drawings of methods of carrying the present invention into effect.

In the drawings:- Figure 1 is a side view of a double pole, high current DC contactor in accordance with the present invention.

Figure 2 is a plan view of a receptacle forming part of a housing for the contactor of figure 1. In figure 2, one set of high current terminals are shown in situ.

Figure 3 is an isometric view of the receptacle of figure 2.

Figure 4 is a front view of a high current terminal member in accordance with the present invention.

Figure 5 is a side view of the terminal member of figure 4.

Figure 6 is a bottom view of the contactor of figure 1.

Figure 7 shows a solenoid assembled with two sets of movable contacts on a push rod.

Figure 8 shows the assembly of figure 7 fitted into the receptacle of figures 2 and 3.

Figure 9 is a bottom view of a closure forming part of the housing for the contactor of figure 1.

Figure 10 shows a high current DC contactor in accordance with the invention fitted with an auxiliary unit comprising a set of auxiliary low current terminals operated by a microswitch.

Figure 11 is a side view of the contactor of figure 10 with a closure in a fitted position.

Figure 12 shows a solenoid assembled with two sets of movable high current contacts and a plunger for operating the microswitch of the auxiliary terminals of the contactor of figure 10.

Figure 13 is a detail of the plunger of figure 12.

Figure 14 is an isometric view of the contactor of figure 10 with the auxiliary unit removed to show the plunger protruding from the housing.

Figure 15 shows the auxiliary unit of the contactor of figure 10 detached from the contactor.

Figure 16 is a rear view of the auxiliary unit of figure 15.

With reference to figure 1, a high current DC contactor in accordance with the present invention includes housing 10 comprising a receptacle 12 and a removable closure 14. Said receptacle 12 comprises a bottom wall 22, a front wall 24, a rear wall 26 and

two side walls 28 as shown in figures 2 and 3. Said bottom wall 22, front and rear walls 24,26 and side walls 28 define a recess 30 which is closed by the closure 14 as shown in figure 1. Suitable fixings (not shown) are provided for securing the closure to the receptacle.

Said recess 30 is partitioned by two opposing transversely extending internal walls 32 to form a solenoid cavity 30a, and a juxtaposed contact cavity 30b. Within the contact cavity 30b, the bottom wall 22 of the receptacle is moulded to accommodate two sets of high current terminals 40, namely a rear set of terminals 40a adjacent the internal walls 32 as shown in figures 2 and 3, and a front set of terminals 40b which are omitted from figures 2 and 3.

As shown in figures 4 and 5, each high current terminal 40 is a unitary member comprising a substantially flat, generally rectangular sintered body 42 that is formed towards one end with a plurality of substantially parallel fingers 44. In this example, each terminal 40 comprises three such fingers, although in other examples two fingers, or more than three fingers may be provided. Each finger

44 has a cross sectional area that is sufficiently small that the finger can be conveniently soldered onto a cooperating terminal on a PCB. Together, the fingers 44 have sufficient conductivity to conduct relatively high currents, for instance 60 or 80amps.

The body 42 may be manufactured from any suitable, electrically conductive material, although in this example, the body is formed from an extruded copper bar.

A contact element 46 is fixed to the main part of the body 42. In this example, the contact element 46 comprises a metal button that is rivetted to the body 42.

Each of the terminals 40 of the rear set 40a is seated in a recess 50 defined by a respective one of the transverse internal walls 32 and a juxtaposed upstanding, moulding portion 52 intermediate said transverse wall 32 and said front wall 24. Each terminal 40 of the front set 40b is seated in a similar recess defined by said upstanding rectilinear moulding 52 and said front wall 54. Each terminal 40 forms a snug fit in its corresponding recess 50, and the bottom wall 22 of the receptacle is perforated at

the bottom of each recess to define three juxtaposed apertures 54. The fingers 44 on each terminal 40 thus extend through the apertures 54 as shown in figures 1 and 6 of the drawings.

The solenoid cavity 30a is shaped to accommodate a solenoid assembly 60 comprising a coil 61, a U-shaped frame 62 and a stop member 63 (see figure 7). Said coil 61 accommodates a cylindrical tube (not shown) which in turn receives a movable armature of the kind well known to those skilled in the art. The frame 62 and stop member 63 form a snug fit within the solenoid cavity 30a of the receptacle as shown in figure 8.

The solenoid is positioned within the solenoid cavity such that the stop member 63 abuts the internal partition walls 32, and an orifice 64 formed in the stop member 63 is positioned between the inner ends of said internal walls 32.

Said orifice 64 is disposed substantially coaxially with the coil 61, and accommodates a rear end 71 of push rod 70 that is accommodated within the contact cavity 30b of the receptacle 12. Said push rod 70 is an integrally moulded plastic component comprising a relatively narrow rear end portion 71, an

intermediate, contact-carrying portion 72 having a diameter greater than the rear end portion 71 and an enlarged front end portion 73 having a forwardly directed shoulder 74 and a forwardly directed, coaxial nib 75. Said intermediate portion 72 carries two elongate, generally rectangular bridging elements 80, namely a rear bridging element 80a, and a front bridging element 80b. Each bridging element 80 is drilled substantially centrally to provide a bore that accommodates the push rod 70. A coil spring 88 is mounted on the push rod 70 between the two bridging elements 80 to urge said bridging elements apart. The front bridging element 80b is thus urged into engagement with the rear side of the front end 73 of the rod, and the rear bridging element 80a is urged rearwardly into engagement with a circlip 76 that engages a groove formed in the intermediate portion 72 of the push rod 70.

As shown in figure 8, the shoulder 74 on the front end 73 of the push rod 70 carries a coil spring 86 which acts between said shoulder 74 and the rear side of the front wall 24 of the receptacle. The front end of the coil spring 86 is accommodated within a recess 25 formed in the front wall 24, and the coil spring thus

serves to centre the push rod 70 within the contact cavity. Said coil spring 86 urges the push rod rearwardly within the cavity, such that the rear end portion 71 of the push rod engages the armature within the solenoid 60.

The rear bridging member 80a carries a pair of rearwardly facing contact elements 82 on opposite sides of the push rod 70. Said contact elements 82 are arranged to contact the contact elements 46 formed on the rear terminals 40a as shown in figure 8. Said coil spring 86 serves to maintain good electrical contact between the rear terminals 40a and the rear bridging element 80a to allow the conduction of a high current between the two rear terminals.

Said front bridging member 80b is similarly equipped with two forward facing contact elements 82 arranged to contact the contact elements formed on the front high current terminals 40b. Normally, the front bridging element 80b is disconnected from the front terminals 40b.

Said coil 61 is provided with two terminals 65 that protrude through the bottom wall 22 of the housing 10

for connection to a low current supply for energizing the coil 61. On energizing the coil, the armature moves within its tube to urge the push rod 70 forwardly within the contact cavity against the action of the coil spring 86. Such movement of the armature causes disconnection of the rear bridging element 80a from the rear high current terminals 40a, and contact of the contacts 82 on the front bridging member 80b on the contacts formed on the front terminals 40b. On de-energizing the coil 61, the electromagnetic force maintaining the armature in the forward position is removed, and the push rod 70 thus returns to its normal rearward position under the action of the spring 86, thus disconnecting the front terminals 40b and reconnecting the rear terminals 40a.

The outer surface of the bottom wall 22 of the receptacle 20 is provided with two upwardly directed, generally cylindrical recesses 23 as shown in figure 6 which extend into said mouldings 52. Similarly, the underside of the closure 14 of the housing is provided with two upwardly extending, generally cylindrical recesses 50 as shown in figure 9. Each of these recesses is adapted to accommodate an optional permanent magnetic to adapt the contactor for use in

high voltage applications. Each of the magnets that can be fitted into the closure 14 is substantially aligned with a respective magnet fitted into the bottom wall of the receptacle to provide an intense magnetic flux therebetween, such magnetic flux serving to blow-out magnetic flux between the fixed and movable contacts within the contact cavity which arise when the contactor is used for voltages in excess of about 48volts. Such blow-out magnets are known to those skilled in the art.

In another example of the present invention, a contactor of the kind described above may be fitted with an optional unit 90 as shown in figure 10 including two sets of auxiliary terminals 92. Said unit 90 comprises a unitary, generally rectilinear surround 94 moulded from a thermoplastics material.

As shown in figures 10 and 15, said surround includes a front wall 95, a rear wall 96 and two side walls 98.

Said front, rear and side walls define a generally rectangular opening 99 that accommodates an integrated, non-latching, single throw changeover microswitch 100. Many suitable switches are available to those skilled in the art as proprietary items, including, for example, the FK4 snap-action switches

available from SAIA-Burgess Electronics. Said integrated switch 100 includes two pairs of connectors which extend forwardly of the switch when fitted in the opening 99 and are accommodated in four respective channels 102 formed in the front wall 95 of the unit.

Said auxiliary terminals 92 are embedded in the front wall 95 of the unit and protrude downwardly therefrom as shown in figure 11. The upper end of each terminal 92 is forked to provide two strips that are disposed on opposite sides of a respective channel 102 to contact the forwardly extending connectors in the integrated switch 100.

Said switch 100 is operated by a microswitch having an actuator button 104 that extends rearwardly of the integrated switch 100 when fitted in the opening 99 and is accommodated within a circular aperture 106 formed in the rear wall 96 of the unit 90.

Said integrated switch 100 is supported within the opening 99 by two pairs of upstanding ribs (not shown) formed respectively on the rear face of the front wall 95 of the unit and on the front face of the rear wall 96 of the unit.

The microswitch operates that such that on pressing the actuator button 104, one pair of the connectors are shorted, whilst the other pair are disconnected, and on releasing the button, the other pair are shorted, whilst the one pair are disconnected.

As illustrated in figure 15, the rear wall 96 of the unit 90 is formed with two upstanding, substantially parallel ribs 108, each of which, in cross-section, has a narrow wasted portion 109 juxtaposed the rear wall 96 and an enlarged rear portion 110. Said ribs 108 are shaped to engage in a pair of correspondingly shaped grooves 112 formed in the front face of the front wall 24 of the receptacle 12 as shown in figure 14. The ribs 108 on the unit 90 are configured to engage slidingly in the grooves 112 on the receptacle 12 for releasably securing the unit to the front end of the receptacle as shown in figures 10 and 11. In the fitted position, the rearwardly protruding microswitch button 104 abuts a small brass plunger member 114 which is mounted on one end of small helical spring 116 as shown in figures 12 and 13, the other end of which helical spring 116 is slidingly fitted over the nib 75 protruding on the front end 73 of the push rod 72. Said helical spring 116 thus

serves to urge the plunger member 114 forwardly within the contact cavity 30b, said plunger member 114 extending through a small orifice 118 formed in the front wall 24 of the receptacle 12 into engagement with the microswitch button 104.

On energizing the coil 61 of the solenoid 60, the forward movement of the pusher rod 72 is transmitted to the plunger member 114 through the helical spring 116, thus depressing the microswitch button 104 to operate the integrated switch 100. The displacement of the pusher rod 72 forwardly from its normal position to the energizing position is slightly greater than that needed to depress the microswitch, and the overtravel is accommodated by compression of the small helical spring 116.

On de-energizing the coil 61, the pusher rod is returned to its normal position under the influence of the coil spring 86, and the plunger member 114 is thus returned to its rearward position releasing the microswitch button 104.

The auxiliary, low current terminals 92 can be used to connect low current devices in tandem with the high current contactor such, for example, as indicator lights and the like.