F I ELD OF TH E I NVENTION The present invention relates to an auxiliary contact block for a low voltage contactor. The auxi liary contact block comprises a connecti ng mechanism for connecting the auxil iary contact block to the low voltage contactor, wherein a low voltage is com monly defi ned as up to about 1 000V AC or 1 500V DC.

PRIOR ART

A contactor is an electrical ly controlled switch device used for switching an electric power or control circuit of an electrical load device. Such a contactor comprises a contacting unit, an actuating unit and an enclosure for housing the actuati ng unit and the contacting unit. The contacti ng unit incl udi ng a movable contact and a stationary contact, both are for carryi ng current when a contact is made between them . The actuati ng unit is for operating the movable contact for electrical connection or disconnection .

An auxil iary contact block may incl ude a plurality of contacti ng units. An auxil iary contact block may be added to a contactor when additional contacts or additional functions are required , for example, to indicate an operation status of a contactor or, to use it as a safety purpose for two con- factors to prevent them from bei ng closed sim ultaneously, otherwise a short circuit occurs. To connect an auxiliary contact block to a contactor, an auxil iary contact block is traditional ly secured by screws to the contactor. Therefore, tools are needed for making such a connection. A patent EP0831 569B discloses an auxil iary switch includi ng a tool free connection mechanism . The auxiliary switch comprises an actuation nipple extending out from a first side-wall of the switch housing and for coupling to a movable switch element of an additional auxil iary switch or electromagnetic switch device. Two snap hooks or catches protrude out from the first side-wall of the switch housing and adjoin pressure pieces disposed on an opposite-facing narrow third side-walls, where the snap hooks is adapted to be engaged into recesses of a housi ng wall of a further auxiliary switch or switch device. The invention enables an operator to connect the auxil iary switch to a lateral wall of an additional auxil iary switch or electromagnetic switch device without using tools. However, when a connection is performed in a li mited space for exam ple, for example, i n a cabinet, it might be difficult to reach the snap hooks in order to remove the auxil iary switch from the electromagnetic switch device, because this needs spaces in both sides of the auxil iary switch .

OBJ ECTS AN D S U MMARY OF TH E I NVENTION

The object of the present invention is to provide an auxil iary contact block with an im proved connecti ng mechanism for connecting or disconnecting the auxi liary contact block to a contactor.

This object is achieved by the auxil iary contact block defined in the preamble of claim 1 , characterized in that the releasi ng member is arranged on the second housing and further com prises a wedge element connected to the pressing element, an inlet is provided on the second housing for receiving the wedge element, the snap-fit element is arranged on the first housing and protrudes out from the inlet, and the wedge element is arranged , upon pressing the releasi ng bar, an latched snap-fit element is pushed aside to the unlatched position so that the auxiliary contact block is unlocked from the contact device.

This structure enables easy attachment to or detachment from a contactor. The attachment com prises sim ply hooking and pushi ng operations, whereas the detachment includes pushi ng and unhooking operations. A tool is not required in either attachment or detachment of the auxil iary contact block.

Preferably, the releasing member is arranged on the top edge of the first housi ng . This means that the inlet is also be arranged on the top edges of the second housing in order to engage a releasi ng operation . Accordi ng to one embodiment of the invention , the auxil iary contact block may further comprise a gauge block arranged on the second housing and adjacent to the snap-fit element so that the snap-fit element will not be pushed further when releasi ng auxil iary contact block from the contactor.

Preferably a second set of snap-fit element, releasi ng member, inlet and gauge block is provided on the same housing as the first correspondi ng one and situated at a distance from the first corresponding one. Having the second set of snap-fit element, releasing member, inlet and a second gauge block enables a stable connection between the auxiliary contact block and the contactor. To be easi ly operated , the fi rst and second releasing members may preferably be arranged in such a d istance so that a detachment action may be operated by j ust one thumb or finger.

Furthermore, the auxil iary contact block may further com prise a connecting hook arranged on the second housing for engaging with the first recess provided on the side wall of the contactor. The connecting hook may be arranged with a distance to the releasing member.

BRI EF DESCRI PTION OF TH E DRAWI NGS

The invention will now be explained more closely by the descri ption of different embodiments of the invention and with reference to the appended figures. shows a perspective view of an auxiliary contact block to be connected to a low-voltage contactor, accordi ng to one embodiment of the invention . shows a partial inner side perspective view of the connecti ng mechanism of the auxi liary contact block shown in Fig. 1 .

Fig. 1 b shows a partial outer side perspective view of the connecti ng mechanism of an auxi liary contact block shown i n fig. 1 . Fig.2 is a perspective view of the low-voltage contactor to which the auxiliary contact block is to be connected. Fig. 3a is an exploded view of a contact block assembly comprising a contactor and an auxiliary contact block.

Fig. 3b is a perspective view of a contactor connected to an auxiliary contact block to form a contact block assembly.

Fig.4a is a top plan view of an embodiment of the auxiliary contact block of Fig. 1.

Fig.4b is a back plan view of the contactor shown in Fig.2.

Fig.4c is an enlarged partial view of the snap-fit element and the gauge block shown in Fig.4a.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS THE INVENTION

Fig. 2 shows a low-voltage contactor 100 to which the auxiliary contact block shown in Fig.1 is to be connected. Such a contactor is used in the industry for controlling an electric power or control circuit of an electrical device such as a motor, a lighting unit, a heating apparatus or a capacitor bank. Contactor 100 may comprise top 180, front 130, back (not visible), right and left sides 150, 160 and base 170 respectively. The contactor 100 further comprises a movable contact and a stationary contact part (they not visible) and, an actuating unit (not visible) for operating the movable contact part to make (dis)connection with the stationary contact part. On the right and/or left side, a first 110 and a second 140 recesses are provided.

Fig. 1, Fig. 1a and Fig.1b show a perspective view, a partial inner per- spective view and a partial outer perspective view of an auxiliary contact block 1 to be connected to a low-voltage contactor 100, accordi ng to one embodiment of the i nvention .

An auxiliary contact block 1 comprises a first 1 1 and second 12 housi ngs connected in paral lel to each other, an actuation nipple 20 extending out from the second housi ng 12, and a connecti ng mechanism for connecting the auxil iary contact block to a contact device. The actuation nipple 20 is adapted to be connected to the actuating unit of a contactor. The connecting mechanism comprising a snap-fit element 40 for locking the auxil iary contact block to the contact device when it is at a latched position and a releasing member 30 for unlocki ng the snap-fit element 40 to an unlatched position .

I n this exam ple, the releasing member 30 is disposed on the top edge 14 of the second housing 12 and comprises a pressing element 32 and a wedge 34 connected to the pressing bar. The pressing element is in the form of a bar and arranged for receivi ng a pressing force. An inlet 60 is provided on the top edge of the second housing 12 for receiving the wedge element 34 when it is pressed . Preferably, the inlet 60 is arranged adja- cent to the releasing member 30.

The snap-fit element 40 is arranged on the first housing 1 1 and has a cantilever with its one end protrudes out from the i nlet 60 through the second housing . This end has a hook shape to be incorporated with the second recess 140 provided on the contactor.

It is advantageous that the releasi ng members are arranged on the top edge of the second housing because this enables a releasi ng action when there is a lim ited space, for example when the contactor is arranged in a cabinet.

The auxil iary contact block may further com prise a connecting hook 1 0. I n this example, the connecting hook is disposed close to the side opposite to the releasing member to be engaged with the first recess 1 1 0 provide on the right or left side of the contactor. The first recess 1 1 0 is provided for engaging the connecting hook 1 0. The second recess 140 is provided for engagi ng the snap-fit element 40. With reference to Fig. 3a and Fig .3b, the auxiliary contact block 1 may be attached or connected to either the right side or the left side of the contactor 1 00. To connect the auxiliary contact block 1 to the contact 100, one may simply hook the connecting hook 10 in the first recess 1 1 0 provided on the side wall of the contactor, then pushi ng the contact block 1 agai nst the contactor so that the snap-fit element 40 is latched in the second recess 1 00 when it is engaged with the latter.

With reference to Fig . 1 a, to release or disconnect the auxil iary contact block 1 from the contact 1 00, a force F is acting on the releasi ng bar 32. The wedge element 34 is arranged in such a way that, upon pressing the releasing bar 32 , it is pressed into the inlet 60 so that it pushes the latched snap-fit element 40 aside to the unlatched position in the direction A and the auxil iary contact block is therefore unlocked from the contact device. Thereafter, it is easily to disconnect the contact block from the contactor by just unhooki ng the connecting hook 10 from the first recess 1 0. Preferably, a gauge block 50 is provided on the second housi ng 12 adjacent to the snap-fit element 40 to prevent the snap-fit element from bei ng pushed further when a releasi ng action is performed . The connection mechanism in the present invention is fully applicable to connect the auxil iary contact block to an additional auxil iary contact block as well .

Fig . 4a, Fig.4b and Fig .4c provide detai led views of the snap-fit element 40, the gauge block 10 and the second recess 140 provided on the contactor.

It should be understood that the invention is not li mited to the above embodiment; it is also applicable to al l possible designs that have modified or equivalent structures.