Electric switch structure in which the actuation axial force is just a small portion of the contact force

Abstract: Electric switch structure by which the forces on the electric contacts are well higher than the forces applied to actuating members, comprising a slider (22, 122) movable within a fixed housing (16, 116) provided with profiles or cams (26, 28; 126, 128) converting the movement of said slider (22, 122) to contact movement in said structure, said profiles or cams (26, 28; 126, 128) opposing their action to that of springs (31, 33; 131, 133) applying closing forces to contact pairs.

Description: Present invention relates to an electric switch structure of the kind in which at least two fixed contact arms are connected by at least a conducting bridge, having at least one movable contact pair opposed to at least a fixed contact pair on said fixed arms. Such a switch can be specifically employed in auxiliary switch blocks assembled on electromechanical devices, such as contactors or relays, in which the smallest possible force from actuating members is required in order to actuate contact closure and/or opening while the force applied to said closing contacts must be well higher than the force required from said actuating members. In the nowadays electromechanical devices, such as contactors, many accessory devices are provided such as latching devices, time delaying devices, and, specifically, contacts having auxiliary tasks, which require high forces from the actuating members. An auxiliary contact device using a linear cam arrangement utilized with a rooted flexure arm is disclosed by US-A-4 712 079. Such a device operates rather well, but has the drawback to have different contact pressures according to the kind of operated contacts, because normally closed contacts have a pressure provided by a spring independentely from the force provided by the linear cam arrangement, while normally open contacts have a pressure directly provided by the linear cam arrangement so that the force required for its contact pressure is directly supplied by actuating members of a relay or contactor. Such an approach meets just for the normally closed contacts the requirements of an auxiliary switch block according to the present invention. Further, the movable contacts are arranged on flexible resilient electrically conducting arms prone to overheating, in case of overcurrents, with the risk of loss of resilience due to annealing connected with said overheating. Such a last drawback could be overcome by using double bridging contacts such as the bridging contacts suggested by US-A- 3 016 440, avoiding to conduct currents through resilient flexible arms, however such bridging contacts, being T shaped with a stem portion inserted in a cavity of a rotatable assembly, are directly actuated by actuating means of the relay or contactor, producing on the contacts pressures directly connected with the forces provided by the actuating means of the relay or contacor itself, so that also this approach does not meet the requirements asked to the present invention. The present invention provides an electric switch structure for relays and contactors, comprising a plurality of auxiliary contacts, wherein each contact is a double interruption contact which can be normally open or normally closed, an insulating housing, a slidable actuating member wich is movable between two end positions by a movable part of a relay or contactor, said insulating housing accomodating said actuating member and said contacts, said actuating member being an insulating member actuated externally of said housing and including cam means thereon, spring members located in said housing each contact including a movable portion, and contact carrying means acted upon by said spring members and carrying said movable portions of said contacts, characterized in that said actuating member includes a slider, said cam means are formed on an inner face of said slider, said contact carrying means including conducting bridges connecting at least two movable contact portions, said bridges being pivotably supported in said housing, said spring members forcing said bridges to engage through protrusions said cams, each bridge being substantially T shaped and having a first cross-arm carrying said movable contact portions and a protrusion cooperating with a respective one of said cams and a second arm provided with a fulcrum abutting against opposed protrusions in said housing, fixed arms connected to said housing and carrying fixed contact portions, said fixed arms terminating with screw clamps for connection with external circuits, said cams means, upon axial movement of said actuating member from one of said end positions to another of said end positions acting on said contact carrying means to move said movable portions relative to said fixed portions against a force of said spring members, so that opening and closure of said contacts are obtained by the axial movement of said actuating member and wherein a force required for said axial movement is substantially due to friction forces caused by said spring members supplying a contact force between the respective movable and fixed portions. According to a preferred embodiment, said slider has two cams thereon, said two cams being indexed in two opposite directions, said second arms of T-shaped bridges being both indexed towards the the tip of said slider to provide normally open and normally closed contacts in the switch. Alternatively, said slider has two cams thereon, said cams having high portions indexed in the same direction towards a tip of said slider and said second arms of said T-shaped bridges being both indexed towards the tip of said slider to provide all normally closed contacts in the switch. Further alternatively, said slider has two cams thereon, said cams having high portions indexed in the same direction towards a base of said slider and said second arms of said T-shaped bridges being indexed towards a tip of said slider to provide all normally open contacts in the switch. The features and advantages of present invention together with further features and advantages, will be better appreciated from the following detailed description of embodiments, provided with the enclosed drawings, wherein: figure 1 is a schematic elevation view of an auxiliary switch block, according to the present invention, applied to a contactor; figure 2 is a schematic view from the front of the apparatus, of two auxiliary switch blocks, according to present invention, applied to a contactor; figure 3 is an open front view of a first embodiment of present invention containing a group of normally open contacts and a group of normally closed contacts; figure 4 is a sectional view, taken along the line 4-4 of the embodiment in figure 3; figure 5 is an open frontal view of a second embodiment of present invention containing two normally open contact groups; figure 6 is a sectional view, taken along the line 6-6 of the embodiment in figure 5. Referring to figures 1 and 2, it is seen that a contactor 10 can have laterally applied one or two auxiliary switch blocks 12 and 14 having control or signalling duties. An example of auxiliary switch blocks provided of a normally open contact group and of a normally closed contact group is shown in figures 3 and 4. The auxiliary switch block consists of a supporting insulating housing 16, comprising a base 18, containing and supporting components, and a cover 20, which closes the housing. A slider 22 is movable along a sliding axis 24 by means of a finger 23, sliding in a slot 25. Slider 22 is provided with profiles or cams 26 and 28 engaging protrusions 30 and 32 pushed by springs 31 and 33, with T shaped movable bridges 34 and 36, provided with movable contact pairs 38, 40 and 42, 44 formed on the cross arms of the bridges and with arms 46 and 48 forming the legs of the T-shaped bridges formed to lean on protrusions 54, 56 and 58, 60 on the base 18 and cover 20, respectively, of the housing 16 to allow a rotation of the legs of the bridges 34 and 36 in order that their movable contacts 38, 40 and 42, 44 lean against or are separated from the fixed contacts 62, 64, 66 and 68 carried by fixed arms 70, 72 and 74, 76 which terminate with respective screw clamps 78, 80, 82 and 84. A second embodiment of said auxiliary switch blocks 12, provided with two normally open contact groups, is shown in figures 5 and 6. The auxiliary switch block of the second embodiment includes an insulating support housing 116, comprising a base 118 containing and supporting components, and a cover 120 which closes the housing. A slider 122 movable along a sliding axis 124 by means of a finger 123, sliding in a slot 125, is provided with profiles or cams 126, 128 engaging protrusions 130 and 132, pushed by springs 131 and 133, with T shaped movable bridges 134 and 136, provided with movable contact pairs 138, 140 and 142, 144 formed on the cross-arms of the T shaped bridges and with arms 146 and 148, forming legs of the T shaped bridges formed to lean against protrusions 154, 156 and 158, 160 formed on base 118 and cover 120, respectively, of the housing 116 to allow rotation of the legs of said bridges 134 and 136 in order that their movable contacts 138, 140 and 142, 144 lean against or separate from said fixed contacts 162, 164 and 166, 168 carried by fixed arms 170, 172 and 174, 176 terminating with respective screw clamps 178, 180 182 and 184. The operation of the first embodiment of this auxiliary switch block, depicted by figures 3 and 4 is as follows. When an auxiliary switch block 12 or 14 is assembled on the contactor 10, the finger 23 protruding from the slider 22, is engaged by a movable equipment of the contactor 10, so that, when said equipment is actuated, for example by the attraction of an electromagnet armature, the finger 23 of the slider 22 trails the same and is moved from the raised position, specifically depicted in figure 4 to a lowered position in which the finger 23 is located at the bottom of the slot 25. This movement of the slider 22 engages the profile or cam 26 against the protrusion 30 of the bridge 34, overcoming the force of the spring 31, raising the bridge 34 and moving the movable contacts 38 and 40, associated with the bridge 34, from the closed position depicted in figure 4, to the open position. At the same time, the movement of the slider 22, forces the profile 28 to disengage from the protrusion 32 of the bridge 36 which, under the push of the spring 33, forces the movable contacts 42 and 44, associated with bridge 36 to move from the open position depicted in figure 4, to the closed position. The operation of the second embodiment of this auxiliary switch block, depicted in figures 5 and 6, is as follows. When the auxiliary switch block 12 or 14 is assembled in a contactor 10, the finger 123 protruding from the slider 122 is engaged by a movable equipment of the contactor 10, so that, when said equipment is actuated, for example by the attraction of the armature of the electromagnet, the finger 123 of the slider 122 trails the same transferring it from the raised position, specifically depicted in figure 6, to a lowered position in which the finger 123 is located at the bottm of the slot 125. This movement of the slider 122 releases both the profiles or cams 126 and 128 from the respective protrusion 130 and 132 of the bridges 134 and 136 which, being pushed by the respective springs 131 and 133 move the movable contacts 138, 140 and 142, 144 associated with the bridges 134 and 136 respectively, from the open position depicted in figure 6, to the closed position.

Claims: Electric switch structure for relays and contactors, comprising a plurality of auxiliary contacts, wherein each contact is a double interruption contact which can be normally open or normally closed, an insulating housing (16, 116), a slidable actuating member wich is movable between two end positions by a movable part of a relay or contactor (10), said insulating housing (16, 116) accomodating said actuating member and said contacts, said actuating member being an insulating member actuated externally of said housing (16, 116) and including cam means (26, 28; 126, 128) thereon, spring members (31, 33; 131, 133) located in said housing (16, 116), each contact including a movable portion, and contact carrying means acted upon by said spring members and carrying said movable portions of said contacts, characterized in that said actuating member includes a slider (22, 122), said cam means (26, 28; 126, 128) are formed on an inner face of said slider (22, 122), said contact carrying means including conducting bridges (34, 36; 134, 136) connecting at least two movable contact portions (38, 40, 42, 44; 138, 140, 142, 144), said bridges (34, 36; 134, 136) being pivotably supported in said housing (16, 116), said spring members (31, 33; 131, 133) forcing just said bridges (34, 36; 134, 136) to engage through protrusions (30, 32; 130, 132) said cams (26, 28; 126, 128), each bridge (34, 36; 134, 136) being substantially T shaped and having a first cross-arm carrying said movable contact portions (38, 40, 42, 44; 138, 140, 142, 144) and a protrusion (30, 32; 130, 132) cooperating with a respective one of said cams (26, 28; 126, 128) and a second arm (46, 48; 146, 148) provided with a fulcrum abutting against opposed protrusions (54, 56, 58, 60; 154, 156, 158, 160) in said housing (16, 116), fixed arms (70, 72, 74, 76; 170, 172, 174, 176) connected to said housing (16, 116) and carrying fixed contact portions (62, 64, 66, 68; 162, 164, 166, 168), said fixed arms (70, 72, 74, 76; 170, 172, 174, 176) terminating with screw clamps (78, 80, 82, 84; 178, 180, 182, 184) for connection with external circuits, said cams means (26, 28; 126, 128), upon axial movement of said actuating member from one of said end positions to another of said end positions acting on said contact carrying means to move said movable portions relative to said fixed portions against a force of said spring members (31, 33; 131, 133), so that opening and closure of said contacts are obtained by the axial movement of said actuating member and wherein a force required for said axial movement is substantially due to friction forces caused by said spring members (31, 33; 131, 133) supplying a contact force between the respective movable and fixed portions. Electric switch structure according to claim 1, characterized in that said slider (22) has two cams (26, 28) thereon, said two cams being indexed in two opposite directions, said second arms (46, 48) of T-shaped bridges (34, 36) being both indexed towards the the tip of said slider (22) to provide normally open and normally closed contacts in the switch. Electric switch structure according to claim 1, characterized in that said slider (22, 122) has two cams (26, 28; 126, 128) thereon, said cams having high portions indexed in the same direction towards a tip of said slider (22, 122) and said second arms (46, 48; 146, 148) of said T-shaped bridges (34, 36; 134, 136) being both indexed towards the tip of said slider (22, 122) to provide all normally closed contacts in the switch. Electric switch structure according to claim 1, characterized in that said slider (122) has two cams (126, 128) thereon, said cams having high portions indexed in the same direction towards a base of said slider (122) and said second arms (146, 148) of said T-shaped bridges (134, 136) being indexed towards a tip of said slider to provide all normally open contacts in the switch.

Inventors: PARDINI FRANCO PAOLO, PARDINI, FRANCO PAOLO
Applicants: CGE SPA, CGE- COMPAGNIA GENERALE ELETTROMECCANICA S.P.A.
Application year: 1989
Main classification: H01H50
IPC codes: H01H50, H01H15, H01H11, H01H1