Motor control, in particular of the energy storage type, for low-voltage safety switches

Abstract

 A motor control, in particular of the energy storage type, for low-voltage safety switches provided with releaser devices and with an actuation handle linked to the movable contacts by means of a system of knee-joint levers, comprises a slider linearly shiftable between two extreme positions, and constrained to the handle for moving it with the getting over of the dead centre of the system of knee-joint levers from and to an extreme position, said slider being provided with a free edge suitable to act on one side of the handle during the stroke thereoffrom the extreme position of switch closed towards the position of switch open, and on it means of temporary constraint being provided, which are active when the handle and the slider are in their extreme position of switch open, as well as during the stroke of the slider from this position to its position of switch closed, at least till to the getting over of the dead centre by the system of knee-joint levers, whilst said temporary constraint means are inactive in the sense of disengaging the handle of the slider when both the handle and the slider are in their extreme position of switch closed.

Description

[0001] The present invention relates to low-voltage safety electric switches and specifically relates to a motor control, in particular of the energy storage type, for such switches.

[0002] It is well known that low-voltage safety switches com prise a mechanism suitable to be hand-actuated by means of a handle, to cause, through a system of knee-joint levers, the shifting of movable contacts from their open ing position, to their closing position, and vice-versa. The two end positions of this handle show visually the condition of "open" or of "closed" of the switch. The switches of this type are also provided with particular devices, called "releasers", capable of automatically shifting the movable contacts to their-opening position, in case of a short-circuit, or of a higher current than the rated value. These releasing devices operate in an electromagnetic and/or thermal way, and, in case of the intervention thereof, the handle of the hand control mechanism is moved to an intermediate position between its two extreme positions, thus showing visually the con dition of switch open following the intervention of the releasing devices. For the realization of a switch of such a briefly illustrated type, reference is made, to purely exemplifying purposes, to the German Patent Application publication N° 31 19 483.

[0003] To the purpose of facilitating the actuation of such a switch, and of allowing, among others, also a remote control thereof, it has already been proposed to couple to the same switch a motor control, in particular a con trol of the energy storage type, comprising a slider suitable to be linearly moved between two extreme positions and constrained to the handle of the switch, to move it getting over the dead centre of the system of knee-joint levers, to and from an extreme position. Such a control, known e.g. from U.S. Patent N° 33 28 731, is provided with energy storage means, in particular springs which are loaded by the shift of the slider towards an extreme position, as well as with locking means suitable to keep the slider in this position against the action of loaded springs, it being possible to unlock these lat ter means, e.g. electromagnetically, so as to allow the slider to freely shift the handle of the switch from said extreme position under the thrust of said springs, with consequent discharge of the energy stored therein.

[0004] This known solution of motor control for safety switch es, as well as other known solutions of the same type, foresee a constant constraint of the handle of the switch to the slider of control mechanism, generally by means of a window provided in the slider wherein the free end of the handle is engaged. As a consequence, the handle of the switch can only assume either one or the other of the two extreme positions corresponding to the positions of switch closed or open following the shift of the slider of motor control. However, as it has been hereinabove specified, such switches are also provided with releaser devices automatically intervening in case of a short-circuit or of an overcurrent, to move the movable contacts of the switch to the open position. This is also possible in the case wherein to the switch a motor control is coupled, in that the movable contacts of the switch, with the intervention of the releaser de vices, can be moved to the position of open, with the hand control handle still remaining in its position indi- eating the condition of switch closed, in which position the handle is kept by the slider of the motor control. In this case, a visual direct indication is therefore missing,by the handle of the switch, of the condition of the switch in which its contacts are open owing to an in tervention of releaser devices, such indication being often required, and being provided in the switches not coupled to a motor control through the intermediate position of the hand control handle.

[0005] Purpose. of the present invention is to obviate this drawback and to create a motor control, in particular of the energy storage type, for low-voltage safety switch es, which allows the hand control handle of the switch to assume, in addition to the two extreme positions indicating the conditions of switch closed and switch open, due to the manual drive, also the intermediate position to the purpose of directly indicating the condition of contacts open following the intervention of releaser de vices.

[0006] In order to achieve this purpose, according to the present invention the linearly movable slider of the mo tor control is suitable to act with a front edge thereof on the hand control handle of the switch in its stroke from its extreme position of switch closed to its position of switch open, while for the action on the handle during the reverse stroke, the slider is provided with temporary constraint means, such means being active when the handle and the slider are in their extreme position of switch open, as well as during the stroke of the slid er from this position towards the position of switch closed at least till to the getting over of dead centre by the system of knee-joint levers connecting the handle with the movable contacts of the switch, while said means are inactive in the sense of disengaging the handle from the slider when the handle and the slider are in their extreme position of switch closed.

[0007] In this way, the manual control handle of the switch can freely move from its extreme position of switch clos ed to an intermediate position owing to an intervention of releaser devices, in order to visually indicate this condition of the switch.

[0008] Said temporary constraint means may be advantageously constituted by two symmetrical double-arm levers hinged on the slider, and provided at the end of one of their arms with hooks suitable to seize the handle of the switch on the opposite side respectively to that on which the slider edge acts, said levers being linked to each other in correspondence of the end of the other one of -their arms, by elastic means tending to mutually space apart the hook ends of the same levers, contrasting cam-shaped fixed means suitable to keep said hook ends close to each other, and hence suitable to keep the switch handle seized when the slider is in its position of switch open, and during a first portion of its stroke from this position to its position of switch closed, and to make free the hook ends of the levers to separate un der the action of said elastic means during the further movement stroke of the slider towards its extreme position of switch closed.

[0009] When the slider moves from its position of switch open towards its position of switch closed, the hook-shaped ends of the two levers hinged onto the same slid er drag therefore the handle of the switch towards its position of switch closed. This drag action continues, thanks to the movement of the slider and to the friction between the hook ends of the levers and the end of the handle, also after that the cam fixed means allow the se paration of the hook ends of the levers and hence the release of the handle, until the system of knee-joint levers linking the handle to the movable contacts of the switch gets over its dead centre. At this time indeed, the handle of the switch trips automatically to its position indicating the condition of switch closed, and the two levers borne by the slider, not being any longer under friction engagement with the handle, move to the position, allowed by the cam-shaped fixed means, wherein their hook-shaped ends are spaced apart.

[0010] The invention shall be described hereinafter in more detail with reference to the attached drawings,schematically illustrating an embodiment thereof, and namely

Fig. 1 shows schematically the switch - energy storage assembly, partly in vertical section,

Fig. 2 is an horizontal section along the line II-II of fig. 1, and

Figs 3 - 5 show, similarly to fig. 2, other positions of the handle of the switch and of the energy storage control slider.

[0011] In figs. 1 and 2, the profile is schematically shown of a low-voltage safety switch, generally indicated with 1, of a type per se known, comprising a case 2 of isolating material, and a manual control handle 3 linked through a system of knee-joint levers (not shown) to the movable contacts of the switch. By moving this handle from an extreme position to a second extreme position and vice-versa, each time getting over the dead centre of the knee joint lever system,_' the movable contacts of the switch can be brought to their closed position and res pectively to their open position.

[0012] The switch 1 is also provided with releaser devices intervening in case of short-circuit and/or in case of overcurrents, to the purpose of opening the contacts of the switch. In case of intervention of these releaser devices, the handle 3 of the switch 1 is shifted to an intermediate position between the two extreme positions indicating the conditions of switch open and switch clos ed, the whole being as it is well known in the art, and as it is disclosed e.g. in the German Patent Application publication N° 31 19 483, a description and illustration in greater detail being therefore needless.

[0013] On the case 2 of switch 1 a supporting frame 4 is fas tened for an energy storage motor control mechanism con tained within a casing 5. Also this control mechanism is per se known in the art, and it shall be described hereinunder only briefly. It is to be noted that the su₂ porting frame 4 is provided with a large centre opening wherein the handle 3 of the switch can freely move. Also the casing 5 is open downward, i.e., on its side fac ing the case 2 of the switch when it is mounted on the frame 4, and moreover said casing 5 is provided, in an upper point relatively to the area within which the han dle 3 moves, with a window protected by a transparent cover, through which it is possible to observe the posi tion taken each time by the handle 3.

[0014] .Within suitable side guides (not shown) provided in correspondence of the lower opening of the casing 5 a slider 6 having the shape of a plate can linearly slide. By means of an edge 7 thereof (shown on the left in the drawings), perpendicular to the sliding direction, the slider 6 can act against a side of the handle 3. In cor respondence of the opposite edge 9 parallel to said edge 7, the slider 6 bears a hook-shaped projection 8, integral with it, which forms, in cooperation with the edge 9, a slot 10 open on one side, and closed on the opposite side, where the hook-shaped projection 8 is connect ed with the body of the slider 6.

[0015] In the casing 5, a disk 12 is rotatably mounted around the axis of a vertical pin 11, said disk 12 being provid ed in its lower face with a stud 13 suitable to enter, during the rotation of the disk 12 in the direction of arrow 14 (figs. 2 to 5), inside said slot 10 of the slid er 6, to cause the linear shifting, in either direction, of the same slider between an extreme position (that shown on the left-hand side in fig. 2) and the other ex treme position (that shown on the right-hand side in figs. 3 and 4).

[0016] The left-hand position (fig. 2) of the slider 6 is the one corresponding to the position of switch open, and the right-hand position (fig. 5) is that correspond ing to the position of switch closed.

[0017] The disk 12, driving by means of its stud 13 the move ments of the slider 6, is caused to rotate, by half a turn (from its position shown in fig. 3 to its position shwon in fig. 2, that is to say, from its position of switch.closed to the position of switch open) by a con trol motor 15, provided, in a way per se known, with stop contacts. During this half-turn rotation, some springs 16 are tensioned (loaded) with a consequent en ergy storage. Locking means constituted e.g. by a small lever 17 cooperating with a peripheral step 18 of the disk 12 and with a stopping pin 19 stop the disk 11 and thereby the slider 6 in their position shown in fig. 2, and under this condition keep the springs 16 under tension. By unlocking these locking means, and viz. by causing a small rotation of the stopping pin 19, the cor responding rotation is obtained of the lever 17, which liberates therefore the disk 12, and the springs 16, releasing the stored energy, cause the disk 12 to rotate by a further half a turn (always in the direction of ar row 14), said disk 12, through its stud 13,engaging the slot 10, moving the slider 6 from its position of fig. 2 to that of fi^g. 3.

[0018] During the shifting of the slider 6 from its position of fig. 3 to that of fig. 2, caused by the motor 15 (which can also be obtained, if desired, by means of an emergency handle 20 of the control mechanism), the same slid er acts through its edge 7 directly on the handle 3 of the switch 1, bringing it to its position of open.

[0019] In order to make it possible for the slider 6 to shift the handle 3 of the switch also in the opposite direction, i.e., from its position of open (fig. 2) to its position of closed (fig. 3), said slider 6 is provided according to the present invention with particular means of temporary constraint. These means shall be now disclosed in detail.

[0020] On its lower face (the one facing the switch case 2), the slider 6 supports a couple of double-arm levers 21 and 22, rotatably mounted around pivots 23 and 24 integral with the same slider. These two levers 21 and 22 are symmetrically shaped and positioned, relatively to the centre axis of the slider 6 parallel to the shifting direction thereof. The ends of the longer arms of the two levers 21 and 22 are bent to a hook-shape 25 and 26, and are suitable to seize the handle 3 of the switch from the opposite side relatively to the side on which the edge 7 of the slider is active, said arms protruding beyond this edge 7. The ends of the shorter arms of the two levers 21 and 22 are linked to each other by means of a spring 27, which tends to cause the levers 21 and .22 to rotate around the pivots 23 and 24, in the sense of parting their hook ends 25 and respectively 26 wide. To this widening apart two fixed cam-shaped guides 28 and 29 are opposing, which are provided on the supporting frame 4, against which the hook ends 25 and 26 of the levers 21 and 22 are held resting by the action of the spring 27. The cam-guides 28 and 29 are each pro vided with a first section 28a and respectively 29a (on the left in the figures) closer to the centre axis of shifting, and, parallel to it, of the slider 6, as well as with a second section 28b and respectively 29b (on the right in the figures) farther from said axis, the two sections said being connected to each other by rak ing sections 28c and respectively 29c. When the hook ends.25 and 26 of the levers 21 and 22 rest against the sections 29a and respectively 28a of the cam-guides, they can seize the handle 3 of the switch (see fig. 2), whilst when they rest against the sections 29b and res pectively 28b, the handle 3 results to be disengaged from said seizure (see figs. 3 and 4).

[0021] In the position of the slider 6 and of the handle 3 corresponding to the position of switch open (fig. 2); the hook-shaped ends 25 and 26 of the levers 21 and 22 are hence predisposed to drag, owing to the shifting of the slider 6 under the thrust of the loaded springs 16, the handle 3 towards its position of switch closed (fig. 3). When such a shifting of the slider 6 takes place af ter that the locking means have been disengaged, the hook-shaded ends 25 and 26 of the levers 21 and 22 come into contact with friction with the side of the handle 3 opposite to that on which the edge 7 of the slider is active, and this friction contact is maintained, during the shifting of the slider 6, even if in the meantime the hook ends 25 and 26 of the levers 21 and 22 would be left free to expand by the sections 29c and 29b and res pectively 28c and 28b of the fixed cam-shaped guides, until the handle 3 reaches its position wherein the sys tem of knee-joint levers gets over its dead centre: this very instant, indeed, the handle 3 trips automatically to its position of switch closed, thus rendering the hook ends 25 and 26 of the levers 21 and 22 free to expand, while the slider 6 with the thus wide apart levers is brought into its extreme position by the stud 13 of the disk 12. Fig. 3 shows this extreme position of the handle 3 and of the slider 6 with the levers 21 and 22 wide apart. In the same fig. 3, by the dotted lines also an intermediate position is shown of the handle 3 and of the levers 21 and 22, with their hook ends being still in engagement condition with the same handle, said intermediate position being roughly corresponding to that wherein the system of knee-joint levers linked to the handle is close to get over the dead centre.

[0022] As shown in particular in fig. 4, when the slider 6 with the levers -21 -and 22 wide apart is in its position corresponding to that of switch closed, the handle 3 is not constrained to the same slider, and is therefore free to move from its position indicating the condition of switch closed (indicated with dotted lines), to an intermediate position (indicated with solid lines) owing to an intervention of the releaser devices of the switch, which bring the movable contacts thereof to their position of open, when a short-circuit and/or an overcurrent take place. It clearly appears therefore, that thanks to the disengagement of the handle 3 from the slider 6, al so the condition of switch open due to the intervention of the releaser devices is directly indicated by the in termediate position of the handle 3.

[0023] Fig. 5 shows lastly an intermediate position of the slider 6 and of the handle 3 during the shifting from their position of switch closed towards the position of switch open. In this phase, it is the front edge 7 of the slider 6 of the motor control, which pushes the han dle 3 towards its position of switch open (fig. 2), while during the movement of the slider 6 the hook ends 25 and 26 of the levers 21 and 22, by sliding in contact with the fixed cam-guides 29 and 28 are gradually brought again into their not spaced apart position (against the action of the spring 27), to be finally ready again to seize the handle 3 when the same reaches its position of switch open.

[0024] As it appears from what has been disclosed, the pres ent invention allows, with the aid of extremely simple means, a motor control to be realized, in particular of the energy storage type, for a safety switch provided with releaser devices, wherein the control handle of the switch is able to visually and directly indicate not only the positions of switch closed and switch open,.but also the condition of switch open owing to an intervention of the releaser devices.

Claims

1. Motor control, in particular of the energy storage type, for low voltage safety switches provided with releaser devices and with an actuation handle linked to the movable contacts by means of a system of knee-joint levers, said control comprising a slider linearly shiftable between two extreme positions, and constrained to the handle for moving it with the getting over of the dead centre of the system of knee-joint levers from and to an extreme position, characterized in that the slider is provided with a free edge suitable to act on one side on the handle during the stroke thereof from the extreme position of switch closed towards the position of switch open, and that on the slider means of tempo- .rary constraint are provided, which are active when the handle and the slider are in their extreme position of switch open, as well as during the stroke of the slider from this position to its position of switch closed, at least till to the getting over of the dead centre by the system of knee-joint levers, whilst said temporary con straint means are inactive in the sense of disengaging the handle of the slider when handle and slider are in their extreme position of switch closed.

2. Motor control as claimed in claim 1, characterized in that the temporary constraint means are constituted by a couple of symmetrical double-arm levers pivoted on the slider, and provided at the end of one of their arms with hooks suitable to seize the handle on its opposite side relatively to the side on which the edge of the slider is active, said levers being linked to each other in correspondence of the end of the other arm thereof, by elastic means tending to space apart from each other the hook ends of the same levers, in opposition to fix ed cam means suitable to keep said hook ends close to each other, and hence to keep the handle seized when the slider is in its position of switch open, and during a first position of its shifting from this position towards the position of switch closed; and suitable to allow the hook ends of the levers to freely expand under the action of said elastic means during the further portion of slider movement towards its extreme position of switch closed.

3. Motor control as claimed in claim 2, characterized in that said fixed cam means are constituted by guides with which the hook ends of the levers are kept in contact by said elastic means, said guides extending sideways in the zone of slider shifting between the two extreme positions thereof, and each having a first section parallel to the direction of shifting closer to the cen tre line of the slider starting from its position of switch open, a second section parallel to the direction of shifting farther from the centre line of the slider towards its position of switch closed, and a raking see tion connecting said first and second sections.

4. Motor control as claimed in claim 3, characterized in that said first section of side guides ends in a position which the handle dragged by the hook-shaped ends of the levers supported by the slider reaches dur ing the shifting from the position of switch open towards the position of switch closed before the getting over of the dead centre by the system of knee-joint lev ers linked to the same handle.

Drawing