GB2179497A - Reversing contact for an electric motor - Google Patents

Abstract

A reversing contactor includes, for a three phase meter, six (input) contacts (6a2,...6c2; 7a2,...7c2) distributed in two planes. Each such contact is disposed opposite an (output) contact (6a1,...6c1; 7a1,...7c1) and can be selectively connected thereto by an individual contact bridge movable between the said planes by an electromagnet. Bars (14) interconnect the coaxial (input) contacts (6a2, 7a2; 6b2, 7b2; 6c2, 7c2). As S-shaped rod (19) and a G-shaped rod (21) so interconnect four of the (output) contacts (6a1, 6b1, 7a1, 7b 1) as to produce an electrical crossover. A U-shaped bar (29) interconnects the other two (output) contacts (6c1, 7c1). The contact supports and bars are located by grooved and apertured casing parts. Of use to obviate external wiring and to reduce bulk. <IMAGE>

Description

SPECIFICATION Reversing contact for an electric motor This invention relates to a reversing contactor, of use more particularly for controlling a reversible electric motor.

In a conventional form of control for a reversible d.c. or three-phase a.c. electric motor, two contactors can be used, the contactor input terminals being interconnected in pairs by direct connections while the output terminals are interconnected by connections which change over two of the conductors relatively to the input order. Also, to obviate short-circuiting mechanical and/or electrical interlocking is provided to prevent simultaneous closure of both contactors.

In DE C2 3 211 685 a single casing receives the two actuating electromagnets with their interlocking and each input connection is in the form of a U-shaped member which carries the fixed contacts and which comprises only one input terminal. The user therefore does not have to make the input connections but still has to make the output connections.

In patent DE Al 3 230 562, a single threeposition electromagnet is used, thus saving space. With the electromagnet in its central position, no contact is in the closed state. As in the construction just described, each input connection takes the form of a U-shaped member carrying only a single input terminal.

Also, since the contact bridges are arranged to move along the same axis, two of the three output connections can be made but an external connection still has to be made. This construction takes more space than a contactor which would have only three input terminals and three output terminals. However, as patent DE Al 3 146 780 makes apparent, arranging the contact bridges on a single line causes difficulties in insulation.

It is therefore the object of the invention to provide a compact reversing contactor in which the contacts are insulated satisfactorily and of a kind such that the user does not have to make external connections making the corresponding terminals time-consuming, expensive and bulky, with the risks of misconnection or, if two conductors of different cross-sections are placed in a single screw type terminal, of unsatisfactory connection.

The invention therefore relates to a reversing contactor, of use more particularly for controlling a more particularly d.c. or three-phase a.c. reversible motor, the contactor comprising an electromagnet, fixed contacts distributed substantially in two planes, the fixed contacts of each plane being disposed opposite one another in pairs, bridges being moved by the electromagnet along parallel axes between two end positions in each of which the bridges electrically interconnect the two fixed contacts of each pair in one of the planes, while on a first side of the pairs U-shaped bars disposed one beside another interconnect in pairs the fixed contacts of one plane with the fixed contacts of the other plane.

In the contactor according to the invention, four fixed contacts interconnected by two adjacent U-shaped bars form part of four pairs whose other four contacts are so interconnected in pairs between the planes, by an Sshaped bar and a G-shaped bar extending around one of the ends of the S-shaped bar, as to be crossed over electrically relatively to the U-shaped members.

Consequently, all the electrical connections are made in the contactor itself. All that the user has to do is to connect, for example, the U-shaped bars to two terminals of a power supply and the S-shaped and G-shaped bars to two terminals of the apparatus to be supplied, only a single conductor being connected per terminal.

The converse is also possible-i.e., the Sshaped and G-shaped bars can be connected to the supply and the U-shaped bars to the apparatus.

Depending upon the direction of energization of the electromagnet, each of the two terminals of the apparatus to be supplied is selectively connected to one or other of the two terminals of the supply. If the apparatus is a d.c. device, two U-shaped bars, one S-shaped bar and one G-shaped bar are sufficient. If the apparatus is a three-phase device, the contactor comprises an extra pair of contacts in each plane and two additional U-shaped bars each providing a between-planes connection of a contact of each of the two additional pairs with the contact of the other pair on the same side.

Other features and advantages of the invention will become apparent from the following description. In the accompanying exemplary and non-limitative drawings: Figure 1 shows the contactor according to the invention in section on the line I-I of Fig.

2 with the electromagnet broken away; Figure 2 is a partial view in section on the line ll-ll of Fig. 1; Figure 3 is a perspective view of the contacts and bars; Figure 4 is an exploded perspective view with the casing and hood broken away, and Figures 5 and 6 are perspective views of the contacts and output bars of two other embodiments of the contactor.

In the example shown in Figs. 1-4, a threephase reversing contactor comprises an insulating plastics casing 1 comprising a central chamber 2 defined by two opposite longitudinal walls 2a and two opposite end walls 2b, in which chamber three rupturing chambers 3 separated from one another by unitary partitions 4 are arranged parallel to the walls 2a.

The contactor also comprises twelve fixed contacts 6, 7. The contacts 6 are disposed in a common top plane P1 visible in Figs. 1 and 2 and are also arranged in three pairs 6a1, 6a2; 6b1, 6b2; 6c1, 6c2, as can be seen in Fig. 3. The two contacts of each pair are apparent one opposite the other in one of the chambers 3 on the opposite walls 2a. The fixed contacts 7 are arranged similarly to the contacts 6 but in a bottom common plane P2 visible in Figs. 1 and 2.

The contactor further comprises a three-position electromagnet 8-i.e., an electromagnet whose armature is movable between two end positions and can also take up a position therebetween. The electromagnet 8 is received in a bottom recess in the casing 1, the recess being disposed on that side of the plane P2 which is remote from the plane P1.

The electromagnet armature is secured to a contact carrier 9 which is made of an insulating plastics and which can be seen in Fig. 1 in the position corresponding to the intermediate position of the armature. The contact carrier 9 moves together with the armature in a direction perpendicular to the planes P1, P2.

The contact carrier 9 carries in each chamber 3 two contact bridges 11, 12. The bridge 11 electrically interconnects the two contacts 6 of the chamber 3 when the armature is in itstop end position, the bridge 11 being separated from such contact when the armature is in its other positions. The bridge 12 electrically interconnects the two contacts 7 of the chamber 3 when the armature is in its bottom end position, the bridge 12 being separated from such contact when the armature is in its other positions.

The two bridges 11, 12 are electrically separated and are disposed between the planes P1 and P2, the bridge 11 being nearer the plane 1 than is the bridge 12.

The three pairs of bridges, as 11, 12, are therefore movable along parallel axes of displacement.

Hereinafter consideration will be given to the central plane PP between the two contacts of each pair and the left-hand side of the contactor as seen in Fig. 1 will be arbitrarily referred to as the input side, the other side of the contactor being arbitrarily referred to as the output side. An input contact and an output contact are therefore defined for each pair of contacts.

The input contacts in each chamber 3 have a common axis parallel to the direction of movement of the bridges, and so have the output contacts.

The two input contacts 6, 7 of each chamber 3 are carried by two end limbs 15 of an electrically conductive U-shaped bar 14. The limbs 15 extend into the chamber 3 by way of two apertures 16 in the wall 2a of the input side.

Between the limbs 15 the three bars 14 are received one beside another outside the chambers 3 in recesses 17 between wings or outer walls 18 of the casing 1, as can be seen in Fig. 4.

According to the invention, on the output side the contact 6b1 is connected by an electrically conductive S-shaped bar 19 to the contact 7a1 associated with an adjacent chamber 3. The bar 19 therefore electrically interconnects the output contacts of two pairs 6b1, 6b2 and 7a1, 7a2 whose input contacts 6b2 and 7a2 are connected to two adjacent U-shaped bars 14.

Also, an electrically conductive G-shaped bar 21 connects the contact 6a1 to the contact 7b1. The bar 21 has a region 23 adjacent one of two wings 22 disposed in extension of the walls 2b of the chamber 2.

The region 23, which is perpendicular to the planes P1 and P2, extends beyond the plane P2 relatively to the plane P1, whereafter the bar 21 is bent twice at right-angles in the same direction at places 24, 25 to return to the plane P1 by extending around that end of the S-shaped bar 19 which is connected to the contact 7a1, whereafter the G-shaped bar 21 has a right-angled bend 30 in the opposite direction to return to the orientation of the plane P2 near the contact 7b1. At the other end of the region 23 the bar 21 has a rightangled bend 26 for connection to the contact 6a1.

Consequently, the G-shaped rod 21 electrically interconnects the output contacts 6a1, 7b1 of two other pairs whose input contacts 6a2, 7b2 are the other two contacts connected to the two adjacent U-shaped bars 14.

In other words, the S-shaped rods 19 and Gshaped rods 21 provide between the output contacts 6a1, 7a1, 6b1, 7b1 of four contact pair connections which are electrically crossed over relatively to the connections made between such pairs by the U-shaped bars 14 on the input side. Nevertheless, and as Fig. 2 clearly shows, the rods 19, 21 are aligned with one another in a plane parallel to the plane PP-i.e., they do not physically cross one another.

The S-shaped rods 19 and G-shaped rods 21 have at each of their ends limbs 27 which extend towards the plane PP and which are engaged in apertures 16 in the adjacent wall 2a to carry the contacts 6, 7 inside the chambers 3.

A U-shaped bar 29 identical to the bars 14 interconnects the contacts 6c1, 7c1.

The bars 19, 21, 29 are received in respective recesses 31 which are left between the wings 22 and which are separated by external partitions 32, 33 extending from the adjacent wall 2a of the casing 1. The wing 32 separating the S-shaped bars and the G-shaped bars extends along the S-shaped bar 19, extends beyond the plane P2 around that end of the bar 19 which is adjacent the plane 2, then extends between the planes P1 and P2 to return to the wing 33 so as to separate that end of the bar 19 which is adjacent the plane P1 and that end of the bar 21 which is adjacent the plane 22.

At its end adjacent the plane P1 each bar 14, 19, 21, 29 is formed with a tapped aperture 34 serving for external electrical connections by means of connecting terminals in the form of screws 39 engaged in the apertures 34.

An insulating plastics hood 36 serves as a releasable cover for the casing 1 so as substantially to close all the recesses 17, 31.

However, the hood 36 is formed above each recess 17, 31 with an aperture 37 prolonged by a well 38 which extends into the recess and through which a screwdriver can extend to operate the screws 39. Also, the hood 36 is formed in the plane P1 with an aperture 41 opposite each recess 17, 31 for outgoing connecting wires.

In the embodiment shown in Figs. 1-4 the bars 14, 19, 21, 29 are devised by bending sheet brass cuts around a single axis perpendicular to the plane PP. The limbs 15, 27 are unitary. The bar 19 and its two limbs 27 are therefore produced with just two bends in opposite directions and the bar 21 and its two limbs 27 are produced with only four bends.

The bars are embedded in the recesses 17, 31-i.e., the bars are located by friction in the apertures 16 and in the recesses 17, 31.

Also, the free edges of the bars in prolongation of the limbs 15 or 27 engaged in the apertures 16 are engaged in grooves 42 in the wings 18, 22, 32, 33. However, the edges corresponding to bends cannot be provided with such guidance.

This disadvantage is obviated in the example of Fig. 5 wherein all the bends except for the bends 24, 26 are made parallel to the planes PP, P1 and P2.

The U-shaped bars are prepared from a straight strip bent twice in the same direction from one end.

The S-shaped bar is prepared from an Sshaped strip whose two initially straight ends are bent at right-angles on the same sidei.e., towards the plane PP.

The G-shaped bar is prepared from a Ushaped strip whose central part 23 is as previously formed with bends 24, 26 to give a U with arms of unequal length, the shorter arm being disposed between the planes P1 and P2 and the longer arm being disposed beyond the plane P2. The two ends of the strip are each bent twice in the same direction to form the limbs in the planes P1 and P2 respectively.

Consequently each limb 15, 27 is guided on both sides in grooves such as grooves 42 shown in Fig. 4.

In the embodiment shown in Fig. 6 the Gshaped bar is devised near the plane P1 as in Figs. 1 to 4 and near the plane P2 as in Fig.

5; consequently, it needs only four bends -i.e., two bends 24, 26 perpendicular to the plane PP near the plane P1 and beyond the plane P2, and two bends parallel to the planes PP and P2 near the plane P2. However, one of the edges of the limb 27 adjacent the plane P1 is not guided since it is in the form of a bend.

The S-shaped bar is prepared from a Ushaped strip whose central zone is bent to an S shape and the two ends are each bent twice at right-angles towards the outside of the S and towards the plane PP to form the limbs 27 in the planes P1, P2 respectively.

The U-shaped bars are devised as in the embodiment of Fig. 5.

The contactor is used and operates as follows: The three input terminals, in the form of the apertures 34 and associated screws 39 on the input side, are adapted to be connected to the three terminals of a three-phase supply and the three output terminals in the form of the apertures 34 and associated screws on the output side are adapted to be connected to the three terminals of a reversible threephase motor. The motor runs in a direction which depends upon the direction of energization of the electromagnet. When the armature is in its top end position, the terminals adajcent the contacts 6a1, 6b1, 6c1 are directly connected by the bridges 11 to the terminals adajcent the contacts 7a1, 7b1, 7c1.

When the armature is in its bottom end position, the terminals adjacent the contacts 6a1, 6b1, 6c1 are connected to the terminals adjacent the contacts 7b1, 7a1, 7c1 respectively, by way of the bars 21, 19, 29, the bridges 11 and the bars 14. When the armature is in an intermediate position, all the contacts on the input side are isolated from the contacts on the output side and so the motor is not energized.

In all the embodiments shown the casing can be devised from just two members joined in the plane PP (see Fig. 4) and each such member can be moulded without a core and without multidirectional mould release. The assembly does not have to have added to it additional members to insulate a crossing of the bars. Also, the chambers 3 and the contacts in them are effectively separated electrically from one another and from the bars and the latter are effectively separated from one another, unlike the arrangement described in DE-A-3 230 562. Also, and referring again to the latter document, the invention obviates waste of space by unused connection zones.

The connecting terminals are very readily accessible since they are coplanar, being disposed in the plane P1 near the contactor surface opposite the electromagnet.

The invention is not of course limited to the examples described and shown and many variants are possible without departure from the scope of the invention.

For instance, the limbs can be fitted to the bars.

To devise a d.c. reversing contactor, all that is necessary is to omit the contacts 6c1, 6c2, 7c1, 7c2 and the associated U-shaped bars 14, 29.

Claims (7)

1. A reversing contactor, of use more particularly for controlling a more particularly d.c.

or three-phase a.c. reversible motor, the contactor comprising an electromagnet (8), fixed contacts (6, 7) distributed substantially in two planes (P1, P2), the fixed contacts of each plane being disposed opposite one another in pairs (6a1, 6a2; 6b1, 6b2;...), bridges (11, 12) being moved by the electromagnet (8) along parallel axes between two end positions in each of which the bridges (11, 12) electrically interconnect the two fixed contacts of each pair in one of the planes, while on a first side of the pairs U-shaped bars (14) disposed one beside another interconnect in pairs the fixed contacts (6a2, 6b2, 6c2) of one plane wiht the fixed contacts (7a2, 7b2, 7c2) of the other plane, characterised in that four contacts of the first side (6a2, 6b2, 7a2, 7b2) interconnected by two adjacent U-shaped bars (14) form part of four pairs whose other four contacts (6a1, 6b1; 7a1, 7b1) are so interconnected in pairs between the planes, by an S-shaped bar (19) and a G-shaped bar (21) extending around one of the ends of the Sshaped bar (19), as to be crossed over elec tricaily relatively to the U-shaped members (14).

2. A contactor according to claim 1, the fixed contacts (6, 7) and the bridges (11, 12) being disposed in an insulated casing (1) having internal partitions (4) which define rupturing chambers (3) and having outer partitions (18, 32, 33), a removable hood (36) covering the casing (1) and connecting terminals (34, 39), characterised in that the bars (14, 19, 21, 29) are embedded in the correspondingly shaped outer partitions (18, 32, 33) and are covered by the hood (36).

3. A contactor according to claim 2, characterised in that each bar (14, 19, 21, 29) is prolonged at each end by a limb (15, 27) which extends through an aperture (16) in the casing (1) into a rupturing chamber (3) and which carries a fixed contact (6, 7).

4. A contactor according to any of claims 1-3, characterised in that the bars (14, 19, 21, 29) are contrived by cutting and bending an electrically conductive sheet metal such as brass.

5. A contactor according to claim 4, characterised in that the U-shaped bars (14) and the S-shaped bars (19) each have only two bends with parallel axes and the G-shaped bar (21) has only four bends (24, 25, 26, 30) with parallel axes.

6. A contactor according to claim 5, characterised in that each bar (14, 29, 21, 29) is formed with a tapped aperture (34) for receiving a screw (39) of a screw type connecting terminal.

7. A reversing contactor, of use more particularly for controlling a more particularly DC or 3 phase AC reversable motor substantially as herein described with reference to the accompanying drawings.