BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to electromagnetic contactors and, more particularly, to interlocks between such contactors for preventing one of the contactors from closing a circuit when the other contactor is closed.
2. Description of the Prior Art
The operation and control of electrical systems, including such devices as reversible motors and multispeed motors, usually includes a contactor for each motor function. A typical circuit includes, for example, a separate manual button for each contactor for the forward and reverse directions of a motor and for each speed of a multispeed motor. As a result, actuation of one forward or reverse circuit includes an associated circuit for deactivating the other of the forward and reverse circuits. Notwithstanding such precautions, it sometimes occurs due to inadvertence or other reasons that both circuits (forward and reverse control buttons), are actuated simultaneously and thereby cause incorrect phase-to-phase line connections in the contactors. For that reason, there is a need for an interlock disposed between the contactors to prevent incorrect phase-to-phase line connections.
Various interlock devices have been provided for overcoming the problem of simultaneous actuation of such contactors. However, most of such interlocks have not been completely satisfactory. For example, U.S. Pat. No. 3,342,958 provides a mechanical interlock which is pivotally movable between contact carriers of two contactors, which carriers are disposed in paths of travel which are not oppositely aligned with respect to the interlock. As a result, simultaneous movement of the contact carriers causes the interlock to twist whereby an undesirable binding action is created in the pivotal mounting of the interlock.
Associated with the foregoing has been a need for signal means for indicating to an operator at a remote station whether a contactor is actuated or not.
SUMMARY OF THE INVENTION
In accordance with this invention, it has been found that the foregoing problems may be overcome by providing an interlock comprising a pivotally mounted member between a pair of contactors, each of which contactors comprises a movable contact carrier structure, electromagnetic means for moving the movable contact carrier structure between open and closed positions with respect to stationary contact structures, the movable contact carrier structure for each contactor being movable in a path of travel parallel to that of the other movable contact carrier structure, the interlock being interposed between the contactors and being rotatable on an axis perpendicular to the plane defined by the parallel paths of travel and being movable by one of the movable contact carrier structures into the path of travel of the other of the movable contact carrier structures, whereby both contactors are prevented from being in closed positions simultaneously. The invention also includes an electrical interlock which is detachably mounted on one or both contactors and which comprises a stationary contact structure and a movable contact structure which movable contact structure is directly attached to the movable contact structure of the contactor, whereby upon movement of the movable contact carrier structure of the contactor, the electrical interlock is a normally open or normally closed device for providing pilot duty such as a pilot light or for actuating accessory equipment such as a relay or another contactor.
The advantage of the interlock system of the present invention is to prevent incorrect phase-to-phase line connections as well as to provide an improved mechanical interlock which avoids the development of binding interference in the pivotal axis of the rotatable interlock member.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of a mechanical interlock disposed between a pair of contactors;
FIG. 2 is a vertical sectional view taken along the line II--II of FIG. 1;
FIG. 3 is a vertical sectional view taken on the line III--III of FIG. 2;
FIG. 4 is a vertical sectional view taken on the line IV--IV of FIG. 3;
FIG. 5 is a vertical sectional view taken on the line V--V of FIG. 2; and
FIG. 6 is a fragmentary sectional view showing another embodiment of a mechanical interlock.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Although the contactors described and shown herein are of the two-pole type, it is understood that other types of contactors may be used in conjunction with the interlock devices of this invention.
In the drawings, an electrical control system is generally indicated at 10, and it includes a mechanical interlock generally indicated at 12 and a pair of spaced contactors 14 and 16. The interlock 12 is disposed between the contactors 14 and 16, and the interlock and contactors are mounted on a base or mounting panel 18.
Generally, the interlock 12 comprises a mounting bracket 20 and a movable member or lever 22. As shown in FIG. 1, the mounting bracket 20 is mounted on the base 18 by a pair of screws 24. The mounting bracket 20 includes an upright support member or flange 26 and a pivot pin 28 (FIG. 5) on which the movable member is rotatably mounted. The pivot pin 28 is reinforced by a support portion or web 30, which extends from the undersurface of the pin to the base of the bracket 20. Moreover, the pin 28 includes an enlarged portion 32 near the upright support 26.
The movable member 22 is preferably a solid body composed of an electrically insulating material, such as nylon, and is provided with a pin-receiving aperture 34 having a slot 36 extending from the underside thereof to the lower end 38 of the member. As shown in FIG. 2, the member 22 is rotatable about the horizontal axis of the pivot pin 28 and the sidewalls of the slot 36 limit the clockwise or counterclockwise extent of rotation when those walls contact the support web 30 below the pin 28. The movable member 22 includes an upper end 40 which is a camming surface adapted to engage a crossbar 42 or 44, respectively, of the contactors 14 and 16. Accordingly, the upper end 40 preferably includes two beveled edge surfaces 46 and 48, which extend downwardly from a ridge 50 to edge walls 52 and 54, which walls extend downwardly and include lower edge wall portions 56 and 58, which in turn terminate at lower corners formed with the lower end 38 of the member. Shoulder surfaces 60 and 62 may be provided respectively between the edge walls 52 and 56 and the edge walls 54 and 58. Although the edge walls 52 and 54 are substantially vertical, it is preferred that they be tapered downwardly and outwardly slightly to prevent binding between the walls and the corresponding crossbar particularly when the originally energized contactor mechanically moves to the open position. The surfaces, ridge 50, and walls 46-62 extend between opposite sidewalls 64 and 66.
The contactors 14 and 16 are similar in construction, although one may be a multi-pole contactor of the three or four-pole type, comprise a housing structure including a housing 68 and a base 70, as shown in FIG. 2. The contactor also comprises a stationary contact structure generally indicated at 72 (FIG. 3), a movable control device 74, and an electromagnet 76 (FIG. 2). The housing 68, being composed of a dielectric or electrically insulating material, is a substantially rectangular body which is mounted on the base 70 and includes similar vertical slots 78 on opposite sides thereof through which end portions of the crossbars extend.
As shown in FIG. 3, the stationary contact structure includes a pair of spaced contacts 80 and 82, and similar conductors 84 on which the contacts are separately mounted. The conductors 84 extend in opposite directions through the housing 68 so that external portions of the conductors are accessible for connection to a circuit for controlling, for example, a motor (not shown). For that purpose, terminal connectors are secured to the outer ends of the conductors 84 to enable connection of each pole unit to an electric circuit.
The movable control device 74 comprises a bridging contact member 88 having contacts 90 and 92, an electrically insulating contact carrier 94, and a carrier base 96 which may be formed integrally with the carrier 94. The movable control device 74 is vertically movable between upper and lower positions in order to provide open and closed circuits between the pairs of contacts 80, 90 and 82, 92. In the alternative, the device may provide for open circuits when the movable control device 74 is in the lowermost position. The movable control device 74 is retained in the upper position as shown in FIG. 2 by suitable means, such as springs, of which one spring 98 is shown.
As shown in FIG. 3, the upper end portion 100 of the contact carrier 94 extends through an opening 102 in the upper surface of the housing 68 to serve as a guide for the movable control device. In addition, the contactor 14 includes electromagnetic means for pulling or actuating the contact carrier 94 downwardly against the biasing springs 98. Although the electromagnetic means is actuated for closing the circuit through the contacts, it may be actuated for the reverse function of opening a circuit and unactuated to close the circuit. The electromagnetic means includes a stationary magnetic member 104 supported on the base 70, the electromagnetic coil 76, and an armature 106 which is secured within the carrier base 96 above the magnetic member 104. The armature 106 is an inverted E-shaped laminated member which is pulled magnetically to the stationary laminated magnetic member 104 when the coil 76 is energized. Thus, the movable control device 74 is pulled downwardly to bring the contacts into engagement.
As shown in FIG. 2, the carrier base or crossbar 42 includes opposite end portions which extend through the vertical slots 78 of the housing 68. When the contactor 16 is actuated, the crossbar 44 moves from the unactuated (broken line) position to the lower (solid line) position, whereupon it contacts the beveled edge surface 48 and causes the movable member 22 to rotate counterclockwise to the solid line position in FIG. 2. Conversely, if the contactor 14 were actuated, the crossbar 42 would be lowered against the beveled surface 48 to cause the member 22 to rotate clockwise to the broken line position as shown in FIG. 2. Thus, in either position of the movable member 22, the actuated contact 14 rotates the movable member 22 by camming action on the beveled surfaces 46 and 48 to prevent or interlock the other contactor from being actuated to the closed circuit position. If, for any reason, such an inadvertence on the part of operating personnel, the control buttons of both contactors 14 and 16 were actuated simultaneously, one of two results would occur. Either both crossbars 42 and 44 would simultaneously engage their corresponding beveled edge surfaces 46 and 48 and hold the member 22 rigidly in place against rotation in either direction, and thereby prevent both contactors from achieving closed circuit status; or, one of the crossbars 42 and 44, moving slightly faster than the other, would influence the member 22 to rotate by the camming action between the crossbar and the corresponding beveled edge surface, and thereby permit the faster moving crossbar to close the circuit through the corresponding contactor and prevent the other contactor from achieving the same result.
More particularly, the movable member 22 has a width between the edge walls 52 and 54 which is greater than the clearance between the crossbars 42 and 44. In addition, the edge walls 52 and 54 are slightly tapered downwardly and outwardly towards the shoulders 60 and 62 so that when a contactor is deenergized, there is sufficient energy in the biasing springs 98 to raise the contactor out of a tight frictional contact with the member.
Another embodiment of the invention is shown in FIG. 6 in which the member 22 differs from that shown in FIG. 2 only in that it is provided with an upright projection 108. The purpose of the projection 108 is to prevent the upper end of the member from ever becoming jammed under one of the crossbars 42 or 44, which event could occur in the embodiment of FIG. 2 where, for example, the several parts became slightly dislodged or misaligned and the ridge 50 (FIG. 2) moved under the crossbar 42. The projection 108 (FIG. 6) prevents such an occurrence.
In addition to the mechanical interlock 12 of FIGS. 1 to 6, the electrical control system 10 may be provided with an electrical interlock which may be used in conjunction with or separately from the interlock 12. As shown in FIGS. 3 and 4, an electrical interlock 110 includes a housing 112 which may be composed of two separable half-portions (FIG. 4) and is detachably mounted on the top of a contactor such as the contactor 14 by suitable means such as a hook 114 and a spring clip 116, which are suitably spaced to adapt the interlock 110 to be mounted to housing members 118 and 120. The interlock structure within the housing 112 may include any suitable switching means such as that shown in FIG. 3 which comprises a stationary contact structure 122 and a movable control device 124. The stationary contact structure 122 includes a pair of conductors 126 extending in opposite directions from stationary contacts 128 and terminal screws 103 at remote ends of the conductors for connection to lead wires for any suitable purpose.
The movable contact device 124 comprises a bridging contact member 132 having contacts 134 for engagement with corresponding contacts 128. The device 124 also includes an electrically insulating contact carrier 136, which is movable vertically within the housing 110. As shown more particularly in FIG. 4, the contact carrier 136 is provided with an opening or window 138, through which the bridging contact member 132 extends and is retained in place by a coil spring 140 in a conventional manner. The lower end of the contact carrier 136 is provided with interlocking means such as a knob 142 which is seated in a knob-receiving opening 144 in the upper end portion 100 of the contact carrier 94. Accordingly, as the contact carrier 94 moves vertically, the carrier 196 moves with it so as to disengage the contacts 128 and 134 and open a circuit to the terminal 130. It is noted, however, that although the contact carrier 136 is actuated for opening a circuit through the terminals, it may be actuated or operated for the reverse function of closing a circuit in the unactuated position corresponding to a closed circuit.
As was set forth above, the terminals 130 for the electrical interlock 100 may be used for a pilot light, which is either turned on or off to indicate opening or closing of the circuit through the contactor 114, or the wires leading from the terminals 130 may be used for actuating auxiliary equipment, such as a relay or for providing current for the contactor 16.
In conclusion, the interlock system of this invention prevents two or more contactors from being actuated in incorrect line connections simultaneously.