GB1559249A - Switching systems - Google Patents

Description

(54) IIMPROVEMENTS RELATING TO SWITCHING SYSTEMS (71) We, GEAR. EICKHOFF MASCHINEN FABRIK U. EISENGIESSEREI mbH, of Bochum, Germany, a German Corporate body, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to switching systems. It is particularly, but not exclusively, concerned with switching systems for motors for coal minding machines such as drum cutting machines. It is a development of the system described in our Patent No. 1432715.

According to claim 1 of that patent there is provided a switching system comprising a first relay for operating switch means for connecting a motor to a power source, a cutout (as defined herein), a cut-in (as defined herein) and a switch in series with said first relay, a second relay for operating said switch, a circuit for bridging said cut-in and said second relay and arranged so that ,when said cut-in is "on" and the second relay has been energised, the latter is mechanically held in its energised position, in which said switch is open.

A cut-in and cut-out as referred to above and in this Specification have the following characteristics. They have three switching positions, namely a neutral or "ofF' position in which they are both open, a working position in which the cut-in is open and the cut-out is closed, and an "on" position in which they are both closed.

- The mechanical interlock of Patent No.

1432715 ensures that the switch in series with the relay that operates the motor switch ineans is held open when the cut-in attains the "on'6 position. It is removed only in the other two positions. Thus if the cut-in should be lammed "on", the section of the circuit in parallel with the bridged circuit is interrupted, and the first relay cannot be reenergised via that section until the jam is cleared and the starting pro cedure can be fully repeated.

The aim of the present invention is to achieve the same result, but to avoid using a purely mechanical interlock.

According to the present invention there is provided a switching system according to claim 1 of Patent No. 1432715, wherein the bridging circuit includes a second switch operable by the first relay to open and close with the switch means, and wherein the second relay is a remanent relay with first and second separately energisable windings, which perform the function of the locking device, respectively operating to open and maintain open the first switch and to close and maintain closed the first switch, the first winding being in a line connected in circuit when the cut-in is "on" and including a third switch operable by the first relay to open and close with the second switch and said switch means, thereby to cause said remanent relay to open the first switch once the switch means are closed and the bridging circuit is made, and the second winding being in a line connected in circuit when the cut-out is "off" and including a fourth switch coupled to said first switch to close when the first switch is open and vice versa, thereby to cause said remanent relay to close said first switch when the cutout is "off".

The remanent relay, an electrical part of the apparatus, now assumes the task hitherto associated with a mechanical part of the apparatus, namely the locking device.

Elimination of the mechanical interlock reduces the structural complication of the system and also its susceptibility to breakdown.

For a better understanding of the invention one embodiment will now be described, by way of example, with reference to the accompanying drawing in which the single figure is a circuit diagram of a switching system with relay control.

A drive motor 1 of a drum cutting machine (not shown) is energised from the mains, designated RST, to which it can be connected vi7 a ganlJed switch array 2 onerable by a relay 3. This relay is in a line 6 connecting, with intermediate switches des cribed below, two control leads 4, 5. The relay 3 also governs normally open switches 7 and 8 which are coupled to the switch array 2. In addition to the relay 3, there are in series in the line 6 a normally closed switch 9, a cut-in 10, a cut-out 11, mechanically coupled to cut-in 10 and an emergency push-button OFF switch 12. There may be more than one such emergency switch, in series. The cut-in 10 and the normally closed switch 9 are bridged by a line 13 containing the switch 7.The cutin 10 and the cut-out 11, which are ganged together, have three switch positions, namely "off" or neutral position 0, locking position I, which is the position for normal operation, and closed or "on" position II, for start-up, in which the line 6 is completed between control leads 4, 5. In neutral position 0, the line 6 is interrupted by both the cut-in 10 and by cut-out 11. Not being energised, the relay 3 has then released the switch array 2 to isolate the drive motor 1 from the mains RST, and has also opened switches 7 and 8. In working position 1, the cut-in 10 breaks the line 6, but the cut-out -11 remains dosed.

A remanent relay 14 actuates the normally closed switch 9. One winding of this relay is located in a line 15, including the switch 8, which bridges the relay 3 and the switch 9. When energised, this winding of the- remanent relay 14 opens the switch 9, and subsequent de-energisation leaves that switch open. The other winding of the remanent relay 14, which when energised restores the switch 9 to its dosed starting position, lies in a line 16 between the control lead 4 and the neutral pole of the cut-out 11. Thus, the line 16 which also includes a normally open switch 17 coupled to the normally closed switch 9, bridges the cut-in 10, the switch 9 and the relay 3 in the line 6.

The circuit operates as follows. Before start-up, the switches are in the positions shown. The cut-out and cut-in are then moved through position I (which will have no effect) to position II, thereby energising relay 3 and closing switches 2, 7 and 8.

Switch 8 being closed energises the winding of remanent relay 14 that opens switch 9 and closes switch 17. But as switch 7 is closed, relay 3 remains latched on. The cutout and cut-in are then moved back to working position I, breaking the circuit through line 15, but as mentioned above switch 9 stays open. For switching off from normal working, the cut-out and cut-in are returned to neutralposition 0, de:energising relay 3 and thereby opening switches 2, 7 and 8, but energizing through line 16 and closed switch 17 the winding of remanent relav 14 thst closes switch 9 and opens switch 17. The circuit is thus restored to the condition shown.

With such a switching device it is always possible, by means of the emergency OFF switch 12, to immobilise the drive motor 1, even if the cut-in 10 should become jammed in its closed position II. In this case, the emergency OH switch 12 briefly interrupts the two lines 16 and 13 by which the relay 3 can be energised and renders the relay 3 dead. The switch array 2 thereupon opens to isolate the drive motor 1 from the mains RST. At the same time the switches 7 and 8 opens to interrupt lines 13 and 15.The switch 9 remains in its position in which it is interrupting the line 6. Thus when the emergency OFF switch 12 returns to its closed position it can no longer establish any con neotion between the two control leads 4 and 5, there is no possibility of renewed starting of the drive motor 1. The same applies if there is a brief power failure.

WHAT WE CLAIM IS : - 1. A switching system according to claim I of Patent No. 1432715, wherein the bridging circuit includes a second switch operable by the first relay to open and close with the switch means, and wherein the second relay is a remanent relay with first and second separately energisable windings, which perform the function of the locking device, respectively operating to open and maintain open the first switch and to close and maintain closed the first switch, the first winding being in a line connected in circuit when the cut-in is "on" and including a third switch operable by the first relay to open and close with the second switch and said switch means, thereby to cause said remanent relay to open the first switch once the switch means are closed and the bridging circuit is made, and the second winding being in a line connected in circuit when the cut-out is "off" and including a fourth switch coupled to said first switch to close when the first switch is open and vice versa, thereby to cause said remanent relay to close said first switch when the cut-out is "off".

2. A system as claimed in claim 1, wherein at least one - unbridged emergency cut-out switch is connected in series- with said first relay.

3. A system as claimed in claim 1 or 2, wherein said cut-in and cut-out are mechanically coupled.

4. A switching system substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. cribed below, two control leads 4, 5. The relay 3 also governs normally open switches 7 and 8 which are coupled to the switch array 2. In addition to the relay 3, there are in series in the line 6 a normally closed switch 9, a cut-in 10, a cut-out 11, mechanically coupled to cut-in 10 and an emergency push-button OFF switch 12. There may be more than one such emergency switch, in series. The cut-in 10 and the normally closed switch 9 are bridged by a line 13 containing the switch 7. The cutin 10 and the cut-out 11, which are ganged together, have three switch positions, namely "off" or neutral position 0, locking position I, which is the position for normal operation, and closed or "on" position II, for start-up, in which the line 6 is completed between control leads 4, 5.In neutral position 0, the line 6 is interrupted by both the cut-in 10 and by cut-out 11. Not being energised, the relay 3 has then released the switch array 2 to isolate the drive motor 1 from the mains RST, and has also opened switches 7 and 8. In working position 1, the cut-in 10 breaks the line 6, but the cut-out -11 remains dosed. A remanent relay 14 actuates the normally closed switch 9. One winding of this relay is located in a line 15, including the switch 8, which bridges the relay 3 and the switch 9. When energised, this winding of the- remanent relay 14 opens the switch 9, and subsequent de-energisation leaves that switch open. The other winding of the remanent relay 14, which when energised restores the switch 9 to its dosed starting position, lies in a line 16 between the control lead 4 and the neutral pole of the cut-out 11. Thus, the line 16 which also includes a normally open switch 17 coupled to the normally closed switch 9, bridges the cut-in 10, the switch 9 and the relay 3 in the line 6. The circuit operates as follows. Before start-up, the switches are in the positions shown. The cut-out and cut-in are then moved through position I (which will have no effect) to position II, thereby energising relay 3 and closing switches 2, 7 and 8. Switch 8 being closed energises the winding of remanent relay 14 that opens switch 9 and closes switch 17. But as switch 7 is closed, relay 3 remains latched on. The cutout and cut-in are then moved back to working position I, breaking the circuit through line 15, but as mentioned above switch 9 stays open. For switching off from normal working, the cut-out and cut-in are returned to neutralposition 0, de:energising relay 3 and thereby opening switches 2, 7 and 8, but energizing through line 16 and closed switch 17 the winding of remanent relav 14 thst closes switch 9 and opens switch 17. The circuit is thus restored to the condition shown. With such a switching device it is always possible, by means of the emergency OFF switch 12, to immobilise the drive motor 1, even if the cut-in 10 should become jammed in its closed position II. In this case, the emergency OH switch 12 briefly interrupts the two lines 16 and 13 by which the relay 3 can be energised and renders the relay 3 dead. The switch array 2 thereupon opens to isolate the drive motor 1 from the mains RST. At the same time the switches 7 and 8 opens to interrupt lines 13 and 15.The switch 9 remains in its position in which it is interrupting the line 6. Thus when the emergency OFF switch 12 returns to its closed position it can no longer establish any con neotion between the two control leads 4 and 5, there is no possibility of renewed starting of the drive motor 1. The same applies if there is a brief power failure. WHAT WE CLAIM IS : -

1. A switching system according to claim I of Patent No. 1432715, wherein the bridging circuit includes a second switch operable by the first relay to open and close with the switch means, and wherein the second relay is a remanent relay with first and second separately energisable windings, which perform the function of the locking device, respectively operating to open and maintain open the first switch and to close and maintain closed the first switch, the first winding being in a line connected in circuit when the cut-in is "on" and including a third switch operable by the first relay to open and close with the second switch and said switch means, thereby to cause said remanent relay to open the first switch once the switch means are closed and the bridging circuit is made, and the second winding being in a line connected in circuit when the cut-out is "off" and including a fourth switch coupled to said first switch to close when the first switch is open and vice versa, thereby to cause said remanent relay to close said first switch when the cut-out is "off".

2. A system as claimed in claim 1, wherein at least one - unbridged emergency cut-out switch is connected in series- with said first relay.

3. A system as claimed in claim 1 or 2, wherein said cut-in and cut-out are mechanically coupled.

4. A switching system substantially as hereinbefore described with reference to the accompanying drawing.