GB1590833A - Drive rod mechanisms for circuit-breakers - Google Patents

Description

(54) DRIVE ROD MECHANISMS FOR CIRCUIT-BREAKERS 871) We, NORTHERN ENGINEERING INDUSTRIES LIMITED, a British Company registèrèd under the Laws of England, of Nei House, Regent Centre, Newcastle Upon-Tyne, NE3 3SB, 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 a drive rod mechanism for a high voltage circuitbreaker. It is particularly, although not exclusively, applicable to puffer type SF6 insulated circuit-breakers.

In our co-pending British Patent Application 44231174 (Serial No. 1 525 460) there is described and illustrated a three-phase high-voltage SF6 circuit-breaker which comprises three vertically mounted interrupter units fixed on individual insulator pedestals on a metal frame and coupled to a common operating mechanism via a common operating rod and individual actuating rods respectively connected to the interrupters.

In the event Of requiring to use more than one interrupter per phase, it is therefore necessary to use a more complex drive rod mechanism, and it is one of the particular objects Of this invention to provide such a mechanism, which is so arranged as to reduce almost entirely any unbalanced bending moments or torsional couples, such as would necessitate excessive strengthening 6f the support iiisulators and associated structures, and would add substantially to the cost and complexity of the overall circuit-breaker.

In accordance with the present invention a drive rod mechanism for operating at least two interrupter units of a highvoltage circuit-breaker, the units being mounted on à common hollow insulator support, comprises a drive member moveable lonigtudinally and connected to a drive mechanism, respective drive rods for the units and respective substantially identical bell-crank levers the intermediate pivot points of which are pivot in spaced positions on a common rigid structure, each bell-crank having one arm pivotally attached to the drive member in a configuration forming therewith a parallel-motion linkage, the other arms of the bell-crank levers being pivotally attached to the respective drive rods, the arrangement being such that when the drive member is moved longitudinally in either direction the bellcrank levers are turned and produce substantially equal longitudinal movements of the drive rods each in a line different from the line of movement of the drive member and the geometrical arrangement being such that substantially no unbalanced bending moments or torsional couples are imposed on the hollow insulator support.

Thus, the longitudinal axes of the drive rods and of the drive member are pteter- ably in a common plane, the drive rods moving in opposite directions to one another but substantially at right angles to the drive member.

The invention further comprises a highvoltage circuit-breaker having two interrupter units mounted on a common hollow insulator support and having a drive rod mechanism as above referred to, each interrupter unit being actuated by a- respective one of the two drive rods.

The two interrupter units may for example be arranged in opposftely-orientated axial alignment, i.e. a T-shaped configuration. In one such arrangement the two interrupter units are mounted end-to-end with their axes horizontal by means of a central fitting to which their adjacent ends are secured, - the central fitting being mounted on the upper end of the insulator support, and the driving member of the drive rod mechanism is coupled to a longitudinally-movable operating rod which extends substantially-vertically within the insulator support and has the operating mechanism coupled to its lower end.

The invention is preferably applied to an SF6 puffer circuit-breaker - comprising a series-connected pair of interrupters mounted one on each side of the vertical insulator support in a 'T' shaped configuration.

The invention may be carried into practice in various ways, but one specific embodiment thereof will now be described by way of example only and with reference to the accompanying drawings, in which: - Figure 1 is a sectional elevation of one phase of a high-voltage circuit-breaker; Figure 1A is a detail view on a larger scale of the upper part of the circuitbreaker showing the bell-crank linkage; Figure 2 is a fragmentary detail of the operating linkage as seen in the direction of arrow "A" in Figure 1; Figure 3 is a fragmentary detail showing in perspective the top bell-crank lever of the operating linkage in Figure 1; and Figure 4 is a load/link vector diagram for the drive-rod and bell-crank levers shown in Figure 1.

In Figure 1 there is shown a ' T ' shaped circuit-breaker configuration in which there are two interrupters 10 comprising moving contact assemblies 11 and fixed contacts 20. The interrupters are shown in the open-circuit position and each interrupter is housed within a gas-filled horizontallydisposed shedded insulator housing 30 which is fixed as by bolting by gas-tight flange rings 33 to flanges 31 of a metal chamber 32 (See Fig. 1A), which is supported by two vertical shedded insulators 35, 36 which are joined centrally by a pair of gas-tight flange rings 33A. The top insulator 35 is joined to chamber 32 by a gas-tight flange ring 33B (See Fig. 1A) and the bottom insulator is mounted on the supporting frame-work 37 by means of a further gas-tight flange ring 33C (Fig. 1).

The interrupters 10 are essentially similar to those described in our co-pending British Patent Application No. 44231/74 (Serial No. 1 525 460) and each comprises a moving contact assembly 11 supported on an electrically conducting supporting assembly 12 which forms an electrical path through chamber 32 to the adjacent interrupter. The moving contact assembly comprises a puffer cylinder 13 made of a conducting material such as copper or copper alloy inelectrical connection with support assembly 12 via transfer contacts 14 and contact ring 15. At the other end of the puffer cylinder 13 there is provided an insulating nozzle 16 within which is housed a contact assembly 17 and auxiliary nozzle contact 18. Further details of the assemblies 11 are as described in our above mentioned Patent Application and since this forms no part of the present invention reference will be made only insofar as is necessary to the understanding of the present invention.

The operating mechanism for the interrupters 10 will now be described and includes an elongate insulating operating rod 40 made of, for example, glass reinforced plastic (g.r.p.). The bottom end of rod 40 has a metal end fitting 41 to which is connected a crank arm 42 fixed on a rotary shaft 43 which is journalled in a bearing housing 45 attached to the underside of support fromework 37. The rotary shaft 43 has a second crank arm 44 for connection to the circuit-breaker operating mechanism, not shown, and to other phases of the circuit-breaker, not shown.

The operating mechanism may take the form described in our co-pending British Patent Application No. 35072/76 (Serial No. 1 590 832). The top end of the operating rod 40 has a metal end fitting 46 having an adjustable screwed bearing 47 fixed by a pinned nut 48. The bearing 47 is connected by a pin 49 to the forked end 51 of a drive member in the form of a link 50. Bell-crank levers 52, 53 are pivotally connected to the link 50. The upper bellcrank lever is shown in greater detail in Figure 3. The bell-crank levers are of identical construction and configuration but differently oriented, and each comprises a central hub portion 52a which rigidly joins two spaced parallel outer arms 54 to a diverging central arm 56. The hub 52a is pivotally mounted on a fixed structure, described below with reference to Figure 1A and pivotal connection of the drive rods to the bell crank levers is also de scribed with reference to Figure 1 A.

As shown in Figure 1A, the bell-crank levers 52, 53 are pivotally mounted by pivot pins 52b, 53b through their hubs inside the chamber 32 on a bearing bracket 38, which is attached to a plate 39 rigidly secured (as by bolting) within the chamber 32. The pairs of outer arms 54, 57 are pivotally connected by pivot pins 54a 57b, respectively, to the link 50. The distance between the connections 54a and 57b of the pairs of arms 54 and 57 to the link 50 is equal to the distance between the pivot pins 52b and 53b, so that the arms 54, 57, the link 50 and the fixed bracket 38 form a parallelogram linkage. The central arms 55 and 56 of the bell-cranks 52 and 53 are connected by pivot pins 55b, 56a respectively, aligned drive rods 60, 61, which are pivotally connected to the respective moving contact assemblies 11 of the interrupters 10.

The bearing bracket 38 is divided and belled out in its central region between the pivots 52b, 53b to allow free movement of the aligned drive rods 60 and 61, and of the bell-crank levers. The drive rod 60 is a single solid rod which passes through a fork space in the link 50 and is pivotally connected to the arm 56 of the bell-crank 52. The drive rod 61 comprises a pair of links which pass outside the drive rod 60 and are connected to the arm 55 of the bell-crank 53. This arrangement allows the drive rods 60, 61 to be positioned axially in line with one another and allows free movement. of the bell-cranks through approximately 60 , i.e. It30" in each direction between the limits of the opening and closing sequences.

As previously mentioned, the interrupters 10 are shown in the open-circuit position in Figure 1, and connection. of the circuit-breaker into an electrical circuit is made by means of terminals 21 which form sealing end caps being sealed to the insulators 30 in a gas-tight manner by flange rings 22; the terminals 21 are connected electrically to the fixed contacts 20. In operation the interior of the circuit-breaker is filled with SF6 gas at a pressure above atmospheric, and when it is required to close the circuit-breaker the circuit-breaker driving mechanism (not shown) which is coupled to the crank arm 44 is operated to move the operating rod 40 substantially vertically upwards. This action applies a turning moment to the bell-cranks 52, 53 to move the drive rod 60 to the right and the drive rod 61 to the left, and this movement is continued until the moving conacts of the assemblies 11 are drive firmly into engagement with the fixed contacts 20; the circuit-breaker is therefore now closed to provide an electrical circuit between the terminals 21.

The geometry of the bell-cranks 52, 53 is such that the arms 54, 55 and 56, 57 are all of equal length and the individual longitudinal axes of the arms 54 and 56, are at 90" to each other as are the longitudinal axes of the arms 55 and 57. The distance between the fixed pivot pins 52b, 53b on the bearing bracket 38 and between the pivot pins 54b, 57b connected to the link 50 are equal and the two bell-cranks 52 and 53 are so disposed relatively to one another that their arms 54 and 57 also form with the fixed bearing bracket 38 a parallelogram linkage, as a result of which the drive rods 60, 61 will be displaced by equal distances in opposite generallyhorizontal longitudinal directions when the operating rod 40 is moved longitudinally.

Figure 4 is a load vector diagram on which the locations of the pivot pins 52b, 53b and 54b, 57b are marked. By taking moments about the pivot pins 52b and 53b it may be shown that a vertical force P applied by the link 50 to the pivot 54b or 57b of the outer arms of either bell-crank will produce a horizontal operating force of equal magnitude P in the respective drive rod 60 or 61, this being the force required to operate the respective interrupter. These forces P are reacted by equal and opposite components of force P at the bell-crank pivots 54b and 57b ad, as shown in the vector diagram of Figure 4, produce resultant reactions R on the bracket 38. It will be seen that the two resultant reactions R when projected intersect on the centreline of the link 50, so that the rotating couples are equal and opposite and since the link 50 is substantially aligned with the centre line of the operating rod 40, and of the support insulators, it follows that-no bending moment is exerted on the vertical support insulators 35, 36, merely a vertical longitudinal reaction. Likewise since both interrupters and their drive rods 60, 61 are horizontally in line, no torsional couple in a horizontal plane is imposed on the support insulators 35, 36.

The load vector diagram of Figure 4 represents an intermediate position of the drive mechanism, and although there are second-order variations during the full range of travel of the mechanism, these may be disregarded since at any stage of the movement the reactions R will still intersect on the centre line of the support insulators 35, 36.

It thus follows that in the specific arrangement described there is virtually no unbalanced loading on the insulators, merely the vertical compressive/tensile reaction component, and this enables an optimum design to be produced without requiring additional strengthening of support insulators and associated structures.

As a further feature, the linkage system fixedly determines the relative contact displacements of the two interrupters, and a heavy frictional or operational load on one interrupter will not cause a difference in contact velocity to occur between the two coupled interrupters.

The arrangement described and illustrated has the advantages that both of the drive rods 60, 61, and therefore the associated interrupters, move at identical speeds, the linkage chamber is of small size and the resultant linkage is extremely simple.

The invention is not limited in its application to SF6 circuit-interrupters, but may be applied to other types of circuitbreakers, nor is the scope of the invention limited to the kind and shape of the bell cranks described in the specific embodiment.

WHAT WE CLAIM IS: - 1. A drive rod mechanism for operating at least two interrupter units of a highvoltage circuit-breaker, the units being mounted on a common hollow insulator support, which mechanism comprises a drive member movable longitudinally and connected to a drive mechanism, respective drive rods for the units and respective

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

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. and are connected to the arm 55 of the bell-crank 53. This arrangement allows the drive rods 60, 61 to be positioned axially in line with one another and allows free movement. of the bell-cranks through approximately 60 , i.e. It30" in each direction between the limits of the opening and closing sequences. As previously mentioned, the interrupters 10 are shown in the open-circuit position in Figure 1, and connection. of the circuit-breaker into an electrical circuit is made by means of terminals 21 which form sealing end caps being sealed to the insulators 30 in a gas-tight manner by flange rings 22; the terminals 21 are connected electrically to the fixed contacts 20. In operation the interior of the circuit-breaker is filled with SF6 gas at a pressure above atmospheric, and when it is required to close the circuit-breaker the circuit-breaker driving mechanism (not shown) which is coupled to the crank arm 44 is operated to move the operating rod 40 substantially vertically upwards. This action applies a turning moment to the bell-cranks 52, 53 to move the drive rod 60 to the right and the drive rod 61 to the left, and this movement is continued until the moving conacts of the assemblies 11 are drive firmly into engagement with the fixed contacts 20; the circuit-breaker is therefore now closed to provide an electrical circuit between the terminals 21. The geometry of the bell-cranks 52, 53 is such that the arms 54, 55 and 56, 57 are all of equal length and the individual longitudinal axes of the arms 54 and 56, are at 90" to each other as are the longitudinal axes of the arms 55 and 57. The distance between the fixed pivot pins 52b, 53b on the bearing bracket 38 and between the pivot pins 54b, 57b connected to the link 50 are equal and the two bell-cranks 52 and 53 are so disposed relatively to one another that their arms 54 and 57 also form with the fixed bearing bracket 38 a parallelogram linkage, as a result of which the drive rods 60, 61 will be displaced by equal distances in opposite generallyhorizontal longitudinal directions when the operating rod 40 is moved longitudinally. Figure 4 is a load vector diagram on which the locations of the pivot pins 52b, 53b and 54b, 57b are marked. By taking moments about the pivot pins 52b and 53b it may be shown that a vertical force P applied by the link 50 to the pivot 54b or 57b of the outer arms of either bell-crank will produce a horizontal operating force of equal magnitude P in the respective drive rod 60 or 61, this being the force required to operate the respective interrupter. These forces P are reacted by equal and opposite components of force P at the bell-crank pivots 54b and 57b ad, as shown in the vector diagram of Figure 4, produce resultant reactions R on the bracket 38. It will be seen that the two resultant reactions R when projected intersect on the centreline of the link 50, so that the rotating couples are equal and opposite and since the link 50 is substantially aligned with the centre line of the operating rod 40, and of the support insulators, it follows that-no bending moment is exerted on the vertical support insulators 35, 36, merely a vertical longitudinal reaction. Likewise since both interrupters and their drive rods 60, 61 are horizontally in line, no torsional couple in a horizontal plane is imposed on the support insulators 35, 36. The load vector diagram of Figure 4 represents an intermediate position of the drive mechanism, and although there are second-order variations during the full range of travel of the mechanism, these may be disregarded since at any stage of the movement the reactions R will still intersect on the centre line of the support insulators 35, 36. It thus follows that in the specific arrangement described there is virtually no unbalanced loading on the insulators, merely the vertical compressive/tensile reaction component, and this enables an optimum design to be produced without requiring additional strengthening of support insulators and associated structures. As a further feature, the linkage system fixedly determines the relative contact displacements of the two interrupters, and a heavy frictional or operational load on one interrupter will not cause a difference in contact velocity to occur between the two coupled interrupters. The arrangement described and illustrated has the advantages that both of the drive rods 60, 61, and therefore the associated interrupters, move at identical speeds, the linkage chamber is of small size and the resultant linkage is extremely simple. The invention is not limited in its application to SF6 circuit-interrupters, but may be applied to other types of circuitbreakers, nor is the scope of the invention limited to the kind and shape of the bell cranks described in the specific embodiment. WHAT WE CLAIM IS: -

1. A drive rod mechanism for operating at least two interrupter units of a highvoltage circuit-breaker, the units being mounted on a common hollow insulator support, which mechanism comprises a drive member movable longitudinally and connected to a drive mechanism, respective drive rods for the units and respective

substantially identical bell-crank levers the intermediate pivot points of which are pivoted in spaced positions on a common rigid structure, each bell-crank having one arm pivotally attached to the drive member in a configuration forming therewith a parallel-motion linkage, the other arms of the bell-crank levers being pivotally attached to the respective drive rods, the arrangement being such that when the drive member is moved longitudinally in either direction the bell-crank levers are turned and produce substantially equal longitudinal movements of the drive rods each in a line different from the line of movement of the drive member and the geometrical arrangement being such that substantially no unbalanced bending moments or torsional couples are imposed on the hollow insulator support.

2. A drive rod mechanism as claimed in Claim 1, in which the longitudinal axes of the drive rods and of the drive member are in a common plane, the drive rods moving in opposite directions to one another but substantially at right angles to the drive member.

3. A drive rod mechanism as claimed in either of the preceding Claims, in which the axes of the two arms of each bell-crank lever subtend a right angle between them at the pivot of the lever.

4. A high-voltage circuit-breaker having two interrupter units mounted on a common hollow insulator support and having a drive rod mechanism as claimed in any one of the preceding Claims, each interrupter unit being actuated by a respective one of the two drive rods.

5. A circuit-breaker as claimed in Claim 4, having two interrupter units arranged in oppositely-orientated axial alignment, and having a drive rod mechanism as claimed in Claim 2, or in Claim 3 when dependent on Claim 2.

6. A circuit-breaker as claimed in Claim 5 in which the two interrupter units are mounted end-to-end with their axes horizontal by means of a central fitting to which their adjacent ends are secured, the central fitting being mounted on the upper end of the insulator support and in which the driving member of the drive rod mechanism is coupled to a longitudinallymovable operating rod which extends substantially-vertically within the insulator support and has the operating mechanism coupled to its lower end.

7. A drive rod mechanism substantially as specifically described herein with reference to the accompanying drawings.

8. A circuit-breaker having a drive rod mechanism, substantially as specifically described herein with reference to the accompanying drawings.