GB2367948A - Switchgear apparatus - Google Patents

Abstract

Switch gear includes a bar member 24 mounted for rotatable movement about a first axis A-A', a plate member 38,40 connected to the bar member and extending substantially radially from the first axis, a rotatable member mounted on the plate and rotatable about an axis radially outward from the first axis, and engaging means 62 operable to abut the rotatable member thereby rotating the plate member and bar member about the first axis thereby enabling electrical connection and disconnection of the power supply.

Description

Switch Gear Apparatus This invention relates to switch gear, in particular for fused switch boxes.

Switch gear housed in a casing with accompanying fuses is widely used and in such apparatus it is well known to have a handle rotatably mounted on the outside of the casing, for example a hinged door. Such handles with their associated mechanisms often act as both a switch and a lock for the door. Thus, in use rotatable movement of the handle makes or breaks internal electrical contacts, thereby isolating exposed parts, and also simultaneously engages or disengages a door locking mechanism.

Switch boxes of this type are commonly used in industrial and commercial premises with three phase power supply networks.

A conventional rotating mechanism used on such switch boxes will now be briefly described. Rotatable movement of a handle located on the outside of a door of the box, typically through an angle of 90 , results in a smaller angular movement, (typically 10-20 ) of a drive arm located on the inside of the door. Twin pronged fork-like extension on this drive arm operably abut against folded lugs located on a generally circular plate and thereby rotate the plate and an elongate contact bar about an axis orthogonal to that of the handle. The contact bar has three axially spaced apart contacting blades, pivotable movement of which operably makes or breaks electrical contacts for each live supply of a three phase power supply. The drive arm operably engages a member fixed within the box to provide a lock mechanism, the lock being opened or closed by angular movement of the drive arm via the handle.

Known rotating mechanisms of the type described above are generally adequate but nevertheless do have a tendency to become difficult to open and close owing to frictional resistance, for example between the fork-like extension and the switch gear with which it co-operates. This can result in a user forcing the mechanism and thereby causing it damage.

The invention seeks to avoid or at least mitigate this and other problems in the art.

One object of the present invention is to provide an improved contact bar rotating mechanism for a switch box with reduced frictional resistance making it easier for a user to open and close.

In the following description the term rotate and its derivatives is intended to include the term pivot and its corresponding derivatives.

According to one aspect of the invention there is provided switch gear having a bar member mounted for rotatable movement about a first axis, a plate member connected to the bar member and extending substantially radially from the first axis, a rotatable member mounted on the plate and rotatable about an axis radially outward from the first axis, engaging means operable to abut the roller thereby rotating the plate member and bar member about the first axis thereby enabling electrical connection and disconnection of the power supply.

According to another aspect of the invention there is provided switch gear having a bar member mounted for rotational movement about an axis, at least one plate member connected to the bar member and extending substantially radially from the axis, engaging means operable to rotate the plate member and bar member about the first axis thereby engaging or disengaging electrical contacts and biasing means operable to hold the switch gear in an engaged or disengaged position, the biasing means including a rod with a forked open end that abuts against a lug fixed to the plate member. Preferably, the rotatable member is mounted on the plate and rotatable about an axis substantially parallel to the first axis and preferably the rotatable member comprises a roller.

In order to provide a mechanically robust bar pivoting mechanism there are preferably two spaced apart plate members with rollers mounted therebetween.

Several rollers may be mounted in an angularly spaced apart relationship on the plate member on a substantially common radial plane with respect to the first axis.

Preferably, there are three such rollers.

The engaging means may comprises one or more prongs, preferably two prongs. The prongs may have a tapered cross section, in which case the included angle (a) of the tapered prong is in the range 5 to 10 , and preferably approximately 7. 5 . The prong may have a curved surface, this may take the form of an arcuate shaped inner surface, in which case the radius (R) of the arcuate shaped inner surface is in the range 50-55 mm. , and preferably 53 mm. The use of a tapered section prong or an arcuate shaped prong assists in reducing friction resistance during operation of the switch.

The engaging means may be adapted operably to move in a plane generally orthogonal to the first axis and may further comprise an arm that rotates about a second axis substantially orthogonal to the first axis. The arm may rotate through an angle in the range of approximately 20'to approximately 30', preferably approximately 23 .

According to another aspect of the invention there is provided switch gear having a bar member supporting a movable electrical contact that is rotatably mounted at one end to a bracket member, the bracket member being connected to or forming an integral part of a mounting for a stationary electrical contact, which operably co-operates with the movable electrical contact. The bracket member may comprise a portion of a resilient material.

According to yet another aspect the invention there is provided switch gear having a moveable contacting blade, electrical contacts located in a terminal block that can be connected and disconnected by movement of the contacting blade, a fuse base that is not part of the terminal block but is separate component electrically connected to at least one contact in the terminal block.

An embodiment of the invention will now be described by way of example only, with reference to the following schematic drawings in which: Figure 1 is a front view of a switch gear box according to the invention with the front hinged door removed, Figure 2 is a perspective view of the bar rotating mechanism in its open position, Figure 3 is a perspective view of the bar rotating mechanism in its closed position, Figure 4 is an exploded view of the mechanism shown in Figures 2 and 3, Figure 5 is a rear view of the drive arm located on the inside of a hinged door, Figure 6 is a front view of a drive arm, Figure 7 shows an end view of the drive arm shown in Figure 6, Figure 8 shows an end view of a drive arm with differing prongs, Figure 9 is a perspective view of the terminal block, contact bar and its end support member shown in Figure 1, and Figure 10 is a perspective view of the drive arm and handle shown in Figure 5.

Figure 1 shows the main components of a fused switch box 10, excluding a door member. An open fronted box 12 is provided with male hinge members 14 sized to mate with female hinge members on a front door (not shown). The box may house three cartridge type fuse holders and fuses (for example, fuses rated at 32A) within fuse bases 16a, 16b and 16c there being one fuse base for each phase of a three phase mains supply. However, the inclusion of fuse bases within the box is not essential. Terminal blocks 18a, 18b and 18c are provided one for each fuse base for connection to one of each of the live phases of a three-phase mains supply. Adjacent terminal blocks 20a, 20b and 20c are provided each being electrically connected to respective fuse bases 16a, 16b and 16c. These fuse bases will normally contain fuses located in fuse holders, which in turn locate in the fuse bases. Each terminal block has a stationary electrical contact 19 electrically connected to its terminal point.

Three U-shaped contacting blades or movable electrical contacts 22 are mounted in spaced apart relationship along one face of a contact bar 24. Contact bar member 24 preferably has a generally square cross section and is mounted for rotatable movement about axis A-A'. Rotatable movement of contact bar 24 operably makes or breaks the stationary electrical contacts 19 on terminal blocks 18,20 and the movable electrical contact 22, thus either connecting or isolating the power supply to the fuses.

Junction block 28 is provided in order to allow connection of the incoming and outgoing negative and earth supplies in a conventional manner. The back wall of the case 12 has several recessed portions containing holes 30, provided to assist securing of the switch box to a wall or the like.

Figure 2 shows a perspective view of bar rotating mechanism 26 in its OFF (open) position and Figure 3 a corresponding view in its ON (closed) position.

The components of bar rotating mechanism 26 are best seen in Figure 4. An inner plate 38 and an outer plate 40 are held side by side and spaced apart by spacers 42a and 42b. Preferably, spacers 42a and 42b are circular in cross section and have a central track dimensioned to accept a biasing member (see latter). Plates 38 and 40 are mounted for rotary movement about a first axis A-A'by means of threaded spindle 44 passing through circular holes 46 and 48 of the inner and outer plates 38 and 40 respectively. The threaded portion of spindle 44 engages a threaded slot 50 provided in a vertical side wall 36 of fixing frame 52. Alternatively, the threaded portion of spindle 44 may pass through an unthreaded hole and be secured by a bolt (not shown) to the side face 36 of fixing frame 52. Both plate 38 and 40 have three radially disposed arms 54 each with a hole 56 provided to mount a roller 58 therebetween. Rollers 58 are free to rotate between the inner and outer plates 38, 40 on an axes parallel to and radially outward from axis A-A'.

The bar rotating mechanism 26 is firmly held in either its ON or its OFF position by means of a biasing arrangement comprising a helical spring 60 located on a rod 62 of generally rectangular cross section with an open forked end 64 dimensioned to engage spacer 42a. Preferably, open forked end 64 comprises a curved recess, most preferably semicircular in shape. The narrower end of rod 62 engages a rectangular slot 66 provided in a comer wall 68 of fixing frame 52 extending orthagonally from the main side face 36. Thus, spring 60 is held in compression between comer wall 68 and spacer 42a. The bar rotating mechanism 26 has two stable positions. A first stable position (as shown in Figure 2 and 3) in which the contacting blades 22 bridge contacts 19 of terminal blocks 18 and 20 (corresponding to the ON position for the switch), and a stable second position where contact bar member 24 has rotated (normally through about 90 ) so that the ends of the contacting blades 22 no longer bridge contacts 19 (corresponding to the OFF position of the switch).

In its first stable position (OFF/open) as shown in Figure 2 the open forked end 64 of rod 62 points away from a base plate 70 of frame 52 In this position the limbs of the contacting blades 22 point directly outwards and perpendicular to the back wall of the open fronted box 12. In its second stable position (ON/closed) as shown in Figure 3 the forked end 64 of rod 62 points towards base plate 70 of frame 52. In

this position the limbs of the contacting blades 22 bridge contacts 19 of terminal zn blocks 18 and 20. The arrangement thus provides a type of over-centring mechanism.

Referring to Figure 9, contact bar 24 has a drive dog 110 at one end and a lug 112 at one end. The drive dog 110 also has a lug (not shown) provided to interface with hole 122 in threaded spindle 44 and also has an extending arm 126 hereinafter referred to as the drive dog extension arm. The other lug 112 may interface with a resilient bracket 114. The bracket 114 may comprise an insulative base section 116 connected to a metallic strip 118 with a hole 120. In use, lug 112 interfaces with hole 120 thereby allowing contact bar 24 to rotate about axis A-A'. Preferably, the base section 116 is integrally formed with the insulative case 124 that houses terminal blocks 18 and 20 (not shown in Figure 9).

Referring to Figures 4 and 9, drive dog extension arm 126 is located within arcuate slot 80 of outer plate 40. The drive dog 110 and connected contact bar 24 are thus operably rotated about a common axis A-A'by operation of bar pivoting mechanism 26 as drive dog extension arm 126 abuts against either face 80a or 80b of arcuate slot 80. The drive dog extension arm 126 also engages rectangular slot 78 in locator member 72, mounted on threaded spindle 44, between plates 38 and 40. Locator member 72 comprises a main disc portion 74 which has a short lug 76 protruding in a direction parallel to axis A-A'. Lug 76 acts as a spacer ensuring that disc portion 74 sits on threaded spindle 44 close to plate 40 and separated from plate 38. Locator member 72 also has a slot 78 which in use is aligned with arcuate slot 80. A lower lug 82 extending ortgagonally from disc portion 74 has a hole to which one end of a spring 84 is attached by hook means. The other end of spring 84 is attached by means not shown to outer plate 40. Spring 84 is in a state of tension and thus applies a bias to locator member 72 tending to move it in an clockwise direction as viewed along axis A to A'so that the drive dog extension arm 126 abuts against face 80b when the mechanism is at rest or during closing of the switch box.

Additional functions of rotating mechanism 26 will now be described. On opening of the switch by handle 102 via bar pivoting mechanism 26 the inner and outer plates 38,40 rotate clockwise about axis A-A'. However, locator member 72 does

not initially rotate owing to it being connected to contact bar 24 via drive dog 110 and by reason of frictional resistance between the U-shaped contacting blades 22 and stationary electrical contacts 19. Thus, initially plates 38,40 rotate and locator member 72 remains stationary resulting in spring 84 being further stretched and the tension therein increasing. During this period rod 62 pivots downwardly about slot 66 and approaches an intermediate (unstable) position where the axis of the rod is parallel to the base plate 70 of frame 52. At this moment drive dog extension 126 is proximal or actually abuts face 80a of arcuate slot 80. Upon continued rotation of the mechanism 26 the over centring mechanism flips from its ON/closed position to its OFF/open position and at that instant bar rotating mechanism 26 and the attached blades 22 rapidly rotate in a clockwise direction about axis A-A. Thus, blades 22 snap free of stationary electrical contacts 19 thereby avoiding a gradual breaking of electrical contact. This arrangement substantially reduces or eliminates arcing of the electrical contacts during opening of the switch. During this disengagement the spring 84 contracts and thereby rotates locator member 72 in a clockwise direction about axis A-A'so that drive dog extension arm 126 again abuts against face 80b.

The biasing action of spring 84 ensures that when mechanism 26 is in its OFF/open position contact bar 24 and attached contacting blades 22 are firmly held in a fully disengaged position, blades 22 being well clear of terminal blocks 18 and 20.

Bar rotating mechanism 26 is actuated by a drive arm assembly mounted on the inside of the switch box door (see Figure 5). A handle 102 located on the outside of the door is connected either directly or indirectly to a sprocket 104 located on the inside of the door. A drive arm 90, attached by pivot 92 to the inside of the door 94, has a twin pronged portion 96 extending outwardly from the door at right angles to the main portion 88 of the drive arm 90. Both prongs may have arcuate inner surfaces (see Figure 7) and so taper somewhat towards their end portions. It has been found that this type of tapered profile reduces frictional resistance during operation of the apparatus. Preferably the radius R (see Figure 7) of the arc is between approximately 50-55 mm. , and more preferably approximately 53mm. The prongs 98 and 100 accordingly form part of means for engaging the bar rotating mechanism 26, at rollers 58.

In an alternative prong arrangement (see Figure 8) the first prong 98 has approximately constant cross section while the second prong 100 tapers inwardly at an included angle a as it extends from the main portion of drive arm 90. Again it has been found that this form of tapering also assists in reducing frictional resistance during operation of the apparatus. Preferably a is in the range 5-10 , and more preferably about 7. 5 .

Drive arm 90 can be moved from its open position (shown as solid lines in Figure 5) to its closed position (shown in broken lines in Figure 5) by pivoting handle 102 in direction B about a second axis by about 90 . Sprocket 104 engages an elongate slot 106 in drive arm 90, the sprocket being connected, not necessarily directly, to handle 102. On turning the handle 102 in direction B through 900 sprocket 104 pivots about the second axis and simultaneously slides from one end of slot 106 to the other end, consequently resulting in movement of pivoting of arm 90 from an open position to its closed position.

When door 94 is mounted on hinges 14 and is closed against open fronted box 12 the pronged portions 96 of drive arm 90 straddle roller 58 (see Figure 10) of the bar rotating mechanism 26.

In use, as handle 102 is rotated about the second axis towards its closed position the pronged portion 96 abuts against roller 58 and thereby rotatably moves plates 38,40, locator member 72, drive dog 100 and hence bar member 24 about axis A-A'so closing contacts 19 of terminal blocks 18 and 20. Simultaneously, the pronged end of drive arm 90 slides under an inwardly extending ledge 108 located at the top of fixing frame 52, thereby locking the door shut. Hence in a single rotary movement of handle 102 power can be switched on and the door is locked to protect the user from possible electrocution.

Claims (21)

1. Claims 1. Switch gear comprising a bar member mounted for rotatable movement about a first axis, a plate member connected to the bar member and extending substantially radially from the first axis, a rotatable member mounted on the plate and rotatable about an axis radially outward from the first axis, engaging means operable to abut the roller thereby rotating the plate member and bar member about the first axis thereby enabling electrical connection and disconnection of the power supply.
2. 2. Switch gear according to Claim 1 wherein the rotatable member is mounted on the plate and rotatable about an axis substantially parallel to the first axis.
3. 3. Switch gear according to any preceding claim wherein the rotatable member comprises a roller.
4. 4. Switch gear according to any preceding claim having two spaced apart plate members and a roller mounted therebetween.
5. 5. Switch gear according to any preceding claim having a plurality of rollers mounted in an angularly spaced apart relationship on the plate member on a substantially common radial plane with respect to the first axis.
6. 6. Switch gear according to Claim 3,4 or 5 having three rollers.
7. 7. Switch gear according to any preceding claim wherein the engaging means comprises a prong.
8. 8. Switch gear according to Claim 7 wherein the engaging means comprises two prongs.
9. 9. Switch gear according to Claim 7 or 8 wherein at least one prong comprises a tapered cross section.
10. 10. Switch gear according to Claim 9 wherein the included angle (a) of the tapered prong is in the range 5 to 10 , and preferably approximately 7. 5 .
11. 11. Switch gear according to Claim 7,8, 9, or 10 wherein at least one prong has an arcuate shaped inner surface.
12. 12. Switch gear according to Claim 11 wherein the radius (R) of the arcuate shaped inner surface is in the range 50-55 mm. , and preferably approximately 53 mm.
13. 13. Switch gear according to any of Claims 7 to 12 wherein the engaging means is adapted operably to move in a plane generally orthogonal to the first axis.
14. 14. Switch gear according to any preceding claim wherein the engaging means further comprises an arm that rotates about a second axis substantially orthogonal to the first axis.
15. 15. Switch gear according to Claim 14 wherein the arm is rotatable through an angle in the range of approximately 20'to approximately 40 .
16. 16. Switch gear independent of or according to any preceding claim wherein a bar member supporting a movable electrical contact is rotatably mounted at one end to a bracket member, the bracket member being connected to or forming an integral part of a mounting for a stationary electrical contact, which operably co-operates with the movable electrical contact.
17. 17. Switch gear according to Claim 16 wherein the bracket member comprises a portion of a resilient material.
18. 18. Switch gear according to any preceding claim wherein biasing means is provided to hold the switch gear in an engaged or disengaged position, the biasing means including a rod with a open forked end that abuts against a curved lug fixed to the plate member.
19. 19. Switch gear comprising a bar member mounted for rotational movement about an axis, at least one plate member connected to the bar member and extending substantially radially from the axis, engaging means operable to rotate the plate member and bar member about the first axis thereby engaging or disengaging electrical contacts and biasing means operable to hold the switch gear in an engaged or disengaged position, the biasing means including a rod with a forked open end that abuts against a lug fixed to the plate member.
20. 20. Switch gear according to Claim 19 wherein the forked open end comprises a curved surface.
21. 21. Switch gear comprising a moveable contacting blade, electrical contacts located in a terminal block that can be connected and disconnected by movement of the contacting blade, a fuse base that is not part of the terminal block but is a separate component electrically connected to at least one contact in the terminal block.