WO2020194191A1

WO2020194191A1 - Grounding device

Info

Publication number: WO2020194191A1
Application number: PCT/IB2020/052767
Authority: WO
Inventors: Troy Lance Timm
Original assignee: Troy Lance Timm
Priority date: 2019-03-25
Filing date: 2020-03-24
Publication date: 2020-10-01

Abstract

A grounding device mountable onto an electrical motor housing proximate an electrical motor shaft, the grounding device including a fixed mounting frame, having mounting means for mounting onto the electrical motor housing and a conductive fibre mounting assembly mounted onto the fixed mounting frame, the conductive fibre mounting assembly defined by a cartridge and conductive fibres mounted onto the cartridge, which fibres extend towards the electrical motor shaft, in which the cartridge is radially adjustable within the fixed mounting frame relative to the electrical motor shaft so that a free end of the conductive fibres are adjusted to be in contact with the electrical motor shaft.

Description

GROUNDING DEVICE

FIELD OF THE INVENTION

THIS invention relates to a grounding device.

BACKGROUND OF THE INVENTION

Grounding rings are well known, and commonly used for grounding rotating shafts of electrical motors to ground potential. This might imply grounding a rotary shaft of an electrical motor to the housing of the electrical motor.

It is well known that shafts of electrical motors, and more specifically motors being controlled by variable frequency drive controllers or variable speed drive controllers build up an electrical potential which is normally dissipated to the motor housing via electrical motor bearings. Due to high voltage potential that builds up between the shaft and the motor housing this electrical dissipation through the bearings can lead to degradation of the bearings and the lubricant used in bearings.

Grounding rings are known in the industry to prevent degradation of bearings and lubricant by conducting electrical potential from the motor shafts to the motor housing, which is held at ground potential.

A grounding ring typically comprise of an annular frame mounted onto the motor housing with the shaft extending through an annular opening. Conductive fibres extend radially inward from the annular ring to make electrical contract with the shaft, thereby to conduct electrical potential from the shaft via the fibres and the annular frame to the electrical motor housing. However, as the conductive fibres are worn away, they might have reduced electrical contact with the shaft, but due to the high electrical potential between the shaft and the conductive fibres, it has been known that a certain degree of ionisation occurs in the air, which still cause some conduction of electrical potential from the shaft to the motor housing. This is however not desirable as such electrical conduction is less efficient and more difficult to quantify or measure.

It is therefore preferable to retain physical contact between the conductive fibres and the rotating shaft as the level of electrical conductivity is better than conductivity through ionisation.

Grounding rings are manufactured in a large variety of sizes, all matched to electrical motor shaft diameters. The large variety of sizes that needs to be carried in stock have a substantial cost implication. Furthermore, as conductive fibres are worn away due to friction with rotating shafts, the earth rings need to be replaced at regular intervals as part of a preventative maintenance program.

The inventor thus identified a need for a ground ring that does not have to be matched to a single shaft diameter and in which the life of the earth ring can be extended when the conductive fibres are worn away.

Reference in this specification to the term “substantially” with reference to annular will be understood to respectively include a cored shape being cylindrical, hexagonal prism, octagonal prim or other prism shape having more than 8 sides. The term grounding device in the specification is intended to include, but not be limited to a grounding ring. SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a grounding device mountable onto an electrical motor housing proximate an electrical motor shaft, the grounding device including

a fixed mounting frame, having mounting means for mounting onto the electrical motor housing;

a conductive fibre mounting assembly mounted onto the fixed mounting frame, the conductive fibre mounting assembly defined by a cartridge and conductive fibres mounted onto the cartridge, which fibres extend towards the electrical motor shaft, in which the cartridge is radially adjustable within the fixed mounting frame relative to the electrical motor shaft so that a free end of the conductive fibres are adjusted to be in contact with the electrical motor shaft.

The mounting means for mounting onto the electrical motor housing may be the form of any one of mounting apertures for fixing the mounting frame with screws directly onto the motor housing and a mounting arrangement attachable to the fixed mounting frame and the electrical motor housing respectively.

The fixed mounting frame may include mounting means onto which the conductive fibre mounting assembly is adjustably mountable.

The mounting means may be in the form of at least one slot or guide channel in the mounting frame, the slot operatively extending radially from the electrical motor shaft.

The conductive fibre mounting assembly may include locking means operable to lock the cartridge in position relative to the fixed mounting frame, such that, in use, the conductive fibres are adjustable to extend the desired distance towards the electrical motor shaft to be in contact therewith. The locking means may be in the form of a set screw receivable into the cartridge to lock the cartridge onto the slot of the fixed mounting frame.

The fibre cartridge may include any one of a slot and at least one socket into which the conductive fibres are mounted.

The fibre cartridge may include a plurality of sockets with an aperture at the base of each socket. The conductive fibres may be stitched in position by a thread extending midway over the conductive fibres that pulls the conductive fibres in position into the socket with the ends of the conductive fibres standing proud from the socket. It is to be appreciated that the fibres may be attached to the cartridge in any other manner such as by glueing, by compression fitted between two parts or clamps, clamping, or the like. Clamping the fibres together may includes to opposed clamps being fixed together with the fibres compressed between them. The plates may be of any conductive material such as metal, aluminium, bronze, copper, or the like.

In one embodiment, the fixed mounting frame may be in the form of an annular disk with an annular opening having a predefined annular diameter. The annular disk may be mountable around an electrical motor shaft with a plurality of conductive fibre mounting assemblies mounted circumferentially around the annular opening and with the conductive fibres directed radially inwards onto the electrical motor shaft.

The mounting means may be in the form of radially extending slots or guide channels in the annular mounting frame spaced equiangularly around the annular opening.

The annular opening may have a predefined inner diameter to accommodate an electrical shaft of an electrical motor. In this embodiment, the cartridges may be adjustable between an extended position in which the free ends of the fibres define a first diameter to accommodate a first predefined shaft diameter and a retracted position in which the free ends of the fibres define a second diameter to accommodate a second predefined shaft diameter.

In this embodiment, the ratio of the second diameter to the annular diameter may be between 0.9:1 and 1 :1 and the ratio of the first diameter to the annular diameter may be between 0.25:1 and 0.5:1.

The invention is now described, by way of non-limiting example, with

reference to the accompanying figure(s).

FIGURE(S)

In the figure(s):

Figure 1 shows a three-dimensional view of an embodiment of a grounding device in accordance with one aspect of the invention;

Figure 2 shows an exploded view of the embodiment of Figure 1 ;

Figure 3 shows a front plate of an annular body of the embodiment of Figure 1 ;

Figure 4 shows a back plate of an annular body of the embodiment of Figure 1 ;

Figure 5 shows a plan view of a cartridge of the embodiment of Figure 1;

Figure 6 shows a three-dimensional view from one side of a grounding device in accordance with another aspect of the invention with cartridges in a retracted condition;

Figure 7 shows a three-dimensional view of the embodiment of Figure 6 from another side with the cartridges in an extended condition;

Figure 8 shows the embodiment of Figure 1 from the front; Figure 9 shows an exploded view of the grounding device of Figure 6;

EMBODIMENT OF THE INVENTION

In Figures 1 to 5 a grounding device (10) is shown. The grounding device (10) includes a fixed mounting frame, in the form of an annular body (12) which is attachable to an electrical motor housing (not shown) proximate an electrical motor shaft of the electrical motor by means of mounting means (60) in the form of threaded sockets, through which fastening screws (not shown) are attachable. It is to be appreciated that other embodiments may also be considered instead of the annular body (12), such as a fixed mounting frame mounted next to the motor shaft.

As set out above, in this embodiment, the fixed mounting frame is in the form of an annular disk (12) with an annular opening, having a predefined annular diameter, the annular disk (12) is mountable around an electrical motor shaft with a plurality of conductive fibre mountings mounted.

The grounding device (10) further includes a conductive fibre mounting assembly (62) mounted onto the annular body (12). The conductive fibre mounting assembly is defined by a cartridge (64) and conductive fibres (66) mounted into four sockets (68) (shown in broken line) in the fibre cartridge (64) (see Figure 5). In this embodiment, the conductive fibres (66) are mounted circumferentially around the annular opening and with the conductive fibres directed radially inwards onto the electrical motor shaft (not shown). As can be seen in Figure 1 the conductive fibres (66) extend towards a position to where an electrical motor shaft will be, in use. In this embodiment, the fibres are folded and stitched into the sockets (68) with a thread extending midway over the conductive fibres to pull the conductive fibres in position into the socket with the ends of the conductive fibres standing proud from the socket. In another embodiment, which the inventor had in mind, the conductive fibre mounting assembly may be in the form of an adjustable iris design with the inner tips/ends of the iris including conductive filaments. In this embodiment, the annular opening may be adjustable like an iris.

The cartridge (64) is radially adjustable within the annular body (12) relative to the electrical motor shaft so that a free end of the conductive fibres (66) may be adjusted to be in contact with the electrical motor shaft.

As can be seen in Figures 1 to 5, the mounting means for mounting the grounding device (10) onto the electrical motor housing is in the form of four threaded mounting sockets (70) for fixing the annular body (12) with screws (not shown) onto the motor housing (not shown).

The annular body (12) includes mounting means in the form of slots (12.1 ) extending radially from the position where the electrical motor shaft would be located in use. The slots (12.1) are provided in a back plate (12A) of the mounting frame. The annular body (12) also has a front cover plate (12B). The set screws (72) are provided to lock the cartridge (64) in a fixed radial position onto the back plate (12A). In use, the conductive fibres are adjusted to extend the desired distance towards the electrical motor shaft to be in contact therewith.

In use, the annular opening is specified to have a predefined diameter to accommodate an electrical shaft of an electrical motor, or a range of diameters of shafts. In this embodiment, the cartridges are therefore adjustable between an extended position in which the free ends of the fibres define a first diameter to accommodate a first predefined shaft diameter and a retracted position in which the free ends of the fibres define a second diameter to accommodate a second predefined larger shaft diameter. In a specific embodiment, the ratio of the second diameter to the annular diameter are between 0.9:1 and 1 :1 and the ratio of the first diameter to the annular diameter are between 0.25:1 and 0.5:1 .

Figures 6 to 9 show another embodiment of a grounding device (10). The grounding device also includes an annular disk shaped body (12), an annular opening defined in the annular body (12), a plurality of slidable fibre mounts or cartridges (16) on which conductive fibres (18) are mounted and mount locks (20) for locking the slidable cartridges (16) in a required position.

As can be seen in Figure 9, the annular body (12) is made up of a back plate (12A) and a front cover plate (12B). The back plate (12A) comprises a back axial end face (22), a front axial end face (24) backwardly from which a plurality of guide channels (26) are recessed into and spaced from one another circumferentially about the back plate (12A), an inner diameter side wall (28) defining the central axial cavity or annular opening (14) and an outer diameter side wall (30).

The front cover plate (12B) comprises a ring-shaped disc-like part (32), having opposing back and front axial end faces (34), and a collar part (36) projecting axially backwardly from an outer periphery of the disc-like part (32), to form a cup-shape front cover plate, together being sized and shaped to receive, in an assembled condition as illustrated in figures 6 to 8, the front axial end face (24) and the outer diameter side wall (30) of the back plate (12A) therein.

It will be appreciated that the guide channels (26) are sized and shaped to accommodate the cartridges (16) therein, in a manner in which the cartridges (16) are slidably movable therealong between extended and retracted conditions. Furthermore, the recessed guide channels (26) define fibre openings (27) in the inner diameter side wall (28) of the back plate (12A) through which the conductive fibres (18) and/or cartridges (16) are movable inwardly and outwardly between the respective extended and retracted conditions. In the extended condition, the cartridges (16) and conductive fibres (18) mounted thereon are moved radially inwardly into the axial cavity (14) such that free ends (18A) of the conductive fibres (18) jointly lie circumferentially along a first virtual circle or circumference “d” having a first predetermined shaft accommodating diameter.

In the retracted condition, the cartridges (16) and conductive fibres (18) mounted thereon are moved radially outwardly such that the free ends (18A) of the conductive fibres (18) jointly lie within or proximity aligned with the annular opening (14) and circumferentially along a second virtual circle or circumference “D” having a second predetermined shaft accommodating diameter.

With the cartridges (16) and conductive fibres (18) operatively moved to the extended condition, retracted condition or any other required condition therebetween, the cartridges (16) lock the conductive fibres (18) in such condition such that the grounding device (10) is adjustable to be installed to shafts within a predetermined shaft diameter range, where the ratio of:

the second predetermined shaft accommodating diameter to predetermined cavity diameter is between about 0.9:1 and 1 :1 ; and

the first predetermined shaft accommodating diameter to predetermined cavity diameter is between about 0.25:1 and 0.5:1 .

The mount locks (20) are made up, per guide channel (26), of at least one lock bolt or set screw (38), one threaded socket (40) defined in each of the cartridges (16) and one lock slot (42) passing axially between the back axial end face (22) of the back plate (12A) and the recessed guide channel (26).

The lock slot (42) comprises a constriction (44), nearer the recessed guide channel end thereof than to the back axial end face (22) sized to enable a shank portion (38A) of the lock bolt (38) to pass therethrough, while restricting a head portion (38B) passage therethrough.

In this manner, the shank portion (38B) of the lock bolt (38) is engageable with the threaded socket (40) defined in the respective cartridge 16, while the head portion (38B) of the lock bolt (38) is slidably captive within the lock slot (42).

It will be appreciated that the lock bolt (38) is movable between a tightened condition and an untightened condition. In the tightened condition, the cartridge (16) is tightened up against the back plate (12A) by the lock bolt (38), consequentially frictionally locking the cartridge (16) in the required condition.

In the untightened condition, the cartridge (16) is loosened from the back plate (12A) and consequentially unlocked such that it is slidably movable along the guide channels (26) to adjust to the required condition. It will be appreciated that the slideable movement of the cartridge (16) is restricted by abutment between the head portion (38B) of the lock bolt (38) and the major ends of the lock slot (42), in which the head portion (38B) of the lock bolt (38) is slideably captive.

In use, and with the cartridges (16) unlocked from the back plate (12A), an installer is capable of slidably moving the cartridges (16) to a measured position using a Vernier calliper tool. Alternatively, the grounding device (10) may include visual graduation indicia (46) on the cartridges (16) for visually setting and locking the cartridges (16), and consequentially the conductive fibres (18) mounted thereon, to a required shaft accommodating diameter quickly and easily. It will be appreciated that the visual graduation indicia may, instead of being on the cartridges (16) as illustrated in Figure 7, be marked out on the annular body To retain the grounding device (10) in the assembled condition, a plurality of assembly bolts (48) pass through fastening apertures (50) defined axially through the front cover plate (12B), and into threaded engagement with correspondingly threaded fastening apertures (52) defined in the back plate (12A). It will be appreciated that these same assembly bolts (48), fastening apertures (50) and threaded fastening apertures (52) are usable to mount to the grounding device (10) mounting legs (not shown) to a motor housing and over the shaft to grounded. Although the invention has been described with reference to a preferred embodiment, it will be appreciated that many modifications or variations of the invention are possible without departing from the spirit or scope of the invention.

Claims

CLAIMS:

1 . A grounding device mountable onto an electrical motor housing proximate an electrical motor shaft, the grounding device including

2. A grounding device as claimed in claim 1 , in which the mounting means for mounting onto the electrical motor housing is in the form of any one of mounting apertures for fixing the mounting frame with screws directly onto the motor housing and a mounting arrangement attachable to the fixed mounting frame and the electrical motor housing respectively.

3. A grounding device as claimed in claim 1 , in which the fixed mounting frame includes mounting means onto which the conductive fibre mounting assembly is adjustably mountable.

4. A grounding device as claimed in claim 3, in which the mounting means is in the form of at least one slot or guide channel in the mounting frame, the slot operatively extending radially from the electrical motor shaft.

5. A grounding device as claimed in claim 4, in which the conductive fibre mounting assembly includes locking means operable to lock the cartridge in position relative to the fixed mounting frame, such that, in use, the conductive fibres are adjustable to extend the desired distance towards the electrical motor shaft to be in contact therewith.

6. A grounding device as claimed in claim 5, in which the locking means is in the form of a set screw receivable into the cartridge to lock the cartridge onto the slot of the fixed mounting frame.

7. A grounding device as claimed in claim 1 , in which the fibre cartridge includes any one of a slot and at least one socket into which the conductive fibres are mounted.

8. A grounding device as claimed in claim 7, in which the fibre cartridge includes a plurality of sockets with an aperture at the base of each socket.

9. A grounding device as claimed in claim 8, in which the conductive fibres are stitched in position by a thread extending midway over the conductive fibres that pulls the conductive fibres in position into the socket with the ends of the conductive fibres standing proud from the socket.

10. A grounding device as claimed in claim 1 , in which the fixed mounting frame is in the form of an annular disk with an annular opening having a predefined annular diameter, the annular disk mountable around an electrical motor shaft with a plurality of conductive fibre mounting assemblies mounted circumferentially around the annular opening and with the conductive fibres directed radially inwards onto the electrical motor shaft.

11. A grounding device as claimed in claim 10, in which the mounting means is in the form of radially extending slots or guide channels in the annular mounting frame spaced equiangularly around the annular opening.

12. A grounding device as claimed in claim 10, in which the annular opening has a predefined inner diameter to accommodate an electrical shaft of an electrical motor.

13. A grounding device as claimed in claim 12, in which the cartridges are adjustable between an extended position in which the free ends of the fibres define a first diameter to accommodate a first predefined shaft diameter and a retracted position in which the free ends of the fibres define a second diameter to accommodate a second predefined shaft diameter.

14. A grounding device as claimed in claim 13, in which the ratio of the second diameter to the annular diameter may be between 0.9:1 and 1 :1 and the ratio of the first diameter to the annular diameter may be between 0.25:1 and 0.5:1.

15. A grounding device as claimed in claim 1 , substantially as herein described and illustrated.