GB1578378A

GB1578378A - Roller bearing for drop rod rapping

Info

Publication number: GB1578378A
Application number: GB4786177A
Authority: GB
Original assignee: Lodge Cottrell Ltd
Current assignee: Lodge Cottrell Ltd
Priority date: 1978-04-26
Filing date: 1978-04-26
Publication date: 1980-11-05

Description

(54) ROLLER BEARING FOR DROP ROD RAPPING (71) We, LODGE-COTTRELL LIMITED a British company of George Street Parade, Birmingham, B3 1QQ, 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:- The present invention relates to improvements in electro-precipitators for removing particulate matter from gas streams.

In the electro-precipitation process, gasborne particles enter a chamber and are therein exposed to an electric field between discharge and collector electrodes. Negative corona discharge is produced at the discharge electrodes while the collector electrodes are kept at earth potential. At the discharge electrodes, the particles are charged and then they move towards the collector electrodes under the influence of the field.

The particles lose charge to the collector electrodes upon which they accumulate.

From time to time the particles clinging to the collector electrodes are dislodged by jarring these electrodes using rapping devices.

The dislodged material falls to the bottom of the chamber and is removed at intervals.

As particles accumulate on the collector electrodes, electrical conditions favouring reverse ionisation can arise. Then, some particles will become positively charged and drift towards the discharge electrodes, ultimately collecting on the discharge electrodes.

The latter electrodes also need rapping periodically, therefore.

Failure to rap the electrode sets properly is extremely detrimental to the electro-precipitation process, since excessive particle accumulation can lead to flashovers. Damage to the precipitator may result. Moreover, with certain particle-laden gases, fire or explosion may be initiated by flashover.

The main object of this invention is to provide rapping apparatus having a drop rod guided by bearing means which is able to remain free from blockage or wear by dust and which is fail safe.

According to the present invention, we provide in an electro-precipitator, electrode rapping apparatus operable periodically to jar an electrode structure of the precipitator to dislodge particles clinging thereto, the apparatus including anvil means on the electrode structure, a rapping rod extending upwardly from the anvil means through a guide bearing, and means for lifting and thereafter releasing the rapping rod to allow it to drop onto the anvil means to jar said electrode structure, the guide bearing comprising a plurality of rollers journalled in a housing of said bearing, the guide bearing embracing the rapping rod and defining a lumen through which said rod is freely movable when lifted and dropped.

The apparatus can comprise at least three guide bearing rollers which make contact with at least three points spaced-apart around the periphery of the rod. Optionally the turning axes of the rollers are coplanar, and where there are three rollers, they can be at 60 to one another.

Preferably, however, there are two guide bearing rollers, which are substantially parallel and so shaped as to constrain the rod from movement in a direction parallel to the two rollers. In this arrangement, the rollers are each necked to constrain the rod from movement in the said direction. Where the rod is of circular cross-section, the necked, rod-engaging periphery of each roller can be of arcuate form. Alternatively, the necked, rod-engaging periphery of each roller can be of shallow V-form.

The rod lifting and releasing means may comprise a rotatively-driven cam shaft having a cam engageable with the underside of an abutment on the rod to lift the rod, the cam thereafter being able to slip out of contact with the abutment in the course of continued rotation of the cam shaft, to allow the rod to drop and strike the anvil means.

The rapping apparatus to be described in detail hereinafter was designed primarily for use with the discharge electrodes of a precipitator. Such apparatus could alternatively, or additionally, be used with the collector electrodes. Where identical or substantially identical rapping apparatus is used for both sets of electrodes, their lifting and releasing means can be driven by a common power plant.

The invention comprehends rapping apparatus for assembly into electro-precipitator rapping apparatus according to the invention, when supplied as a kit of parts, the kit including inter alia, a rapping drop rod, a guide bearing therefor comprising a plurality of rollers journalled in a housing of the bearing, the guide bearing embracing the rapping rod and defining a lumen through which the rod is freely movable lengthwise, and rod lifting and releasing means.

The invention furthermore comprehends an electro-precipitator when fitted with rapping apparatus embodying the invention.

Further details of the invention will now be given by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a fragmentary perspective view of rapping apparatus of an electro precipitator according to the invention; Fig. 2 is a fragmentary side elevation of the rapping apparatus used for a discharge electrode structure; Fig. 3 is a fragmentary perspective elevation of the rapping apparatus used for a collector electrode structure; and Fig. 4 is a side elevation of a guide bearing of the rapping apparatus.

Referring now to the drawings, there is shown an electro-precipitator 10 which has a casing 11 defining a chamber 12 into which particle-laden gas to be cleaned is fed. The gas flows, in the direction indicated by arrow A of Fig. 3, between interleaved discharge and collector electrode structures 14 and 15, respectively. Discharge electrode structure comprises a frame 16, only the top portion of which is seen and has vertically extending wires or rods, not shown, and is charged to a level typically -30 to -100 KV. The collector electrode structure 15 is maintained at ground potential.

In service, particulate matter builds up on both the electrode structures 14 and 15 (hereinafter respectively referred to simply as the discharger and collector, or electrode(s).

Periodically, the accumulated matter needs to be dislodged if the precipitator is to continue functioning properly. Dislodgement is accomplished by inducing a shock acceleration in the electrodes 14, 15, and in particular by jarring or rapping them. Figs. 1 to 3 illustrate rapping apparatus which features drop rods 20.

Each drop rod 20 is an elongated bar which extends vertically from above the casing 11 into the chamber 12. At its lower end, 21, each rod is engageable with anvil means 23 formed by or mounted on the dis charger frame 16 or on a corresponding col lector-supporting frame 22. The top end of each rod 20 has a collar 25 affixed thereto.

Rods 20 are vertically movable -in tubes 26 which extend downwardly from above the casing 11 to just above frame anvil means 23.

Bellows or flexible gaiters 27 seal the top ends of tubes 26, and the latter pass through seal insulators 29 or glands 42 in the top of the casing 11.

The rods 20 are guided for vertical movement by guide bearings 30 to be described hereafter.

To operate the rods 20 to apply the required rapping blows on their respective electrode structures 14, 15 lifting and releasing means is provided. The said means comprise cams 32 fast upon rotatively journalled cam shafts 33. The cam shafts 33 are rotated by a common power plant 35 to which said shafts are coupled by sprocket-and-chain drive transmissions 36. There is one cam shaft 33 seen adjacent the top of Fig. 1 which serves to operate the rods 20 for rapping the collectors 15. A second cam and cam shaft arrangement is provided for operating the rods 20 which extend through the lead through insulators 29 to the dischargers 13.

In operation, rotation of cam shaft 33 through one revolution causes a cam 32 to rotate into contact with the underside of the collar 25 of an associated rod 20. Continued rotation of shaft 33 and hence of the cam 32 results in lifting of the collar and hence the rod whereby its bottom end is raised from anvil means 23. Finally, the rotating cam 32 slips from under the collar 25, whereupon the rod 20 is released to drop under gravity until its bottom end 21 strikes or raps the anvil means 23. The vertical stroke through which rod 20 moves is clearly apparent from Fig. 2, wherein the lifted position of its top and bottom ends is shown dotted. The cams 32 preferably include adjusters 37 for presetting the lengths of the vertical strokes.

The raising and releasing of the collector rapping rods, at least, is preferably according to a preset sequence. This will be apparent from a consideration of Fig. 1. As shown, the cams 32 are secured to the cam shaft 33 such that each is angularly staggered about said shaft relative to the others. Stated otherwise, the collar-engaging points of the cams 32 all point in different preset directions as required to produce the required phased operation of the rapping rods 32.

The rapping rods 20 each extend through a guide bearing 30 which is supported on framing 40, 41 disposed above the casing 11.

The guide bearing 30 has a plurality of rollers 43 rotatably journalled in housing means 44 of the bearing. The rollers 43 define a lumen in which the rod 20 is a close-fit. The rod 20 is, of course, freely movable in a vertical direction thanks to rotation of the rollers 43.

The lumen has the effect of preventing substantial movement of rod 20 in the plane of Fig. 4-in practice the said plane is horizontal.

In the embodiment illustrated, the bearing 30 has two substantially parallel rollers 43 mounted on shafts 45 between spacer tubes 46 so as to be centrally disposed in the housing means 44.

The said lumen which prevents horizontal displacement of rod 20 is the result of the necked shape of each roller 43. The necked peripheral profile 48 shown in the drawings is of shallow V-form, whereby there is contact between the rollers and the rod 20 at four angularly-spaced points around the periphery of the rod. The neck profile 48 need not necessarily be of V-form, but could be arcuate to match the circular cross-section of the rod.

In the construction disclosed above, the rapping rods are all vertically disposed and movable. For some precipitator designs, it may be desired to incline the drop rapping rods 20 to the vertical. Then, two or more bearings 30 would be provided to support and guide the inclined rods.

WHAT WE CLAIM IS 1. In an electro-precipitator, electrode rapping apparatus operable periodically to jar an electrode structure of the precipitator to dislodge particles clinging thereto, the apparatus including anvil means on the electrode structure, a rapping rod extending upwardly from the anvil means through a guide bearing, and means for lifting and thereafter releasing the rapping rod to allow it to drop onto the anvil means to jar said electrode structure, the guide bearing comprising a plurality of rollers journalled in a housing of said bearing, the guide bearing embracing the rapping rod and defining a lumen through which said rod is freely movable when lifted and dropped.

2. Apparatus according to claim 1, comprising at least three guide bearing rollers which make contact with at least three points spaced-apart around the periphery of the rod.

3. Apparatus according to claim 1, comprising two guide bearing rollers, the rollers being substantially parallel and so shaped as to constrain the rod from movement in a direction parallel to the two rollers.

4. Apparatus according to claim 3, wherein the rollers are each necked to con strain the rod from movement in the said direction.

5. Apparatus according to claim 4, wherein the rod is of circular cross-section and the necked, rod-engaging periphery of each roller is of arcuate form.

6. Apparatus according to claim 4, wherein the rod is of circular cross-section and the necked, rod-engaging periphery of each roller is of shallow V-form.

7. Apparatus according to any of the preceding claims, wherein the rod lifting and releasing means comprises a rotativelydriven cam shaft having a cam engageable with the underside of an abutment on the rod to lift the rod, the cam being able to slip out of contact with the abutment in the course of rotation of the cam shaft after lifting the rod, to allow the rod to drop and strike the anvil means.

8. An electro-precipitator including rapping apparatus as claimed in any of the preceding claims 1 to 7, wherein the rapping apparatus is arranged to apply rapping blows to discharge electrode structure of the precipitator.

9. An electro-precipitator including rapping apparatus as claimed in any of the preceding claims 1 to 7, wherein substantially identical rapping apparatus is provided to apply rapping blows to discharge electrode structure and to collector electrode structure of the precipitator.

10. A precipitator according to claim 9, wherein the rod lifting and releasing means of the discharge electrode rapping apparatus and of the collector electrode rapping apparatus are driven from a common power plant.

11. A precipitator according to claim 8, 9 or 10, wherein the or each rapping apparatus has its anvil means located inside a casing of the precipitator, and the rod extends upwardly through the top of the casing, while the guide bearing and rod lifting and releasing means are supported above the casing.

12. Rapping apparatus when supplied as a kit of parts for assembly into the electroprecipitator rapping apparatus as claimed in any of the preceding claims, the kit including a rapping drop rod, a guide bearing comprising a plurality of rollers journalled in a housing of the bearing, the guide bearing embracing the rapping rod and defining a lumen through which the rod is freely movable lengthwise, and a rod lifting and releasing means.

13. Electro-precipitator equipment substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The lumen has the effect of preventing substantial movement of rod 20 in the plane of Fig. 4-in practice the said plane is horizontal. In the embodiment illustrated, the bearing 30 has two substantially parallel rollers 43 mounted on shafts 45 between spacer tubes 46 so as to be centrally disposed in the housing means 44. The said lumen which prevents horizontal displacement of rod 20 is the result of the necked shape of each roller 43. The necked peripheral profile 48 shown in the drawings is of shallow V-form, whereby there is contact between the rollers and the rod 20 at four angularly-spaced points around the periphery of the rod. The neck profile 48 need not necessarily be of V-form, but could be arcuate to match the circular cross-section of the rod. In the construction disclosed above, the rapping rods are all vertically disposed and movable. For some precipitator designs, it may be desired to incline the drop rapping rods 20 to the vertical. Then, two or more bearings 30 would be provided to support and guide the inclined rods. WHAT WE CLAIM IS

1. In an electro-precipitator, electrode rapping apparatus operable periodically to jar an electrode structure of the precipitator to dislodge particles clinging thereto, the apparatus including anvil means on the electrode structure, a rapping rod extending upwardly from the anvil means through a guide bearing, and means for lifting and thereafter releasing the rapping rod to allow it to drop onto the anvil means to jar said electrode structure, the guide bearing comprising a plurality of rollers journalled in a housing of said bearing, the guide bearing embracing the rapping rod and defining a lumen through which said rod is freely movable when lifted and dropped.