GB2186508A

GB2186508A - Variable intensity rapping

Info

Publication number: GB2186508A
Application number: GB08604065A
Authority: GB
Inventors: Terence Bernard Fowle Cottrell
Original assignee: Dresser UK Ltd
Current assignee: WLTD Ltd
Priority date: 1986-02-19
Filing date: 1986-02-19
Publication date: 1987-08-19
Also published as: GB8604065D0

Abstract

A rapping mechanism for an electrostatic precipitator comprising a drop rod (10) having a collar (12), a lever rotatable about an axis (30) in a plane which intersects the collar, the lever end remote from the axis engaging the underside of the collar to lift the collar and rod during rotation of the lever, and actuating means (17) for changing the relative position of the locus (32) of the lever end and the periphery of the collar in said plane, whereby to vary the amount the rod lifts, and thus the force with which it impacts an anvil on dropping. As shown, the collar (12) is oval, and the actuating means is a lever (17) for rotating the drop rod (10) about its axis, to vary the position of the collar. Alternatively, the drive shaft for the lifting lever may be movably mounted, to change the locus of the lever end. <IMAGE>

Description

SPECIFICATION Variable intensity rapping This invention relates to the rapping mechanism used in electrostatic precipitators.

In the industrial cleaning of gases, electrostatic precipitators are widely used to remove from gases, for example flue gases from a boiler, solid particles and dustthatwould otherwise pollute the atmos where and the surrounding district. In such precipitators, the gas to be cleaned is passed through an electric field in an electrode system which results in the solid particles acquiring an electric charge and consequently being attracted to and deposited upon electrodes in the system. A build-up of dust on the electrodes quickly reduces the efficiency ofthe precipitator and it is normal practice to remove dust on the electrodes by submitting the electrode system to periodic mechanical shocks, a process known as "rapping".

Awell known rapping system involves a rod which rests on an anvil connected to the top of a number of electrodes and which extends upwardlythrough the electrode system. At its top the rod is provided with a collar which is engageable by a rotating leverwhich, engaging the collarfrom below, lifts the collar and thus the rod to the point at which the end ofthe lever clears the edge of the collar. The rod is then free to drop as a hammer and impacts upon the anvil causing mechanical shockwaves and vibration in the electrode system of sufficient intensity to dislodge dust on the electrodes, the dust falling to the bottom of the precipitator for removal. This system is ex tremelyefficientand simple but has no means of adjusting the intensity of the rapping.

It is an object of the present invention to provide a simple rapping mechanism in which the intensity of rapping is adjustable.

The present invention is a rapping mechanism for an electrostatic precipitator comprising a drop rod having a collar, a lever rotatable about an axis in a plane which intersects the collar, the lever end remote from the axis engaging the underside ofthe collarto liftthecollarand rod during rotation ofthe lever, and actuating means for changing the relative position of the locus of the lever end and the peripheryofthecollarin said plane.

Embodiments ofthe present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure lisa part sectional elevation of an embodi mentofa rapping mechanism according to the present invention; Figure2 is a sectional view on the line ll-ll of Figure 1; Figure 3 is a plan view ofthe top ofthe mechanism shown in Figure 1; Figure 4 is an elevation of a second embodiment of the present invention; and Figure 5 is an elevation of a third embodiment of the present invention.

Referring now to Figures 1 to 3, the top end of a drop rod 10 passesthrough a combined guide/ support structure 11 and is provided with an oval collar 12.

The guide/support structure 11 comprises a base plate 13, which is itself supported by means not shown, a locating ring 15 in which rests a lever boss 16 from which a control lever 17 projects, and means for securing the boss 16 in position qom prising a ring 20 bolted to the locating ring 15, the boss 16 having a portion 22 of increased diametertrapped between shoulders 23 and 24 or the locating rtng 15 andsecur- ing ring 20 respectively.

The boss 16 is loosely keyed to the drop rod 10, i.e.

the keys 26 correctly fit the keyways 27 in the boss 16 but are undersize forthe keyways 28 in the rod 10 thus allowing the rod 10to rise and fall freelywhile still constraining the rod to rotate with the boss 16. It should also be noted that the keys 26 and keyways28 are of a sufficient length to allowforthe maximum riseandfalloftherod 10.

A lifting lever rotates about a centre 30 to one side ofthe drop rod and the locus of the roller at the lever tip as it rotates clockwise is indicated at 32.

It can readily be seen that as the lifting lever rotates its rollertip engages the underside of the collar 12 and then lifts the collar, and thus the rod 10, until the roller moves out beyond the periphery of the collar 12. Atthattime the rod 10 drops until its bottom end (not illustrated) strikes the anvil. It can also be seen thattheactual amountthatthe rod lifts depends upon the distance ofthe periphery of the collar, in the plane of rotation of the lifting lever, from the axis of the rod and in this embodiment it is that distance that is variable by rotation ofthe oval cam by means of the lever 17. Clearly the cam need be rotatable through an angle of slightly more than 90 .

In Figure 1 can be seen push/pull rods 35 connecting the outer end of the lever 17 with the outer ends of one or more adjacent levers 17 for other drop rods.

In Figure 4 is illustrated an alternative embodiment in which the drop rod 40 is conventional in its mounting and construction and in particularthe collar41 at its upper end is, as is normal, circular. In this embodiment adjustment of the interaction between the collar 41 and the lever roller 42 is effected by movement ofthe drive shaft 43 for the lifting leverthus changing the locus of the roller 42 and its engagement with the collar 41.

The drive shaft 43, which runs along a line of drop rods, is supported at intervals in bearings 45 and each bearing is carried on a support 46 pivoted at one end and resting on an oval cam 47. The cam 47 is rotatable on a shaft 48 which runs parallel to the shaft 43 and carries a cam at each bearing along the length of the drive shaft 43.

Rotation of the cam shaft 48 thus adjusts between upper and lower limits the position of the support46 and thus the locus of the lever roller 42, its engage mentwith the collar 41 and hence the lift of the drop rod.

It should be noted that in this embodiment all the drop rods controlled bythe one drive shaft43Op- erate simultaneously whereas in the em bodiment of Figure 1 the drop rods along the shaftcentred at 30 can be operated, if desi red, at different times.

The embodiment of Figure5 is essentially a modification of the embodiment of Figure 4 in thatthe oval cam 47 is replaced by a linkage system. Thesup- port 46 forthe bearing 45 is supported by a pair of parallel links 50 which are connected to the support 46 via a pivot pin 51 at their top ends and, at their bottom ends, to a single link 52 via a pivot pin 53. The single iink 52 is in turn pivoted on a pin 55 mounted on a fixed support 56. Extending transversely ofthe links 50,52from the pin 51 is a pair of links 57 which, atthe end remote from the pin 51, are connected by a pin 59to a link60 rotatable bya shaft61. Rotation of the shaft 61 causes the linkage system to adjust the angle ofthe support 46 in the same way as the oval cam did in the embodiment of Figure 4.

In all the embodiments described it is desirable to prevent adjustment ofthe rapping mechanism during operation and any suitable electricai or mechanical interlock system may be provided.

Claims

1. A rapping mechanism for an electrostatic pre cipitatorcomprising a drop rod having a collar, a lever rotatable about an axis in a plane which intersects the collar, the lever end remote from the axis engaging the underside of the collar to lift the collar and rod during rotation ofthe lever, and actuating means for changing the relative position of the locus ofthe lever end and the periphery of the collar in said plane.

2. Amechanism as claimed in claim 1, in which the collar is oval and is rotatable about the axis ofthe rod.

3. A mechanism as claimed in claim 2, in which the rod is rotatable and the collar is fixed to the rod, a lever being connected with the rod to control the rotation thereof.

4. Amechanismasclaimedinclaim1,inwhich the locus ofthe lever end is changed.

5. A mechanism as claimed in claim 4, in which the lever pivots about an axis which is fixed relative to a support member, the position of the support member being adjustable.

6. A mechanism as claimed in claim 5, in which the support member is mounted on a pivot and on a cam, rotation of the cam adjusting rotation of the support member about its pivot and thereby the position ofthe lever axis and the locus of the lever end.

7. A mechanism as claimed in claim 5, in which the support member is mounted on a pivot and on a linkage, one link of said linkage being pivotable about one end to adjustthe linkage and thereby rotation of the support member about its pivot, the position ofthe lever axis and the locus ofthe lever end.

8. Arapping mechanism substantially as hereinbefore described with reference to, and as shown in,theaccompanying drawings.

9. An electrostatic precipitator having a plurality of rapping mechanisms as claimed in any preceding claim, the rapping mechanisms being interconnected to provide simultaneous operation of there- spective actuating means.