GB2080152A

GB2080152A - Discharge rapping mechanisms

Info

Publication number: GB2080152A
Application number: GB8024230A
Authority: GB
Original assignee: Forth & Foyle Erection Service
Current assignee: Forth & Foyle Erection Service
Priority date: 1980-07-24
Filing date: 1980-07-24
Publication date: 1982-02-03
Also published as: GB2080152B

Abstract

Rapping mechanisms are used in electrostatic precipitators, to cause attracted particles to fall from collector plates. The rapping mechanism includes a long vertical suspension rod 10 connected to a piston and cylinder 12 actuated by a pneumatic or hydraulic source 14. One or more levers 30 are mounted on the suspension rod, each connected to a row of swingable hammers 32. When the suspension rod is raised, each lever rotates a horizontal rod 34, which lifts the hammers away from an anvil associated with a set of collector plates. As the suspension rod is lowered, the horizontal rod is rotated in reverse and the hammers are swung downwards to strike the anvil. The piston and cylinder cushions the down stroke of the suspension rod thus reducing percussion shock. <IMAGE>

Description

SPECIFICATION Discharge rapping mechanisms This invention relates to discharge rapping mechanisms.

Such mechanisms are used in electrostatic precipitators and include groups of hammers which, when operated, rap against anvils or plates and cause dust, ash or the like particles to fall from collector plates which, having been charged with electricity, attract the particles from a dust-laden gas flow. Each group of hammers is at present operated by a crank which lifts and drops a long suspension rod and this in turn operates a trip mechanism to move the hammers.

The trip mechanism is located in the gas flow passage where, because of high temperature, no lubrication is possible; thus, the operating parts are in metal-to-metal contact and, consequently, there are frequent breakdowns in the trip mechanism which, of course, is a disadvantage made more so because of the inaccessibility of the mechanism. Thus, one group of hammers may become inoperative for a long period of time, i.e. until the system can be shut down and allowed to cool.

Each group of hammers includes two vertically spaced horizontal rows, each with its own trip mechanism.

Further disadvantage of the presently known rapping mechanisms is that the crank lifts and drops the suspension rod. This rod passes through a porcelairr insulator and the percussion caused by the suspension rod dropping can often crack the insulator.

A further disadvantage is that the crank is operated by a geared drive motor and as this is usually located some distance above the ground, e.g. 120', there tends to be a lack of maintenance; also, it is difficult to change the rate at which the crank operates, i.e. to alter the rapping cycle.

It is an object of the present invention to obviate or mitigate the aforesaid disadvantages.

According to the present invention, there is provided a discharge rapping mechanism including a piston and cylinder means to vertically move an elongate suspension rod which carries a lever arm connected to a row of swingable hammers, said piston and cylinder means providing a damping effect on the downward movement of the suspension rod.

Preferably, each suspension rod carries two lever arms, each connected to a row of swingable hammers.

Preferably also, the levers are so positioned on the suspension rod that there is a slight over-ride relative to the stroke of the piston.

The piston and cylinder is preferably pneumatically operated, but may be hydraulically operated.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawing which illustrates a rapping mechanism according to the invention.

The rapping mechanism includes a long vertical suspension rod 10 the upper end of which is connected to a piston and cylinder member 1 2 actuated by a pneumatic source 14, though, alternatively, the source may be hydraulic.

Below the piston and cylinder, the rod passes through a first insulator 1 6 and then after a short gap through a second support insulator which is mounted on top of the horizontal gas flow passage 20. The remainder of the suspension rod is located in the gas passage. The support insulator has a central tube 22 through which the rod extends, and this tube also extends into the gas flow passage and is connected to the upper beam 24 of a discharge frame, i.e. a frame from which the collector plates are suspended; a similar lower frame 26 is also provided and the suspension rod extends to the lower end of the lower frame.

Two levers 30 are mounted on the suspension rod within the gas flow passages and each lever is connected to a row of swingable hammers. These hammers are adapted to swing against an anvil or plate at the lower end of each set of collector plates when the suspension rod is lifted and lowered.

Each lever comprises an arm which extends horizontally to engage a horizontal rod 34 from which the hammers 32 depend. When the suspension rod is raised, the lever rotates the horizontal rod which lifts the hammers away from the anvil. As the suspension rod is lowered, the horizontal rod is rotated in reverse and the hammers are swung downwards to strike the anvil.

Advantages of the rapping mechanism here it before described, are as follows: 1. The piston and cylinder cushions the down stroke of the suspension rod thus reducing percussion shock to the structure.

2. Trip mechanisms are eliminated and replaced by simple levers with less chance of breakdown.

3. The piston and cylinder is easily maintained and easily adjusted to alter the rapping cycle.

1. A discharge rapping mechanism, including a piston and cylinder means to vertically move an elongate suspension rod which carries a lever arm connected to a row of swingable hammers, said piston and cylinder means providing a damping effect on the downward movement of the suspension rod.

2. A mechanism as claimed in claim 1, in which each suspension rod carries two lever arms, each connected to a row of swingable hammers.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Discharge rapping mechanisms This invention relates to discharge rapping mechanisms. Such mechanisms are used in electrostatic precipitators and include groups of hammers which, when operated, rap against anvils or plates and cause dust, ash or the like particles to fall from collector plates which, having been charged with electricity, attract the particles from a dust-laden gas flow. Each group of hammers is at present operated by a crank which lifts and drops a long suspension rod and this in turn operates a trip mechanism to move the hammers. The trip mechanism is located in the gas flow passage where, because of high temperature, no lubrication is possible; thus, the operating parts are in metal-to-metal contact and, consequently, there are frequent breakdowns in the trip mechanism which, of course, is a disadvantage made more so because of the inaccessibility of the mechanism. Thus, one group of hammers may become inoperative for a long period of time, i.e. until the system can be shut down and allowed to cool. Each group of hammers includes two vertically spaced horizontal rows, each with its own trip mechanism. Further disadvantage of the presently known rapping mechanisms is that the crank lifts and drops the suspension rod. This rod passes through a porcelairr insulator and the percussion caused by the suspension rod dropping can often crack the insulator. A further disadvantage is that the crank is operated by a geared drive motor and as this is usually located some distance above the ground, e.g. 120', there tends to be a lack of maintenance; also, it is difficult to change the rate at which the crank operates, i.e. to alter the rapping cycle. It is an object of the present invention to obviate or mitigate the aforesaid disadvantages. According to the present invention, there is provided a discharge rapping mechanism including a piston and cylinder means to vertically move an elongate suspension rod which carries a lever arm connected to a row of swingable hammers, said piston and cylinder means providing a damping effect on the downward movement of the suspension rod. Preferably, each suspension rod carries two lever arms, each connected to a row of swingable hammers. Preferably also, the levers are so positioned on the suspension rod that there is a slight over-ride relative to the stroke of the piston. The piston and cylinder is preferably pneumatically operated, but may be hydraulically operated. An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawing which illustrates a rapping mechanism according to the invention. The rapping mechanism includes a long vertical suspension rod 10 the upper end of which is connected to a piston and cylinder member 1 2 actuated by a pneumatic source 14, though, alternatively, the source may be hydraulic. Below the piston and cylinder, the rod passes through a first insulator 1 6 and then after a short gap through a second support insulator which is mounted on top of the horizontal gas flow passage 20. The remainder of the suspension rod is located in the gas passage. The support insulator has a central tube 22 through which the rod extends, and this tube also extends into the gas flow passage and is connected to the upper beam 24 of a discharge frame, i.e. a frame from which the collector plates are suspended; a similar lower frame 26 is also provided and the suspension rod extends to the lower end of the lower frame. Two levers 30 are mounted on the suspension rod within the gas flow passages and each lever is connected to a row of swingable hammers. These hammers are adapted to swing against an anvil or plate at the lower end of each set of collector plates when the suspension rod is lifted and lowered. Each lever comprises an arm which extends horizontally to engage a horizontal rod 34 from which the hammers 32 depend. When the suspension rod is raised, the lever rotates the horizontal rod which lifts the hammers away from the anvil. As the suspension rod is lowered, the horizontal rod is rotated in reverse and the hammers are swung downwards to strike the anvil. Advantages of the rapping mechanism here it before described, are as follows: 1. The piston and cylinder cushions the down stroke of the suspension rod thus reducing percussion shock to the structure. 2. Trip mechanisms are eliminated and replaced by simple levers with less chance of breakdown. 3. The piston and cylinder is easily maintained and easily adjusted to alter the rapping cycle. CLAIMS

3 A mechanism as claimed in claim 2, in which the levers are so positioned on the suspension rod that there is a slight over-ride relative to the stroke of the piston.

4. A mechanism as claimed in any one of claims 1 to 3 in which the piston and cylinder is pneumatically operated.

5 A discharge rapping mechanism substantially as hereinbefore described with reference to the accompanying drawings.