GB2083158A - Rotary drum cam and follower arrangement for driving a reciprocating grate - Google Patents

Abstract

A reciprocating grate in a coal fired boiler using an underfeed stoker comprises a first set of longitudinally extending members (14) connected with an upper cam roller (46) engaging in a slot (40) of a rotary cam (38). A further set of members (16) is connected with a lower cam roller (46) in the slot (40), and the configuration of the slot (40) is such that rotation of the cam (38) effects relative reciprocating movement of the members (14, 16). A single motor (28) drives both the cam (38) and a screw conveyor (24) for removing ash. <IMAGE>

Description

SPECIFICATION Improvements in and relating to reciprocating grates for solid fuel boilers This invention is concerned with apparatus for driving and controlling a reciprocating grate, particularly such a grate in a solid fuel boiler having an underfeed stoker.

According to the present invention there is provided apparatus for driving and controlling a reciprocating grate, said apparatus comprising means for driving a rotary part which has a cam arrangement, and follower means operatively associated with the cam arrangement and connected with at least one member of the grate, the cam arrangement being such that rotation of the rotary part effects reciprocating movement of the follower means and the grate member.

Preferably the cam arrangement comprises a continuous slot in the rotary part and the follower means comprises a cam roller engaging in the slot and connected with the grate member.

According to the present invention there is also provided apparatus for driving and controlling a reciprocating grate in a solid fuel boiler having an underfeed stoker, said apparatus comprising a grate having a pluraity of longitudinal members extending substantially parallel to one another, at least one set of certain ones of the longitudinal members being interconnected for movement together, means for effecting reciprocating movement of the longitudinal members comprising a rotary part having a cam arrangement, means for driving the rotary part, and a follower connected with the or each interconnected set of longitudinal members and operatively connected with the cam arrangement, whereby rotation of the rotary part effects reciprocating movement of the longitudinal members, the or each follower being arranged such that the or each set of longitudinal members is reciprocable relative to the other set of longitudinal members.

Preferably the cam arrangement comprises a continuous slot in the rotary part and the or each follower comprises a cam roller engaging in the slot.

Preferably also conveyor means for the products remaining after combustion is arranged below the grate. The conveyor means may comprise a screw conveyor and the drive for the latter and the rotary part may comprise a single electric motor. Advantageously an output shaft of the electric motor directly drives the screw conveyor and indirectly drives the rotary part through a transmission.

The apparatus provided with cam rollers may also provided with fixed guides associated with the cam rollers whereby the latter are constrained to move in a longitudinal direction in accordance with the configuration of the cam slot. The rotary part with the cam arrangement and the or each cam follower are preferably located within a housing, through a wall of which the longitudinal members of the grate extend to be connected with the or each cam follower, a sealing arrangement being provided around the entry of the longitudinal members through said wall. The sealing arrangement may comprises a hollow structure arranged to eject air over the longitudinal members externally of the housing so as to prevent ingress to the housing of any products remaining after combustion.

Advantageously the screw conveyor is housed within a casing, the latter having an opening at the location where the products remain after combus tion have to be deposited. The flight of the conveyor may be reversed over a part of the conveyor extending between the opening and the drive input to return any products to the opening which may previously have overshot the opening.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings, in which Figure 1 is a side elevation of an apparatus according to the invention; and Figure 2 is a plan view of the apparatus of Figure 1.

The apparatus as shown in the drawings is intended for use in association with a coal fired boiler using an underfeed stoker, although it should be appreciated that different types of solid fuel may be used. Such a boiler has a retort on which the fuel is burned and the fuel is continually fed from below the retort and through the fire. Air for combustion is blown into the sides of the retort by means of a fan.

Referring to the drawings apparatus for removing the products left after combustion comprises a grate arranged to one side, and below the level of the retort, the grate comprising a plurality of longitudin ally extending members 10 arranged parallel to and iaterally spaced from one another. The members 10 are formed by a fixed member 12 at each outer side of the grate, a plurality of members 14 intercon nected at one end for movement together, and, between each pair of adjacent members 14, a further member 16, the members 16 also being intercon nected together at one end for movement together.

The members 12 to 16 are supported by a frame of the apparatus with the interconnected ends of the members 14, 16 being located within a housing 18 having an end wall 20 through which the members 14, 16 extend to define the grate.

Belowthe grate there is provided a longitudinal casing 22 within which is located a screw conveyor 24, the casing 22 being open upwardly at the location of the grate such that products remaining after combustion, for example ash, falling through the grate can be moved by the conveyor 24 to a desired external location where they can be depo sited through an opening 26. In the embodiment - described the conveyor 24 transfers the ash from belowthe grate to a location belowthehousing 18.

An electric motor 28 has its output shaft in alignment with the shaft of the conveyor 24, such that when the output shaft is coupled to the conveyor 24, the latter receives a direct drive from the motor 28. In a section 30 of the conveyor 24 between the opening 26 and the connection with the output shaft of the motor 28, the flight of the conveyor 24 is reversed such that in the event of any ash overshoot ing the opening 26, the ash is returned to the opening by the reverse flight.

The motor 28 is also used to provide the drive for reciprocating the members 14,16 of the grate. By means of suitable gearing and a transmission chain 32, drive from the output shaft of the motor 28 is transmitted to a drive shaft 34 which extends through a bearing block 36, parallel with the motor output shaft, and mounts a rotary cam 38. The cam 38 has a slot 40 around its periphery, the slot 40 being angled relative to a plane extending at 90" to the axis of the drive shaft 34 so as to have an innermost location 42 towards the end of the rotary cam 38 adjacent to the bearing block 36 and an outermost location 44 towards the free end of the cam 38. Engaging within the slot 40 are a pair of cam rollers 46, the rollers 46 being positioned in the same vertical plane so as to engage in the slot 40 from above and below the cam 38.The upper roller 46 is mounted at one end of a connection plate 48, the other end of which interconnected the members 14 of the grate, while the lower roller 46 is mounted at one end of a connection plate 50, the other end of which interconnects the members 16 of the grate.

Each of the plates 48, 50 mounts a further roller 52 on the opposite side from the roller 46, each roller 52 engaging in a respective fixed guide track 54 mounted in the housing 18, such that the roller 46 is prevented from any tendency towards lateral movement following the cam slot 40, and thus the respective connection plate 48, 50 and the grate members 14,16 are contrained for longitudinal movement.

Where the members 14, 16 extend through the wall 20, a hollow tubular structure 56 is arranged around the members 14, 16. The structure 56 is arranged to receive a supply of air and has apertures so arranged as to emit such air in a direction towards the grate so as to prevent ash for example from being able to pass through to the housing 18.

The rotary cam 38 is preferably formed from a high nickel/chrome steel to give qualities of tensile strength and is preferably flame hardened so as to provide a desirable surface hardness. The output from the motor 28 is preferably connected through a shear pin arrangement such that on the application of any excess load the pin will shear to de-couple and thus protect the motor.

In operation, the products remaining after combustion pass on to the grate formed by the members 12 to 16, where further burning of any unburnt fuel can take place. Depending on the type of fuel being fed to the boiler and the use to which the boiler is being put, the longitudinal members 14,16 are arranged to reciprocate at a desired rate over a distance defined by the spacing of the locations 42, 44 so as to take up any clinker or the like which may otherwise form and prevent ash falling through the grate on to the conveyor 24. The rate of reciprocation is adjustable within defined parameters. The reciprocating grate thus enables continuous removal of ash which can be transported to any external location.

Such an apparatus provides a much simpler control arrangement than heretofore in that a single electric motor may be used both to drive the reciprocating grate and the screw conveyor. The conversion of the rotary drive into the reciprocating movement of the grate is achieved by a much simplified arrangement and the overall apparatus is therefore less complicated and expensive to manufacture, is easier to service and repair, and is less bulky thus taking up less valuable space.

Various modifications may be made without departing from the invention. For example the grate may be defined by a different number of longitudinal members than that shown. Although preferable, it is not considered essential that some form of guide track be provided for the cam rollers, and also of course it will be appreciated that the screw conveyor can be adapted to transfer the products remaining after combustion to a location other than that shown. The above may comprise other types of motors such as an hydraulic motor, and the motor may align with the rotary cam instead of the screw conveyor. If desired a separate motor may be provided to drive each of the rotary cam and the conveyor.

Claims (15)

1. Apparatus for driving and controlling a reciprocating grate, said apparatus comprising means for driving a rotary part which has a cam arrangement, and follower means operatively associated with the cam arrangement and connected with at least one member of the grate, the cam arrangement being such that rotation of the rotary part effects reciprocating movement of the follower means and the grate member.

2. Apparatus according to claim 1, wherein the cam arrangement comprises a continuous slot in the rotary part and the follower means comprises a cam roller engaging in the slot and connected with the grate.

3. Apparatus for driving and controlling a reciprocating grate in a solid fuel boiler having an underfeed stoker, said apparatus comprising a grate having a plurality of longitudinal members extending substantially parallel to one another, at least one set of certain ones of the longitudinal members being interconnected for movement together, means for effecting reciprocating movement of the longitudinal members comprising a rotary part having a cam arrangement, means for driving the rotary part, and a follower connected with the or each interconnected set of longitudinal members and operatively connected with the cam arrangement, whereby rotation of the rotary part effects reciprocating movement of the longitudinal members, the or each follower being arranged such that the or each set of longitudinal members is reciprocable relative to the other set of longitudinal members.

4. Apparatus according to claim 3, wherein the cam arrangement comprises a continuous slot in the rotary part and the or each follower comprises a cam roller engaging in the slot.

5. Apparatus according to claim 4, wherein thes slot is angled relative to a plane extending at 90" to the axis of the rotary part.

6. Apparatus according to claim 4 or 5, including a fixed guide provided for the or each cam roller, whereby the latter is constrained to move in a longitudinal direction in accordance with the con figuration of the slot.

7. Apparatus according to any of claims 3 to 6, wherein the rotary part with the cam arrangement and the or each cam follower are preferably located within a housing, through a wall of which the longitudinal members of the grate extend to be connected with the or each cam follower, a sealing arrangement being provided around the entry of the longitudinal members through said wall.

8. Apparatus according to claim 7, wherein the sealing arrangement comprises a hollow structure arranged to eject air over the longitudinal members externally of the housing so as to prevent ingress to the housing of any products remaining after combustion.

9. Apparatus according to any of claims 3 to 8, wherein conveyor means for the products remaining after combustion is arranged below the grate.

10. Apparatus according to claim 9, wherein the conveyor means comprises a screw conveyor.

11. Apparatus according to claim 10, wherein a single electric motor is provided for driving the rotary part and the screw conveyor.

12. Apparatus according to claim 11, wherein an output shaft of the electric motor directly drives the screw conveyor and indirectly drives the rotary part through a transmission.

13. Apparatus according to any of claims 10 to 12, wherein the screw conveyor is housed within a casing, the latter having an opening at the location where the products remaining after combustion have to be deposited.

14. Apparatus according to claim 13, wherein the flight of the conveyor is reversed over a part of the conveyor extending between the opening and the drive input to return any products to the opening which may previously have overshot the opening.

15. Apparatus for driving and controlling a reciprocating grate substantially as hereinbefore described with reference to the accompanying drawings.