GB1593603A

GB1593603A - Intermittent drive mechanism

Info

Publication number: GB1593603A
Application number: GB34229/77A
Authority: GB
Original assignee: Serck Industries Ltd
Current assignee: Serck Industries Ltd
Priority date: 1978-05-05
Filing date: 1978-05-05
Publication date: 1981-07-22

Description

(54) INTERMITTENT DRIVE MECHANISM (71) We, SERCK INDUSTRIES LIMITED, a British Company, of Warwick Road, Birmingham, 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: This invention relates to a device for providing an intermittent drive. The invention is particularly'but not exclusively useful in providing a drive for shaking the bags of a bag filtration installation.

It is well-known to use gas filtration apparatus comprising a filtration box including a number of compartments into each of which in operation of the apparatus, dustladen air is sucked or blown through an inlet for dirty air in the lower part of the compartment for removal of dust from the air, prior to escape of the latter past an open main damper in the upper part of the compartment, by filter bags located in the compartment and comprising long stockings of textile material impervious to the dust and disposed parallel to the direction of air flow, each compartment being adapted separately to be shut off in turn from filtering duties for cleaning purposes so that filtering can proceed without any interruption or alteration in the flow of matter to be filtered, and including a scavenging damper in its upper part, and the filter bags being clamped into a spigot tube at their lower ends and attached at their upper ends to a movable hanger frame upon which bag-shaking mechanism is adapted to act. In a cleaning sequence, the main damper closes off the outlet for filtered air and hence stops normal filtering flow, and a reverse flow of clean air is introduced into the compartment past an opened scavenging damper in the upper part of the compartment so that the air flows through the filter bags in the opposite direction to the flow when dirty air is being filtered. At a variable predetermined time during this reverse flow the bags are shaken by said mechanism to facilitate removal of collected dust from the inside of the bags.

Hitherto, the cleaning cycle of such apparatus has required either a plurality of motors and controls therefore or a single motor in combination with a gearbox and a system of levers.

An o'bject of the present invention is to provide a simple and inexpensive intermittent drive which may, for example, be used in the above cleaning cycle.

In accordance with the invention there is provided an intermittent drive device comprising a lead screw, a screw-threaded nut received on the lead screw, means for rotatably driving the lead screw selectively in either direction so as to cause translational movement of the nut, a guide member extending parallel to one portion of the lead screw and arranged to engage the nut to prevent rotation thereof, the lead screw having a further portion on which the nut is not engaged by the guide member, resilient means arranged to apply a force to the nut transversely to the longitudinal axis of the lead screw when the nut is on the further portion of the lead screw, and a driven member mounted adjacent the further portion of the lead screw for rotation therewith when engaged by the nut.

The drive means may conveniently comprise a reversible electric motor driving the lead screw through a belt and pulleys.

Preferably, the nut has one or more flats on its outer periphery, and the guide member is a bar presenting a plane surface parallel to the lead screw.

The resilient means may suitably comprise a roller journalled on an axis parallel to the lead screw and one or more springs biasing the roller towards a central location intermediate the minimum and maximum radial dimensions of the nut.

The driven member preferably comprises an eccentric disc carrying on one face friction material for engagement by the nut, and a connecting rod one end of which is journalled on the periphery of the eccentric disc and the other end of which is connected to an oscillating lever system.

In another aspect, the invention provides a bag filtration apparatus including an intermittent drive device as defined above connected to shake a filter bag. Preferably, the apparatus includes a main air damper and a scavenging air damper, the arrangement being such that, as the nut traverses the lead screw towards said further portion, it sequentially closes the main air damper and opens the scavenging air damper, and vice versa.

An embodiment of the invention will now be described, by way of example, referring to the accompanying drawings in which: Figure 1 is a somewhat diagrammatic elevation partly in cross-section of a bag filtration apparatus embodying the drive of the invention; Figure 2 is a cross-section taken on the line 2-2 of Fig. 1 but in a different operational condition; Figure 3 is a detailed side elevation to an enlarged scale of part of the apparatus of Fig. 1; and Fig. 4 is an end view of the part shown in Fig. 3.

Referring to Fig. 1, the apparatus includes a housing 10 within which a filter bag 12 is suspended from a frame 14. The frame 14 is suspended by hangers 16 from shafts 18 (see also Fig. 2) which are mounted in bearings 20 for oscillatory rotation, as will be described, from time to time to shake the bag 12. The housing 10 communicates with a trunk 22 and thence selectively with a main air conduit 24 and a purge air conduit 26 under the control of respective pivotal dampers 28, 30.

In normal operation, air is drawn up wardly through the apparatus to the con duit 24, trapping dust and dirt on the exterior of the filter bag 12. It is necessary periodically to clean the filter bag 12, which requires closing the main air damper 28, opening of the scavenging air damper 30 to blow clean air from the conduit 26 in reverse flow through the apparatus, and shaking the filter bag 12.

To this end, an intermittent drive device includes a shaft 32 journalled in bearings 34. The shaft 32 is screw-threaded along most of its length to form a lead screw. A reversible electric motor 36 is drivingly connected to the shaft 32 via a belt and pulleys indicated at 38. An externally-square nut 40 is threaded on the shaft 32, and is normally restrained against rotation by a guide bar 42.

In Fig. 1, the parts are shown in the normal operating condition i.e. with the main air damper 28 open and the scavenging air damper 30 closed. (In Fig. 2 the nut 40 is shown in the opposite position).

Each damper is connected by a suitable linkage to a respective pivoted crank 44, 46 which is positioned to have one or other of its ends in the path of the nut 40. Each of the cranks 44, 46 is provided with an over-centre biasing spring (not shown) to drive it positively to either of the positions in which the respective damper is fully open or fully shut.

In use, when it is desired to clean the filter bag, the motor 36 is operated to rotate the shaft 32 in a direction to move the nut 40 from the position shown in Fig.

1 and it will be appreciated that the actuation of the motor may be controlled by an automatic timer. As the nut 40 moves to the right of Fig. 1, it engages first the crank 44 which springs over-centre to close the main air damper 28, and then the crank 46 which springs over-centre to open the scavenging air damper 30.

At the other end of the shaft 32, aii eccentric disc 48 is journalled for rotation on the snaft, and is capable of limited axial movement on the shaft. A ring 50 rigid with the shaft 32 limits movement of the disc 48 to the right. Disc-shaped pads 52 of friction material are secured to the end faces of the disc 48.

The guide bar 42 stops short of the disc 48, and in the intervening space a resiliently mounted nylon-surfaced roller 54 is provided. As seen in tigs. 3 and 4, the roller 54 is mounted on a crank member 56 pivoted to a support 58, the crank being urged towards a rest position by a pair of tension springs 60. As shown in Fig. 4, in the rest position the roller contacts the nut intermediate its maximum and minimum radial dimensions.

Thus, after the nut 40 has opened the scavening air damper 30, it continues to be driven along the shaft 32, restrained against rotation by the guide bar 42. On reaching the end of the guide bar 42, the nut 40 is contacted by the roller 54 and the tension of the springs 60 is sufficient to restrain rotation of the nut 40 and cause it to continue to be driven along the shaft 32. When the nut 40 comes into abutment with the eccentric disc 48, however, the roller oscillates to permit the nut to rotate with the shaft and thus to drive the disc 48.

Reverting to Figs. 1 and 2, the eccentric disc carries a ring 62 having a projecting arm 64. The outer end of the arm 64 is drivingly connected to the shafts 18 via cranks 66 and a connecting rod 68.

Thus, in its extreme position the nut drives the eccentric disc 48 to oscillate the shafts 18 and shake the bag 12.

After a predetermined time interval, the electric motor 36 is reversed, causing the nut 40 to transverse to the left in Fig. 1 to sequentially stop the shaking action, close the scavenging air damper, and open the main air damper.

Although in the above embodiment a single filter bag has been described for simplicity, it will be appreciated that in practicc, as is well known, a number of bags will be mounted on a single frame within a closed compartment.

It will also be appreciated that, while the preferred embodiment described utilises the drive device of the invention in a bag filter apparatus, the device may be used in other applications where an intermittent drive is desired.

WHAT WE CLAIM IS: 1. An intermittent drive device comprising a lead screw, a screw-threaded nut received on the lead screw, means for rotaably driving the lead screw selectively in either direction so as to cause translational movement of the nut, a guide member extending parallel to one portion of the lead screw and arranged to engage the nut to prevent rotation thereof, the lead screw having a further portion on which the nut is not engaged by the guide member, resilient means arranged to apply a force to the nut transversely to the longitudinal axis of the lead screw when the nut is on the further portion of the lead screw, and a driven member mounted adjacent the further portion of the lead screw for rotation therewith when engaged by the nut.

2. An intermittent drive device according to claim 1, wherein the drive means comprises a reversible electric motor driving the lead screw through a belt and pulleys.

3. An intermittent drive device according to claim 1 or claim 2, wherein the nut has one or more flats on its outer periphery, and the guide member is a bar presenting a plane surface parallel to the lead screw.

4. An intermittent drive device according to any one of claims l to 3, wherein the resilient means comprises a roller journalled on an axis parallel to the lead screw and one or more springs biasing the roller towards a rest position intermediate the minimum and maximum radial dimensions of the nut.

5. An intermittent drive device according to any preceding claim, wherein the driven member comprises an eccentric disc carrying on one face friction material for engagement by an end face of the nut, and a connecting rod one end of which is journalled on the periphery of the eccentric disc.

6. An intermittent drive device according to claim 5, wherein the other end of the connecting rod is connected to an oscillating lever system.

7. An intermittent drive device substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

8. A bag filtration apparatus including an intermittent drive device as claimed in any preceding claim connected to shake a filter bag.

9. A bag filtration apparatus according to claim 8, comprising a main air damper and a scavenging air damper, the arrangement being such that, as the nut traverses the lead screw towards said further portion, it sequentially closes the main air damper and opens the scavenging air damper, and vice versa.

10. A bag filtration apparatus substantially as hereinbefore described with reference to, and as illustrated 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 **. practicc, as is well known, a number of bags will be mounted on a single frame within a closed compartment. It will also be appreciated that, while the preferred embodiment described utilises the drive device of the invention in a bag filter apparatus, the device may be used in other applications where an intermittent drive is desired. WHAT WE CLAIM IS:

1. An intermittent drive device comprising a lead screw, a screw-threaded nut received on the lead screw, means for rotaably driving the lead screw selectively in either direction so as to cause translational movement of the nut, a guide member extending parallel to one portion of the lead screw and arranged to engage the nut to prevent rotation thereof, the lead screw having a further portion on which the nut is not engaged by the guide member, resilient means arranged to apply a force to the nut transversely to the longitudinal axis of the lead screw when the nut is on the further portion of the lead screw, and a driven member mounted adjacent the further portion of the lead screw for rotation therewith when engaged by the nut.