FILTER CLEANING DEVICE

Abstract: The present invention relates to a filter cleaning device, preferably for the cleaning of gases, such as welding fumes. To provide a filter cleaning device which efficiently cleans the filter without need for dismounting it, the filter cleaning device comprises at least one rotary filter (10) with outwardly directed projections (17), and at least one impending means (12) which upon rotation of the filter (10) causes the projections (17) to give way and permits them to revert, whereby a shaking movement is imparted to the projections (17) to make them shake off the impurities adhering to them and toss the impurities aside by the action of the rotation of the filter (10).

Description: The present invention relates to a filter device for cleaning gases, comprising a filter container having a gas inlet, a filter cartridge and an outlet for impurities, whereby the contaminated gas is brought to flow through a filter body in the filter cartridge having outwardly directed pleat-like projections such that impurities sit on the outside of said filter body while the gas flows into an inner space in the filter cartridge and out therefrom through an outlet, and whereby mounting means are provided for a relative rotation between the cartridge and a mechanical impeding device, so as to impart to the pleat-like projections of the filter body a shaking movement for shaking loose impurities adhering thereto. Filter devices of the above type are already known from e.g. US-A-3 898 414. This publication illustrates a filter cartridge which is fixed and thus, is unable to remove impurities shaken loose. This results in a poor cleaning effect. Furthermore, in the prior art filter device of US-A-3 898 414, the filter body is provided standing upright. A drawback with upright filter bodies is that it is difficult to exchange the filter cartridge and that the device gets a great total height which is sometimes unacceptable. The object of the present invention is to provide a relatively low filter device with improved cleaning effect, wherein the filter cartridge can be mounted from the side and wherein the filter cartridge is protected from damages caused by hot and/or sharp objects that are suck into the filter device through a gas inlet provided on top of the filter cartridge. This is arrived at according to the invention substantially by the filter cartridge of the abovementioned filter device being amounted for rotation in relation to the fixed impeding device and being disposed in the filter container under the gas inlet, a baffle being further provided between the gas inlet and the filter cartridge. While the filter cartridge is rotatably mounted relative to the fixed impeding device, it is capable of throwing away impurities shaken loose by means of centrifugal force. This results in a substantially improved cleaning effect. By disposing the filter cartridge as defined, said filter device gets a low height and the filter cartridge is easy to mount and demount from the side. Finally, by using a baffle between the gas inlet and the filter cartridge, the gas inlet may be provided centrally on the upper side of the filter device without hot and/or sharp objects flowing therethrough into said filter device damaging the filter material in the filter cartridge. The invention will be more fully described below with reference to the accompanying drawings, in which: Figure 1 is an exploded view of a filter container comprising a filter cleaning device according to the invention; Figure 2 is a side view and part section of the filter container in Figure 1; Figure 3 is a section of part of a filter in the filter container and of impeding means cooperating therewith; Figure 4 is a section of a part of another filter; and Figure 5 diagrammatically illustrates a rotation control apparatus for controlling the rotation of the filter. The filter device 1 illustrated in the drawings is adapted for the filtration of contaminated welding fumes or other contaminated gases, preferably those occuring in places of work. The filter device 1 comprises a filter container 2 which is composed of a plurality of parts which can be mounted together, viz. a filter casing 3 having a gas inlet 4; two end walls 5 and 6 which can be screwed to the filter casing 3; a fan housing 8a to be disposed on one end wall 6 having a suction fan 8 and a gas outlet 9 for the discharge of cleaned gas; a filter cartridge 10 removably mounted in the filter casing 3 for rotation in the end walls 5 and 6; an electric motor 7 disposed on one end wall 6 to rotate the filter cartridge 10; impeding means 12 comprised in the filter casing 3 and cooperating with the filter cartridge 10; a baffle 13 disposed between the gas inlet 4 and the filter cartridge 10 to prevent sparks and other incoming hot particles from impinging on the filter cartridge 10; and finally a collection assembly 14 connected to the filter casing 3 for collection of impurities from the filter cartridge 10. The filter cartridge 10 consists of a filter body 15 in the form of a pleated cylinder of a suitable filter material 16, for instance about 0,7 mm thick filter paper. The filter body 15 is pleated in such a way that the filter material 16 will form outwardly directed projections 17. The filter body 15 is provided with an end wall face 18d having an axially extending tubular outlet socket 19 and a gear 20. The other side of the filter body 15 is provided with an end wall face 21 having a hole 22 for a pin 24 on a cover 25 which is adapted to be applied to the outer side of the end wall 5 and to close the opening 5a of the end wall 5 for the filter cartridge 10. The end wall 6 has an outwardly directed collar 26 and the electric motor 7 has a drive gear 27 which is situated inside the end wall 6. The impeding means 12 comprises a profile bar 28 which at the bottom of the filter casing 3 extends between the end walls 5, 6 and is retained by them. A longitudinal strip 30 of elastic material is engaged in a longitudinally extending recess 29 in the profile bar 28. Three or more tabs 31 are arranged on said strip 30 to extend a distance in between the projections 17 of the filter cartridge 10 when the latter is mounted in position in the filter casing 3. For the mounting of the filter cartridge 10 in the filter casing 3 said cartridge is passed through the opening 5a of the end wall 5 and fully introduced into the filter casing 3, the tubular outlet socket 19 of the cartridge penetrating into the outwardly directed collar 26 of the end wall 6. As a result, the filter cartridge 10 will be rotatably mounted in the collar 26 via the tubular outlet socket 19. Moreover, the gear 20 of the filter cartridge will get into driving engagement with the drive gear 27 of the electric motor 7, and the tabs 31 of the impeding means 12 will each be positioned in a gap between the projections 17. Besides, the other end wall face 21 of the filter cartridge 10 will bear with its outer egde against the egde portions of the openings 5a so that the filter cartridge 10 can rotate also in relation to the end wall face 21. With this design the suction fan 8 will suck contaminated gas via the gas inlet 4 into the inner space 32 of the filter casing 3 and through the filter body 15 to which the impurities will adhere. The gas thus cleaned will flow via a space 33 in the filter body 15, the tubular outlet socket 19 and the suction fan 8 to the gas outlet 9 and via said outlet out of the filter device 1. Cleaning of the filter cartridge 10 takes place in that the electric motor 7 is started and the filter cartridge 10 is rotated by said motor in relation to the impeding means 12. At this rotation each pleat-like projection 17 of the filter body 15 will abut against the tabs 31 which force the projections 17 to give way (see Figure 4). When being deflected the projections 17 will bend somewhat and while the filter material 16 possesses elastic properities, the projections 17 will flex back in a whiplash manner when they revert after having passed the tabs 31. Subjected to such a whiplash effect the projections 17 will shake off impurities collecting on the outside of the filter material 16. The size of the whiplash effect is dependent upon the type of the filter material 16 and upon the distance over which the tabs 31 protrude in between the projections 17, and can be varied by using a filter material 16 of another type and/or by shifting the tabs 31 so as to change their degree of protrusion. Once each projection 17 has passed the tabs 31 a sufficient number of times they will have shaken off impurities to such an extent that the filter material is entirely free from impurities or substantially entirely free from impurities. By designing the strip 30 and the tabs 31 (the tabs 31 consists preferably of plastic material which has been riveted to the strip 30) with a predetermined rigidity in relation to the filter material 16, it is possible to attain the requisite shaking action without undesired heavy wear of the filter material 16. The impurities shaken loose are tossed off the filter cartridge 10 as they are subjected to centrifugal force by the rotation of the filter cartridge 10 and are thus prevented from re-contaminating the filter material. If desired, the outer portions of the projections 17, which cooperate with the tabs 31, can be provided with a coating 34 of wear- resistant material. This will increase the rigidity of the impeding means 12 and thus the whiplash effect so that the filter material 16 is not worn to an undesired extent. The impurities shaken loose fall down into a hopper-shaped portion 35 of the collection assembly 14. Said hopper-shaped portion 35 has a downwardly directed connection 36 joining the hopper-shaped portion 35 to a collection receptacle 37 for collection of the impurities. In the connection 36 there is provided a valve seat 38, and on the profile bar 28 of the impending means there is suspended a valve member 39 via a spring 40. The weight of said valve member 39 and the spring force of the spring 40 are so selected that the pressure (pressure below atmospheric) generated in the space 32 when the suction fan 8 is operating, causes the valve member 39 to rise and engage the valve seat 38 to close the connection 36. When the connection 36 is closed gas (air) is prevented from flowing via an opening 41 in the collection receptacle 37 into the space 32. When the suction fan 8 stops or when the pressure below atmospheric in the space 32 diminishes because the filter cartridge 10 is clogged by impurities, the action of the pressure below atmospheric on the valve member 39 will cease or diminish so that the valve member 39 sinks, thus leaving the valve seat 38 and opening the connection 36, whereby impurities can fall down into the collection receptacle 37 through said connection 36. In Figure 2 the valve member 39 is shown in closed position (position A) by full lines and in open position (position B) by dash and dot lines. The valve member 39 of the valve mechanism 38, 39 may be adapted to cooperate with a control apparatus 42 for controlling the rotation of the filter cartridge and/or the operation of the suction fan an/or the position of a damper (not shown, which is intended to control the air flow to, inside or from the filtration device) in dependence upon the pressure in the space 32. The control apparatur 42 comprises a switch mechanism 43 which registers the supply of current from a current source 44 either to the electric motor 7 for rotation of the filter cartridge 10 or to a drive 45 for driving the suction fan 8 and/or a damper. The switch mechanism 43 of the control apparatus 42 comprises a relay 46 keeping a contact means 47 in a position (shown by full lines) in which the current source 44 is connected to the drive 45. If the pressure below atmospheric in the space 32 changes so that it is no longer capable of retaining the valve member 39 in position A (because the suction fan 8 is stopped and/or the damper is shut or the filter cartridge 10 is clogged by impurities to certain extent), the valve member 29 sinks to position B thereby actuating a contact means 48 (shown by broken lines in Figure 5) which cooperates with the relay 46 and causes it to shift the contact means 47 to a position (shown by dash and dot lines) in which the operation of the drive 45 is interrupted and the current source 44 is switched to the electric motor 7 instead so that the rotation of the filter cartridge 10, i.e. the cleaning function, is started. When the pressure below atmospheric in the space 32 again changes, because the filter cartridge 10 has been cleaned or for other reasons, to such an extent that the valve member 39 again changes position, the contact means 47 also changes position, whereby the rotation of the filter cartridge 10 is stopped and the drive 45 is started. The control apparatus 42 can be actuated by the pressure in the space 32 in another manner than via a valve mechanism 38, 39. Thus, a pressure sensing means 49 may be arranged in the space 32 for the filter cartridge 10 and another proper pressure sensing means 50 in the space 33 within the filter cartridge 10. With the aid of these pressure sensing means 49, 50 the pressure difference over the filter cartridge 10 can be sensed and when said pressure difference exceeds a certain value - because the filter body reaches an undesired clogging level of impurities - the switch mechanism 43 is actuated so as to cause the contact means 47 to interrupt the operation of the drive 45 and start the operation of the electric motor 7, i.e. the rotation of the filter cartridge 10. When the pressure difference over the filter body 15 again sinks to a lower value - because the filter body 15 has been cleaned from impurities to a sufficient extent - the switch mechanism 43 is caused to reset the contact means 47 for interrupting the operation of the electric motor 7, i.e. the rotation of the filter cartridge 10, and for starting the operation of the drive 45. The control apparatus 42 also comprises a timer 51 which allows timing of the electric motor 7 and the drive 45. The timer 51 cooperates with the relay 46 in such manner that said relay for instance interrupts the operation of the drive 45 (the suction fan 8 and/or the damper) via the contact means at a given time and starts the operation of the electric motor 7 (start of the rotation of the filter cartridge). The timer 51 can control the relay 46 such that it maintains this position of the contact means 47 for a given time, whereupon said relay switches the contact means 47 to the initial position. Alternatively, the timer 51 can control the relay 46 such that it performs the latter switching of the contact means 47 at a given time. With the aid of this timer the rotation of the filter cartridge, i.e. the cleaning of the filter, can be started after the filtration work of the filtration device and proceed as long as no filtration is going on. Thus, cleaning can take place automatically during predetermined breaks on a workday and immediately after the workday. Due to the functions of the control apparatus 42 the filtration stops and the cleaning starts automatically when the filter need to be cleaned because a certain clogging level is exceeded and/or because frequent cleaning operations are desired when the filtration function is not exploited on account of breaks in the work with the filter or after work with the filter. The filter device 1 illustrated in the drawings also comprises a safety device in the form of a fire damper 52 which is adapted to close the tubular outlet socket 19 in dependence on the temperature in the space 32 and/or the space 33. The fire damper 52 is mounted in the end wall face 18 of the filter cartridge 10 and consists of damper disks 53 and 54 which are held in a folded-together position (shown by full lines in Figure 2) by release means 55, e.g. a heat-sensitive wire. The damper disks 53, 54 are moved apart by the action of a coil spring 56. If the temperature in any of or both spaces 32, 33 rises above a predetermined limit, for instance because of a fire in the filter material or said material begins to glow, the release means 55 melts and the damper disks 53, 54 are urged apart by the coil spring 56 so as to obstruct the entrance to the tubular outlet socket 19 (see the positions of the damper disks indicated by dash and dot lines in Figure 2). As a consequence, the fire cannot spread through the outlet of the filter device 1, which might otherwise be the case because of the fanning action of the suction fan. The present invention is not restricted to the embodiment described above and illustrated in the drawings. Thus, the filter cleaning device can be used in connection with filter devices other than filters for filtration of welding fumes. The number of filters to be cleaned may also vary. If use is made of a filter cartridge of the illustrated type the end wall face 18 with its gear 20 (or merely the gear 20) may be removably mounted on the filter body 15 such that the gear 20 and eventually the end wall face 18 can be loosened from a spent filter body 15 and reused by application to a fresh filter body 15. The end wall face 21 may also be removable for the same reason. The filter body 15 may be pleated altogether to form the projections 17 as shown in Figure 3, or the filter body can comprise inner parts from which the projections extend. The fixed impeding device 12 is preferably positioned between the filter cartridge and the collection assembly 14 in order that the filter cartridge shall discharge its impurities at the bottom and that said particles shall be tossed away downwardly towards the collection assembly 14, which implies a reduced risk of the filter cartridge 10 being re-contaminated. The design of the impeding means 12 may vary depending int. al. on the type of filter with which it is used and it may have one or more tabs 31 and/or several units arranged at various points around the filter. Besides, the impeding means 12 may comprise units which are mounted for rotation about the filter or are movable in another manner. The parts 31 of the impending means 12 each penetrate between two projections 17 at a time, but there may be parts that penetrate between two successive projections 17. The rotation of the filter may in a simple equipment be brought about manually instead of by means of an electric motor, and a smoke exhausting or other gas exhausting device (not shown) may be connected to the filter device. The control system may be otherwise designed and possess further functions and the rotary speed of the filter may be variable and/or adjustable to sundry types of filters and/or impending means.

Claims: A filter device for cleaning gases, comprising a filter container (2) having a gas inlet (4), a filter cartridge (10) and an outlet (35) for impurities, whereby the contaminated gas is brought to flow through a filter body (15) in the filter cartridge (10) having outwardly directed pleat-like projections (17) such that impurities sit on the outside of said filter body (15) while the gas flows into an inner space (33) in the filter cartridge (10) and out therefrom through an outlet (9), and whereby mounting means are provided for a relative rotation between the cartridge and a mechanical impeding device (12), so as to impart to the pleat-like projections (17) of the filter body (15) a shaking movement for shaking loose impurities adhering thereto, characterized in that the filter cartridge (10) is mounted for rotation in relation to the fixed impeding device (12) and is disposed in the filter container (2) under the gas inlet (4) and that a baffle (13) is provided between the gas inlet (4) and the filter cartridge (10). A filter device as claimed in claim 1, characterized in that the fixed impeding device (12) is disposed beneath the filter cartridge (10). A filter device as claimed in claim 1 or 2, characterized in that an outlet of the filter cartridge (10) is defined by an outlet socket (19) through which one end wall (18) of said filter cartridge (10) is rotatably mounted in the filter container (2) and that a gear (20) is provided on the filter cartridge (10), which gear, when the outlet socket (19) is in its rotatable position in the filter container (2), is in operating engagement with a gear (27) in a device (7) for rotating the filter cartridge (10). A filter device as claimed in claim 3, characterized in that the outlet socket (19) and the gear (20) are provided on the same end wall (18) of the filter cartridge (10). A filter device as claimed in one of the preceding claims, characterized in that the filter cartridge (10) and the fixed impeding device (12) are operable for cleaning the filter cartridge (10) only when the flow of gas through the filter body (15) is interrupted. A filter device as claimed in claim 5, characterized in that a control apparatus (42) starts the cleaning function by rotating the filter cartridge (10) relative to the fixed impeding device (12), and by deactivating a fan (8) for feeding gas through the filter cartridge (10) and/or closing a throttle for preventing gas flow. A filter device as claimed in claim 6, characterized in that the control apparatus (42) rotates the filter cartridge (10) and deactivates the fan (8) and/or closes the throttle in dependence on variations in the difference between the gas pressure in a space (32) outside and a space (33) inside the filter cartridge (10).

Inventors: NEDERMAN, BILL PETER PHILIP
Applicants: AB PH. NEDERMAN & CO.
Application year: 1985
Main classification: B01D46
IPC codes: B01D46