Patent Application
20090049810
This invention relates to an improved filter bag and frame combination for use in a compact self-contained dust collector in light industrial use. In particular, the invention relates to the combination of a multi-pocket filter bag with a collar having an elastic hem that can easily be stretched over a frame having an outwardly-extending flange for secure attachment.
An air filtering apparatus may take a variety of forms depending upon the application for which it is intended. In industrial applications, the filtration unit typically includes a housing, sometimes referred to as a bag house, that is divided into two internal chambers: 1) a dirty air chamber and 2) a clean air chamber. The two chambers are divided by a wall, known as a tube sheet, on which some type of filter media is mounted such that contaminated air is drawn by a fan into the dirty air chamber, through the filter media and openings in the tube sheet, to the clean air chamber. The filtered air is then either exhausted to the outside atmosphere or recycled to the industrial work environment.
One popular form of filter medium is a plurality of relatively flat bag or pocket type filters positioned in a side-by-side relationship and suspended from a frame. This type of filter provides maximal surface area through which the dirty air is drawn, allowing large amounts of contaminants to be collected prior to the filter media becoming clogged. Typically, the collection bag or pockets are occasionally shaken in order to physically dislodge accumulated particulates so that they may be collected for disposal and the useful life of the filter extended between more thorough cleanings or replacement.
The principles of operation summarized above are described in U.S. Pat. No. 3,733,790, issued May 22, 1973, to Leo A. Pierce, the specification of which is incorporated by reference herein. Several evolutionary improvements have been made to that apparatus, including improvements on how the plurality of filter bags are assembled, mounted, and installed. For example, U.S. Pat. No. 4,323,376, issued Apr. 6, 1982, to Arthur P. Rosenquest discloses an improved filter bag construction in which the plurality of bags are unitarily formed, can be hung on a support frame, and lifted as a unit by means of a mechanical apparatus into sealing contact with the tube sheet. Yet another means for addressing the securement of a filter bag to a frame is shown in U.S. Pat. No. 6,740,142, issued May 25, 2004, to John M. Buettner, et.al., specifically at
Another prior art design (which will be described in greater detail below) is shown in
Each of the above-described embodiments, though improvements in their own right over the original design, remain difficult for an untrained or unskilled person to properly assemble and position without engaging in many frustrating attempts. Units in which this type of filter assembly are used may be found in service in light duty situations, such as dust collection for a high school or vocational school shop. In such installations, it is often the building custodian, rather than a specially trained technician, who is responsible for routine maintenance and replacement of filter bag units. A simple, reliable and low cost solution for inserting and attaching the multi-pocket filter bag to the frame and insertion into position against the tube sheet is needed.
The present invention provides an improved dust filtration unit of the type characterized by a filter bag having a plurality of pockets conjoined to a unitary opening with the opening having a collar that extends circumferentially around the opening and a frame for supporting individual pockets and circumferentially supporting the opening. The improvements comprise the frame having a circumferentially flange outwardly extending from the frame to define a perimeter. The filter bag includes an elastic or drawstring hem at the outer edge of the collar such that, when the bag is inserted within the frame, the hem edge of the collar may be stretched over the flange for secure supporting attachment thereto.
The outwardly extending flange provides a widened face against which the collar can be engaged against an elastomeric gasket when installed in the filtration unit. The frame may include substantially vertical sidewall portions having an upper or other edge from which the circumferentially flange outwardly extends.
According to another aspect of the invention, it includes a method of assembling a filter bag onto a support frame comprising the steps of providing a filter bag having a plurality of pockets conjoined to a unitary opening. The opening has a collar that extends circumferentially around the opening and includes an elastic or drawstring hem at an outer edge of the collar. A frame is provided having a circumferential flange outwardly extending from an edge of the frame to define a perimeter. The bag is inserted into the frame and the elastic or drawstring hem edge of the collar is stretched over the flange and drawn tight for supporting attachment thereto.
Like reference numerals are used to denote like parts throughout various figures of the drawing, wherein:
Referring to the various figures of the drawing, and first to
The filtration apparatus 10 may also include a vibrating mechanism 30 of well known construction which, when the dust collecting apparatus is not operating, mechanically dislodges heavy accumulations of particulate contaminates (dust) from the filter media 26. After being shaken off the filter media 26, the particulate contaminants fall by gravity into a collection chute 32 and further into a collection bin 34, which may be emptied as required.
Referring now to
In the prior art design, the collar portion 48 of the bag 36 is folded over the upwardly directed sidewall 42 of the frame 40 (see
Referring in particular to
The present invention provides a simple and low cost solution to this problem. Referring now to
In practice, the rigid spacers 138 are inserted into the pockets of the bag 136 and inserted into the frame 140 in the ordinary way. However, the collar portion 148 of the bag 136 is simply fitted over the outwardly directed flange 156 by stretching the elastic or securing the drawstring hem 158. The bag 136 and collar 148 are now securely held in place without the need for a retainer ring (shown at 50 in
The outwardly extending flange 158 can take any suitable form or be of any width sufficient to cause the collar 148 of the bag 136 to remain secure on the frame 140. Many other variations may be made to the illustrated and described embodiment without departing from the spirit and scope of the invention.
