TECHNICAL FIELD

The present invention relates to a wall of a frame for an air filter unit having a length-direction and-a cross-direction perpendicular to the length- direction and two long sides extending essentially in the length direction and two short sides extending essentially in the cross direction, said wall comprising a handle.

BACKGROUND OF THE INVENTION

Air filter units are comprised of metal frames, preferably of galvanised steel or stainless steel, in which a filter package of fibrous material is mounted. The frame functions partly to hold the components together, partly to protect the filter package from external loads, which could be detrimental to the efficiency of the filter package. During the use of the air filter unit, the filter package gets more and more contaminated and finally the air filter unit must be substituted by a fresh one. The used air filter unit must be disposed of, preferably by incineration of the filter package. Before incineration, the filter package must be removed from the frame.

The disposal of used air filter units creates problems in several aspects. Firstly, the used air filter units must be stored before transportation to an incineration plant or the like which requires a lot of space. The space requirement can be reduced if the filter packages are dismounted from the frame, the components take less space if stored separately than in assembled condition. Furthermore, the space required by filter packages, can be reduced by compacting. It would therefore be advantageous if the walls of the frame can be made by a material that can be incinerated so that a used air filter unit can be incinerated and compacted without dismounting.

Furthermore, two opposite walls of a frame for an air filter unit comprise usually a handle to facilitate handling of the air filter unit and for example introduce and extract a filter-unit from-a-filtephousing; In order to withstand such handling without risk for damage of a filter package contained within the frame, the walls containing handles must be quite rigid.

The objective of the present invention is to facilitate a reduction of the space taken by stored, used air filter units, facilitate the disposal of used air filter units and reduce the weight of the frame of an air filter unit while still providing a sufficient rigidity of walls containing handles.

SUMMARY OF THE INVENTION

These objectives are accomplished by a wall of a frame for an air filter unit having a length direction and a cross direction perpendicular to the length direction and two long sides extending essentially in the length direction and two short sides extending essentially in the cross direction, said wall comprising a handle, characterised in that the wall is made of plastic material and comprises at least one stiffening groove.

In a preferred embodiment the at least one groove is directed in a direction forming an angle with the direction of the handle, and the handle is extended over a recess in the wall. The handle is preferably directed in the cross direction of the wall and grooves are extending from the recess towards the opposite short sides of the wall. Advantageously, the handle and the recess thereunder are disposed centrally in the wall and two grooves are extending from the recess towards each short side of the wall, said two grooves diverge from each other in a direction from the recess towards the short side of the wall. The handle is a flexible band of plastic material extending in the cross direction over a recess in the wall, the ends of the band being affixed to the wall. Advantageously, the ends of the band are slidingly affixed to the wall. -The wall is preferably made of a-polystyrene (PS) or-an acrylonitrile- butadiene-styrene (ABS).

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the enclosed figures, of which;

Fig. 1 schematically discloses a plan view from the side of a wall of a frame for an air filter unit according to a preferred embodiment of the present invention, and

Fig. 2 discloses a cross-sectional view taken along line II-II in figure 1.

DESCRIPTION OF EMBODIMENTS

Figures 1 and 2 disclose a short sidewall 1 of a frame for an air filter unit. The frame (not shown) consists of two opposite short sidewalls and two opposite long sidewalls, each short sidewall being provided with a handle 2. The frame holds and protects a filter package (not shown).

The handle 2 is affixed to the wall 1 by two rivets or buttons 3 and 4, respectively, said buttons being integral parts of wall 1. In the preferred embodiment shown in the figures, the handle consists of a strip of flexible material having slits 4,5 in the respective ends thereof. The stems of the buttons 3,4 are disposed in those slits 4,5. The slits 4,5 have a length in the length direction of the handle that is longer than the dimension of the stem of the buttons 3,4 and a width more or less corresponding to the dimension of said stems in a direction transverse to the length direction of the handle. Thereby, the ends of-the handle can be drawn towards each-other when-the middle part of the handle is lifted upwardly, i.e. in a direction perpendicular to the plane of wall 1.

In order to enable easy access to the handle 2, wall 1 is provided with a recess 7 underneath the handle. Such a recess also increases the rigidity of wall 1, which is necessary, if, as is the case for wall 1, the wall is made of plastic material. Otherwise, deformation of the wall due to the loads during handling of the air filter unit, for example lifting such a unit and introduce it into a filter housing, might damage the filter package held by the frame. The size and depth of the recess 7 should at least be such as to allow the fingers of a hand to easily pass between the bottom of the recess and the underside of the handle 2. Therefore, the depth of the recess should be at least 6 mm, preferably 8 mm. Said recess and the movability of the ends of the handle 2 allow easy access to the handle for a user.

The wall 1 is also provided with stiffening pairs of grooves 8,9 and 10,11, respectively disposed on opposite sides of the recess 7 as seen in the length direction of the wall. Each pair of grooves 8,9 and 10,11, respectively starts in the recess 7 and runs towards the nearest short side while the grooves in the respective pair of grooves diverge relative to each other. The depth of the grooves decrease gradually in a direction towards the short side of the wall 1 as is indicated by interrupted lines in figure 2. The grooves 8-11 end near the respective short side of the wall 1. The angle between the diverging grooves 8,9 and 10,11, respectively is about 50°. The wall 1 is thereby stiffened over the largest part of its length and over a large part of its width by the grooves 8- 11 and the recess 7.

The wall 1 is made of an incinerable plastic material, preferably a polystyrene -(PS)-Or an acrylonitrile-butadiene-styrene (AB S) .-However, other plastic material such as polypropylene (PP) could also be used. The wall is preferably made by vacuum forming. The handle 2 is made of ABS or other plastic material.

By the present invention a non-corrosive frame of a material that can be incinerated is produced. Such a frame facilitates reduction of the space taken by stored, used air filter units, facilitate the disposal of used air filter units and reduce the weight of the frame of an air filter unit while still providing a sufficient rigidity of walls containing handles .

The described embodiment can of course be modified within the scope of invention. The handle can of course be of another type, for example an integral part of the wall. However, the handle should preferably not extend outside the plane of the wall when an air filter unit is positioned within a filter housing. The recess can have another shape than the shape disclosed in figures 1 and 2 and the number of grooves extending on either side of the recess could be less than or more than two. All grooves provided in the wall should form an angle with the direction of the handle. If only one groove is provided on either side of the recess, this groove should be disposed in the length direction of the wall. The recess need not be disposed in the centre of the wall but can be placed nearer one of the short sides than the other. If the handle extends outside the plane of the wall the recess thereunder can be deleted. The scope of invention shall therefore only be determined by the wording of the enclosed patent claims.