Abstract:
The invention relates to a cassette filter, especially a filter for fine or suspended matter from a folded package of filter material fitted in a frame. Said frame comprises profiled strips ( 1 ) of identical design and corner connectors ( 6, 7 ) that retain the end pieces ( 20, 21 ) of the profiled strips ( 1 ). The corner connectors ( 6, 7 ) are provided with end caps ( 12, 13 ) that can be superimposed pair-wise at a right angle.

Description:
DESCRIPTION  
         [0001]    Plants which have pure air spaces make high demands on the purity of the interior air. Air cleaned of dust and microorganisms is necessary in the plants in order to maintain the desired air purity. In addition to filter pads and pocket filters, cartridge filters are a common component in air filters. Cartridge filters have a folded package which is aligned perpendicularly to the flow direction and an outer frame. The folded package and the frame are sealed against one another using a sealing material. The folded packages are formed using fanfolded filter paper. In air filters for suspended matter, synthetic materials which can be processed in liquid form are exclusively used as sealing material. A nonwoven filter may also be placed into fine filters as sealing material.  
           [0002]    The outer frame lends the filter the necessary mechanical stability, protects the filter package from damage, and allows for tightly fitting the filter element into a receptacle. Wood, sheet metal, or extruded aluminum sections are used as frame material. In framing of cartridge filters using a seal made of synthetic material processed in liquid form, the four frame parts are simultaneously joined perpendicularly to one another and bonded with the folded package. The advantage of this technique is in the fact that no additional casting molds or a specific configuration of the frame parts are necessary. However, the disadvantage is that the synthetic material used for the seal is not completely liquid so that the folded package occasionally does not penetrate the synthetic material at all points, thus creating leaks.  
           [0003]    A different possibility for manufacturing the cartridge filter includes pouring a liquid casting compound into a prepared casting mold which represents one side of the frame and subsequently setting the folded package into the liquid. After curing of the casting compound, the step is repeated for the other sides of the folded package. Using this technique, the folded package always penetrates the liquid synthetic material completely, so that leaks are prevented. Since a liquid synthetic material is cast, the frame part itself must be formed as a casting mold, or additional auxiliary devices are necessary to prevent the sealing means from running. During joining, for example, additional bars are attached to the frame part as casting edges which prevent the casting compound from running. After curing of the casting compound, these auxiliary devices are again removed. Since the marketplace demands cartridge filters in almost any dimension, separate equipment is required for the production of each frame. By using wood frames or even deep-drawn or cast frame parts, the variety of models can only be satisfied very expensively since each dimension requires a separate deep-draw tool, for example.  
           [0004]    The object of the present invention is therefore to improve the manufacture of cartridge filters, their framing in particular, and to create an alternative for producing frames having different dimensions in a simple manner and which may then be assembled together with the folded package to form a cartridge filter.  
           [0005]    In a cartridge filter, a filter for fine or suspended matter or the like in particular, the object is achieved according to the present invention in that the frame is composed of profiled strips of identical design and of corner joints retaining the profiled strips at their ends, the corner joints having end caps which may be joined in pairs one on top of another. Such a frame design makes it possible to form all four frame parts as a trough, so that the folded package may be fully sealed all around using a low-viscosity liquid synthetic material. Other variants of the seal, which may be used with the same frame design, are also possible.  
           [0006]    It is possible to manufacture the profiled strips individually in predefined sizes. The preferred way of manufacturing, however, calls for the profiled strips to be made of an endless extruded section cut to length. The extruded section may be extruded plastic or also extruded aluminum. Profiled strips of a specified width, but of any length, may be manufactured in this way using one single set of tools.  
           [0007]    It is advantageous to give the profiled strips a U-shaped design, viewed in cross section, and to bend the edges of the profiled strips inward, thereby supporting the connection with the corner joints, which will be explained in greater detail in connection with the drawing. At least one guide strip aligned along the profiled strips and preferably having a T shape in cross section is attached to the bottoms of the profiled strips and connects to the groove base with the lower end of the T. These T-shaped elevations support the plug connection between the profiled strips and the corner joints. In addition, after curing of the casting compound, the T-shaped elevations intensify the adhesion to the component, thus increasing the adhesive strength between the casting part and the frame part.  
           [0008]    According to the present invention, for each frame there are two identical corner joints situated on the sides of the frame opposing each other, the corner joints being insertable into the profiled strips. Each corner joint has a U-shaped step which may be inserted in the front of the particular profiled strip to form a positive fit. In addition, the U-shaped step has a longitudinal slot which surrounds the guide strip. The corner joints additionally have end caps which can be joined in pairs one on top of another.  
           [0009]    For manufacturing the filter frame, two frame parts are initially formed, the top side and the bottom side, for example, two equally long profiled strips including two identical corner joints at their ends by inserting same into the profiled strip. In addition, the two other frame parts, the right side and the left side of the frame, are provided by two equally long profiled strips and corner joints inserted at their ends, these corner joints having end caps which may be slipped over the corner joints of the first frame parts. Thus, the top side and the bottom side of the frame are initially cast with the folded package and the right and left sides are subsequently cast and slipped onto the prefabricated folded package.  
           [0010]    The lateral outer walls of the outer end caps and the outer walls of the associated profiled strips are aligned flush to one another, so that a frame is created which has flat outer walls.  
           [0011]    No locking devices are needed for the plug connection between the corner joints and the profiled strips, since the parts may be fixedly connected to one another by clamping, so that they do not fall apart during the casting and joining steps. As soon as the casting compound is cured, it also glues the individual parts of the frame sides. 
       
    
    
     SHORT DESCRIPTION OF THE DRAWING  
       [0012]    [0012]FIG. 1 shows a profiled strip in an oblique view from the top,  
         [0013]    [0013]FIG. 2 shows an inner corner joint in an oblique view,  
         [0014]    [0014]FIG. 3 shows an outer corner joint, also in an oblique view, and  
         [0015]    [0015]FIG. 4 shows two prefabricated side parts made of profiled strips including an inner and an outer corner joint. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    The design of cartridge filters is known per se, so that only the design of the cartridge frame according to the present invention is explained on the basis of the following figures.  
         [0017]    [0017]FIG. 1 shows profiled strip  1  in a perspective side view from the top. Profiled strip  1  is a piece of an endless extruded section cut to length. It has a U-shaped design, viewed in cross section, including side walls  3  protruding upward from bottom  2 . Edges  4  of sidewalls  3  are bent inward. Guide strips  5 , which have a T shape in cross section, are attached in longitudinal direction to bottom  2  of profiled strips  1 . The lower end of the T is connected to bottom  2 .  
         [0018]    [0018]FIGS. 2 and 3 each show a corner joint  6  and  7 , corner joint  6  in FIG. 2 representing the inner corner joint, and corner joint  7  in FIG. 3 representing the outer corner joint. Corner joints  6  and  7  are manufactured in the form of cast parts, plastic injection molded parts, for example. Each corner joint  6 ,  7  has a U-shaped step  8  which may be inserted in the front of profiled strip  1 , forming a positive fit. In addition, step  8  has two longitudinal slots  9  which surround guide strips  5 . The designs of the profiled strips including guide strips  5 , sidewalls  3 , and edges  4  and the corner joints  6  and  7  are coordinated in such a way that by inserting corner joints  6  and  7  into profiled strip  1  a positive, secure connection between the same is established. The depth of slots  9  determines the depth of the insertion. In addition, corner joints  6  and  7  are laterally provided with stop faces  10  and  11  which contact sidewalls  3  of profiled strips  1 . End cap  12  of corner joint  6 , referred to as the inner corner joint, has dimensions such that end cap  13  of outer corner joint  7  may be slipped over end cap  12 . For this purpose, end cap  12  has a slightly smaller design. The dimensions of lateral outer walls  14  of outer end caps  13  are selected in such a way that they are aligned flush with outer walls  3  of associated profiled strips  1 . In a completely assembled frame, face wall  15  of outer end cap  13  completely covers face wall  16  of inner end cap  6 .  
         [0019]    [0019]FIG. 4 shows two end pieces  20  and  21  of profiled strips  1  which are provided with corner joints  6  and  7 . Corner joints  6  and  7  are inserted into end pieces  20  and  21 , respectively.