Method for making a scroll type housing for a centrifugal blower
BACKGROUND OF THE INVENTION 
     Conventional methods of construction for scroll type housings include the welding of a plurality of parts, riveting, and rolling of edge portions after assembly etc. While generally satisfactory, such methods involve the use of separate and unnecessary parts, jigs, fixtures and it is usually required that the scroll member be rolled at least to its approximate final configuration prior to attachment to the other components. 
     SUMMARY OF THE INVENTION 
     It is the general object of the present invention to provide a method for making a scroll type housing wherein all attachment means are integrally formed on the parts of the housing thus wholly eliminating separate and external attachment means and effecting savings in jigs, fixtures and other auxiliary equipment, making possible complete assembly by one operator and thus eliminating intermediate material handling, and eliminating the pre-rolling of a scroll member into an approximate final configuration. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an assembled scroll type housing constructed in accordance with the method of the present invention, a centrifugal blower being illustrated in assembled position within the housing. 
     FIG. 2 is a perspective view of a side plate of a scroll type housing to be constructed in accordance with the method of the present invention. 
     FIG. 3 is a perspective view of a discharge plate of a housing to be constructed in accordance with the present method. 
     FIG. 4 is a side view of a scroll member designed for use with the present method and illustrated in a generally flat preform condition. 
     FIG. 5 is a side view of the scroll member and discharge plate in assembled positions. 
     FIG. 6 is a sectional view of the scroll member and discharge plate and a first side plate in a position of partial assembly. 
     FIG. 7 is a sectional view similar to FIG. 6 but showing a first side plate fully assembled with the discharge plate and scroll member and a second side plate in a position of partial assembly. 
     FIG. 8 is a side view of a fully assembled scroll housing. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring particularly to FIG. 1, it will be observed that a scroll type housing illustrated therein comprises a flat discharge plate 10, a scroll member 12, and similar or identical left and right hand side plates 14, 16. A centrifugal blower disposed within the housing is or may be of conventional construction. 
     The discharge plate 10, best illustrated in FIG. 3 is constructed of sheet material in flat form, preferably of metallic construction, and takes a generally rectangular plan form as shown with a rectangular discharge opening 20 therethrough. 
     In accordance with the invention, at least one integral side plate attachment means is formed adjacent each of a first pair of opposing parallel edges 22,22 of the discharge opening 20. As shown and as presently preferred, the said integral attachment means comprises a narrow upstanding flange 24 extending along each edge 22 and at least one lug 26 spaced from the flange and projecting from the plate in the same direction as the flange. Preferably two (2) lugs 26,26 are provided as illustrated and are spaced apart along the flange. 
     A second pair of edges 28,28 in opposing relationship across the opening 20, optionally have narrow elongated offset sections 29,29 which are of shallow depth, preferably slightly in excess of the thickness of a scroll member to be described hereinbelow. 
     A scroll member 12, best illustrated in FIG. 4 is also formed of sheet material, preferably of metallic construction, and of a flexible characteristic so as to be readily bent in a gradual arcuate configuration as required for scroll formation. The width of the scroll member 12 is approximately equal to the length of the second pair of parallel opposing edges 28,28 at the discharge opening 20 and at each end of the member, an integral narrow end flange 30 is formed. The integral flanges 30,30 project generally at right angles from the scroll member and generally in the same direction. Adjacent its right hand end, as best shown in FIG. 4, the scroll member 12 also has a pre-formed cut-off section 32 which at least approximates the desired final configuration of the cut-off section of the scroll housing. 
     Integrally formed side plate attachment means on the scroll member 12 may vary as to characteristic and number but preferably at least one opening is provided adjacent each side edge of the scroll member and, more particularly, three (3) openings 34,34 are provided along each such edge. The openings 34,34 are approximately equally spaced apart along their respective edges and each opening is preferably formed by lancing a small portion in two small parallel slits so as to provide an outwardly covered opening. That is, small cover portions 36,36 are offset outwardly from the plane of the scroll member in the formation of the openings 34,34. 
     First and second or left and right hand side plates 14, 16 are formed of sheet material, preferably metallic, and each plate has a scroll-shaped periphery and a transverse linear edge 38 at its discharge end. Preferably, each side plate also has a narrow laterally extending flange 40 which terminates at said linear discharge edge. Air inlet openings such as 42 in the plates may also be flanged, single as well as double inlet blower constructions being contemplated within the scope of the invention and, further, formed in place inlet flanges or rings are within the inventive concept as well as separate after attached inlet rings. 
     In accordance with the invention each side plate is provided with at least one integral attachment means adapted to cooperate with the aforementioned scroll attachment means and at least one integral attachment means adapted to cooperate with the aforesaid discharge plate attachment means. As shown, each side plate is provided with three integral lugs spaced to cooperate with the three openings adjacent a side edge of the scroll member 12. Preferably, each lug 44 is formed integrally on a small flexible extension 46 of its adjacent flange 40. Thus, inward flexing of the lugs 44,44 is facilitated for purpose to be set forth hereinbelow. 
     In the practice of the method of the present invention, the parts are provided as hereinabove set forth. Thereafter, the scroll member 12 is gradually arcuately bent to bring the opposite ends thereof toward each other with the end flanges 30,30 facing outwardly and in opposite directions. Bending continues until the overall dimension between inner and outer edges of opposite flanges 30,30 is less than the distance between the second pair of opposing edges 28,28 of the opening 20 in the discharge plate 10. With the scroll member so held, its discharge end is entered through the discharge opening 20 with the end flanges 30,30 extending parallel with the edges 28,28 and the member is thereafter allowed to flex outwardly to position the flanges 30,30 in overlapping relationship with the discharge side of the plate 10. When the plate 10 is provided with the narrow offset portions 29,29, the flanges are entered therein so as to provide a flat surface on the discharge side of the plate 10. As will be apparent, the edges 28,28 of the opening 20 engage the scroll member 12 adjacent the flanges 30,30 and restrain the member against outward springing movement with the flanges serving to prevent withdrawal of the member from the discharge opening. Thus, a partial condition of assembly exists with the parts taking the relative positions shown in FIG. 5. 
     In a next succeeding step of assembly, a side plate such as the left hand plate 14 shown in FIG. 6 is positioned within the scroll member 12 and the linear edge 38 thereof is entered between the lugs 26,26 and the small flange 24. The side plate may be conveniently held at an angle with respect to its final right angularly related position adjacent the discharge plate and the plate may thereafter be swung about its discharge end in a pivoting action as indicated by arrow 46 in FIG. 6. The small lugs 44,44 on the plate will thus be flexed inwardly and then spring outwardly into the scroll openings 34,34 whereby to complete assembly of the side plate within the scroll and discharge plate. In FIG. 7 the assembly of a second or right hand side plate 16 is illustrated and it will be apparent that the steps in assembly are identical with those set forth above for the left hand plate 14. 
     With the two side plates finally assembled within the scroll member and discharge plate a desirably rigid construction of a high degree of structural integrity is provided. Assembly operations may be accomplished by a single operator in a wholly manual procedure. There are no jigs or fixtures required, no separate attachment means such as rivets, screws, or welding are necessary and yet an end product is achieved, simple in construction, durable and dependable in use, and capable of assembly in an easy and convenient manner and at substantial economic advantage.