Patent GB-698074-A (GB)
Title: Variable filter screens
IPC: G02B5/24
Filed: 1949-06-07
Abstract: 698,074. Variable filter screens. APARICIO, L. R. June 26, 1950 [June 7, 1949], No. 15087/49. Addition to 610,074. Class 97 (i). The deformable closed reservoir of the variable filter screen described in the parent Specification is collapsed by operating mechanical means (1) to bend a resilient strip bearing against the middle of a pressure bar engaging the reservoir throughout its length, or (2) to force against the reservoir a pressure frame having the same outline as the reservoir. Helical springs or a resilient metal casing may be provided to urge the transparent members of the screen towards one another. The reservoir may be subjected to a continuous resilient pressure in which case manually operable means are provided to vary the separation of the members. The screen shown in Figs. 1 and 4 comprises transparent members 20, 21 surrounding which is a reservoir 22 of flexible material having an enlarged portion 23 normally containing sufficient fluid to provide between the members 20, 21 a filter layer of any desired thickness when the reservoir is collapsed. A rigid pressure bar 36 engages the portion 23 and is operated to collapse the reservoir when a spring steel strip 37 bearing against the bar and fixed at one end by a clamp 38 is bent by rotating a screw 42. When the pressure on the reservoir is released, the transparent members return towards one another under the action of spring clamps 50 and helical springs 51, the tension of which is adjustable. In another form, the transparent member 121, Fig. 8, has attached thereto a rigid frame 128 having wedge surfaces 129, 130 engaged by similar wedge surfaces on a member 131 that is guided for horizontal movement at 132. Such movement is effected by a lever 134 which is fulcrumed at 137 and has a ball-andsocket connection with member 131. The wedge surfaces are so arranged that movement of member 131 in one direction causes the transparent members 120, 121 to move towards one another and thereby force fluid into a reservoir 123 which is acted upon continuously by spring- urged bars 126, which return movement of member 131 allows the members 120, 121 to separate and fluid to flow therebetween. In Fig. 5 (not shown), is illustrated a screen having a reservoir of resilient material which is collapsed by a screw-operated pressure frame 78 acting against helical springs urging the transparent members towards one another. Another form is described, Fig. 9 (not shown), wherein the reservoir is flexible and is encircled by an elastic band and the separation of the transparent members is controlled by a rotatable ring having pins thereon simultaneously engaging a rigid cam surface and one surface of the member 121 or a helical slot in a part attached to one member and a longitudinal slot in a part attached to the other member. The reservoir in a further form is of resilient material and the two members have attached thereto parts which are in screw-threaded engagement, Fig. 11 (not shown). The reservoir may be surrounded by a spring-metal casing. One or both of the transparent members may be provided with a reflection-reducing coating.