Patent GB-774842-A (GB)
Title: Slit mechanisms
IPC: G01J3/04
Filed: 1955-05-31
Abstract: 774,842. Spectrometric apparatus. FASTIE, W. G. and CROSSWHITE, H. M. May 31, 1955 [June 3, 1954], No. 15602/55. Class 97(1) A slit mechanism for spectroscopic apparatus comprises a pair of elements defining a slit and mounted on a support deflectable to move one element relative to the other in the plane of the elements to vary the width of the slit means being provided to apply a load to the support to produce a deflection thereof according to Hoote's Law so that the gap between the slit elements varies directly with the applied load. As shown in Fig. 4 the deflectable support consists of an elastic ring 182 carrying bars 22 supporting the slitdefining members 32, 33 and supported by lugs 188, 190, 192 and 194 on a frame 196. The upper and lower portions of the ring are engaged by the plungers 203 of bellows 198, 200 respectively, connected by tubes 204, 202 and a one-way joint 210 a bellows 98 operated, by a screw 105. The bellows and connecting tube are filled with a hydraulic fluid such as oil so that adjustment of the screw 105 causes one or the other of the bellows 198, 200 to operate upon the ring 182 and distort it about the lugs which are nodal points, such distortion varying the gap between the slit members 32, 33 proportionally to the pressure applied which latter therefore gives a measure of the slit width and can be indicated on a gauge 122. In a modification distortion may be effected by weights connected to cords running over pulleys and attached to the ring 182 at the points of attachment of the bars 22. Alternatively a spring may be attached to the end of a pivoted lever arm bearing at an intermediate point on the top of the ring 182. In a further modification the ring may be supported with the bars 22 extending vertically and may be distorted by hanging weights therefrom. In such modification the slit width is varied by movement of only one of the slit-defining members. Fig. 7 shows curved slits 267, 269 serving as entrance and exit slits of a monochromator comprisng a dispersing element 320. The slits are formed by jaws 266, 268 connected to elastic members 270, 272 which are deformable hydraulically by bellows 306, 308 to vary the widths of the slits simultaneously, the variation being effected in synchronism with the rotation of the element 320 by a bellows 332 operated by a cam 324 to suit the slit widths to the wavelength passing therethrough. In a modification the connecting bars 302, 304 are omitted and the slits varied independently by suitably arranged bellows. In the arrangement shown in Fig. 8 the two curved slits 458, 460 are formed between the inner surface of an elastic ring 412 and a bar 452 having circularly curved ends 448, 450 and mounted concentrically with the ring. The ring is supported by bearing surfaces 486, 487 and is distorted to vary the slit widths by pressure of a plunger 439 on the upper surface thereof the plunger being operated by a lever 432 pivoted at 434 and having a weight 444 movable therealong or a variable weight 442 hung from the end. In a modification the ring 412 is locally thickened adjacent the slits and supported asymmetricaly with respect to the plunger 439 to prevent the inner surface thereof adjacent the slits from departing from a circular section as the ring is distorted. Specification 731,943 is referred to.