US3717401A

US3717401A - Adjustable width-slit mechanism

Info

Publication number: US3717401A
Application number: US00081405A
Authority: US
Inventors: R Powell
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1969-10-23
Filing date: 1970-10-16
Publication date: 1973-02-20
Anticipated expiration: 1990-02-20
Also published as: GB1327394A

Abstract

Two members having parallel edges defining a slit between them are each mounted on a pair of equal-length parallel flat springs extending away from the edges with their flat faces normal to the plane of the slit so that the edges move in that plane as the springs deflect. The slit width is adjusted by effecting such movement. For this purpose two flexible connections made of springy material are rigidly attached at one end to each member and have their other ends connected to a common adjustment member whose movement is colinear with the connections. The flexible connections may be flat strips rigidly connected to the adjustment member, or preferably wires having a common loop which loosely engages the adjustment member, the loop being springloaded against the latter by a spring connected between each slit-defining member and the fixed plate on which they are mounted.

Description

United States Patent 1191 Powell 1451 Feb. 20, 1973 s41 ADJUSTABLE WIDTH-SLIT OTHER PUBLICATIONS MECHANISM Strong, J, Rev. Sci. lnst., v. 120, Apr., 1941, pp [75] Inventor: Royal Edward Powell, Newbury, En- 213-214.

gland [73] Assignee: United Kingdom Atomic Energy j i 'F 7 T Auflmmy London England ssistam xammervans Attorney--Larson, Taylor & Hinds [22] Filed: Oct. 16, 1970 211 Appl. 196.; 81,405 {57] ABSTRACT Two members having parallel edges defining a slit between them are each mounted on a pair of equal- [30] Foreign Application Priority Dam length parallel flat springs extending away from the Oct. 23, 1969 Great Britain ..5i,9l9/69 edges with their flat faces normal to the plane of the slit so that the edges move in that plane as the springs [52] 11.8. CI. ..350/27l d flect. Th slit width is adjusted by effecting such [51] Int. Cl ..G01j 3/04 mo e e For thi purpose t o flexible connections [58] Field of Search ..350/266, 271, 272 made o p gy al are r gidly attached at o e end to each member and have their other ends con- [56] Referu cit d nected to a common adjustment member whose movement is colinear with the connections. The flexible UNITED STATES PATENTS connections may be flat strips rigidly connected to the 3,394,977 7/1968 sun ..350/271 adjustment 'l p'efe'ably wiles s 2,408,512 10/1946 Gradisar ..3so/271 P Whlch y engages the adiuslmem 3,242,796 3/1966 Strickler .3so/271x ber, the loop being Spring-loaded against the 3,462,227 8/1969 Tipotsch 350/271 X latter by a spring connected between each slit-defining 2,795,170 6/1957 Hansen etal ..350l27l member and the fixed plate on which they are 2,796,804 6Il957 Franke ..350/27l mounted, 3,393,959 7/1968 Van Den Brock ..350/27l 3,410,189 11/1968 Spokowski ..350/271 X 6 Claims, 4 Drawing Figures 1 ,2 l I l PATENTED 3. 7 l 7. 401

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A LEE A? BACKGROUND OF THE INVENTION This invention relates to slit mechanisms of adjustable width. It has one application in mass spectrometers and may also be used in other particle or optical apparatus. In a mass spectrometer it can be used to provide the source and collector beam-defining slits.

Existing adjustable slip mechanisms which use, for example, a wedge action to control the separation between two members defining the slit between them, tend to be expensive, and may have disadvantages in use due to stiction between parts in rubbing contact, particularly in baked apparatus. The present invention provides an adjustable slit mechanism which is relatively inexpensive to produce and which has no parts in rubbing contact.

SUMMARY OF THE INVENTION According to the present invention an adjustable slit mechanism comprises two members having parallel edges defining said slit between them, each member being mounted on a pair of equal-length parallel flat springs extending away from said edges with their flat faces normal to the plane of the slit so that said edges move in the plane of the slit as the springs deflect, and a flexible connection made of springy material and rigidly attached to each member for effecting said movement in order to adjust the width of the slit.

The flexible connections may extend from said members in a direction substantially parallel to the slit, and may be substantially colinear therewith. They may be rigidly connected to a common adjustment member arranged to move in a direction substantially colinear with the connections. The flexible connections may be flat strips having their flat faces normal to the plane of the slit.

Alternatively the flexible connections may loosely engage a common adjustment member arranged to be movable in a direction substantially colinear with the connections, spring-loading means being provided to apply to each of said two members a force which acts in said direction away from said adjustment member and in use loads said connections against said adjustment member. Such flexible connections may,l:e wires and include a common loop which loosely engages said adjustment member. A said spring-loading means may be connected between each of said two members and a fixed member to which said pairs of flat mounting springs are secured. The spring-loading means may be arranged to apply to each of said two members a force acting in a direction to close the slit.

To enable the nature of the present invention to be more readily understood, attention is directed, by way of example, to the accompanying drawings, wherein DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view, partially in section, of an embodiment of the invention forming the collector beamdefining slit of a mass spectrometer.

FIG. 2 is a view in the direction II-II of FIG. 1.

FIG. 3 is a view, similar to FIG. 1, of another embodiment of the invention.

FIG. 4 is a view in the direction IV-IV of FIG. 3.

DESCRIPTION OF EMBODIMENTS Referring to these drawings, a circular plate 1 having a rectangular aperture 2 is mounted within the evacuated volume of a mass spectrometer, an outer wall of which is indicated at 3. Located over the aperture 2 are a pair of rigid flat members 4, 5 whose adjacent edges define a slit 6 lying, in FIG. 1, in the plane of the paper. The members 4, 5 have upturned ends which are spotwelded to pairs of parallel flat springs 7, 7' and 8, 8'. The faces of these springs are normal to the plane of the drawing and of the slit.

The ends of the springs remote from members 4 and 5 are spot-welded to supports 9 and 10 which are similar in shape to members 4 and 5 and which are secured to plate 1 by screws 1 l.

To one end of members 4 and 5 are rigidly attached flexible strips of

spring material

12 and 13 respectively. These strips are spot-welded to rigid angle pieces 14, the springs 7' and 8' being sandwiched between the angle pieces 14 and the upturned ends of the members. The other spot-welded attachment portions of the springs are similarly sandwiched between member or support and a further piece of rigid metal, as shown for example at 15; this arrangement defines more accurately the line of attachment of the flexible springs to the relatively rigid member or support.

The

strips

12 and 13 enter a slot in a rod 16 which forms an adjustment member, and are secured thereto by a bolt 17. The rod 16 can be moved axially by tuming a knob 18 having a calibrated scale 19 which rotates relative to a fixed scale 20. The illustrated mechanism for efl'ecting this movement will be familiar to those skilled in the mass spectrometer art, but briefly the rod 16 is spring-loaded against the inside of knob 18 by a spring 21 which bears at one end on a bush 22 and at the other on a knurled nut 23 threaded on to the rod. The bush 22 is located in a member 24 which is mounted on the wall 3 in a vacuum-tight manner, and from which extends a vacuum-tight metal bellows 25 fastened to a disc 26 on the rod 16.

In operation rotation of knob 18 produces axial movement of rod 16. Assuming rod 16 is moved rightwards in FIG. 1, the effect is to impart a corresponding movement to members 4 and 5. As they move rightwards the width of the slit between their edges increases, but because

springs

7, 7' and 8, 8 are of equal length the edges remain parallel to each other. The slit width is found to vary approximately as the square of the axial displacement of rod 16. Normally a calibration chart of scale reading against slit width is used to set the width.

In a known manner the adjacent edges of members 4 and 5 may be chamfered to a reduced thickness, eg to 0.005 inch or less, to define the slit, or sharp-edged metal pieces, eg portions of razor blades, may be spotwelded or otherwise secured thereto to provide such edges.

The slit can be set up by securing one of the supports 9, l0 tightly to the plate 1, and bringing the two edges together. The screws securing the other support to the plate are then tightened.

To ensure that the beam can be cut ofi completely, the sharp-edged portions may be attached to opposite surfaces of each of the members 4 and 5, so that, in a known manner, the edges overlap instead of contacting when brought together.

The dimensions and materials are not critical, but by way of example plate 1 in FIG. 1 is approximately 1.5 inches in diameter and the portion of the drawing to the left of bolt 17 is approximately to scale. The members 4 and 5 and supports 9 and 10 are of 0.015 inch stainless steel; the springs 7, 7', 8, 8' and connections l2, 13 of 0.005 inch stainless steel and 0.125 inch wide. The springs and connections may be made of an alloy such as Nimonic 90 to meet baking conditions.

DESCRIPTION OF PREFERRED EMBODIMENT In FIG. 3 the

members

304 and 305 are shown with their slit-defining edges abutting one another, ie the slit is closed. The construction is similar to FIG. 1, but the

flat strips

12 and 13 are replaced by

wire connections

312 and 313 made of springy material. The latter are constituted by a length of wire whose ends are welded to sandwiching portions 314 and which is bent to form a loop 337 which loosely engages a peg 338 at the end of rod 316. Loop 337 makes point contact with peg 338 as shown. The

members

304 and 305 are spring-loaded to the closed position by a pair of

wire springs

339 and 340 which are spot-welded to plate 301 at 341 and which engage holes in right-

angled extensions

341 and 342 of the

flat springs

307 and 308.

In use the

springs

339 and 340 load the loop 337 against peg 338 to prevent any backlash, and also apply a slit-closing force to the

members

304 and 305 when rod 316 is moved axially leftwards in the drawing to reduce the slit width. By contrast, in FIG. 1 the slitclosing force is applied through the

strips

12 and 13 which are rigidly secured to rod 16. It should be noted that neither embodiment depends on the action of the mounting springs 7, 8, etc and 307, 308 etc to close the slit. The latter act only as mounting members and are made of springy material to maintain the accurate location of the slit-defining members.

In FIG. 3 the

connections

312 and 313, and the

springs

339 and 340, are suitably made of 0.028 inch diameter Nimonic 90.

The embodiment of FIG. 3 has the advantage of easier assembly in that the flexible connections to rod 316 do not have to be rigidly secured thereto with good accuracy, as is the case in FIG. 1.

In a modification of the embodiment of FIG. 3, the

springs

339 and 340 are set to hold the slit open, eg by pulling

members

304 and 305 to the leftward of the position shown in FIG. 3, and a slit-closing force is applied by rightward movement of rod 316.

It will be seen that the invention provides an adjustable slit mechanism in which there are no parts in rubbing contact, and therefore there can be no stiction, which is especially important in baked apparatus. A

further advantage is the fine control at narrow slit openings with progressively coarser control at wider openings resulting from the approximately square-law displacement of rod 16.

I claim: 1. An adjustable-width slit mechanism comprising: first and second members having linear edges arranged parallel to one another to define between them a slit having uniform width along its length, said members being movable in a common plane t adjust said width of said slit; eac member being mounted on a pair of equallength parallel flat springs extending away from said member in a direction which is parallel to said plane and substantially normal to said edge of the member, said springs having their flat faces normal to said plane;

slit adjustment member movable in a direction substantially colinear with said slit;

first elongate flexible connector means made of springy material extending between and attached to said first member and said adjustment member; and second elongate flexible connector means made of springy material extending between and affixed to said second member and said adjustment member;

movement of said slit adjustment member in said direction colinear with said slit efl'ecting motion of said first and second members to adjust the width of said slit.

2. A slit mechanism as claimed in claim 1 wherein said first and second connector means each comprises a flat strip having its flat faces substantially normal to the plane of the slit.

3. A slit mechanism as claimed in claim 1 wherein said first and second connector means each engage said adjustment member, spring-loading means being provided to apply to each of said first and second members a force which acts in said direction colinear with said slit and away from said adjustment member and in use loads said first and second connector means against said adjustment member.

4. A slit mechanism as claimed in claim 3 wherein said first and second connector means comprise wire and include a common loop which loosely engages said adjustment member.

5. A slit mechanism as claimed in claim 3 wherein said spring-loading means is connected between each of said first and second members and a fixed member to which said pairs of flat mounting springs are secured.

6. A slit mechanism as claimed in claim 5 wherein said spring-loading means is arranged to apply to each of said first and second members a force acting in a direction to close the slit.

Claims

1. An adjustable-width slit mechanism comprising: first and second members having linear edges arranged parallel to one another to define between them a slit having uniform width along its length, said members being movable in a common plane to adjust said width of said slit; each member being mounted on a pair of equal-length parallel flat springs extending away from said member in a direction which is parallel to said plane and substantially normal to said edge of the member, said springs having their flat faces normal to said plane; slit adjustment member movable in a direction substantially colinear with said slit; first elongate flexible connector means made of springy material extending between and attached to said first member and said adjustment member; and second elongate flexible connector means made of springy material extending between and affixed to said second member and said adjustment member; movement of said slit adjustment member in said direction colinear with said slit effecting motion of said first and second members to adjust the width of said slit.