US3699789A

US3699789A - Dial structure for mechanism requiring both lineal and rotary input operating movements

Info

Publication number: US3699789A
Application number: US157405A
Authority: US
Inventors: Anthony J Potzick
Original assignee: Mosler Safe Co
Current assignee: Mosler Safe Co
Priority date: 1971-06-28
Filing date: 1971-06-28
Publication date: 1972-10-24
Anticipated expiration: 1989-10-24

Abstract

Dial structure for use with a lock or other mechanism which requires both rotary and axial input movements of an operating spindle. The structure includes an operating knob for imparting both such movements to the spindle, and a dial having position indicia and which is responsive to and follows rotary movement but not lineal movement of the knob. Other features include a bearing connection which provides a universal joint of the spindle in the dial frame, to accommodate minor misalignment of the dial structure with respect to the mechanism. A mask screens all position indicia except that in a narrow aperture, which is visible only to the operator.

Description

United States Patent Potzick 1 Oct. 24, 1972 [541 DIAL STRUCTURE FOR MECHANISM REQUIRING BOTH LINEAL AND ROTARY INPUT OPERATING MOVEMENTS [72] Inventor: Anthony J. Potzick, Cincinnati,

Ohio

[73] Assignee: The Mosler Safe Company, Hamilton, Ohio 22 Filed: June 28,1971

21] App1.No.: 157,405

[52] US. Cl. ..70/329, 70/332, 116/ 133, 200/167 R [51] Int. Cl. ......E05b 15/00 [58] Field of Search ..70/31 1, 329, 330, 332, 445, 70/464; 116/133; 200/4, 167 R, 172 R PriMary EkZirhih er AIbert G Craig, Jr. Attorney--Wood, Herron & Evans [57] ABSTRACT Dial structure for use with a lock or other mechanism which requires both rotary and axial input movements of an operating spindle. The structure includes an operating knob for imparting both such movements to the spindle, and a dial having position indicia and which is responsive to and follows rotary movement but not lineal movement of the knob. Other features include a bearing connection which provides a universal joint of the spindle in the dial frame, to accommodate minor misalignmentof the dial structure with respect to the mechanism. A mask screens all position indicia except that in a narrow aperture, which is visible only to the operator.

[56] References Cited UNITED STATES PATENTS 15 i r 1,308,521 7/1919 Butter ..70/311 M I M /5 Z 45 40 I w ,2 42

o 7 /3 K a5 /9 PATENTED E 24 197? 3,699,789

DIAL STRUCTURE FOR MECHANISM REQUIRING BOTH-I LINEAL AND ROTARY INPUT OPERATING MOVEMENTS This invention relates to dial structure, and more particularly to dial structure for use with locks and other mechanisms of the type which require both rotary and linear input movements of a spindle for operation.

Locks of the type referred to are known in the art. By way of example, two such locks are disclosed in Potzick US. Pat. No. 3,436,941, issued Apr. 8, 1969, and in Potzick US. Pat. No. 3,518,856, issuedJuly 7,1970. To operate such locks, an actuating knob is turned to certain angular positions in a prescribed sequence. This turns a spindle connected to the lock. Each angular position, once dialed, is then set into the lock by a linear movement imparted to a spindle. Both types of the motion are necessary in running the combination.

Dial structure for use with such locks, and providing for both such types of spindle movement, should afford security against surreptitious attack, and should function smoothly and precisely.

One mode of surreptitiously learning something about the combination of a lock having a dial that requires a rotary input sequence, is to place a scribe or other marking device on the rotary dial, in such position that it will scratch on an adjacent fixed surface the arcs over which the dial is turned in running the combination. To avoid this, the dial structure should have no exposed clearance gap between the rotary elements and adjacent fixed or frame structure. I

Moreover, the dial should expose the indicia or numbers of the combination actually being run, only to the operator and not to anyone standing elsewhere. A common technique of gaining unauthorized entrance to a safe is simply to observe the combination as it is set by an authorized operator.

The dial should be structured so that it is not readily removed from its mounting, and, in the event it is removed, there should be no easy access to the locking mechanism.

The locks of the cited patents are responsive only to angularly precise (or whole number) dial settings and are not responsive to settings adjacent the proper numbers. I found it desirable that the dial structure for use with such locks should have a dial member which, after it has been turned rotationally to a given angular position, should not thereafter move axially when the knob or spindle is moved axially to set that rotational position into the lock. Such movement could render it difficult to retain the proper angular position during the setting movement, especially if the dial moved so as to obscure the position indicia even momentarily.

Although not important from a security standpoint, it is desirable as a practical matter that the dial be fully and smoothly'operable even though there may be a slight misalignment of the dial spindle axis with the lock axis. Such misalignment (of small magnitude) sometimes occurs by reason of the fact that the lock and dial are usually located on opposite sides of a heavy safe door or file drawer panel into which it is difficult to drill. If the spindle axis is rigidly positioned with respect to the dial structure, such misalignment causes sticky or tight operation. At the same time, any spindle wobble permitted by a loose or sloppy bearing derrogates from a substantial and secure feel of the setting knob.

The mounting process to obtain precise alignment is rather complicated, since the spindle must be exactly located to extend squarely and perpendicularly into the locking mechanism. I have found it desirable to provide a dial structure wherein the spindle has a degree of universal movement which eliminates the necessity of troublesome precise alignment. This will, for example, permit the dial to function smoothly with a lock as to which it is ofi center within the ordinary range of assembly imperfections.

Apart from these functional considerations, it is psychologically important that dial structure present a solid and secure aspect, both visually and by feel in operation.

This invention is directed to a dial structure which includes a setting knob that is linearly and rotationally movable to actuate a locking or other mechanism, for example such as those disclosed in the Potzick patents. It provides the features discussed above.

Briefly, the setting knob is attached to a drive member in which are formed longitudinal bearingreceiving grooves. The spindle is attached to the drive member and extends through the panel or door of a lockable enclosure. Its inner end is attached in use to a mechanism for transmitting as inputs thereto the linear and rotary motions of the setting knob. A dial mounting supporting frame has a hub having an annular bearing race around it. The dial member includes a tube having bearing receiving apertures through it, and an outer visible surface provided with angular position indicia on it.

It is preferable to include a mask around the hub and dial which covers and obscures the dial position indicia, with the exception of the single indicia appearing in a window or aperture in the mask. The window is shaped so that the indicia is visible through only a small angle of view, such that it can be seen only by the operator and by no one else. The mask covers screws or bolts which mount the structure in position over a spindle bore through the mounting surface, e.g., a lockable enclosure.

Bearings are captured within the apertures of the tube of the dial. On one side of the dial tube (preferably the outside), these bearings track in the annular race in the hub, and on the other side (preferably the inside) they track in longitudinal grooves in the drive member. Rotary movement of the knob and drive member is imparted to the bearings by the sides of the longitudinal grooves. The bearings transmit to the dial their rotation around the axis of the drive member, so that the dial rotates in unison with the knob. When the knob is moved lineally, the bearings track in the longitudinal grooves in the dial member, and do not impart movement (either lineal or rotational) to the dial, so that the dial remains stationary. Thus, the positional relation of the indicia on the dial to an index mark on the frame varies rotationally when the knob is turned, but not when the knob is moved axially. In preferred embodiment the dial tube encircles the drive member, and both of them extend into the hub. A skirt or outer sleeve of the dial at least partially encircles the hub. In a modified embodiment the relation of the dial to the member drive is reversed; that is, the drive member may encircle the dial tube, with the hub interiorily of the tube.

It is an advantage of this invention that it provides dial structure capable of imparting both linear and rotary motion to a lock mechanism, wherein the position indicating dial is rotatable but is held against linear mo tion.

It is a further advantage of this invention that it provides dial structure wherein the position indicating indicia on the dial are masked so as to be visible through only a relatively small angle of view.

It is a further and highly important advantage of my invention that it provides dial structure which is selfprotected by its own elements against surreptitious attack.

It is a further advantage of this invention that it provides dial structure for imparting linear and rotary motion through a spindle to a lock mechanism, wherein the spindle has universal movement, thereby rendering unnecessary precise alignment of the dial structure with the locking mechanism.

These and other advantages will become apparent from the detailed specification and drawings, in which:

FIG. 1 is a perspective view, partly broken away in axial section, of a preferred form of dia] construction in accordance with the invention, showing the setting knob, the dial member, the mask and the frame;

FIG. 2 is a transverse section taken along line 22 of FIG. 1; and

FIG. 3 is an axial section taken along line 3--3 of FIG. 2.

Referring now to FIG. 1 of the drawings, the dial structure of a preferred embodiment of the invention is indicated generally at 10. The elements of the dial are shown as mounted for use on a mounting surface 11 which may be a safe door. A spindle 12 extends through an aperture 13 provided in the door of the enclosure. The spindle inner end or shank 14 is adapted for connection to a mechanism (not shown), such as either of the locks disclosed in the previously cited patents.

The dial mechanism itself comprises a fixed dial frame 15. The frame may be mounted to the door 1 1 by machine screws 9 as shown in FIG. 3, or other means. In the preferred embodiment frame 15 is generally circular and has an integral outer flange or skirt 16 and an inner hub 17 provided with an axial bore 18. In its surface bore 18 has an annular bearing race 19 in the form of a groove for receiving several ball bearings 20. While a V-shaped race 19 is shown, its configuration will depend upon, and vary with, the shape of the particular bearings used. For instance, if a roller or pin bearing were utilized instead of the roller bearings shown, the race'may conform generally to the shape of the roller or pin, so as to permit bearing movement circumferentially around the hub. The race for the bearing 20 restrains them against longitudinal or axial movement parallel to the axis of spindle 12, but allows the hearings to move freely around the hub.

Dial means in the form of a dial member is provided about the hub 17, and is coaxial with it. It is the function of this member visually to show the angular position of the shaft. The dial member has an inner tubular member or hollow cylinder 26 within bore 18 which is connected to an integral radially extending flange 27. An outer sleeve 28 is concentric with tube 26, and surrounds the outside of hub 17. The sleeve may be integral with flange 27 or, as shown in FIGS. 1 and 3, may be attached in a groove 29 of flange 27. Outer sleeve 28 is provided with numerals, letters or other position indicating indicia as, for example, the numeral 4 shown in FIG. 1 near the end 43 of sleeve 28, which numerals identify the rotational position of the dial with respect to a stationary index mark to be described.

The hollow inner cylinder 26 is provided with cross apertures 30 in which the bearings 20 are confined and through which they extend. These apertures are shaped to receive the particular bearings used, and in the preferred embodiment illustrated are circular for receiving the ball bearings 20. Apertures are provided for holding a plurality of bearings (three in the example shown) so that the movable elements will operate smoothly. Each aperture 30 may be shaped so as to hold a bearing in a closely sized or snap fit. Such a construction facilitates assembly of the dial mechanism, as will be described.

The spindle 12 is attached to and moves with a drive member or shaft 35 which is connected at its outer end to a setting knob 36 which is grasped by the operator in use. Drive member or shaft 35 is supported for axial sliding movement in the inner cylinder 26 of the dial member 25. For this purpose shaft 35 has longitudinal grooves or slots 37 to receive the respective bearings 20, one groove being provided for each bearing. These grooves hold the balls in constant angular position with respect to the drive shaft 35, and allow the drive shaft 35 to be reciprocated relative to dial member 25 while the balls are confined against such reciprocal movement by the annular race 19.

The setting knob 36 has a skirt 38 with an end 39 which partially overlaps the periphery of flange 27 of dial member 25. As will be seen, this overlap prevents finger pinching when knob 36 is moved axially relative to the dial. It is desirable to permit some play (not shown) in the fit of shaft 35 within the dial inner cylinder 26. This enables the bearing 20 to act, over a limited range, as a universal bearing to accommodate any small off-center alignment of spindle 12 with respect to the lock.

A mask or cov'er 40 covers the area between the dial outer tube 28 and frame flange 16. The mask is in the shape of an annulus with a cross-section best seen in FIG. 3. A flange 41 extends radially under the inner end 43 of the outer cylinder 28 of a dial member 25, and mask 40 is held in place between frame 15 and the dial member and can only be removed if the dial member is first removed. The mask covers the screws 9, so that they are not accessible. The mask also blocks insertion of a scribe or marking device under the dial, such as is sometimes used surreptitiously to learn dial movements in running the combination. Mask 40 is held against rotation by an integral pin extending into a hole in frame 15.

The mask has sequentially shaped aperture-or cutout 42. Except at this aperture, mask 40 conceals from sight the position indicating indicia on dial 25; that is, every number is covered except that which appears in the aperture (see FIG. 1). Thus only a single indicia (the number 4 in FIG. 1) is visible at any one time, and since the aperture 42 is rather narrow as shown, this single indicia is visible only in a small angle of view.

The operator will himself obscure this indicia from other viewers.

The general appearance of the dial structure is visually pleasing. The various structural elements may be made of steel which is brushed or knurled.

The dial is mounted and assembled by first securing frame 15 to the structure 11 with screws 9. The mask 40 is then pressed into position within flange 16 of the frame 15, around hub 17. Dial member 25 is then inserted with inner cylinder 26 telescoped in the bore 18 of the hub 17 and with outer cylinder 28 around the outside of the hub. The bearings 20 are then placed into their respective apertures 30 in the inner cylinder 26 of dial member 25 so that they extend into bearing race 19 in the hub. The bearings 20 may conveniently be held by a snap-fit into the respective apertures. Alternately, the bearings may be greased so that the grease holds them in place during assembly. Grease may be utilized whether or not the bearings snap fit into aperture 30.

The spindle 12 and drive shaft 35 of setting'knob 36 are then inserted through the center of tube 26. The setting knob is angularly adjusted such that the inner ends of longitudinal grooves 37 are aligned with the angular positions of the bearings. The end 14 of spindle 12 is then connected to the locking mechanism so as to impart the rotational and reciprocal input movements to the lock. If, as is desirable, bearings 20 permit slight universal movement of drive shaft 35, there is no necessity to precisely align the dial structure with the spindle-receiving connections of the locking mechanism.

The lock mechanism to which spindle 12 is connected in use to operate may have spindle connecting elements which are oppositely spring-loaded to bias the spindle to a neutral axial position (see the abovereferred to Potzick patents). For purposes of explanation, the neutral position of the spindle is assumed to be, and preferably should be, about midway between its maximum movements as indicated by arrows A and B (see FIG. 3). These elements tend to eliminate any wobble which accompanies the universal movement of the spindle and gives the setting knob a substantial, secure feel.

Angular positions of the spindle are set into the locking mechanism by pushing the setting knob against a predetermined spring bias in one direction (arrow A); the locking mechanism is reset by pulling the setting knob against a predetermined spring bias in the other direction (arrow B).

In operation, the setting knob 36 is rotated manually by the operator in either direction as indicated by an arrow C in FIG. 1. This rotary movement turns drive shaft 35 and spindle 12. Spindle 12 transmits this rotary motion to the lock mechanism for activation thereof. As drive shaft 35 turns, it moves the bearings 20 in the same circular motion, because the later are captured within the grooves 37. The bearings are constrained to move in a clockwise or counterclockwise direction by bearing race 19. As drive shaft 35 turns the bearings 20 in a circular motion, the bearings drive the inner cylinder 26 of dial member 25 in the same direction since they extend through apertures 30. In this manner, rotary motion is imparted to dial member 25 as the bearings roll within the apertures 30. Thus, as the setting knob 36 is turned, it drives spindle 12 and the dial member 25 so that dial outer cylinder 28 is rotated, bringing successive position-indicating indicia into view in aperture 42 of mask 40.

The lock is operated by rotary positioning of the spindle followed by setting the desired dial position into the various locking elements by a reciprocal movement of the spindle, before it is rotated to the next position. At the selected number, knob 36 is pushed inwardly (arrow A). As the drive shaft 35 moves inwardly, bearings 20 remain in their same lateral position and the dial does not follow this longitudinal movement. Hence the number or position indicia thereon does not shift relative to the frame and remains visible in the aperture during the longitudinal setting movement. Dial member 25 is held against such movement by confinement of bearings 20 within the annular bearing race 19 and in apertures 30 in the inner cylinder 26 of dial member 25.

For releasing or resetting the locking mechanism, an oppositely directed longitudinal movement (assumed to be in the direction of arrow B) is applied to the setting knob- 36. Again, no longitudinal movement is imparted to dial member 25, for the same reasons as stated above. The skirt 38 of setting knob 36 is shaped so that the tips of the operators fingers may bear against the mask 40 to exert a reaction pulling force on the knob.

Thus the dial member is held by the bearings against longitudinal movement and may not be removed by one desiring to place a scriber or other device under the dial later to scratch marks on the dial which might show its angular movements when turned according to the combination.

The fact that the dial does not move longitudinally affords a number of other advantages as well. If the dial member were to be moved outwardly, the particular position indicia could be more readily visible to unauthorized viewers. Also, the whole mechanism may be more accurately operated and positioned where the indicia is not variably separated from its index mark as indicated at 45 and where it is never obscured during longitudinal setting movements. Maintaining the indicia in close proximity to this index mark allows the spindle to be positioned quickly and precisely. Furthermore, maintaining the dial longitudinally stationary permits it to be used to hold the mask 40 in position covering the indicia and the screws 9. Further, nonmovement of the dial in a longitudinal direction affords a more substantial appearing and functioning dial.

An alternate structure contemplates reversal of the relative radial positions of the dial and the drive shaft. in this case a hub is provided with an annular bearing race in the outer surface thereof, rather than in the inner surface, with the dial and drive shaft exteriorly surrounding the hub.

Other modifications of my invention will become apparent to those of ordinary skill in the art without departing from the scope thereof and I intend to be bound only by the following claims.

Having specifically described my invention, I claim:

1. Dial structure for imparting rotary and linear movements to a spindle, comprising,

a dial frame including a hub,

setting knob means including a drive member and a spindle,

dial means with angular position indicia thereon, said dial means including a tubular member provided with bearing receiving apertures,

said dial means and tubular member being coaxial with said knob means,

bearings extending through and captured within said apertures in said tubular member, said bearings being received on one side of said tubular member in an annular race in said hub which confines them lineally but permits bearing movement around the hub,

said bearings being received on the other side of said tubular member in longitudinal races in said drive member which can move lineally relative to the bearings but not rotationally without driving the bearings about the annular race,

means mounting and supporting said drive member for both rotational and lineal axial movement relative to said frame,

means mounting and supporting said dial means for rotational but not lineal movement,

rotary motion of said setting knob means being imparted to said dial means through said bearings, but reciprocal motion of said setting knob means being isolated by said annular race from said dial means.

2. Dial structure for use with mechanism of the type which is activated by rotary and linear spindle movement, said structure comprising,

a dial frame with a central hub having a bore through a bearing race extending around the inside surface of said bore,

a setting knob having a drive shaft connected to it and a spindle extending axially from said shaft for operable connection in use to said mechanism,

a dial having a visible portion with position indicia at angularly spaced intervals on it,

said dial connected to a tube extending into said bore,

said tube having bearing-receiving apertures extending transversely through it in line with said race in said bore,

means journalling said dial and tube for rotational movement relative to said hub,

said shaft extending into said tube,

said shaft having angularly spaced longitudinal bearing-receiving grooves in line with the respective apertures,

and bearings confined by and between the annular bearing race in the hub and the longitudinal grooves in the drive shaft, said bearings extending through the apertures in said tube, rotary move- I ment of the knob and drive shaft thereby imparting rotary movement to the dial through the bearings, and linear movement of the drive shaft imparting no linear movement to the dial.

3. Dial structure as in claim 2 wherein said setting knob includes a flange portion partially overlapping said dial.

4. Dial structure as in claim 2 wherein said dial frame includes a peripheral flange, and further including a mask means for covering selected portions of the dial and being positioned between said peripheral flange and said central hub.

5. Dial structure as in claim 4 wherein said mask means includes a portion captured between said dial frame and said dial.

6. Dial structure as in claim 5 wherein said dial frame is secured to mounting surface by mounting means and wherein said mask covers and conceals said mounting means.

7. Dial structure as in claim 4 wherein said mask means is provided with an aperture for displaying position indicia to a restricted angle of view.

8. Dial structure as in claim 7 wherein said position indicia are located on the dial but are covered by the mask means, except when exposed at said aperture.

9. Dial structure as in claim 2 wherein said bearings are ball bearings.

10. Dial structure as in claim 2 wherein said tube is loosely fit into said bore so as to form a universal-type joint about said bearings.

11. Dial structure as in claim 2 wherein said bearingreceiving apertures receive said bearings in a snap tit.

12. Dial structure for use with a mechanism of the type which is activated by rotary and linear spindle movement, said structure comprising,

a dial frame with a central hub having a cylindrical bore through it,

an annular bearing race within said bore,

a setting knob having a drive shaft connected to it and a spindle extending axially from said shaft for connection in use to a mechanism for operating the latter,

a dial member including an outer sleeve and an inner tube concentric with said sleeve, the outer sleeve having exposed position-indicating indicia on its peripheral surface, the inner tube being spaced from said sleeve by an annular gap between them,

said shaft being received within said inner tube of said dial member for relative longitudinal sliding movement therein,

said dial member being joumaled by said hub for rotational movement relative to said hub,

the inner tube of said dial member extending into the bore of said hub between said shaft and the surface of said bore,

the outer sleeve of said dial member at least partially surrounding and covering said hub,

said inner tube having bearing-receiving apertures extending transversely through it in line with said race in said bore,

said shaft having angularly spaced longitudinal bearing-receiving grooves,

and bearings confined by and between the annular bearing race in the hub and the longitudinal grooves in the drive shaft, said bearings extending through the apertures in the inner tube of the dial member such the rotary movement of the knob and drive shaft imparts rotary movement to the dial member through the bearings, and linear movement of the drive shaft imparts no linear movement to the dial member.

13. Apparatus as in claim 12 including,

a masking means secured around the dial member and covering the indicia on said dial member,

said masking means including an aperture positioned to expose the position indicia to a relatively small angle of view.

Claims

1. Dial structure for imparting rotary and linear movements to a spindle, comprising, a dial frame including a hub, setting knob means including a drive member and a spindle, dial means with angular position indicia thereon, said dial means including a tubular member provided with bearing receiving apertures, said dial means and tubular member being coaxial with said knob means, bearings extending through and captured within said apertures in said tubular member, said bearings being received on one side of said tubular member in an annular race in said hub which confines them lineally but permits bearing movement around the hub, said bearings being received on the other side of said tubular member in longitudinal races in said drive member which can move lineally relative to the bearings but not rotationally without driving the bearings about the annular race, means mounting and supporting said drive member for both rotational and lineal axial movement relative to said frame, means mounting and supporting said dial means for rotational but not lineal movement, rotary motion of said setting knob means being imparted to said dial means through said bearings, but reciprocal motion of said setting knob means being isolated by said annular race from said dial means.

2. Dial structure for use with mechanism of the type which is activated by rotary and linear spindle movement, said structure comprising, a dial frame with a central hub having a bore through it, a bearing race extending around the inside surface of said bore, a setting knob having a drive shaft connected to it and a spindle extending axially from said shaft for operable connection in use to said mechanism, a dial having a visible portion with position indicia at angularly spaced intervals on it, said dial connected to a tube extending into said bore, said tube having bearing-receiving apertures extending transversely through it in line with said race in said bore, means journalling said dial and tube for rotational movement relative to said hub, said shaft extending into said tube, said shaft having angularly spaced longitudinal bearing-receiving grooves in line with the respective apertures, and bearings confined by and between the annular bearing race in the hub and the longitudinal grooves in the drive shaft, said bearings extending through the apertures in said tube, rotary movement of the knob and drive shaft thereby imparting rotary movement to the dial through the bearings, and linear movement of the drive shaft imparting no linear movement to the dial.

9. Dial structure as in claim 2 wherein said bearings are ball bearings.

11. Dial structure as in claim 2 wherein said bearing-receiving apertures receive said bearings in a snap fit.

12. Dial structure for use with a mechanism of the type which is activated by rotary and linear spindle movement, said structure comprising, a dial frame with a central hub having a cylindrical bore through it, an annular bearing race within said bore, a setting knob having a drive shaft connected to it and a spindle extending axially from said shaft for connection in use to a mechanism for operating the latter, a dial member including an outer sleeve and an inner tube concentric with said sleeve, the outer sleeve having exposed position-indicating indicia on its peripheral surface, the inner tube being spaced from said sleeve by an annular gap between them, said shaft being received within said inner tube of said dial member for relative longitudinal sliding movement therein, said dial member being journaled by said hub for rotational movement relative to said hub, the inner tube of said dial member extending into the bore of said hub between said shaft and the surface of said bore, the outer sleeve of said dial member at least partially surrounding and covering said hub, said inner tube having bearing-receiving apertures extending transversely through it in line with said race in said bore, said shaft having angularly spaced longitudinal bearing-receiving grooves, and bearings confined by and between the annular bearing race in the hub and the longitudinal grooves in the drive shaft, said bearings extending through the apertures in the inner tube of the dial member such the rotary movement of the knob and drive shaft imparts rotary movement to the dial member through the bearings, and linear movement of the drive shaft imparts no linear movement to the dial member.

13. Apparatus as in claim 12 including, a masking means secured around the dial member and covering the indicia on said dial member, said masking means including an aperture positioned to expose the position indicia to a relatively small angle of view.

14. Apparatus as in claim 13 wherein said frame is mounted by attachment means and wherein said masking means covers said attachment means.

15. Apparatus as in claim 12 wherein each of the bearing apertures in the inner tube of the dial means receives the bearing therein by a snap fit.