US2942482A - Variable limit stop mechanism - Google Patents

Description

June 28, 1960 UGGETT ETAL 2,942,482

VARIABLE LIMIT STOP MECHANISM Filed Jan. 30, 1959 CAVITY DIFFERENTIAL GEARING TO ONE OR MORE SIMILAR DRIVES.

TRIMMER 0R 5 SUBSIDIARY CONTROL MAN RANGE OR TUNlNG CONTROL M 2 H uvmvroxs,

JOHN A. L/GGETT 8 FREQUENCY Y JOSEPH E MC SPAR/PAN. 22% fi fw zfi A T'TORNEX VARIABLE LIMIT STOP MECHANISM John A. Liggett, Haddonfield, and Joseph F. McSparran, Westmont, NJ, assignors to the United States of America as represented by the Secretary of the Army Filed Jan. 30, 1959, set. No. 190,309

6 Claims. 01. 74-10.2)

This invention relates to shaft positioning means, and more particularly to apparatus for facilitating coarse and fine adjustment of the tuning mechanism of electronic components.

The objects of the present invention are to provide improved and simplified shaft positioning apparatus for automatically limiting the operating range of a subsidiary device whose limits of operation are varied either manually or by some external driving means as a function of a physical quantity, such as time. Other features and advantages of this invention will be apparent from the fol lowing description taken in connection with theaccom panying drawings, in which:

Figure 1 is a plan view of a shaft positioning apparatus embodying this invention; and

Figure 2 is a graph showing the eifect of the shaft'rotation on the frequency change of the .driven electronic component.

Rotary limit stops are used in many devices to protect parts such as lead screws, contacts, gears, and several others from damage. In electronic devices, the limit stops are often utilized to restrict the tuning range of different resonant circuits. The present invention is particularly concerned with the utilization of these known rotary limit stops in a novel combination of shaft positioning apparatus for tuning ultra-high frequency cavity resonators. The preferred mechanism embodying the principles of this invention comprise a main range or tuning control geared to several interrelated driven devices and to subsidiary controls or trimmers having on their shafts two sets of limit stops for controlling the rotation thereof in opposite angular directions; the main control and the trimmers are mechanically coupled to the driven device through a differential or epicyclic gear.

In Figure 1, a cavity resonator 25 is tuned by a slug 24 fixedly secured at one end thereof to bevel gear 23; any suitable type of securing means could be employed to fix the gear to the end of slug 24. The teeth of the bevel gear 23 are adapted to be driven by the idler bevel gear 22 rotatably mounted on the ofiset portion 6' of the trimmer shaft 6. The idler gear 22 is in turn adapted to be rotated by the bevel gear 21 fixedly secured to gear 20 and rotatably mounted therewith upon shaft 6. Gear 20 is driven by gear 32, fixed on the driving shaft 33, with knob 1. Two collars 7 and 13 fastened to shaft 6 by set- screws 8 and 14, respectively carry conventional tumbler stop washers 9 having radially and axially projecting fingers 31, the function of which will be described later. Collars 7 and 13 are mounted on shaft 6 above and below gear 112, as shown. Gear 12 is rotatably mounted on shaft 6.

Trimmer control knob 5, securely fastened to shaft 6, cannot be turned in either direction when the parts are in the positions shown in Figure 1. Rotation of the knob in the counterclockwise direction, arrow 27, is prevented by the restraint on collar 7 caused by the pileup of stop washers 9 against an outwardly projecting stop shoulder 1 or lug 11 of radially mounted rotary stop member 19 securely fastened to gear 12. The rotation of gear 12 is in turn controlled by the main range or tuning control knob 1.

Trimmer control knob 5 cannot be turned in the clockwise direction, arrow 28, due to the restraint on collar 13 caused by the pileup of stop washers 9 against stud 17 protruding from a stationary limit stop 16. A friction load 29 is fastened to the stationary support 16 in order to provide friction on trimmer shaft 6.

By releasing dial lock 26 and turning the main control knob 1 in a clockwise direction, arrow 30, gear 3 drives gearj12 and stop lug 11 in a counterclockwise direction around shaft 6. The displacement of lug 11 allows trimmer control 5 to be turned counterclockwise until 1 the stop washers 9 again pile up against lug 11. Clearly,

'1 ratio canbe suitably varied for any desired ratio of setting of the trimmer limit to main control. Also, the number of stop washers 9 on each collar and the spacing therebetween can be suitably selected for any number of desired stop limits. By allowing an initial space be- 1 tween fingers 31 of the stop washers 9 and the limit lugs 11 and 17, any-desired minimum range of control of the trimmer Smay be established.

In operation, the cavity resonator is tuned by slug 24 which is, coupled thru the diiferential gear train to the main control knob 1. This selects the desired carrier frequency. Knob 1 drives shaft 33 with attached gears 3 and 32. As previously mentioned, gear 3 drives gear 12 to control the limit of movement of trimmer shaft 6 by setting lug 11. The opposite limit of rotation of shaft '6 is determined by lug 17.

Gear 32 drives gear 20 and attached gear 21, which in turn drives gears 22. and 23, for shaft .6 is held against rotation by brake 29. As shaft 6 is freed by the backing off of lug 11 from the position shown in Figure 1, shaft 6 can now be moved within the limits permitted by stops 11 and 17, provided sufficient force is applied to knob 5 to overcome brake 29. This movement of shaft 6 will drive gear 22 around gear 21 to rotate gear 23 and shaft 24. Dial lock 26 may be engaged to prevent turning of shaft 33 and gears 32, 20 and 21 during this operation. In the actual equipment the main control tunes several cavities which do not track exactly, the precise tuning of each cavity being performed by the separate trimmers 5 through the differential gear trains.

In Figure 2 the effect of the rotation of the main or trimmer controls on the frequency change of the resonant shaft 6 as the main tuning control approaches the less sensitive end of the tuning range.

The limit stops on the trimming control prevent tuning in a wrong carrier frequency or the unwanted sideband.

Due to the non-linearity of the tuning curve, it is necessary to have limit stops which have broad limits at one end, of the frequency band and narrow limits at the opposite end. These requirements are easily accomplished'by the Patented June 28, 1960 vention.

While this invention has been described in conjunction with present preferred embodiments thereof, it should be apparent that the invention is not limited thereto. In particular, gear 12 can be driven by other means than those shown in Figure 1, such as geared down synchronous motors, etc. The limits on the trimmer control would then be set with respect to other functions, such as time. Moreover, the driven device could be any electrical or mechanical component such as variable inductors, otentiometers, capacitors, etc.

What is claimed is:

l. A control mechanism for varying an adjustable tuning element including, in combination, a first shaft having a first gear mounted thereon; a second shaft disposed parallel to said first shaft and having a second gear mounted thereon; a first and a second set of stop members rotatably mounted on said second shaft, the second gear being in mesh with said first gear; a stationary limit stop; a rotary limit stop fixedly secured to said second gear and concentrically mounted therewith upon said second shaft; the rotation of the second shaft in one angular direction being prevented by the pile up of said first set of stop members against said stationary limit stop, and in the opposite angular direction by the pile up of said second set of stop members against said rotary limit stop.

2. The control mechanism of claim 1, wherein means are secured on said first shaft for controlling the position of said rotary limit stop.

3. The control mechanism of claim 1, wherein a third gear is fixedly secured to said first shaft and a fourth gear is rotatably mounted upon said second shaft, the third and the fourth gear being in mesh, and means me- 4 ohanically coupling said second shaft and said fourth gear to said tuning element.

4. The mechanism of claim 3, wherein said means is a differential gear.

5. The mechanism of claim 4, wherein said tuning element is a cavity resonator.

6. In a control mechanism for monitoring an adjustable element of a tuning device, a first shaft for broad tuning of said element having a first gear mounted thereon; a

second shaft for limited tuning of said element disposed parallel to said first shaft; a second gear in mesh with said first gear rotatably mounted on said second shaft; a first and a second set of stop washers rotatably mounted on said second shaft; a stationary limit stop, a rotary limit stop fixedly secured to said second gear and concentrically mounted therewith upon said second shaft; the rotation of the second shaft in one angular direction being prevented by the pileup of said first set of stop washers against said stationary limit stop, and the rotation in the opposite angular direction being prevented by the pile up of said second set of stop washers against said rotary limit stop; and a differential gear mechanically coupling said second shaft to said adjustable element.

References Cited in the file of this patent UNITED STATES PATENTS 1,699,785 Geiger Jan. 22, 1929 2,378,941 May June 26, 1945 2,396,714 May Mar. 19, 1946 2,496,456 Elliott Feb. 7, 1950 FOREIGN PATENTS 780,270 Great Britain July 31, 1957 921,813 Germany Dec. 30, 1954

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