US2652976A - Sextant - Google Patents

Description

Filed oct. 4, 1949 Sept. 22, 1953 v P. F. EVERITT ET Ax. 2,652,976.

` sExTANT 4 Sheets-Sheet l A 'Inemora Sept. 22, 1953 P. F. EVERITT ET A1.

SEXTANT 4 Sheets-Sheet 2 Filed Oct. 4.' 1949 L///A/ 1 j A! omeys Sept. 22, 1953 P. F. EvERlTT ET AL v 2,652,975

' SEXTANT Filed Oct. 4. 1949 4 Sheets-Sheet 5 38 F/Gj4.

| WHHHII HHH' Sept. 22, 1953 Filed oct. 4. Y1949 P. Fu EvERlTT ET AL 2,652,976

4 Sheets-Sheet 4 Patented Sept. 22, 1953 SEXTANT Philia .FltancisgEvetitt, Seven Kingapandj A.lohn Keeble, Ilford, England, assignors, by-mesne lassignments, to Kelvin & Hughes Limited', Glasgow, a British company -Anlllicationzctolmn 4, 1949,*Se1iaLNoeLl9AS3 In Great Britain October 5,1948

3 Claims.

1 'Ihis invention relates to., sextants of the kind in which an integrating: device. gives an average of continuous readings. Itfhas been proposed to `provide such anfarrangmentain:which concentric disc dials are provided to give the required readings at one side of the instrument while other readings are observed through windows in an adjacent side of the instrument.

The main object of the present invention is to provide a device in which the mechanism is of simpler construction than heretofore and all readings can be taken from one side of the instrument e. g. at right angles to the sighting telescope. i

According to the invention an integrating device has a cone which drives a cylinder through one or more ballsrcarried iria cagethat, isv driven along the cylinder, and the cylinder is geared to a shaft which carries the cone rotatably thereon, and a series of live-.drums are mounted around the shaft and marked on their peripheral surfaces, two indicating degrees and minutes of altitude respectively and the other three being integration `aligning drums, two of which are connected respectively to the shaftandthe, cone and are geared by differential gearing to the third, the arrangementbeingsuch that after use the three integration drums are reset to their initial positions the' otherdrums directly indicate the average altitude.

Thus the; markings on the drums can all be read from one side of the instrument, and a Asimple andV reliablev mechanism is used.

A constructionalform of theeinvention will now be described by way of example with reference to the accompanying diagrammatic drawings wherein:

Figure lis; a view partly inv vertical section and partly in, elevation ofv a periscopic sentant made in` accordanceA with `the invention;

Eigurez is a vertical sectional view of., the integrating mechanism shown in elevationin Eigure 1,;

Figure 3 is a sectionalfvew on theline 3-3 Qn/FigureZ'vwith certain parts (a counter-shaft and parts carried thereby)` removed;

,Figure 4 is a sectionalview on the line Li-ll on lligure 2;

Figure 5 is a perspective view of al detail shown in Figure 2;

,Figure 6 is-an axialview of thepar-ts shown inFigure drawnfto, a smallerscale; and

Eigure.- 7. is a` sectonalfviewon the ,line '1 -1.. on yliigureG.

The; sexta-nt casingehas I abort-like. part I li-and a periscopic tube II and an eyepiece telescope 9.

In theupper'end of" the tube II is mounted a sighting prism I-2adjustable by means of an arm I3 the lower endl of'which is fixed to a nut I'4 on a micrometer -screw I5 associated with an anti-backl lash nut IS. Thus the means comprisingV the prism I2 is adjustable by the screw I5 according to observed altitude. The screw I5 is carried by a spindle I1 which carries a worm-wheelv I8 driven by worm I9 which in turn is driven by an electricv motor 20 through a reversible drive controlled by any suitable switch and'nger control sothat the-operator by driving in one direction or the otherv when required` can adjust the prism according to observed altitude by retaining the heavenly body under observation in the eyepiece telescope.

The spindle I1 also carries a pinion 2I, having a Vback-lash adjuster 23, in mesh with a gear- Wheel 22V thatv is fixed to-a sleeve 24 that carries a cone 25'that is fixed to the sleeve 24. The cone is carried; in bearings 26, 2l, and supports a spindle 2S on which it is Vfreely rotatable.

Y".ll'ie conedrives balls 3Q, whichdrive-a cylinder 32 carried on a spindle 33 whichv carries a gearwheel 3ft` inmesh with a pinion 35, and backlash adjuster 35', on the spindle or countershaft 2S.

The spindle 33 Vis mounted in a bracket 38 that is pivotally supported on hardened cones 3S, 45 V(Figure 4*). A leaf spring 4I presses on the bracket to hold the cylinder against the adjacent `ball 33. The balls 353' are carried by a. cage '42 `to which is attached arack 44 driven by a motor and pinion (not shown) at a constant speed.

Five-reference drums I, 2, 3, 4, 5 are;k provided side by side and coaxial with the spindle 28., They can allbe seen through one or more appropriate openings or windows in one side of the box Ifii. The drums I, 2, 3, all carry markings such asA, B, C, etc., to facilitate resetting them to their initial or zero positions. Thedrums @and dare marked inr degrees and minutes of altitude respectively.

Looking-at the sighting windows the drums are I, 2, 3, the integration aligning drums; No..A 4 thedegree indicating drum, and No. ithezminute indicating drum. No. I is secured to the aforesaid shaft`28 and No. 3 and No. 5 are mountedon the sleeve 24. attached to the cone. Two drums 3 and 5 are provided because 3 carries alignment markingsA and 5 carries minute markings which is more convenient than having both sets ofmarkingson one drum. No. I carries pinions 6 meshing with a sun-wheel 'l carriedamf` `the sleeve 24 and with a sun-wheel 8 carried by drum 2, the rst sun-wheel having one tooth less than the other sun-wheel so that drum 2 has differential movement. Drum 4 is carried freely and driven by a gearing device 9, mounted on an eccentric 48 on the sleeve 24, and connected to a fork 4'I engaged by an eccentric 49 on the end of the spindle I1. The device 9 consists of inner and outer pinions the inner one having one tooth less than the outer pinion. The outer wheel moves one tooth for every revolution of the eccentric 48. The gearing 9, 41, 48, 49, is of known type sometimes called a two-gear clock mechanism. The inner of the pinions 9 must be restrained from rotating. one end to the inner pinion and prevents the inner pinion from rotating. Movement of the eccentric 48 causes the inner pinion to move eceentrically so that its teeth engage progressively with the teeth of the outer of the pinions 9. As there is one tooth less on the inner pinion than the outer pinion, the latter moves round one tooth for every revolution of the eccentric 4t. The eccentric d keeps the inner pinion with the upm permost tooth always uppermost. Without the eccentric lil the upper tooth would oseillate oil dead centre corresponding to the rocking motion of the fork- 4l. Drums 2 and 4 are freely mounted on the sleeve 2d and drums 3, 5 are fixed on 'the sleeve 24.

The operation or the device is as follows:

The operator precomputes the approximate altitude of the heavenly body to be observed, and sets the computed figure on drums 4 and 5 by operating the motor 2S. This will not affect the drums I, 2 and 3 because the rack 44 will be stationary and the ball drive 3ft will be at the left hand end or Figure 2 giving a lzl drive ratio between the cone 25 and the cylinder 32. Then he sights the heavenly body and starts the drive to the rack 44 which advances uniformly. Duringthe movement of the rack fifi. he continues to maintain the heavenly body in the telescope eyepiece sight by operation oi the motor 2t whereby the cone is driven variably as controlled by the the operator and whereby motion according to the sighting angle is applied through sleeve 21; to the drum 3 and is also applied through the cone, balls, cylinder, and spindle 2t, to the drums i and 2 this motion being varied according to the position of the balls along the cone; at the same time the drum 5 is driven from the sleeve 24 and the drum 5 drives the drum 4 through the two gear clock mechanism. After any period of reading the integrator drums i, 2 and are reset to bring their zero marks into alignment by operating the motor 2@ and screw l5 (without yet returning the rack 4t), and the average alti tude is then directly indicated by the drums 4 and 5.

It is not necessary to return the drums 4, 5, to their original positions as they can start from any position. The drunis i, 2 and 3 and rack 44 are nally brought back. to their normal positions with these drui .s in alignment and the instrument is then ready to start a fresh operation.

The invention may be used in conjunction with the invention described in the speciiications of applications of even date Nos. 119,492-45.

Theory of integrator The action or" the above described mechanism is as follows:

Suppose the gear ratio between the cone and the cylinder at time t is (A-i-Kt) The fori; 4l is fixed atdH(A-|-Kt) Then if A=1 i. e. the initial gear ratio being 1:1

- Vthe relative movement of the cone and cylinder is icv Then, over a period of integration the total relative movement is H L Ki+dH Now, the required average altitude H'ab Integration by parts:

Where H1 is final altitude at time T.

Then

Thus the average consists of the iinal altitude minus an amount H L KtdH the drums I, 2, and 3"into alignment since the misalignment H 0 KtdH and relative gear ratio is KT.

We claim:

l. A sextant having a cone, means for driving the cone in accordance with observed altitude, a cylinder, a ball device for driving said cylinder from said cone, means for traversing the ball device along the cone and cylinder, a shaft on which the cone is rotatably mounted for independent rotation, means for driving said shaft from said cylinder, iive drums mounted for rotation about the axis of said shaft and marked on their peripheral surfaces so that two of said drums indicate minutes and degrees of altitude respeo tively and are driven from the cone, the other drums beingintegration aligning drums, the first of said integration aligning drums being attached to said shaft, the second being connested to and driven by the cone, and the third being freely mounted for receiving differential rotation from the first integration aligning drum and the cone.

2. A sextant as claimed in claim l having a micrometer screw parallel to the axis of the cone, a reversible motor reversible means for driving the screw from the motor, means adjustable by the screw according to observed altitude, and

gear wheel connecting the screw and cone.

3. A sextant as claimed in claim 1 wherein said References Cited in the me of this patent means for driving the cone includes an electric motor, a spindle, a worm and worm-wheel driv- UNITED STATES PATENTS ing said spindle, a sleeve, and gearing connec- Number Name Date tions between the sleeve and spindle, said sleeve 5 2,140,579 Gray Dec. 20, 1938 carrying the cone and the minute indicatingv 2,431,555 Wodalef, a1 Sepa, 13, 1949 drum, and a reduction device conveying motion from the spindle to the degree indicating drum FOREIGN PATENTS to provide the operative connection between said Number Country Date degree indicating drum and said means for driv- 10 590 164 Great Britain July 10s 1947 ing the 00ne- 603706 Great Britain June 22 1948 PHILIP FRANCCIIS EVERITT. JOHN KEEBLE.

Images