US2742085A - Timing apparatus - Google Patents

Description

April 17, 1956 A. E. BENNETT ET AL 2,742,085

TIMING APPARATUS Filed June 3, 1953 2 Sheets-Sheet 1 I I9 45 24-- l4 30 Invenlons mm B Q Attorney April 7, 1956 A. E. BENNETT ETAL 2,742,085

TIMING APPARATUS Filed June 3, 1955 2 Sheets-Sheet 2 Inventor m R Q By M Attorney United States Patent 0.

MING MRAT S Albert Edward Bennett and John Christopher Howard Geisow, Abingdon, England, a ssignors to The Minister of Supply, London, England Appli at un 3, 1 3, Seria N 35 ,3 Claims. (21. 161-1) This invention relates to timing devices for producing control signals separated by accurately determined time intervals.

The timing device of the invention comprises an escapernent wheel,a pallet for said escapement wheel, loading means connected with the escapement wheel to rotate it towards a zero position, means for rotating the wheel in the direction against the loading means the amount of such rotation governing the time setting of the device, means for operating the pallet to release the escapement wheel at a sharply defined instant constant in each cycle f mo nt of the Pa let a cont si n s itch, me ns or ope t n e cont l signa sw tch a n in ta t a rat l related t he fi mo ement o t e pal e a r setting the timing device an 1 3 5 for operating the en r l nal w t h t n i sta t ac rate y related o the movernent of the escapement wheel on to its zero position.

A process timer embodying the invention is now described with reference to the drawings wherein Fig. 1 is a side elevation partly in section, Fig. 2 is a seetional view in the line lI-II of Fig. 1, Fig. 3 is a sectional view on the line III-III of Fig. 1, Fig. 4 is a front elevation and Fig. 5 is a sectional view of a modified pallet arrangement.

Referring to Figs. 1 and 4, there is provided a bezel 1 attached by screws 2 to an annular ring 3 having a heel; locating plate 4 attached by screws 5. The ring 3 has a bevelled edge 6 moving over a scale 7 marked off in equal divisions. A mark 6:: (Fig. 4) is provided on the edge 6 for setting the bezel, relative to the scale 7, to a predetermined number of divisions on the scale. (In Fig. 4 it is shown set to fifteen divisions.) The bezel is released for rotation by means of a bezel release knob 8 which disengages a bezel release blade 9 from a fixed toothed Wheel 10. The blade 9 is spring loaded by a leaf spring 11 (also shown in Fig. 3). A knurled hand wheel 12 is attached to a shaft 13 which carries a pointer 14, a step arm 15, a ratchet escapement wheel 16, a cam arm 17 and another cam arm 18. The hand wheel 12 is rotatable until the stop arm 15 meets a stop 19 on the ring 3. The position of this stop depends upon the degree of rotation given to the bezel 1 and ring 3 in setting them. During rotation of the hand wheel the shaft 13 also rotates to tension further a pretensioned fiat coil spring 20 and to rotate the wheel 16; the pallet 45 on the shaft 52 and the wheel 16 functioning as a ratchet/pawl device. Also during rotation of the hand wheel 12 the cam arm 18 is moved off a spring-set 21 to make contact there to start a synchronous motor 22. A sector-shaped block 23 attached to the toothed wheel 10, in conjunction with the stops 19, prevents the bezel 1 being rotated off the scale. This sector shaped block also acts as a stop for the stop arm 15 to limit the rotation of the escapement wheel to a portion of a revolution only. A Window 24 is provided.

The rigid supporting parts of the apparatus consists of a back support plate 25 and a front support plate 26 which are held apart with three bolts 27 and spacing tubes 28. The toothed wheel 10 is supported from the plate 26 by spacers 30 and bolts 29. The scale 7 is fixed to the block 23.

The release system for the apparatus is now described. In Fig. 1 the synchronous motor 22 drives a shaft 31 through dogs 32, 33 (shown disengaged). Referring to Fig. 2, the shaft 31 carrie Pin 34 for striking and deflecting a weighted blade 35 attached to a leaf spring 36 fixed to a pillar 37 by a screw 38. On the overswing in the return of the blade 35 under the tension of the spring 36 the blade strikes an adjusting screw 39 passing through a crank 40 to cause a rotary deflection of a shaft 41 to move a detent 42, also on the shaft 41, to operate spring-set 43 so that the lower spring 46 moves off the land .49 to fall on the land 48. This spring-set has connections for the transmission of a start control signal. Also attached to the shaft 41 there is, as shown in Fig. 3, a snail cam 44 whieh is fixed in relation to the pin 34 so that the cam operates the pallet 45 coincident with the operation of spring-set 43. The pallet 45, which is loaded against the snail by spring 50 attached to spacer 30 by screw 51, allows the wheel 16 to escape one tooth pitch for every rotation of the snail cam 44 until the wheel 16 has returned to its zero position. The escape of one tooth pitch is carried out in two steps, the first being an inaccurately determined small step in which the pallet rises slowly up the cam face and the second, being as large as possible, is accurately determined by the pallet dropping off th dg of the snail cam thereby giving a fast large movement to ensure a rapid operation which is accurate with relation to the initial contact operation. On the last release of the wheel 16, the cam arm 17 attached to the shaft 13 restores the lower spring 46 of spring-set 43 from th? land 4. to the land .49; the detent 42 moving under pressure from spring 47. On the closing of the contacts of spring-set 43 a stop control signal is transmitted. Immediately after the restoration of spring 46 the cam arm 18 operates the spring-set 21 to break the supply connections to the synchronous motor 22.

The setting up and operation of the timer consists of two simple operations. First, the bezel is set at the appropriai number of scale divisions and secondly the hand wheel 12 is rotated until it reaches the stop on the bezel. This second operation starts the synchronous motor auto matically and thereafter start and stop" control signals are sent out with an interval between them governed by the bezel setting and the speed of the synchronous motor. The timer automatically stops itself after the stop control signal has been transmitted. Each scale division on the dial 7 represents one revolution of the synchrous motor. The range of the timer may be changed by changing the speed of the motor. The accuracy of the timer is governed by the synchronous motor. The movements concerned with the presetting and restoration are performed in discrete steps, whereby positional errors are completely eliminated and timing errors are only dependent upon any variation in the time taken by the last movement of the escapement. The strength in the restoring spring 20 is available for contact operation so that heavy currents may be switched.

In Fig. 5 an escapement wheel 16a on a shaft 13:: is movable manually in one direction to increase the tension in a fiat coil spring 20:: and is movable in the other direction by the tension in the spring 20a, and under control of the pallet 45a or pallet 60. Pallet 45a, pivoted on pin 52a on pallet 60, has detents 61, 62. Pallet 45a is the pallet operated at regular time intervals for use when the timer is controlling a process. The pallet 60, in the form of a forked member, is pivoted on pin 63 and has a detent 64; the other detent being that pro- 3 vided by detent 62 of pallet 45a. Pallet 60 may be operated manually to move the escapement wheel 16a to a lower setting thus avoiding the longer waiting periods required when moved under the control of pallet 45a.

Three leaf springs 65, 66 and 67 are provided, and a stop 68. Leaf spring 65 is mounted on pallet 60 and presses on pallet 45a to bias it. Leaf spring 66 biases pallet 60 and leaf spring 67, which is very stiif compared with spring 65, biases pallet 45a when it has lifted an amount governed by the clearance between spring 67 and pallet. This provides that detent 62 clears the teeth on wheel 16a when pallet 60 is rocked. The stop 68, in conjunction with leaf spring 66, ensures that pallet 60 rests in a definite position so that pallet 45a is correctly located for operation.

Timing devices according to the invention have an application for controlling apparatus used in the accurate counting, over a period, of events having a fast recurrence such as particle and photon omissions from radioactive specimens.

Alternative modifications to the process timer specifically described above may be carried out. The motor 22 may be replaced by a clockwork mechanism; a gear change arrangement may be provided between dogs 33 and 32 so that for a single speed motor a range of timing periods may be made available or facilities provided for the rapid return of the escapement wheel to a lower or zero position after an initial sitting. By providing additional cams and spring-sets it is possible to arrange that intermediate control signals are transmitted between the start and stop signals.

We claim:

1. A timing device for producing control signals spaced by accurately determined intervals comprising an escapement wheel, a pallet for said escapement wheel, loading means connected with the escapement wheel to rotate it in one direction towards a Zero position, means for rotating the wheel in the opposite direction against the loading means the amount of such rotation governing the time setting of the device, means for operating the pallet to release the escapement wheel at a sharply defined instant constant in each cycle of movement of the pallet, a control signal switch, means for operating the control signal switch at an instant accurately related to the first movement of the pallet after setting the timing device and means for operating the control signal switch at an instant accurately related to the movement of the escapement wheel on to its zero position.

2. A timing device for producing control signals spaced by accurately. determined intervals comprising an escapement wheel rotatable through a portion of a revolution only and a pallet therefor,a spring associated with the escapement wheel to drive it in one direction toward a zero position, a spring associated with the pallet to load it in one position, means for rotating the wheel in the opposite direction to wind the spring, the amount of such rotation governing the time setting of the device, a cam to operate the pallet against the spring pressure to release the escapement wheel in sharp steps for each pallet operation, a switch operated on the first and last movements of the pallet for each setting of the escapement wheel and constant speed driving means for said cam operated to commence driving when the escapement wheel is off-set from its zero position and to stop driving when the escapement wheel moves to its zero position.

3. A timing device according to claim 2 wherein the teeth of the pallet are shaped in a manner to allow it to function as a ratchet device when the escapement wheel is rotated against the loading means.

4. A timing device according to claim 2 having means associated with the pallet so that it can be manually operated to restore the escapement wheel to its zero position.

5. A timing device according to claim 2 wherein said pallet is supported at one end of an arm pivoted part way along its length, the arm being spring biassed against a stop so that said pallet engages the escapement wheel, a detent at the other end of the pivoted arin to engage the escapement wheel when the pivoted arm is depressed against its spring loading, the arm and one detent of said pallet forming etfectively another pallet arrangement and a further spring biassing said one detent clear of the escapement wheel when the detent at said other end of the pivoted arm is engaging the escapement wheel.

References Cited in the file of this patent UNITED STATES PATENTS 317,240 Stephenson May 5, 1885 1,035,574 Gerhardt 1. Aug. 13, 1912 1,279,647 Bryce Sept. 24, 1918 1,536,145 Royal May 5, 1925 1,726,520 Kramer Aug. 27, 1929 2,025,511 Johnson Dec. 24, 1935 2,096,620 Robertson Oct. 19, 1937

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