US2574841A - Timing apparatus - Google Patents

Description

Nov. 13, 1951 w. M. POWELL ETAL TIMING APPARATUS Filed Sept. 28, 1949 2 SHEETSSHEET l INVENTORS. W/LSON M POWELL ALBERT W. HUGHES A TTORNEK Patented Nov. 13, 1951 UNITED STATES PATENT OFFICE TIMING APPARATUS 4 Wilson M. Powell and Albert W. Hughes, Berkeley, Calif., assignor to the United States of America as represented by the United States Atomic Energy Commission Application September 28, 1949, Serial No. 118,302

4 Claims. 1

This invention relates to a new and improved timing apparatus and more especially to a timing apparatus suitable for controlling the several closely spaced sequential events inherent in the operation of cloud chambers. In its broader aspects, however, the invention may be employed in connection with the timing of operations of any suitable combination of associated apparatus and thus is not limited exclusively to cloud chamber usages.

As is known, the operation of cloud chambers, when employed to provide photographic records of ionizing events resulting from controlled operation of particle accelerators, requires exceptionally rapid and accurate timing means. Conventional timing means often are used for the slower and. preliminary phases of preparation of the chamber prior to reception of the ion beam, as for example the giving of a warning signal, the resetting of a clearing field, the resetting of a generator circuit or the preliminary slow expansion of the chamber volume. However, when these preliminary preparations have been com pleted a fast and dependable timing means, commonly called the cloud chamber fast timer, is needed to achieve optimum results from the chamber and its associated particle accelerator which provides the particles responsible for the ionizing events. Moreover, due to the lapse of time required for the preliminary preparations, as well as delays caused by other factors, it is not feasible to have the fast timing means operating continuously. As a consequence, special design features permitting quick starting and stopping, low moments of inertia and the like are demanded in the construction of such means. The present invention therefore has as an object the provision of a new and improved fast timing means suitable for controlling the final stages of cloud chamber operations.

A second object is to provide a new and improved intermittently operable timing means for jointly controlling a cloud chamber and a particle accelerator.

Another object is to provide a timing means having an improved mechanical driving structure afiording intermittent rotation of a timer shaft.

Another object is to provide a timing means having a plurality of adjustable switch elements adapted to provide positively spaced functioning thereof.

A further object is to provide a timing means having relatively small inertia of moving parts.

Other objects and advantages will become more apparent as the description proceeds when considered in conjunction with the accompanying drawings in which I Figure 1 is a diagrammatic view illustrating one arrangement of the timing means with respect to the cloud chamber, particle accelerator and camera;

Fig. 2 is a perspective view of the timing means showing the drive mechanism therefor;

Fig. 3 is a sectional view of a portion of the timing means taken along the vertical axis of the timer shaft; and

Fig. l is an end view showing the motor mounting with the surrounding housing for the structure being shown in section.

Referring first to Fig. 1, one utilization is shown by means of which the timer l0 may control the sequence of operation of the clearing field of a cloud chamber H, the fast expansion means 12 of said chamber, the oscillator l3 of a particle accelerator it, such as a cyclotron, the arc pulse means l5 of said particle accelerator, the camera means It and the necessary stopping means for the timer itself. As will be apparent, appropriate conductors, sources of electrical current, actuating devices dependent upon impulses from timer H), and the like, forming no part of the present invention, may be employed as desired for carrying out the control of the chamber and accelerator. By proper calibration of the timer in a manner later to be disclosed, these several events may be controlled so as to be effected within a total elapsed time of approximately 0.25 second. As will further be apparent to those skilled in the art, conventional cloud chambers, cameras and particle accelerators may be employed in connection with our invention and no detailed description thereof is required for a full understanding of our improved apparatus. In addition, it will be further understood that other timing apparatus may be employed in connection with the preliminary operations of these several units of the combination prior to the control exerted by timer I 0 for the final, fast operation of the combined structures.

As shown in Figs. 2 and 3, the timer means IE! may be constructed as a compact unit having a vertically disposed front wall 20 and rear wall 2|. At one end of said walls a cross member 22 provides a bearing surface 23 in which one end of the rotatable main timer shaft I00 is journalled. Adjacent the other end of said walls a second cross member 25 is located between said walls thus providing a second mounting in which the shaft may be journalled and resulting in an open framework upon which the several elements of the timing apparatus may be positioned for easy adjustment and maintenance.

For the purpose of mounting the driving connection from a suitable motor to shaft H59, a platform including upper and lower plates 38 and 3| respectively is provided. At one end each plate is securely affixed to cross member 25 while at a point spaced inwardly from the other end of each plate, a spacer 24 is located serving as a 1 further bearing for said shaft as well as a braking abutment therefor. The lower plate 3i preferably extends farther beyond said spacer than does its companion upper plate 38 and said lower plate terminates in a bifurcated portion 32 through which a suitable pin 33 may extend for a purpose later to become apparent.

Mounted in cantilever fashion upon the side of cross member 25 near rear wall 2 i, as by means of an appropriate bracket 36, is a small electric motor 31, preferably of the synchronous type and connected by any suitable means (not shown) to a source of power. Motor 31 is provided with a suitable gear reduction means including a driven gear 38 adapted to mesh at all times with a gear 39. During operation of the cloud chamber and the particle accelerator, motor 3'? is permitted to run continuously thus effecting a continuous rotation of gears 38 and 39. By a suitable gear ratio any desired speed of rotation may be imparted to the timer shaft I00, one speed which has been found to be satisfactory being that of 120 revolutions per minute.

In view of the intermittent usage required by cloud chamber operation, a clutch and braking arrangement best shown in Fig. 3 is adapted for the intermittent application of the power from motor 3'! to shaft H30. Spacer 2 is provided on oneside with a circular aperture into which extends a rotatable sleeve 46 rigidly affixed to gear 38 and serving to support said gear in meshed rotation with gear 38. A conventional ball bear ing 4| may be disposed between spacer 2d and gear 39 for transmitting axial thrust forces. At its other side spacer 24 may have a conical braking surface A2 against which a complementary shaped braking element 63 is adapted to bear atpredetermined intervals. As shown, sleeve it at no time is in contact with braking element 43. Element 43 is rigidly affixed to a reciprocable stub shaft having a slot 5| in one end thereof and intowhich a projection 52 in the end of timer shaft lllfl projects at all times. Moreover, shaft 50 is of such size and weight as to have comparatively little inertia in rapid starting and stopping. An adjustable bushing 55 mounted in cross member provides one bearing surface for a compression spring 55 while a washer 55 resting against a ball bearing 51 in turn positioned against the rear, wall of braking element 33 provides a second bearing surface for said spring. As will now be apparent from Fig. 3, spring 55 normally holds the braking member 48, the stub shaft 59 and the engaged timer shaft 585 in stationary position and a positive controlled action is required to effect rotation of these shafts.

One means for effecting the desired rotation ly mounted upon pin 33 at its lower end and is connected to the core 5! at its upper end. Suitable electrical connections, not shown, serve to actuate the solenoid core and thereby to move the arm 62 with appreciable leverage at the desired time. A tension spring 63 may be employed to hold arm 62 in ready position. As an example, a lead from the last to operate of switches Ill] ma be used to interrupt the electrical connection to the solenoid. Adjacent the lower portion of arm 62 an adjustable buffer means 65 is positioned and is adapted to be adjusted when desired, as by a suitable set screw 65. As said arm 62 moves inwardly of the platform, said buffer means contacts the outer end of stub shaft and quickly moves it inwardly, thus effecting a release of the braking means 43 from contact with surface 42 and permitting rotation of the engaging shafts.

As shown in Fig. 3 the rotating gear 39 is provided with a conical cavity H1 with which a complementary conical surface H on the end of stub shaft 58 is adapted to engage. Upon actuation of arm 62 as above described this portion of the stub shaft engages with the gear 39 and since a simultaneous release of the braking means has occurred, shaft 50 and shaft Ids instantly begin to rotate.

The thus described means for eifecting rotation of shaft Hill contributes in large measure to the realization of the objects of our invention, as now will be found from the following description.

Upon timer shaft its a plurality of separately adjustable control groups are mounted, in this case shown as six. Since each such group preferably is identical in structure with the other groups, a description of one is considered suflicient. Referring now to Figs. 2 and 3, it will be noted that the several control groups are mounted side by side in closely spaced relation upon shaft its beginning immediately adjacent the cross member 2.5 of the mounting framework and extending to a point immediately adjacent the outer cross member 22. As a result, a compact structure is provided and both the length and inertia of drive shaft W9 is thus further reduced.

Surroundhig shaft ifiii and independently movable with respect thereto is a switch supporting means, here shown as a circular plate EM provided with a circumferential rim Hi2 adapted to bear indicia of time intervals. Plate iili preferably is provided with a hub section m3 adapted to be loosely supported upon the rotatable timer shaft lfiii. As will be apparent, if the small amount of friction caused by resting the plate IE3! upon the timer shaft tends to hamper the quick starting and. stopping of the shaft, such plate may conveniently be entirely supported for adjustable movement upon Walls 253 and 2! without departing from the invention. In some cases, however, a small amount of friction is useful in controlling the movement of the low inertia timer shaft and the arrangement as shown has. been found to be satisfactory in such cases. To the hub section :93 a worm gear I04 is rigidly affixed and is adapted to mesh with a rotatable worm ii ii mounted upon shaft I33. This shaft may be mounted at one end in front wall 29 and at the other end in rear wall 2! and is adapted to be turned as by means of a knob ifll. Any suitable means for preventing play or back-lash in worm 35 may be used, such as a compression spring, not shown, located adjacent rear wall 2!.

Rigidly affixed to one side of plate Nil at an appropriate height is a conventional microswitch element 5- i 6 having connections, not shown, leading to a unit to be controlled. For example, the switch lie herein shown may normally be the first to operate and may conveniently lead to the cloud chamber clearing field apparatus as di- 5 agrammatically shown in Fig. 1. Depending from switch H is a contact arm HI and actuating roller H2 therefor so arranged that when the arm. is lifted the desired action of switch I Ill will occur.

Cooperating with the roller H2 is a circular, relatively thin and light weight cam plate H5 rigidly affixed to shaft I00 by any suitable means and bearing one or more light weight adjustable members such as the lugs of dogs H6. These members may be securely adjusted in place upon the circumference of plate H5, in the path of contact with roller H2, by means of set screws or similar fastening means. Since lugs H6 may be positioned at any point on the circumference of cam plate H5 and since shaft I06, in the example given, may rotate at a speed of twice per second, it will be obvious that the operation of the microswitch can be calibrated to extremely small intervals of time. Upon the rim I02 of the corresponding plate lill a scale H3, preferably reading in hundredths of a second intervals, is placed and may be viewed from the exterior of front wall as through the transparent closure H4.

As will be apparent, any desired number of the above-described control groups may be mounted side by side upon timer shaft 16!! and the leads from the switches H0 thereof may be connected to the apparatus desired to be controlled in conjunction with the cloud chamber operation. In so assembling the apparatus the indicia upon the several plates Hll preferably are positioned along a reference line and the lugs I I6 placed upon plates H5 along the same or an equivalent reference line. After determining the units to be controlled, the relative timing therebetween and the sequence of control, the several plates ii)! are turned by means of knobs IE1 until the proper time intervals are shown by scales H3 against the proper reference line. Thereafter upon rotation of shaft Illa the desired sequence and timing of operation of switches H0 will occur. Normally the last switch H0 to operate serves to interrupt the current to solenoid '65 so that the shaft ii!!! is bought quickly to rest as heretofore described. After the solenoid 60 is inactivated and the timer shaft comes to rest a variable interval of time may elapse before the apparatus is again used, Accordingly, a separate connection of any conventional nature, such as a push button, not shown, may be employed to energize solenoid 60.

Whereas the apparatus as above described may be employed for many usages it will be apparent that on occasion additional features may be desired without changing in any way the essential nature of the invention. For example, the timing apparatus as a unit may be fitted, after adjustment of the control groups, into various types of dust tight enclosures provided with the essential apertures for electrical leads. As shown in Fig. 4 one such enclosure may be fitted against the rear portion of wall 20.

Having thus described our invention with respect to one embodiment thereof, it will be apparent that numerous modifications may be made within the spirit and scope of the invention. Therefore, it is not desired to limit the invention to the exact details shown except insofar as they may be defined in the following claims.

What is claimed is:

1. In a timing apparatus having an intermittently rotatable timer shaft, cam means affixed to said shaft and a switch adjustable in position with respect to said cam and operable thereby,

the improvement comprising, means for controlling rotation of said shaft and including, a. constant speed motor having a shaft driving gear adapted to rotate continuously, a reciprocable stub shaft in axial driving engagement with said timer shaft, a support for said stub shaft, 9. braking member on said stub shaft adapted to engage said support in one position of the stub shaft, means normally holding said stub shaft in braking position, a clutch member on said stub shaft adapted to engage the shaft driving gear in a second and axially displaced position of the stub shaft and intermittently operable clutch engaging means adapted to force the stub shaft into engagement with the shaft driving gear and to release the braking member from engagement with the support.

2. In a timin apparatus having an intermittently rotatable timer shaft, cam means affixed to said shaft and a switch adjustable in position with respect to said cam and operable thereby, the improvement comprising, means for controlling rotation of said shaft and including, a constant speed motor having a shaft driving gear adapted to rotate continuously, a reciprocable stub shaft in axial driving engagement with the timer shaft, a support for said stub shaft, a braking member on said stub shaft adapted to engage said support in one position of the stub shaft, a direct acting compression spring normally holding said stub shaft in braking position, a clutch member on said stub shaft adapted to engage the shaft driving gear in a second and axially displaced position of the stub shaft, a solenoid, and intermittently operable clutch engaging means connected to said solenoid and operable to force the stub shaft into engagement with the shaft driving gear and to release the braking member from engagement with the support.

3. In a timing apparatus having an intermittently rotatable timer shaft, cam means affixed to said shaft and a switch adjustable in position with respect to said cam and operable thereby, the improvement comprising, means for controlling rotation of said shaft and including, a constant speed motor, a centrally bored rotary element in continuously driven relationship with said motor, a reciprocable stub shaft in axial driving engagement with said timer shaft and extending through said bore, a support for said stub shaft, a braking member on said stub shaft adapted to engage said support in one position of the stub shaft, means normally holding said stub shaft in braking position, a clutch member on said stub shaft adapted to engage the shaft driving gear in a second and axially displaced position of the stub shaft and intermittently operable clutch engaging means adapted to force the stub shaft into engagement with the shaft driving gear and to release the braking member from engagement with the support.

4. In a timing apparatus having an intermittently rotatable timer shaft, cam means affixed to said shaft and a switch adjustable in position with respect to said cam and operable thereby, the improvement comprising, means for controlling rotation of said shaft and including, a constant speed motor having a shaft driving gear adapted to rotate continuously, a reciprocable stub shaft in axial driving engagement with said timer shaft, a support for said stub shaft, a braking member on said stub shaft adapted to engage said support in one position of the stub shaft, sprin means adjustably mounted on said 7 su or n i r e m force t ansmittin elaiiQn to sa d b i gmem r e n m ll olding said stub shaft in braking position, a clutch member on said stub shaft adapted to engage the shaft driving gear in a second and axially displaced position of the stub shaft and intermittently operable clutch engaging means adapted to force the stub shaft into engagement with the shaft driving gear and to release the braking member from engagement with the sup- 10 port.

WILSON M. POWELL. ALBERT W. HUGHES.

8 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,828,126 Brown 0013. 20, 1931 2,085,849 Dollison et a1. July 6, 1937 2,143,692 Haar Jan. 10, 1939 2,163,419 Warren June 20', 1939 2,181,422 Gawan Nov. 28, 1939

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