US3580046A

US3580046A - Method and apparatus for testing rotation-responsive delay devices

Info

Publication number: US3580046A
Application number: US833007A
Authority: US
Inventors: Oliver F Cheney
Original assignee: Delaware Valley Armaments Inc
Current assignee: Delaware Valley Armaments Inc
Priority date: 1969-06-13
Filing date: 1969-06-13
Publication date: 1971-05-25
Anticipated expiration: 1988-05-25

Abstract

Arming delay-devices, suitable for delaying the arming of an artillery shell until it is well away from the gun by which it is fired, are tested in production by rotating each of them in a test stand and determining the number of turns of the device required for it to become armed.

Description

I United States Patent 3,580,046

[72] Inventor Oliver F. Cheney [56] References Cited Philadelphia, Pa. UNITED STATES PATENTS No 1969 27,515 8/1943 Ferrone 73/5 Patented y 2551971 2,353,436 5/1951 Brown... 73/167 [73] Assignee Delaware Valley Armaments, Inc. f y Pmlce ML Laure] Twp, NJ Assistant ExaminerDenis E. Corr Attorney-l-lowson and l-lowson [54] METHOD AND APPARATUS FOR TESTING 4 ROTATION-RESPONSIVE DELAY DEVICES 8 Claims, 6 Drawing Figs.

[52] U.S. Cl 73/5, ABSTRACT: Arming delay-devices, suitable for delaying the 73/167 arming of an artillery shell until it is well away from the gun by [51] Int. Cl F42c 21/00 which it is fired, are tested in production by rotating each of [50] Field of Search 73/5, 167; them in a test stand and determining the number of turns of 89/6 the device required for it to become armed.

Z30 25a UPT/COQL D. a. Z5 Z4 l: SENSOR M 1 ADJUST/151.1: Z/Z M PR5 SE7 [45 NUMBER I Z s0u,4 c 5 Mara/P J 00/1/7904 LfiNTRflL Z/g/ *cwawr sroP LINE A 0. SUPPL Y METHOD AND APPARATUS FOR TESTING ROTATION- RESPONSIVE DELAY DEVICES BACKGROUND OF INVENTION This invention relates to method and apparatus for testing rotation-responsive delay-devices, particularly arming delaydevices for use with shells.

It is known to employ delay-devices in explosive shells for the purpose of delaying, until a predetermined time after firing, the automatic arming of the shell which enables it to explode. In some cases the delay-device may be utilized to cause such explosion to occur, but in other cases it is used as a safety device to prevent explosion of the shell until after the shell is well away from the gun by which it was fired. For this purpose rotation-responsive delay-devices are known which contain a mechanical time-delay mechanism controlling the arming of the device, which mechanism is set to its unarmed condition before the shell is put into the gun and responds to shell rotation after firing of the gun so as to move progressively toward its armed condition during the early portion of the flight of the shell.

The short arming times and high timing accuracies required in such delay-devices make it inevitable that there will be a significant spread in operational characteristics of the delaydevice when it is made by mass-production techniques. It is also inevitable that an occasional one of the mass-produced devices, if placed in a shell, would cause too-early arming of the shell, or a too-late arming resulting in a dud" which would not explode because the delay-device had not become armed by the time that shell explosion was desired. For the safety of personnel and of the guns, it is important that the delay-device not arm itself too early, and obviously the firing of duds preferably is to be prevented also. From the economic viewpoint of the producer, it is also often important to avoid the delivery to a buyer of even one earlyor late-arming delay-device in a batch, since a random checking of the delay-devices or of the complete shell assemblies by the buyer which results in finding a defective device in a batch may well result in rejection of the entire batch. For all of these reasons it is desirable to subject each delay-device to a simulated performance check before it is delivered to the customer.

The present invention is concerned primarily with a method and apparatus for performing such checks or tests. Previously such tests have been made by attempting to rotate the delaydevice exactly at a specified fixed rate of rotation for a specified brief time period and sensing whether the device has armed itself in the specified time.

A number of difficulties have been encountered with such a test procedure which have made it difficult to perform accurately and frequently over long periods. First, it requires very accurate maintenance of the rotation frequency at the prescribed value throughout the test interval, combined with accurate time measurement or accurate control of the duration of the test interval. Since the duration of the test is itself typically short, e.g. 0.8 second, the time period during which the rotational speed rises from zero to the specified constant speed must be very short and preferably constant for all tests in order to achieve accuracy and reliability of measurements. Ideally the rotational speed is a step function, rising instantaneously from zero to exactly the prescribed test speed and remaining constant at the latter value throughout test; in some tests it is also necessary to stop the rotation nearly instantaneously to obtain accurate results. In any practical system such nearly instantaneous starting and/or stopping is difficult to provide, and departures from the ideal situation have been found to result in test inaccuracies of practical importance. It is particularly difficult to provide accurate test performance repeatedly over long periods of time, especially in view of the unusual stresses produced on the equipment by sudden startup and/or stopping and in view of unavoidable changes in the equipment due to wear.

A possible alternative for avoiding problems of rapid rotational startup and/or stopping is to place the delay-device in rotation at the desired angular velocity while it is unarmed and before it is actuated, to actuate it only after it has come up to the specified speed so that it will then proceed toward its armed condition, and to measure the interval between such actuation and the time at which the armed condition is achieved. This requires a special arrangement for producing and sensing the initial actuation of the device while the device is rotating at a high rate, and again requires that the speed of rotation be held constant throughout the test interval.

Accordingly, it is an object of the invention to provide a new and useful method and apparatus for the testing of delaydevices.

Another object is to provide such method and apparatus which is of improved accuracy and reliability, especially over long periods of repeated use.

Another object is to provide such method and apparatus whichis simple and convenient to operate.

A further object is to provide such method and apparatus which does not require accurate measurement or control of rotation rate or test duration.

SUMMARY .OF INVENTION We have found that in certain types of delay-devices which operate in response to rotational motion thereof, the time required for the device to change from its initial unarmed condition to its armed condition (i.e. the time-to-arm) is inversely proportional to its angular velocity of rotation, at least over a substantial range of angular velocities. That is, the faster the device is rotated the faster it advances toward its armed condition and the shorter the time-to-arm 1, This relation is expressed by the following equation:

where w is the angular velocity of the delay-device about its axis and K is a constant characteristic of the delay-device. Such a characteristic has been found typical, for example, in delay-devices of the type using a centrifugally operated runaway escapement.

In accordance with the invention there is provided a method and apparatus for the testing of such delay-devices having a time-to-arm inversely proportional to the rate of rotation thereof, in which the criterion or measurement utilized in testing is the number of turns of rotation of the fuse required to produce arming thereof, i.e. the turns-to-arm, rather than the time-to-arm at a specified rotation rate. It has been found that, with this method and apparatus of the invention, the rotational speed may vary substantially during test without reducing the accuracy of the test, thereby avoiding the necessity for producing step-changes in rotational rate and for controlling accurately the rate of rotation. Preferably the delay-device is placed in its unarmed' condition while at rest and is then rotated at a rate subject to variation, the number of turns being counted and used as the test criterion. For example, in one preferred embodiment the unarmed fuse is placed into rotation, the turns are counted, the time at which arming occurs is sensed, and the number of accumulated turns which have been performed, from the beginning of rotation up to the time of arming, is determined. The resultant turns-to-arm figure is then utilized as the criterion of an acceptable fuse. In an alternate embodiment, a predetermined number of turns less thanthat for which the fuse is to become armed are applied to the fuse, rotation is then stopped, and the armed or unarmed condition of the fuse is observed; if the fuse has become armed in this time it is rejected. Similarly, a predeter mined number of turns corresponding to the desired maximum range-to-arm may be applied to' the delay-device, and those fuses which are not armed by this number of turns may be rejected we duds."

During these tests the speed of rotation is not critical, and startup and arresting may be at relatively slow rates. Ac-

cordingly the principal sources of the difficulties outlined above for time-to-arm tests are avoided, and accurate, reliable, repetitive measurements made possible in mass production over long periods of time.

Such tests in terms of turns-to-arm are not only easier to make and more accurate than time-to-arm tests, but are also meaningful with respect to the end use to which the delaydevice is to be put. To a first approximation, the range-to-arm R, of a delay-device obeying equation (1) above is substantially equal to T /G where t,, is the turns-to-arm and G is a constant characteristic of the geometry of the gun (including its barrel rifling) from which the shell is to be fired. Hence for any gun of given geometric characteristics, the range-to-arm R is determined'directly by the turns-to-arm T substantially independently of the muzzle velocity. In this respect the situation is somewhat analogous to rollinga ball along a flat surface so that its rate of rotation is proportional to its forward velocity; the number'of turns made by the ball in travelling a given distance will be independent of its forward velocity, and the numberof turns it makes in travelling to any position will therefore be a measure of the distance it has travelled. Similarly for a shell fired from a given gun having predetermined barrel rifling whereby the rate of rotation of the shell upon exit from the gun is substantially proportional to muzzle velocity, the number of turns made by the shell in flight is a measure of the range through which it has travelled, and the number of turns in flight required to arm the delay-device (T,,) is therefore a measure of the range at which arming occurs (R forthat or a similar gun.

When using the tums-to-arm criterion of the invention, the rotational startup and/or slowdown speed pattern is not important, and there is therefore no need for instantaneous startup or stopping and noneed to measure or to maintain the rotational speed constant during test. Because of this, substantial improvements in accuracy and reliability of testing have been realized. I

BRIEF DESCRIPTION OF FIGURES Other objects and features of the invention will be more readily understood from a consideration of the following detailed description taken with the accompanying drawings in which:

FIG. I is a fragmentary side view, with parts broken away, showing the position in a conventional shell of a delay-device of the type suitable for testing by the method and apparatus of the invention;

FIG. 2 is an end view showing one face of the conventional delay-device of FIG. 1, with its cover plate removed;

FIG. 3 isa schematic diagram showing one form of test apparatus in accordance with the invention;

FIG. 4 is a schematic diagram showing another form of apparatus in accordance with the invention;

FIGS. 5 and 6 are graphical representations to which reference will be made in explaining the operation of the apparatus of FIGS. 3 and 4 respectively.

DETAILED DESCRIPTION Referring now to the specific embodiments of the invention shown in the drawings by way of the example only, FIG. 1 illustrates an explosive shell 10 containing as a component thereof an arming delay-device 12 of a type suitable for testing by the method and apparatus of the invention. The shell may be of the type comprising a main body portion 14 containing a main explosive charge intended to explode in response to impact of the firing pin 16, against the ground or similar object. Actuation of firing pin 16 by impact detonates the adjacent detonator 17 to produce an impulse which, when the system is fully armed, travels along the interior of a flash tube 20 to the front surface of the delay-device 12 and through a central opening in the delay-device 12 to a detonator 21, which in turn explodes to detonate a booster-charge pellet 22 and, in turn, the main explosive charge contained in the rear of the shell behind the booster cup 22A.

However, arming delay-device 12 has an unarmed condition in which the central opening through it is blocked and detonator 21 not aligned with bore 20, and contains a timing mechanism responsive to rotation of the shell to move progressively toward its armed position in which the central opening is unblocked and detonator 21 aligned withbore 20. In use, the arming delay-device 12 in its unarmed condition is installed in the shell before the shell is to be used and, when the shell is fired, the rotation of the shell due to the barrel rifling causes the arming delay-device to move progressively toward its armed condition and to reach the armed condition when the shell is at an appropriate distance away from the gun.

Typically the shell assembly may also comprise an auxiliary delay plunger assembly 23 which closes off communication between flash tube 20 and delay-device 12 until the shell begins to rotate in the gun, at which time assembly 23 is promptly actuated centrifugally to open the path to delaydevice 12. Also sometimes employed is an interrupter .assembly 24 which can be manually adjusted either to open the central bore from the flash tube to the assembly 23, or to divert the explosive impulse through a parallel path (not shown) thereby to introduce a further fixed delay in explosion of the shell.

The above-described shell assembly and delay devjce 12 may be of known types, such as those used in conventional army artillery shells. In the present case the delay-device 12 is of a type in which the time for it to become armed is inversely proportional to its rate of rotation, a characteristic which has been found to exist in most centrifugally operated delay mechanisms and particularly those of the runaway. escapement type.

FIG. 2 illustrates the important operative components of one such known type of arming delay-device 12. since such delay-devices and timing mechanisms are well known in the art, all of the structural details are not shown or described in detail. In general, a segmentally toothed rotor gear assembly 40 is mounted for rotation on the body 42 of the delay-device 12, by means of a rotor shaft 44 radially displaced from the shell axis 47. The rotor gear assembly 40 carries the detonator 21 behind it, and is'appropriately weighted so that its center of gravity is displaced from the axis of rotor shaft from the shell axis- 47, and at least initially is also displaced from that shell diameter which passes through the rotor axis and the shell axis. Accordingly, upon rotation of the shell about axis 47, the center of gravity of rotor gear assembly 40 tends to move toward its radially outermost position, thereby exerting a torque on the rotor gear assembly about the rotor axis.

For safety purposes, the rotor gear assembly 40 is initially held in its completely unarmed position (as shown) bya pair of

rotor detents

50 and 52, which engage corresponding depressions in the edge of the rotor gear and are normally spring-biased into this position by means of corresponding detent springs 56 and 58 respectively. When the shell is fired, the first small fraction of a revolution of the shell is sufficient to cause the rotor detents to pivot outwardly about their respective detent shafts 64 and 66 and thus free the rotor gear assembly 40 for progressive rotation about its shaft axis; this typically occurs at about 1,000 to 2,000 rpm.

In the example shown in FIG. 2, rotor gear assembly 40 then responds to shell rotation to rotate progressively further in the counterclockwise direction, with respect to body 42, about an axis through rotor shaft 44. The teeth of rotor gear assembly 40 thereby drive the pinion of the first gear-and-pinionassembly 60, the support shaft 61 of which assembly is rotatably mounted on body 42. The resultant rotation of gear-andpinion assembly 60 drives a second gear-and-pinion assembly 64, with which it engages; the latter gear-and-pinion assembly then drives the pinion of the escape wheel and pinion assembly 68, the support shaft for which is also rotatably mounted on body 42. The escape wheel of the assembly 68 is toothed in appropriate manner to engage the balance pins 72 and 74 of the pivoted balance 76, and to cause the latter balance to oscillate back and forth rotationally about a pivot 77.

The above-described mechanism is commonly known as a centrifugally operated runaway escapement, and responds to rotation of the shell in such manner that the arming time required for the detonator 21 to move counterclockwise from its initial unarmed position into an armed position coaxial with the shell axis 47 (shown dotted at 21A) is inversely proportional to the rate of rotation of the shell. There are a variety of mechanisms which exhibit this characteristic, and its existence may be determined by analysis or simply by measurements of the times required for arming at different rates of rotation of the mechanism.

The mechanism of FIG. 2, it will be understood, would normally be covered on its front face with a cover plate having a central aperture coaxial with the shell axis 47, thereby to protect the mechanism. Detection of the existence of the armed or unarmed condition is conveniently enabled by the fact that, in the unarmed condition, the metal of the surface of the rotor gear assembly 40 is visible at the center of the shell axis, and may for example be of reflective brass; the visible end of the detonator 21, on the other hand, may be a dull red so that when the delay-device becomes armed the dull red color is visible at the shell axis, through the central opening in the cover plate. This facilitates both visual and optical sensing of the armed and unarmed conditions of the mechanism.

There will now be described in detail the method and apparatus preferably utilized in accordance with the invention to test delay-devices of this class, namely those in which the time for arming is inversely proportional to the rate of rotation thereof.

Referring now to FIG. 3, the apparatus illustrated therein is suitable for applying a specific predetermined number of turns of rotation to an arming delay-device, for example to determine whether it arms itself too soon. In essence, the minimumacceptable number of turns-to-ann is first determined, and the apparatus shown then serves to provide this number of turns to each delay-device to be tested, after which the delay-device can be examined to determine whether it has armed itself during the test. If it has, it is rejected because of its too-early arming characteristic. Those devices not becoming armed during the test are deemed acceptable, at least with respect to their minimum arming-time characteristics.

In the FIG. 3 embodiment, an upright cuplike spinner 200 is designed to receive the delay-device 12, the bottom of the spinner being provided with an upright pin 201 which extends into a corresponding bore in the lower end of delay-device 12 so that spinning of spinner 200 causes delay device 12 to spin along with it at the same rate. A drive shaft 202 is operatively connected to spinner 200, and is itself supported for rotation on appropriate bearings (not shown). A driven pulley 206 at the opposite end of the drive shaft 202 is coupled by means of a belt 208 to a driving pulley 210, which is rotated by electric motor 212 thereby to rotate drive shaft 202. Electrical power for driving motor 212 is supplied from an AC supply line 216 by way of a suitable motor control circuit 218 which responds to operation of a start control 220 to start operation of the motor and which responds to application of a current to stop terminal 222 thereof, over line 224, rapidly to arrest motion of the motor. There are many types of motors which may be utilized for this purpose, although for convenienceand to avoid problems of brush life it is preferred to use an AC motor, and to apply a direct current through the normal AC windings in the direction to stop the motor rapidly.

Drive shaft 202 is provided with a decimal disc 230 which rotates with shaft 202 and contains around its outer periphery a plurality (in this case of optically distinguishable transverse regions such as 232; for example, the region between the elements 232 may be black and the elements such as 232 may be of bright reflecting material. An optical sensor 236, containing a conventional lens and photocell arrangement, is positioned so as to sense the passage of each of the elements 232 through a predetermined position adjacent the sensor, and to produce an electrical pulse in response to each such passage. In this way, l0 pulses are produced by the optical sensor 236 for each full revolution ofdrive shaft 202.

The electrical output of the optical sensor 236 is passed through a conventional direct-current amplifier 238 to a counter and comparison unit 240. Unit 240 comprises a pulse counter 242 supplied with the pulses from DC AMPLIFIER 238 and effective to count them, beginning from the time at which the motor is started by operation of the starter control 220. A reset line 245 is preferably connected from the start control 220 to the reset input of counter 242 so as to reset it at the starting of each new testing operation.

Circuit 240 also comprises a comparator 244 supplied with the signal from counter 242 and from an adjustable preset number source 246, which can be manually adjusted to apply to comparator 244a signal representative of a chosen number corresponding to the number of turns which are to be applied to the delayalevice 12 during test. Comparator 244 compares the count from counter 242 with the number information supplied form source 246 and, when these two numbers become equal, produces an output current on line 224 to motor control circuit 218 to effect arresting of the rotation of motor 212. Because of delays in the motor control circuit and in the motor braking, the number represented by the signal from number source 246 is typically smaller than the turns to be applied by the number of turns made during the relay-operating and braking times.

Each of the variouselements of the circuit of FIG. 3 may be constructed in accordance with known conventional practice, and hence the details thereof need not be described herein. It is sufficient to point out that in view of the characterization of the various elements and their operation set forth above, it will be apparent to one skilled in the art that the apparatus of FIG. 3 applies a predetermined number of turns to the delay-device 12 upon operation of the start control 220 by an operator, and that the criterion utilized in the operation of the apparatus is the number of turns made by the delay-device l2, and not the time for which it runs; furthermore, no special control or measurement is provided for maintaining a particular frequency of rotation of delay-device 12 during the test, and startup times are not critical.

FIG. 4 illustrates another embodiment of apparatus for testing of arming delay-devices such as 12. In this case sufficient turns are applied to assure arming of those delay-devices having acceptable characteristics, and an indication is provided of the number of turns required to arm the particular delaydevice being tested. The delay-device 12 is again mounted in an appropriate cuplike spinner 310 for rotation by motor 312 by way of belt 313 and drive shaft 314, the operation of the motor being controlled by a suitable motor control circuit 316 supplied with AC supply current over line 318. A toothed ring 320 of magnetic material is provided at the bottom of spinner 310, and rotates with drive shaft 314. The'teeth of ring 320 cooperate with a magnetic pickup 322 to produce electrical pulses from magnetic pickup 322 each time one of the teeth passes a predetermined position adjacent the pickup; suitable forms for such a pickup, including types utilizing electromagnets, are well known in the art. Electrical pulses from pickup 322 are thereby applied to the count input of a pulse counter 324 when spinner 310 has been placed in rotational motion by operation of the motor start control 329.

The cylindrical detonator 21 in the delay-device 12 is provided with an upper surface which is optically differentiable from the surrounding upper surface of the delay-device 12, as previously described. That is, in this example it is provided with a dull red coating so that the central aperture in delaydevice 12 is closed by a shiny metallic surface when the device is unarmed and is closed by a dull red surface when it becomes armed. This provides a convenient method for optically detecting the armed condition of the device.

More particularly, a suitable light source 336, including the usual lamp and lens system, directs illumination upon the center of the upper surface of delay-device 12, the reflection of this light being sensed'by an optical sensor 338, which may include the usual lens arrangements and photocell. devices suitable for such purposes. Optical sensing unit 338 then supplies a relatively large current to photocell amplifier 340 when delay-device 12 is unarmed but, when, it becomes armed, the resultant reduction in reflected light from the dull-red end of the detonator 21 will cause an abrupt drop in the current to the photocell amplifier. Accordingly, a recognizable pulse is produced by photocell amplifier 340 when the delay-device becomes armed. Alternatively, the change in hue at the center of the delay-device due to arming may be sensed by including one or more color-selective filters in the optical-sensing means, so as to sense changes in reflected light of a selected color (e.g. red) or to sense and compare two colors of reflected'light (e.g. red and green) for the armed and unarmed conditions.

The latter output pulse from photocell amplifier 340 is supplied to stop terminal 323 of counter 324 to stop the abovedescribed counting of the turns indicating pulses from magnetic pickup 322. Counter 324 then indicates the number of turns of the delay-device 12 required for it to become armed. This information may be displayed in conventional manner by counter 324 so as to enable visual reading thereof by an operator. However, in the present embodiment further apparatus is provided to produce an automatic optical indication of whether the turns-to-arm is within or outside a preset accepted tolerance range.

More particularly, the count produced by counter 324 is supplied to a comparator logic circuit 328, to which there is also supplied numerical information from an adjustable upperlimit number source 330 and an adjustable lower-limit number source 332. The latter two sources of numerical information may be adjusted by the operator to provide any desired upper and lower limits defining an acceptable tolerance range for the turns-to-arm of the delay-device.

Comparator logic circuit 328 operates, in response to a control pulse from photocell amplifier 340 delivered over line 339, to compare the count achieved by counter 324 with the upper and lower limits established by

sources

330 and 332. In this embodiment, comparator logic circuit 328 produces an output current from output terminal 350 thereof when, and only when, the count finally achieved by counter 324 lies between the upper and lower limits established by

sources

330 and 332. This output current passes through an accept" lamp 354 to the motor-stop control terminal 356 of motor control circuit 316, so that the motor is thereby automatically stopped and the accept" lamp illuminated to indicate to the operator that the unit is acceptable. On the other hand, if the count achieved by-counter 324 is outside the range established by the upper and lower limits of

sources

330 and 332, an output current is produced from output terminal 362 of comparator logic circuit 328, which passes through the reject lamp 364 to the motor stop terminal 356. Under such conditions, the reject lamp is illuminated instead of the accept" lamp, and the operator is thereby warned that an unacceptable unit has been tested; the motor is at the same time automatically stopped in preparation for testing of the subsequent unit.

Resetting of the counter may be provided automatically in response to operation of the start control 329 by way of an appropriate reset line 370 connected to the reset terminal of counter 324.

Again, as in the case bf the embodiment of FIG. 3, the rate of rotation of the delay-device l2 and the duration of its rotation are not critical, since it is merely the total number of turns provided which is used as the criterion for acceptance or rejection of the device, and neither startup, stopping nor speed of running between start and stop are in any way critical.

Considering now FIG. with particular reference to the operation of the apparatus of FIG. 3, there is shown therein a graph in which ordinates represent revolutions per minute of the spinner 200 and of the delay-device 12 contained therein, and abscissae represent time in milliseconds measured from the time t at which rotation of the spinner is started. When the speed has risen to about 1,500 rpm, the speed level d is reached at which the

detents

50 and 52 of FIG. 2 move outwardly to release the rotor gear assembly 40 and thereby actuate the delay-device so that it immediately begins to move toward its armed position. The full test speed of 3,000 rpm. is reached in about 60 milliseconds and is continued for another 650 milliseconds, at which time braking of the motor 212 will begin; braking of the motor will be substantially completed at about 800 milliseconds, or 0.8 second after the motor was started.

Using prior-art test procedures, the operation shown in FIG. 5 would represent an attempt to rotate the delay-device at a test speed of 3,000 r.p. m. for a period of 650 milliseconds. For such a test to be satisfactory, the test speed would have to be accurately controlled, during repetitive tests and over long periods of time, at the exact value of 3,000 rpm, with resultant complexity, expense an inherent susceptibility to at least some degree of error. In addition, even if the speed were so controlled during the 650 millisecond interval, rotation during the finite startup and stop intervals would produce additional arming motion of the delay beyond that intended to be applied during the 650 millisecond interval. Such motion occurs upon startup, between the time when the speed has reached the detent-release speed d and the time t, at which the test speed is achieved, and also occurs upon arrest, between the time t;, when braking starts and the time t when the motor actually stops. The effects on time-to-arm of these startup and stop intervals will vary between different types of test equipment, between different embodiments of the same type of equipment and, importantly, between different times and con ditions of operation of the same test equipment because of wear, aging and changes in environmental conditions. For these reasons also, such prior art testing procedures and apparatus involve substantial inaccuracies in measurement and/or additional expense in construction and maintenance of the apparatus.

With the method and apparatus of the invention on the other hand, counter 242 counts the total number of turns applied to the delay-device from the initial startup time t to the final arrest time t.,, and the comparator 244 operates to stop the motor at the appropriate time so as to apply the desired total number of turns to the delay-device. For example, in terms of turns, rotation of the delay-device is initiated at the time t increases in about one-half turn to the detent-release level d, achieves maximum velocity at the time I, after a total of about two turns, continues for an additional 30 turns at which point comparator 244 puts out a stop signal, and continues for an additional 2% turns while the relays in the motor control circuit 218 respond to the stop pulse to begin arrest of motor 212. An additional two turns may typically be required to bring the motor to a complete stop. Thus, in the assumed practical embodiment, about 4% turns occur after the comparator 244 produces its stop signal, so that if, as in the example shown, 36 /2 turns are to be applied, the adjustable preset number source 246 would be adjusted to the number 32; or, the system can be arranged so that the latter number source is adjusted to equal the total turns desired 36 /2) and the comparator 244 internally arranged so as to effectively subtract 4% turns from this number and thereby produces an output stop pulse when counter 242 reaches the 32-turn count.

With this operation in accordance with the invention, the criterion is the total turns applied to the delay-device, and the manner in which the speed or rotation varies during the test period is therefore not critical; in particular, the exact form of startup speed-characteristic, and the exact value of the rotational speed between the startup and arrest intervals, are not critical and. may be varied without substantially altering the accuracy of the test. Of course, as in previously described operations, account should be taken of the fact that the detents prevent the delay-device from responding to rotation during the first half-tum of the device. With any reasonably rapid motor startup characteristic, this does not introduce any substantial error in the measurements; however, it should be recognized that, in the operation shown in FIG. 5, the complete delay-device has been supplied with 36 /2 turns, but the escapement mechanism has been supplied with only 36 turns.

Referring now to FIG. 6 with particular regard to the operation of the apparatus of FIG. 4, again ordinates represent revolutions per minute, but in this case abscissae represent turns applied to the delay-device about its axis. it is assumed in this example that the general form of the pattern of rotational motion applied to the spinner 310 is similar to that discussed with reference to FIG. 5, except that the rotation is applied for a longer time and through a greater number of turns, so as to assure that all acceptable delay-devices will have been armed before the motor 312 is arrested. In this example it is assumed that, devices which arm themselves between 34 and 46 turns areacceptable, and those outside this range are not. ln the example shown, the device is assumed to arm itself at 40 turns, which stops counter 324 and actuates comparator logic circuit 328. The number 40 for the tums-to-arm can be visually read on counter 324, and the comparator and logic circuit determines whether this number is between the minimum and maximum allowable limits for test; if so, the comparator and logic circuit then produces an'output signal through the accept lamp 354 to light it and to institute arresting of motor 312 preparatory to testing of the next delay-device. If the photoelectrically measured tums-to-arm is less than 34 or greater than 46, the comparator and logic circuit 328 will apply its output through reject lamp 364, indicating an unacceptable device, and will again arrest the motor 312.

Again, in connection with the procedure described with reference to FIG. 6, since tums-to-arm are sensed and used as the criterion of test, variations in startup of the motor, in the rate of rotation during the main portion of the test interval, and in the arresting operation do not have a significant effect upon the accuracy of results and hence are not critical.

It will therefore be appreciated that there has been provided method and apparatus for testing delay-devices of the type in which the time delay is inversely proportional to the rate of rotation thereof, whereby inaccuracy, complexity, difficulties of maintenance, and cost are substantially reduced by use of a tums-to-arm criterion.

While the invention has been described with particular reference to specific embodiments thereof in the interest of complete definiteness, it will be understood that it may be embodied in a variety of other diverse fonns differing substantially from those specifically shown and described without departing from the scope and spirit of the invention as defined by the appended claims.

lclaim:

l. The method of testing the action of an arming delaydevice for a projectile of a type to be fired flom a rifled barrel with imparts spin to said projectile, said delay-device comprising a centrifugally operable element supported on a body which spins with said projectile, said element being responsive to centrifugal forces generated by spinning of said body to move with respect to said body from an initial unarmed position to asecond armed position in a time inversely proportional to the rate of said spinning, said method comprising placing said element in its unarmed position, spinning said body at a rate which is subject to variation, counting the number of turns made by said body during said spinning, and selecting said delay-device as satisfactory on the basis of the number of said turns required for said element to move from said unarmed to said armed position thereof.

2. The method of claim I in which said spinning is continued sufficiently long to cause said element to move to said armed position, and comprising the steps of detecting the time at which said element reaches said armed position and detecting the number of said turns which have been made at the time when said element reaches said armed position.

3. The method of claim 1, comprising the step of arresting said spinning after a predetermined member of said turns have been made, and then detecting whether said element has reached said armed position.

4. Apparatus for testing the action of an arming delaydevice for a projectile of a type to be fired from a rifled barrel which imparts spin to said projectile, said delay-device comprising a centrifuga lly operable element supported on a body which spins with said pro ectile, said element being responsive to centrifugal forces generated by spinning of said body to move with respect to said body from an initial unarmed position to a second armed position in a time inversely proportional to the rate of said spinning, said apparatus comprising:

means for spinning said body during an interval including a period in which the rate of said spinning is subject to variation; means for counting the number of turns made by said body during said spinning; and

means actuated by said counting means for enabling determination of the number of said turns which have been made by said body;

said actuated means comprising means for arresting said spinning after a predetermined number of said turns.

5. Apparatus for testing the action of an arming delaydevice for a projective of a type to be fired from a rifled barrel which imparts spin to said projectile, said delay-device comprising a centrifugally operable element supported on a body which spins with said projectile, said element being responsive to centrifugal forces generated by spinning of said body to move with respect to said body from an initial unarmed position to a second armed position in a time inversely proportional to the rate of said spinning, said apparatus comprising:

means for spinning said body during an interval including a period in which the rate of said spinning is subject to variation;

means for counting the number of turns made by said body during said spinning; and

means actuated by said counting means for enabling determination of the number of said turns which have been made by said body; said apparatus comprising means .for sensing, and producing a signal representative of, the time at which said element reaches said armed position, and in which said actuated means comprises means for terminating counting of said turns in response to said signal. 6. Apparatus for testing a fuse having an arming time inversely proportional to the rate of rotation thereof about a predetermined axis therein, comprising:

means for rotating said fuse about said axis at a rate and for a time sufficient to operate said fuse from its unarmed condition to its armed condition;

means for sensing the time of occurrence of said armed condition and for producing a first signal representative of said time;

means for counting the number of turns of said fuse during said rotation; and

means responsive to said first signal for terminating the operation of said counting means when said fuse becomes armed.

7. The apparatus of claim 7, for testing of a fuse having a mechanical element movable during operation to a predetermined position indicative of the armed condition of said fuse, in which said sensing means comprises optical-sensing means for detecting the time at which said element attains said predetermined position.

8. The apparatus of claim 7, in which said means for rotating said fuse comprises motor means operatively connected to said fuse.

Claims

1. The method of testing the action of an arming delay-device for a projectile of a type to be fired from a rifled barrel with imparts spin to said projectile, said delay-device comprising a centrifugally operable element supported on a body which spins with said projectile, said element being responsive to centrifugal forces generated by spinning of said body to move with respect to said body from an initial unarmed position to a second armed position in a time inversely proportional to the rate of said spinning, said method comprising placing said element in its unarmed position, spinning said body at a rate which is subject to variation, counting the number of turns made by said body during said spinning, and selecting said delaydevice as satisfactory on the basis of the number of said turns required for said element to move from said unarmed to said armed position thereof.

2. The method of claim 1 in which said spinning is continued sufficiently long to cause said element to move to said armed position, and comprising the steps of detecting the time at which said element reaches said armed position and detecting the number of said turns which have been made at the time when said element reaches said armed position.

4. Apparatus for testing the action of an arming delay-device for a projectile of a type to be fired from a rifled barrel which imparts spin to said projectile, said delay-device comprising a centrifugally operable element supported on a body which spins with said projectile, said element being responsive to centrifugal forces generated by spinning of said body to move with respect to said body from an initial unarmed position to a second armed position in a time inversely proportional to the rate of said spinning, said apparatus comprising: means for spinning said body during an interval including a period in which the rate of said spinning is subject to variation; means for counting the number of turns made by said body during said spinning; and means actuated by said counting means for enabling determination of the number of said turns which have been made by said body; said actuated means comprising means for arresting Said spinning after a predetermined number of said turns.

5. Apparatus for testing the action of an arming delay-device for a projective of a type to be fired from a rifled barrel which imparts spin to said projectile, said delay-device comprising a centrifugally operable element supported on a body which spins with said projectile, said element being responsive to centrifugal forces generated by spinning of said body to move with respect to said body from an initial unarmed position to a second armed position in a time inversely proportional to the rate of said spinning, said apparatus comprising: means for spinning said body during an interval including a period in which the rate of said spinning is subject to variation; means for counting the number of turns made by said body during said spinning; and means actuated by said counting means for enabling determination of the number of said turns which have been made by said body; said apparatus comprising means for sensing, and producing a signal representative of, the time at which said element reaches said armed position, and in which said actuated means comprises means for terminating counting of said turns in response to said signal.

6. Apparatus for testing a fuse having an arming time inversely proportional to the rate of rotation thereof about a predetermined axis therein, comprising: means for rotating said fuse about said axis at a rate and for a time sufficient to operate said fuse from its unarmed condition to its armed condition; means for sensing the time of occurrence of said armed condition and for producing a first signal representative of said time; means for counting the number of turns of said fuse during said rotation; and means responsive to said first signal for terminating the operation of said counting means when said fuse becomes armed.