US2127605A - Stroboscopic apparatus - Google Patents

Description

Aug. 23, 1938. A, HE ETAL 2,127,605

S TROBOSCOP I C APPARATUS Filed May'29, 1935 3 She ets-Sheet 1 IIIIIIIII A "'41," W M' l l\\ I Aug. 23, 1938- A. A. KUCHER ET AL STROBOSCOPIC APPARATUS Filed May 29, 1935 3 Sheets-Sheet 2 Aug. 23', 1938.- A K gER' 2,127,605

STROBOSCOPIC APPARATUS Filed May 29, 1935 3 Sheets-Sheet 3 2993942 III! Patented Aug. 23, 1938 UNITED STATES PATENT OFFICE srnonoscorro aPPAnA'rUs Andrew A. Kucher and Floyd E. Gray,

Dayton, Ohio Application May 29, 1935, Serial No. 24,058

' 3 Claims.

accurate in operation andrelatively inexpensiveto manufacture.

A further object of our invention is to provide a stroboscope for the inspection of rapidly moving elements in which the element may be inspected during periods of acceleration or at various constant speeds.

A still further object of our invention is toindicate the frequency of the periodic motion of the element under observation.

It is a further object of our invention to provide apparatus of this character which is portable and which may be readily set up for operation.

These and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a'perspective view of a stroboscope constructed in accordance with our invention;

Fig. 2 is a wiring diagram of the apparatus shown in Fig. 1; v

Fig. 3 is a sectional view of a tachometer mechanism and is taken in line III-III of Fig. 4;

Fig. 4 is a sectional view taken along line IV-IV of Fig. 3;

Figs. 5,. 6, and '7 are diagrams of various connections of some of the elements of Fig. 2;

Fig. 81s a sectional view of amodifled form of our improved apparatus; and

Fig. 9 is a wiring diagram of the form of apparatus shown in Fig. 8.

.The operation of stroboscopic apparatus of the type disclosed herein is generally known in the art, but, briefly stated, it consists in intermittent- ,ly illuminating a rapidly moving elementat a frequency coinciding with the frequency of the periodic motion of the moving element whereby an 11- lusiozr is presented in which the element appears to be stationary. Therefore, the element may be viewed and studied during operation.

Stroboscopes in the past have been bulky, heavy and inconvenient to operate, especially where the element to be observed is so located that its illumination is diflicult. We have obviated these diiiiculties by providing a light, portable in- 50 strument which may be easily set up for operation. We have, furthermore devised a stroboscope with -a tachometer attachment whereby studies of moving elements may be made. Indications of the frequency of the periodic motion of the element under observation are provided by ourimproved device, both during acceleration and at times when the frequency of the. element is constant. A descriptionof the construction and operation of our improved stroboscope will now be made.

Referring now, particularly, to Figs. 1 to 6, in-

, clusive, the apparatus is shown arranged within a portable carrying case having a section III which encloses various control and power instrumentalities and a lid I l which houses the illuminating device l2, for example, a gas filled electric discharge lamp. A reflector I2A may be disposed in the lid ll behind the lamp l2. For flexibility in operation, the lid II is detachable from the control section III, whereby it may be arranged for illuminating the element under observation at a point remote from the control section It). Disconnecting type hinges l3 may be employed for this purpose and a flexible-cable l4 may be employed for electrically connecting the illuminating device l2 to the power apparatus within the section Ill. The carrying case may also include a lock l5 and a carrying handle I6.

The control and power instruments arranged within section ID of the carrying case are shown in Fig. 2 and will now be described. Alternating current is supplied for the operation of the stroboscope by means of conductors l1 and I8 con- ,nected to'a detachable plug I9, and a main switch 2i is provided in the conductor 18 for controlling the energization of all of the apparatus. Other major elements of the power and control apparatus contained within the section I 0 are a motor driven switch mechanism, generally indicated at 22, a rectifier 23, a rheostat 24 for controlling the speed of the motor driven switch mechanism 22, a multi-position switch 25 for a purposeto be referred to hereinafter, astep-up transformer 28 for providing a relatively high voltage for the electric discharge lamp l2, a jack 2'! to be described here-. inafter and an indicating instrument 28. Switches 2| and 25 andthe rheostat 24 are, respectively, provided with operating handles 2IA, 25A and 24A,.shown in Fig. l. A panel 29 is fixed in the section l0 and carries indicia, as shown, for indicating the positions of the switches 2| and 2B and the rheostat 24.

The motor driven switch mechanism 22 is em ployed for controlling the energization of the lamp l2 and includes a small motor 3| having an energization winding 32 and a rotatable shaft 33. Various types of motors may be employed, but I prefer to use a small, variable speed, alternatingcurrent motor operating at a commercial voltage and frequency. The switch mechanism includes a small rotatable contact 84 insulated from and 1'0- winding 32 of the motorhas one of its terminals output leads til and tated by the motor shaft 33. Qooperating with the rotating contact it are a plurality of brmhes till to 38, inclusive, which are insulated from each other and which are so disposed that adjacent brushes may be bridged by the rotating contact S6. The

connected to the line conductor it and the oppo site terminal of the winding 32 is connected to the other line conductor it by a circuit including a conductor til, rheostat 2 3, a conductor 3 t. and the switch it.

Direct current is employed for energizing the lamp it because of the flicker present with the use of alternating current on a gas filled electric discharge lamp. Direct current is obtained by the use of the rectifier which is shown by way of example as a full wave rectifier having a rectifying tube t2 and a transformer it. The primary M of the transformer is connected to the alternating current line conductors i l and it and is controlled by the switch 2i. The secondary oi the transformer it includes first and second wind lugs t5 and it, respectively; the winding 45 being connected to the plates of the full wave rectifier tube 62 and the winding 35 furnishing the filament current. Other elements of the rectifier include the usual resistor i and condenser 416 which are connected across the direct current As the operation of full wave rectifier-s is well-known in the art. no further description of them is deemed necessary.

. Enereization of the lamp it is efiected from the direct current leads it and iii in a manner to'be hereinafter described. The energizing circuit includes the transformer 26 which has a primary winding 52 and a secondary winding i553 connected to the terminals oi the lamp it? by means of the flexible cable l6. Electrically connected in the circuit oi. the primary winding is the meter 28, which responds to and preferably indicates the frequency of energization of the circuit. While other types of meters may be employed, we prefer to use a dampened ammeter calibrated in the manner set forth. The meter 28 may be arranged in the case iii (Fig. l.) where it will be readily available for reading as the various control handles are adjusted dining on oration.

As pointed out in detail hereinafter, the rotat ing switch tit is connected in the direct current circuit for controlling the eneraisation of the transformer 26 and the lamp l2. llhe multi-posltion switch 25 is inserted in this circuit and is connected to the brushes 3b to 88, inclusive, for changing the connections thereto, whereby the number or energizations of the lamp 82 per revolution or the switch 538, may be varied as the switch 25 is moved from one position to another. With this arrangement a greater range of operation may be obtained than is afforded by the speed range or the motor ell. For example, assmile the high speed of the motor Si is 3M0 R. P. M. and that the lamp is energized once per revolution, then the highest speed of the element arsacos The contact 55 is connected to the direct current lead m'by means of a conductor H and a pair of closed contacts" and 13 of the Jack 2?. Contact 63 is connected to the prlmm E2 oi the transformer 26 by means of a conductor it. The contacts (it, 97, t9 and (it are electrically connected as shown to the brushes til, 30, ill, and so, respectively.

In the first position of the'switch 25, segment (ii bridges contacts 55 and 58, and the segment t2 bridges contacts El and 68. For the rotating contact 84! momentarily engages brushes 5 86, the primary 52 of the transformer E6 is ergized through a circuit including direct current lead 419, contacts 72 and it, conductor ll, contact 56, segment 6i, contact lid, brush ro toting contact 36, brush 3. contact ill, segment E52, contact 58, conductor it. primary [32, meter 2t] and the opposite direct current lead iii. A high voltage is induced momentarily in the secondary which causes an electrical discharge in the filled lamp l2 and efiects illumination. in this. position of the switch 25, the brushes tit and t ment (it bridges contacts 68, Mi, and ill, and the segment on connects contacts EB, lit, and G6? The efiect of these connections is shown in 6 from which it will be apparent that the circuit including conductors ii and i l is energized twice per revolution, 1. e., when the rotating contact at bridges brushes 3?: and I8 and when it bridges brushes 3t and 3'1. Therefore, the lamp i2 is;

illuminated twice per revolution of the motor ill or once for every degrees of travel of the contact 2%.

In the remaining position of the switch, indlcated as number 6, contacts Elli, b6, and G9 are connected by segments 65 and O'l, the letter being electrically connected together. Likewise. the connected segments (56 and 68 engage the con.- tacts 5?, B8, and 6b. The silent oi these connections-is shown in Fig. '7 from which it will be seen that the circuit including conductors ii and, it is energized four times per revolution of the contact 35 or, in other words, once every Bil degrees of travel of thecontact St. The lamp ii? is illuminated, therefore, four times per revolution oi the motor 8 I. I

Operation When a study of arapidly rotating element is to be made, the lamp I2 is arranged to illuminate the same. 4 operation of the motor 3| and the rectifier 23. The switch 26 is adjusted to the proper setting dependent-upon the speed of the element to be observed.

AdJustment of the speed oi the motor my a The switch 2| is closed for initiating M is made by moving the handle 24A of the rheostat 24 until the element under observation appears to be stationary. As mentioned heretofore, this will occur when the frequency 01 lllumination by the lamp l2 coincides with the Ire- 2,127,805 I V J quency of revolutions of the element. A-physical study of the element at high speed may then be made and any defects in the element, flexing thereof under load or other operating'characteristics may be observed. -By referring to the meter 29, the exact speed of the element may be noted, which speed is the equivalent of the frequency of illumination indicated by the meter.

The description of operation in the foregoing referred to a rotating element but it will be understood that studies of reciprocating or oscillating elements may be made as easily as are those of rotating elements. Furthermore, the frequency of the -periodic motion of the element being studied will be indicated by the meter 28 when the illusion of a stationary element is obtained.

In order that a rotating element under observation may be viewed during periods of acceleration, we provide a tachometer-drive mechanism l5, shown in Figs. 3 and 4, which includes friction cone 15A carried by a spindle I9. The cone 15A may be held in engagement with the usual lathe center in the end of the shaft of the element so that the rotating spindle E6 of the mechanism 15 is rotated in synchronism with the shaft of the element. A switch contact "ill is rotated by the spindle l9 and bridges stationary brushes 19 and 19 during each revolution. The brushes l8 and 19 are connected by conductors 8i and 82, Fig. 2, to contacts 83 and 94, respectively, of a plug 85. The latter is inserted in the jack 2! at times when the tachometer-drive mechanism is to be used. The jack 21 includes, in addition to the normally closed contact 12 and i3, a contact 89 which is engaged by the contact 94 when the plug 95 is inserted in the jack 21. At this time the plug contact 83 engages contact 12 and the con-. tact l9 bears against an insulated portion of the plug 85 and, therefore, the circuit including the conductors H and 19 is open Accordingly, the

rotating switch driven by motor Si is ineffective to control the energlzation of the lamp 12 due to the open circuit at contact I9.

During operation'of the stroboscope with the tachometer-drive mechanism 1.5, the motor 3| may be stopped by adjusting the rheostat 29 to its off position. The switch 2| remains closed, however, for energizing the rectifier 29. The illumination of the lamp i2 is under control of the rotat- I ing switch contact ll of the tachometer drive mechanism 15. The controlling circuit may be traced from the direct current lead 49 of the rectifier 23, Jack contact 12, contact 89, conductor 9!, brush it, rotating contact I1, brush l9, conductor 82, contacts 94 and 99, conductor 14,-transformer primary 52, meter 29 and the opposite direct current lead iii of the rectifier 28.

The lamp i2 is illuminated at a frequency equivalent to the frequency of rotation of the shaft of the element under observation. It will be apparent that the frequency of illumination increases directly with an increase in frequency of rotation of the element being observed. .Therefore, the illusion of a stationary element is obtained throughout the period of acceleration and prior embodiment. Themotor 9| has a shaift 99 which drives the rotating switch contact 34 and an indicating needle 9| of the tachometer by means of a magnetic induction connection generally indicated at 92. As connections of this kind are well-known, it is not deemed necessary to describe their construction or operation. It will suffice to say that the faster'the motor shaft 99 is rotated, the farther the needle 9| is advanced so that. the speed of the motor may be read on a scale which we show at 93. The scale 93 is preferably carried by the panel 29 and a transparent shield 94 is arranged above the scale 93 and needle ill for protective purposes.

Arranged at the bottom of the shaft 99 is 'a connection for coupling a tachometer thereto for driving the shaft 99 and the indicating needle 9| when the tachometer is to be used. The coupling 1 may be provided in any desired manner as, by a square socket 95 arranged in the motor shaft 99 and a rotatable square shaft 96'forming a part of a tachometer mechanism, generally indicated at 911. The tachometer-drive 91 includes the usual friction cone 98 which drives the shaft 96 bymeans of a flexible shaft mechanism shown at 99. A fitting l9l may be provided for attachment to a fixed bushing I92 in the case l9, when the square shaft 96 is inserted in the socket 95 of the motor cept that the jack 21 and the meter 29 have been omitted. The other elements of the control and power apparatus are similar to those of the prior embodiment and are similarly connected. For purposes of description, the elements which are common to both embodiments are designated by like numerals. g

When operating the stroboscope disclosed in Figs. .8 and 9, the main switch 2| is closed for energizing the rectifier 29 and motor 3|. The rheostat 24 .is adjusted, until the desired speed of the motor 3i is obtained. At this speed, the lamp i2 will'be energized by the rotating switch contact 29 as it passes over the brushes 35 to v98, inclusive, and the moving element being studied will appear stationary; all of which has been previously described.

Thespeed of the observed element may be obtained by referring to the needle 9i and scale 93. In this connection, the speed indicated by the needle 9| can be directly taken as that of the elefor each revolution of the motor shaft 99. With the switch 25 inits second position, the brushes will be connected as shown in Fig. 6 and the lamp i2 will be illuminated twice for each rotation of the motor shaft 99. Therefore, the speed of the element being observed must be twice the speed of the motor 9! and the indication bythe needle 9i shouid'be multiplied by two in order to obtain the correct speed of the observed element. Likewise, a multiplier of four is used to obtain the correct speed of the "observed element if the switch 25 is in its number four position, or the position in which 'the'lamp is illuminated four times for each revolution of the motor shaft 99.

With the tachometer drive .91 connected to the motor shaft to, the motor ii is deenergized, for example, by adjusting the rheostat 24 to open the circuit of the motor winding 32. switch it, however, is closed forenergizing the rectifier 23. The tachometer drive 9! drives the rotating switch contmt M and the speed indicating needle 9i. llhe frequency of illumination of the lamp it is in synchrony with the frequency oi rotation oi the observed element which appears stationary. The speed can be read directly from the position of the needle 9! as the switch. 25 should be in its first or number one position for operation with the tachometer-driving device 97?.

While we have disclosed our improved strob-oscopic apparatus embodying a. gas-filled electric discharge lamp, it is to be understood that other forms of lampsmsy be employed which rapidly illuminate upon application of a suitable poten-- tial thereto and which darken instantly with the removal of the potential. Furthermore, we have shown a hill Wave rectifier of the type employing an electric discharge tube but it is to be understood that other iorms of rectifying devices may be used.

While we have shown our invention in two forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof, and we desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims. 7

What we-clsim is:

i. In apparatus for inspecting a moving element and for indicating the frequency of the periodic motion thereof, the combination oi an electrical circuit, means for illuminating said element connected in said circuit, a rotatable switch structure having a plurality of clrcunrferentlally Y spaced stationary contacts and a rotatable memher for sequentially bridging adjacent stationary contacts as it is rotated, said rotatable switch being connected in said circuit with said illuminating means for controlling the energization thereof. a motor for rotating the br'idging member, a second switch structure having a plurality oflstationary contacts connected, respectively, to the staionary contacts of the rotatable switch structure and other stationary contacts connected in the electrical circuit, said second-switch structure having an element selectively movable to a plurality of positions. said element including segments adapted for bridging predetermined The main issect groups of the stationary contacts in the diflerent positions of the element, the connections between the stationary contacts of the first mentioned switch structure and the said predetermined groups of contacts of the second switch structure being so arranged that different predetermined groups or said first mentione contacts are connected in the circuit in the di ere'nt positions of the movable element so that the number of energizations ofthe illuminating means per revolution of the motor is varied, means for varying the speed of said motor and means responsive to the speed of the motor for indicating the frequency of energlzation of the illuminating means.

'2. In apparatus for inspecting a. rapidly mcv ling element and for indicating the frequency of the periodic motion thereof, the combination oi an electrical circuit, means for illuminating said element connected in said circuit, a rotatable switch structure having a plurality of circumferentially spaced stationary contacts connected in said electrical circuit with said illuminating means for controlling the energization thereof and having a rotatable member for sequentially bridging adjacent stationary contacts as it is rotated, a motor having a drive shaft connected to the bridging member, means for controlling the energization of the motor and for adjusting the speed of said motor, means for indicating the speed of the drive shaft of the motor, a device for connection to the element under observation and rotatable in synchrony with the periodic movement of the element, and means for readily connecting said device to the motor drive shaft for motivating the same so that the frequency of the periodic motion of the element is indicated by the indicating means.

3. In a portable stroboscope. the combination of a carrying case having a detachable cover, an electric discharge lamp arranged within said cover, rectifying means disposed within said carrying case and including a direct current output circuit for energizing said lamp, 9. source of alternating current for energizing said, rectifying means, a flexible cable connecting said direct current circuit to said lamp so that the lamp may be arranged remote from said case during operation,

means connected in said direct current circuit for intermittently energizing the same and disposed in said carrying case. means arranged in said case for varying the frequency of operation of the energizing means, and means carried by said case for indicating the frequency of energlzation of the energizing means.

ANDREW A. KUCHER. FLOYD E. GRAY.

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