US1585319A - Periodic electric signaling device - Google Patents

Description

May 18 1926.

-A. TUPPER PERIODIC ELECTRIC SIGNALING DEVICE Filed March 19, 1923 2 Sheets-Sheet 1 L wanker W Gm): un s May as ,1926. 7 1,585,319

' A. W. TUPPER PERIODIC ELECTRIC SIGNALING DEVICE Filed March 19, 1923 2 Sheets-Sheet 2 IIIE JUL.

I .25 f1 g'wue niox in; 6 M W f I Patented May 18, 1926.

UNITED STATES PATENT OFFICE.

ARTHUR W. T'UPPER, OF RIVERDALE, MARYLAND, ASSIGNOR TO J. AUSTIN STONE, J'. HANSON BOYDEN, AND WILLIAMLC. PRENTISS, JOII I NTLY, ALL OF WASHINGTON,

DISTRICT OF COLUMBIA.

ammonia nrlncrarcsrenanme nnvrcn.

Application filed March 19, 1923. Serial No. 626,133.

This invention relates to electric signaling' devices and more particularly to.t1me controlled mechanism for periodically closing an electric circuit so as to set up ;a series of impulses. A Broadly speaking, the present invention relates to apparatus of the same type as that disclosed in my prior co-pendin application, Serial No. 506,442, filed October 8,

10.1921, designed for producing a series of duration of the flash or current impulse pro-.

duced in the signaling circuit, and to provide improved means whereby a plurality of such flashes may be produced at each oscil lation of the periodic time controlled mechanism.

With the above. and other objects in View, the invention consists .in the construction, combination and arran ement of arts her einafter described and c aimed, an shown in the accompanying drawings, forming part of this specification, in which Fig. 1 is a sectional plan viewmf the line 1-1 of Fig. 2";

Fig. 2 is a side elevation of the same;

Fig. 3 is an end elevation thereof;

Fig. 4 is a fragmentary sectional elevation of my improved circuit closing mechahim, the section being taken substantially on the line y-y of Fig. 7;

Fig. 5 is a plan view of such mechanism, showing the parts in slightly different p081 tion- V Fig. 6 is a. view similar to Fig. 4, but showin the parts in a position corres ondingwit h that of Fig. 5, the section eing taken substantially on the line 6-6 of Flg. 5 looking in the direction of the arrow, such section aso corresponding to that of the line :v-w of Fig. 7;

my improved apparatus, taken substantial y 011- v Fig. 7 is an inverted sectional plan view of part of the circuit closing mechanism .shown in the preceding figures;

0 Fig. 8 is a fragmentary plan view of the electro-magnetic impelling mechanism shown in Fig. 1, but illustrating the parts in a different position;

Fig. 9 is a perspective view of the armature and associated parts; and I Figs. 10 and 11 are elevations of a special sto buffer which I prefer to use, showing di erent positions of the parts.

Referring to the drawings in detail, my

improved apparatus comprises a suitable base 1 on which is mounted, by means of spacing blocks 1, a frame comprising top and bottom movement plates 2 and 3, rigidly held in spaced relation by means of posts 4. Any other means of supporting the" ereinafter described mechanism may, of course, be employed, if desired.

Mounted in adjustable bearings 5 and 6, carried by the bottom and to plates respectively, is an oscillatory shaft i, havin shaped ends resting in suitable soc ets in the bearings 5 and 6, after the manner of the balance wheel ofa clock. A cross bar 8 is carried by the shaft 7 near its upper end and mounted on this cross bar are a pair of weights 9. These weights are preferably slidably mounted on the cross bar 8, so that their distance from the shaft 7 may be adjusted as desired, the weights being held in adjusted position by means of set screws 10. It will thus be seen that the parts 7, 8 and 9 constitute a momentum device in the nature of a balance wheel, and it will be under'stood that the inherent period of oscillation of said device may be regulated by adjusting the weights 9 toward and from the shaft. In order to cause said momentum device to oscillate, I provide a spiral spring 11, similar to the hair spring of a watch movement, such spring being secured at its inner end to the shaft 7 and anchored at its outer end to a post 12, carried by the top plate 3. Rigidly secured t6 and projecting radially from the shaft 7 at a point below the cross bar 8, and preferably in the same plane therewith, is an arm 13, carrying near its end a contact 14, made of suitable non-oxidizing metal.

A vertical rock shaft 15 is mounted in COIIG- till pivot bearings between the plates 2 and 3, near one edge-thereof, as clearly shown in the drawings, and has rigidly secured there to a soft iron. armature 16, the shape of which is best shown in Fi 9. This armature is secured to the sha t 15 as by means of screws or rivets 17 Also, carried by the shaft 15 on the opposite side thereof from the armature 16 is a counterweight 18, the purpose of which is to balance the armature in case the a paratus is set in any other position .than horlzontal.

Arranged to cooperate with the armature 16 is a pair of electro-magnets 19, mounted on an iron angle bracket 20, by means of screws 21, the bracket 20 being itself rigidly secured to the bottom plate 2. In order to retract the armature when the magnets 19 are de-energized, I provide a spring 22 secured at one end to the armature and anchored at the other end to a post 23, set

' of the momentum device, comprising the art-s7, 8 and 9,and prevent it from swingmg through more than 360, I provide a stop which is shown as comprising a post 26 with a block of yielding or soft material at the upper end thereof to constitute a buffer. This is so placed as to be in the path of the arm 13, as the latter swings around. Th1s sto buffer shouldv be of non-resilient materia, so as to eliminate; as far as possible,

. any tendency of the arm 13 to rebound therefrom. V

Secured to the armature 16 by means of screws or rivets 3O but s aced therefrom by means of suitable insulation 30 is a resilient contact arm 27, having an upturned end 28, carr ing a suitable contact 29, of non-oxidiza le metal. When the, parts are assembled, the contact 29 is at such a height as to be engaged bythe contact 14, carried by the arm 13, when the latter is in certan angular positions. Carried by the contact arm 27 and insulated from the armature 16 is a clip 31 adapted to receive a suitable wire connection for completing the circuit as hereinafter described.

Also, rigidly secured at one end to the armature 16, is a spring lever 32, so positioned as to lie substantially in the plane of the arm 13, and of such len th that itsv free end projects into the path OI movement of-such arm. The contact arm 27 is preferably rel-' atively thin and weak, requiring but a very small force to flex the same, while the s ring lever 32 is relatively strong and sti requiring considerable force to bend it.

By reference to Fig. 1, it twill be seen that be traced as follows. Beginning with clip 31 connected with the contact arm 27, a wire 33 extends from such clip to a binding screw set into a block of insulation 34 carried by the bottom plate 2, and from this binding screw extends a wire 35 to one side of the magnet coils, the other side of which is connected by wires 36 and 37, to one side of a suitable battery 38. The other side of this battery is grounded by connecting a wire 39, extending therefrom, to a bracket 40, secured to the bottom plate 2. The arm 13 is, of

course, electrically continuous with the shaft 7 and frame of the apparatus, so that whenever, the contacts 14 and 29 are in engagement, a circuit is closed through the magnet windings 19 over the path just described, and such magnets are energized.

B efore proceeding to the description of the operation-of the mechanism so far described, let it be borne in mind that the spring 11 is So designed and the parts so positioned that when no current is flowing, and the apparatus is idle, the contacts 14 and 29 are in engagement. The reason for this is that the contact arm 27 is located a little in advance of the limit of movement of the arm 13, due to the natural free swing of the momentum device and therefore, such device comes to rest with the spring 11 under suflicient tension to hold the contact 14 in engagement with the contact 29. From this, it follows that as soon as current is supplied to the magnet windings, the armature is drawn forward and the free end of the spring 32 is caused to impinge upon the arm 13 "and thus impart an impulse to the momentum device, thereby causing it to start .automatically. It will be noted, also, that the end of spring 32 is always so positioned as to lie within the path of movement of the arm 13. 4.

While I have shown and described the element 13 as an arm, it is obvious that as in my prior application, the same effect may be produced by a pin, stud, or other member. Therefore, I shall refer to the element 13 broadly as an abutment, meaning byv this, a rigid part of the momentum device.

Assuming the device to have been started to oscillate as above described, and assuming it to be moving in the direction indicated by the arrow in Fig. 1, it will be seen that as such'movement continues, the contact 14 first engages the contact 29, thus closing the circuit to the magnets 19. It will be noted that after this circuit is closed, the momen- I tum device still continues to move in the direction of the arrow for an appreciable distance during the time that the magnetism generated by the windings 19 is building up. After a definite time interval, this magnetism reaches a maximum and draws the armature 16 toward the magnets, and at this instant, or perhaps just previous to this critical moment, the abutment 13 engages the end of spring 32. Thus, at the moment of such engagement, the spring 32 is moved by the armature 16 in a direction opposite to that in which the abutment 13 is moving. Therefore, by virtue of placing the contact 29 in advance of the spring 32, a sufficient distance to compensate for the magnetic lag of the magnets 19, these magnets become fully energized and operate the armature at exactly the proper instant to impart the most effective driving impulse to the momentum device. It can be readily seen that if the abutment were permitted to strike the spring 32 and begin to rebound,.before the armature begins .to move, that the effective impulse which it would be possible for the spring 32 to give, would be very much reduced. By my improved method of closing the circuit, a definite time interval in advance of the engagement of the abutment with" the spring; I am enabled to impart to the abutment a driving impulse before the rebound begins. To state it another way, the armature is actuated at such a time as to apply to the abutment 13 a force tending to start it on its reverse swing while, it is still moving in the other direction, and before such reve rse swing has actually begun.

Moreover, as in my formed application, the spring 32 acts as a yielding buffer against which the abutment 13 impinges, and this spring is thereby momentarily flexed by the inertia of the momentum device, thus storing energy, which energy is returned to the momentum device .when the spring 32 makes its driving stroke, as described.

In my former application, however, it was necessary to have the spring lever comparatively weak so that the spiral or hair spring could flex it sufliciently to maintain the contacts closed so as to make the device self-starting. For this reason, the circuit to the magnet remains closed during a comaratively long interval, at each oscillation.

y virtue of my improved arrangement,

however, the circuit closing'arm is entirely independent of the spring lever which gives the impulse, with the result that the spring lever can be made relatively stiff, thus requiring a correspondingly shorter interval in which to give an impulse to the momen tum device. In practice, I have found that with a momentum device having a natural ppriod of one second or more, it is possible to'so adjust-the parts that the circuit of the driving magnets remains closed for .only the 1/20th part of a second. This renders the" currerit consumption almost negligible. a

In order to periodically open and close an electric circuit at each oscillation .of the mo mentum device above described and thus produce the desired flashes or other electric signals, I provide the, following improved mechanism. Mounted on the shaft 7, referably near the bottom thereof, is a co ar@41 having a radially projecting arm or member 42. As clearly shown in Fig. 7, the lower side of this member is beveled along each edge, as indicated at 43, and between the beveled edges extends a substantially'flat portion 43'of a width which gradually decreases as the distance from the shaft 7 inshaft, as indicated by the line g g in Fig. 7,,

has somewhat the appearance shown in Fig. 4, in which the lower cam face is relativel wide. a

A resilient contact spring or arm 45 has an end portion 44 rojecting laterally there d to lie in the path of the.

from and arrange cam face of the member 42. This contact spring 45 is secured as by means of screws 45 to a block 46 of insulating material,

which block is itself secured to the bottom plate 2 by means of a pivot pin or screw 47',

as clearly shown in Figs. 1 and 5.

Asecond contact spring 48 is also mounted on the block 46 as by means of screws -48 and has a portion arranged to underlie the spring 45, so that the two sprlngs ove r lap at one point. At such overlapping points the springs 45 .and 48 are provided with contacts 49 and 50 respectively, which contracts are adapted to be forced together whenever the'end 44 of the spring 45 1s in engagement with the cam face of the member 42. Referring to Fig. 1, it w1ll be seen that if an electric lamp 55 or other signal;-

device is connected by means of conductors 53 and 54, with the grounded bracket 40 and the screw 45 holding the spring 45, the cir--.

cuit through such lamp or signal device will be closed whenever the contacts 49 and 50 are brought together.

Set into the upstanding portion of the angle bracket 40 is a pair of adjustable set screws 51, 52, arranged to bear against the face of the block 46 at opposite sides of the pivot 47 thereof. In Fi 1, the screws 51- and 52 are shown as prQ ecting through the.

bracket 40 to substantially the same extent, with the result that the end 44 of the spring 45 engages the cam :face of the member 42 at su stantially the middle int thereof, radially speaking. When, hliwever, the screw 52 is advanced and the screw 51 retracted, as shown in Fig. 5, the block 46 is swung u on its pivot 47 carrying the arms 45, 48 with it, and thus shifting the end 44 of the spring 45 radially outward away from the shaft 7. When in this position, the end 44 of the spring 45 engages onlythe outer end of the cam member 42, at a point where the cam face thereof'is relatively narrow, with the result that such cam face, as the momentum device swings, passes quickly over the end 44, thus depressing the spring 45 and closing the lamp circuit for only a brief period. llf, however, it is desired to lengthen the duration of the signal period or flash, the screw 51 is advanced while the screw 52 is retracted so as to swing the block 46 in the opposite direction and thus cause the end 44 of the spring 45 to approach the shaft 7, more closely.' VJhen in this position, the end 44 engages with a wider portion of the cam face 43, as shown in Fig. 4, with the result that the time during which the spring 45 is held down and the lamp circuit closed, at each oscillation, is relatively long. I

he timing effect of the tapering cam face 43 is also increased by reason of the fact that the radiallyouter portions thereof move at a greater speed than the portions closer to the shaft. Therefore, even if the cam face were of uniform width, shifting the spring end 44 toward or from the shaft wouldincrease or decrease the time interval, owing to the different speeds of the different portions of the cam face; However, with the construction shown, the variation of the time interval is produced by acombination of the tapering face and a variable distance from the center, andtherefore, a comparatively slight adjustment of the springs 45, 48 produces a considerable variation 1n the duration of the signal impulses.

It will be understood that the cam member 42 rides over and depresses the spring 45 twice during each com lete oscillation, and, since the momentum evice is substantiall the same distance from the end of its stro e during the two engagements of the cam member with the spring, it is obvious that the duration of these two engagements, for any given setting of the contact s rings, is substantially equal. In other wor s, my improved mechanismdelivers a plurality of im ulses at each oscillation, all of the im pn ses being of substantially the same duration, but I have provided means whereby the duration of these impulses, or their length relative to the period of the momentum device may be varied asdesired.

If the cam member 42 is so located on the shaft that it engages the contact spring 45 substantially as the momentum device reaches the end of its swing, it is obvious that but a single impulse w1l1 be produced at each oscillation, instead of two impulses, as described.

While l have shown only a single cam four or more such impulses may he pro-.

duced. Moreover, by so locating one of the cam members that it engages the spring end 44 just as the momentum device reaches the end of its swing, this cam member will dwell for a longer time upon the contact spring. lln this way, relatively long and a series of relatively short signal impulses may be preduced at each oscillation.

lit wil be understood that any desired arrangement of cam members may be employed and in this way, each particular signal may be caused to emit a certain characteristic group of flashes indicative of its position or of the special danger conditions of which it is desired to give warning, accord ing to a predetermined code.

While l have shown a pair of spring arms 4548 arranged to be forced together by the mechanical engagement of one of them with the cam member 42, it is obvious that the same results can be obtained by dispensing with the spring 48 and having the cam member 42 itself serve as an electrical contact co-operating with the spring 45 to com plete the circuit. In other words, the cam member 42 may be arranged for either a mechanical or electrical function, without deartin from the spirit of the invention.

nstea of the stop post 26, shown in the. other figures, ll may and preferably do employ the yielding bufi'erdevice illustrated in Figs. 10 and 11. This device comprises a bracket 56 having a substantially horizontal portion 57 from which is freely suspended a strip or thong 58 of soft leather, rawhide, or similar flexible, non-eleas'tic material, so located as to lie in the path of the abutment arm 13. Moreover, the bracket 56 is of such a height that "there is provided between the portion 57 thereof, and the path of the arm 13' a clearance but little greater than the thickness of the strip or thong 58.

As a 'result, when the arm en ages the strip, as shown in Fig. 11, the strip is bent sharply between the arm and bracket, and this action sets up a resistance which quickly brings themomentum device-to a. stop. Obviously, since the lower end of the strip 58 is free, there can be absolutely no rebound of the arm 13, the strip exertin drag ing 1 or braking efi'ect whlch is comp ete y cad-beat in its action.

a kind of a electromagnet will be ment carrie ing an oscillatory momentum device, a normally out of contact with but adapted to a voltage higher than ,necessary, so that,

when the voltage drops a little, after long use, it will still be sufficient to operate the the device.

What I claim is 1. Periodic timing mechanism com risever engage said device near the end of each oscillation thereof to impart driving impulses thereto, an electromagnet for operatmg sai-d lever, and means controlled by the movement bf said momentum device at each oscillation thereof for closing the circuit of said electromagnet at such, a point in the c cle as to compensate for the magnetic lag thereof andcause it to move said lever at the moment when such movement will be most effective to impel the device.

2. Periodic timing mechanism comprising an oscillatory momentum device, a lever normally out of contact .with but adapted to engage said device near the end of each oscillation thereof to impart a driving impulse thereto, an electromagnet for operatmg said lever and means controlled by the movement of said device for closing the ci'r cuit to said electromagnet .a predetermined time before said lever and device come into engagement, whereby said electromagnet becomes fully-energized and causes the said lever to operate at the moment of such engagement.

3. Periodic timing mechanism comprising an oscillator momentum device, an abutment carrie by said device, a lever projecting into the path of movementof said abutment, an electromagnet for operating said lever so as to impart a driving impulse to the device at the point of reversal thereof after said abutment and lever have come into engagement, and means controlled by the movement of saidodevice at each oscillation thereof for closing the circuit of said electromagnet a predetermined time before such engagement takes place, whereby, at the moment that engagement occurs, the fully energized and the lever operated effectively.

4. Periodic timing mechanism comprising an oscillator momentum device, an abut by said device, a lever projecting into the path of movement of said abutment, an electromagnet for operating said lever so as to impart a driving impulse to thegdevice after ,said abutmentand lever have come intoengagement, a contact carried by said device, a resilient contact arm mounted in the path of movement of said net having a pivoted armature,

contact, said arm and contact controlling the circuit of said electromagnet, the an lar disposition of the parts being such t at said contact first engages said resilient arm, and the device then continues to move in the same direction while the magnetism builds up, flexing said resilient arm, and the said abutment finally engaging said lever as the latter begins to move, under the influence of said electromagnet, in a direction opposite ,that in which said abutment was moving at the moment of engagement, whereby said momentum device is started on its reverse swin 7 5. Periodic timing mechanism compris-, ing an oscillatory momentum device, an abutment carried by said device, an electromagnet having a pivoted armature, a

lever carried by said armature and projecting into the path of movement of said abutment, said lever serving, when in engagement with said abutment, and when operated by said armature, to impart, an impulse to said device, a contact carried by said device, and a co-operating, resilient contact arm carried by said armature, said contact arm controlling the circuit of said electromagnet, the arrangement being such, that as said device oscillates, said contact engages said arm and thus completes the circuit of said electromagnet prior to the engagement of said abutment wlth said operating lever.

6. Periodic timing mechanism comprising an oscillatory momentum device, an abutment carried by said device, an electroma net having a pivoted armature, a relative y stiff spring lever carried by said armature and projecting into the path of movement of saidabutment, a contact carried by said device, a relatively thin, flexible contact arm also carried by said armature and disposed in the path of movement of said contact, said arm and contact controlling the circuit of said electromagnet, the angular relation of the parts being such that, as the momentum device oscillates, the said contact engages said contact arm in advance of the engagement of said abutment and spring lever.

7 Periodic timing mechanism comprising an' oscillatory momentum device, an abutment carried by said device, an electromaga relatively stiff spring lever carried by said armature and projecting into the path of movement of said abutment, a contact carried by said device, a relatively thin, flexible contact arm also carried by said armature and disposed in the path ofmovement of said contact, saidarm and contact controlling the circuit of said electromagnet, and said spring lever, serring, when in engagement with said abutment, and when moved by said armature, to iimpart a driving impulse to said momentum evlce.

8. Periodic timing mechanism comprising an oscillatory momentum device having its mass symmetrically disposed about its axis of oscillation, an abutment carried by said device, a resilient lever projecting into the path of movement of said abutment and serving as a yielding buffer against which said abutment strikes so as to arrest the motion of'the momentum device at the end of each oscillation, and means for giving to said spring-lever a definite movement in a direction contrary to that in which said abutment is moving when it engages the same, so as to apply to said momentum device a force tending to impart to it a reverse impulse before the return swing has'actually begun.

9. Periodic timing mechanism comprising an oscillatory momentum device, an abutment carried by said device, a spring lever projecting into the path of movement of said abutment and serving as a yielding buffer against which said abutment strikes so as to arrest the motion of the momentum device at the end of each oscillation, and means for applying to said momentum device, through said spring lever, and while still moving in one direction, a force tending to swing it in the opposite direction.

10. Periodic timing mechaism comprising an oscillatory momentum device, an abutment carried by said device, a spring lever projecting into the path of movement of said abutment andserving as a yielding buffer against which said abutment strikes so as to arrest the motion of the momentum device at the-end of each oscillation, an electro-magnet for moving said spring lever in such a direction as to impart a return impulse to said momentum device, by means of said abutment, and means independent of said spring lever for automatically closing the circuit of said electro-magnet near the end of each oscillation of said momentum device.

11. The combination with an oscillatory time controlled device, and means for continuously oscillating said device at a substantially uniform rate, of an electric circuit independent of said oscillating means, means operated by said device for producing a plurality of equal electrical impulses in said circuit at each oscillation thereof, and means for varying the duration of said impulses relative to the period of oscillation of said device.

12. The combination with an oscillatory time controlled device, and meansfor continuously oscillating said device at a substanti ally uniform rate, of an electric circuit,

means operatedliy said device for producing a groupof electr cal impulses in said circuit at each oscillation thereof, and means for varyingthe relation between the length of said impulses and the period of said timecontrolled device, while malntainlng uni-' form the duration of all impulses making up the group.

13. The combination with an oscillatory shaft, and means for continuously oscillating the same, of a member carried by and projecting radiallyfrom said shaft, said member being shaped on oneside to constitute an axially "inclined cam surface, and a resilient contact arm mounted so as to be engaged by said member as the shaft oscillates, to close a circuit for a definite period, and means for adjusting the position of said contact arm toward and away from said shaft, whereby the length of the period during which the circuit is closed may be varied.

14C. The combination with an oscillatory shaft, and means for continuously oscillating the same, of a member carried by and projecting radially from said shaft, a resilient contact arm mounted so as to be engaged by said member as the shaft oscillates, to close a circuit for a definite period, and means whereby the position of said member on the shaft may be angularly adjusted so as to cause the circuit to be closed either once or a plurality of times at each oscillation of said device.

15. The combination with an oscillatory shaft, and means for continuously oscillating the same, of a member carried by and projecting radially from-said shaft, said member having a face the width of which varies progressively radially, and a resilient contact arm mounted so as to be engaged by said member as the shaft oscillates, to close a circuit for a definite period, and means for adjusting the position of said contact arm toward and away from said shaft, whereby the length of the period during which the circuit is closed may be varied.

16. The combination with an oscillatory shaft, and means for continuously oscillating the same, of a member carried by and projecting radially from said shaft, said member having a cam face, the width of which varies progressively radially, of a resilient contact arm so mounted that the cam face of said member engages and rides over the same during each oscillation of said shaft thus closing a circuit during the time of such engagement, and means for adjusting the position of said contact arm toward and away from said shaft, so that it may be caused. to co-operate with parts of the said cam face of difi'erent widths, whereby the duration of such engagement may be varied.

17. The combination with an oscillatory shaft, and means for continuously oscillating the same, of a, member carried by and proiecting radially, from said shaft, said member being shaped on one side to form an axial cam face, such cam face having a substantiallv flat portion of progressively varying width, radially of the shaft, of a resilient contact arm' mounted with its ends so each oscillation of said shaft, thus closing a circuit for a definite period, and means for so adjusting the end of said contact arm as to cause it to be engaged by parts of said flat cam face of different widths, as desired, whereby the duration of the time of passage of such face over the end of said contact arm, and the consequent period of closure of the circuit, may be varied.

18. In a periodic timing mechanism, the combination with an oscillatory momentum device having a controlling spring, of means for imparting an impulse thereto at each oscillation as it approaches the end of its swing in one direction, and a yielding, nonresilient stop buffer for limiting the movement of said device at the end of its swing in the other direction.

19. In a periodic timing mechanism, the combination with an oscillatory momentum device having a controlling spring, of means for imparting thereto at each oscillation, an impulse of more than sufiicient power-to cause it to execute another oscillation, and means in addition to said spring for absorbing any excess of ener over that required to maintain said device in continuous full oscillation, whereby the period of said I momentum device is preserved substantially constant.

In testimony whereof I afiix my signature.

ARTHUR W. TUPPER.

Images