US2591317A - Safety mechanism for centrifugal separators - Google Patents

Description

April 1, 1952 J. E. THOLL SAFETY MECHANISM FOR CENTRIFUGAL SEPARATORS 7 Sheets-Sheet 1 Filed Feb. 27, 1947 April 1, 1952 J. E. THOLL 2,591,317

SAFETY MECHANISM FOR CENTRIFUGAL SEPARATORS Filed Feb. 27, 1947 7 Sheets-Sheet 2 April 1, 1952 J. E. THOLL SAFETY MECHANISM FOR CENTRIFUGAL SEPARATORS 7 Sheat-Sheet 3 Filed Feb. 27, 1947 J. E. THOLL 2,591,317

SAFETY MECHANISM F OR CENTRIFUGAL SEPARATQRS 7 Sheets-Sheet 4 April 1, 1952 Filed Feb. 27, 1947 April 1, 1952 J. E. THOLL SAFETY MECHANISM FOR CENTRIFUGAL SEPARATORS 7 Sheets-Sheet 5 Filed Feb. 27, 1947 April ,1, 1952 J. E. THOLL 2,591,317

SAFETY MECHANISM FOR CENTRIFUGAL SEPARATORS Filed Feb. 27, 1947 7 Sheets-Sheet 6 April 1, 1952 J. E. THOLL 7 SAFETY MECHANISM FOR CENTRIFUGAL SEPARATORS Filed Feb. 27, 1947 '7 Sheets-Sheet '7 TIMER ARRANGEMENT 3 PHASE LINES RELEASE I PUSH BUTTON LINE Patented Apr. 1, 1952 SAFETY MECHANISM FOR CENTRIFUGAL SEPARATORS J o hn E. Tholl, Needham, Mass., assignor to Amerlcan Tool & Machine 00., Boston, Mass, a corporation of Massachusetts Application February 27, 1947, Serial No. 731,278

13 Claims. I (01. 233-1) m closed by a large cover usually hinged to the curb. Because it is entirely possible for an operator, in attempting to reach across the basket of one of these large machines, to have an arm caught in some way with a revolving part of the basket where he is liable to be pulled into the machine, it has been a common practice to lock these covers and to provide some means for preventing them from being opened while the machine is running. A typical example isshown in the 'patent to Williams No. 1,991,374, assigned to the assignee of the present invention.

' As heretofore made, these locking mechanisms have not been satisfactory, common objections to them being that they are very noisy; parts of the cover lock controlling mechanism are liable to become so fouled up as to be inoperative; and they are subject to frequent breakage.

The present invention deals particularly with the foregoing considerations, and it aims to devise a mechanism for locking the cover of a machine of the type above referred to while the machine is running, which will be exceptionally reliable; quiet in operation; and which can be manufactured economically.

The nature of the invention will be readily understood from the following description when read in connection with the accompanying drawings, and the novel features will be particularly pointed out in the appended claims.

In the drawings,

Fig. 1 is aside view of a centrifugal separator equipped with a cover locking mechanism embodying the present invention;

Fig. 2 is a view, partly in side elevation and partly in vertical section, of the construction shown in Fig. 1;

Fig. 3 is a plan view, somewhat diagrammatic in character, of the mechanism shown in Fig. 1.

Fig. 4 is a plan view, with parts in section. showing a portion of the locking mechanism on a larger scale;

Fig. 5 is a side view of the parts shown in Fig. 4;

Fig. 6 is a side view, partly in section, of an automatic release which preferably is used in the construction shown in the several figures;

Fig. 'lis a side view showing another embodiment of the invention;

Fig. 8 is a plan view of some of'the parts shown in Fig. 7;

Figs. 9 and 10 are front and side views, respectively, showing some of the parts illustratedin Fig. 7 on a larger scale; and

Fig. 11 is a wiring diagram showing the control units for the driving motor for the machine.

Referring first to Figs. 1, 2 and 3, the construction there shown comprises a centrifugal separator of the link-suspended type, including a basket, a portion of which is shown at 2 in Fig. 2', the basket being enclosed in a casing or curb 3. Usually the casing has an aperture in its top,

larger in diameter than the opening in the bas-,

ket cap, and this aperture is normally closed by a cover 4 which is secured to a rock shaft 5 supported in suitable bearings mounted on the easing. In the particular construction shown, a lever 6 is secured to this rock shaft, so that by swinging the lever backwardly the cover may be swung into its open position and, when desired, it may be eased back into its closed position again.

In order to lock the cover against opening, the shaft 5 is provided with a latch member 1 secured rigidly to it and adapted to cooperate with a latch plate 8, pivoted at l0, Fig. 3, to rock in a horizontal plane into a position where it underlies a shoulder I, Fig. 2, on the member I, and thus prevents any substantial opening movement of the cover.

For the purpose of swinging the latch plate 8 out of its locking relationship to the part I, it is pivotally connected to one end of a link or rod H, the opposite end of which is similarly con nected to one arm of a bell crank control lever :2, best shown in Figs. 2 and 3, the lever being provided with a handle or knob by means of which it can be operated. This lever is secured to the upperend of an upright rock shaft 13, Figs. 1 and 2, supported in bearings secured to the side of the curb. It will be obvious from an. inspection of Fig. 3 that if the control lever I2 is swun in a counter-clockwise direction it will rock the latch 8 out of locking relationship to its cooperating member I, after which the cover 4 can be swung into its open position.

So far as the parts above described are concerned, the construction is esentially like that illustrated in the patent above referred to. The

present invention provides a novel mechanism for locking the control lever l2 against swinging movement of an extent sufficient to release the latch .8 from its companion member 1 so 'tionship to the member 7.

long as the machine is running. For this purpose a short arm l4, Figs. 2 and 3, secured to the lower end of the rock shaft is, is connected by by a screw 22 which extends into a reduced space between the heads of a spool-shaped end.

portion of -the,plunger. At its left-hand end, Fig. 4, the bracket l8'is providedwith two. I) and c which extend laterally in directions roughly parallel to the axis of the barrel a but which diverge somewhat from said axis. Strad dling this barrel portion a. of thebracket, are the two legs 23-23 extending "rearwardly from; but

formed integral with, a shoe 24 whichlies in the space between the arms b and c. This shoecani swing in a'horizontal plane by virtue of the fact that the rearward end portionsor" the legs 23--23 are pivotally connected to the barrel. a by pivot screws 25-45, Fig. 5, but such. swinging. movement of the shoe is positively, but. adjustably, limited in one direction by the set screw. 23 and is 'yieldingly limited in the opposite direction by the" spring 21, both the spring and the screw 4 that the control lever [2 is locked out of the greater part of its operating movement.

Normally, however, with the machine station-- ary, the hole e in the shoe 24 is in alignment with the plunger and its guiding aperture in thebracket 18, so that the entire counter-clockwise movement .of' the control lever. l2, necessary to move the latchout of the path of the -member T, can be completed and the cover 4 then can be opened.

This locking-mechanism is simple in construction, extremely reliable in operation, absolutely silent, and it can be manufactured economically. Its construction is-such that it is not liable to get out of order.

it is desirable to make it impossible for a care less operator to start up the machine when the entering rather deep sockets in the opposite 7 sides of the-shoe.

It should be'obscrved that. the outer end ofthe shoe 24 lies close to the periphery of the. pulley 28 which is secured to the lower end of the spindle.

for the basket 2; this pulley being belteconnected to any suitablesoureeof power. Normally. the entire assembly of this locking mechanism is held. away from theperiphery of the pulley by means. of acoiled spring 30, Fig; 3, anchored at one-end to a clip 3 l', which is secured to'the barrel section a; crime bracket by means of the screw 22' previously. mentioned, while its other end is secured to stationary arm-32.

If it-should be'attempted, while the-basket is rotating, to swingthe operating lever I2 for-the latch. Bfar enough in a counter-clockwise direction, Fig. 3, to release the latch from the member 1, the first part of that movement would operate through the link l5 and the horn d of the lever l6 toswing the bracket l8, and the parts mounted on it, inwardly, or toward the left, Figs; 3 and 4,

against the tension of the spring 30, far enough a to bring the shoe 24 into contact with the peripheral surface of the pulley 28, or the .belt on said pulley. This pulley would be turning in .the direction indicated by the arrow, Fig. 3, and would immediately act on the shoe 24 to swing it laterally against the tension of the spring 2?. Any further force applied in this direction through the control lever l2 would tend to move the plunger 2flinwardly. If the holee, Fig. 4, in the shoe 24 V were in line with the plunger, as is the case when the machine is stationary, then this movement could proceed, but with the shoe 24 moved out of its normal position, the end of the plunger would strike the inner surface of the shoe and prevent any'further counter-clockwise"movement of the control lever I2. This actionoccurs: before the latch'B has been moved out 'ofits locking rela- Consequently, any attempt to release the cover when the machine isin operation is definitely prevented by the fact cover 4 is open, and an important feature of thisinvention resides in an interlocking mechanism connecting the control .lever 12 with both the brake mechanism for stopping the machine and also withthc source of power for driving it so as" tov accomplish this result. For this purpose. a:

brakeband 33 extending around the brake drum section 28, Fig. 2', of the pulley 28, is anchoredtat one end by extending the pull rod at this end. of

the brake band through a, fixed lug 34 and through a strong spring 35 confinedbetween. said lug and a nut on the end of the rod. Its opposite end is.

similarly associated-with an anchoring block .36"

end of a brake shaft42, similar tothe shaft 13 and supportedclosely beside the latter in bearingsmounted on the sidewall of :the curb. A brake operating .leveror handle 43 is. secured to the upperend of this-shaft. Inthe particularcon struction shown, bothxthe springs 35 and 31 tend to. tighten the brake. band.33 around the brake drum 2a,. and thus to stop the/machine. Cone: sequently, the brake must betreleased'against the pressure of thesesprings, and-Fig. 3 showsthe brake .mechanism in its released condition, such release having been. effected by swinging the'brakelever 43 into the position illustrated in saidiigure, thus forcing the pull rod 40 inwardly where, it compresses the spring 3? and loosens thegrip of the brake band on the pulleyv 28. t is necessary to lock the brake lever 43 in this condition, and a mechanism, later to be described. is provided to accomplish this object.

The interlocking mechanism above referred to, comprises two cams, one shown at 44, Fig. 2, on the shaft l3, and the other at 45 on the shaft 42. They may be alike and are related as shown in plan at Fig. 2 Cooperating with these cams are two arms 46 and 4?, respectively, both secured fast; on a rock shaft 48, and the arrangement is such that when the control lever 12 for the cover looking mechanism is in position to release the cover, then the lever 46 is held by the cam 44 in its extreme outward position. Also secured on the shaft 48 is. an'arm 53 which, at this time, bears against the stop button 5| and holds that button in. This stop button controls the application of power to the main switch for the electric motor that drives the machine, and when it is'pushed in it is impossible to start up the machine. The circuit connections for accomplishing this result will be obvious from an inspection of the wiring diagram shown in Fig. 11, the driving motor being there indicated at M and the stop and start buttons at 5! and 53. 7

When the machine is stopped by. operating-the lever" to apply'the' brake, its cam 45 operates the rock shaft 48 to press the stop button-| inward, thus cutting off the power before the brake is fully applied.

It should be noted that this interlocking mecha nism makes it impossible to start up the machine without first locking the cover. Both the brake and-the power must be off when the cover is unlocked. Also, the power is shut off automatically, due to the operation of the stop button 5! by either the movement of the speed lock control lever I2 into position to unlock the cover, or by the movement of the brake handle 43 into its brake-applying position.

- r In operating centrifugals of this type, it is com mon to control them with a time mechanism gov erning the entire cycle of operations of the ma chine. In that event, and even in some other situations, it is desirable to usea brake lock which can be released either automatically or by hand. Such an arrangement is shown in my pending application Serial No. 659,239, filed April 3, 1946, which matured into Patent No. 2,498,314, audit is advantageously incorporated in the present machine. This lock involves a plate 52, Figs. 2 and 3, rigid with the brake lever 43 and projecting laterally therefrom. In it is a notch to receive a spring-pressed latch 54, Fig. 6, mounted in the casing 55. Consequently, when the brake is pushed in to its off position, as shown in Fig. 3, theplate slides through a slot in said casing and is locked in that position by the latch 54. Associated with this mechanism, however, is an elec tromagnet 58 for either remote or automatic control, arranged to act on a plunger 51, so that when the electromagnet is energized, it lifts the plunger, and the small upper end of the plunger engages the latch 54, lifts it out of the notch in the plate 52, and allows the spring in to release the brake from its locking mechanism. The plate has a narrow slot lit in it, through which the reduced end 58 of the plunger passes as the brake lever 43 is forced outwardly by the brake setting spring or springs.

As above indicated, both springs 35 and 3? cooperate to apply the brake, and the brake lever must be forced into its locked and brake releasing position, as shown in Fig. 3, against the tension of these springs.

The electromagnet 5% may be operated by the time-control mechanism above referred to, or simply by one or more push buttons located at convenient points in the plant, or manually by pushing upwardly on the palm plate 6| which is fastened to the lower end of the plunger.

This invention is applicable, also, to installations of other types, and one such application is illustrated in Figs. 7 to 10, in which an hydraulic or pneumatic mechanism is provided to open and close the cover.

Referring first to Fig. 7, it will be seen that the cover 4 for this machine is hinged or pivoted on a'shaft 5, as in the construction above described. Also, that an arm 62 fast on said shaft is connected by a link 63 with a piston slidable in the upright cylinder 64. The opposite ends of this cylinder are connected by pipes 55 and 65 to a control device, here shown as a valve 61, of a common form, through which fluid under pressure can be admitted to either end of the cylinder 64, as may be desired, to raise or lower the cover. For convenience this mechanism will be considered to operate hydraulically, it being understood that it may be replaced by a pneumatic mechanism, as its equivalent, if desired.

When fluid isadmitted to the top of the cy1inder 64, it operates through the connections above described to openthe cover 4, and the latter is closed by a reversal of these operations. Also connected with the cover is a counter-weight 68, slidable in a guide 'Hl secured to the curb, the weight being connected by a cord or chain ll, guided over a pulley 69, to an arm 12 secured to the shaft 5'. This reduces the work required of the hydraulic mechanism.

The valve 61 includes a plunger 13 arranged to be operated by a lever "i4 provided with a ball end handle and pivoted on the valve frameat f, Fig. 10. It is connected with the plunger bya pin and slot arrangement, the construction being such that when the handle is down the valve is open, the plunger 13 is down, the piston is up, and the cover 4' is closed.

This machine preferably is equipped with a speed lock mechanism exactly like that above described, including the shaft 13 and .control lever 12. The brake mechanism also may be like that above described, including the vertical shaft. 42 and the control lever 43, together with. theelectromagnet release for the brake enclosed in the casing 55. The same cams 44 and 45 on the respective shafts I3 and 42 also are used to operate the stop button through the actuation of the shaft 56 and the arm 56 secured to it, as in the construction previously described. An additional power interlock, however, is usedin this case ineluding two features, as follows:

Fi1'st.-A lug 15, Figs. 8 and 9, extending upwardly and rearwardly from the brake lever 43 lies in the path of another lug 16 fast on the latch-control lever 12, so that the latter cannot be swung counter-clockwise far enough to re lease the latch 8 when the brake lever 43 is in its brake-releasing position and the stop button 5i also is released, as it must necessarily be when, the machine is in operation. This is an added safety feature and while it may be used alone without the speed lock previously described, if desired, it would be possible, without the latter, for thebhorator to release the brake lever 43, pull out the lever [2, thus releasing the latch, and raise the cover before the basket comes to a full stop. With the speed lock in the machine, this could not happen. I

Second.-Secured rigidly on the cover control shaft i3 is a plate l7, Figs. 8, 9 and 10, provided with a hole 9 near its inner edge, as shown in Fig. 8, which is adapted to receive the upper re duced end of the valve'plunger is when that plunger is up and the cover 4 is'closed. In order to open the cover, the valve lever is must be raised and the valve plunger 13 must be permitted -to slide up through the hole 9 in the plate Tl so as to open the valve in the proper direction to cause fluid to flow through the pipe and in to the upper end of the cylinder 64 where it will force the piston in the cylinder 64 down. This operation is prevented by the plate ll, unless that plate has been moved by the lever 62 its unlocked position, which movement will bring the hole in the plate 17 into alignment with the plunger '63 and permit the desired operation'of the valve.

This interlocking relationship of the levers l2 and 43 makes it absolutely'impossible to unlock the cover until the brake has been applied and the power has been cut off the driving motor. Also, it makes it impossible to start up the motor until the lever [2 has been moved back into its cover-locking position. The other interlock betweenthei: cover controlling lever: l2 and the valves :61 assures that power cannot beapplied to the hydrauliccylinder to open the cover until it has been unlocked by the lever l2.

Typical embodiments of my invention have been :herein'described and shown, but it will be evident that the invention may beembodied in other :forms Without departing from the spirit or scope-of the invention.

Having thus described my invention, what I desire to claim as new is:

l. In a centrifugal separator, the combination of rotary basket, a driving member for rotat ing the basket, a curb in'which said basket is sub stantially enclosed, said curb having an opening therein above said basket, a cover for closing said opening, alatchfor. holding said cover closed, power driven mechanism for opening said cover, a device controlling the application of power to open said cover, a lever operable'to release said latch, and connections between said lever and said device including a pivoted locking apparatus responsive to movement of the said driving member to prevent the operation of said mechanism to open said cover until said lever has been operated to release said latch.

2. Ina centrifugal separator, the combination of a rotary basket, a curb in which said basket is substantially enclosed, said curb having an opening therein above said basket, a cover for closing said opening, a latch for holding said cover closed, power driven mechanism for opening said cover, an electric motor connected-with said basket to revolve the same, a brake for stopping rotation of said basket, a lever connected with said latch to release it, a second lever connected with said brake-for operating it, interlocking connections between said levers for preventing the operation of the first lever to release said latch until the second lever has been operated to apply the brake, a'device for controlling the application of power tothe'mech'anism to open said cover, and interlocking connections between said device and said cover releasing lever arranged to prevent the opening .of the cover by said power driven mechanism until said latch has been released and said brake has been applied.

3. In a centrifugal separator according to preceding claim 2, a construction including a switch controlling the flow of power to said motor, connections between said brake operating lever and said switch whereby the operation of the latter lever to apply the brake also opens said switch to cut ofi power from said motor, whereby it is impossible to operate the control device to open said cover by power until the latch has been released by said first lever and the power has been 7 out off the motor and the brake has been applied by said second lever.

4. In an apparatus for locking the coverof an enclosed centrifugal separator, the combination of a latch for holding the cover closed, rock shaft means operabletorelease said latch power. driven mechanism for opening the cover, valve means for stopping andstarting the power driven mechanism, and'a locking mechanism controlling the operation of said valve means; said mechanism including parts normally held in alignment with each-other, a plunger associated with them for movement through portions of said parts when they are in alignment to release said latch, and

erationand it is attempted to operate said means to release said latch.

5. In an apparatus for locking the cover'of-an said latter members being so associated witheach other and with the power mechanism of the centrifugal separator as to prevent openingv of the cover when power is on the machine.

6. In an apparatus for locking the cover of an enclosed centrifugal separator, the combination of a latch for holding said cover closed, means operable to release said latch, said means including a control lever, a member connected with said control lever to be moved thereby, a second member associated withthe power mechanism of the apparatus to be moved by it into the path .of movement of said first member, one of said members including a plunger adapted to enter a hole in the other to complete its range of movement, said members being so associated with each other and with the power mechanism of the centrifugal separator that, when power is on, said control lever is prevented from moving far enough to release said latch, and means operable to move said obstructing member out of the path of movement of the'first member when themachine is not running;

7. In a centrifugal separator, the combination of a rotary basket, a curb in which said'basket is substantially enclosed, said curb having an opening therein above said basket, a'cover for closin said opening, a latch for holding said cover closed, means operableto release said latch, said means including a handle, an electric motor connected with said basket to revolve it, a switch controlling the supply of power to said motor, a brake for said basket, a lever connected with said brake to apply it and to release the same, connections between said lever and said switch operatingin response to movement of the lever into its brake releasing position to actuate said switch to cut off power from the motor, means for locking said lever in its brass releasing position, electromag netic means operable to release said lockin means, and interlocking connections betweensaid handle, the basket driving mechanism, and said lever constructed and arranged to prevent the operation of said handle to release said latch so long as said brake is released or said basket continues to revolve.

8. In a centrifugal separator, the combination In a centrifugal separator, the combination of a rotary basket, a curb in which said basket is substantially enclosed, said curb having an opening therein above said basket, a cover for closing said opening, a latch for holding said cover closed, means operable to release said latch,

said means including a vertically disposed shaft and a handle on said shaft for rotating the shaft, an electric motor connected with said basket to revolve it, a switch controlling the supply of power to said motor, a cam on said vertically disposed shaft, and a lever arranged to be operated by the rotation of said cam with said vertically disposed shaft to open said switch to cut off the power from said motor before said latch can be released by said handle.

10. In a centrifugal separator, the combination of a rotary basket, a curb in which said basket is substantially enclosed, said curb having an opening therein above said basket, a cover for closing said opening, a latch for holding said cover closed, means operable to release said latch, said means including a vertically disposed shaft and handle, an electric motor connected with said basket to revolve it, a switch controlling the supply of power to said motor, a brake for said basket, a lever connected with said brake to apply it and to release the same, connections between said lever and said switch operating in response to movement of the lever into its brake applying position to actuate said switch to cut off power from the motor and for movement into its brake releasing position to release said switch, and connections between said handle and said switch including cam means on the vertical shaft for holding the switch in its open position where it cuts off power from the motor so long as said latch is released.

11..In a centrifugal separator, the combination of a rotary basket, a curb in which said basket is substantially enclosed, said curb having an opening therein above said basket, a cover for closing said opening, a latch for holding said cover closed, means operable to release said latch, said means including a handle, an electric motor connected with said basket to revolve it, a switch controlling the supply of power to said motor, a brake for said basket, a lever connected with said brake to apply it and to release the same, a shaft on which said lever is mounted, connections between said shaft and said switch arranged to operate the latter to open the motor circuit when the lever is moved into its brake applying position and to release said switch when the lever releases said brake, another shaft arranged to be operated by said handle, connections between the latter shaft and said switch for holding the switch in its opencircuit position so long as said latch is in its coverreleasing position.

12. In a centrifugal separator, the combination of a rotary basket, a curb in which said basket is substantially enclosed, the curb having an opening therein about said basket, a cover for closin said opening, a latch for holding said cover closed, means operable to release said latch, said means including a vertical rock shaft and a handle, an electric motor connected with said basket to revolve it, a switch controlling the supply of power to said motor, a brake for said basket including a second vertical rock shaft and a lever connected between said second vertical rock shaft and the brake to apply it and release the same, interlocking connections between said handle and said lever constructed and arranged to prevent the operation of said handle to release the latch until said lever has been operated to apply said brake, means preventing the operation of said latch releasing means as long as said basket continues to revolve, said interlocking connections including a pair of spaced-apart cams one of the spaced-apart cams being fixed on the said first vertical rock shaft, the second cam of the pair being fixed on the said second vertical rock shaft, a transversely disposed rock shaft arranged in close proximity to the cams, a pair of arms supported on the said transversely disposed rock shaft and being operatively connected to the said spaced-apart cams, and a switch operating arm fixed on the said transversely disposed rock shaft adapted to move into and out of contact with the said electrical motor switch in response to movement of either of the said spaced-apart cams.

13. In a centrifugal separator, the combination of a rotary basket, a curb in which said basket is substantially enclosed, said curb having an opening therein about said basket, a cover for closing said opening, a latch for holding said cover closed, means operable to release said latch, said means including a handle and a vertical shaft, an electric motor connected with the said basket to revolve it, a switch controlling the supply of power to said motor, a brake for said basket, a lever connected with said brake and operable to release the brake when it has been applied, connections between said lever and said switch for causing, at the time the brake is applied, movement of the lever into position to actuate said switch to cut ofl power from the motor and for causing movement of the lever into position to release said switch when the brake is released, said connections being further arranged to operate in response to rotation of said vertical shaft, said handle and said brake being so related to each other that the handle cannot release said k file of this patent:

UNITED STATES PATENTS Number Name Date 1,674,662 Rowntree June 26, 1928 1,692,804 Bock Nov. 27, 1928 1,758,594 Carroll May 13, 1930 1,797,602 Bryson Mar. 24, 1931 1,828,227 Juengst et al Oct. 20, 1931 1,865,584 Perry July 5, 1932 1,940,812 Roberts Dec. 26, 1933 1,971,466 Schaum Aug. 28, 1934 1,989,213 Schenck Jan. 29, 1935 1,991,874 Williams Feb. 19, 1935 2,254,388 Olcott Sept. 2, 1941 2,261,936 Johnson Nov. 11, 1941 2,342,812 Martinson Feb. 29, 1944 2,390,030 Paulson Nov. 27, 1945 FOREIGN PATENTS Number Country Date 306,545 Great Britain Nov. 14, 1929 573,101 Germany Mar. 28, 1933 306,545 Great Britain Nov. 14, 1929

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