US2736247A - Hornbostel - Google Patents

Description

Feb. 28, 1956 L, HORNBOSTEL 2,736,247

VANE TYPE STOCK INLET VANE TYPE sToCK INLET Lloyd Hornbostel, Beloit, Wis., assignor to Beloit Iron Works, Beloit, Wis., a corporation of Wisconsin Application December 4, 1951, Serial No. 259,756

6 Claims. (Cl. 9244) This invention relates to an improved stock inlet for a paper machine and, more particularly, to a stock inlet having improved ow control means therein.

Transversely extending bafes or walls within the stock inlet boxes are used in the paper making art in an attempt to quiet stock ow through the box and to prevent the occurrence of eddy currents within the stock ilowing therethrough. However, such bailies serve to divide the box into a plurality of stock compartments, and it is known that dead areas are formed within the sep arate compartments and that stock rolling can occur within the compartments. The paper stock within such dead areas tends to form lumps detrimental to paper quality when later introduced onto the forming wire, while the rolling stock within the separate compartments interferes with the uniform flow of stock through the inlet, thus aiding in the formation of dead areas.

Various devices which have been substituted for transversely extending baies often have been found to reduce the length of stock travel in the inlet box to such an extent that uniform flow across the box cannot be adequately controlled. Ordinarily, the incoming stock is conducted to the inlet box from a suitable source by means of a pipe substantially narrower in width than the inlet box. Stock discharged into the box from the pipe tends to iiow heavily through the box from the pipe discharge directly to the box discharge or slice gate, and accordingly fails to spread out uniformly during its travel through the box. The problem is additionally complicated in the case of pressurized inlet boxes, wherein air pressure on the surface of the stock is employed to accelerate the ow of stock from the box onto the forming wire, since in such pressurized stock inlet boxes a high rate of flow of the stock is used with a comparatively small overall volume in the stock inlet box.

The present invention provides an improved vane type iiow distributor arrangement within the inlet box, permitting the use of a relatively short travel path through the inlet box and also permitting the use, in combination with such a ow distributor arrangement, of rectifier means such as rectifier rolls in certain arrangements so as to obviate the necessity of employing transversely extending batiies with the attendant operational di'iculties heretofore encountered.

In general, the stock inlet box of the present invention includes a head box for a paper making machine provided with means for introducing stock into the interior of the box and a stock outlet immediately adjacent the forming wire of the paper making machine. At the inlet to the box there are positioned a plurality of independently adjustable flow directors adapted to divert stock flow laterally in controllable amounts, thereby to elfect equal or uniform flow in the stock all the way across the head box. Arrectifier roll or a stack of superimposed rolls extends transversely across the interior of the inlet behind the flow director means for the purpose of replacing the baffle arrangement heretofore employed, and preferably a second rectifier roll or group United States Patent Ice of rolls is disposed adjacent the box outlet opening to additionally control the ilow of stock through the opening onto the paper machine forming wire.

Since the depth of the stock pond in the head box and the air pressure exerted against the stock pond surface are calculated to give a definite velocity of stock ow in a horizontal path through the box onto the forming wire, the size and number of laterally directed flow distributors and the number of rectifier rolls in the stack and the size of the rolls will be determined by the Velocity desired for stock flow. Preferably, the depth of stock of the box is held constant by suitable means' acting in conjunction with or regulated by air pressure in a pressurized closed inlet box, the depth being controlled so that an appreciable amount of stock cannot iiow over the top of the flow distributor means and the top rectier roll in the stack. On the other hand, the depth should also be controlled lso that the flow distributor means and the rectifier roll will be submerged.

The flow distributor means are preferably independently adjustable vanes extending vertically from the floor of the inlet box to just below the controlled stock level. The vanes may be arranged accordingly in a flow distribution chamber at the stock inlet opening, which comprises a duct expanding laterally from a pipe inlet means to approximately the head box width at its exit. The vanes positioned in the expanding duct are independently adjustable so that they may be adjusted to distribute the necessary amountof stock laterally at different iiow rates in order to effectively equalize the ow'of stock across the box. Also, it is preferable that the expanding duct is adapted to receive vertical, preferably upward stock flow from a pipe so that it impinges upon a baille which converts the vertical stock flow to horizontal stock flow directed toward the vanes.

The rectifier rolls of the stack arespaced apart only su'iciently for operating clearance and should not provide a flow gap therebetween. A gap of from l; to 1/2 inoh between roll peripheries is satisfactory. Thus, the only restriction to the ow of stock past the vanes through the box is presented by theprectier roll stack, and this resistance to liow is uniform throughout the entire depth of the stock pond.

The vanes effectively equalize the ow of stock all the way across the box as it approaches the rectifier roll stack, so that the rectifier roll stack is not subjected to a substantially greater ow of stock at any one given point which might happen to be aligned with the pipe inlet means from the stock source. In this manner, uniform ilow both laterally and longitudinally is effected, and the rolling of stock, the occurrence'of dead spots, and the creation of eddy current is prevented.

The additional rectier rolls at the outlet end of the stock inlet box are arranged in spaced relation from the outlet opening to form any desired roll pattern, such as the illustrated arcuate arrangement, which will provide a uniform restriction to the flow of stock toward the outlet. The rolls are grouped so that the stock must flow therethrough, and each of the rolls extends transversely to-the path of stock flow. By spacing the rectifier rolls of this group from the stock outlet, any eddy currents generated by the ow of stock through the rolls are dissipated prior to introduction of the stock onto the forming wire, and the group arrangement of the rolls also prevents the by-passing of stock around the rolls onto the forming wire.

It is therefore an important object of thepresent invention to provide an improved stock inlet for a paper making machine in which uniform flow of stock through the inlet is obtained without the employment of solid baffles, walls, or the like which are designed to increase appreciably the travel path of the stock through the inlet box.

Another important object of the present invention is to provide an improved stock inlet for a paper making machine suitably adapted for high velocity stock flow through a pressurized closed head box, employing flow distributors or vanes which are directed laterally and angularly with respect to the direction of stock flow in order t"o equalize the stock flow across the head box.

A further object of the present invention is to provide an improved stock inlet box having a plurality of laterally directed vanes cooperating with a plurality of rectifier rolls arranged in spaced relation from the outlet end of the box in order to effectively accomplish uniform stock flow.

Still another important object of the present invention is to provide an improved stock inlet for paper making machines wherein vane pipe flow distributors cooperate with bafe means to receive upward flowing stock from a pipe, to convert the same to horizontally flowing stock and finally to uniformly distribute the horizontally flowing stock laterally.

Other objects, features and advantages of this invention will become apparent to one skilled in the art from the following description of the embodiment illustrated in the accompanying drawings.

On the drawings:

Figure l is a top plan view of a stock inlet box embodying the invention, having the top lid removed; and

Figure 2 is a sectional elevational view, taken substantially along the line ll-II of Figure l, showing parts in whole view and parts diagrammatically.

As shown on the drawings:

Reference numeral refers generally to a stock inlet box embodying the invention. The stock inlet box 19 has a horizontal floor 11 and arising vertically therefrom, on opposite sides thereof, side walls 12 and 13 and a front vertical wall 14, slidably engaged on its front outside surface with a slice gate 15. The slice gate 15 has an inwardly turned top langel which mounts a set screw assembly 17 for adjusting the position of the beveled slice tip 18 with respect to the beveled forward tip of the iloor 11.

The relative positions of the forward tip of the floor 11 and the beveled slice tip 18 determine the size of the box outlet opening and, therefore, the amount of stock which flows out of the inlet box and onto the forming wire 19 which is trained about the breast roll 20.

As is best shown in Fig. 2, the inlet box 10 has a generally horizontal oor 11 extending longitudinally (in the direction of stock flow) from an inlet opening at the left hand and to an outlet opening at the right hand end.

As shown best in Figure 1 in plan view, the floor 11 of the inlet box 1li is generally rectangular in shape from the forward end underneath the front wall 14 back between the side walls 12 and 13 until the ends of the side walls are reached. Thereafter, the iioor 11 tapers sharply 1n the portion designated by the reference numeral 11a, finally forming a curved apex portion. designated by the reference numeral 11b. The vertically extending back wall of the inlet box 1t) is shaped to conform with the contour of the floor 11 and, therefore, consists of a curved central portion 21 having one arm 22 extending angularly and forwardly to join the side wall 12 and another correspondingly shaped arm 23 extending angularly and forwardly to join with the side wall 13. u

A top member 24 (shown diagrammatically in Figure 2) completes the stock inlet box 1d. The top member has substantially the same contour as that of the floor 11 and joins with the vertically extending wall members 12, 13, 14, 21, 22 and 23 to form a closed box. The box so formed is adapted to be pressurized, or to permit the flow of a stock therethrough under controlled air pressure. As shown diagrammatically in Figure 2, the means for effecting air pressure against the stock in the inlet box may consist of a compressedv air inlet line 25 having a valve 26 therein for controlling: the ow of compressed 4. air into the box 10. The valve 26 is, in turn, connected by an air line 27 to a compressed air tank 23 wherein compressed air is maintained at a given pressure by means of the compressed air pump 29.

It will be appreciated that by the use of compressed air alone under given flow conditions it will be possible to maintain a given stock level in the box. On the other hand, such a procedure is greatly simplified by the use of compressed air in conjunction with a blow hole 3i) suitably positioned, for example, in the side wall 12, at the desired stock level, designated herein by the reference numeral 31.

In maintaining a stock level 31 by the use of combination air pressure and the hole 30, it can be seen that if the stock level rises above the hole 30 the additional effect of air pressure will tend to force the stock level back down again by increasing the rate of flow of stock onto the forming wire. On the other hand, if the stock level falls back down to the level of the hole 3i), then the air pressure above the stock pond is instantly released through the hole 3l?.

A pair of spray lines 32 extend transversely from one side wall 13 to and through the other side wall 12 and are connected to a suitable water source (not shown). The spray lines 32 contain small holes in the bottom pe ripheral portion of each and are adapted to send out a fine spray of water, so as to effectively wet the inside walls of the stock inlet box 10 and thereby prevent the settling out of small stock particles upon the inside walls during slight fluctations in stock level.

Near the rear apex portion 11b of the tapered door 11 is an opening 33 at which is suitably mounted a stock inlet pipe 34. The inlet pipe 34 is connected to a suitable stock source (not shown) adapted to supply the stock under pressure and thereby to introduce into the inlet box 10 a vertical upward flow of stock, as shown by the arrows in Figure 2.

The upwardly owing stock, entering through the pipe 34 and the opening 33, impinges against a baffle 35 extending horizontally in spaced relation with the opening 33. The bale 35 is a generally circularly shaped, ilat, rigid sheet extending from the curved central portion 21 on the back wall and conforming therewith on one side and having a protecting wall 35 joining and rising vertically from the forward arcuate edge portion of the baffle 35 not joined to the curved central portion 21 of the back wall; The baie 35 is preferably positioned so that it is just below the level 31 and the protecting wall 36 prevents iiow of stock above and behind the bale 35 into what might constitute a dead spot in the stock inlet box 10. It will thus be seen that the batlle 35 converts vertical stock flow to horizontal stock ow in the inlet box 1() and in so doing it diverts the horizontal flow of stock against a-plurality of (generally upright) vanes 37.

As shown best in Figure 2, wherein only one vane 37 is shown for the sake of simplicity, the vane 37 is an essentially rectangular vertically extending sheet of suitable rigid material such as a metal. The vane 37 has a sleeve portion 37a positioned near the leading edge 37b. The sleeve portion 37a receives and ixedly engages a shaft 38 extending throughout the sleeve 37a from the top of the vane 37 out to the bottom of the sleeve 37a through an aperture in the floor 11. A hub 39 is mounted on the bottom ofk theshaft 38 below the floor 11. The hub 39, the shaft 38 and the apertured portion of the floor 11 cooperate to permit rotation of the shaft 38 and to form a fluid-tight seal so as to avoid stock leakage. The hub 39 and the shaft 3S are mounted for rotation upon the floor 11 by means (not shown) which are well known in the art and the axial movement of the shaft 38 is prevented thereby.

Each of the vanes 37 is independently adjustable. An adjusting arm 40 extends generally parallel to the door 11 and below the floor 1.1- and is connected to the hub 39 for rotation thereof'. The adjusting arm 40 is slotted longitudinally to receive slidably a Wingnut assembly 41'." The bolt portion of the-wing `nut assembly 41is adapted*- to slidably engagel an arcuate slot or groove 42 cut in the bottom edge of the oor 11. It will be appreciated that when the wing nut is loose in the wing nut assembly 41, the actuating arm 40 may be moved to rotate the vane 37 and the wing nut assembly will slide freely in the arcuate groove 42 and the slotted portion of the adjusting arm 40. When the proper position hasl lbeen reached the wing nut may be tightened and the vane 37 is then held in position. l

By the use of the-individually adjustable vanes 37 it is possible to make adjustment for various ow rates so that proper distribution laterally of the flowing stock may be obtained in each case. It can also be seen that the overall travel path of the stock is not appreciably affected by the use of the instant vanes 37. As the stock leaves the vanes 37 it flows uniformly across the inlet box 10, in that the rate of flow at any of the various points on either side section of the inlet box is substantially the same as the rate of flow through the middle of the inlet box 10. The rate of flow is thus equalized or uniform at all points across the stock inlet box 10 as the stock passes out of the expanding duct portion defined by the tapered oor portion 11a and the arms 22 and 23 of the back wall.

As the stock departs from the vanes 37 it comes into contact with a plurality of superimposed horizontally aligned rectifier rolls, in this case a pair of rolls 43 and 44, rotatably journaled in the opposite side walls 12 and 13 of the box 10 and adapted to be rotated by suitable means (not shown), as for example by means of individual variable lspeed reversible electric motors.

The stack of superimposed rectifier rolls 43 and 44 presents a uniform restriction to the flow of stock entering into the full width of the box 10.4 It Will be noted that the top roll 43 extends to just below the stock level 31.. The rolls 43 and 44 are spaced apart through the height of the stacks, the peripheries of the rolls preferably being about 1A to 1/2 inch apart. Such a distance is not sufficient to open a flo-w path between the rolls, while the rolls are maintained out of peripheral contact to prevent the formation of pressure nips therebetween which might interfere with the uniform stock flow through the box. The direction of drive of the rolls relative to one another is selective to suit conditions desired and the rolls Vare preferably rotated at very low speeds with rotation serving merely to clean the holes. The speed of rotation may be. as low as about 5 to 10 R. P. M., with the holes being cleaned by the reversed flow through the rolls as they are rotated. Thus a ow through the box is caused by the introduction of stock under pressure into the box 10 and not by any pumping action which might be exerted by the rolls 43 and 44. p

As has been Vmentioned before, it is preferred that the stack of rolls 43 and 44 be of such height that the upper roll 43 is substantially submerged within the stockvflowing through the inlet box 10. 'It is likewise preferred that the vertically extending vanes 37 each do not extend above the top peripheralportion of the upper roll 43, and the vanes 37 will likewise be substantially submerged within the -stock flowing through the inlet box 10. It will be appreciated that the extent to which the uppermost roll 43 and the vanes 37 are submerged is exaggerated in Figure V2, for the sake of emphasizingthis preferred feature of the invention. Actually, the extent to which the rolls or the vanes are submerged is essentially that extent which is necessary to avoid the possibility of stock particles collecting at the top portions of such members. In addition, the rotation of the rolls 43 and 44 tends to reduce appreciably any tendency of stock particles to collect on such members. The divergent, probably fluctuating, flow against the leading edge 37b of the vanes 37 caused by the sharp change of direction of the stock thereat, also tends to reduce appreciably any accumulation of stock particles upon the leading edge 37b" of each vane.

The individual rolls 43 and 44 are each provided with a plurality of graded perforations in a manner well known in the art, such as to diminish in capacity inwardly from the ends of the rolls, the ends of each of the rolls being scalloped or perforated with semi-apertures formed by the intersection of the terminal apertures of the ends of the rolls. The aperture arrangement is such that a uniform flow rate along the entire length of the roll is maintained, the frictional drag or skin effect on the flow of the flowing stock normally imparted by the stationary side walls 12 and 13 of the box 10 being thus compensated for by the reduced capacity hole of the mid-section of the roll.

It will, of course, be appreciated that the equalizng effect of the variations in the apertures in the rolls s essentially a nal touch in the flow control and is not adapted to equalize radically different flow rates across the inlet box. The vanes 37 of the instant apparatus serve' to accomplish the basic equalization of ow, whereas the rolls 43 and 44 more or less perfect the uniformity of flow.

Although in the specic embodiment of Figure 2 a stack consisting of two rectifier rolls 43 and 44 has been shown, it will be appreciated that the number of rolls in the stack and the relative sizes of the rolls may be varied in accordance with the level of stock within the chamber. Under some` conditions, it is possible to use only one rectifier roll with a given height of stock and the number of rolls in the stack generally increases in accordance with an increase in desired depth for the stock pond.

In Figures l and 2 it will also be noted that a plurality of rectier rolls, in this case a pair of rolls'45 and 46, are mounted adjacent the front wall 14 of the box 10. The rolls 45 and 46 are peripherally apertured and are substantially identical in construction with the rolls 43 and 44. The rolls 45 and 46 are each provided with a separate, variable speed reversible motor (not shown) t0 provide individual control for the direction of speed of rotation of each roll. lt is preferred that the rolls 45 and 46, which are spaced as hereinbefore explained, be driven in opposite directions to ow stock uniformly and at a given rate onto the forming wire 19. The rolls 45 and 46 may be so arranged, as illustrated, so that the portion of the peripheries nearest the slice tip 1S falls on an arc subtended by a radius having its center generally forward of the inlet box and along the forming wire 19.

The rolls 45 and 46 are preferably mounted in a bridging arrangement adjacent the outlet opening so as to control the entire ow of stock from the inlet box onto the forming wire 19. It has been found that one roll positioned adjacent a slice, as heretofore conventionally employed in the art, sometimes results in the streaking of stock deposited on the wire and the formation of fingers on the wire, or a broom effect in the deposited stock. By the employment of the plurality of bridging rolls 45 and 46, any turbulence which might be introduced in the stock by the passage through the rolls 45 and 46 may be dissipated prior to introduction of the stock onto the forming wire 19. i

As in the case of the rolls 43 and 44, it is desirable to have the uppermost rolls 45 substantially submerged below the stock level 31, for the reasons hereinbefore mentioned.

It will thus be seen that by the combination of the vanes 37 and the stack of rectifying rolls 43 and 44, it is possible to obtain substantially uniform stock flow both longitudinally of the direction of flow and transversely of that direction. The baffle 35 and the expanding duct housing the baffle 35 and the vanes 37 are uniquely adapted to effect the main correction or equalization of the stock flow laterally and the rectifier rolls 43 and 44 in cooperation therewith accomplish the final touches in the stock control. j f

This is a continuation-impart of my copending application,SerialrNo. 81,951, filed March 17, 1949 and issuedY September 14, 1954 as U. S. Patent No. 2,688,905, and ow'nedfbyy the assignee-of this application.

It will, of course, be understood that various details of construction may be varied through a Wide range without departing from the principles of this invention, and it is, therefore, not the purpose` to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. A stock inlet box for a paper'making machine coniprising a head box having a generally horizontal floor extending longitudinally from an inlet opening at one end for receiving stock from a source thereof to an outlet opening at the other end for flowing stock onto the forniing Wire of the machine, a duct mounted at the head box inlet, said duct expanding laterally from a pipe inlet opening to a head box size exit from which stock ilows into the head box inlet, a horizontally aligned transversely extending rectifier roll mounted Within the box in spaced relation from the duct exit to present a uniform restriction to the flow of stock through the box for preventing rolling of stock and the formation of dead stock areas within the box, laterally directed upright vanes mounted in the duct for equalizing the stock flow across the head box, and means for maintaining a level of stock in the box that will submerge the roll and the vanes.

2. A stock inlet box for a paper making machine cornprising a head box having a generally horizontal floor extending longitudinally from an inlet opening at one end for receiving stock from a source thereof to an outlet opening at the other end for ilowing stock onto the forming wire of the machine, a duct mounted at the head box inlet, said duct expanding laterally from a pipe inlet opening to a head box size exit from which stock flows into the head box inlet, means llowing stock upwardly through said pipe inlet, a horizontal baille opposing said pipe inlet to convert upward ilow of stock therefrom into horizontal tlow in said duct, a horizontally aligned transversely extending rectier roll mounted within the box in spaced relation from the duct exit to present a uniform restriction to the flow of stock through the box for preventing rolling of stock and the formation of dead stock areas within the box, laterally directed upright vanes mounted in the duct for equalizing the stock ilow across the head box, and means for maintaining a level of stock in the box that will submerge the roll and the vanes.

3. A stock inlet box for a paper making machine comprising a head box having a generally horizontal iloor extending longitudinally from an inlet opening at one end for receiving stock from a source thereof and to an outlet opening at the other end for ilowing stock onto the forming wire of the machine, a duct mounted at the head box inlet, said duct expanding laterally from a pipe inlet opening to a head box size exit from which stock flows into the head box inlet, means flowing stock upwardly through said pipe inlet, a horizontal baille opposing said pipe inlet to convert upward ilow of stock therefrom into horizontal ilow in said duct, a plurality of superimposed horizontally aligned transversely 'extending rectifier rolls mounted within the box in spaced relation from the duct exit to present a uniform restriction to the llow of stock through the box for preventing rolling of stock and the formation of dead stock areas within the box, laterally directed upright vanes mounted in the duct for equalizing the stock flow across the head box, and means for maintaining a level of stock in the box that will submerge the roll and the vanes.

4. A stock inlet box for a paper making machine comprising a head box having a generally horizontal iloor extending longitudinally from an inlet opening at one end for receiving stock from a source thereof to an outlet opening at the other end forllowing stock onto the forming wire of the machine, a duct mounted at the head box inlet, said duct expanding laterally from a pipe inlet opening toa head box size exitl from which stock flows into thehead'box inlet, a plurality of superimposedhorizontally aligned transversely extending rectifier rolls mounted within thebox inspaced relation from the duct exit to present a uniform restriction to the flow of stock through the box for preventing rolling of stock and the'formation of dead stock areas within the box, laterally directed up right varies mounted in the duct for equalizing the stock ilow across the head box, and means for maintaining a level of stock in the box that will submerge the roll and the vanes.

5. A stock inlet box for a paper making machine comprising a head box having a generally horizontal iloor extending longitudinally from an inlet opening at one endfor receiving stock from a source thereof to an outlet opening at the other end for flowing stock onto the forming wire of the machine, a duct mounted at the head box inlet, said duct expanding laterally from a pipe inlet opening to a head box size exit from which stock flows into the head box inlet, a horizontally aligned transversely extending rectifier roll mounted within the box in spaced relation from the duct exit to present a uniform restriction to the flow of stock through the box for preventing rolling of stock and the formation of dead stock areas within the box, laterally directed upright vanes mounted in the duct for equalizing the stock flow across the head box, means for maintaining a level of stock in the box that will submerge the roll and the vanes, and means for controllably exerting air pressure against the stock in said box.

6. A stock inlet for a paper making machine comprising a closed head box having a generally horizontal lloor extending longitudinally from an inlet opening at one end thereof for receiving stock from a suitable source to an outlet opening adjacent the other end for flowing stock onto the forming wire of the machine, a duct mounted at the head box inlet, said duct expanding laterally from a pipe inlet opening to a head box size exit from which stock iiows into the head box inlet, a horizontal baille in said duct positioned to convert upward inlet stock flow to horizontal stock ilow, a plurality of upright vanes directly behind said baille, each of said vanes being independently adjustable to divert stock flow laterally in controllable amounts, a vertically extending stack of rectifier rolls extending transversely to the horizontal stock flow behind said vanes, a plurality of horizontally aligned rectifier rolls mounted adjacent said outlet opening to permit dissipation of turbulence in the stock prior to its exit through saidropening, means for controllably exerting air pressure against the stock in the closed head box, and means for maintaining a level of stock in the box that will submerge said rolls and said vanes.

References Cited in the file of this patent UNITED STATES PATENTS 1,771,600 Yoder July 29, 1930 1,846,406 Sweeny Feb. 23, 1932 1,909,150 Bell-Irving et al May 16, 1933 2,186,761 Malkin Jan. 9, 1940 2,281,293 Lang Apr. 28, 1942 2,345,647 Witham Apr. 4, 1944 2,381,286 Hornbostel et al. Aug. 7, 1945 2,396,695 Goodwillie Mar. 19, 1946 2,465,445 Goldsmith Mar. 29, 1949 2,509,822 Hornbostel May 30, 1950 2,548,108 Hornbostel Apr. 10, 1951 2,550,552 Goodwillie Apr. 24, 1951 2,608,912 Davis sept. 2, 1952 2,664,033 Hornbostel et al Dec. 29, 1953 2,684,690 Lee July 27, 1954 2,688,905 Hornbostel Sept. 14, 1954 FOREIGN PATENTS 254,873 Germany Dec. 17, 1912 359,594 Great Britain Oct. 29, 1931 469,203 Great Britain July 21, 1937 478,859 Canada Nov. 27, 1951

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