US2982411A

US2982411A - Moisture separation from granular materials

Info

Publication number: US2982411A
Application number: US599652A
Authority: US
Inventors: Freerk J Fontein
Original assignee: Stamicarbon BV
Current assignee: Stamicarbon BV
Priority date: 1955-07-22
Filing date: 1956-07-23
Publication date: 1961-05-02
Anticipated expiration: 1978-05-02

Description

y 1951 F. J. FONTEIN I 2,982,411

MOISTURE SEPARATION FROM GRANULAR MATERIALS Filea July 23, 1956 3 Sheets-Sheet 1 May 2, 1961 F. J. FONTEIN MOISTURE SEPARATION FROM GRANULAR MATERIALS 3 Sheets-Sheet 2 Filed July 23, 1956 FIG. 4

May 2, 1961 F. J. FONTEIN MOISTURE SEPARATION FROM GRANULAR MATERIALS 3 Sheets-Sheet 3 Filed July 23, 1956 INVENTOR Faisal J. Fomsm ATTORNEYS United States Patent MOISTURE SEPARATION FROM GRANULAR MATERIALS Freerk J. Fontein, 'Heerlen, Netherlands, assiguor to Stamicarbon N .V., Heerlen, Netherlands The present invention relates to moisture separation from granular materials and more particularly to a process and apparatus for eifecting the complete or partial removal of moisture from fine-grained material of substantially uniform composition containing an amount of free moisture such that the pores between the grains of material are partially filled with liquid.

. The invention is especially applicable to the treatment of material of such small particle size that due to the capillary rise, the liquid in the fine pores between the particles is only expelled from the material if a given force is exerted thereon, as, for example, in completely or partially removing moisture from fine coal, crushed ore and other fine-grained materials.

A well-known practice for effecting the removal of liquid from such material embodies the use of centrifuges having a perforated wall in which the liquid is driven towards the wall of the basket under the influence of centrifugal force and forced out through the perforations. However, centrifuges of this type are subject to severe wear with the result that their maintenance is costly.

It has also been suggested to effect the dewatering of granular material by means of conical centrifuges having imperforate walls. With this type of centrifuge the material to be treated is supplied through the center of the centrifuge so as to form a moving layer therein. At or near the edge of the imperforate wall a slot is formed through which the liquid driven towards it by the centrifugal force can issue. However, this slot serves only as an outlet for the water. Should fine-grained material, such as filter slurry or the like, be treated in a centrifuge of this type either the slot' would have to be made so narrow as to become obstructed by the slurry or the slurry would,

together with the liquid, be forced out through the slot so that the apparatus would no longer accomplish its purpose.

It has further been suggested to store the fine-grained moist material, such as fine coal or the like, in bunkers where the liquid'is allowed to settle into the lower part. After the material has remained in the bunkers for a given length of time, during which period a separation has taken place into an upper layer of low liquid content and a lower layer of high liquid content, the lower layers are extracted from a few bunkers and deposited in a storage bunker where the liquid is again allowed to settle or is removedfrom the material in some other way. Next, the drier part is discharged separately from each bunker. This construction has the distinct disadvantage of requiring a large bunker space.

Accordingly, it is an object of the present invention to provide an improved apparatus and method for effecting the complete or partial removal of moisture from finegrained material of substantially uniform composition containing free moisture which substantially overcomes the disadvantages outlined above.

Another object of the present invention is the provision of an apparatus of the type described which is' continuare provided for recycling the moisture-rich ice A further object of the present invention is the provision of an apparatus of the type described having im-v proved means for forming and supporting a continuously moving layer of moisture laden fine-grained material so that the moisture therein will become concentrated in a fractional layer thereof during its movement.

A still further object of the present invention is the provision of an apparatus of the type described having improved means for separating the moisture concentrated fractional layer from a moving layer of moisture laden fine-grained material.

Still another object of the present invention is the provision of an apparatus of the type described which is simple in construction, easy to operate and economical to operate and maintain.

A still further object of the present invention is the provision of an improved process for effecting the removal of liquid from fine-grained material of substantially uniform composition containing free moisture which includes forming a continuously moving layer of such material, supporting the moving layer so that the moisture therein will become concentrated during its movement in a fractional layer thereof and separating the moisture concentrated fractional layer from the moving layer.

These and other objects of the present invention will become more apparent during the course of the following detailed description and appended claims.

The invention may best be understood with reference to the accompanying drawings wherein an illustrative embodiment is shown.

In the drawings:

Figure 1 is a vertical sectional view of an apparatus embodying the principles of'the present invention;

Figure 2 is a top view of the apparatus shown in Figure 1;

Figure 3 is a somewhat schematic side elevational view of another form of apparatus embodying the principles of the present invention;

Figure 4 is a view similar toFigure 3 showing another form of apparatus;'

Figure 5 is a diagrammatic longitudinal sectional view of a still further form of apparatus;

Figure 6 is a fragmentary view showing a modification of the separating means of the apparatus of Figure 5; I

stationary flat table 1, over which a number of blades or scrapers 2, 2', of which only a few are shown, are moved in the direction indicated by the arrow. To this end, the blades 2, 2' are fastened to endless chains 3, 3', trained about a pair of spaced gear wheels 4. The gear wheels may be driven by any suitable driving mechanism (not shown).

The table 1 may have any suitable length and the material to be treated, e.g. filter slurry, is supplied to one end thereof from a funnel 5. Near the other end of the table, a slot-like opening 6 is provided, which extends perpendicular to the longitudinal axis of the table. A slide 7 includes a projecting lip 9 which, at a distance from the underside of the table, can shut off the entire slot-like opening 6 over a certain length. Beneath the lip 9 a funnel 10 is disposed in which the moisture-rich product is collected.

Conduits

11 and 12 and a pump 13 product collected in the funnel 10.

The operation of the apparatus is as follows: From the funnel 5, which is fed in a manner not illustrated in the drawing, a layer of suitable width of the material to be treated fiows continuously onto the table, where it is taken along by the blades or

scrapers

2, 2, and Where a layer A of a certain thickness is formed.

At the start, the layer A has a uniform moisture content, but as the layer is transported the liquid sinks and in the bottom part of layer A, a layer B of higher moisture content is formed, which layer gradually becomes thicker, topped by a layer C having a moisture content which gradually becomes smaller than the original content. At the slot-like opening 6, the whole layer B or part of it may be discharged. This discharge can be controlled by means of the lip-shaped projection 9, as here a sloping face 14 is formed, the angle of which depends on the moisture content of the material. However, when a certain moisture content is exceeded, the material will start to flow across the edge of the lip. By changing the position of the slide 7 a greater or smaller amount of wet material may be discharged. The drier portion C of the layer is discharged at 15, and the moisture-rich material is returned to a suitable place in the feed of funnel through

conduits

11 and 12, by means of pump 13.

If very wet material is being treated, the table 1 may be wholly or partly perforated, if desired, in order that excess amounts of liquid which may have sunk into layer B, may be removed therethrough. It is evident that other devices for moving the layer may also be used without departing from the invention eg a scraper chain, or the like.

In Figure 3, where corresponding parts have been denoted with the same reference figures as in Figures 1 and 2, the table 1 is formed by an endless belt 17, which moves on rollers 18 in the direction indicated by the arrows. The material to be treated is supplied through funnel Sat the one end as before. At the other end there is provided a horizontally disposed plate 19, which is preferably adjustable in the vertical direction. The layers B and C are separated, by means of the plate 19, after which layer B flows into the funnel and is recycled, whereas layer C is discharged at 15.

The apparatus illustrated in Figure 4 comprises a flat table 21, which, as shown, has the construction of a screen mounted at an angle to the horizontal plane greater than the angle of repose of the natural slope of the wholly or partially moisturefreed product to be discharged. The upper end of the table or screen 21 connects to the delivery end of a sieve bend 22 (see my copending application Serial No. 475,251, filed December 14, 1954, now Patent No. 2,916,142), onto which the material to be treated, e.g. water and fine coal, is tangentially fed, as from 23. The larger part of the water plus part of the fine product are collected in the collecting tank 24 of the sieve bend and discharged at 25. At the end of the table 21 there is provided a pair of

blades

27a and 27b constituting a controlling element which can pivot around a horizontal shaft 26 and parallel to the underside of the table 21. The controlling element blade 27a at the screen side of the table 21 projects beyond the screening deck, and the blade 27b projects at the other side of the screening deck.

A slot 28 is defined between the controlling element blades 27a and27b and the lower end of table 21. Under the table 21 a collecting tank 29, which ends in a funnel 30, is provided. The discharge 31 of this funnel, into which also the overflow of the blade 27b opens, leads to a pump 32, the delivery pipe of which is connected to a conduit 33 leading to the feed side'of sieve bend 22.

It will be understood that the underside of the collect ing tank 29 may be closed by a wall, which is indicated at 34 by a dotted line, and the water admitted through the screen is discharged as at 35, if desired.- According to the invention, the

blades

27a and 27b of the controlling element may be positioned at an angle to each other, which angle is adjustable.

Any suitable means may be provided for effecting this adjustment, one example of such a means being shown in Figure 7. As shown in Figure 7, the

blades

27a and 27b are flat plates connected at one end to the horizontal shaft 26 by means of

hinges

51 and 52. The shaft 26 is supported by a frame, generally indicated at 50. Adjusting means in the form of turnbuckles 53 are hingedly connected at their ends at 54 and 55 between the

plates

27a, 27b respectively and the frame 50 and serve to adjust the position of the

plates

27a and 27b relative to each other. Each turnbuckle 53 comprises a spindle 56 pro vided with left and right hand threads and

housings

57 and 58 with corresponding inner threads, hingedly connected to the frame 50 and one of the

plates

27a, 27b. As shown in the drawing, shaft 26 is parallel to the lower edge of the screen 21 and is positioned substantially in the elongation of the screen 21. The latter is supported by angleirons mounted on the frame (not shown). The dryer material is collected in tank 60.

The overflow from sieve bend 22 falls onto the sloping table 21 and slides downwards until it is checked by the blade 27a. The water contained in the coal sinks to the bottom layer and part of it drips through the screen 21 into the collecting tank 29, resulting in the upper layer of bed A becoming drier. The

controlling element

27a and 27b is now so adjusted that the blade 27a takes up a position at which the upper surface 36 of the bed C is so inclined that the drier coal slides across the edge of the blade 27a. The wet coal, which is contained in the bottom part B of layer A can be discharged into funnel 30 through slot 28 and across blade 27b, which has been given the most suitable position to this end, after which this coal can be returned to the start of the process by means of pump 32 and through conduit 33, Wet fine coal is delivered only if it has a moisture content of, e.g. 40%. Measurements indicate that the decrease in moisture content of the dry fine coal effected in this way can be about 5%.

In Figure 5 there is shown a centrifuge 42, in which the moving layer is formed on a smooth imperforate wall 41 by centrally feeding the material to be treated into the centrifuge from a funnel 43. Separated from the centrifuge wall 41 by an annular slot 44, a conical or cylindrical body 45 is provided over the upper edge of the centrifuge, which body is positioned at an angle to the wall 41. A conical or cylindrical wall 46 is connected to the lower edge of the body 45 so that material forced out through the slot 44 is checked by the wall 46. Under the slot 44 there is a collecting tank 47 for the moisture-rich material, which may be recycled by means of devices of the nature previously indicated, but not shown in the drawing. At the upper edge of the body 45 there is provided a discharge device for thematerial that is completely or partially freed of liquid, which device is not shown in the drawing. The centrifuge 42 is made to rotate by means of a motor 48.

The moving layer is here formed on the bottom of the centrifuge and moves upwards along the conical wall 41, the liquid contained in the material being forced towards the wall by the centrifugal force, so that a moisturerich layer and a drier layer are formed on the wall and closer to the axis of the centrifuge, respectively. The moisture-rich layer can escape through the slot 44 and is checked by the Wall 46, so that the discharge of too great an amount of material at that place is prevented. The amount discharged may be controlled by vertical shifting of the

body

45, 46.

Figure 6 shows a modification of the separating means of Figure 5. The annular slot 44 is formed by a conical or cylindrical wall 45', the lower end of which is on the inside of the wall 41. The layer which has been separated off is checked by a horizontal wall 49 and a .material to be. treated to form the layer.

vertical wall 46'. The width of the slot canbe controlled by vertical shifting of the body 45, 49.

thematerial or in some'other part correspondingtherewith and then separating the lower part from the overlying part.

Naturally, whena fine-grained material containing an amount of free liquid such that the pores between the grainsrof material are partially filled with liquid is spread outin layer formation, the liquid contained therein will settle into the lower part of" the layer where it will be retained either wholly or partially due to capillary action and it is this latter part that. is separated by the process of the present invention. It is well known that fine.- grained material may, at different moisture contents, form slopes of different gradients, but also that such slopes cease to exist when the moisture content exceeds a given maximum value in which case the material starts flowing together with the liquid, which characteristic is utilized in the present invention to eifect separation.

For this reason the separation and removal of the parts with the higher and lower moisture contents according to the invention is preferably effected by the adjustment ofthe means of separation disposed at or near the end of the layer, which causes the material, at predetermined moisture contents, to form a slope with a gradient corresponding withthe predetermined contents, so that the material having a moisture content lower than that to which the slope has been adjusted, or equal to or higher than that at which the material starts flowing together with the moisture, is automatically carried oif along the means of separation.

The moving layer formed may extend horizontally or pass along the wall of a centrifuge in a direction away from the axis of. rotation and at an oblique angle to it.

Experiments made by the applicant on the removal of moisture from filter slurry in a centrifuge with a perforate wall and in a centrifuge with a smooth wall, in which the lowermost moisture-rich layer was removed and recycled, have shown that the moisture content of the remaining layer was about equal in both cases, so that it is recommendable to replace the centrifuge wall which issubject to severe wear by a smoothwall and to cut otf the lowermost layer. According to the invention, however, the layer may also travel downwards along an inclineunder the influence of its own weight.

The invention also contemplates the provision of various apparatus which serve to perform the above process and comprise means defining a surface for supporting a moving layer andmeans for continuously supplying the Moreover, means of separation is provided at or near the end of the supporting surface for the purpose of separating the layer high in moisture content and the layer low in moisture content from one another, in addition to which, means are provided for carrying oif the separated fractions.

, Preferably, the means for separating the layer into a fraction high in moisture content and a fraction low in moisture content can be disposed relative to the supporting plane so that at least part of the material constituting the layer is enabled by the means to form a slope, the gradient of which depends on a predetermined moisture content ofthe material, permitting the material having a moisture. content lower than that to which the slope has been adjusted or equal to. or higher than that at which the material starts flowing togetherwith the liquid, to be automatically carried: off, along. said' means.

In one of the embodiments of the present invention 'of a layer of substantially uniform thickness.

d the supporting surface comprises a substantially horizontally disposed table or the like and means are provided for moving the material along the table in the form A slot is provided in the table near the delivery end thereof, which extends over a distance not shorter than the width of the layer to be formed, while under the table and at some distance therefrom a plate is provided which extends over the full width of the slot and reaches beyond the edge'thereof in the direction of the delivery end of the table.- The construction of the plate is such that the material resting on it can form a slope, while the means 'forcollecting the fraction of the material rich in moisture is disposed substantially under said slot.

In another embodiment of the present invention, the supporting surface comprises a constant speed conveyor belt onto which'thematerial to be treated is loaded at thefeed end and the means of separation comprises a plate mounted at the other end of the conveyor, the plate being disposed with its end substantially parallel with the conveyor and at'such a distance from the upper surface thereof that the fractions high in moisture content and low in moisture content may be separated from one another. Here again, the slot-like aperture should preferably be adjustable.

In yet another embodiment of thepresent invention the supporting surface comprises a stationary, flat plane set at an angle to the horizontal and having a gradient greater than that of the natural slope at apredetermined moisture content of the material low in moisture content, and the means for supplying the material is disposed at the upper feed end of the inclined plate, while at the lower end of the plate and at some distance therefrom a separating plate is disposed which forms a slot-like aperture with the plate and extends on either side of it. The dimensions of the plate are such that boththe fraction low in moisture content and the fraction high in moisture content may form a slope, the gradients of which correspond'with that of the slope of the material at the predetermined moisture content of fractions either low in moisture content or'high in moisture content.

This embodiment has the advantage of comprising no moving parts for advancing the material while the layer offers a relatively great height for the liquid to settle. In addition, the means of separation also serves as a lower support for the layer. In this embodiment the dry portion of the layer with'an admissible moisture content will flow across the edges of the plate on the one side'and the portion rich in moisture on the other.

It is advantageous to dispose the means of separation in such a way as to cause the moving layer slope upwards.

In this way, the settling liquid is forced to flow down along the inclined plane towards the slot resulting in a concentration of the moisture content in the material present there and thus promoting the discharge of this moisture-rich material through the slot. More specifically, the means of separation is pivoted on a horizontal shaft disposed substantially parallel with and in the elongation of the inclined supporting plane. By this measure the slope of the upper face of the layer may be adjusted. The means of separation may consist of two plate-shaped members on either side of the shaft, the angle between the said'parts being adjustable so that the discharge of the fraction rich in moisture and the fraction low in moisture content may be controlled separately.

Both in the apparatus where the layer moves on a stationary, horizontal plane and in those where the layer moves on a stationary, inclined plane, the supporting plane may be provided, wholly or partly, with perforations through which the liquid collecting in the lowermost layer of the material may flow away, while means may be provided for carrying off this liquid.

means are provided for supplying the material to be treated to the centrifuge through the center thereof, the slot according to the invention is wide enough to allow the passage of the material, while around this slot and at some distance therefrom a plate is provided which rotates together with the wall of the centrifuge and has such dimensions that the material between the slot and the plate will form a slope whose gradient with respect to the vertical substantially corresponds with the gradient of the slope of the material at a given moisture content. In this way, the moisture content of the material issuing through the slot can also be kept in hand, while moreover material lower in moisture content can be prevented from discharging through the slot. This means may comprise a vertical, or practically vertical, wall around the outer periphery of the slot.

In another embodiment of the present invention the slot is provided by a body of revolution, having a cylindrical or conical wall arranged to rotate together with the centrifuge. The body is concentrically arranged around the centrifuge wall, the lower end thereof extending into the centrifuge to within a short distance from the wall. The plate which serves as a support for the material discharged through the slot is attached to the body. Preferably, it should be possible to displace the body of revolution along the axis thereof.

In all the embodiments mentioned, it is of importance that material which is rich in moisture that has been discharged through a slot-like opening should be given a support under or beside the slot, so that the material may form a natural slope. When the moisture content in the lower layer rises above a given value, the slope will tend to become less steep so that automatically more material rich in moisture will be carried off. This value is attained when the material is oversaturated with liquid.

It thus will be seen that the objects of this invention have been fully and effectively accomplished. It will be realized, however, that the foregoing specific embodiment has been shown and described only for the purpose of illustrating the principles of this invention and is subject to extensive change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.

I claim:

1. A process for effecting the complete or partial removal of moisture from fine-grained material of substantially uniform composition containing an amount of free moisture such that thepores between the grains of said material are partially filled with liquid, which comprises the steps of forming a continuously moving layer of said moisture containing material, supporting said moving layer so that the moisture therein will settle during its movement from one part of said layer into an adjacent part so as to form successive layers with increasing moisture contents, and separating a fractional layer with the highest moisture contents from said moving layer, the grain-distribution in said fractional layer being substantially equal to the distribution in the main layer, said fractional layer being separated from said moving layer by removing the support thereof and then supporting the fractional layer at a position spaced from the position of support removal in the direction of travel of said moving layer such that the material of the separated fractional layer will form a slope having a gradient which prevents said fractional layer from being discharged when the moisture decrease has not reached a predetermined value and automatically enables discharge of the material of said separated fractional layer when the moisture decrease has surpassed said predetermined value.

2. Apparatus for effecting the complete or partial removal of moisture from fine-grained material of substantially uniform composition containing an amount of .free moisture such that the pores between the grains of said material are partially filled with liquid comprisf ing means defining a surface for supporting a moving layer of moisture containing material along a predetermined path between a feed station and a separation station, means for feeding material at said feed station to said surface, said surface being disposed to support the moving layer of material so that the moisture therein will settle during its movement from one part of said layer into an adjacent part so as to form successive layers with increasing moisture contents, the layer of highest moisture content being disposed adjacent said surface, and means forming a slit-like aperture disposed in cooperating relation with respect to said surface for separating a fractional layer with the highest moisture contents from said moving layer and for supporting the separated fractional layer so as to enable the material of said separated fractional layer to form a slope having a gradient suflicient to cause automatic flow of material with a moisture content exceeding a predetermined value.

3. Apparatus as defined in claim 2 wherein said surface-defining means comprises a substantially horizontal table and wherein conveyor means are provided for efiecting continuous movement of said moving layer over said table.

4. Apparatus as defined in claim 2 wherein said surface-defining means comprises a stationary flat plate disposed at an angle to the horizontal and arranged to have the material fed at its upper end so that said moving layer will pass downwardly thereover, said plate having a gradient greater than that of the natural slope of the material at a predetermined low moisture content.

5. Apparatus as defined in claim 4 wherein said plate is perforated.

6. Apparatus as defined in claim 4 wherein said aperture-forming means comprises movable elements disposed below the lower end of said plate in spaced relation thereto, said elements extending transversely of said plate on both sides thereof and arranged to form a slope on the upper surface of the moving layer on the plate having a gradient which corresponds to the natural slope of the material with a moisture content of a maximum permissible amount.

7. Apparatus as defined in claim 6 wherein said movable elements comprise blades independently mounted for pivotal adjustment about an axis spaced below the lower end of and in the plane of said plate.

8. Apparatus as defined in claim 2 wherein said surface terminates adjacent said separation station and wherein said aperture-forming means comprises plate means spaced from the terminal end of said surface and disposed to engage the moving layer so that said separated fractional layer will pass between said surface end and plate means and form a slope having a gradient sufiicient to cause flow of material with a predetermined moisture content together with the moisture, said plate means and said main layer supporting surface enclosing a space open at one end for discharging the separated layer of highest moisture content. 7

9. Apparatus as defined in claim 2 wherein said surface-defining means comprises a substantially horizontal table over which said moving layer is continuously moved, said table terminating adjacent said separation station, and wherein said aperture-forming means comprises a first plate having an end spaced from the terminal end of said table so as to form a slot through which said fractional layer passes and a second plate mounted below said slot for adjustment in the direction of layer movement.

10. Apparatus as defined in claim 2 wherein said surface-defining means comprises an upper substantially horizontal flight of an endless conveyor arranged to effect the continuous movement of said moving layer, and wherein said aperture-forming means comprises a horizontally disposed plate mounted above said upper flight for vertical adjustment in accordance with the thickness of said fractional layer.

11. Apparatus as defined in claim 2 wherein said surface-defining means comprises a smooth imperforate conical wall of a centrifuge arranged to receive the material at its axis of rotation, and wherein said aperture-forming means'comprises plate means adjacent the upper edge of said conical wall defining therewith a slot through which said fractional layer passes.

12. Apparatus as defined in claim 11 wherein said plate means comprises an annular plate mounted for rotation with said centrifuge conical wall, said plate having an edge portion spaced from said conical wall to define said slot.

13. Apparatus as defined in claim 12 wherein said edge portion is spaced outwardly from the terminal edge of said conical wall.

14. Apparatus as defined in claim 13 wherein said edge portion is spaced inwardly from the terminal edge of said conical wall closer to the centrifuge axis of rotation, and wherein said plate includes a wall extending upwardly from said edge portion at an angle with respect to said conical wall.

15. Apparatus as defined in claim 2 wherein said surface defining means comprises a smooth, imperforate wall of a conical centrifuge arranged to have the material fed at its axis of rotation so that the moving layer will pass outwardly from said axis of rotation, and wherein said aperture-forming means includes plate means arranged opposite said slit-like aperture at the outer face of said centrifuge wall and spaced apart from said slit-like apertial-ly uniform composition containing an amount of free ture, said plate means being rotatably mounted in the moisture such that the pores between the grains of said material are partially filled with liquid which comprises the steps of establishing a continuous supply of said material at a feed position, imparting a centrifugal action to the supply of material at said feed position, supporting the material moving under said centrifugal action in layer formation from said feed position to a discharge position so that the moisture therein will settle during the movement between said positions from the part of the layer remote from the support into the part of the layer adjacent the support so that at said discharge position the moving layer has a moisture content which increases in a direction toward the support, and continuously separating a fractional layer with the highest moisture contents from the moving layer at said discharge position, the grain-distribution in said fractional layer being substantially equal to the distribution in the layer at said feed position.

References Cited in the file of this patent UNITED STATES PATENTS 926,031 Stover June 22, 1909 1,818,640 Miller Aug. 11, 1931 1,880,273 Pardee et al. Oct. 4, 1932 2,644,583 Cannon et al. July 7, 1953 FOREIGN PATENTS 371,753 Great Britain Apr. 28, 1932