USRE23321E

USRE23321E - Mold cleaning apparatus

Info

Publication number: USRE23321E
Authority: US
Publication date: 1951-01-09

Description

Jan.9,1951

N. w. BIGGS EIAL Re. 23,321

MOLD CLEANING APPARATUS 2 Sheets-Sheet 2 Original Filed Oct. 31, 1946 J zu/Efiiaas HaEE'fs ZZZ 152 5 5901? ZZZflendeasozz Reissued Jan. 9, 1951 23,321 MOLD CLEANING APPARATUS Norris W. Biggs, Miami Shores, Fla., and George M. Henderson, Akron, Ohio, assignors to The B. F. Goodrich Company, New York, N. Y., a

corporation of New York Original No. 2,479,299, dated August 16, 1949, Se-

rial No. 706,980, October 31, 1946. Application for reissue May 15, 1950, Serial No. 162,131

Matter enclosed 'in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue 13 Claims.

This invention relates to cleaning apparatu for removing undesirable deposits from molds and especially from tire molds and inner tube molds.

In the manufacture of tires and inner tubes a mold lubricant such as soapstone is usually used to facilitate escape of air from between the tire or inner tube and the mold, and to lessen adhesion of the article to the mold surface. A portion of the lubricant sometime adheres to the mold surface forming a deposit which increases with the number of articles molded and becomes of a size which produces blemishes in the tires and tubes if not removed.

Cleaning of the molds involves special requirements because the deposits, after being exposed to the high temperatures of molding, are baked onto the mold walls, and hav tenacious properties. It is desirable that the cleaning operation be such as to be effected without requiring removal of the molds from the vulcanizers especially where the vulcanizers are of the watch-case or unit press type, so that each mold and vulcanizer will be out of service for a minimum period of time. rently used are of the insert type, in which aluminum or other soft metal mold face inserts are used, it is desirable that the operator may observe the cleaning operation to avoid damaging the inserts.

Objects of the invention are to provide apparatus for cleaning a mold surface conveniently and effectively, to provide for applying a powdered abrasive to the surface to be cleaned, to provide visibility of the surface being cleaned, to provide for removing the residue of the cleaning operation, to provide for isolating the cleaning operation, to provide for lightweight and maneuverability of the mechanism, and to provide for convenience of assembly and operation.

These and further objects will be apparent from the following description, reference being had to the accompanying drawings in which:

Fig. 1 is a plan view of the apparatus constructed in accordance with and embodying the invention, parts being broken away, and a tire mold being indicated by broken lines.

Fig. 2 is a section taken along line 22 of Fi 1.

Fig. 3 is a section taken along line 3-3 of Fig. 1.

Fig. 4 is a plan view of a modified construction,

parts being broken away.

Fig. 5 is a section taken along line 5-5 0 Fig. 4.

Since many of the molds our- Fig. 6 is a plan view of a further modified construction.

Fig. 7 is a section taken along line 'l-'[ of Fig. 6.

' Fig. 3 is a plan view of a still further modified construction.

Fig. 9 is a section taken along lin 99 of Fi 8.

Fig. 10 is a section taken along line Ill-l0 of Fig. 8.

Fig. 11 is a view in sectional elevation of a still further modification.

Fig. 12 is a section taken along line l2-l2 of Fig. 11.

Apparatus constructed in accordance with and embodying the invention is shown in Figs. 1 to 3, in which the cleaning apparatus is mounted on a section of a tire mold l I shown in broken lines. Cleaning of the mold II is accomplished by the action of a powdered abrasive such, for example, as sand, carbide of silicon grit, nut shells, aluminum oxide or even corn meal, which is carried by a suitable fluid such as air to the surface to be cleaned. The air is conducted to the apparatus in a conduit 12 and the abrasive in a conduit I3. The air and abrasive conduits l2 and I3 are connected to a mixing and applying member such as a gun It. A trigger [5 may be installed in the gun M to actuate a valve to regulate the flow of air and abrasive, and a nozzle It which may be flattened and flared as desired, is mounted in the gun to cause the abrasive to leave the gun in a stream with such a configuration thatcleaning action will be most effective.

A residue collecting member which comprises an annular base plate [1, is mounted on the mold section II by suitable fasteners such as bolts I8, and wing nuts 19. A cover plate 2| is mounted on the base plate I1 for movement of the late relative to the base plate and has a central aperture in which a close-fitting vertical post 22 is disposed. The post may be tubular and have a supporting plate 23 integral with it, which plate is adapted to rest upon the inner periphery of the mold II, for closing the opening that is present in the center of the mold.

A collar 25 is mounted on the post 22 and is fixed thereto as by a pin 26 which passes through the collar and post. A wearing washer 21 is mounted on the cover plate 2|, and set screws 28 are threaded in collar 25 to slide on the wearing washer upon rotation of the cover plate 2! and to regulate the height of the member 22 with respect to the cover plate. Handles 29 are mounted on the cover plate 2l,for manually turning the cover plate relative to the base plate l1 and rela--' tive to the post 22. l 7

The adioi'rfing surfaces of ith' mold 1II=, supporting plate 23, base plate ll and cover plate 2| may be provided with gaskets 31 of rubber or other rubber-like material to make substantially air-tight seals therebetween. Thecover-plate 2| has a window opening whichis partiall .covered by elements 32 of transparent material such as glass, acrylate resins such as po1ymethylrneth-- acrylate, transparent rubber, transparent poly-a vinyl chlorides or the like materials, which may be mounted on the cover plate '-2 'l iby studs and wing nuts. A slot-like opening 20 between the transparent elements 32 is provided for the insertion of the gun M, which conducts the abrasive and-air to .the mold surface. The base ,plate IT has an aperture 3'!) connected to a "conduit .33 leading to a suction-producing apparatus such as a vacuum pump or the like. The aperture 30 may be elongated andrectangular, in which case an adapter member 34 may be interposed between the conduit 33 and the aperture. H

In operation, the apparatus shown in Figs. :1, '-2 andB of the -drawingsis mounted on the mold II by wing nuts I9 threaded on studs l8 andhy ad justing setscrews 28 in such a manner that there is a minimum of leakage in the junction rat the gaskets 31. T-he operatorzmay then insert-the gun I4 in the slot 20 between the transparent elements 32 and b moving the trigger set up a flow of air and abrasive against the .mold :sur- -face to remove undesirable .incrustations and tie-- posits therefrom. At the same time the suction producing apparatus may be .started .to provide 'a low-pressure area at the aperture '30 in the base plate I 1. As 'theabrasiv'e strikes-the deposits and incr-ustations on the mold fill it will clean the mold. The residue ofabrasivejandlrmovedifnold deposits is usually .a dust-like "substance, Tana will be carried by'the air. Since the .air pressure at the .gun {4 will be greater thanthaft "at 'the base plate aperture 30, air and residue will now to the 'base plate aperture for removal from mem'cid.

The mold races which "forinfthe intricate "tirie tread desi nseu'r'renn 'us'ed ohtiies have a number of indentations. The :a'epos t which form in these indentations are more di'fiicult to remove than the deposits whi'ch for'm on the smooth surfaces of the infield. .A11 'th'e deposits may be removed by subjecting the entrrejm 1d surface to a flow of the abrasiveffo'r"a siifiicient period of time, however, with tire molds having inserts of soft metal such as aluminiin'i, the t' of cleaning must be limited or the inserts ll be damaged and cause blemishes to appear "in the molded 'tire. Damage may 'b.e 1p'r'ev'ented fbyfina- .nipula'ting the nozzle to providea 'fiowjdta'bra 'sive atan angle to the mold surface which will clean each indentation in the shortest period "time. Also if the o e ator maynbse'r ethe cperation, he may limit *th'efcleaning action at a given spot in the mold to the minimum required "and thus :prevent damage. Therefore *it is *iiesirable to provide ai'ate of removal of the abrasion such asto prevent an accumulation of par-- gun I4 is inserted. The escape of residue or air "outwardly through 17118 51015 '20 is minimized b the Iioiv in thecontrary direction as .aibdvei'iescribed and the consequent induction of air through this :slot.

A modified construction is shown in Figs. 4 and 5*111 which features are included to provide for automatic operation. Instead of a collar, a gear -35.is mounted on the post 22. The gear 35 meshes with a .gear 136 Z'm'o'unted on a shaft 31 which is mounted r'otatablyin the cover plate 2| and may be turned by a motor unit 38 mounted also on the plate '2. l.

nmnuuitw member 39 has air and abrasive conducting conduits I2 and I3 connected to it. Valves M and 42 are installed in the Y member .to prov;ide means for regulating-the flow and mix-- ture' or air and abrasive. The "Y member is mounted on a swing 'join't member "43 which has a projection 44 slidabl'y inserted in the tubular member 22 and may be fixed thereto :by a :set screw 45 threaded in the tubular .member. A conduit-member and aiiexible hose member I! connect the swinging element of the swing .jo'int member .43 with the nozzle 16. As .in the ,pre- =viously described :einbodiment, the nozzle I6 is xiisposed between the transparent elements 32, Q32 and directed iteward th'e mold, but in the em- 'bodiment shown in and .5 a supporting member 48:is.mounted on ithemdtor uiiit and "the nozzle is .adj ustab'ly secured thereto as by ,a stud and wing nut 4'9 disposed "in :a slot '5'! Jim thfe"'s'i'1'pporting member.

In the operation of the embodiment of Figs. 4 and 5, .the air and abrasive isupp'lyand mixture are regulated by valves 4| and 42 ."and the nozzle is may he stratthe desired position and secured thereto b the .w'ingfnut T49. "-The motor .u'n'it'3'8 .may be aeuvateaana fca'iis'e'thesha'ft 3.1 to move the gear 35 'lin'meshihg engagement with the stationary lge'a'r 3i5 fto'move'th'e coverplate'and'nozzle .rdtataiblyfoverthe in'old 11.. When the apparatus is properly adjusted the cleaning operation will .h'e autc'znaticfana "the'iieces'sity'for manuanymow The nozzle may be moved manually, .however, "to ca eer the now of ab'rasivefagainst particularly tenacious deposits by loosening the wing nut 49.

Another modification, which incorporates a residii'e collecting 'Iii'e'n'iber coverin "a segment of the mold, rather than the entire annulus, is shown in Fi s. 6 and 7.. The collectin menipe'r pompr e's 'afpliiralityoi elements ='or"pl2ites i2 ofthe tran parent material joined :to'gether'a'nd extendingffidm ftheinoldseg'rnentedges toanfapex. An air and abrasive "conducting "member such as *a con uit 53 is dispojs'edin ism-aperture at-t'he apex of thepla'te 52 land hasa no'zile --lli"for directing the abrasive torhemom surmce. nimnuatmsive's lllifilying conduits and f3 ar epimec'tea .to the "conduit 53ahd a val've SBiSinelude in the air'conduit I3 *to regulate the flow of air to the tiire andtheconductingmemberifi and mounted thereon in such a manner tha t 'th'e c'onducting -'member 53 *and the no'zfile =16 may be tlirected to all portions of the covered segment of the mold I I wnnmn air-tighVsea-l is m'aintained' between the conducting member and the collecting memver. show'n in thfe drawings he bellows j dint 54 has a tubular shape with cir'c mre'rentiamcrriighted fcltls Which ma be e'xte'nded or contracted to provide flexibility of movement of the nozzle I6. The material of the bellows joint 54 may be clamped on the conducting member 63 by a ring member 54a and clamped on the edges of the aperture in the plate 52 by strips 54b which are secured to the plate 52 by fastening means such as pins 54c. A gasket member 55 of flexible material such as rubber or other rubber-like material is mounted on the plates 52 which abut the mold segment II for minimizing leakage therebetween. If desired, this gasket member may be in the formpf a brush-like structure to accommodate itself better to depressions in the mold surface. An aperture GI! is provided in the plates 52 and connected to a suction-producing apparatus by a conduit 33 for removing the cleaning residue from the mold I I.

This embodiment may be operated by placing it in the mold segment, and the air and abrasive flow regulated by turning valve 50. The flow of air through conducting member I3 will create an air-pressure differential, which will draw abrasives through conduit I2 into the air stream. The nozzle It may then be manipulated to direct the stream of abrasive and air to the desired portion of the mold segment. The residue from the cleaning operation may be removed by actuating the suction-producing apparatus causing suction at the aperture 60. After one segment is cleaned, the air flow may be stopped by turning valve 50 and the mechanism moved 'to clean another segment of the mold II, or the mechanism may be moved progressively along the mold surface without stopping flow of abrasive.

The embodiment shown in Figs. 8, 9 and is also constructed for enclosure of a segment of p the mold. A covering member 56 extends from the inner peripheral edge to the outer peripheral edge of a segment of the mold II and a wall member 51 is mounted on the covering member 56 and disposed between one radially extending edge of the covering member and the mold surface. Thecovering member may enclose completely the space overlying the mold surface but it is not essential for good results. An arm TI is mounted on the covering member 56 and mounted rotatably on an axial standard 58 which is mounted on the mold II at the inner periphery. The standard 53 has a mounting flange I3 extending radially to the inner periphery of the mold and mounted on the mold by bolts I4 and nuts I5. The movement of the arm 11 may be restricted by a nut I6 which is threaded on the standard 58. The standard 58 and arm 'I'I restrict the movement of the covering member to rotation about the mold center and provide for the reduction of leakage at the adjoining edges of the mold and covering member.

Air and abrasives are conducted to the mold by a nozzle I6 connected to a conducting member 53 which receives air from conduit I3 and abrasive from conduit I2, a regulating valve 50 being included. The nozzle is manually directed toward the mold surface of the covered segment through the end opening between the free edge of the cover 56 and the mold surface. An aperture is provided in the wall member 51 to which a suction producing apparatus is connected by a conduit 33to produce a low-pressure area at the aperture in the wall member 51 for removing the cleaning residue. A handle 59 is mounted on the 6 between the mold II and the wall member 51 to minimize leakage at these points.

In operation of this embodiment, the standard 58 is mounted on the mold II, the suction producing apparatus is set in operation and the abrasive and air are applied to the mold in the desired quantity by adjustment of the valve 50 and may be directed against the mold surface manually. As the mold is cleaned, the residue collecting member may be moved to cover other portions of the mold by means of the handle 59. This may be a progressive movement, or sectors may be selected as desired.

In Figs. 11 and 12 the invention is motor driven and is applied to a watchcase type mold 60, BI, but may be used on other types also. A residue collecting member which comprises a cover plate 62 is mounted on an annular base plate 63 having flanged edges abutting the mold El. Gasket sealing members 3| are interposed between the surfaces of the base plate and the outer circumference of the mold SI for sealing thereof.

At' the center of the cover plate an aperture is provided through which a tubular member 64 is inserted and rotatably mounted therein. On the mold side of the cover plate a radially extending hollow arm 65 is mounted on the tubular member 64 and connects the tubular member to a flexible conduit member 65. A suitably shaped nozzle I6 is connected to the flexible conduit member 66 and mounted on adjustable link members 61, which are mounted on the arm 65.

The opening at the cenmr of the mold is covered by a plate 68 which is urged against the mold by a spring 69 interposed between the end of the tubular member 64 and the plate 68. Gasket members 3| are interposed between the plate 68 and the mold to provide a seal therebetween.

On the exposed face of the cover plate 62 a motor unit 38 is mounted, which drives a shaft 63. A bevel gear 'II is mounted on the shaft 63 andmeshes with a bevel gear 12 which is mounted on the tubular member 64 for turning the tubular member and appurtenances.

Air and abrasives are conducted to the apparatus by conduits I2 and I3, which are connected to a swivel joint member 10 secured to the tubular member 64 in a manner such that the tubular member may rotate relative to the conduits I2 and I3 without obstructing the passage of air and abrasive fromthe conduits to the nozzle I6.

The cover plate 62 has openings through which the cleaning operation may be observed. These openings are covered by transparent elements 32 and secured to the plate 62 as by wing nuts. The residue of the cleaning operation is removed by suction through an aperture 40 in the base plate 63 to which suction-producing apparatus is connected by a conduit 33.

In operation the apparatus of Figs. 11 and 12 is mounted on the mold GI as shown in Fig. 11, and the nozzle I6 is adjusted to a desired position. The suction-producing apparatus is activated and the air and abrasive is supplied through conduits I2 and I3, and directed to the mold surface by the nozzle I6. The nozzle may be moved to other portionsof the mold progressively or as desired by means of the motor unit 38, which turns shaft 31 and gear II to urge gear I2 to rotate about the tubular member 64 and move arm about the mold BI. The apparatus may be used toclean the upper mold member of the watchcase mold by inverting the appa- Iiaaai rates and holding it suspended against the mold member 60 by suitable means such clamps.

Variations may be .made without departing from the scopeof the invention as it is donned in the following claims.

'Wcclaim:

1-. Apparatus for cleanin the face of a tire mold having tread and sidewall forming confisurations', said ap aratus comprising a curved of the space overlying" the mold face with a mar- 'ginalportion of said member dis osed at a marginal portion of the mold face, a nozzle for directting the now of mold cleaning substance against relatively small spots of said mold face, said nozzle being in communication with the mold face, said apparatusbeing arranged to permit swinging movement of the nozzle relative to said covering member and mold face by manipulation of the operator to direct said flow of cleaning substance against selected spots of the mold face within the area enclosed by said covering member, and suction means for withdrawing the cleaning substance from said space in face u as well as in other dispositions of the mold.

2. Apparatus for cleaning the face of a tire mold having tread and sidewall forming configurations, said apparatus comprising a circular cov ering member mounted with its axis coinciding with the axis of the tire mold for totally enclosing the space overlying the mold face with a marginal portion of said member disposed at a marginal portion of the mold face, a nozzle for directing the flow of a mold cleaning substance against relatively small spots of said mold face, said nozzle being disposed within said covering member, said apparatus being arranged to permit swinging movement of the nozzle with respect to the mold face by manipulation of the operator to direct said flow of cleanin substance against selected spots of the mold face, and suction means for withdrawing the cleaning substance from said space in face" up as well as in other dispositions of the mold.

3. Apparatus for cleaning the face of a tire mold having tread and sidewall forming configurations, said apparatus comprising a circular covering member having an axis coincidin with the axis of the the mold and being mounted on said tire mold in a manner ermitting relative rotation coaxially with respect to the tire mold and totally enclosing the space overlying the mold face with a marginal portion of said member disposed ata marginal portion of the mold face, a nozzle for directing the flow of a mold cleaning substance against relatively small spots of said mold face, said nozzle being disposed within said covering member, said apparatus being arranged to permit swin ingmovement of the nozzle with respect to the mold face by mani ulation of the operator to direct said flow of cleaning substance against selected spots of the mold face, and Suetion means for withdrawing the cleaning substance from said space in face up as well as in other dispositions of the mold.

4. Apparatus for cleaning the face of a tire mold having tread and sidewall forming configurations, said apparatus comprising an inner plate structure with a marginal portion disposed at the inner peripheral margin of the mold face and covering the central region of the mold, a cover plate structure with a marginal portion disposed at the outer peri heral marginal portion of the mold face enclosing the space overlying the mold face and said inner plate structure, a nozzle for direct* ing the fiowof mold cleaning substance against relatively" small spots of said mold face, said nozzlc being in communication with the mold face, said apparatus being arranged to permit swinging movementof the nozzle relative to said cover plate structure by manipulation of the operator to direct said flow of cleaning substance against selected spots of the mold face, and suction means for withdrawing the cleaning substance from said space,

Apparatus for cleaning the face of a tire mold having tread and sidewall forming configurations, said apparatus comprisin an inner supporting plate structure with a marginal ortion disposed at the inner peri heral margin of the mold face and covering the central region of the mold, a post supported by said inner supporting platestructure, a cover late structurc with a marginal portion disposed at the outer marginal portion of the mold face enclosing the space overlying the mold face and said inner supporting plate structure, a nozzle for directing the flow of mold cleaning substance against relatively small spots of said mold face, an arm member extending outwardly from said post andmountcd on said cover late structure in a manner to ermit rotation. of said arm member relative to said post, said nozzle being mounted on said arm for rotative movement about said post and for swinging movement'- of the nozzle relative to said cover plate structure to direct said flow of cleaning substance against selected spots of the mold face, and suction means for withdrawing the cleaning substance from said space.

6'. Apparatus for cleaning the face of a tire mold having tread and sidewall forming configurations, said apparatus comprising an inner supporting plate structure with a marginal portion disposed at the inner peripheral margin of the mold face and covering the central region of the mold, a post supported by said inner supporting plate structure, a base ring at the outer peripheral margin of the mold face and a cover plate structure seated on and rotatable relative to said base ring for enclosing the s ace overlying the mold face and said su orting plate structure, a nozzle for directing the flow of mold cleaning substance against relatively small spots of said mold face, an arm member extending outwardly from said post and mounted on said cover plate structure in a manner to permit rotation relative to said post, said nozzle being mounted on said arm for rotative movement about said post to said cover plate structure to direct said flow of cleaning substance against selected spots of the p, mold face, and suction means for withdrawing the cleaning substance from said" space.

7. Apparatus for cleaning the face of a tire mold having tread and sidewall forming configurations, said ap aratus comprising a domed cove'ring member comprising a plate of transparent material with a marginal portion disposed at a marginal portion of the mold face for com letely enclosing the space overlying a segment of the mold face, a h'ozzle for directing the flow of mold cleaning substance against relatively small spots of the mold face, said nozzle being mounted at the apex of said domed covering member for swinging movement relative thereto by manipulation of the operator to direct said flow of cleaning substance against selected spots of the segment, and suction means for withdrawing the cleaning substance from said space in face up as well as in other dis ositions of the mold.

8. Apparatus for cleaning the face of a tire mold having tread and sidewall forming conflgurations, said apparatus comprising an inner plate structure with a marginal portion disposed at the inner peripheral margin of the mold face and covering the central portion of the mold, a cover plate structure with a marginal portion disposed at the outer marginal portion of the mold face enclosing the space overlying the mold face and said inner plate structure, a nozzle for directing the flow of mold cleaning substance against relatively small spots of said mold face, an arm member interposed between said plate structures and mounted on said structures at the central portion of the mold for rotation of the arm about the axis of the mold, said nozzle being mounted on said arm for rotative movement with said arm and for swinging movement oi the nozzle relative to said mold to direct said flow of cleaning substance against selected spots of the mold face, and suction means for withdrawing the cleaning substance from said space.

9. Apparatus for cleaning the concave face of a tire mold having tread and sidewall forming configurations, said apparatus comprising a structure for enclosing said concave face of the mold including a window of transparent material in said structure through which said face may be viewed from the outside of said structure, said window being mounted for relative movement of said window and the mold one with respect to the other about the axis of the mold, an opening in said window, means for directing a flow of mold-cleaning substance against said face of the mold including a nozzle extending through said opening in said window and means for adjusting the position ofsaid nozzle in said opening with respect to said window to direct said flow of cleaning substance against selected spots of said concave face. 7 I

10. Apparatus for cleaning the concave face of a tire mold having tread and sidewall forming configurations, said apparatus comprising a structure for enclosing said concave face of the mold including a window of transparent material in said structure through which said face may be viewed from the outside of said structure, said window being mounted for relative rotation of said window and the mold one with respect to the other about the ascis of the mold, an opening in said window, means for directing a flow of mold-cleaning substance against said face of the mold including a nozzle extendin through said opening in said window and said nozzle being mounted in said opening for adjustment in the l radial direction of said mold to 'direct said flow of cleaning substance against selected spots of said concave face.

11 Apparatus for cleaning the concave face of a tire mold having tread and sidewall forming configurations, said apparatus comprising a struci the mold including a nozzle extending through said opening in said window.

12. Apparatus for cleanin the concave face of a tire mold having tread and sidewall formin configurations, said apparatus comprising a structure for enclosing said concave face of th mold including a window of transparent material in said structure through which said face may be viewed from the outside of said structure, said window being mounted for relative movement of said window and the mold one with respect to the other over the mold face, an openin in said window and means for directing a flow of moldcleaning substance against said face of the mold including a nozzle extending through said opening in said window.

13. Apparatus for cleaning the concave face of a tire mold havin tread and sidewall forming configurations, said apparatus comprising a structure for enclosing said concave face including a cover plate, a window of transparent material mounted in said cover plat through which said concave face of the tire mold may be viewed from the outside of said structure, said cover plate bein mounted for relative rotation of said cover plate and the mold one with respect to the other about the axis ofthe mold, an opening in said cover plate in the proximity of said window, and means for directing a flow of mold-cleanin substance against said concave face of the tire mold including a nozzle extending through said opening in said cover plate.

, NORRIS W. BIGGS.

GEORGE M. HENDERSON.

REFERENCES CITED The following references are ofrecord in the file of this patent or the original patent:

UNITED STATES PATENTS Number Name Date 537,160 King Apr. 9, 1895 914,783 Boland Mar. 9, 1909 1,940,539 Fritsche Dec. 19, 1933 FOREIGN PATENTS Number Country Date 108,256 Australia Aug. 11, 1939 332,849 Great Britain July 31, 1930 380,330 France Oct. 4, 1907