US2962754A

US2962754A - Rotor supporting and driving construction

Info

Publication number: US2962754A
Application number: US626630A
Authority: US
Inventors: Kleist Dale; Henry J Snow
Original assignee: Owens Corning Fiberglas Corp
Current assignee: Owens Corning
Priority date: 1956-12-06
Filing date: 1956-12-06
Publication date: 1960-12-06
Anticipated expiration: 1977-12-06
Also published as: FR1188069A; DE1070792B; GB835829A

Description

Dec. 6, 1960 D. KLEIST ETAL ROTOR SUPPORTING AND DRIVING CONSTRUCTION w 3 Sheets-Sheet 1 Filed Dec. 6, 1956 INS/.ENTDRS lZaLz' .712 Hz BIS T.

NH? .7. 51mm By W d AT TYS.

Dec. 6, 1960 D. KLEIST ETA].

ROTOR SUPPORTING AND DRIVING CONSTRUCTION 3 Sheets$heet 2 Filed Dec. 6, 1956 [NI/ENTERS: DALE K2215 T,

HENRY J 5M7 ATTYEI'.

ROTOR SUPPORTING AND DRIVING CONSTRUCTION Filed Dec. 6, 1956 3 Sheets-Sheet 3 I 46 i I 5 44 M I I5 ff INS/ENTERS: i2 40 $40 DALE .Kzzrsrr', 6 V J r HENRY J SNUW;

5 I a V f0 ATTYS United States Pate' ROTOR SUPPORTING AND DRIVING CONSTRUCTION Dale Kleist, St. Louisville, and Henry J. Snow, Newark,

Ohio, assignors to Owens-Corning Fiberglas Corporation, a corporation of Delaware Filed Dec. 6, 1956, Ser. No. 626,630

4 Claims. (Cl. 18-2.6)

This invention relates to method and apparatus for mounting high speed rotor constructions and more especially to the mounting of rotors utilized for subjecting heat-softened material to centrifugal forces to fashion, process or subdivide the material into linear formations, bodies, filaments or fibers.

Rotor constructions have been employed to establish centrifugal forces utilized to form discrete bodies from mineral material in softened condition which may be delivered into a gaseous blast for further attenuation to fine fibers.

Heretofore rotor constructions utilized for the purpose have been provided with a threaded hub portion engaged with a threaded portion of a hollow shaft, driven or rotated by a motor through a pulley and belt arrangement. The heat softened or molten material is delivered through the hollow shaft into the rotor and is extruded through the openings in the peripheral wall thereof under the influence of centrifugal forces.

The rotor and supporting means are subjected to very high temperatures during operation, and under the intense heat to which the rotor and shaft are subjected, it becomes exceedingly diflioult and sometimes impossible to remove the rotor from the shaft for purposes of service or replacement, which difliculties result in prolonged interruption of operation of the machine, in decreased production and proportionate increase in the cost of the end product.

The present invention embraces a method of mounting a rotor or spinner wherein the same is normally maintained in operative relation with a driving means but which may be readily and quickly removed for purposes of service, repair or replacement. The invention described and claimed herein embraces an apparatus for processing heat-softened material including a rotor having material distributing means therein and a supporting sleeve drivingly, yet removably connected with a hollow shaft, the latter being a component of an electrically energizable driving means arranged to rotate the rotor at a speed to project the heat-softened material by centrifiugal forces through orifices in a wall of the rotor.

An object of the invention is the provision of a rotor construction and mounting means therefor wherein the driving means is integrated or directly connected with the rotor support or mounting means providing a highly efficient and compact arrangement.

Another object of the invention resides in a rotor or spinner construction and mounting means wherein the rotor is associated with a quill, the latter being connected with a driving mechanism by interlocking means which may be readily connected and disconnected and which is substantially unaffected by intense heat or high temperatures to which the apparatus may be subjected during operation.

Another object of the invention is the provision of a centrifugal apparatus wherein an electrically energizable motor is provided having its armature formed directl A 2,962,754 Patented Dec. 6, i960 on the supporting shaft for the rotor construction and which embodies means to accommodate circulating cooling fluid for controlling the temperature adjacent the motor.

Another object of the invention is the provision of improved method and means for effectively distributing the molten or heat-softened material over a peripheral zone or Wall of the rotor.

Another object is the provision of a method and arrangement for supporting a rotor in a manner to compensate for expansion and contraction of the rotating parts without effecting the rotor retaining means or the dynamic balance of the rotating parts.

Another object of the invention is the provision of a rotor of comparatively thin walled hollow character and embodying a peripheral wall substantially concentric with the axis of rotation integrated or joined with frustoconically shaped or askew sections or walls which are substantially symmetrical about a horizontal plane through the central zone of the peripheral wall normal to the axis of rotation whereby expansion and contraction of the frusto-conically shaped sections or walls of the rotor are substantially equal so that no unbalanced distortion of the rotor occurs during its operation at any temperature.

Another object of the invention resides in a method and means of mounting a shaft, quill and rotor components whereby these components may be quickly and easily assembled and disassembled for purposes of repair and replacement without disturbing other components of the apparatus.

Further objects and advantages are within the scope of this invention such as relate to the arrangement, operation and function of the related elements of the structure, to various details of construction and to combinations of parts, elements per se, and to economies of manufacture and numerous other features as will be apparent from a consideration of the specification and drawing of a form of the invention, which may be preferred, in which:

Figure 1 is a side elevational view of a form of apparatus of the invention, certain parts being shown in section;

Figure 2 is a top plan view of a ment shown in Figure 1;

Figure 3 is an elevational view of a rotor and quill assembly of the arrangement shown in Figure 1, certain parts being shown in section;

Figure 4 is an elevational view of a hollow shaft or spindle including certain associated elements shown in cross section;

Figure 5 is an isometric view showing the upper portion of the quill construction;

Figure 6 is an isometric view illustrating the upper portion of the hollow shaft and component elements associated therewith;

Figure 7 is a fragmentary plan view illustrating a portion of the construction shown in Figure 6;

Figure 8 is a fragmentary plan view of another portion of the apparatus shown in Figure 6;

Figure 9 is a fragmentary elevational view of the upper portion of the shaft and quill construction illustrating a method of and means for securing the quill construction to the shaft;

Figure 10 is a vertical detail sectional view illustrating the quill in unlocked relation with the supporting shaft;

Figure 11 is a fragmentary sectional view similar to Figure 10.

The apparatus of the invention and the method of using the apparatus are particularly adaptable for forming elongated discrete bodies or filaments from heat-softenable material such as glass and attenuating the bodies portion of the arrangeto fibers, but it is to be understood that we contemplate the utilization of the apparatus and the method for forming bodies or fibers from other mineral materials, such as slag or fusible rock, or wherever the invention may be found to have utility.

Referring to the drawings in detail, and initially to Figure 1, there is illustrated an apparatus or fiber-forming unit of the invention for forming elongated discrete bodies of heat-softenable mineral materials, such as glass, and attenuating the discrete bodies to fine fibers through the utilization of a high velocity gaseous blast.

In the embodiment illustrated in Figure 1, molten mineral material S, such as a stream of molten glass, is delivered from a feeder 11 of a forehearth (not shown) containing a supply of the material into the fiber-forming unit 10. The fiber-forming unit or apparatus is adapted for forming the material S by centrifugal forces into a plurality of discrete bodies or primaries which may be attenuated into fine fibers.

The fiber-forming apparatus shown in Figure l embraces a rotor construction 12 adapted to receive the material which is extruded or projected through openings in a wall of the rotor to form the bodies or primaries. The discrete bodies or primaries so formed are engaged by an annular gaseous blast, the gases of which are directed under high pressures and high velocities into engagement with the discrete bodies or primaries for attenuating or forming them into fine fibers.

The fiber-forming unit or apparatus is inclusive of a motor housing 14 and a second housing 16 disposed beneath the housing 14 and which encloses means for directing a high velocity attenuating blast into engagement with bodies or filaments delivered outwardly of the rotor construction 12.

The rotor construction 12 is supported upon and is adapted to be driven by a shaft or spindle 29 within which is telescoped a quill or thin walled sleeve 22, the rotor being mounted upon the lower end of the quill 22. An inwardly extending wall 26 of the housing 14 is formed with a central boss portion 27 which is recessed to receive an outer race 28 of an anti-friction or ball bear-ing 30. The exterior surface zone of the lower end of shaft 29 is formed with a recess to accommodate the inner race 32 of the bearing 30.

Mounted upon the upper portion of the housing 14 is a plate or closure member 36 having a central hub portion 38 recessed to accommodate an antifriction or ball bearing 40. The

antifriction bearings

30 and 40 provide means for journally supporting the hollow shaft 2%). Telescoped within the shaft 20 is the thin-walled sleeve or quill 22 which, as shown in Figures 3 and 5, is formed at its upper end zone with a pair of bayonet-type slot configurations including angularly disposed slots or zones 42 terminating in horizontal portions 44, the slots 42 'being in communication with upwardly or longitudinally extending slots 46, the

slots

42, 46 and portions 44 cooperating with means hereinafter described for establishing a drive connection between the quill 22 and the hollow shaft 20.

The lowerextremity of the hollow shaft 20 is formed with a chamfered or beveled edge 48 which, in assembly, engages a. reciprocally shaped abutment or surface 49 formed upon an enlarged portion 50 of the quill 22. Through the cooperation of the

engaging chamfcred surfaces

48 and 49, the quill 22 is properly centered with respect to the shaft 20 as illustrated in Figure 1.

In the arrangement of the present invention, the rotor 12 is securely held to the supporting quill or sleeve 22 as by welding 55 shown in Figure 3 or by bolts or other suitable securing means.

A novel method and means are provided for securing the rotor supporting quill 22 in driving relation with the drive shaft 20. This arrangement is particularly shown in Figures 1 and through 11. The upper portion 4 of the hollow shaft or spindle 20 is formed with a cylindrical portion 60 of decreased diameter which forms a ledge 61. Supported on the ledge 61 and surrounding the cylindrical surface 60 of the shaft is an annular member or sleeve 63. Engaging the upper edge zone of the annular member 63 is the inner race 65 of the antifriction or ball bearing 40.

Surrounding the cylindrical surface 60 of the shaft are annular elements or

rings

67 and 69, the rings being snugly yet slidably fitted onto the cylindrical portion 60 of the shaft Zil. Each of the rings or

annular elements

67 and 69 is formed with sockets or recesses 70, each pair of sockets being in aligned registration and parallel with the axis of the shaft 20 as shown in Figures 5 and 8. Each pair of aligned sockets or recesses 70 rweives an expansive coil spring 72 which normally biases the

rings

67 and 69 away from each other.

The upper limit of movement of the ring 69 is defined by means of a snap ring 74 which engages in a kerf 75 formed in the cylindrical surface 60 of the shaft 20 as particularly shown in Figure 6. Thus the expansive pressure of the springs 72 holds the ring 67 in engagement with the inner race 65 of the bearing 40, holding the latter in engagement with the annular member 63.

As particularly shown in Figures 4, 6 and 9, the upper portion of the shaft 20 is formed with diametrically arranged slots 76 defined by walls 77 which terminate .in slotted portions of greater width defined by walls 78, the slots being shaped with the defining walls parallel with the axis of the shaft.

The annular element or ring 67 is formed with diametrically opposite bores 80 which snugly receive tenons 82 each having an enlarged cylindrical head portion 84, the latter extending into the slots defined by the walls 77, as shown in Figures 6 and 9. The tenon portions 82 are pressed into the bores 80 so as to be fixedly retained in the annular member 67.

The headed portions 84 extending into the slots 76 defined by walls 77 prevent the ring 67 from rotation relative to the shaft 20.

As shown in Figures 6 and 7, the annular member or ring 69 is also formed with diametrically arranged bores into which tenons 88 are snugly received. The tenons 88 are formed with integral cylindrical portions 90 of larger diameter and of a dimension to snugly yet slidably fit into the slots 76. Thus the portions 90 extending into the slots 76 serve to prevent rotation of the annular member 69 relative to the shaft so that the annular member 69 is capable of movement axially of the shaft 20 and is rotatable with the shaft together With the annular member 67. The springs 72 will at all times exert a biasing pressure acting upon the raceway 65 to hold the same in position.

Also formed as integral portions of the heads or members 90 are projecting tenons 92, the tenons 92 being of diameters to be snugly yet slidably received in the L- shaped or bayonet-type slots composed of vertical zones 46 and angularly arranged zones 42 as shown in Figures 3 and 5, the angular zones of the slots 42 terminating in substantially horizontal end zones 44.

The tenon portions 92 extend into the slots in the quill 22 in order to establish a driving connection between the shaft 20 and the quill 22. Such interconnection is of a character which permits the ready removal and reassembly of the quill in the shaft and is unaifected by intense heat or wide temperature variations to which the apparatus is subjected.

Means is provided for temporarily holding the shaft 20 against rotation during application or removal of the quill construction. A cover plate 94 is secured to the member 36 and is formed with a radial slot in which is fitted a rectangularly shaped plate or key 96 provided with a T-shaped slot 97 shown in Figure 6, adapted to receive a cylindrically shaped head portion 98 of a member 99.

aseavsa The member 99 is formed with a portion 100 threaded into a bore 101 formed in the member 36. The portion 100 is provided with a knob or grip member 102 to facilitate rotation of the member 99, the threaded portion 100 cooperating with the threads in the opening 101 to eflect longitudinal movement of the plate or key 96. The key or plate 96 is normally withdrawn from engagement with one of the slots defined by walls 78 in the shaft 20 when the shaft, quill and rotor are rotating during fiber-forming operations.

The method of fixing or connecting the rotor and quill assembly to the shaft 20 is as follows: the shaft 20 is first locked in a stationary position by manipulating the knob 102 to advance the locking plate or key 96 into one of the slots in the shaft defined by the walls 78, the shaft being shown in locked position in Figure 6. The quill or sleeve 22 carrying the rotor 12 is telescoped upwardly through the hollow shaft 20.

The quill 22 is rotated to a position in which the tenon portions 92 enter the vertical slotted zones 46 in the quill, and the quill is further advanced in an upward direction until the tenons 92 are disposed adjacent the lower ends of the slotted zones 46 with the chamfered surfaces 48 and 49 in abutting engagement. This position of the quill and shaft is illustrated in Figure 10. The quill is then rotated by grasping the rotor and rotating the same in a clockwise direction as viewed in Figure 5 causing the tenon portions 92 to traverse the angularly disposed slots 42.

During the rotation of the quill 22 relative to the shaft 20, the angularity of the slots 42 causes the annulus or annular member 69 to be drawn or moved toward the annulus or annular member 67. This operation further compresses the springs 70 exerting additional pressure holding the inner race 65 of the bearing 40 in close engagement with the annular member 63.

The quill 22 is rotated until the tenon portions 92 are disposed in the horizontal slot portions or zones 44 at the terminae of the angular slots 42, this position of the parts or components being shown in Figures 9 and 11. In this position, the quill is held securely to the shaft 20 as the chamfered extremity 48 of the shaft 20 abuts the beveled surface 49 on the quill 22 under the compressive pressure of the coil springs 70.

The horizontal slotted zones 44 in the quill in engagement with the tenons 92 maintain the annulus 69 in its lowermost position as shown in Figures 9 and 11. The locking key 96 is then withdrawn from the slot in the shaft. The shaft 20 and quill 22 are rotated in a direction to hold the tenons 92 in engagement with the end walls of the horizontal slotted zones 44 and in this manner the quill and rotor are held in assembled driving relation with the shaft 20 and any relative longitudinal movement between the quill and shaft due to expansion or contraction is compensated by the springs 70.

The quill and rotor assembly may be removed from the shaft in the following manner: The shaft 20 is rotated to a position to align the key 96 with a slot bounded by walls 78 in the shaft and the manipulating knob 102 rotated in a direction to advance the key 96 into the slot. The rotor and quill assembly may then be turned or rotated by hand or suitable tool in a counter clockwise direction as viewed in Figures 5 and 9, which movement causes the tenon portions 92 to traverse the angular slots 42 to a position in registration with the vertical slotted zones 46. In this position the quill may be withdrawn downwardly and away from the shaft 20.

The arrangement includes means for exerting a constant biasing pressure upon the outer race 104 of the anti-friction or ball bearing 40. As particularly shown in Figures 6, 10, and 11, an annular member 106 is disposed vvithin the bore in the boss portion 38, the lower wall of member 106 engaging the upper edge wall of the outer race 104.

The member 106 is formed with a plurality of circumferentially spaced sockets or bores 107, each of which receives an expansive coil spring108. Disposed above the upper extremities of the coil springs 108 in a recess formed in member 36 is a retaining plate or member 109. The plate 109 is held in place by means of the member 94.

In the arrangement shown in Figure 1, the shaft, rotor and quill arrangement is driven by an electrically energizable motor wherein the motor armature or rotor is carried directly upon the shaft 20. As particularly shown in Figures 1 and 4, the armature 112 is keyed or otherwise arranged to rotate with the shaft and is held in position by a locking ring 113 threaded upon the shaft. The field structure or stator (not shown) of the motor is mounted within the housing 14.

The motor housing may be provided with a chamber or passage (not shown) through which a cooling or temperature controlling fluid may be circulated. The chamber or passage is connected with pipes or conduits 115 and 116 for conveying fluid into and away from the chamber or passage. While any fluid may be utilized for conveying excess heat away from the motor, water, oil or air under pressure may be used satisfactorily for the purpose.

The rotor structure 12 illustrated in Figures 1 and 3 is fashioned with comparatively thin wall sections in order to reduce the weight of the rotor to a minimum. The rotor may be made of metals or alloys capable of withstanding the intense heat from the molten glass such as stainless steel, and by fashioning the rotor with thin walls, it may be made of rare metals having long wearing characteristics such as platinum, rhodium or the like. The rotor is formed with a perforated peripheral wall portion or band 118 concentrically arranged with respect to the axis of the quill 22 and may be tapered slightly outwardly and downwardly as shown in Figure 3.

It is to be understood that the peripheral wall 118 may be cylindrical about the central axis of the rotor or the same may be inclined or of frusto-co-nical shape of substantial angularity depending upon the character of the attenuating blast engaging the bodies projected from the rotor. The wall 118 of the rotor is provided with a comparatively large number of orifices or apertures 120 through which the molten material is projected under the influence of centrifugal forces of rotation to form the material into discrete bodies or primary filaments.

The upper portion of the wall 118 is joined or integrally formed with an angularly arranged connecting portion or wall 122 terminating in a ledge portion 123 Welded as at 55 to the quill 22 or otherwise secured thereto. The lower zone of the circular wall 118 is joined or integrally formed with an angularly disposed Wall portion 124 extending in a direction opposite to the angularity of the portion 122. The angularity of the portions 122 and 124 is substantially symmetrical about a plane through the central zone of the wall portion of the rotor normal to the axis of rotation.

The walls 122 and 124 are of substantially the same shape and thickness whereby they will expand and contract substantially uniformly irrespective of Wide temperature variations so that no distortion of the rotor occurs. The lower wall 124- of the rotor terminates at a zone 126 defining a circular opening through which gases in the rotor may escape.

The rotor arrangement may be provided with means for distributing the molten glass or other molten fiberforming material to a zone or region at the inner surface of the wall portion 118 so as to provide a uniform supply of material adjacent the orifices 120 in order that elongated bodies or primaries of uniform character may be formed. As shown in Figures 1 and 3, there is provided with a material distributing means in the form of a cup-like member or basket 130 having an imperforate bottom wall 132, a circular cylindrical side wall 133 terminating at its upper zone in an outwardly extending circumferentially spaced flange or ear portions 135. The

cup-like member 130 may be secured to the quill 2.2 by bolts 139 or other suitable means.

The cup-like member 130 may be provided with an annular means or ring 140 to prevent or avoid distortion of the cup construction. The circular cylindrical wall 133 of the cup construction is formed with a plurality of orifices or outlets 142 which are suflicient in number and size to accommodate transfer or delivery of an adequate supply of molten glass or fiber-forming material into contact with the inner zone of the Wall 118 of the rotor.

The molten glass or other material is delivered through the hollow interior of the quill 22 and engages the bottom wall 132 of the cup 130. Centrifugal force of the rotating cup propels or projects the molten material through the openings 142 in the cup wall 133, the material being delivered on the interior surface of the wall 118 adjacent the orifices 120. Centrifugal forces propel or project the material through the orifices 120 in the rotor wall to form discrete bodies or primaries.

The discrete bodies or filaments delivered from the rotor may befurther processed into fine fibers by attenuation. Figure 1 illustrates an arrangement wherein a gaseous blast of intensely hot gases is projected as an annular blast into engagement with the bodies or primaries. Disposed adjacent and beneath the motor housing 14 is a burner unit 16 including a substantially circu lar cylindrical casing or housing 145.

The burner construction may be formed with an annular combustion chamber or confined zone 147 lined with walls of high temperature resistant refractory 148.

The burner arrangement is inclusive of a vertical metal Wall 150 which surrounds the lower zone of the quill 22 forming an annular space 152 to retard transfer of heat between the burner and quill. Spaced from the annular wall 150 is an annular wall 154, the space 155 between the walls forming a chamber or passage to accommodate the circulation of a cooling fluid such as water conveyed into and away from the chamber by inlet and

outlet pipes

157 and 158.

Combustible mixture is admitted into the combustion chamber 147 through a manifold 160 connected with a supply.

Secured to a lower wall of the housing 145 is an annularly shaped orifice plate or member 164 which is held in place by suitable means. The plate 164 is formed with an unobstructed, annularly-shaped outlet or orifice 166 which is restricted so that the burned gases or products of combustion from the chamber 147 are discharged through the annular orifice 166 as an intensely hot, high velocity annular blast projected adjacent the periphery of the rotor wall 118 concentric relation therewith.

The annular blast of gases projected from the orifice engages the discrete bodies or primaries extruded or projected through the openings 120 in the rotor wall, attenuating the bodies or primaries to fine fibers.

The mixture of fuel and air delivered into the chamber 147 is in ratio whereby the mixture will be substantially completely burned within the chamber so that the burned gases or products of combustion are projected at high velocity through the orifice 166. The burning gases within the chamber 147 are at very high temperatures, in the nature of 2000" F. or more, so that the burned gases provide an intensely hot blast of high velocity for attenuating the bodies or primaries delivered outwardly from the rotor into fibers.

It is apparent that, within the scope of the invention, modifications and different arrangements may be made other than is herein disclosed, and the present disclosure is illustrative merely, the invention comprehending all variations thereof.

We claim:

1. Apparatus of the character disclosed, in combination, a support, a hollow shaft member journaled on the support, means for rotating the shaft member, aquill member in telescoping relation with the shaft member, one of said members having a slot formed in a wall thereof, means associated with the other said members adapted to extend into the slot for removably securing the quill member and shaft member together and establish a driving connection between the shaft and quill members, a rotor carried by the quill member, said quill member and shaft member being formed with abutting surfaces, and resilient means reacting on said quill member and shaft member biasing the said surfaces into abutting relation.

2. Apparatus of the character disclosed, in combination, a support, a rotor, a hollow shaft member journaled on the support, a quill member disposed within the shaft member, slots formed in a wall of each of the members, an annulus surrounding the shaft member, projections carried by the annulus extending into the slots in said members for establishing a drive connection between said members, said quill being connected with the rotor, resilient means biasing the quill member in one direction lengthwise of the shaft member, and electrically energizable means for driving the shaft member, quill member and rotor.

3. Apparatus of the character disclosed, in combination, a support, a shaft journaled on the support, means for rotating the shaft, a quill in telescoping relation with the shaft, a rotor supported on the quill, said shaft and quill having slots formed in the walls thereof, an annular member surrounding the shaft and quill and being slidable lengthwise thereof, said annular member having projections extending into said slots whereby a driving connection is established between said shaft and quill, resilient means biasing said annular member in a direction lengthwise of the shaft to provide for relative movement between the shaft and quill due to expansion and contraction caused by temperature changes.

4. Apparatus of the character disclosed including, in combination, a support, a tubular shaft member journalled on the support, a sleeve member in telescoping relation with the shaft member, a rotor connected with the sleeve member, said rotor having a peripheral wall formed with a plurality of orifices, slots formed in a wall of each of the members, an annulus provided with means extending into the slots for establishing a drive connection between said sleeve and shaft members, resilient means biasing the sleeve member in one direction lengthwise of the shaft member, an electrically energizable motor having an armature mounted on said shaft member, a housing supporting a stationary field of the motor, means associated with the housingv adapted to accommodate a fluid for controlling the temperature adjacent the motor, and means for delivering heatsoftened material through the sleeve member into the rotor, the centrifugal forces of rotation of the rotor projecting the material through the orifices in the peripheral wall of the rotor.

References Cited in the file of this patent UNITED STATES PATENTS 430,420 Ooulson June 17, 1890 1,256,288 Barnes et al. Feb. 12, 1918 1,498,717 Coffin June 24, 1924 2,040,168 De Bats May 12, 1936 2,431,205 Slayter Nov. 18, 1947 2,571,069 Shearman Oct. 9, 1951 2,613,968 Harstick et al. Oct. 14, 1952 2,624,912 Heymes et al. Ian. 13, 1953 2,816,826 Brennan Dec. 17, 1957