US3369716A

US3369716A - Hopper means having hyperbolic side walls

Info

Publication number: US3369716A
Application number: US556935A
Authority: US
Inventors: Jr Clarence E Hulbert
Original assignee: Capvac Ind Inc
Current assignee: Capvac Ind Inc
Priority date: 1966-06-13
Filing date: 1966-06-13
Publication date: 1968-02-20
Anticipated expiration: 1985-02-20

Description

Feb. 20, 1968 C. E. HULBERT, JR

Filed June 15, 1966 3 Sheets-Sheet l zao /57 X /34 J L 27/ 3/2 /0 V SOL 601v 7'ROL 50L .270 RMEL :h= 32 VACUUM PRESSURE X I MBA/V5 I L i I -I 35 I CLARENCE E. Hume/7J2 INVENTOR.

ATTORNEY Feb. 20, 1968 c. E. HULBERT, JR 3,369,716

HOPPER MEANS HAVING HYPERBOLIC SIDE WALLS Filed June 15; 1966 5 Sheets-Sheet 3 SOL CLARENCE E Hume/w, JR.

1 N VEN TOR.

A TTORNE'Y United States Patent 3,369,716 HOPPER MEANS HAVING HYPERBOLIC SIDE WALLS Clarence E. Hulbert, Jr., Houston, Tex., assignor to Capvac Industries, Inc., Freeport, Tex., a corporation of Texas Filed June 13, 1966, Ser. N0. 556,935 4 Claims. (Cl. 222-373) ABSTRACT OF THE DISCLOSURE Apparatus for continuous movement of bulk, granular material having an angle of repose as high as ninety degrees. Said apparatus includes vessel means having a funnel chamber with an irregular side and control means coupled to said vessel means for controlling vacuum and pressure applied to said vessel means from a vacuum source and a pressure source.

This invention pertains generally to bulk material moving apparatus and particularly to apparatus adapted for moving bulk material, such as hygroscopic. material, which heretofore has not been movable in large volumes in a rapid manner. The present invention is adaptable particularly to moving bulk materials, through a wide range of sizes and shapes such as lump coal, gravel, finely ground cake flour, cereals, and light fluify talc.

The present application is related to my copending application, Serial Number 463,781, filed June 1-4, 1965, and entitled Abrasive Flow System and Methods.

While various means have been employed to move dry materials by conveyor, no known funnel or other device has been capable of providing a fail safe, non-clogging, escape method for dry products to flow through metering means, without requiring bin vibrators and shakers to prevent the various materials from bridging, rat holing, clinging, or packing. The present invention is adaptable for use in a plurality of conveying functions which will be set forth in the following description.

Among the conveying devices known to applicant are those disclosed in the following United States Letters Patent:

2,851,553-Grostick, issued September 9, 1958. 2,979,235-Greaves, issued April 11, 1961. 3,071,297 Lee, issued January 1, 1963.

Although these patents disclose various means for moving material none of such patents has provided satisfactory results in certain areas of material moving. Particularly, sodium chloride, ammonium sulfate and ammonium phosphate have been difficult to move with known apparatus and the rapid moving of this material has been limited generally to belt conveyors or buckets. Such material is in crystal form at room temperature and the angle of repose varies from about 30 when dry to about 85 when moist. Thus, the three mentioned materials along with other members of the alkalyne family of materials exhibit hygroscopic properties which make these materials very difficult to convey through known hoppers and other material moving means. These materials do not lend themselves readily for movement with known apparatus because the materials surface tension and capillary attraction restricts the fiow through hoppers and other mechanism being used for moving the material.

The present invention is adapted for providing a satisfactory solution to the problems which have heretofore been encountered in the attempted movement of various types of material including material having hygroscopic properties.

3,369,716 Patented Feb. 20, 1968 Thus, it is an object of the present invention to provide improved apparatus and methods for the old art of funneling bulk materials from bins, hoppers and the like.

Another object of the present invention is to provide means to employ less space distance from the hopper or bin to the outlet by providing two dissimilar irregular, curved surfaces.

Still another object of the present invention is to provide an escape means for materials whose structure heretofore required shakers or vibrators to provide a substantially constant velocity to the product being moved.

Still another object of the present invention is to provide by gravitational force the required energy level necessary by kinematic functions, to cause material to flow evenly without restriction due to mass, friction coeflicient, cohesive attraction and molecular structure of such material.

A still further object of the present invention is to provide a means to insure a material to flow with a near top level attitude, thus allowing measuring instruments to obtain accurate data heretofore accomplished by weight controls or inaccurate readings which were the result of the inverted repose angle of the dry product material whose repose angle would constantly vary in accordance with its ever changing moisture content.

Still another object of the present invention is to provide an unrestricted passage of any dry material whose cohesive attraction and surface tension does not defy the force of gravity and whose mass is such that it is smaller than the midsection passageway of the device of the present invention.

Still another object of the present invention is to provide a constant flow of any material having cohesive strength to metal lower than the weight value of the mass and gravitational force of such material. For example, grain and other animal feed products containing molasses and other sticky substances will flow Without restriction when their mass and cohesive characteristics fall within the mentioned limits.

Yet another object of the present invention is to provide a universal structure adaptable for use on various configurations, sizes and types of material collecting and discharging devices whose characteristics require a constant flow without restriction, are closely coupled and require low profile, while utilizing a gravitational discharge method.

In the drawings, FIGURE 1, is a combined side elevational view of the vessel and circuit schematic of the control system of the present invention;

FIGURE 2 is a combined funnel shape and chart having curves incorporated in the present invention plotted on X and Y axes;

FIGURE '3 is a cross-sectional top view of a portion of the curves incorporated in the present invention taken along line 3-3 of FIGURE 2;

FIGURE 4 is a sectional elevational view of the material mover mechanism of the present invention utilized with a vacuum pump; and

FIGURE 5 is a sectional elevational view of the material mover mechanism of the present invention utilized with a pressure source.

Briefly stated, the present invention includes a method and means for providing unrestricted uniform feed characteristics to bulk products whose physical nature has heretofore not been adaptable to existing methods. It will be appreciated that the principles involved in the present inventon may be utilized from the Cartesian curve form to many shapes and dimensions as long as the primary principles of the present invention are maintained, and that the shape shown and described may be 'altered in lines of space and configuration. The mathematical functions contained in the present invention are part of the universal laws of nature but employed to provide a method and means for discharging materials whose structure and shapes have been difficult to handle.

Referring now'to the drawings in detail, FIGURE 1 is a combined side view of a vessel and a schematic of the control system of the present invention. Vessel means includes an upper semi-spherical portion 134. Generally the interior construction of the vessel means 10 closely follows the construction disclosed in my copending United States patent application, Serial No. 463,781, filed June 14, 1965, and entitled, Abrasive Flow System and Methods. An inlet 52 is utilized for bringing material into the chamber of vessel means 10.

It will be appreciated that the vessel means 10 explained in detail in my copending patent application provides a lower material collecting and metering system chamber. While the device of my copending patent application is suitable for the purpose disclosed and claimed therein, the lower material collecting and metering system chamber of my prior copending application is removed and a hyperbolic mover means is substituted by connecting to the inner chamber walls to the top section of vessel means 10 thereby providing the hyperbolic mover device of the present invention with complete access to all materials which pass into the top inner chamber. The lower opening of hyperbolic mover means can be connected to a metering valve or rotating feeder valve well known in the art.

The equipment of the present invention including the hyperbolic mover means is fully portable and may be mounted on a truck, trailer or skid.

Vessel means 10 has coupled to the upper semi-spherical portion 134 an inlet 52 for material which is fed to the vessel means. A pressure relief valve 154 is coupled to the semi-spherical portion 134 as is a pressure discharge valve 156. The pressure relief valve 154 may be spring loaded and allows the vessel means 10 to vent to the atmosphere. The pressure discharge valve 156 vents to the atmosphere and is coupled through lead 157 to a timer housed in control panel 12. Pressure discharge valve 156 also may be manually operable. An electric motor indicating device 280 is utilized for indicating the upper level of material positioned in vessel means 10. The electrical motor device 280 is coupled through lead 300 to the control panel 12.

A lower level electric motor device 290 is positioned on valve means 10 and coupled through lead 302 to control panel 12.

Solenoid 312 is coupled to the vessel means 10 and through lead 314 to the control panel 12.

Valve 270 and solenoid 271 are coupled to the vessel means 10 and through lead 316 to the control panel 12.

Valve 268 and solenoid 269 are coupled through lead 318 to the control panel 12.

Vacuum-pressure means 320 is coupled through conduit connecting line 322 to valve 279. It will be appreciated that such vacuum-pressure means may be either a vacuum pump or a pressure device such as a compressor. As will be explained subsequently, the vacuumpressure means depends on how the equipment of the present invention will be used. In one application of the invention, both vacuum and pressure is provided alternately and continuously.

Generally material enters the vessel means 10 through inlet 52 and is discharged through valve 268 at the lower portion of the vessel means 10. The control panel 12 provides indication and selected actuation of the valves as will be explained in greater detail subsequently. The control panel provides selective control of the components of the present invention and may vary in construction according to the requirements of a particular job. It will be appreciated that the material inlet 52 may be coupled to suitable means such as hose which will allow material to be picked up and moved through the vessel means 10.

The valve 268 may be a solenoid actuated valve or a star valve which allows continuous flow of material through the vessel means 10.

FIGURE 2 is a simplified representation of the curved surfaces and the interior cylindrical portion of the vessel means of the present invention set forth along X and Y coordinates. As shown in FIGURE 2 the X coordinate is horizontal and has been positioned at the

junction point

50 and 51 of the cylinder wall 38. The Y coordinate has been positioned at the midway point of the diameter of the cylinder formed by wall 38 so that Y is substantially in the center of the cylinder formed by wall 38.

It will be appreciated therefore that the area designated as I in FIGURE 2 is positive in the Cartesian system, area II is negative, area III is positive and area IV is negative.

The curve designated as A in the accompanying table for curve A is the same as surface 40 while curve B in the accompanying table for curve B represents curved surface 41. Thus, in the tabulation for curve A, since curve A lies in area III all value of X and Y are negative. It will be appreciated in reviewing the tabulation for curve A that Y (prime) is 0 for the first four readings of X in the right hand portion of the table for curve A. As the value of X is 4 in the right hand portion for the table for curve A, Y is 8 and Y (prime) is 18. Y (prime) is the extention of Y to indicate that there is an intercept or dual value of Y when plotting the curve A. As shown in the lower portion of the table for curve A, X is positive for areas I and IV and negative for areas II and III while Y is positive in areas I and II and negative for areas III and IV. An important part of the present invention is the fact that there is an intercept relationship of the curve A as shown in the table for curve A where X is 4, Y is 8 and 18. The fact that there is an intercept indicates that the curve A is not identical or even substantially the same as curve B as will be explained subsequently.

Curve B which is the curve portion 41 is tabulated in the table for curve B and it might be noted that all values for X are positive while all Y values are negative. The lower portion of the table for curve B indicates the areas where X and Y are positive and are negative.

It will be appreciated, therefore, that curve A and curve Bare not identical. The equations for curve A and curve B are not set forth with great accuracy although the tables for curve A and the tables for curve B have proven to be satisfactory in practicing the present invention. It will be appreciated in viewing FIGURE 2 that curve A and curve B of the present invention are not the same in structure, function, or result as the curved members disclosed in US. Patents 2,979,235 and 3,071,297. The 3,071,297 patent specifically discloses a structure wherein there is a constant decrease in the inner crosssectional area while moving toward the discharge opening. In the 2,979,235 patent the angle of the bottom wall to the horizontal has been limited to approximately the equivalent or slightly greater than the angle of repose of the material being handled. The curves utilized in the present invention are not limited in the manner set forth in the 2,979,235 and 3,071,297 patents. The structure of the present invention allows various types of material to be readily moved over the

curved surfaces

40 and 41 without build-up at any point on the curved surfaces.

As is well known in the bulk material art, the angle of repose of bulk material is the angle, less than ninety degrees, which the slope of bulk material forms with respect to a horizontal plane. In moving bulk material through a conventional funnel the slope of the funnel has a configuration substantially the same as the inverted triangle formed by the two slopes determined by the angle of repose of certain bulk material. The present invention provides two dissimilar, irregularly shaped mem-- bers which act to provide a varying angle X where X=l80 degrees minus (the angle of repose times two).

Referring again to FIGURE 2 it will be seen that the mass of material is greater along curve B than along curve A in relation to the Y axis. Thus, more compression is forced on the material along surface 41 while the lower portion of surface 40 has less compressive force than at any other portion of the

surfaces

40 and 41. The upper portion of surface 49 is a slave to the frictional value caused by the repose angle of the material moving transverse to the Y axis. It will be appreciated that the Y axis is not equidistant from

points

43 and 45. Thus, it will be seen that the lower portion of surface 40 provides increased impetus to material moving downwardly. Therefore, the primary object of moving heretofore difiicultto-move-material may be achieved rapidly and effectively because the lower part of the material is moved by breaking the center fiow of the material.

FIGURE 3 is a cross-sectional top view taken along line 33 of FIGURE 2 to show variations of the curved surfaces.

Curved surfaces

40 and 41 are shown coupled to

planar members

60 and 62. Points 50. and 51 are shown in FIGURE 3 in broken lines to indicate that surfaces such as 64 and 66 might be utilized if the

curved portions

40 and 42 are extended to

points

50 and 51. Also, surfaces 68 and 70 might be utilized with the

curved portions

40 and 41. The broken lines shown in FIGURE 3 merely are attempts to indicate that the planar surfaces such as

surfaces

60 and 62 actually utilized and shown in FIGURES l and 2 are not necessary but may be of any suitable configuration such as that indicated by surfaces 64 and 66 or by surfaces 68 and 70. The only requirement for the

curved surfaces

40 and 41 of the present invention is that they conform substantially to the tables set for curves A and B. Ease of construction apparently would dictate that surfaces 60 and 62 be planar rather than curved as shown in the broken lines of curves 64 and 66 and curves 68 and 70.

FIGURE 4 is a sectional elevational view of the vessel means utilized in practicing the present invention when vacuum is provided to such vessel means from a vacuum pump (not shown). Vessel means has positioned thereon an inlet 52 which allows material or product to be brought into the chamber 186 when plunger 256 is opened. Plunger 256 is closed by air cylinder 178 which is coupled to valve 310 operated by solenoid 312. As explained previously pressure relief valve 154 is coupled to the upper semi-spherical chamber 134 and allows venting to the atmosphere of upper outer chamber 144. Discharge line in valve 156 also is positioned on semispherical portion 134 and allows chamber 144 to be vented to atmosphere when the valve 156 is manually operated. Electric motor device 280 is coupled through stem 182 to a level control paddle 184 in a manner well known in the art. The level control paddle 184 along with the electrical device 280 provides a signal for operating air cylinder 178 and plunger 256 as explained in my prior copending patent application.

Inner suction header 160 extends circumferentially to allow attachment of filters such as

filters

146 and 148.

Filters

146 and 148 may be constructed of perforated pipe having sock covers.

Inner top chamber opening 162 allows communication from the product collector chamber 186 to the top outer chamber 144 thereby providing inner space dust velocity reduction within the vessel means 10. A centripetal separator baffle 172 has a centripetal separator ledge 170 for air control thereby causing movement of the material within the vessel means 10 to allow the proper movement of material.

Wall 38 defines the inner product collecting chamber 186. Such chamber 186 has a semi-spherical upper portion and a cylindrical lower portion and converges downwardly to the outlet 42.

Surfaces

40 and 41 provide the downward opening and the configuration of surface 40 6 and 41 has been explained in detail previously in conjunction with FIGURES 2 and 3. v

Disposed below the

filters

146 and 148 is an inner filter storage area 150 and an inner filter storage area 152.

A paddle 284 is disposed on stem 282 and coupled to electric control 290. The paddle 284 and the electrical device 290 provide a signal for actuation of air cylinder 178 in a manner similar to that described in connection with upper paddle 184 and electric control 280.

A dust door 198 is positioned in surface 40 to allow dust collected in the inner filter storage area 150 to be passed out of outlet 42 when dust door. 198 is opened by actuation of the control stem 192. Similarly a dust door 202 is positioned in surface 41 to allow dust which has been accumulated in dust collection area 152 to be discharged downwardly through outlet 42 upon actuation of stem 196.

The vessel means 10 may be positioned on a suitable frame 292 with rivets or bolts such as 294 and 296.

A star valve 266 may be positioned within housing 268 to allow communication of outlet 42 with a pressurized material collecting pan 234 coupled to outlet line 16. Inlet line 22 is in communication with product collecting pan 234 and outlet 16. The star valve 266 may be of any type well known in the material handling art. Such valve is a rotating bulk product material feeder valve for measuring the product discharge and for supplying an air lock from product collecting pan 234.

The vessel means 10 shown in FIGURE 4 is utilized with a vacuum pump coupled to valve 270 which has solenoid 271 coupled thereto. Valve 270 is coupled to elbow 158 which is in communication with the inner suction headed 160. Valve 270 is a multiport valve which may for example be a Rockwell-Nordstrom Valve arrangement No. l-three way, two port, degree turn, two position valve. Valve 270 is operated by air cylinder having a two position stroke. The air cylinder of valve 270 is actuated by an air electric solenoid valve. In position No. 1 wherein vacuum is utilized the air cylinder to air cylinder unit 178 opens and .valve 270 opens to the vacuum pump by the solenoid signal. In position No. 2 during the pressure cycle the air cylinder 178 closes and valve 270 closes to vacuum supply but opens to pressure. The return to vacuum is controlled by a timer device which opens vessel pressure discharge valve 156 to atmosphere to release the pressure which has built up in the vessel. When the pressure within the vessel has been vented to atmosphere through the vessel pressure discharge valve 156, another signal is transmitted to the solenoid operating valve 270 and to the solenoid operating air cylinder 178. Thus it will be apparent from the above explanation that the sequence of operation of the vessel means 10 when a star valve 266 is utilized will be such that the movement of material through the outlet 42 will be continuous. As explained previously FIGURE 4 shows the vessel means of the present invention adapted for use with a vacuum pump (not shown) which may be coupled to the valve 270 in a manner well known to those skilled in the vessel art in the material moving art. While operating with a vacuum pump as shown in FIGURE 4, the upper electrical control unit 280 will cut off the vacuum pump in the event that too much material is stored in the chamber 186. The lower electrical control unit 290* will actuate the vacuum pump when the material in chamber 186 falls below the level of paddle 284.

Referring again to FIGURES 2 and 3, it will be apparent from the configuration of

surfaces

40 and 41 that material which is being brought into the inner product collecting chamber 186 is positioned along

members

40 and 41. The configuration of these members is such that the material flow downwardly through outlet 42 is continuous and may allow many different kinds of material to be effectively dischargedv from the vessel and move through the outlet 16. The configuration of

members

40 and 41 prevents rat holing or material accumulation along such members even though the material which is being moved may possess sticky characteristics which have heretofore prohibited or limited mass movement thereof.

Thus it will be apparent from the foregoing explanation of FIGURE 4 that FIGURE 4 represents one embodiment of the present invention with valve 270 positioned for coupling to a vacuum pump. The star valve 266 provides continuous flow of material which is brought in through inlet 52 from outlet 42.

FIGURE is a cross-sectional elevational view of the vessel means utilized with a pressure source coupled to valve 270 after valve 270 is rotated 90 degrees. The valve utilized with the embodiment shown in FIGURE 5 may be a full bore pattern two way, hard surface valve which may be manually operated or operated by an air cylinder. Member 269 opens and closes the outlet 42 with respect to the product collecting pan 234.

Thus it will be apparent in reviewing FIGURE 5 that when presure is utilized on the vessel means 10 through valve 270, that the air cylinder 178 operates rubber plunger 256 to periodically discharge material which has been accumulated within chamber 186 through operation of the level indicator

devices having paddles

184 and 234. For example, member 269 will be closed during a filling cycle while the air cylinder 178 provides downward movement of plunger 256 to allow material to be brought in through inlet 52 to the product accumulation chamber 186 while vacuum is provided. As material accumulates within the chamber 186 and as the paddle on the upper level indicator is actuated, plunger 256 is actuated by the air cylinder 178 to close the inlet 52 and the member 269 is opened to allow discharge of the material which has been accumulated in chamber 186. Also pressure is applied to the chamber 186 through valve 270 which was actuated by upper level controller 280 to discharge the material in chamber 186.

Paddle 284 actuates a timer device in the control panel 12 and a signal is provided to open the upper discharge valve 156 to release pressure within vessel means 10 dropping the pressure within vessel means 10 to atmospheric pressure after a brief interval of time, which may be on the order of several seconds, the timer device provides a pneumatic signal to close

valves

269 and 156 and actuates air cylinder 178 to open plunger 256 and allows valve 290 to be coupled to a vacuum pump. Vacuum is provided to the vessel means 10 until the above action is repeated. The operation of the vessel means 10 as shown in FIGURE 5 includes a pressure source such as an air compressor and vacuum source such as a vacuum pump. The pressure and vacuum act together on an alternate basis to move material in the vessel means 10.

As explained previously in conjunction with FIGURE 4 the vessel means 10 allows movement of heretofore unmovable material or material which has been difficult to move without the problems previously encountered. The operation of the vessel means 10 is achieved through coordinated operation of member 269, plunger 256 and pressure relief valve 156.

While my prior copending patent application provided means for conveying various material by positive and negative pressure it will now be appreciated that the present invention will move material heretofore diflicult to move by pneumatic conveyor means.

By incorporating the hyperbolic mover of the present invention the disclosure of my copending application it is now possible to move hygroscopic materials such as fertilizer in bulk at very high quantity thus economically allowing loading and unloading of ships, barges, railroad cars, and other storage facilities.

It will be appreciated that the principles involved in the present invention when incorporated with my original vessel means will serve a dual function by being available to unload material from ships, barges, railroad cars,

bulk storage systems and convey such material to other suitable storage means, or to measure, weigh and convey by metered volumes said material to any point for use in blending or manufacturing other products.

The present invention utilizes heretofore unavailable pneumatic principles to provide satisfactory means for the movement of any bulk material. It will capture all the product dust and return it into the product collecting point or capture the dust for other purposes.

Through pneumatic conveying at high pressure of abrasive materials as set forth in my prior copending application it is also possible to convey these abrasive materials whose characteristics are hygroscopic or other materials that contain a high moisture saturation that have been in the past very difficult to convey.

Although preferred embodiments of the invention have been shown and described, it will be apparent to those skilled in the art of vessel construction and pneumatic conveying that many modifications may be made of the present invention without departing from the spirit of the invention as defined by the following claims. Although such claims are presented in indented format to facilitate reading and understanding thereof, such indented format is not to be construed as a structural or functional limitation of the elements or steps related in such claims.

FOR CURVE A Upper Iimi.X-=O Y=0 Lover Iimi. as X a reach s 0 (Y 21 or:

(Y .8 5 D.a. of

Note: All valies of it & are negative x Y x Y Y II I H H) q... x x --b III IV I m i FOR CURVE "B" UJper Limit X D Y kwer: Limit x .7 Y 21 Note X values Are all POSLtiVE Y Are all Negative X Y I X Y Q- X x I claim:

1. A system for continuously moving bulk material, said system including in combination vessel means having an inlet and an outlet for the bulk material, said vessel means including a chamber having first and second curved surfaces, said first curved surface and said second curved surface originating on substantially the same horizontal plane and converging downwardly whereby said first curved surface follows substantially the shape of a hyperbola and said second curved surface follows substantially the shape of an irregular hyperbola so that the weight of the bulk, granular material at any point on a horizontal plane through said first curved surface and through said second curved surface is considerably greater on the said second curved surface than on the said first curved surface, said first and second curved surfaces have beginning points on a substantially horizontal plane equidistant from a substanttially vertical plane with the middle lower portion and ending points of said first and second curved surfaces having different distances from said vertical plane whereby bulk material having a high angle of repose will move by gravity along said first and second curved surfaces, and

vacuum-pressure means coupled to said vessel means for providing selected pressure and vacuum to said vessel means.

2. A system defined by claim 1 wherein a source of bulk material having a high angle of repose is included in said combination.

3. A system defined by claim 1 wherein said vessel means includes a valve having an open position and a closed position in communication with said outlet, and said vacuum-pressure means includes a vacuum pump and a compressor selectively and periodically in communication with said vessel means.

4. A hopper for continuously moving by gravity bulk, granular material having an angle of repose as great as ninety degrees, said hopper including in combination first, second, and third curved surfaces each having substantially the shape of a hyperbola with said second curved surface being intermediate said first and said third curved surfaces, and a fourth curved surface intermediate said first curved surface and said third curved surface, said fourth curved surfacing having a vertical directrix determined by a point on any horizontal plane passing through said first, second, third and fourth curved surfaces with said point being the corner nearest the center of said horizontal plane of an imaginary square formed on said horizontal plane with said square having an area equal to substantially one-fourth of the total area of said horizontal plane bounded by said first, second, third and fourth curved surfaces.

References Cited UNITED STATES PATENTS 410,116 8/1889 Richards 222-56 1,052,653 2/1913 Crowley 222-194 X 2,590,458 3/ 1952 Prickett 222- 2,636,208 4/ 1953 Leeper 222-462 X 2,694,415 11/1954 Green 222-460 X 2,851,553 9/1958 Grostrick 340-246 X 2,979,235 4/1961 Greaves 222-185 3,071,297 1/1963 Lee 222-462 3,110,420 11/ 1963 Brewer 222-56 3,159,314 12/1964 De Lucca 222-460 X 3,198,366 8/ 1965 Hartley 222-56 3,212,671 10/1965 Rock 222-56 3,217,927 11/1965 Bale et a1 222-56 3,253,745 5/ 1966 Skelton 222-56 WALTER SOBIN, Primary Examiner.