US3489117A - Trapezoidal chine hull for displacement ships - Google Patents

Description

13, 1970 w. H. MESSERSCHMIDT 3,489,117

TRAPEZOIDAL CHINE HULL FOR DISPLACEMENT SHIPS Filed Feb. 23, 1968 3 Sheets-Sheet 1 I NV EN TOR 24 W91 75/7 fyfssffis'aw/ r ATTORNEYS 1970 w. H. MESSERSCHMIDT 3,489,1 7

TRAPEZOIDAL CHINE HULL FOR DISPLACEMENT SHIPS Filed Feb. 23, 1968 5 Sheets-Sheet 2 as i 74 '7z 70- I m 2 I l J J d 4 Z I I ATTORNEYS Jan. 13, 1970 w. H. MESSERSCHMIDT 3,489,117

TRAPEZOIDAL CHINE HULL FOR DISPLACEMENT SHIPS Filed Feb. 23, 1968 3 Sheets-Sheet 5 MENTOR We rze/yas'saesa/r/war ATTORNEYS United States Patent 3,489,117 TRAPEZOIDAL CHINE HULL FOR DISPLACEMENT SHIPS Walter H. Messerschmidt, Rostock, Germany, assignor to Institut fur Schilfbau, Rostock, Germany Filed Feb. 23, 1968, Ser. No. 730,666 Claims priority, application Germany, July 14, 19 67,

Int. Cl. B63b 1/04 US. Cl. 114-56 11 Claims ABSTRACT OF THE DISCLOSURE An improved hull for displacement ships in which a trapezoidal hull-form is combined with a multi-chine hull-form. The resultant trapezoidal-chine hull has one, two or three chines located at the turn of the bilges, with inclined sides of from 50 to 80 with respect to the horizontal, and a juncture which extends continuously around the entire hull, above but closely adjacent to the loaded waterline of the vessel. The juncture joins the inclined sides to a substantially vertically-oriented shipside which is superadjacent to the juncture. The ship also has internal fore and aft bulkheads along each side which rise from a position adjacent the turn of the bilges to the level of the vertically-oriented shipside portion, thus forming an internal loading space which is T-shaped in cross-section. The foregoing abstract is not intended to define the scope of the invention and is only provided to permit a cursory review of the gist of the invention.

Background and brief description of the invention This invention relates to an improved hull design for displacement ships. The innovative hull is essentially a combination of a trapezoidal hull-form and a multi-chine hull-form, which will be referred to as a trapezoidal-chine hull.

Modern shipping has been hampered by the lack of a hull design which is capable of fully exploiting the breakthroughs which have recently been achieved in other areas of ship design. In order to be Well-designed and hence fully effective, a hull design must take into account many parameters, from initial construction costs to operating costs, which are based on speed and efliciency of the vessel both when under way and when being turned around in port. Moreover, other criteria must be considered, including the seaworthiness of the vessel and other related safety factors.

A large amount of research and development has recently been undertaken with respect to the design of certain portions of a modern vessel. One such develop ment concerns the introduction of the bulbous bow, which in many cases has resulted in the improvement of the hydrodynamic characteristics of ships. Additionally a number of other innovations have been suggested and in certain cases adopted, including stern bulges, various appendages, and new forecastle and square stern designs.

However, despite these developments in other areas of design, there has not been any profound alteration of the overall form of a ships hull. The vast majority of all displacement ships still retain a hull design which is characterized by rounded bilges, essentially pointed ends, and vertical sides amidships.

There have, of course, been many prior attempts to cope with the problems involved in the optimum design of a ships hull. However, the solutions which have been adopted are directed to the resolution of a particular aspect of the overall problem, such as hydrodynamic resistance to the motion of the ship, rather than to an adequate solution of the whole rang of problems.

3,489,117 Patented Jan. 13, 1970 "ice Previously, there have been proposals for the adoption of a multi-chine hull; it has also been suggested that a trapezoidal hull could be employed in displacement vessels. However, previous multi-chine designs have been restricted in their use to small ships, mainly tugs and fishing boats. The trapezoidal hull-form has been used for some specialpurpose freighters, such as gas tankers and timber carriers, as well as in modern coasters. A true trapezoidal hull however, is uneconomical due to the presence of superfluous top hamper and surplus deck weight. Moreover, the embarkation of pilots and coming along side is made difiicult where a geometrically exact trapezoidal hullform is employed.

Additional attempts to solve the hull design problem have included some rather unique developments such as multi-hull ships (including those with an S-shaped section) and submersible and semi-submersible vessels, as well as hydrofoils and air-cushioned craft. Unfortunately, however, all of these developments possess only a limited range of utility at the present time. Moreover, the advantages claimed for these developments seem to be based more or less exclusively on their hydrodynamic characteristics, while virtually ignoring the formidable problems which arise with respect to the loading and off-load ing of general cargo which would be carried in these vessels. This is regrettable, since it is recognized that the decisive factors in any overall economic evaluation of a proposed design are first, speed while underway and second, ease of loading and off-loading or speed of tumaround in port.

The importance of speed of turn-around is demonstrated by the fact that modern cargo handling developments tend to increase the open ship, which includes unusually large hatch-areas. Another aspect of the emphasis in this area is illustrated by the increasing frequency of installation of stem and/or side ports. Another example of the attempt to speed up turn-around in port is to be found in the increasing use of Pickaback (or container) freighters, as well as dock freighters and articulated ships. All of these vessels are capable of significantly reducing turn-around time, although the landward side of the operation must be efiiciently organized in order to assure this time reduction. Moreover, existing designs of Pickaback freighters possess inherent disadvantages in that the engines have to be located against the external sides of the ship, which causes a safety problem; also the relatively high center of gravity or weight of each floating container when on board constitutes a further safety hazard.

In consonance with the aforementioned safety considerations, it must also be kept in mind that in the future there will most likely be gradual but widespread transition to nuclear propulsion. The introduction of nuclear propulsion is likely 'to result in completely new requirements in the design of ships hulls. These designs relate both to the margin of safety with respect to all types of damage, and also to the potential problems associated with ship oscillation or vibration.

It is apparent therefore, that prior attempts to design a ships hull which adequately resolves all of the aspects of the hull design problem have been less than completely successful. As mentioned previously, it would seem that the failure of these prior attempts is primarily due to the fact that they tended to concentrate on solving one narrow aspect of the problem, at the expense of the remaining factors.

On the other hand, the present invention effectively solves the hull design problem by employing a total approach to the resolution of the problem in its entirety.

As mentioned previously, an attempted solution will be completely adequate only if it satisfactorily balances each of the factors which influence or bear on the 3 problem. Thus, the hull must be capable of being constructed more rapidly and hence less expensively than the prior traditional hull-forms. Also, it should be constructed from flat, rather than from curved plates. Moreover, the hull should be built in such a manner that a maximum amount of internal space will be available in order to facilitate and expedite loading and offloading of the vessel, regardless of whether the cargo is stowed in large or small containers. In consonance with the foregoing, the hull should be constructed so as to result in an increase in the useful space or deck area above the waterline in vessels other than freighters.

Once under way, the improved hull design should endow the vessel with added speed, both in smooth water and on the open'sea. Itshould also provide added strength and an increased safety margin against impact or collision damage, particularly when nuclear propulsion is employed.

It is also important that the hull be designed so as to minimize alternations in trim and immersion consequent upon variations in the loadng of the shp. This feature would enable the hull to be feasibly furnished with a bulbous bow, thereby ensuring that the propeller and propulsion units are uniformly loaded.

The hull design of the present invention is able to achieve each of these desirable objectives by the employment of a tarpezoidal-chine hull. The hull-form is trapezoidal in transverse or cross-section, and has at least one chine at the turn of the bilge. The trapezoidalchine hull has upwardly-extending inclined sides Which terminate at a juncture which extends around the hullform above the loaded waterline of the vessel; The juncture joins the inclined sides to a substantially vertical shipside portion which is super-adjacent to the juncture.

It is to be noted that hereinafter the term trapezoidal hull is used in its accepted meaning to. define a hull wherein in relation to the block coetficient along' a more or less large portion of the length of the vessel the outline of a given tranverse section through the hull (for instance, in the plane of a hull-frame member) is a trapezoid whose included angles are identical to those of any other such transverse section. Thus, a line representing the side of the hull, inclined at an angle to the plane passing through the vessels centerline, is substantially parallel in each transverse section to a similar line in other adjacent transverse sections.

The juncture is preferably formed above, but conveniently closely adjacent to, the loaded waterline of the trapezoidal-chine hull. The hull can advantageously include either one, two or three chines located at the turn of the bilges of the vessel. It is preferred that the internal arrangement of the hull should include side tanks formed integrally with the outer hull. The side tanks and associated bulkheads run generally fore and aft of the vessel. The bulkhead rises vertically from a point approximately adjacent to the turn of the bilges substantially to the level of a horizontal plane which passes through the juncture. This internal arrangement results in a loading space which is of a T-shaped crosssection, which is especially well adapted for the reception and handling of cargo or the mounting of propulsive units (including nuclear propulsion) as well as for other uses. The correct position and length of the chines in the underwater hull should be chosen so as to secure the most advantageous streamline.

The portion of the hull above the slanted or inclined sides has been referred to as a substantially verticallyoriented shipside. While this portion of the shipside is approximately vertically-oriented entirely around the hull, it is oriented precisely at a right angle to the horizontal amidships. The vertical shipside portion is important not only because it eliminates superfluous top hamper and surplus deck weight, but also because it greatly facilitates coming along side and the embarkation of pilots. The surplus deck weight/hamper problem is repeatedly encountered in known trapezoidal hull-forms which have a constant, continuous shipside slant both above and below the loaded waterline. Moreover, the present invention possesses demonstrable hydrodynamic advantages regarding its underwater shape or design when compared with other known trapezoidal hull-forms which have a vertical shipside both above and below the loaded waterline. Also, the slant of the underwater shipside portion of the present invention reduces the size of the conventional double bottom of the hull without in any way imparing its safety function.

The construction of the trapezoidal-chine hull also affords significant advantages both in cargo-carrying and cargo-handling. At the deck level, a comparatively greater width is available, thus permitting a large hatch area of similar opening. When containers are to be carried as deck cargo, a procedure which involves difficulties in vessels having vertical sides, the present hull affords a substantial measure of stability to the ship. This results in a significant reduction in the period of rolling or pitching of the vessel under different loading conditions, particularly where high-speed cargo liners are being used.

Furthermore, the height of the double bottom tank of the hull may be significantly reduced, consistent, of course, with inspection requirements, since the necessary tank volume can be provided by the side tanks which are fitted amidships. If desired, one pair of these side tanks can be constructed and utilized as roll-damping tanks. Because the internal tank sides are vertical, the reception and handling of containers in general cargo ships is greatly facilitated by the present invention. As a matter of fact, the trapezoidal-chine hull makes it possible to use a bulk cargo ship either as an ore ship or an oil ship.

Any weakening of the double bottom as far as longitudinal strength is concerned, due to the reduction in its height, is more than compensated for by the box-beam construction of the side tanks. In fact, this structural distribution affords a resistance to torsion which is better than that of known open-hull vessels.

Additionally, the bracing arrangement and the described structural form result in a reduced depth of penetration during a collision due to the great energy required to deform the structure. At the same time, the reserve buoyancy is in fact increased by the presence of the aforementioned fore and aft internal bulkheads. The protection of the propulsion unit, especially when a nuclear unit is employed, is also maximized by the present space distribution arrangement.

The angle of inclination of the slanting or inclined sides of the hull can, of course, be varied in order to achieve optimal design for various ships. The particular variation would depend upon the parameters of the desired overall ship-form, particularly upon the ratio of breadth to draft. Normally however, the angle of inclination will preferably be within the range of 50 to Moreover, for the great majority of vessels, the optimum angle of inclination would be 65'. This would apply when the ratio of breadth to draft is approximately 2.5 (regarding the definition of breadth see column 5, line 65).

When the angle of inclination is within the aforementioned range, the trapezoidal-chine hull can be maintained over most of the length of the vessel. Since this particular hull-form minimizes alterations or fluctuations in both im mersion and trim consequent upon variations in loading, this specific construction can be said to be optimal for a vast majority of the vessels which would normally be in service.

Another particular feature of the invention resides in the fact that a hull design is provided in which the parameters can readily be determined mathematically, particularly for the underwater portion of the hull. Accordingly,

the portion of the hull below the juncture should, over the major part of the vessels length and/or surface, satisfy (in a fore and aft section) the equation:

where x xx and Z is the zero point of a section. The zero point lies in the middle of the ship, preferably in a plane determined by the outer line of the juncture just above the loaded waterline. Each section of the vessel between adjacent hull frame members will then be of approximately trapezoidal volume.

The forward end of the vessel should preferably be provided with a forecastle which is constructed so as to reduce the depth of penetration when the ship is in a collision, without impairing the seaworthiness of the vessel. Moreover, the ship should be provided with a bulbous bow. The stern of the ship should preferably be of triangular square-stern configuration.

It is apparent therefore, that the total approach of the present invention has succeeded in effectively solving the many problems heretofore associated with hull design. The trapezoidal-chine hull allows a shipbuilder to fully achieve the desirable objectives of economy and speed of construction, stability and maneuverability under Way, whether in smooth water or on the open sea, quick turnaround and ease of cargo handling while in part, and an efficient overall operating procedure, while simultaneously enhancing the safety of the vessel.

In addition to the advantages mentioned above, other advantages will become apparent in the more detailed description of the invention which follows; reference will be made to the accompanying drawings in which:

FIGURE 1 is a front view of the trapezoidal-chine hull of the invention, depicting the three-chine embodiment;

FIGURE 2 is a view of the stern of the hull of FIG- URE 1;

FIGURE 3 is a transverse cross-section taken amidships through the trapezoidal-chine hull of FIGURE 1, and includes a showing the T-shaped cross-section internal loading space of the ship;

FIGURE 4 is a bottom half-plan view of two adjacent sections of a trapezoidal multi-chine hull;

FIGURE 5 is a perspective schematic view of the halftrapezoidal outline of a volumetric hull section between adjacent hull frame members, illustrating the co-ordmate system employed and the meaning of the symbols in the previously expressed equation;

FIGURE 6 is a front view of a two-chine modification of the invention; and

FIGURE 7 is a front view of a second modificatlon of the invention, depicting a trapezoidal hull with a single chine.

Detailed description of the invention Referring to FIGURE 1 of the drawings, a front view of the trapezoidal multi-chine hull is shown, including the outline of successive transverse hull sections of the forward portion of the ship, The plane of the centerline of the vessel is indicated at 10 and the fore end of the vessel (which is generally indicated at 12) comprises a trapezoidal hull-form 14. The hull-form is substantially trapezoidal in transverse or cross-section. Depending upon the parameters of the ship shape, particularly the ratio of breadth to draft (the breadth being measured at the midship section of a conventional ship shape with an angle of 90 whereby its area corresponds to the area of the trapezoidal multi-chine hull), the inclined or slanting sides 16 are inclined at an angle a which is preferably within the range of 5080, to the horizontal; the optimal inclination is 65, particularly when the ratio of breadth to draft is 2.5. In FIGURE 1 contrary to FIGURE 6 and FIGURE 7 this angle of inclination is identical throughout the minor portion of the length of the trapezoidal chine hull. Thus, the outlines of the slanting shipside 16 are in most of the transverse sections not parallel to one another. At the turn of the bilges, generally indicated at 24, the hull-form is provided with three chines, 26, 28 and 30. A chine is normally defined as a longitudinal member lying along the bilge at a given point. The bilge is generically defined as that portion of the ships bottom lying between the flat bottom and the sides of the ship.

The loaded waterline of the ship is designated at 32. Located above, but closely adjacent to the loaded waterline 32 is a juncture 34 which extends continuously or entirely around the hull-form. Juncture 34 indicates the point at which the inclined or slanting shipsides 16 changes its angle of inclination with the horizontal (or with the water) and assumes a substantially-vertical orientation with respect to the horizontal. This is generally indicated at 36 in the drawings. While the shipside is approximately vertically-oriented entirely around the hull, it is oriented at exactly 90 to the horizontal in the midships section. The hull is provided with the normal weather-deck 40, the forward portion of the ship being provided with an upstanding forecastle generally indicated at 42, which is covered by the forecastle deck 44.

Referring to FIGURE 2 of the drawings, a view of the stern of the hull of FIGURE 1 is depicted. Here the numerical designations are substantially identical to those of FIGURE 1, except that the three chines are indicated at 46, 48 and 50. Also, it will be noted that the stern 52 is a triangular square-stern.

Turning now to FIGURE 3 of the drawings, a transverse midships section taken abaft the beam through the hull of FIGURE 1 is shown. This view illustrates the internal loading spaces of the ship. As in FIGURES l and 2, the slanting sides of the multi-chine trapezoidal hull are generally indicated at 14. Two of the chines are shown, that is, chines 26 and 28. Juncture 34 is shown, as is the vertical shipside amidships (which is indicated at 36). The weather deck 40 is also depicted.

The ships bottom has an outer skin 60 and an inner skin 62, between which is located a conventional bottom tank 64. At each side of the vessel within the hull, a vertical fore and aft bulkhead 66 extends upwardly from the turn of the bilges adjacent chine 26, terminating at a point which lies on a horizontal plane through juncture 34. Bulkhead 66 combines with deckplate 68 and the slanting hull-skin 16 of the trapezoidal-chine hull to define a pair of side tanks 11. Side tank 11 serves not only as a fuel tank or the like, but can also serve as a roll-damping tank. Moreover, side tank 11 provides a box-beam construction along each side of the vessel, which greatly increases its torsional strength.

Consequently, the side tanks 11 together with the inner skin 62 and the upper decks, such as Weather deck 40, define an internal space-distribution arrangement generally indicated a 13 which is T-shaped in cross-section. The space is well adapted to receive cargo of any kind, including both large and small containers, as well as a propulsive unit, crews quarters and so forth.

FIGURE 4 of the drawings depicts a bottom half-plan view of two adjacent sections of the trapezoidal multichine hull. It should be noted that the plan view shown is first of all a half-plan taken above the ships centerline 10, and secondly a half-plan taken about the midship section 70. The line of the chines are indicated at 72 and 74. The plan view of FIGURE 4 is a typical waterlines plan of a part of the forebody according to FIGURE 6, the outline of the vertical shipside of the middle body section immediately forward of the midship section 70 is indicated at 76, and the outline of the vertical shipside of the hull section immediately forward thereof is indicated at 82. The outer skin at the loaded waterline of the first-called hull section has been indicated as 78, while the skin of the section forward of 78 is indicated at 84. The outer skin at waterlines 80 and 86 is designated in the same manner. It is thus apparent that ultimately the outer skin joins the chine 74 at a point 7 which has been designated 88 in FIGURE 4 of the drawlngs.

Referring now to FIGURE 5 of the drawings, a perspective schematic view of a half-trapezoidal outline of a hull section between adjacent hull-frame members is depicted. It is apparent from the drawing that the section is three-dimensional in nature. The ships centerline is indicated at 10. One of the features of the instant invention resides in the fact that a hull design is provided in which the parameters can readily be determined mathematically, particularly for the underwater portion of the hull, As mentioned previously, the angle of inclination of the slanting external hull can be varied in order to achieve an optimal result in any specific vessel. Normally, the angle of inclination will preferably be within the range of 50-80 and for the great majority of vessels the optimum angle of inclination would be 65. The latter condition would apply when the ratio of breadth to draft is approximately 2.5.

Returning to a consideration of FIGURE of the drawings, the cordinates x, y and z are shown, as well as the related symbols x and x y y and and Z1. These symbols collectively designate the various components of the three dimensional section such as its length, Width, and height. Accordingly, in the preferred embodiments of the trapezoidal-chine hull, the underwater body below the continuous juncture 34 should satisfy the equation:

yrl/o ?/0 'J0 where x xx and Z is the zero point of a section. The zero point lies in the middle of the ship, preferably in a plane determined by the outer line of the juncture just above the loaded waterline. Each section of the vessel between adjacent hull-frame members will then be of approximately trapezoidal volume.

FIGURES 6 and 7 of the drawings depict two modifications of the basic concept of the invention. FIGURE 6 is a front view of one half of the forebody. It will be noted that the vessel of FIGURE 6 is similar to that depicted in FIGURE 1 except for the facts that two chines indicated at 90 and 92 in FIGURE 6 are employed rather than three and that the angle of inclination of the hull frames is identical throughout the major portion of the length of the trapezoidal chine hull. Thus, the outlines of the slanting shipside 16 are in most of the transverse sections substantially parallel to one another, as is shown by outlines 16, 17, 18, 19, 20, 21, 22 in FIGURE 6 of the drawings. Once again, the vessel has a slanted or inclined side 16, a loaded waterline 32, a juncture which extends continuously around the entire hull of the vessel, and a vertical shipside portion located amidships of the vessel. The vertical shipside 36 terminates at weather deck 40. The forward end of the vessel also possesses a forecastle 42, including a forecastle deck 44.

Referring to FIGURE 7 of the drawings, a second embodiment of the basic concept is depicted. Again, many of the reference numerals employed in FIGURE 7 are identical to those of FIGURE 6. In this embodiment however, there is only one chine 94. As mentioned previously, the basic concept of the present invention will satisfactorily solve the hull design problem regardless of whether one, two or three chines are employed in any given vessel hull. The choice as to how many chines will be employed will depend upon the specific environment in which the vessel is used.

The forward end of the vessel should preferably be provided with a forecastle which is constructed so as to reduce the depth of penetration when the ship is in an impact or collision, without impairing the seaworthiness of the vessel. Additionally, the ship should also be provided with a bulbous bow. The stern of the vessel should preferably be of a triangular square-stern configuration.

The trapezoidal chine hull according to the present invention allows a vessel to be constructed rapidly and in an economic manner. It also ensures stability and maneuverability under way, whether in smooth water or on the open sea. Another important feature of the invention is that quick turn-around and ease of cargo handling while in port are achieved. Furthermore, all of the foregoing features can be attained while simultaneously enhancing the overall safety of the vessel, due to the inventive aspect of the trapezoidal-chine hull.

Although the trapezoidal chine hull for displacement ships has been described with reference to a particular embodiment, it will become apparent to those skilled in the art that variations can be made in the hull. All such variations as would be obvious to those skilled in this art are intended to be included Within the scope of this invention.

What I claim is:

1. A displacement ship comprising:

a trapezoidal-chine hull which is substantially trapezoidal in transverse section, said hull including at least one chine located at the turn of the bilges of said ship,

said hull having inclined sides extending upwardly from bow to stern of said ship,

a juncture positioned above the uppermost extremity of each of said inclined sides,

said juncture extending continuously around said hull above the loaded waterline of said ship,

said juncture joining said inclined sides to a substantially vertically-oriented shipside which is superadjacent to said juncture, and

internal fore and aft bulkheads extending upwardly at each side of said ship from a point adjacent to the turn of the bilges to a point which lies on a horizontal plane through said juncture, such that an internal loading space of substantially T-shaped cross-section is formed in said ship.

2. The displacement ship of claim 1 in which a pair of internal fore and aft side tanks are defined within said ship by said bulkhead, said inclined sides, and a pair of deck plates, said deck plates lying in the horizontal plane of said juncture between the respective uppermost extremities of said bulkheads and said inclined sides.

3. The displacement ship of claim 2 in which said side tanks function as roll-damping tanks in order to afford increased stability to said ship. I

4. The displacement ship of claim 2 in which said side tanks provide a box-beam construction along each side of said ship, in order to afford increased torsional strength to said ship.

5. The displacement ship of claim 1 wherein the ratio of breadth to draft is 2.5, and the angle of inclination of said inclined sides is 65.

6. The displacement ship of claim 1 in which said juncture is above but closely adjacent to said waterline.

7. The displacement ship of claim 1, having at least two chines located at the turn of the bilges.

8. A displacement ship of claim 1, having three chines located at the turn of the bilges.

9. The displacement ship of claim 1 in which the midships segment of said substantially vertically-oriented shipside is oriented at a right angle with respect to the plane of the water.

10. The displacement ship of claim 1 wherein the angle of inclination of the inclined sides of the trapezoidal chine-hull with respect to the horizontal is in the range of 50-80.

11. A trapezoidal-chine hull for a displacement ship comprising:

a hull-form including at least one chine located at the turn of the bilges;

said hull-form having lower inclined side walls and upper substantially vertically-extending side walls with the juncture between said side walls forming a continuously extending chine above the design water line of said hull-form;

said hull-form for the greater part of its length defining a series of upper and lower volume portions which are above and below said continuously extending chine respectively.

each of said upper volume portions, defined by said hull-form, being substantially trapezoidal in horizontal cross-section and substantially rectangular in transverse vertical cross-section;

each of said lower volume portions, defined by said hull-form, being substantially trapezoidal in horizontal cr0ss-section and substantially trapezoidal in the transverse section halfplane; and

internal fore and aft bulkheads extending upwardly at each side of said hull-form from a point adjacent the References Cited FOREIGN PATENTS 348,822 5/ 1931 Great Britain. 404,603 1943 Italy. 906,734 5/ 1945 France.

ANDREW H. FARRELL, Primary Examiner

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