US3060972A - Flexible tube structures - Google Patents

Description

Oct. 30, 1962 G. J. SHELDON 3,060,972

FLEXIBLE TUBE STRUCTURES Filed Aug. 22, 1957 3 Sheets-Sheet 1 IO F16. l

INVENTOR.

GILBERT J. SHELDON BY fifl-mak ATTORNEXS Oct. 30, 1962 G. J. SHELDON 3,050,972

FLEXIBLE TUBE STRUCTURES Filed Aug. 22, 1957r 3 SheetsSheet 2 74 INVENTOR.

Gl LBERT J. SHELDON ATTORNEYS Oct. 30, 1962 G. J. SHELDON 3,060,972

FLEXIBLE TUBE STRUCTURES Filed'Aug. 22, 1957 s Sheets-Sheet s INVENTO GILBERT J. SHEL N BY M A TTORNE'YS United States Patent Office 3,060,972 Patented Oct. 30, 1962 1 3,060,972 FLEXIBLE TUBE STRUCTURES Gilbert J. Sheldon, Irondequoit, N.Y., assignor to Bausch & Lornb Incorporated, a corporation of New York Filed Aug. 22, 1957, Ser. No. 67%,566 Claims. (Cl. 138-120) The present invention relates to flexible tube structures and particularly to a tube structure the flexing of which may be controlled both to its extent and in its radius of curvature.

The present invention is particularly adapted for endoscopic devices which heretofore have been restricted in bending in only one direction and to a single extent and radius of curvature. In the use of the present day endoscope for viewing the walls of a cavity of the human body, it has been necessary to reposition the endoscope a number of times into the cavity in order to examine even a portion of the cavity walls, all at great discomfort to the patient. Since the endoscopes currently being utilized have restricted flexing capabilities, complete viewing of the walls of the cavity has been impossible.

The flexible tube of the present invention is also capable of being utilized as a housing for an optical system for other purposes, such as, for viewing remote objects around corners or in other inaccessible places. When suitably encased with a plastic or rubber sheathing, the present invention may be adapted for underwater usage wherein movement of the submerged end may be effected by suitable controls located at the dry end. The present invention is also adapted to support a tool at its working end so that manipulation of the tool can be accomplished at the remote control end thereof.

In any of its many uses, the flexible tube structure of the present invention may be easily disassembled and reassembled if it is desired to lengthen or shorten the structure or to condition the structure for a predetermined radius of curvature. As a housing for any number of working tools such as an optical system for endoscopic use, the structure may be opened up, so to speak, for permitting any modification, removal or insertion of the optical system or part thereof. Various elements of the tube structure itself may be interchanged or replaced, added or removed. In its essence, the present tube structure is composed of various building blocks which may be built up in various arrangements for a number of purposes.

The primary object of the present invention is to provide a flexible tube structure the flexing of which is adapted to be controlled both as to extent and radii of curvature.

Another object of the invention is to provide a flexible tube structure which may be used for supporting working tools and for controlling manipulation thereof.

Still another object of the invention is to provide a flexible tube for endoscopic devices or other examining instruments which is simple in structure, economical to manufacture and maintain, and capable of being modified with a minimum amount of effort.

These and other objects and advantages reside in certain novel features of construction, arrangement and combination of parts as will hereinafter be more fully described, pointed out in the appended claims and will appear when taken in conjunction with the drawing wherein:

FIG. 1 is a side elevational view of one form of the flexible tube structure constructed in accordance with the invention;

FIG. 2 is a side elevational view of the details of the structure of FIG. 1, parts being in section for better illustration and showing various shapes that the structure may assume;

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a fragmentary perspective view of a portion of the tube structure illustrating the manner in which the structure is assembled and arranged for receiving tools therein;

FIG. 5 is an exploded perspective view of one of the tube sections showing the component parts thereof in greater detail;

FIG. 6 is a side elevational view of another form of the flexible tube structure;

FIG. 7 is similar to FIG. 6 but illustrates some of the various shapes the tube structure may assume;

FIG. 8 is a cross-sectional View taken along line 8-43 of FIG. 6;

FIG. 9 is a side elevational view, parts being in section, of another modified form of the present invention;

FIG. 10 is an exploded perspective view of the structure shown in FIG. 9;

FIGS. 11 and 12 are similar to FIG. 9 but illustrate successive flexing of the tube structure; and

FIG. 13 is a plan view of a modified tube section.

Referring now to the drawings, and more particularly to FIGS. 1-5, there is shown a flexible tube structure generally indicated by thereference numeral 10 and comprising a plurality oftube sections 12 arranged in an end to end relationship. As shown in FIGS. 3 and 5, each of thetube sections 12 is composed of two identicalsemi-circular elements 14, 16, each of which is formed with a pair of axially spaced connectinglugs 18 at one end and asingle lug 20 at the other end. When theelements 14, 16 are joined together to form a single tube section, thelug 20 of each of the elements is retained between the twolugs 18 of the other element. Thelugs 18 and 20 are suitably shaped so that when the elements are joined, the outer surface of thetube section 12 is unbroken and conforms with the surrounding circular surface. As shown in FIGS. 2 and 3, thelugs 18 and 20, when interlocked, form continuous transverse thickened portions or ridges which extend radially inwardly slightly from the circumference of the tube section and are diametrically opposed.

A similar pair ofridges 22 are formed on the inner wall surfaces of the tube sections and these are arranged in diametrically opposed positions at about a displacement from the ridges formed by thelugs 18 and 20. Each of the ridges is formed with openings which in the present embodiment are in the form ofapertures 24, 26, respectively, and in the case of thelugs 18 and 20, theapertures 24 extend in axial alignment when theelements 14, 16 are joined together, as shown in FIGS. 1 and 2.

Theapertures 24 in each of the tube sections are adapted to accommodate aflexible cable 28 which extends through the length of thetube structure 10. Similarly, theapertures 26 are adapted to accommodate anotherflexible cable 30. It will be apparent that when thetube sections 12 are arranged in axial alignment as shown in FIG. 1, theapertures 24 of each of the tube sections are in axial alignment with the corresponding apertures in the preceding tube section and theapertures 26 of each of the tube sections are in axial alignment with the corresponding apertures in the preceding tube section.

One end of each of thecables 28, 30 may be directly secured to theterminal tube section 32 or connected indirectly thereto by means ofsuitable sleeves 34 which are made small enough to be swaged upon the ends of the cables and may be suitably welded to thesection 32. The other ends of thecables 28 are similarly encircled bysleeves 36 with the ends swaged thereto. Acoil spring 38 encircles each of thecables 28 and is held in com- 3 pression between thesleeve 36 and the adjacent tube section. Thecables 30 may be connected together and held taut around a suitable control pulley, this structure being shown in FIG. 7 and will be described hereinafter.

A plurality of spacerannular elements 40 which may be in the form of washers or sleeves are positioned on the cables between some of the tube sections and for purposes of this invention, such washers or sleeves are utilized in that portion of the tube structure where flexing thereof is desired. As shown in FIG. 1, the flexed portion of thetube structure 10 is provided with these annular elements. To complete the structure of the embodiment of FIG. 1, theentire structure 10 may be suitable covered with a rubber orplastic sheathing 42 which would provide a smooth and continuous finish for the structure and perm-it the use of the structure in water or other moist surrounding without aifecting the elements of the structure.

In operation, a pulling force exerted upon one of thecables 30 will produce flexing of the terminal portion of the tube structure, or that end illustrated in the righthand portion of the structure of FIG. 1. The amount or extent of flexing is controlled by the amount of force exerted upon thecable 30 and it is possible to flex this end of the structure until the same assumes substantially the shape of a complete circle. A desired radius of ourvature or any change thereof is determined by the axial length of theannular elements 40, and in the case of washers, this would be determined by the thickness thereof, and in the case of sleeves, by their length. If a large radius of curvature is desired, washers or sleeves having short lengths should be utilized, and in the event a sharp flexing, or one having a small radius, is desired, sleeves having relatively long lengths should be utilized. This relationship is illustrated in FIG. 2 wherein use of thelarge sleeves 44 has permitted a sharp flexing of the tube structure andsmall sleeves 46 have permitted only a slight flexing. Any other desired shape of the flexed portion of the tube structure may be planned by simply using various sizes of spacer washers or sleeves.

Radii of curvature may also be varied by utilizing tube sections having other axial dimensions. In the embodiment of FIGS. 1-5, the tube sections are relatively wide, that is, their axial dimensions are long when compared to the embodiments shown in FIGS. 6-l3. In FIG. 2, if the tube sections were replaced by ones having a smaller width, or in fact, by a tube section which is in the form of a plate, the flexing would even be sharper if the same number of tube sections are used. On the other hand, if a greater number of these plates or narrow tube sections are used, the radii of curvature are progressively increased. Therefore, the width of the tube sections, whether they be in the form plates or a size similar to that shown in FIG. 2, or the number of these tube sections utilized, will each contribute to the control of the raddi of curvature.

For purposes of further description thecables 30 are considered as control cables while thecables 28 are to be treated as tying cables. A pulling force exerted on either of thecontrol cables 30 will flex the cable :in the plane defined by both the cables 34) and, thecables 28 will retain the tube sections to maintain the length of thetube structure 10, along its axis, which during flexing will assume the form experienced by thecables 28, substantially constant. During a flexing operation, the coil springs 38 serve as override mechanism and to assist in maintaining the length of the tube structure, along its axis, substantially constant. If thespacers 40 were perfectly rounded at their ends and of a predetermined radii of curvature, there would be no necessity for the coil springs 38 since, no matter what shape or form the tube structure assumes, its axial length would never vary and theanchor sleeves 34, 36 for thecables 28 would be suflicient for maintaining the length of the tube structure constant. However, since there is no need in the present invention for perfectly machined parts, the coil springs 38 cooperate with theanchor sleeve 36 to permit slight changes in the length of the tube structure if the occasion arises. Any change in length will be extremely small and will be caused solely by the inaccuracies of the various elements of the tube structure especially in thespacers 40. Thus, the tube sections are constantly held together during flexed or non-flexed conditions of the tube structure and the constant length of the tube structure may be attributed to theanchor sleeves 36 which are swaged to the ends of thecables 28 or to the use of thecoil spring 38 in conjunction with thesleeve 36.

It will be apparent that thetube structure 10 is capable of moving theterminal section 32 in a relatively wide arc with the radius of curvature thereof struck from a point between the last tube section which does not flex and the adjacent tube section which does flex, such point being illustrated in FIG. 1, at 48. For endoscopic use, this characteristic has the particular advantage in that different parts of a cavity under inspection may be viewed without the necessity of continual withdrawal of the tube structure and rotation thereof during inspection.

Another advantage of the present invention is the simplicity of assembly and the arranging of worktools within the tube structure. In FIG. 4, a portion of the tube structure is illustrated with one of the tyingcables 28 removed and the individual tube sections opened up, so to speak. To accomplish this, one of the cables. 28 is disengaged from itsanchor sleeve 34 and pulled through thelugs 18, 20, whereupon one of theelements 14, 16 in each tube section is pivoted about the remaining tyingcable 28. With all of the tube sections in this position, any desired optical system or other equipment may be installed, modified or replaced in the interior of the tube structure.

The present invention is also adapted to serve as a flexible control linkage for a tool which may be conveniently mounted at theterminal tube section 32 thereof. In an arrangement of this sort, thetube structure 10 would serve as a remote control linkage for the tool and would provide a flexible housing for any electrical wires, hoses, flexible shafts, etc. for the tool.

The embodiment of FIGS. 6-8 is similar to that of FIGS. 1-5 and differs therefrom only in compounding the various functions of the latter. The tube structure comprisestube sections 50, 52 which for purposes of illustration, are shorter in axial length than the sections shown in FIG. 1. Theupper portion 54 of the tube structure includes thetube sections 50 of the same structure as the tube section illustrated in FIG. 3, however, thelower portion 56 includes thetube sections 52 having a structure of the cross-section as .shown in FIG. 8.

Each of thesections 52 is provided with two pairs of diametricallyopposed apertures 58, 60 which are similar toapertures 24, 26, respectively, shown in FIG. 3. Thetube sections 52 also include another pair ofapertures 62 which are diametrically opposed with respect to each other but in close adjacency with theapertures 60. Thesections 50, 52 also include the interlocking lugs which are provided on thetube sections 12 thus permitting easy assembly and opening up of the tube structure of FIG. 6.

A pair of tying cables 64- is threaded through the pairs ofapertures 58, respectively, with one end of each of the cables secured to a terminal tube section of theupper portion 54 and the other ends swaged or otherwise secured to sleeves 66. coil springs 68 are held in compression between the sleeves 66 and theadjacent tube section 70 and serve the same purpose as does thespring 38 in the embodiment of FIG. 1. As in the previous embodiment,annular elements 72 in the form of spacer washers or sleeves are provided between some of the tube sections for both upper andlowe portions 54, 56, depending, as previously described, on the amount of flexing desired. In FIGS. 6 and 7, it will be noted that the lengths of the sleeves for the upper portion are greater than those of the lower section.

A pair ofcontrol cables 74 are threaded through theapertures 60, respectively, in thelower portion 56 and the ends of these cables are secured at 76 to thetube section 78 which is the terminal section for theportion 56. Another pair ofcontrol cables 80 are threaded through theapertures 62 and then extended through bothportions 54, 56 of the tube structure. In FIG. 7, the terminal ends of thecables 80 are secured at 82 to theterminal section 84 of theportion 54.

The other ends of thecables 80 remote from its ter minal ends are joined together and looped around apulley 86 which is suitably connected to acontrol knob 88 by ashaft 90. Similarly, the ends of thecontrol cables 74 remote from its terminal ends are joined together and looped around apulley 92. Asuitable knob 94 is rigidly connected to thepulley 92 for imparting rotation thereto.

In operation, rotation of theknob 88 in either direction will correspondingly impart a pulling force to one of thecables 80 and release, correspondingly, tension in the other cable. Such a pulling force will flex theupper portion 54 while thelower portion 56 remains straight. it it is desired to extend the terminal end of the tube structure at different radii of curvature, theknob 94 may be rotated in the same direction as the rotation of theknob 88, as shown in FIG. 7. The apparatus may assume other shape or conditions of flexing depending upon the extent and manner desired. For example, from the condition shown in FIG. 7, theknob 88 may be rotated in order to straighten theupper portion 56 resulting in two straight sections separated by a flexed portion. Theknob 88 may be rotated in the complete opposite extreme so that the upper portion is curved oppositely to that shown. In this case, the tube structure would assume an S-shape.

In the embodiment of FIGS. 9-13, thetube sections 100 are shown to be thin plate-like units as compared to the tube sections in the previous embodiments. It will be understood that this diflerence is merely for illustration purposes and that the tube sections for all of the embodiments may be of any desired length. Similarly, thetube sections 100 may be composed of two interlocking semi-circular ring elements, such as shown in FIG. 5. The advantage of the thin type of section is that in the use of a great number of the sections for a relatively short radius of curvature, the flexed tube structure will assume a more perfect smoothly curved structure rather than a many-sdided arc which results when the tube sections are long, such as shown in FIG. 1.

Each of thetube sections 100 is formed with a pair ofopposed openings 102 in the form of round apertures and a pair ofopposed openings 104 in the form of slots. Theapertures 102 receive a pair ofcontrol cables 106, respectively, and these may be suitably anchored on the terminal tube section (not shown). The other ends of thecables 106 may be connected together and arranged around a pulley in much the same fashion as in the previous embodiment.

The present embodiment differs from the previously described embodiments in the use of flexure strips, preferably of spring material, instead of tying cables andcoil springs 38, 68. A pair of resilient flexure strips 108 having spaced notches or cut-outs 110 andspacer portions 112 therebetween is adapated to be received in theopenings 104, respectively. To provide the tube struc ture with flush external and interior surfaces, the width of thestrips 108 is made equal to the width of the tube sections and the depth of theopenings 104 made equal to the portion of the strips above thenotches 110 which in turn will receive the portion of the tube sections below theopenings 104. The entire tube structure shown in FIGS. 9l2 may be encased in a rubber or plastic jacket or sheathing 114 which serves to maintain the flexure strips 108 in proper relationship with respect to the tube sections. It will be appreciated that the present embodiment is rather easy to assemble or disassemble, requiring only the holding of the tube sections and the insertion or removal of the strips 103 from their respective positions. The unique advantage in using a spring flexure strip instead of cables is that twisting of the tube structure is minimized or eliminated in the event that a relatively heavy tool is associated therewith either internally or mounted at the end.

The amount of flexing of the tube structure shown in FIGS. 912, depends upon the length of thespacer portions 112 and/ or the length of thetube sections 100, such requirements being determinative for the variance of flexing in the embodiments of FIGS. 1 and 6. If longer tube sections are to be utilized, the notches would be correspondingly longer. In FIGS. 11 and 12 there is shown, in step sequence, the progress of flexing when a force is exerted upon one of thecables 106. This progress would hold true for all of the embodiments of the invention. The force would initially flex the flexure strip portions between the two end tube sections until one end of the terminal tube section abuts the first succeeding section whereupon the continuing force will flex the flexure strip portions between the first succeeding section and the next succeeding section, and so on, until the desired amount of curvature is attained.

By having thenotches 110 interlockingly engaged with a corresponding slot, the tube sections are held from displacement along the axis of the tube structure. Consequently, this engagement erves to retain the tube sections to maintain the length of the tube structure along its axis substantially constant. If a permanent arrangement is desired, a notched flexure strip may be dispensed with and one having continuous edges could be threaded through theslots 104. A weld may then be applied to every juncture of the strip with a tube section.

In FIG. 13, there is shown an oval tube section having thickened portions on two sides thereof which may be substituted for the circular tube sections of the structure shown in FIG. 9. The advantage in the use of the oval tube section when the tying flexible element, whether it be a cable or flexible strip, is associated with the ends of the section having the greater diameter, is that there is less tendency for the tube structure to twist while being flexed, which may occur if the tying flexible elements are not sufficiently taut or the parts are loosely fitted. This has particular advantage for a device similar to the structure shown in FIG. 6 wherein there is a tendency for the structure to twist when a force is exerted on thecables 80. The twisting here would be occasioned because of the ofl center location of theopenings 62 for thecables 80. Since one of theopenings 62 is closer to one of theopenings 58, a torque will be developed tending to twist the structure when the cable is pulled. In the use of an oval tube section, the tying flexible element has a greater moment arm, that is, the distance between the element and the axial center of the tube section, than the moment arm for the control cable. Therefore, the cable may be located off-center somewhat and its use thereof will not affect the alignment of the tube structure.

From the foregoing description, it will be appreciated that the present invention provides a flexible tube structure which may be flexed in a controlled manner, both as to extent and as to its radii of curvature. The flexible tube structure may be easily disassembled and reassembled, may be shortened or lengthened and may serve as a housing or a flexible support for various tools. While only specific assemblies are illustrated and described, it will be understood that this is for brevity only and that various other arrangements may be utilized. For example, the embodiment of FIG. 6 may be compounded into any number of individual flexing portions requiring only the addition of more openings and control cables for the additional portions. It will be understood that all of the tube sections in any of the embodiments may be oval in cross-section. While not illustrated, the tube sections for any of the embodiments may include many openings in order to accommodate control wires, or cables for tools, housed within the tube structure or at the end thereof. These openings as well as those for the various flexible elements described may be made in thickened protruding portions of the tube sections such as those shown in FIGS. 3 and 8 or in the walls of the tube sections such as shown in FIG. 13. These and many more modifications and arrangements of the present invention may be made or employed without departing from the spirit or scope of the appended claims.

I claim:

1. A flexible tubular structure comprising, a plurality of tubular sections arranged in end-to-end relationship, spacer means defining longitudinal openings positioned diametrically opposed to each other and pivotally positioning said tubular sections relative to each other, a plurality of openings in said tubular sections each of which is aligned with corresponding openings on the preceding tubular section to form at least two pairs of aligned openings extending longitudinally of the tubular structure, a first pair of cables extending through one of said pairs of openings, a second pair of cables extending longitudinally through the second pair of openings in said tubular sections and the longitudinal openings in said spacer means, means securing one of the ends of each of said first pair of cables to the tubular section adjacent to the ends or" said cables, means securing the other ends of each of said first pair of cables and one end of each of said second pair of cables tothe tubular section adjacent said other ends of said first pair of cables, whereby a pulling force exerted upon either cable of said second pair of cables will produce a flexing of the tubular structure.

2. A flexible tubular structure comprising, a plurality of tubular sections arranged in end-to-end relationship, spacer means positioned diametrically opposed relative to each other and pivotally positioning said tubular sections in spaced relation to each other, each of said tubular sections consisting of two semi-circular ring elements interlockingly connected at their respective ends, a plurality of openings formed in said tubular sections each of which is aligned with the corresponding openings of the preceding tubular section to form at least four series of aligned openings extending longitudinally of said tubular structure, two of said series of openings extending through connecting ends of said ring elements, said spacers positioned between adjacent ends of said tubular sections one at each of the connecting ends of the tubular sections in axial alignment with openings therethrough, a first pair of cable strung through the series of openings which extend through the interconnecting ends of the ring elements, and the spacers associated therewith, a second pair of cables strung through the second of said series of two aligned openings, means securing the first ends of each of said first pairs of cables to the tubular section adjacent said ends, means securing the second ends of each of said first pair of cables to the tubular section adjacent said other end of said first pair of cables, means securing the first ends of said second pair of cables to thereby permit flexing of the tubular structure upon exerting a pulling force upon one of said second pair of cables.

3. A flexible tubular structure comprising, a plurality of tubular sections arranged in end-to-end relationship, a plurality of spacer elements diametrically disposed to pivotally position said tubular sections in spaced relation, a plurality of openings in said tubular sections axially aligned with the corresponding openings of the preceding tubular section to form at least four series of aligned openings extending longitudinally of the tubular sections, a plurality of openings extending longitudinally through said spacer elements, said spacers positioned between the adjacent ends of said tubular sections in axial alignment with a pair of the openings therein, a first pair of cables strung through the series of openings which extend through said spacers associated therewith, a second pair of cables strung through the second two of said series of aligned openings, means securing the common ends of said cables to the section adjacent the ends of said cables, means tensioning the opposite ends of said cable extending through said spacers, thereby permitting a pulling force exterted upon either side of said second pair of cables to produce a flexing of the tubular structure.

4. A flexible tubular structure comprising, a plurality of tubular sections arranged in end-to-end relationship, a plurality of angularly spaced axial passages in said tubular sections each of said passages axially aligned with corresponding passages of adjacent tubular sections to form at least two pairs of aligned openings extending longitudinally of the tubular structure, two spacers positioned between adjacent ends of said tubular sections to pivotally position said tubular sections in spaced relation relative to each other, an arcuate surface on the engaging ends of said spacers to permit said tubular sections to roll on the arcuate surface of said spacers when said tubular sections are flexed relative to each other, a first pair of flexible elements extending through one of said pairs of openings and said spacers associated therewith for tensioning said tubular sections, a second pair of flexible elements extending through a second pair of openings in said tubular sections, means securing one of the ends of said second pair of flexible elements to the adjacent tubular section whereby a pulling force exerted on one of said second pair of flexible elements will produce a flexing of the tubular structure.

5. A flexible tubular structure comprising, a plurality of tubular sections arranged in end-to-end relationship, a plurality of openings extending longitudinally through each of said tubular sections each of which is aligned with the corresponding opening of the adjacent tubular section to form at least two pairs of aligned openings extending longitudinally of the tubular structure each of said pairs being diametrically opposed, a first pair of flexible elements extending through said firs-t pair of openings, a second pair of flexible elements extending through the second pair of axially aligned openings, spacer means positioned between adjacent ends of successive tubular sections and arranged in the plane defined by said first pair of flexible elements, said spacers pivotally positioning adjacent tubular sections relative to each other, means preventing movement of the portions of said flexible elements adjacent the end tubular section of the tubular structure, means preventing movement of the portions of said first pair of flexible elements adjacent to the end tubular section relative to said first end section whereby a pulling force exerted on either of said first pair of elements will produce a flexing of the tubular structure about the spacer elements.

References Cited in the file of this patent UNITED STATES PATENTS 731,496 Pairier et al. June 23, 1903 944,830 Sussman Dec. 28, 1908 1,044,044 Hardesty Nov. 12, 1912 1,482,576 Myers Feb. 5, 1924 2,241,576- Barton May 13, 1941 2,498,692 Mains Feb. 28, 1950 2,540,141 Shafer Feb. 6, 1951 2,799,274 Eisenhut July 16, 1957 2,975,785 Sheldon Mar. 21, 1961 FOREIGN PATENTS 179,905 Austria Oct. 25, 1954 339,757 France Apr. 26, 1904 UNITED STATES PATENT. OFFICE CERTIFICATE OF CORRECTION Patent No. 3,060,972 October 30, 1962 Gilbert J. Sheldon It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 15, for "of", second occurrence, read in column 13,- line 13 for "suitable" read suitably line 49, for "plates" readplate line 52, after "form" insert of line 55, for "raddi" read radii column 5,line 48, for many--sdided" read many-sided line 64', for "adapated" read adapted column 7, line 53, for "cable" read cables Signed and sealed this 23rd day of April 1963.

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD. Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Non 3,060,972 October 30, 1962 Gilbert J. Sheldon It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 15, for "of",second occurrence, read incolumn 3, line 13 for "suitable read suitably line 49 for "plates" readplate line 52, after "form" insert of line 55, for "raddi" read radii column 5,line 48, for "many-sdided" readmanysided line 64, for "adapated" read adapted column 7, line 53, for "cable" read cables Signed and sealed this 23rd day of April 1963.

(SEAL) littest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents

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