US2684577A

US2684577A - Expansible pile-driving core

Info

Publication number: US2684577A
Application number: US295445A
Authority: US
Inventors: Edward A Smith
Original assignee: Raymond Concrete Pile Co
Current assignee: Raymond Concrete Pile Co
Priority date: 1952-06-25
Filing date: 1952-06-25
Publication date: 1954-07-27
Anticipated expiration: 1971-07-27

Description

July 27, 1954 E. A. SMITH 2,684,577

' W EXPANSIBLE FILE-DRIVING CORE Filed June 25. 1952 4 Sheets-Sheet 1 l I INVENTOR.

fowA o /4.-5M/7'H ATTO k/VEVS. 6 62 July 27, 1954 I s n- 2,684,577

EXPANSIBLE FILE-DRIVING CORE Filed June 25. 1952 4 Sheets-Sheet 2 INVENTOR. Eon/Aka 145 11. u

BY. f

A TOK/VE/J.

July 27, 1954 E. A. SMITH EXPANSIBLE FILE-DRIVING coRE 4 Sheets-Sheet 3 Filed June 25, 1952 INVEN TOR.

Ill-c;

IJlllll ED WARD 14.5/7/771.

July 27, 1954 I s n- 2,584,577

EXPANSIBLE FILE-DRIVING CORE Filed June 25, 1952 4 Sheets-Sheet 4 m 7 INENTOR. EDWARD A. J /TH.

Patented July 27, 1954 UNITED STATES 'ATENT OFFICE EXPANSIBLE PILE-DRIVING CORE Application June 25, 1952, Serial No. 295,445

9 Claims. 1

This invention relates to expansible mandrel or driving core constructions adapted for use Within pile shells for imparting impacts from a pile driving hammer to the interior portions of the shells.

Heretofore collapsible mandrel or driving core means of various types have been used for this purpose comprising a number of elongated leaves interconnected by mechanical linkages and other parts, the leaves being adapted to be forced radially outwardly into engagement with the interior walls or other parts of the pile shell. But such linkages and mechanisms become relatively complicated and heavy if so constructed as to be relied on to apply adequate expansion pressure to the leaves throughout and all along a lengthy core. Also, if the leaves are positively retained in their expanded positions by mechanical means, unless such retaining means are closely spaced, the leaves may become bent if the pile shells during driving meet obstructions causing inward crushing forces.

In efforts to avoid these difficulties, expansible driving cores have been proposed in forms having on the exterior thereof flexible means expansible by internal fluid pressure to frictionally engage the pile shells. But since such flexible means would be directly in contact with the interior surface of the pile shell, if the latter should become crushed or torn during the driving, then the fluid-containing flexible means would be injured or destroyed. Also the flexible fluid-containing means will be exposed to possibilities of excessive wear or cutting when the core is being handled during installation or removal. Another expedient has been to arrange the leaves each as a rigid structure of a segment-shaped cross-section, around a central flexible member expansible by fluid pressure, the leaves being retractable by springs upon deflation of the expansible member, but such an arrangement, aside from involving various complications, does not insure that the leaves will be held in their correct relative positions for proper frictional engagement all around the interior Walls of the pile shell to make possible the imparting of the forces of the hammer blows uniformly to various parts of the shell. Also with the central part of the core thus occupied by the expansible member, the latter prevents use of any dependable rugged centrally located means for positively retracting the leaves and for pulling the assembly out of the shell after the latter has been driven.

With the present invention, the above-noted difliculties are eliminated by providing a core having a plurality of the leaves arranged about a central space containing a pull-rod connected by linkage means to the several leaves and, in between each two adjacent leaves, an expansible member is located, which may be in the form for example of a length of readily available hose such as used for fire hose purposes. With this arrangement, the pull-rod and the linkage means may be used to initially expand the core, leaving the final expansion to be accomplished by means of fluid pressure in the hose lengths and when it is desired to collapse the core, upon releasing the fluid pressure in the hoses, the pullrod may be used forcibly and positively to collapse the core and to pull the assembly from the shell, even though the shell in driving may have become distorted so as to bind against the core. The pull-rod and linkage arrangement, in conjunction with the separate hose lengths between each pair of leaves, assures that the latter will be correctly positioned at all times.

Other and more specific objects, features and advantages of the invention will appear from the detailed description given below, taken in connection with the accompanying drawings which form a part of this specification and illustrate by way of example the presently preferred embodiments of the invention.

In the drawings:

Fig. 1 is a vertical sectional view of a preferred form of core constructed in accordance with the invention and showing such core (with some sections broken away) positioned within a steptapered form of corrugated sheet metal pile shell;

Figs. 2 and 3 are enlarged views showing parts of the pull-rod and linkage means connected thereto in two different positions of operation respectively;

Fig. 4- is a sectional View taken substantially along line 4-4 of Fig. 1;

Fig. 5 is a sectional view taken substantially along line 5-5 of Fig. 1 and showing the core parts in expanded relation;

Fig. 6 is a sectional view taken substantially along lines 6-45 of Fig. 1 and showing the core parts in collapsed relation;

Fig. '7 is a vertical sectional view similar to Fig. 1, but with certain parts removed so as to particularly show the arrangement of one of the expansible hose lengths;

Fig. 8 is an enlarged vertical sectional View, partly broken away, showing a preferred manner of securing the ends of the lengths of hose;

Fig. 9 is a sectional View taken substantially along line 9-9 of Fig. 8;

Fig. 10 is a vertical sectional view of the upper portion of a core embodying the invention, but having a modified form of headpiece, this View also showing the manner in which this modification may be used with so-called shelling up equipment as disclosed in my co-pending appiication Serial No. 273,920, filed February 28, 1952;

Figs. l1, l2 and 13 are detail sectional views showing different modifications of that part of the core construction which engage." pile shell portions at and adjacent joints in the shell; and

Figs. i l and 15 respectively are cross-sectional and vertical elevational views showing a modification of certain portions of the core assembly.

Referring to Fig. 1 in further detail, the core head portion in the construction here shown is indicated at it, such portion being adapted to receive throughsuitable follower pieces or the like, the impacts from the pile driving hammer. In the particular construction here shown, the core has four leaves l6, ll, l8 and 59 (Figs. il-6) each of whi h, at its upper end, is detachably connected. as by links as with the headpiece, such links being pivoted as at 2! and comprising loops arranged to releasably embrace lugs as at 22 formed on the upper ends of the leaves.

As best shown in Figs. 445, each of the leaves may comprise an outer portion of arcuate crosssection. A pair of plates as at 23, 2d are each welded along one of these arcuate members along adjacent each vertical edge of the latter, as indicated for example at 25. The plates as at 23, 241 may be rigidly held in the relative positions shown, by welding in position therebetween another member such as a plate 26 having suitable gaps or openings therethrough at various points to permit the links hereinafter described to pass therethrough.

Thus each. of the le ves comprises a rigid structure of generally sector like cross-section. Between each adjacent pair of such leaves, one of the above-mentioned lengths of hose 2? is located and extends in the usual case substantially from end to end of the core structure. For this purpose, hose of rubberlaminated and covered with fabric may be used, preferably a good grade of hose of the type readily availabl as fire hose. Thus expansible members of this form do not have to be specially designed and constructed for the purpose.

As shown in Fig. 6, the hoses 2'5 are in substantially collapsed condition with the leaves retraeted from the pile shell indicated at so. In Fig. 5, the hoses are shown expanded after being inflated with compressed air or other fluid, and a the result of the engagement of opposed side walls of each hose with plates such as at 23, 24 on two adjacent leaf structures, the latter, by the conjoint action of the hoses, have been moved apart and outwardly so that the arcuate portions thereof engage under pressure against the interior surfaces of the pile shell. It will be noted that the plates. such as 23, 2-41 are so located as to provide therebetween a radially extending space of substantially rectangular cross-s ction and the plate surfaces present extended areas against which the walls of the hoses may bear under pressure without any danger of abrupt bending, cutting or cracking of the hose walls. Furthermore, the position of each leaf when in its expanded location is under the control of two of the hose lengths and the spacing between each adjacent pair of leaves is controlled by a separate hose,

non and accordingly the action of the hoses in expanding is such as to press each leaf outwardly in proper position so that it exerts uniform pressure against the pile shell throughout the length of the shell, and entirely around the inside surface of the shell, except for the relatively narrow gaps between each pair of leaves.

To prevent the hoses from moving out of place at the above-mentioned gaps, any suitable means may be provided at various points along the length of the core, for example as shown in Figs. 5 and 6, pins as at 3| may be used for this purpose. Qne end of each such pin may be fixed in place in any suitable way, for example in one of the plates 2t, whereas the other end of each such pin 3! may extend into and through an opening in an opposite plate such as at 23, such opening preferably having sufficient clearance about the pin so as to insure that the pin will not interfere with the desired relative movement of the leaf structures.

The upper end portion of each leaf may include a solid metal extension portion of segmental cross-section, as indicated at its, ila, its and lilo in Fig. i. The upper ends of these solid portions, as shown in Fig. 1, extend up into contact with the underside of the core head, the links 28 serving to retain the core head in contact therewith when impacts are being imparted by the head to the remainder of the core.

As shown in 4 and 74 the upper end of each hose may be clamped as by a member 33, secured as by screws 3:5 to an extension of one of the leaf plates 23, the interior of the end of the hose being cemented to a suitable fitting as at 35 containing a cavity 3% communicating with a fluid-pressure connection 3': for the admission and exhaust of gas, air or other fluid, into the hose. As indicated in Fig. l, the hoses may be connected in pairs as by passages a l, 37, connected to one inlet as at 38, so that for the four hoses, fluid may be admitted through a total of two inlets 351, But since each hose is individually secured, it may be read y removed and replaced individually upon becoming worn or iniured without disturbing the other hoses.

As shown in Figs. 3 and 9, the lower end of each hose may be secured in flattened closed condition within a flattened tubular clamping member as at at, secured in place as by screws ll on a solid bottom portion as at 52 on each leaf (see Figs. 7 and 8).

The interior surfaces of he end of each hose may be cemented in gas tight relation to the fittings as and the interior surfaces within the lower end of each hose may be cemented together to effectively seal the lower end If desired, portions along one side of each hose, as indicated at 27a in Fig. 8, may be cemented to one of the plates as at 23 for the purpose of retaining the hose in place, and in that event,

ins d i, such as above described for that purpose, may be omitted. As will be apparent from 4, two of the leaves it and it may each have two of the hoses mounted along the sides thereof, in which case the other two leaves ii and is would not be equipped with hoses. This avoids the necessity of providing fluid pressure inlets on more than two of the leaves.

Referring pair .ularly to Fig. l, a pull-rod or center bar 55 ex.. 5 axially through the core. (A' heavy wire cable could be subs ,ituted for this red.) At several points down along its length, this rod is connected by links it to each leaf. As best shown in Figs. 2 and 3, the inner end of each of these links is pivotally connected as at 4?! to a collar member at, fixed upon the rod. The outer end of each link is pivotally connected as at ts to pairs of lugs as at 59 welded to the interior of the arcuate portion of each leaf. Each link is slotted as at 5! to receive the pivot pins 89, the slot formation being such that when the rod 45 is in its downward position, as indicated in Fig. 2, each leaf will be pushed out toward the pile shell, but not necessarily in contact therewith, and when the rod 45 is pulled upwardly as shown in Fig. 3, each leaf will be forcibly pulled inwardly out of contact with the pile shell 38 with sufiicient clearance to insure that there will be no difliiculty in withdrawing the core from the shell, even though the shell may have become somewhat distorted in driving. The slots 5! also, as shown in Fig. 2, extend in wardly far enough so that when the rod 45 is in its downward position, the pivoting pin '59 will still have enough clearance in the slot to permit the leaf to be forced further out into engagement with the pile shell under the pressure of the expanding hoses. Yet, in case there is no shell embracing the core or part of the core, the slots are such that the ends thereof will engage with the pins 459 and prevent each leaf from being moved too far out in extended position. Thus in case it is desired to use a particular core construction both for pile shells of corresponding length and for pile shells which are shorter, this may readily be done without causing the upper portions of the core to be expanded too far, or out of proper relation to receive the impacts from the core head.

While links it are shown in Fig. 1 only at one position, it will be understood that similar links are provided at several vertically spaced locations as conditions may warrant along the length of the core.

The upper end of the rod 45 may be formed with an enlargement 52 located within a recess 53 in a neck portion 54 on the underside of the core head. A plurality of cushioning discs as at 55 may be inserted in this cavity above the enlargement and a plurality of annular cushioning members 56 encircle the rod 45 just below the enlargement 52. These rings may be retained in place by transversely removable key members til. All these cushioning members may be formed of any suitable hard elastic material such as laminated plastic material of a nature which will withstand such force of the impacts as may tend to be imparted by the core head to the upper end of the rod E5, the purpose of the cushioning means being to prevent any such force from being applied to the rod 45 as might tend to damage the rod or its connected parts.

As shown in Fig. 1, the outer surface of the lower end of the neck portion 54 may be formed with an upwardly and outwardly tapered por tion 58 for engaging complementary tapered surfaces as at as on each leaf. Similarly, tapered surface-engaging portions may be provided as at 60 at the very upper ends of each leaf at the areas of engagement with the upper end of the neck 5%. These tapered surfaces insure that the neck ii -l will act to retain each leaf properly spaced from the others when in expanded position.

As also shown in Fig. l, the lower end of the pile shell may be closed by a boot plate 62 welded to a boot ring or the like 53, which in turn is welded at its periphery to the lower edge of the pile shell. A drive plate 62 is preferably interposed between the lower end of the core and the pile shell closure means. This drive plate may be provided with a retrieving pin 65 extending up from its center portion into a cavity Within the lower end of rod A5 and detachably secured therein as by a key 56.

As further shown in Fig. l, at each region where a core leaf passes a joint as at 6'! in the pile shell, the leaf may be formed with a solid metal insert as at $8. In the outer surface of the member $3, an annular cavity as at 69 may be provided for receiving the connecting member at the shell joint til. Three different possible modifications of the structure at this region are shown in Figs. 11, 12 and 13.

As shown in Fig. 11, a pile shell section 39a is welded at the joint 5! to a plow ring 10. The next shell section 3% has its end portion in threaded engagement with a corrugated sheet metal collar portion it, which is welded to the plow ring it. The core leaf portion 68 as well as the other leaf portions of the core, may be provided on their exterior surfaces with a series of half-round bar or rod portions as at 12, welded in place and in positions such as to have threadlike engagement with the corrugations of the shell sections. The upper side of the cavity 69 be formed with a shoulder 73 for engagement with a shoulder it on the plow ring 10. Thus through the medium of the bars or rods 12 and the shoulders at H, M, impacts applied to the core leaf are imparted to the shell at closely spaced points all around and along the shell structure. Hence if the pile shell or the shell sections are quite long, even though same have to be subjected to very heavy drivin forces, they will be pulled down into the earth by engagement at each of the corrugations and hence straightening out of the corrugations due to excessive tension in the metal is avoided. Some of the gripping bars or rods as shown at 12 may be omitted, particularly at locations nearer the upper end of the shell. In cases where the shoulders l3, is will suffice for imparting of the impacts to the shell, the rods or bars 12 may all be omitted, although even in that event the core leaves will generally be held against the interior surfaces of the shell with sufficient pressure by the action of the expanded hoses so that there will be frictional engagement all along between the core and shell. In case shell sections such as 3% are welded directly to the plow ring, then screw collars such as at it may, of course, be omitted.

The form shown in 12 is similar except that the core is formed with a protruding driving shoulder portion '55 for engaging with a form of connection member which has internally an annular recess with which portions such as at "iii on the core leaves have driving engagement. With this form of construction, the amount by which the core has to be collapsed for removal can be made somewhat less than with the form of Fig. 11.

In the form shown in Fig. 13, pile shell sections as at 38c and tilt; are telescoped somewhat at one within the other, and welded or threaded together at if without the use of any driving shoulder means. In this form the rods or bars as at F2 are relied on for imparting the driving impacts to the shell.

When the core is to be inserted in a pile shell, it is suspended by connecting the core head to a hoisting cable on the pile driving rig, and while the links 23 are disconnected. At that time, the

neckzportion F54 of1 the core head will be partially located above the upper .ends of thecore leaves and the pullrodxtdwith the linksin the position shown at 56 iniFig. 3, will serve to suspend the core leaves while same are being lowered into the shell. When the core leaves are down in placeiin the shell, the core head is thrust down- :wardly to the position shown in Fig. 1, whereupon :the rod d5 spreads the leaves by the action of the links 56 as shown in Figs. 1 and 2. Then the 'links ifl are hooked onto the lugs 22. At this time thus-collapsing the core. As will be apparent at the'upper portion of Fig. l, the neck portion 56 of the core head is so shaped that when it is raised, the upper ends of the leaves are free to move inwardly. The core as now collapsed is free to be raised out of the shell while being suspended by the core head.

With the formof the invention shown in Fig. .10, the core parts are the same as of Fig. 1, exceptthat here the upper part of the core head at 81! is made-of substantially the same diameter as the core itself when the leaves are expanded. The core head here has a recess M at its upper end for receiving an extension 82 formed on a messenger plug 83, such as described in my above-mentioned co-pending application. Impacts-from the pile driving hammer, 1e lower portion of which is here indicated at 8-3, are imparted through a suitable follower 35 to such messenger plug. The latter is so constructed and adapted to be'raised and lowered by the use of a sheave frame 86, that in shelling up the core in the pile shell, the messenger plug may be lowereddown through the pile shell to pick up a core located in a previously driven hole or shell and pull such core up intoproper position within the shell, whereupon the boot pieces are applied to the lower end of the shell and the assembly is ready for driving, all as more fully explained in my said application Serial No. 273,920.

Insome cases it may be found desirable to provide means in addition to the links at 26 at the upperend of the core for holding the leaves in their correct relative positions vertically. For this purpose, as shown in Fig. at the gaps between leaves, oneof the leaves may be provided with a recess as at 99 and the adjacent leaf with a tongue-like portion 9! within the recess 98 in a manner more fully'apparent from the cross sectional view of Fig. .14. Tongue and recess formations of this kind may be located at various vertically spaced points along the core as may be found desirable.

While, as is apparent from Fig. 1, the invention is here shown in a form adapted for driving a step-tapered type of pile shell having shell sections as at til, and Ell", the core may, of course, be made of uniform diameter throughout its entire length, or if preferred with a slight uniform taper, depending upon the particular type ofpile shell being driven. If the lower part of the pile shell is substantially smaller than the upper part, then it may be desirable to provide hose lengths in the lower part of smaller size than in-theupper part, or specially tapered hoses may in some cases bepreferred.

The hoses may beinflated by connecting to the inlets as at 38, 38 containers or other sources of compressed air, nitrogen or othergas which may be readily available at the location'where the pile driving work is being done. In'the usual case, a pressure of about lbs. per square-inch within the hoses will be ample. Also, if desired, the hoses may be partly filled with Water or other liquid, thus makingit unnecessaryto fill them completely'with compressed gas each time the core is installed in a pile shell. A volume of liquid may be'used such that same is just sufficient to fill the hoses when in their so-called collapsed positions. On collapse of the core by the pull rod and linkages, the compressed gas in the hoses will be expelled, while the liquid therein will remain, thus reducing to a substantial extent the expense required for compressed gas supplies and also reducing to some extentrthe time required to introduce and to exhaust the fluid pressure.

It will thus be seen that a collapsible core assembly isprevided in which fluid pressure may be effectively used to uniformly apply expanding pressure to the core leaves while by the use of the four symmetrically located hose lengths, the central portion of the core is left available for installation of the center bar or the equivalent 55 for mechanically operating the links 53. The center bar, in conjunction with the links and hoses, operates to maintain the leaves in their correct relative positions at all times. The center bar and links make it possible initially to expand the core while leaving the final powerful expansion to be accomplished .bythe fluid pressure. The center bar and linksfurther provide a convenient and effectivemeans for forcibly and positively collapsing the core when the bar is pulled up in the normal mannerfor withdrawing the core from the pile shell. The upper-portion of the center bar alsofunctionsto hold the head of the core inproper alignment so that the hammer impacts are delivered equally to all of the core leaves.

Occasionally sand orother material mayenter the core through holes in the pile shell. Such holes may be due either to faulty manufacture, or to compression or puncturing by rocks or other obstructions in the ground. When such material enters a collapsible core, it tends to make its collapse quite difiicult, but the positive mechanical action of the center bar and links as above described is such as to ordinarily satisfactorily overcome this difficulty so that there is little chance, upon removing the core, of pulling the complete shell up along with the core due to any failure of the core tocollapse properly.

.Although certain particular embodiments of the invention are herein disclosed for purposes of explanation, various further modifications thereof, after-study of this specification, will be apparent to those skilled in the art to which the invention pertains. Reference should accordingly be had to the appended claims in determining the scope of theinvention.

What is claimed and desired to be secured by Letters Patent is:

1. An expansible core for driving pile shells comprising a plurality of leaf structures extending longitudinally of the core and arranged around about the core axis with generally radial spaces therebetween, and hoses extending longitudinally of the core and along between adjacent leaf structures within said spaces respectively, whereby upon filling such hoses with fluid under pressure the leaf structures may be forced outwardly of the core and into contact under pressure with the interior surfaces of a pile shell.

2. An expansible core for driving pile shells comprising a plurality of leaf structures extending longitudinally of the core and arranged around about a central space, a member extending longitudinally of the core in said space, linkage means at spaced points connecting said memher with each of said leaf structures whereby upon longitudinal movement of said member in one direction said structures are thrust outwardly of said central space by a limited amount and upon movement of said member in the opposite direction the structures are retracted, and hoses extending longitudinally of the core along between adjacent lea f structures, whereby upon filling such hoses with fluid under pressure the leaf structures may be thrust further outwardly into contact under pressure with the interior of a pile shell.

3. An expansible core for driving pile shells comprising a plurality of leaf structures extending longitudinally of the core and arranged around about a central space, a core head for applying impacts to the upper ends of said leaf structures, mechanism including a rod connected to said core head and extending down into said central space and connected by linkage means to said leaf structures for thrusting the leaf structures outwardly when the core head is lowred into normal position onto the leaf structures said mechanism acting to retract the leaf structures inwardly when the core head is raised, and hoses extending longitudinally of the core along between adjacent leaf structures, whereby upon filling said hoses with fluid under pressure the leaf structures may be thrust further outwardly for contact under pressure with the interior surfaces of a pile shell.

4. An expansible core for driving pile shells comprising a plurality of leaf structures extending longitudinally of the core and arranged around about the core axis with generally radial spaces therebetween, and fiuid pressure expansible means extending longitudinally of the core along between adjacent leaf structures within said spaces respectively, the leaf structures each comprising a portion of arcuate cross-section for engagement with the interior surface of the pile shell and two plate portions extending inwardly from the longitudinal edges of said arcuate portion respectively, the expansible means each being positioned to engage one of such plate means on one leaf structure and one of such plate means of another of said leaf structures.

5. An expansible core for driving pile shells comprising a plurality of leaf structures extending longitudinally of the core and arranged around about a central space, each of said leaf structures having a generally sector shaped cross-section, fluid pressure expansible means extending longitudinally of the core along between adjacent leaf structures whereby upon filling such expansible means with fluid under pressure the leaf structures may be forced outwardly into contact under pressure with the interior surfaces of a pile shell, a core head for applying impacts to the upper ends of said structures, and mechanical means connected to said core head and extend ing down in said central space with connections to said leaf structures for retracting the latter when the core head is raised.

6. An expansible core for driving pile shells comprising a plurality of leaf structures extending longitudinally of the core, and fluid pressure expansible means also extending longitudinally of the core along between two adjacent leaf structures, a substantial portion of the interior of said means being filled with liquid whereby upon filling the remainder thereof with gas under pressure said two leaf structures may be forced apart and into contact under pressure with the interior surfaces of the pile shell, by the use of a substantially lesser quantity of gas under pressure than would be required to fill said means under adequate pressure by the use of gas alone.

7. An expansible core for driving pile shells comprising a plurality of leaf structures extending longitudinally of the core and arranged around about a central space, a center bar extending along within said space, a core head for imparting impacts to the upper ends of said structures, means for retaining the upper end of said center bar against substantial vertical movement with respect to the said core head and including cushioning means to cushion the bar against impacts applied to the core head, and linkage means interconnecting said center bar at spaced points along its length to said leaf structures for forcing the latter in directions inwardly and outwardly of the core respectively when the core head is raised and lowered with respect to said structures.

8. An expansible core for driving pile shells comprising a plurality of leaf structures extending longitudinally of the core and arranged around about the core axis, a radially extending space being provided between at least two of said leaf structures, each of said leaf structures having a cross-sectional outline of generally sector shape, and a hose extending along between two adjacent leaf structures and normally contained Within said space whereby when such hose is filled with fluid under pressure the leaf structures may be forced outwardly of the core axis.

9. An expansible core for driving pile shells comprising a plurality of leaf structures extending longitudinally of the core and arranged around about the core axis, each of said leaf structures having a cross-sectional outline of generally sector shape, and hoses extending along between the sides of adjacent leaf structures for forcing the latter outwardly of the core axis when the hoses are filled with fluid under pressure, two of said hoses being mounted on opposite sides respectively of alternate leaf structures for pressing against the intervening adjacent leaf structures respectively.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,865,653 Upson July 5, 1932 2,170,188 Cobi Aug. 22, 1939 2,313,625 Cobi Mar. 9, 1943 2,625,015 Cobi Jan. 13, 1953