US2881593A - Expansible mandrel for driving molds for concrete piles - Google Patents

Description

w. H. coal 2,88

EXPANSIBLE MANDREL FOR DRIVING MOLDS FOR CONCRETE FILES April 14,1959

5 Sheets-Sheet 1 Filed "Jan. 31, 1955 W. H. COB! April 14, 1959 EXPANSIBLE MANDREL FOR DRIVING MOLDS FOR CONCRETE PILES 5 Sheets-Sheet 5 Filed Jan. 51, 1955 W. H. CO BI April 14, 1959 FOR CONCRETE FILES EXPANSIBLE MANDREL FOR DRIVING MOLDS 5 Sheets-Sheet 4 Filed Jan. 31, 1955 April 14, 1959 w. H. coal I 2,881,593

EXPANSIBLE MANDREL FOR DRIVING MOLDS FOR CONCRETE FILES Filed Jan. 51, 1955 5 Sheets-Sheet 5 United States Patent EXPANSIBLE MANDREL FOR DRIVING MOLDS FOR CONCRETE PILES Walter H. Cobi, Port Chester, N.Y., assignor to Pneumatic Pile Corporation, New York, N.Y., a corporation of New York Application January 31, 1955, Serial No. 484,898 7 Claims. (Cl. 61-79) The invention relates to expansible pile driving mandrels, and particularly to expansible and contractable mandrels or cores capable of insertion into the empty shell or mold for a concrete or cast-in-place pile and of driving the shell into the ground under hammer blows.

The invention particularly relates to mandrels of this type which have come to be known as pneumatic mandrels, and in which the expansion is caused by the application of fluid pressure to container means within the mandrel.

It is a principal object of the invention to provide a mandrel of the pneumatic type, comprising annularly arranged metallic segments or sectors contacting during operation the inner surface of the shell or mold, and in which the forces from the hammer blows are substantially evenly distributed over the cross-sectional area of the mandrel at any point along its length, thereby insuring substantially straightline driving of the strata.

It is another object of the invention to provide such a mandrel in which the longitudinal elements will be firmly positioned within the shell in the expanded condition of the mandrel to insure stable operation.

It is a further object to provide an expansible and contractable mandrel which can be effectively expanded by a lower fluid pressure per unit area than in previous arrangements.

It is a more specific object to provide stronger, inflatable, flexible container means than was previously provided for expanding the mandrel, and which is subject to less wear by depending for effective action upon a change of the cross-sectional shape from deflated to inflated condition and by substantially avoiding any expansionor stretching of the wall material of the container during such action.

It is still another object to simplify the construction and assemblage of such a mandrel by reducing the number of parts and simplifying their adjustments for operation.

In accordance with a preferred form of the invention, the mandrel is made up of a series of annularly arranged metallic segments, which may be quadrants, disposed throughout the length of the mandrel for contacting the inner surface of the shell of the pile, and of a centrally disposed flexible container means for the pressure fluid adapted to apply radially effective pressures to the surrounding segments, when inflated.

In accordance with a principal feature of the invention the annually arranged metallic segments and the centrally disposed container means have cross-sectional areas shaped in such a manner that during inflation the container means will engage the segments under pressure over areas of greater width than has hitherto been possible, one advantage being that the specific pressure necessary to effect the required contact pressure between segments and pile shell need only be very low as compared with present practice. This reduces the strength requirements and the pile into the ground, at least to the extent permitted by the nature of demand on associated equipment, and greatly simplifies operation.

In accordance with an associated feature of the invention the said flexible container means is in the form of a long tubing of substantially non-elastic wall material and has, when normally deflated, an inherent configuration of cross-sectional area which includes a plurality of contacting or pressure portions alternated with flexible fold portions.

This permits considerable expansion of the tubing from deflated to inflated condition without any substantial elastic stretching of the wall material and consequent wear against the contacting metal.

In accordance with another related feature the said metallic segments are shaped cross-sectionally to each present to the container means an inner surface of considerable width through substantially the whole length of the mandrel, so that the corresponding surface portions of the container means may lay themselves flexibly against those inner metallic surfaces during inflation and thus distribute the fluid pressure evenly over said inner surfaces. One very important advantage of this is the possibility it affords of shaping the opposed surfaces properly so that the circumferential width of the effective pressure areas may remain constant during the inflating action or may even increase considerably.

In accordance with still another feature of the invention the tubing or container for the fluid pressure is built up of a plurality of comparatively short manufacturing lengths which, since the cross-sectional shape of the tubing does not readily lend itself to direct joining, are terminated in suitable pairs of caps, each pair being supported in distinct junction sectors incorporated in the metallic segments, one sector in each, and joined by suitable pieces of hose to pass the pressure fluid between adjacent lengths of tubing. The support of tached tubing lengths is constructed to permit the radial movements of the outer junction sectors with their joined segments.

Other features and advantages of the invention will be apparent from the following detailed description.

This description should be read in conjunction with the attached drawings, which show a preferred embodiment of the invention. It should however be understood that the invention is not limited by the terms or expressions used in this description, nor by the specific details or arrangements of parts shown in the drawing. The scope of the invention in its various aspects is defined by the attached claims.

In the drawings:

Fig. 1 is a vertical sectional view of the upper portion of the. expansible mandrel or core showing the mandrel in place within the upper portion of the shell or mold and expanded ready for use;

Fig. 2 is a similar vertical view of a middle portion and the lower portion of the mandrel;

The sections of Figs. 1 and 2 are taken along a diametrical plane through the mandrel, as indicated by line 2- -2 in Figs. 4, 5 and 6.

Fig. 3 is a similar vertical sectional view of the middle portion of the mandrel shown in Fig. 2 but shown here in contracted condition, this section being taken along a plane indicated by line 33 in Fig. 7;

Fig. 4 is a cross-sectional View taken along line 4-4 in Figs. 1, 2 and 8;

Fig. 5 is a cross-sectional view taken along line 55 in Figs. 1, 2 and 8;

Fig. 6 is a cross-sectional view taken along line 6-6 in Figs. 2 and 8;

Fig. 7 is a cross-sectional view similar to Fig. 6, except that it shows the mandrel in contracted condition, and may be considered as taken along line 77 in Fig. 3

the central caps and their at- Fig. 8 is a detailed vertical cross-sectional view taken along line 8- 8 in Figs. 4, 5 and 6.

The drawings show in general an expanded mandrel in 'operative position within-apile shell or mold 10, except for Figsf3 and 7 which show the mandrelcontracted within the shell 10. The shell isof the corrugated type, having corrugations running parallel-around the shell and-in immediate succession along the entire length; which corrugations may, if desired,- be-helical.

'In the embodiment shown in the drawing'the mandrel is made up offoursimilar segments or quadrants 12, 14, 16, 18 which extend through substantially the entire length of the mandrel. Through most-of the length of the-mandrel each segment includes a .u-shaped channel member-21 and an outer curved-plate-22which is welded along its entire length to the two edges of the channel member 21, as will appearfrom-Figs.-6 and 7. The member 21- and the,plate 22may-be ofsteel drawn or otherwise formed to the desiredshapes and dimens'ions. Both the members 21 and the plates .22 receive the force from the-hammer blows at their upper ends and transmit the force through their entire length to the bottom end of the mandrel. When the length of the mandrel, as required for any particular job, exceeds the manufacturing lengths of these members and plates, successive portions are welded or bolted together'endwise, so that each segment formsa continuous structure.

The channel members 21, being welded along thesedges of the plates 22, extend their backs 24 inwardly toward the centrally located pressure container or tubing 30, where theypresent aslightly curved surface 26 continuously in contact with tubing 30 along itsientire length.

As can be seen in Fig. 6 where thefour metallic segments or sectors are shown in the expanded condition of the mandrel and in contact with the shell .10, the four plates 22 are separated byspaces23 between their edges, which allow for the contraction of themandrel, .as'shown in Figs. 3 and 7.

The tubular container 30 is shown in inflated condition inFig. 6 and in deflated condition inFig. 7, the views showing the corresponding cross-sectional configurations of the container wall under the two conditions.

"When deflated the tubing 30 has a generally tubular shape which may approach the cylindrical shape. It has four-external pressure portions 'or- surfaces 32, 34, 36, and38 separatedby four fairly deep folds or grooves 39 throughout its length (see also- Fig. 3).

The wall in thepreferred form of the container comprises:an outer layer-42am an innerv layer 44- of flexible material: and an intermediate layer=46 of strands. of thin strong yarn properly'wovenor spun about the inner layer to form a practically non-elastic reenforcement for the wall. The strands are preferably of nylon. The material in layers :42 and 44 is preferably of a rubberlike composition capable of heatcuring for imparting thereto an inherent or cured-in tendency to retain, after final curing, any particular wall thickness and wall shape given thereto during curing. This material may include rubber, neoprene, Buna or other similar substances in any'su'itable proportions.

The shape shown in Fig. 7 may be termed that of a four-leaf clover.

When inflated the'tubing 30 will assume a shape which in part conforms to the shape of the confining metal elements and in part is that of a self-sustained wall portion. In the present instance the shape is practically cylindrical, as shown in Fig. 6.

For structural and other reasons it has been found desirable to manufacture the tubing30 in lengthsof -12 feet.

Fob-this, purpose, and in accordance with-a further feature of the invention, a junction section is provided for joining adjacent tubing sectionswithin a unit mandrel.

A junction section 50-Iis shownin 'Fi gs.--2' and '3 under inflated and 'deflated: 'conditions,- respectively. Some tde- 4% tails of the section are shown in Fig. 8 and cross-sections are shown in Figs. 4 and 5.

Through the length of the section the four channel members 21 are replaced by four iron sectors 51, which may be castings, each of which is shaped with an outer curved surface 52 conforming to and contacting the inner surface of the plate 22 and with an inner curved surface 54 which together with the other three surfaces 54provides a hollow space within the mandrel. Each casting 51 is welded at its two ends to the adjacent channel mem bers 21, and in manufacture these castings and members may be placed as a unit within the much longer associated curved,.plate 22 and welded thereto along the edges of the plate in a continuous manner. 'Thus the sector 51 is fitted in as a rigid continuationlinto the quadrant for extending the hammer blows through the mandrel.

The adjacent ends of two successive lengths of the tubing 30 :are terminated within thehollowtspace of the junction between surfaces 54. As will: appearifrom Fig. 8 the end of the tubing is closed by a suitable sealingcap assembly 60, comprising inner and outer rings 62, 64, and a plug 66.

Specifically, the end of the tubing in fully inflated shape is shown in Fig. 8 as clamped between a shouldered ring 62 having an inside surface with shallow grooves, and an inner ring 64 forcibly expanded for airtight sealing. The shoulder portion of ring 62 has an inner thread into which is screwed the end portion 67 of the plug 66, this joint being made airtight bythe packing "68. The .end portion 67 has a deep external groove 70 into which extends a projection 72 from the surface.54;ofreach.iof the castings 51, (see also Fig. 5), these projections .being disposed in a transverse plane so thatthey may readily slide in and out of the groove as themandrel'is deflated v and inflated.

Across the groove 70, and locatedinthe horizontal spaces between the projections 72 from the four quadrants, are vertical posts 73 (Fig. 5), which-arese'cured in the plug section 66 of the cap and thus serve to prevent rotation of the cap.

The plug 66 has a series of bores 74 for connecting the interior of the tubing 30 to a pair of hose taps 76, and pieces of hose 78 connect between the taps :on the two caps 60 located within the same junctionsection thereby establishing a continued circuit for the pressure fluid to all container sections 30.

The surfaces 54 are. inclined inwardly at each end of the. junction sectionfor lining up with-the inner surfaces 26 of the adjacent channel members' ZI. The largest diameterof surfaces 54' is large enoughto 'permit'the junction sections .51 to close in about the caps 60-at full deflationv of the mandrel without interference.

It may thus be observed that a plurality of-junction sections may be distributed at uniform intervalsofsay 12'14' in the interior of a mandrel with a length of tubing 30 stretched in each interva1 between the junctions.

With the grooves of the two end caps fitted in over corresponding projections 72 a length of tubing'30 will be suspended within the mandrel and may be stretched to a desired tautness, the length of the tubing being lightly guided along the surfaces 26 between'successive junction sections 50 both in inflated and deflated condition, as indicated in Figs. 6 and 7.

At the bottom end of the mandrel, as shown in Fig. 2, a termination of the mandrel and container'may be made by means of a junction'section 90, practically identical with the upper half of the junction section 50 and including four sectors or castings '91, which may conveniently .be welded at their upper "ends to the adjacent channel 'members20. The hose'taps 96"in' the container cap 60 at the lower end-of the 'tubing'30 in said junction section 91 are plugged tight 'for termination of'thepressure fluid circuit.

At the top end of the mandrel, as shown in Fig. 1, a special termination 100 is used, the lower portion of which may be of the same construction as that of the lower half of the junction 50. In this instance the castings 101, corresponding to the castings 51, are extended upward into heavy end portions 102 connected to the mandrel head 110. The uppermost container cap 60 has two hose connections 104 through bores in end portions 102 to outer hose nipples 106 to which hoses from the pressure rig are attached, only one set of these hoses appearing in Fig. 1.

The entire mandrel may thus be visualized as comprising the top section 100, a series of junction sections 50, bottom section 90 and a plurality of main sections therebetween. The outer curved plates 22 may extend continuously from the top section 100 to the bottom section 90. The junction sections may be 12 to 14' apart, and may extend the same distance from the top and bottom ends. The spaces between said junction sections are occupied by the tubing sections 30, and by the channel members 21 within the quadrants, constituting the main sections.

For usual practice, the expanded mandrel may be 16" in diameter with an inflated center tubing of 3 /2"5" in diameter.

This entire structure is held together by bolts 111 and springs 112 which also permit and limit its expansion and contraction. It has been customary with prior constructions to distribute such bolts fairly evenly along the length of the mandrel. In accordance With the invention the bolts 111 with their individual springs groups at the top, bottom and junction sections. Such spacing along the mandrel is justified by the stiffness of the quadrants secured by the spokelike effect of the channel members 21 and the curvature and heavy thickness of theplates 22, which also are needed for the proper trans mission of the hammer blows.

Referring, for example, to Fig. 2 it will be seen that the adjacent cap terminations 60 of the container sections 30 are separated sufficiently in the lengthwise direction to give room for a group of crossing bolts 111. A ridge 114 rises from the inner surface 54 of each quadrant, the ridge being high and wide enough to provide for the location of springs and bolt heads, as further illustrated in Figs; 4 and 8. The bolts are provided in pairs crossing at 90 between oposed quadrants. As shown particularly in Fig. 4, a spring 112 lies under the head of a bolt 111 in one quadrant while another spring 112 lies under a nut on that bolt in'the opposite quadrant. The total length of the bolt is such that the bolt does not project beyond the outer surface of the mandrel in contracted condition. The size and number of bolts through the mandrel will of course be determined by the diameter of the mandrel and the dimensions of the structural elements. Since the bolts and springs are last to be inserted in the assembling of the mandrel, holes 116 are drilled in the outer plates 22 for their passage and also to provide additional space for the bolt ends during contracted condition of the mandrel.

' As illustrated in Figs. 1 and 2, suflicient space is also provided beyond the end caps 60 and the respective upper and lower ends of the mandrel to accommodate bolts 112 in the top and bottom sections 100 and 90, respec tively.

In'the contracted condition of the mandrel, the springs 112 still have sufiicient compression to force the edges of adjacent plates. 22 into firm contact with each other, thereby insuring the safe insertion into and removal from the pile shell 10 of the whole mandrel.

From the foregoing description it may be seen that in deflated condition of the tubing 30 the springs 112 will hold the quadrants in closed mutual contact and in contact with the effective surfaces 32, 34, 36, 38 of the tubings 30. Under this condition the tubing will nearly assume its cured-in shape. Or it may, if desired, be

112 are bunched in i slightly too large and be compressed by the springs under this condition, thereby reducing the required depth of the folds 39 in the relaxed or cured-in shape.

With the cross-section of the tubing having the shape of a four-leaf clover, the effective surfaces or pressure areas engaging the juxtaposed metal surfaces 24 may have an appreciable width as indicated by the space W in Fig. 7. With the admission of fluid, usually air, under pressure the containers will be inflated causing the mandrel to expand until the plates 21 press against the inside of the shell 10. The pressure may then be further increased to insure firm contact between mandrel and shell. At this time the extra portions of the container wall in the longitudinal folds between the effective surfaces W will supply wall material enough to permit the tubing to take a greatly expanded shape which is practically cylindrical and which permits full utilization of the iron surfaces 26, with a contact width W. This contact width may with careful design be about -75% of the total expanded surface of the expanded tubing. Thus with a tubing diameter of about 4 inches and a mandrel diameter of about 10 inches the ratio of specific pressures at the two surfaces of tubing and mandrel may approach the 10 to 4 value.

While the pressure thereafter is being withdrawn for relaxation of the mandrel, the inherent tendency of the wall material will cause the fold portions to cave in first and gradually assume their full depth as the pressure portions resume their natural diameter.

In prior pressure containers, as represented by Patents 2,313,625, issued March 9, 1943, and 2,635,015, issued January 13, 1953, to the present inventor and employed by him to considerable extent, the central container element was complicated by the use of a tubing which was of elastic material and required a flexible essentially nonelastic wrapper interposed between the tubing and the mandrel quadrants to withstand the high concentrated pressures from the narrow contact areas presented by the quadrants. In contrast, the present invention utilizes a strong and substantially non-elastic wall for the container, which thus not only has ample strength to receive the contact pressure, but particularly is capable of sustaining the inner pressure over the unsupported areas between the channel numbers 21. The use of unelastic material is made possible by the introduction of extra wall area in the folds between the contact areas. The contrast with the prior art, referred to, is emphasized by the greatly increased effective contact area in expanded condition which permits a much lower pressure per unit area for a given pressure between mandrel and shell. This is secured particularly by the increase of the container diameter relative to mandrel diameter, which in turn permits a reshaping of the quadrant structure to present wider contact areas.

A further advantage of the use of substantially nonelastic wall material is found in the fact that there will be close adherence, which almost resembles an adhesion, between the contacting surfaces of the plastic container and the metallic channel members. Thus there will be little, if any, tendency to relative shifting between the opposed surfaces either in the transverse or the longitudinal direction during expansion and contraction. Thus, when this adherence is left undisturbed there will be little, if any, rubbing action between the opposed surfaces due to the violent vibrations during driving operations with a consequent reduction, if not elimination, of

wear.

It has before been proposed to use certain types of firehose with an outer cord layer for pressure containers in driving mandrels of this general type. Such hose has however been found to change its length by 10% or more between inflated and deflated conditions. Such elastic hose, when fastened at both ends in a mandrel, would thus crimp up badly during expansion, and would be pinched between the quadrants during deflation, soon resulting in cuts in the'hose wall. In accordance with the present invention the'tubing'is suspended between the tightly secured end caps which in turn are held in position by the projections 72..from the quadrant elements, and may thus be kept tight both in expanded and contracted condition because of the slight elasticity of the wall material, with the chance of cutting being eliminated.

Though the present embodiment of the invention is shown and described herein as a mandrel comprising four longitudinal segments or sectors with four pressure surfaces engaging a pressure container having four expansion folds between those surfaces, it should be understood that, withouta 'departure'from the spirit and scope ofz'the invention, the 'mandrel may comprise six segments'with six pressure surfaces engaging a central con tainer'with three or six expansion folds between surfaces, or maycomprise a larger number of segments.

Itshould also be understood that the number of effective'surfaces presented by the mandrel segments and by the central containerneed not be the same. Thus a tubing with three effective surfaces may be used with mandrels having three, four, 'five'or six segments. In such case it may be desirable to twist each length of tubing, one or two turns, or a half turn, for example, to evenly distribute the contact areas.

It should further be understood that the shape of the plates 22 engaging the inner surface of the shell may differ from that shown in the drawing and may be made to conform to other shapes of the shell than the circular shape shown. Thus, the plates may be flat to conform with a square shell, or they maybe of an angular crosssection to conform with polygonal cross-sections of a shell with more than four corners.

When the grooves'of the corrugated shell are distributed helically, the plates 22 may have welded to their outer surfaces a series of half round helix bars 122 (Fig. 8) for engagement with such grooves. The bars may be placed at intervals of, for example, about a foot along the 'length of the mandrel. By this means the driving force of the hammer blows may be well distributed over the Whole length of the shell to overcome the friction with the ground during driving.

Considering now more specific features of the mandrel illustrated, it may be noted that the top assembly of the mandrel includes the drive head 110 (shown in Fig. l) which is in the form of a cylindrical block with a de pression 131 in the top surface for receiving the-metal encased wooden hammencu'shion 132, and with a depression 133 in the bottom surface fitting loosely over the end portion 102 of the mandrel. The head has two parallel holes 134 through the body portion thereof to receive steel cables for raising and lowering the whole mandrel.

Two mild steel bufler plates 135 .are positioned against the bottom of the depression 133 and engage the upper aligned end surfaces of the endportions 102 for evenly distributing the hammer blows to these elements during operation.

The drive head 110 is loosely connected to the upper end of the mandrelproper by a lifting bolt 140 fastened in ancentral hole 141 in the:drive head by means .of spherically surfaced washers 142, 143 held against spherically surfaced shoulders in the hole 141 by a nut 144 on the shouldered bolt:140.

The lower end of the bolt extends a short distance into the .interiorof the mandrel where it carries a spider 145 having axhub portion for fastening to the bolt and two pairs'offlat Wings 146, 147-extending into the spaces 24 between the endportions 102. As may be seen in Fig. l, the'wings 146extendin under' and clear a pair of crossbol'ts 148 which crossthe spaces 24 and pass through holes in the'opposed faces of the end portion 102. Anothenpair ofcross-bolts, not 1 shown, are placed at a '8 lower level than the pair 148 to clear them and pass over wings 147.

The bottom assembly of the mandrel is contained by the lower end of the shell 10 and the boot 150 welded thereto, as shown in Fig. 2. The boot may be of iron, and has an upper cylindrical portion 151 for protection of the lower edge of the shell, a shoulder portion 152 for receiving a share of the force from the junction sections 90, and a central cup portion 153holding a casting 154 with a top surface partly in abutment with the bottom of the junction sections toalso receive force therefrom. The casting. 154 is part of the mandrel proper, and has a central eye bolt 155 reaching up about the lower'crossbolt 111 in the junction section 90, so that it willfollow the remainder of.the. mandr'elinremoval from.and.insertion into the shell 10.

When the. mandrel islbeing. lifted out of a shell which has been driven in place, a steel cable is passedthrough the holes 134 in thedriveflheadand up about'thelbase or the hammer, and the mandrel. is. lifted bodily up into the leads of the driving rig. After the drive head has been raised a short distance, an inch or less, for example, the two pairs of wings 146, 147 will engage the corresponding pairs of cross-bolts whereupon the entire mandrel will rise with the drive. head.

By means of the spherical mounting of the liftingbolt in the drivehead a certain freedom of. self-adjustment between'the drivehead and thetop of themandrel is available during therough. lifting. operations. Theupper and lower nuts on bolt 140 are preferably of the.type known as elastic stop nuts, whichlock themselves on to the bolt.

Mandrels of this type may be used under greatly varying conditions and with shellsof greatly varying. lengths and cross-sections. The dimensions of the mandreland its parts therefore may vary greatly. The mandrelmay bedesigned for shells 100 feet or more in length.

The fluid pressure is preferably obtained from anair compressor, and the pressure for the longest mandrels need not exceed 30 lbs. per square inch. The compression springs maybe tensioned. to 300 lbs.

When the mandrel is collapsed, the half round bars 122 on its outside surface clear the inside of the corrug-ated shell by at least A" all around, and the expansion may amount to an increase in diameter ofthe mandrel of. an inch and ahalf or even. more. It will, of course be understood that the foregoing pressures and dimensions. are merely examples'of. thosethat may be-employed.

' There is somedemand for pile .driving mandrels which are tapered over the lower part or over substantiallythe whole length. The pneumatic mandrel, constructedas described hereinbefore, lends itself to the tapered construction. This is,partly on account of its extremely simple interior construction. .If the mandrel is to be tapered, the tubings and the end caps thereformay be kept at the .maximum dimensions used at the largest diameter of the mandrel, and the tapering may besecured by the gradual reduction in dimensions of the longitudinal iron elements in the four or six. sectors surrounding the tubing.

The terms and expressions which. I have employed are used as terms of description and not of limitation, and I have no. intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, but recognize .that various modifications are possible within thescopeof the invention claimed.

I claim:

1. A driving mandrel for the shell of a pilewhichcomprises'aplurality of longitudinal mainsections cachinclnding a centrally disposed expansible'fluid pressurev container'having self-restoring, longitudinal foldstand a pluralitybf'metal sectors disposed between .the shell..and said container, said man'drel'further comprising an expansible junction section disposed in each interval between adjacent main sections for joining the containers and the metal sectors thereof, each junction section including a plurality of sector castings for joining corresponding metal sectors and a plurality of bolt and spring means extending between diametrically opposed castings for contraction of said metal sectors about the containers in said main sections, each of said containers in adjacent main sections including a pressure tight cap termination having an outlet for a hose connection between the caps, said caps and hose being disposed within said junction section, and said caps being slidably fastened in said junction section to permit transverse expansion and contraction of the section and to permit longitudinal tightening of the associated containers through the length of said main sections.

2. An expansible mandrel for insertion into a metal shell to receive hammer blows for driving the shell into the ground, said mandrel comprising a plurality of elongate sections having a cross section of generally sector shape, each of said sections having a curved rim portion engageable with the interior surface of said shell, each of said sections having a channel portion comprising a pair of wings extending inwardly from said rim portion toward the vertical central axis of the mandrel and a pressure receiving wall of substantial width extending transversely between the inner ends of said inwardly extending wings and positioned between said rim portion and said axis, said transverse pressure receiving walls of said plurality of sections defining a central opening the center of which is said axis, bolt means connecting said sections and spring means normally urging said sections inwardly toward said axis, an elongate flexible pressure container mounted within said central opening, said pressure container having a substantially unstretchable peripheral wall of rubber-like material having a plurality of longitudinally disposed pressure portions and a longitudinally disposed fold portion between each pair of adjacent pressure portions, each of said pressure portions lying in engagement with one of said transverse pressure receiving walls, said folds moving outwardly upon inflation of said pressure container thereby causing said pressure container to expand without change in the peripheral and longitudinal dimensions of said container wall and said container wall thereby moving said pressure portions outwardly against said pressure receiving walls, causing said sections to move radially outward to engage said rims with said shell and, upon deflation, said folds resuming their inwardly extending position to decrease the diameter of said container from its expanded condition thereby permitting said spring means to move said sections radially inward out of contact with said shell.

3. An expansible mandrel for insertion into a metal shell to receive hammer blows for driving the shell into the ground, said mandrel comprising a plurality of elongate sections of generally sector shape in cross section, each of said sections having a curved rim portion engageable with the interior surface of said shell, each of said sections having a channel portion comprising a pair of wings extending inwardly from its rim portion toward the vertical central axis of said mandrel and a pressure receiving wall of substantial width extending transversely between the inner ends of said wings and positioned between said rim portion and said axis, said transverse pressure receiving walls defining a central opening the center of which is said axis, yieldable means connecting said sections and normally urging said sections toward said axis to move said sections to contracted position, an inflatable and deflatable elongate tubular flexible pressure container within said central opening having a tubular peripheral wall surrounding said vertical axis, said tubular wall of the pressure container extending between said axis and said pressure receiving walls of said mandrel sections, said peripheral wall being made of substantially unstretchable rubber-like material and having a plurality of longitudinally disposed pressure-portions each of which engages a pressure receiving wall of one of said sections and having a longitudinally disposed, inwardly extending, fold between each pair of adjacent pressure portions, said folds moving outwardly upon inflation of said pressure container causing said pressure container to expand to increase its diameter without stretching of said peripheral wall thereby causing said pressure portions to move outwardly against said pressure receiving walls thereby causing said sections to move radially outward to cause said rim portions to engage the interior surface of said shell with clamping contact and, upon deflation of said container, said folds resuming their inwardly extending position to decrease the diameter of said container from its expanded condition thereby permitting said sections to move radially inward into contracted position, out of clamping contact with said shell.

4. An expansible mandrel for insertion into a metal pile shell to receive hammer blows for driving the shell into the ground, said mandrel comprising a plurality of elongate sections of generally sector shape in cross section, each of said sections having a curved rim portion engageable with the interior surface of said shell, each of said sections having a channel portion comprising a pair of wings extending inwardly from the ends of its rim portion toward the vertical central axis of the mandrel and terminating short of said axis and each section having a pressure receiving wall of substantial width extending transversely between said wings from the inner ends of said wings, said pressure receiving walls providing a longitudinal central opening, bolt means connecting diametrically opposite sections, compression springs on said bolts urging said sections toward said axis, a flexible, inflatable, deflatable, elongate tubular pressure container mounted in said central opening, the tubular peripheral wall of said container being made of reinforced rubber material such that said tubular wall is unstretchable longitudinally and peripherally, said tubular wall having longitudinally disposed pressure areas, one for each of said pressure receiving walls, and said tubular wall having a longitudinally disposed fold between each adjacent pair of pressure areas normally extending inwardly, each of said pressure areas being in engagement with one of the transverse pressure receiving walls of said sections, means for introducing fluid pressure into said container to inflate said container, said folds upon inflation of said container expanding outwardly, without change in the peripheral dimensions of said container wall and causing said pressure areas to exert pressure on said pressure receiving walls to move said sections radially outward against the force of said springs to move said rim portions against said shell, said folds upon deflation of said container moving to their normal inwardly extending position permitting said springs to move said sections inwardly away from said shell.

5. An expansible mandrel for insertion into a metal pile shell to receive hammer blows for driving the shell into the ground, said mandrel comprising a plurality of elongate sections having a generally sector shape in cross section, each having a rim portion engageable with said shell, each of said sections also having a channel portion comprising a pair of wings extending inwardly from said rim portion toward the vertical central axis of the mandrel and an arcuate shaped pressure receiving wall extending transversely between said inwardly extending wings, said pressure receiving walls providing an elongate central opening, an inflatable, deflatable, elongate, flexible tubular pressure container having an unstretchable tubular wall of reinforced rubber material surrounding said vertical axis and mounted in said central opening, and said wall lying between said central axis and said pressure receiving walls, said container tubular wall having a plurality of longitudinally disposed pressure areas, each of which engages one of said pressure receiving walls, and said tubular wall having a longitudinally disposed,'inwardly extending fold between each adjacent pair of pressure area s, bolts connecting opposed sections, spring means mounted on said bolts normally urging said sectionstoward said axis, means for introducing fluid pressure into said pressure container, said folds expanding outwardly upon inflation of said container thereby increasing the diameter of said container without stretching said tubular wall, thereby increasing the diameter of said container and causing said pres sure areas over a major portion of the periphery of said tubular wall to press against said pressure receiving areas to cause said sections to move radially outward and thereby'force said rim portions against said shell, said folds returning to'their inwardly extending positions on deflation .of said container to decrease the diameter of said container from its inflated condition thereby permitting said springs to return 'said sections inwardly away from said shell.

'6. A mandrel constructed "according to claim 2 in which thepressure receiving walls of said sections are arcuat'ely shaped.

7. A mandrel .constructed according to claim 6 in which there are four sections each having a cross section of "generally quadrant'sector shape and in which the rim portion. of each section has an arcuate length of approximately 90 when said mandrel is in contracted position and in which said bolts extend diametrically to connect "diametrically opposite sections.

References Cited in the file of this patent UNITED STATES PATENTS 865,653 Upson'et-al. July 5, 1932 2,170,188 Gobi ,Aug. 22, 1939 2,312,587 Price Mar. 2, 1943 2,313,625 Cobi Mar. 9, 1943 2;625,015 'Cobi Jan. 13, 1953 2,684,577 Smith Ju1y27, 1954

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