US2881592A - Expansible mandrel for driving molds for concrete piles - Google Patents

Description

April 14, 1959 Y w. H. coBl 8 EXPANSIBLE MANDREL FOR DRIVING MOLDS FOR CONCRETE FILES Filed May 29, 1953 V 6 Sheets-Sheet 1 April 14, 1959 w, c051 2,881,592

EXPANSIBLE MANDREL FOR DRIVING MOLDS FOR CONCRETE; FILES Filed May 29. 1955 e Shets-Sheet 2 zkmebg [Ill/II April 14, 1959 2,881,592

EXRANSIBLE MANDREL FOR DRIVING MOLDS FQR CONCRETE PILES Filed May 29, 1953 +1. cos;

6 Sheets-Sheet '5 April 1959 w. H. COB! 2,881,592

EXFANSIBLE MANDREL FOR DRIVING MOLDS FOR CONCRETE FILES Filed May 29. 1953 6 Sheets-Sheet 4 A; f0 Z3 53 5/ g 36 III/III] w. H. COB! A ril 14, 1959 EXPANSIBLE MANDREL FOR DRIVINQ, MOLDS FOR CONCRETE PILES e Sheets-Shet 5 Filed May 29, 1953 Filed may 29. 1953' April 14, 1959 wQi-l. COBI 2, EXPANSIBLE MANDREL FOR DRIVING oms FOR CONCRETE FILES e Sheets-Sheet 6 United States Patent EXPANSIBLE MANDREL FOR DRIVING MOLDS FOR CONCRETE PILES Application May 29, 1953, Serial No. 358,357 24 Claims. (Cl. 61-79) The invention relates to expansible pile driving mandrels, and particularly to expansible and contracta-ble 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 aspneumatic mandrels and in which the expansion is caused by the application of fluid pessure 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 segments or quadrants contacting the inner surface of the shell or mold, and in which the forces from thte hammer blows are substantially evenly distributed over the cross-sectional area of the mandrel at any point along its length thereby insuring a substantially straightline driving of the pile into the ground, at least to the extent permitted by the nature 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 a stronger, inflatable, flexible container than was previously provided for expanding the mandrel, and which is subject to less wear, by depending for its effective action upon a change of its cross-sectional shape from deflated to inflated condition and substantially avoiding any expansion or 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 feature of the invention, the mandrel is made up of a series of annular arranged segments or quadrants extending throughout the length of the mandrel for contacting the inner surface of the shell of the pile, and a series of annularly arranged flexible container means alternating with the segments and adapted to apply circumferentially effective pressures to the intermediate segments, when inflated. Thus each segment will be forced outward into contact with the shell under the influence of a force that is the resultant of the two circumferential forces applied thereto by two adjacent containers. In this manner all three sides of a segment will be subjected to opposing forces during operating condition and the segment thus will be held firmly in position. Similarly each container will be held firmly in position by two adjacent segments, the great friction between the segments and the container surfaces positively eliminating any shifting of the container in the radial or even the lengthwise direction of the mandrel Ice 2,881,592

during the rough driving operation. Thus the container means, instead of being in the form'of a single tubeu'nit engaging inner corners of all of the mandrel segments, comprises a plurality of tube units, one tube unit between every two adjacent segments. With this arrangement each tube unit will be in contact with large surfacesof two segments, thus requiring a comparatively low inner specific fluid pressure to produce the necessary force between the segments and the shell.

In accordance with another feature the individual container tubes are in continuous contact with the adjacent segment surfaces even in deflated condition. Thus the change in tube volume from deflated to inflated condition will be a minimum and it is possible to avoid any appreciable elongation of the tube wall during inflation, thereby increasing the life of the tubes. Furthermore, without the need of stretching, the tube maybe covered on' the outside with a non-stretching but flexible layer which may be of a much tougher and better wearing-material thenthe liquid or gas impervious material in the tube wall proper.

In accordance with still another feature each tube unit is produced or cured in a flattened shape corresponding to its shape in the mandrel during deflated condition. Thus the springs for contracting, or forcing inwardly, the mandrel segments need not compress the tubes, and may be of comparatively light construction. This feature also greatly simplifies the assembling and dismantling of the mandrel inasmuch as the flat deflated tube may be readily laid in position between the segments without the need of tampering or locking down by'bolts or tools.

In accordance with yet another feature the contracting spring means are radially disposed to apply radially directed pressure to the segments. This feature permits of a simpler construction as well as of easier access "to the springs and assembling bolts. 1

Other features and advantages of the invention will be hereinafter described and claimed:

The following detailed 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 sectional view of the lower portion of the expansible mandrel, showing the mandrel in place within the lower portion of the shell and expanded ready for use. The sections of Figs. 1 and 2 are taken along a diametrical plane through the mandrel as indicated by line 11 of Fig. 3.

Fig. 3 is a cross-sectional view taken along line 3-3 in Fig. 1.

Fig. 9 is similar to Fig. 3, except that it shows the mandrel contracted.

Patented Apr. 14, 1959 L Fig. 10 is similar to Fig. 5, except that it shows the mandrel contracted.

Fig. 11 is similar to Fig. 6 except that it shows the mandrel contracted.

The following are detail Views of certain parts: ,Fig. 12 is taken along line 12-12 in Fig. 3;

Fig. 13 is taken along line 13-13 in Fig. 4;

Fig. 14 is similar to Fig. 13 except that it shows the relation of the parts when the mandrel is contracted;

Fig. 15 is partly in cross-section and is taken along line 15-15 in Fig. 4;

Fig. 16 is taken along line 16-16 in Figs. 4 and 8;

Fig. 17 is a side view of the parts in Fig. 16;

Fig. .18 is partly in cross-section and is taken along line 18-18 in Fig. and

Fig..19 isa cross-sectional view taken along line 19-19 in :Fig. 18.

The drawings show in general an expanded mandrel in operative position within a pile shell or mold 10, except forFigs. 9, 10, 11 which show the mandrel contracted within the shell 10. The shell is of the corrugated type, having corrugations running .helically and in immediate succession along the entire length.

In the embodiment shown in the drawing the mandrel is made up of four similar segments or quadrants 12, 14, 16, 18which extend through the entire length of the mandrel. Each segment includes an angle member 21 and a curved plate 22 which is welded along its entire length to the two edges of the angle member 21. The member 21 and the plate 22 may be of steel drawn to the desired shapes and dimensions. Both the members 21 and the plates 22 receive the force from the hammer blows at their upper ends and may transmit the force through their entire length to the bottom end of the mandrel. When the length of the mandrel exceeds the manufacturing lengths of these members and plates, successive portions are welded together, so that each segment forms one continuous structure.

Ascan be seen in Fig. 6 where the four segments are shown in the expanded condition of the mandrel and in contact with the shell 10, the four plates 22 are separated by spaces 23 between their edges, which allows for the contraction of the mandrel, as shown in corresponding Fig. 11.

As will further appear from Fig. 6 the angle irons or members 21 are welded to the plates 22 well inside the edges of the plates so that a space 24 is formed between adjacent angle irons 21 which is wider than the space 23. Thus when the mandrel is collapsed, as shown in 'Fig. 11, and the plates 22 engage, the space 24 still remains though of much reduced width.

In the four spaces 24 between the angle irons 21 pressure containers 32,34, 36 and 38 are located; they are tubular and extend through the length of the mandrel, except for short distances at top and bottom.

Each tubular container is mainly of flexible material 41 (see Figs. 18 and 19-) impervious to the fluid used for the pneumatic expansion of the mandrel, and the outer surface is covered by a hard wearing fabric 42, woven thereabout. The material 41 is preferably vulcanized rubber and the fabric 42 is of thread with a large percentage of nylon fibre and this may further be coated with a plastic covering. Other materials may be found suitable for these purposes. 'Each of the tubes or containers 32, 34, 36 and 38 is closed at its upper end by an end plug 45 through which the pressure fluid may be admitted. The bottom of each tube is closed by a similar end plug 46, which however 'hasnopassage for the pressure fluid.

In the manufacture of the tubular containers, the tubes are formed and cured in the flat shape shown in Fig. 11, so that, when the mandrel is contracted, they fit the narrowed space 24 without exerting any appreciable pressure on the angle irons 21. The inflated condition of dhe tubes 32, 34, 36, 38 is shown in Fig. 7, the tubes approaching the cylindrical shape without the tube walls being substantially elongated peripherally.

Compression springs 50 and bolts 51 are distributed at intervals of a few feet along the whole length of the mandrel. Such a bolt is shown in Fig. 6 for the expanded condition and in Fig. 11 for the contracted condition. For the mounting of a bolt two triangular filler blocks 53 are welded in position in the angles of the angle irons 21 of the diametrically opposed segments or quadrants 12 and 16 and suitable holes are provided in the irons 21 and the blocks 53 for passing of the bolt between adjacent tubes 32, 34 and 36, 38. A spring 50 surrounds each end of the bolt and sets on the shoulder of the widened hole 54 in the block 53. Each spring is tightened by a nut and washer 55 on the end of the bolt. Openings or holes 58 in the plates 22, large enough to pass the springs and washers 55, permit of the insertion of the bolts and the tightening of the nuts.

Figs. 2 and 7 show other bolts 51 and filler blocks 53 for the segments 14 and 18, these bolts thus being at right angles to the similar bolts between segments 12 and 16, and alternating with them throughout the length of the mandrel. These latter bolts between segments 14 and 18 thus pass between adjacent tubes 34, 36 and 38, 32.

In the contracted condition of the mandrel, shown in Fig. 11, the springs 50 still have suflicient compression to force the edges of adjacent plates 22 into firm contact, thereby insuring the safe insertion into and removal from the pile shell 10 of the whole mandrel.

It may thus be seen that the mandrel is expanded by four tubular pneumatic containers located in a circle with, and alternating with, four segments of the mandrel. During inflation each segment or quadrant is acted upon by two containers on two of its sides and will be forced outward into engagement of its third side, the plate 22, with the inner surface of the pile shell by the radial resultant of the two angularly directed forces applied by the pressure containers. Thus during operation the segments will be held firmly in position relatively to one another and will be evenly distributed relatively to the .shell. In this manner an even distribution between the four segments of the forces applied by the strokes of the driving hammer is insured during operation, so that the pile may automatically be driven into the ground along a straight line, in so far as permitted by the compositions of the strata.

It may further be seen that the mandrel is contracted by contracting spring means which include bolts and springs connecting alternate, opposite segments together. During deflation of the containers the spring means act along radial lines upon the segments and thus force the segments directly towards the center of the mandrel until their edges come into firm engagement, so that the mandrel along its entire length may readily clear the corrugated shell during removal therefrom.

Though the present embodiment of the invention is shown and described herein as a mandrel comprising four segments, four tubes and contraction spring means between opposed segments, it should be understood that, without a departure from the spirit and scope of the invention, the mandrel may comprise six segments and six tubes, or a larger even number of segments and tubes with contraction spring means between opposed segments.

It should further be understood that the shape of the plates 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 fiat to conform with a square shell, or they may be of an angular crosssection to conform with polygonal cross-sections of a shell with more than four corners.

Considering now more specific features of the mandrel, each curved plate 22 is reenforced at its upper end by a short similarly curved protecting plate 61 welded along its edges to the outside of the plate 22.

In the present instance of :1 corrugated shell, the plates 22 have welded to their outer surfaces a series of half round helix bars 62, as shown in Fig. 2, which are disposed along helical lines to fit into the grooves of the helically corrugated shell. The sets of circumferential bars are placed at intervals of about a foot or more along the length of the mandrel. By this means the driving force of the hammer blows may be partly distributed over the whole length of the shell to overcome the friction with the ground during driving.

The top assembly of the mandrel includes a drive head 70, shown in Fig. 1 which is in the form of a cylindrical block with a depression 71 in the top surface for receiving the metal encased wooden hammer cushion 72, and with a depression 73 in the bottom surface fitting loosely over the protecting plates 61 of the mandrel. The head has two parallel holes 74 through the body portion thereof. 3

Two mild steel buffer plates-75 are'positioned against the bottom of the depression 73 and engage the upper aligned end surfaces of the angle irons 21 and plates 22 for evenly distributing the hammer blows to these elements during operation.

The drive head 70 is loosely connected to the upper end of the mandrel proper by a lifting bolt 80 fastened in a central hole 81 in the drive head 70 by means of spherically surfaced washers 82, 83 held against spherically surfaced shoulders in the hole 81 by a nut 84 on the shouldered bolt 80.

The lower end of the bolt extends a short distance into the interior of the mandrel where it carries a spider 85 having a hub portion for fastening to the bolt and two pairs of flat wings 86, 87 extending into the spaces 24 between the angle irons 21. As may be seen in Figs. 1, 3 and 12 the wings 86, 87 extend in under and clear two pairs of cross-bolts 88, 89 which cross the spaces 24 and pass through and beyond holes in the opposed faces of the angle irons 21 and in the associated plates 22 and 61 and extend a short distance beyond the plates 61 in the expanded condition of the mandrel. Each bolt has a head at one end; while the other end is tapered for easy passage through the plates at the time of assembly. Short screws 88', 89' are placed through said other ends of the bolts 88, 89 and are provided with nuts (as shown in Figs. 3 and 12) to prevent the bolts from being shaken out during the operations. The pair of cross bolts 88 are placed at a higher level than the pair 89 to clear them. When the mandrel is deflated and is to be lifted out of a shell which has been driven in place a steel cable is passed through the holes 74 in the drive head and up about the hammer base of the driving rig, and the mandrelis lifted bodily up into the leads of the driving rig. After the drive head 70 has been raised a short distance, an inch more or less, the two pairs of wings 86, 87 will engage the corresponding pairs of cross-bolts 88, 89 whereupon the entire mandrel will rise with the drive head. It will be noted that the upper edges of the spider wings are sloped downward inwardly, thereby applying an inward force to the cross-bolts during lifting in case the upper free end of the mandrel has not been sufficiently contracted. By means of the spherical mounting of the lifting bolt 80 in the drivehead a certain freedom of self-adjustment between the drivehead and the top of the mandrel is available during the rough lifting operations. The upper and lower nuts on bolt 80 are preferably of the type known as elastic stop nuts, which may be depended upon to lock themselves on to the bolt.

The bottom assembly of the lower end of the shell the mandrel is contained by and the boot 11 welded thereto. As shown in Figs. 2 and 8 a heavy plate 90 is placed between the bottom of the boot and the aligned bottom cross-sectional surfaces of theangle irons 21 and ture 45 includes a piece tubular container, say container plates 22 to receive the forces of the hammer blows and impart them to the boot. The plate 90 has a central hollow upright 91, which at its upper end carries a crossbar 92 which extends in both directions through snug holes in diametrically located angle irons 21, so that, when the mandrel is inserted into or removed from the shell, the plate 90 will follow as a part thereof. The hole 93 in the upright is slightly oblong in order to relieve the crossbar 92 from the forces of the hammer blows during driving. The bar 92 passes snugly through holes in the angle irons 21 when these move in and out during the expansion and contraction of the mandrel. One end of the bar 92 is slightly tapered for easy insertion'through the associated holes, and the other end is slotted and carries a key projection 94, as shown in Figs. 16 and 17. Holes 95 and 96 in plates 22 register with the ends of bar 92, the hole 96 having a slot 97 in its upper side. The bar is normally locked in position by having its key 94 on the under side, but when it becomes de sirable to remove the bar the key is turned upward, say by a screwdriver acting in the end slot, and the bar may be driven out by pushing it with a rod through the hole 95.

Now referring to specific features of the pneumatic equipment illustrated, the fixtures 45 and 46 at the upper and lower ends of the tubular containers 32, 34, 36, 38 are substantially similar.

As will appear most clearly from Figs. 18 and 19 a fixof tubing 101 having at its upper end a nipple 102 for receiving a small pneumatic hose 103, a piece of rod 104, a plate welded alongits edges to tubing 101 and rod 104 and two clamping plates 106 and 107, which may be clamped to the walls of a 32, by means of a plurality of short bolts 108. In assembling these parts the tubing 101, rod 104, plate 105 and the inner surface of the tubular container, say 32, are coated with a liquid sealing compound; the tubing, plate and rod are placed as a unit inside the opposite faces of the flat end of the tube 32; the plates 106, 107 are forced down from opposite sides against the outside flat sides of tube 32; and the plates are screwed tight and thereby force the portions of tube 32 tight about the tubing, plate and rod. With the proper width of the clamping plates 106 and 107 a tight end seal for the tube 32 is obtained which will withstand pressures considerably higher than the normal operating pressure applied to the pneumatic system. The tubing 101 affords access to the interior of the tube 32 for the pressure fluid.

The plate 106 is extended upward beyond the end of the tube 32 into an ear 111 having a hole into which is welded a bushing 112 which extends across the space 24 and is of a length to fit between the faces of two angleirons 21 when the mandrel is contracted, as shown in Fig. 10. A crossrod 113 extends through the bushing 112 and through snug holes in the adjacent faces of the angleirons. The crossrod 113 moves freely through the angle irons during inflation and deflation and is of such length as not to interfere with the plates 22 when the mandrel is contracted. If desired, one pair of diametrically disposed rods 113 may be set at a slightly higher level than the other pair to avoid interference between their ends.

The fixtures 46 at the bottom of the tubular containers differ from the fixtures 45 mainly in that they afford no passage for the pressure fluid, because the nipple 102 is closed by a plug 115 which may be screwed in with sealing compoun The upper fixtures 45 connect their associated tubular containers 32, 34, 36, 38 through the individual hoses 103 to a manifold or fluid distributor which, as shown in Figs. 1 and 4, is located in the center of the upper end of the mandrel. The manifold is shown more in detail in Fig. 15. It comprises an intermediate tubular section 122, an upper hollow end section 123, and a lower solid end section 124. Both said sections 123 and 124 are welded to the middle section 122. The middle section has hollow projections 126 extending partly downward and being threaded,to each receive a nipple 127 for connection of the upper end of the corresponding pneumatic hose 103. The circuit for the fluid pressure is completed through the hollow end section 123, a common nipple 128 screwed through the wall of section 123, a pneumatic hose 129 which connects to a suitable nipple arrangement 130 fixedly mounted on a bracket 131 welded to the outside of one of the upper reenforcing plates 61, the nipple arrangement having an exterior female nipple 132 suitable for attachment of the long hose connection running down the rig to the control valve and the compresser in the crane.

The manifold is carried by a crossbar 140 passing through its lower section 124 and through holes in diametrically opposite angle irons 21. The crossbar 140 is similar to the crossbar 92 near the bottom end of the mandrel, and reference may thus be had to Figs. 16 and 17 and the related description for details of construction and of removal of the bar through the plates 22 when it becomes desirable to remove the manifold.

- Inasmuch as the edges of adjacent plates .22 and 61 contact each other when the mandrel is contracted a clearance 150 has been provided for the nipple arrangement 130 by cutting out semicircular pieces from the plates 21 and 61 of sections 12 and 18, as shown in Figs. 13 and 14.

It will further be noted that the inward projecting corners of the angle irons 21 have been milled off attheir upper ends to provide suflicient space for the spider '80 and the manifold 120.

In assembling the mandrel, two sections 12 and 14 are laid side by side with the tube container 34 between them. The distance between the crossbolt 113 at opposite ends of the tube is several inches shorter than the distance between the corresponding holes in the flat sides of the flatirons 21. Thus the tube is attached first at one end by insertion of the bolt 113 into the fixture 45 and through the opposite faces of the angle-irons 21, and then the tube is stretched so that the other bolt may be inserted in the fixture 46 and through the angle-irons 21 at their other end. Four more bolts 113 are then inserted and the tubes 32 and 36 are stretched and placed on the bolt. The manifold with hoses attached are then put in position, three hoses 103 are connected to their tubes, the fourth hanging free, and tube 129 is connected to fixture 130.

Then two sections 16 and 18 are laid side by side with the tube 38 stretched between them on bolts 113 at opposite ends. This assemblage is then laid on the first assemblage with the four protruding bolts 113 and the fourth hose 103 is connected to the tube fixture 45 of tube 38. The bar 140 is then driven in the manifold ward.

Then all the compression bolts 51 are inserted and their springs tightened. The bottom plate is put in place and its bar 92 inserted and locked in position by turning its key downward. The drive head 70 with the bolt 80 and spider 85 attached is placed in position over the upper end of the mandrel and the four bolts 88, 89 put in place to loosely attach the drive head to the mandrel. The mandrel then is ready for operation under fluid pressure.

Mandrels of this type may be used under greatly varying conditions and with shells of greatly varying lengths 120 and locked by turning its key down- .and cross-sections. The dimensions of the mandrel and its parts therefore may vary greatly. The mandrel may be designed for shells 100 feet or more in length.

The fluid pressure is preferably obtained from an air compressor, and the pressure for the longest mandrels meed not exceed 80- lbs/sq. in. The compression springs position through I may be tensioned to 300 lbs. and may be spaced 5 feet apart, more or less, along the mandrel.

When the mandrel is collapsed the half round helix bars 62 on its outside surface clear the inside of the corrupated shell by the least 4 all around, and the expansion may amount to an increase in diameter of the mandrel of about an inch and a half. It will, of course, be understood that the foregoing pressures and dimensions are merely examples of those that may be employed.

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 the scope of the invention claimed.

I claim:

1. An expansible mandrel for insertion into a metal shell to receive hammer blows for driving the shell into the ground, said mandrel including a plurality of segments each having a rim portion engageable with said shell and an angular frame portion extending inwardly fromsaid rim portion, the angular frame portion of each segment having faces angularly disposed with respect to each other, and the frame portion of each segment being adjacent to frame portions of other segments, a plurality of flexible pressure-containers each disposed between faces of a pair of adjacent frame portions for applying pressure to said faces to produce resultant forces moving said rim portions into engagement with said shell, and resilient means opposing said forces.

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 segments each having a rim portion engageable with said shell and an angular frame portion extending inwardly from said rim portion, the angular frame portion of each segment having faces angularly disposed with respect to each other, and the frame portion of each segment being adjacent to frame portions of other segments, and a plurality of flexible pressure-containers each disposed between faces of a pair of adjacent angular frame portions for applying pressure thereto.

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 segments each having a rim portion engageable with said shell and an angular frame portion extending inwardly from said rim portion, the angular frame portion of each segment having faces angularly disposed with respect to each other, and the frame portion of each segment being adjacent to frame portions of other segments, a plurality of flexible pressure-containers each disposed between faces of a pair of adjacent angular frame members, resilient means acting upon said mandrel segments to urge them into inwardly retracted positions wherein said rim portions are out of engagement with said shell, and .means for directing fluid-pressure to said containers for forcing said segments outwardly to engage said rim portions with said shell.

4. An expansible mandrel as defined in claim 3, wherein said resilient means comprises bolts extending diamettrically through oppositely disposed mandrel segments and spring means cooperating with said bolts for urging said oppositely disposed segments inwardly toward each other.

5. A mandrel as defined by claim 1 wherein said pressure containers are substantially flattened when uninflated and are expansible by change of shape under fluid pressure without substantially stretching of their material.

6. A mandrel as defined by claim 1 wherein each of said pressure containers is attached at its ends to faces of adjacent frame portions of said mandrel segments.

i said segments, means 7. A mandrel as defined by claim 4, inclu ing apin passing through said pressure-directing means and also through diagonally opposite mandrel segments for attaching said directing means to said segments.

8. Amandrel as plate at the lower ends of said segments, an extension from said plate, and a pin projecting through said ex-' tension and through diagonally opposite mandrel sec-' tions for attaching said plate to said segments.

- 9. A mandrel as defined by claim 1, including a drive head overlying said mandrel through certain faces of angular frame portions of said. mandrel segments, other pins extendingtransversely of the first-mentioned pins through other faces of said angular frameportions, and means depending from said drive head for engaging said pins to raise the mandrel out of the shell when said drive head is lifted.

10. A mandrel as defined by claim 1, including a drive head overlying said mandrel segments, pins extending through certain faces of angular frame portions of said mandrel segments, other pins extending transversely of the first-mentioned pins through other faces of said angular frame portions, and means. depending from said drive head for engaging said pins to raise the mandrel out of the shell when said drive head is lifted, said depending means having arms with inclined surfaces underlying said pins to both raise said mandrel segments and insure inward movement thereof to disengage said rim portions from the shell as said drive head is lifted.

11. A mandrel as defined by claim 1, including a drive head overlying said mandrel segments means depending from said drive head into a central space between said mandrel segments and adjacent the longitudinal axis of said mandrel, and means extending transversely from said depending means for raising said segments out of the shell as the drive head is lifted.

12. A mandrel as defined by claim 1, including a drive head overlying said mandrel segments, means depending from said drive head into a central space between said mandrel segments and adjacent the longitudinal axis of said mandrel, and means extending transversely from said depending means for raising said segments out of the shell as the drive head is lifted, and curved bearing means between said depending means and said drive head to enable self-adjustment of said depending means with respect to said drive head during lifting of said segments.

13. 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 segments disposed about a longitudinal axis of said mandrel, each of said segments having a rim portion engageable with said shell and an angular frame portion extending inwardly from said rim portion toward said axis, the angular frame portion of each segment having faces angularly disposed with respect to each other, and the frame portion of each segment being adjacent to frame portions of other segments, a plurality of flexible pressure-containers, each disposed between the faces of frame portions of an adjacent pair of said mandrel segments and located between said axis and the rim portions of for supporting said pressure-containers from said mandrel segments, and manifold means for directing fluid pressure to said pressure-containers for applying force to said frame portions and moving said segments outwardly to engage said rim portions with said shell.

14. 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 segments each having a rim portion engageable with said shell and an angular frame portion extending inwardly from said rim portion, the angular frame portion of each segment having faces angularly disposed with respect to each other, and the frame portion of each segment bedefined by claim 1, including a bottom tween faces of a pair of adjacent segments, pins extending ing adjacent to frame portions of other segments, a plurality of flexible pressure-containers each disposed beangular frame members, and means for directing fluid-pressure to said containers for forcing said mandrel segments outwardly to engage said rim portions with said shell, a pin passing through said pressure-directing means and also through diametrically opposite mandrel segments for attaching said directing means to said segments, the rim portion of one of said segments having an opening therein with a slot projecting therefrom, and said pin having a key projection adapted to pass through said slot when aligned therewith, said pin being mounted in said pressure-directing means 7 for rotation to bring said key out of alignment with said slot after said key has been passed therethrough.

15. A mandrel as defined by claim 1, including a bottom plate at the lower ends of said segments, an extension from said plate, and apin projecting through said extension and through diagonally opposite mandrel segments for attaching said plate to said segments, the rim portion of one of said mandrel segments having an opening therein with a slot projecting therefrom, and said pin having a key projection adapted to pass through said slot when aligned therewith, said pin being rotatably mounted in said extension from said plate to bring said key out of alignment with said slot after said key has been passed therethrough.

16. An expansible mandrel as defined by claim 2, wherein each of said pressure-containers is attached at an end to a bracket member having a portion extending into said end and another portion extending outwardly beyond said end, and means projecting through the last mentioned bracket portion for attaching said container to a section of said mandrel.

17. An expansible mandrel as defined by claim 2, wherein each of said pressure containers is substantially flat when uninflated and has projecting into one end thereof a plate having integral therewith a tube for directing fluid pressure into said container, said plate also having a portion projecting beyond said container end and forming a bracket for attachment of the container generally radial spaces to a segment of said mandrel.

18. An expansible mandrel as defined by claim 2, wherein each of said presure containers is substantially fiat when uninflated, bracket members attached to opposite ends of said containers for connecting them to segments of said mandrel, and tubes integral with certain of said bracket members and projecting into said containers for directing fluid pressure thereinto.

19. 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 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.

20. 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 fluid 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.

21. 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 1 and extending down in said central space with connections to said leaf structures for retracting the latter when the core head is raised.

22. An expansible core for driving pile shells comprising a plurality of leaf structures extending longitudinally 1 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 20 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.

23. An expansible mandrel for insertion into a metal 25 shell to receive hammer blows for driving the shell into the ground, said mandrel including a plurality of opposited disposed segments each engageable with a portion of the shell diametrically opposite the portion engaged by the other of said segments, each of said segments comprising an arcuate plate for engagement with a portion of the shell and a rigid pressurereceiving member ing from one of said segments to the other and spring means at opposite end portions of said bolt and bearing against portions of said mandrel segments.

24. An expansible mandrel as defined in claim 23, wherein said segments are diametrically disposed with respect to each other with an intervening space therebetween, and the bolt extends through both segments and the intervening space.

References Cited in the file of this patent UNITED STATES PATENTS 2,313,625 Cobi Mar. 9, 1943 2,321,146 Jones June 8, 1943 2,625,015 Cobi Jan. 13, 1953 2,684,577 Smith July 27, 1954

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