US3375881A - Pile driver - Google Patents

Description

April 2, 1968 R. E. MYERS ET PILE DRIVER 2 Sheets-Sheet 1' Filed March 7, 1966 INVENTORJ.

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April 2, 1968 R. E. MYERS ET AL FILE DRIVER 2 Sheets-Sheet 2 Filed March 7, 1966 INVEN M United States Patent Filed Mar. 7, 1966, Ser. No. 532,244 9 Claims. (Cl. 173---139) This invention relates to new and useful improvements in pile drivers, and has particular reference to pile drivers of the type comprising a ram mounted slidably on columns extending vertically between upper and lower heads, the columns and heads comprising a frame adapted to be supported by a crane or the like to be positioned over a pile to be driven.

The principal object of the present invention is the provision of means tending largely to overcome a very common cause of breakage of the columns. Said columns extend between the upper and lower heads and are commonly rigidly secured in said heads, by means of keys or the like. The cutting of key slots in the columns seriously weakens said columns, and they are often subjected to extreme tensile stresses, as will appear, due to elastic rebound of the column being driven, or due to faulty operation by allowing the ram to strike the lower head. As a result, breakage of the columns at their ends is a common occurrence necessitating costly repairs. According to the present invention, the columns are relieved of all tensile stress by slidable engagement thereof in sockets provided therefor in the heads, auxiliary members better suited to withstanding heavy shock loads being provided to connect the heads to sustain the tensile stresses and weight load. These auxiliary members may constitute a series of pre-tensioned steel cables disposed symmetrically with respect to the hammer axis.

Certain other objects are the provision of means for insuring equal tension of all of the cables extending between the heads, for insuring parallelism of said cables with the hammer axis, and for preventing possible whipping motion of the cables.

Other objects are simplicity and economy of construction, efficiency and dependability of operation, and adaptability to be applied to many pro-existing pile drivers as a modification thereof.

With these objects in view, as well as other objects which will appear in the course of the specification, reference will be had to the accompanying drawing, where in:

FIG. 1 is a side elevational View of a pile driver embodying the present invention, shown in operative relationship to a pile to be driven,

FIG. 2 is a sectional view FIG. 1,

FIG. 3 is an enlarged top plan view of the hammer,

FIG. 4 is a fragmentary sectional view taken on line IV IV of FIG. 3,

FIG. 5 is an enlarged sectional view taken on line V- V of FIG. 2,

FIG. 6 is a fragmentary sectional view taken on line VIVI of FIG. 5,

FIG. 7 is an enlarged sectional view taken on line VII-VII of FIG. 2, and

FIG. 8 is a fragmentary sectional view taken on line VIII-VIII of FIG. 7.

Like reference numerals apply to similar parts throughout the several views, and the numeral 2 applies generally to the frame of the hammer, comprising an upper head 4 commonly known as the cylinder, a lower head 6. commonly known as the base, and a plurality of cylindrical columns or posts 8 extending between said cylinder and base parallel to the vertical axis of the hammer. Formed in cylinder 4 is a vertical cylindrical bore 10 in which a taken On line IIII of 3,375,881 Patented Apr. 2, 1968 piston 12 is operably mounted. A vertical piston rod 14 is affixed at its upper end to piston 12, and extends slidably downwardly through a suitable, packing gland 16 mounted in the lower end wall of the cylinder. At its lower end, piston rod 14 is affixed, by suitable means including keys 18, to a ram 20 having the form of a heavy rectilinear block mounted for vertical sliding movement on columns 8. Afiixed in said ram is a cylindrical ram point 22 which extends downwardly and which, when the ram is lowered, enters a cylindrical bore 24 formed vertically through bore 6. The pile 26 to be driven, illustrated as a cylindrical pipe, is ordinarily provided with a pipe cap 28 which seats against the lower surface of the base. Said cap may be provided on its lower side with a series of concentric steps 30 of different diameters whereby to engage pipes of various diameters. Also, the cap extends upwardly into bore 24 of the base and is provided at its upper endwith a socket filled with a cushioning material 32 such as a hard fiber material or bronze: or other relatively soft metal for receiving the impact of ram point 22. The cap is ordinarily secured loosely to bore 6 by any suitable means, not shown, as a matter of convenience. The. axial length of ram point 22 is such that it can engage cap 28 before ram 20 contacts thetop of base 6, so long as frame 2 is properly suspended with base 6 resting on the cap as shown.

Affixed to the top of cylinder 2 as by screws 34 is a cylinder cap 36 carrying a horizontal support pin 38 suitable for engagement by a crane hook or the like, whereby the hammer frame is suspended. Cylinder 2 is provided at its upper end with outward lateral extensions 40 forming guideways 42 at diametrically opposite sides of the cylinder and at its lower end with extensions 44 forming similar guideways 46. Base 6 also has guideways 48 formed at opposite sides thereof. The guideways 42, 46 and 48 at each side of the hammer are aligned in a direction parallel to the hammer axis, and said guideways are adapted to receive slidably therein a pair of parallel guide leads, not shown, which are supported by the crane, or otherwise, whereby the frame :2 is supported coaxially with the pile 26 to be driven. Air or steam is admitted to the lower end of cylinder bore 10, whereby to elevate piston 12 therein and to elevate ram 20 on columns 8, and" exhausted from the cylinder bore when the piston reaches the top of its stroke, whereby to allow ram 20 to fall by gravity so that ram point 22 delivers a blow to cap 28, and pile 26, by suitable valving means carried by the cylinder. This valve means is not directly pertinent to the present invention and is not shown, although it is well knownv in the art.

In the: operation of the hammer as described above, breakage of columns 8, particularly at their lower ends, is a common and recurring source of trouble, necessitating expensive repairs. Heretofore the ends of said columns have been rigidly fixed respectively in the cylinder head 4 and base 6- by one means or another, usually by forming matching key slots in the column and heads and driving heavy keys into said slots. Said slots, of course, substantially reduced the strength of each column, and a very large tensile shock load could be imposed on the columns under several circumstances. For example, the operator of the crane, through carelessness or lack, of skill, might suspend the hammer frame with base: 6 spaced slightly above cap 28, so that ram 20 could engage base 6 before ram point 22 engaged cap. 28, and the resulting blow to. the base was of course transmitted directly to. the. columns 8 as a tensile shock load. Even if the hammer were operated properly, severe tensile stresses in the columns could still occur. For example, if pile 26 should be engaged at its lower end in a very soft earth formation, so that it runs very freely when the hammer strikes the pile may fall more rapidly than the inertia of the hammer frame 2 will permit it to follow, so that ram 20 may strike base 6 as described above. Also, pile 26, particularly if it is long, will be axially compressed by the force of each hammer blow, and rebound powerfully after the force of the blow is spent. This upward rebound of the pile delivers a heavy upward blow to base 6 through cap 28, and this blow is transmitted through columns 8 to cylinder head 4. The resulting upward impetus of cylinder 4- continues by inertia, placing columns 8 under tension. This action, placing the columns alternately in tension and compression, continues in a vibrating manner until it is gradually damped out.

According to the present invention, columns 8 are relieved of all tensile stresses. Instead of being ragidily fixed in the cylinder and base heads, it will be seen, as best shown in FIG. 1, that the upper end of each column is slidably engaged in a socket 50 formed therefor in cylinder head 4, and that the lower end of each column is slidably engaged in a socket 52 formed therefor in base 6. Each end of each column abuts a cushion member 54 disposed in the closed end of the associated socket. Said cushion member may be formed of a hard fibrous material as shown, or of bronze or other metal which is relatively soft as compared to the steel of which the columns and heads are formed.

A false head 56 is inserted between cylinder 4 and cap 36, and is also secured in place by screws 34. Said false head comprises a very thick plate having diametrically opposite extensions 58, said extensions being aligned with upper guideways 42 of the cylinder, but not extending as far from the cylinder axis as said guideways. Mounted on the top surface of each extension 58 is a solid, semi-cylindrical upper cable guide 60, said guide being upwardly convex and the axis thereof being radial to the cylinder axis. Said cable guide is rigidly positioned on its false head extension 58 by dowel pins 62 (see FIG. 4), and the semi-cylinder surface thereof has a series of helically extending cable grooves 64 formed therein. Similarly, a lower cable guide 66 is disposed at each side of base 6, seating upwardly against a pair of shoulders 68 formed in guideways 48, and positioned thereon by dowel pins 70 (see FIG. 8). However, the cable grooves 72 of the lower guides are not helical, but are peripheral (see FIG. 7).

A steel wire cable 74 is disposed at each side of the hammer, and is wound alternately around upper cable guide 60 and lower cable guide 66 at that side, and lying in the cable grooves of said guides, whereby each cable presents a series of cable reaches extending between the cylinder and the base. The terminal reaches 76 of each cable (see FIGS. 1 and 2) are dead-ended in any suitable manner such as by being extended downwardly through bores 78 provided radially therefor in upper cable guide 60 (see FIGS. 3 and 4), through individual bores 78 provided therefor in false head 56, and being secured to themselves below said false head as by cable clamps 80. The continuous reaches of each cable, starting at upper guide 60, extend successively through individual bores 82 provided therefor in false head 56 (see FIG. 4), bores 84 provided therefor in shoulders 86 of the cylinder extensions 40 forming upper guideways 42 (see FIG. 4) bores 88 formed in shoulders 90 of the cylinder extensions 44 forming lower guideways 46 (see FIG. 6), and bores 92 formed in shoulders 68 of the guideways 48 of the base.

The two cables 74 are preferably pre-stretched before they are trained over the guides and secured in place, as by stressing them to a substantial proportion of their elastic limits, and maintaining this loading for a substantial period of time. They are also stressed, one reach at a time, as they are trained about their cable guides, preferably to about one half of their elastic limits.

There are several features of the invention which perhaps should be discussed in greater detail. It will be readily apparent that the columns 8 are never subjected to tensile stresses, but only to compressional forces. They Cir may thus be solid, having no keyways or other reductions of cross-sectional area. There is thus virtually no tendency of the columns to fracture or break, these failures nearly always occurring in tension. Also, since the columns are stronger in compression than in tension, the invention permits the use of smaller columns, or columns made of a lower grade, less expensive steel.

The entire tensile load between the cylinder and base is absorbed by the cables 74, which are much better adapted to withstand shock tensile loading than are the rigid columns. This is true because the cables are generally considerably more elastic or stretchable than the columns, since they are rendered relatively free to elongate by straightening of the wire strands thereof and reduction of the cable diameter. Hence they tend to cushion the tensile shocks by distributing the absorption of the kinetic energy through longer time periods. Moreover, the cables are highly flexible as compared to the columns, and so are much freer to accommodate themselves to Slight angularities or lack of exact parallelism between the hammer axis and the direction of the hammer blow, these angularities often existing or developing as a result of manufacturing tolerances, wearing of parts, or strains of actual usage. In hammers wherein the columns are rigidly secured in the heads, these angularities often result in bending stresses as well as tensile stresses in the column, thus accelerating their eventual failure.

The pre-stressing of the cables, as well as the stressing thereof as they are applied, tends to remove any initial easy stretching of the cables, which might exist due to slight irregularities in the cable twisting process, or due to slight disarrangement of the cable strands. The cables are thus rendered of a more uniform, even strength, so that the two cables, or different reaches of each cable, are less likely to develop uneven effective lengths or tensions as they become gradually more stretched in actual service. Also, the pre-stressing renders the cables more difficult to stretch still further in use, so that columns 8 are seated very forcibly against column cushions 54 and cannot be pulled as far from said cushions as the cables are stressed, as would be possible if the cables were not pre-stressed. This reduces the hammer blows of the heads against the ends of the columns as the cable reaches rebound from tensile strains and hence reduces any tendency of the column ends to be fiared by said hammer blows, which flaring could cause wedging of the columns in their sockets. The cushions 54 themselves are of course also useful for this purpose.

It will be seen that the axial lead of the helical cable grooves 64 of top cable guides 60 is such that adjacent reaches of each cable are spaced apart the same distance as the peripheral cable grooves 72 of the lower guides. Thus by aligning the upper and lower guides properly, provision is made that all of the reaches of the cables are disposed precisely parallel to the axis of the hammer. Thus any tension induced in the cables by hammer blows in the manner discussed cannot induce torsional stresses in the hammer frame. Also, cable grooves 64 and 72 are smooth so that the cables may slip freely therein. Thus if necessary the cables can adjust themselves slidably in said grooves in order to insure that all of the reaches of each cable will be under equal stress to insure maximum load capacity. The number of cable reaches required will of course depend on the weight and length of fall of ram 20, which of course determines the maximum kinetic energy the cables may be required to absorb. Finally, the close guiding of each reach of the cables intermediate its ends, by inclusion thereof in bores 84, 8'8 and 92 of the hammer frame as previously described, prevents or greatly inhibits any possible lateral whipping of the cables during the instants .of actual use that said cables may develop some slack due to axial compression of the columns. Such whipping can substantially increase the wearing of the cables and reduce the effective life thereof.

While we have shown and described a specific embodiment of our invention, it will be readily apparent that many minor changes of structure and operation could be made without departing from the spirit of the invention as defined by the scope of the appended claims.

What we claim as new and desire to protect by Letters Patent is:

1. In a pile driver hammer:

(a) an upper head adapted to be suspended whereby to support said hammer,

(b) a lower head spaced below said upper head,

(c) a plurality of parallel, spaced apart columns extending vertically between said heads, the opposite ends of each column being engaged slidably in sockets provided therefor, respectively in said upper and lower heads,

((1) a plurality of reaches of flexible steel cables extending between and interconnecting said upper and lower heads, said cables being tensioned whereby to seat said columns firmly in said sockets,

(e) a ram carried slidably on said columns intermediate said heads and adapted at the bottom of its stroke to deliver a downward blow to a pile over which said hammer is suspended, and

(f) power means for moving said ram on said columns.

2. The structure as recited in claim 1 wherein said cable reaches are disposed parallel to the vertical axis of said hammer, and are symmetrically disposed with respect thereto.

3. The structure as recited in claim 1 with the addition of:

(a) a pad of cushioning material disposed in each of said sockets between the closed end of said socket and the end of the column engaged therein.

4. The structures as recited in claim 1 with the addition of:

(a) guide means carried by said heads intermediate the points of attachment of said cable reaches to said heads, said guide means permitting longitudinal movement of said cable reaches relative thereto but restraining said cable reaches against lateral whipping movement.

5. The structure as recited in claim 1 wherein a plurality of said cable reaches constitute a single continuous length of cable, and wherein said cable is attached to said heads by means of a pair of cable guides rigidly alfixed respectively to said upper and lower heads, said cable being trained alternately around said guides to form a plurality of reaches extending between said heads, the extreme ends of said cable being dead-ended.

6. The structure as recited in claim 5 wherein the surface of each of said cable guides engaged by said cable is cylindrically curved about an axis radial to the, hammer axis.

7. The structure as recited in claim 5 wherein the surface .of each of said cable guides engaged by said cable is cylindrically curved about an axis radial to the hammer axis, and is smooth whereby to permit longitudinal slippage of said cable thereon, whereby to insure uniform tension of all of the reaches of said cable. 1

8. The structure as recited in claim 6 wherein. the cylindrically curved surface of one of said cable guides has helically extending cable grooves formed therein, and the cylindrically curved surface of the other of said cable guides has peripherally extending cable grooves formed therein, the axial lead of said helical cable grooves, in the arc thereof engaged by said cable, being equal to the axial spacing between said peripheral grooves of the other guide, whereby all of the reaches of said cable are maintained parallel, and wherein said guide members are aligned on said heads so that all of said ca-ble reaches extend parallel to the axis of said hammer.

9. The structure as recited in claim 8 wherein the surfaces of all of said cable grooves of both of said cable guides are smooth, whereby to permit longitudinal slippage of said cable therein.

225,190 2,948,122 8/1960 Smith 173-139 3,053,231 9/1962 Fairchild 173-139 JAMES A. LEPPINK, Primary Examiner.

Claims (1)

1. IN A PILE DRIVER HAMMER: (A) AN UPPER HEAD ADAPTED TO BE SUSPENDED WHEREBY TO SUPPORT SAID HAMMER, (B) A LOWER HEAD SPACED BELOW SAID UPPER HEAD, (C) A PLURALITY OF PARALLEL, SPACED APART COLUMNS EXTENDING VERTICALLY BETWEEN SAID HEADS, THE OPPOSITE ENDS OF EACH COLUMN BEING ENGAGED SLIDABLY IN SOCKETS PROVIDED THEREFOR, RESPECTIVELY IN SAID UPPER AND LOWER HEADS, (D) A PLURALITY OF REACHES OF FLEXIBLE STEEL CABLES EXTENDING BETWEEN AND INTERCONNECTING SAID UPPER AND LOWER HEADS, SAID CABLES BEING TENSIONED WHEREBY TO SEAT SAID COLUMNS FIRMLY IN SAID SOCKETS, (E) A RAM CARRIED SLIDABLY ON SAID COLUMNS INTERMEDIATE SAID HEADS AND ADAPTED AT THE BOTTOM OF ITS STROKE TO DELIVER A DOWNWARD BLOW TO A PILE OVER WHICH SAID HAMMER IS SUSPENDED, AND (F) POWER MEANS FOR MOVING SAID RAM ON SAID COLUMNS.

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