US3162252A

US3162252A - Pile driving hammer

Info

Publication number: US3162252A
Application number: US214624A
Authority: US
Inventors: James G Holland; Silva K Cobi
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-08-03
Filing date: 1962-08-03
Publication date: 1964-12-22
Anticipated expiration: 1981-12-22

Description

Dec. 22, 1964 w. H. coBl PILE DRIVING HAMMER 2 Sheets-Sheet 1 Filed Aug. 3, 1962 Flea.

Dec. Z2, 1964 Filed Aug. 3, 1962 HORSE POW ER TIME ELAPSED IN SECONDS 2 Sheets-Sheet 2 REVOLUTIONS PER MINUTE F'IG,

United States Patent Otice 3,162,252 Patented Dec. 22, 1964 Cobi, deceased Filed Aug. 3, 1962, Ser. No. 214,624 8 Claims. (Cl. 173-91) This invention relates to pile driving and, more particularly, to an improved hammer for driving piles.

In the driving of piles, whether steel pipes or beams, wood timbers, sheet piling or shells driven with a mandrel, it is conventional practice to employ'a hammer. The' pile member to be driven is held with one end at the position where the pile is to be located and driven from its opposite end with thehammer. Thus the driving blows of the hammer are applied through the member. Driving continues until the member is capable of sustaining a predetermined load. This may be determined after the member is driven by actually applying a load and measuring the bearing capacity or, more common, during driving by driving the member to a particular blow count. Where blow count is employed, it is usually determined by the number of hammer blows required to drive the member a measured distance, the number of blows and the distance depending on load bearing requirements and the type and size of the hammer and pile.

` Typical of the hammers heretofore employed for driving piles is the Vulcan #l hammer. This hammer consists in a 5000 lb. weight or ram which is lifted by steam or air to a height of three feet above the upper or free end of thepile. The ram is then released or dropped and allowed to fall by gravity and hit the upper end of the Each blow with this type of hammer imparts a 15,000 ft. lbs. impact to the pile. Other hammers, also employed for this purpose, use rams of other weights. In some hammers, the steam or air is applied in two directions, that is, not only to lift the ram but, also, to drive the ram downward against the free end of the pile. In any event, whether of the free falling type or driven down- Ward by steam or air, such hammers utilize heavy rams and rely, primarily, on the weight of the ram to drive the p ile. l

3 The heavy ram hammers heretofore employed for driv ing piles, whether of single or double action, do not permit variation in the magnitude of impact nor in the number of impacts which can be delivered during a given interval of time. The Weight of the ram and, hence, the impact force is fixed. Because of the weight of the ram, its inertia and the manner in which such heavy ram must be operated., the time between impacts is large. For example,

the Vulcan #l hammer, commonly used, operates at sixty blows per minute. Little, if any, `variation can be made in the time interval of impacts ofthis or the other hammers employed commercially for driving piles.

ySince piles are driven in a widevariety ofsoils, the

force actually required to drive a pile varies widely. Piles may be driven in muck ormud, sand, clay, through shale'formations, past boulders, obstructions and under a wide variety of conditions. Initial drivingl may be at one condition and, during driving, various other types of conditions may be encountered. Each type of soil and each obstruction encountered during Ldriving presents a different :driving requirement.V In muck or mud very little forcel may be required to drive-the pile member.

In other strata, however, greater forces may be required. In some strata the pile member can be driven relatively fast. In others, slower driving may be desired. Where the weight of the hammer and the impact time interval is fixed, as has been the case in hammers heretofore employed for driving piles, the type of soil strata and the speed at which the pile member can be driven has, for the most part, been ignored.

It is an object of the present invention to provide an improved pile driving hammer.

A further object of the invention is to provide a hammer in which the impact force and impact time interval can be adjusted to suit soil and driving conditions.

A still further object is to provide such a hammer to drive pile members more rapidly and efliciently.

These and other objects will be more apparent from the following description and the attached drawings in which FIG. l is a side elevational view of the hammer of the instant invention;

PIG. 2 is a sectional view taken along the line 2 2 of FIG. l;

FIGS. 3 and 4 are graphs illustrating certain operating characteristics of a hammer employing the teaching of the instant invention.

The pile driving hammer of the instant invention employs as the ram a piston, relatively light in weight which can be operated at relatively high frequency. The piston is lifted a relatively short distance and forced, with great impact, against the housing. In the illustrated embodiment, the piston is lifted by a cam and, as it clears the cam step, is driven back into engagement by air pressure applied to the opposite face of the piston. As the piston strikes the housing, a driving impact is delivered to the housing and, through the housing, to the pile.

The hammer of the instant invention is, preferably, fixed to the upper end of the pile member to be driven and is adapted to deliver driving impacts to the member in a downward direction, in an upward direction or, if desired, both downward and upward. Thus, the hammer of the instant invention may be utilized to pull, as Well as drive, a pile.

Referring now to the drawings, there is shown a housing 2, having an upper cover 4 and lower cover 6, covers 4, 6 being fastened to housing 2 by capscrews 8. Cam 19 is xed on shaft 12 rotatably supported in housing 2 by bearing 14, 16. Shaft 12 and cam 10 are driven by a motor, not shown.

Cylinder 1S is formed integral with cover 4 and cylinder 20 with cover 6. Plate 22, provided with a lifting eye 26, is fastened to cylinderl by capscrews 24, and with gasket 25, forming an air-tight closure on the cylinder. Plate 28, gasket 29, and block 30, are fastened to cylinder 2t) by capscrews 32, plate 28 and gasket 29 forming an air-tight closure on cylinder 20. At its end opposite to plate 28, block 30 is fastened to pile member 34 by capscrews 36. Pile member 34 is shown, as a rod. It is to be understood such showing is only for purposes of illustration and any type of pile member may be substituted.

Yinders 18, 20.

6 for engagement by camming surfaces 4'8 on cam 10j. Piston 40, 42 are each provided with sealing rings 60 which may be of any material suitable to seal the piston and maintain pressure'in the cylinder as the piston is operated. Where lubrication of the rings is required,

cylinder

18, 20 may be provided with lubrication lines 62 and a sight-glass lubrication feed 64. V'Preferably rings 60 are of a synthetic resin, such as of tetrafluoroethylene polymer, sold by E. I. du Pont de Nemours & Co. as Teflon Where such material isrused, lubrication is not required. Each

cylinder

18, 20 is provided with an air conduit 70, pressure `gauge 72 and valve 74.

' In operation, the hammer assembly is first connected Vto the pile member to be driven. In the illustrated embodiment, assuming member 34 to be the pile member to be driven, the hammer assembly is connected to member 34 by

capscrews

32, 36 and block 30. The pile member and hammer assembly are then hoisted into place by a lead or cable passed through lifting eye 26. With the pile member and hammer assembly in place, shaft V12 and cam 10 are rotated in the direction of the arrow in FIG. 2, camming surfaces 48l contacting and lifting the pistons as the camming surfaces pass under the pistons. As can be seen from the relative positions of

pistons

40, 42 in FIG. 2, camming surfaces 48 raise the pistons off covers 4, .6, respectively. vAs the step'onthe camrning surfacesV passes under Iand clears each piston,

the piston is free to re-engage the cover, the'extending required for the cam.

Covers

4, 6 form

anvils Vfor pistons

40, 42, respectively.

piston in the air cylinder has a diameter of twelve inches or an area of one hundred 'and' thirteen square inches. The height the piston is raised by the camming surfaces is one-half inch. The weight of the piston is one hundred seventy-two pounds or a mass of 5.38 pounds per foot per secondz.

The vdriving energy or horsepower input level of the hammer'is determined fromv the yfollowing formula:

Horsepower=F Xh n/66'00 By substituting various pressures and speeds` in the above formula, the graph of FIG. 3 has been prepared. This'graph is most helpful in selecting operating condi- [tions for'the hammer. For example, assuming a driving ener-gy input levelV or driving horsepower of 325 horsepower is desired, by kreferring to the graph of FIG. 3 it is determined that such horsepowerl can be attainedV at a cylinder operating pressure of`300 p.s.i. by rotating the cam at 2500 r.p.m.y or aty a cylinder operating pressure of '250 p.s.i. by rotating the cam at 3000 r.p.m.

kpiston portion being slightly shorter than thel clearance f Preferably, when rotation of shaft 12 and cam 10 is initiated, little, if any, pressure is in

cylinders

18, 20, respectively. If desired, valves 74 may be opened to vent

cylinders

18, 20 to the atmosphere.

After shaft 12 and cam 10 arev rotating at the desired speed, valve 74 is turned to admit air under pressure to the cylinder. Depending on the operation desired, air under pressure may be deliveredto either or bot-h of cyl- Air is admitted to the cylinder until the pressure in the cylinder reaches the desired operating pressure. Valve 74 may thenbe closed provided, however, after the valve is closed, the desired pressureis maintained in the cylinder.

WithV air in the cylinder, air pressure on top of the VIt is of course necessary that, to be effective, the piston must deliver the impact after bei-ng lifted by one-came' between cam steps the Apiston is clear of the cam. Thel elapsed time in which such a cam isfree of they piston is calculated by multiplying 1 over the cam impulses per second by two-thirds; This calculation has been made for vvarious rotation speeds and plotted against time in the piston forces the piston toward cam 10. VAs cam 10 rotates, camming surface 48 engages the extending piston portion, forcing the piston outward intothe cylinder. AsV

the step portion of camming'surface 48 clears the piston', the piston is released by the cam, the air pressure 'behind the pistondriving the pistondownward linto impact en gagement with the cover, the covering formingV al1YV anvil to receive the impact. through the housing to the pile. Forl reasons which Will be more aparent hereinafter, the cam is designed to lift The impacts are transmitted'v the piston to the desired height but -is -free orl'. the piston j weights,'jthe instant hammer applies relatively light* iin`V pacts tothe pile butv applies such impacts at high frequency to attain high driving energy orrhorsepowerinput levels.. By adjustingthe impact force and impact frequency, the driving energy or horsepowerrinput level ymay be regulated to meet particular driving conditions. Thus,

as required, the'hammer of the instant inventionmay be regulated to raise-jor lower the energy input. or horsepower for'drivingV the pile.

- ForQa-morecornplete understanding of* the Voperation'` I ofV thefdevice of thev instantinvention, ai'represent'.f-itive-` hammer is selectedand explained'in conjunction with FIGS. 3'and v4, vIn the selecte'dfha'mrner the head cnfftlvie.t

graph of FIG. 4. By referring to this vportion of the graph at 2500 r.p.m., one of Ithe operating speeds selected, the elapsed time inY seconds in which the cam is out'of contact or clear of the piston 1is .0053 second. At 3000 r.p.m., the Vother selected speed, theelapsed time is .0045

second. n After rselecting the operating pressure and cam speed,

it is next necessary to determine whether; atthe selectedy operating pressure, the piston will deliver its impact within theelapsed time'during which kthe cam is free of kthe piston.

formulae: 4

' F=m a and y 1 Y Y I i =\/2 s/a.

. Where:

F =area of the piston times the air pressure a; acceleration of the piston m=mass of the piston or 5.38 Y l=elapsed timerequiredffor pistontravel Vs=distance, in feet, traveled by the piston, of 1/ 24 .65., v

K Calculations of 'pifs'tonvtravel have been made for varions pressures and plottedagainstrtime on theV graph of Y FIG. 4.,. By referring ito'this portion of the graph, Avat an v [operating-pressure bf' Y3v00'p.si. theA elapsed `tirnerequired` .forthefpiston tof deliver .itsv impact is .00364 second.

Since 1.00364 second is ajshorterr'period'of Atime than is .0053 second,k thee`lap,sec lv time of cam vtravel at 2500 r.p.m.', `the cam ycan be ,rotated` at A2500 r.p.m. when the piston isoperatedagainstfanrair pressurey of 300 p.s.i.

' With respect to the other. ofthe selected operating conditions, namely,fair.pressure ofrr250 p.s.i. and cam rota- This' is 'determined from the followingA tion speed of 3000 r.p.m., from the attached graph the piston will deliver its impact in an elapsed time of .004 second. As noted above, at 3000 r.p.m. the cam is out of contact with or clears the piston for .0045 second. Since the elapsed time of cam travel is longer than the elapsed time required for the travel of the piston, the cam may be operated at the selected speed of 3000 r.p.m. when the operating pressure is 250 p.s.i.

The driving energy or horsepower input level of the selected hammer may be regulated by varying the pressure in the cylinder above the piston and the number of impacts delivered in a unit of time, the latter being regulated by varying the speed of rotation of the cam. In making these adjustments, however, care must be exercised to permit adequate time for the piston to reseat or deliver its impact before the cam is in position to again lift the piston. Where the operating pressure and cam speed do not permit adequate time for the piston to reseat before the cam is again in position to lift the piston, more favorable operating conditions should be selected. In the alternative, a piston of a different weight, or mass, or a cam having a different camming surface configuration might be substituted.

As has been heretofore noted, the impact force and time interval between impacts can be regulated with the hammer of the instant invention to suit driving conditions. This not only permits more efficient and more rapid driving, but allows the pile to be driven Without noticeable vibration in the earth in the area around the pile driving operation. This is Iof particular importance where, as is roften the case, the piles are being driven in a densely populated area or adjacent to large buildings or structures. By adapting the driving forces to actual driving conditions, vibration in the earth formation .adjacent the pile can be controlled, substantially reduced and, to a large extent, eliminated.

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

What is claimed is:

1. A hammer for driving piles comprising a housing, a cylinder in said housing, a cover at one end of said cylinder, a plate at the opposite end of said cylinder, a piston in said cylinder, said cylinder and said piston forming a chamber on one side of said piston, means in said chamber for forcing said piston into engagement with said plate, an extension on said piston extending through vsaid plate, and means on said housing for engaging said piston extension to move said piston toward said cover,

said last mentioned means including means for releasing said piston after said piston has been moved toward said cover to permit said means in said chamber to move said piston into engagement with said plate.

2. A hammer for driving piles comprising a housing, a cylinder in said housing, a cover at one end of said cylinder, a plate at the opposite end of said cylinder, a piston in said cylinder, said cylinder and said piston forming a chamber on one side of said piston, means in said chamber for forcing said piston into engagement with said plate, an extension on said piston extending through said plate, a cam mounted for rotation on said housing and having a camming surface for engagement with said piston extension to move said piston toward said cover and means on said camming surface for releasing said piston after said piston has been moved toward said cover to permit said means in said chamber to move said piston into engagement with said plate.

3. A hammer for driving piles comprising a housing, a cylinder in said housing, a cover at one end of said cylinder, a plate at the opposite end of said cylinder, a piston in said cylinder, said cylinder, said cover and said piston forming an air-tight chamber on one side of said piston, said air in said chamber forcing said piston into engagement with said plate, an extension on said piston extending through said plate, and means on said housing for engaging said piston extension to move said piston toward said cover, said means including means for releasing said piston after said piston has been moved toward said cover to permit said air in said chamber to move said piston into engagement with said plate.

4. A hammer for driving piles comprising a housing, a

cylinder in said housing, a cover at one end of said cylinder, a plate at the opposite end of said cylinder, a piston in said cylinder, said cylinder, said cover and said piston forming an air-tight chamber on one side of said piston, said air in said chamber forcing said piston into engagement with said plate, an extension on said piston extending through said plate, a cam mounted for rotation on said housing and having a camming surface for engagement with said piston extension to move said piston toward said cover and means on said camming surface for releasing said piston after said piston has been moved toward said cover to permit said air in said chamber to move said piston into engagement with said plate.

5. In a hammer for driving piles as recited in claim 4 in which said cam has a plurality of camming surfaces placed equidistant around said cam, each of said camming surfaces being positioned on said cam for engaging said piston extension to move said piston toward said cover and for releasing said piston after said piston has been moved toward said cover to permit said air in said airtight chamber to move said piston into engagement with said plate.

6. A hammer for driving piles comprising a housing, a pair of oppositely disposed axially aligned cylinders in said housing, each of said cylinders having a cover at the remote ends of the cylinders and a plate at the adjacent ends of the cylinders, a piston in each of said cylinders, said cylinder, said plate and said piston forming an air-tight chamber on one side of said piston in each of said cylinders, air in said chamber in each of said cylinders for forcing said piston into engagement with said plate, an extension on said piston extending through said plate, a cam mounted for rotation on said housing intermediate said cylinders and having a camming surface for engagement with said extension on said pistons to move said pistons away from said plates toward said covers and means on said camming surface for releasing said pistons -after said pistons have been moved toward said covers to permit said air in said chambers to move said pistons into engagement with said plates.

7. In a hammer for driving piles as recited in claim 6 in which each of said cylinders includes means for releasing said air from said chamber.

8. In a hammer for driving piles as recited in claim 6 in which said housing includes means for connecting said housing to a pile member.

References Cited in the tile of this patent UNITED STATES PATENTS 1,257,762 Sturtevant Feb. 26, 1918 2,317,158 Westover Apr. 20, 1943 2,776,539 Pearson Jan. 8, 1957

Claims

1. A HAMMER FOR DRIVING PILES COMPRISING A HOUSING, A CYLINDER IN SAID HOUSING, A COVER AT ONE END OF SAID CYLINDER, A PLATE AT THE OPPOSITE END OF SAID CYLINDER, A PISTON IN SAID CYLINDER, SAID CYLINDER AND SAID PISTON FORMING A CHAMBER ON ONE SIDE OF SAID PISTON, MEANS IN SAID CHAMBER FOR FORCING SAID PISTON INTO ENGAGEMENT WITH SAID PLATE, AN EXTENSION ON SAID PISTON EXTENDING THROUGH SAID PLATE, AND MEANS ON SAID HOUSING FOR ENGAGING SAID PISTON EXTENSION TO MOVE SAID PISTON TOWARD SAID COVER, SAID LAST MENTIONED MEANS INCLUDING MEANS FOR RELEASING SAID PISTON AFTER SAID PISTON HAS BEEN MOVED TOWARD SAID COVER TO PERMIT SAID MEANS IN SAID CHAMBER TO MOVE SAID PISTON INTO ENGAGEMENT WITH SAID PLATE.