Cushioned drive cap for a pile driver

Claim 2

A force-transmitting cap interposable between a pile drive hammer and a driven pile, said cap comprising a hollow rigid cylinder element having a rigid circumferential wall, a closed axial end and an open axial bore at the other axial end; a piston sealingly guided in said bore for reciprocating movement and having an outer end face operative when hit for inwardly depressing the piston; an internal chamber in said bore sealed by said piston for receiving a pressurized body of gas and a body of liquid; at least one closable passage extending from said chamber to the outside of said cap for flowing gas or liquid into and out of said chamber; an impact surface disposed at said other axial end and dimensioned for direct, substantially uncushioned impact transfer, cooperating stop surfaces on said piston and said cylinder element operative to abut against each other for limiting the distance by which the piston can project outwardly beyond said impact surface to a predetermined distance D; means for limiting the pressure in the body of gas to a predetermined pressure value; said piston being guided in said bore for leakage-free inward depression to positions beyond the level of said impact surface; the wall of the cylinder element, the impact surface and the predetermined distance D being dimensioned to permit at said predetermined pressure value a two-step impact transfer transmitting part of the impact energy via the pressurized body of gas and the other part of the impact energy directly via the impact surface as substantially uncushioned force peak; a displaceable separating member accommodated in the interior of the hollow cylinder element and subdividing the interior of the cylinder element into two pressurization compartments; the separating member comprising a slidable internal piston having a central bore and a flexible separating diaphragm having a peripheral edge clamped in a circumferential groove in the inner circumferential surface of the slidable internal piston.

Claim 3

A force-transmitting cap interposable between a pile drive hammer and a driven pile, said cap comprising a hollow rigid cylinder element having a rigid circumferential wall, a closed axial end and an open axial bore at the other axial end; a piston sealingly guided in said bore for reciprocating movement and having an outer end face operative when hit for inwardly depressing the piston; an internal chamber in said bore sealed by said piston for receiving a pressurized body of gas and a body of liquid; at least one closable passage extending from said chamber to the outside of said cap for flowing gas or liquid into and out of said chamber; an impact surface disposed at said other axial end and dimensioned for direct, substantially uncushioned impact transfer, cooperating stop surfaces on said piston and said cylinder element operative to abut against each other for limiting the distance by which the piston can project outwardly beyond said impact surface to a predetermined distance D; means for limiting the pressure in the body of gas to a predetermined pressure value; said piston being guided in said bore for leakage-free inward depression to positions beyond the level of said impact surface; the wall of the cylinder element, the impact surface and the predetermined distance D being dimensioned to permit at said predetermined pressure value a two-step impact transfer transmitting part of the impact energy via the pressurized body of gas and the other part of the impact energy directly via the impact surface as substantially uncushioned force peak; a displaceable separating member accommodated in the interior of the hollow cylinder element; the separating member comprising a sealed container mounted in the interior of the cylinder element and subdividing the interior of the cylinder element into a first compartment and into a second compartment, the second compartment being internal to and enclosed by the first compartment.

Claim 4

A force-transmitting cap interposable between a pile drive hammer and a driven pile, said cap comprising a hollow rigid cylinder element having a rigid circumferential wall, a closed axial end and an open axial bore at the other axial end; a piston sealingly guided in said bore for reciprocating movement and having an outer end face operative when hit for inwardly depressing the piston; an internal chamber in said bore sealed by said piston for receiving a pressurized body of gas and a body of liquid; at least one closable passage extending from said chamber to the outside of said cap for flowing gas or liquid into and out of said chamber; an impact surface disposed at said other axial end and dimensioned for direct, substantially uncushioned impact transfer, cooperating stop surfaces on said piston and said cylinder element operative to abut against each other for limiting the distance by which the piston can project outwardly beyond said impact surface to a predetermined distance D; means for limiting the pressure in the body of gas to a predetermined pressure value; said piston being guided in said bore for leakage-free inward depression to positions beyond the level of said impact surface; the wall of the cylinder element, the impact surface and the predetermined distance D being dimensioned to permit at said predetermined pressure value a two-step impact transfer transmitting part of the impact energy via the pressurized body of gas and the other part of the impact energy directly via the impact surface as substantially uncushioned force peak; a displaceable separating member accommodated in the interior of the hollow cylinder element; the separating member comprising a sealed container mounted in the interior of the cylinder element and subdividing the interior of the cylinder element into a first compartment and into a second compartment, the second compartment being internal to and enclosed by the first compartment.

Claim 5

A force-transmitting cap as defined in claim 2, furthermore including elastically yieldable mounting means mounting the sealed container in the interior of the hollow cylinder.

Claim 6

A force-transmitting cap as defined in claim 2, the elastically yieldable mounting means comprising bearing springs suspending the container in the interior of the hollow cylinder.

Claim 7

A force-transmitting cap as defined in claim 2, the sealed container being a generally rigid container having a displaceable wall which permits the volume of the second compartment to change during operation of the force-transmitting cap.

Claim 8

A force-transmitting cap for transmitting the blow of a pile-drive hammer to a pile, said cap having a rigid circumferential wall, a closed first axial end wall, an open axial bore at the other axial end, a second axial end wall around said bore, and a constricting shoulder forming an internal step in said bore; a piston sealingly guided in said bore for reciprocating axial movement between an outermost position and inwardly depressed positions, said piston having an outer end face operative when hit for inwardly depressing the piston, and having an external shoulder directly abutting in said outermost position against said constricting shoulder of the cap; a sole undivided internal chamber in said bore sealed by said piston for receiving a body of gas and a body of liquid in direct contact with each other; a valve-containing passage extending from said chamber to the outside surface of the cap for flowing gas or liquid from outside the cap into said chamber for precompressing said body of gas to a predetermined operating pressure P urging the piston with predetermined force directly against said abutting shoulder of the cap; the external side of said second axial end wall of the cap being designed as an impact surface for direct steel-to-steel impact transfer, said piston being guided in said bore for leakage-free inward depression of its outer end face beyond the level of the impact surface; the walls of the cap, the impact surface and a distance D by which the piston in its outermost position projects outwardly beyond the impact surface being dimensioned to obtain at said operating pressure P a two-step impact transfer transmitting to the pile during telescoping inward depression of said piston part of the impact energy as a cushioned resilient driving force via the precompressed body of gas, and the other part as a substantially uncushioned force peak by direct steel-to-steel impact via said impact surface and the rigid circumferential wall of the cap, while the precompressed body of gas maintains its resilient driving force on the pile.

Claim 9

A force-transmitting cap for transmitting the blow of a pile-drive hammer to a pile, said cap having a rigid circumferential wall, a closed first axial end wall, an open axial bore at the other axial end, a second axial end wall around said bore, and a constricting shoulder forming an internal step in said bore; a piston sealingly guided in said bore for reciprocating axial movement between an outermost position and inwardly depressed positions, said piston having an outer end face operative when hit for inwardly depressing the piston, and having an external shoulder directly abutting in said outermost position against said constricting shoulder of the cap; a sole undivided internal chamber in said bore sealed by said piston for receiving a body of gas and a body of liquid in direct contact with each other; a valve-containing passage extending from said chamber to the outside surface of the cap for flowing gas or liquid from outside the cap into said chamber for precompressing said body of gas to a predetermined operating pressure P urging the piston with predetermined force directly against said abutting shoulder of the cap; the external side of said second axial end wall of the cap being designed as an impact surface for direct steel-to-steel impact transfer, said piston being guided in said bore for leakage-free inward depression of its outer end face beyond the level of the impact surface; the walls of the cap, the impact surface and a distance D by which the piston in its outermost position projects outwardly beyond the impact surface being dimensioned to obtain at said operating pressure P a two-step impact transfer transmitting to the pile during telescoping inward depression of said piston part of the impact energy as a cushioned resilient driving force via the precompressed body of gas, and the other part as a substantially uncushioned force peak by direct steel-to-steel impact via said impact surface and the rigid circumferential wall of the cap, while the precompressed body of gas maintains its resilient driving force on the pile.

Claim 10

A force-transmitting cap as defined in claim 6, the predetermined distance D being limited to a value between 3 and 30 mm.

Claim 11

A force-transmitting cap for transmitting the blow of a pile-driver hammer to a pile, said cap having a rigid circumferential wall, a closed first axial end wall, an open axial bore at the other axial end, a second axial end wall around said bore, and a constricting shoulder forming an internal step in said bore; a piston sealingly guided in said bore for reciprocating axial movement between an outermost position and inwardly depressed positions, said piston having an outer end face operative when hit for inwardly depressing the piston, and having an external shoulder directly abutting in said outermost position against said constricting shoulder of the cap; a closed internal chamber defined by the inner walls of said bore and said piston, separating means subdividing said chamber into a liquid compartment to be completely filled with a body of liquid, and a gas compartment completely filled with gas, said separating means comprising a flexible diaphragm having a peripheral edge sealingly clamped in a circumferential groove at an inner wall defining said chamber; at least one valve-containing passage extending from said chamber to the outside surface of the cap for flowing gas or liquid from outside the cap into said chamber for precompressing said body of gas to a predetermined operating pressure P urging the piston with predetermined force directly against said abutting shoulder of the cap; the external side of said second axial end wall of the cap being designed as an impact surface for direct steel-to-steel impact transfer, said piston being guided in said bore for leakage-free inward depression of its outer end face beyond the level of the impact surface; the walls of the cap, the impact surface and a distance D by which the piston in its outermost position projects outwardly beyond the impact surface being dimensioned to obtain at said operating pressure P a two-step impact transfer transmitting to the pile during telescoping inward depression of said piston part of the impact energy as a cushioned resilient driving force via the precompressed body of gas, and the other part as a substantially uncushioned force peak by direct steel-to-steel impact via said impact surface and the rigid circumferential wall of the cap, while the precompressed body of gas maintains its resilient driving force on the pile.

Claim 12

A force-transmitting cap for transmitting the blow of a pile-driver hammer to a pile, said cap having a rigid circumferential wall, a closed first axial end wall, an open axial bore at the other axial end, a second axial end wall around said bore, and a constricting shoulder forming an internal step in said bore; a piston sealingly guided in said bore for reciprocating axial movement between an outermost position and inwardly depressed positions, said piston having an outer end face operative when hit for inwardly depressing the piston, and having an external shoulder directly abutting in said outermost position against said constricting shoulder of the cap; a closed internal chamber defined by the inner walls of said bore and said piston, separating means subdividing said chamber into a liquid compartment to be completely filled with a body of liquid, and a gas compartment completely filled with gas, said separating means comprising a flexible diaphragm having a peripheral edge sealingly clamped in a circumferential groove at an inner wall defining said chamber; at least one valve-containing passage extending from said chamber to the outside surface of the cap for flowing gas or liquid from outside the cap into said chamber for precompressing said body of gas to a predetermined operating pressure P urging the piston with predetermined force directly against said abutting shoulder of the cap; the external side of said second axial end wall of the cap being designed as an impact surface for direct steel-to-steel impact transfer, said piston being guided in said bore for leakage-free inward depression of its outer end face beyond the level of the impact surface; the walls of the cap, the impact surface and a distance D by which the piston in its outermost position projects outwardly beyond the impact surface being dimensioned to obtain at said operating pressure P a two-step impact transfer transmitting to the pile during telescoping inward depression of said piston part of the impact energy as a cushioned resilient driving force via the precompressed body of gas, and the other part as a substantially uncushioned force peak by direct steel-to-steel impact via said impact surface and the rigid circumferential wall of the cap, while the precompressed body of gas maintains its resilient driving force on the pile.

Claim 13

A force-transmitting cap as defined in claim 8, wherein said piston has an internal recess defining a space forming part of the internal chamber, said gas compartment is disposed in said recess and the peripheral edge of the flexible diaphragm is clamped in a circumferential groove in the inner circumferential wall of said recess.

Claim 14

A force-transmitting cap as defined in claim 8, wherein the separating means comprises a slidable auxiliary piston having a central opening and the flexible diaphragm is clamped in said opening of the auxiliary piston.

Claim 15

A force-transmitting cap as defined in claim 8, wherein the separating means comprise a sealed rigid container mounted in the internal chamber of the cap and subdividing said chamber into a liquid compartment and a gas compartment internal to and enclosed by the liquid compartment, said container having at least one displaceable wall element selected from a flexible diaphragm, a slidable auxiliary piston, and a slidable auxiliary piston having a central opening and a flexible diaphragm clamped in said opening.

Claim 16

A force-transmitting cap as defined in claim 11, furthermore including elastically yieldable mounting means mounting the sealed container in the internal chamber of the cap.

Claim 17

A force-transmitting cap as defined in claim 11, the elastically yieldable mounting means comprising bearing springs suspending the container in the internal chamber of the cap.