Reciprocating linear hydraulic motors

Claim 2

A linear reciprocating motor comprising: a housing including an elongated piston cavity defined in part by a transverse wall; an elongated piston in said cavity; spring means exerting a force on said piston tending to drive it endwise through said cavity towards said transverse wall; hydraulic means for driving the piston endwise through the cavity in the opposite direction, in opposition to the force of said spring means, with said spring means being compressed by said piston as it so moves, said hydraulic means including a pressure surface on said piston spaced axially from said transverse wall and in fluid communication therewith, and means for delivering a hydraulic fluid to said transverse wall and said pressure surface, including control valve means comprising a linear reciprocating valve member movable between a first position in which hydraulic fluid is admitted to the pressure surface and the transverse wall, for moving the piston against the spring means and compressing the latter, and a second position in which such hydraulic fluid is removed from said pressure surface and flow of additional hydraulic fluid to said pressure surface is blocked by said valve member, resulting in the force of the hydraulic fluid being removed from said piston and said piston being forcibly moved by the spring means endwise through the cavity towards said transverse wall, said valve member having a first end portion which is in communication with the inflowing hydraulic fluid and receives an endwise force therefrom tending to move said valve member towards its first position, a second end portion, biasing force means acting on said second end portion and tending to move the valve member towards its second position, with said inflowing hydraulic fluid by itself exerting a force on said valve member that is larger than then biasing force, said valve means further comprising means for directing some of the hydraulic fluid against the valve member, to exert a force on the valve member acting in the same direction as the biasing force wHen the valve member is in its first position, with the combined forces of said biasing force means and said hydraulic fluid being larger than the force of said inflowing hydraulic fluid and being sufficient to move said valve member into its second position.

Claim 3

A motor according to claim 32, wherein the spring means is a body of a compressible fluid sealed within a chamber which is expansible towards the piston.

Claim 4

A linear reciprocating motor comprising: a housing including an elongated piston cavity defined in part by a transverse wall; an elongated piston in said cavity; spring means exerting a force on said piston tending to drive it endwise through said cavity towards said transverse wall; hydraulic means for driving the piston endwise through the cavity in the opposite direction, in opposition to the force of said spring means, with said spring means being compressed by said piston as it so moves, said hydraulic means including a pressure surface on said piston spaced axially from said transverse wall and in fluid communication therewith, and means for delivering a hydraulic fluid to said transverse wall and said pressure surface, including control valve means comprising a valve member movable between a first position in which hydraulic fluid is admitted to the pressure surface and the transverse wall, for moving the piston against the spring means and compressing the latter, and a second position in which such hydraulic fluid is removed from said pressure surface and flow of additional hydraulic fluid to said pressure surface is blocked by said valve member, resulting in the force of the hydraulic fluid being removed from said piston and said piston being forcibly moved by the spring means endwise through the cavity towards said transverse wall, wherein said valve member is annular and surrounds a portion of said piston, said valve member includes a first end surface which is seated against a portion of said transverse surface when the valve member is in its second position, and a second end surface which is subjected to the force of the spring means, such force tending to urge the valve member towards said transverse surface, and said housing includes passageway means for delivering hydraulic fluid to the first end surface of said valve member, for exerting a force on said first end surface which moves the valve member from its second position into its first position.

Claim 5

A linear reciprocating motor comprising: a housing including an elongated piston cavity defined in part by a transverse wall; an elongated piston in said cavity; spring means exerting a force on said piston tending to drive it endwise through said cavity towards said transverse wall; hydraulic means for driving the piston endwise through the cavity in the opposite direction, in opposition to the force of said spring means, with said spring means being compressed by said piston as it so moves, said hydraulic means including a pressure surface on said piston spaced axially from said transverse wall and in fluid communication therewith, and means for delivering a hydraulic fluid to said transverse wall and said pressure surface, including control valve means comprising a valve member movable between a first position in which hydraulic fluid is admitted to the pressure surface and the transverse wall, for moving the piston against the spring means and compressing the latter, and a second position in which such hydraulic fluid is removed from said pressure surface and flow of additional hydraulic fluid to said pressure surface is blocked by said valve member, resulting in the force of the hydraulic fluid being removed from said piston and said piston being forcibly moved by the spring means endwise through the cavity towards said transverse wall, wherein said valve member is annular and surrounds a portion of said piston, said valve member includes a first end surface which is seated against a portion of said transverse surface when the valve member is in its second position, and a second end surface which is subjected to the force of the spring means, such force tending to urge the valve member towards said transverse surface, and said housing includes passageway means for delivering hydraulic fluid to the first end surface of said valve member, for exerting a force on said first end surface which moves the valve member from its second position into its first position.

Claim 6

A motor according to claim 3, wherein said housing includes an internal tubular guide for said valve member in which said valve member moves, means forming a bypass chamber which at least partially surrounds the valve member, said valve member including side wall opening means through which the hydraulic fluid flows from the piston pressure surface into said by-pass chamber when the valve member is in its second position and the piston is traveling through its power stroke.

Claim 7

A motor according to claim 4, wherein said housing includes means forming an internal annular seat generally at the entrance to said exhaust chamber, and said valve member includes an exterior annular closure portion which seats tightly against said seat when the valve member is in its first position, and prevents hydraulic fluid from flowing into the by-pass chamber so that it instead exerts a force on the pressure surface of the piston.

Claim 8

A motor according to claim 5, wherein the tubular guide for said valve member includes means forming an expansible chamber with said valve member, in surrounding relationship to said valve member, and said valve member includes a piston ring portion defining a movable wall of said chamber, and said valve member includes side wall opening means through which the hydraulic fluid flows from the region of the piston pressure surface into said expansible chamber when the valve member is in its first position and the piston is retracted against the spring means, whereby the hydraulic fluid exerts a force on said piston ring which in combination with the spring means fOrce on the valve member acts to move the valve member from its first position into its second position.

Claim 9

A motor according to claim 6, wherein said motor includes passageway means for exhausting the fluid from the expansible chamber into the by-pass chamber when the valve member is in its second position and the piston is moving through its power stroke.

Claim 10

A motor according to claim 7, wherein said housing includes a separate cavity for said valve member which is offset from the piston cavity, and said valve member includes a first end surface which is seated against a portion of said transverse surface when the valve member is subjected to the force of the spring means, such force tending to urge the valve member towards said transverse surface, and said housing includes passageway means for delivering hydraulic fluid to the first end surface of said valve member, for exerting a force on said first end surface which moves the valve member from its second position into its first position.

Claim 11

A motor according to claim 8, wherein said housing includes means forming a by-pass chamber which at least partially surrounds the valve member, said valve member including side wall opening means through which the hydraulic fluid from the piston pressure surface is exhausted when the valve member is in its second position and the piston is moving through its power stroke.

Claim 12

A motor according to claim 9, wherein said housing includes means forming an internal annular seat generally at the entrance to said by-pass chamber, and said valve member includes an exterior annular closure portion which seats tightly against said seat when the valve member is in its first position, and prevents hydraulic fluid from flowing into the by-pass chamber so that it instead exerts a force on the pressure surface of the piston.

Claim 13

A motor according to claim 10, wherein the cavity for said valve member includes means forming an expansible chamber with said valve member, in surrounding relationship to said valve member, and said valve member includes a piston ring portion defining a movable wall of said chamber, and said housing includes passageway means through which the hydraulic fluid flows from the region of the piston pressure surface into said expansible chamber when the valve member is in its first position and the piston is retracted against the spring means, whereby the hydraulic fluid exerts a force on said piston ring which in combination with the spring means force on the valve member acts to move the valve member from its first position into its second position.

Claim 14

A motor according to claim 11, wherein said motor includes passageway means for exhausting the fluid from the expansible chamber when the valve member is in its second position and the piston has moved substantially through its power stroke.

Claim 15

A linear reciprocating motor comprising: a housing including an elongated piston cavity defined in part by a transverse wall; an elongated piston in said cavity; spring means exerting a force on said piston tending to drive it endwise through said cavity towards said transverse wall; hydraulic means for driving the piston endwise through the cavity in the opposite direction, in opposition to the force of said spring means, with said spring means being compressed by said piston as it so moves, said hydraulic means including a pressure surface on said piston spaced axially from said transverse wall, and means for delivering a hydraulic fluid to said surface, including control valve means movable between a first position in which the hydraulic fluid is admitted to the pressure surface, for moving the piston against the spring means and compressing the latter, and a second position in which the hydraulic fluid is exhausted from the pressure surface, resulting in the piston being forcibly moved by the spring means endwise through the cavity towards said transverse wall; and limit means for isolating the piston from the force of said spring means before the piston reaches the transverse wall, so that the piston is not driven hard against the transverse wall by the spring means but is free to coast to a stop position as it approaches the transverse wall before reversing its direction of travel.

Claim 16

A linear reciprocating motor comprising: a housing including an elongated piston cavity defined in part by a transverse wall; an elongated piston in said cavity; spring means exerting a force on said piston tending to drive it endwise through said cavity towards said transverse wall; hydraulic means for driving the piston endwise through the cavity in the opposite direction, in opposition to the force of said spring means, with said spring means being compressed by said piston as it so moves, said hydraulic means including a pressure surface on said piston spaced axially from said transverse wall, and means for delivering a hydraulic fluid to said surface, including control valve means movable between a first position in which the hydraulic fluid is admitted to the pressure surface, for moving the piston against the spring means and compressing the latter, and a second position in which the hydraulic fluid is exhausted from the pressure surface, resulting in the piston being forcibly moved by the spring means endwise through the cavity towards said transverse wall; and limit means for isolating the piston from the force of said spring means before the piston reaches the transverse wall, so that the piston is not driven hard against the transverse wall by the spring means but is free to coast to a stop position as it approaches the transverse wall before reversing its direction of travel.

Claim 17

A motor according to claim 13, wherein a fluid containing chamber exists axially between said transverse wall and said piston and the fluid therein provides a cushioning stop for said piston.

Claim 18

A motor according to claim 13, wherein the spring means is a body of a compressible fluid sealed within a chamber which is expansible towards the piston.

Claim 19

A motor according to claim 15, wherein the limit means comprises a barrier for the fluid spring chamber and means for arresting movement of said barrier independently of said piston, positioned so that the barrier is stopped before the piston reaches said transverse wall and serves to isolate the spring force from the piston.

Claim 20

A motor according to claim 16, wherein a fluid containing chamber exists axially between said transverse wall and said piston and the fluid therein provides a cushioning stop for said piston.

Claim 21

A motor according to claim 16, wherein an axial wall means is connected to said barrier and is in part at least tubular and outwardly bounds at least a portion of said piston.

Claim 22

A motor according to claim 18, wherein a bearing is radially received between said axial wall means and an inner side wall portion of the cavity for guiding said axial wall means.

Claim 23

A motor according to claim 15, wherein the stop member for said wall means is a mechanical spring.

Claim 24

A motor according to claim 20, wherein an axial wall means is connected to said barrier and is in part at least tubular and extends axially from said barrier in at least partial surrounding relationship to the near end portion of the piston, and said mechanical spring is annular in shape and has a central opening for loosely receiving said axial wall means, and a bearing is radially received between said axial wall means and an inner side wall portion of the cavity, for guiding said axial wall means.

Claim 25

A motor according to claim 21, wherein a fluid containing chamber exists axially between said transverse wall and said piston and the fluid therein provides a cushioning stop for said piston.

Claim 26

A gas spring powered impact tool, comprising: a linear impact member; a reciprocating linear hammer in line with said member; a compressed gas spring in line with said hammer, for forcibly driving said hammer endwise through a power stroke, into impacting contact with said member; and a hammer return hydraulic system including means for alternately delivering hydraulic fluid pressure against the hammer for moving it endwise against the compressed gas spring, for retracting the hammer and storing energy in the compressed gas spring, and releasing said hydraulic fluid from the hammer, so that the stored energy in the compressed gas spring can drive the hammer through its power stroke.

Claim 27

A gas spring powered impact tool, comprising: a linear impact member; a reciprocating linear hammer in line with said member; a compressed gas spring in line with said hammer, for forcibly driving said hammer endwise through a power stroke, into impacting contact with said member; and a hammer return hydraulic system including means for alternately delivering hydraulic fluid pressure against the hammer for moving it endwise against the compressed gas spring, for retracting the hammer and storing energy in the compressed gas spring, and releasing said hydraulic fluid from the hammer, so that the stored energy in the compressed gas spring can drive the hammer through its power stroke.

Claim 28

An impact tool according to claim 24, including means for trapping a body of the hydraulic fluid being a portion of the hammer and a portion of the housing to provide a fluid stop at the end of the power stroke.

Claim 29

A linear reciprocating motor comprising: a housing including an elongated piston cavity defined in part by a transverse wall; an elongated piston in said cavity; spring means exerting a force on said piston tending to drive it endwise through said cavity towards said transverse wall; hydraulic means for driving the piston endwise through the cavity in the opposite direction, in opposition to the force of said spring means, with said spring means being compressed by said piston as it so moves, said hydraulic means including a pressure surface on said piston spaced axially from said transverse wall and in fluid communication therewith, and means for delivering a hydraulic fluid to said transverse wall and said pressure surface, including control valve means comprising a valve member movable between a first position in which hydraulic fluid is admitted to the pressure surface and the transverse wall, for moving the piston against the spring means and compressing the latter, and a second position in which such hydraulic fluid is removed from said pressure surface and flow of additional hydraulic fluid to said pressure surface is blocked by said valve member, resulting in the force of the hydraulic fluid being removed from said piston and said piston being forcibly moved by the spring means endwise through the cavity towards said transverse wall, and means in said housing defining an expansible chamber for receiving some of the hydraulic fluid when the piston is at least partially retracted against the spring, said means including a movable surface on said valve member, said movable surface on said valve member being directed such that fluid in said chamber acting on said movable surface tends to urge the valve member towards its second position.

Claim 30

A linear reciprocating motor comprising: a housing including an elongated piston cavity defined in part by a transverse wall; an elongated piston in said cavity; spring means exerting a force on said piston tending to drive it endwise through said cavity towards said transverse wall; hydraulic means for driving the piston endwise through the cavity in the opposite direction, in opposition to the force of said spring means, with said spring means being compressed by said piston as it so moves, said hydraulic means including a pressure surface on said piston spaced axially from said transverse wall and in fluid communication therewith, and means for delivering a hydraulic fluid to said transverse wall and said pressure surface, including control valve means comprising a valve member movable between a first position in which hydraulic fluid is admitted to the pressure surface and the transverse wall, for moving the piston against the spring means and compressing the latter, and a second position in which such hydraulic fluid is removed from said pressure surface and flow of additional hydraulic fluid to said pressure surface is blocked by said valve member, resulting in the force of the hydraulic fluid being removed from said piston and said piston being forcibly moved by the spring means endwise through the cavity towards said transverse wall, and means in said housing defining an expansible chamber for receiving some of the hydraulic fluid when the piston is at least partially retracted against the spring, said means including a movable surface on said valve member, said movable surface on said valve member being directed such that fluid in said chamber acting on said movable surface tends to urge the valve member towards its second position.

Claim 31

A motor according to claim 25, further comprising means in said housing including a portion of said piston for trapping fluid in said chamber, so that said fluid will hold the valve member in its second position, until the piston has moved a predetermined distance through its power stroke.

Claim 32

A linear reciprocating motor comprising: a housing including an elongated piston cavity defined in part by a transverse wall; an elongated piston in said cavity; spring means exerting a force on said piston tending to drive it endwise through said cavity towards said transverse wall; hydraulic means for driving the piston endwise through the cavity in the opposite direction, in opposition to the force of said spring means, with said spring means being compressed by said piston as it so moves, said hydraulic means including a pressure surface on said piston spaced axially from said transverse wall and in fluid communication therewith, and means for delivering a hydraulic fluid to said transverse wall and said pressure surface, including control valve means comprising a linear reciprocating valve member movable between a first position in which hydraulic fluid is admitted to the pressure surface and the transverse wall, for moving the piston against the spring means and compressing the latter, and a second position in which such hydraulic fluid is removed from said pressure surface and flow of additional hydraulic fluid to said pressure surface is blocked by said valve member, resulting in the force of the hydraulic fluid being removed from said piston and said piston being forcibly moved by the spring means endwise through the cavity towards said transverse wall, valve member having a first end portion which is in communication with the inflowing hydraulic fluid and receives an endwise force therefrom tending to move said valve member towards its first position, and a second end portion subject to the force of said spring means, with the force of said spring means tending to move the valve member in the opposite direction towards its second position, with said inflowing hydraulic fluid by itself exerting a larger force on said valve member and with said valve means further comprising means for directing some of the hydraulic fluid against the valve member, to exert a force on the valve member acting in the same direction as the force exerted by the spring means, when the valve member is in its first position and the piston is against the spring means and has compressed same, with the combined forces of said spring means and said hydraulic fluid being larger than the force of said inflowing hydraulic fluid and being sufficient to move said valve member into its second position.

Claim 33

A linear reciprocating motor comprising: a housing including an elongated piston cavity defined in part by a transverse wall; an elongated piston in said cavity; spring means exerting a force on said piston tending to drive it endwise through said cavity towards said transverse wall; hydraulic means for driving the piston endwise through the cavity in the opposite direction, in opposition to the force of said spring means, with said spring means being compressed by said piston as it so moves, said hydraulic means including a pressure surface on said piston spaced axially from said transverse wall and in fluid communication therewith, and means for delivering a hydraulic fluid to said transverse wall and said pressure surface, including control valve means comprising a linear reciprocating valve member movable between a first position in which hydraulic fluid is admitted to the pressure surface and the transverse wall, for moving the piston against the spring means and compressing the latter, and a second position in which such hydraulic fluid is removed from said pressure surface and flow of additional hydraulic fluid to said pressure surface is blocked by said valve member, resulting in the force of the hydraulic fluid being removed from said piston and said piston being forcibly moved by the spring means endwise through the cavity towards said transverse wall, valve member having a first end portion which is in communication with the inflowing hydraulic fluid and receives an endwise force therefrom tending to move said valve member towards its first position, and a second end portion subject to the force of said spring means, with the force of said spring means tending to move the valve member in the opposite direction towards its second position, with said inflowing hydraulic fluid by itself exerting a larger force on said valve member and with said valve means further comprising means for directing some of the hydraulic fluid against the valve member, to exert a force on the valve member acting in the same direction as the force exerted by the spring means, when the valve member is in its first position and the piston is against the spring means and has compressed same, with the combined forces of said spring means and said hydraulic fluid being larger than the force of said inflowing hydraulic fluid and being sufficient to move said valve member into its second position.

Claim 34

A linear reciprocating motor comprising: a housing including an elongated piston cavity defined in part by a transverse wall; an elongated piston in said cavity; spring means exerting a force on said piston tending to drive it endwise through saId cavity towards said transverse wall; hydraulic means for driving the piston endwise through the cavity in the opposite direction, in opposition to the force of said spring means, with said spring means being compressed by said piston as it so moves, said hydraulic means including a pressure surface on said piston spaced axially from said transverse wall and in fluid communication therewith, and means for delivering a hydraulic fluid to said transverse wall and said pressure surface, including control valve means comprising a valve member movable between a first position in which hydraulic fluid is admitted to the pressure surface and the transverse wall, for moving the piston against the spring means and compressing the latter, and a second position in which such hydraulic fluid is removed from said pressure surface and flow of additional hydraulic fluid to said pressure surface is blocked by said valve member, resulting in the force of the hydraulic fluid being removed from said piston and said piston being forcibly moved by the spring means endwise through the cavity towards said transverse wall, and means in said housing including a portion of said piston for transferring the hydraulic fluid from said pressure surface into an expansible chamber near the spring end of said piston which chamber is bounded in part by a movable surface on said piston, said chamber including outlet means leading to exhaust, so that when the piston is moved by new hydraulic fluid towards said spring the fluid in said chamber is forced therefrom by the piston through the outlet means to exhaust.

Claim 35

A linear reciprocating motor comprising: a housing including an elongated piston cavity defined in part by a transverse wall; an elongated piston in said cavity; spring means exerting a force on said piston tending to drive it endwise through saId cavity towards said transverse wall; hydraulic means for driving the piston endwise through the cavity in the opposite direction, in opposition to the force of said spring means, with said spring means being compressed by said piston as it so moves, said hydraulic means including a pressure surface on said piston spaced axially from said transverse wall and in fluid communication therewith, and means for delivering a hydraulic fluid to said transverse wall and said pressure surface, including control valve means comprising a valve member movable between a first position in which hydraulic fluid is admitted to the pressure surface and the transverse wall, for moving the piston against the spring means and compressing the latter, and a second position in which such hydraulic fluid is removed from said pressure surface and flow of additional hydraulic fluid to said pressure surface is blocked by said valve member, resulting in the force of the hydraulic fluid being removed from said piston and said piston being forcibly moved by the spring means endwise through the cavity towards said transverse wall, and means in said housing including a portion of said piston for transferring the hydraulic fluid from said pressure surface into an expansible chamber near the spring end of said piston which chamber is bounded in part by a movable surface on said piston, said chamber including outlet means leading to exhaust, so that when the piston is moved by new hydraulic fluid towards said spring the fluid in said chamber is forced therefrom by the piston through the outlet means to exhaust.

Claim 36

A gas spring powered impact tool, comprising: a linear impact member; a reciprocating linear hammer in line with said member; a compressed gas spring in line with said hammer, for forcibly driving said hammer endwise through a power stroke, into impacting contact with said member; a hammer return hydraulic system including means for alternately delivering hydraulic fluid pressure against the hammer for moving it endwise against the compressed gas spring, for retracting the hammer and storing energy in the compressed gas spring, and releasing said hydraulic fluid from the hammer, so that the stored energy in the compressed gas spring can drive the hammer through its power stroke; and means for isolating the hammer from the force of said spring means before the hammer reaches the end of its power stroke, so that the hammer is free to coast to a stop position before reversing its direction of travel.

Claim 37

A gas spring powered impact tool, comprising: a linear impact member; a reciprocating linear hammer in line with said member; a compressed gas spring in line with said hammer, for forcibly driving said hammer endwise through a power stroke, into impacting contact with said member; a hammer return hydraulic system including means for alternately delivering hydraulic fluid pressure against the hammer for moving it endwise against the compressed gas spring, for retracting the hammer and storing energy in the compressed gas spring, and releasing said hydraulic fluid from the hammer, so that the stored energy in the compressed gas spring can drive the hammer through its power stroke; and means for isolating the hammer from the force of said spring means before the hammer reaches the end of its power stroke, so that the hammer is free to coast to a stop position before reversing its direction of travel.

Claim 38

A gas spring powered impact tool, comprising: a linear impact member; a reciprocating linear hammer in line with said member; a compressed gas spring in line with said hammer, for forcibly driving said hammer endwise through a power stroke, into impacting contact with said member; and a hammer return hydraulic system including means responsive to the position of said hammer for alternately delivering hydraulic fluid pressure against the hammer for moving it endwise against the compressed gas spring, for retracting the hammer and storing energy in the compressed gas spring, and releasing said hydraulic fluid from the hammer, so that the stored energy in the compressed gas spring can drive the hammer through its power stroke, said means releasing hydraulic fluid from the hammer immediately following each retraction of said hammer, and said means delivering additional hydraulic fluid pressure against the hammer, for again retracting the hammer, in response to each travel of the hammer through a power stroke.

Claim 39

A gas spring powered impact tool, comprising: a linear impact member; a reciprocating linear hammer in line with said member; a compressed gas spring in line with said hammer, for forcibly driving said hammer endwise through a power stroke, into impacting contact with said member; and a hammer return hydraulic system including means responsive to the position of said hammer for alternately delivering hydraulic fluid pressure against the hammer for moving it endwise against the compressed gas spring, for retracting the hammer and storing energy in the compressed gas spring, and releasing said hydraulic fluid from the hammer, so that the stored energy in the compressed gas spring can drive the hammer through its power stroke, said means releasing hydraulic fluid from the hammer immediately following each retraction of said hammer, and said means delivering additional hydraulic fluid pressure against the hammer, for again retracting the hammer, in response to each travel of the hammer through a power stroke.

Claim 40

A gas spring powered impact tool according to claim 37, wherein said hydraulic system includes a valve member having a first end portion which is in communication with the inflowing hydraulic fluid and receives an endwise force therefrom tending to move said valve member towards a first position in which hydraulic fluid is admitted to said hammer, a second end portion, biasing force means acting on said second end portion and tending to move thE valve member in the opposite direction towards a second position in which it blocks flow of hydraulic flow to the hammer and the hydraulic fluid pressure on the hammer is released, with said inflowing hydraulic fluid by itself exerting a larger force on said valve member than said biasing force means, and valve means for directing some of the hydraulic fluid against the valve member, to exert a force on the valve member acting in the same direction as the biasing force when the valve member is in its first position and the piston is against the compressed gas spring and has compressed same, with the combined forces of said biasing force and said hydraulic fluid being larger than the force of said inflowing hydraulic fluid and being sufficient to move said valve member into its second position.

Claim 41

An impact tool according to claim 30, wherein said means for alternately delivering hydraulic fluid to and exhausting it from the hammer includes valve member movable between a first position in which the hydraulic fluid is admitted to the hammer, for moving said hammer against said spring means and compressing the latter, and a second position in which said fluid is exhausted from the hammer and additional flow to the hammer is blocked by said valve member, resulting in the force of the hydraulic fluid being removed from said hammer and said hammer being forcibly moved by the spring means endwise through its power stroke.

Claim 42

A gas spring powered impact tool, comprising: a linear impact member; a reciprocating linear hammer in line with said member; a compressed gas spring in line with said hammer, for forcibly driving said hammer endwise through a power stroke, into impacting contact with said member; a hammer return hydraulic system including means responsive to the position of said hammer for alternately delivering hydraulic fluid pressure against the hammer for moving it endwise against the compressed gas spring, for retracting the hammer and storing energy in the compressed gas spring, and releasing said hydraulic fluid from the hammer, so that the stored energy in the compressed gas spring can drive the hammer through its power stroke; and means for trapping a body of the hydraulic fluid between a portion of the hammer and a portion of the housing to provide a fluid stop at the end of the power stroke.

Claim 43

A gas spring powered impact tool, comprising: a linear impact member; a reciprocating linear hammer in line with said member; a compressed gas spring in line with said hammer, for forcibly driving said hammer endwise through a power stroke, into impacting contact with said member; a hammer return hydraulic system including means responsive to the position of said hammer for alternately delivering hydraulic fluid pressure against the hammer for moving it endwise against the compressed gas spring, for retracting the hammer and storing energy in the compressed gas spring, and releasing said hydraulic fluid from the hammer, so that the stored energy in the compressed gas spring can drive the hammer through its power stroke; and means for trapping a body of the hydraulic fluid between a portion of the hammer and a portion of the housing to provide a fluid stop at the end of the power stroke.