# US 8,739,895 B2 · Machine tool > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,739,895 B2 - Document ID: US8739895B2 - Status: Granted - Kind: B2 - Application number: 12/800,896 - Filed: 2010-05-25 - Published: 2010-12-02 - Granted: 2014-06-03 - Earliest claimed: 2009-05-28 - Assignees: Hilti Aktiengesellschaft - Applicants: Markus Hartmann; Alexander John - Inventors: Markus Hartmann; Alexander John - Web page: https://patentgrep.com/patent/US8739895B2 ## CPC - B25D 11/005: {Arrangements for adjusting the stroke of the impulse member or for stopping the impact action when the tool is lifted from the working surface} - B25D 11/125: {with a fluid cushion between the crank drive and the striking body} - B25D 17/06: Hammer pistons; Anvils {; Guide-sleeves for pistons} - B25D 2211/003: Crossed drill and motor spindles - B25D 2217/0023: Pistons - B25D 2250/035: Bleeding holes, e.g. in piston guide-sleeves - B25D 2250/131: Idling mode of tools - B25D 2250/345: Use of o-rings - B25D 2250/365: Use of seals - B25D: PERCUSSIVE TOOLS {(percussive machines for forging B21J; hand-held drilling machines, in general B23B45/00, for wood B27C3/08; drilling machines, used for mining or quarrying, with reciprocating tool which is turned intermittently when out of contact with the working face E21B1/00)} ## Abstract The machine tool includes a pneumatic percussion mechanism having a cup-shaped exciter cylinder (21) with an inner chamber (31) which is open in the direction of impact (26), and a free piston (22) which is movable in the inner chamber (31). A recess (32) and at least one ventilation opening (35), spaced at a distance from the recess (32) in the direction of impact (26), are provided in a shell-type wall (39) of the inner chamber (31). The free piston (22) includes a sealing element (53) which seals off the at least one ventilation opening (35) when the sealing element (53) is oppositely situated from the at least one ventilation opening (35), and which in the region of the recess (32) is separated at a distance from the shell-type wall (39) when the sealing element (53) is oppositely situated from the recess. ## Claims ### Claim 1 A machine tool for impacting a work piece comprises: a pneumatic percussion mechanism having a cup-shaped exciter cylinder with an inner chamber open in a direction of impact, the inner chamber being defined, at least partially, by a shell-type wall, the shell type-wall having at least one ventilation opening and a recess, the at least one ventilation opening spaced at a distance from the recess in the direction of impact; and a free piston movable in the inner chamber, the free piston including a sealing element located in the inner chamber and contacting an inner surface of the shell-type wall, the sealing element sealing off the at least one ventilation opening when the sealing element is oppositely situated from the at least one ventilation opening, the sealing element, when in the region of the recess, being separated at a distance from the shell-type wall when the sealing element is oppositely situated from the recess. ### Claim 2 (depends on 1) The machine tool as recited in claim 1 wherein a width of the recess is greater than a width of the ventilation openings. ### Claim 3 (depends on 1) The machine tool as recited in claim 1 wherein the recess has an annular shape. ### Claim 4 (depends on 1) The machine tool as recited in claim 1 wherein at least three of the ventilation openings are situated in a plane perpendicular to the direction of impact. ### Claim 5 (depends on 1) The machine tool as recited in claim 1 wherein the ventilation openings are provided in a uniform angular distribution around an axis of the percussion mechanism. ### Claim 6 (depends on 5) The machine tool as recited in claim 5 wherein the ventilation openings are situated in a spiral around the axis. ### Claim 7 (depends on 1) The machine tool as recited in claim 1 wherein further comprising a drive for periodically moving the exciter cylinder by one stroke height along the direction of impact, and a distance of the recess from the at least one ventilation opening is less than one-half the stroke height. ### Claim 8 (depends on 7) The machine tool as recited in claim 7 wherein the distance of the recess from the at least one ventilation opening is less than thirty percent of the stroke height. ### Claim 9 (depends on 1) The machine tool as recited in claim 1 wherein the movable free piston has an air channel for connecting oppositely situated sides of the free piston in the direction of impact, the air channel being interrupted by the sealing element. ### Claim 10 (depends on 1) The machine tool as recited in claim 1 further comprising a guide tube within which the exciter cylinder is movably situated, the guide tube having an outlet opening with a front edge in the direction of impact, and during a blank blow the sealing element being situated behind the front edge in the direction of impact, and in the impact position being situated in front of the front edge. ### Claim 11 (depends on 10) The machine tool as recited in claim 10 wherein the exciter cylinder has at at least one location an outer cross section forming an airtight seal with an inner cross section of the guide tube. ### Claim 12 (depends on 1) The machine tool as recited in claim 1 further comprising a drive mechanically connected to the exciter cylinder. ### Claim 13 (depends on 12) The machine tool as recited in claim 12 wherein the exciter cylinder has an articulated joint connected to the drive. ### Claim 14 (depends on 12) The machine tool as recited in claim 12 wherein the drive drives the exciter cylinder in a periodic linear motion. ### Claim 15 (depends on 1) The machine tool as recited in claim 1 wherein the piston has at at least one location an outer cross section forming an airtight seal with an inner cross section of the shell-type wall. ### Claim 16 A machine tool for impacting a work piece comprising: a drive; a pneumatic percussion mechanism having a cup-shaped exciter cylinder driven by the drive and having a shell-type wall defining at least partially an inner chamber open in a direction of impact, the shell type-wall having at least one ventilation opening and a recess, the at least one ventilation opening spaced at a distance from the recess in the direction of impact; and a free piston movable in the inner chamber, the free piston including a sealing element sealing off the at least one ventilation opening when the sealing element is oppositely situated from the at least one ventilation opening, the sealing element, when in the region of the recess, being separated at a distance from the shell-type wall when the sealing element is oppositely situated from the recess. ### Claim 17 A machine tool for impacting a work piece comprises: a pneumatic percussion mechanism having a cup-shaped exciter cylinder with an inner chamber open in a direction of impact, the inner chamber being defined, at least partially, by a shell-type wall, the shell type-wall having at least one ventilation opening and a recess, the at least one ventilation opening spaced at a distance from the recess in the direction of impact; and a free piston movable in the inner chamber, the free piston including a sealing element sealing off the at least one ventilation opening when the sealing element is oppositely situated from the at least one ventilation opening, the sealing element, when in the region of the recess, being separated at a distance from the shell-type wall when the sealing element is oppositely situated from the recess; wherein the movable free piston has an air channel for connecting oppositely situated sides of the free piston in the direction of impact, the air channel being interrupted by the sealing element.