EP0222698B1 - Bohrhammer mit pneumatisch angetriebenem Schlagkolben - Google Patents

Bohrhammer mit pneumatisch angetriebenem Schlagkolben Download PDF

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Publication number
EP0222698B1
EP0222698B1 EP86810462A EP86810462A EP0222698B1 EP 0222698 B1 EP0222698 B1 EP 0222698B1 EP 86810462 A EP86810462 A EP 86810462A EP 86810462 A EP86810462 A EP 86810462A EP 0222698 B1 EP0222698 B1 EP 0222698B1
Authority
EP
European Patent Office
Prior art keywords
piston
pistons
air cushion
closure part
cylinder
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP86810462A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0222698A1 (de
Inventor
Franz Chromy
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hilti AG
Original Assignee
Hilti AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hilti AG filed Critical Hilti AG
Priority to AT86810462T priority Critical patent/ATE42490T1/de
Publication of EP0222698A1 publication Critical patent/EP0222698A1/de
Application granted granted Critical
Publication of EP0222698B1 publication Critical patent/EP0222698B1/de
Expired legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25D—PERCUSSIVE TOOLS
    • B25D16/00—Portable percussive machines with superimposed rotation, the rotational movement of the output shaft of a motor being modified to generate axial impacts on the tool bit
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25D—PERCUSSIVE TOOLS
    • B25D17/00—Details of, or accessories for, portable power-driven percussive tools
    • B25D17/06—Hammer pistons; Anvils ; Guide-sleeves for pistons
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25D—PERCUSSIVE TOOLS
    • B25D2211/00—Details of portable percussive tools with electromotor or other motor drive
    • B25D2211/06—Means for driving the impulse member
    • B25D2211/068—Crank-actuated impulse-driving mechanisms

Definitions

  • the invention relates to a rotary hammer with a cylinder for guiding a drive piston which can be moved to and fro by motor and a percussion piston with the interposition of an air cushion, at least one of the two pistons having a connecting channel leading outwards from the air cushion space.
  • leakage losses are the result of inadequate sealing between the pistons and the cylinder, caused in particular by wear on sealing elements on the piston side.
  • poor lubrication and failure of any heat-sensitive sealing elements promote such leakage losses.
  • a disadvantage of this design is the risk that damage to device parts can already occur due to the impact of the percussion piston required to break out the base part.
  • the invention has for its object to provide a hammer drill with a pneumatic hammer mechanism, in which a prevention of damage resulting from leakage of the air cushion is ensured.
  • the object is achieved in that the connecting channel is closed by a closure part made of material with a low melting point.
  • the invention takes advantage of the knowledge that, as a result of the leakage losses, the power on the percussion piston decreases. Since the power delivered by the engine to the drive piston remains unchanged, the thermal power of the striking mechanism increases with increasing leakage losses, which increases the overall operating temperature.
  • the connecting channel is kept closed by the closure part. If, for example, a temperature that is 20% higher than the normal operating temperature occurs, the closure melts. This opens the connection channel and the air cushion breaks down.
  • the coefficient of thermal expansion of the closure part can be approximately equal to or greater than that of the pistons.
  • the percussion piston which is pneumatically decoupled from the drive piston after the closure part has melted, assumes a rest position, regardless of any further reciprocation of the drive piston.
  • the operator can suddenly discontinue the delivery of the punch. As a result, he will take the device out of operation. This prevents consequential damage to the drive elements for the striking mechanism or other device parts.
  • the device By replacing the locking part and carrying out the necessary maintenance measures, such as replacing the sealing elements and lubricating the striking mechanism, the device can be brought back into operational condition without damage.
  • the connecting channel is preferably designed as a bore penetrating the pistons in the axial direction.
  • the connecting channel expediently runs concentrically or - formed by several bores - symmetrically to the longitudinal axis of the pistons.
  • the closure part is advantageously arranged at the end of the piston facing the air cushion. This location of the pistons is in the spatial vicinity of the locations of the device that are relevant for increased temperature, so that the closure part is directly exposed to the effects of heat. This ensures a sensitive and precise reaction of the closure part even at different ambient temperatures of the device.
  • closure part is positively held in the connecting channel by means of undercuts.
  • the back stitches can be, for example, closed circumferential grooves or thread grooves.
  • the closure part extends in the form of a plug, for example, over part of the longitudinal extent of the bore. It is possible to insert the closure part into the bore as a fully formed plug or in the casting process.
  • the closure part is arranged on the drive piston. This is particularly advantageous for maintaining a good fit of the closure part in the bore. While the percussion piston is constantly exposed to abrupt decelerations due to its impact on the tool, which could lead to a locking part mounted therein being displaced, the drive piston can be moved back and forth, for example, by a crank mechanism without abrupt deceleration.
  • the closure part preferably consists of a tin alloy.
  • This material is particularly suitable because its coefficient of thermal expansion corresponds approximately to the coefficient of thermal expansion of the drive piston, which is preferably made of aluminum.
  • Suitable tin alloys are especially soft solders according to DIN 1707 with selectable melting points from 150 ° to 250 ° C.
  • a housing 1 consists of a housing 1, in which a cylinder 4 is rotatably supported by a front ball bearing 2 and a rear roller bearing 3.
  • the cylinder 4 is designed as a receptacle for an indicated drilling tool 5.
  • the latter has driving grooves 5a for engaging locking elements, not shown.
  • a sealing ring 6 supported on the housing side is intended to prevent dirt from entering the device and the escape of lubricants.
  • a bevel gear 7 is arranged on the cylinder 4 and is connected to the cylinder 4 in a rotationally fixed manner by a locking pin 8.
  • the bevel gear 7 and the cylinder 4 are driven in rotation by a motor-driven bevel pinion 9.
  • An eccentric shaft 11 is also driven by the motor (not shown), which moves a drive piston mounted in the cylinder 4, generally designated 13, via a connecting rod 12 .
  • the drive piston 13 is penetrated concentrically to its longitudinal axis by a bore 16 which serves as a connecting channel between the cylinder space adjoining the drive piston 13 in the drilling direction and the recess which is open to the outside.
  • the drive piston 13 also carries an annular sealing element 19 which interacts with the cylinder 4.
  • closure part 17 engages positively in the undercuts 16a in the form of thread grooves.
  • an impact piston In the cylinder 4 in front of the drive piston 13 there is also an impact piston, generally designated 21, which is displaceably mounted. This has a shaft 22 for transmitting impact pulses to the drilling tool 5 and a head 23 on the rear. The head 23, like the drive piston 13, is provided with a sealing element 24.
  • the percussion piston 21 is likewise set in a reciprocating movement by the air cushion standing between the two pistons in the cylinder 4 in a phase-shifted manner.
  • the cylinder 4 has blow-off bores 4a on the front side.
  • a compensating bore 4b is provided in the cylinder 4, which ensures the periodic build-up of the air cushion.
  • the melting temperature of the closure part 17 is at the elevated temperature level that is reached before the pistons 13, 21 collide.
  • the melting of the closure part 17 leads to the venting of the cylinder space located between the pistons 13, 21 to the outside via the bore 16.
  • the percussion piston 21 is thus no longer activated by the drive piston 13, which is moved back and forth by motor, and remains in an end position on the drilling direction side. The operator notices that the punch has not been delivered and will then take the device out of operation. Costly consequential damage, such as might occur if the pistons 13, 21 collide, is reliably prevented in this way.
  • the hammer drill described is suitable for rotating and striking drive of the drilling tool 5.
  • the arrangement according to the invention can also be used in devices which only impart impact energy to a tool.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Percussive Tools And Related Accessories (AREA)
  • Supply Devices, Intensifiers, Converters, And Telemotors (AREA)
  • Earth Drilling (AREA)
  • Drilling And Boring (AREA)
EP86810462A 1985-11-02 1986-10-20 Bohrhammer mit pneumatisch angetriebenem Schlagkolben Expired EP0222698B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT86810462T ATE42490T1 (de) 1985-11-02 1986-10-20 Bohrhammer mit pneumatisch angetriebenem schlagkolben.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3539030 1985-11-02
DE19853539030 DE3539030A1 (de) 1985-11-02 1985-11-02 Bohrhammer mit pneumatisch angetriebenem schlagkolben

Publications (2)

Publication Number Publication Date
EP0222698A1 EP0222698A1 (de) 1987-05-20
EP0222698B1 true EP0222698B1 (de) 1989-04-26

Family

ID=6285104

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86810462A Expired EP0222698B1 (de) 1985-11-02 1986-10-20 Bohrhammer mit pneumatisch angetriebenem Schlagkolben

Country Status (6)

Country Link
US (1) US4732219A (enrdf_load_stackoverflow)
EP (1) EP0222698B1 (enrdf_load_stackoverflow)
JP (1) JPS62107985A (enrdf_load_stackoverflow)
AT (1) ATE42490T1 (enrdf_load_stackoverflow)
AU (1) AU583952B2 (enrdf_load_stackoverflow)
DE (2) DE3539030A1 (enrdf_load_stackoverflow)

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ZA908924B (en) * 1990-01-15 1991-08-28 Sulzer Ag A percussion device
JP3459493B2 (ja) * 1995-05-25 2003-10-20 株式会社マキタ 打撃工具
DE19828423C2 (de) * 1998-06-25 2000-05-18 Wacker Werke Kg Antriebskolben für ein Luftfederschlagwerk
DE10034742A1 (de) * 2000-07-17 2002-01-31 Hilti Ag Werkzeug mit zugeordnetem Schlagwerkzeug
EP1584420B1 (de) * 2004-04-07 2014-06-11 HILTI Aktiengesellschaft Bohr- und/oder Meisselhammer mit elektropneumatischem Schlagwerk und einer Vorrichtung zur variablen Einstellung der Schlagenergie
JP4916872B2 (ja) * 2006-12-26 2012-04-18 株式会社マキタ 打撃工具
JP2012196728A (ja) * 2011-03-18 2012-10-18 Makita Corp 打撃工具
JP6026861B2 (ja) * 2012-11-19 2016-11-16 株式会社マキタ 打撃工具
US9573262B2 (en) 2012-11-19 2017-02-21 Makita Corporation Impact tool
EP3181302A1 (de) 2015-12-14 2017-06-21 HILTI Aktiengesellschaft Handwerkzeugmaschine

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3688848A (en) * 1971-03-15 1972-09-05 Black & Decker Mfg Co Air spring bleed assembly
DE2729596A1 (de) * 1977-06-30 1979-01-11 Hilti Ag Bohrhammer mit pneumatisch angetriebenem schlagkolben
GB2052346B (en) * 1979-06-18 1983-02-02 Kango Electric Hammers Ltd Rotary hammer drills
US4336847A (en) * 1980-06-27 1982-06-29 Hitachi Koki Company, Limited Percussion drill

Also Published As

Publication number Publication date
ATE42490T1 (de) 1989-05-15
EP0222698A1 (de) 1987-05-20
AU6461886A (en) 1987-05-07
US4732219A (en) 1988-03-22
DE3539030A1 (de) 1987-05-07
JPS62107985A (ja) 1987-05-19
JPH0553584B2 (enrdf_load_stackoverflow) 1993-08-10
AU583952B2 (en) 1989-05-11
DE3662983D1 (en) 1989-06-01

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