EP0222698A1 - Drill hammer with an air-driven impacting piston - Google Patents

Drill hammer with an air-driven impacting piston Download PDF

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Publication number
EP0222698A1
EP0222698A1 EP86810462A EP86810462A EP0222698A1 EP 0222698 A1 EP0222698 A1 EP 0222698A1 EP 86810462 A EP86810462 A EP 86810462A EP 86810462 A EP86810462 A EP 86810462A EP 0222698 A1 EP0222698 A1 EP 0222698A1
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EP
European Patent Office
Prior art keywords
piston
air cushion
pistons
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.)
Granted
Application number
EP86810462A
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German (de)
French (fr)
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EP0222698B1 (en
Inventor
Franz Chromy
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Hilti AG
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Hilti AG
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Publication date
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Priority to AT86810462T priority Critical patent/ATE42490T1/en
Publication of EP0222698A1 publication Critical patent/EP0222698A1/en
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Publication of EP0222698B1 publication Critical patent/EP0222698B1/en
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    • 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.
  • 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 at least one of the two pistons has a connecting channel leading outward from the air cushion space and the connecting channel is closed by a closure part made of material with a low melting point.
  • 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 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.
  • a particularly vibration-proof fit of the closure part in the bore is achieved in a further development of the invention by the closure part being 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.
  • the drive piston can be moved back and forth without abrupt deceleration, for example from a crank mechanism.
  • 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 connecting rod 12 For coupling the connecting rod 12 to the drive piston 13, the parts mentioned are crossed by a bolt 14, the end section of the connecting rod 12 crossed by the bolt 14 engaging in a pocket-like recess 15 in the drive piston 13.
  • 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 impulses 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.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Percussive Tools And Related Accessories (AREA)
  • Earth Drilling (AREA)
  • Supply Devices, Intensifiers, Converters, And Telemotors (AREA)
  • Drilling And Boring (AREA)

Abstract

A hammer drill has a cylinder within a housing with the cylinder forming a piston chamber. A drive piston is reciprocally mounted within the piston chamber and is displaced by a motor. A percussion piston is located within the piston chamber with an air cushion space located between the two pistons. As the drive piston reciprocates, it moves the percussion piston back and forth by way of the air cushion located between them. One of the pistons has a conduit open at one end to the air cushion space and at the other end to the exterior of the cylinder. A closure plug is located in the one end of the conduit and closes off air flow from the air cushion space into the conduit at regular operating temperatures. If the temperature in the air cushion space rises due to air leakage from the space, the closure plug melts and connects the conduit with the air space so that the reciprocation of the percussion piston stops before the pistons strike against one another and cause damage.

Description

Die Erfindung betrifft einen Bohrhammer mit einem Zylinder zur Führung eines motorisch hin und her verschiebbaren Antriebskolbens und eines Schlagkolbens unter Zwischenschaltung eines Luftpolsters.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.

Bei bekannten Bohrhämmern mit einem sogenannten pneumatischen Schlagwerk, das über einen in einem Zylinder motorisch hin und her bewegten Antriebskolben und über einen Schlagkolben verfügt. der unter Zwischenschaltung eines Luftpolsters ebenso hin und her bewegt wird, kann sich als Folge zunehmender Leckverluste ein ausreichendes Luftpolster nicht mehr aufbauen, so dass durch Zusammenschlagen der Kolben Schäden am Schlagwerk und darüberhinaus an den Antriebsorganen für das Schlagwerk sowie an weiteren Geräteteilen auftreten können.In known rotary hammers with a so-called pneumatic percussion mechanism, which has a drive piston which is moved to and fro in a cylinder and a percussion piston. which is also moved back and forth with the interposition of an air cushion, a sufficient air cushion can no longer build up as a result of increasing leakage losses, so that when the pistons are knocked down, damage to the striking mechanism and, in addition, to the drive elements for the striking mechanism and other device parts can occur.

Die Leckverluste sind die Folge mangelhafter Dichtung zwischen den Kolben und dem Zylinder, hervorgerufen insbesondere durch Verschleiss kolbenseitiger Dichtelemente. Zudem fÖrdern mangelhafte Schmierung und Ausfall von gegebenenfalls wärmeempfindlichen Dichtelementen solche Leckverluste.The 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. In addition, poor lubrication and failure of any heat-sensitive sealing elements promote such leakage losses.

Zur Vermeidung über das Schlagwerk hinausgehender kostspieliger Schäden als Folge von Leckverlusten ist bei einem bekannten Bohrhammer (DE-OS 2 729 596) am Antriebskolben ein Bodenteil vorgesehen, das beim Aufprallen des Schlagkolbens ausbricht. Dadurch wird der zwischen den beiden Kolben liegende Raum nach aussen entlüftet, so dass der Schlagkolben mangels eines Luftpolsters nicht mehr hin und her bewegt wird.In order to avoid costly damage beyond the striking mechanism as a result of leakage losses, a bottom part is provided on the drive piston in a known hammer drill (DE-OS 2 729 596) which breaks out when the impact piston strikes. As a result, the space between the two pistons is vented to the outside, so that the percussion piston is no longer moved back and forth due to the lack of an air cushion.

Ein Nachteil dieser Ausbildung besteht in der Gefahr, dass durch das zum Ausbrechen des Bodenteiles erforderliche Aufprallen des Schlagkolbens bereits Schäden an Geräteteilen auftreten können.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.

Der Erfindung liegt die Aufgabe zugrunde, einen Bohrhammer mit pneumatischem Schlagwerk zu schaffen, bei dem eine Verhinderung von aus Leckverlusten des Luftpolsters resultierenden Schäden gewährleistet wird.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.

Erfindungsgemäss wird die Aufgabe dadurch gelöst, dass wenigstens einer der beiden Kolben einen vom Luftpolsterraum nach aussen führenden Verbindungskanal aufweist und der Verbindungskanal von einem Verschlussteil aus Material mit niedrigem Schmelzpunkt verschlossen ist. Die Erfindung macht sich die Erkenntnis zunutze, dass zufolge der Leckverluste die Leistung am Schlagkolben abnimmt. Da die vom Motor an den Antriebskolben abgegebene Leistung unverändert bleibt, steigt die Wärmeleistung des Schlagwerkes zunehmend mit grösser werdenden Leckverlusten. wodurch sich die Betriebstemperatur insgesamt erhöht.According to the invention, the object is achieved in that at least one of the two pistons has a connecting channel leading outward from the air cushion space and 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 output of the striking mechanism increases with increasing leakage losses. which increases the overall operating temperature.

Bei regulärer Betriebstemperatur oder unter dieser liegender Anlauftemperatur wird der Verbindungskanal vom Verschlussteil geschlossen gehalten. Tritt gegenüber der regulären Betriebstemperatur eine beispielsweise um 20 % erhöhte Temperatur auf, schmilzt das Verschlussteil. Dadurch öffnet sich der Verbindungskanal und das Luftpolster bricht zusammen.At regular operating temperature or below this start-up 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.

Bei der Materialwahl ist zu beachten, dass das Schmelzen eintritt, ausreichend bevor es zu einem Zusammenprallen der Kolben kommt. Zudem ist durch geeignete Wahl des Wärmeausdehnungskoeffizienten die ausreichende Abdichtung vor Eintritt des Schmelzens sicherzustellen, dh. der Wärmeausdehnungskoeffizient des Verschlussteiles kann gegenüber jenem der Kolben etwa gleich oder grösser sein. Der nach dem Schmelzen des Verschlussteiles vom Antriebskolben pneumatisch entkoppelte Schlagkolben nimmt, unabhängig von weiterer Hin-und Herbewegung des Antriebskolbens, Ruheposition ein.When choosing the material, it should be noted that melting occurs sufficiently before the pistons collide. In addition, a suitable choice of the coefficient of thermal expansion must ensure adequate sealing before melting begins, ie. 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 back and forth movement of the drive piston.

Für den Handhabenden ist als Folge des Schmelzens des Verschlussteiles ein plötzlicher Abbruch der Schlagabgabe feststellbar. Folglich wird er das Gerat ausser Betrieb nehmen. Folgeschäden an den Antriebsorganen für das Schlagwerk oder an weiteren Geräteteilen werden somit unterbunden. Durch Ersetzen des Verschlussteiles und Ausführung der erforderlichen Wartungsmassnahmen, wie Austausch der Dichtelemente und Schmieren des Schlagwerkes, kann das Gerät ohne Schaden wieder in betriebsbereiten Zustand gebracht werden.As a result of the closure part melting, 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. 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.

Vorzugsweise ist der Verbindungskanal als eine die Kolben in Achsrichtung durchsetzende Bohrung ausgebildet. Um eine gleichmässige Gewichtsverteilung der Kolben zu erzielen, verläuft der Verbindungskanal zweckmässig konzentrisch oder-gebildet durch mehrere Bohrungen - symmetrisch zur Längsachse der Kolben.The connecting channel is preferably designed as a bore penetrating the pistons in the axial direction. In order to achieve a uniform weight distribution of the pistons, the connecting channel expediently runs concentrically or - formed by several bores - symmetrically to the longitudinal axis of the pistons.

Mit Vorteil ist das Verschlussteil an dem zum Luftpolster weisenden Ende der Kolben angeordnet.The closure part is advantageously arranged at the end of the piston facing the air cushion.

Diese Stelle der Kolben liegt im räumlichen Nahbereich der für erhöhte Temperatur massgeblichen Stellen des Gerätes, so dass das Verschlussteil der Wärmeeinwirkung direkt ausgesetzt ist. Damit ist ein sensibles und präzises Reagieren des Verschlussteiles auch bei unterschiedlichen Umgebungstemperaturen des Gerätes gewährleistet.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.

Ein im besonderen erschütterungsfester Sitz des Verschlussteiles in der Bohrung wird in Weiterbildung der Erfindung erreicht, indem das Verschlussteil mittels Hinterstichen im Verbindungskanal formschlüssig gehaltert wird. Bei den Hinterstichen kann es sich beispielsweise um in sich geschlossene umlaufende Rillen oder um Gewinderillen handeln.A particularly vibration-proof fit of the closure part in the bore is achieved in a further development of the invention by the closure part being positively held in the connecting channel by means of undercuts. The back stitches can be, for example, closed circumferential grooves or thread grooves.

Das Verschlussteil erstreckt sich in Form eines Pfropfens beispielsweise über einen Teil der Längserstreckung der Bohrung. Es ist möglich, das Verschlussteil als fertig geformter Pfropfen oder im Giessverfahren in die Bohrung einzubringen.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.

Nach einem weiteren Vorschlag der Erfindung ist das Verschlussteil am Antriebskolben angeordnet. Dies ist insbesondere für die Beibehaltung eines guten Sitzes des Verschlussteils in der Bohrung von Vorteil. Während der Schlagkolben durch dessen Aufprallen am Werkzeug fortwährend abrupten Abbremsungen ausgesetzt ist, was zu einem Verschieben eines hierin gelagerten Verschlussteiles führen könnte, lässt sich der Antriebskolben ohne abrupte Abbremsung beispielsweise von einem Kurbeltrieb hin und her verschieben.According to a further proposal of the invention, 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. During the percussion piston through it Impact on the tool is constantly subjected to abrupt decelerations, which could lead to a locking part mounted therein being displaced, the drive piston can be moved back and forth without abrupt deceleration, for example from a crank mechanism.

Vorzugsweise besteht das Verschlussteil aus einer Zinnlegierung. Dieses Material eignet sich im besonderen, da dessen Wärmeausdehnungskoeffizient etwa dem Wärmeausdehnungskoeffizienten des vorzugsweise aus Aluminium bestehenden Antriebskolbens entspricht. Als Zinnlegierungen eignen sich im besonderen Weichlote nach DIN 1707 mit wählbaren Schmelzpunkten von 150° bis 250° C. Die Erfindung wird nachstehend anhand einer Zeichnung, die ein Ausführungsbeispiel wiedergibt, näher erläutert. Es zeigen:

  • Fig. 1 einen Bohrhammer, teilweise im Längsschnitt;
  • Fig. 2 einen Ausschnitt 11 aus Fig. 1 in vergrösserter Darstellung.
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, in particular, soft solders according to DIN 1707 with selectable melting points from 150 ° to 250 ° C. The invention is explained in more detail below with the aid of a drawing which shows an exemplary embodiment. Show it:
  • Figure 1 shows a hammer drill, partly in longitudinal section.
  • Fig. 2 shows a detail 11 of FIG. 1 in an enlarged view.

Der Bohrhammer nach Fig. 1 besteht aus einem Gehäuse 1, in welchem durch ein vorderseitiges Kugellager 2 und ein rückseitiges Rollenlager 3 ein Zylinder 4 drehbar gelagert ist. Im vorderen Bereich ist der Zylinder 4 als Aufnahme für ein andeutungsweise erkennbares Bohrwerkzeug 5 ausgebildet. Letzteres weist Mitnahmenuten 5a zum Eingriff nicht dargestellter Verriegelungselemente auf. Ein gehäuseseitig abgestützter Dichtring 6 soll das Eindringen von Schmutz in das Gerät und das Austreten von Schmierstoffen unterbinden.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. In the front area, 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.

Auf dem Zylinder 4 ist ein Kegelrad 7 angeordnet, das durch einen Sicherungsstift 8 mit dem Zylinder 4 drehfest verbunden ist. Der Drehantrieb des Kegelrades 7 bzw. des Zylinders 4 erfolgt durch ein motorisch angetriebenes Kegelritzel 9. Ferner wird vom nicht gezeigten Motor auch eine Exzenterwelle 11 angetrieben, die über einen Pleuel 12 einen im Zylinder 4 gelagerten, insgesamt mit 13 bezeichneten Antriebskolben hin und her bewegt. Zur Kupplung des Pleueles 12 mit dem Antriebskolben 13 sind die genannten Teile von einem Bolzen 14 durchquert, wobei der vom Bolzen 14 durchquerte Endabschnitt des Pleueles 12 in eine taschenartige Vertiefung 15 des Antriebskolbens 13 eingreift. Der Antriebskolben 13 ist konzentrisch zu dessen Längsachse von einer Bohrung 16 durchsetzt, die als Verbindungskanal zwischen dem in Bohrrichtung an den Antriebskolben 13 anschliessenden Zylinderraum und der nach aussen offenen Vertiefung dient. Im bohrrichtungsseitigen Endabschnitt der Bohrung 16 ist lagefest ein pfropfenförmiges Verschlussteil 17 aus einer Zinnlegierung, die sich durch niedrigen Schmelzpunkt auszeichnet, angeordnet. Der Antriebskolben 13 trägt ferner in einem umlaufenden Einstich 18 ein mit dem Zylinder 4 zusammenwirkendes ringförmiges Dichtelement 19.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 . For coupling the connecting rod 12 to the drive piston 13, the parts mentioned are crossed by a bolt 14, the end section of the connecting rod 12 crossed by the bolt 14 engaging in a pocket-like recess 15 in the drive piston 13. 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. A plug-shaped closure part 17 made of a tin alloy, which is characterized by a low melting point, is fixed in position in the end section of the bore 16 on the drilling direction side. In a circumferential recess 18, the drive piston 13 also carries an annular sealing element 19 which interacts with the cylinder 4.

Wie die Fig. 2 verdeutlicht, greift das Verschlussteil 17 formschlüssig in Hinterstiche 16a in Form von Gewinderillen ein.As illustrated in FIG. 2, the closure part 17 engages positively in the undercuts 16a in the form of thread grooves.

Im Zylinder 4 ist in Bohrrichtung vor dem Antriebskolben 13 auch ein insgesamt mit 21 bezeichneter Schlagkolben verschiebbar gelagert. Dieser weist einen Schaft 22 zur Uebertragung von Schlagimpulsen an das Bohrwerkzeug 5 sowie rückseitig einen Kopf 23 auf. Der Kopf 23 ist ebenso wie der Antriebskolben 13 mit einem Dichtelement 24 versehen.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 impulses 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.

Durch die Hin- und Herbewegung des Antriebskolbens 13 wird der Schlagkolben 21 von dem zwischen den beiden Kolben im Zylinder 4 stehenden Luftpolster entsprechend phasenverschoben ebenso in hin- und hergehende Bewegung versetzt. Um dabei das Vorlaufen des Schlagkolbens 21 in die gezeigte schlagabgebende Stellung nicht zu hemmen, weist der Zylinder 4 vorderseitig Abblasbohrungen 4a auf. Des weiteren ist im Zylinder 4 eine Ausgleichsbohrung 4b vorgesehen, welche den periodischen Aufbau des Luftpolsters sicherstellt. Mit zunehmender Einsatzdauer des Bohrhammers lasst die Wirkung der Dichtelemente 19, 24 nach, was zur Folge hat, dass Leckverluste auftreten und folglich der Antriebskolben 13 und der Schlagkolben 21 bei der aufeinander zugerichteten Hubbewegung immer näher aneinander gelangen.As a result of the reciprocating movement of the drive piston 13, 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. In order not to inhibit the advance of the percussion piston 21 into the blow-off position shown, the cylinder 4 has blow-off bores 4a on the front side. Furthermore, a compensating bore 4b is provided in the cylinder 4, which ensures the periodic build-up of the air cushion. With increasing use of the rotary hammer, the effect of the sealing elements 19, 24 diminishes, which has the consequence that leakage losses occur and consequently the drive piston 13 and the percussion piston 21 come closer and closer to each other during the stroke movement directed towards one another.

Gegenüber der regulären Betriebstemperatur kommt es aufgrund der Leckverluste zu einer sich zunehmend erhöhenden Temperatur. Die Schmelztemperatur des Verschlussteiles 17 liegt auf jenem erhöhten Temperaturniveau, das erreicht wird, bevor ein Aufeinanderprallen der Kolben 13,21 erfolgt. Das Schmelzen des Verschlussteiles 17 führt zum Entlüften des zwischen den Kolben 13, 21 liegenden Zylinderraumes über die Bohrung 16 nach aussen. Der Schlagkolben 21 wird somit von dem motorisch weiter hin und her bewegten Antriebskolben 13 nicht mehr aktiviert und bleibt in einer bohrrichtungsseitigen Endstellung stehen. Der Handhabende bemerkt ein Ausbleiben der Schlagabgabe und wird daraufhin das Gerät ausser Betrieb nehmen. Kostspielige Folgeschäden, wie sie bei einem Zusammenprallen der Kolben 13, 21 entstehen könnten, werden auf diese Weise zuverlässig unterbunden.Compared to the regular operating temperature, there is an increasing temperature due to the leakage losses. 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.

Zur neuerlichen Inbetriebnahme des Bohrhammers ist die erforderliche Wartung durchzuführen, wobei ein neues Verschlussteil 17 und neue Dichtelemente 19, 24 eingebracht werden.The required maintenance must be carried out to restart the hammer drill, with a new closure part 17 and new sealing elements 19, 24 being introduced.

Der beschriebene Bohrhammer ist für drehenden und schlagenden Antrieb des Bohrwerkzeuges 5 geeignet. Selbstverständlich ist die erfindungsgemässe Anordnung aber auch bei Geräten einsetzbar, die einem Werkzeug nur Schlagenergie vermitteln.The hammer drill described is suitable for rotating and striking drive of the drilling tool 5. Of course, the arrangement according to the invention can also be used in devices which only impart impact energy to a tool.

Claims (6)

1. Bohrhammer mit einem Zylinder zur Führung eines motorisch hin und her verschiebbaren Antriebskolbens und eines Schlagkolbens unter Zwischenschaltung eines Luftpolsters, dadurch gekennzelchnet, dass wenigstens einer der beiden Kolben (13, 21) einen vom Luftpolsterraum nach aussen führenden Verbindungskanal (16) aufweist und der Verbindungskanal (16) von einem Verschlussteil (17) aus Material mit niedrigem Schmelzpunkt verschlossen ist.1. hammer drill with a cylinder for guiding a drive piston which can be moved back and forth by motor and a percussion piston with the interposition of an air cushion, characterized in that at least one of the two pistons (13, 21) has a connecting channel (16) leading outwards from the air cushion space and the Connection channel (16) is closed by a closure part (17) made of material with a low melting point. 2. Bohrhammer nach Anspruch 1, dadurch gekennzeichnet, dass der Verbindungskanal als eine die Kolben (13, 21) in Achsrichtung durchsetzende Bohrung (16) ausgebildet ist.2. Hammer drill according to claim 1, characterized in that the connecting channel is designed as a bore (16) penetrating the pistons (13, 21) in the axial direction. 3. Bohrhammer nach Anspruch 1 oder 2. dadurch gekennzeichnet, dass das Verschlussteil (17) an dem zum Luftpolster weisenden Ende der Kolben (13.21) angeordnet ist.3. hammer drill according to claim 1 or 2, characterized in that the closure part (17) is arranged at the end facing the air cushion of the piston (13.21). 4. Bohrhammer nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass das Verschlussteil (17) mittels Hinterstichen (16a) im Verbindungskanal (16) formschlüssig gehaltertwird.4. hammer drill according to one of claims 1 to 3, characterized in that the closure part (17) by means of undercuts (16a) in the connecting channel (16) is positively held. 5. Bohrhammer nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass das Verschlussteil (17) am Antriebskolben (13) angeordnet ist.5. Hammer drill according to one of claims 1 to 4, characterized in that the closure part (17) is arranged on the drive piston (13). 6. Bohrhammer nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass das Verschlussteil (17) aus einer Zinnlegierung besteht.6. Hammer drill according to one of claims 1 to 5, characterized in that the closure part (17) consists of a tin alloy.
EP86810462A 1985-11-02 1986-10-20 Drill hammer with an air-driven impacting piston Expired EP0222698B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT86810462T ATE42490T1 (en) 1985-11-02 1986-10-20 HAMMER DRILL WITH PNEUMATIC DRIVEN IMPACT PISTON.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3539030 1985-11-02
DE19853539030 DE3539030A1 (en) 1985-11-02 1985-11-02 DRILLING HAMMER WITH PNEUMATICALLY DRIVEN PISTON

Publications (2)

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

Family

ID=6285104

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Application Number Title Priority Date Filing Date
EP86810462A Expired EP0222698B1 (en) 1985-11-02 1986-10-20 Drill hammer with an air-driven impacting piston

Country Status (6)

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

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 (en) * 1995-05-25 2003-10-20 株式会社マキタ Impact tool
DE19828423C2 (en) * 1998-06-25 2000-05-18 Wacker Werke Kg Driving piston for an air spring hammer mechanism
DE10034742A1 (en) * 2000-07-17 2002-01-31 Hilti Ag Tool with assigned impact tool
EP1584420B1 (en) * 2004-04-07 2014-06-11 HILTI Aktiengesellschaft Drilling and/or chipping hammer with electro-pneumatic percussion mechanism and device for variable setting of the impact energy
JP4916872B2 (en) * 2006-12-26 2012-04-18 株式会社マキタ Impact tool
JP2012196728A (en) * 2011-03-18 2012-10-18 Makita Corp Impact tool
JP6026861B2 (en) * 2012-11-19 2016-11-16 株式会社マキタ Impact tool
US9573262B2 (en) 2012-11-19 2017-02-21 Makita Corporation Impact tool
EP3181302A1 (en) 2015-12-14 2017-06-21 HILTI Aktiengesellschaft Manual machine tool

Citations (4)

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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 (en) * 1977-06-30 1979-01-11 Hilti Ag DRILL DRILL WITH PNEUMATICALLY DRIVEN PISTON
GB2052346A (en) * 1979-06-18 1981-01-28 Kango Electric Hammers Ltd >Improvements relating to rotary hammer drills
US4336847A (en) * 1980-06-27 1982-06-29 Hitachi Koki Company, Limited Percussion drill

Patent Citations (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 (en) * 1977-06-30 1979-01-11 Hilti Ag DRILL DRILL WITH PNEUMATICALLY DRIVEN PISTON
GB2052346A (en) * 1979-06-18 1981-01-28 Kango Electric Hammers Ltd >Improvements relating to rotary hammer drills
US4336847A (en) * 1980-06-27 1982-06-29 Hitachi Koki Company, Limited Percussion drill

Also Published As

Publication number Publication date
AU6461886A (en) 1987-05-07
JPH0553584B2 (en) 1993-08-10
EP0222698B1 (en) 1989-04-26
AU583952B2 (en) 1989-05-11
ATE42490T1 (en) 1989-05-15
US4732219A (en) 1988-03-22
DE3539030A1 (en) 1987-05-07
JPS62107985A (en) 1987-05-19
DE3662983D1 (en) 1989-06-01

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