EP1967329A2 - Hand tool machine with pneumatic striking mechanism - Google Patents

Abstract

The hand tool with a pneumatic impact-action tool includes a striker (8) with an outer radial collar (11) which is encompassed by an abutment ring (12), the outside diameter of which is smaller than the guiding inside diameter of the guide tube (6) for the striker. The mass ratio of the abutment ring to the striker is at least 0.25. The abutment ring is formed tangentially in two sections. The abutment ring is enclosed radially on the outside by an encompassing closed assembly sleeve (19).

Description

The invention refers to an at least partially striking hand tool with a pneumatic impact mechanism such as a chisel hammer or a hammer drill.

A pneumatic percussion mechanism has a guided in a guide tube and driven by an air spring air piston, which usually strikes a limited axially movable striker, which hits even the front end of a limited axially movable tool.

In unusual operating conditions such as tool-side directed clearances with tool lifted off the ground as well as back-reflected, oppositely directed impact impacts with a hard-elastic Armierungstreffer the striking mechanism comes from the optimized normal operating condition and generates amplified vibrations, which must be damped.

After W003024671 has a beating hand tool with a pneumatic percussion on a damping element, wherein the flying piston has an axially offset by a tapered outer cone, which penetrates rubbing into a radially narrower steel ring of the damping element and thereby at idle over a long axial pre-damping a large part of the kinetic energy of the flying piston dissipated in the viscoelastic damping element.

After DE3910398 two striker are arranged within an axially fixed, three-part guide sleeve with Elastomerdämpfring, wherein the guide sleeve forms two Innenradialfasen frontally abutted against which each Außenradialfase Außenradialbundes the striker during idle and the associated contact friction and the viscoelastic Elastomerdämpfring the kinetic energy of the flying piston dissipated.

After EP1238759 In addition, the striker forms a second, axially spaced outer radial collar, which surrounds the elastomeric damping ring with an inner radial collar Sparks happen and thereby viscoelastic expands, which additionally reduces kinetic energy.

After DE4400779 is an anvil in axial play freely movable within a radially outwardly elastically biased, axially frictionally movable in the guide tube sliding sleeve made of metal, which forms two frontal Innenradialfasen, each associated with a Außenradialfase a Außenradialbundes the striker. During idling the tool-side Innenradialfase the sliding sleeve is radially expanded, whereby the friction force of the sliding sleeve increases and is dissipated correspondingly more kinetic energy. The rest of the kinetic energy is dissipated with a visco-elastic damping ring, which is hit by the sliding sleeve together with the striker.

The object of the invention is a robust, durable implementation for damping the blank. Another aspect is the shortening of the Leerschlagweges the striker and thus the overall length.

The object is essentially achieved by the features of claim 1. Advantageous developments emerge from the subclaims.

Thus, an at least partially striking hand-held power tool with a pneumatic percussion on a driven by an air spring piston which strikes a limited guided in a guide tube and two axial stops axially movable striker, which forms a Außenradialbund, axially from both sides of a coaxially arranged outside shock ring each with an inner radial edge radially includes and the outer radial collar axially limited freely movable, wherein the outer diameter of the shock ring is smaller than the leading inner diameter of the guide tube and the mass ratio of the shock ring to the striker is at least 0.25.

Due to the bumpers axially limited freely movable thrust ring, which is guided almost frictionless to the striker on the guide tube, forms (with empty shot) of the striker with the shock ring from a shock system, which draws on mutual power surges as a result of the striker part of its kinetic energy and this transfers to the bumper ring. This is done by always a part of the kinetic energy is dissipated in the real (not ideal elastic) force impact via contact and internal material friction, even if in Stospaaarung steel / steel with a Stosparameter of about 0.95 this part is only 10% per power surge. In detail, the striker encounters the empty shot with a topper speed by the power surge on the Außenradialbund on the tool-side inner radial edge of the previously stationary (with respect to the power tool) shock ring, whereby the striker braked and the shock ring is accelerated until it again strikes with its machine-side Innenradialflanke on the outer radial collar and emits kinetic energy to the striker again. In addition, when striking the striker on an axial stop a not insignificant loss of energy during the leading back reflection power surge occurs. This interplay is continued over a large number of momentum, until in the (temporal) border crossing of the shock ring has the same final speed as the striker and thereby largely come to rest by the energy losses. However, a deceleration of the striker or a time delay of its reentry into the effective range of the percussion piston is sufficient for a successful blanking damping. Thus, the slowly returning striker reaches the incoming impact on the next working point late in the piston delayed, causing the percussion from the cycle and the flying piston reaches the tool side offset to the working point blanking position, which ventilates the air spring and the percussion virtually shuts off.

Advantageously, the thrust ring is formed tangentially in two parts, more advantageously of two half-shells, which are firmly connected to each other after assembly (eg. Welded), whereby the shock ring around the Außenradialbund of the striker is assembled around.

Advantageously, the tangentially formed two-part thrust ring is radially outwardly of a circumferentially closed mounting sleeve includes, which is further advantageously radially inwardly resiliently biased and provided with internal thread, whereby a positive and reibkraftschlüssige mounting of the tangentially formed two-piece thrust ring with external thread is possible.

Advantageously, an axially limited freely movable axial Bundspiellänge the Außenradialbunds to the shock ring in the range between 1 mm and 5 mm, further advantageously at 2 mm, which during the stable impact operation, in which the flying piston at the operating point strikes the striker and this virtually motionless on the Front end of the limited axially movable tool hits, the striker is offset infinitely only within the axial collar length, causing no force surges to the shock ring and consequently takes place in this loss-free stable impact operation.

It is advantageous in the guide tube an axially double-sided ring stopper for the shock ring available, which further advantageously machine side made of viscoelastic material is, whereby the shock ring is reflected back directly (without mediation on the striker) on the guide tube and dissipates energy.

Advantageously, an axially limited freely movable axial Ringpiellänge of the shock ring to the ring stops in the guide tube in the range between 10 mm and 20 mm, more advantageously at 15 mm, which on the one hand at idle multiple energy dissipating reflections of the shock ring to the striker done before the shock ring itself on an annular stop in the guide tube impinges, on the other hand, the Leerschlagweg of the striker is less than in a comparable implementation without shock ring.

Advantageously, the outer radial collar is arranged on a machine side radially tapered Axialhals the striker, whereby the outer diameter of the Außenradialbundes and thus also of the shock ring is less executable (as in a striker without axial neck), whereby the space occupied by the Leerschlagdämpfung space is limited.

The axial abutment surfaces formed on the outer radial collar and the counter abutment surfaces formed on the two inner radial edges are advantageously chamfered in the same axial direction, further advantageously with a radial chamfer angle in the range between 30 ° and 80 °, whereby a radial expansion of the shock ring takes place during the axial shock of the axially oblique chamfer , which dissipates a significant part of the impact energy in ring vibrations and heat by the associated micro friction.

• Fig. 1 als Handwerkzeugmaschine
• Fig. 2 als Einzelheit im Längsschnitt, vergrössert

The invention will be explained in more detail with respect to an advantageous embodiment with:

• Fig. 1 as a hand tool machine
• Fig. 2 as a detail in longitudinal section, enlarged

To Fig. 1 has a rotating and striking a tool 7 driving hand tool 1 a pneumatic percussion 2 with a coupled by an air spring 3 with an exciter piston 4 flying piston 5, which strikes in the illustrated striking position on a guided in a guide tube 6 striker 8.

To Fig. 2 is the axial freedom of movement of the striker 8 limited by two in the guide tube 6 (the striker 8) angeodnete axial stops 9a, 9b. The striker 8 also forms an outer radial collar 11 on a machine side radially tapered Axialhals 10, the axially from both sides with a Innenradialflanke 14 radially comprises a coaxial outer thrust ring 12 and the Außenradialbund 11 axially limited free is movable, wherein the mass ratio of the shock ring 12 to the striker 8 is exactly 0.25. The axial abutment surfaces 15a formed on the outer radial collar 11 as well as the counter abutment surfaces 15b formed on the two inner radial flanks 14 are axially chamfered in terms of their amount equal to a radial chamfer angle [alpha] of 30 °. In the guide tube 6 also two axially double-sided ring stops 16a, 16b are provided for the shock ring 12, wherein the machine-side ring stop 16b is identical to the machine-side axial stop 9b and is made of viscoelastic material. The tangentially formed from two half-shells 17a, 17b butt ring 12 with external thread 18 was placed around the Außenradialbund 11 during assembly and surrounded by a circumferentially closed mounting sleeve 19, which is resiliently biased radially inward and provided with internal thread 20. The outer diameter of the shock ring 12 (including mounting sleeve 19) is slightly smaller than the (this virtually frictionless leading) inner diameter of the guide tube 6. Here is an axially limited freely movable axial collar length B of the outer radial collar 11 to the shock ring 12 at 2 mm and an axially limited freely movable axial Ringpiellänge R of the shock ring 12 between the ring stops 16a, 16b in the guide tube 6 at 15 mm, the Leerschlagweg L of the striker 8 between the tool-side axial stops 9a, 9b at 18 mm.

Claims (8)

At least partially hammert hand tool with a pneumatic percussion (2) and a by an air spring (3) driven air piston (5), which guided in a guide tube (6) and two axial stops (9a, 9b) limited axially movable striker (8 ), which forms a Außenradialbund (11) of a coaxially outer thrust ring (12) axially on both sides, each with a Innenradialflanke (14) radially and the Außenradialbund (11) axially limited freely movable, characterized in that the outer diameter of the thrust ring (12) is smaller than the leading inner diameter of the guide tube (6) and that the mass ratio of the thrust ring (12) to the striker (8) is at least 0.25. Powered hand tool according to claim 1, characterized in that the thrust ring (12) is formed tangentially in two parts. Powered hand tool according to claim 2, characterized in that the thrust ring (12) is surrounded radially outwardly by a circumferentially closed mounting sleeve (19). Powered hand tool according to one of claims 1 to 3, characterized in that an axially limited freely movable axial shoulder length (B) of the outer radial collar (11) to the thrust ring (12) in the range between 1 mm and 5 mm. Powered hand tool according to one of claims 1 to 4, characterized in that in the guide tube (6) an axially double-sided ring stop (16a, 16b) for the shock ring (12) is present. Powered hand tool according to claim 5, characterized in that an axially limited freely movable axial Ringpiellänge (R) of the shock ring (12) to the annular stops (16a, 16b) in the guide tube (6) in the range between 10 mm and 20 mm. Hand tool according to one of claims 1 to 6, characterized in that the Außenradialbund (11) on a machine side radially tapered Axialhals (10) of the striker (8) is arranged. Hand tool according to one of claims 1 to 7, characterized in that the Außenradialbund (11) formed axial abutment surfaces (15a) and the at the two Innenradialflanken (14) formed counter-abutment surfaces (15b) in terms of amount equal to chamfered axially.

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