U.S. patent application number 11/594207 was filed with the patent office on 2007-05-17 for motor driven drilling hammer.
This patent application is currently assigned to Metabowerke GmbH. Invention is credited to Michael Keller.
Application Number | 20070107920 11/594207 |
Document ID | / |
Family ID | 36118295 |
Filed Date | 2007-05-17 |
United States Patent
Application |
20070107920 |
Kind Code |
A1 |
Keller; Michael |
May 17, 2007 |
Motor driven drilling hammer
Abstract
The invention concerns a motor-driven drilling hammer with
percussion and rotary drive, and a drill sleeve (14) which is
disposed in a housing and is drivingly connected to a tool or a
chuck for receiving the tool. In order to improve vibration
damping, the drilling hammer is designed such that the drill sleeve
(14) is connected on its outer periphery (30) to a spring means
(32) of an elastomeric material (34) which has a wall thickness of
1 to 10 mm, and wherein the spring means (32) holds a damping mass
(36) which can be deflected relative to the drill sleeve (14) in
the peripheral direction and in the longitudinal direction (20) of
the drill sleeve (14) due to the elasticity of the spring means
(32), thereby effecting damping and reduction of vibration.
Inventors: |
Keller; Michael;
(Nuertingen, DE) |
Correspondence
Address: |
DREISS, FUHLENDORF, STEIMLE & BECKER
POSTFACH 10 37 62
D-70032 STUTTGART
DE
|
Assignee: |
Metabowerke GmbH
Nuertingen
DE
|
Family ID: |
36118295 |
Appl. No.: |
11/594207 |
Filed: |
November 8, 2006 |
Current U.S.
Class: |
173/48 |
Current CPC
Class: |
B25D 2222/57 20130101;
B25D 2217/0092 20130101; B25D 17/24 20130101 |
Class at
Publication: |
173/048 |
International
Class: |
E02D 7/02 20060101
E02D007/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 16, 2005 |
EP |
05 024 979.6 |
Claims
1. A motor-driven drilling hammer for driving a tool or a chuck
receiving a tool, the drilling hammer comprising: a housing; a
percussion and rotary drive disposed in said housing; a drill
sleeve disposed in said housing and cooperating with said
percussion and rotary drive and with the tool or the chuck for
receiving the tool; a spring means having an elastomeric material
with a wall thickness of 1 to 10 mm, said spring means connected to
an outer periphery of said drill sleeve; and a damping mass held by
said spring means for deflection of said damping mass relative to
said drill sleeve in a peripheral and longitudinal direction of
said drill sleeve due to an elasticity of said spring means,
thereby effecting damping and reduction of vibrations.
2. The drilling hammer of claim 1, wherein said elastomeric
material continuously surrounds said drill sleeve in said
peripheral direction and is substantially cylindrical.
3. The drilling hammer of claim 1, wherein said elastomeric
material is segmented.
4. The drilling hammer of claim 1, wherein said elastomeric
material has perforations, recesses or openings in a radial,
tangential, or axial direction.
5. The drilling hammer of claim 1, wherein said elastomeric
material has a wall thickness of 4 to 8 mm.
6. The drilling hammer of claim 1, wherein said elastomeric
material has an axial extension in said longitudinal direction of
said drill sleeve of 5 to 20 mm.
7. The drilling hammer of claim 1, wherein said damping mass is
substantially cylindrical.
8. The drilling hammer of claim 1, wherein said damping mass has an
axial extension in said longitudinal direction of said drill sleeve
of 5 to 20 mm.
9. The drilling hammer of claim 1, wherein said damping mass has an
axial extension in said longitudinal direction of said drill
sleeve, which is 3 to 8 times a wall thickness thereof.
10. The drilling hammer of claim 1, wherein said damping mass and
said spring means are designed to damp vibrations of between 30 and
100 Hz or, for small drilling hammers, between 70 to 80 Hz.
Description
[0001] This application claims Paris Convention priority of EP 05
024 979.6 filed Nov. 16, 2005 the complete disclosure of which is
hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] The invention concerns a motor-driven drilling hammer with a
percussion and rotary drive, and a drill sleeve which is disposed
in a housing.
[0003] One problem of drilling hammers is that the percussion drive
causes strong vibrations transferred from the percussion mechanism
to the housing and handle components. It has been proposed to
provide a demolition hammer with a spring/mass system, wherein the
oscillations caused by the axially operating percussion drive are
damped by a mass which is pretensioned on both sides by
springs.
[0004] It is the underlying purpose of the present invention to
effectively reduce vibrations in drilling hammers.
SUMMARY OF THE INVENTION
[0005] This object is achieved with a drilling hammer of the
above-mentioned type in that the drill sleeve is connected on its
outer periphery to a spring means of an elastomeric material which
has a wall thickness of 1 to 10 mm, wherein the spring means has a
damping mass which can be displaced in the peripheral and
longitudinal directions of the drill sleeve relative thereto due to
the elasticity of the spring means, thereby effecting damping to
reduce vibrations.
[0006] In the inventive drilling hammer, the damping mass may
oscillate in a translatory and also rotary direction. The
spring/mass system is thereby designed, such that oscillation of
the damping mass in the translatory and rotary directions is, in
each case, counter-phased to the oscillations of the drill sleeve,
such that these oscillating frequencies are cancelled or
effectively damped. This reduces the overall oscillation excitation
of the drilling hammer by these two main components. In accordance
with the invention, it has turned out that, especially for small
and medium-sized drilling hammers, the vibrations at the handle are
primarily generated by the percussion and rotary forces acting on
the tool. Since the percussion and rotational speed of drilling
hammers remain largely constant during operation, the oscillations
can advantageously be damped to reduce vibrations. The inventive
design reduces vibrations in a highly effective fashion, since
translatory and also rotary oscillations can be damped.
[0007] The inventive arrangement of the damping mass permits
cancelling of at least two dominant excitation frequencies by one
single mass. The design of the spring/mass system depends on the
geometry and weight of the damping mass, and the geometry and
design of the elastomeric spring means. In order to reduce e.g. the
damping frequency, the elastomeric mass may be thicker or the
weight of the damping mass may be increased. This must be achieved
in each case through suitable design of the spring/mass system in
correspondence with the frequencies to be damped, which are
generated during operation of the drilling hammer.
[0008] With particular advantage, the elastomeric material may
continuously surround the drill sleeve in the peripheral direction,
and be substantially cylindrical. This produces a very
load-resistant connection between the damping mass and the drill
sleeve, which is also largely insensitive to shearing loads. In
certain cases, it may also be advantageous to segment the
elastomeric material, i.e. to provide several bordering or
spaced-apart segments of elastomeric material on the outer
periphery of the drill sleeve or to provide the elastomeric
material with perforations, recesses or openings in a radial,
tangential or axial direction.
[0009] For the use of small and medium-sized drilling hammers, a
wall thickness of the elastomeric material of 4 to 8 mm has proven
to be advantageous. In one further preferred embodiment, the
elastomeric material has an axial extension in the longitudinal
direction of the drill sleeve of 5 to 20 mm.
[0010] The damping mass may moreover advantageously be
substantially cylindrical. This yields a symmetric mass
distribution which is uniform and continuous in the peripheral
direction around the drill sleeve, which is suitable in view of
vibration damping. The axial extension of the damping mass may
advantageously also be 5 to 20 mm. It is preferably 3 to 8 times
its wall thickness.
[0011] The damping mass/spring system is moreover advantageously
designed to damp vibrations of between 30 and 100 Hz. For smaller
drilling hammers, the oscillations to be cancelled are
preferentially between 70 and 80 Hz.
[0012] Further features, details and advantages of the invention
can be extracted from the enclosed claims, the drawing and the
following description of a preferred embodiment of the inventive
drilling hammer.
BRIEF DESCRIPTION OF THE DRAWING
[0013] FIG. 1 shows a sectional view of a relevant region of a
drilling hammer; and
[0014] FIG. 2 shows a perspective view of the drilling hammer
according to FIG. 1, illustrating the rotary drive of the drill
sleeve.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] The figures show a region 2 comprising the drive components
of an inventive drilling hammer. A region comprising the
electromotor and a handle region of the drilling hammer are not
shown. A main drive shaft extends through the indicated rotary duct
4 into the region 2 and drives a shaft 6 (in a manner not shown).
The shaft 6 has a wobble plate arrangement 8 (best shown in FIG. 2)
which drives a percussion mechanism 10 of the drilling hammer, and
a toothed wheel 12 (only shown in FIG. 2) which rotates a drill
sleeve 14.
[0016] The percussion mechanism 10 has a sleeve 18, which defines a
cylindrical chamber 16 and can be moved, i.e. axially reciprocated,
by the wobble plate arrangement 8 in the longitudinal direction 20
of the drill sleeve 14. The sleeve 18 is disposed inside the drill
sleeve 14, concentrically thereto, and can be axially moved
relative thereto. A free flight body is provided as beater 22
within the cylindrical chamber 16, which forms a pneumatic spring
24 together with the sleeve 18. When the sleeve 18 is accelerated
to the left in FIG. 1 by the wobble plate arrangement 8, the beater
22 initially remains in its position due to its inertial mass,
thereby forming an underpressure within the cylindrical chamber 16,
which then causes delayed acceleration of the beater 22. When the
sleeve 18 is moved again to the right in FIG. 1, the cylindrical
chamber and the air contained therein are compressed, in particular
to between 10 and 20 bar, which greatly accelerates the beater 22
towards the right and towards an intermediate piston 26. The impact
surface 28 of the beater 22, facing the intermediate piston 26,
strikes the intermediate piston 26 and is thereby immediately
stopped, wherein the momentum is transferred to the intermediate
piston 26 which subsequently strikes a tool, a drill or chisel,
transferring a further momentum (percussion or hammer operation).
When the intermediate piston 26 rebounds to the left in FIG. 1, it
strikes the drill sleeve 14 via an intermediate elastomeric ring
30, thereby generating vibrations which are transferred to the
housing of the device and which are experienced by the user as
being unpleasant.
[0017] A spring means 32 of an elastomeric material 34 is provided
on the outer periphery 31 of the drill sleeve 14. In the example
shown, the spring means 32 or the elastomeric material 34
continuously surround the outer periphery 30 of the drill sleeve 15
in the peripheral direction. It is substantially cylindrical and
has a wall thickness of between 1 and 10, in particular, 4 and 8
mm. A damping mass 36 which also has a cylindrical basic geometry,
is provided radially outside on the elastomeric material 34, and in
the example shown, concentrically to the drill sleeve 14. The
damping mass 36 can be deflected in a resilient fashion relative to
the drill sleeve 14 by the spring means 32 of elastomeric material
in an axial, longitudinal direction 20 as well as in a peripheral
direction. The connection between the damping mass 36 and the drill
sleeve 14 basically provides six degrees of freedom due to the
elastomeric material 34. The damping mass/spring system is designed
such that, due to the resilient deflectable arrangement of the
damping mass 36, the damping mass 36 can oscillate in a translatory
and rotary direction with a respective phase which is opposite to
that of the excitation oscillations acting on the drill sleeve, to
thereby damp, cancel, or provide effective reduction of vibration.
This eliminates two main components of the overall oscillation
excitation of the drilling hammer.
* * * * *