Tool driving or impacting – Including means to vibrationally isolate a drive means from...
Reexamination Certificate
2000-01-13
2001-09-11
Smith, Scott A. (Department: 3721)
Tool driving or impacting
Including means to vibrationally isolate a drive means from...
C173S162200
Reexamination Certificate
active
06286610
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a percussion hammer and/or hammer drill, having a hammer casing which surrounds a percussion mechanism together with drive and holder for a percussion tool and is surrounded, at a distance, by an outer shell which, at selected coupling points, is elastically connected to the hammer casing and at whose end which is remote from the tool in the direction of impact thereof there is a handle.
A tool of this nature is known from DE 40 00 861 C2. In this tool, the vibrations acting on the hand or arm of the person guiding the tool are only reduced to an insufficient extent. Moreover, the spring or damping action has not yet been made sufficiently adaptable to different operating conditions in the prior art.
2. Description of the Related Art
In the design which is known from DE 40 00 861 C2—in the arrangement which is known for tools of this nature—a transmission casing and a motor casing which is connected to the transmission casing follow one after the other in the direction of impact of the tool, starting from the driven tool. These two elements are referred to above for short as the hammer casing. The vibrations which are emitted from this hammer casing are damped with respect to the handle located on the outer shell at the end which is remote from the tool by means of the elastic support between the hammer casing and the outer shell.
To provide reliable guidance for such tools, it is known, and highly advantageous, if a second handle is arranged as close as possible to the percussion tool which projects out of the transmission casing, in order for it to be possible to hold the tool with both hands and to obtain a guide length which is as long as possible.
In the tool which is known from DE 40 00 861 C2, the outer shell does not surround the entire hammer casing, but rather only the section which is formed by the motor casing. This document does not show a second handle. If it were desired to provide such a second handle, it would have to be connected to the transmission casing, and consequently all the vibrations which, as a result of the hammer casing being separate from the outer shell surrounding the motor casing only reach the first handle in damped form, would be transmitted to this second handle without any damping. Not only is this unpleasant when handling the tool, it also impairs reliable guidance of the tool.
DE 34 05 922 A1 has disclosed a handheld power tool in which a hammer casing, which has a handle, surrounds a tool drive, a percussion mechanism and a holder for a percussion tool. The percussion mechanism is secured in the hammer casing via damping elements, while the drive, which is formed by an electric motor, is rigidly connected to the hammer casing. The vibrations which are produced when the electric motor is operating are therefore transmitted to the handle without any damping.
OBJECTS AND SUMMARY OF THE INVENTION
The invention is therefore based on the object of designing a percussion hammer and/or hammer drill of the type mentioned at the outset in such a way that it can be held with both hands at the same time, and in such a manner that the vibrations which emanate from the hammer casing only reach the handles, which are used to hold and guide the hammer and are assigned to both hands, in highly damped form, so that the vibrations acting on the hands and arms are reduced as far as possible, and guidance of the hammer is improved.
It is also intended for it to be possible to design spring or damping elements which are arranged in the area of the connection between the hammer casing and the outer shell in such a way that they have spring characteristics which can be set as desired in six degrees of freedom, and furthermore the forces acting on these connecting areas are to be kept as low as possible.
In a percussion hammer and/or hammer drill of the type described, the solution consists in the fact that the outer shell extends as far as or at least almost as far as the percussion-tool holder which projects out of the hammer casing, where it is or can be provided with a second handle, and preferably the coupling points on the two sides of the hammer casing are arranged symmetrically with respect to the longitudinal center plane of the hammer or drill.
The arrangement according to the invention not only provides vibration damping for the second handle, but also, due to the arrangement of both handles on a single component which is elastically connected to the hammer casing, provides synchronous damping of both handles, i.e. there is no relative movement between the two handles, thus making handling and guidance of the tool comfortable and safe.
If the outer shell, on both sides of the hammer casing, is connected to the hammer casing at in each case two coupling points, the line of action of the tool preferably intersects a plane which includes the coupling points, which number four in total.
According to a particularly advantageous configuration, the outer shell, on both sides of the hammer casing, is connected to the hammer casing at in each case three coupling points, which do not lie on a common straight line.
A further highly advantageous configuration consists in the fact that the connections at the individual coupling points are produced by means of elastomeric elements, and preferably a body made from elastomeric material is attached to the hammer casing at each coupling point, which body has a hole which is at least substantially perpendicular to the longitudinal center plane of the hammer casing and in which a bolt, which projects inward from the outer shell, engages.
According to a further advantageous configuration, the bodies made from elastomeric material are each held in a sleeve on the hammer casing.
According to a further advantageous variant, the outer shell is made from plastic, thus providing, together with the arrangement of the elastomeric elements, a particularly effective electrical insulation.
Another advantageous configuration consists in the fact that the elastomeric bodies have different resilient properties in different directions, in which case the bodies of elastomeric material preferably have different dimensions in two diametral directions which intersect one another in the axis of the hole, thus making it possible to achieve different spring or damping actions for example in the direction of vibration of the tool and transversely with respect to this direction.
The geometry of the bodies and the arrangement of the coupling points with respect to one another allow the spring characteristics to be set as desired in six degrees of freedom, allowing even very long spring excursions.
Preferably, the elastomeric bodies are thicker parallel to the direction of impact of the hammer or drill than perpendicular to this direction. According to another advantageous embodiment, this can be achieved by providing the elastomeric bodies with an elliptical outer contour.
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patent: 34 05 922 C2 (1985-08-01), None
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Berger Rudolf
Maurer Thomas
Boyle Fredrickson Newholm Stein & Gratz SC
Smith Scott A.
Wacker-Werke GmbH & Co. KG
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