Tool driving or impacting – Impacting devices – With impact cushioning means
Reexamination Certificate
2000-04-06
2001-05-22
Smith, Scott A. (Department: 3721)
Tool driving or impacting
Impacting devices
With impact cushioning means
C173S093500, C173S162200, C173S211000
Reexamination Certificate
active
06234256
ABSTRACT:
The present invention relates to a tool, in particular a power screw driver, comprising an output shaft which is rotatably mounted in a housing and is driven by a motor and which extends substantially coaxially to a longitudinal axis of the housing.
Such a tool is, for instance, known from DE 3503032 C2 or G 8310596. DE 3503032 C2 discloses a pneumatically operated power screw driver in which the substantially cylindrical housing simultaneously serves to hold the tool. The output shaft which is driven by a compressed-air motor projects from the housing and serves to transmit impacts to screws, nuts, or the like, which are to be tightened or unscrewed.
G 8310596 discloses a portable device for burring edges of drilled holes with very limited access possibilities. The corresponding housing simultaneously serves as a grip tube for the tool. An associated motor is accommodated in the housing and drives a shaft having an end that projects from the housing and has arranged thereat a tool head for removing burs.
In the two prior-art tools and, in particular, in the power screw driver, vibrations and impacts are observed in the entire tool. These vibrations or impacts are transmitted via the housing, which simultaneously serves as a grip member, to a user's hand. As a consequence, the hand and, in particular, the wrist are strained considerably. Such strain is intensified by the fact that because of the vibrations the user must firmly grip the tool in order to hold the tool in an accurate position.
It is therefore the object of the present invention to improve a tool of the type described in such a manner that the tool can be held comfortably, in controlled manner and with little force.
In connection with the features of the preamble of claim
1
, this object is achieved by the measure that a grip sleeve which is rotatable relative to the housing is fitted over the housing, and at least one damping device that counteracts a pulse-like rotation of the grip sleeve relative to the housing is disposed between the housing and the grip sleeve.
Rotation of the grip sleeve relative to the housing is only observed in the case of impacts which are transmitted by tool vibrations or the like in pulse-like fashion to the grip sleeve. Such an impact and the associated pulse-like rotation of the grip sleeve relative to the housing are suppressed or at least attenuated by the damping device counteracting said rotation.
Such a damping device may be designed in the form of a shock absorber and may, for instance, function pneumatically or hydraulically.
In a preferred embodiment, the damping device is of a mechanical type and comprises at least one compression spring fixed between housing and grip sleeve. In such a case, the grip sleeve is only connected via the compression spring in non-rotatable fashion to the tool proper via the housing. The spring fully receives the developing starting torque of the motor and dampens the tool vibrations or impacts transmitted in pulse-like fashion to the grip sleeve.
To fix the compression spring relative to the housing and the grip sleeve in a simple manner, each of the damping devices comprises two abutment bodies which are acted upon by ends of the compression spring and which are arranged one after the other in the circumferential direction of housing and grip sleeve and are each in contact with the two members. As a result, the starting torque, the tool vibrations or other impacts are transmitted to the compression spring via the abutment bodies which are in contact with the housing, whereby said spring is tensed and exerts a restoring force in a direction opposite to the relative rotation between housing and grip sleeve, whereby said rotation is attenuated. This takes place in an analogous manner for the two possible rotational directions.
For an easy support of the damping device, the device is disposed between an annular flange which projects substantially radially from the housing, and an annular chamber which is formed at a first end of the grip sleeve and is open towards the annular flange. This yields a receiving means for the damping device that is defined by annular flange and annular chamber.
To locate the damping device in a simple manner between the annular flange and the annular chamber, the annular flange comprises a stepped portion which faces the annular chamber and which can be disposed at least in part in said chamber. The stepped portion forms an obstacle for the damping device by which the damping device is fixed in axial direction.
To form the annular chamber in a simple manner and directly next to the outside of the housing, it may be advantageous when the annular chamber is formed by an end section of the grip sleeve which is radially spaced apart from the outside of the housing.
To provide a smooth outside of the tool in this connection and to protect the damping device against damage and contamination at the same time, it is also of advantage when a free end of the end section ends in radially spaced-apart relationship with the stepped portion and extends in alignment with the outer end of the annular flange.
As a result of the aligned arrangement of the outer end of the annular flange and the free end of the end section, the tool is of a relatively smooth design and has a reduced number of edges.
For a simple arrangement of a plurality of damping devices, annular chamber and stepped portion comprise at least three circumferentially spaced-apart grooves for receiving a respective damping device, with the grooves being open in radial direction towards the housing and the grip sleeve, respectively, and in the axial direction. The damping device is here held by the respectively associated grooves of housing and grip sleeve
In a simple embodiment, the grooves have the same length and/or are equally spaced apart Preferably, a corresponding groove length and a corresponding groove spacing are each 60°, based on an center point angle of a cylindrical grip sleeve.
Simple abutment bodies are formed by two abutment balls which are force-actuated by the compression spring towards groove ends. The abutment balls are easily insertable into associated grooves, with the groove ends possibly having a curvature adapted to the balls.
In an embodiment of the invention, the housing may be screwed by means of an inner thread to a motor sleeve at a rear end which is covered by the grip sleeve. To hold the grip sleeve on motor sleeve and housing, the motor sleeve is preferably provided at its end opposite to the housing with a radially projecting end stop for abutment on a rear end face of the grip sleeve. When housing and motor sleeve are screwed to one another, the grip sleeve is thus slid onto the housing and/or the motor sleeve. The grip sleeve can here be held between end stop of the motor sleeve and rear end of the housing with an axial play.
To bring the abutment balls into contact with all groove ends in the case of two associated grooves of housing and grip sleeve and to give the grooves in housing and grip sleeve a similar design at the same time, it is of advantage when the grooves in the stepped portion and in the grip sleeve have substantially the same depth in radial and axial directions. In one embodiment of the invention, the grooves in the stepped portion and in the grip sleeve may, for instance, be arranged in axial direction next to one another, with the abutment balls in axial direction engaging into both grooves and being in contact with the corresponding groove ends. In the radial direction, the balls can be fully received by the corresponding grooves. In another embodiment, the grooves in the grip sleeve and in the housing are opposite in radial direction, with the balls in radial direction projecting into the two grooves and being in contact with corresponding groove ends.
To ensure an adequate contact with the groove ends of the groove in the housing and in the grip sleeve, it is here advantageous when the groove depth in radial direction is substantially equal to the radius of the abutment balls.
To hold the balls and the compr
Coats & Bennett PLLC
Cooper Power Tools GmbH & Co.
Smith Scott A.
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