Tool driving or impacting – Drive adjustable to completely change kind of drive – Adjustable to impacting device
Patent
1993-06-25
1995-01-10
Smith, Scott A.
Tool driving or impacting
Drive adjustable to completely change kind of drive
Adjustable to impacting device
173109, B25D 1104
Patent
active
053798481
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a drill hammer.
More particularly, it relates to a drill hammer which has a housing and a motor accommodated in the housing and transmitting its torque via a gear unit to a rotary drive sleeve and to a tool holder, and a switch is provided for switching from drilling operation to chisel operation and vice versa. A drill hammer which can be switched from drill operation to chisel operation is already known from EP 318 480 B2, but its switching device is not synchronized. This means that switching cannot be carried out with only one hand at the switch grip when the toothings to be engaged are positioned in such a way that one tooth faces another. Further, the switching sleeve is a difficult part to manufacture and is produced by precision casting with broached toothings, internal grinding, and hardening of the entire part.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a drill hammer of the above mentioned general type, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a drill hammer which has the above specified elements and in which the switch has coupling members and an axially displaceable switching sleeve which can be acted upon by externally operated switching means, wherein in accordance with the invention, the coupling members can be disengaged by the switching sleeve against the force of a spring.
When the drill hammer is designed in accordance with the present invention, it has two main advantages over the prior art. On the one hand, the switch for changing from one type of operation to the other can be operated at any time with one hand and on the other hand manufacture of the switching parts is considerably simplified. In particular, the volume of the parts to be hardened is reduced. It is particularly advantageous that the sliding sleeve connected with the switching lever is not directly provided with teeth which must engage. Rather, the latter are arranged at separate, spring-loaded coupling parts. This also eliminates the need for a complete hardening of the entire sliding sleeve.
Advantageous further developments and improvements of the drill hammer are made possible by further steps. In particular, the switching sleeve is advantageously constructed as a toothless sliding sleeve. The retaining ring follows the axial movement of the sliding sleeve as the result of spring force as soon as the internal toothing arranged at the retaining ring can engage in the external toothing at the rotary drive sleeve. The retaining ring is secured against rotation in the circumferential direction relative to the gear casing, e.g. by a pin, so as to lock the rotary drive sleeve in such a way that it is fixed with respect to relative rotation in chisel operation. Synchronized switching to rotary operation is achieved by means of a spring-loaded toothed gear wheel which engages in the associated external toothing at the rotary drive sleeve when the sliding sleeve is in the appropriate position.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a longitudinal section through a drill hammer;
FIG. 2 shows a cross section according to line II--II in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The drill hammer which is shown in section has a housing 2 in which a gear casing 3 is inserted chiefly in the rear portion. The two housing parts 2, 3 can also be constructed as one piece. Further, a motor, not visible in the drawing, with motor pinion 4 is accommoda
REFERENCES:
patent: 3774699 (1973-11-01), Schmuck
patent: 3837409 (1974-09-01), Consoli et al.
patent: 3847229 (1974-11-01), Wanner et al.
patent: 4066136 (1978-01-01), Wanner et al.
patent: 4763733 (1988-08-01), Neumaier
patent: 4895212 (1990-01-01), Wache
Robert & Bosch GmbH
Smith Scott A.
Striker Michael J.
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