Rotary hammer

Abstract

A rotary hammer includes a spindle 18 which can be rotatably driven by an intermediate shaft 24 by way of a drive device. A tool holder 16 is arranged for rotation with the spindle 18, and for releasably holding a bit or tool for selective rotation and / or reciprocation. A pneumatic hammering arrangement facilitates repeated impacting of the bit or tool for reciprocation within the tool holder (16). A mode change mechanism includes a knob 18 for selectively operating the rotary hammer in any of three modes, identified as a rotary drive only mode, a hammer only mode and a rotary hammer mode.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001]This application is a Reissue of U.S. Pat. No. 6,666,284 B2, issued Dec. 23, 2003, which claims priority to Great Britain application Serial No. 0008465, filed Apr. 17, 2000. <?insert-end id="INS-S-00001" ?>BACKGROUND OF THE INVENTION[0002]This invention relates to a rotary hammer, and particularly relates to a rotary hammer with a mode change mechanism for switching the rotary hammer for operation in any one of a hammer only mode, a rotary drive only mode and a rotary hammering mode.[0003]In a hammer only mode of a conventional rotary hammer, a bit is inserted into a tool holder of the hammer and is repeatedly struck by a hammering mechanism and is not rotatably driven. In a rotary drive only mode, the bit is rotatably driven and is not subject to impacts from the hammering mechanism. In a rotary hammering mode, the bit is repeatedly struck by the hammering mechanism and is simultaneously rotatably driven.[0004]Conventional rotary ...

AI Technical Summary

Benefits of technology

[0009]Therefore, it is an object of this invention to provide a rotary hammer having a simple and reliable mode change mechanism for selectively operating in a hammer only mode, a rotary hammer mode, or a rotary drive only mode.

[0011]A further object of this invention is to provide a rotary hammer having a mode change mechanism which utilizes primarily standard engineering parts which are sturdy and inexpensive to manufacture, and relatively easy to assemble.

[0013]This invention further contemplates the mounting of the hammer drive sleeve and the spindle drive member rotatably on the intermediate shaft, and the mounting of the mode change sleeve shiftably and non-rotatably along the intermediate shaft. This facilitates use of the mode change sleeve to transfer rotary drive from the intermediate shaft to the hammer drive sleeve and / or the spindle drive member by simply shifting the mode change sleeve along the intermediate shaft to selectively engage the hammer drive sleeve and / or the spindle drive member. The parts required for this mode change mechanism are standard engineering parts, such as a shaft and sleeves rotatable or non-rotatable on the shaft and optionally shiftable along the shaft. The sleeves have parts such as gear wheels or teeth, which are selectively engageable with each other. Such parts can be manufactured inexpensively and of sturdy structure, and can be easily assembled to provide a simple and reliable mode change mechanism.

[0015]Still, in further contemplation of this invention, in a preferred arrangement, the hammer drive sleeve is located towards the rear of the mode change sleeve and has a driven member, preferably a set of teeth, which is engageable with a driving member, also preferably a set of teeth, on the mode change sleeve to transmit rotary drive from the intermediate shaft to the hammer drive sleeve. Preferably, the mode change sleeve driven member, which engages the intermediate shaft driving member, is axially extended and also forms the mode change sleeve driving member, which is engageable with the hammer drive sleeve driven member, to transmit rotary drive from the intermediate shaft to the hammer drive arrangement. Using a single extended driven and driving member, such as an extended set of teeth, again simplifies the structure of the mode change sleeve.

[0016]This invention also contemplates, in a preferred arrangement, the spindle drive member being located towards the front of the mode change sleeve and has a driven member, preferably a set of teeth, on the mode change sleeve to transmit rotary drive from the intermediate shaft to the spindle drive member. Again, it is preferred that the mode change sleeve driven member which engages the intermediate shaft driving member is axially extended to also form the mode change sleeve driving member which is engageable with the spindle drive member to transfer rotary drive from the intermediate shaft to the spindle drive member. Using a single extended driven and driving member, such as an extended set of teeth, again simplifies the structure of the mode change sleeve.

Problems solved by technology

However, mechanisms of this type tend to be relatively complex, use parts which are intricate and / or difficult to manufacture inexpensively in bulk, with sturdy qualities that can withstand sustained use of the hammer, and / or are relatively difficult to assemble.

Such parts are relatively expensive to manufacture in such a way that the parts can survive sustained use of the hammer and still provide smooth changes between the different modes of operation of the hammer.

Also, the assembling of the parts to provide such a mode change arrangement is relatively difficult, which further adds to the cost of manufacturing such hammers.

This results in additional cost and complexity.

Images