GB2038674A

GB2038674A - Rotary percussive tool

Info

Publication number: GB2038674A
Application number: GB7943745A
Authority: GB
Original assignee: VNI I PK I MEKH I RUCH; VNI PK I MEKH
Current assignee: VNI I PK I MEKH I RUCH; VNI PK I MEKH
Priority date: 1978-12-27
Filing date: 1979-12-19
Publication date: 1980-07-30
Also published as: SE437233B; DE2951420C2; SE7910546L; GB2038674B; DE2951420A1; SU947416A1

Abstract

A rotary percussive tool, comprising a casing 1 has a drive with a drive gear 11, a bushing 12 having a non- round hole 13 for insertion of a shank of a boring tool 7 and a protective clutch 22, 23 mounted thereon and meshing with the drive gear to limit torque on the boring tool. The tool has a driven gear 15 which is mounted on the bushing 12 for independent rotation and meshes with the drive gear 11. The driven gear has a hole 20 for insertion of a drilling tool, and provides drilling tool rotation without torque limiting. The boring tool shank 14 is engaged by a reciprocating member 5 actuated by a piston 3. A tool for impelling only has a round shank to avoid rotation with the sleeve 12. <IMAGE>

Description

SPECIFICATION Rotary percussive tool The invention relates to rotary percussive tools to be used in the construction, prospecting, mining and drilling of various materials.

It is contemplated a rotary percussive tooo, comprising a casing accommodating a drive, a mechanism for rotation of a boring tool comprising a drive gear a bushing having a non-round inner hole for insertion of a boring tool shank, a protective clutch installed on said bushing and meshing with the drive gear, a driven gear mounted on the bushing for an independent rotation relative thereto and meshing with the same drive gear which meshes with the protective clutch, a hole in the driven gear for insertion of a drilling tool therein.

The advantage of the tool according to the invention resides in that, when the tool functions as a drill, maximum torque developed by the motor is transmitted to the working tool, and when the tool functions as a rotary hammer, that is in the rotary hammering mode, the torque at the boring tool is limited by the protective clutch.

The invention will be described with reference to a specific embodiment of a percussive rotary tool according to the invention illustrated idn the accompanying drawings, in which: Figure 1 is a partial sectional view of a rotary percussive tool; Figure 2 is a drilling tool; Figure 3 is a working tool to be used when the tool functions in the hammering mode.

A rotary percussive tool shown in Figure 1 comprises a casing 1 having a drive (not shown), a barrel 2 having a pneumatic impact mechanism with a hammer piston 3 which, under the action of regular changes of pressure in a working chamber 4 of the impact mechanism coperates by means of an intermediate member 5 with an impact tool 6 (Figure 3) or a boring tool 7. The barrel 2 has idle stroke openings 8 arranged below the upper end of the hammer 3 at the moment of its cooperation with the boring tool 6.

A mechanism for rotation of the boring tool 7 or a drilling tool 9 (Figure 2) is accommodated in the casing 1 (Figure 2) and comprises a drive shaft 10 having a drive gear fitted thereon, a bushing 12 having a hexagonal hole 13 for insertion of a shank 14 and for transmitting torque to the boring tool 7 and a driven gear 15 mounted on the bushing 12 loosely in the radial direction and on a slidingcontact bearing 16 common therewith, as well as on an upper plate 17 of a shock absorber 18 bearing against the casing 1 through a lower plate 19. The driven gear 15 meshes with the drive gear 11 and has a hexagonal hole 20 for insertion of a shank 21 and for transmitting torque to the drilling tool 9.The hexagonal hole 20 of the driven gear 15 is greater in size than the hexagonal hole 13 of the bushing 13, and the shank 21 (Figure 2) of the drilling tool is respectively shorter than the shank 14 of the boring tool 7 Afriction-type protective clutch is installed on the bushing 12 and is formed by a set of gears 22 which also mesh with the cmmon drive gear 11 as the driven gear 15 and which are axially and radially free on the bushing 12, as well as friction plates 23 radially fixed to and axially movable along the bushing 12. The set of gears 22 and friction plates 23 are axially compressed by means of a spring 24 and a nut 25. By providing a pre-set axial compression force applied to the plates 23 and gears 22 a pre-set torque to be transmitted to the boring tool 7 is adjusted.

To prevent transmission oftorqueto an impact tool 6, the shank of such tool is cylindrical in shape.

The tool can function in three different modes by inserting in the casing 1 working tools for respective purposes, the shanks of the tools being of such length and cross-sectional size as to ensure one of the three operation modes: rotary hammering, hammering and drilling.

In operation in the rotary hammering mode, the boring tool 7 is inserted in the tool casing so that its houlder bears against the lower plate 19 of the shock absorber 18. The shank 14 of the boring tool 7 has cross-sectional dimensions such as to ensure hammering mode of the tool on the one hand and torque transmission through the bushing 12 and frictional clutch on the other hand. In dase the boring tool 7 is jammed in the rock, the gears 22 slide with respect to the friction plates 23 thereby limiting the force transmitted to the hands of the operator.

In case the tool functions as a hammer, the impact tool 6 is inserted in the casing 1 of the tool so that its shoulder bears against the lower plate 19 of the chock absorber 18. The shank 26 of the impact tool has a length sufficient to obtain the hammering mode. The shank is of a round section so that torque transmission to the impact tool is eliminated.

The drilling mode is ensured by inserting the drilling tool 9 in the casing 1 of the tool so that the shoulder of the drilling tool bears against the lower plate 19 of the shock absorber 18. The shank 21 of the drilling tool is shorter than the shank 26 of the impact tool 6 or the shank 14 ofthe boring tool 7. The hammer piston and the intermediate member 5 are thus shifted in such a position as to uncoverthe idle stroke openings 8, and the working chamber communicates with atmosphere. Free passage of air to the working chamber 4 through the idle stroke openings 8 prevents pressure therein from changing. Since forces associated with pressure changes in the working chamber are not applied to the hammer piston, its hammering cooperating with the shank 21 of the drilling tool 9 is eliminated. Crosssectional dimensions of the shank are such that it does not radially engage the bushing 12, but the meshing with the drive gear is ensured. The torque is transmitted from the drive through the drive gear 11 directly to the driven gear 15 and then to the shank 21 of the drilling tool 9. Maximum torque developed by the drive is directly transmitted to the tool to ensure an efficient drilling performance.

Bearing in mind that the shank 21 of the drilling tool meshes with the bushing 12 on which the protective torque overload clutch is installed, an increase in torque resistance at the drilling tool does not result in operation of the protective clutch and its wear so that the reliability of the tool as whole is improved.

Claims

CLAIMS:

1. A rotary percussive tool, comprising a casing having a drive, a mechanism for rotation of a boring tool including a drive gear, a bushing having a non-round hole for insertion of the shank of the boring tool, a protective clutch mounted on said bushing and meshing with the drive gear, a driven gear mounted on the bushing for an independent rotation relative thereto and meshing with the same drive gear which meshes with the protective clutch, a hole of the driven gear for insertion of a drilling tool.

2. A rotary percussive tool substantially as hereabove described with reference to, and as shown in the accompanying drawings.