# US 6,296,586 B1 · Tensioning device for a chain or a belt drive for a motor of a hand machine tool

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- Number: US 6,296,586 B1
- Document ID: US6296586B1
- Status: Granted
- Kind: B1
- Application number: 09/416,517
- Filed: 1999-10-08
- Granted: 2001-10-02
- Earliest claimed: 1998-10-09
- Assignees: Dolmar GmbH
- Inventors: Marc Walkenhorst; Andreas Singer
- Web page: https://patentgrep.com/patent/US6296586B1

## CPC

- B27B 17/144: {with adjustment by at least one threaded screw}
- B24B 23/00: Portable grinding machines, e.g. hand-guided; Accessories therefor (B24B7/18 takes precedence; for grinding seat surfaces B24B15/00; having a flexible shaft B24B27/027; grinders for cutting-off B24B27/08; dust extraction equipment B24B55/10; details or components, e.g. casings, bodies of portable power-driven tools not particularly related to the operation performed B25F5/00)
- B24B 27/08: being portable
- B27B: SAWS FOR WOOD OR SIMILAR MATERIAL; COMPONENTS OR ACCESSORIES THEREFOR (saws specially adapted for pruning or debranching A01G3/08; sawing apparatus specially adapted for felling trees A01G23/091; features not restricted to a particular type of wood saw B23D, e.g. attaching saw blades B23D51/00; machine tool frames, beds, pillars or like members, in general B23Q1/01)
- B24B: MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING (grinding of gear teeth B23F, of screw-threads B23G1/36; by electro-erosion B23H; abrasive or related blasting B24C; tools for grinding, buffing or sharpening B24D; polishing compositions C09G1/00; abrasives C09K3/14; electrolytic etching or polishing C25F3/00; grinding arrangements for use on assembled railway tracks E01B31/17); DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS

## Abstract

A tensioning device for a chain or a belt drive for a motor of a hand machine tool, especially for a chain saw or a grinding or abrasive cutting-off machine, with a longitudinally movable bracket, such as a bracing or an arm, which can be fixed together with a cover with at least one bolt with a screwable nut to a casing or to another part of the hand machine tool, whereby the tensioning device has an adjusting screw extending in the longitudinal direction of the bracket on which a rider screw is movable to-and-fro by rotating the adjusting screw, the rider screw having a trunnion extending through an opening of the bracket so that, for tensioning the chain or the belt drive, the bracket follows a movement of the rider screw. Here a length of the trunnion is configured such that, the cover being set upon the hand machine tool, and the bracket being placed between the cover and the hand machine tool, the bolt projects sufficiently far through the cover for screwing on the nut only if the trunnion penetrates into the opening of the bracing.

## Claims

### Claim 1

A tensioning device for an endless drive member for a motor of a hand machine tool, said device comprising:
a fixed part of a machine hand tool having at least one protruding bolt,
a cover having at least one hole extending through the cover to receive the at least one protruding bolt of the fixed part,
a longitudinally movable endless member tensioning bracket with at least one hole extending therethrough to receive the at least one protruding bolt of the fixed part and which can be fitted onto the at least one bolt together with the cover and fixed to the fixed part by a nut screwable onto the bolt,
an adjusting screw extending in the longitudinal direction, and
a rider screw carried by the adjusting screw and movable to and fro in the longitudinal direction by rotating the adjusting screw,
the rider screw having a trunnion extendable though a mating opening of the bracket so that, for endless member tensioning purposes, the bracket follows the longitudinal movement of the rider screw,
the trunnion having a length so selected that, in assembling the cover and bracket with the protruding bolt and with the fixed part of the machine, with the bracket being first placed on the bolt and the cover being next placed on the bolt, the bolt projects sufficiently far through the cover to permit screwing of the nut onto the bolt only if the trunnion penetrates into the mating opening of the bracket.

### Claim 2 (depends on 1)

A tensioning device according to claim 1, wherein,
the bolt has a predetermined length LB, the trunnion has a predetermined length LZ, the cover in the area of the passage of the bolt has a predetermined thickness DD and the bracket has a predetermined thickness DA, the length LZof the trunnion being such that the relationship
LZ≧LB−(DD+DA)
is fulfilled.

### Claim 3 (depends on 1)

A tensioning device according to claim 1, wherein
the trunnion has a predetermined length LZ, the bracket has a predetermined thickness DA and the cover in the area of the passage of the bolt has a recess with a predetermined thickness TD as well as a predetermined thickness DD, the length LX of the trunnion being such that the relationship
LZ≧TD−(DD+DA)
for the marginal condition
LZ≦DA+DD+TD
is fulfilled.

### Claim 4 (depends on 1)

A tensioning device according to claim 1, wherein
the adjusting screw is connected with a drive screw over a spiral gearing or a worm gear.

### Claim 5 (depends on 3)

A tensioning device acceding to claim 3, wherein
the trunnion penetrates into a groove configured in the fixed part of the hand machine tool, the groove having a predetermined depth TN such that the relationship
TN>LZ−DA
is fulfilled.

### Claim 6 (depends on 4)

A tensioning device according to claim 4, wherein
the drive screw can be actuated from outside the cover by means of a tool.

### Claim 7 (depends on 4)

A tensioning device according to claim 4, wherein
the drive screw is connected with an adjusting wheel which is manually actuatable from outside the cover.