Endless belt power transmission systems or components – Means for adjusting belt tension or for shifting belt,...
Reexamination Certificate
1999-10-08
2001-10-02
Bucci, David A. (Department: 3682)
Endless belt power transmission systems or components
Means for adjusting belt tension or for shifting belt,...
C474S117000, C474S113000, C030S386000
Reexamination Certificate
active
06296586
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The invention refers to 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 shows an adjusting screw extending in the bracket longitudinal direction 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.
2. Prior Art
A tensioning device according to the type is known from DE-OS-25 09 194. However, there results here the disadvantage that an operating person does not exactly know, when mounting the cover, if the tensioning device is in its predetermined position for which the trunnion projects through the opening of the bracket or if the trunnion strikes on the bracket. In the latter case a drawing up of the nut on the bolt leads to an undesired damaging of the cover or of the bracket.
SUMMARY OF THE INVENTION
The aim of this invention is to make avsilable an improved tensioning device of the above mentioned type which eliminates the above mentioned disadvantages.
This aim is achieved by a tensioning device of the above mentioned type.
To this end, the invention provides for that a length of the trunnion is configured so that, the cover being set upon and the bracket being placed between the cover and the hand machine tool, the bolt for screwing on the nut projects sufficiently far through the cover only if the trunnion penetrates into the opening of the bracing.
This has the advantage that, when assembling the hand machine tool and especially when drawing up the nut on the trunnion, a damaging of the cover or of the bracket is efficiently avoided by the trunnion which is in the opening of the bracket, since the trunnion projects sufficiently far though the cover, the trunnion striking on the bracket, in order to be able to screw a nut thereon. Thus an operating person immediately recognizes, because of the bolt which is not accessible, that a adjusting of the tensioning device has not been correctly selected and can immediately correct it.
In a preferred embodiment, the bolt shot is a predetermined length L
B
, the trunnion a predetermined length L
Z
, the cover in the area of the passage of the bolt a predetermined thickness D
D
or a recess with a predetermined depth T
D
and the bracket a predetermined thickness D
A
, whereby the length L
Z
of the trunnion is selected such that the relationship L
Z
≧L
B
−(D
D
+D
A
) or the relationship L
Z
≧T
D
−(D
D
+D
A
) is fulfilled. Here it should be noted that the bolt, as generally usual, does not project beyond the chain cover, i.e. L
Z
≦D
A
+D
D
+T
D
.
In order to avoid damages of the hand machine tool casing, the trunnion penetrates into a groove configured on the hand tool machine, whereby the groove shows a predetermined depth T
N
so that the relationship T
N
>L
Z
−D
A
is fulfilled.
The adjusting screw is appropriately connected over a spiral gearing or a worm gear with a drive screw, whereby for a simple and quick tensioning of the chain or of the belt drive the drive screw is actuatable from outside the cover by means of a tool and/or is connected resistant to torsion with an adjusting wheel which is manually operatable from outside the cover.
REFERENCES:
patent: 2765821 (1956-10-01), Strunk
patent: 3194284 (1965-07-01), Walker
patent: 3382898 (1968-05-01), Walker
patent: 3611646 (1971-10-01), Cameron
patent: 3866320 (1975-02-01), Progl
patent: 5177871 (1993-01-01), Martenson
patent: 5491899 (1996-02-01), Schliemann et al.
patent: 5497557 (1996-03-01), Martinsson
patent: 3831110A1 (1990-03-01), None
patent: 4222075A1 (1994-01-01), None
patent: 3841644 C2 (1997-12-01), None
Singer Andreas
Walkenhorst Marc
Bucci David A.
Charles Marcus
Dolmar GmbH
McCormick Paulding & Huber LLP
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