Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Internally threaded fastener element – e.g. – nut – etc. – Multipart
Reexamination Certificate
1999-07-27
2001-08-14
Wilson, Neill (Department: 3627)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Internally threaded fastener element, e.g., nut, etc.
Multipart
C411S354000, C411S535000, C411S917000
Reexamination Certificate
active
06273659
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to a locking mechanism for a rotary working member, and in particular it relates to an improvement of the technique for locking/relaxing rotary operating parts—such as the grinding disks of rotary grinders or the rotary wire cutters of lawnmowers—to rotary drive shafts.
FIG. 14
shows the typical configuration of a conventional locking mechanism of the above type. In this locking mechanism, a working member D and a locking flange
3
are loosely fitted to the small-diameter threaded part
1
b
of a rotary drive shaft
1
equipped with a large-diameter part
1
a
and a small-diameter threaded part
1
b
. A locking nut
5
is also screwed to the small-diameter threaded part
1
b
of rotary drive shaft
1
. During locking, locking nut
5
is made to turn, thereby pressing working member D via locking flange
3
against the end surface of large diameter part
1
a
of rotary drive shaft
1
, and working member D is thereby locked to rotary drive shaft
1
. Also, during relaxation, a special tool such as a two-point spanner is used to turn locking nut
5
in the unscrewing direction.
However, rotary drive shaft
1
turns in the unscrewing direction, which is contrary to the usual screwing direction of locking nut
3
, and performs a specific operation with its working member D. Here, the resisting force from the workpiece—for example, the material being ground if the working member is a rotary grindstone—acts on locking nut
3
via working member D, but this resisting force points in the screwing direction of locking nut
3
. Accordingly, as the work progresses, locking nut
3
is forced to turn further in the screwing direction by this resisting force, and its locked state becomes stronger. That is, it performs self-locking during the work.
When strong self-locking occurs in this way, it becomes very hard to relax it using a special tool. For example, in the case of rotary lawnmowers used by ordinary consumers, the relaxation operation becomes impossible as a result of this self-locking, and they have to be returned to the manufacturer for servicing.
Also, in the case of a conventional locking mechanism as mentioned above, it is assumed that a special tool will be used for locking/relaxation, and it is thus necessary to provide such a tool. If the tool is inadvertently lost, the lawnmower will again have to be returned to the manufacturer for servicing. In particular, incomplete care and loss of special tools is commonplace in the case of ordinary consumers and the necessity of a special tool is thus highly inconvenient.
Furthermore, even if this sort of special tool is used, repeated locking and relaxation under advanced self-locking conditions can often wear down the tool and make it unable to perform the desired function. For example, the pin or the like which temporarily locks the drive shaft during relaxation can often wear down relatively early.
In the light of such circumstances of the prior art, the present invention aims to maintain a securely locked state during working when the working member is locked to the rotary drive shaft in the locking mechanism of a rotary working member, and to perform relaxation easily by simple manual operation without a special tool during removal and replacement.
SUMMARY OF THE INVENTION
The essence of this invention is that the operating ring is externally fitted, with the ability to rotate, to the main body of the locking nut in between the locking flange and the flange of the locking nut; a ball bearing is inserted between the operating ring and the locking flange; three or more arc-shaped grooves are formed—facing toward each other and extending in concentric shapes in the circumferential direction—in the mating surfaces of the flange of the locking nut and the operating ring; locking balls are accommodated inside the arc-shaped grooves of the flange of the locking nut and the operating ring which face toward each other; the total dimension—in the axial direction of the rotary drive shaft—of each pair of arc-shaped grooves which accommodate the locking balls is set smaller than the diameter of a locking ball; and a localized indentation is formed at the bottom surfaces on at least one side of the said pairs of arc-shaped grooves.
When the locking nut is screwed to the small-diameter threaded part of the rotary drive shaft during locking, the working member is pressed against the end surface of the large-diameter part of the rotary drive shaft via the locking balls, and adopts a locked state. When the operating ring is manually turned during relaxation, the locking balls fall into the indentations of the arc-shaped grooves and the locking nut escapes from its state of being pressed against the operating ring. Accordingly, the locking nut turns easily in the unscrewing direction.
In essence, this invention involves changing from the conventional locking system based on a sliding pressure contact mode to a locking system based on a rolling pressure contact mode. As a result, the frictional coefficient (&mgr;) in the pressure contact locking mode decreases to about 0.01 from about 0.3 in the conventional case. A result of reducing the frictional coefficient in this way is that it can easily be made to escape from the pressure contact locking mode with a far smaller force.
Other objects, features and aspects of the present invention are discussed in greater detail below.
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Nelson Mullins Riley & Scarborough LLP
Power Tool Holders Incorporated
Wilson Neill
LandOfFree
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