Lock structure using nut

Details Lock structure using nut Lock structure using nut

2000-02-04

2001-07-10

Wilson, Neill (Department: 3627)

Expanded, threaded, driven, headed, tool-deformed, or locked-thr

Having structure to restrict rotation of threaded, mating...

Structure is coaxial, distinct member that restricts nut piece

C411S237000, C411S295000

Reexamination Certificate

active

06257815

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lock structure for fixing and locking a member to be fixed such as a bearing screwed on a rotary shaft, by thrusting the fixed member in the axial direction.
2. Related Art
When a nut screwed on a bolt or a screw shaft is fastened, a stress in the thrusting direction is generated in the nut so that a frictional force is generated between the screwed face or the nut and the fixed member to stop the turn of the nut. In short, the fixed state by the nut is held. It is, however, known that if a vibration or impact is applied to that nut or screw shaft, the thrusting force is instantly dropped by an elastic deformation so that the nut is accordingly turned to get loose. In order to prevent this looseness of the nut, there has been known in the prior art the double lock nut in which a lock nut different from the fastening nut is used so that the fastening nut and the lock nut are screwed in their thrusting directions thereby to establish a high frictional force on their individual screwed faces.
According to a lock nut structure of the prior art, for example, a fastening nut
101
is fastened so far on a bolt
100
as to come into abutment against a washer
102
, as shown in
FIG. 7
, and a lock nut
103
is then fastened so far as to come into contact with the fastening nut
101
. Next, with the fastening nut
101
being slightly returned or being fixed by a wrench, the lock nut
103
is further fastened by the wrench. Thus, stresses in the upper direction (or X-direction) and in the downward direction (or Y-direction) of
FIG. 7
are generated in the fastening nut
101
and the lock nut
103
thereby to thrust them into contact. As a result, the screwed face
104
of the upper lock nut
103
is forcibly thrust upward (in the X-direction) of
FIG. 7
by the screwed face
105
of the bolt
100
, and the screwed face
106
of the fastening nut
101
is forcibly thrust downward (in the Y-direction) of
FIG. 7
by the screwed face
105
of the bolt
100
. Thus, the facial pressure and the frictional force on the screwed faces rise to prevent the turns or looseness of the fastening nut
101
and the lock nut
103
.
In Japanese Utility Model Laid-Open No. 6-18719, on the other hand, there is disclosed a nut locking structure in which the end face of a lock nut contacting with a fastening nut is an inclined face obliquely intersecting the axis of the lock nut.
According to this structure of Japanese Utility Model Laid-Open No. 6-18719, the fastening nut is fastened on a bolt, and the lock nut is fastened. From the instant when the lock nut abuts the fastening nut, the inclined face of the lock nut is turned by the clearance of the meshing portions of the lock nut and the bolt while being inclined in the direction to take facial contact with the end face of the fastening nut. As a result, a bending moment acts on the bolt, and a reaction to the bending moment acts on the bolt to fix the lock nut and the fastening nut.
However, what is mainly intended by the double lock nut structure of the prior art is the function to lock the fastening nut
101
such that the fastening nut
101
is thrust downward (in the Y-direction of
FIG. 7
) by the lock nut
103
. However, the fastening nut
101
thrusts the fixed member or the like downward (in the Y-direction) of FIG.
7
and receives the reaction upward (in the X-direction). If the fastening nut
101
is thrust downward (in the Y-direction) by the lock nut
103
, therefore, the reaction from the fixed member is received by the lock nut
103
. As a result, the fastening nut
101
is just interposed between the lock nut
103
and the fixed member so that it does not perform the locking action. Thus, there is no locking function between the fastening nut
101
and the lock nut
103
so that the fastening nut
101
or the lock nut
103
is easily loosened when a vibration is applied thereto.
On the other hand, let the case be considered, in which the fastening nut
101
is fastened and then locked by the lock nut
103
, as shown in FIG.
7
. Then, the screwed face
106
, as held in contact by the fastening nut
101
, is released by the lock nut
103
to lower the double nut effect. Moreover, the fastening nut
101
is fastened with its end face being unstably inclined.
In the structure of Japanese Utility Model Laid-Open No. 6-18719, on the other hand, the abutting faces of the two nuts are inclined in the radial direction. As the lock nut is fastened, therefore, there increases the bending load on the shaft on which those nuts are screwed. This raises a disadvantage that the deflection of the shaft increases.
In the prior art, moreover, there is known a structure in which set screws
111
of a precision lock nut
110
are inserted radially of the precision lock nut
110
to thrust a threaded shaft
112
. In the construction of this kind, however, when the set screws
111
are fastened, the individual axial forces and the individual radial forces of the set screws
111
grow different, as indicated by arrows in
FIG. 8
, because the inclinations of the threaded faces thrust by the set screws
111
are different for the individual set screws
111
. This established a deflection in the threaded shaft
112
. When the set shoes
111
shown in
FIG. 8
are fastened, more specifically, the directions and magnitudes of the loads along the threaded face are different for the individual set screws
111
so that the differences act as the bending load on the threaded shaft
112
thereby to deflect the threaded shaft
112
. As a result, the shaft is so largely deflected that it cannot be employed as a rotary shaft rotating at a high speed.
Thus in the precision lock nut
110
of the prior art, if the set screws
111
are adjusted to stress the correction of the deflection of the threaded shaft
112
, the set screws
111
cannot be sufficiently fastened for the locking purpose so that the nut gets loose. This makes it necessary to perform the fastening operation by the set screws
111
in cooperation with the locking action of the nut and the correction of the deflection of the shaft. As a result, there is a problem that it is obliged to perform the difficult fastening works taking a long time.
SUMMARY OF THE INVENTION
An object of the invention is to lock a nut member fixing a member to be fixed, by thrusting it in the axial direction, reliably without causing any deflection in a shaft member screwing the nut member.
Another object of the invention is to make a locking work for fixing a nut member and a work for correcting a deflection of a shaft member, independent of each other.
In the invention, a lock nut member is arranged on the opposite side of a member to be fixed, across a nut member thrusting the fixed member in the axial direction, and is screwed like the nut member on a shaft member. Moreover, the lock nut member and the nut member are connected to each other through their externally threaded portion and internally threaded portion, which have a lead angle different from that of the threaded portion of the shaft member.
As the lock nut member is turned relative to the nut member, therefore, a thrusting force between the three components, i.e., the nut member, the lock nut member and the shaft member increases to lock the nut member firmly, because the lead angle of the threaded portion for the shaft member and the lead angle of the threaded portion for the nut member are different. In this case, no load in the radial direction is especially established so that the deflection of the shaft member can be prevented.
In the invention, on the other hand, the nut member can be provided with set screws which are screwed in the radial direction of the nut member. A stress in the radial direction with respect to the shaft member is generated by screwing the set screws so far as to come into abutment against the shaft member. As a result, the deflection of the shaft member can be corrected by screwing the set screws. In short, it is possible to perform the locking work of

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