Torque wrench

Details Torque wrench Torque wrench

2002-10-29

2004-06-01

Meislin, D. S. (Department: 3723)

Tools

Wrench, screwdriver, or driver therefor

Machine

C081S478000, C081S059100

Reexamination Certificate

active

06742418

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved torque wrench for fastening or unfastening screws such as a bolt or a nut.
2. Description of the Related Art
A widely used hand wrench has a handle, a ratchet mechanism housed in the head of the handle, and an output shaft rotatably disposed at the head. By turning the handle clockwise and counterclockwise in a reciprocating manner, the ratchet mechanism allows the output shaft to rotate in one direction and thus a socket attached to the output shaft to fasten or unfasten a screw.
In order to construct a torque wrench utilizing such a hand wrench, the handle is formed of a sheath tube
31
, as shown in FIG.
9
.
The sheath tube
31
is pivotally attached to the base of a head
32
at the front thereof. The sheath tube
31
has a pestle
33
extending backwards from the head
32
inserted thereinto. Also, the sheath tube
31
has a slider
34
disposed in the central part thereof. The slider
34
and the pestle
33
oppose each other at the slanted opposing surfaces thereof and are connected by a link toggle
35
disposed orthogonal to these opposing surfaces.
In addition, the sheath tube
31
has a torque adjusting screw
36
and a nut
37
, which is screwed together with the torque adjusting screw
36
, disposed in the rear part thereof. Furthermore, the sheath tube
31
has a coil spring
38
placed between the nut
37
and the slider
34
.
The head
32
has an output shaft
39
rotatably disposed in the center thereof.
In order to fasten a screw by using the torque wrench having the above-described structure, the sheath tube
31
is turned clockwise and counterclockwise in a reciprocating manner.
With this arrangement, by turning the output shaft
39
via the ratchet mechanism in its fastening direction, the torque wrench fastens a screw inserted in a socket attached to the output shaft
39
.
After the screw is placed at the predetermined position thereof, and when the fastening torque reaches a predetermined value by further turning the sheath tube
31
clockwise and counterclockwise, the link toggle
35
is activated and then the pestle
33
and the slider
34
hit against each other at the opposing surfaces thereof. A hitting sound caused by the above hitting or a turning lash of the sheath tube
31
allows an operator to determine if the torque wrench reaches a predetermined fastening torque of the screw.
A power torque wrench in which a motor for transmitting a rotating torque to the output shaft
39
is incorporated into the foregoing structure of the hand torque wrench is considered. However, when the motor is disposed in the rear part of the sheath tube
31
, the pestle
33
extending from the head
32
, the slider
34
, and so forth disposed in the central part of the sheath tube
31
hinder the power torque wrench to have a structure in which the torque of the motor is transmitted to the output shaft
39
.
To solve this problem, as disclosed in Japanese Patent Application Publication No. 8-112775 and also as shown in
FIG. 10
, another power torque wrench is constructed such that the sheath tube
31
has a motor
40
disposed above the front half thereof so that the torque of the motor
40
is transmitted to the output shaft
39
.
With this structure, in the fastening operation of this torque wrench, the motor
40
rotates the output shaft
39
at high speed so as to place a screw at the predetermined position thereof. After the screw is placed, the sheath tube
31
is turned by hand up to a predetermined fastening torque in a similar fashion to that of the hand torque wrench.
In the foregoing power torque wrench, the motor
40
is additionally attached above the sheath tube
31
. Accordingly, the enlarged height of the whole torque wrench not only makes the handling of the torque wrench difficult but also may cause a problem in that, when a working space is tight or there is an obstruction around an object to be fastened, the motor
40
hinders an operator to perform his or her fastening work. Also, the torque wrench becomes unstable because of the center of gravity of the torque wrench is shifted upwards by the motor
40
, thereby resulting in the poor operationality thereof.
SUMMARY OF THE INVENTION
In view of the above problems, the present invention has been made. Accordingly, it is an object of the present invention to provide a torque wrench which has a motor, which is housed therein but not additionally attached thereon, so as to make the whole size thereof compact, achieves improved handling and operationality, smoothly transmits the torque of the motor to an output shaft, and also allows an operator to fasten a screw with a predetermined fastening torque by hand.
A torque wrench according to the present invention comprises a motor; an output shaft; a straight hollow handle comprising a grip, housing the motor therein, integrally formed therewith at the rear thereof; a head disposed at the front of the hollow handle and rotatably supporting the output shaft in the vertical direction so as to be orthogonal to the longitudinal direction of the hollow handle; a transmission shaft disposed in the hollow handle; a rotation-direction changeover mechanism which transmits the rotation of the motor to the output shaft via the transmission shaft; a sheath tube which covers the front half of the hollow handle with a predetermined gap between the inner surface of the sheath tube and the outer surface of the hollow handle, and which is connected to the head at the front thereof and to the front of the hollow handle; a slider moveably disposed around the hollow handle in the longitudinal direction of the hollow handle such that the front end surface of the slider opposes the rear end surface of the sheath tube; a torque transmitting mechanism disposed between the mutually opposing end surfaces of the slider and the sheath tube; and a torque adjusting mechanism disposed in the rear of the slider and around the rear half of the hollow handle.
With this structure, although the hollow handle is formed so as to be independent from the head rotatably supporting the output shaft, the torque of the motor housed in the grip at the end of the hollow handle is reliably transmitted to the output shaft via the transmission shaft in the hollow handle, and also a screw can be fasted by hand.
Accordingly, since the whole structure of the torque wrench becomes compact, the torque wrench can be easily handled and stably operated so that a screw is smoothly fastened even when a working space is tight or there is an obstruction around the screw.
In addition, by rotating the motor when the rotation-direction changeover mechanism is changed over to a fastening mode of a screw, the output shaft is quickly rotated only in the fastening direction of the screw so that the screw is quickly fastened to the seating surface thereof.
When the screw is seated on the seating surface, by turning the hollow handle by hand clockwise and counterclockwise in a reciprocating manner, the torque of the manual turning operation is transmitted to the sheath tube via the torque transmitting mechanism. Then, the sheath tube turns about the output shaft in a reciprocating manner so that the screw is further fastened via the rotation-direction changeover mechanism only when the sheath tube turns outwards.
Furthermore, when the frictional force between the screw and the seating surface reaches a value corresponding to the predetermined fastening torque set by the torque adjusting mechanism, the torque transmitting mechanism is activated so as to reliably determine that the screw has been fastened with the predetermined fastening torque.
In the torque wrench according to the present invention, the rotation-direction changeover mechanism is preferably characterized in that the head has a center hole vertically extending therethrough, the output shaft is formed as a regular polygonal column extending in the vertical direction and having side surfaces, and rotatably disposed in the center hole of the head, a space is form

Affiliated with

Also associated with

Rating

Torque wrench does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Torque wrench, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Torque wrench will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3300568