Impulse wrench

Details Impulse wrench Impulse wrench

2000-05-03

2001-01-30

Smith, Scott A. (Department: 3721)

Tool driving or impacting

Impacting devices

With anvil arranged to transmit torsional impact to tool

C173S093000, C173S177000, C173S218000

Reexamination Certificate

active

06179063

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a power-operated wrench for rotating threaded fasteners and, more particularly, to a wrench that tightens fasteners to a predetermined torque.
BACKGROUND AND SUMMARY OF THE INVENTION
Impulse wrenches are known in the art for tightening threaded fasteners. Certain types of wrenches heretofore known have a rotating manifold with a large bore formed therein, and a rotating spindle having a set of spring-biased vanes mounted thereon. The bore inside the manifold is provided with a pair of diametrically opposed lands. During operation, the manifold rotates relative to the spindle so that the vanes sweep along the interior of the manifold bore. This sweeping action creates a pressure differential on opposing sides of the vanes. When the vanes contact the lands, the spindle and manifold are momentarily coupled together in a force transmitting relationship and a rotary impulse is transmitted to the spindle through the vanes, thereby affecting a turning movement of the spindle and the fastener to which it is engaged.
These types of wrenches require extremely tight tolerances when forming the bore inside the manifold to ensure the vanes can sweep properly along the bore interior. As a result of such tolerances requirements, the cost of manufacturing such wrenches is relatively high.
Other types of arrangements for delivering impulses to the spindle have also been provided in the art. U.S. Pat. No. 3,210,959 to Brown discloses an arrangement wherein the manifold carries a single-acting piston that slides in a reciprocating manner within a radial bore formed in the impulse manifold. The output spindle has an eccentric portion disposed adjacent the radial piston. During a fastener tightening operation, the manifold rotates relative to the spindle such that the piston engages the spindle once each rotation to deliver a rotary impulse to the spindle. An overflow chamber is communicated to a chamber defined in part by the radial piston via a restricted orifice. As the eccentric portion of the spindle contacts the piston, the piston is cammed radially outwardly and pressurized fluid is forced through the restricted orifice. As a result, the piston rides over the eccentric spindle portion and then a return spring forces the piston back towards the spindle. When the torsional resistance of the fastener reaches a selected maximum level, a sufficient amount of fluid is forced out through the restricted orifice during each rotation to enable the piston to ride over the eccentric spindle portion without delivering sufficient force to further tighten the fastener. The maximum level for the torsional resistance of the fastener can be adjusted by turning a screw to vary the restriction of the orifice.
U.S. Pat. No. 5,735,354 discloses a piston-type arrangement that uses a single double-acting piston, and in another embodiment a piston-type arrangement using a pair of diametrically opposed pistons.
The advantage of a piston-type arrangement is that the high manufacturing expenses associated with machining the manifold bores for the vane-type arrangements within close tolerances are avoided. However, neither of the radial piston arrangements disclosed in the patents mentioned above have a suitable mechanism for shutting off the flow of power to the tool. In the '959 patent, the maximum torque level is set by varying the restriction of the aforementioned orifice by tightening or loosening a screw. The wrench of the '959 patent itself, however, continues to run after the threshold torque level has been reached. Thus, a user must visually verify that the maximum torque level has been reached by watching to see if the fastener is continuing to be tightened. As a result, the user may have a tendency to keep running the wrench more than necessary during each operation to ensure that the fastener is tightened. It can be appreciated that in high usage applications, such as in automobile assembly plants, extra running of the wrench can quickly add up over time and cause unnecessary premature wear on the wrench components.
The '354 patent does not disclose any mechanism for shutting off the power to the wrench or for ensuring that the torque applied by the fastener does not exceed a predetermined level. However, the applicants of the present application are aware of a commercially available impulse mechanism (the mechanism includes the manifold and the spindle, not the entire wrench) available from Robert Bosch GmbH, the assignee of the '354 patent, that is similar to the double-acting piston arrangement disclosed in the '354 patent. The Bosch mechanism uses a deceleration-sensitive shut-off structure for stopping the flow of power to the wrench. Deceleration-sensitive shut-off structures are problematic because they often measure the torque applied to the fastener inaccurately. Specifically, deceleration-sensitive shut-off structures measure the rotational deceleration of the wrench components to determine the torque being applied to the fastener. This method of measuring torque is inaccurate when tightening fasteners and using fastener engaging tools (i.e., the sockets used for engaging threaded bolts) of varying weights because these weights will affect the overall deceleration of the wrench components, thus resulting in inconsistent measurements and inconsistent torque delivery between fasteners of varying weights. In addition, these deceleration-sensitive mechanisms must be periodically adjusted to ensure the proper torque is being delivered.
Thus, there exists a need for a piston-type wrench that has a shut-off structure that functions effectively and consistently to shut-off power to the wrench when a fastener has been tightened to a preset torque. To meet this need, the present invention provides an impulse wrench for use in conjunction with a fastener engaging tool and a power supply to selectively rotate threaded fasteners. The wrench comprises a housing and an impulse manifold rotatably mounted within the housing. The manifold has a spindle receiving space and an impulse piston receiving space. An impulse delivering piston is mounted inside the impulse piston receiving space for reciprocating movement and has an impulse delivering surface and a pressurizing surface. The piston and the piston receiving space are constructed and arranged such that the pressurizing surface and an outer end portion of the piston receiving space cooperate to define at least a portion of a high pressure chamber which is filled with a substantially incompressible fluid.
An output spindle is rotatably mounted within the spindle receiving space and has an impulse receiving portion positioned adjacent the impulse delivering surface of the impulse piston. The output spindle connects with the fastener engaging tool such that rotation of the spindle rotates the fastener engaging tool. A power-operated motor is operatively connected to the impulse manifold. The motor is constructed and arranged to rotate the manifold about the driving axis thereof using power from the power supply. An actuator is selectively movable between (a) an actuated position enabling the power supply to communicate power to the motor and (b) a non-actuated position preventing the power supply from communicating power to the motor.
The impulse receiving portion of the output spindle and the impulse delivering portion of the impulse piston are constructed and arranged with respect to one another such that, when the motor is connected with the power supply and the fastener engaging tool is connected with the spindle and engaged with a threaded fastener, movement of the actuator to the actuated position thereof communicates power from the power supply to the motor to cause the motor to rotate the manifold relative to the spindle, thereby momentarily engaging the impulse delivering surface of the impulse piston with the impulse receiving portion of the spindle so that (a) an impulse is delivered to the spindle to apply torque to the spindle which in turn transmits the torque to the fa

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