Tool driving or impacting – Drive controlled by relative axial movement of tool – Drive motor controlled
Patent
1996-08-29
1998-02-17
Smith, Scott A.
Tool driving or impacting
Drive controlled by relative axial movement of tool
Drive motor controlled
173128, 173206, B25B 2102
Patent
active
057182965
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a storing energy type of impact control mechanism for pneumatic wrench.
BACKGROUND ART
The pneumatic wrench is an efficient tool for mounting and dismounting bolt and nut with compressed air as power. During operation, the compressed air drives blades to rotate the rotor and then a flying hammer (inertial weight) is driven which, after being rotated to a certain speed, will push out an impact pin to drive the wrench shaft and associated sleeve pieces of various specifications to tighten up or loosen bolt and nut. Usually a centrifugal valve is fitted in the flying hammer which centrifugal valve slides through the centrifugal force produced by the rotating flying hammer, thereby realizing a function of change direction of air ducts, i.e. realizing a reciprocation motion of making the impact pin stretch out of the flying hammer or retract back to the flying hammer. The impact pin, when stretching out, drives a wrench shaft to impact bolt or nut, and the wrench is at a waiting state when the impact pin retracts back.
In the prior art, the structure and its air duct changing function of a centrifugal valve 113 are shown in FIG. 1 and FIG. 2. Therein, the numeral 108 denotes a flying hammer, 100 denotes the rotating axis of the flying hammer, 114 denotes a shallower concentric annular slot on the outer periphery of the centrifugal valve 113, 128 denotes a wall-bridging limiting slot at one end of the centrifugal valve 113, 116 denotes a wall-bridging limiting rod fitted in the flying hammer 108, for use in match with the wall-bridging limiting slot 128 at one end of the centrifugal valve 113, 103 and 131 denote respectively a timing pin located in the centrifugal valve 113 and a spring to push out the timing pin, 102 denotes a plunger located in the flying hammer 108 and able to push the timing pin 103, 132 denotes a retaining ring embedded on the wall of the centrifugal valve chamber 119, and 10a and 11 denote respectively a compressed air inlet duct and a stretching air duct located in the flying hammer 108. FIG. 1 shows the state when the flying hammer 108 is in a waiting mode, the centrifugal valve 113 under the pulling force P of the spring is located in the centrifugal valve chamber 119 of the flying hammer 108. At this moment, one end of the centrifugal valve 113 presses tightly against the retaining ring 132, while the air duct 10a is not in communication with air duct 11, so that compressed air can not enter the stretching air duct inlet 9 (In FIG. 6, it is in communication with air duct 11, which is to be described in detail below) to push out an impact pin 1, and can only enter a retracting air duct inlet 5 through other air ducts (to be discussed in detail below) to enter further an impact pin chamber 18 and to make the impact pin 1 retract to a state as shown in FIG. 6. FIG. 2 shows that when the flying hammer rotates and the plunger 102 pushes the timing pin 103 into the centrifugal valve 113, the centrifugal valve 113 under the centrifugal force overcomes the spring force and is located in the centrifugal valve chamber 119 of the flying hammer 108. At this moment, the bottom end of the wall-bridging limiting slot 128 at one end of the centrifugal valve 113 presses tightly against the wall-bridging rod 116, and the air duct 10a is in communication with the concentric annular slot 114 on the outer periphery of the centrifugal valve 113, so that compressed air through the stretching air duct inlet 9 in communication with the stretching air duct 11 enters the impact pin chamber 18 (See FIG. 7) to push out the impact pin 1; while the residual air originally left in the impact pin chamber 18 discharges through the retracting air duct inlet 5 (to be described in detail below).
The following drawbacks exist in the above-mentioned structure: (1) Due to mutual constraint of the structure, the concentric annular slot 114 on the outer periphery of the centrifugal valve 113 is very shallow, usually only 0.5 mm in depth, so that when as a passage to join air
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patent: 4291771 (1981-09-01), Perraud
patent: 4899836 (1990-02-01), Venot
patent: 5117921 (1992-06-01), Bartels et al.
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