JPH0420750B2 - - Google Patents

Description

Detailed Description of the Invention (Related Field) This invention relates to a cam-type impact wrench in which an anvil pin is formed by a spring liner into which one end of a cam release spring is fitted, which is constantly acting in the return direction to a hammer cam that gives reciprocating motion to the anvil pin. It is related to the support structure of.

(Prior art) In the cam type impact wrench, the cam release spring does not move in a constant direction towards the axis, but moves in a fluctuating manner away from the axis, making the anvil pin unstable and unable to move effectively. Ta. This unstable operation caused parts to wear out and caused problems in terms of durability. More specifically, in the prior art, since there is no member to guide the cam release spring, the anvil and anvil pin operate unstablely, and as a result, the anvil pin frequently breaks.

If an anvil pin breaks, it will naturally need to be replaced, but it is extremely problematic from an economic and work efficiency standpoint, as it is necessary to have a spare anvil pin on hand and to disassemble the impact wrench to replace it. There was a need for improvement.

One of the improvement measures is US Pat. No. 4,313,505 (Figure 1). This consists of a hammer 1 that is rotationally driven by an air motor, an anvil 2 that generates a rotational impact force, and is held in a groove 3 provided inside the hammer 1, and is held against a protruding ear 4 of the anvil 2. An anvil pin 7 which is movable in the axial direction against the force of the cam release spring 5 and has a small diameter portion 6 in the intermediate portion is engaged with the anvil pin 7 to move the anvil pin 7 to a position where an impact force is to be generated. a diametrically opposed recess 1 in the hammer 1 having an axially displacing cam sleeve 8 and a corresponding ball cam 9 and engaging the end of the anvil pin 7;
0, the anvil pin 7 is positioned correctly in the axial direction and applies an impact force to the anvil 1 in the axial direction.

A ring-shaped member 11 having a recess 10 in this way
By incorporating the anvil pin 7, the anvil pin 7 can reciprocate in the axial direction while being guided by the recess 10 and the groove 3 provided in the hammer 1. However, since the ring-shaped member 11 is shorter than the length of the cam release spring 5 when it is extended, a gap is created between the jaws of the anvil 2 and the ring-shaped member 11. Furthermore, since the inner diameter of the ring-shaped member 11 is larger than the outer diameter of the cam release spring 5, a gap is also created between the two. When the anvil pin 7 rapidly moves toward the ear-like protrusion of the anvil 2 due to the rotational impact, the ring-shaped member 11 that should guide the anvil pin 7 is deviated from the axis, so the anvil pin 7 The tip of the pin hits the jaw of the anvil, damaging the jaw and simultaneously damaging the anvil pin itself.

(Objective) One of the objects of the present invention is to provide an anvil pin support structure that can stably transmit the rotational force coming from the rotor shaft of a power impact wrench to the anvil.

Another object of the present invention is to eliminate the instability of the cam release spring by providing a spring liner to minimize deviation from the axial center of the cam release spring, thereby ensuring stable reciprocating motion of the anvil pin. It's about doing.

Yet another purpose is to provide a stable support structure for an anvil pin in an impact wrench that allows the tip of the anvil pin to smoothly reach the ear without hitting the jaw of the anvil and generate a strong impact force. It's about doing.

(Summary of the Invention) The problem with the above prior art is that the anvil pin is caused by an unstable movement due to the deviation from the axis of the ring-shaped member, and the cause of this deviation from the axis of the ring-shaped member is the cam release. Focusing on the problem of spring rattling, the present invention has developed a method of installing the cam release spring 35 by fitting the anvil 26 side of the cam release spring 35 into a dish-shaped spring liner 36.
The feature is that the center of 5 is always kept coincident with the axis.

Furthermore, the outer diameter of the spring liner 36 is made equal to or slightly larger than the jaw of the anvil 26 to prevent the tip of the anvil pin 24 from colliding with the jaw of the anvil 26, thereby preventing damage to the anvil pin. It has certain characteristics.

(Example) One example will be described with reference to FIG. 4 and subsequent figures. Reference numeral 20 denotes a motor shaft, which has a spline shaft 21 at its tip. 22 is a hammer, which engages with the spline shaft 21 at one end. The hammer 22 is hollow and provided with diametrically opposed axial grooves 23 . An anvil pin 24 is located in the groove 23.
is fitted so as to be movable in the axial direction.

25 is an anvil shaft, and a pair of ear-shaped anvils 26 are integrally provided in the middle part. 27 is a spline, and 28 is a cam pilot stem. 2
9 is a cam pilot rotatably fitted to the stem 28, and 30 is a cam ball. A hammer cam 31 is slidably engaged with the spline 27 of the anvil shaft. The hammer cam 31 has a cam portion 32 at one end and a large-diameter drive portion 33 that engages with the annular groove 24a of the anvil pin 24 at an intermediate portion.

The opposite side of the cam portion 32 of the hammer cam 31 is a cylindrical portion 34, into which a cam release spring 35 is fitted. 36 is a dish-shaped spring liner, which has a center hole 36a that fits into the anvil shaft. The outer diameter of the spring liner 36 is approximately equal to or slightly larger than the diameter of the jaw portion of the anvil 26. The inner diameter of the spring liner is slightly larger than the outer diameter of the cam release spring 35. 37 is an anvil spacer.

(Operation) The tool rotates in both forward and reverse directions. Fourth
The state in the upper half of the figure shows a non-operating state, and in this state, no axial movement is given to the hammer cam 31 and the anvil pin 24. come ball 30
is fitted in a circumferential groove 22a provided in the hammer 22 over, for example, 76 degrees and in a ball race 29a of the cam pilot 29, and this circumferential groove 22a
The ball 30 engages with the end of the circumferential groove 2 to drive it.
The end of 2a is spherical. When the ball 30 engages with the cam portion 32 of the hammer cam 31, the hammer cam 31 is driven by the rotation of the hammer 22.

When the hammer cam 31 is driven and rotated, the anvil shaft 25 is rotated. When the anvil shaft 25 resists, the cam ball 30 rests on the surface of the cam portion 32. An axial movement is then imposed on the hammer cam 31 via the large-diameter drive 33 which engages the anvil pin 24, so that the trajectory of the anvil pin 24 intersects the ear-shaped anvil 26. Impact force is then applied to the anvil 26. anvil pin 24
The end diameter of the anvil 26 is given to the anvil 26. The diameter of the end of the anvil pin 24 is shaped to match the concave portions on both sides of the anvil 26.
When the anvil 4 moves in the direction of impacting the anvil 26, it is moved in the axial direction by the hammer cam 31 while moving in a helical manner. When the axial movement ends (the state shown in the lower half of FIG. 4), the cam ball 30 rests on the cam portion 32. Then, the hammer cam 31 and anvil pin 24 are connected to the cam release spring 3 again.
5 moves it in the opposite direction.

(Effects) As described above, one end of the cam release spring is fitted into a dish-shaped spring liner with a diameter equal to or slightly larger than the jaw part of the anvil.
The axial center position of the cam release spring is always stable during operation. As a result, the operation of the anvil pin that generates the impact force is stable, so there is no possibility of damage caused by hitting the jaws of the anvil.

This further increases the life of the anvil pin,
It is extremely economical, and it also saves wasted time required for anvil pin replacement, which is favorable in terms of work efficiency.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional impact wrench. FIG. 2 is a cross-sectional view taken from FIG. FIG. 3 is a cross-sectional view as well. FIG. 4 is a sectional view of the impact wrench according to the present invention. FIG. 5 is a cross-sectional view taken from FIG.
Figure 6 is a partially cutaway front view of the anvil shaft. FIG. 7 is a cross-sectional view of FIG. 6. FIG. 8 is a sectional view of the spring liner. Figure 9 is a sectional view of the hammer. 1st
Figure 0 is a left side view of Figure 9. In the figure: 1...Hammer, 2...Anvil, 3...Concave groove, 4...Protruding ear, 5...Cam release spring, 6...Small diameter part, 7...Anvil pin, 8...Cam sleeve , 9... ball cam, 10... recess, 11... ring-shaped member, 20
... Motor shaft, 21 ... Spline shaft, 22 ...
Hammer, 22a...circumferential groove, 23...groove, 24...
...anvil pin, 24a... annular groove, 25... anvil shaft, 26... (ear-shaped) anvil, 27...
...Spline, 28...Campilot stem,
29...Cam pilot, 29a...Ball race, 30...Cam ball, 31...Hammer cam, 32...Cam section, 33...Large diameter drive section, 34
...Cylindrical part, 35...Cam release spring,
36... Spring liner, 36a... Center hole.

Claims (1)

[Claims] 1. In an impact wrench including a hammer 22 and an anvil 26 rotatable around an axis,
The hammer 22 is used to impact the anvil 26.
A cylindrical anvil pin 24 that slides in the axial direction
and a large diameter drive part 33 that engages the cam part 32 at one end and the annular groove 24a of the anvil pin 24 at the middle part.
and a hammer cam 31 having a cylindrical portion 34 into which a cam release spring 35 is fitted at the other end,
The hammer cam 31 is always connected to the anvil 26 by a cam release spring 35.
The cam release spring 35 is fitted at its tip into a dish-shaped spring liner 36 whose outer diameter is equal to or slightly larger than the diameter of the jaw of the anvil 26, and the cam release spring 35 is urged away from the spring. A support structure for an anvil pin in a cam type impact wrench, characterized in that the anvil pin 24 moves on the outer surface of the liner 36 toward the jaw of the anvil 26.