JP3915956B2 - Driving machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a shock absorber for stopping a striking piston in a pneumatic driving machine for driving a stopper such as a nail using compressed air as a power source.
[0002]
[Prior art]
As disclosed in Japanese Patent Laid-Open No. 3-178784, a striking piston housed in a cylinder is driven by compressed air, and a stop is struck by a driver coupled to the striking piston. Pneumatic navigators that when compressed air in the return air chamber acts on the lower surface of the striking piston and returns to the top of the cylinder when exhausted to the atmosphere will cause the impact of the striking piston to fall below the striking stroke. A shock absorber comprising a bumper for absorbing and stopping at the dead center is provided.
[0003]
Since the conventional driving machine is used at a compressed air pressure of 10 atm or less, the diameter of the driving piston has to be increased in order to obtain the required driving energy. Therefore, the diameter of the bumper can be increased, and there is a margin in design.
[0004]
[Problems to be solved by the invention]
Recently, deregulation has made it possible to use high-pressure compressed air, enabling the design of small, high-powered driving machines. Therefore, if the diameter of the striking piston is reduced according to the high pressure compressed air and the bumper is designed to be small according to the diameter of the striking piston, the impact force of the striking piston increases by using the high pressure compressed air. There is a problem that the burden on the bumper increases and the durability of the bumper decreases. On the other hand, if the bumper is designed by a conventional method, the bumper becomes large and the lower portion of the driving machine becomes thick, and there is a problem that it is impossible to reduce the size and weight of the driving machine.
[0005]
An object of the present invention is to provide a shock absorber for a driving machine that optimizes the shape of the bumper and is small and highly durable.
[0006]
[Means for Solving the Problems]
The above object is achieved by making the bumper have a shape in which the upper sectional area is maximized and the sectional area gradually decreases from the upper part to the lower part.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The shock absorber of the present invention will be described below with reference to FIGS. 1 and 2 showing an embodiment.
[0008]
As is well known, the driving machine slidably accommodates the striking piston 3 in the cylinder 2 and integrally couples the driver 4 to the striking piston 3. The compressed air supplied above the striking piston 3 in the cylinder 2 drives the striking piston 3 shockingly from the top dead center toward the bottom dead center, and is injected below the nose portion 1 by the driver 4. The stopper supplied to the part (not shown) is driven out.
[0009]
An accommodating portion 8 of the bumper 7 is formed between the cylinder 2 and the nose portion 1. The bumper 7 accommodated in the accommodating portion 8 receives the lower surface of the striking piston 3 and absorbs the impact force of the striking piston 3. .
[0010]
The bumper 7 is made of, for example, a viscoelastic material such as urethane rubber, and the bumper upper portion 9 has the largest cross-sectional area, and the bumper 7 is formed in a shape in which the cross-sectional area gradually decreases from the bumper upper portion 9 to the bumper lower portion 10. The center line 14 of the cross section of the upper part 9 is curved or inclined radially inward. Further, a vertically long gap 12 is provided between the outer peripheral portion of the bumper upper portion 9 and the inner wall of the cylinder 2. An inner peripheral portion and an outer peripheral portion of the upper end portion of the bumper 7 are R-shaped, and an annular concave portion 11 having the same shape as the bumper 7 is provided on the bumper contact surface of the lower surface of the impact piston 3. The outer peripheral portion has an R shape that matches the shape of the bumper upper portion 9 of the bumper 7.
[0011]
According to the above configuration, when the bumper 7 receives an impact, distortion concentrates on the bumper upper part 9 in the initial stage of deformation, but since the cross-sectional area of the bumper upper part 9 is formed large, The deformation is suppressed, the deformation is transmitted to the bumper lower part 10, and damage from the bumper upper part 9 can be avoided. By providing an annular recess 11 having the same shape as the bumper 7 on the bumper contact surface on the lower surface of the impact piston 3, the bumper upper portion 9 is fitted into the annular recess 11 of the impact piston 3 when the impact piston 3 and the bumper 7 collide. Therefore, local deformation of the corner portion 13 is suppressed and damage is suppressed. In addition, since the inner peripheral part and outer peripheral part of the annular recessed part 11 of the striking piston 3 are formed in an R shape, even if the cores of the bumper 7 and the striking piston 3 are displaced and come into contact with each other, the cores are aligned after contact. Since it is corrected, breakage from the corner 13 can be prevented.
[0012]
Since the elastic material such as rubber constituting the bumper 7 is deformed with a constant volume, the bumper upper portion 9 tends to be deformed radially outward with respect to the load from the striking piston 3. However, since the center line 14 of the cross section of the bumper upper portion 9 is curved or inclined inward in the radial direction, the load of the striking piston 3 acts in a direction to suppress the deformation of the bumper upper portion 9 in the radially outward direction. Therefore, no tensile stress that causes damage is generated inside the bumper 7. Further, when the bumper 7 is deformed outward in the radial direction, the gap 12 is set so that the circumferential strain is equal to or less than the allowable strain. Therefore, at the stage of the initial deformation of the bumper 7, the bumper 7 is It can expand freely outside. As a result, the spring constant of the bumper 7 can be kept low, the impact load on the driving machine main body can be reduced, and the life of the driving machine main body can be extended.
[0013]
Next, in the middle stage of deformation, the bumper upper part 9 swells outward in the radial direction, but since there is an initial gap 12, the contact pressure between the bumper 7 and the inner wall of the bumper housing 8 is small, and as a result, the frictional force is small. Since the bumper upper part 9 is easy to slide downward and is easily deformed, it can be deformed in a state of uniform compressive stress with good balance from the bumper upper part 9 to the bumper lower part 10 of the bumper 7 as shown in FIG. Is possible.
[0014]
At the final stage of deformation, the thickness of the lower bumper 10 is thinner than that of the upper bumper 9, so that it is easier to deform than the upper bumper 9. Since the generation of stress can be suppressed, the life of the bumper 7 can be extended.
[0015]
According to the above-described embodiment of the present invention, the strain concentrated on the bumper upper portion 9 in the early stage of deformation is reduced by maximizing the cross-sectional area of the bumper upper portion 9 and gradually reducing the cross-sectional area from the bumper upper portion 9 to the bumper lower portion 10. It can be relaxed and the durability of the bumper 7 can be improved. Further, by bending or inclining the bumper upper portion 9 inward in the radial direction, no tensile stress that causes damage is generated in the bumper 7, so that the durability of the bumper 7 can be improved. In particular, a viscoelastic material such as urethane rubber constituting the bumper 7 is weak against tensile stress and strong against compressive stress. Therefore, the effect of not generating tensile stress is great, and the life of the bumper 7 is further extended. By installing a gap 12 between the bumper upper portion 9 and the bumper accommodating portion 8 of the cylinder 2, the spring constant of the bumper 7 can be kept small, so that the impact load can be reduced and the life of the driving machine main body can be reduced. Can be lengthened. Further, even if the bumper upper part 9 is deformed outward in the radial direction by the gap 12, the contact pressure with the cylinder 2 is reduced, and the bumper upper part 9 is easily slid downward and deformed in a state of uniform compressive stress as a whole. It is possible to reduce the size. By installing an annular recess 11 having the same shape as the upper end surface of the bumper 7 on the lower surface of the striking piston 3, the recess 11 and the upper end of the bumper are fitted to each other at the time of collision, and due to local deformation of the corner 13 of the bumper 7. Generation of cracks can be prevented. Since the inner peripheral portion and the outer peripheral portion of the recess 11 are formed in an R shape, even if the bumper 7 and the striking piston 3 are misaligned and contacted, the corners are corrected so that the cores match after contact. Various effects such as prevention of breakage from 13 can be achieved.
[0016]
【The invention's effect】
As described above, according to the present invention, local deformation due to high-speed collision with the striking piston can be suppressed, and a compact and highly durable shock absorber can be provided.
[Brief description of the drawings]
FIG. 1 is a fragmentary cutaway view showing an embodiment of a shock absorber according to the present invention.
FIG. 2 is a cross-sectional view of a main part showing a state where a striking piston and a bumper collide with each other.
[Explanation of symbols]
1 is a nose portion, 2 is a cylinder, 3 is a striking piston, 4 is a driver, 5 is a communication hole, 6 is a return air chamber, 7 is a bumper, 8 is a bumper accommodating portion, 9 is a bumper upper portion, 10 is a bumper lower portion, 11 Is an annular recess, 12 is a gap, 13 is a corner, and 14 is a center line of the cross section.

Claims (1)

A driving machine in which a striking piston is slidably accommodated in a cylinder and a substantially cylindrical bumper is provided below the cylinder to receive the lower surface of the striking piston,
The bumper has a shape in which the upper cross-sectional area is maximum and the cross-sectional area gradually decreases from the upper part to the lower part. When the bumper is deformed outward in the radial direction between the outer periphery of the bumper and the inner wall surface of the cylinder, the circumferential distortion of the bumper is less than the allowable strain. The outer diameter of the upper bumper is made smaller than the outer diameter of the lower bumper and the lower bumper lower than the inner diameter of the upper bumper so that the gap between the lower outer periphery of the bumper and the inner wall surface of the cylinder becomes substantially zero. A driving machine characterized in that an inclined portion is provided on the inner periphery of the bumper so that the inner diameter of the bumper increases .

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