JPH0255199B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a percussion chisel to be attached to a percussion device, and more particularly, to an improvement of a percussion chisel to be attached to a percussion device (so-called breaker) for crushing concrete, rocks, or paved road surfaces. The present invention relates to a percussion chisel that can optimize the mass ratio relationship to the hammer body in the device, thereby increasing the crushing force of the percussion device and extending the life of the percussion chisel itself.

This type of striking device uses compressed air generated by a compressed air generator, often seen at road construction sites, to lead the compressed air to the striking device body via a hose, and uses the expansion force of this compressed air to push the piston. In addition to the configuration in which the hammer is moved up and down to continuously strike the striking chisel attached to the tip of the device, there is also a structure in which the hammer is moved up and down to continuously strike the striking chisel attached to the tip of the device. There are portable striking devices that can be used to obtain
(see issue).

In order to understand the significance of the present invention and its unique effects, it is necessary to understand the structure and operation of such a percussion device.Next, an example of the above portable percussion device will be explained based on FIG. explain.

Inside the cylindrical body, there is an outer cylinder 2.
is formed, and a movable cylinder 3 is fitted inside this so as to be able to reciprocate up and down. This movable cylinder 3 and the free piston 4 fitted inside the movable cylinder 3 constitute a so-called striking mechanism A. Here, the striking mechanism refers to the driving body B that reciprocates.
and a driven body C that follows this driving body B via an elastic body such as air. The purpose is to obtain the desired impact energy by accelerating the driven body C using the elastic force and thereby striking the object to be hit at a much higher speed than the reciprocating speed of the driving body B. . As the elastic body, in addition to using air as in this example, a coil spring can also be used. In this example, the movable cylinder 3 is a driving body B driven via a crank mechanism 5, and the free piston 4 is a driven body. However, on the contrary,
It is also possible to connect a piston-shaped driving body to a crank mechanism, fit a cylindrical driven body to the outside of the driving body, and make the air sealed between them function as an elastic body.

A striking rod 6 is protruded from the lower part of the free piston 4, and when the free piston 4 moves downward at high speed following the movement of the movable cylinder 3, this striking rod 6
protrudes downward from a through hole 7 formed in the lower part of the movable cylinder 3 and strikes the top of the striking chisel 8.

Further, in this example, a jacket body 9 is provided on the outside of the outer cylinder 2 to form a double cylinder, and the outer cylinder 2 is provided with ventilation holes 10 on the upper and lower sides.
By providing 11, a region above the movable cylinder 3 in the outer cylinder 2 and a region below the movable cylinder 3 are communicated with each other, and the resistance to the vertical movement of the movable cylinder 3 is reduced.

The inside of the movable cylinder 3 is divided into an upper air pressure chamber 12 and a lower air pressure chamber 13 by the free piston 4. These pneumatic chambers 12 and 13 are alternately compressed by the inertia lag of the free piston 4, and the resulting air elastic force accelerates the vertical reciprocating motion of the free piston 4. In this example, an appropriate number of through holes 14 are provided in the side wall of the movable cylinder 3, and the vacuum pressure in the upper air pressure chamber 12 is freely controlled by communicating the upper air pressure chamber 12 with the outside air when the free piston 4 moves downward. This prevents the piston 4 from interfering with the acceleration when it moves downward, and when the free piston 4 moves upward, the lower pneumatic chamber 1
3 and the outside air, the lower pneumatic chamber 13
This prevents the vacuum pressure from interfering with the upward movement of the free piston 4.

A striking chisel 8, which is struck by the striking mechanism A, is attached to the lower part of the main body 1.
In this example, it is configured as follows.

A boss portion 15 of a predetermined length is formed at the bottom of the outer cylinder 2 and communicates between the inside of the outer cylinder 2 and the outside, and the upper shaft portion of the striking chisel 8 is slid up and down and reciprocated on this boss portion 15. It is supported as much as possible. The percussion chisel 8 is supported so as to have the same axis as the movable cylinder 3 or the free piston 4, and its top protrudes slightly into the outer cylinder 2. The outer diameter of the boss portion 15 below the portion slightly lower than the upper end is slightly smaller than the inner diameter of the cylindrical holder 16 extending downward from the lower outer circumference of the outer cylinder 2. A compression coil spring 18, which is a compression elastic body, is fitted into a cylindrical space 17 formed on the outer periphery of the portion 15. It is engaged with the upper step portion of the portion 19 via a collar 20 or the like. As a result, the striking chisel 8 is always elastically biased downward.

The lower end of the striking chisel 8 projects outward from a through hole 21 formed in the lower bottom of a cylindrical holder 16 extending from the lower outer periphery of the outer cylinder 2. Note that the diameter of this through hole 21 is the same as that of the striking chisel 8.
By making the shaft diameter larger than the diameter of the shaft and smaller than the large diameter portion 19, it functions as a stopper to prevent the striking chisel 8 from slipping out.

In the striking device A, when the crank mechanism 5 is driven to cause the movable cylinder 3 to reciprocate up and down, the free piston 4 fitted inside the movable cylinder 3 moves into the upper pneumatic chamber 12 and the lower pneumatic chamber 1.
3's alternating compression shots accelerate its downward speed to a much faster rate than the downward speed of said movable cylinder 3, causing it to crash into the top of the striking chisel 8 with a large kinetic energy. The striking chisel 8, which is given impact kinetic energy by the free piston 4, should destroy the object to be struck with its impact force.

However, when attempting to actually crush a hard object such as concrete using the percussion device as described above, the tip of the percussion chisel 8 becomes extremely hot, and in severe cases, this The tip of the chisel sometimes melted due to the heat. This fact has been known among workers for a long time, but the cause has not been investigated deeply, and countermeasures have been taken, such as changing the material of the tip of the chisel to cemented carbide. It stayed. However, when striking a hard object, as mentioned above, heat is generated that can even melt steel, so no matter how hard the tip of the chisel is made, as long as it is made of steel, the fundamental It is not a solution.

The inventor of the present invention has carefully observed the behavior between the percussion chisel and the target object when using the percussion device, and has found that heat generation at the tip of the chisel is caused by the intense reciprocating movement of the chisel, as described above. It was discovered that the cause was the sliding friction that occurred between the tip and the object being struck. Such reciprocating motion of the chisel occurs because, in conventional striking devices, the mass of the hammer body (free piston in the above example) that strikes the chisel is relatively small compared to the mass of the chisel. I discovered that it does.

Conventionally, the influence of the relationship between the mass of the chisel and the mass of the hammer body that strikes it on the striking crushing force has not been considered, even if the mass of the hammer body is smaller than that of the chisel. If you increase the speed of the hammer body, you can increase the kinetic energy of the hammer body and therefore increase the crushing force of the chisel.
This is thought to be due to the fact that this mechanical common sense vaguely existed in this industry.

It is true that even if the mass of the hammer body is smaller than that of the striking chisel, if the speed of the hammer body is increased, the chisel that collides with it will receive a large amount of kinetic energy corresponding to the increased speed of the hammer body. It will be done. However, in this case, a large portion of the kinetic energy of the hammer body before the collision is converted into the energy of the rebound motion of the hammer body after the collision, and the conversion efficiency into the motion of the chisel is poor. In addition, in the actual percussion action, not only the relationship between the hammer body and the chisel, but also
It is also necessary to consider the relationship between these and the object to be hit.

Now, consider a case where the tip of the chisel 8 hits an object D as shown in FIG. The mass of the hammer body E is smaller than that of the chisel 8. When the hammer body E strikes the rear end of the chisel 8 at a speed V, a certain amount of striking energy is given to the chisel E. Depending on the hardness of the object D, a part of the energy is consumed to break the object D, and the remaining energy is consumed to bounce the hammer body E back.
At the same time, the chisel itself 8 also repulses from the object D to be struck. As a result of experiments, it was found that the phenomenon of repulsion of the chisel itself becomes more pronounced as the weight of the hammer body becomes smaller relative to the mass of the chisel. This is considered to be because the hammer body E is instantly bounced back after colliding with the chisel 19, and the chisel 8 itself can retreat rearward.

The fact that the chisel 8 itself struck by the hammer body E repulses against the striking object D as described above means that when the chisel 8 is continuously struck by the hammer body E, the chisel 8 hits the striking object D. This means that it makes a vigorous reciprocating motion with respect to D.
The above-mentioned heat generation phenomenon at the tip of the chisel is caused by the reciprocating frictional movement of the chisel against the object being struck.

On the other hand, if the mass of the chisel 8 is approximately equal to or less than that of the hammer body E, the impact acceleration given to the chisel 8 by the collision of the hammer body E will be greater than in the above case. Therefore, more energy is consumed for crushing the object D than in the above case, and for this reason, the chisel 8
The amount of energy that penetrates into the object D to be struck increases.
In this case, the crushed and crumbled object to be hit exerts a cushioning effect, and the chisel 8 hardly ever rebounds against it. Therefore, even if the chisel 8 is continuously struck, the chisel 8 will not make violent reciprocating motions, and high temperatures will not be generated due to frictional heat.

In this way, whether or not the chisel 8 in the striking device can effectively crush the object D to be struck depends not on the speed of the hammer body E or the hardness of the tip of the chisel 8, but on the strength of the hammer body E. It depends on how effectively the kinetic energy can be converted into impact acceleration motion of the chisel 8. If the mass of the chisel 8 is made larger than the mass of the hammer body E as in the past, no matter how much the speed of the hammer body E is increased, most of the kinetic energy is lost due to the rebound movement of the hammer body E after striking or The portion that is converted into a repulsive movement of the chisel 8, etc. and converted into an impact acceleration movement of the chisel 8 in the driving direction becomes extremely small. As a result, as mentioned above, not only does the crushing force at the tip of the chisel decrease, but also the chisel itself repulses due to the decrease in crushing force, and this causes frictional heat.
The life of the chisel will be extremely shortened.

As a result of the inventor's experimental observations, in order for the chisel to be able to effectively crush the target object, the mass of the chisel must be approximately 1.1 times the mass of the hammer body at most.
It has been found that it is preferable to keep the amount at most twice that.

On the other hand, it is not possible to increase the crushing force by simply reducing the mass of the chisel and its outer diameter. In other words, by reducing the outside diameter of the chisel, it is possible to make it easier for the chisel to penetrate into the object to be struck, but especially when striking an object with viscoelasticity such as asphalt, the object may be wedged. It does not reach the point of dividing by . As described above, the chisel in the striking device needs to have an outer diameter of a certain value or more. In the past, the influence of the mass relationship between the chisel and the hammer body on the crushing force of the chisel was not considered because, as mentioned above, the chisel must have a certain outer diameter. This is probably because reducing the weight of a chisel was thought to be outside the scope of common sense due to the need to obtain strength from the chisel.

The present invention has been made based on the experimental observation described above, that is, in order to extend the life of the chisel, it is necessary to eliminate the violent reciprocating movement of the chisel during striking, thereby reducing frictional heat between it and the object to be struck. It is necessary to prevent this from occurring, and in order to eliminate the repulsive reciprocating motion of the chisel as described above, it is sufficient to make the mass of the chisel approximately equal to or less than the mass of the hammer body. This was based on the consideration that in order to maintain the crushing power of the chisel, it was necessary to increase the outer diameter to some extent, and the purpose was to reduce the weight of the blow without shortening the outer diameter. An object of the present invention is to provide a striking chisel for equipment.

In order to achieve this objective, the present invention takes the following technical measures.

That is, the present invention provides a percussion chisel that is supported in the lower part of a percussion device main body so as to be able to reciprocate a predetermined distance in the axial direction, and that transmits impact force to an object by receiving a percussion from a percussion body that is reciprocated within the main body of the percussion device. It is characterized in that it is integrally constructed from the upper end to the lower end, and that a closed cavity including the axis is formed inside.

This makes it possible to reduce the overall weight of the percussion chisel by a considerable amount while keeping the outer diameter of the percussion chisel to the same extent as the conventional one. As a result, it is possible to make the weight of the chisel approximately equal to or less than the weight of the hammer body, which eliminates the phenomenon that conventionally occurs when striking, that is, the reciprocating movement of the chisel against the object to be struck. It is possible to minimize the generation of frictional heat between the object and the object being struck, dramatically extending the life of the chisel, and also to transfer most of the kinetic energy of the hammer body to the impact acceleration movement of the chisel. The crushing force of the chisel can be significantly increased compared to conventional methods. However, since the outer diameter of the chisel has not been reduced due to weight reduction, the function of splitting the object to be crushed by a wedge effect is not impaired.

Embodiments of the present invention will be specifically described below with reference to the drawings.

The shape of the vicinity of the top of the percussion chisel 8a according to this embodiment is similar to the shape of the vicinity of the top of the conventional percussion chisel 8 attached to the percussion device shown in FIG. It can be attached to the striking device as is. That is, a large diameter portion 19a is formed at a predetermined location on the top shaft portion, and the collar 20 engages with this portion in order to transmit the elasticity of the coil spring 18 to the chisel 8a.

As is clear from the figure, in the percussion chisel 8a of this embodiment, in order to form a cavity 22 inside, the chisel itself 8a is divided into two parts, a proximal end member 23 and a distal end member 24, each with a shaft. Holes 25 and 26 having a constant depth in the direction are formed, and these are integrally connected by taper fitting.

That is, the distal end member 24 has an axial hole 26 formed with a tapered portion 27 near the entrance, while the distal shaft portion 28 of the proximal end member 23 is formed in the axial direction hole 26 of the distal end member 24. A tapered shaft part that can fit into the tapered part 27 is formed, and an axial hole 25 is also formed in this tapered shaft part 28. The tapered shaft portion 28 is connected by fitting into the tapered shaft portion 28.

In this embodiment, the distal end member 24 and the proximal end member 23 are connected by taper fitting, but it goes without saying that this may also be done by screw means. Further, the inner diameter and depth of the axial holes formed in each of the members may be determined as appropriate depending on how much weight the percussion chisel 8a is to be reduced in relation to the hammer body. Further, the axial hole 25 provided in the base end member 23 may or may not be provided as necessary.

Furthermore, it is convenient to fill the cavity 22 with a light sound-dampening material, such as asbestos, because this material exhibits a sound-dampening effect.

As described above, the percussion chisel attached to the percussion device according to the present invention can reduce its weight without reducing its external size, so the weight of the chisel can be optimized in relation to the weight of the hammer body. Not only can the crushing force of the striking device be strengthened, but also the life of the chisel can be extended. The percussion chisel of the present invention is applicable not only to a percussion device including a percussion mechanism consisting of a movable cylinder and a free piston fitted therein, as shown in Fig. 1, but also to a percussion chisel using a compressed air generator. It goes without saying that it can also be used as a percussion chisel for a percussion device configured to reciprocate the hammer body up and down by utilizing the expansion force of the compressed air generated. It is.

Note that in the claims of the present application, the cavity provided in the percussion chisel is defined as a closed cavity when it is open in the axial direction of the chisel, or when there is a wedge for dividing the upper and lower members. This excludes the case where a large hole is provided in the side wall for inserting a shaped tool, and the case where a small hole is provided in the side wall of a chisel that has a hollow part inside is excluded in order to avoid the wording of the claims. The configuration is naturally included in the technical scope of the present invention from the spirit of the present invention.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an example of a percussion device for attaching a percussion chisel according to the present invention, FIG. 2 is an experimental overview diagram for explaining the significance of the present invention, and FIG. It is a sectional view showing an example. 8a... striking chisel, 22... hollow part.

Claims (1)

[Scope of Claims] 1. A striking device that is supported in the lower part of a striking device main body so as to be able to reciprocate a predetermined distance in the axial direction, and that transmits impact force to an object upon receiving a strike from a striking body that is driven reciprocally within the device main body. A chisel, which is integrally constructed from the upper end to the lower end, and
A percussion chisel attached to a percussion device, characterized in that a closed cavity containing an axis is formed inside the percussion chisel.