JPH0433586B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a dry striking protection device for dealing with dry striking operations under no-load conditions in impact tools such as hammer drills and electric hammers.

Conventional technology In this type of conventional device, for example, a movable tapered surface provided on the side of a striking member fitted inside a cylinder and driven by air pressure engages with a fixed tapered surface provided on the cylinder side when no load is applied. The hammer is press-fitted in a shape to restrict the retreat of the striking member and prevent the striking member from being driven dry.

Problems to be Solved by the Invention In the case of the above-mentioned conventional device, the engagement between both tapered surfaces is uncertain and engagement errors occur frequently, and the main body side is damaged due to the impact of the striking member. There was a problem in that when the resultant force was increased, it was difficult to separate the two tapered surfaces that had engaged with each other.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dry striking protection device for a striking tool that can reliably protect the striking tool from blank striking operations by solving the above-mentioned problems.

Means for Solving the Problems The present invention provides axial movement of a cylinder fitted with a piston that moves forward and backward in conjunction with a drive mechanism, and a striking member that is driven by air pressure by the forward and backward movement of the piston. The piston is normally supported by a spring in the retracting direction, and when the piston moves forward in an unloaded state, the pressing force of the striking member is transmitted to the spring via the cylinder, Further, the gist of the device is a dry firing protection device configured such that an exhaust hole penetrating through the cylinder is closed by the forward movement of the cylinder, thereby restricting the repulsion and retreat of the impact member from the forward end. It is.

Embodiment Next, an embodiment in which the present invention is applied to an electric hammer will be described with reference to the drawings. It is a substantially cylindrical cylinder that is supported concentrically with respect to the barrel 2, and its front and rear ends are connected to the support surface 2a near the front end of the barrel 2, and through a locking ring 3 that is locked to the rear end of the barrel 2 with a pin 21. It is supported by a key 22 so as to be unrotatable but movable in the cylinder axis direction, and near the center thereof are air relief holes 1a, 1a, impact holes 1b, 1b with a smaller diameter than the relief hole 1a, and air supply holes. The holes 1c are provided through the holes in order from the front, and the relief holes 1a on the inner peripheral surface thereof
A conical locking surface 1d tilting downward toward the front is formed slightly in front of the seal holder 4 screwed onto the front end of the barrel 2, and a locking surface 1d formed at the front end of the support surface 2a of the barrel 2. A forward end and a backward end of the cylinder 1 are respectively defined by the stepped portion 2b,
The escape hole 1a is communicated with the outside air when the cylinder 1 moves to the backward end, and is closed by the support surface 2a of the barrel 2 when the cylinder 1 moves forward.

A piston 5 is slidably fitted into the rear end of the cylinder 1, and a crank 8 is rotatably supported in a crank housing 6 connected to the rear of the barrel 2 and driven to rotate by a motor 7. The cylinder is connected via a crank rod 9 so that it can move forward and backward in the axial direction of the cylinder.

Reference numeral 10 denotes a first hammer that is tightly fitted in front of the piston 5 so as to be slidable in the cylinder axial direction into the cylinder 1, and a conical engagement surface 10a is provided at the front of the first hammer to lock the cylinder 1. It is formed to be able to engage with the surface 1d, and when the piston 5 moves forward and backward, it moves forward and backward in conjunction with the piston 5 due to fluctuations in air pressure in the front and rear air chambers 11A and 11B of the cylinder 1, which are partitioned by the first hammer 10. be moved.

Reference numeral 12 denotes a bit holder that is connected to the front end of the cylinder 1 so as to be able to move together in the axial direction of the cylinder in order to insert the bit 13 into the front end of the cylinder 1.
2a extends through the bit holder 1, and is connected to the cylinder 1 via a pin 14 inserted through the front end of the cylinder 1 and the rear end of the bit holder 12.

15 is externally fitted on the bit holder 12 in order to always urge the cylinder 1 in the backward direction.
This is a spring interposed between the seal holder 4 and the seal holder 4.

Bit 16 indicates the striking action of the first hammer 10.
The shaft hole 12a of the bit holder 12
A second hammer is inserted into the rear part so as to be slidable in the cylinder axial direction and is interposed between the first hammer 10 and the bit 13, and is
A long groove-shaped engagement groove 1 is formed in the second hammer 16 opposite to the hole 12b in order to engage the locking ball 17 inserted into the hole 12b penetrated near the rear end.
The locking ball 1 is configured to move independently in the cylinder axial direction by the movement range specified by 6a, and to move together with the bit holder 12 and the cylinder 1 at the moving end.
It is connected to the bit holder 12 and the cylinder 1 via 7.

18, 18 are key grooves 13a, 13 of the bit 13
A pair of keys 19 are inserted into the vicinity of the front end of the bit holder 12 so as to be engaged with the keys 18, and the keys 19 are rotated relative to the vicinity of the front end of the bit holder 12 in order to restrict and allow movement of both keys 18 in the radial direction. Chain ring that can be fitted externally, 20 is chain ring 1
9 is a cover fitted on the outside.

Next, the operation and effects of the embodiment having the above configuration will be explained.

First, a case will be described in which a normal impact operation is performed on a workpiece. First, the bit 13 is brought into contact with the surface to be machined and pressed, and the first hammer 10 retreats beyond the striking hole 1b via the second hammer 16, which retreats accordingly (at this time, as shown in FIG. As shown in FIG.
). This state (Figure 1)
The striking operation against the workpiece is started. That is, the interior of the rear air chamber 11B is pressurized and depressurized by the forward and backward movement of the piston 5, whereby the first hammer 10 moves forward and backward and strikes the second hammer 16. A striking action is repeatedly transmitted to the bit 13 each time the piston 5 moves back and forth.

On the other hand, in an unloaded state in which the bit 13 is separated from the machining surface or in an unloaded state in which the bit 13 is not inserted, the piston 5 is actuated to move the first hammer 10
When the second hammer 16 is held at the forward end position in the bit holder 12 by advancing it to the forward end position where the engaging surface 10a of the first hammer 10 and the locking surface 1d of the cylinder 1 contact, ), the first hammer 10, which has moved forward with the movement of the piston 5, has its locking surface 10a meshing with the engaging surface 1d of the cylinder 1, and is locked in the forward end position so that it cannot perform idle striking, or is locked in the forward end position. Due to the poor engagement between the stop surface 10a and the engagement surface 1d, it rebounds from the forward end (see FIG. 4(b)).

When the first hammer 10 rebounds and retreats, the cylinder 1 is pressed by the first hammer 10 and moves forward against the spring 15, closing the relief hole 1a and sealing the front air chamber 11A. A suction action is applied to the hammer 10 by the back pressure in the front air chamber 11A, and the amount of retreat of the first hammer 10 is limited, and the first hammer 10 retreats slightly within a range that does not exceed the striking hole 1b, and the first hammer 10 retreats. The cylinder 1 released at
(See Figure C).

Furthermore, in this state, the piston 5 operates and the first
Even when the hammer 10 moves forward and backward, the inside of the rear air chamber 11b is communicated with the outside of the cylinder 1 through the striking hole 1b, and the air pressure is reduced. The pressing force of the first hammer 10 is transmitted to the spring 15 via the cylinder 1 and buffered (see FIG. 4D).

Therefore, even when the first hammer 10 rebounds and retreats, the idle striking action of the first hammer 10 is reduced and impact on the cylinder 1, barrel 2, bit holder 12, etc. is suppressed, and the main body H is moved back by the first hammer 10. The cylinder 1, barrel 2, and bit holder 12 are securely protected from dry striking operation due to the impact action of the first hammer 10.
This has the effect of preventing damage such as, etc., and increasing the durability of the electric hammer.

In addition, as shown in FIGS. 5A, 5B, and 5C, there is an electric hammer in which a piston 5A and a hammer 23 which is an integral part of both the hammers 10 and 16 of the above embodiment are fitted in the cylinder 1A, and an electric hammer in which the piston 5A and the hammer 23 of the above embodiment are fitted, An electric hammer in which a piston 5B is fitted in a covered cylindrical hammer 24, or a covered cylindrical piston 5 in a cylinder 1C.
The dry striking protection mechanism of the above embodiment can also be applied to an electric hammer or the like in which the piston 5C is fitted and the hammer 25 is fitted in the piston 5C.

Effects of the Invention That is, the present invention supports a cylinder that is fitted with a piston that moves forward and backward in conjunction with a drive mechanism, and a striking member that is driven by air pressure by the forward and backward movement of this piston, so as to be movable in the axial direction. Further, the piston is always urged in the retracting direction by a spring, and when the piston moves forward under no load, the pressing force of the striking member is transmitted to the spring via the cylinder, and Since the exhaust hole penetrated through the cylinder is closed by the advance of the cylinder, the rebound retreat of the striking member from the forward end is restricted.
This has the effect of reliably protecting the impact tool from the dry striking operation and preventing damage caused by the dry striking operation.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is a cutaway side view of essential parts of an electric hammer, FIG. 2 is a cross-sectional view taken along the line X--X of FIG. 1, and FIG. 3 is also taken along the Y--Y line. Cross-sectional views, Figures 4A, 4B, 3D, and 4 are side sectional views of main parts showing the dry striking operation of the first hammer in order, and Figures 5A, B, and
C is a schematic side sectional view showing another example of the striking mechanism. 1... Cylinder, 1a... Relief hole, 1d... Locking surface, 5... Piston, 10... First hammer, 1
1A, 11B...Air chamber, 12...Bit holder, 13...Bit, 15...Spring, 16
...Second hammer.

Claims (1)

[Claims] 1 A cylinder that is fitted with a piston that moves forward and backward in conjunction with a drive mechanism and a striking member that is driven by air pressure by the forward and backward movement of this piston is supported so as to be movable in the axial direction, and is always supported by a spring. An exhaust gas provided through the cylinder biases the piston in the retracting direction, and transmits the pressing force of the striking member to the spring via the cylinder when the piston advances under no load. 1. A dry striking protection device for a striking tool, characterized in that a relief hole is closed by the advancement of the cylinder, and rebound retreat of the striking member from the advancing end is restricted.