JP3756725B2 - Impact tool - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hammering tool such as a hammer or a hammer drill provided with a blanking prevention device in order to prevent a hammering operation when a bit is not attached to the front end of a housing.
[0002]
[Prior art]
A hammer drill 40 is shown in FIG. 4 as a conventional striking tool. The hammer drill 40 is rotated by a rotation transmission mechanism in the main body housing 41 and pivotally supports a tool holder 42 to which a bit can be attached at the front end (left side in FIG. 4), while in the small diameter portion 43 of the tool holder 42, An intermediate element 45 located at the rear of the bit is slidably provided, and a piston cylinder 46 is slidably accommodated in the large-diameter portion 44 of the tool holder 42 through the air chamber 47 from the rear. It is inserted. Therefore, when the piston cylinder 46 is reciprocated by the crank rod 50 of the crank mechanism 49, the striker 48 is interlocked via the air chamber 47, and the strike force is transmitted to the bit by striking the intermediate element 45.
As an idling prevention device, a structure including an O-ring 51 provided in the tool holder 42, a striking portion 52 in front of the striking element 48, and a flange 53 formed at the front end thereof is known. This is because when the piston cylinder 46 reciprocates in the state where no bit is attached, the striker 48 advances longer than usual by the absence of the bit, and the hitting portion 52 is inserted into the O-ring 51. Due to the gripping of the portion 52 and the retaining action by the interference with the flange 53, the linkage between the striker 48 and the piston cylinder 46 is cut off, and the subsequent idle shot is prevented.
[0003]
[Problems to be solved by the invention]
As described above, in the hammer drill 40 using the O-ring 51 on the tool holder 42 side to prevent blank shots, in order to increase the reliability of blank shot prevention, the inner diameter of the O-ring 51 is reduced to grip the striking portion 52. It is necessary to strengthen the power. However, on the other hand, the deformation amount of the O-ring 51 and the interference with the flange 53 are increased, and the durability is lowered. Therefore, a means for increasing the gripping force by arranging a plurality of such O-rings 51 in the axial direction is also conceivable. However, the arrangement place in the tool holder 42 is required to be long in the axial direction. In addition, the tool holder 42 and the striker 48 may need to be resized, leading to an increase in cost.
[0004]
SUMMARY OF THE INVENTION An object of the present invention is to provide an impact tool that can more effectively prevent idling with a simple configuration.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is directed to an O-ring that slides on the sliding contact surface of the striker with the piston cylinder and seals the air chamber at all times with the inner periphery of the piston cylinder. While the front of the ring, when the striker moves forward without the bit being attached to the housing, the outer ring separates from the piston cylinder and contacts the front end of the piston cylinder in the retracting direction of the striker. When the front end of the piston cylinder with which the elastic ring abuts is opened, a tapered portion having a diameter that increases toward the front is formed .
In addition to the object of claim 1, the invention described in claim 2 is provided in order to further improve the reliability of prevention of blank shots, when the striker moves forward without a bit being installed in the housing. A gripping member capable of gripping the front end is provided.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall view of a hammer drill 1 as a striking tool, FIG. 2 is a partial longitudinal sectional view thereof, and the hammer drill 1 is disposed in front of a motor housing 4 incorporating a motor 2 (on the left side in FIG. 1). A housing 5 is connected, and a cylindrical tool holder 6 having a small diameter portion 7 and a large diameter portion 8 and an intermediate shaft 9 are rotatable in the main body housing 5 in parallel with the output shaft 3 of the motor 2. Is pivotally supported. Here, the rotation of the output shaft 3 is transmitted to the intermediate shaft 9 via the first gear 10 connected to the rear of the intermediate shaft 9, and the rotation of the intermediate shaft 9 is a gear portion formed in front of the intermediate shaft 9. 11 is engaged with the second gear 12 mounted on the large diameter portion 8 of the tool holder 6 and transmitted to the tool holder 6.
A bit 13 is detachably and integrally attached to the small diameter portion 7 of the tool holder 6 from the front, and an intermediate element 14 is slidably received behind the bit 13. The intermediate element 14 is restricted from sliding backward by balls 16, 16... Provided in the small diameter portion 7 so as to protrude toward the axial center at the position of the ball bearing 15 that pivotally supports the tool holder 6. The large-diameter portion 8 accommodates a piston cylinder 17 having a front opening in a slidable manner. A striking element 19 having a striking portion 20 projecting forward is provided in the piston cylinder 17 via an air chamber 18. It is slidably accommodated.
[0007]
On the other hand, the intermediate shaft 9 is spline-coupled with a clutch 22 that is urged rearward, and meshes with a connecting body 23 that is rotatably mounted on the intermediate shaft 9 behind the intermediate shaft 9. It meshes with a bevel gear 25 provided at the lower end of a crankshaft 24 that is pivotally supported above the shaft 9. Therefore, the rotation of the intermediate shaft 9 is transmitted to the crankshaft 24 via the clutch 22 and the connecting body 23. However, the clutch 22 can be switched between meshing with the connecting body 23 and release thereof by a switching knob 26 provided on the lower surface of the main body housing 5.
An eccentric pin 27 projects from the upper surface of the crankshaft 24 and is connected to a connecting pin 28 provided at the rear end of the piston cylinder 17 by a crank rod 29. Therefore, when the crankshaft 24 rotates with the clutch 22 engaged with the connecting body 23, the rotation is converted into the reciprocating motion of the piston cylinder 17 by the crank rod 29.
[0008]
Then, O-rings 30 and 31 are provided on the front and rear at the sliding contact portion of the striker 19 with the inner peripheral surface of the piston cylinder 17. The rear O-ring 30 is for sealing the air chamber 18, but the front O-ring 31, which is an elastic ring of the present invention, is always in the inner periphery of the piston cylinder 17 during a normal striking operation. When the bit 13 is not attached to the small diameter portion 7 of the tool holder 6, the striking element 19 moves forward from the piston cylinder 17. Reference numeral 32 denotes a tapered portion formed so as to increase in diameter toward the front at the opening of the front end of the piston cylinder 17.
Further, an O-ring 33 as a gripping member is also arranged at the inner peripheral rear end of the small diameter portion 7 of the tool holder 6. The O-ring 33 has an inner diameter smaller than the diameter of the flange 21 provided around the front end of the striking portion 20 in the striking piece 19, and the bit 13 is not attached to the small diameter portion 7 of the tool holder 6. The striking part 20 can be inserted with advance.
[0009]
In the hammer drill 1 configured as described above, when the bit 13 is attached to the small diameter portion 7 of the tool holder 6 as shown in FIG. 16 abuts and stops. Therefore, when the motor 2 is driven at a position where the clutch 22 meshes with the connecting body 23 and the piston cylinder 17 reciprocates from the intermediate shaft 9 via the crankshaft 24 and the crank rod 29, the striker 19 via the air chamber 18. Are reciprocated in conjunction with each other, hitting the intermediate element 14 during forward movement, and transmitting the hitting force to the bit 13. Further, since the rotation of the intermediate shaft 9 is also transmitted to the tool holder 6 via the second gear 12, both the striking and rotation operations are applied to the bit 13. In this hammer drill mode, the front O-ring 31 does not escape from the piston cylinder 17 even in the forward position due to the stroke setting of the striker 19 described above, and the sliding contact with the inner peripheral surface of the piston cylinder 17 is not caused. Maintained.
[0010]
When the motor 2 is driven in a state where the bit 13 is not attached to the tool holder 6, as shown in FIG. 2, the intermediate element 14 and the striker 19 can move forward longer than in the normal striking operation because there is no bit 13. 3, with the advancement of the striker 19, the O-ring 31 in front of the striker 19 is disengaged from the piston cylinder 17, and at the same time, the striker 20 at the tip is fitted into the O-ring 33 on the tool holder 6 side and is gripped as it is. Therefore, the striker 19 is prevented from moving in the backward direction by the contact between the O-ring 31 and the front end of the piston cylinder 17, the gripping of the strike portion 20 by the O-ring 33 and the retaining action of the flange 21. Even if the piston cylinder 17 continues to reciprocate, the striker 19 is not interlocked, and the subsequent idling is prevented.
On the other hand, when the bit 13 is mounted again on the tool holder 6 from here, the rear end of the bit 13 pushes the meson 14 backward, so that the meson 14 pushes the striker 19 backward, and the striking portion 20 is moved from the O-ring 33. Since the O-ring 31 is inserted again into the piston cylinder 17 while being escaped, it can be used in the aforementioned hammer drill mode. The tapered portion 32 at the front end of the piston cylinder 17 serves as a guide when the O-ring 31 returns into the piston cylinder 17 and prevents the O-ring 31 from deteriorating.
[0011]
As described above, according to the above configuration, in the state where the bit 13 is not mounted, the O-ring 31 of the striker 19 is disengaged from the piston cylinder 17 and is prevented from moving backward, thereby preventing idling. Therefore, a large contact area with the piston cylinder 17 can be ensured by using the O-ring 31 mounted on the striking element 19 having a large diameter, and the effect of preventing idling is effectively exhibited. Further, since there is little deformation of the O-ring 31, there is no need to worry about a decrease in durability. Furthermore, since these functions and effects can be obtained only by adding the O-ring 31 to the striker 19, there is no need to consider the arrangement location or design change on the tool holder 6 side, and it is easy and low-cost to prevent blank shots. It becomes feasible.
On the other hand, here, the tool holder 6 is provided with an O-ring 33 that can grip the striker 19 when the striker 19 moves forward without the bit 13 being mounted, thereby restricting the movement of the striker 19 to the rear. Will be more reliable, and the reliability of prevention of idling will increase. In particular, it is not necessary to set the tightening of the striking portion 20 with the O-ring 33 strongly, and the durability of the O-ring 33 is improved by making the O-ring 31 on the striking element 19 side exclusively bear the prevention of idling. The following effects can also be obtained.
[0012]
In the above embodiment, an example in which the O-ring 33 on the tool holder 6 side is used in addition to the O-ring 31 on the striker 19 side is described. However, a gripping member such as the O-ring 33 is omitted, Even if the idle hitting prevention device is configured only by the O-ring 31 (elastic ring) on the striker 19 side, the same idling prevention effect can be obtained.
In addition, the elastic ring is not limited to the O-ring, and a ring having a semicircular or polygonal cross section may be used as long as it can be inserted into and removed from the piston cylinder during normal striking operation and during non-running. You can also. Furthermore, the gripping member is not limited to the O-ring, and a rubber sleeve whose inner diameter is tapered forward, a plurality of rubber balls arranged concentrically, or the like may be employed.
On the other hand, in the above embodiment, the meson is interposed between the bit and the striker, but the present invention can be adopted even if there is no meson and the striker strikes the bit directly.
[0013]
【The invention's effect】
According to the first aspect of the present invention, in the state where the bit is not attached, the elastic ring attached to the striking element escapes from the piston cylinder and prevents backward movement, thereby preventing idle driving. Therefore, a large contact area with the piston cylinder can be ensured by using the elastic ring that is externally mounted on the striking element having a large diameter, and the effect of preventing idling is effectively exhibited. Further, since the elastic ring is hardly deformed, there is no need to worry about a decrease in durability. Furthermore, since these functions and effects can be obtained only by adding an elastic ring to the striker, it is not necessary to consider the arrangement location on the housing side, design change, etc., and it is possible to realize idling prevention at a simple and low cost. .
And since the taper part of the piston cylinder front end acts as a guide when the elastic ring returns into the piston cylinder, the deterioration of the elastic ring can be prevented.
According to the second aspect of the present invention, in addition to the effect of the first aspect, a gripping member is provided in the housing that can grip the front end of the striker when the striker advances without the bit being attached. As a result, the movement restriction of the striker to the rear becomes more reliable, and the reliability of prevention of idling is increased. In particular, it is not necessary to set the tightening of the striking member strongly by the gripping member, and the secondary effect of improving the durability of the gripping member is obtained by making the elastic ring on the striking member side exclusively bear the prevention of idling. It is done.
[Brief description of the drawings]
FIG. 1 is an overall explanatory view of a hammer drill.
FIG. 2 is a cross-sectional explanatory view showing an idling prevention operation.
FIG. 3 is an explanatory cross-sectional view showing an idling prevention operation.
FIG. 4 is a cross-sectional explanatory view showing a conventional idling prevention device.
[Explanation of symbols]
1 .... hammer drill, 5 .... main body housing, 6 .... tool holder, 9 .... intermediate shaft, 13 .... bit, 14 .... medium, 17 .... piston cylinder, 18 .... air chamber, ... Child, 20 ... strike part, 21 ... flange, 30, 31, 33 ... O-ring.

Claims (2)

A striking element is accommodated through the air chamber, and a piston cylinder having an opening at the front is provided so as to be able to reciprocate into the housing, and the reciprocating movement of the striking element in conjunction with the reciprocating movement of the piston cylinder causes In the impact tool that enables the impact force to be transmitted to the installed bit,
An O-ring that always slides in contact with the inner periphery of the piston cylinder and seals the air chamber on the sliding contact surface of the striker with the piston cylinder, and in front of the O-ring, the bit on the housing When the striker moves forward without being mounted, the elastic ring contacts the front end of the piston cylinder in the retracting direction of the striker by moving away from the piston cylinder, while the elastic ring contacts. A striking tool in which a tapered portion having a diameter increasing toward the front is formed when the piston cylinder front end is opened . The striking tool according to claim 1, wherein a gripping member capable of gripping a front end of the striking member when the striking member moves forward in a state where the bit is not mounted is provided in the housing.

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