1. Filed of the Invention
The present invention relates to an impact drill for use in a drilling operation on the concrete, mortar or tile, for example, and more particularly to an impact drill having a drill mode for performing a drilling operation by rotating a drill bit and an impact drill mode for performing a drilling operation by rotating and vibrating the drill bit.
2. Description of the Related Art
Reference numeral 5 denotes a stationary ratchet disposed at a position opposed to the rotational ratchet 4, in which the serrated irregularities are formed on one face 5a of the stationary ratchet. The stationary ratchet 5 has a hollow cylindrical shape, and is fixed to the inner cover 18, irrespective of the rotation and axial movement of the spindle 2.
On the other hand, a motor 8 is disposed inside the housing 7 linked to the handle portion 6. A rotational driving force of the motor 8 is transmitted via a gear 10 fixed to a rotation shaft 9 to a second pinion 11. The second pinion 11 has two pinion portions 11a, 11b having a different number of teeth, which are engaged with a low speed gear 12 and a high speed gear 13, respectively. When the second pinion 11 is rotated, both the gears 12, 13 are also rotated.
Reference numeral 14 denotes a clutch disk engaged with the spindle 2 and mounted to be slidable in the axial direction. If the clutch disk 14 is inserted into a concave portion of the low speed gear 12, the rotation of the second pinion 11 is transmitted via the low speed gear 12 and the clutch disk 14 to the spindle 2, as shown in
Reference numeral 15 denotes a change lever for changing the operation mode of the impact drill, namely, between a drill mode and an impact drill mode. A change shaft 16 is press fit into the change lever 15, whereby when the change lever 15 is rotated, the change shaft 16 is also rotated. The change shaft 16 has a notch portion 16a, as shown in
(A) Drill Mode
When a drill bit (not shown) attached in the drill chuck 3 is contacted with a machined surface and the handle portion 6 is pressed in a direction of the arrow in
(B) Impact Drill Mode
In an impact drill mode, the notch portion 16a of the change shaft 16 is brought into the position of
In drilling the machined surface, if the spindle 2 is rotated in the state of
However, when the impact drill described above is operated in the impact drill mode, the vibration caused by rotation of the spindle in the state where the irregular faces of the ratchets 4 and 5 are contacted under pressure is transmitted not only to the drill bit, but also through the stationary ratchet 5 and the inner cover 18 from the housing 7 to the handle portion 6. Therefore, there is a problem that the user of the impact drill undergoes a great vibration, and feels uncomfortable. Especially when the impact drill is continuously employed for a long time, care must be taken not to transmit the vibration to the user and cause adverse effect on the health of the user.
Several proposals for reducing the vibration transmitted to the user have been made. For example, in JP-B-2-30169, a structure was disclosed in which a clutch cam 22 is supported movably in the axial direction of the spindle 20, and biased and urged to a rotary cam 21 by a spring 23, as shown in
In
The spring 23 is provided between the flange 22b of the clutch cam 22 and a plate 24a engaging a groove 22a of the clutch cam 22, and always urges the clutch cam 22 toward the rotary cam 21. Thus, when the spindle 20 is moved backward, the cam faces 21a and 22c are contacted under pressure. If a pressing force applied to the spindle 20 overcomes a resilience of the spring 23, the spring 23 is compressed, so that the clutch cam 22 is moved backward (to the right in the figure).
When the clutch cam 22 is moved forward from the back position due to a resilient force of the spring 23, it collides with the rotary cam 21, so that the rotary cam 21 is vibrated together with the spindle 20. With this structure, since the vibration caused by contact between the cam faces 21a and 22c is relieved by the spring 23 and transmitted to the handle portion (not shown), there is the effect that the vibration transmitted to the user is reduced as compared with the structure in which the ratchet 5 is firmly disposed as shown in
In a case of the drill as disclosed in JP-B-2-30169, since the clutch cam 22 permits the spindle 20 to slide in the axial direction, and regulates the rotation, the slide faces 22e, 22e are vertically formed on both sides of the flange portion 22b, and the clutch cam 22 is carried between both the guide faces 26 of a retainer 24 extending from the plate 24a, as shown in
When this structure has additionally a function of rotating the spindle 20 at high speed and low speed in the same manner as in
It is an object of the invention to solve the above-mentioned problems associated with the prior art, and to provide an impact drill can reduce the vibration transmitted to the user without losing a drilling ability at high and low speed rotation.
According one aspect of the invention, there is provided with an impact drill including: a spindle rotated by a motor and movable in an axial direction; a drill chuck fixed to the spindle and mountable with a drill bit; a first ratchet fixed to the spindle and having a face including an irregular portion; a second ratchet having a face including an irregular portion opposed to the face of the irregular portion of the first ratchet and movable in the axial direction, and a spring for urging the second ratchet in a direction of the first ratchet, in which the spindle is given an axial vibration by a contact and separation action between the irregular faces of the first and second ratchets due to a relative rotation of the first ratchet to the second ratchet, wherein the second ratchet is supported to be rotatable within a predetermined range in a rotational direction thereof.
According to another aspect of the invention, the second ratchet is supported to be rotatable by an angle or more from a first position at which the irregular face of the second ratchet overrides the irregular face of the first ratchet to a second position at which the irregular face of the second ratchet engages the irregular face of the first ratchet, when the first ratchet is in a stopped state.
According to another aspect of the invention, the second ratchet is supported to be rotatable by 0.6 times an angle or more from a first position at which the irregular face of the second ratchet overrides the irregular face of the first ratchet to a second position at which the irregular face of the second ratchet engages the irregular face of the first ratchet, when the first ratchet is in a stopped state.
According to another aspect of the invention, the second ratchet is supported to be rotatable by 0.3 times an angle or more from a first position at which the irregular face of the second ratchet overrides the irregular face of the first ratchet to a second position at which the irregular face of the second ratchet engages the irregular face of the first ratchet most deeply, when the first ratchet is in a stopped state.
According to another aspect of the invention, a notch portion is provided on an outer circumference of the second ratchet. A projection portion provided in a main frame portion of the impact drill is inserted into the notch portion. A predetermined clearance is provided between the notch portion and the projection portion.
According to another aspect of the invention, a width across flat of two parallel faces is provided in a part on a cylindrical portion of the second ratchet. A notch portion opposed to the width across flat is provided on a main frame portion of the impact drill. A predetermined clearance is provided between the width across flat and the notch portion.
According to another aspect of the invention, a projection portion is provided on an outer circumference of the second ratchet. The projection portion is inserted into a notch portion provided in a main frame portion of the impact drill. A predetermined clearance is provided between the projection portion and the notch portion.
According to another aspect of the invention, an elastic body is disposed in the predetermined clearance. A thrust bearing is provided between the second ratchet and the spring, or/and between the spring and a side wall portion extending from the main frame portion.
It is possible to produce a sufficient impact force between the second ratchet and the first ratchet at high and low speed rotation, whereby an impact drill having excellent drilling ability and unlikely to transmit vibration to the main body is provided. Accordingly, the user of the impact drill does not feel uncomfortable, and injure one's health.
Before explaining the embodiments of the invention, there will be described a phenomenon in which when the clutch cam collides with the rotary cam, its impact force is weakened.
First of all, in the case of high speed rotation, if the rotary cam 21 is rotated (leftward in the figure) in the state as shown in
At the stage of
If a front surface 22f of the clutch cam 22 and a front surface 21f of the rotary cam 21 collide as shown in
Next, a collision situation will be described below where under the conditions that the number of rotations of the rotary cam 21, the weight of the clutch cam 22 and the spring constant of the spring 23 are set up to give rise to the above phenomenon at the time of high speed rotation, the low speed rotation of about half the number of rotations is made.
First of all, if the rotary cam 21 is rotated in the state of
Then, at the stage of
As described above, if the settings are made such that one great impact force is generated at high speed rotation, two or more small impact forces are generated at low speed rotation, degrading the drilling ability of the drill.
Embodiments of the invention, has been achieved to solve the above-mentioned problems, and will be described below in detail by way of example.
As shown in
The second ratchet 105 has a notch portion 105e in a part of the outer cylindrical portion 105b, and the main frame portion 101 is provided with a projection 101a, whereby the projection 101a is inserted into the notch portion 105e. As a result, the rotational notion of the second ratchet 105 is blocked. This embodiment has a feature that there is a clearance 130a between the notch portion 105e and the projection 101a, so that the second ratchet 105 can be rotated within a predetermined range.
A side wall portion 122 extends in a direction of the spindle inside the rain frame portion 101, and a spring 120 is provided between the side wall portion 122 and the cylindrical bottom portion 105c. Reference numeral 109 denotes a rotation shaft to which a rotational driving force is transmitted from a motor (not shown), in which its rotational driving force is transmitted via a gear 110 to a second pinion 111. Reference numeral 112 denotes a low speed gear, 113 denotes a high speed gear, and 114 denotes a clutch disk, in which when the clutch disk 114 is at the position as shown, a rotational force is transmitted via the low speed gear 112 to the spindle 102.
On the other hand, if the clutch disk 114 is rotated to the position where the high speed gear and the spindle 102 are engaged by rotating a change lever 117, a rotational force of the second pinion 111 is transmitted via the high speed gear 113 to the spindle 102. Accordingly, the spindle 102 can be rotated at low speed or high speed depending on the rotated position of the change lever 117. The experiment of the present inventor has revealed that the vibration transmitted to a hand in the drilling operation is reduced owing to the above constitution.
First of all, in the case of high speed rotation, if the first ratchet 104 is rotated (leftward in the figure) in the state as shown in
As shown in
At the stage of
A collision situation will be described below where under the conditions that the number of rotations of the first ratchet 104, the weight of the second ratchet 105 and the spring constant of the spring 120 (
At low speed rotation, as the first ratchet 104 is rotated, as shown in
The second ratchet 105 is provided with the notch portion 105e as previously described, in which a whirl-stop projection 101a extending from the main frame portion 101 engages this notch portion. And there is a clearance 130a between the notch portion 105e and the projection 101a, in which the rotation angle θ of the clearance 130a is equivalent to the rotation angle α of the back side 104g in the first ratchet 104 as shown in
Thus, at the time of
An impact force at the time of collision is very small, because the second ratchet 105 gets rid of the first ratchet 104 upon a light collision, with a small loss of elastic energy.
Thereafter, the second ratchet 105 further moves forward in a direction to the first ratchet 104, and moves to the right. Consequently, the second ratchet 105 and the first ratchet 104 collide on the front sides 105f and 104f, as shown in
And the second ratchet 105 is moved to the left due to the rotation of the first ratchet 104 at the stage of
At the low speed rotation of
Accordingly, supposing that the relative angle rate between the first ratchet 104 and the second ratchet 105 is zero at minimum, the rotation angle θ is set such that θ>α. That is, the second ratchet is set such that when the first ratchet is in a stopped state, it is supported to be rotatable by an angle or more from the position at which the irregular face of the second ratchet overrides the irregular face of the first ratchet to the position at which the irregular face of the second ratchet engages the irregular face of the first ratchet most deeply. In this way, when the rotation angle rate A of the first ratchet 104 is considerably slow, the left side 105k of the notch portion 105e is not restrained by the left side 101k of the projection 101a, so that the second ratchet 105 can move forward.
Also, the rotation angle may be set such that θ≧0.3α. That is, the second ratchet may be set such that when the first ratchet is in the stopped state, it is supported to be rotatable by 0.6 times an angle or more from the position at which the irregular face of the second ratchet overrides the irregular face of the first ratchet to the position at which the irregular face of the second ratchet engages the irregular face of the first ratchet most deeply. In this way, at the considerably slow rate, the left side 105k of the notch portion 105e and the left side 101k of the projection 101a collide, but the loss of elastic energy can be reduced.
Also, the rotation angle may be set such that θ≧0.3α. That is, the second ratchet may be set such that when the first ratchet is in the stopped state, it is supported to be rotatable by 0.3 times an angle or more from the position at which the irregular face of the second ratchet overrides the irregular face of the first ratchet to the position at which the irregular face of the second ratchet engages the irregular face of the first ratchet most deeply. In this way, at the slightly slow rate, the left side 105k of the notch portion 105e and the left side 202k of the projection 101a collide, but the loss of elastic energy can be reduced.
With first embodiment of the invention, a great impact force is obtained at the high and low speed rotation, whereby the impact drill having the excellent drilling ability is provided.
With this constitution, even if the second ratchet 105 is rotated, a rolling friction with the spring 120 is reduced by the thrust bearing 132a. Also, if the second ratchet 105 is rotated in a state except for the thrust bearing 133b, the spring 120 is rotated together with the second ratchet 105, but a rolling friction with the side wall portion 122 is reduced owing to existence of the thrust bearing 133.
One or both of the thrust bearings 132a and 133b may be employed. Also, the thrust bearing 132a, 133b can be employed only with a ball. With this constitution, the rotation of the second ratchet 105 can be made smoother.
Number | Date | Country | Kind |
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P2004-061806 | Mar 2004 | JP | national |