Patent Grant
6951057
The present invention relates to a portable circular saw having a rotatably driven circular saw blade, and more particularly, to a type having an arrangement for controlling a lateral inclination angle of a circular saw blade with respect to a base.
A conventional portable circular saw is shown in
The main body 120 rotatably supports a circular saw blade 21. The saw blade 21 is rotatable about an axis of a saw blade shaft 21A. The main body 120 houses therein an electric motor (not shown) and a power transmission mechanism (not shown) for rotatably driving the circular saw blade 21. Further, a main handle 22 is provided at a top end of the main body 120, and a subordinate handle 23 is provided at a front side of the main body 120. The term “front” and “rear” will be referred to in connection with a cutting direction. A saw cover 124 is provided integrally with the main body 120 for covering an upper half of the circular saw blade 21. Further, a safety cover (not shown) is provided pivotably movably about the saw blade shaft 21A for covering a lower half portion of the circular saw blade 21 during non-operating state. The safety cover is provided with a safety cover lever 25. A user can manually hold the safety cover lever 25 at its suitable angular position for maintaining a pivot position of the safety cover. When cutting a workpiece W from its rear end to its front end, the safety cover is automatically pivotally moved about the saw blade shaft 21A to automatically expose the lower half region of the circular saw blade 21 to an atmosphere. On the other hand, if the circular saw is to be moved from the front end to the rear end of the workpiece for forming a window or a frame hole, the safety cover lever 25 is latched by a user's finger to maintain an open state of the safety cover.
A slant position fixing member 111 upstands from the base 10. The slant position fixing member 111 is positioned at a front side of the base 10 and is provided with a scale or a gauge indicating an inclination angle of the circular saw blade 21 with respect to the base 10. A tiltable plate 126 is provided integrally with the front side of the saw cover 124 and at a position in confrontation with the slant position fixing member 111. The tiltable plate 126 is pivotally movably supported to the slant position fixing member 111 through a pin 12. The pin 12 extends in parallel with the base 10 and in a direction perpendicular to the saw blade shaft 21A. Therefore, the main body 120 is pivotally movable about the pin 12 between its upstanding position shown in
The slant position fixing member 111 is formed with an arcuate slot 111a whose center of radius is coincident with an axis of the pin 12 serving as a pivot shaft of the tiltable plate 126. A fastening unit 30 is provided for fixing the pivot position of the tiltable plate 126 with respect to the slant position fixing member 111 when a tilting angle of the circular saw blade 21 with respect to the base 10 becomes a desired angle. The fastening unit 30 includes a thread and a lever 31. The thread penetrates through the arcuate slot 111a and threadingly engages the tiltable plate 126. The lever 31 is provided at one end of the thread. A base end face of the lever 31 serves as a pressure surface. In accordance with the threading advancing and retracting movement of the thread in accordance with the pivotal movement of the lever 31, the pressure surface of the lever 31 presses against the slant position fixing member 111 or is released therefrom. Because the lever 31 is provided, the thread can be rotated with a reduced force without employing a tool. The lever 31 is directed in parallel with the base 10 when the circular saw blade 21 is directed perpendicular to the base 10.
In use of the portable circular saw 101, when the circular saw blade 21 is directed perpendicular to the base 10 as shown in
On the other hand, if an angled cutting as shown in
However, in case of the angled cutting shown in
In order to prevent the finger from being abutted against the lever 31, the subordinate handle 23 must be displaced rearwardly, i.e., must be positioned closer to the main handle 22. However, with such an arrangement, force imbalance may occur for holding the portable circular saw 101, and further, operability of the portable circular saw 101 in case of forming a window may be remarkably degraded. To be more specific, in cutting operation for forming a window, the safety lever 25 must be manually held at a frontward pivot position as shown in FIG. 14. Here, a hand of a finger that hold the safety cover lever 25 also holds the subordinate handle 23. Therefore, if the subordinate handle 23 is disposed close to the main handle 22, it becomes impossible to hold the safety cover lever 25 at its frontwardly shifting position by the finger of the hand while that hand also holds the subordinate handle 23. Consequently, a desirable cutting operation for forming a window cannot be performed.
Further, the subordinate handle 23 is preferably positioned spaced away from the circular saw blade 21 in the axial direction of the saw blade shaft 21A so as to easily observe the circular saw blade 21 when the operator looks down and peeps into the circular saw blade 21. However, due to the spaced away location of the subordinate handle 23, the rising-up free end of the lever 31 may abut the subordinate handle 23 to lower operability of the subordinate handle 23.
It is an object of the present invention to overcome the above-described problems and to provide an improved portable circular saw capable of providing a sufficient operability and capable of easily observing a cutting direction even in case of the angled cutting.
This and other objects of the present invention will be attained by a portable circular saw including a base, a main body, a slant position fixing member, a tiltable plate, and a fastening unit. The base is to be opposed to a workpiece. The main body rotatably supports a circular saw blade and is pivotally movable relative to the base. The slant position fixing member upstands from the front portion of the base. The slant position fixing member has an abutment surface. The tiltable plate is connected to the main body and is positioned in confrontation with the slant position fixing member and is pivotally movable relative to the base about a pivot axis. The fastening unit includes a thread and a lever member. The thread passes through the slant position fixing member and is threadingly engaged with the tiltable plate. The lever member is provided at one end of the thread and has a pressure surface in pressure contact with the abutment surface of the slant position fixing member for fixing the tiltable plate to the slant position fixing member to maintain a desired slant angle of the circular saw blade with respect to the base. The abutment surface is configured to increase rotation angle of the thread in accordance with an increase in slant angle of the circular saw blade.
In the drawings:
A portable circular saw according to a first embodiment of the present invention will be described with reference to
A portable circular saw 1 according to the first embodiment has a main body 20 substantially the same as the main body 120 shown in
The saw cover 24 has a front end portion pivotally movably connected to a tiltable plate 26 by a pivot pin 27. Further, the tiltable plate 26 is pivotally movable about a pin 12 in a direction indicated by an arrow A. Therefore, an inclination angle of the circular saw blade 21 with respect to a base 10 can be changeable in a direction indicated by the arrow A in accordance with the pivotal position of the main body 20 in the direction A. Thus, angled cutting (
A cutting depth adjusting mechanism 40 is shown in FIG. 3. This mechanism 40 is adapted for controlling and maintaining a desired hip-up posture of the main body 20. A link 41 upstands from an upper rear surface of the base 10 at a position immediately behind the saw cover 24. The link 41 is formed with an arcuate slot 41a whose center of radius is coincident with the pivot pin 27. A clamp lever 42 is pivotally movably provided at a rear portion of the main body 20. The clamp lever 42 is provided with a bolt (not shown) extending through the arcuate slot 41a and threadingly engaging with the saw cover 24. By the pivotal manipulation of the clamp lever 42, a hip up posture of the main body 20 can be fixed or released. For example, in
Further, the subordinate handle 23 is positioned at a front side of the main body 20 in the cutting direction and at a position as low as possible with respect to the main body 20. With this arrangement, the subordinate handle 23 can be positioned spaced away from the main handle 22 for facilitating holding of the portable circular saw 1 in a well-balanced manner during cutting operation.
A fastening unit 30 (described later) includes a thread 32 and a lever 31. The subordinate handle 23 is positioned farther away from the circular saw blade 21 in the axial direction of the saw blade shaft 21A than the thread 32 is from the circular saw blade 21. Therefore, the circular saw blade 21 can be observed easily without obstruction of the subordinate handle 23 when the operator peeps into the circular saw blade 21 during cutting operation.
The slant position fixing member 11 upstands from the front side of the base 10 in the cutting direction. The slant position fixing member 11 has a width W (
The thread 32 of the fastening unit 30 extends through the arcuate slot 11a and threadingly engages the tiltable plate 26, and the lever 31 is connected to one end of the thread 32. The lever 31 has a base end face portion which serves as a pressure surface 33 pressing against the slant position fixing member 11 upon threading advancing and retracting movement of the thread 32 by the pivotal movement of the lever 31 so as to maintain and release the tilting angle of the main body 20. The thread 32 can be rotated about its axis by the lever 31 with a reduced force without any additional tool.
In the illustrated embodiment, the fastening unit 30 and the slant position fixing member 11 are arranged such that the free end of the lever 31 can be positioned at the same level of or lower than the height of the thread 32 upon completion of fastening regardless of the tilting angle of the circular saw blade 21 with respect to the base 10. That is, the slant position fixing member 11 has an abutment surface 11A in pressure contact with the pressure surface portion 33. The abutment surface 11A is a slant surface inclined at a predetermined angle so as to permit the rotation angle of the thread 32 about its axis to increase in proportion to an increase in the tilting angle of the circular saw blade 21.
Taking the above condition in mind, the abutment surface 11A must meet with the following relationship:
z≦y−(θ/360)p
According to this inequality, the thread 32 can at least further rotate by (θ/360)p, which prevents the free end of the lever 31 from being positioned higher than the thread 32. In other words, the free end can still be positioned at the same level of the thread 32 as shown by a position B in FIG. 5. However, if (y−z) is excessively large, rotatable angle of the lever 31 becomes also excessive, and may further be rotated in a clockwise direction in
z≦y−(p/2)−(θ/360)p
With this inequality, maximum pivot position of the lever 31 is shown by the position D in
More specifically, provided that the tilting angle of the circular saw blade 21 is in a range of from 0 degree to 55 degrees, a thread pitch P of the thread 32 is 1 mm, and the thickness y is 10 mm. The abutment surface 11A is configured such that the thickness of the slant position fixing member 11 is gradually small in accordance with an increase in tilting angle of the circular saw blade 21. In case the tilting angle of the circular saw blade 21 is 45 degrees, the thickness z is calculated to 9.875 mm. Further, as shown in
With this arrangement, in cutting the workpiece W from its rear end toward the front end while the posture of the circular saw blade 21 is vertically fixed, the safety cover 28 (
In case of the window formation where the circular saw blade 21 must be moved from the front to the rear of the workpiece W, a finger is latched to the safety cover lever 25 to maintain an open phase of the safety cover 28. That is, during window forming operation, the safety cover lever 25 must be held at its frontward pivot position as shown in
Further, in case of the angled cutting shown in
In case of the angled cutting, since the lever 31 is directed substantially in parallel with the base 10 or the free end of the lever 31 is positioned lower than the thread 32, the workpiece portion immediately in front of the circular saw blade 21 can be easily observed, facilitating cutting while visualizing the marking line M. Further, the finger of the hand pressing the subordinate handle 23 does not abut the lever 31, providing a sufficient operability. This implies that the subordinate handle 23 can be disposed as frontward as possible from the main body 20. As a result, a distance between the main handle 22 and the subordinate handle 23 can be increased as much as possible to provide a balanced holding to the portable circular saw 1. Furthermore, the subordinate handle 23 is positioned remote from the circular saw blade 21 in the axial direction of saw blade shaft 21A as long as possible. In such a case, the finger pressing the subordinate handle 23 does not abut the lever 31.
Further, in any kind of cutting or grooving, the thickness of the slant position fixing member 11 is gradually increased downwardly. Therefore, pressing the main body 20 toward the workpiece W will increase the pressing force of the pressure surface 33 of the fastening unit 30 aginst the abutment surface 11A. Consequently, accidental downward pivotal movement of the tiltable plate 26 together with the pivotal movement of the main body 20 toward the base 10 can be prevented.
Moreover, in case where the main body 20 is oriented in its hip-up posture by adjusting the cutting depth adjusting mechanism 40, the position of the subordinate handle 23 is further lowered. However, since the free end of the lever 31 is not directed upwardly, interference of the finger holding the subordinate handle 23 with the lever 31 can still be avoided, to thus enhance operability.
A portable circular saw according to a second embodiment of the present invention will be described with reference to FIG. 8. In the first embodiment, the slant position fixing member 11 is constituted by a single component in which the abutment surface 11A in pressure contact with the pressure surface 33 is a slant plane whereas another side opposite to the abutment surface 11A is a flat plane extending substantially perpendicular to the base 10. In contrast, in the second embodiment, a slant position fixing member 51 includes a main fixing member 51A whose thickness is uniform in its height, and an adjustment plate 51B having a fixing surface fixed to the main fixing member 51A and a pressure contact surface 51Ba slanted at a predetermined gradient. The adjustment plate 51B can be formed of a light weight metal.
With this arrangement, the main fixing member 51A can be roughly machined as long as the adjustment plate 51B is precisely machined. Thus, the resultant slant position fixing member 51 can be produced easily. If necessary, a sheet like member can be interposed between the main fixing member 51A and the adjustment plate 51B for finely controlling the inclination angle of the pressure contact surface 51Ba.
With this arrangement, a rising-up tendency of the free end of the lever 31 is permitted by the vertical surface 61A at a small tilting angle range of the main body 20, which range will provide a lesser rising-up tendency of the free end. On the other hand, the rising-up tendency is prevented by the slant surface 61B at a greater tilting angle range of the main body 20, which range will provide an increased rising-up tendency unless the slant surface 61B is provided.
More specifically, the first arcuate slot 81a and the second arcuate slot 81b allow the thread 32 to pass therethrough, and have a common center of radius coincident with the pivot axis of the tiltable plate, i.e., the axis of the pin 12 (FIG. 1). The first arcuate slot 81a permits pivotal movement of the circular saw blade 21 from its initial vertical position (zero degree) to 45 degrees. The second arcuate slot 81b has a radius smaller than the radius of the first slot 81a and permits pivotal movement of the circular saw blade 21 from 45 degrees to its maximum slant angle of 55 degrees. An uppermost end of the first arcuate slot 81a and a base end of the second arcuate slot 81b are communicated with each other by a radial slot 81c. Thus, the thread 32 is movable through a cranked path indicated by a dotted chain line in FIG. 11.
A link plate 86 is fixed to the tiltable plate. The link plate 86 is formed with a guide groove 86a having a rectangular shape for allowing the thread 32 to move in the radial slot 81c in a radial direction of the slot 81a or 81b. A thread member 87 threadingly engageable with the thread 32 is disposed slidably within the guide groove 86a and unremovably therefrom. An abutment surface 81A of the slant position fixing member 81 in pressure contact with the pressure surface of the fastening unit 30 is slanted similar to the foregoing embodiments. Incidentally, the thread 32 is positioned at an angle β from the base 10 when the circular saw blade 21 is in its vertical posture. Therefore, angle scale formed in the slant position fixing member 81 is displaced by angle β.
With this arrangement, if the slant angle of the circular saw blade 21 is less than 45 degrees, the thread 32 is moved within the first slot 81a. The lever 31 is fixed when the circular saw blade 21 becomes a desired slant angle.
In order to fix the slant angle of the circular saw blade 21 to 45 degrees, when the thread 32 is moved to the stroke end 81a1 of the first arcuate slot 81a, the thread 32 can be moved radially inwardly within the radial slot 81c. When the thread 32 is manually moved radially inwardly, the thread member 87 in threadingly engaging relation to the thread 32 is slidingly moved within the guide groove 86a in a direction indicated by an arrow E in FIG. 12. Thus, the slant angle 45 degrees of the circular saw blade 21, which angle is the typical angled cutting angle, can be easily provided. Further, the thread 32 can be introduced into the second arcuate slot 81b for providing the slant angle of the circular saw blade 21 more than 45 degrees.
While the invention has been described in detail with reference to specific embodiments thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention.
For example, the pressure contact surface 51Ba of the adjusting plate 51B in the second embodiment can be formed into stepped surfaces of the fifth embodiment. Further, the pressure contact surface 51Ba of the second embodiment can have a vertical plane and a slant plane corresponding to the vertical plane 61A and slant plane 61B of the third embodiment.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2002-007795 | Jan 2002 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 2543486 | Briskin | Feb 1951 | A |
| 3292673 | Gregory | Dec 1966 | A |
| 5121545 | Nonaka et al. | Jun 1992 | A |
| 5452515 | Schilling | Sep 1995 | A |
| 5570511 | Reich et al. | Nov 1996 | A |
| 6202311 | Nickels, Jr. | Mar 2001 | B1 |
| 6601305 | Fukuoka | Aug 2003 | B1 |
| 20010037578 | Mori et al. | Nov 2001 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20030131484 A1 | Jul 2003 | US |
