JP7537239B2 - Power tools - Google Patents

Description

The present invention relates to an electric tool that drives a rotary blade.

In general, handheld electric circular saws operate the rotary blade by pressing a trigger switch on the handle that is held by the hand, and an internal brake is activated by releasing the finger, stopping the rotation of the rotary blade. Although such handheld electric circular saws are heavy, they can basically be operated with one hand, so there is a high possibility that the operator will lose balance while working and cause a cut. Therefore, an electric circular saw that can be operated with both hands to increase safety has been proposed (Patent Document 1).

The invention described in Patent Document 1 describes an electric circular saw that includes a handle portion equipped with a switch for driving a rotary blade, and a grip portion equipped with a locking means for controlling the switch in the handle portion. This invention is structured so that the switch cannot be turned on or off unless the locking means is released with one hand, so the worker must use both hands to operate the handle portion and the grip portion simultaneously, allowing for highly stable work.

Meanwhile, handheld electric circular saws are fitted with a rotary blade that is sized according to the material being cut. However, when the material being cut is a wooden beam used in building construction, the diameter of the rotary blade becomes large, and it takes time to brake the rotary blade. Therefore, even if it is possible to operate it with both hands as in the invention described in Patent Document 1, there is a possibility that the user will lose balance and injure themselves before the rotary blade stops. Therefore, inventions have been proposed that shorten the time it takes for the rotary blade to stop (for example, Patent Document 2).

The invention described in Patent Document 2 describes a handheld electric circular saw that includes a tool that is motor-driven by a rotating shaft and a braking device that brakes the tool. In this invention, the braking time of the rotating shaft can be shortened by pressing the brake portion of the braking device against the peripheral surface of a brake drum fixed to the rotating shaft. In addition, the brake portion is fixed to an operating part that has a return spring, and the brake portion can be easily pressed against the peripheral surface of the brake drum by moving this operating part in a linear direction.

JP 02-303776 A JP2002-59311A

However, with the invention described in Patent Document 2, the operator must move the operating part each time in order to press the brake part against the brake drum, which is time-consuming. In addition, when operating the operating part, the electric circular saw must be supported with one hand, which may cause the operator to lose balance and cause a cut, as mentioned above.

The present invention was made in consideration of the above-mentioned problems, and aims to provide an electric power tool that can be operated with both hands and can shorten the braking time of the rotary blade.

The first electric power tool of the present invention comprises a tool body having a drive unit for driving a rotary blade and a handle portion provided with a trigger switch, a grip switch fixed to the tool body, and an external brake that is activated when the grip switch is released to stop the rotation of the rotary blade, and is characterized in that the drive unit is activated by applying a predetermined operation to the trigger switch and the grip switch, and is stopped by releasing either the trigger switch or the grip switch.

The second electric power tool of the present invention is characterized in that the tool body has a cover covering one side of the rotary blade, the external brake is a disc brake having a brake pad pressed against the one side of the rotary blade and a main body portion that supports the brake pad and presses the brake pad against the rotary blade, and the main body portion is removably fixed to the surface of the cover that is the side opposite to the rotary blade.

The third power tool of the present invention is characterized in that it includes a controller that controls the activation or deactivation of the grip switch and the external brake, and the controller is fixed to the surface of the cover.

According to the first power tool of the present invention, the drive unit is actuated by applying a predetermined operation to both the trigger switch and the grip switch. Therefore, the drive unit cannot be actuated unless the handle is gripped with one hand to operate the trigger switch and the grip switch is gripped with the other hand to operate it, which inevitably requires two-handed operation and improves safety when operating the power tool. In addition, since the rotation of the rotary blade can be directly stopped by an external brake in addition to the operation of the trigger switch and grip switch, the braking time of the rotary blade can be shortened and safety improved.

According to the second power tool of the present invention, the main body of the external brake is removably fixed to the surface of the cover, which is the surface opposite the rotary blade side. Therefore, by removing the main body and the brake pads supported by the main body from the cover, worn brake pads can be easily replaced, improving maintainability.

According to the third power tool of the present invention, the controller that controls the activation or deactivation of the grip switch and the external brake is fixed to the surface of the cover. Therefore, the control of the grip switch and the external brake can be inspected without disassembling the tool body, improving maintainability.

FIG. FIG. FIG. Front view showing external brake A side view of the external brake showing the armature moving. 5 is a schematic diagram showing a current flow in the tool body and a grip switch. FIG. Grip switch electrical circuit diagram. Electrical circuit diagram of the tool body.

The best embodiment of the power tool of the present invention will be described below with reference to the drawings. The power tool of the present application is mainly a handheld electric circular saw, but it can also be an electric tool with a rotary blade such as a grinder. Here, the case of a handheld electric circular saw will be described. Note that the "cover" in the present invention corresponds to the second cover 26 in this embodiment.

As shown in Figures 1 to 3, the electric power tool 1 of the present application includes a tool body 2 having a handle portion 24 provided with a drive portion 22 for driving a rotary blade 21 and a trigger switch 23, a grip switch 3 fixed to the tool body 2, an external brake 4 that is activated when the grip switch 3 is released to stop the rotation of the rotary blade 21, and a controller 5 that controls the activation or deactivation of the grip switch 3 and the external brake 4.

As shown in the figure, the tool body 2 is composed of a disk-shaped rotary blade 21, a drive unit 22, a handle unit 24, a first cover 25 that covers the outer peripheral surface of approximately the upper half of the rotary blade 21, a second cover 26 that covers approximately the upper half of one surface 21a of the rotary blade 21, and a base 27 that is fixed to the lower end of each cover 25, 26 and placed on the upper surface of the workpiece. The drive unit 22 is fixed to the surface 26a of the second cover 26, which is the surface opposite the rotary blade 21 side, and the inside of the protective cover 22a contains a motor M (described later) and an internal brake BR (neither shown) that stops the motor M when it is activated.

The handle portion 24 is a C-shaped member that is gripped during work, and as shown in FIG. 1, it comprises a first horizontal portion 24a extending horizontally, an extension portion 24b extending downward from one edge of the first horizontal portion 24a, and a second horizontal portion 24c extending horizontally from the lower end of the extension portion 24b toward the first horizontal portion 24, and the edges of the first horizontal portion 24a and the second horizontal portion 24c opposite the extension portion 24b side are fixed to the first covering cover 25. In addition, a trigger switch 23 is provided in the recessed corner formed by the first horizontal portion 24a and the extension portion 24b, and can be pressed.

The grip switch 3 shown in FIG. 2 is a grippable rod-shaped member fixed to the tool body 2, protruding from the surface 26a of the second cover 26 in the direction opposite to the rotary blade 21, and its tip is bolted to the protective cover 22a of the drive unit 22. The grip switch 3 can be gripped and rotated.

The external brake 4 shown in Figures 2, 4, and 5 is a typical electric disc brake consisting of a disk-shaped brake pad 41 pressed against one surface 21a of the rotary blade 21, a main body 42 that supports the brake pad 41 and presses the brake pad 41 against the rotary blade 21, an armature 43 fixed to the plate surface of the brake pad 41 on the main body 42 side, a spring pin 44 that connects the main body 42 and the armature 43, and a support plate 45 that supports the main body 42. Inside the main body 42, there are built-in brake coils 42a through which current flows when energized, springs 42b that extend in a direction approximately perpendicular to the plate surface of the brake pad 41, and guide bushes 42c that are provided between the springs 42b and the armature 43.

As shown in FIG. 2, the external brake 4 is installed so that the plate surface of the brake pad 41 faces one surface 21a of the rotary blade 21, and is integrated with the tool body 2 by bolting the main body 42 to the surface 26a of the first cover 26. The first cover 26 has a cutout at the portion where the brake pad 41 and armature 43 are located. The controller 5 shown in FIGS. 1 and 3 is bolted to the surface 26a of the first cover 26, similar to the main body 42 of the external brake 4. In this way, since the controller 5 is installed outside the tool body 2 rather than inside it, inspections of the grip switch 3 and the control of the external brake 4 can be performed without disassembling the tool body 2, improving maintainability.

Next, the control of the power tool 1 will be described with reference to Figs. 6 to 8. As shown in the schematic diagram of Fig. 6, an AC current can be passed through the tool body 2, and a DC current converted from the AC current by the DC power supply PS can be passed through the grip switch 3. When the plug (not shown) attached to the power tool 1 is inserted into an outlet and the grip switch 3 is gripped and rotated as described above, the contacts of the grip switch 3 shown in Fig. 7 are closed, and a DC current flows through the first coil CR1 and the second coil CR. When the first coil CR1 is energized, the first contact CR1a and the second contact CR1b in Fig. 6 linked to the first coil CR1 are closed, and an AC current flows through the tool body 2. When the second coil CR2 is energized, the third contact CR2a and the fourth contact CR2b in Fig. 7 linked to the second coil CR2 are closed, and a DC current flows through the brake coil 42a, generating an electromagnet.

When the trigger switch 23 is pressed with the first contact CR1a and the second contact CR1b closed, the contact of the trigger switch 23 shown in Figure 8 is switched. This contact is a combination of a make contact and a break contact, and when not energized, the contact on the side of the brake coil BR1 built into the internal brake BR of the drive unit 22 is closed, but when the trigger switch 23 is pressed, the contact on the side of the motor M that drives the rotary blade 21 closes, and current flows through the motor M to drive the rotary blade 21. Then, when the trigger switch 23 is released, the contact on the side of the brake coil BR1 closes again, and the internal brake BR brakes the motor M.

On the other hand, when a current flows through the brake coil 42a shown in Figure 5, the generated electromagnet attracts the armature 43 toward the main body 42 against the spring force of the spring 42b, releasing the external brake 4. When the grip switch 3 is released by releasing the switch, the electromagnet gradually weakens, and the spring force of the spring 42b exceeds the electromagnet, causing the armature 43 to press against the brake pad 41. The brake pad 41 is pressed against the rotary blade 21, and the frictional force directly stops the rotation of the rotary blade 21.

Next, the procedure for the worker will be described. After inserting the plug described above into the outlet and energizing the power tool 1, the worker holds the handle 24 shown in FIG. 1 with one hand and holds the grip switch 3 with the other hand. Then, the grip switch 3 is rotated and the trigger switch 23 provided on the handle 24 is pulled to drive the rotary blade 21 and cut the workpiece (not shown). At this time, when the trigger switch 23 is released, the internal brake BR described above is activated to brake the rotary blade 21, as in a conventional electric circular saw. After cutting the workpiece, the two switches are released in the order of the trigger switch 23 and the grip switch 3, and the internal brake BR and external brake 4 are activated to stop the rotation of the rotary blade 21.

In this way, the drive unit 22 of the tool body 1 is not activated unless the trigger switch 23 is pressed and the grip switch 3 is rotated, so that it is necessarily operated with both hands, which improves safety when operating the power tool. In addition, the rotation of the rotary blade 21 can be directly stopped by the external brake 4, separately from the operation of the trigger switch 23 and the grip switch 3, so that the braking time of the rotary blade 21 can be shortened and safety can be improved without waiting for the motor M to be stopped by the internal brake BR of the drive unit 22. Furthermore, since the external brake 4 is activated simply by releasing the hand from the grip switch 3, the operation of the operator can be made easier and the possibility of causing a cut accident can be reduced. As mentioned above, the main body 42 of the external brake 4 is fixed to the second cover 26 with bolts, so that worn brake pads 41 can be easily replaced by removing the main body 41, resulting in a power tool 1 with excellent maintainability.

The embodiment of the present invention is not limited to the above-mentioned embodiment, and can be modified as appropriate without departing from the scope of the concept of the present invention.

The power tool of the present invention can be suitably used as a handheld electric circular saw.

REFERENCE SIGNS LIST 1 Power tool 2 Tool body 21 Rotary blade 21a One surface of the rotary blade 22 Drive unit 23 Trigger switch 24 Handle unit 26 Second cover (cover)
26a Surface of second cover (cover) 3 Grip switch 4 External brake (disc brake)
41 Brake pad 42 Main body 5 Controller

Claims (2)

A tool body having a drive unit for driving the rotary blade and a handle unit provided with a trigger switch;
a grip switch fixed to the tool body;
an external brake that is activated when the grip switch is released to stop the rotation of the rotary blade;
the drive unit is activated by applying a predetermined operation to the trigger switch and the grip switch, and is stopped by releasing either the trigger switch or the grip switch;
The tool body has a covering cover that covers one surface of the rotary blade,
the external brake is a disk brake including a brake pad pressed against the one surface of the rotary blade, and a main body portion supporting the brake pad and pressing the brake pad against the rotary blade,
The power tool, wherein the main body is removably fixed to a surface of the covering cover that is a surface opposite to the rotary blade side. a controller for controlling activation or deactivation of the grip switch and the external brake;
The power tool of claim 1 , wherein the controller is fixed to the surface of the covering cover.

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