JPH0453666A - Motor-driven tool - Google Patents

Abstract

PURPOSE:To prevent an output shaft from popping out even in the case of a retaining ring supporting the output shaft being removed by any chance, by forming a through-hole on the case composing a speed reducer, extending the output shaft from this through-hole via a slight gap, and providing a flange having the outer diameter larger than the inner diameter of the through-hole at the inside of this output shaft case. CONSTITUTION:In case the retaining ring 12 retaining an output shaft 6 is removed by any chance, the output shaft 6 tries to be pulled out of a case 2 but the put shaft 6 being pulled out is checked with the flange 13 equipped at the inside of the case 2 being abutted on the case 2. A bearing 7b can then be protected with this flange 13 checking the dust intruded from the slight gap of the case 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a power tool that includes a tool such as a grindstone on an output shaft extending from a speed reducer.

[Prior Art] In a power tool such as a disc grinder, a tool such as a grindstone is directly attached to an output shaft extending from a reduction gear.

For this reason, the output shaft is subjected to external forces from various directions, and must have sufficient durability against this.

[Problems to be Solved by the Invention] However, in this type of power tool, there is a risk that the output shaft may come out of the case due to the convenience of assembly or the structure.

Generally, a retaining ring or the like is installed inside the case to prevent the retaining ring from moving in the axial direction, but if the retaining ring has assembly or manufacturing defects, it will naturally become ineffective and the restraining force of the output shaft will be reduced due to some external force. Sometimes it disappears and disappears.

That is, the conventional structure is shown in Fig. 2. Fig. 2 is a vertical cross-sectional view of the reducer part of a disc grinder, which is a type of electric tool, and □ constitutes the reducer 1. An output shaft 3 of an electric motor (not shown) extends inside the case 2, and the output shaft 3 is equipped with a full gear 4.

A vehicle gear 5 that meshes with this vehicle gear 4 is attached to an output shaft 6, and both ends of this output shaft 6 are connected to bearings 7.
a, 7b.

Further, the output shaft 6 has a threaded portion 8 formed in a portion extending from the case 2, and is configured to be screwed with a tool such as a grindstone (not shown).

Further, the output shaft 6 is formed with a holding portion 9 for abutting and supporting a tool screwed into the threaded portion 8 .

A slight gap 10 is formed between the support part 9 and the case 2 to prevent dust from entering, and a clearing core 11 is provided between the support part 9 and the bearing 7b.

A retaining ring 12 is attached to the upper part of the output shaft 6, and the retaining ring 12 prevents the output shaft 6 from coming out from the case 2.

However, such a configuration is dangerous because if the retaining ring 12 comes off, the output shaft 6 will easily come out of the case 2.

The output shaft 6 and the retaining ring 12 are each designed to have sufficient mechanical strength, but if there is a slight manufacturing defect or assembly defect, it may cause shocks that may occur in practice. It may come off.

If such an accident were to occur, rotating tools would pose a direct danger to humans, so it was necessary to have a safe structure.

In addition, this type of power tool has another problem with the output shaft 6.
There have also been cases where dust has entered through the gap 10 between the case 2 and the case 2, passed through the clear core 11, and damaged the bearing 7b.

This is especially true when the tool is a grindstone, as it generates a large amount of dust, so countermeasures such as increasing the amount of cleanliness have been resorted to.

In view of these circumstances, the present invention aims to eliminate the conventional problems and provides a power tool that achieves a fail-safe against the danger of the output shaft coming off and protects the bearing. be.

[Means for Solving the Problems] The present invention forms a through hole in a case that constitutes a reducer,
The problem is solved by extending the output shaft from this through hole through a slight gap, and providing a collar having an outer diameter larger than the inner diameter of the through hole on the inside of the case of the output shaft. .

[If the stopper that stops the output shaft comes off, the output shaft will try to come out of the case, but the flange provided inside the case will hit the case and prevent the output shaft from coming out.] prevent.

This flange can protect the bearing by preventing dust from entering through a small gap in the case.

[Embodiment] The present invention will be explained based on an embodiment shown in the drawings. Fig. 1 is a vertical sectional view of a main part of a power tool according to an embodiment of the present invention.

In FIG. 1, the same parts of the power tool as the conventional power tool shown in FIG. It is a point.

In such a configuration, the power tool has a bearing 7b on the output shaft.
is press-fitted, and then the intermediate gear 5 is attached and fixed with a retaining ring 12 so that it does not come off.

Then, a bearing 7a is attached to the output shaft 6 assembled in this way.
Press-fit and store in case 1.

The case 1 is provided with a clear core 11 at a portion where the output shaft 6 extends, and configured to such an extent that the clear core 11 and the collar 13 come into contact with each other.

A through hole 14 through which the output shaft 6 passes is formed in the case 2, and the outside diameter of the collar 13 is larger than the inside diameter of this through hole.

In the power tool assembled in this way, if the stopper 12 comes off, the collar 13 hits the case 2 at the through hole 14, so it will not come off.

Therefore, the output shaft 6 will not come out with the tool attached, and fail-safe is achieved.

Furthermore, the flange 13 acts as a barrier for dust entering through the gap 10 even if it crosses the center 11, so that it does not reach the bearing 7b.

[Effects of the Invention] As described above, according to the present invention, since the flange is formed on the output shaft inside the case, even if the stopper supporting the output shaft comes off, the output shaft will not pop out. , it is possible to realize a fail-safe, protect the bearing from dust, and obtain a safe and long-life power tool, which is extremely effective.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a main part of a power tool according to an embodiment of the present invention. FIG. 2 is a longitudinal sectional view showing the main parts of a conventional power tool. 2...Case, 4.5...Full gear, 6...
Output shaft, 7a, 7b...Bearing, 10-...Gap, 11...Seishin, 12...Shutdown, 13...
Tsuba, 14...through hole.

Claims (1)

[Claims] In a power tool that has a reducer integrated into the electric motor and a tool such as a grindstone on the output shaft of this reducer, a through hole is formed in the case that constitutes the reducer, and the output shaft is inserted through the through hole with a small gap. A power tool comprising: a collar extending through the output shaft and having an outer diameter larger than an inner diameter of the through hole on the inside of the case of the output shaft.