BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to a handheld electric grinder and, more particularly, to multifunction handheld electric grinder.

2. Description of Related art

As shown in FIG. 1, a conventional handheld electric grinder 12 is a common tool, and is primarily used in polishing. Most conventional handheld electric grinders are of high rotating speeds. In order to allow handheld electric grinders to possess various polishing speeds, some conventional handheld electric grinders have an adjustment button to control the rotating speed.

However, conventional handheld electric grinders can only be used in polishing, but cannot apply to other fields because of their mechanism design. In order to expand the application range of handheld electric grinders so that they can deal with more diversified jobs, the present invention aims to provide an improved handheld electric grinder.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a handheld electric grinder, in which a mechanism is externally joined on the main body thereof. This mechanism is joined on the surface of the main body of the handheld electric grinder by means of screw fitting, snap fitting, or button fitting to enhance the joining strength between them.

Another object of the present invention is to provide a handheld electric grinder, which makes use of a speed-change gear set to output different rotating speeds by changing the rotating speed of a drive shaft so as to match various front-end accessories, thereby saving the cost.

Yet another object of the present invention is to provide a handheld electric grinder, which makes use of a push-button device to control the rotation of a drive shaft. Before changing the front-end accessory, the user can apply a force to the push-button device to let the drive shaft be unable to rotate. The user can then successfully detach and replace the front-end accessory.

To achieve the above objects, the present invention provides a handheld electric grinder, which comprises a first shell body and a second shell body. The first shell body contains an electric motor and a rechargeable battery area therein, and is connected to the electric motor via a drive shaft. The electric motor is driven to let the drive shaft generate a first rotating speed. A first adapter is disposed at one end of the drive shaft. The first adapter can be directly connected with accessories such as electric grinding head and brush, or can be connected with a connector of a speed-change gear set in the second shell body. After the speed-change gear set changes the first rotating speed to a second rotating speed, a driven shaft outputs the second rotating speed. The first adapter and the second adapter can be connected with accessories such as hexagonal socket, screwdriver, brush and electric grinding head.

The first shell body and the second shell body have a first connection portion and a second connection portion thereon, respectively. The first connection portion and the second connection portion are connected together by means of one or the combination of two of button fitting, snap fitting, and screw fitting to enhance the joining strength between them. A push-button device is disposed on the first shell body to control the rotation of the drive shaft. Before changing the front-end accessory, the user can apply a force to the push-button device to let the drive shaft be unable to rotate. The user can then successfully detach and replace the front-end accessory.

BRIEF DESCRIPTION OF THE DRAWINGS

The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which:

FIG. 1 is a diagram of a handheld electric grinder in the prior art;

FIG. 2 is a perspective view of a handheld electric grinder of the present invention;

FIG. 3 is a cross-sectional view of a handheld electric grinder of the present invention;

FIG. 4 is a cross-sectional view of the front section of a handheld electric grinder of the present invention;

FIG. 5 is a cross-sectional view of the rear section of a handheld electric grinder of the present invention; and

FIG. 6 is a perspective view of a handheld electric grinder according to another embodiment of the present invention.

REFERENCE NUMERALS

22: first shell body
24: second shell body
26: first connection portion
28: second connection portion
30: electric motor
32: drive shaft
34: first adapter
36: fan
38: switch
40: battery area
42: battery
44: power cord
46: AC/DC adapter
48: connector
50: speed-change gear set
52: driven shaft
54: second adapter
58: positioning hole
60: push-button device
62: elastic component
64: screw-fitting device

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIGS. 2 and 3, a handheld electric grinder of the present invention comprises a first shell body 22 (front-end part) and a second shell body (rear-end part). A first connection portion 26 is disposed on the surface of the first shell body 22. A second connection portion 28 is disposed on the surface of the second shell body 24. The first connection portion 26 and the second connection portion 28 are connected together by means of one or the combination of two of button fitting, snap fitting, and screw fitting.

Exemplified with the combination of screw fitting and snap fitting, the first connection portion 26 includes a first thread and a first snap-fitting portion, and the second connection portion 28 includes a second thread and a second snap-fitting portion that match the first connection portion 26. When the first connection portion 26 and the second connection portion 28 are connected together, they are first screw fitted and then snap fitted together, or first snap fitted together and then screw fitted. All these variations are embraced within the scope of the invention. This kind of design can enhance the joining strength between them.

As shown in FIG. 4, an electric motor 30, which can be a DC motor, is located in the first shell body 22. One end of a drive shaft 32 is connected with the electric motor 30, and the other end is a first adapter 34. The drive shaft 32 protrudes out of the first shell body 22. When the electric motor 30 is driven to rotate, the drive shaft 32 is led to generate a first rotating speed. The drive shaft 32 has a fan thereon for radiating heat. The other end of the electric motor is connected to a switch 38, which sticks out of the outer surface of the first shell body 22.

A push-button device 60 is disposed on the first shell body 22 to control the rotation of the drive shaft 32. Before changing the front-end accessory, the user can apply a force to the push-button device 60 to let the drive shaft 32 be unable to rotate. The user can then successfully detach and replace the front-end accessory. An elastic component 62 is fixed on the first shell body 22 to support the actuation of the push-button device 60. In this embodiment, the elastic component 62 is a reed.

The switch 38 controls whether a battery 42 placed in a battery area 40 of the first shell body 22 is electrically connected to the electric motor 30 or not. The battery 42 can be a primary battery or a secondary battery. The battery 42 is used to drive the electric motor 30. A power cord 44 extends outwards from within the battery area 40, and an AC/DC adapter 46 is disposed on the power cord 44. When the other end of the power cord 44 is plugged in a power socket, the secondary battery 42 can be recharged. When the switch 38 is on, the battery 42 and the electric motor 30 are close-circuit; when the switch 38 is off, the battery 42 and the electric motor 30 are open-circuit.

Moreover, the switch 38 is connected with a locking device, which is used to lock the state of the switch 38 to be always-on or always-off. The user can directly stir the locking device to control the state of the switch 38.

The operation manner of the above handheld electric grinder is illustrated below. First, the user determines whether to plug the power cord 44 of the handheld electric grinder with a power socket or not. The user then controls the on/off state of the switch 38 to drive the electric motor 30 to rotate. The electric motor 30 rotates to generate a first rotating speed. Based on the accessory connected with the first adapter 34, the handheld electric grinder can be applied in different situations.

The first adapter 34 can be connected with a different front-end accessory such as electric grinding head or a brush. The shape and position of the first adapter 34 can vary. For instance, the first adapter 34 can be of a cross-groove shape, a hexagonal shape, or a circular shape. All these variations are embraced within the scope of the invention. After the components in the first shell body 22 are assembled, the structure can be used as a standalone handheld electric grinder. If the first rotating speed is to be changed, the second shell body 24 and components therein can be attached to the first shell body 22. The second shell body 24 contains devices that can change the first rotating speed to a second rotating speed therein.

As shown in FIG. 5, a speed-change gear set 50 is disposed in the second shell body 24. Two sides of the speed-change gear set 50 are connected with a connector 48 and a driven shaft 52, respectively. The driven shaft 52 protrudes out of the second shell body 24. A second adapter 54 is disposed at the other end of the driven shaft 52. The second adapter 54 is used to connect a front-end accessory such as a hexagonal socket, a screwdriver, a brush, or an electric grinding head. The speed-change gear set 50 is a planetary gear set. A positioning hole 58 is formed on the second shell body 24. When the speed-change gear set 50 is arranged in the second shell body 24, a movable positioning clip 56 slides in the positioning hole 58 to fix the speed-change gear set 50 with the second shell body 24.

When the second shell body 24 and the first shell body 22 are connected together, a screw-fitting device 64 at the lapping position of the connector 48 and the first adapter 34 is used to fix the connector 48 and the first adapter 34. Because the connector 48 laps the first adapter 34, the first rotating speed output by the drive shaft 32 can be sent to the speed-change gear set 50. The speed-change gear set 50 changes the first rotating speed to the second rotating speed that is output by the driven shaft 52. Collocated with different front-end accessories such as hexagonal socket, screwdriver, brush, and electric grinding head, the handheld electric grinder can carry out various kinds of operations.

Besides, the speed-change gear set 50 can be an accelerating gear set or a decelerating gear set. When the speed-change gear set 50 is an accelerating gear set, it increases the first rotating speed to the second rotating speed. When the speed-change gear set 50 is a decelerating gear set, it decreases the first rotating speed to the second rotating speed.

The operation manner of the above handheld electric grinder with the rear section attached thereto is illustrated below. The user first connects the front section and the rear section of the handheld electric grinder together, and then determines whether to plug the power cord 44 of the handheld electric grinder with a power socket or not. Next, the user controls the on/off state of the switch 38 to drive the electric motor 30 to rotate. The electric motor 30 rotates to generate a first rotating speed. Through the acceleration or deceleration of the speed-change gear set 50, the first rotating speed is changed to a second rotating speed. The second adapter 54 is connected with various kinds of front-end accessories such as hexagonal socket, screwdriver, brush and electric grinding head.

FIG. 6 is a perspective view of a handheld electric grinder according to another embodiment of the present invention. The internal structure of this embodiment is the same as that of the first embodiment. They only differ in the outer appearance and the connection manner of the first connection portion 26 and the second connection portion 28.

Although the present invention has been described with reference to the preferred embodiment thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have been suggested in the foregoing description, and other will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.