Patent Application
20160243693
The present invention relates to an electric handheld sanding tool and particularly to an electric handheld sanding tool equipped with a cooling fan between an electric motor and a circuit module to provide cooling of the electric motor and the circuit module to improve cooling efficiency.
Advance of mechanical hand tool technology has gradually adopted electric power as the main driving source of hand tools to replace those driven by pneumatic power to overcome the problem of the pneumatic hand tools of unable to function in high speeds.
However, the mechanical hand tool using the electric power rather than the pneumatic power encounters first a problem of element cooling efficiency. In the past the pneumatic mechanical hand tool can perform heat exchange through working air at the same time without accumulating waste heat in the mechanical hand tool. But the electric mechanical hand tool uses an electric motor to get working power. In the event that the mechanical hand tool does not have a heat convection design the electric motor and other related elements could easily accumulate waste heat and result in abnormal conditions.
Hence, the present mechanical hand tool industry has devoted a great deal of research and efforts trying to improve cooling efficiency of the hand tools. For instance, China patent No. CN201371407Y and European patent No. EP1285727B1 disclose a technique by deploying an air fan in a casing of a mechanical hand tool. However, the air fan mainly aims to provide cooling of a sanding element of the mechanical hand tool by dispersing waste heat generated during high speed spinning of the sanding element. But on the electric hand tool driven electrically, aside from the waste heat generated by the sanding element, the electric motor and its related control module also generate waste heat. If the electric motor and the related control module do not have proper cooling waste heat will accumulate in the casing of the mechanical hand tool and temperature will rise, and could result in the electric motor and the control module unable to function at a desired working temperature, and abnormal operation tends to take place easily.
The primary object of the present invention is to solve the cooling problem of the conventional sanding hand tool resulted from switching from pneumatic driving to electric driving.
To achieve the foregoing object the present invention provides an electric handheld sanding tool with improved cooling efficiency. It includes a host body and a sanding assembly. The host body includes a body and a handgrip extended from the body. The body has a housing space inside. The sanding assembly includes an electric motor located in the housing space to output driving power through a transmission shaft and a circuit module coaxial with the electric motor and connected to external power to control operation of the electric motor. The transmission shaft at one end where the circuit module is located is defined as a first transmission portion and another end opposing the circuit module as a second transmission portion. The second transmission portion is connected to a sanding element which is exposed outside the host body and driven by the second transmission portion to generate sanding motion. The circuit module and the electric motor are interposed by a cooling fan located on the first transmission portion. The cooling fan has a baseboard, an axial coupling portion located on the baseboard and connected to the first transmission portion, a plurality of vanes located on the baseboard and centered about the axial coupling portion in a radial fashion, and an airflow orifice. The body of the host body has at least one air outlet corresponding to the vanes. The body further has at least one air inlet corresponding to either of the circuit module and the electric motor such that the transmission shaft can be driven by the circuit module to synchronously drive the first transmission portion and the second transmission portion to drive the sanding element and the cooling fan. And the vanes spin to draw cold airflow through the air inlet to pass through the airflow orifice and dispel operation heat generated by the electric motor and the circuit module via the air outlet.
In one embodiment the body of the host body has the air inlet corresponding respectively to the circuit module and the electric motor.
In another embodiment the circuit module has a heat transmission element facing the cooling fan to dispel the operation heat generated by the circuit module through the cold airflow drawn in by the vanes.
In yet another embodiment the circuit module includes a control unit located in the body coaxial with the electric motor and a power supply unit located in the handgrip and connected to the control unit to get working power from the external power to perform power transformation.
In yet another embodiment the electric motor includes a bearing located on at least either one of the first transmission portion and the second transmission portion.
In yet another embodiment the baseboard of the cooling fan is located at one side thereof facing the circuit module, and the vanes are located at another side facing the electric motor.
In yet another embodiment the baseboard of the cooling fan is located at one side thereof facing the electric motor, and the vanes are located at another side facing the circuit module.
In yet another embodiment the baseboard has a plurality of connection ribs centered about the axial coupling portion to define the airflow orifice.
In yet another embodiment the sanding element is a sand cloth belt which is perpendicular to the axial direction of the electric motor and extended to expose outside the host body.
In yet another embodiment the electric sanding handheld tool further includes a dust cover coupled with the host body and partially covered the sanding element.
In yet another embodiment the dust cover includes a hood and an opening formed on the hood to allow the sanding element to pass through.
In yet another embodiment the hood has an air inlet corresponding to the second transmission portion, and the electric sanding handheld tool includes an auxiliary air fan coupled on the second transmission portion corresponding to the air inlet and driven by the transmission shaft to draw the cold airflow from the air inlet to dispel operation heat generated by the sanding element through the opening.
The invention, by means of the structure set forth above, compared with the conventional techniques, can provide advantageous features as follows:
1. By deploying the cooling fan between the electric motor and the circuit module, and through the corresponding air outlet and the air inlet, while the electric motor is spinning the cooling fan can synchronously draw cold airflow to disperse heat from the electric motor and the circuit module.
2. The heat transmission element is located corresponding to the cooling fan, hence the spinning vanes can provide the cold airflow to disperse operation heat of the circuit module.
3. The invention provides an auxiliary air fan moved synchronously with the transmission shaft to provide cooling for the sanding element located on the second transmission portion, therefore can reduce operation heat generated by the sanding element during sanding motion.
Please referring to
Based on the structure set forth above, the electric motor 21 has a transmission shaft 211 to output driving power. The transmission shaft 211 has a first transmission portion 212 defined at one end where the circuit module 22 is located and a second transmission portion 213 at another end opposing the circuit module 22. The second transmission portion 213 is exposed outside the body 10 and coupled with the sanding element 23. When the electric motor 21 is in operation it drives the sanding element 23 to generate sanding motion. Also referring to
In addition, the cooling fan 30 is provided on the first transmission portion 212 between the circuit module 22 and the electric motor 21. The cooling motor 30 includes a baseboard 31, an axial coupling portion 32 located on the baseboard 31 and connected to the first transmission portion 212, a plurality of vanes 33 centered about the axial coupling portion 32 and arranged in a radial fashion, and an airflow orifice 34. The cooling fan 30 can be adjusted in position according to airflow design. In one embodiment the baseboard 31 is located at one side of the cooling fan 30 facing the circuit module 22 and the vanes 33 are located at another side facing the electric motor 21; or the baseboard 31 is located at one side of the cooling fan 30 facing the electric motor 21 and the vanes 33 are located at another side facing the circuit module 22. Moreover, the baseboard 31 can have a plurality of connection ribs 35 centered about the axial coupling portion 32 to define the airflow orifice 34. In addition, the body 11 has at least one air outlet 112 corresponding to the vanes 33, and at least one air inlet 113 corresponding to either of the circuit module 22 and the electric motor 21.
Based on the implementation fashion of the air inlet 113 corresponding to the electric motor 21 an embodiment example is discussed as follows. Please referring to
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As a conclusion, the invention mainly includes a host body and a sanding assembly. The sanding assembly is installed in the host body and includes an electric motor, a circuit module and a sanding element. The circuit module and the electric motor are interposed by a cooling fan moving synchronously with the electric motor. The host body has at least one air outlet corresponding to the cooling fan, and at least one air inlet corresponding to either of the circuit module and the electric motor so that while the electric motor is driven by the circuit module the sanding element and the cooling fan also are driven at the same time. The cooling fan spins to draw in cold airflow through the air inlet to pass through the airflow orifice to dispel the operation heat generated by the electric motor and the circuit module through the air outlet, thus can provide improvement to resolve the problem of heat accumulation of the conventional sanding hand tool caused by switching from pneumatic driving to electrical driving.
While the preferred embodiments of the invention have been set forth for the purpose of disclosure, they are not the limitation of the invention, modifications of the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention.
