This non-provisional patent application claims priority under 35 U.S.C. §119(a) from Patent Application No. 0723914.8, filed in Great Britain on Dec. 7, 2007.
The present invention relates to cooling systems for power tools and in particular is relevant to cordless power tools.
A cordless power tool such as a drill is typically constructed with working components such as a motor and drill shaft being located in an upper generally cylindrical casing. A handle extends from below the cylindrical casing and is typically provided with a battery pack at its bottom end. Wiring from the battery pack typically extends up through the handle to electrical circuitry located either in the handle or the motor compartment.
U.S. Pat. No. 6,455,186 describes a battery cooling system for a cordless power drill in which air is drawn into intake openings in the main casing through a passage in the handle through passages in the battery casing and out through openings in the battery casing. A fan is located in the handle or battery casing to provide circulation of air over the batteries.
The present invention provides an alternative type of cooling system for a power tool.
According to a preferred embodiment of the invention a cooling system in accordance with the present invention provides improved cooling of heat generating components of the power tool.
Accordingly, in one aspect thereof, the present invention provides a power tool having a cooling system, comprising: a motor housing having a main chamber, a tool motor accommodated within the main chamber, a handle for holding the power tool, the handle having a cooling passage for the transfer of cooling fluid, an inlet leading to the cooling passage and an outlet leading away from the cooling passage, and a power tool component which generates heat, disposed in the handle, in thermal contact with the cooling passage between the inlet and the outlet.
Preferably, the power tool further includes a flow induction device for inducing flow of cooling fluid from the inlet to the outlet.
Preferably, the flow induction device is located at least partially in the main chamber of the cooling passage.
Preferably, the flow induction device comprises one or more fans.
Preferably, the flow induction device is a fan driven by the power tool motor.
Preferably, the power tool component is a speed control circuitry.
Preferably, a heat sink for the speed control circuitry is located at least partially in the cooling passage.
Optionally, the flow induction device is a fan mounted on the heat sink.
Preferably, a battery casing is provided, having one or more of said inlets and accommodating a number of batteries, and the handle extends between the main chamber and the battery casing.
Preferably, the cooling passage comprises a cooling conduit of high heat transfer material and wherein a heat sink of the power tool component is directly attached to the cooling conduit.
Alternatively, a heat pipe is disposed in the cooling passage, the heat pipe being in direct contact with a heat sink of the power tool component.
Alternatively, the cooling passage comprises a rubber tube and further includes a heat transfer box connected to the rubber tube and at least partially housing a cooling portion of the power tool component.
Preferably, the cooling portion of the power tool component comprises fins of a heat sink.
According to a second aspect, the present invention provides a power tool having a cooling system, comprising: a motor housing having a main chamber, a tool motor accommodated within the main chamber, a handle for holding the power tool, a heat pipe accommodated in the handle, and a power tool component which generates heat, disposed in the handle, wherein the power tool component is in thermal contact with the heat pipe.
Preferably, the heat pipe is cooled by a flow of cooling air within the main chamber.
Preferably, the heat pipe makes thermal contact with a heat sink of a battery attached to the handle
Preferably, the flow induction device may have a dedicated source of power.
Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:
A number of horizontal ventilation slots 13 are provided in a vertical column on each side of the housing 11 in order to provide ventilation for the chamber 14. These ventilation slots 13 are located behind the motor 12 and may serve as air inlets and/or outlets. Additional ventilation slots 13 may be provided adjacent the motor 12.
A handle 15 extends below the housing 11 and includes a passage 16 which extends from the chamber 14 to a battery casing 17 at the bottom of the handle 15. Air inlet passages 18 are located through the handle 15 and lead directly into passage 16. An opening 19 is also located in the bottom of the handle to allow air flow from inside the battery casing to the passage 16. The battery casing accommodates a power tool battery which may be in the form of a number of battery cells.
A trigger switch 20 is located under housing 11 in a front upper section of handle 15. Speed control circuitry 21 is connected behind the trigger inside the handle and is provided with a heat sink 22 to assist with dissipation of heat. The speed control circuitry 21 represents a power tool component 21 which generates heat. At least the fins of the heat sink 22 are located within the cooling passage 16 to dissipate the heat from the speed control circuitry.
In accordance with the embodiment shown in
As shown in
According to a fourth embodiment of the present invention shown in
A fifth embodiment of the present invention as shown in
According to a sixth embodiment of the invention, as shown in
In summary in the third embodiment of the invention an external flow induction device (fan) may be located outside the housing 11 to draw air up through passage 16 and out through opening 25. Alternatively, an external blower (fan) may be attached at the lower end of the handle 15 to blow air through passage 16 and out through slots 13.
According to a seventh embodiment of the invention, as shown in
It is noted that inlet passages 18 are located through the handle 15 and through the tube 30.
It is preferred that the tubes parts 30 and 31 are fixed to respective hollow spigots forming the openings in the upper and lower walls 32, 33.
The box 34 provided in the above variation allows a simple method for configuring the heat sink 22 and tube 30 so that a cooling system can be incorporated into the power tool.
In the variation described above the box 34 may be configured so that once the fins of the heat sink 22 are located inside it the box is sealed with a sealant or equivalent to ensure fluid passing through the tube 30 does not escape from the box 34. However, this is not essential and some air leakage may provide an advantage in some situations.
According to an alternative embodiment of the invention the box 34 is not sealed and the fins of the heat sink 22 are located partially or fully inside the box 34. The box 34 may have an open back face as well as an open front face.
According to an eighth embodiment of the present invention as shown in
The heat pipe shown in
According to one embodiment of the invention, the heat pipe 39 is cooled at one end by blowing air over it or sucking air from the immediate vicinity. In such an embodiment it would be preferred that this occurs within the chamber 14 of the motor housing 11.
In
It should be noted that although embodiments have been described in which cooling has been achieved utilising fans or impellers, any device which is able to initiate fluid flow is also encompassed by the invention. For example this includes blowing and sucking devices such as those that include moving diaphragms or bellows.
According to any one of the previously disclosed embodiments, air movement is achieved utilising one or more air pumps.
According to a further embodiment of the present invention transfer of heat from within the power tool is enhanced by providing a heat transfer means through the battery casing 17. As shown in
In addition to the above it is noted that any device utilised for initiating flow of fluid within the cooling system may be powered by its own power supply or from the power supply of the power tool. Other options also include utilising the power of the power tool motor shaft, compressed air or any other driving means.
In addition to the above it is noted that additional outlets may be provided in housing 11 to provide additional avenues for exit of heated air.
In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.
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0723914.8 | Dec 2007 | GB | national |
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