Patent Application
20140251105
The present disclosure relates to portable or bench top power tools, such as a miter saw, and particularly to a safety mechanism to prevent damage to the saw blade.
In a typical power tool, the working tool is specifically adapted to the type of material being cut. For instance, in a woodworking miter saw the saw blade is configured to cut various grades and densities of wood. The saw blade material is chosen to efficiently perform the cut, endure the typical high rotational speeds of operation and have a suitable blade life before the saw teeth become too dull to use. As long as the saw blade only encounters the expected wood material the blade will perform well over its expected life. However, workpieces are often contaminated with a non-wood body, and particular a metallic body such as a staple, nail, wire and the like. When the rapidly rotating saw blade encounters the metallic contaminant the teeth of the blade can be irreparably damaged or in a worst case scenario striking the metallic contaminant can cause workpiece kick-back or otherwise dislodge the workpiece from the work surface of the power tool.
There is a need for a safety mechanism that can detect the presence of a metallic contaminant before the workpiece is engaged by the working tool.
A power tool is provided that comprises a base defining a work surface for supporting a workpiece and a tool assembly supported on the base and having a working tool configured to perform an operation on the workpiece when it is supported on the work surface. In one aspect of the present disclosure, a sensor is supported by the base in proximity to the work surface that is configured to detect a ferrous contaminant in the workpiece. The sensor is arranged relative to the work surface to detect the contaminant in the workpiece when the workpiece is supported on the work surface for operation by the tool assembly. The sensor is operable to generate a signal when a contaminant is detected and to provide that signal to a user interface that is configured to generate an output sensible by the operator of the power tool when the sensor detects a contaminant.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the invention is thereby intended. It is further understood that the present invention includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the invention as would normally occur to one skilled in the art to which this invention pertains.
A portable power saw 10 is shown in
According to the present disclosure, a number of sensors are integrated into the base assembly 20 to detect the presence of a ferrous contaminant in a workpiece to be cut by the miter saw 10. Thus, a sensor 50 may be disposed immediately adjacent the gap 32 in the fence assembly through which the saw assembly passes during the cut. In one embodiment, the sensor 50 is a magnetic sensor having a sensor field F that projects above the work surface 22 and that has a range sufficient to detect a ferrous contaminant C at the uppermost portion of a workpiece W, as depicted in
It can be appreciated that the base assembly 20 must be formed of a non-ferrous material to avoid detection by the sensor. It may also be necessary for the fence 30 to be formed of a non-ferrous material if the sensor is close enough to the fence for the field F to intersect the fence. As is typical with portable miter saws of the type shown in
The sensor 50 may be of the type used in magnetic locators, such as the Magna-Trak 102 locator sold by CST Corporation. The Magna-Trak 102 locator utilizes a pair of sensor coils, such as coils 50a and 50b, that each generate a corresponding magnetic field Fa and Fb, as illustrated in
In one embodiment, the sensor 50 may be configured to simply detect the presence of a ferrous contaminant and to provide a signal to a user interface 60. The sensor can thus include circuitry and/or a microprocessor to evaluate signals from the sensor components (such as coils 50a, 50b) and to generate a signal(s) usable by the interface 60. The sensor may further include circuitry and/or a microprocessor configured to eliminate a false-positive, such as by comparing the sensor signal to a predetermined threshold value. The user interface 60 may include circuitry and/or a microprocessor configured to process the sensor signal(s) to generate a sensible output, such as an audible or a visual alert. In one embodiment, the user interface may include an indicator light, such as a red light, which is positioned at a location that is clearly visible to the tool operator so that the alert cannot be missed prior to activating the power tool. Alternatively, or in combination, the interface may generate an audible alarm signal, although the audible alarm must be loud enough to be heard when the saw assembly has been activated. In yet another alternative, the user interface 60 may include a processor that is integrates with the control circuitry for the power tool to prevent activation of the saw assembly and/or to cut power to the saw assembly, thereby preventing the cut from being made. This alternative may be less desirable because the operator may be aware of the ferrous contaminant and will deliberately avoid the contaminant during the cut.
The sensor 50 may be configured to generate a variable signal to help precisely locate the ferrous contaminant. For instance, a sensor such as the Magna-Trak 102 locator is configured to generate a signal that varies in intensity in relation to the proximity of the ferrous material to the pair of magnetic fields. Thus in one mode of operation of the contaminant detection system disclosed herein, the tool operator may position the workpiece on the sensor 50 prior to activating the saw assembly to determine if a contaminant is present. If the user interface 60 presents a “contaminant present” signal, the operator may move the workpiece across the sensor and evaluate the variable signal to locate the contaminant. In some embodiments, the sensor or user interface may be configured to provide a numerical read-out indicating the depth of the contaminant in the workpiece. The operator may then remove the contaminant or may simply mark the location of the contaminant so that the location can be avoided during the ensuing miter cut.
The power tool 10 may be provided with additional sensors, such as sensor 51, disposed at different locations on the base assembly 20 and/or fence assembly 30. Multiple sensors can be used to help locate the position of a ferrous contaminant in the workpiece or may provide a wider or tailored detection range.
The sensor(s) 50, 51 may be mounted to the base so that it is flush with or immediately adjacent the underside of the work surface 22. In order to provide the most useful indication of the location of the contaminant, the sensor(s) are preferably located immediately adjacent the slot 25, in the case of a power saw, or immediately adjacent the path of the working tool for other types of power tools. The user interface 60 may be mounted to the base assembly, saw assembly, handle, motor housing, or may be provided as a stand-alone component that is electrically connected to the sensor(s) 50, 51. The user interface may incorporate a processor that receives a signal from the sensor(s) and activates the sensible output. The processor may be an analog component such as a switch that is triggered by a signal generated by the sensor(s), the switch providing electrical power to the sensible output. Alternatively, the processor may be a more sophisticated microprocessor that receives and evaluates the signal generated by the sensor(s) to control the sensible output accordingly. The processor may be integrated into an existing processor of the power tool forming part of a safety system for the tool.
The present disclosure contemplates a power tool having a work surface for supporting a workpiece and for supporting a tool assembly, such as a miter saw assembly, in which a ferrous material sensor is associated with the work surface that is operable to detect the presence of a ferrous contaminant in the workpiece prior to being contacted by the tool assembly. It can be appreciated that although the illustrated embodiment is a power saw, other tools are contemplated for use with the workpiece contaminant sensor 50 disclosed herein. For instance, the tool may be a power drill rather than a saw.
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same should be considered as illustrative and not restrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications and further applications that come within the spirit of the invention are desired to be protected.
This application claims priority under 35 U.S.C. §119 to U.S. Provisional Application No. 61/776,571, filed on Mar. 11, 2013, the disclosure of which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61776571 | Mar 2013 | US |
