Patent Publication Number: US-7722435-B2

Title: Sander

Description:
FIELD 
   The present disclosure relates to power sanders and more specifically to a power sander with a visual indicator that provides visual feedback to a user indicative of the magnitude of a pressing force that is exerted by a user onto the sander. 
   BACKGROUND 
   Power sanders are used in a wide variety of applications such as woodworking. One factor important to achieving satisfactory results is providing a proper amount of pressing force onto the workpiece during sanding. For example, a user should ensure that they do not bias the sanding paper too heavily in one area as opposed to others to avoid a displeasing finish and/or surface irregularities. In addition, it is desirable to achieve optimum performance from the sander to complete a given job more efficiently. Accordingly, there remains a need in the art for providing a sander having user feedback indicative of an amount of user bias being applied to a workpiece. 
   SUMMARY 
   A sander can include a housing, an indicator disposed on the housing, and a motor assembly in the housing. The motor assembly can include an output member. A platen can be driven by the output member. A sensor assembly can be configured to sense a condition in which a pressing force in excess of a predetermined force is applied to the sander in a direction normal to the platen and generate a sensor signal in response thereto. A controller can receive the sensor signal from the sensor assembly and control operation of the indicator in response thereto. 
   The sensor assembly can include a force sensing resistor. The force sensing resistor can be disposed adjacent to a gripping portion of the power sanding tool. The indicator can include at least one light source. The controller can illuminate the light source according to a schedule. The schedule can include at least two distinct illumination techniques. The first illumination technique can be selected by the controller when the magnitude of the force transmitted between the platen and the workpiece is greater than or equal to a first predetermined threshold. A second illumination technique can be selected by the controller when the magnitude of the force transmitted between the platen and the workpiece is less than the first predetermined threshold. The gripping portion can include a gel-like material. 
   Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 

   
     DRAWINGS 
     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
       FIG. 1  is a perspective view of an exemplary power sander tool constructed in accordance with the teachings of the present disclosure; 
       FIG. 2  is a sectional view of the sander of  FIG. 1  taken along line  2 - 2 ; 
       FIG. 3  is a detailed perspective view of a visual indicator of the sander of  FIG. 1 , shown with a lens of the visual indicator removed for illustration; 
       FIG. 4  is a sectional view of a power sander tool constructed in accordance to additional features of the present disclosure; 
       FIG. 5  is a perspective view of an exemplary power sander tool constructed in accordance to additional features of the present disclosure; 
       FIG. 6  is a sectional view of the sander of  FIG. 5  taken along line  6 - 6 ; 
       FIG. 7  is a rear perspective view of a lens of the visual indicator constructed in accordance to additional features of the present disclosure; and 
       FIG. 8  is a cross-section of the lens taken along line  8 - 8  of  FIG. 7 . 
   

   DETAILED DESCRIPTION 
   With initial reference to  FIGS. 1 and 2 , an exemplary sander constructed in accordance with a first example of the present teachings is shown and generally identified at reference numeral  10 . The sander  10  can include a housing  12  having a pair of clam shell portions  14  and  16 , and a top housing portion  18 . The sander  10  can further include a drive unit  20  and a sanding platen  22  that can be driven in an orbital fashion as will be described. A user interface panel  24  can be arranged on a forward portion of the top housing portion  18 . The user interface panel  24  can include a visual indicator  26 . A power cord  28  can extend from the housing  12  to supply electrical current to the sander  10 . 
   The sander  10  will be further described. The drive unit  20  can include an electric motor  30  mounted within the housing  12  and having an output shaft  32 . A fan  36  can be mounted on the output shaft  32  for rotation therewith. The fan  36  can include a plurality of upwardly projecting blades  40 . The blades  40  can be generally arranged to draw air in from an opening  42  ( FIG. 1 ) between the housing  12  and the sanding platen  22  and direct the air toward the motor  30 . In this manner, the upwardly projecting fan blades  40  can operate to generate a cooling airflow when the motor  30  is turned on to help cool the motor  30  during operation of the sander  10 . A bearing (not shown) can be eccentrically located radially with respect to the output shaft  32 . The sanding platen  22  can be operably secured to the output shaft  32 . The bearing in turn, can cause an orbital movement of the sanding platen  22  in response to driving rotation of the output shaft  32 . It is appreciated that while the particular example described is an orbital sander, the present teachings may be similarly applied to other sander tools such as random orbital sanders and belt sanders for example. 
   The sanding platen  22  can be fixed to the housing  12  by a series of flexible elastomeric legs  44 . In the example shown, three elastomeric legs  44  are used, one toward the front of the sander  10  and a pair disposed toward the rear of the sander  10 . The elastomeric legs  44  can be fixed between the sanding platen  22  and the housing  12 , i.e. they are not removable in use by the operator. A corresponding series of clamping flanges  46  can be formed in the housing  12  for capturing first ends of the elastomeric legs  44 . Second ends of the elastomeric legs  44  can be fixedly secured to the sanding platen  22  by mounting rings (not shown). Other configurations may be employed for securing the elastomeric legs  44  between the housing  12  and the sanding platen  22 . 
   The sanding platen  22  can be formed in any desired manner. In the particular example provided, the sanding platen  22  has a substantially flat bottom surface  48 , a curved upper surface  50  and a peripheral edge with a point  52  that provides the sanding platen  22  with an iron-shape. The point  52  can be used for sanding corners or other detained areas. An abrasive sheet (not shown) can be applied to the flat bottom surface by way of a hook and loop fabric fastener e.g., Velcro®. An underside of the abrasive sheet can have a first Velcro surface which can be attachable to a second Velcro surface (not shown) provided on the flat bottom surface  48  of the sanding platen  22 . According to one example, a portion of the sanding platen  22  adjacent to the point  52  of the peripheral edge can be detachable from the remainder of the sanding platen  22 . The detachable portion can be loosened or completely detached from the sanding platen  22  and rotated through 180 degrees, or even replaced, as the edges on either side of the point become worn. Further details of the detachable portion can be found in commonly owned U.S. Pat. No. 5,839,949, which is hereby incorporated by reference. 
   The user interface panel  24  according to the example shown can include the visual indicator  26 , a first button  54 , and a second button  56 . The first button  54  can be an “ON” button and the second button  56  can be an “OFF” button. As such, electrical power can be supplied through the power cord  28  to the sander tool  10  with the first button  54  depressed. Alternatively, electric power may be provided by a battery that can be coupled to the housing  12 . Likewise, electrical power can be disconnected from the sander tool  10  with the second button  56  depressed. In one example, the respective first and second buttons  54  and  56  can be configured such that only one button may be depressed at one time. In this way, the user interface panel  24  can be configured such that depression of one button will influence the other button to retract or “pop-out”. Other button/switch configurations are contemplated for selectively communicating electrical power to the sander tool  10 . 
   The sander  10  can further include a user feedback assembly  60 . The user feedback assembly  60  can include a sensor assembly  62 , a controller  64  and the visual indicator  26 . The sensor assembly  62  can include a first sensor portion  66  fixed for rotation with the fan  36  and a second sensor portion  68  fixed to the housing  12  and in proximity to the first sensor portion  66 . According to one example, the first sensor portion  66  can include a magnet  70  and the second sensor portion  68  can include an inductor  72 . The magnet  70  can be secured in a cavity  74  formed in the fan  36 . In one example, the inductor  72  can include a wire wound resistor. According to the example shown, with each 360 degree rotation of the fan  36 , the magnet  70  can pass in close proximity to the inductor  72 . As such, the inductor  72  can produce an output, such as a voltage, each time the magnet  70  passes in close proximity of the inductor  72 , or with each 360 degrees of rotation of the fan  36 . The output can be electrically communicated to the controller  64 . A first printed circuit board (PCB)  76  can be secured in the housing  12  adjacent to the inductor  72  for communicating with the second sensor portion  68 . 
   The sensor assembly  62  in the particular example provided is configured to provide a signal that is related to a rotational speed of the output shaft  32 , and as such, those of ordinary skill in the art will appreciate that the sensor assembly  62  could employ a commercially available Hall-effect sensor and that the other types of sensors could be substituted for the particular sensor assembly described above. For example, an anisotropic magneto-resistive (AMR) sensor could be employed. 
   The controller  64  can include a second PCB  77  in electrical communication with the first PCB  76 . According to one example, the controller  64  can be configured to communicate various electrical outputs to the visual indicator  26  based on the voltage received from the sensor assembly  62 . For example, the controller  64  can communicate a first output to the visual indicator  26  based on the voltage satisfying a first threshold or range, and a second output to the visual indicator based on the voltage satisfying a second threshold or range. According to other examples, the controller  64  can communicate additional outputs to the visual indicator  26  based on the voltage satisfying other ranges or criteria. 
   With additional reference to  FIG. 3 , the visual indicator  26  can include a semi-transparent lens  78  ( FIG. 1 ) generally covering a plurality of light emitting diodes (LED&#39;s)  80 ,  82 ,  84 ,  86 , and  88 . The LED&#39;s, collectively referred to at  90 , can be in electrical communication with the controller  64 . According to the example shown, four green LED&#39;s  80 ,  82 ,  84 ,  86  and one red LED  88  are provided. The LED&#39;s  90  can be mounted onto a third PCB  92 . The third PCB  92  can define a plurality of inset portions  94 . As will be described, the controller  64  can control the illumination of the LED&#39;s  90  to illuminate one or more of the LED&#39;s  90  based on the output signal of the sensor assembly  62 . In this way, the output of the controller  64  for illuminating the respective LED&#39;s  90  can be a function of the rotational speed (RPM) of the electric motor  30 . In general, the rotational speed of the electric motor  30  can be inversely proportional to a user applied downward force (pressure) to the tool  10  (i.e. in a direction normal to the sanding platen  22 ). As can be appreciated, a reduction in rotational speed of the fan electric motor  30  can result from an increase in user applied downward force to the tool  10 . 
   An illumination sequence according to a first example will be described. According to a first example, the controller  64  can communicate a first output to the visual indicator  26  when the output signal of the sensor assembly  62  indicates that the electric motor  30  is driven at a speed within a first speed range, a second output to the visual indication  26  when the electric motor  30  is driven at a second speed range, and a third output to the visual indicator when the electric motor is driven at a third speed within a third speed range. The first speed range can correspond to a first range of downward force applied by the user into the sander and transmitted between the platen  23  and a workpiece (such as an optimal force needed for contour detail sanding for example). The second speed range can correspond to a second range of downward force (such as an optimal force needed for stock removal for example). The third speed range can correspond to a third range of downward force (such as an excessive amount of force). In the particular example, the first range of speeds&gt;the second range of speeds&gt;the third range of speeds. 
   According to one example, the first output can include concurrent illumination of the first and second green LED&#39;s  80  and  82 . The second output can include concurrent illumination of all four of the green LED&#39;s  80 ,  82 ,  84 , and  86 . The third output can include illumination of only the red LED  88 . Other configurations and scenarios are contemplated. 
   As can be appreciated, over time, continued use of the sander  10  can lead to an increased or decreased rotational speed of the electric motor  30 . Various factors may contribute to decreased rotational speed of the electric motor  30  such as build up of sanding material dust for example. In another example, a line voltage supplied by a wall outlet (not shown) through the power cord  28  to the tool  10  can fluctuate causing an increased or decreased rotational speed of the motor  30 . Due to such outside influences that could otherwise cause a false output to the visual indicator  26 , the sander  10  can have a calibration feature, 
   In one example, the feedback assembly  60  can be configured to operate in a calibration mode at startup. In the calibration mode, an operator can turn on the sander  10  and let the platen  22  orbit freely, or at “no-load” (i.e., without external engagement, such as with a workpiece) for a predetermined time period. The time period can be any suitable time such as 3 seconds for example. In one example, the respective speed ranges described above can be set as a percentage of a measured “no-load” speed. It is appreciated that the respective speed ranges can additionally or alternatively be set at a predetermined speed of the motor  30 . In this way, any change in output performance can be accounted for in the controller  64  by re-establishing the speed ranges described above. Accordingly, the calibration mode can assure that the various electrical outputs communicated from the controller  64  to the visual indicator  26  are related to a magnitude of a force transmitted between the platen  22  and a workpiece. The controller  64  can be configured to communicate an output to the visual indicator  26  to illuminate a designated LED of the LED&#39;s  90  based on the feedback assembly  60  operating in a calibration mode. 
   Turning now to  FIG. 4 , a power sander tool constructed in accordance to additional features will be described and is generally identified at reference numeral  110 . Like reference numerals have been used to denote like components of the power sander tool  10  described above. The sander  110  can include a housing  112 , a drive unit  120 , a sanding platen  122 , and a user interface panel  124 . The user interface panel  124  can include a visual indicator  126 . A power cord  128  can extend from the housing  112  to supply electrical current to the sander  110 . 
   The drive unit  120  can include an electric motor  130  mounted within the housing  112  and having an output shaft  132 . A fan  136  can be mounted on the output shaft  132 . The fan  136  can include a plurality of upwardly projecting blades  140 . The blades  140  can be configured as described above. The output shaft  132  can include a first gear  133  mounted thereon. 
   A user feedback assembly  160  can be disposed in the sander  110 . The user feedback assembly  160  can include a sensor assembly  162 , a controller  164 , and the visual indicator  126 . The sensor assembly  162  can include a DC generator  163 . The DC generator  163  can include a rotor  164 , which can be driven by the output shaft  132 , and a stator  165  that can be disposed about the rotor  164  within a housing of the DC generator  163 . In one example, a second gear  167  can be coupled to the rotor  164  and meshingly engaged with the first gear  133 . The DC generator  163  can output a signal to the controller  164 . The output signal can have a voltage that is based on the rotational speed of the output shaft  132 . 
   The visual indicator  126  can be configured as described above in relation to the visual indicator  26 . As can be appreciated, the controller  164  can be configured to communicate various electrical outputs to the visual indicator  126  based on the voltage received from the DC generator  163 . In this way, the output of the controller  164  for illuminating the respective LED&#39;s  190  is related to the rotational speed of the electric motor  130 . The LED&#39;s  190  can be illuminated according to any desired scheme, such as the one described above. 
   According to one example, the DC generator  163  can also be used to provide power for the visual indicator  126 . Furthermore, the DC generator  163  can be electrically isolated from the AC power cord  128 . An AC to DC transformer therefore would not necessarily be needed to power the visual indicator  126 . It is further contemplated that the DC generator  163  can also be used to produce low voltage power for other accessories. 
   Turning now to  FIGS. 5 and 6 , a power sander tool constructed in accordance to additional features will be described and is generally identified at reference numeral  210 . Like reference numerals have again been used to denote like components of the power sander tool  10  described above. The sander  210  can include a housing  212 , a sanding platen  222 , a user interface portion  224 , and a drive unit (not shown). The user interface portion  224  can include a visual indicator  226 . The visual indicator  226  can include a first and a second LED  280  and  288 , respectively. In one example, the first LED  280  can be a first color such as green and the second LED  288  can be a second color such as red. A power cord  228  can extend from the housing  212  to supply electrical current to the sander  210 . 
   A user feedback assembly  260  can be disposed in the sander  210 . The user feedback assembly  260  can include a sensor assembly  262 , a controller  264 , and the visual indicator  226 . The sensor assembly  262  can include a force sensing resistor (FSR)  292  arranged generally between a user engaging portion  294  on a first side and a rigid member  296  on an opposite side. The user engaging portion  294  can include a gel-like portion  298  disposed generally at an upper surface of a handle  299  of the sander  210 . The rigid member  296  can include any rigid portion of the sander  210  that can generally resist a downward force directed at the gel-like portion  298  in a direction toward the sanding platen  222 . 
   In general, the FSR  292  can be a conventional FSR and can include two parts (not specifically shown). One part can include a resistive material applied to a film, while the second part can include a set of digitating contacts applied to another film. The FSR  292  can use the electrical property of resistance to measure the force (or pressure) applied thereto. The resistive material can make an electrical path between the two sets of conductors on the other film. When a force is applied to the FSR  292 , a better connection can be made between the contacts, hence the conductivity can be increased. 
   The controller  264  can be configured to communicate various electrical outputs to the visual indicator  226  based on the conductivity of the FSR  292 . In this way, the output of the controller  264  for illuminating the respective LED&#39;s  280  and  288  can be a function of the conductivity of the FSR  292 . The LED&#39;s  280  and  288  can be illuminated according to any desired scheme. In one example, the controller  264  can communicate a first output to the visual indicator  226  based on the conductivity satisfying a first threshold or range. The first range can correspond to a first range of downward force (such as an optimal force needed for contour detail sanding for example). The controller  264  can communicate a second output to the visual indicator  226  based on the voltage satisfying a second threshold or range. The second range can correspond to a second range of downward force (such as an excessive amount of force). In the particular example, the second output can be communicated to the visual indicator  226  when the downward force exceeds the first range. According to one example, the first output can include illumination of only the first green LED  280 . The second output can include illumination of only the red LED  288 . The visual indicator  226  can be configured differently such as similar to the visual indicator  26 . 
   With reference now to  FIGS. 7 and 8 , the semi-transparent lens  78  used in combination with the visual indicator  26  illustrated in  FIG. 1  will be described in greater detail. The semi-transparent lens  78  generally defines a semi-transparent portion  310  having a forward end  312  and a rearward end  314 . The semi-transparent portion  310  can have a thickness and includes a first inboard surface  316  and a second inboard surface  318 . The first inboard surface  316  and the second inboard surface  318  can be offset by a first distance D 1 . A chimney  320  can be formed generally centrally on the semi-transparent portion  310  and offset toward the rearward end  314 . In one example, the chimney  320  can be integrally formed with the semi-transparent portion  310 . The chimney  320  can initiate at an area between the second inboard surface  318  and an outboard surface  321  ( FIG. 8 ) of the lens  78 . In one example, the chimney  320  can initiate at a midpoint between the second inboard surface  318  and the outboard surface  321 . A channel  322  can be defined on the semi-transparent portion  310  generally around the chimney  320 . The channel  322  can define a distance D 2  between the chimney  320  and the second inboard surface  318 . The channel  322  can assist in isolating light emitted through the chimney  320  from crossing outside of the chimney  320  and also light emitted outside of the chimney  320  (i.e. through the second inboard surface  318 ) from crossing into the chimney  320 . 
   An isolating material  326  can be disposed around the chimney  320  generally in the channel  322 . The isolating material  326  can include any material that inhibits light passage therethrough such as an elastomeric material for example. A plurality of posts  328  can be formed on the semi-transparent lens  78 . 
   The semi-transparent portion  310  can define a plurality of prisms  330 . The prisms  330  can be formed on the first inboard surface  316 , the second inboard surface  318 , and the outboard surface  321 . The prisms  330  can be adapted to disperse the emitted light from the LED&#39;s  90 . The lens  78  generally defines a first area  332  adapted to disperse light from the LED  80 , a second area  334  adapted to disperse light from the LED  82 , a third area  336  adapted to disperse light from the LED  84 , a fourth area  338  adapted to disperse light from the LED  86 , and a fifth area  340  adapted to disperse light from the LED  88 . According to another example, some or all of the first, second, third, and fourth areas  332 ,  334 ,  336 , and  338  can include a chimney for isolating emitted light from a respective LED  90 . 
   In an assembled position, a distal end  344  of the respective posts  328  can nest in the recessed portions  94  ( FIG. 3 ) of the third PCB  92 . In the example provided, the LED  88  is a distinct color from the remaining LED&#39;s  80 ,  82 ,  84  and  86 . The chimney  320  can specifically isolate the LED  88  while inhibiting passage of emitted light from the other remaining LEDs  80 ,  82 ,  84 , and  86 . Again, the configuration of the channel  322  and the isolating material  326  can assist in facilitating the isolation of light emitted by the LED  88  through the chimney  320 . In addition, the offset nature of the respective prisms  330  on the first inboard surface  316 , the second inboard surface  318 , and the outboard surface  321  facilitates dispersion of light emitted through the semi-transparent lens  78 . The resulting configuration can communicate to a user what is occurring with the LED&#39;s  90  of the visual indicator  26  without distracting the user from a sanding task. 
   While the disclosure has been described in the specification and illustrated in the drawings with reference to various embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure as defined in the claims. For example, while the preceding discussion described illumination of respective LED&#39;s as “ON” and “OFF”, it is appreciated that the illumination of one or all of the LED&#39;s may comprise an LED that grows brighter in proportion with downward force. Furthermore, the mixing and matching of features, elements and/or functions between various embodiments is expressly contemplated herein so that one of ordinary skill in the art would appreciate from this disclosure that features, elements and/or functions of one embodiment may be incorporated into another embodiment as appropriate, unless described otherwise above. Moreover, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiments illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out this disclosure, but that the disclosure will include any embodiments falling within the foregoing description and the appended claims.