Turning now to
The tension/release mechanism 18 includes a release arm 20 that is rotatably connected to the belt sander 10 and may be rotated by the user to selectively apply and remove the tension in the endless belt of sandpaper. The belt release arm is operatively engaged with a pinion gear 30 through a non-circular pin 28. The pinion gear 30 engages corresponding rack gear teeth 51 on a projection 52 from a support member that is ultimately rotatably connected with the forward roller wheel 60.
The release arm 20 can be rotated about an axis 20a from a tension position (shown in
In the embodiment shown in
There are a multitude of possible shapes and sizes for the central 22 and second 21 portions of the release arm 20. Preferably, the central portion 22 is shaped to be substantially thinner than the distance between the two flat exterior surfaces of the first section 23 of the release arm 20 with the bottom surface of the central portion 22 being uniform with the bottom surface of the first section 23. This geometry reduces the material requirements, which reduces the weight of the belt sander 10. More importantly, the design provides room for the user to manipulate the second section 21 of the release arm in order to transfer the mechanism from the tension position to the release position. It is preferred that the second portion 21 be formed so that a line through the length of the second portion 21 is substantially perpendicular to a line through the length of the central portion 22. As shown in
In the embodiment shown in
A pinion gear 30 is provided with a “D” shaped hole 32 to receive the pin 28 to transfer the torque within the pin 28 to the pinion 30 to cause it to rotate. The pinion gear 30 includes a plurality of teeth 31 along the circumference of the pinion 30. The teeth 31 of the pinion gear 30 engage with corresponding rack gear teeth 51 on a rearwardly extending leg 52 that is a component of a support member 50.
The pinion gear 30 and the projection 52 are housed in the support housing 48. A spring 41 is positioned within the support housing 48 and biases the support member 50 forward to apply tension to the sanding belt to allow for normal use of the belt sander 10. The support housing 48 is rigidly attached to the housing 12 through the use of screws 11 or other attachment mechanisms known in the art. Alternatively, the support housing 48 may be formed as an integral portion of the housing 12.
In the embodiment shown in
The support member 50 contains three portions, a central portion 54, a roller support arm 56, and the projection 52 that extends rearwardly and perpendicularly from an end of the central portion 54. The roller support arm 56 extends perpendicularly from the opposite end of the central portion 54. All three portions of the support arm 50 are oriented along the same horizontal plane. The roller support portion 56 of the support arm 50 includes suitable structure to rotatably support the front roller 60 as understood by those of ordinary skill in the art.
In operation, the user rotates the release arm 20 in the counter-clockwise direction (as viewed from the top of the belt sander 10) from the tension position toward the front of the sander 10 to release the tension in the sand paper belt (not shown) to allow for belt replacement. The rotational axis of the release arm 20 is orthogonal to a plane formed along the bottom surface of the sandpaper roll. The rotation of the release arm 20 causes the pinion gear 30 to rotate. The rotation of the pinion gear 30 causes the support member 50 to move linearly in a direction toward the rear of the sander 10 against the force of the biasing spring 41 due to the meshed connection between the pinion gear teeth 31 and the corresponding rack gear teeth 51 on the projection 52. This lateral movement of the support member 50 causes the front roller 60 to move linearly rearward, releasing the tension on the sanding belt to allow for removal of the sanding belt.
When the arm 20 is sufficiently rotated to remove the tension of the sanding belt, the release arm 20 is sufficiently stabilized in the release position by a catch 70 in the tension/release mechanism 18, as is shown in
After the sanding belt has been replaced, the user may reapply the tension to the belt by releasing the release arm 20 from the wedge 72. In performing this step, the user lifts the release arm 20 upward to allow it to pass over the top edge 74 of the wedge 72 and travel down the inclined surface 73 until reaching its normal height. After the release arm 20 clears the wedge 72, it returns to the tension position with the aid of the biasing spring 41. The rotation of the release arm 20 causes the pinion gear 30 to rotate in a clockwise manner (when the belt sander 10 is viewed from above), which causes the support member 50 and the front roller 60 to move linearly toward the front end of the belt sander 10. This motion of the front roller 60 applies tension to the sanding belt to allow for operation on a workpiece.
An alternate embodiment of the tension/release mechanism 100 is provided and shown in
As best shown in
The cam shaft 140 is connected to rotate with the release lever 120 and is inserted into the aperture 137 in the cam plate 132, as mentioned above. The cam shaft 140 includes an engagement section 142 formed with the same size and shape as the aperture 137 in the cam plate 132 to allow the engagement section 142 to be inserted into the aperture 137 to prevent relative rotation between the cam shaft 140 and the cam plate 132. The cam shaft 140 additionally includes an aperture 144 that receives a pin 127 to establish a connection between the release lever 120 and the cam shaft 140. Alternatively, the release lever 120 and the cam shaft 140 can be connected to prevent relative rotation using other structures known to those of ordinary skill in the art. The cam shaft 140 is also formed with a collar 146 that establishes an upper barrier of the support housing 150.
The cam plate 132 engages a recessed portion 173 in an idle arm 172, best shown in
The recessed portion 173 is formed as a cut out, or recess, in the idle arm 172. The recessed portion 173 includes a rear side wall 174, a forward side wall 176, and center wall 175. The side walls 174, 176 each form edges 174a, 176a with a respective end of the center wall 175, such that an oblique angle is formed between each of the side walls 174, 176 and the center wall 175. In some embodiments the side walls 174, 176 are oriented to be perpendicular to each other. The recessed portion 173 includes a flat bottom wall 177.
When the components of the tension/release mechanism 100 are assembled (and when the release lever 120 is in the tension position as shown generally in
When the forward flat surface 135 contacts the rear side wall 174, the release lever 120 has reached the release position (as generally shown in
The rearward movement of the idle arm 172 compresses the spring 190 resulting in additional force applied between surface 135 on the cam plate 132 and surface 174 of the idle arm 172. These forces created by the spring 190 on the flat surface 135 on the cam plate 132 and the rear side wall 174 to retain the release arm 121 (and the front roller 60 is retained in the rearward position to allow the endless roll of sandpaper to be replaced) in the release position (as shown generally in
As mentioned above, the cam plate 132 and the idle arm 172 are supported and enclosed by the support housing 150. The support housing 150 includes a central aperture 156 that accepts the idle arm 172 and a cam plate housing 160 that accepts and encloses the cam plate 132. The structure of the support housing 150 and the cam plate housing 160 supports the cam plate 132 and the idle arm 172 to maintain engagement between the two components. Additionally, a spring 190 is enclosed within the central aperture 156 of the support housing 150 between a rear end of the support housing 150 and an engagement surface 178a at a rear end 178 of the idle arm 172. The spring 190 biases the idle arm 172 toward the forward end of the belt sander 10 to maintain tension in the roll of sandpaper. Finally, as discussed above, the cam shaft 140 includes a collar 146 that provides an enclosure for the cam plate housing 160 where the cam shaft 140 and cam plate 132 are inserted into the support housing 150. The support housing 150 additionally includes a cover plate 154 that is connected to the support housing in a conventional means and retains the cam shaft 140 and cam plate 132 within the support housing 150.
The release lever 120 is connected to the cam shaft 140 and can be rotated to rotate the cam plate 132. The release lever 120 includes three sections, an engaging section 123, a central section 122 and a handle 121. The engaging section includes a top finger 124 and a bottom finger 129. The top finger 124 comprises two components 125, 126 that are connected together with a pin 127 through apertures 125c, 126c in each of the pieces. When the two components 125, 126 are connected together, they form a “C” shape (when viewed from the top of the belt sander), with the two internal surfaces 125a, 126a of the “C” that face each other being flat and parallel. The inner portion of the “C” shape is sized to receive the top portion 149 of the cam shaft 140, with the pin 127 extending through the apertures 125c, 126c in the engaging section 123 and an aperture 144 in the cam shaft 140. With this connection between the release lever 120 and the cam shaft 140, rotation of the release lever 120 causes complementary rotation of the cam shaft 140 and therefore the cam plate 132, as discussed above. The bottom finger 129 includes a concave surface 129a that engages a cylindrical exterior surface on the cam plate housing 160 to provide rotational stability to the release lever 120.
The central section 122 of the release lever 120 extends outward from the engaging section 123 and connects with the handle 121. Preferably the central section is formed to allow the users fingers to easily grab the handle 121. As shown in
In some embodiments, the tension/release mechanism 100 includes a detent and recess to selectively retain the release lever 120 in the tension position and prevent the movement of the release lever 120 during the operation of the belt sander 10. As best shown in
The cover plate 154 is formed with a recess 208 that accepts the detent ball 202 when the release lever 120 is in the tension position. The connection between the detent ball 202 and recess 208 is beneficial because it gives the user a perceptible “click” when the detent ball 202 is positioned within the recess 208, which notifies the user that the release lever 120 is in the tension position. Additionally, the use of the detent and recess is preferred because it aides in retaining the release lever 120 in the tension position, which substantially eliminates any chattering or vibration of the release lever 120 during operation of the belt sander 10.
In use, the tension/release mechanism 100 is operated as follows. To release the tension in the roll of sandpaper, the user rotates the release lever 120 from the tension position toward the front of the belt sander 10 (in the counter-clockwise direction as viewed from the top of the belt sander 10). The rotational axis of the release arm 20 is orthogonal to a plane formed along the bottom surface of the sandpaper roll. The rotation of the release lever 120 causes the cam plate 132, which is engaged with the rear side wall 174 of the idle arm 172, to rotate. The rotation of the cam plate 132 causes rolling contact between the curved side surface 134 of the cam plate 132 and the rear side wall 174 of the idle arm 172. This causes the idle arm 172 (and the remaining components of the support member 170 as attached to the front roller 60) to move linearly in a direction toward the rear of the belt sander 10 against the force of the biasing spring 190. This rearward movement of the front roller 60 removes the tension on the roll of sand paper for convenient replacement. When the release lever 120 is rotated approximately ninety degrees with respect to the sander, the front flat surface 135 of the cam plate 132 becomes parallel to the rear side wall 174. The flat front surface 135 and the rear side wall 174 make full contact with each other. This rotational movement compresses the spring 190 creating a biasing force which serves to retain the release lever 120 in the release position (as generally shown in
After the roll of sandpaper has been replaced, the user rotates the release lever 120 in the opposite direction toward the tension position. With sufficient torque placed on the release lever 120, the lever overcomes the frictional contact between the front flat surface 135 of the cam plate 132 and the rear flat wall 174 of the idle arm 172 and rotates toward the tension position. When the release lever 120 is rotated, the curved side surface 134 of the cam plate makes rolling contact with the rear side wall 174 of the idle arm 172, which moves the idle arm 172, the remaining members of the support member 170 and the front roller 60 in the forward direction within the sander until tension is restored in the endless roll of sandpaper. In embodiments with the detent ball 202 located within the release lever 120 and the recess 208 on the cover plate 154, the detent ball 202 engages the recess 208 when the release lever 120 reaches the tension position.
It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.
This application is a divisional application of and claims priority from U.S. application Ser. No. 11/528,777, filed on Sep. 28, 2006, which is fully incorporated by reference herein.
Number | Date | Country | |
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Parent | 11528777 | Sep 2006 | US |
Child | 11929352 | US |