Abstract:
The present invention relates to a belt brake for a band saw such as a band saw on a sawmill utilized for sawing lumber. The belt brake provides added safety by stopping the blade of the band saw when the operator deactivates the band saw, for example, by turning the band saw off or operating the band saw clutch. The belt brake activation may be synchronized with the band saw&#39;s clutch mechanism.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a belt brake for a band saw such as a band saw on a sawmill utilized for sawing lumber. 
       BACKGROUND OF THE INVENTION 
       [0002]    A conventional band saw is often used in sawmills. Such a band saw typically has a relatively large, circular, endless band saw blade, mounted along the path of travel of wood placed on a suitable moving bed with a drive mechanism for advancing the wood against the blade. Alternatively, the wood remains stationary and the band saw is mounted on a carriage which is capable of transverse displacement along the wood. 
         [0003]    The blade moves in a generally circular path, typically around two rotating coplanar band wheels, one of which is powered by a motor, either via direct drive or a belt drive. The second band wheel rotates under the force transmitted through the movement of the blade. In the case of a belt drive, a tensioning pulley may provide variable tension to the belt so that an operator can activate or deactivate the rotation of the blade by adjusting tension on the tensioning pulley, rather than starting or stopping the motor. This method creates much less wear on the motor and belt. Often the tensioning pulley is adjusted by means of a clutch. 
         [0004]    One problem with such a method, however, is that when the tension on the belt is decreased, though the blade eventually comes to a stop, entropy from the large and heavy band wheels results in continued rotation for a fairly long time before the blade stops completely. This creates a safety issue for the user, since the user may deactivate the band saw and forget that it is still in motion. This safety issue is exacerbated by the fact that the sound from the motor may change when the clutch is activated. 
         [0005]    There are several prior inventions for band saws. 
         [0006]    U.S. Pat. No. 4,275,632 describes a portable sawmill comprising a U-shaped support or carriage, holding a band saw. Canadian Patent No. 1,200,180 describes a portable sawmill having a band saw on a carriage. The LumberMate™ band sawmill (Canadian Patent No 2,488,216 and Canadian Industrial Design Application no. 132823) is a portable sawmill having a band saw with a circular band saw blade which rotates around two band saw wheels. 
         [0007]    There is a need for an improved band saw having a brake assembly for stopping the blade of the band saw when it is deactivated by a user. 
       SUMMARY OF THE INVENTION 
       [0008]    According to one aspect of the invention is provided a band saw having1. A band saw having: an endless saw blade driven around a first band wheel and a coplanar second band wheel configured to provide a cutting area between the first band wheel and the second band wheel; a motor for driving the saw blade; the motor providing rotational force to drive a band wheel; further characterized such that: the band saw comprises a brake belt, the brake belt having a first end, a second end, and a belt surface between the first end and the second end, the brake belt being configured such that a portion of the belt surface travels along a brake wheel connected to the first band wheel or the second band wheel; at least one of the first end and second end being displaceable such that the brake belt has a first, tense position which provides frictional force to the brake wheel, and a second, loose position which provides significantly less or no frictional force to the brake wheel. 
         [0009]    In certain embodiments, the brake belt is biased towards the first, tense position. 
         [0010]    In certain embodiments, the brake belt can be displaced from the first, tense position to the second, loose position by a user. 
         [0011]    In yet further embodiments, the displacing of the first and/or second end of the brake belt and the moving of the tensioning pulley is synchronized. 
         [0012]    In yet further embodiments, when the tensioning pulley is in the first, disengaged position, the brake belt is in the first, tense position, and when the tensioning pulley is in the second, engaged position the brake belt is in the second, loose position. 
         [0013]    In yet further embodiments, wherein the tensioning pulley is connected to a clutch handle by means of a Bowden cable, which is capable of displacing a pivoting clutch assembly on which the tensioning pulley is mounted. 
         [0014]    In yet further embodiments, the first end and/or the second end of the brake belt is connected to the pivoting clutch assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a front perspective view of a band saw according to one aspect of the present invention, with the protective cover off so that the internal components can be viewed, and is labeled with its major components. 
           [0016]      FIG. 2  is a line drawing, right angled view of the band saw of  FIG. 1 . 
           [0017]      FIG. 3  is a line drawing, left angled view of the band saw head of  FIG. 1 . 
           [0018]      FIG. 4  is close-up front perspective view of the clutch and brake mechanism of the band saw of  FIG. 1 . 
           [0019]      FIG. 5  is a photograph of the clutch and brake mechanism of the band saw of  FIG. 4 . 
           [0020]      FIGS. 6-9  are various close-up photographic views of the band saw of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    The present invention provides a simple and effective adjustable band brake for a band saw. As shown (but optionally), the band brake is integrated into a clutch mechanism of a band-driven band saw. 
         [0022]    The band brake provides braking action on the band saw blade. Without such a brake, the bandwheels and blade would continue rotating for a prolonged period of time, notwithstanding that the operator has released the engine throttle to idle. The band brake provides an effective, reliable and low cost solution in a manner that can fit within the very narrow confines of the bandwheel guard housing. 
         [0023]    The brake provides substantial safety over a non-braking band saw. As set out below, the brake can be configured such that it is automatically engaged upon release of the engine throttle. 
         [0024]    An embodiment of the present invention will now be described as shown in  FIGS. 1-9 . 
         [0025]    As seen in  FIG. 1 , band saw  20  has a saw head plate stack  22  which acts as support for drive band wheel  24  and free band wheel  26 , which are coplanar. Not shown is a front cover (guard housing) for the band saw, which would cover the inner workings of the band saw and act as a safety barrier. Band saw blade  28  is entrained on and travels along outer wheel  30 ,  32  of drive band wheel  22  and free wheel  24 , respectively, and travels along cutting section  34 , located between the drive band wheel  24  and free band wheel  26 . Band saw blade  28  has transversely extending teeth capable, when in motion, of cutting wood. An inner wheel  36  of drive band wheel  24  is connected to a motor  38  by way of drive belt  40  which runs along inner wheel  36  and drive pulley  42 . Tension on drive belt  40  is controlled by way of tensioning pulley  44 . In use, motor  38  turns drive pulley  42 , which, in turn, turns drive band wheel  24  and, as a result, saw blade  28 , which rotates around drive band wheel  24  and free band wheel  26 . The free band wheel  26  rotates under the force transmitted through the movement of the saw blade  28 . 
         [0026]    Tensioning pulley  44  can also be used as a clutch for the saw blade  28 ; instead of continuously shutting off and turning on the motor  38  to activate the cutting action of saw blade  28 , tension can be released from drive belt  40  by adjusting tensioning pulley  44 . Releasing tension in drive belt  40  results in the free spinning of drive pulley  42  and a decrease of rotatory force on saw blade  38 , resulting in the stopping of the saw blade  38 . Starting and stopping saw blade  38  in this manner decreases wear on motor  38  and drive belt  40 , improving the longevity of these parts. However, starting and stopping saw blade  38  in this manner, without a brake, would result in the free spinning of saw blade  38  before it eventually comes to a stop once the entropy of the saw blade  38  and the band wheels  24 ,  26  is dispersed. 
         [0027]    As seen in  FIGS. 2 and 3 , tensioning pulley  44  is controlled by a user through pivoting clutch assembly  49 . As shown, a clutch cable  46  is a Bowden cable with a fixed hollow outer cable housing and a displaceable inner cable. When the user operates a clutch handle (not shown), typically by squeezing a trigger (not shown), it displaces the inner cable, which is connected through clutch post  50  to clutch pivoting assembly  49 . The clutch pivoting assembly  49  rotates around clutch pivot  52 , and is biased in one direction through clutch spring  54 . Thus, when the clutch handle (not shown) is displaced by the user (activated), the clutch pivoting assembly  49  rotates to a second position so that tensioning pulley  44  provides tension to drive belt  40 , causing the rotation of the drive band wheel  24 , and as a result, the rotation of the blade  28  and the free band wheel  26 , through the rotatory force of the motor  38  through the drive pulley  42 . When the clutch handle (not shown) is deactivated (for example, released by the user), the clutch pivoting assembly  49  rotates back to a first position such that tensioning pulley  44  no longer provides sufficient tension to the drive belt  40  to cause rotation of the drive band wheel  24 . Clutch pivoting assembly  49  rotates back to this position due to biasing means in the form of clutch spring  54 . 
         [0028]    The brake assembly is shown in  FIGS. 4 to 9 . A brake belt  56  is attached at a first or fixed end  60  by bake belt clamp  58 , which acts as an anchor point. The brake belt  56  has a belt surface which travels along a brake wheel  62  connected to drive band wheel  24 , and is attached at its second or movable end  64  to second brake belt clamp  66 . Second brake belt clamp  66  is connected to pivoting assembly  49  such that, when pivoting assembly  49  is in its second position, the brake belt  56  is pulled to a taught position which provides frictional resistance between belt surface and brake wheel  62  sufficient to quickly slow down and stop the drive band wheel  24  and, as a result, the band saw blade  28 . As the user engages or activates the clutch handle, clutch pivoting assembly  49  rotates to the second position, providing tension to the drive belt  40  as discussed above, but also displacing the second end of brake belt  64  towards the brake wheel  62 , which adds slack to the brake belt  56 , removes frictional tension from drive band wheel  24  at brake wheel  62 , thus deactivating the brake. 
         [0029]    Thus, in this manner, presently provided is a simple and efficient braking mechanism for a band saw, whereby the clutch mechanism is combined with the braking mechanism. The braking mechanism allows reliable and cost effective braking in a manner that can fit within the very narrow confines of the bandwheel guard housing. 
         [0030]    As would be understood by a person of skill in the art, the provided embodiment can be modified for specific needs. For example, in some applications, both of the ends of the brake belt can be attached to the pivoting assembly, to provide additional frictional force on the brake wheel  62 , or where it is desired to provide more uniform braking force. In other applications, the brake belt can be attached to a second, separate pivoting assembly, operated for example by a second Bowden cable. This can be useful where a different amount of displacement is required for the brake belt as compared to the tensioning pulley, or, for example, where a different biasing strength is needed. The second Bowden cable can be attached to the clutch handle, or, alternatively, may be attached to a separate brake handle, for operation of the brake separately from the clutch. In certain other embodiments, depending on the desired configuration and the design limitations of the specific band saw, the brake belt can travel along a brake wheel on the free band wheel instead of on the drive band wheel. 
         [0031]    It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims. 
       Element List 
       [0000]    
       
           20  bandsaw 
           22  sawhead plate stack 
           24  drive band wheel 
           26  free band wheel 
           28  band saw blade 
           30  outer drive band wheel 
           32  outer free band wheel 
           34  cutting section 
           36  inner drive band wheel 
           38  motor 
           40  drive belt 
           42  drive pulley 
           44  tensioning pulley 
           46  clutch cable 
           48  clip 
           49  pivoting assembly 
           50  clutch post 
           52  clutch pivot 
           54  clutch spring 
           56  brake belt 
           58  brake belt clamp (fixed anchor point) 
           60  first or fixed end of brake belt 
           62  brake wheel 
           64  second, or movable end of brake belt 
           66  brake belt clamp (movable anchor point)