Abstract:
A method and apparatus for tensioning a continuous loop, such as a cutting blade installed on a band saw having a frame, a manually rotatable tensioner, a first pulley rotatably connected to the manually rotatable tensioner, a second pulley spaced away from the first pulley, and a cutting blade strung between the first pulley and the second pulley, generally including the steps of positioning an adjustable body, such as a reciprocally actuated rod, between the manually rotatable tensioner and the second pulley, extending the adjustable body in a direction away from the second pulley and toward the manually rotatable tensioner so that the manually rotatable tensioner and the first pulley move in direction away from the second pulley, withdrawing the adjustable body in a direction toward the second pulley so that the manually rotatable tensioner and the first pulley move in a direction toward the second pulley.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of earlier filed U.S. Provisional Patent Application Ser. No. 60/213,821, filed Jun. 23, 2000, entitled “Quick Release Device.” 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to tensioners and, more particularly, to tensioners for band saw cutting blades and the like. 
     2. Brief Description of the Prior Art 
     As shown in FIG. 1, band saws A generally include a frame B, a first pulley shroud C connected to the frame B, a manually rotatable tensioner, such as a screw-type tensioner D, removably and slideably attached to the frame B by slots E, a first pulley F (shown in phantom) rotatably attached to the screw-type tensioner D, a second pulley G (shown in phantom) lying in the same plane as the first pulley F and rotatably attached to the frame B, a second pulley shroud H connected to the frame B, a continuous cutting blade I attached to the first pulley F and the second pulley G, a blade guide attachment bar J, and a motor O connected to the second pulley G. 
     In normal operation, the cutting blade I must be tensioned to make the cutting blade I taut. Conversely, when the cutting blade I is worn or replacement is desired, the cutting blade I must be detensioned so that the cutting blade I can be removed from the first and second pulleys F,G. 
     Tensioning the cutting blade I is normally accomplished by positioning the cutting blade I on the first and second pulleys F,G and then moving the first pulley F, which lies in substantially the same plane as the second pulley G, directly away from the second pulley G. Detensioning is accomplished by moving the first pulley F toward the second pulley G. Movement of the first pulley F is facilitated by the screw-type tensioner D shown in FIG.  1 . As shown in FIG. 2, the screw-type tensioner D includes a tension body K that receives, usually in a common thread arrangement, a rotatable shaft L. The tension body K is fitted into the slots E formed by the frame B so that the tension body K is moveable with respect to the frame B, as illustrated by the arrows Y 1  and Y 2 . The tension body K further includes a shaft N that receives the first pulley F shown in FIG.  1 . 
     With continuing reference to FIG. 2, a first end M of the rotatable shaft L contacts the frame B, so that when the rotatable shaft L is rotated in a tightening direction, shown by arrow Z 1 , the tension body K and the first pulley F move in the Y 1  direction. This tightens the cutting blade I. When the rotatable shaft L is rotated in a loosening direction, shown by arrow Z 2 , the tension body K and the first pulley F move in the Y 2  direction. This creates slack in the cutting blade I. 
     Another type of manually rotatable tensioner is disclosed in U.S. Pat. No. 769,497 to Seymour (hereinafter “the Seymour patent”). The Seymour patent discloses a tensioner having a rack and pinion arrangement actuated by a rotatable handwheel. 
     One drawback of the prior art manually rotatable tensioners, such as the screw-type and the handwheel-type discussed above, is that they are rotated incrementally by hand. Therefore, each time the cutting blade is retensioned, the correct number of turns of the rotatable shaft L or the handwheel must be approximated. This involves a process of trial and error, which is inaccurate and time consuming. 
     SUMMARY OF THE INVENTION 
     To help eliminate some of the drawbacks of the prior art rotatable tensioners, it is an object of the present invention to provide a tensioner which is easily operated and does not require significant amounts of trial and error manipulation during retensioning of the cutting blade. 
     The present invention generally includes a method and apparatus for tensioning a belt, saw blade, or other continuous loop. One method to adjust the tension of a cutting blade installed on a band saw having a frame, a manually rotatable tensioner positioned adjacent to the frame, a first pulley rotatably connected to the manually rotatable tensioner, a second pulley spaced away from the first pulley, and a cutting blade strung between the first pulley and the second pulley includes the step of positioning an adjustable body between the manually rotatable tensioner and the second pulley. This step is followed by one or more of the following steps, including extending the adjustable body in a direction away from the second pulley and toward the manually rotatable tensioner so that the manually rotatable tensioner and the first pulley move in direction away from the second pulley or withdrawing the adjustable body in a direction toward the second pulley so that the manually rotatable tensioner and the first pulley move in a direction toward the second pulley. The adjustable body is preferably a rack, and the manually rotatable tensioner is preferably a screw-type tensioner having a manually rotatable shaft with opposing ends. Additional steps may include positioning the rack adjacent to an opposing end of the manually rotatable shaft, extending the rack in a direction away from the second pulley to tension the cutting blade, and withdrawing the rack in a direction toward the second pulley to detension the cutting blade. 
     Another method to adjust the tension of a cutting blade installed on a band saw having a frame, a screw-type tensioner positioned adjacent to the frame, the screw-type tensioner having a rotatable shaft with opposing ends, a first pulley rotatably connected to the screw-type tensioner, and a second pulley spaced away from the first pulley generally includes the steps of positioning a rack and a rotatable pinion gear between the screw-type tensioner and the second pulley, wherein the rack and pinion gear are connected by an intermeshed relationship, and the rack is movable by the pinion gear, extending the rack in a direction away from the second pulley to tension the cutting blade, and withdrawing the rack in a direction toward the second pulley to detension the cutting blade. 
     A band saw according to the present invention generally includes a frame having a motor connected to the frame, a first pulley and a second pulley, with the first pulley rotatably connected to the manually rotatable tensioner and the second pulley rotatably connected to the motor, a pull-type tensioner positioned between the manually rotatable tensioner and the second pulley, and a cutting blade strung between the first pulley and the second pulley. The manually rotatable tensioner is preferably a screw-type tensioner. The pull-type tensioner may include a mount defining a pivot shaft receiving orifice, a pivot shaft received in the pivot shaft receiving orifice, the pivot shaft having a first end and a second opposite end, a pinion gear positioned adjacent to the first end of the shaft, a handle positioned adjacent to the second opposite end of the shaft, and a rack connected by an intermeshed tooth relationship with the pinion gear. In operation, the handle is rotated in a first direction with respect to the mount, and the pinion gear acts to extend the rack in a direction away from the mount. When the handle is rotated in a second direction, opposite to the first direction, the pinion gear acts to withdraw the rack in a direction toward the mount. 
     These and other features of the present invention will be clarified in the Detailed Description of the Preferred Embodiments taken together with the attached drawings in which like reference numerals represent like elements throughout. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective side view of a band saw according to the prior art with a screw-type tensioner installed, the screw-type tensioner having a tension body and a manually rotatable shaft, wherein a second end of the manually rotatable shaft engages a frame of the band saw; 
     FIG. 2 is a perspective side view showing engagement of the manually rotatable shaft of the screw-type tensioner on the band saw frame of FIG. 1; 
     FIG. 3 is a top perspective view of a pull-type tensioner according to a first embodiment of the present invention; 
     FIG. 4 is a front view of the pull-type tensioner shown in FIG. 3; 
     FIG. 5 is a side view of the pull-type tensioner shown in FIG. 3; 
     FIG. 6 is a top perspective view of a first pulley shroud being separated from a frame in preparation for installing the pull-type tensioner shown in FIGS. 3-5; 
     FIG. 7 is a top perspective view of a second section of a mount according to the first embodiment of the present invention; 
     FIG. 8 is a top perspective view of the second section of the mount shown in FIG. 7 being positioned between the first pulley shroud and a frame; 
     FIG. 9 is a top perspective view of the second section of the mount shown in FIGS. 7-8 positioned adjacent to a screw-type tensioner; 
     FIG. 10 is a top perspective view of a first section of the mount being attached to the second section of the mount, shown in FIGS. 7-9, by a fastener; 
     FIG. 11 is a top perspective view of the fastener shown in FIG. 10 being installed; 
     FIG. 12 is a top perspective view of the pull-type tensioner shown in FIGS. 3-5 and  9 - 11  being clamped to the frame with fasteners; 
     FIG. 13 is a top perspective view of the pull-type tensioner shown in FIGS. 3-5 installed on a band saw between the frame and a screw-type tensioner; 
     FIG. 14 is an exploded view of a pull-type tensioner according to a second embodiment of the present invention; and 
     FIG. 15 is a perspective view of the pull-type tensioner shown in FIG.  14 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A first embodiment pull-type tensioner  10  according to the present invention is shown in FIGS. 3-13, and is also described in U.S. Provisional Patent Application No. 60/213,821, herein incorporated by reference in its entirety. 
     Referring to FIGS. 3-5, and particularly FIG. 3, a pull-type tensioner  10  according to a first embodiment of the present invention preferably includes a mount  12  having a first section  14  and a second section  16 . The first section  14  is generally C-shaped and includes a first bracket portion  18 , a second bracket portion  20 , and a third bracket portion  22 . The first bracket portion  18  forms a first fastener-receiving orifice  24 . The second bracket portion  20  is positioned perpendicularly adjacent to the first bracket portion  18 , with the second bracket portion  20  forming a first shaft-receiving orifice  26 , a second fastener-receiving orifice  28 , and a plurality of adjustment orifices  30 . The third bracket portion  22  is positioned perpendicularly adjacent to the second bracket portion  20  and opposite and parallel to the first bracket portion  18 . The third bracket portion  22  forms a rack orifice  32 . 
     As shown in FIGS. 3 and 4, the second section  16  of the mount  12  forms a third fastener-receiving orifice  34 , a second shaft-receiving orifice  36 , and a rack guide  38 . The first section  14  of the mount  12  and the second section  16  of the mount  12  are formed from metal or other suitable material and are connected to one another by a fastener  40  (FIG. 3 only), such as a threaded screw, which is received by the second fastener-receiving orifice  28  formed by the second bracket portion  20  and the third fastener-receiving orifice  34  formed by the second section  16 . 
     As shown in detail in FIG. 4, when assembled, the first section  14  and the second section  16  of the mount  12  form a mount cavity  42 . As shown in FIGS. 3 and 4, a rack  44 , forming rack grooves  46 , is movably housed in the rack guide  38  formed by the second section  16  of the mount  12 . 
     With continuing reference to FIGS. 3 and 4, a handle attachment member  48  has a first side  50  and a second side  52 , with the second side  52  forming a pivot shaft orifice  54 , a handle orifice  56 , and a pin orifice  58 . The handle attachment member  48  is positioned adjacent to a first end  60  of a pivot shaft  62 , with the pivot shaft orifice  54  receiving the first end  60  of the pivot shaft  62 . A handle  64 , having a knob end  66  and a second handle end  68 , is received in the handle orifice  56  of the handle attachment member  48 . A pin  70 , biased by a spring (not shown), is received in the pin orifice  58 . 
     With continuing reference to FIGS. 3 and 4, the pivot shaft  62  extends from the second bracket portion  20  of the first section  14  of the mount  12  to the second section  16  of the mount  12 , with the first end  60  of the pivot shaft  62  received in the first shaft-receiving orifice  26  and a second end  74  of the pivot shaft  62  received in the second shaft-receiving orifice  36 . A pinion gear  76  is attached to the second end  74  of the pivot shaft  62  and is preferably positioned inside the mount cavity  42 . The pinion gear  76  forms pinion teeth  78  which intermesh with the rack grooves  46  of the rack  44 . 
     As shown in FIG. 4, when the pin  70  is inserted in a pin orifice  58 , the pin  70  protrudes beyond the second side  52  of the handle attachment member  48  and engages one of the plurality of adjustment orifices  30  (see FIG. 3 or  5 ) formed by the second bracket portion  20  of the mount  12 . With particular reference to FIGS. 4 and 5, when the pin  70  is pulled directly away from the first side  50  of the handle attachment member  48 , the handle  64  can be rotated in a first direction A 1  or a second direction A 2  (clockwise or counterclockwise). 
     The following few paragraphs describe the movement of various parts of the first embodiment of the present invention. For reference, it should be assumed that the rack  44  is initially positioned so that the rack  44  is withdrawn or housed in the rack guide  38 , and is not protruding through the rack orifice  32  formed by the third bracket portion  22 . Moreover, the handle  64  should initially be assumed to be approximately aligned at position P 1 , as viewed in FIG.  5 . The initial alignment of the rack  44  and the handle  64  is not critical to the overall operation of the present invention, but this alignment will provide the reader with a clear frame of reference. The frame of reference is important because if the handle  64  is positioned at position P 2  (opposite to position P 1  in FIG. 5) and the rack  44  is positioned so that it does not protrude through the rack orifice  32 , rotation of the handle  64  clockwise from position P 2  to position P 1  would extend the rack  44  away from the mount  12 , through the rack orifice  32 . The movement of the handle  64  would then initially be in a direction opposite to the movement direction of the rack  44 . Because the following describes coordinated movement between the handle  64  and the rack  44 , the initial starting orientations discussed above should be presumed. 
     With continuing reference to FIGS. 4 and 5, when the handle  64  is rotated in the first direction A 1 , the pivot shaft  62  and the attached pinion gear  76  rotate. Because the pinion gear  76  and the rack  44  (shown in FIG. 4) are engaged in a tooth and groove arrangement, the rotation of the pinion gear  76  causes the rack  44  (FIG. 4) to extend in a direction away from the mount  12 . When the handle  64  is moved in a second direction A 2 , opposite to the first direction A 1 , the rack  44  (FIG. 4) withdraws in a direction toward the mount  12 . 
     The first embodiment pull-type tensioner according to the present invention is preferably used in conjunction with a screw-type tensioner and can be installed on band saws in the following manner. The following steps and illustrations highlight a  14 ″ JET brand of bandsaw. However, the steps are also applicable to other popular brands of bandsaws. 
     Retrofitting a band saw  72  with a pull-type tensioner  10  according to a first embodiment of the present invention includes the steps of disconnecting power to the band saw  72  for safety and loosening the screw-type tensioner  79 , if installed, by rotating the manually rotatable shaft  81  in a counterclockwise or loosening direction. As shown in FIG. 6, the next step is loosening the first pulley shroud  80  so that the first pulley shroud  80  can be pulled away from the frame  82  of the band saw  72 . The first pulley shroud  80  does not have to be completely removed, but only pulled slightly away from the frame  82 . As shown in FIG. 7, the next step is sliding the second section  16  of the mount  12 , with the rack  44  removed, between the frame  82  and the first pulley shroud  80 . As shown in FIG. 8, the next step is installing the rack  44  in the rack guide  38  formed by the second section  16  of the mount  12 . As shown in FIG. 9, the next step is sliding the first section  14  of the mount  12  over the frame  82 , with the rack  44  fully seated in the rack guide  38  and the handle  64  rotated and locked in the last available adjustment orifice  30 . This ensures that the pinion gear  76  engages the rack  44  in the proper position. As shown in FIG. 10, the next step is rotating the handle  64  in the first direction A 1  and attaching the first section  14  of the mount  12  to the second section  16  of the mount  12  using a fastener  40 . As shown in FIGS. 11 and 12, the next step is clamping the mount  12  to the frame  82  by fasteners  40  received by the first bracket portion  18  of the mount  12  and by fasteners  40  received by the second bracket portion  20  of the mount  12 . The first pulley shroud  80  is then retighted and the manually rotatable shaft  81  of the screw-type tensioner  79  is adjusted so that a rack-receiving surface  45  of the rack  44  engages the rotatable shaft  81 . Finally, power is restored to the band saw. 
     FIG. 13 shows the pull-type tensioner  10  according to the present invention positioned beside the frame  82  for clarity. However, in actual operation, the screw-type tensioner  79  fits in slots  83 . When the pull-type tensioner  10  according to the first embodiment of the present invention is installed on the frame  82  of a band saw  72 , the rotatable shaft  81  of the screw-type tensioner  79  should not have to be readjusted during subsequent tensioning or detensioning of a continuous cutting blade. Subsequent tensioning of the cutting blade is accomplished completely by the first embodiment pull-type tensioner by moving the pin  70  so that it no longer engages a corresponding adjustment orifice  30 . The handle  64  is then moved in the first direction A 1 , causing rotation of the pinion gear  76 . The rotating pinion gear  76  causes the rack  44  to extend away from the mount  12  and a second pulley  84 , which is spaced away from a first pulley  86 , until the rack-receiving surface  45  of rack  44  begins to exert a force on the rotatable shaft  81  of the screw-type tensioner  79 . The screw-type tensioner  79  and the first pulley  86 , rotatably attached thereto, thus also move in a direction away from the mount  12  and the second pulley  84 . This extension of the rack  44  and movement of the first pulley  86  away from the second pulley  84  tensions a cutting blade strung between the first pulley  86  and the second pulley  84 . The pin  70  is then moved into another adjustment orifice  30  to fix the handle  64 , rack  44 , and pinion gear  76  in place. 
     Detensioning a cutting blade is accomplished by moving the pin  70  so that the pin  70  no longer engages a corresponding adjustment orifice  30 . The handle  64  is then moved in a second direction A 2 . Rotation of the pinion gear  76  causes the rack  44  to withdraw in a direction toward the mount  12  and the second pulley  84 . This withdrawal of the rack  44  causes the screw-type tensioner  79  and the first pulley  86 , which is rotatably attached thereto, to move in a direction toward the mount  12  and the second pulley  84 . The movement of the first pulley  86  in a direction toward the second pulley  84  detensions the cutting blade strung between the first and second pulleys  86 ,  84 . 
     A second embodiment pull-type tensioner  10 ′ according to the present invention is shown in FIGS. 14 and 15. The second embodiment pull-type tensioner  10 ′ is similar to the first embodiment pull-type tensioner  10 , with like reference numerals indicating like parts. However, while there are similarities between the embodiments  10 ,  10 ′, such as the rack and pinion operation and the coordinated handle and rack movement discussed in detail above, there are some differences between the first and second embodiments. 
     For example, in the second embodiment pull-type tensioner  10 ′ shown in FIGS. 14 and 15, the first bracket portion  18  of the first section  14  of the mount  12  described in connection with the first embodiment pull-type tensioner  10  is not required because the second embodiment pull-type tensioner  10 ′ is bolted, welded, or otherwise connected to the frame, such as by the fasteners  40  shown in FIG.  14 . By comparison, the first embodiment pull-type tensioner  10  is clamped to the frame  82 . Second, as shown in FIG. 14, the mount  12 ′ of the second embodiment pull-type tensioner  10 ′ does not form a rack guide  38  which envelops the rack  44 . Instead, the second embodiment pull-type tensioner  10 ′ preferably includes a rack holder  88  which only supports the rack  44 . Finally, as shown in FIG. 14, the mount  12 ′ of the second embodiment pull-type tensioner  10 ′ preferably defines one or more dovetail-shaped slots  90 A,  90 B which, as shown in FIG. 15, receive a tongue  92  defined by the handle  64 ′. As shown in FIG. 15, when the handle  64 ′ is moved in the first direction A 1 , the tongue  92  defined by the handle  64 ′ can be seated in the first dovetail-shaped slot  90 A. When the handle  64 ′ is moved in a second direction A 2 , the tongue  92  can be seated in the second dovetail slot  90 B. 
     The second embodiment pull-type tensioner  10 ′ is installed in generally the same way as the first embodiment pull-type tensioner  10 , except that the first pulley  86  and the first pulley shroud  80  are preferably completely removed from the frame  82  of the band saw during installation of the second embodiment pull-type tensioner  10 ′ and then reinstalled. The added installation time of the second embodiment pull-type tensioner  10 ′ is offset by two safety features. First, as shown generally in FIG. 15, to disengage the tongue  92  from any of the dovetail-shaped slots  90 A,  90 B, the handle  64 ′ is first moved in the first direction A 1  until the tongue  92  clears a corresponding slot stop  94 , and then the handle  64 ′ is moved in a third direction A  3  until the tongue  92  clears the slot stop  94 . These movements, designed with safety in mind, help reduce the risk of accidental dislodgment of the handle  64 ′ during operation of the band saw  72 . Second, as shown in FIG. 14, the L-shape of the handle  64 ′ provides a visual indicator that the cutting blade is either tensioned or not tensioned. When the cutting blade is tensioned, the handle  64 ′ does not obscure a work platform of the band saw  72 . However, when the cutting blade is detensioned, a curved end  96  of the handle  64 ′ lays on the work platform, in front of the operational cutting surface of the cutting blade. 
     In sum, the present invention seeks to provide a quick, efficient method and apparatus for tensioning a continuous loop, such as a cutting blade. In operation, the present invention is preferably used in conjunction with existing screw-type tensioners. 
     The invention has been described with reference to the preferred embodiment. Obvious modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.