Abstract:
A cam lever arrangement is provided which permits the loosening and tightening of the chain on the chain saw blade tool with a simple lever motion. The lever arrangement is connected to the motor housing cover door. Opening the door automatically loosens the chain. Closing the door automatically tightens the chain. Precision adjustments to tension are easily made in the cam lever arrangement by hand manipulation of a turnbuckle which is free from pressure when the lever is in the release position.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to chain saws, and in particular, to an improvement that enables the chain of a chain saw to be loosened or tightened without requiring loosening of locking nuts that secure a chain-carrying blade of the saw to the motor housing of the saw. 
     Chain saws include an elongated flat blade having a peripheral edge about which a cutting element, also known as a chain, extends in a continuous, endless loop. The distal free end of the chain is used for cutting. The proximal end of the chain extends around a sprocket gear that engages the chain and causes it to rotate around the peripheral edge of the elongated flat blade when the sprocket gear is rotated. The sprocket gear is attached to the output shaft of a motor means that is housed in a motor housing, and the proximal end of the elongated flat blade is secured to the motor housing. 
     An elongated slot is formed in the proximal end of the elongated flat blade, and a pair of externally threaded post members that are secured to the motor housing respectively extend through the slot. A pair of internally threaded locking nuts respectively threadingly engage the post members and securely lock the elongated flat blade against movement when the nuts are tightly sealed. 
     To tighten or loosen the chain, both locking nuts must be loosened. After the blade position is manipulated until the chain is loosened or tightened to a desired taughtness, the locking nuts must then be tightened again. It can take several minutes to perform the above-described procedure. The locking nuts are very tight, and must be loosened and re-tightened with a socket wrench or other high torque tool. This process is awkward and requires strength and a level place to brace the saw. It is not uncommon to drop one of the nuts requiring a search for the nut in the usual debris where chain saw operations generally take place. This further lengthens the time of the adjustment process. 
     Speed of adjustment may be an important factor in certain applications such as fire fighting where a quick loosening or tightening of the chain is important. Ease of adjustment actually has a safety element to it as chain saw users are likely to continue working with a dangerously loose chain as it stretches during use if it cannot easily be tightened. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the above problems by providing an improvement to chain saws, wherein a simple cam lever arrangement is provided which permits the loosening and tightening of the chain on the chain saw blade tool with a simple lever motion. The lever arrangement is connected to a distal post member and to the sprocket cover door. Opening the door automatically loosens the chain. Closing the door automatically tightens the chain. Precision adjustments to tension are easily made in the lever arrangement by hand manipulation of a nut on a small threaded cylinder which is free from pressure when the lever is in the release position. 
    
    
     These together with other objects of the invention, along with various features of novelty which characterize the invention, are pointed out with particularity in the claims annexed hereto and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated a preferred embodiment of the invention. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a chain saw of the prior art. 
     FIG. 2 is a perspective view of a chain saw modified in accordance with the present invention. 
     FIG. 3 is an exploded view of the chain saw of FIG. 2 modified to receive the present invention enhancements. 
     FIG. 4 is a side view of an unmodified chain saw with the cover removed. 
     FIG. 5 is a perspective view the invention base plate. 
     FIG. 6 is a side view of the chain saw view of FIG. 4 with a turnbuckle holding plate and base plate installed. 
     FIG. 7 is a top view of FIG.  6 . 
     FIG. 8 is a side view of the cam assembly. 
     FIG. 9 is a top view of the cam assembly shown in FIG.  8 . 
     FIG. 10 is a top view of the chain saw view of FIG. 4 with a turnbuckle holding plate, base plate and cam assembly installed and in an open position. 
     FIG. 11 is a side view of FIG. 10 in a closed position. 
     FIG. 12 is a top view of FIG.  11 . 
     FIG. 13 is a view of the cover inside surface. 
     FIG. 14 is a top view of the cover with cam levers attached. 
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Referring to the drawings in detail wherein like elements are indicated by like numerals, there is shown a typical chain saw  1  comprised of a motor housing  2 , a handle  3  attached to said housing  2 , a safety shield  4  attached to each side of the housing  2 , an elongated, flat, plate-like chain saw blade  20 , and an endless chain  10  with cutting teeth  11 , said chain  10  extending around the perimeter  21  of said blade  20 . For purposes of exposition, the chain saw  1  is positioned in a horizontal orientation. The chain  10  extends in a continuous, endless loop. The proximal end  12  of the chain  10  extends around a sprocket gear  5  that engages the chain  10  and causes it to rotate around the peripheral edge  21  of the elongated flat blade  20  when the sprocket gear  5  is rotated. The sprocket gear  5  is attached to the output shaft (not shown) of a motor means (not shown) that is housed in a motor housing  2 . 
     The chain saw flat blade  20  has a proximal end portion  22  and a distal end potion  23 , said ends defining a horizontal, longitudinal axis, said flat blade proximal end portion  22  being secured to the motor housing  2 . The flat blade  20  has an outer surface  24  and an inner surface  25 , said surfaces interconnected by a perimeter edge  26 , said flat blade surfaces  24 ,  25  lying in parallel vertical planes. The inner surface  25  is defined as that flat blade surface abutting the motor housing  2 . The distal portion  13  of the chain  10  about the distal free end  23  of the flat blade  20  is used for cutting. An elongated slot  27  is formed through the flat blade proximal end portion  22 , said slot  27  having a longitudinal axis coincident with the longitudinal axis of the flat blade  20 . The chain saw  1  also has a removable cover  9  covering the flat blade proximal end  22  and chain  12  for safety reasons. 
     Normally, a pair of externally threaded post members  6 ,  7  that are secured to the motor housing  2  respectively extend through the slot  27 . Normally, a pair of internally threaded locking nuts  8  respectively threadingly engage the post members  6 ,  7  and securely lock the flat blade  20  against movement when the nuts  8  are tightly sealed. Prior art chain saws loosen the locking nuts  8  and slide the flat blade  20  forward or backward to tighten or loosen the endless chain  10 . When the desired position is attained the locking nuts  8  are tightened on the post members  6 ,  7  and the flat blade  20  held in place. 
     In this embodiment of the invention, the rearmost post member  6  is shortened so that the post member portion extending through the flat blade slot  27  is removed. The conventional flat blade  20  is also modified by the addition of one or more holes threaded  28  in the flat blade proximal end portion  22 . 
     The present invention includes a turnbuckle assembly  30  comprised in part of a holding plate subassembly  31  and a turnbuckle  40 , and a cam assembly  60  with a base plate  100 . The turnbuckle  40  interconnects the turnbuckle assembly  30  with the cam assembly  60 . 
     The holding plate subassembly  31  is comprised of a flat holding plate  32  with one or more holes a hole  33  formed therethrough, said holding plate  31  being connected to the flat blade outer surface  24  by means of one or more threaded screws  34  inserted into the holding plate hole  32  and engaging one or more of the flat blade threaded holes  28 . The holding plate  31  has a pivot element  35  attached thereto, pivotally interconnecting a screw socket element  36  with said holding plate  31 . The screw socket element  36  has a central, round aperture  37  formed therein. An elongated threaded screw  38  is inserted into said aperture  37 , wherein said threaded screw  38  extends forwardly in a distal direction generally parallel to the longitudinal axis of the flat blade  20 . The threaded screw  38  is adapted to threadingly engage a turnbuckle  40  as is described more fully below. See FIGS. 6 and 7. 
     The base plate  100  has an outer surface  101 , an inner surface  102 , a proximal end  103 , a distal end  104 , and two opposing, parallel sides  105 , said proximal end  103  and distal end  104  defining a base plate longitudinal axis. The base plate  100  has an aperture  106  formed therein, at a selected position along the central longitudinal axis of the base plate  100 . The base plate proximal end  103  has a stabilizer tab  107  formed thereon, said stabilizer tab  107  protruding at an angle past the base plate inner surface  102 . The base plate distal end  104  has a distal end flange  108  formed thereon, said distal end flange  108  extending past the base plate outer surface  101  at an approximate 90° angle to the plate outer surface  101 . The base plate sides  105  each have a side flange  109  formed thereon, said side flanges  109  extending past the base plate outer surface  101  at an approximate 90° angle to the plate outer surface  101 . See FIG.  5 . 
     The base plate  100  is adapted to being set onto the flat blade outer surface  24  wherein said base plate aperture  106  is adapted to fit over the chain saw foremost post member  7 . The base plate longitudinal axis is coincident with the longitudinal axis of the flat blade  20 . The base plate  100  is positioned so that the base plate proximal end  103  is oriented toward the flat blade proximal end  22 , and the base plate distal end  104  is oriented toward the flat blade distal end  23 . The base plate stabilizer tab  107  is adapted to fit into the flat blade elongated slot  27 . The base plate inner surface  102  is that surface positioned against the flat blade outer surface  24 . See FIGS. 6 and 7. 
     The turnbuckle  40  is comprised of a cylindrical body  43  having a proximal end  41  and a distal end  42 , said proximal end  41  and distal end  42  defining a turnbuckle longitudinal axis, said turnbuckle longitudinal axis being parallel to said flat blade longitudinal axis. The turnbuckle  40  has a central, longitudinal, threaded aperture  44  formed therein extending from said proximal end  41  to said distal end  42 . The holding plate subassembly threaded screw  38  engages the turnbuckle threaded aperture  44  entering first at the turnbuckle proximal end  41 . The turnbuckle cylindrical body distal end  42  terminates in a round retaining end cap  46 . The cylindrical body  43  may also have a textured external surface  45 . 
     As stated above the turnbuckle  40  interconnects the turnbuckle assembly  30  with the cam assembly  60 . This is done by means of a U-shaped bracket  50  with two parallel elongated members  52  interconnected by a transverse cross member  53 . The cross member  53  has a central aperture  54  formed therein. The cross member central aperture  54  is adapted to receive the cylindrical body  43  wherein the turnbuckle cylindrical body distal end round retaining end cap  46  has a diameter greater than the cross member central aperture  54 . The turnbuckle cylindrical body distal end round retaining end cap  46  is positioned on one side  55  of the cross member opposite a side  56  facing the rest of the turnbuckle  40 . The turnbuckle cylindrical body distal end round retaining end cap  46  is on the same cross member side  55  as the two parallel elongated members  52 . 
     The parallel elongated members  52  have free ends  57  opposite the ends  58  joined to the cross member  52 . The two ends  57 ,  58  of each elongated member  52  define the longitudinal axis of each member, said elongated member longitudinal axis being normally parallel to the flat blade longitudinal axis. Each elongated member  52  has a lateral aperture  51  formed therein near to said member free end  57 , each said lateral aperture  51  having a central axis parallel to the cross member  53 . 
     The turnbuckle assembly  30  engages the invention cam assembly  60  by means of the U-shaped bracket  50 . The cam assembly  60  is comprised of two, generally parallel, elongated cam levers  61  and an interconnecting pivot subassembly  70 . Each cam lever  61  has two ends, a cam end  62  and a lever end  63 , said ends defining a longitudinal axis for each cam lever  61 . Each cam lever  61  has an elongated camming edge  64 , an opposite engagement edge  65 , and two flat, opposing interconnecting sides  66 . The elongated camming edge  64  has an irregular, curvilinear cam surface  67  formed near to the cam end  62 . Each cam lever  61  has two lateral apertures formed therein along the cam lever longitudinal axis, extending through the interconnecting sides  66 , a first aperture  68  near to the cam end  62  and a second aperture  69  a specified longitudinal distance from the first aperture  68 . The U-shaped bracket  50  is attached to the cam assembly  60  by means of a fastener  49  inserted through each cam lever first aperture  68  into each U-shaped bracket elongated member lateral aperture  51  respectively. The purpose of the base plate  100  is to hold the entire cam assembly firmly in place and to spread cam pressure to a wider area for additional stability with bigger chain saws. The cam lever cam surfaces  67  each strike an area on the base plate outer surface  101 . 
     The pivot subassembly  70  is comprised of a pivot ring  71  in a rectangular holding plate  72 . The pivot ring  71  is adapted to fit over the foremost post member  7 . The holding plate  72  has two opposite, lateral, small arms  73 , each extending through a cam lever second aperture  69 . The holding plate  72  is held securely to the post member  7  by a threaded nut  74  and lock-washer. In an alternate embodiment, the foremost post member  7  would have two side holes adapted to receive two spring-forced locking pins from an overlapping sleeve. A user would thus not need to turn and tighten a nut in a small space but simply would drop the sleeve over the post to lock onto the post member  7 . The sleeve would be releasable by finger pinching two mini-levers on top of the sleeve. 
     As stated above most chain saws will also have a removable cover  9  covering the flat blade proximal end  22  and chain  12  for safety reasons. This cover  9  is modified for the present invention resulting in cover  90 . The cover  90  has an outside surface  91 , inside surface  92 , front  93 , rear  94 , top  95  and bottom  96 . The cover front  93  is defined as that part of the cover  90  closest to the flat blade distal end  23  when the cover  90  is closed over the flat blade proximal end  22  and chain  12 . The cover rear  94  may slant forward from bottom  96  to top  95  due to the position of the chain saw handle  3 . The cover exterior surface  91  is entirely smooth with no bolts, nuts, turning mechanisms or latch releases exposed to dirt when the chain saw is operated horizontally to cut stumps off close to the ground. 
     The cover inside surface  92  is modified by the addition of two sets of holding rails  97 , said rails being adapted to slide over the cam levers  61 , slidably holding the cam lever engagement edges  65  adjacent the cover inside surface  92 . A unique feature on the present embodiment is a slide-action cover serving several purposes. Manually sliding the cover rearward disengages a cam assembly latch  85  that is completely protected underneath the cover  90 . To attain this feature, a push block  98  is installed on the cover inside surface  92  and the cam assembly  60  is modified. 
     The cam levers  61  are interconnected by a plate  80  interconnecting the parallel lever sides  66 . The plate  80  extends centrally a predetermined distance toward the lever cam ends  62  and lever ends  63 . The plate  80  has a central opening  81  formed therein, said central opening  81  having a longitudinal axis parallel to the longitudinal axes of the cam levers  61 . The plate has an exterior surface  82  and an interior surface  83 , said exterior surface  82  being adjacent the cam lever engagement edges  65  and said interior surface  83  being adjacent the cam lever camming edges  64 . A spring-loaded L-shaped rod  84  is secured to the plate interior surface  83  and positioned so that the rod 90° end  86  protrudes through the central opening  81 . The other end of the rod terminates in a latch-hook  85  bending away from the plate interior surface  83 . 
     The cover push block  98  engages the rod 90° end  86  so that pulling the cover rearward, causes the rod 90° end  86  to move rearward, thereby causing the latch  85  to move rearward and release from the latching bar  87  installed on the motor housing  2  to the rear of the sprocket gear  5 . The cover  90  can then be swung open thereby releasing and opening the cam levers  61 . 
     In operation, as the cover  90  is closed the cam levers  61  pivot about the pivot assembly pivot ring  71  on the post member  7  pulling the turnbuckle assembly U-shaped bracket  50  forward. This in turn forces the holding plate  32  and attached flat blade  20  forward. The endless chain  10  about the flat blade perimeter  21  must also attempt to move forward. Because the endless chain  10  is anchored by the sprocket gear  5 , the result is that the endless chain becomes stretched, i.e., tightened. As the cover becomes completely closed, the cam lever camming edge  64  becomes parallel to the flat blade outer surface  24 , and the cam surface  67  engages the base plate outer surface  101 , thereby holding the cam levers  61  and attached cover  90  in a closed position. The tension between cam assembly  60  and flat blade  20  is adjustable by means of the turnbuckle assembly turnbuckle  40 . Turning the turnbuckle  40  moves the turnbuckle in either direction along the screw threaded body  38 . The endless chain  10  about the flat blade  20  may be loosened by the reverse operation of opening the cover  90 . 
     It is understood that the above-described embodiment is merely illustrative of the application. For safety, a spring bolt  98  or other latching means may be added to the cover rear  94  for locking engagement with chain saw housing  2 . Other embodiments may be readily devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.