Abstract:
A quick attach rotary mower blade system includes a blade holder secured to a mower spindle with a shoulder bolt, a pair of upwardly extending protrusions on the blade holder, and a spring biased plunger extending downwardly from the blade holder. A rotary mower blade has a center hole that slides over the shoulder bolt, compresses the spring biased plunger, and rotates over the protrusions to an engaged position.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to rotary mower blades on grass mowing machines, and specifically to the removal and installment of rotary mower blades to a mower deck spindle. 
       BACKGROUND OF THE INVENTION 
       [0002]    One issue that may dissatisfy users and customers of grass mowing machines is the amount of time and difficulty needed to remove and install rotary mower blades for sharpening or replacement. The blades normally are installed with a center attachment bolt and washer assembly that threads into a mower deck spindle assembly. The bolt then needs to be torqued to secure the blade to the spindle assembly. Depending on the size of the mower deck and the number of spindle assemblies, center attachment bolts may be difficult to reach and attach a wrench or socket to each bolt and tighten it sufficiently. Additionally, due to limited ground clearance and accessibility to the underside of the mower deck, there may be limited space to provide adequate leverage to the wrench or socket to break the bolt loose. The amount of torque required to break a bolt loose can be substantial if the blade has not been changed for a long time. This may require an additional lever or wood block to lock the blade into position for proper torqueing of the bolt. 
         [0003]    Some users and customers of grass mowing machines may need to change rotary mower blades frequently because of heavy usage, such as mowing every day. Others may need to change rotary mower blades when the grass mowing machines are used at a distance from the blade changing tools. Additionally, users and customers may need to change rotary mower blades each time a different blade type is required. Each blade type may have a different depth, thicknesses, or edge shape to meet requirements of cut quality, lift, mulching, etc. 
         [0004]    A quick attach rotary mower blade system is needed that allows removal and installment of a blade without a wrench or socket. A quick attach rotary mower blade system is needed that is easy to use. A quick attach rotary mower blade system is needed that does not require application of high torque to a center attachment bolt under the mower deck. A quick attach rotary mower blade system is needed that may secure blades having different depths, thicknesses, and edge shapes. A quick attach rotary mower blade system is needed that requires little or no modification of existing rotary spindles and/or mower blades. 
       SUMMARY OF THE INVENTION 
       [0005]    A quick attach rotary mower blade system includes a blade holder having a pair of L-shaped arms that hold a mower blade. A plunger extends downwardly from the blade holder, and has a face that is spring biased to press against the mower blade and hold the mower blade in engagement with the pair of L-shaped arms. A shoulder bolt secures the blade holder to a spindle and has an unthreaded shoulder with a smaller diameter than a central opening in the plunger and a central opening in a mower blade. The plunger may slide along the unthreaded shoulder and the mower blade may be removed and installed while the blade holder, spring loaded plunger and shoulder bolt remain attached to the spindle. 
         [0006]    The quick attach rotary mower blade system allows removal and installment of a blade without a wrench or socket. The system is easy to use and does not require application of high torque to a center attachment bolt under the mower deck. The quick attach rotary mower blade system may secure blades having different depths, thicknesses, and edge shapes, and requires little or no modification of existing rotary spindles and/or mower blades. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is an exploded perspective view of a quick attach rotary mower blade system according to a first embodiment of the invention. 
           [0008]      FIG. 2  is a perspective view, partially in section, of a quick attach rotary mower blade system after the blade is installed according to a first embodiment of the invention. 
           [0009]      FIG. 3  is a perspective view, partially in section, of a quick attach rotary mower blade system before the blade is installed according to a first embodiment of the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0010]      FIGS. 1-3  show one embodiment of quick attach rotary mower blade system  100  for use with one more rotary mower blades under a mower deck. The quick attach rotary mower blade system may be used to manually remove and install mower blade  138  to mower spindle  104  without tools. All of the components of the quick attach rotary mower blade system, including blade holder  102 , coil spring  124 , plunger  126 , and shoulder bolt  132 , remain attached to the spindle when the mower blade is removed. 
         [0011]    In one embodiment, the quick attach mower blade system may include blade holder  102  which may be a one-piece steel or hard plastic molded structure that may be secured to spindle  104 . Spindle  104  may be rotatably mounted to flange  106  which may be attached with threaded fasteners  108  to the underside of a mower deck. The blade holder may have outer frame  113  and a pair of L-shaped arms  118  that extend downwardly from opposing sides of the outer frame to hold a mower blade. Each L-shaped arm may include a generally vertical part extending down from the frame, and a generally horizontal part that is under the mower blade when the mower blade is installed. The horizontal part may be spaced apart from the outer frame sufficiently so that mower blade  138  may fit between the horizontal part and the outer frame. The blade holder also may have a central opening  112  that is coaxial with the internally threaded central opening  110  of spindle  104 , and a rim  127  where washer  122  may be positioned. 
         [0012]    In one embodiment, the quick attach rotary mower blade system may include a spring loaded plunger  126 . Coil spring  124  may provide a downward spring force axially against plunger  126 . As a result, the face  128  of the plunger may press down against mower blade  138 . The coil spring may be positioned between washer  122  and/or blade holder  102 , and plunger  126 . The coil spring may have a conical shape to minimize the spring&#39;s thickness in its compressed state. Plunger  126  may be a sheet metal component having a downward face  128  and a drum shape. The plunger also may have a plurality of retaining fingers  130  that extend upwardly from the plunger&#39;s outer circumference. Each retaining finger may extend through a notch  116  in blade holder  102 . Each retaining finger may contact a stop  114  at the base of each notch to limit how far the plunger may extend from the blade holder, and retain the plunger to the blade holder. Notches  116 , stops  114 , and rim  127  may be provided on shelf  121  between central opening  112  and outer frame  113  of the blade holder. 
         [0013]    In one embodiment, the quick attach mower blade system may include shoulder bolt  132 . The shoulder bolt may be threaded to the internally threaded opening  110  of spindle  104 , and remains secured to the spindle whenever the mower blade is removed. The shoulder bolt may be threaded to the spindle by turning the shoulder bolt&#39;s head  136 . Adjacent the head, the shoulder bolt may have an unthreaded shoulder  134  having a slightly larger diameter than head  136 , and an axial length of about ½ inch to about 1 inch. The unthreaded shoulder  134  also may have a larger diameter than opening  123  in washer  122 , so the shoulder bolt and washer may be used to secure the blade holder on the spindle. However, the unthreaded shoulder  134  may have a smaller diameter than central opening  129  in plunger  126 , so the plunger may slide up and down the shoulder bolt during installation of the mower blade. The unthreaded shoulder also may have a slightly smaller diameter than central opening  140  in the mower blade, so the mower blade may be installed or removed by sliding over the shoulder bolt, without removing the shoulder bolt. 
         [0014]    In one embodiment, the quick attach mower blade system may include a pair of upwardly facing protrusions  120  on the blade holder. The protrusions may engage a pair of holes  142  in the mower blade. Adding holes to the mower blade requires a modification to conventional mower blades, but is relatively easy and inexpensive. One of the upwardly facing protrusions may be provided on the horizontal part of each L-shaped arm. The pair of protrusions  120  may be located asymmetrically on the L-shaped arms, or may have different shapes or sizes. Similarly, the pair of holes  142  may be located asymmetrically on the mower blade, or may have different shapes or sizes. As a result, the mower blade may be installed in only one position and not upside down. 
         [0015]    In one embodiment, an operator may install mower blade  138  onto the quick attach mower blade system easily and without tools. First, as shown in  FIG. 3 , the operator may manually position the mower blade in the gap between the pair of L-shaped arms  118 . The operator then may push the mower blade up against plunger  126  to compress coil spring  124 . The operator may push the mower blade up high enough for the bottom of the blade to clear protrusions  120 , and then may pivot the mower blade on its central axis  140  over the protrusions onto the L-shaped arms. The operator may pivot the mower blade until the mower blade contacts the vertical part of each L-shaped arm. At this point, the pair of holes  142  in the mower blade should be positioned over the pair of upwardly extending protrusions  120 . When the operator stops pushing the mower blade up, the plunger may urge the mower blade down toward the horizontal part of the L-shaped arms, pushing the pair of holes  142  over the pair of protrusions  120 . After installation, as shown in  FIG. 2 , the coil spring may continue to apply spring force against the plunger, holding the mower blade in place and holding protrusions  120  inside holes  142 . 
         [0016]    In one embodiment, an operator also may remove mower blade  138  from the quick attach mower blade system easily and without tools. First, the operator may push the mower blade up against plunger  126  to compress coil spring  124 , until protrusions  120  are out of holes  142 . While continuing to push the mower blade up, the operator may pivot the mower blade over the protrusions and toward the gap between the pair of L-shaped arms  118 . The operator may stop pushing the mower blade up when the mower blade reaches the gap. 
         [0017]    Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.