Abstract:
Methods and apparatus are provided for the slitting of material using a wheeled slitting apparatus. One example includes a carriage body having wheels and a handle and a blade positioning device attached to the carriage. The blade positioning device has a body that includes a slot and a clamping bar positioned in the slot and further includes a cutting blade positioned within the slot between the body and the clamping bar and held in place by a handwheel assembly that clamps the cutting blade between the body and the clamping bar in a tightened position. Such an apparatus provides for a safe, fast and efficient technique for slitting materials such as roofing membranes, carpeting, vinyl flooring and the like.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    Embodiments of the present invention generally relate to a tool for slitting sheets, membranes, coverings, coatings, layers and the like and, more particularly, to an improved blade positioning and change device. 
         [0003]    2. Description of the Related Art 
         [0004]    Utility knives are hand held devices that are commonly used to aid in the removal of covering materials such as roofing membranes, carpeting, vinyl flooring and the like. The user typically kneels or bends over, holds the housing, applies downward pressure while pulling the knife towards the user and uses the blade for cutting the covering materials. The use of the utility knife in such manner can be dangerous to the user and the depth of the cut may vary greatly. Some of the deficiencies of the prior art utility knives were solved by the wheeled slitting tool device disclosed in U.S. Pat. No. D415,174, entitled “roofing tool” wherein a common utility knife was adjustably attached to a wheeled carriage allowing for the fixed positioning of the utility knife with respect to the covering material to be cut. The wheeled slitting tool of the prior art was positioned with its wheels on top of the material to be cut allowing the user to stand away from the blade and push the wheeled slitting tool, and the cutting blade thereby, away from the user&#39;s body. 
         [0005]    Utility knives typically comprise a knife housing that is provided with a slot that receives a blade such that the blade extends from the housing. The blade of the typical utility knife includes a plurality of slots opposite the cutting edge that cooperate with at least on locking tab in the knife housing to fix the position of the blade relative to the knife housing. The knife may have only one position for the blade or may be adjustable allowing multiple positions of the blade from fully retracted to fully extended. The blade generally fits loosely within the slot allowing the blade to bend and break during use. 
         [0006]    When the blade becomes worn, dull or breaks the blade may be removed and replaced with a new blade. Some utility knives require the time consuming disassembly of the housing to change the blades wherein a screwdriver is typically employed. Many of the utility knives in the prior art include features for facilitating the changing of the blades without tools. The utility knives of the prior art which include such quick blade change features are not robust enough for use in the device disclosed in a wheeled slitting tool which frequently results in the failure of the locking tabs. 
         [0007]    Accordingly, techniques and apparatus for rigidly positioning a knife blade for use with a wheeled slitting tool are desirable. 
       SUMMARY OF THE INVENTION 
       [0008]    Embodiments of the present invention generally provide techniques and apparatus for rigidly positioning a knife blade within a housing of a wheeled slitting tool. 
         [0009]    One embodiment of the present invention provides an apparatus for at least partially slitting a covering or layered material with a wheeled slitting device having a blade positioning device. The apparatus generally includes a blade positioning device that allows for rigid clamping and positioning of a cutting blade relative to the material and further allows for a quick and tool free replacement of the cutting blade. 
         [0010]    Another embodiment of the present invention provides for positive locking of the cutting blade within the blade positioning device wherein the components of the blade positioning device include locking tabs and notches that cooperate with notches in the cutting blade prevent the cutting blade from slipping during use. 
         [0011]    Yet another embodiment of the present invention provides a method for at partial slitting a covering or layering material. The method generally includes positioning the cutting blade to a predetermined depth of cut and positioning the wheeled slitting tool on top of the material and urging the wheeled slitting tool in a forward direction to produce a slit in the material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    So that the manner in which the above-recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0013]      FIG. 1  illustrates a side view of an example wheeled slitting tool including a blade positioning device, in accordance with certain aspects of the present invention; 
           [0014]      FIG. 2  illustrates a rear view of an example wheeled slitting tool including a blade positioning device, in accordance with certain aspects of the present invention; 
           [0015]      FIG. 3  illustrates a front view of an example wheeled slitting tool including a blade positioning device, in accordance with certain aspects of the present invention; and 
           [0016]      FIG. 4  illustrates a pre-assembly plan view of a blade positioning device, in accordance with certain aspects of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Embodiments of the present invention provide a wheeled slitting tool including a robust blade positioning device, thereby effectively providing a safe and effective tool for slitting horizontally oriented layered materials. 
       An Example Wheeled Slitting Tool 
       [0018]      FIGS. 1-3  illustrate an exemplary wheeled slitting tool  100  including blade positioning device  200  in accordance with one embodiment of the present invention. Wheeled slitting tool  100  is further comprised of carriage body  101  having wheels  102  positioned thereon and rotatably fixed to axles  103  and further having handle  104  pivotly attached at bolted joint  105 . Blade positioning device  200  is adjustably secured to carriage  101  via rigid mounting plate  106  by bolts  201  and wingnuts  202  within slot  107 . 
         [0019]    Blade  203  may preferably be any known standard utility knife blade such as Stanley® FatMax® utility blade part number 11-700L. Blade  203  is removably fixed to body  206  of blade positioning device  200  by clamp bar  204  and hand wheel  205  as will be more fully described herein after with reference to  FIG. 4 . The position of blade  203  is fixed relative to blade positioning device  200  but is linearly adjustable along the adjustment direction  112  with respect to carriage  101  within slot  107 . As can be appreciated, the linear adjustment along adjustment direction  107  allows the user to set the depth of the cut. 
         [0020]    The exemplary wheeled slitting tool  100  may advantageously be used to slit a variety of layered materials  110 . Layered material  110  may be any known material applied in a horizontal manner and capable of being at least partially penetrated by a known utility knife as described herein above. Layered material  110  may or may not be adhered to a sub layer  111 . An example of a layer material  110  may be a membrane roofing material known in the industry such as TPO or PVC with a sub layer comprised of an insulating board. Other examples of layer material  110  include carpeting, vinyl flooring, plastic sheeting, tarpaulins and the like. The layered material  110  may be partially cut (scored) or cut completely through depending on the thickness and hardness of the layered material  110  and the setting of the blade positioning device  200  along the adjustment direction  112 . The position of blade  203  may be adjusted to preserve the integrity of a sub layer  111 , as illustrated by cut  113  in  FIG. 2 , or may be positioned to penetrate the sub layer and multiple layers of material as will be more fully explained herein below. Another advantage of the exemplary embodiment of the wheeled slitting tool  100  is that it can be used to penetrate and slit large contiguous sheets of layered material  110  without the need to provide an access hole in the sheet of layered material. 
         [0021]    Carriage  101  may be comprised of steel tubing and joint plates  108  and mounting plate  106  may also be comprised of a suitable steel and may be fixed to carriage  101  in any known manner, such as by welding. Axles  103  may be comprised of a threaded steel rod positioned in wholes (not shown) within carriage  101 . Wheels  102  may be comprised of a resilient neoprene material and rotatably fixed to axles  103  by nuts  109 . 
         [0022]    As illustrated in  FIG. 4 , the components comprising blade positioning device  200  are shown separately with blade  203  positioned within slot  207  in body  206 . Body  206  is adjustably positioned onto mounting plate  106  by passing bolts  201  through slot  107  in the mounting plate, through holes  219 ,  220  and fixing wingnuts  202  on the bolts. Body  206  is preferably comprised of a steel material and slot  207  may be machined into body  206  by any known method. Slot  207  includes locking tabs  208  and  209  that engage notches  210  and  211  in blade  203  thereby fixing the position of blade  203  relative to body  206 . Clamping bar  204  is preferably comprised of a steel material is sized to fit within slot  206  and further includes notches  212  and  213  and a through hole  214 . Handwheel  205  is also preferably comprised of a steel material and includes a threaded portion  215 , a shoulder  216  and outer surface  217 . Outer surface  217  may be knurled to allow for better grip by the user to tighten the assembly as will be more fully explained hereinafter. 
         [0023]    The exemplary embodiment of blade positioning device  200  shown in  FIG. 4  is assembled by placing blade  203  within slot  207  and engaging notches  208  and  209  with locking tabs  210  and  211  as shown. Clamp bar  204  is then positioned over blade  203  within slot  207  with notches  212  ad  213  engaging locking tabs  208  and  209 . Threaded portion  215  of handwheel  205  is inserted into through-hole  217  of clamp bar  204  and threadably engaged within the screw threads of hole  218  within slot  207  of body  206 . Blade  203  is then releasably clamped within blade positioning device  200  by urging shoulder  216  against clamp bar  204  by the user hand tightening handwheel  205  within threaded hole  218 . The blade positioning device may also include a washer (not shown) between the shoulder  216  and the clamping bar  204 . The outer diameter of surface  217  is selected to provide for a tool-less assembly/disassembly by a user while allowing for a high mount of clamping force to be produced through the hand tightening by the user. Unlike the prior art knife housing, with the exception of cutting edge  221  and point end  222  the blade  203  is fully supported within the blade positioning device. The combination of the materials of the body  206 , clamping bar  204  and handwheel  205  and the clamping force of shoulder  216  against the clamping bar provides for an extremely rigid support of blade  203 . 
         [0024]    In practice, when the blade  203  becomes worn, dull or breaks the blade may be removed and replaced quickly with a new blade without the need for tools by the user. The blade replacement procedure begins by first loosening handwheel  205  and unscrewing it a sufficient amount to release both the notches  212 ,  213  in clamping bar  204  and notches  210 ,  211  in blade  203  from their engagement with locking tabs  208 ,  209 . Blade  203  can then be removed from slot  107  and discarded. A new blade  203  is then inserted into slot  207  with the notches  210 ,  211  engaged with locking tabs  208 ,  209  and clamping bar is similarly positioned within slot  207  with notches  212 ,  213  engaging locking tabs  208 ,  209 . The user then tightens handwheel  205  providing sufficient hand torque to rigidly clamp blade  203  within assembly  200 . The user may then resume use of wheeled slitting tool  100  as described more fully immediately herein below. 
       An Example Use of a Wheeled Slitting Tool 
       [0025]    The exemplary embodiment will now be described with reference to  FIGS. 1-4  as it applies to the slitting and removal of a particular example of a membrane roofing system typical in large commercial style roofs. One such style membrane roof is comprised of single-ply fleece backed thermoplastic polyolefin (TPO) membrane illustrated as layer  110  and further comprised of large sheets of TPO material in 45-60 mil thicknesses and heat weldable along an edge seam to maintain waterproof integrity. The membrane  110  is typically applied on top of a mechanically fastened layer of insulation illustrated as layer  111  and may be self-adhered to the insulation or adhered with a separate layer of glue (not shown). Such membrane roofing systems are well known in the art and available from a variety of manufacturers. The TPO membrane material  110  has a finite life and needs to be removed and replaced periodically to prevent a breach of the roofing system by water from rain or snow. In accordance with the exemplary embodiment of wheeled slitting tool  100  described herein above a user will apply the wheeled slitting tool removed the membrane material  110 . The user first installs a blade  203  in the manner described herein before with reference to  FIG. 4 . The user then determines the thickness of the membrane  110  and adjusts the depth of the cut  113  by loosening wingnuts  202  and sliding blade positioning device  200  along adjustment direction  112  from a retracted position (not shown) to a predetermined depth corresponding to the desired depth of cut in layer  110 . The desired position may be set to merely score the material with point  222  of the cutting blade  203  or if a deeper cut is desired it may be positioned along adjustment direction  112  such that cutting edge  221  is employed to slit the covering material  110  and even sub layer  111 . Once the desired position has been set, the user tightens wingnuts  202  to fix the blade positioning device  200  relative to the carriage  101 . The user then grasps handle  104 , places the wheels  102  of wheeled slitting device on the surface of the membrane layer  110 , and applies sufficient downward force on handle  104  to permit blade  203  to at least partially penetrate the membrane  110 . The user forces the wheeled slitting tool  100  along the slitting direction  115  while walking and pushing the tool. The slitting process is repeated to provide discrete pieces of membrane  110  that may be manageably rolled up and removed from the roof (not shown). If, in the process of slitting membrane  110 , the blade  203  becomes worn, dull or breaks, the blade may be removed and replaced quickly with a new blade by the user by employing the replacement procedure described herein above. 
         [0026]    While the foregoing is directed to embodiments and uses of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.