Abstract:
The present invention is a hand held utility knife for cutting and trimming materials such as carpet, vinyl, wallpaper and the like. The utility knife comprises a knife body adapted for grasping in a single hand and at least one knife blade mounted proximate a guide end in the knife body and having a cutting direction axis. The guide end includes at least one guide cheek defining a planar surface disposed at an angle theta relative to the knife blade such that the guide cheek is adapted to slidably engage and move parallel along an adjacent planar surface thereby ensuring that the blade cuts material at a uniform and preselected angle. The guide cheek ensures the knife cuts in a uniform angular relationship relative to an adjacent planar surface such that the guide minimizes rotation of the knife body about the cutting direction axis.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to utility knives and more particular to a multi purpose utility knife which is particularly suited for trimming in corners and edges. 
     BACKGROUND OF THE INVENTION 
     Utility knives for cutting articles such as carpet, wall paper, drywall and other articles are well known in the art. For example, U.S. Pat. No. 5,561,906 titled Carpet Knife to Armand Desmarais issued Oct. 8, 1996 describes a knife specifically designed for trimming of carpets and also for creasing of carpets in the corners. U.S. Pat. No. 4,744,146 to Gregory Schmidt for an Adjustable Blade Safety Knife with Carton-Cutting Guide issued May 17, 1988 describes utility knife having a safety guard and also a feature for guiding the knife when utilizing the knife for cutting carton. 
     There are also a number of other knives which are currently being sold on the market place which have various functions and are designed for cutting in specific applications or are designed for broad use for a number of applications. 
     Tradesman which are installing carpeting and/or vinyl flooring and/or wall paper at one stage of the installation process must trim off the excess carpet, vinyl or wall paper so that the edge end will evenly butt up against a wall or ceiling or trim pieces as the case may be. The installation of carpet, vinyl flooring and wall paper requires trimming off the excess materials in either corners or edges of a room where the carpet or vinyl abuts against a surface perpendicular or normal to the material being laid. Currently this trimming is normally done utilizing a standard utility knife similar to the one described in U.S. Pat. No. 5,561,906 wherein the person trimming must ensure that he is trimming the carpet and/or other material in such a manner to leave a flush even edge along the perpendicular or normal wall. During the trimming a standard utility knife must be angled property to ensure a square edge and to ensure that the cut is as uniform and as close to the wall as possible. Unfortunately even holding the knife at an improper angle will result in a longer and/or shorter cut. Therefore, during the trimming process constantly holding the knife at the proper trimming angle is an important aspect of the trimming process. 
     Therefore, it is desirable to have a knife which help controls the angle at which cutting takes place and aids in guiding the knife along at the proper angle as the trimming is carried out. 
     SUMMARY OF THE INVENTION 
     The present invention a hand held utility knife for cutting and trimming materials such as carpet, vinyl, wallpaper and the like, the utility knife comprises: 
     a) a knife body adapted for grasping in a single hand; 
     b) at least one knife blade mounted proximate a guide end in said knife body and having a cutting direction axis; 
     c) said guide end including a means for guiding said knife in a uniform angular relationship relative to an adjacent planar surface such that the guide means minimizes rotation of the knife body about said cutting direction axis. 
     Preferably the guide means comprises at least one guide cheek defining a planar surface disposed at an angle theta relative to said knife blade such that said guide cheek is adapted to slidably engage and move parallel along an adjacent planar surface thereby ensuring that the blade cuts material at a uniform and preselected angle. 
     Preferably the guide means comprises at least two guide cheeks defining a planar surface each disposed at an angle theta relative to said knife blade such that said guide cheeks are adapted to slidably engage and move parallel along adjacent planar surfaces, such as a floor and wall, thereby ensuring that the blade cuts material at a uniform and preselected angle. 
     Preferably the utility knife is specifically adapted for cutting and trimming in corners where two planar surfaces, such as where a floor and wall meet, wherein the guide means comprises a corner guide including first and second guide cheeks each defining a planar surface and disposed at an angle theta relative to said knife blade such that said first guide cheek is adapted to slidably engage and move parallel along a first planar surface, such as a floor, and said second guide cheek is adapted to slidably engage and move parallel along a second planar surface, such as a wall, thereby ensuring that the blade cuts material at a uniform and preselected angle. 
     Preferably the guide means comprises first guide cheek disposed at an angle theta one relative said knife blade and second guide cheek disposed at an angle theta two relative to said knife blade, and said angle theta one plus theta two equals angle alpha the angle between first guide cheek and second guide cheek. 
     Preferably wherein the angle alpha is approximately 90 degrees and angles theta one and theta two are each 45 degrees, which are the preferred angles for trimming of material in corners having two planar surfaces oriented substantially 90 degrees relative each other. 
     Preferably wherein the knife body comprises a utility end and said guide end, said the utility end including a second knife blade, such that the guide end is used for cutting and trimming in corners and the second knife blade mounted in said utility end is used for conventional utility knife cutting and trimming operations. 
     Preferably the knife body comprises a utility end and said guide end, wherein the utility end including a second chisel end, such that the guide end is used for cutting and trimming in corners and the second chisel end is used for creasing, smoothing and like operations when installing carpet, vinyl, wallpaper and the like. 
     Preferably the knife body comprises a chisel end proximate said guide end, such that the guide end is used for cutting and trimming in corners and the chisel end is used for creasing, smoothing and like operations when installing carpet, vinyl, wallpaper and the like, and said second knife blade mounted in said utility end is used for conventional utility knife cutting and trimming. 
     An alternate embodiment of the present invention a utility knife attachment for use with commercially available hand held utility knives, the utility knife attachment comprises: 
     a) a knife attachment body including a guide end; 
     b) a means for releasably connecting said knife attachment to commercially available utility knives; 
     c) at least one knife blade at said guide end mounted in said knife body and having a cutting direction axis; 
     d) said guide end including a means for guiding said knife in a uniform angular relationship relative to a planar surface such that the guide means minimizes rotation of the knife body about said cutting direction axis. 
     The utility knife attachment preferably wherein the guide means comprises at least one guide cheek defining a planar surface disposed at an angle theta relative to said knife blade such that said guide cheek is adapted to slidably engage and move parallel along an adjacent planar surface thereby ensuring that the blade cuts material at a uniform and preselected angle. 
     The utility knife attachment preferably wherein the guide means comprises at least two guide cheeks defining a planar surfaces disposed at angles theta relative to said knife blade such that said guide cheeks are adapted to slidably engage and move parallel along adjacent planar surface, such as a floor and wall, thereby ensuring that the blade cuts material at a uniform and preselected angle. 
     The utility knife attachment preferably specifically adapted for cutting and trimming in corners where two planar surfaces, such as where a floor and wall meet, wherein the guide means comprises a corner guide including first and second guide cheeks each defining a planar surface and disposed at an angle relative to said knife blade such that said first guide cheek is adapted to slidably engage and move parallel along a first planar surface, such as a floor, and said second guide cheek is adapted to slidably engage and move parallel along a second planar surface, such as a wall, thereby ensuring that the blade cuts material at a uniform and preselected angle. 
     The utility knife attachment preferably specifically adapted for cutting and trimming in corners where two planar surfaces, such as where a floor and wall meet, wherein the guide means comprises first guide cheek disposed at an angle theta one relative said knife blade and second guide cheeks disposed at an angle theta two relative to said knife blade, and said angle theta one plus theta two equals angle alpha the angle between first guide cheek and second guide cheek. 
     The utility knife attachment preferably specifically adapted for cutting and trimming in corners where two planar surfaces, such as where a floor and wall meet, wherein the angle alpha is approximately 90 degrees and angles theta one and theta two are each 45 degrees, which are the preferred angles for trimming of material in corners having two planar surfaces oriented 90 degrees relative each other. 
     The utility knife attachment preferably wherein the knife attachment body comprises a chisel end proximate said guide end, such that the guide end is used for cutting and trimming in corners and the chisel end is used for creasing, smoothing and like operations when installing carpet, vinyl, wallpaper and the like. 
     A further alternate embodiment in combination a knife attachment and a commercially available hand held utility knife, the combination comprising said knife attachment releasably attached and mated to said commercially available hand held knife with said connecting means such that the knife attachment mated together with said utility knife is adapted for cutting and trimming in corners where two planar surfaces, such as where a floor and wall meet. 
     Preferably said combination comprising: 
     a) said knife attachment releasably attached and mated to said commercially available hand held knife with said connecting means; 
     b) wherein said connecting means includes a boot connector for snugly receiving the cutting end of said commercially available utility knife; and 
     c) said connecting means further comprising a locking screw for releasably clamping said knife attachment to said cutting end of said commercially available utility knife such that such that the knife attachment mated together with said utility knife is adapted for cutting and trimming in corners where two planar surfaces, such as where a floor and wall meet. 
     Preferably said combination comprising: 
     a) said knife attachment releasably attached and mated to said commercially available hand held knife with said connecting means; 
     b) wherein said connecting means includes a boot connector for snugly receiving the cutting end of said commercially available utility knife; and 
     c) said connecting means further comprising a locking screw for releasably clamping said knife attachment to said cutting end of said commercially available utility knife such that the knife attachment mated together with said utility knife is adapted for cutting and trimming in corners where two planar surfaces, such as where a floor and wall meet. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described by way of example only, with references to the following drawings in which: 
     FIG. 1 is a side elevational view of the present invention, a utility knife. 
     FIG. 2 is a top plan view of the present invention, a utility knife. 
     FIG. 3 is a front elevational view of the present invention, a utility knife. 
     FIG. 4 is a back elevational view of the present invention, a utility knife. 
     FIG. 5 is a bottom plan view of the present invention, a utility knife. 
     FIG. 6 is a schematic perspective view showing the first side of the present invention, a utility knife. 
     FIG. 7 is a schematic perspective view showing the second side of the present invention, a utility knife. 
     FIG. 8 is a schematic plan view with the first side removed showing the interior of the second side of the utility knife. 
     FIG. 9 is a schematic plan view of the interior of the utility knife with the second side removed showing the interior of the first side. 
     FIG. 10 is a side elevational view of an alternate embodiment of the present invention, a knife attachment 
     FIG. 11 is a top plan view of the knife attachment. 
     FIG. 12 is a front elevational view of the knife attachment. 
     FIG. 13 is a back elevational view of the knife attachment. 
     FIG. 14 is a bottom plan view of the knife attachment. 
     FIG. 15 is a schematic perspective view showing the first side of the knife attachment. 
     FIG. 16 is a schematic perspective view showing the second side of the knife attachment. 
     FIG. 17 is a perspective schematic view of the knife attachment being deployed together with a utility knife which is generally commercially available. 
     FIG. 18 is a schematic cutaway view showing a commercially available utility knife deployed inside the knife attachment. 
     FIG. 19 is a perspective schematic view of the knife attachment being deployed together with a utility knife which is generally commercially available. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Definitions 
     “thin planar materials”; as used in this patent refers to thin planar materials normally cut by utility knifes. These materials include, but are not limited to carpet, vinyl, vinyl flooring, wall paper and paper. 
     “Interior corner”; as used in this patent refers to corners having an interior angle of 180 degrees or less. Normally such interior corners define an interior angle of 90 degrees. Examples of the most common interior corners are: where two interior walls meet, where a wall and ceiling intersect, and where a wall and floor intersect. 
     The present invention, a utility knife is shown generally as  100  in FIGS. 6 and 7. Utility knife  100  is comprised of a knife body  102  having a first side  104  and a second side  110 , first side  104  also includes utility section  108  and guide section  106 . First side  104  and second side  110  mate together along parting line  112 . Knife body  102  has a guide end  114  and a utility end  116 . Guide end  114  i s comprised of a corner guide  118  having a first guide cheek  120  and a second guide cheek  122 . Guide end  114  also includes a first blade  123 . Utility end  116  is shown with a second blade  124  in place, however, second blade  124  is optional and utility end  116  can be used with or without second blade  124 . 
     First guide cheek  120  and second guide cheek  122  of corner guide  118  are substantially planner surfaces disposed at specific angles theta  126  relative to the knife blade  123 . The angle theta one  125  being the angle between the first plane  140  of first guide cheek  120  relative to first blade  123 . The angular relationship between the second plane  142  of second guide cheek  122  and first blade  123  is shown as angle theta two  127 . The angular relationship between the first plane  140  relative to the second plane  142  particularly as shown in FIG. 3 being the front elevational view of the utility knife  100  is angle alpha  128 . (Note: The angle theta  126  is measured from the planes defined by first or second guide cheeks  120  and  122  and the planar surface of blade  123 ) 
     Screws  130  securely attach utility section  108  to second side  110  as well as a guide section  106  to second side  110 . Screws  130  are the type that can easily be opened and closed by using either a screw driver and/or a coin for quick access into the interior of knife body  102 . 
     The shape of knife body  102  is not critical, however the shape as shown in FIGS. 1 through 9 is an ergonomic design which is comfortable to hold in the users hand. In addition, optionally knife body  102  has a chisel end  132  which can be used for creasing carpets and/or vinyl, however alternatively second chisel end  129  of utility end  116  without second blade  124  in place can also be used to crease carpet and or vinyl. 
     Utility end  116  therefore can be used as either a traditional utility type knife with second blade  124  in place or can be used as a chisel end or blunt instrument for creasing carpets and/or vinyl and/or wall paper. The radius and shape of chisel end  132  may be varied from either rounded and blunt to fairly sharp. The same also applies to the utility end  116  proximate where second blade  124  emerges from knife body  102 , namely second chisel end  129  can be rounded or fairly sharp. 
     Referring now to FIGS. 8 and 9 which show the interior of knife body  102 , FIG. 8 shows the interior of second side  110  having first blade  123  and second blade  124  in situ and said blades  123  and  124  being held in place by first blade holder  154  and second blade holder  156  which is integrally part of second side  110 . In addition, second side  110  has defined therein a spare blade compartment  150  housing spare blades  152 . Screws  130  threadably engage with threaded screw apertures  146  for mating utility section  108  and guide section  106  together with second side  110 . FIG.  8  and FIG. 9 show utility knife  100  taken apart along parting line  112  and laid open to show the interior of second side  110 , utility section  108  and guide section  106 . 
     In use corner guide  118  of utility knife  100  serves to ensure the correct orientation of first blade  123  while cutting. For example, when trimming vinyl flooring along a floor wall interface which normally are oriented approximately 90 degrees relative each other, first guide cheek  120  for example would be sliding parallel and along the floor whereas second guide cheek  122  would be sliding parallel and along to the wall. In this example, utility knife  100  would have an angle alpha  128  of roughly 90 degrees since that is angle between most walls and floors and angle theta  126  would each be 45 degrees. In this manner the angle of first blade  123  would be held at an angle substantially bisecting the angle between the floor and the wall, namely the material would be cut at approximately a 45 degree angle relative to the floor or the wall. Therefore corner guide  118  minimizes rotation of the knife body  102  about cutting direction axis  188 . As one moves the blade along the floor and the wall, the guide cheeks  120  and  122  maintain contact with the floor and walls in order to maintain a uniform angle of first blade  123  relative to the material that is being cut. Those skilled in the art of cutting vinyl flooring and/or carpeting and/or wall paper and/or any other materials requiring trimming near floor/wall interfaces know that the angle of the blade that is cutting the material is critical since a change in angle means a potential change in length of the material that is left to abut into the corner. Preferably the angle of the blade should bisect the angle between the normal surfaces since this angle leaves material behind which evenly abuts the normal surface (ie. Wall or ceiling). 
     Therefore, preferably the angle alpha  128  is approximately 90 degrees and both angles theta  126  are 45 degrees. In other situations however, different values of alpha  128  and theta  126  may be preferable depending on the amount of material that one wishes to leave abutting into a corner area and also the relative orientation between the wall and floor for example. It is also possible to maintain a constant value of the angle alpha  128  and change the ratio between theta one  125  of the first guide cheek  128  and the value of theta two  127  of the second guide cheek  122 . In this manner rather than bisecting the angle between a wall and floor for example the material could be cut at a 60 degree angle relative to the floor and/or a 40 degree angle relative to the floor and/or any other angle which is found to be appropriate to the user. 
     In addition to being especially useful for trimming carpet and vinyl flooring, utility knife  100  can also be used for trimming wall paper which abuts into a corner and/or any other materials requiring trimming which need to be trimmed off at an interface between a surface being covered and where the covering material ends by abutting a normally disposed surface such as a wall or ceiling or trim piece. 
     In addition utility knife  100  has a chisel end  132  on guide end  114  which can be used to crease carpet or vinyl and/or wall paper to force the covering material into the corner where the trimming is to take place. In addition Utility knife  100  has at utility end  116  with a second blade  124  which optionally can be used depending on the situation. If a great deal of utility cutting is required, then the user may choose to place second blade  124  in situ and use utility end  116  as a normal hand held type of utility knife. 
     On the other hand by removing second blade  124 , second chisel end  129  can be used for a variety of purposes including creasing of carpet and vinyl and/or can be shaped for smoothing and/or other functions required of carpet layers, vinyl floor layers and/or wall paper hangers. 
     In order to change the blade, either guide section  106  can be removed independently of utility section  108  or both compartments can be removed simultaneously. By threadably removing screws  130  first sides  104  can be removed from second side  110  exposing spare blade compartment  150  and spare blades  152  housed therein. First blade  123  can be removed from first blade holder  154  and replaced as well as second blade  124  can be removed from second blade holder  156  and replaced. 
     An alternate embodiment of the present invention is shown in FIGS. 10 through 19 a knife attachment shown generally as  200 . Referring to FIG. 17 and 18 a utility knife  220  has a handle end  225 , a cutting end  223 , and a blade  207 . Referring to FIG. 17 and 18 utility knife  220  which is of the type which is readily commercially available and may be manufactured out of metal or plastic and may be of the type having single blades and/or retractible blades and/or blades which can be sharpened by breaking off a portion of the blade (also known as disposable utility knives). 
     The alternate embodiment shown as knife attachment  200  comprises a knife attachment body  201 , having a guide end  211 , chisel end  212 , and a boot connector  214  having a first side  202  and a second side  204  and is connected to utility knife  220  using locking screw  216 . Knife attachment  200  also has a corner guide  230  (analogous to the previous embodiment, utility knife  100  which has a corner guide  118 ) with a first guide cheek  208  and a second guide cheek  210  having a blade  206  disposed there between. Knife attachment  200  has cutting direction axis  245  defined along the cutting direction of the blade. Boot connector  214  is dimensioned to snugly fit onto the end of utility knife  220  not shown in FIGS. 15 and 16. 
     The angle theta one  241  being the angle between the first guide check  208  relative to the first blade  206 . The angular relationship between the second guide check  210  and first blade  206  is shown as angle theta two  239 . 
     Locking screw  216  is designed to clamp down onto the body of utility knife  220 , therefore holding knife attachment  200  together with utility knife  220 . Knife attachment  200  may utilize the blade  207  as shown in FIG. 18 which is integrally part of utility knife  220  and/or it may have its own blade  206  which comes with knife attachment  200  as shown in FIG.  17 . Knife attachment  200  may or may not have parting line  250  and may or may not be capable of being split in half along parting line  250 , but rather may be one integral unit manufactured out of metal and/or plastic for snugly fitting boot connector  214  onto utility knife  220 . In analogous fashion to the previous embodiment, (utility knife  100 , having angle alpha  128  and theta  126 ) knife attachment  200  has analogous angles theta  240  theta one  241  and theta two  239  and alpha  242 . 
     FIG. 18 shows schematically how a commercially available utility knife  220  mates into boot connector  214  of knife attachment  200 . Utility knife  220  mated together with knife attachment  200  functions in a similar manner as the previous embodiment utility knife  100 . Other ways known in the art of connecting and locking together knife attachment  200  with utility knife  225  can be utilized without departing from the spirit of this invention. It may not be necessary to use locking screw  216  but rather a pin arrangement, dovetail arrangement, friction fit or any other means known in the art may be used. 
     In use knife attachment  200  is attached to a utility knife  220  which is of the type commercially available in the industry. FIG. 17 and 18 depict schematically how one such knife may look, however, knife attachment  200  can be configured to mate snugly with many other types of the utility knifes that are available on the market. In particular it can be adapted to work with the disposable blade type utility knives, the retractable blade type utility knives and/or the type of utility knives that are sharpened by breaking away a portion of the knife blade itself. Alternatively knife attachment  200  may have its own blade  206  which can be made to be replaceable. Knife attachment  200  may or may not have a first side  202  and second side  204  which can be split apart for replacement of blades  206  therein. Knife attachment  200  preferably is made of one integral unit wherein the blade  207  utilized comes with the utility knife  220 . Comer guide  230  works in analogous fashion as corner guide  118  does as described above in the previous embodiment a utility knife  100 . 
     First guide cheek  120  is analogous to first guide cheek  208 , and second guide cheek  122  is analogous to second guide cheek  210 . Knife attachment  200  mated together with a utility knife  220  functions in analogous fashion as described above for utility knife  100 . 
     A person skilled in the art will realize that knife attachment  200  is an attachment to retrofit existing utility knives in order to provide existing utility knifes with a guide for producing a more uniform cut of materials which require trimming along corners and/or specific edges. 
     It will be apparent to persons skilled in the art, various modifications and adaptations of the structure described above are possible without departure from the spirit of the invention, the scope of which is defined in the appended claims.