Abstract:
A loop pile cutter includes an added blade holder thumbscrew that provides an additional clamping force to hold a blade holder right side and blade holder left side against a base mounting bracket. The added blade holder thumbscrew also guides the blade holder along the base mounting bracket. In particular, the added blade holder thumbscrew inserts within a slot in the base mounting bracket. Since the added blade holder thumbscrew is removable, the slot may be closed-ended. The combination of an added blade holder thumbscrew and a closed-ended slot in the base mounting bracket reduces deflection of the blade holder from carpet tufts that resist being parted by a center row guiding edge.

Description:
BACKGROUND 
       [0001]    This invention relates generally to flooring tools, and in particular to loop pile cutters used to cut seams in carpets. 
         [0002]    A loop pile cutter is commonly used in carpet seaming. Modern carpets are constructed with tufts of colored yarn material that are knitted in rows into a backing material by machines. The tufts form the “face” of the carpet, which faces up and is visible on the floor of a room. The backing faces down and holds the yarns together. 
         [0003]    The carpet is manufactured in standard width rolls. The roll widths are cut to the dimensions of the room. In many cases, they are seamed together with a hot melt adhesive tape to form a single, one piece floor covering. In other cases, primarily in commercial settings, the carpet is glued directly to a subfloor with seams simply abutted. In either case, the quality of the installation depends on proper preparation of the edges of the carpet forming the seams. 
         [0004]    The loop pile cutter prepares carpet edges for seaming by trimming the backing material as closely as possible to a row of carpet tufts. Without this trimming, the rough edges of backing can protrude past the tufts. This can create unsightly gaps at the seam. Loop pile cutters have a left blade and a right blade, which allow the tool to trim the carpet close to the tufts on both sides of the seam, greatly reducing such gaps. 
         [0005]    As described in U.S. Pat. No. 3,543,400 to Scott, and U.S. Pat. No. 5,881,463 to Casteel, the distinguishing feature of a loop pile cutter (compared with other carpet seam cutters) is a blade holder that is adjustable in height in relation to a base. With reference to FIG. 1 of Scott, the base 14 is made with a supporting plate 12 with two L-shaped angle members 69 forming the base bottom. The base 14 rides on a subfloor. Supporting plate 12 has slot 38, and arm portion 18. Arm portion 18 has an inclined upper edge 20. Both slot 38 and upper edge 20 are formed at an acute angle of about 30 degrees in relation to the base 14. Slot 38 and upper edge 20 form the guide surfaces for the height adjustment of the blade holder. 
         [0006]    The blade holder that fastens on the base 14 is formed with a pair of left and right retaining plates 24 welded to a guide plate 28 (FIG. 3) forming a center. Guide plate 28 forms carpet engaging edge 32 which guides the cutter between rows of carpet tufts. 
         [0007]    The retaining plates are also riveted together along with handle 26 at two upper flat areas. As shown in FIG. 3, these flat areas are bordered by of two angled, upwardly jogging “shoulders” 25. The angle of the shoulders 25 corresponds to the upper edge 20 of arm portion 18 (FIG. 1) once the blade holder of this cutter is assembled onto base 14. Thus, shoulders 25 (FIG. 3) ride upon and are guided by the inclined plane defined by upper edge 20 of arm portion 18 (FIG. 1). As shown in FIG. 1, this incline defines a range of height adjustment for the blade holder in relation to the base 14. 
         [0008]    As shown in FIG. 1, the blade holder has had two nuts 42 (not shown) welded onto a retaining plate outer surface. The nuts 42 (not shown) receive two threaded thumb screws 36, 64. Thumb screw 36 runs through slot 38 for to hold the blade holder at a selective height above base 14. When thumb screw 36 is tightened into a first nut 42, the inside of retaining plates 24 are clamped and frictionally held against the outside of supporting plate 12. This clamping action of thumb screw 36 holds the blade carrier at a height above base 14. 
         [0009]    As shown in FIG. 5, blades 54, 56 are held on their outer surfaces by the inner walls of retaining plates 24. These inner walls form recesses 48, 50 (FIGS. 2 and 3). As shown in FIG. 5, blades 54, 56 are held on their inner surfaces by guide plate 28 that forms carpet engaging edge 32 (FIG. 1). Left and right blades 54, 56 are offset slightly from the centerline of the cutter by a half thickness of guide plate 28. 
         [0010]    As further shown in Scott&#39;s FIG. 1, a second thumb screw 64 is threaded into a second nut 42 (not shown) welded onto a retaining plate outer surface. Thumb screw 64 serves primarily to adjustably hold left and right blades 54, 56 (FIG. 3) within blade recesses 48 and 50 (FIGS. 2 and 3). The angle of blade recesses 48 and 50 (FIG. 2) in relation to base 14 is the same 30 degree angle as upper edge 20 of arm portion 18 and slot 38 for height adjustment. 
         [0011]    The reason that the blades 54, 56 must be adjusted in height within the area defined by blade recesses 48, 50 (FIG. 2) is as follows: The blade holder must be moved up or down to accommodate various thicknesses of carpet. As the blade holder is moved up or down on upper edge 20 of base 14, blades 54, 56 must be correspondingly extended or retracted so that they may seat within a recesses 58 in base 14 (FIG. 1). As shown in FIGS. 1 and 3, recesses 58 keep blades 54, 56 from deflecting horizontally due to resistance from the carpet. 
         [0012]    Deflection of the blades themselves could result in the cutter shearing off parts of carpet tufts which are meant to be preserved, or could also result in carpet backing material not being trimmed. To produce the best looking seam, both these problems must be avoided. Hence, all the loop pile cutters discussed herein have blade holders similar to recesses 48, 50 (Figure and 3) and recesses 58 (FIGS. 1 and 3) to prevent deflection of the blades. 
         [0013]    As further shown in Scott&#39;s FIG. 1, the approximately 30 degree angle formed by blade recesses 48 and 50 (FIG. 3), the inclined upper edge 20 of support plate 12, and slot 38, are designed to place the blades 54, 56 approximately at a 30-degree angle in relation to carpet entering at carpet receiving slot 34. This angle is preferred because it exposes a long surface of blades 54, 56 where the cross section of the carpet backing is expected to pass. A lower angle may cause the carpet tufts to trap under the blade and be sheared. A higher angle would place less blade surface in the area of the carpet backing, resulting in faster blade wear, less efficient cutting, both of which can cause the carpet to rise up and wad against carpet engaging edge 32. 
         [0014]    Thus, the loop pile cutter of Scott provides a base and a blade holder that is adjustable in height. As shown in FIG. 1, a carpet edge to be trimmed enters a carpet receiving slot 34 defined as the open area between the edge referred to as carpet receiving slot 34 of base 14 and the lower edge of carpet engaging edge 32. The height adjustment allows carpets of various thicknesses (varying by height of tufts and thickness of carpet backing) to enter carpet receiving slot 34. Carpet engaging edge 32 guides the cutter between two rows of carpet tufts as the user pushes on handle 26 (FIG. 1). 
         [0015]    In use, as shown in FIG. 1, first the height of the blade holder must be adjusted such that carpet engaging edge 32 of guide plate 28 (FIG. 5) presses deep between two rows of carpet tufts all the way down to the carpet backing (best seen in FIG. 5). Thumb screw 36 is tightened to hold this height. 
         [0016]    Regarding the selection of the left blade 54 and right blade 56, the directional terms left and right in the disclosure of Scott are made from the perspective of section 3-3 facing down carpet engaging slot 34 in the direction of the blades. As shown in FIG. 4, a left blade 54 is extended into a recess 58 (FIG. 1) in base 14 in order to trim close to a left side of a carpet tuft (making “cut” 78). In such case, a right blade 56 is retracted (raised up) into blade recess 50 (FIG. 3) so that it will not cut any carpet. Alternatively, as shown in FIG. 5, a right blade 56 is extended into a recess 58 (FIGS. 1 and 3) to trim close to a right side of a carpet tuft (making cut 80). In such case, a left blade is 54 is retracted (raised up) into a recess 48 so that it will not cut any carpet. With both edges of the carpet prepared in this manner, the carpet tufts should abut precisely with no gap due to excess carpet backing. This produces an improved carpet seam. 
         [0017]    However, as the loop pile cutter of Scott is pushed through a row of carpet, the carpet engaging edge 32 (FIG. 1) encounters side loads from carpet tufts which resist being parted. As shown in FIG. 3, to the extent that there is play between side plates 24 and upper arm 18 of base 12, these side loads can cause shifting of the entire blade holder to the left or right off the centerline of base 14. The side loads can also cause bending of supporting plate 12. This shifting of the components and bending of the main base bracket component (supporting plate 12) will be referred to as deflection of the blade holder. Deflection of the blade holder can cause the cutter to turn to the left or the right as it moves between the rows of tufts. This can cause the cutter to shear tufts close to the blade, or even skip out between the rows of tufts which are intended, into another adjacent set of tuft rows. If such skipping occurs, the edge will not match with another properly cut edge, and the trimming operation on the improperly cut side must be repeated. 
         [0018]    With the cutter of Scott, as shown in FIG. 1, the cutter&#39;s main resistance to deflection is the clamping action of thumb screw 36 holding retaining plates 24 against arm portion 18 of supporting plate 12. Only one thumb screw is provided to produce all necessary clamping force, and the position of this screw is at considerable distance from side loads that cause the deflection. Some means of reducing the deflection of the blade holder assembly would tend to reduce the undesirable shearing of tufts or skipping out of tuft rows that may occur. 
         [0019]    Another loop pile cutter with a different blade holder construction is disclosed in U.S. Pat. No. 5,881,463 to Casteel. As shown in Casteel&#39;s FIG. 2, the loop pile cutter has a similar base 102 and a mounting bracket 104. Mounting bracket 104 has an open-ended slot 114 for holding a blade carrier, and a second slot 112, which is closed-ended. The angle formed by the centerlines of both slots 112, 114 in this cutter is the same 30 degree angle as in Scott. 
         [0020]    As shown in FIG. 1, blade support 300 is an assembly forming the blade holder of this cutter. Blade support 300 includes a center plate 301 (FIG. 8). As shown in FIG. 8, center plate 301 has a tongue 302. Tongue 302 has also has a centerline at a 30 degree angle in relation to its bottom edge. This makes tongue 302 insertable into open-ended slot 114 of mounting bracket 104 (FIG. 2). Tongue 302 can thus be slideably positioned on the incline of open-ended slot 114 (FIG. 2). As shown in FIG. 1, this allows blade support 300 to be positioned at a selective height above base 102 (FIG. 2). As shown in FIG. 8, center plate 301 also has a hole 306 for passage of a threaded fastener. 
         [0021]    To form the blade holders of this cutter, as shown in FIGS. 9 and 10, bar spacers 308, 308′ and nose spacers 310, 310′ are attached (as by welding or riveting) to either side of center plate 301. The bottom edges of bar spacers 308, 308′ form top bearing surfaces 312, 312′. These define the top boundary of the left blade compartment 319 and right blade compartment 319′ (FIG. 13), respectively. The top edges of nose spacers 310, 310′ form bottom bearing surfaces 314, 314′. These define the bottom boundary of the left blade compartment 319 and right blade compartment 319′ (FIG. 13), respectively. As with blade recesses 48 and 50 of Scott, left blade holder 319, and right blade holder 319′ hold the blade at about a 30 degree angle in relation to base 14. 
         [0022]    As shown in FIG. 13, left side plate 316 and right side plate 316′ are mounted as by riveting or welding onto bar spacers 308, 308′ and nose spacers 310, 310′. Left side plate 316 and right side plate 316′ define the outer boundary of left blade compartment 319 and right blade compartment 319′. As shown in FIGS. 11 and 12, the left side plate 316 and right side plate 316′ additionally have “openings” that align with hole 306 through center plate 301 (FIG. 8). 
         [0023]    As shown in FIG. 1, threaded fastener 10 may pass through the “openings” in side plates 316, 316′ (FIGS. 11 and 12), though hole 306 (FIG. 8) in the center plate, and then be threaded into in a nut (not shown) attached to a side plate outer surface. As shown in FIG. 1, tightening the threaded fastener 10 holds the blades 14, 14′ at a height within the blade support assembly 300. 
         [0024]    Bar spacers 308, 308′ and nose spacers 310, 310′ (FIGS. 9 and 10) serve one additional function in that, once attached to center plate 301 (FIG. 8) and left side plate 316 and right side plate 316′ (FIGS. 11 and 12), they hold all these components together if threaded fastener 12 (FIG. 1) is removed. As shown in FIG. 1, this is helpful if blade support assembly 300 must be removed from base 102 (FIG. 2). This may be required during maintenance or cleaning of the cutter. 
         [0025]    As shown in FIGS. 11 and 12, left side plate 316 and right side plate 316′ additionally have holes 318, 318′ respectively for insertion of a second threaded fastener 12 (FIG. 1). Threaded fastener 12 (FIG. 1) passes through a hole 318 in left side plate 316 (FIG. 12), slot 112 in mounting bracket 104 (FIG. 2), hole 318′ in right side plate 316′ (FIG. 11), and threads into a nut (not shown) mounted on a side plate outer surface. As shown in FIG. 1, when threaded fastener 12 is tightened, the inner surfaces of left and right side plates 316, 316′ (FIGS. 11 and 12) are clamped and frictionally held against mounting bracket 104 of base plate 100 (FIG. 2), holding blade support 300 (FIG. 1) at a selective height. 
         [0026]    The cutter of Casteel has the same or worse problems of deflection of its blade holder. As shown in FIG. 1, threaded fastener 12 provides the only resistance to side loads, but is again at a distance from the outer end of blade support 300 (element 18). The loop pile cutter also includes bar spacers 304, 304′, and nose spacers 310, 310′ (FIGS. 9 and 10) forming the blade compartments. These actually tend to hold left side plate 316 and right side plate 316′ (FIGS. 11 and 12) apart. This creates built-in play between the inner surfaces of left side plate 316 and right side plate 316′ (FIGS. 11 and 12) and mounting bracket 104 (FIG. 2). As a result, threaded fastener 12 is less able to clamp the inner surfaces of left side plate 316 and right side plate 316′ (FIGS. 11 and 12) against mounting bracket 104 (FIG. 2). 
         [0027]    Furthermore, as shown in FIG. 2, slot 114 which accepts tongue 302 of center plate 301 (FIG. 8), is open-ended. In use, as blade support assembly 300 (FIG. 1) encounters resistance from carpet tufts and begins to deflect, the open-ended shape slot 114 of promotes bending of mounting bracket 104. If this open-ended slot 114 were closed-ended, the bending resistance of mounting bracket 104 may be improved, and blade support assembly 300 would have greater resistance to deflection. 
         [0028]    As shown in FIG. 12, open-ended slot 114 (FIG. 2) is formed with an open end so that tongue 302 of center plate 301 (FIG. 8) of blade holder assembly 300 (FIG. 1) can be removed entirely from open-ended slot 114 (for maintenance, for example). Open ended slot 114 is economical in that no additional parts are required to provide the functions of a holder and an inclined plane for adjustably mounting blade holder assembly 300. However, open ended slot 114 promotes bending of mounting bracket 104. 
         [0029]    Therefore, for several reasons, blade support 300 of the loop pile cutter of Casteel may deflect even more under side loads than the blade holder of Scott. 
         [0030]    Another prior art loop pile cutter with a different blade holder construction, manufactured by Crain Cutter Company, is shown in  FIG. 1  of this application. Loop pile cutter  10000  has a base  10200  with a base mounting bracket  10205 . As shown in  FIG. 2 , base mounting bracket  10205  includes an open ended slot  10210 , a blade holder screw slot  10215 , a flat  10220 , and bottom edge  10225 . The centerlines of open ended slot  10210 , blade holder screw slot  10215 , as well as the angle formed by bottom edge  10225 , all form an approximately 30 degree angle in relation to a base bottom surface  10230  of base  10200 . 
         [0031]    The exploded view of blade holder  10500  in  FIG. 2  shows holder right side  10505 , holder center  10540 , and holder left side  10570 . Holder right side  10505  includes right inward jog  10510 , right spot weld surface  10515 , right partial pierce  10520 , right hand attached nut  10525 , and a blade holder screw through hole  10530 . Holder left side  10570  includes left inward jog  10575 , left spot weld surface  10580 , left partial pierce  10585 , left hand attached nut  10590 , and a blade thumbscrew passage hole  10595 . Right inward jog  10510  and left inward jog  10575  are also at a 30 degree angle in relation to base bottom surface  10230  once assembled onto base  10200 . Holder center  10540  includes a center row guiding edge  10545 , and a center blade screw passage hole  10550 . 
         [0032]    Blade holder  10500  is assembled by spot welding blade holder center  10540  between holder right side  10505  and holder left side  10570  at right spot weld surface  10515  and left spot weld surface  10580 . After spot welding, holder right side  10505  and left side  10570  abut one another at right partial pierce  10520  and left partial pierce  10585 . 
         [0033]    The function of the abutting surfaces formed by right partial pierce  10520  and left partial pierce  10585  is to produce an inexpensive pair of guide surfaces on both parts, which is insertable within open ended slot  10210 . Once inserted into slot  10210 , these guide surfaces serve to guide the height adjustment of blade holder  10500  at an angle of approximately 30 degrees in relation to base  10200 . 
         [0034]    As shown in  FIG. 1 , blade holder center  10540 , once spot welded together with holder right side  10505  and holder left side  10570 , forms the center row guiding edge  10545  of the cutter, as well as blade pocket separator  10555 . 
         [0035]    As shown in  FIG. 2 , right inward jog  10510  of holder right side  10505  forms the bottom of right blade pocket  10535 . Left inward jog  10575  of holder left side  10570  forms the bottom edge of a left blade pocket  10600 . Bottom edge  10225  of base holder bracket  10205  forms the top of both right blade pocket  10535  and left blade pocket  10600 . 
         [0036]    Right slotted razor blade  10625  is held in right blade pocket  10535 , and left slotted razor blade  10650  is held in left blade pocket  10600 . Right slotted razor blade  10625  and left slotted razor blade  10650  are held at a selective height within right blade pocket  10535  and left blade pocket  10600  by blade thumb screw  10675 . Blade thumb screw  10675  passes though blade screw passage hole  10595  of holder left side  10570 , through the slot of left slotted razor blade  10650 , through center blade screw passage hole  10550 , through the slot of right slotted razor blade  10625 , and threads into right hand attached nut  10525 . Thus, when blade thumbscrew  10675  is tightened, blade holder right side  10505  is drawn inward to clamp and frictionally hold right slotted razor blade  10625  at a height. The blade thumbscrew head bottom  10676  of holding thumbscrew  10675  tightens down on the outer face  10651  of left slotted razor blade  10650  to frictionally hold left slotted razor blade  10650  at a height. 
         [0037]    Blade holder thumb screw  10400  passes through a blade holder screw through hole  10530  in holder right side  10505 , a holder slot  10215  in base mounting bracket  10205 , and threads into a left hand attached nut  10590 . Thus, as lower holder thumbscrew  10400  is tightened, holder right side  10505  and holder left side  10525  are drawn together and frictionally held against flat  10220  of base mounting bracket  10205 . As shown in  FIG. 1 , thumb screw  10400  provides the cutter&#39;s main resistance to side loads at row guiding edge  10545  causing deflection of blade holder  10500 . 
         [0038]    Much as with the cutters of Scott and Casteel, as shown in  FIG. 1 , blade holder thumb screw  10400  is at a distance from center row guiding edge  10545 , which reduces its ability to resist deflection. Much with as the bar spacers 308, 308′ and nose spacers 310, 310′ (FIGS. 9 and 10) of Casteel, the abutting left partial pierce  10520  and right partial pierce  10585  work as a permanent separator between holder left side  10505  and holder right side  10570 . As shown in  FIG. 2 , this separation further reduces the ability of body holder screw  10400  to effectively clamp holder right side  10505  and holder left side  10570  against base holder bracket  10205 . The result is that the blade holder can deflect. Much as with the cutter of Casteel, open ended slot  10210  promotes bending of base mounting bracket  10205 , further reducing the ability blade holder  10500  to resist deflection. 
         [0039]    What is needed is a loop pile cutter with an improved blade holder assembly and blade holder mounting bracket in its base that can better resist deflection. 
       SUMMARY 
       [0040]    Embodiments of the invention comprise a loop pile cutter with an added blade holder thumbscrew that provides an additional clamping force to hold a blade holder right side and blade holder left side against a base mounting bracket. The added blade holder thumbscrew also guides the blade holder along the base mounting bracket. In particular, the added blade holder thumbscrew inserts within a slot in the base mounting bracket, which in one embodiment is formed at a 30-degree angle in relation to the base of the tool once assembled. Since the added blade holder thumbscrew is removable, the slot may be closed-ended. The combination of an added blade holder thumbscrew and a closed-ended slot in the base mounting bracket reduces deflection of the blade holder from carpet tufts that resist being parted by a center row guiding edge. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0041]      FIG. 1  is a perspective view of a prior art loop pile cutter. 
           [0042]      FIG. 2  is an exploded view of the loop pile cutter of  FIG. 1 . 
           [0043]      FIG. 3  is a perspective view of a loop pile cutter, in accordance with an embodiment of the invention. 
           [0044]      FIG. 4  is an exploded view of the loop pile cutter of  FIG. 3 . 
       
    
    
       [0045]    The figures depict various embodiments of the present invention for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein. 
       DETAILED DESCRIPTION 
       [0046]    As shown in  FIG. 3 , loop pile cutter  20000  of the present invention has a blade thumbscrew  23010 , and a lower blade holder thumbscrew  23020 , which are similar to the prior art loop cutters. Loop pile cutter  20000  additionally has upper blade holder thumb screw  23030 . With regard to loop pile cutter  20000  of the present invention, blade thumbscrew  23010  is described as a “blade thumbscrew” because its function is to hold the blades within blade holder  21000 . 
         [0047]    In contrast, it is not the function of blade thumbscrew  23010  to hold the blade holder  21000  on a base mounting bracket  20020 . Instead, holding the blade holder  21000  is the function of lower blade holder thumbscrew  23020  and upper blade holder thumb screw  23030 . Hence, lower blade holder thumbscrew  23020  and upper blade holder thumb screw  23030  are referred to as “blade holder thumbscrews.” 
         [0048]    As shown in  FIG. 3 , loop pile cutter  20000  has a base  20010  with a base mounting bracket  20020 , and blade holder  21000 . As shown in  FIG. 4 , base mounting bracket  20020  has two closed-ended slots for clamping blade holder  21000  onto base mounting bracket  20020 , lower blade holder slot  20040 , and upper blade holder slot  20060 . Base mounting bracket  20020  additionally has a flat  20080 , and a bottom edge  20100 . The centerlines of lower blade holder slot  20040  and upper blade holder slot  20060 , as well as the angle formed by bottom edge  20100 , all form an angle of 30 degrees in relation to a base bottom surface  20110  of base  20010 . 
         [0049]    The exploded view of the parts of the blade holder  21000  shows a holder right side  21100 , holder center  21300 , and a holder left side  21500 . Holder right side  21100  includes a right inward jog  21110 , right spot weld surface  21120 , right blade attached nut  21130 , right lower blade holder attached nut  21140 , and right upper blade holder attached nut  21150 . Holder left side  21500  includes a left inward jog  21510 , a left spot weld surface  21520 , a left blade through hole  21530 , left lower blade holder through hole  21540 , and a left upper blade holder through hole  21550 . Right inward jog  21110  and left inward jog  21510  will also be at a 30-degree angle in relation to base bottom surface  20110  when assembled with base  20010 . Holder center  21300  includes center row guiding edge  21310 , and center blade through hole  21320 . 
         [0050]    Blade holder  21000  is assembled by spot welding holder center  21300  between holder right side  21100  and holder left side  21500  at right spot weld surface  21120  and left spot weld surface  21520 . As shown in  FIG. 3 , blade holder center  21300 , after being spot welded between holder right side  21100  and holder left side  21500 , forms center row guiding edge  21310  and blade pocket separator  21330  defining two blade pockets within blade holder  21000 . 
         [0051]    As shown in  FIG. 4 , right inward jog  21110  of holder right side  21100  forms the bottom edge of a right blade pocket  21160 . Left inward jog  21510  forms the bottom edge of a left blade pocket  21560 . Bottom edge  20100  of base mounting bracket  20020  forms the top of both right blade pocket  21160  and left blade pocket  21560 . 
         [0052]    Right slotted razor blade  22010  is held in right blade pocket  21160  and left slotted razor blade  22020  is held in left blade pocket  21560 . Right slotted razor blade  22010  and left slotted razor blade  22020  are held at a selective height by blade thumbscrew  23010 . Blade thumbscrew  23010  passes through a left blade through hole  21530 , the slot in left slotted razor blade  22020 , center blade through hole  21320 , the slot in right slotted razor blade  22010 , and threads into right blade attached nut  21130 . When blade holding thumbscrew  23010  is tightened, blade holder right side  21100  is drawn towards blade holder center  21300 , which clamps right blade  22010  at a height. Blade thumbscrew head bottom  23011  bears on an outer surface  22021  of left slotted razor blade  22020  to hold left slotted razor blade  22020  at a height. 
         [0053]    Lower blade holder thumbscrew  23020  passes through left lower blade holder through hole  21540 , lower blade holder slot  20040  in base mounting bracket  20020 , and threads into right lower blade holder attached nut  21140 . Thus, as lower blade holder thumbscrew  23020  is tightened, holder right side  21100  and holder left side  21500  are drawn together and frictionally held against flat  20080  of base mounting bracket  20020 . 
         [0054]    As shown in  FIG. 4 , upper blade holder thumbscrew  23030  passes through left upper blade holder through hole  21550 , upper blade holder slot  20060  in base mounting bracket  20020 , and threads into right upper blade holder attached nut  21150 . Thus, as upper blade holder thumbscrew  23030  is tightened, holder right side  21100  and holder left side  21500  are further drawn together and frictionally held against flat  20080  of base mounting bracket  20020 . 
         [0055]    In the loop pile cutter  20000  of an embodiment of the invention, upper blade holder thumbscrew  23030  and lower blade holder thumbscrew  23020 , once tightened, cooperatively clamp holder right side  21100  and holder left side  21500  and against a base mounting bracket  20020 . The lack of a member that causes spreading, such as shoulders 25 of Scott (FIG. 3), or bar spacers 308, 308′ and nose spacers 310, 310′ of Casteel (FIGS. 9 and 10), or the abutting right partial pierce  10520  and right partial pierce  10585  of Crain (FIG. 2), combined with the increased clamping force from upper blade holder thumbscrew  23030 , produce uniform, face to face contact between the inner sides of holder right side  21100 , holder left side  21500 , and base mounting bracket  20020 . This minimizes play in the assembly and increases the ability of the blade holder  21100  to resist deflection. 
         [0056]    As shown in  FIG. 3 , the positioning of upper blade holder thumbscrew  23030  is closer in proximity to an end  21315  of center row guiding edge  21310  than lower blade holder thumbscrew  23020 . It is also closer to an end of a center row guiding surface than the thumbscrew 36 (FIG. 1) of Scott, threaded fastener 12 of Casteel (FIG. 1), or thumbscrew  10400  (FIG. 1) of Crain. While these elements all perform the function of clamping a blade holder to a base mounting bracket, upper blade holder thumbscrew  23030  is positioned better to resist the leverage generated by side loads from carpet tufts on center row guiding edge  21310  ( FIG. 3 ) which can cause deflection of blade holder  21000 . 
         [0057]    As previously explained, from time to time a loop pile cutter may need to be disassembled for maintenance or cleaning. When such is necessary with the loop pile cutter  20000 , as shown in  FIG. 4 , lower blade holder thumbscrew  23020  and upper blade holder thumbscrew  23030  are removed from lower blade holder slot  20040  and upper blade holder slot  20060  in base mounting bracket  20020 . This allows the blade holder  21000  to be removed from base  20010  for maintenance or cleaning. 
         [0058]    As shown in  FIG. 4 , because upper blade holder thumbscrew  23030  is removable, upper blade holder slot  20060  may be closed-ended. This improves the ability of base mounting bracket  20020  to resist bending forces generated by side loads from carpet tufts on center row guiding edge  21310  ( FIG. 3 ). 
         [0059]    In use, as shown in  FIG. 3 , first of all the loop pile cutter  20000  is adjusted to the thickness of carpet. If new blades are to be installed, blade holding thumbscrew  23010  is removed. Loop pile cutter  20000  is placed on a subfloor surface (surface beneath the loose piece of carpet being trimmed). Lower blade holder thumbscrew  23020  and upper blade holder thumbscrew  23030  are loosened. This allows the blade holder  21000  to be raised or lowered at a 30 degree angle in relation to base  20010 . Blade holder  21000  is raised to the height of the tufts of the carpet, then pressed downward as deeply as possible between two rows of carpet tufts until center row guiding edge  21310  contacts the carpet backing. This sets the proper height of center row guiding edge  21310  in relation to base  20010 . Once at proper height, the carpet can enter at the space between a base top surface  20050  and center row guiding edge  21310 , which will be referred to as a carpet opening  20090 . Once the carpet is inserted at carpet opening  20090 , center row guiding edge  21310  can guide loop pile cutter  20000  between two rows of carpet tufts. 
         [0060]    As shown in  FIG. 3 , once the proper carpet opening  20090  is set, any standard slotted razor blades, such as left slotted razor blade  22020  and right slotted razor blade  22010  ( FIG. 4 ), may be inserted into right blade pocket  21160  or a left blade pocket  21560 . If a right edge of carpet is to be trimmed for seaming, left slotted razor blade  22020  is lowered into a left blade holding channel  20120  in base  20010 . (Right blade holding channel  20110  and left blade holding channel  20120  are more easily seen in  FIG. 4 .) When a right edge of the carpet is to be trimmed, an opposite side right slotted razor blade  22010  ( FIG. 4 ) will be held up out of the way within right blade pocket  21160  ( FIG. 4 ) such that it will not cut any carpet. As shown in  FIG. 3 , once right slotted razor blade  22010  ( FIG. 4 ) and left slotted razor blade  22020  ( FIG. 4 ) are properly positioned, blade holding thumbscrew  23010  is tightened, clamping the blades at that height. 
         [0061]    As shown in  FIG. 3 , once carpet is inserted into carpet opening  20090 , with center row guiding edge  21310  guiding loop pile cutter  20000  between two rows of carpet tufts, left slotted razor blade  22020  will cut as close as possible to a row of carpet tufts on a right edge of carpet that is becoming the right side of a seam. Any excess carpet backing on a right side of the carpet is removed by left slotted razor blade  22020 . 
         [0062]    As shown in  FIG. 4 , if a left side of a carpet is to be trimmed, a right slotted razor blade  22010  is lowered into a right blade holding channel  20110 , and a left slotted razor blade  22020  is raised up in left blade pocket  21560  out of the way so that it will not cut. Blade holding thumbscrew  23010  is tightened. As shown in  FIG. 3 , carpet is inserted into carpet opening  20090 , with center row guiding edge  21310  guiding loop pile cutter  20000  between two rows of tufts. Right slotted razor blade  22010  ( FIG. 4 ) will cut as close as possible to a row of carpet tufts on a left edge of carpet. 
         [0063]    The foregoing description of the embodiments of the invention has been presented for the purpose of illustration; it is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above disclosure. Finally, the language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of the embodiments of the invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.