Abstract:
A cushion back cutter is formed from a first side plate, a second side plate, and a center plate between the first and second side plates. The center plate includes a slot that forms a blade holding pocket with a bottom opening to receive one or more blades. A blade clamp is inserted into the blade clamp opening of the first side plate, and a blade clamp fastener tightens to cause the blade clamp to press the blades against the second side plate to hold the blades in position. The center side plate forms a row guide for guiding the blades of the cutter between adjacent rows of carpet tufts. The row guide may include a region having continuous notches, which tend to move the carpet tufts out of the path of the blades to avoid shearing them.

Description:
BACKGROUND 
       [0001]    This invention relates generally to flooring tools, and in particular to cushion back cutters. A cushion back cutter is a tool for precisely trimming the edges of carpet seams in preparation for making the seams. As shown in  FIG. 1 , a prior art cushion back cutter  100  has a body  110 ; a row separator  115 ; a row guide  120  that is a straight, thin, beveled surface forming the bottom of the cutter; a blade holding pocket  125  for holding a slotted razor blade  130 ; and a blade thumbscrew  140 .  FIG. 2  shows greater detail of one slotted razor blade  130  that is commonly used in the carpet installation trade and in particular with cushion back cutters. Slotted razor blade  130  is generally rectangular in shape, and both long sides have edges  132  that are sharpened along their entire length. Slotted razor blade  130  also includes central slot  134 . 
         [0002]    As shown in  FIG. 1 , to install slotted razor blades  130  into the prior art cushion back cutter, blade thumbscrew  140  must first be unscrewed and completely removed. Next, the user inserts the blades in the bottom of blade holding pocket  125  (which has an opening in the bottom of the cutter). Blade thumbscrew  140  can then be re-inserted through a hole in one side of the body, through the central slot  134  in the slotted razor blade  130 , and can be tightened into a nut (not shown) welded onto the outside of the opposite side of the body. The slotted razor blade can be extended or retracted from bottom of row guide  120  by loosening the blade thumbscrew  140  and moving the blade inwardly or outwardly from within the blade holding pocket  125 . 
         [0003]    The angle A of the blade holding pocket  125  holds the slotted razor blade  130  at an angle A of approximately 30° so that a surface B of an edge  132  is exposed to cut the carpet&#39;s backing. Surface B is long and cuts with a slicing action. This improves cutting efficiency and blade life, which is important when cutting through coarse carpet backings with thick attached cushions. The distance C between the bottom of the row guide  120  and the bottom corner of slotted razor blade  130  determines the depth of cut. The thicker the carpet&#39;s backing, the greater the distance the slotted razor blade  130  must be extended. When the desired depth of cut is established, blade thumbscrew  140  is tightened down, and the cutter is ready to trim seam edges. 
         [0004]    Carpet tufts are inserted into carpet backing material in lines. To use cushion back cutter  100 , the front of the cutter at row separator  115  is first used as a kind of divider to start a small parted area between two lines of carpet tufts. Once the small parted area is formed, the cutter is pushed forward at handle  180  and row guide  120  maintains the part between the lines of tufts. As shown in  FIG. 8 , once row guide  115  enters a row between a left line of tufts  201  and a right line of tufts  202 , row guide  115  is able to guide the forward motion of the cutter and to position slotted razor blade  130  between the rows of tufts. Thus, as slotted razor blade  130  moves forward with the cutter, the slotted razor blade  130  should cut through the carpet&#39;s backing  203 , including any attached cushion  204 , but should not cut into carpet tufts. 
         [0005]    In prior art cushion back cutters, a single slotted razor blade may be inserted into the blade holding slot of the cutter, or a number of them may be inserted. In some prior art cushion back cutters, two or more slotted razor blades are inserted within the same blade holding slot, but only one of them is extended to a cutting position to trim the seam edge (with the others being retracted into blade holding slot). As disclosed in U.S. Pat. No. 3,453,401 to Scott, two slotted razor blades are inserted, but only one is extended to a cutting position, to cut closely to the carpet tufts on the left or right side of a carpet row as desired. When the blade cuts closely to the tufts, a minimum amount of carpet backing will remain at the finished seam, which can reduce unsightly gaps between the tufts. Alternatively, as disclosed in U.S. Pat. No. 3,453,401 to Anderson, the cutter may hold three blades in order to cut left, right, or dead center (as may be required on certain carpets). 
         [0006]    Prior art cushion back cutters are economically produced by spot welding stamped sheet metal parts together. As shown in  FIG. 3 , the prior art cushion back cutter  100  includes a left side plate  150 , a center plate  160 , and a right side plate  170 , all of which are spot welded together to form the body  110  of the cutter. A slot  162  in center plate  160  provides the necessary space to form blade holding pocket  125  in the middle of the cutter that receives slotted razor blades  130 . Left side plate  150  and right side plate  170  form the left and right walls of blade holding pocket  125 . Center plate  160  includes a bottom bevel  164  forming the row guide  120  of the cutter. Left side plate  150  includes a blade thumbscrew hole  152  and a blade window  154  marked with blade window graduations  156  for setting blade depth. Right side plate  170  includes a nut  172  spot welded onto its outer surface for blade thumbscrew  140 . 
         [0007]    A problem with the prior art cushion back cutter  100  relates to blade change. Slotted razor blades  130  become dull after trimming long lengths of carpet seam edges, and must be changed repeatedly. Moreover, because the slotted razor blade is sharpened on both edges  132 , and because only surface B ( FIG. 1 ) of the blade  130  is being used for actual cutting, the slotted razor blade can be removed from the cutter, rotated, and re-used up to three more times after the first edge becomes dull. But this requires that the user perform the required steps to change or rotate a blade. 
         [0008]    As shown in  FIG. 3 , to change or rotate a slotted razor blade  130 , blade thumbscrew  140  must be completely unscrewed and removed from the cutter. This is because blade thumbscrew  140  runs through central slot  134  in slotted razor blades  130 . Removing blade thumbscrew  140  is time-consuming and can result in loss of the thumbscrew, which is an expensive part. Furthermore, the maximum depth that the slotted razor blade can cut is limited by the upper end  135  of central slot  134  of slotted razor blade  130  hanging up on blade thumbscrew  140 . 
         [0009]    It would therefore be desirable to have some other means to hold the blades that did not pass a screw through their central slot, which could improve efficiency of blade change and rotation and might also allow the blade to be extended further to cut thicker carpet backings and attached cushion. 
         [0010]    As shown in  FIG. 1 , another problem with the prior art cushion back cutter  100  relates to the row guide  120  forming the base of the cutter. In prior art cushion back cutters, row guide  120  is formed as a continuous, straight bottom surface on cushion back cutter  100 . In some cushion back cutters, the row guide  120  may be beveled to improve its ability to penetrate and follow between the lines of carpet tufts. 
         [0011]    However, because row guide  120  is formed as a straight and continuous surface, if a carpet tuft becomes trapped beneath row guide  120 , it remains trapped until it is eventually sheared off by a slotted razor blade  130 . Due to variations in manufacturing, individual carpet tufts frequently encroach the area between rows of tufts where the cushion back cutter needs to pass. As a result, carpet tufts can be run over and can become trapped by row guide  120  and inadvertently sheared off. If carpet tufts are sheared off by the blade, this will result in gaps in the tufts at the seam. This can produce an unsightly seam, particularly on patterned carpet. 
         [0012]    It would therefore be desirable to have some means to prevent carpet tufts from becoming trapped beneath the row guide, which could reduce shearing off of the carpet tufts and thereby produce better looking seams. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  illustrates a prior art cushion back cutter. 
           [0014]      FIG. 2  illustrates a slotted razor blade usable in a cushion back cutter, such as the prior art cushion back cutter shown in  FIG. 1 . 
           [0015]      FIG. 3  illustrates an exploded view of the prior art cushion back cutter of  FIG. 1 . 
           [0016]      FIG. 4  illustrates a side view of a cushion back cutter, in accordance with an embodiment of the invention. 
           [0017]      FIG. 5  illustrates an exploded view of the cushion back cutter of  FIG. 4 . 
           [0018]      FIG. 6  illustrates a side view of the cushion back cutter of  FIG. 4 , with the slotted razor blade  1030  extended. 
           [0019]      FIG. 7  illustrates an alternative embodiment of a center plate  2060  for use with the cushion back cutter of  FIG. 4 . 
           [0020]      FIG. 8  illustrates a front view of a prior art cushion back cutter inserted between two rows of carpet tufts. 
           [0021]      FIG. 9  illustrates a side view of a cushion back cutter, in accordance with another embodiment of the invention. 
           [0022]      FIG. 10  illustrates an exploded view of the cushion back cutter of  FIG. 9 . 
       
    
    
       [0023]    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 
       [0024]    As shown in  FIG. 4 , cushion back cutter  1000  has a body  1010 , a row separator  1015 , a row guide  1020 , a blade holding pocket  1025 , and a handle  1080 . At least one slotted razor blade  1030  can be inserted into blade holding pocket  1025 , though blade holding pocket  1025  may be formed wider to accept two or three blades. In addition, cushion back cutter  1000  includes a blade clamp  1040  and a blade clamp thumbscrew  1050 . Blade clamp thumbscrew  1050  is offset or fastened “outside the perimeter” of slotted razor blade  1030 , and need not pass through the central slot  1034  of slotted razor blade  1030 . 
         [0025]    To install blades, blade clamp thumbscrew  1050  need only be loosened a few turns, without having to be removed, which in turn loosens blade clamp  1040 . Afterwards, slotted razor blades  1030  can be inserted into the bottom opening of blade holding pocket  1025 . As slotted razor blades  1030  are inserted further into blade holding pocket  1025 , they easily slide beneath blade clamp  1040 . When a desired depth of cut is set, blade clamp  1040  can be tightened down on an outside surface of a slotted razor blade  1030  by re-tightening blade clamp thumbscrew  1050 , and all blades will be held at their desired positions. 
         [0026]    Blade clamp  1040  presses on an outer surface of a slotted razor blade  1030  to hold it in position. As a result, the depth of cut of slotted razor blade  1030  is not limited by the blade clamp screw  1050  hanging up on an upper end  1035  of central slot  1034 . As shown in  FIG. 6 , when installed in cushion back cutter  1000 , slotted razor blade  1030  can be clamped into position with its bottom corner extended further from row guide  1020 . This results in a depth of cut D that is greater than depth of cut C of the prior art cushion back cutter  100  shown in  FIG. 1 . This allows cushion back cutter  1000  to cut through carpets with thicker backings, or even to double cut two overlapping pieces of carpet, as is sometimes necessary. 
         [0027]    As shown in  FIG. 4 , cushion back cutter  1000  also has a row guide  1020  with a series of notches  1021 . Notches  1021  are rounded in shape and continuous along a portion of row guide  1020 . Notches  1020  allow carpet tufts (which may become trapped beneath row guide  1020 ) the opportunity to escape from beneath the row guide  1020  before being cut. In particular, the carpet tufts have an opportunity to stand up into their natural position if temporarily released from downward pressure by the relief provided by any of notches  1021 . Furthermore, notches  1021  tend to push any trapped carpet tufts aside as they pass by or across the tufts. Thus, in two different ways, notches  1021  act to reduce the problem of carpet tufts becoming trapped beneath the row guide  1020  and eventually being sheared off by a slotted razor blade  1030 . 
         [0028]    In one embodiment, the notches have a depth that is greater than the thickness of a carpet tuft for which the cutter is designed. For example, the notches may have a depth of at least 0.100 inches. In another embodiment, the notches have a continuous contour to avoid trapping any carpet tufts. 
         [0029]    Row guide  1020 , in addition to having notches  1021 , also includes a bevel  1022  formed on its bottommost surface. Both the notched area formed by notches  1021  as well as straight area  1023  of row guide  1020  have this bevel  1022 . Bevel  1022  helps row guide  1020  including notches  1021  and straight area  1023  penetrate as deeply as possible into the tight area between two lines of carpet tufts and to pass through this area smoothly. 
         [0030]    The beveled straight area  1023  of row guide  1020  establishes the final part between the left and right lines of carpet tufts after notches  1021  have cleared as many carpet tufts as possible. This ensures that the parted carpet tufts will not re-enter the area directly in front of slotted razor blade  1030  and as a result be sheared off. 
         [0031]      FIG. 5  shows the exploded view of cushion back cutter  1000 , which includes a left side plate  1150 , a center plate  1160 , and a right side plate  1170 , all of which are spot welded together to form a body  1010 . Center plate  1160  includes a slot  1162 , which provides space to form blade holding pocket  1025  in the middle of the cutter to receive slotted razor blades  1030 . Left side plate  1150  and right side plate  1170  form the left and right walls of blade holding pocket  1025 . Center plate  1160  additionally includes a row guide  1161 , notches  1163 , and a bottom bevel  1165  formed on notches  1163  and continuing all the way to slot  1162 . Left side plate  1150  includes a blade window  1154  and blade window graduations  1156 , both to assist in setting the depth of cut of slotted razor blades  1030 . Left side plate  1150  additionally includes a blade clamp opening  1157  and a blade clamp screw passage hole  1158 , which is positioned outside the perimeter of the position of blades  1030  once they are inserted into blade holding pocket  1025 . Center plate  1160  has a blade clamp screw passage hole  1168  in a position corresponding with blade clamp screw passage hole  1158  of left side plate  1150 . Right side plate  1170  also includes a nut forming a blade screw tapped hole  1178  spot welded to its outer surface in a position corresponding with blade clamp screw passage hole  1158  of left side plate  1150 . 
         [0032]    Blade clamp  1040  includes an upper portion  1041  with a blade clamp screw passage hole  1042  and an offset bottom portion  1043  that steps down from upper portion  1041 . Bottom portion  1043  of blade clamp  1040  is insertable into blade clamp opening  1157  of left side plate  1150 . Blade clamp thumbscrew  1050  is inserted through blade clamp screw passage hole  1042  of blade clamp  1040 , through blade clamp screw passage hole  1158  of left side plate  1150 , through blade clamp screw passage hole  1168  of center plate  1160 , and threaded into a nut forming blade screw tapped hole  1178  that is spot welded onto an outer surface of right side plate  1170 . When blade clamp thumbscrew  1050  is tightened down onto upper portion  1041  of blade clamp  1040 , the lower portion  1043  is pressed against slotted razor blades  1030  to hold them in their desired positions. 
         [0033]      FIG. 7  shows center plate  2060 , which is an alternative embodiment of the center plate  1160  shown in  FIG. 5 . Center plate  2060  includes an upper portion  2061  and a lower portion  2062 . Upper portion  2061  and lower portion  2062  can be spot welded with left side plate  1150  and right side plate  1170  (both shown in  FIG. 5 ) to produce a body similar to body  1010  of  FIG. 4 . However, lower portion  2062  can be processed separately from upper portion  2061  in automated industrial processes, such as batch de-burring. Such processes can produce bending in a part shaped like the center plate  1160  of  FIG. 5 , making it unable to be spot welded. This is because the center plate  1160  of  FIG. 5  has a large area removed at slot  1162 , which makes it prone to being bent by such processes. 
         [0034]    Alternative embodiments of cushion back cutters, and other types of carpet seam cutters that include a row guide, may include notches on the row guide to reduce shearing of carpet tufts.  FIG. 9  shows cushion back cutter  2000 , which is an alternative embodiment of the cushion back cutter  1000  of  FIG. 4 . Cushion back cutter  2000  includes front pocket  2010  and rear pocket  2020  for holding two slotted razor blades  2030 . As shown in  FIG. 10 , space for slotted razor blades  2030  is created by machining a front pocket  2015  in the left (back) side and a rear pocket  2025  in the right (front) side of center plate  2060 . When left side plate  2050  and right side plate  2070  are positioned in relation to center plate  2060 , front blade pocket  2010  and rear blade pocket  2020  are formed for holding slotted blades  2030 . Thus, slotted razor blades  2030  slide into cushion back cutter  2000  and are held in a cutting position by the perimeter defined by front pocket  2015  and rear pocket  2025 . Center plate  2060  additionally has notches  2061 , a straight area  2062 , and bottom bevel  2065  which form the row guide  2120  of cushion back cutter  2000 . 
         [0035]    In another embodiment, notches on a row guide such as those described above are used in connection with a carpet seam cutter, such as the one shown in U.S. Pat. No. 8,567,075B2 to Hetts et al., which is hereby incorporated by reference in its entirety.  FIG. 4  of Hetts shows a loop pile cutter  20000  that includes a blade holder  21000  including a holder right side  21100 , a holder center  21300 , and a holder left side  21500 . Notches, a straight area, and a bottom bevel may be added to center  21300  to reduce shearing of carpet tufts. 
         [0036]    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.