Carpet Plug Cutter

Abstract

A tool for cutting circular plugs of carpeting solely by rotary cutting action and without the use of impact forces is disclosed. Cutter blade assemblies for use in such tool providing serrated cutting edges with various types of serrations are described. Means for quickly and easily interchanging cutter blade assemblies of various diameters in the tool are disclosed.

Description

BACKGROUND OF THE INVENTION

This invention relates to a tool for cutting circular plugs from installed carpeting, without otherwise disturbing the carpeting, in order to provide access through the carpeting or to remove stained or burned sections from the carpeting for subsequent replacement by circular plugs cut from undamaged carpeting and more particularly to such a tool designed for rotary cutting action without the use of impact forces.

Carpet repair tools for cutting circular plugs from installed carpeting, comprising a circular blade adapted to be driven through the carpeting by impact, have been proposed heretofore. However, such tools have a number of disadvantages in use, the most severe of which is that the carpet must be cut by a single impact on the tool, if possible. It will be understood that an impact applied to the tool will tend to cause it to bounce away from the carpet after the impact thereon. Thus, if the carpet is not cut cleanly by the tool upon first impact it will be necessary to return the tool to exactly the same position for second and subsequent impacts. This is difficult to do because the location of the initial partial cut will tend to be hidden by the nap or pile of the carpet. Even if the tool is manually held against the carpet when impacted, the tool will tend to move slightly after each impact resulting in ragged and uneven cutting by the circular blade about its periphery including possible damage to the adjacent nap or pile of the carpet.

On the other hand, if the initial impact is greater than necessary to cut the carpet cleanly about the entire periphery of the blade of the tool, it may damage the underlying pad or even the floor beneath the pad in addition to the carpet itself. Various schemes have been proposed to limit the travel of the blade upon impact to no more than necessary to cut through the carpet, as shown for example in U.S. Pat. No. 3,171,200. However, all of such schemes necessarily transfer some part of the impact force to another member of the tool thus either tending to make it more difficult to secure a clean circular cut if the impact is marginally low or tending to compress or dent the underlying pad and flooring if the impact is too great. It will be understood that the blade of such prior art tools must be kept uniformly sharp about its entire periphery in order to avoid ragged cutting action and minimize the required impact.

It is an object of this invention to provide a tool for cutting circular plugs from carpeting without the use of impact forces.

It is a further object of this invention to provide a tool for cutting circular plugs from carpeting in which the likelihood of the tool making a ragged or uneven cut is reduced.

It is another object of this invention to provide a tool for cutting circular plugs from carpeting in which the importance of uniform sharpness of the blade is reduced.

It is yet another object of this invention to provide a tool for cutting circular plugs from carpeting which may be used to cut plugs of various sizes with greater ease, accuracy, and safety and with less maintenance than similar tools of the prior art.

SUMMARY OF THE INVENTION

The carpet plug cutter of this invention comprises a hollow tubular housing one end of which is open and terminates in a plane perpendicular to the axis of the housing. A plurality of carpet engaging pins are mounted at such one end of the housing and extend therefrom along the axis of the housing. An elongated drive rod having one end within the housing and the other end projecting from the other end of the housing is mounted at such other end of the housing for reciprocal movement of its axis of elongation along the axis of the housing and for rotation about its axis of elongation. The end of the drive rod within the housing is adapted to removably receive a cutter blade assembly and the other end of the drive rod is provided with knob means having a dimension transverse to the axis of the housing which is at least equal to the radius of the housing. A spring means is provided between the housing and the drive rod to bias the drive rod into its position of maximum spacing between the housing and the knob means. The cutter blade assembly includes a hollow cylindrical blade member having one end provided with a serrated and beveled knife edge. The blade member is removably mounted at its other end on the end of the drive rod within the housing and coaxially with the axis of elongation of the drive rod. In use a cutter blade assembly of the desired diameter is mounted on the end of the drive rod and the open end of the housing is placed against the carpet. The drive rod is manually forced into the housing, against the force of the spring, and rotated about its axis of elongation to bring the serrated knife edge into cutting engagement with the carpet. The carpet gripping pins insure that the tool is held in place and that the housing is held against rotation during operation.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a top view of a tool according to a preferred embodiment of this invention.

FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1 showing a cutter blade according to one embodiment of this invention.

FIG. 3 is a top view of a cutter blade assembly suitable for use in a tool according to another embodiment of this invention.

FIG. 4 is a side view in elevation of a cutter blade assembly for use in a tool according to a further embodiment of this invention.

DETAILED DECRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2 a tool according to a preferred embodiment of this invention is shown. The tool comprises a hollow tubular housing 10 which may be a hollow metal cylinder for example. Carpet gripping means are provided at one end 11 of the housing 10 and in the embodiment shown such means comprise a plurality of elongated sharpened pins 12 spaced about the periphery of the housing 10 and extending along the axis thereof.

The other end 13 of the tubular housing 10 is provided with an appropriate means such as the strut and guide structure 14 shown in FIGS. 1 and 2 for rotably supporting an elongated cylindrical drive rod 16 with its axis of elongation along the axis of the housing 10 and with one end 15 within the housing 10 and the other end 17 projecting therefrom. The projecting end 17 of the drive rod 16 is provided with a portion extending transversely of the axis of elongation thereof by means of a knob 18 affixed thereto. The transverse dimensions of such knob 18 must be at least equal to the radius of the tubular housing 10 for reasons which will be discussed hereinafter.

A compression spring 19 is received about the drive rod 16 with one end of such spring 19 bearing on the knob 18 and the other end of the spring bearing on the facing surface of the strut and guide structure 14 in order to urge the drive rod 16 toward maximum projection of the end 17 thereof from the housing 10. It will be understood that the end 15 of the drive rod 16 within the housing 10 is provided with an appropriate stop means or enlargement to prevent it from passing through the strut and guide structure 14 under the influence of the spring 19. The force of the spring 19 should be sufficient to maintain the drive rod 16 in the position relative to the housing 10 shown in FIG. 2 when the tool is not in use regardless of the orientation of the tool. Otherwise, the force exerted by the spring 19 is not critical except that it will tend to oppose the movement of the drive rod 16 with respect to the housing 10 when the tool is in use and should therefore be kept as small as practical. Similarly, the abutment between the spring 19 and the knob 18 will tend to introduce friction when the knob 18 is rotated to rotate the drive rod 16 with respect to housing 10 in use. Thus, an appropriate bushing or other means of reducing friction may be interposed between the end of the spring 16 and the knob 18 as necessary or desirable.

A cutter blade assembly 20 is removably mounted on the end 15 of the drive rod 16 within the housing 10. The cutter blade assembly comprises a hollow cylindrical blade member 22 having one end 21 beveled and serrated to form a cutting edge and the other end 23 mounted on a rigid plate 24. The plate 24 is provided with a portion 25 of a socket wrench type coupling means for engagement with a mating portion 26 provided on the end 15 of the drive rod 16. As shown in FIG. 2 the male portion 25 of the socket wrench type coupling means is provided on the plate 24 and the female portion 26 in the end 15 of the drive rod 16, however, it will be understood that this arrangement could be reversed as shown in FIG. 3. It will also be understood that it is contemplated that a number of cutter blade assemblies similar in structure to the assembly 20 but each having a cylindrical cutting blade 22 of different diameter from the others will be used interchangeably in the tool to cut circular carpet plugs of different diameters as necessary or desirable.

Referring to FIG. 3 a top view of a cutter blade assembly 20 which may be made in a series of diameters suitable for use in a tool according to this invention is shown. As shown in FIG. 3 a socket wrench type coupling may be provided by a square socket 25'in the plate 24 adapted to receive a square shank 26' provided on the end 15 of the drive rod 16, for example. The plate 24 may be provided with apertures 28 in order to reduce the mass of the assembly and to enable the cutting operation to be observed while it is in progress.

Referring to FIG. 4 it will be seen that the cylindrical blade 22 may be conveniently made by sharpening and serrating one edge of an elongated flat strip of steel which is then wrapped around the periphery of the plate 24 at its other edge and the ends thereof fastened to the plate by means of screws 29, for example. The length of the strip is selected in relation to the diameter of the plate 24 so that the ends of the strip will abut each other to form a non-overlapping seam 30 when the assembly is completed. Thus, the blade 22 may be easily removed and flattened to facilitate resharpening of the cutting edge thereof as necessary. It has been found that a bevel of about 5.degree. on the cutting edge 21, 21' of the blade 22 provides efficient cutting action in the tool of this invention.

It will be noted that the serrations in the cutting edge 21' of the blade 22 shown in FIG. 4 are different from the serrations in the cutting edge 21 of the blade shown in FIG. 2. In both cases the serrations are made of alternately concave and convex arcuate surfaces and such serrations are an essential feature of this invention in order to enable manual rotary cutting action. It has been found that serrations of a variety of arcuate shapes may be used but they are subject to certain important limitations.

If no serrations at all are provided in the cutting edge, it is substantially impossible to manually perform any rotary cutting action since a great deal of downward pressure and a very large number of rotation of the blade would be required even in cutting a carpet plug of small diameter, thus exhausting the operator. According to this invention serrations are provided which enable a proper balancing between the downward pressure, the number of rotations, and the rotary force required to cut a plug from an average carpet without exhausting the physical capabilities of the average manual operator. If a large number of small serrations are used they will either require a large amount of downward force, as in the case of no serrations at all, or they will require a large amount of rotational force depending on the angle at which the surface of the serrations engage the carpet. According to one aspect of this invention, it has been found that serrations formed of arcuate surfaces will tend to provide a balance between the required downward force and the required rotational force which would be practical for manual operation. However, according to another aspect of this invention it has been found that the use of a large number of small serrations would tend to require a large number of rotations of the blade to cut through the carpet which would be exhausting and time consuming for the average manual operator.

According to the teaching of this invention carpet plugs up to a diameter of about 3 inches are practical to cut manually by rotary cutting action if the serrations are formed of alternately concave and convex arcuate surfaces. Tests indicate that the number of serrations spaced about the cutting blade should be at least five and not more than about twenty. Although it is believed that a "wavy edge" blade in which all of the arcuate surfaces have the same curvature, as shown in FIG. 2, is preferable in terms of avoiding operator fatigue it has been found that a "scalloped edge" blade in which the convex arcuate surfaces have greater curvature than the concave surfaces, as shown in FIG. 4, is also practical for use in manually cutting carpet plugs up to about three inches in diameter accordng to this invention. It is believed that the radius of curvature of the arcuate surfaces forming the serrations must be between 0.05 inch and 0.05 inch in order to provide efficient cutting action.

In order to provide sufficient leverage to enable the average operator to manually cut the average carpet with a tool according to this invention, it is necessary that the end 17 of drive rod 16 have a transverse dimension, such as is provided by knob 18, at least equal to the radius of the housing 10. It will be understood that the diameter of the housing 10 of the tool determines the maximum diameter of the cutter blade assembly 20 that can be used therein since the cutter blade assembly is received in such housing. This arrangement protects the cutting edge 21, 21' from damage when the tool is not in use and tends to prevent any accidental cutting, including injury to the operator, by the cutting edge 21, 21'. The socket wrench type coupling between cutter blade assemblies 20 and the drive rod 16 enables assemblies 20 with various diameters of cutting blades 22 to be used interchangeably in the tool and the structure of the cutter blade assemblies 20 provides for ease in removal of the blades 22 for efficient resharpening thereof in their flattened or strip condition. In addition, the resharpening of serrations formed of arcuate surfaces according to this invention has been found to be most satisfactory and efficient as compared to the resharpening of serrations formed of rectilinear surfaces, for example. Furthermore, it has been found that maintenance requirements, including resharpening of the blade 22, for the tool according to this invention are far less stringent than for similar devices of the prior art.

Claims

What is claimed is:

1. A tool for cutting circular plugs of carpeting comprising:

a. a hollow tubular housing having an open end terminating in a plane perpendicular to the axis of the housing;

b. carpet gripping means about the periphery of said open end of said housing;

c. an elongated drive rod mounted on the other end of said housing, one end of said drive rod being within said housing and the other end of said drive rod projecting from said other end of said housing, said drive rod being mounted for reciprocal movement of the axis of elongation thereof along the tubular axis of said housing and for rotation about said axis of elongation, said other end of said drive rod being provided with a portion extending transversely of the axis of elongation thereof for a distance at least equal to the radius of said tubular housing;

d. spring means urging said other end of said drive rod to project from said housing, and

e. a cutter blade assembly comprising a hollow cylindrical blade of smaller diameter than said housing, a beveled cutting edge with arcuate convex serrations formed therein at one end of said blade and means removably mounting the other end of said blade on said one end of said drive rod within said housing coaxially with said axis of elongation of said drive rod.

2. A tool as claimed in claim 1 wherein said carpet gripping means comprise a plurality of elongated sharp pins spaced about the periphery of said open end of said housing and extending therefrom in a direction substantially parallel to the axis of said housing.

3. A tool as claimed in claim 1 wherein said dimension of said other end of said drive rod transverse to the axis of elongation thereof is provided by a knob having transverse dimensions greater than the radius of said tubular housing.

4. A tool as claimed in claim 1 wherein said means removably mounting said other end of said cylindrical blade on said one end of said drive rod within said housing comprises a socket wrench type coupling therebetween.

5. A tool as claimed in claim 4 wherein said cylindrical blade is formed by bending a flat strip into a circle with the ends of said strip in abutment and said means removably mounting said blade on said drive rod includes a rigid plate member with a circular periphery to which said blade is attached.

6. A tool as claimed in claim 1 wherein said serrations of said serrated cutting edge are formed by alternately concave and convex arcuate surfaces.

7. A tool as claimed in claim 6 wherein said concave and convex arcuate surfaces have substantially the same curvature.

8. A tool as claimed in claim 6 wherein said concave arcuate surfaces have a curvature less than the curvature of said convex arcuate surfaces.

9. A tool as claimed in claim 6 wherein said serrations include at least about five and not more than about twenty convex arcuate surfaces.

10. A tool as claimed in claim 9 wherein said concave and convex arcuate surfaces have a radius of curvature between 0.05 inch and 0.05 inch.