U.S. patent number 3,786,564 [Application Number 05/298,839] was granted by the patent office on 1974-01-22 for carpet plug cutter.
Invention is credited to Melvin G. Acheson.
United States Patent |
3,786,564 |
Acheson |
January 22, 1974 |
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.
Inventors: |
Acheson; Melvin G. (Sacramento,
CA) |
Family
ID: |
23152206 |
Appl.
No.: |
05/298,839 |
Filed: |
October 19, 1972 |
Current U.S.
Class: |
30/124;
30/310 |
Current CPC
Class: |
B26F
1/3846 (20130101); B26B 27/00 (20130101) |
Current International
Class: |
B26F
1/38 (20060101); B26B 27/00 (20060101); B26b
003/08 () |
Field of
Search: |
;30/124,130,301,286,310,316 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Jones, Jr.; James L.
Assistant Examiner: Peters; J. C.
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.
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.
* * * * *