US 2776484 A
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Description (OCR text may contain errors)
Jan. 8, 1957 R. w. RESNER HAND TOOL Filed Jan. 7, 1954 INVENTOR. Wfiaam HAND TOOL Robert W. Resner, Chicago, Ill.
Application January 7, 1954, Serial No. 402,730
2 Claims. c1. 30-287) My invention relates to hand tools and includes among its objects and advantages a cutting tool particularly useful in the building trades in putting up what is known as dry wall.
The long-conventional lath and plaster interior finish is fast nearing extinction, and the inner surfaces of wall structures for dwellings and many other buildings are now usually in the form of relatively large slabs or panels of gypsum or other plaster, made up at the factory and surfaced with tough paper on both sides. In trimming such a panel to exact size, it is necessary to lay a straight edge along it and cut in deeply enough to score the panel enough to guide the breaking of it, after which the material can be broken along the line of the cut to produce a generally straight edge which will include some surface roughness near the center of the material beyond the groove made by the scoring knife. This surface roughness may be smoothed with a conventional rasp, but guidance of a naked rasp to work effectively on the roughened edge requires skill and effort.
When such a panel is to be fitted between two previously installed panels, and particularly when it forms a concave dihedral angle with one or more of the previously fitted panels, considerable difiiculty is encountered if the cut panel happens to be from to of an inch too wide in a few spots. This creates a serious problem when all the panels lie in the same plane, but in a concave dihedral angle, matters become much worse. Access to the edge of the final panel is very difficult, and removal of the panel to machine down the wide spot is also difficult. Frequently, putting the panel almost in place to see if it will fit, wedges it to such an extent that it is. quite difiicult to remove. Usually, also, the wedged in panel is the inner partition of a wall of which the outer partition is already built, so that access to the other side of it to put it out, is impossible.
In the accompanying drawings:
Figure 1 is a plan view of the contact side 'of a'tool according to the invention:
Figure 2 is a plan view of the rasp side;
Figure 3 is a longitudinal section on line 33 of Figure 1;
Figure 4 is a rear end view;
Figure 5 is a section on line. 55 of Figure 1';
Figure 6 is a section on line 66 of Figure 1;
Figure7 is a perspectiveview of the blade-retaining clip; and 1 Figure 8 is an enlarged section on line 8-8 of Figure 1.
In the embodiment selected for illustration of the invention, the tool comprises a main body of aluminum having substantially the external contour of a rectangular parallelepipedon, and functioning as a blade holder and as a handle.
The guide face 10 of the body lies all in one plane except for the shallow central fingertip groove 12 running from the rear end a little more than half the length of the tool, and the shallow, flat-bottomed recess 18 receiving I i United States Patent 2,776,484 Patented Jan. 8, 1957 the cutting blade 14. The cutting blade 14 is of the lenticular configuration clearly illustrated in the drawings, and its cutting edge 16 is defined by bevelling the blade on one side only, so that the apex of the cutting edge is in the plane of the plane blade surface engaging the bottom of the depression 18. The side walls of this depression incline inwardly toward each other, as clearly indicated at 20 in Figure 1, far enough to overlie the bevel face 22 leading to the edge 16. The guide surface it) of the body lies about ten-thousandths of an inch above the exposed face of the blade 14. The edge 16 is only used for actual cutting at and near the tip of the blade, and may be left a little bit blunt from some such point as 22 (see Figure l) to the corresponding rearwardly inclined point at 24, on both sides of the blade.
The body itself is slitted at 26 longitudinally down the center, and then in an arcuate path at 28 over almost to one side of the tool. The remaining attachment at 30 is sufficiently yielding to permit the tightening screw 32 to pull the relatively movable jaw 34 against the relatively fixed jaw 36, and grip the blade 14 with great firmness. Beyond the points 22 and 2-4, the side walls of the depression 18 do not press tightly against the blade edge, and for convenient clearance in practical manufacturing, I fashion an additional recess 38 at the rear of the depression 13, which extends back a substantial distance away from the rear tip of the tool, to make sure that this most active cutting part is not contacted with great force by the metal of the body.
7 Because the metal of the body is of ordinary aluminum or the like, and the blade 14 is of tempered steel, it will be obvious that the aluminum will yield enough to let the steel seat itself firmly when the screw 32 is tightened.
In manufacture, it is convenient to die-cast the body, with just the right amount of metal around the edges of the recess 18, and subsequently form the dovetail groove with high precision by positioning a hardened steel die in the recess and pressing the movable jaw inwardly to generate the exact contour by cold working of the body metal. This not only gets precision, but the cold working strengthens the metal in the dovetail.
When one end of the blade has worn dull with use, it is a simple matter to loosen the tightening screw 32, take the blade out, and put it in again, reversed end for end, for anotherperiod of use. As a matter of convenience, I extend the use period of a single tool by fashioning a cavity 40 in the rear end of the tool to house one or more spare blades 42.
having a back 44, a top panel 46, and a bottom panel 48. The panels 46 and 48 may be embossed to form buttons 50 and 52 to snap into receiving sockets illus: trated as holes 54 and 56. At either end of the back 44 I provide recesses 58 in the body, so that a small nail or the like can be slipped under the back 44 to pry the clip out and get at the blades 42.
Along the side of the body remote from the blade 14 and fingertip groove 12, I cut down the body to define a central channel 60,.in which the rasp 62. is positioned with its working teeth 64 facing outwardly.
Suitable means are provided for retaining the rasp in place. I have illustrated a pair of set screws 66 entering notches 68 (see Figure 2) in the edges of the rasp.
With the parts assembled, the side flanges 70 of the I channel 60 project a little beyond the outer edges of the teeth 64, so that the tool can be laid against the edge of the cut panel with the teeth 64 in correct working position, andthe flanges 70 straddling the material and functioning as reliable guides to keep the tool in correct, aligned position.
On the opposite edges, I provide longitudinal shallow The blades 42 may be retained in place in any suitable way, as by a sheet metal clip grooves, similar to the fingertip groove 12, identified as a thumb and fingertip groove 72 and a fingertip groove 74.
In use for scoring, the tool is held with its longitudinal dimension at right angles to the forearm of the user, with the fingertips of the user resting in the groove 12 and wrapped around the groove 74, while the side having the groove 72 rests against the palm of the user. In this position, the grooves 72 and '74 have relatively no function. Holding the tool in this way, the point 16 can easily be laid beside a straight edge and guided surely and firmly in scoring a suitable, deep groove through the paper surfacing and into the plaster. The fact that the blade point 16 is offset to one side from the center of the edge areas receiving the chief gripping force of the users hand, affords a slight but gentle tendency of the tool to rotate clockwise around its longitudinal axis as viewed from the rear. This is not conspicuously noticeable but it does afford a slight assistance in good muscular control in guiding the knife in good working contact with the straight edge.
A more important advantage of positioning the cutting edge 16 close to the plane of surface is realized when the edge of a final panel gets wedged into a dihedral angle. By laying the guide surface 10 flat against the surface of the previously installed panel, the cutting edge 16 is positioned spaced away from that surface by a distance sufiicient to chamfer away only a very thin shaving, or slice, from the edge of the wedged panel. Such a shaving, of course, with ordinary plaster, turns to powder as it is shaved off.
For this purpose, the user lays the thumb of the right hand in the groove 74 with the tips of all four fingers in the groove 72, and presses the guiding surfaces 10 and 14 against the previously installed panel. After very brief experience it is possible to remove very tiny increments from the edge that wedges, and work it into final, assembled position with a good, tight fit in a very short space of time. Any ordinary knife would be without guidance and would be as likely to gouge into the previously installed panel as into the final panel.
In the embodiment disclosed, I have indicated a blade 14 having a thickness of thirty-thousandths of an inch, and a surface 10 offset from the cutting edge 16 by fortythousandths of an inch, so that the blade 14 clears the guiding surface of the previously installed panel by only ten-thousandths of an inch. This produces a cut of fortythousandths of an inch for each guided slice, which is a good working thickness for fitting the panel with fairly high accuracy. Where the crack along the abutting edge of the panel is to be sealed air-tight subsequently by means of tape, plaster, paint, or various combinations of inside finishes, the accuracy of the edge fit of the panel itself is much less important, and a workman can get the panel in place faster with a tool in which the edge 16 is offset sixty-thousandths or eighty-thousandths of an inch from the guide surface 10. But in erecting structures that are to be used Without an interior finish that closes the crack, it is preferable to take thinner slices and secure a better joint.
Others may readily adapt the invention for use under various conditions of service by employing one or more of the novel features disclosed or equivalents thereof. I prefer to taper the end of the body adjacent the blade 14 for a short distance on either side, as indicated at 76 4 in Figures 1 and 2, and for a slightly greater distance along the opposite face, as indicated at 78 in Figures 2 and 3. The channel defined by the flanges is left open at both ends, but the floor of the channel is offset at 80 (see Figure 3) to leave enough metal to receive the screw 32 and form a stop for the rasp 62.
In the embodiment disclosed, the guide surface 10 extends throughout the entire length of the handle. Especially for rough or fast work, it may be desirable to have the guide surface proper extend only about half the length of the handle, from the end adjacent the cutting knife back to the middle, while the surface beyond lies at an angle inclined away from the plane of the surface 10 by ten degrees or fifteen degrees. The opposite side of the body can remain straight and be parallel to the guide surface 10, or inclined at a smaller angle, but the butt of the tool will ride farther away from the guiding surface of the previously installed panel, and nestle more comfortably into the palm of the users hand.
As at present advised with respect to the apparent scope of my invention, I desire to claim the following subject matter:
1. A hand tool comprising an elongated body having a longitudinally extending plane, guiding contact face; said body being thick enough to be readily grasped in one hand, with the grasping hand entirely on the same side of said guiding contact plane as the body; said body having greater transverse dimensions parallel to said guiding contact plane than normal thereto; and a substantially rigid, flat cutting blade projecting beyond the forward end of said body; the space beyond the said forward end being unobstructed except for said blade; said blade being set in a plane offset from the median plane of said body and close to and parallel to said contact face; said blade having a forwardly tapered point; said blade having cutting edge portions running back from said point on both sides; whereby said tool may slide with its guiding contact face in surface engagement with a first, guiding piece of solid material, and cut thin shavings from the edge of another piece of material lying with its edge in abutment with said guiding piece of material.
2. A tool according to claim 1 in which said blade is symmetrical about a transverse median plane, and reversible end for end; and said blade has a hardened metal edge; and said body has a dovetailed recess shaped to receive and engage the edge of said blade on both sides of said transverse median plane of symmetry; said recess having soft walls of relatively yielding material, and being adapted to grip the cutting edge portions of said tool without impairing the cutting edge; and means for moving the sides of said recess toward each other to clamp said blade.
References Cited in the file of this patent UNITED STATES PATENTS