US2130370A - Pencil pointer - Google Patents

Description

p 1938. H. w. SPOONER 2,130,370

PENCIL POINTER Filed Nov. 23, 1935 llllllllllllll 9 5 Pi y. 2

6 71 6:7 Z2 4 0/ 6 i um u 7\ \l 7 a g Patented Sept. 20, 1938 UNITED STATES PATENT OFFICE 7 6 Claims.

This invention relates to improvements in pencil pointers, also frequently called pencil Sharpeners, and specifically to that type of device which is usually held in one hand while the 5, pencil is rotated by the fingers ofthe other hand against the edge of a knife held in fixed relationship to the longitudinal axis of the pencil.

In pencil pointers of this type the knife is sometimes made practically an integral part of the lOentire device, as by welding to a metal body. Various other designs'combine a body molded or machined from plastic compounds such as phenol resin, together with a knife of special design which.

is not readily renewable. Thus when the knife has become dulled through repeated use the entire device becomes practically useless to the owner for want of some means of renewing the knife alone. Moreover, the usual device of this type is so short as not to provide a proper guide for the body of the pencil ,thereby allowing it to vacillate while beingrotated, resulting in the frequent breaking of leads, either at the point, or, by fiexure, inside the wooden envelope. If the angle between the axis of the pencil-and the edge of the knife is comparatively large, as is frequently the case, the tapered section will be short and the point stubby, necessitating frequent sharpenings to retain a reasonably fine point.

To overcome these various objections I have invented the pencil pointer. described below, in which the problem of renewing the knife is solved by the, use of discarded razor blades, which the device is built to accommodate. These blades have been found to be amply keen for removing lightshavings from wood and graphite, even after becoming too dull to be used comfortably for shaving. The keenness of these blades as compared with the usual knife employed for this purpose permits a long, gradually tapered point to be obtained without breakage. I obtain a hollow or concave point by flexing the blade into the shape desired in the finished pencil.

The use of .this type of blade, and its fiexure 4; into a curve, introduce some problems that are not readily apparent, but which will be set. forth in the following description.

In the accompanying. drawing some of the parts are shown in an enlarged scale to insure vclearness.

Fig. 1 is a side view of a pencil consisting of a wooden envelope or body enclosing a graphlteor colored core or lead, after being sharpened With this device.

55.- Fig. 2 is a sectional view of the device, taken on a vertical plane through the center line of the hole provided to guide the pencil.

Fig. 3 is a view of the top of the complete device.

Fig. 4 is an end view of the device.

Fig. 5 is a greatly enlarged section of a portion of the device showing the relative positions of the blade and the pencil.

Fig. 6. is a similar section of a pencil pointer of the usual type, shown for purposes of comparison. f

Fig. 7 is a similar section showing the impracticability of using a razor blade in a pencil pointer of ordinary design.

Fig. 1 shows the hollow, graceful lines that may be obtained in a pencil point by using this improved device.

In Fig. 2, I represents the bodyof the device. 2 represents a razor blade of popular type, which blades are usually made about .007 thiok and are therefore somewhat flexible. I utilize this characteristic of this type of blade to obtain the curved or hollowed pencil point by clamping the blade against the concave upper surface of body I by means of cover plate 3, which has a convex curved surface of suitable form for the purpose. Pressure is applied to the blade 2 through cover plate 3 by means of the milled or knurled nut 4 and screw 5 (shown in Fig. 3). In body I a cored or drilled hole, I, of a form approximating that desired in the finished pencil point, is provided to guide the pencil and permit it to be rotated by hand againston-e edge of blade 2. For the removal of chips 2. slot, 8, is provided, approximately the full length of blade 2 and exposing its edge when viewed from the upper surface of the device. To hold the blade securely in position dowels 6, 6 are provided as shown in Fig. 3. These dowels fit with re'asonablesnugness in corresponding holes or slots in the blade; or, if desired, a tongue may be substituted for the dowels to fit a blade having a longitudinal slot in place of round holes. 1

The device is. used by inserting the end of an ordinary wooden pencil in the hole l provided therefor, pressing the pencil gently forward and at the same time rotating it clockwise against the edge of the blade 2. This removes a practically'continuous chip, the thickness of which is dependent on the position of the edge of the blade 2 referred to the periphery'of hole '5'.

Fig. 6 represents a pencil pointerof the usual design in this general class; In'thistype of pencilpointer the knife, 9, is. ordinarily from four to eight or ten times as thick asithe razor blades which I employ. It is usually held in horizontal alignment by abutting its rear side against a shoulder provided for that purpose in the body of the device, and it is held in vertical alignment by clamping it down against the body by means of a small screw. The thickness and consequent stiffness of the blade 9 is depended upon to hold it in alignment, and the under side and edge are invariably intended to be substantially straight. This imposes a straight taper on the pencil and precludes obtaining a hollow or concave point as shown in Fig. 1.

In Fig. 6, e indicates the edge of a knife 9 of ordinary type, and e] a portion of its under side. This surface cf, considered in cross section as shown, is tangent, or substantially so, to a radius drawn from the center of pencil H) to the edge e of knife 9. Consequently, as pencil I is rotated and the chip cg removed, the slight reduction in the diameter of the pencil I!) permits it to clear the surface cf of knife 9. Theoretically it would touch only at edge e, which is also the point of tangency.

Fig. '7 shows what would happen if a razor blade of the type in question were used in the same manner. Because of the comparative thinness and consequent flexibility of blade 2 it could not be self supporting, but must be held rigidly against body I by means of clamp or cover plate 3. However, these blades are invariably beveled on each side of the central plane, the ground edge e-d being at an angle with the flat surface d -f. Repeated micrometer measurements and careful calculations show that the angle included between one beveled edge cd and the central plane of the blade 2 is, on the average, about 9 42'. The arc e-h, starting from the edge of blade 2, has as its center a point lying in a vertical plane intersecting the edge e of blade 2. Therefore the central plane of the blade is tangent to a radius of the pencil I0 (and also a radius of the hole 1), and any bevel on the blade 2, however slight, lying below the central plane of blade 2 must encroach within the periphery e-h. of hole 7. Hence the purpose of the device would be defeated, as insertion of pencil ID in hole I would merely bring it in contact with the protruding surface e-d of blade 2 rather than with its cutting edge e. Theoretically, the periphery of the pencil would rub against blade 2 at the point on beveled edge ed.' which is nearest to the center of the hole 1, thus resulting in the burnishing, rather than the cutting of the pencil.

To overcome these difiiculties I employ the construction shown in Fig. 5, in which 0 represents a point in the axis of the pencil l0, e represents the edge of blade 2, ce a radius intersecting the edge e, and e--b a line tangent to radius ce. Also, the line 02-0 is drawn vertically through the axis of the pencil l0 and lies in a vertical plane which coincides with the axis of pencil l0 throughout the length of the latter. At one point the plane represented by ac intersects the longitudinal edge e of blade 2, so that a horizontal angle is formed between the axis of pencil I0 and edge of blade e when viewed in plan, as in Fig. 3. In the design shown. this angle is 2 0'. The axis of the pencil l0 and hole I must be inclined vertically also, in order to produce a properly tapered point. The combination of the vertical and horizontal angles determine the position of the blade edge e relative to any point along the axis of pencil III. This position, and the resulting angle a.ce must be such as to permit the line eb, tangent to the radius ce, to coincide with, or preferably to fall slightly below, the blade surface cd, thus insuring clearance between the blade 2 and pencil ID as the periphery of pencil It] leaves edge e. The combination of the vertical and horizontal angles above mentioned also determines the depth of feed, or thickness of the chip e-g, and as the axis of pencil l0 intersects edge e at a point coinciding with the finished point of the pencil, the thickness of chip e--g varies, from any desired value at the beginning of the taper down to zero, theoretically, at the tip of the point. This results in smooth, easy operation, a minimum of breakage, and points of any degree of length and sharpness desired.

It would be possible to use double-beveled blades in this type of sharpener by inclining them at an angle so as to insure clearance between the beveled surface cd of blade 2 and the periphery of pencil I0. But this would complicate the problems of construction and make it necessary to keep the edge of the blade nearly, if not quite, straight. I therefore prefer to employ the construction above described.

While I have described my invention with great particularity, especially with reference to a spe cific embodiment thereof, it is not to be construed that I am limited to the design shown in the drawing, for, from the information which I have disclosed, a variety of similar devices could be designed by those skilled in the art without departing from the spirit of my invention as embodied in the following claims.

What I claim is:--

1. A pencil pointer comprising a body and a replaceable blade having its upper and lower faces beveled along at least one side to form a cutting edge, said body having a longitudinally extending concaved seat for said blade, a cover plate having a convex surface complementary to said seat effective to clamp the blade fixedly in position so as to shave thin chips from a pencil when the latter is rotated against the edge of the blade and means formed in said body to guide a pencil so that the periphery thereof will engage in a curved line contact with the extreme cutting edge of the blade and clear the beveled lower portion thereof, said beveled lower portion being positioned substantially perpendicular to the radii connecting the axis of the pencil with the extreme cutting edge of the blade.

2. A pencil pointer comprising a body and a. blade whose upper and lower faces are both beveled along at least one side so as to form a cutting edge approximately coinciding with the central plane of the blade, clamping means 'coacting with said body to flex the blade longitudinally so as to give its cutting edge a curved form, means formed in said body efiective to guide a pencil so that it may be rotated manually against the curved edge of the blade, said clamping means and said pencil guiding means being so relatively disposed that the lower beveled portion of the blade is positioned substantially perpendicular to radii connecting the axis of the pencil and the extreme cutting edge of the blade.

3. A pencil pointer designed to form a hollowed or concave conical point on a pencil of the woodencased variety, consisting of a body having a longitudinally concave curved seat, ailexible blade, an easily removable cover plate adapted to hold said blade against said concave surface, projec tions to secure the blade and hold its edge in fixed relationship to the body of the device, and a guide adapted to receive the end of a pencil and permit it to be rotated against the edge of said blade; the said guide being so positioned that radii drawn from points in its axis to the cutting edge of the blade will be approximately perpendicular to the adjacent beveled surface of the blade.

4. A device for shaping the ends of wood-en cased pencils, consisting of a body, a flexible blade with at least one double-beveled edge, a longitudinally curved cover plate adapted to flex the blade longitudinally and clamp it to said body, means to secure said cover plate to said body, means to hold the blade against lateral move ment, and a guide hole in said body whose axis as viewed in side elevation is inclined at an acute angle to the plane of the blade and as viewed in plan is disposed at an acute angle to the edge of the blade.

5. A pencil pointer comprising a body carrying a double-beve1ed-edge blade held in longitudinally curved condition and fixed relationship to the axis of a pencil guiding hole formed in said body; said axis being disposed at a compound angle relative to the cutting edge of said blade.

6. A pencil pointer comprising a body having a passage adapted to receive and guide the end of a wood-encased pencil, and a double-beveled blade curving inwardly into said passage and. toward the axis thereof, for the purpose of shaping the end of a pencil rotated therein against the edge of said blade so that the tapered portion of said pencil shall have a concave contour, the lower bevel of the blade adjacent to its cutting edge being approximately perpendicular to radii drawn from the said cutting edge to the axis of the said passage, said axis being disposed at an acute angle as viewed either fiatwise or edgewise of said blade.

HENRY W. SPOONER.

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