US2229633A - Pencil lead and the method of making the same - Google Patents

Description

L. E. BEST Jan. 28, 194-1.

PENCIL LEAD AND THE METHOD OF MAKING THE SAME Filed Dec; 28, 1939' R Y 6 5 m w m M 55 0. o .1 M w. MY M 1 w ,w n own m 0 MW W4 w 1 M w 3 j I x Patented Jan. 28, 1941 PATENT OFFICIE rnucn. LEAD AND 'rnn ME G THE SAME OD OF Leonard E. Best, Summit, N. J. Application December 28, 1939, Serial No. 311,323 v 2 Claims. (Cl. 120-83) This invention relates to pencil leads, and to the method of making the same.

The invention relates to the manufacture of lead pencils, and has specialreference to the preparation of leads and crayons intended to be used when sheathed in a wooden casing and held therein by glue, or other water soluble adhesive.

In the manufacture of'black leads (so-called) it is customary to impregnate the clay graphite mixes with. waxes after baking. In distinction to black leads which are made with graphite and core of lead before it clay, colored leads or crayons usually do not contain graphite or clay but do contain a considerable portion of wax. The wan surface of these leads is water repellent, and in consequence the sheaths of not join with the lead or crayon, whereby a loosepencil in respect to its lead and sheaths together.

One of these methods is the sulphuric acid dip to destroy the waxy surface. Another is to use chemical crystals between the core and the grooves of the casing; another is to subject the has been placed into the casing to a mechanical action, one of such mechanical means being the sand blast process.

The objections to these various methods of the prior art are that they are essentially dirty, dangerous to the operatives and relatively expensive, and as regards those that utilize the mechanical processes of indentation by sand blasting, for instance, while the peripheral surface of the leads are subjected to indentations, the wax which permeates the entire clay graphite mixture is meretherefore is still present when the glue isbeing applied. While some of these attempts overcome certain objections, they present others, it

This invention overcomes manybbjections of theprior art, and it is simple, clean and inexpensive in operation; and the invention consists chine which is utilized such peripheral surface, and

tion along the entire peripheral surface of the leads. a

As the black leads contain graphite which is a conductor, the lead is used as a part of the electric circuit and subjected-to an arcing action, 5 whereas since the colored leads made of pigment and wax are non-conductors, they are not used as conductors but are subjected to the action of an electrical are which acts upon theperipheral surface of the lead to remove the outer peripheral surface insofar as the wax film is concerned, in the same manner as in the case of the arc upon the black lead used as a. conductor, The wax film being secured, in consequence, the clay graphite constituents on the one hand, and the pigment constituent on the other, come into direct contact with the glue in the sheaths of the casing and thereby an intimate adhesion between lead and casing is obtained, as a result of which the lead'core, be it black lead or colored lead,-is securely held in the wooden casing and by such a secure holding the lead pencil at its point is structurally strengthened.

The invention will be further described in regards to the embodiments thereof, which will be shown in the drawing, and the invention will be finally pointed out in the claims.

- In the accompanying drawing:

Figure 1 is a plan view of the improved mafor the treatment of pen: cil leads made of clay, graphite and wax;

Figure 2 is a side view thereof;

.Figure 3 is a drawing taken from a microphotograph of-the outer surface of the lead-after it has been treatedin the machine shown in 3 Figures 1 and 2; I v

Figure 4 is a' transverse section taken on line 4-4 of Figure 3; V

Figure 5 .is an enlarged transverse section of 4 the lead while it is being moved in the machine 40 shown in Figures 1 and 2;

Figure 6 is a transverse section of the lead as imbedded in the two sheaths forming the casing: and

Figure 7 is a drawing of two electrodes with the colored lead thefebetween whereby the colored lead is subjected to the arcing action of the electrodes. 7

Similar characters of reference indicate the same parts throughout the various views.

Referring to the drawing, and more particu* larly to Figure 6, there is there shown a finished lead penpu made up in: the sheath in and the sheath ll, each having a semicircular bore I2 which is provided with glue. Within these two semicircular bores l2 there is placed, after the glue has been applied thereto, a lead l3 which forms its core. The glue is also applied between the peripheral surfaces of the sheaths l0 and II, as at I4, and joins these together. This is known. The inventionis shown as embodied in an enlarged view of the core l3 as shown in Figure 4, and this shows pitted and partly otherwise removed by attrition, as v various cavities relatively large or small indicated by IS in Figure 4. These indentations result from the removal of the wax film or coating of the lead. The removal of the wax somewhat inside of the initial periphery. is brought about by rotating a lead as shown in Figure 5, while moving the same, and subjecting it to an electric arc.

- In Figure 5 the general direction of the moveing action of an upright relatively of course, wax

with the description ment of the lead I3 is indicated by the arrow i6, and which movement is broughtabout by a pushrod i1 secured to a belt l8 moving in the direction of the arrow l8. Above the belt there are guide rods or tracks 20 upon' which the lead. I3 rests. of the lead [3 in the direction of the arrow IE, it is rotated in the direction of the arrow 2!, and as the lead I3-is part of an electrical circuit passing through the guide rail or tracks 20, an arcing action takes place as indicated by 22, as the circular outer surface of the lead circumferentially leaves the guide rail 20. This arcing action acts upon the wax, and the high temperatureof the are probably volatilizes or decomposes the wax,-and in consequence removes the same from the peripheral surface of the lead.

In Figure 5' the lead'is shown in the position where. about three-quarters of its circumference has already been acted upon and the remaining circumference, that indicated generally by 23, is smooth,.i. e., it has that smoothness usually attendant leads after they have been prepared and are generally ready for insertion in the casing.

In Figure 3 is shown a reproduction of a microphotographshowing the actions of the arcing upon the lead, described in connection with Figure 5.

The important thing,.therefore, is to subject a lead-consisting of a mix or clay, graphite and wax to an arcing action such as described in conresult of'which the the wax portion removed so that the remainder of the composition such as the clay and graphite may readily bind with the glue when the pencil is being completed in commercial form, as described in connection with Figure 6. There is, within the lead, and it is desirable to encase the arckciied lead before the inner wax oozes to the free rom wax surface.

g the leads in accordance One manner of treat of Figure 5 is shown in.Fig-' ures 1 and 2. In the embodiment of the device or machine there shown; which may be varied so as to carry out the actions described in connection with Figure 5, there are in Figure 2 three standards 38, 3| and 32, and adjacent the standard 38 is a supply hopper 33 supplying. the leads l3 to the machine, and adjacent to the other end standard 32 is a collecting member 34 to receive the leads which have been subjected to the electrical action. These standards 38, 3| and 32 each support in which in turn support drums 33 or the like upon which belts 31 and 88 are carried. One e tshown by the belt 40, and by By the movement reason for this follows. The leads, and in leads made of a disposed in spaced relationship to each other. Y

The belts are actuated by a pulley wheel 38 and the operation of the pulley wheel 38, the shafts 35.are rotated due to the action of the belts.

.Referring now to Figure 1, it will be seen that disposed at either side of the belt 31 there are tracks 20, and in the embodiment shown these tracks 20 converge from the standard iifl towards the standard 3|. These tracks 28 are each con nected with an electrical conductor, tor being indicated by Al, and the other by 42, and these conductors 4l and 42 are suitably connected with an electrical circuitoperated by a switch 43, the electrical circuit having a transformer the circuit being an alternatingcurone conduc-.

rent circuit. Between the standards 3! and 82 the guide rails 20 also converge, and they con-'- verge towards the standard 32, and these guide rails ortracks 20 are continuous from the conductors 4i and 42, so that they are also under the action of the electrical current, the ends of the tracks 20 being insulated from each other by a suitable space or by a block ofinsulating material 45. As each of these tracks 20 are substantially one from the standard 30 to the standard 32, the arrangement of the belts 31 and 38, as before described,'is made, 'namely, in the wider space between the tracks 28, the belt 31 is between the tracks 20, whereas when these tracks converge to almost contact with each other, the belts 38 are spaced at each side thereof. Another arrangement is that it is desirous of subjecting moves from one end to the other of ,the machine, to the arcing The belts themselves are provided with upright standing rods l1, and these rods are arranged in pairs, each pair acting upon a lead.

The operation of the machine described is as this, case the black clay graphite mixed with wax, are inserted into the hopper 33, and they automatically drop upon the belt 31. As they drop upon this belt 31, a pair of upright rods l1 abut against each lead, and due to the movement of the belt in the direction of the arrovfl'l the leads are moved in the direction of the arrow 41 and roll upon the tracks 28 at each side of the belt 31. It will be noted that the lead now indicated by the lead from end to end inwardly. 31 moves the lead i3a to the position of the lead l3b, the arcing action works towa dsthe center until the position of the lead reach'es about that of Be. Thereafter, the lead is moved by the two belts 38, and the electrically actuated tracks 20 'act upon the shown in Figure 1 until when the lead 1.3g reaches the position shown in Figure -1, the central portion of the lead has been arced, and thereby the arcing action has taken place throughout the entire length of the lead, and, due to the rotation of the lead, has

. cumference thereof.

' In connection with the arcing action upon .crayons or colored leads, the lead- 50 is subiected to a rotation action as shown by the arrow 5| in Figure and is moved lonthrough a gap 52 the electrode 54.

the entire peripheral surface of e each lead, as it inner'portion of the lead [3 as taken place throughout the cirthe necessary equipment so compact and inex- By the action of theme between the electrodes 53 and 54, the peripheral surface of the colored lead '50 is thereby acted upon in substantially the same manner as described in connection with the leads l3 in Figure 1.

It has been seen that in treating black leads, the conductivity of the graphite is utilized to carry an electric current through the lead, and by rolling the leads over a suitable set of tracks' which form a part of the same electrical circuit that thereby a continuous series of small electrical surface discharges that destroy the waxy surface are obtained, whereby the leads so treated may be properly glued in the wooden sheaths which form the casing. It has also been seen that in treating crayons which are non-con- -ductors, the crayon is subjected to a continuous electrical discharge or electrical are that completely surrounds it and carbonizes the surface waxes.

In both of these methods,relatively low voltages and current densities are used, so that they are essentially inexpensive and simple. The degree of treatment is readily controlled bythe usual electrical instruments giving a wide range of effects at the will of the operator. The action of the process of treating the leads is rapid, and

pensive that it can to the existing ing, and can be form a very flexible addition processes for pencil manufacturincluded in such a way that the permeates the entire lead, and it is therefore preferable to encase these leads within a reasonable time after their electrical treatment, toprevent the wax from the interior of the leads from oozing out to the surface.

When pencils are made using leads processed in the manner described and bonded to the sheaths, they are structurally strong, and give greater service than those made with the conventional untreated leads.

Q The manifold indentations of various con- 'or 400 F., and coking above 500 the entrance of the glue, and

It is believed that the wax which is acted upon by the electric are or arcing action in either volatilized or carbonized, the carbonization due to the high temperature of the are being probably of the character of coking. It is now generally said that carbonization takes place up to 350 F.

temperature coking between1000 F. and 1200 F. Graphitizing of carbon takes v 1200 F., and generally around 1800 F. to 2300 F. or 2500 F. Wax used for impregnating leads melts at about F. or F. and volatllizes or decomposes at about 400 F., these temperatures depending upon the particular constituency of the wax.

Various changes may be made in the structural features of the machines described, the invention here being also the treatment by an electrical arc action upon the peripheral surface of a waxed lead, be it graphite or colored, whereby the peripheral surface is brought into a conditionto obtain a permanent binding effect with the enclosing casing, and various changes may be made within the principle of the invention described without departing from theiscope of the subjoined claims. I

I claim:

1. The method of treating pencil leads which consists in subjecting the peripheral surface of the pencil leads to the action of an electrical arc throughout the exterior peripheral surface of the lead, whereby the waxy peripheral surface is removed, whether film or otherwise.

2. An improved lead consisting of a pencil lead having a peripheral. surface substantially free excellent intera binding effect between the lead, core and the casing.

F., and high place beyond from waxy constituents with indentations orinterstices upon said surface of the character resulting from an electrical arcing action upon a

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