Micrometer pencil

May 26, 1970

3,513,554

F. H. BICKFORD

MICROMETER PENCIL

Filed Aug. 16, 1968

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INVENTOR.

FRANKLIN H.BICKFORD.

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ATTORNEY

3,513,554

Patented May 26, 1970

United States Patent Office

3,513,554 MICROMETER PENCIL Franklin H. Bickford, 504 4th St., Liverpool, N.Y. 13088 Continuation-in-part of application Ser. No. 568,835, July 29, 1966. This application Aug. 16, 1968, Ser. No. 753,278

Int. CI. GOlb 3/28, 5/18

U.S. CI. 33—170 10 Claims

ABSTRACT OF THE DISCLOSURE

Micrometer pencil comprising a mechanical pencil having manual relatively movable barrel portions for advancing the pencil lead, the barrel portions being provided with indicia whereby the degree of advance is indicated and the pencil thereby made to serve as a depth micrometer.

This application is a continuation in part of my copending application No. 568,835 filed July 29, 1966, now abandoned.

This invention relates to a combination writing instrument and micrometer, and more particularly to a mechanical pencil modified by the addition of a scale, correlated with the pitch of the screw mechanism which advances the writing element, to enable accurate measurements of rectilinear dimensions.

The primary object of the invention is to provide a marking instrument having the dual function of marking and measuring, thue enabling a user to immediately make accurate measurements with his writing implement and avoid the interruptions and delays normally involved in seeking a different measuring instrument.

Another object of the invention is to provide a writing instrument in the form of a mechanical pencil in which the lead may be advanced with respect to the barrel of the pencil and said advancement accurately measured on a micrometer scale.

A further object of the invention is to provide a mechanical pencil, of the above described characteristics, which is formed by merely adding a scale and an index to the relatively rotatable barrel parts of a conventional mechanicsl pencil, said scale being correlated with the pitch of the screw of the lead advancement mechanism to multiply the same for accurate reading.

Still another object of the invention is to provide a mechanical pencil, of the above described characteristics, which is of simple construction, inexpensive to fabricate, easy to use, and reliable and efficient in operation. :

The novel features that are considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawing, wherein like reference characters indicate like parts throughout the several figures and in which:

FIG. 1 is an elevational view of a micrometer pencil according to a preferred embodiment of the invention;

FIG. 2 is an elevational view taken at right angle to FIG. 1, with parts broken away to reveal internal parts of the pencil in section;

FIG. 3 is an enlarged, fragmentary, elevational view similar to FIG. 1, showing the parts as indexed to an initial position ready for the start of a measuring operation;

FIG. 4 is a view similar to FIG. 3, showing the parts after advancement of the lead to complete a given measuring operation;

FIG. 5 is a fragmentary enlarged view of the slotted sleeve 42 twisted to provide calibration; and

FIG. 6 is a sectional view taken on the line 6—6 of FIG. 5.

Referring now more particularly to the drawing, one embodiment of the invention is illustrated in FIG. 1 as comprising a conventional mechanical pencil, generally indicated by the character 19, having two relatively rotatable barrel portions 12 and 14, a lead 16, eraser 18, and a spring clip 20 for securing the pencil in the pocket of a user. To modify the conventional mechanical pencil to accomplish the dual function of writing and measuring, a micrometer scale 22 is added to the barrel part 14 and a band 24 is frictionally rotatable with respect to the barrel part 12. The graduations, or divisions 26 of the micrometer scale are correlated to the pitch of the advancing mechanism within the barrel of the pencil, as will be further explained later. As a result, each complete revolution of barrel portion 14 will indicate advancement of the lead 16 by the pitch distance of the screw mechanism, so that advancement of the lead may be measured by counting the total revolutions of barrel portion 12 and adding the remaining partial revolution as indicated by the registration of the index band 24 with the graduations of the micrometer scale 22.

While the specific construction of the lead advancing mechanism is immaterial and any conventional mechanism may be utilized in the present invention, there is shown in FIG. 2 one type of lead advancing mechanism for illustrative purposes and to clarify and complete the understanding of the invention. Lower barrel portion 14 has secured thereto a conical end 28 which may, if desired, be terminated in a short cylindrical ferrule 39 through which the lead 16 is propelled and retracted. The bore of a lower barrel 14 has an enlargement at its upper end in which is slidably housed a sleeve 32 which extends above the top of barrel portion 14. The upper barrel 12 is slidably telescoped over the upper end of sleeve 32 with a friction fit so that if the lower barrel is held in the fingers of one hand, the upper barrel 12 may be rotated relative thereto carrying the sleeve 32. The upper end of the sleeve is closed by a plastic cap 34, leaving a compartment 36 above the cap in barrel portion 12 below the eraser 18. Partially inserted in sleeve 32 with a friction fit is an intermediate sleeve 38 which extends downwardly to near the bottom of the lower barrel 14. Fixedly to the intermediate sleeve is a helical screw thread 49, shown as a stiff helix and which if desired may preferably be integrally formed in the interior of said sleeve to rigidify the screw thread. Seated within the intermediate sleeve is an inner sleeve 42 having a longitudinal slot 44 running down one side for its complete length. The upper end of said inner sleeve is flanged outwardly at 46 to overlie sleeve 38 in a manner permitting relative rotation of sleeve 38 with respect to the inner sleeve 42. The lower end of inner sleeve 42 is secured to the lower barrel portion at the bore of the conical part 28 in any suitable manner, not shown, so that the inner sleeve 42 is fixed for rotation with the lower barrel 14 when the latter is held by the user.

The rod of carbon 16, or lead, moves axially within the inner sleeve 42 and abuts at its upper end with a pusher rod 59 having a radially directed lug 52 which extends radially through the slot 44 of sleeve 42 into the space between turns of helix 49. Thus, the pusher rod 59 acts to propel the lead 16 downwardly and out of ferrule 39 upon rotation of the upper barrel 12 carrying sleeves 32 and 38 and the helix 49, when the lower barrel 14 is held fixed, thus causing the follower lug 52 to move along between the turns of helix 49, rotation being restrained by the slot 44 in the inner

3,513, ³ sleeve 42 affixed aginst relative rotation with respect to barrel 14. It will be seen that the pusher rod 50 is disposed within a sleeve 51 having a second lug 53 engaging between the turns of the helix 40. Such sleeve as shown in FIG. 2 extends beyond the end of the pusher _rrod and embraces a substantial portion of the upper ⁰end of the lead 16. It will also be seen that the sleeve 51 is provided with a slot 55, through which the lug 52 extends, to engage between the turns of the helix 40. As the helix rotates relative to the lugs 51 and ₁₀53 both rod 50 and sleeve advance together to propel the lead out of the ferrule 30. As is well understood, when both lugs are propelled to the lower end of the barrel 14, lug 53 advances beyond the end of the last turn of the helix, and is prevented from advancing 45 further, while further rotation of the helix 40 advances pusher rod 50. In this manner the stub end of a spent lead is ejected. Such relative axial movement is limited by the length of slot 55, which closely conforms to the distance the sleeve 51 extends beyond the end of 20 the pusher rod 50, as shown in FIG. 2. Hence upon reverse rotation of the helix to retract lug 52, after discharge of the spent end of lead from the sleeve 51, the helix first retracts pusher rod 50, until the lug 52 engages the upper end of slot 55. When this occurs, 25 both lugs 52 and 53 are required to be retracted together, the lug 53 is reengaged between the lower end turns of helix 40 and the sleeve 51 and rod 50 are thereafter retracted together in the axial relationship shown in FIG. 2. A new length of lead 16 can be in- 30 serted at any time, and retracted by the friction grip between sleeve 51 and the upper end of the lead.

The scale 22 is a band firmly secured to lower barrel 14 by adhesive, cement, or in any other suitable way, so that one complete rotation of the upper barrel 12 35 advances the follower lugs 52 of the pusher 50 the exact distance between centers of adjacent teeth 40 of the lead advancing mechanism. Since the developed length of the circumference of scale 22 may in practice be ten times the pitch of helix 40, a multiplication of 40 scale is obtained which greatly increases the accuracy of measurement and obviates the need for a magnifying lens or similar optical aid. The diameter of the barrel and scale 22 may be further increased, if desired, to obtain greater multiplication. In any case, these diameters are correlated to yield a desired multiply- 45 ing ratio with the pitch of the screw mechanism. The graduations 26 of scale 22 will represent equal portions of such pitch distance. The graduations may be chosen so that each represents a decimal or, other fraction, of the pitch distance and the user by counting the 50 total revolutions and adding the fractional part of the last revolution as represented by the registration of the index mark 54 with the closest scale division 26 may accurately determine the distance which the lead has been propelled from any given starting point. The in- 55 dexing mark 54 on the band 24, by rotation of said band 24 on barrel 12, is made to register with the zero on scale 22 at the start of the measuring operation and desirably also conforms to the position of the lead 16 when its lower end is exactly flush with the lower end 60 of the pencil barrel (FIG. 3). Thus, for example, if the pitch of the helix 40 is made exactly 0.1 inch and the scale 22 is divided in 100 equal units peripherally of the band and the pencil barrel, each scale unit will represent one-thousandth of an inch. In the illustrated 65 scale, twenty graduations are utilized so that each division of the scale represents five-thousandths of an inch, the spaces between graduations being interpolated to onethousandth of an inch visually.

To rotatably secure the indexing band 24 to the upper 70 barrel portion 12, the lower edge of the band is turned over the lower end of the barrel portion and the upper edge is slightly inturned to ride in a shallow groove in the outer surface of the upper barrel portion.

It will be readily apparent from the above descrip- 75

554 tion that the micrometer pencil may be used in the following manner. When the pencil is used for writing purposes, the upper barrel portion 12 is turned while the lower barrel portion 14 is held fixed to propel the lead 16 so as to protrude a suitable short distance out of the barrel as, for example, shown in FIG. 2. The instrument is then held in one hand as normally for writing purposes, further expulsive and retractive adjustments in the protrusion of the lead being made in the conventional manner whenever desired, or needed. When the writer, or user, desires to measure a dimension, as for example the depth 56 of a flange of a small piece part 58 shown in FIG. 1, he retracts the lead in the usual manner so that its lower edge is flush with the lower edge of the pencil barrel or just protrudes very slightly out of the barrel. To insure a very accurate alignment of the end of the lead 16 with the end of the barrel, the pencil may be held vertically and rubbed across a surface to abrade the lower edge of the lead into exact alignment with the lower edge of the pencil barrel, as shown in FIG. 3. When this is accomplished, the band 24 is turned, while the other parts of the pencil are held fixed, so that the index mark 54 aligns with the zero graduation of the scale 22. The lower transverse shoulder 31 of the pencil barrel, or ferrule 30, is then seated on the upper edge 60 of the flange of part 58, as shown in FIG. 1, and the lower barrel 14 is held still while the upper barrel 12 is rotated to advance the lead until its lower edges strikes the bottom surface 62 of part 58 so that the amount of protrusion of the lead exactly represents the depth of flange. This depth is indicated in FIG. 1 as being exactly 0.1 inch by reason of the registration of the zero on scale 22 with the index mark 54 on band 24 corresponding to exactly one revolution of the upper barrel 12 which is the pitch distance of the lead advance mechanism.

FIG. 4 represents the relative positions of the index band 24 and the scale 22 when the preceding steps have been followed in the making of a measurement which is exactly twenty-five thousandths of an inch, the lead 16 being shown dimensionally in the illustration as protruding exactly that distance corresponding to the registration of the indexing mark 54 with the division 25 on scale 22.

Since due to shrinkage, or manufacturing tolerances, or other causes, the pitch of the helix 40 may vary slightly so as to effect movement of the lead 16 through increments slightly at variance to the indicia, it is desirable to compensate for any such error, so as to render the micrometer action absolutely accurate. If there be such an error, this may be corrected, see FIG. 5, by modifying the sleeve 42 so that its slot, 44 which normally extends elementally of the sleeve, is caused to assume a slight wind or low pitch helix in one direction or the other, and to such a degree as is necessary to effect the correction to compensate for the error and provide calibration.

In this manner, a pencil, already in production and for which dies and molds have been made, can be modified by adding indicia, and converted into a micrometer pencil. If the pitch of the helix of such a pencil should not provide the requisite accurate number of increments of movement of the lead for use with the scale increments, compensation can be easily had by applying a suitable pemanent uniform pitch to the slot 44. In this manner the peripheral scale 22 can be subdivided into a plurality of uniform angular divisions, such as for example 6 divisions of 60 degrees, 8 divisions of 45 degrees, 10 divisions of 36 degrees, or 20 divisions of 18 degrees, etc. Without the corrective feature of adding a compensating pitch to the slot 44, one rotation of the barrel might result in movement of the lead through a distance of 0.09 or 0.11 of an inch so that the scale 22 could not be subdivided into ten equal graduations each spaced 36 degrees, with each graduation corresponding to ten thousandths of an inch of movement of the lead.

The operation explained above makes obvious the utility and convenience of the improved pencil wherein the

3,513, propelled lead serves a dual function of writing and measuring. Pencil 10 provides a compact combination tool, for these dual purposes, which occupies no more space than an ordinary pencil and is always accessible when carried in the pocket of the user. The dual functions manifestly enhance the value of the pencil. In certain ⁵measurements as, for example, that illustrated in FIG. 1, the lead, or marking element, assists in the measuring function not only by providing the movable measuring element but by marking the surface against which it engages so that, when the pencil is withdrawn, the mark ¹appearing upon said surface indicates that the pencil lead has actually engaged the surface and attests to the verity of the depth measurement taken. The diameter of pencil lead 16 is much smaller than that of the ordinary probe of a micrometer, so that the pencil is admirably suited for depth gauging of very small parts or Openings, normally not accessible to conventional micrometers.

From the above explanation of the invention, many modifications will become readily apparent. For example, ₂θ the scale may be calibrated in decimals, or fractions, in centimeters or other units of measurement, rather than inches. The barrel of the pencil need riot be round, as illustrated, but may have other cross-sectional shapes such as square, hexagonal, octagonal, and the like. The ₂₅pencil barrel and certain screw mechanisms parts may be made of transparent materials in which case an additional scale may be added longitudinally disposed on one of the two barrel parts, so that the movements of the lead pusher lug 52 may be viewed through the transparent θθ barrel of the pencil and this movement'' read on the longitudinal Scale to obviate the necessity for counting the number of rotations of the index mark 54 past the zero of scale 22. Obviously, the screw mechanism for advancing and retracting the lead may be changed, and in fact mech- _3ganism may be used which merely advances the lead with resulting slightly less convenience in use. While the invention has been illustrated as applied to a mechanical pencil, it is equally applicable to other types of writing instruments such as ball point pens, in which case an ₄₀elongated ink cartridge having a ball point at its bottom would be substituted for the lead in the pencil illustrated herein.

Although a certain specific embodiment of the invention has been shown and described, it is obvious that _4gmany modifications thereof are possible. The invention, therefore, is not to be restricted except insofar as is necessitated by the prior art.