US3630628A

US3630628A - Propelling pencils

Info

Publication number: US3630628A
Application number: US873983A
Authority: US
Inventors: John Roman
Original assignee: MERMAID ENGINEERING CO Ltd
Current assignee: MERMAID ENGINEERING CO Ltd
Priority date: 1968-11-04
Filing date: 1969-11-04
Publication date: 1971-12-28
Anticipated expiration: 1988-12-28
Also published as: GB1222448A

Abstract

A propelling pencil having a tube with an internal double start screw thread, one end of the tube being surrounded by a resiliently flexible sleeve which engages with a portion of an operating member to restrain it against axial movement along the tube while permitting its rotation. An outer casing covers the tube and constricts the sleeve to further restrict the movement of the operating member. The rotation of the operating member moves a threaded element engaging the threaded tube axially along the tube to urge a pencil lead along a guide mounted at the other end of the tube which includes a block of resilient material formed with a puncture through which the lead extends and by which the lead is held.

Description

United States Patent [72] Inventor John Roman London, England [21 Appl. No. 873,983 [22] Filed Nov. 4, 1969 [45] Patented Dec. 28, 1971 [73] Assignee Mermaid Engineering Company Limited London, England a part interest [32] Priority Nov. 4, 1968 [33] Great Britain [31] 52,145/68 [54] PROPELLING PENCILS l 1 Claims, 4 Drawing Figs.

[52] U.S. Cl 401/68 [51] lnt.Cl 343k 21/08 [50] Field of Search 401/68-78, 65, 87

[56] References Cited UNITED STATES PATENTS 1,490,244 4/1924 Wahl 401/76 1,828,527 l0/l93l Fischer 401/77 X 2,319,823 5/1943 Moore 401/87 X FOREIGN PATENTS 422,767 l/l935 Great Britain 401/75 Primary Examiner-Lawrence Charles Attorney-Beveridge & De Grandi ABSTRACT: A propelling pencil having a tube with an internal double start screw thread, one end of the tube being surrounded by a resiliently flexible sleeve which engages with a portion of an operating member to restrain it against axial movement along the tube while permitting its rotation. An outer casing covers the tube and constricts the sleeve to further restrict the movement of the operating member. The rotation of the operating member moves a threaded element engaging the threaded tube axially along the tube to urge a pencil lead along a guide mounted at the other end of the tube which includesa block of resilient material formed with a puncture through which the lead extends and by which the lead is held.

, PROPELLING PENCILS The invention relates to propelling pencils.

According to the invention a propelling pencil comprises a guide within which a pencil lead is movable longitudinally, an internally threaded tube coaxial with the guide, an element engaging the thread within the tube, and having a part engageable with a lead in said guide, a rotatable operating member extending axially along the internally threaded tube engaging the element in such a manner that rotation of the operating member rotates the element and causes it to move axially along the tube relative to the operating member, a flexibly resilient sleeve surrounding part of the internally threaded tube, adjacent the end thereof, a portion of the operating member extending beyond the end of the internally threaded tube, said portion being engageable with a portion of the flexibly resilient sleeve in a manner to restrain the operating member against axial movement while pivoting its rotation.

Preferably the portion of the operating member comprises a radially outstanding portion which is received within an internal circumferential groove in the end of the resiliently flexible sleeve.

The internal circumferential groove may be formed in a part of the resiliently flexible sleeve which is of increased internal diameter so as to provide an annular gap between the inner surface of the sleeve and the outer surface of the threaded tube, the portion of the operating member having said radially outstanding part being tubular and projecting into said annular gap.

The radially outstanding part of the operating member may be in the form ofa peripheral flange.

it is also preferred that the end of the resiliently flexible sleeve is formed with a number of slots extending along the length thereof to facilitate expansion of the sleeve to receive said portion of the operating member.

Preferably there is provided an outer tubular casing surrounding said resiliently flexible sleeve and arranged, when placed over the sleeve, to engage its outer surface and press the parts of the sleeve between said slot inwardly so that they engage more tightly the portion of the operating member.

The parts of the resiliently flexible sleeve between the slots may be formed with outwardly projecting bosses which are engaged by the inner surface of the outer casing.

Preferably the guide includes a block of resilient material mounted in fixed relation to the internally threaded tube and formed with an axially extending puncture through which the lead may pass and be held by the resilience of the material until urged through the puncture by movement of the aforesaid element or direct movement of the lead by external force.

The block of resilient material may be cylindrical having conical indentations in both ends, the deepest point of each indentation coinciding with one end of the puncture.

The aforesaid part engageable with the lead may comprise a rod attached at one end to the element within the internally threaded tube and extending axially along the threaded tube so that the other end may impinge upon an end of the lead and push it through the block of resilient material.

The screw thread of the internally threaded tube is preferably a double start screw thread.

The following is a more detailed description of an embodiment of the present invention reference being made to the accompanying drawings in which:

FIG. 1A is a longitudinal section of a part of a propelling pencil;

FIG. 1B is a longitudinal section of the remainder of the propelling pencil; and

FIG. 2 is a cross section of the propelling pencil on the line 2-2 of FIG. 1A.

FIG. 3 is a cross-sectional view of the propelling pencil taken on line 33 ofFIG. 1A.

A propelling pencil has an outer tubular casing 11 within which is a tube 13 internally threaded at one end. The threads 14 of the end of the tube 13 engage with the threads 15 of a solid cylindrical screw-threaded element 16. The threads 15 of the element 16 are only on one-half of its cylindrical surface as shown in FIG. 3, the other half having no thread on it. The threads 14 and 15 are double start threads to minimize backlash and the element 16 is formed from plastics and moulded around the end ofa wire 31 which extends along the axis of the tube 13 and serves to reject the lead (not shown) as the element 16 moves along the tube 13.

To move the element 16 along the tube 13 there is provided an operating member which comprises a rod 19, of arcuate cross section as shown in FIG. 3, connected to a tubular knob 20 which is of sufiicient diameter to fit over the threaded end of the tube 13. The arcuate cross section of the rod 19 is of such a radius that it will fit between the unthreaded portion of the element 16 and the inner wall of the threaded tube 13 so that rotation of the rod 19 by the knob 20 causes the element 16 also to rotate and hence move axially relatively to the tube 13 and the rod 19.

The knob 20 has one end formed with a gripping piece 22 and the other end stepped to form a tubular portion 23 of smaller diameter than the rest of the knob 20. The tubular portion 23 is formed with an annular ridge 17 at the extremity thereof.

The knob 20 and rod 19 are restrained from axial movement relatively to the threaded tube 13 by cooperation of the tubular portion 23 with a plastics sleeve 24 made from polypropylene or like material. The sleeve 24 fits over the outside of the tube 13. At its end nearer the knob 20, the sleeve 24 is of increased internal diameter, so as to provide an annular space 57 between it and the tube 13 and is split by two iongitudinally extending diametrically opposed cuts 28 which divide the sleeve into two jaws 29. At corresponding points on the inside of each jaw 29 are thickened portions 58 within which are cut circumferential grooves 30 which are so positioned that when the tubular knob 20 is pushed over the end of the threaded tube 13 the radially outstanding annular ridge 17 engages with the grooves 30 of the jaws 29 which then restrain the knob 20, and hence the rod 19 from axial movement relatively to the threaded tube 13, while still permitting rotational movement thereof. Formed on each jaw 29, within the annular space 57, is an upstanding boss 59 which projects outwardly beyond the thickened portion 58. The operating casing 11 fits over the end of the tube 33 and engages with the bosses 59 when it is in the position shown in FIG. 1B. Thus the bosses 58 and jaws 29 are forced radially inwards and thus the jaws 29 grip the knob 20 to prevent its easy rotation. If the knob 20 could rotate easily the element 16 might be rotated and forced back along the tube 13 by external pressure on the lead.

The unthreaded end of the tube 13 fits tightly around an extension tube 36, coaxial with the tube 13 and which houses an annular stop 37 against which the element 16 urges a spring 55 at the limit of its travel down the tube 13. The section of the inside of the extension tube 36 beyond the stop 37 and the spring 55 is lined with a sleeve 38 of plastics material. The tube 36 is covered on the outside by the end 25 of the sleeve 24 and this end of the sleeve is formed with three longitudinal fins 26. Extending around the fins 26 there is a casing 33 which provides, with the fins 26, three compartments 34 into which may fit spare leads for the pencil. These leads are kept in the compartments 34 by an annular stopper 35 which fits over the end 38 of the extension tube 36 and has a shoulder 39 which abuts the end of the tube 38 when the end of the stopper 35 abuts the openings to the compartments 34.

A tube 41 of brass extends coaxially along the case 40 and is fitted into a ferrule 42 formed with a central bore 48 and an annular rebate 43 which abuts one end 44 of the case 40. The ferrule 42 is continued from the rebate 43 with a thread 45 surrounding the tube 41 and engaged by an annular nut 46 of such a shape that it fits tightly within the case 40 when drawn down by the screw thread 45 upon rotation of the ferrule 42. The tapered end of the ferrule 42 holds a tube 47 of, for example, stainless steel, which is press-fitted within the central bore 48 of the ferrule 42 and extends as far as the shoulder 49 of the central bore.

Between the end of the brass tube 41 and the shoulder 49 is a block 50 of resilient material of cylindrical shape and formed with conical indentations 51 at its opposite ends. These indentations 51 act as guides by which the lead, which lies along the tube 41, may be directed into a puncture 52 extending between the apices 53 of the indentations 51. The puncture is formed by piercing the block 50 and not by drilling or moulding a hole in it. The block 50 will therefore hold a lead, by its resilience, in any position to which the lead may be moved while lying within the block 50. It will also allow the rod 31 to pass through it, as shown in FIG. 1A.

By anticlockwise rotation of the knob 20 the element 16 and its associated wire 31 are retracted towards the end of the threaded tube 13 thus leaving no part of the wire 31 extending inside the brass tube 41. A lead may then be inserted into either the brass tube 41 or the stainless steel tube 47 and moved until it is held by the resilient block 50 with one end level with the outer end 54 of the stainless steel tube 47. The knob 20 is then turned in a clockwise direction thus moving the element 16 down the threaded tube 13 thus moving the wire 31 into the brass tube 41 until its end 55 contacts the end of the lead. By further rotation of the knob 20 the lead may then be moved to a position where a sufficient portion projects beyond the end of the stainless steel tube 47 to enable the propelling pencil to be used as such. When it is required to retract the lead the knob is rotated anticlockwise, withdrawing the wire 31 from the lead so that the lead may be pushed into the tube 47, the lead being held in its retracted position by the resilience of the block 50.

The type of propelling pencil described above is particularly suitable for use with leads whose diameter is small, for example one-half millimeter, since the lead is gripped resiliently and is not gripped rigidly by a metal sleeve which could cause breakage of such fragile leads.

lclaim:

1. A propelling pencil comprising:

a. a guide within which a pencil lead is movable longitudinally,

b. an internally threaded tube coaxial with the guide,

c. an element engaging the thread within the tube said element having a part engageable with said lead in said guide,

d. a rotatable operating member having a first portion extending axially along the internally threaded tube and engaging the element so that rotation of the operating member rotates the element and causes it to move axially along the tube relative to the operating member, said rotatable operating member having a second portion lying outside of said tube near one end thereof,

e. a flexibly resilient sleeve surrounding part of said internally threaded tube, adjacent said end, f. said second portion being engageable with means in said flexibly resilient sleeve for restraining the operating member against axial movement while permitting its rota- Hon.

2. A propelling pencil according to claim 1 wherein said second portion of said operating member comprises a radially outstanding portion which is received within an internal circumferential groove in said resiliently flexible sleeve.

3. A propelling pencil according to claim 2 wherein the internal circumferential groove is formed in part of the resiliently flexible sleeve which is of increased internal diameter so as to provide an annular gap between the inner surface of the sleeve and the outer surface of the threaded tube, the portion of the operating member having said radially outstanding part being tubular and projecting into said annular gap.

4. A propelling pencil according to claim 3 wherein the radially outstanding part of the operating member is in the form of a peripheral flange.

5. A propelling pencil according to claim 2 wherein the end of the resiliently flexible sleeve is formed with a number of slots extending along the length thereof to facilitate expansion of the sleeve to receive said second portion of said operating member.

6. A propelling pencil according to claim 5 wherein there is provided an outer tubular casing surrounding said resiliently flexible sleeve and arranged, when placed over the sleeve, to engage its outer surface and press the parts of the sleeve between said slots inwardly so that they engage more tightly said second portion of the operating member.

7. A propelling pencil according to claim 6 wherein the parts of the resiliently flexible sleeve between the slots are formed with outwardly projecting bosses which are engaged by the inner surface of the outer casing.

8. A propelling pencil according to claim 1 wherein said guide includes a block of resilient material mounted in fixed relation to the internally threaded tube and formed with an axially extending puncture through which the lead may pass and be held by the resilience of the material until urged through the puncture by movement of said element or direct movement of the lead by an external force.

9. A propelling pencil according to claim 8 wherein said block of resilient material is cylindrical having conical indentations in both ends, the deepest point of each indentation coinciding with one end of the puncture.

10. A propelling pencil according to claim 8 wherein the said part engageable with the lead comprises a rod attached at one end to the element within the internally threaded tube and extending axially along the threaded tube so that the other end may impinge upon an end of the lead and push it through said block of resilient material.

11. A propelling pencil according to claim 1 wherein the screw thread of the internally threaded tube is a double start screw thread.

Claims

1. A propelling pencil comprising: a. a guide within which a pencil lead is movable longitudinally, b. an internally threaded tube coaxial with the guide, c. an element engaging the thread within the tube said element having a part engageable with said lead in said guide, d. a rotatable operating member having a first portion extending axially along the internally threaded tube and engaging the element so that rotatIon of the operating member rotates the element and causes it to move axially along the tube relative to the operating member, said rotatable operating member having a second portion lying outside of said tube near one end thereof, e. a flexibly resilient sleeve surrounding part of said internally threaded tube, adjacent said end, f. said second portion being engageable with means in said flexibly resilient sleeve for restraining the operating member against axial movement while permitting its rotation.