US3404055A

US3404055A - Method for assembling miniature tubing

Info

Publication number: US3404055A
Application number: US661372A
Authority: US
Inventors: Wieland Franz; Joseph J Ciol; Jacob W Zansitis
Original assignee: Rapidograph Inc
Current assignee: Rapidograph Inc
Priority date: 1967-08-17
Filing date: 1967-08-17
Publication date: 1968-10-01
Anticipated expiration: 1985-10-01
Also published as: GB1170227A; FR1573768A; CH477993A; DE1761739A1

Description

Oct. 1, 1968 F. WIELAND ET AL 3,404,055

METHOD FOR ASSEMBLING MINIATURE TUBING Filed Aug. 17, 1967 2 Sheets-Sheet 1 m k5 R g 5? M INVENTORS FRANZ WIELAND JOSEPH J. CIOL JACOB W. ZANSITIS ATTORNEYS 0a. 1,1968 F. WlELAND ETAL 3,404,055

METHOD FOR ASSEMBLING MINIATURE TUBING Filed Aug. 17, 1967 2 Sheets-Sheet]? Q5 w N L. N R

' INVENTORS FRANZ WIELAND OSEPH J. CIOL OB W. ZANSITIS ATTORNEY$ United States Patent 01 ice 3,404,055 Patented Oct. 1, 1968 METHOD FOR ASSEMBLIN G MINIATURE TUBING Franz Wieland, Bethlehem, Pa., Joseph J. Ciol, Parlen,

N.J., and Jacob W. Zansitis, Easton, Pa., assignors to Rapidograph, Inc., Bloomsbury, N.J., a corporation of New Jersey Filed Aug. 17, 1967, Ser. No. 661,372 9 Claims. (Cl. 156-294) ABSTRACT OF THE DISCLOSURE Method of assembling miniature tubing in co-axial alignment, particularly assembling of jewel points in stainless steel holders as used in stylographic writing instruments, the outside diameters of said jewel points being in the range 0.0080.052 of an inch.

Background of the invention (1) Field of the inventin.This invention relates to the fitting of relatively brittle jewel-type points in stylographic writing instruments, particularly the secure fitting of jewel points having an outside diameter of 0.008 of an inch or less without crimping of metal fasteners about the brittle jewel point enabling drawing of a consistently fine line over contemporary drafting media.

The present invention is the result of a demand for increasingly finer lines in technical drawing. Contemporary drafting media include a coated Mylar plastic film which rapidly abrades conventional stainless steel tips. Jewel points have been used before, but manufacturing difficulties have been encountered with jewel points having an outside diameter of less than 0.010 of an inch. According to the present invention, jewel tips having an outside diameter in the range 0.008-0.0520 of an inch are securely fitted in stainless steel holders, enabling the writing of lines of uniform width for distances up to one mile over Mylar drafting film, including the fine line drawn by jewel points 0.008 of an inch in diameter.

(2) Description of the prior art.-Paul, 2,600,426: Directed to the fitting of jewel points in stainless steel holders wherein a conical jewel is secured to a metallic capillary tube by means of flaring a reduced neck of the capillary tube outwardly at its end so as to overlie a portion of the rounded end of the jewel. According to this arrangement, the metallic capillary tube extends throughout the entire jewel and overlaps the jewel in its core area. A basic shortcoming of this arrangement is that as the jewel wears and the neck of the capillary tube wears, the flared out end is worn off, resulting in a loose fitting or the falling off of the jewel. Also, the tapered surface of the jewel precludes its Writing a line of consistent width as it becomes worn. The insertion of the metallic capillary tube through the jewel requires an increase in the diameter of the jewel and precludes its adaptability for small diameter writing points.

Young, 3,292,595: Concerns the insertion of metallic carbide tips in stainless steel holders and specific-ally describes the difliculty of forming jewel points with a relatively thin wall in the order of say .004 of an inch required to form a thin line of approximately .008 of an inch. According to Young because of extreme tolerances and extreme care, as well as the impossibility of swedging the jewel into its fitting in commercial production, the jewel tip is unsatisfactory for many drafting requirements. It is pointed out that the swedging of the jewel in a metallic fitting would cause destruction of the jewel, especially as the diameter of the jewel is reduced to those diameters, e.g., .008 of an inch attainable in tungsten carbide and like metallic fittings.

Great Britain, 1,045: Concerns the fitting of a drilled jewel, for example, metal, vulcanite wood or ivory in a setting formed of gold. In Great Britain 1,045 the jewel is tapered, precluding the writing of a consistently thin line, also the crimping or fitting of the gold about the face can result in a fracture of the jewel and, of course, the gold fitting could not be sufficiently hard to enable use of the resulting instrument in automated drafting machines.

Summary of the invention According to the present invention, a housing is formed from a larger sized diameter tube such as a stainless steel tube by counterboring its core at one end to an inner diameter approximating the outer diameter of the jewel tube to be fitted. The jewel may be a smaller size diameter tube, having its wall as thin as 0.002 of an inch, an inner diameter or core of 0.004 of an inch and a total outer diameter of 0.008 of an inch. The housing is locked against movement, then the jewel is threaded on an elongated wire mandrel extending through the core of the jewel and coaxially towards the locked housing. Epoxy resin glue is placed on the exterior or periphery of the jewel tube, care being taken to avoid placing of glue on the ends of the tube. The jewel is then advanced with the mandrel into the housing. The mandrel is then removed and the housing is set in a vertical position. The glue is then cured and, finally, the jewel tip is radiused by brushing with diamond paste.

Extremely close tolerances, in the range of 0.0002- 0.0005 of an inch are required to be maintained in order to achieve the necessary close fitting of jewel and holder components.

Brief description of the drawings FIG. 1 is an enlarged perspective view of the jewel fitting, showing the writing instrument casing in phantom;

FIG. 2 is a longitudinal cross-section, showing one type of jewel assembly seated within its stainless steel housing;

FIG. 3 is a longitudinal section of another type of jewel fitting in a stainless steel housing; and

FIG. 4 is a longitudinal section of yet another form of fitting, according to the present invention.

Description of the preferred embodiments Jewel housing 10 may be machined from stainless steel or other metal to include interior core 12 and elongated neck extension 14 defining Ia counter-bored jewel housing 16 with a radially outwardly extending shoulder 19, intermediate the core 12 and housing 16. Jewel housing 10 may be tapered inwardly as at 22 so as to provide a beveled edge encircling the cylindrical jewel 25 which includes wall 24, core 26 of equivalent diameter to core 12 and writing end 28 having a radially inwardly extending radius 30.

Housing 16 is machined so as to provide a flat bottom shoulder 19 essential for complementary engagement with the corresponding bottom 32 of jewel 25. Jewel 25 may be machined as a true cylinder without anterior radiused tip or writing edge, jewel cylinder 25 having a wall thickness as thin as 0.002 of an inch and an interior diameter or core of 0.004 of an inch, making an overall outer diameter of 0.008 of an inch.

Prior to fitting, jewel 25 is cleaned by boiling in nitric acid for approximately 10 minutes, then rinsed clean under water and finally cleansed with a cleaner such as Du Pont cleaner trademarked Vyathene. Jewel 25 is then threaded onto an elongated wire mandrel, illustrated in phantom in FIGS. 2-4, and with the mandrel protruding in front of the jewel approximately 0.100 of an inch towards the core of housing 16 which is then fixed against movement. With jewel 25 on the wire mandrel, both wire mandrel and jewel are pushed towards the jewel housing. A thermosetting epoxy resin is then applied on the outer periphery of jewel 25 at three spaced points. lPlacing of the epoxy on either end 32 or 28 of the jewel tube is studiously avoided. After gluing, jewel 25 and the wire mandrel are inserted into housing 16. The extrusion of the mandrel beyond jewel end 32 and into core 12 of the holder 10, aligns jewel 25 coaxially with holder 10, as well as its housing 16. Jewel 25 is then pressed into housing 16 so that jewel end 32 abuts and fits firmly against inner shoulder 19 within the housing. Excess epoxy, if any, is urged radially inwardly onto chamfer 18 and, thus, does not subsequently interfere with the fiow of ink through coaxially aligned core 12 and core 26. The mandrel is removed and excess epoxy forming around the juncture between the leading edge or shoulder 22 of the housing and jewel 25 periphery is removed.

Housing and jewel are then supported with the jewel 25 extending vertically upwardly so as to permit the epoxy to gravitate downwardly toward shoulder 19. Then, the epoxy may be heat set or cured by suspending the entire assembly within a heating furnace, for example, at a temperature of 250 F. for two hours. Thereafter, shoulders on the jewel are radiused smooth by means of diamond paste and brushing. After radiusing, jewel 25 and housing 10 are cleaned again with Vyathene or similar cleaner and inspected by shadowgraph. To insure that the bore is clear, the wire mandrel is inserted through the jewel tube core 26 and into core 12 so as to remove any diamond paste particles that may not have been removed by cleaning.

As an illustration of the dimensions achievable and the tolerances required, jewel 25 in FIG. 2 can have an outer diameter of 0.0100 of an inch with a tolerance of plus or minus 0.0001 of an inch. Radius 30 is in the area of 0.0015 of an inch with a tolerance of 0.0002 of an inch. Tube core 26 inner diameter is 0.0060 of an inch plus or minus 0.0002 of an inch. The outer diameter to the inner diameter is within 0.0005 TIR (total indicator reading). Jewel assembly 24 is 0.021 of an inch in length plus or minus 0.001 of an inch.

Housing 16 has a depth of 0.0135 of an inch plus or minus 0.001 of an inch. The entire housing 10 is 0.246 of an inchthe outer diameter of the housing base portion 11 is 0.0216 of an inch, plus or minus 0.0005 of an inch and the outer diameter of neck portion 14 being 0.0170 of an inch plus or minus 0.0005 of an inch. The inner diameter of core 12 is 0.0060 of an inch plus or minus 0.0005 of an inch. The inner diameter of housing 16 is 0.0109 of an inch, plus or minus 0.0001 of an inch (housing 16 inner diameter and jewel 25 outer diameter being within 0.0002 TIR), thus assuring a sliding fit of jewel 25 within housing 16.

It is obvious that other methods of assembly can be employed to obtain the same results as those disclosed. For instance, instead of first threading the jewel tip on the mandrel and having the mandrel protrude approximately 0.100 of an inch from the jewel tip :and pushing the mandrel and jewel toward the housing, the mandrel could be inserted into the core of the housing and then the jewel tip could be threaded on the free end of the mandrel, glue applied to the jewel tip and then the jewel tip could be pushed into the housing.

In addition, the radiusing of the jewel tip, the proportions of the housing and jewel fitting may be varied without departing from the spirit and scope of invention, as defined in the sub-joined claims.

We claim:

1. Method for assembling miniature tubing of varying diameters in coaxial alignment, comprising:

(a) forming a housing from a larger diameter tube by counterboring its core to an inner diameter 4 approximating the outer diameter of a smaller diameter tube; (b) locking said larger diameter tube against movement;

(0) threading the smaller diameter tube on an elongated mandrel extending through the core of said smaller diameter tube;

(d) applying glue to exterior side portions of said smaller tube;

(e) advancing said mandrel and said smaller diameter tube coaxially towards said larger diameter tube;

(f) urging said smaller diameter tube coated with glue into the counterbored core of said larger diameter tube so that a portion of said smaller diameter tube extends outwardly of said larger diameter tube; and

(g) removing said mandrel from both said tubes.

2. Method for assembly miniature tubing as in claim 1, including longitudinally extending said mandrel towards said larger diameter tube and beyond the end of said smaller sized diameter tubing approximately 0.100 of an inch.

3. Method for assembling miniature tubing of varying diameters as in claim 1, including forming a radially extending shoulder within said large size diameter tube intermediate its core and an inner end of said housing.

4. Method for assembling tubing as in claim 3, including radiusing a leading edge of said portion of said smaller diameter tube extending outwardly of said larger diameter tube.

5. Method for assembling tubing as in claim 4, wherein said radiusing is accomplished by brushing within the range .0015 to .008 of an inch.

6. Method for assembling miniature jewel tubular points in tubular holders comprising:

(a) forming a housing in a large diameter tubular holder by counterboring its core to an inner diameter approximating the outer diameter of a smaller jewel tubular point;

(b) locking said larger diameter tubular holder against movement;

(c) threading the smaller diameter jewel tubular point on an elongated mandrel extending through the core of said smaller diameter jewel tube;

(d) applying glue to exterior peripheral portions of said smaller diameter jewel;

(e) advancing said mandrel and said jewel coaxially towards said larger diameter tube;

(f) urging said jewel coated with glue into the counterbored core of said larger diameter tube so that a portion of said smaller diameter jewel extends outwardly of said tubular holder;

(g) removing said mandrel from both said jewel and said tubular holder;

(h) curing said glue; and

(i) radiusing by brushing the leading edge of that portion of said jewel extending outwardly of said tubular holder.

7. Method for assembling jewel tubular points in tubular holders as in claim 6, including vertically suspending said tubular holders with said jewel point uppermost after gluing, so as to enable gravity flow of said glue about said jewel within said housing.

8. Method for assembling jewel tubular points in tubular holders as in claim 7, including final cleaning of jewel tubular point and tubular holder core by inserting said mandrel axially therethrough.

9. Method for assembling miniature tubing of varying diameters in coaxial alignment, comprising:

(a) forming a housing from a larger diameter tube by counterboring its core to an inner diameter approximating the outer diameter of a smaller diameter tube;

(b) locking said larger diameter tube against movement;

(c) inserting an elongated mandrel into core of said larger diameter tube;

(d) threading the smaller diameter tube over the free end of said mandrel;

(e) applying glue to exterior side portions of said smaller tube;

(g) removing said mandrel from both said tubes.

References Cited UNITED STATES PATENTS Andrews et al. 401-265 X Kaufman 156-294 X Higgins 156-294 X Kovacs 401-265 Paulsen 401-265 X Roller 401-265 Delaruelle et al. 156-294 X HARQLD ANSHER, Primary Examiner.