US 2879586 A
Description (OCR text may contain errors)
vIVIEIITfli-M, 5 7 H. R.'FEHLlNG ETAL- 2,879,586
METHOD FOR THE PRODUCTION OF BALL TIP WRITING INSTRUMENTS Filed Oct. 6, 1952 v United States Patent METHOD FOR THE PRODUCTION OF BALL TIP WRITING INSTRUMENTS Hans Reinhard Fehling, London, and Ernest Arthur Wicks,
Maple Durham, Reading, England, assiguors to Compania Uruguaya de Fomento Industrial S.A., Montevideo, Uruguay This invention concerns reservoir writing instruments of the ball tip type wherein the writing extremity or nib comprises a writing ball rotatably housed in and partly protruding from a socket or housing, which ball is supplied with ink from a reservoir by means of a feed duct or a passage of capillary size which communicates with the base of the socket or housing so that, as the ball is rotated by being moved over and in contact with a surface such for example as that of a sheet of paper, a thin film of ink is carried by the ball through the narrow gap between it and its housing and is deposited as a trace on the said surface; specifically the invention relates to writing extremities of such instruments.
Heretofore it has been customary to machine writing extremities for such instruments from solid bar stock, and to form such extremities in the manner described in British patent specification 609,817 H. G. Martin, or 564,172 L. J. Biro, U. S. Patent No. 2,390,636. The object of the present invention is a simplified form of writing extremity and a simple method of manufacturing same.
The invention therefore provides a method for the production of a writing extremity for a ball tip writing instrument of the type specified from a tube having an internal diameter substantially equal to the diameter of the ball, which comprises the steps of forming a constriction in the bore of the tube and thereby producing a socket base or stop for preventing movement of the writing ball down the tube, and deforming the end of the tube to retain the ball in the socket.
Preferably, the deformation is elfected by constricting an end of the tube to provide a lip for retaining the ball in the socket; specifically the internal constriction in the tube is formed by pressure applied externally to the said tube.
It is preferred that the constriction in the bore shall consist of a plurality of (and preferably three) inward protrusions, for this results in the production of a plurality of bore seat portions separated by axially-extending ink channels.
Preferably, but not necessarily, a part-spherical base seat is formed simultaneously with the act of constriction by inserting into the tubular material a member having a part-spherical end surface and applying the external pressure in such manner that the local constriction is moulded partly around said part-spherical end surface.
The invention further includes in or for a ball tip writing instrument of the type specified, a writing extremity of tubular form with the ball socket at one end between an inturned lip on the tube and a local constriction in the bore of the tube produced by inward deformation of the material of the tube Walls. The inward deformation, or the maximum inward deformation is preferably presented at a plurality of circumferentially spaced locations producing spaced base seat portions separated by axially extending ink channels.
The foregoing and other features of the invention are incorporated in the writing extremity andin the method of manufacture which will now be described in detail with reference to the accompanying drawings in which Figure l is a sectional elevation through the ball socket part of a writing extremity according to this invention;
Figure 2 is a plan view thereof with the ball removed;
Figure 3 is a sectional elevation illustrating the tool employed in effecting the constriction and in producing part-spherical base seats for the ball,
Figure 4 illustrates a method of forming the lower part of the lateral seat surrounding the ball;
Figures 5 and 6 illustrate a further method of forming the lateral and the base seat.
Referring to Figures 1 and 2 the writing extremity 1 is made from metal tube having a bore 2 slightly larger than the diameter of the writing ball 3, which latter is conveniently 1 mm. in diameter. If the tube is made of an aluminium alloy sold under the registered trademark Duralumin it may have a wall thickness of approximately 0.25 mm. It may be produced by any manufacturing process known in the manufacture-of tubular material; for example, it may be extruded, or cold drawn.
The exterior of the tube is indented at 4 at a plurality of locations which are preferably equally spaced apart about the circumference. A convenient and desirable number for such indentations is three.
The indentations are, of course, efiected by externally applied pressure and they result in the bore of the tube being constricted by an equal number of inward prot1usio-ns 5 which as shown are separated by axially extending ink channels 6. These inward protrusions constitute a base seat for the ball 3 and they are preferably but not necessarily provided with part-spherical base seating surfaces 7 of the same radius as the ball. The ball is held in position by the inward constriction of the lip 8 of the tube 1. This inward constriction is eifected by spinning or swaging and preferably the end of the tube is chamfered as at 9 to assist in producing constriction.
The constricted lip 8 is disposed above the equator of the ball (such equator being indicated by the chain dotted line 10) and is preferably so produced that the inner surface of the constricted lip also assumes a part-spherical configuration constituting a part-spherical lateral seat 11. As shown in Figure 1 this lateral seat 11 is disposed wholly or substantially wholly above the equator 10, but the constriction of the lip 8 may be so carried out that the lateral seat extends also below the equator of the ball.
It will further be appreciated that owing to the fact that the writing extremity is manufactured from a tube having a cylindrical bore of substantially the same diameter as the ball 3 the wall of the ball socket extending between the lateral seating and the inwardprotrusions is of cylindrical formation as indicated at 12. Therefore there is also produced a ball-encircling cavity 13 with which the channels 6 connect.
The constriction of the lip 8 may be so carried out that the gap between the ball and its socket or housing is not less than .001 mm. and not more than .01 mm. when this gap is measured in the manner described in British patent specification No. 629,283 H. G. Martin, the writing extremity being then well adapted for use with an oleaginous ink the viscosity of which is not less than 15 poise at 37 C.
Figure 3 illustrates a tool which is employed in the manufacture of the writing extremity. It consists of a body 14 having a bore 15 of a size to permit the insertion and removal of the tube 1 but afiording a comparatively close fit for said tube. This bore is of a predetermined depth terminating in a shoulder 16 and co-axially therewith there is a smaller bore 17 of substantially the same diameter as the bore of the tube, on which is fixed a male member 18 having a part spherical-end 19 protruding to a predetermined extent into the bore 2. At appropriate locations around the circumference of the tool there are radially slidable indenting punches 20-. In. the drawing the punch at the left hand side is shown in the inner position and that at the right hand side shown in. the outer position. The ends of these punches are appropriately shaped to produce the indentations 4, and the plane in which, their axes lie is spaced a predetermined distance from the shoulder 16. Although the punches are shown as, having conical ends, they may with advantage be substantially square-ended so that the inward protrusions are formed by what is, to some extent, a shearing of the metal of the tube walls.
In operation the tube 1 with its end chamfered as at 9 in Figure 1 is inserted in to the bore 15 until it is pressed against the shoulder 16. The member 18 being fixed in position in the tool, the part-spherical end 19 of said member is thus entered into the bore of the tube. The punches 20 are then forced inwards to a predetermined extent which may for example be limited by enlarged heads 21. Thus the indentations 4 are formed, and owing to the disposition of the plane of the axes of said punches with regard to the part-spherical end 19 the inward protrusions 5 are moulded partly about said end 19 thereby producing the part-spherical base seat surfaces 7.
The punches 20 may be forced in by mechanical means such for example as a ring'cam, or hydraulically or pneumatically or in any other suitable manner. They are likewise retracted in any suitable manner.
After the retraction of the punches the tube 1 is extracted, a ball, which may be the writing ball or a similar ball is dropped into the end of the tube so as to rest on the surface 7' and then the lip of the tube is constricted by spinning or swaging. At any stage during these operations the tube may be cleaned of dirt and swarf by a jet of compressed air.
In the modified method of forming the lower lateral seat, Fig. 4 (i.e. that part of the lateral seat which is below the ball equator) there is used tubing 1 having a bore of slightly less diameter than the hall. For example, if the writing ball is 1 mm. diameter, the tube bore may be 0.90 mm. diameter. The member 18 being about the same diameter as the ball, when the hemispherical end 19 is entered into the tube said member 18 acts as a punch and the bore of the upper end of the latter is enlarged to 1 mm. and is caused to conform to the said end 19 so that a part-spherical lower lateral seat 21 is produced.
In the modified method illustrated in Figs. 5 and 6, the tool 14 is void of the member 18, so that neither the base seat 7, nor the lower lateral seat below the equator of the ball 3, are formed while this tool is in use but are formed during a subsequent swagingprocess. After removal of the indented tube from the tool 14, a ball 3 is inserted in the end of the tube (Fig. 5) and then, by use of a swaging die 22 as shown in Fig. 6 the end of the tube is constricted about the ball to produce the upper and lower lateral seat and the ball is pressed onto the protrusion 5' to form base seatings in them. To obtain the correct protrusion of the ball after swaging, the included angle in the interior of the swaging tool 22 should be about 80 and-the included angle to which, the end of the tubeis chamfered (as at 9) before swaging should be about 62".
In the manufacture of the writing extremity there may be employed either a conventional automatic in which various tools are mounted on a turret or the like and are indexed so as to be presented one after another to the work piece, or a specially constructed machine in which successive tools are disposed at spaced locations around a circle and a work carrier carrying a plurality ofwork pieces is indexed so as to present each work piece to each of the tools in turn.
If a conventional automatic is employed the sequence of operations is as follows (a length of-v the tubing being inserted in the machine head stock):
(1) The tube is fed out to a stop on the turret.
(2) The end of the tube is faced and tapered.
(3) The head stock is brought to a standstill, the tube entered into the tool described and the latter is operated as already described to form the inward protruberances (and if desired the base seat, or base seat and lower lateral seat).
(4) The ball is inserted.
(5) The head stock is restarted and the ball is fixed in position by spinning or swaging.
(6) The length of tube appropriate for the writing extremity is parted off from the tubular stock.
If the specially constructed machine is employed the tubular stock may be cut to appropriate lengths on a separate machine or as an additional operation on the special machine and the sequence of operations in respect of each writing extremity is as follows:
(1) A cut length or blank is fed into a loading collet on a turn table (there being a plurality of such collets at spaced locations around the turn table).
(2) The end of the blank is chamfered.
(3) The constrictions and inward protruberances (and if desired the base seat, or the base seat and the lower lateral seat) are formed by the tool already described.
(4) The ball is inserted.
(5) The ball is secured by spinning or swaging.
(6) The finished writing extremity is ejected by compressed air.
What we claim is:
l. A method for the production of a writing extremity for a ball tip writing instrument of the type specified, from tubing, which comprises the steps of forming a local constriction in the bore of the tube at one end thereof by externally-applied indenting pressure thereby producing a base in the bore constriction for a ball socket, forming a part-spherical base seat for the ball simultaneously with the act of constriction by inserting into the tube a member having a part-spherical end surface and applying the external pressure whereby the local constriction is moulded partly around said part-spherical end surace whereby said base seat is formed, inserting a ball member in the base, and constricting an end of the tube to provide a lip retaining the ball in the socket upon said base seat.
2. A method of making a writing extremity for a ball point pen of the type specified, consisting in inserting a hollow tube of bore substantially equal to the diameter of the writing ball in a female die, inserting into the end of the bore, through the die, a tool having a part-spherical end face, forming a plurality of inwardly extending protrusions in the tube by applying pressure to at least three points spaced around theperiphery of the tube and extending through holes formed in the die, said protrusions eon tacting said part-spherical end face and being molded thereby, removing the tube. and inserting a ball, and applying a tool to the end of the tube, with the ball in position to swage the end of the tube in the formation of a ball-retaining lip.
3. A method for the production of a writing extremity for a ball tip writing instrument which comprises taking a tube of uniform inner diameter, introducing abutment means in the tube, applying indenting pressure at circumferentially spaced points on the exterior part of the tube adjacent the abutment means whereby the inner periphery of the tube, at points corresponding to said circumferentially spaced points, is caused to protrude in molded contact with said abutment means to form a base seat for the ball, inserting a ball member in said tube on said base seat, and constricting an end of the tube to provide a retaining lip for theball.
(References on following page) 5 References Cited in the file of this patent UNITED STATES PATENTS Thomas Sept. 7, 1886 Eisler Dec. 16, 1941 Schrader et a1. Feb. 21, 1950 Segal Mar. 14, 1950 Knobel July 28, 1953 Cloutier Sept. 20, 1955 Belgium June 30, 1952