US2032887A - Method of tipping metallic bases - Google Patents

Description

March 3, 1936. c. PFANSTIEHL 2,032,887

METHOD OF TIPPING METALLIC BASES Filed Aug. 14, 1935 5 Sheets-Sheet 1 M; 25%,? a w 1% w XZVKQNMOv fwa fw: Hm MWM 5 March 3, 1936.

c. PFANSTIEHL 2,032,887 METHOD OF TIPPING METALLIC BASES Filed Aug. 14, 1935 5 Sheets-Sheet 2 March 3, 1936.

c. PFANSTIEHL 2,032,887

METHOD OF TIPPING METALLIC BASES Filed Aug. 14, 1955 5 Sheets-Sheet 3 Patented Mar. 3, 1936 UNITED STATES PATENT OFFICE METHOD OF TIPPING METALLIC BASES Carl Pianstiehl, Highland Park, Ill., asslgnor to Pfanstiehl Chemical Company, a corporation of Illinois Application August 14, 1935, Serial No. 30,229

supplied substantially entirely through the tip.

In my copending application Serial No. 753,220, filed November 15, 1934, is described an alloy composed of cobalt, tungsten, chromium and carbon which is particularly suitable for tipping pen points and other articles such as meter bearings. When a tiny particle of this material is superheated to an extraordinary degree and then very suddenly cooled, occasionally a particle will develop a depression of considerable size, apparently due to the formation of a double carbide of considerably less volume than the individual carbides. When tipping a base with such an alloy, it has sometimes been found preferable not to tack the tip to the base in the first instance, but on the contrary, in some instances, better results have been obtained by contacting the materials and maintaining them in lightly pressed contact, and then performing the welding operation and supplying a portion of the heat more directly to the base. If an alloy such as cobalt 46.8%, chromium 30.8%, tungsten 19.2%, and carbon 3.2%, is used as a tip for a gold pen, or for a. stainless steel meter bearing pivot, the melting point is low enough that either the entire tip will melt, or else cooling means will have to be applied to the pen nib at such a distance that too much of the nib will melt. With such pellets it is desirable to perform the tipping operation without entirely melting the pellet, and without melting too much of the gold or other base.

It is likewise of importance that the heat be external to the tip and base, and that the heat be instantaneously and automatically cut off when the proper amount of the tip has melted. By

having the heat external and by otherwise providing for a great cooling, prompt freezing occurs. The use of an ionized hydrogen atmosphere is likewise of importance in this connection.

In accordance with this invention, the tip is placed in a holder where a portion of it is cooled, the base is contacted under light pressure with the tip, and the welding heat applied, preferably by means of an electric arc.

The invention is illustrated in the drawings, in which Fig. 1 represents a plan view of the welding apparatus; Fig. 2 is a sectional elevation along line 2 in Fig. 1; Fig. 3 is a sectional'elevation taken along the line 3 in Fig. 1; Fig. 4 is an elevation partly broken away showing the details of the setting device; Fig. 5 is a similar view of the device rotated into position above the electric contact; Fig. 6 is a sectional plan view along the line 6 in Fig. 2;v Fig. '7 is an elevation partly in section showing a pen nib in pressed contact with a tip; Fig. 8 is a similar view showing the nib after welding; and Fig. 9 is a diagrammatic wiring diagram of thewelding circuit.

10 The welding apparatus comprises a Pyrex glassenclosed chamber 30 within which are two or more tungsten filaments 29 which are set in copper posts 35 and 36. The chamber 30 is set in rubber gaskets (l0 and 40, gaskets 80 being preferabhr mounted in a recess within the base 34 which may be suitably of Bakelite or Alberene stone. Within the chamber 30, centrally located with respect to posts 35 and 3B, is a support 50 for the tip. This support is suitably a tungsten rod which is set in a copper block 5 l which is in turn mounted on a copper plate 52 secured to the base 34. The support 50 is preferably tapered somewhat at the top and is recessed as shown in Figs. 7 and 8 to provide a. resting-place for a tip. The recess is preferably of a conical shape, and preferably having considerable depth with respect to its.

width. It is preferred that the angle of the cone as measured by the V of the cross-section be from say 75-105. While a tungsten support is preferred, other refractory materials may be used. A tip H, generally spherical in shape, is shown in the depression 52 in the support 50. The chamber is closed at the top by the cover 31 which rests upon the gasket and is held in place by the posts 53. For simplicity of manufacture and assembly, theposts 53 are removably mounted upon the base 34 by means of the screws 54 and the cover is removably held on the posts 53 by means of the screw-nuts 55. The cover 31 is provided with a central aperture through which a holder l3 may pass. This holder is of light con-- struction, preferably of a light material such as Dow-metal or aluminum. In the case of pen points and light objects such as meter bearing pivots, it is preferred that the weight of the holder, together with the base to be welded, shall not exceed 15 to 25 grams. If the weight does exceed this amount, it is preferable to employ oftsetting means, such as a spring, whereby the weight resting upon the tip shall not exceed this amount.

The holder I3 is provided with jaws I 2, adapted to hold a base, such as a pen-nib l0.

Mounted on the side of the holder, as shown in h by means of the relay 61. The falling of the Figs. 3, 4 and 5, is a setting device which operates to adjust possible drop of the holder to the desired amount. This device consistsof a plunger 56 mounted in frictional engagement within a .sleeve 51 which is held within the lug 58 mounted upon the holder i3. The'frictional engagement may be increased by a spring 59, if desired.

After the welding operation has been completed and the holder I! removed from the chamber 30,

the plunger 56 is pressed down, a new base clamped in the jaws l2 and the holder lowered into the chamber again. The lower face 60 of the plunger contacts a shelf 6| on the cover 31 and is forced back within the sleeve 51 until the base or pen-nib contacts the tip II. The holder I3 is then rotated until the plunger is directly over the contact 62. Preferably, an arm 63 is carried by the holder I3 which is stopped by the pin 64 mounted in the cover 31 at the appropriate point so that the plunger will overlie the contact. The contact 62 is mounted upon a light spring 65 which operates to break the arc circuit. The pressure necessary to move the spring to the contact is of course less than .that necessary to overcome the frictional resistance of the sleeve 51 and the spring 59. The position of the contact 62 is adjustable, for example by means of a set screw 66.

For mostpen points and similar articles, the

contact is preferably mounted from .015" to .018" below the plunger 51 so that as soon as the pen nib has dropped that amount the arc will be automatically cut off. The amount of the desired drop depends upon the size and thickness of the nib and tip, the larger pen nibs not requiring so large a drop inasmuch as the amount of gold or welding material supplied by a small drop is greater. It has been found that an amount of drop between .008" and .025" is the preferred range for articles such as pen-points and meter bearing pivots.

This arrangement provides a lost motion device whereby differences in the size or position of the parts is compensated for, so that an absolutely uniform drop is provided for with any setting of the contact 62.

Likewise, automatic means are provided for cutting oil. the are when the proper amount of the base has melted. In this way prompt freezing is secured by radiation and by the ionized gas, all of the surroundings being cool.

As described in my Patent 2,005,752, it is much preferred that the welding operations be carried out in an atmosphere of hydrogen, and a hydrogen supply line 3| is shown in Fig. 6. The holder l3 fits loosely enough within the cover 31 that the hydrogen can escape around it.

As shown in Fig. 9, the arc circuit comprises a 220 or volt A. 0. supply which is stepped up by the transformer 44 to 800-4000 volts. The tungsten filaments are continuously heated by a high amperage low voltage current, for example, 30 amperes and 1V -volts from the step-down transformers 45 which may be connected to an ordinary 110 volt A. C. supply. The operation of the arc is'started by pressing the button 46 which may be attached to a holding circuit (not shown). When such a holding circuit is employed, the arc is adjusted to stay on for 1 to 1 seconds, unless cut off sooner, as hereinafter described. The operation of the push-button closes the arc circuit plunger 51 upon the contact 62 breaks the relay and shuts oi the are at once.

The hot filament ionizes the hydrogen and thereby greatly lowers the resistance of the gap at; that only 800 to 1000 volts is necessary to start e arc.

The magnetic shunt I1 is provided in the transformer 44 in order to prevent any sudden excessive rush of current upon the establishment of the arc.

In carrying out the welding operation, a tip ll of a material suitably of higher melt point than the base, but relatively low with reference to high melt point so-cailed iridium" tips, is placed in the recess 52 of the tungsten support 50, and the pen nib or other base is grasped in the Jaws l2 of the holder l3 with the nib exposed as much as 1%" beyond the end of the jaws. This is several times as much as was permissible in the method described in my Patent 2,005,752, owing to the fact that the heating is less and that the arc isimmediately and automatically cut oil! when its work has been completed. In the meantime, the tungsten filament current has been started so that the filaments are hot and a stream of hydrogen is passed gently through the chamber 30 and ionizes as it pases the filament. The stream should be sufiiciently slow so that the atmosphere in the chamber is substantially quiescent. The holder I3 is then placed in the welding apparatus and the button 45 pressed. In the distance of about it," between the filaments, an arc will start readily upon 700-800 volts in an ionized hydrogen atmosphere. I

The tungsten support50 is cooled by radiation, and also by the copper holder 5|. If desired, the holder 5| may be extended nearer to the top of the support 50. During the welding operation the lower part of the tip H is cooled by the support 50 and does not melt. The top of the support and the position of the filaments 29 are so correlated that the heat of the arc plays substantially entirely over the tip II and greatly upon the support or base. Some of the arc plays upon the nib, but preferably very little. As a result, much of the heat is supplied to the base from the tip, as is desirable where the base has a lower melting point than the tip. In ordinary practice, little or none of the tip is melted, but the nib melts, and the melted material runs about the tip, whereupon the base falls and shuts oil. the arc circuit resulting in immediate freezing of the molten metal.

This method is suitable primarily for tipping bases with tips of minute cross-section. In ordinary practice, these tips will not exceed and most of them will range from .05" to .06".

In the case of tips prepared from my alloy described in my copending application Serial No. 153,220, the normal sphere will have a diameter of the order of .055" to .065" and this method is peculiarly satisfactory for tips of that alloy. particularly for those containing higher percentages of cobalt, such as herein described.

It is extremely important in connection with such alloy that it be gold coated in the manner described in application Serial No. 753.220-

The foregoing description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible in view of the prior art.

What I claim as new, and desire to secure by Letters Patent, is:

l. The method of tipping a metallic base with a metallic tip which comprises bringing tip and base into contact, heating tip and base while in lightly pressed contact to melt contacted metal without completely fusing the tip, and instantaneously freezing the molten material upon fusion of the desired quantity, whereby the tip is welded to the base.

2. The method of tipping a metallic base with a metallic tip which comprises bringing tip and base into contact, externally heating tip and base while in lightly pressed contact to melt contacted metal without completely fusing the tip, and instantaneously freezing the molten material upon fusion of the desired quantity, whereby the tip is welded to the base.

3. The method as set forth in claim 1, in which the base is maintained substantially vertically above the tip during the fusing operation.

4. The method as set forth in claim 1, in which the fusion of metal is accomplished by an electric arc.

5. An apparatus for welding a minute metallic tip to a metallic base, a recessed support for the tip, arc filaments at the level of the recess, adapted to produce an are about the upper portion of a tip resting in said recess, means for supporting a base vertically above said recess, means for lightly pressing a base upon a tip resting in said recess, means for freezing the molten metal instantaneously upon drop of said base supporting means due to fusion of contacting metal.

6. Apparatus as set forth in claim 5, in which lost motion means are provided for overcoming variations in the position of the tip and base.

7. The method of tipping a metallic base with a metallic tip which comprises bringing tip and base into lightly pressed contact, the base being maintained substantially vertically above the tip, and externally heating base and tip to fuse a portion of the contacting metal without completely fusing the tip, whereby the tip is welded to the base.

8; The method as set forth in claim 7, in which the lower portion of the tip is cooled.

9. The method of tipping a metallic base with a metallic tip which comprises bringing tip and base into lightly pressed contact, the area of contact being small, the base being maintained substantially vertically above the tip, and externally heating base and tip to fuse a portion of the contacting metal without completely fusing the tip, whereby the tip is welded to the base.

10. The method as set forth in claim 'I in which the major portion of the heat is applied to the tip, and in which the lower portion of the tip is cooled.

cam. PFANS'I'IEHL.

Images