US1304625A - Process of riveting - Google Patents

Description

J. P. SUNDERLAND. PROCESS QF RIVETING. APPLICATION m'tb JULY 31. ms.

Patented May 27, l9l9.

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1 2,4 0? g mmnm ATTORNEY I. P. SUNDERLAND. PROCESS OF RIVETING. APPLICATION FILED JULY-3L 1913.

Patented May 27, 1919.

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A ITO/ME) J. P. SUNDERLAND. PROCESS k mvsrme. APPLICATION FILED JULY 31.19181 1,304,625, Patented May 27, 1919.

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JOHN P. SUNDEBLAND, OF ALBANY, NEW YORK, ASSIGNOR, BY DIRECT AND MESNE ASSIGNMENTS, TO GEORGE G. MILN'E, OF'RYE, NEW YORK.

PROCESS OF RIVETLNG.

Specification of Letters Patent.

Patented May 27, 1919.

Original application filed August 1, 1917, Serial No. 183,831. Divided and this application filed July 31, 1918. Serial No. 247,480.

To all whom it may concern Be it known that 1, JOHN P. SUNDERLANI a citizen of the United States, and aresident of Albany, in the county of Albany and State of New York, have invented, certain new and useful Improvements in Frocesses of Riveting, of which the following is a specification.

My invention relates to improvementsm methods or processes of riveting in which rivets and the like are heated by'means of electrical energy. This application is a d1v1- sion of my prior application Serial No. 183831 filed August 1st, 1917. It has been heretofore suggested that rivets and pieces of iron may be heated by the electric current to soften the metal thereof so as to make it workable. For example it is known that plates may be secured together by passing rivets through holes there- 1n and then passing a current through the rivets and heating them until they are sufliciently soft and then upsetting the ends of 1 the rivets while heating and current through the rivet continues. According to this method the-rivet or bolt is put in place in the work before it is heated because when thoroughly heated the end of the rivet has become so melted or softened and the end so enlarged by the pressure of the contact device thereon that it has been impossible to get the heated rivets into the holes for which they were fitted. To overcome this melting or burning of the end of the rivet it has been suggested to apply the electrical contact below the end of the rivet to be upset so that no current passes through this end, but the end is heated from radiation from the other part of the rivet. (See U. S. Patent 722727 This method involves a great waste of time and energy since not only is a longer time required with any given current, but owingto the method of contact and longer time more energy is lost by conduction of heat through the contacts and radiation, and indeed it is doubtful if the rivet would ever become hot enough at its end, for good work. 7

I have discovered, however that by adopting different conditions, rivets and the like mav be heated with extreme rapldity, and with a minimum expenditureof energy, and at the part where softening of the metal is desired so that little or no heat is 10st in the parts where little or no heat is required, and so that the ends of the rivets are not burned or melted, whereby the shape thereof is not changed and they may be readily inserted in the proper sized holes in the work after the heating operation.

Further and more specific objects, features and advantages will more clearly appear from the detail description given below taken 1n connection with the accompanying drawlngs which form a part of this specification and which illustrate an apparatus sultable for carrying out my improvements.

In the drawings,

Figure 1 is a side view of such an apparatus;

Fig. 6 is a diagram illustrating diagrammatically' the transformer connections and windings.

Referring to the various figures, 1 represents a base board on which is secured an insulating board or sheet of asbestos 2. Secured upon one end of the base is an electrical contact headof soft metal, such as copper, 3, extendin along the front of the apparatus. Pivote to the framework at 5 are two pairs of arms 4, in the ends of which are secured respectively, electricai contact heads of soft metal, such as copper, 6, the heads being insulated from the arms 1, which support them. Handles 7 are suitably secured to the arms 4, so that the heads 6 may be raised and lowered away from and toward the head 3 to permit the insertion of rivets'8 between the heads, with one end of each rivet abutting the head 3 and the other end of each rivet abutting one of the heads 6.

9 represents a transformer, suitably secured to the base, and having bolted to the top thereof brackets 10, which may serve as handles for the apparatus. The primary of the transformer consistsof three sets of windings 11,12 and113, consisting of 100 turns each, of copper wire, wound upon a laminated iron core 14 (see Fig. 5). The secondary windings of the transformer consist of four main turns 15, 16, 17 and 18. Each turn comprises a solid copper bar, bent to make one turn about the core 14. The upper ends of turns 15 and 17 are connected together by copper straps 19, the lower ends of turns 16 and 18 are connected together by copper straps 20, the upper end of turn 16 is connected to the lower end of turn 15 by copper straps 21, and the upper end of turn 18 is connected to the lower end of turn 17 by copper straps 22. Bolted between the straps 19 are two sets of copper strap conductors 23 and 24, one-half ofthe straps 23 being bolted to the underneath side of one of the heads 6, and the other half of the straps 23 being bolted to the top of the head 6, as clearly indicated in Fig. 1. Likewise, one-half of the straps 24 are bolted to the underneath side of the other head 6, and the other half of straps 24 are bolted to the upper side of the other head 6, so that each head 6 is electrically connected to the upper ends of turns 15 and 17 through flexible connections. Bolted between the straps 20 are two sets of flexible electric strap conductors 25 and 26, which are similarly bolted to the lower head 3, half being bolted to the underneath'side of said head, and half being bolted thereto on the upper ledge of the head, as clearly indicated in Fig. 1.

I also provide two extra secondary turns on the transformer, these turns being indicated at 27 and 28 (see Fig. 5). The turn 27 lies adjacent the turn 15 and is in electric contact therewith substantially over its.

whole length. The turn 28 lies adjacent the turn 16, but-is insulated therefrom by insulating material 29. The upper end of turn 27 is electrically connected to the upper end of turn 28 by copper c necting straps 30. The lower end of turn 7 is connected to the lower end of turn- 28 by connecting straps 31.

Surrounding the primary and secondary windings is a laminated magnetic structure of soft iron 32, the shape of the laminations being shown in Fig. 5. In this figure, the shape of the laminations of the core structure 14 is also shown.

The ends of the primary turns are brought out from the primary coils to a connection box 33. 1

Pivoted to a cross-bar 34 (see Fig. 2) are two sets of arms 35 and 36. Back of the said arms 35 is a wedge-shaped member 37, and back of the arms. 36 is a wedge-shaped member 38, the members 37 and 38 being connected to the upper end of the (see Fig. 2) and con and 40, pivoted at 41 nected to lever arms 43 and 44, respectively,

so that, upon depressing the lever arm 43 g or 44, the wedge-shaped member connectedunder pressure.

;-a'relatively large its ends, so as to make an electrical contact with the rivet intermediate its ends.

Bolted between the conducting straps 31 is a set of copper connecting straps 45, d1- vided into four groups, the'outer end of each group being secured to make electrical connection with the inner end of one of the arms 35 and 36, respectively (seeFigs. 1 and 2).

Any suitable connections 46 may be made to the ends of the lever arms 43 and 44, so that these-arms may be depressed to cause the arms 35 and 36 to electrically engage the rivets therebetween, and likewise any suitable means may be provided to cause the arms 43 and 44 to be retained in their depressed condition, so that the arms 35 and.

rivets during the heating thereof.

In operation, the rivets are placed between the heads 3 and 6, and the head 6 lowered thereon so as to hold the rivets there'between In the machine shown, the pressure is about eight pounds.

' Assuming the transformer to be energized, current then passes from the secondary terminals through the heads 3 and 6 and through the rivet, causing the rivet to be heated from its flat end down; that is, it becomes hottest at its flat end and the rivet gradually becomes softened from its flat end downwardly or toward its head.

I find that the successful heating of rivets by electric current depends on maintenance of certain conditions of voltage applied, and

ratio between contact resistance and effective mpedance 1n the rivet such as is foundv in the operation of the apparatus as above described. The heating of the rivet is caused by liberation of heat energy due to the opposition to the current. This opposition may be divided into two classes, that due to the contact resistance heads and the ends of the rivet and that due to the effective impedance in the rivet which may consistof ohmic resistance, hysteresis losses, eddy current losses, inductance and skin effect losses. with the shape and size of the rivet andthe material from which it is made, and the nature of the current employed. In the apparatus described the contact resistance between the'contacts and the ends of the rivet such that the upper or flat end of the rivet I heats faster than the shank or middle portion of therivet. This appears to be due to amount of heat liberated atthis end at the point of contact, by the current overcoming the contact resistance. In this manner theheat is concentrated where it is needed most so that the final These vary materially between the contact heating of the rivet is accomplished in a minimum time and with a minimum consumption of energy.

However, this is perhaps not the most important feature, because, if the end of the rivet is melted or burned by this so-called concentration of heat, it is not suited to be afterward inserted in the hole in the work because of the damaged end. This burning of the rivet is the local melting or liquefying of the rivet at the end of the rivet adjacent the contact. 'Burned rivets are thrown away as scrap and even by the old methods of heating by coal or oil flame this loss is very large. I have found, however, that by using a relatively low voltage this burning of rivets can be entirely eliminated without material loss in time in completing the heating of the rivets. If an excessive voltage is used, so much heat is generated at the contact that it can not be conducted into the body of the rivet fast enough to prevent local overheating and burning of the rivet at the ends. To prevent burning with the apparatus described I may use an applied voltage of about 2 volts or slightly less. However, the highest voltage which will not burn depends not only upon the size, shape and material of the rivet, and nature of the current but also upon the speed with which the contact heads conduct the heat away from the end of the rivet, and the pressure applied. I find. however, that according to the preferred form of the invention itis best to use below six volts.

I find that with the apparatus described the rivet heats up relatively slowly at the head end or rounded end of the rivet. I believe this to be due to the fact that this end of the rivet being roundedtends to bite into the copper head more and form a. better electrical connection therewith, so that there is less contact resistance at this head end and hence less generation of heat there due to the contact resistance. I find that some rivets have a small projection in the center of the head end, apparently produced in the forging of the rivet, and that when such rivets are heated according to my methods, even less heat seems to be generated by the contact resistance at the head end.- \Vhere the head end has a flat surface contacting with the electrical contact head, substantially equal in area to the area. of the upper end of the rivet, I find that the generation of heat at the lower end seems to be substantially equal to the generation of heat at the upper end and the rivet is heated from both ends inwardly. It will be understood that by suitable adjustment of conditions the effective internal impedance in the rivet and the contact resistances may be such that all parts of the rivet will heat up equally fast or thecenter will heat' up fastest, but the heating'of the end fastest has the important advantage that the rivet is heated sufficiently for practical purposes in very much less time and with the consumption of much less energy, considerations which are of great importance, speed being an especially important factor in present day commercial operations.

If a long rivet is being heated, it is desirable to make use of the third contact device or devices 35 and 36, in which case lever arm -13 is depressed, causing extra current, generated in the secondary turns 27 and 28, to be passed through the upper end portion of the rivet, so as to more quickly heat that portion of the rivet which is desired to be heated and without burning the rivet,that is, causing it to become too soft at the end that is to be upset later.

Suitable switching apparatus is provided, as shown in Fig. 6, whereby the number of turns of primary windings may be varied,- that is, some of the turns may be cut out. For that purpose, a switch 50 is provided, adapted to make contact with contact 51, if all 300 turns are desired to be in circuit. lVhen the switch is thrown to contact 52, only 275 turns will be in circuit, and when thrown to contact 53, only 200 turns will be in circuit, the supply mains being connected, one to the switch 50 and the other to contact 54.

In the apparatus particulary illustrated in the drawings, I prefer to apply 220 volts at 60 cycles across the primary and to have the transformer so Wound that about 3 amperes will flow in the primary when the secondary is open-circuited.

It will be noted that the four main sec ondary turns are connected in pairs,-two pairs in parallel, and two pairs in series.

When heating rivets inch in diameter by 1 inch long, I preferably use the 300 turns of primary windings, and when so con nected the calculated voltage on the secondary with the secondary open-circuited is about 1.4 volts.

With rivets e inch diameter by 1. inches long, I preferably cut .out part of the primary turns, so as to use only 27 5 primary turns, thus producing a calculated open-circuit secondary voltage of about 1.6 volts.

hen heating rivets 1 inch in diameter by 2. inches long, I preferably use about 200 turns in the primary and a calculated opencircuit secondary voltage of about 2 volts.

If a inch diameter by 3 inch long rivet is being heated, I preferably increase the open-circuit secondary voltage to about 2.5 volts, and if a e inch diameter by 4% inch long rivet is being heated, I preferably in crease the calculated secondary voltage to about 3.5 volts.

If, however, a voltage materially higher than the above values is used in the above described machine shown in the drawings,

I find that the rivets are apt to 'be burnt. On the other hand, great a voltage as is advantageous, in order that the rivets may be heated as quickly as possible. i

I find that the smaller size rivets may be heated more quickly and without burning by applying a voltage of about 2 volts (actual voltage applied with heating current flowing) if proper conditions of contact etc. are maintained. The voltage applied when the heating current is flowing I find to be about .3 or .4 volt lower than the calculated open circuit voltage in the above described.

apparatus.

While by changing contact, impedance and current conditions greater voltages may be used without burning the rivets I preferably keep the applied voltage during heating under about 5-} or 6 volts. Thus, the transformer should be so designed and wound or the source of electric current be so selected and connected as to send a current through the heads and rivet of such size as to heat the rivet soft the required distance without burning the end of the rivet.

With the above apparatus, I am enabled to heat rivets in from 30 to 60 seconds without burning.

While I prefer to use alternating current as energizing means, certain of my improve ments may be found advantageous in case a direct current is used.

At the ends of the core 14, I provide air spaces 60 filled with shellac, so that, in case the secondary should become short-circuited, flow of excessive secondary current will be prevented.

It is not necessary, to the broader aspects of m invention, that the apparatus be providec with two heads 6, but I find that if a plurality of heads 6, with cooperating head or heads 3, is provided, supplied from the same source or transformer, and in parallel a plurality .of rivets may be heated simultaneously. I find that, even although such plurality of rivets may be inserted simultaneously, one will always become heated before the other, so that the operator may insert and remove the rivets alternately, and thus greatly increase the speed with which rivets may be heated by the apparatus. As shown in the drawings, only one head 3 is provided, but this is equivalent to two eads, as one portion cooperates with one head 6 and the other portion cooperates with the other head 6.

Since the third contact device 35 is connected to secondary windings on the trans former, which embrace only two turns in parallel, the voltage applied between the contact devices 35 and 36 and the head 6 will be about half of the voltage applied between the heads 6 and 3.

It will be noted that the other or upper it is desirable to use as terminal of the secondary windings 27 and 28 is common with the upper terminal of the Winding 15 and. connections 23.

While I have described my improvements in great detail'and in respect to an appara tus for carrying them out in one form, I do not desire to be limited to such details or form, since many changes and modifications may be made and the invention embodied in widely differing forms, without departing from the spirit and scope of the invention in its broader aspects. I desire to cover all forms and methods coming within the language or spirit of the appended claims.

What I claim is 1. In the process of riveting the steps which consist in heating the rivets by passing an alternating current therethrough from a contact making electrical contact with the end of the rivet opposite the rivet head, until the end portion of the rivet is substantially softened, the'ratio between contact resistance at said end and the effective impedance in the rivet being such that the end of the rivet heats up faster than the shank or middle portion of the rivet, and the voltage applied being insuificient to burn the said end of the rivet, and then discontinuing the current through the rivet, before inserting and upsetting the rivet in the work.

2. In the process of riveting the steps which consist in heating the rivets by passing an alternating current therethrough from a contact making electrical contact with the end of the rivet opposite the rivet head, until the end portion of the rivet is substantially softened, the voltage applied being insufiicient to burn the said end of the rivet, and then discontinuing the current in the work. I

3. The'method of heating rivets or the like which consists in passing an alternating current therethroughfrom a contact making electrical contact with the end of the rivet or the like to be-heated, until the end portion is substantially softened, the ratio between contact resistance at said end and the eflective impedance in the rivet or the like being such that the said end portion heats up faster than the shank or middle portion of the rivet or the like, and the voltage applied being insuflicient to burn the said end of the rivet or the like.

4. In the process of riveting the steps which consist in heating the rivets by passing an alternating current therethrough from a contact making electrical contact with the end of the rivet opposite the rivet head, until the end portion of the rivet is shank or middle portion of the rivet, and then discontinuing the current through the rivet before upsetting or working the softened metal of the rivet and before inserting the rivet in the work.

5. The method of heating rivets which consists in passing an alternating current therethrough from a contact making electrical contact with the end of the rivet opposite the rivet head, until the end portion of the rivet is substantially softened, the voltage applied being insufiicient to burn the said end of the rivet.

6. In the process of riveting the steps which consist in heating the rivets by passing an alternating current therethrough from a contact making electrical contact with the end of the rivet opposite the rivet head, until the end portion of the rivet is substantially softened, the ratio between contact resistance at said end and the effective impedance in the rivet being such that the end of the rivet heats up faster than the shank or middle portion of the rivet, and the voltage applied being between 1 volt and 6 volts and insufiicient to burn the said end of the rivet, and then discontinuing the current through therivet before inserting the rivet in the work.

7. The method of heating rivets or the like which consists in passing an alternating current therethrough from a contact making electrical contact with the end of the rivet or the like to be'heated, until the shank or end portion is substantially softened, the Voltage applied being between 1 volt and 6 volts, and insufficient to burn the said end of the rivet or the like.

8. In the process of riveting the steps which consist in heating the rivets by passing an alternating current therethrough from a contact making electrical contact with the end of the rivet opposite the rivet head, the voltage applied being between 1 volt and 6 volts and insufficient to burn the said end of the rivet, and then discontinuing the current through the rivet before inserting the rivet in the work.

9. The method of heating rivets which consists in passing a current therethrough from a contact head contacting with the end of the rivet opposite the rivet head, until the end portion of the rivet is substantially softened. the voltage applied being insufficient to burn the end of the rivet and the contact with the end of the rivet being such that the greatest heat is generated at the end of the rivet, and then discontinuing the heating of the rivet before upsetting the end of the rivet.

10. The method of heating rivets which consists in passing a current therethrough from a contact head contacting with the end of the rivet opposite the rivet head, until the end portion of the rivet is substantially softened, the voltage applied being insufficient to burn the end of the rivet and the contact with the end of the rivet being such that the greatest heat is generated at the end of the rivet.

11. In the process of riveting the steps which consist in heating the rivets by passing a current therethrough from a contact head contacting with the end of the rivet opposite the rivet head, the voltage applied being insufiicient to burn the end of the rivet and then discontinuing the heating of the rivet and inserting the rivet in the work.

12. The process of heating rivets which consists in passing an electric current through a plurality of rivets in parallel with one another from a single source of current whereby one becomes heated before another, the voltage applied being insuliicient to burn the rivets and the rivets being removed from the heating circuit before the heated rivets are inserted in the work.

13. In the process of riveting the steps 7 which consist in heating the rivets by passing an electric current through a plurality of rivets in parallel with one another from a single source of current whereby one becomes heated before another, and removing the rivets alternately from the heating circuit and before the heated metal thereof is upset or worked and before the rivets are inserted in the work.

14. The process of heating rivets or the like which consists in passing an electric current through a plurality of rivets or the like in parallel with one another from a single source of current whereby one becomes heated before another, the voltage applied pricing insufiicient to burn the rivets or the 1 e. 15. The process of heating rivets which consists in passing an electric current through a plurality of rivets in parallel with one another from a single source of current whereby one becomes heated before another, the ratio of contact resistance with the rivets to effective impedance in the rivets being such that the ends of the rivets heat up more quickly than the shank or middle portion of the rivets.

16. In the process of riveting the steps which consist in heating the rivets by passing a current therethrough from one circuit substantially from end to end of the rivet and passing another current through a portion only of the length of the rivet which it is desired to heat most and discontinuing the heating of the rivets before inserting in the work.

17. The process of heating rivets which consists in passing a current therethrough from one circuit substantially from end to end of the rivet and passing another current through a portion only of the length of the rivet which it is desired to heat most, the

voltage applied being insufiicient to burn the most. and the rivets being removed from the end of the rivet which it is desired to heat heating circuit before the heated metal theremost. of is upset or worked and before the rivets 18. The process of heating rivets which are inserted in the work.

consists in passing a current therethrough Signed at Albany, in the county of Albany from one circuit substantially from end to and State of New York, this 29th day of end of the rivetand passing another circuit July, A. D. 1918.

through a portion only of the length of the JOHN v P. SUN DERLAND. rivet which it is desired to heat most the \Vitnesses: voltage applied being insufficient to burn the A. A. SHEPARD,

end of the rivet which it is desired to heat M. L. SUNDERLAND.

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