US3068336A

US3068336A - Induction heating cut-off means

Info

Publication number: US3068336A
Authority: US
Inventors: Richard F Tamm
Original assignee: Continental Can Co Inc
Current assignee: Continental Can Co Inc
Priority date: 1960-11-23
Filing date: 1960-11-23
Publication date: 1962-12-11
Anticipated expiration: 1979-12-11
Also published as: DE1169053B

Description

Dec. 11, 1962 R. F. TAMM 3,068,336

INDUCTION HEATING CUT-OFF MEANS Filed Nov. 25, 1960 INVENTOR. Emumzo F TAMM "3 mfwzz, mg/mwzy ATTQQNEYS United States Patent ()fiicc 3,068,335 Patented Dec. 11, 1962 3,068,336 INDUCTION HEATING CUTOFF MEANS Richard F. Tamm, Elmhurst, Ill., assignor to Continental Can Company, Inc., New York, N.Y., a corporation of New York Filed Nov. 23, 1960, Ser. No. 71,348 19 Claims. (Cl. 219-75) This invention relates in general to new and useful improvements in the can making art, and more particularly relates to novel means for severing connecting tabs extending between and connecting together adjacent can bodies.

It has been proposed to form can bodies by first providing the desired metal stock in strip form, which metal stock is then welded into an elongated tube. After the tube has been formed, the tube is broken apart at pre determined intervals along score lines which normally are formed in the stock prior to the forming of the tube therefrom. The individual can bodies are not completely broken apart in that they remain connected together by connecting tabs extending along the line of the welded seam. In the formation of can bodies, it is necessary that these connecting tabs be completely removed without the removal of an excessive amount of the end of a can body. It is to this that the present invention relates.

. The present invention proposes to separate can bodies or other tubular members which are connected together by connecting tabs by electrically heating the connecting tabs to effect the melting thereof. While electrical current may be introduced into the connecting tabs by direct contact of electrodes with the surface of the can bodies, it has been found convenient in the formation of the tube to provide a protective lacquer coating at least over the Welded seam, such lacquer coating being required in the finished can. As a result, it is not feasible to attempt to pass the necessary electrical current through the connecting tabs utilizing direct contacting electrodes.

' In view of the foregoing, it is the primary object of this invention to provide a novel method of attaining separation of two conductive bodies joined by a restrictive conductive bridge, which method includes the applying of alternating magnetic field effects to the bridge thereby inducing an electric current flow in the bridge of such intensity that the material of the bridge is either melted .or is raised to a temperature at which the bridge is physically weakened, after which the bodies may be pulled apart, and the heating effect being primarily restricted to the bridge with the heating of the bodies being insuflicient to have any detrimental effects on either the material of the bodies or coating which may be disposed on the bodies.

Another object of this invention is to provide an induction heating coil, which coil is specifically shaped so as to generally permit the passage of can bodies and other interconnected tubular members adjacent thereto and to concentrate the flow of electrical current in the can bodies in the connecting tabs extending between and connecting together adjacent can bodies so that the connecting tabs may be rapidly heated to the temperature necessary to effect the melting thereof with a minimum expenditure of electrical energy and a minimum heating of the can bodies adjacent the connecting tabs.

' Another object of the invention is to provide a novel apparatus for severing connecting tabs between tubular members, such as can bodies, the apparatus including means for feeding and guiding the tubular members with adjacent ends of adjacent tubular members being spaced apart and being connected together only by the connecting tabs, and there being disposed along the path of the tubular members an induction heating coil, which induction heating coil functions to concentrate electrical current in the connecting tabs as they pass adjacent the induction heating coil to effect the rapid heating and melting of the connecting tabs.

Still another object of the invention is to provide a novel induction heating coil for effecting the electrical heating and melting of connecting tabs extending between tubular members, such as can bodies, the induction heating coil having two elongated legs connected together by an arcuate intermediate interconnecting portion to permit tubular members to pass between the legs, and the legs being provided with intermediate portions of a generally V-shaped outline which are also arcuate in transverse section so as to concentrate the flow of electrical current in the tubular members in the area of the connecting tabs therebetween so that the heating of the tubular members is primarily limited to the connecting tabs.

A further object of the invention is to provide a novel method of severing connecting tabs between adjacent tubular members, the tubular members being in the form of can bodies and the like, the method including the steps of passing the tubular members along a predetermined path with opposed ends of adjacent tubular members being spaced apart and disposed in angular relation and the tubular members being connected together only by connecting tabs extending therebetween, and passing the so arranged tubular members through an induction heating coil to efiect the concentrated flow of electrical current through the connecting tabs with the electrical current rapidly heating and effecting the melting of the connecting tabs.

Still another object of the invention is to provide a novel apparatus for severing connecting tabs between ad'- jacent tubular members, the apparatus including suitable feed and guide means for feeding the tubular members along a predetermined path with the feed and guide means including means for tensioning the connecting tabs between adjacent tubular members, and there being provided induction heating means for effecting the concentrated flow of electrical current through the connecting tabs at such time as the tabs are tensioned whereby the tabs may be rapidly heated through the concentrated flow of electrical current to a temperature where the tabs are physically weakened, after which the tension applied thereto will be sufiicient to pull the tubular members apart.

With the above, and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims, the several views illustrated in the accompanying drawing:

In the drawing:

FIGURE 1 is a schematic elevational view showing generally the details of the apparatus provided for the induction heating of the connecting tabs between tubular members in accordance with the invention.

FIGURE 2 is an enlarged fragmentary plan view, showing the specific relationship of the induction heating coil, two tubular members and the connecting tab therebetween, the view showing the concentration of electrical current within the connecting tab.

FIGURE 3 is an enlarged fragmentary elevational view similar to FIGURE 2, and shows further the rela-= tionship of the induction heating coil, the two tubular members and the connecting tab, as well as the flow of electrical current through the connecting tab.

FIGURE 4 is a perspective view of the induction heating coil, and shows the specific configuration thereof.

In accordance with the invention, an elongated tube is formed having a welded seam. The tube is then partially broken at predetermined intervals along score lines to define individual tubular members which may be in the form of can bodies and will be so referred to hereinafter. The can bodies are referred to by the letter B and are connected together by connecting tabs T which are disposed along the welded seam S.

After the can bodies B have been partially broken apart, they are suitably guided so that adjacent ends of adjacent can bodies are in spaced relation and the can bodies are connected together only by the connecting tabs T. While this may be accomplished in many ways, one of the easiest ways of accomplishing this is to pass the can bodies B about an arcuate path. For illustrative purposes, the can bodies B are passed through a plurality of sets of guide rollers 5, 6, 7 and 8. Each set of guide rollers includes at least two guide rollers disposed in opposed relation, and it is preferred that the guide rollers be generally of an hourglass shape so as to at least partially confine the can bodies B. Further, it is preferred that at least one set of the guide rollers 5, 6 and 7 be driven, and that the guide rollers 8 be driven so as to remove the separated can bodies B. It may also be desirable to drive the guide rollers 7 and 8 at different speeds so as to apply a tensile stress in the connecting tabs T during the heating thereof.

The apparatus of this inventionalso includes an induction heating coil C which is formed in accordance with the following principles. are magnetically linked, analternating current flowing in onecircuit will induce a current in the other. The magnitude of the induced current is proportional to the magnitude of the primarycurrent, the frequency, the ratio of the number of turns in the two circuits, and the degree to which thetwo circuitsare magnetically interlinked. If a single turn coil is positioned closely parallel to a conducting plane, such as a thin sheet of metal, a current will be induced in the sheet. The magnitude of this current. is. a function of the primary current, the current frequency and varies inversely with the distance between the coil and the metal sheet. This induced current produces 1 R heat; hence, the greater the current density, the greater the rate of heat generation.

At frequencies used in radio frequency induction heating, the current takes the path of least impedance and concentrates in a section of the metal which is directly in line with, and follows as closely as possible, the path of the primary current in the coil. At the higher frequencies, the skin effect becomes important. This effect manifests itself in a tendency for the current to concentrate closer to the surface of the conductor as the frequency is increased.

As set forth above, the induced current magnitude is a function of coil proximity to the surface; i.e., the smaller the distance, the greater the current. The current density varies in a similar manner; i.e., at small distances, the general outline of the induced current will conform more closely to the outline of the induction coil, and therefore the heat effect will be more concentrated. For example, if a coil having the general outline of a dumbbell is held close to a conducting surface, the induced current and heat zone will have a similar shape. As the coil is moved away from the conducting surface, the dumbbell shape of the induced current degenerates into two circles of more diffuse outline, and the heated area will have a similar shape.

For the problem of can body separation from broken, welded, prescored tubing moving continuously past a stationary, continuously energized induction coil, one may choose to induce a dumbbell-shaped current in the tubular members with the narrow waist area of the current being centered over the welded seam to produce maximum heating effect along the seam. Such a current shape and resultant heat Zone can be achieved with a coil of the general shape of the illustrated induction heating coil C. The induction heating coil C is formed of a pair of generally parallel legs 9 which are connected together by an intermediate connecting portion 10. Each of the legs 9 includes an elongated rear portion 11, an

When two electrical circuits offset intermediate portion 12 which is generally V-shaped in outline, and a forward portion 13, the forward portion 13 being disposed at a slight angle to the rear portion 11. Each forward portion 13 terminates in an upwardly slop ing portion 14 which, in turn, is connected to the connecting portion 10.

It is to be noted that the connecting portion 10 is arcuate in transverse section so that it arches up and over can bodies B passing between the legs 9 Also, it is to be noted that the V-shaped intermediate portions 12 are disposed in opposed relation with the apices thereof spaced apart and that the V-shaped intermediate portions 12 are arcuate in transverse cross-section so as to conform generally to the arcuate cross-section of the can bodies B.

The required amount of electrical energy is supplied to the induction heating coil C by a transformer, generally referred to by the numeral 15. The transformer 15 includes a primary winding 16 which is connected by wires 17, 18 to a suitable power source. The transformer 15 also includes a secondary winding 19 which is 6011f nected to one of the legs 9 by a wire 20. The other end of the secondary winding 19 may be directly connected to the other of the legs 9, or may be connected to a control device 21 by means of a wire 22. The control device 21 is then connectedto the other of the legs 9 by a wire 23. The control device 21 may be of any suitable type which will detect the spacing between adjacent can bodies B and the positioning of a connecting tab T with respect thereto. and thus pulse the flow of electrical current to the induction heating coil C in timed relation to the passage of the connecting tabs T therethrough.

It will be noted from FIGURES 2 and 3 in particular that the intermediate V-shaped portions 12 of the induction heating coil-C converge generally towards the path of the connecting tabs T. The apices of the V-shapcd portions 12 approach the can bodies B more closely than the other portions of the induction heating coil C, which, although tending in general to conform to the curved shape of the can bodies B, gradually recede from the surfaces thereof in order to render the heating effect more diffuse. The final position of the induction heating coil C and its current level are so chosen that the heat produced in the welded seam area of the can bodies B is below a level that would damage the metal or a coating which may be thereon when the can bodies B are within the influence of the induction heating coil C. However, when a connecting tab T is centered under the induction heating coil C, the current path for the dumbbell waist of the induced current is suddenly greatly restricted by the narrow width of the connecting tab T, the current density and heating effect is greatly magnified, and the connecting tab area rapidly reaches softening or melting temperature levels.

The flow of electrical current through the connecting tabs T is sufficient to heat the connecting tabs T to a melting temperature to permit the rapid melting and parting of the connecting tabs T. As pointed out above, if desired, the rollers 7 and 8 may differentially be driven so as to produce a tension in the connecting tabs T and thus the separation of the can bodies B can be a function of heating and tensile stress. However, the severing of the connecting tabs T may be accomplished by heating and melting alone. It is also pointed out that the current flow may be pulsed utilizing a control device, such as the control device 21, so that the flow of induced current is T is disposed generally between the V-shaped portions limited primarily to that time at which a connecting tab 12 of the induction heating coil C.

Although the induction heating coil C illustrated and described herein is a desirable form of induction heating coil to be used in accordance with this invention, it is to be understood that other shapes of induction heating coils could be utilized in accordance with the invention. For example in a timed, pulsed operation, it may be more advantageous to devise a coil shape which produces an intensely heated area of small dimension centered at the tab location such as a small diameter solenoid or a conically-shaped solenoid.

- It will be readily apparent from the foregoing description of the apparatus and operation thereof that direct electrical contact with the metal of the can bodies is not required. Accordingly, can bodies and other tubular members, either having exposed metal or coated, may be readily separated utilizing the apparatus.

From the foregoing, it will be seen that novel and advantageous provision has been made for carrying out the desired end. However, attention is directed to the fact that variations may be made in the example method and apparatus disclosed herein without departing from the spirit and scope of the invention, as defined in the appended claims.

I claim:

1. An apparatus for severing selected connecting tabs between adjacent conductive metal bodies comprising feed and guide means for moving bodies along a predetermined path, and an alternating-current-carrying conductive loop having first and second serially-connected branches configured and disposed symmetrically with re spect to the path of motion of said tabs, said first and second branches respectively comprising an intermediate portion disposed substantially parallel to an edge portion of one of said bodies, thence substantially parallel to and closely spaced apart from the proximate connecting edge of said tab, and thence parallel to the adjacent edge portion of a next proximate one of said bodies, whereby a maximum concentration of induced current in the connecting tabs is elfected for the heating of said tabs.

2. The apparatus of claim 1 wherein said feed and guide means includes two sets of feed members disposed on opposite sides of said induction heating means for driving adjacent bodies at different rates to thus tension the connecting tabs therebetween and assist in the separation of the bodies.

3. An apparatus for severing selected connecting tabs between tubular members comprising feed and guide means for moving the tubular members in a predetermined path with adjacent ends of the tubular members spaced apart and disposed in angular relation and the tubular members being connected together by connecting tabs disposed at the apices of angles between the tubular members, and means positioned along said path for inducing heating current into the tubular members and for producing a maximum concentration of current in the selected connecting tabs to effect the concentrated heating of the selected connecting tabs, said means including a specially shaped induction heating coil.

4. The apparatus of claim 3 wherein said feed and guide means includes two sets of feed members disposed on opposite sides of said induction heating means for driving adjacent bodies at different rates to thus tension the connecting tabs therebetween and assist in the separation of the bodies.

5. The apparatus of claim 3 wherein said induction heating coil extends generally longitudinally of the path of the tubular member and has opposed intermediate portions for effecting the concentration of current in the tabs.

6. The apparatus of claim 3 wherein said induction heating coil has a pair of legs extending generally longitudinally of the path of the tubular members on opposite sides thereof, and an intermediate connecting portion, said legs having intermediate opposed portions directed generally towards the path of the connecting tabs for effecting the concentration of current in the tabs.

7, The apparatus of claim 3 wherein said induction heating coil has a pair of legs extending generally longitudinally of the path of the tubular members on opposite sides thereof, and an intermediate connecting portion, said legs having intermediate opposed portions directed generally towards the path of the connecting tabs for efiecting the concentration of current in the tabs, said intermediate connecting portion and said leg portions being generally arcuate in elevation and closely following the outlines of the tubular members.

' 8. The apparatus of claim 3 wherein said induction heating coil has a pair of legs extending generally longitudinally of the path of the tubular members on opposite sides thereof, and an intermediate connecting portion, said legs having intermediate opposed portions directed generally towards the path of the connecting tabs for effecting the concentration of current in the tabs, said intermediate opposed portions being generally V-shaped.

9. The apparatus of claim 3 wherein said induction heating coil has a pair of legs extending generally longitudinally of the path of the tubular members on opposite sides thereof, and an intermediate connecting portion, said legs having intermediate opposed portions directed generally towards the path of the connecting tabs for effecting the concentration of current in the tabs, said intermediate connecting portion and said leg portions being generally arcuate in elevation and closely following the outlines of the tubular members, said intermediate opposed portions being generally V-shaped.

10. The apparatus of claim 3 together with means for controlling the flow of current through said induction heating coil in timed relation to the movement of the tubular members.

11. A method of attaining separation of two conductive metal bodies joined by a restrictive conductive bridge with a surface extending from one body across the bridge and onto the other body, which comprises inducing in each body at areas thereof adjacent the bridge eddy current effects with like magnetic polarity at said surface, whereby the intersection of the eddy currents causes current flow from one induction area to the other and back to thereby heat and weaken the bridge, and then pulling the bodies apart.

12. A method of attaining separation of two conductive metal bodies joined by a restrictive conductive bridge with a surface extending from one body across the bridge and onto the other body, which comprises moving the bodies, inducing in each moving body at areas thereof adjacent the bridge eddy current effects with like magnetic polarity at said surface, whereby the intersection of the eddy currents causes current flow from one induction area to the other and back to thereby heat and weaken the bridge.

13. A method of attaining separation of two conductive metal bodies joined by a restrictive conductive bridge with a surface extending from one body across the bridge and onto the other body, which comprises moving the bodies, inducing in each moving body at areas thereof adjacent the bridge eddy current effects with like magnetic polarity at said surface, whereby the intersection of the eddy currents causes current flow from one induction area to the other and back to thereby heat and melt the bridge.

14. The method of attaining separation of two conductive bodies joined by a restrictive conductive bridge, which method comprises applying alternating magnetic field efiects to the bridge thereby inducing an electric current flow in the bridge of such intensity that the material of the bridge is raised to a temperature at which the bridge is physically weakened, and then pulling the bodies apart.

15. A method of severing connecting tabs extending between and connecting together adjacent tubular members, the method comprising the steps of disposing adjacent tubular members at small angles to each other with the tubular members being out of engagement with one another except for the connecting tabs, and passing the tubular members through an induction heating coil and concentrating current flow in the connecting tabs to efl'ect the heating and melting of the connecting tabs.

16. The method of claim 15 wherein the fiow of current through the induction heating coil andthe tubular members is timed in relation to the movement of the tubular members to limit current fiow in the tubular members to the general areas of the connecting tabs.

17. An induction heating coil for severing connecting tabs extending between and connecting together tubular members, said induction heating coil comprising a pair of elongated legs disposed generally in parallel relation, and an intermediate connecting portion, said legs having intermediate portions of a generally V-shaped outline disposed in opposed relation.

18. The induction heating coil of claim 17 wherein said connecting portion and said opposed portions of the legs are arcuate in transverse section to permit the passage of tubular members generally within the confines of the induction heating coil.

19. An apparatus for severing selected connecting tabs between tubular members comprising feed and guide means for moving the tubular members in a predetermined path With adjacent ends of the tubular members spaced apart and disposed in angular relation and the tubular members being connected together by connecting tabs disposed at the apices of angles between the tubular members and an a1ternating-current-carrying conductive loop having first and second serially-connected branches configured and disposed symmetrically with respect to the path of motion of said tabs, said first and second branches respectively comprising an intermediate portion disposed substantially parallel to an edge portion of one of said bodies, thence substantially parallel to and closely spaced apart from the proximate connecting edge of said tab, and thence parallel to the adjacent edge portion of a next proximate one of said bodies, whereby a maximum concentration of induced current in the connecting tabs is effected for the heating of said tabs.

References Cited in the file of this patent UNITED STATES PATENTS 2,187,740 Hothersall Jan. 23, 1940 2,467,201 Frazier Apr. 12, 1949 2,507,817 Rapp et al May 16, 1950 2,512,893 Gahr June 27, 1950 2,599,229 Bukaty June 3, 1952 2,655,588 Wadhams Oct. 13, 1953 2,716,693 Wadhams Aug. 30, 1955