US 3764767 A
Method and apparatus for embossing wood or the like with three-dimensional designs in which a rotary mounted embossing wheel is heated to a high temperature by induced currents. The heated wheel bears on stock driven past the wheel to emboss the stock by heat and pressure.
Description (OCR text may contain errors)
INDUCTION EMBOSSING BACKGROUND OF INVENTION It is known to emboss wood or the like with a heated embossing wheel pressed against the stock as it moves past the wheel. In this manner there is formed ornate moldings, picture frames and the like. Conventionally such an embossing wheel has been heated to a high temperature by the application of gas flames to the periphery of the wheel as it is rotated. This manner of heating an embossing wheel has various drawbacks including the possibility of igniting the stock as well as difficulties in heating the wheel to the desired high temperature and controlling such temperature. Additionally, prior art apparatus of this general type has been limited to relatively low speed operations wherein stock is fed through the apparatus at a speed limited to about feet per minute.
There has been developed a material improvement in the conventional method described above. This improvement consists in heating of the embossing wheel electrically by incorporating a heating element in the wheel itself and electrically energizing the element. This then overcomes numerous prior art problems but does raise certain other problems. Electrical energization of the heating element or elements requires some manner of connecting a power source thereto. This may, for example, include collector rings, brushes and the like, for the embossing wheel rotates during use and must be continuously heated in order to carry out the embossing operation.
The present invention provides the advantages of electrical heating without the prior art requirements of electrical connections to the embossing wheel.
SUMMARY OF INVENTION The present invention, in common with prior art embossing systems, provides a rotary mounted embossing wheel above a work table with drive means for moving a stock across the table in bearing contact with the embossing wheel to rotate the latter as the stock is embossed. In distinction to prior art systems, the present invention provides for heating the embossing wheel by inducing circulating currents in the wheel. In accordance herewith a ferromagnetic yoke is mounted with the pole pieces closely adjacent opposite sides of the rotary mounted embossing wheel. An annular portion of the wheel completes the magnetic circuit and the rim of the wheel itself forms the secondary winding of a transformer. Thus, by energizing a primary winding wound about the yoke, there is produced a circulating current in the closed circuit secondary. Inasmuch as the secondary comprises but a single turn a very substantial current may be induced in the secondary by the provision of a substantial number of primary turns having only a reasonable amount of current passed therethrough. In this manner then the embossing wheel may be rapidly heated to a very high temperature and this temperature may be readily controlled merely by controlling the current passed through the primary winding about the yoke.
DESCRIPTION OF FIGURES The present invention is illustrated as to a single preferred embodiment thereof in the accompanying drawings wherein:
FIG. 1 is a perspective view of apparatus in accordance with the present invention and adapted to carry out the method of this invention;
FIG. 2 is an end view of the embossing portion of the apparatus of FIG. 1;
FIG. 3 is a partial sectional view taken in the plane 3-3 of FIG. 2;
FIG. 4 is a side elevational view of the embossing wheel of the present invention; and
FIG. 5 is a sectional view taken in the plane 5-5 of FIG. 4.
DESCRIPTION OF PREFERRED EMBODIMENT The method of the present invention comprises the controlled induction of a current in a metallic embossing wheel having a three-dimensional pattern or design formed about the rim or periphery thereof. This heating current in the wheel is induced by a current passed through a primary winding about a magnet yoke having the pole pieces thereof spaced closely adjacent opposite sides of the wheel. This primary current is an alternating current so that through normal transformer action a current is induced in the secondary of the transformer comprising the rim of the wheel.
The embossing wheel, or more particularly the rim of the wheel, is raised to a high temperature by the induced current in the wheel producing an IR heating effect. The embossing wheel is mounted for free rotation and wood stock or the like is moved tangentially of the wheel in bearing relation thereto for rotating the wheel in contact with the stock. Embossing is accomplished by a combination of heat and pressure on the stock. By the induction of a sufficient current in the wheel the heating effect achieved may be maximized so as to maintain a desired wheel rim temperature even though the wheel passes very rapidly along the stock or vice versa. Thus, the present invention provides not only for simply and efficiently heating an embossing wheel but also for maximizing the possible speed of embossing. It is possible in accordance with the method hereof to emboss wood stock such as wood molding or the like at a rate of the order of 200 feet per minute or more. This speed then approximates that of molding machines forming wood moldings so that the present invention is adapted for combination with wood cutting operations wherein raw stock is operated upon to produce desired general stock configurations and is then further operated upon to emboss such stock all in a single pass. The method hereof further provides for a precise control of embossing wheel temperature by controlling the current passed through the winding about the magnetic yoke.
Considering now apparatus of the present invention as illustrated in the drawings, reference is first made to FIG. 1 thereof wherein there will be seen to be provided a table 11 mounted upon a base 12. An embossing wheel 13 is mounted for free rotation above the table upon a shaft- 14 carried by uprights 16 and 17 extending upwardly from the table 12. Upon the table there are provided movable fences l8 and 19 for guiding stock 21 longitudinally of the table beneath the wheel 13. There is also provided drive means in the form of a rotary driven roller 22 extending in part above the table beneath the wheel for engaging the under side of stock 21 and forcing it to move along the table in bearing relationship to the wheel. Vertical separation between the embossing wheel 13 and drive roller 22 may be adjusted, for example, by a hand wheel 23 geared to the uprights l6 and 17 so as to move the embossing wheel up and down relative to the table and drive roller 22.
Heating of the wheel is herein accomplished by the provision of an electrical system or transformer 26 described in more detail below and adapted for energization through a control unit 27 which may be connected to a power outlet by a cord 28 and plug 29. The control unit which may include a rheostat and the like for controlling current output and has a control knob 31 thereon for this purpose.
Considering heating of the wheel somewhat further and referring to FIGS. 2 and 3, there will be seen to be provided a magnet yoke 41 mounted as by non-ferrous brackets 42 and 43 upon the uprights 16 and 17. This yoke, which may be formed of laminated iron, has the pole pieces 46 and 47 disposed immediately adjacent opposite sides of the embossing wheel 13 with a minimum air gap of the order of 0.002 to 0.003 inch, for example. A primary winding 48 is wrapped about the yoke 41 for the purpose of inducing magnetic flux in the yoke by the passage of an alternating current through such winding. Preferably the winding 48 is comprised as a large number of turns of wire electrically insulated from each other and connected to the above-noted control unit 27 to thus establish a large number of ampere turns about the magnet yoke. The illustration of the winding 48 in the drawings hereof is only exemplary and is not intended as an indication of the number of turns of winding. There may also be provided additional magnet yokes and windings coupled to the wheel as indicated at 49 and 50 of FIG. 3 to maximize current induced in the wheel.
Considering now the embossed wheel itself as illustrated in various views of the drawings and particularly FIGS. 4 and thereof, it is noted that the wheel may be formed of four major components. The peripheral or rim portion 51 of the wheel is formed of metal capable of being heated by high electrical current and of withstanding a high temperature and suitably indented on the outer surface thereof as a pattern for embossing wood or the like. Radially inward of this rim there is formed a magnetically conducting portion 52 of the wheel which serves as a continuation of the magnetic yoke 41 bridging the gap between pole pieces 46 and 47, thus forming a continuous magnetic core. The wheel rim 51 comprises a single turn secondary winding of the transformer about the portion 52 of the magnetic circuit. The magnet portion 52 of the wheel 13 may, for example, be formed of a large plurality of silicon iron wires or the like, each extending laterally across the wheel and all bound together as, for example, by a high temperature epoxy resin or the like. Alternatively, it is possible merely to form this portion 52 as a ferromagnetic annulus. Between the rim 5! and wheel portion 52 there is provided an electrical insulation layer 53 separating the magnetic circuit from the secondary winding. Radially interior of the magnet portion 52 there is provided a heat insulating portion 54 of the wheel engaging the portion 52 and adapted to fixably engage the support of shaft 14. The heat insulating portion 53 may be formed of a variety of material and, if it is deemed necessary that same be formed of a metal, stainless steel is known to be a realtively poor heat conductor in this class.
Further with regard to the structure of the embossing wheel l3 it is noted that the embossing rim 5] may, as a practical matter, be mounted upon an annular metal piece about the wheel portion 52. [t is to be appreciated that there are a variety of possible wheel structures wherein a portion at least of the wheel serves as a secondary winding of the transformer formed by the winding 48 upon the core 4!. Additionally it is noted in this respect that the wheel portion 54 is provided for the purpose of minimizing heat transfer to the support shaft 14. The periphery of the embossing wheel is raised to a temperature of the order of l,000F and necessarily maintained at this elevated temperature during embossing. Consequently the problem of minimizing heat transfer to the support bearings of the shaft 14 may be substantial. In order to minimize heat flow from the wheel to shaft bearings and supports the shaft may be hollow and a cooling fluid passed therethrough, for example. It is also possible in accordance with the present invention to provide heat shields and heat radiators as necessary to limit or minimize the transfer of heat to surrounding elements of the present invention from the embossing wheel.
Operation of the apparatus of the present invention illustrated in the drawings and described above is believed relatively apparent from the foregoing description. In this respect it is noted that there is provided switching means 61 for energizing the drive roller 22 and which may, for example, incorporate speed control means for varying the rotational velocity of the drive roller in order to control the rate of feed stock 21 through the device. There may also be provided means for pivoting the embossing wheel upwardly away from the table in order to facilitate replacement of the embossing rim 51 thereon in order to change the design embossed by the wheel. Such means may include provision for pivoting the uprights 16 and 17. It is also noted that the lateral position of the fences l8 and 19 may be adjusted to accommodate the passage of different width stock 21 through the apparatus.
Operation of the present invention is accomplished by energizing the heating means 26 by connecting the plug 29 to a power supply outlet and adjusting the control 31 on the control unit 27. This then passes a desired current through the primary 48 of the transformer to thus establish a desired heating current in the rim 5] of the embossing wheel. This current induced in the embossing wheel by the alternating current nature of the current through the primary winding 48 produces a heating effect. The current circulating through the secondaryof the transformer 26 uniformly heats the embossing rim 51 of the embossing wheel 13 to the necessary high temperature for embossing. The height of the embossing wheel above the drive roller is then adjusted as by the adjusting wheel 23 and stock 21 is then fed between the previously adjusted fences l8 and 19 on the table 11 until it is engaged by the drive roller so that it is driven across the table to consequently rotate the embossing wheel. The pressure between the embossing wheel and the stock together with the high temperature of the embossing wheel rim then impresses a three dimensional design upon the stock fed across the table. As noted above, the stock may be fed at a very considerable speed as, for example, 200 feet per minute while the embossing wheel is continuously heated to maintain the high temperature of the embossing rim thereof. Control over the temperature of the embossing wheel is readily controlled by adjusting the control knob 31 of the unit 27 so as to adjust the current flowing through the primary winding 48 of the transformer 26. It is noted that the pole pieces 46 and 47 of the magnet yoke 41 are spaced very closely adjacent to the sides of the embossing wheel in order to achieve as close a magnetic coupling as possible. While it may be possible to employ an air core transformer so as to do away with the necessity of mounting the magnet yoke 41 above the embossing wheel, it is noted that a higher efficiency of induced current in the wheel is achieved by incorporating this magnet yoke in the device.
Although the present invention has been described above with respect to preferred steps in the method or process hereof and in terms of a single preferred embodiment of the apparatus, it will be appreciated by those skilled in the art that various modifications and variations in the foregoing are possible. It is thus not intended to limit the present invention to the precise terms of description or details of illustration.
What is claimed is:
l. A method of embossing wood stock and the like with a rotary mounted wheel having an electrically conducting embossing rim about the periphery thereof comprising the steps of disposing a magnetic yoke with poles thereof on opposite sides of said wheel in close proximity thereto radially between the wheel mounting and wheel rim,
coupling an electrical winding to said yoke,
energizing said electrical winding with an alternating current voltage to thus induce a current about the complete circumference of the rim of said wheel for heating the wheel rim,
controllably varying the amplitude of said energizing alternating current to control the temperature of said embossing wheel rim, and
moving stock tangentially past the embossing wheel in bearing relation thereto for embossing the stock.
2. The method of claim 1 further defined by insulating the rim of the embossing wheel from the rotary mounting thereof to minimize heat transfer to the mounting.
3. The method of claim 2 further defined by said insulating being both with regard to the flow of electricity and heat to limit induced current to the wheel rim and peripheral heat to the wheel rim.
4. Improved embossing apparatus for wood stock or the like comprising an embossing wheel rotatably mounted in position for engagement with wood stock or the like, said embossing wheel having a metal embossing rim comprising a single closed turn winding about said core whereby said induced heating current circulates about said rim,
an electrical winding,
a magnet core having poles closely spaced from sides of said embossing wheel for coupling said winding and embossing wheel, and
means energizing said winding with an alternating current for inducing a heating current in said wheel.
5. The apparatus of claim 4 further defined by said embossing wheel including an annular portion formed of a large plurality of ferromagnetic wires extending laterally across the wheel, and said magnet core extending into close proximity with opposite ends of said wires for close magnetic coupling thereto.
6. The apparatus of claim 5 further defined by said wheel including an annular insulating layer between said wire portion and an embossing rim and an annular heat insulating portion radially inward from said wire portion.