US3730081A

US3730081A - Rotory hot die embosser with tapered shaft and insulated embossing wheel

Info

Publication number: US3730081A
Application number: US00216061A
Authority: US
Inventors: G Colledge
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-01-07
Filing date: 1972-01-07
Publication date: 1973-05-01
Anticipated expiration: 1990-05-01

Abstract

A high speed, high temperature embossing machine for embossing wood products and a high temperature embossing wheel therefor is disclosed. The embossing wheel is electrically heated by elements carried at the rim thereof to temperatures as high as 1,400*F., and an embossing feed rate as high as 200 feet per minute may be employed. A large diameter hollow wheel filled with a thermally insulating material and a tapered, elongated shaft are employed to minimize heat transfer to the shaft bearings for high speed operation. Embossing wheel tilting and embossing wheel raising and lowering mechanisms are also disclosed.

Description

llnited @tates Patent 1 1 Colledge 11] agner 1451 May1,1973

1 1 ROTORY HOT DIE EMBOSSER WITH TAPERED SHAFT AND INSULATED EMBOSSING WHEEL [76] lnventor: Gary C. Colledge, 13900 Marguesas Way, Marina Del Rey, Calif. 90291 22 Filed: Jan. 7, 1972 211 Appl. No.: 216,061

[52] US. Cl. ..l0l/25, 101/31, 101/5 [51] Int. Cl. ..B44b 5/00 [58] Field of Search ..1()1/58, 10l/2225, 27, 31, 216, 375, 378; 29/110,

[56] References Cited UNITED STATES PATENTS 3,097,592 7/1963 Friedman ..lOl/3l X 2,366,293 l/l945 Slernberg 4 1 ..lOl/3l 3,146,698 9/1964 Worth 1 .4 lOI/ZS 3,294,014 12/1966 Kneisel l lOl/25 X 1,710,340 4/1929 Bresson ct a1v l()l/25 X 1,600,487 9/1926 Roehlen 101/25 3,188,259 6/1965 Leger 101/25 X 2,752,632 7/1953 Winstead ..101/25 X Primary ExaminerRobert E. Pulfrey Assistant Examiner-E. M. Coven At!0rneyManfred M. Warren et a1.

[ 5 7 ABSTRACT A high speed, high temperature embossing machine for embossing wood products and a high temperature embossing wheel therefor is disclosed. The embossing wheel is electrically heated by elements carried at the rim thereof to temperatures as high as 1,400F., and an embossing feed rate as high as 200 feet per minute may be employed. A large diameter hollow wheel filled with a thermally insulating material and a tapered, elongated shaft are employed to minimize heat transfer to the shaft bearings for high speed operation. Embossing wheel tilting and embossing wheel raising and lowering mechanisms are also disclosed.

10 Claims, 2 Drawing Figures ROTORY IIOT DIE EMBOSSER WITH TAPERED SHAFT AND INSULATED EMBOSSING WHEEL BACKGROUND OF THE INVENTION There is presently a substantial industry involved in the embossing of picture frame moldings, furniture and cabinet parts, doors, and a host of related articles. Previously, these products have been embossed virtually exclusively by heated embossing wheels in which an open flame is used to heat the embossing die. These machines typically run at a temperature of about 500F. or less and at speeds of about 30 to 40 feet per minute or less. The embossing wheel is usually a smaller diameter wheel which is often not evenly heated by the gas flame, and the relatively low temperatures and small diameter of the wheel necessitate a relatively low embossing speed. Additionally, embossing machines which use an open flame inherently create a safety problem, particularly in light of the fact that such machines are used in wood working shops where sawdust and the like is often present. One example of an open flame embossing machine is disclosed in U.S. Pat. No. 2,703,463.

Another approach has been taken in connection with the embossing of wood and plastic products in an attempt to reduce the hazard created by the open flame embossing machines. Instead of using an open flame, the embossing dies may be heated externally by means of electrical resistance coils or a radiation source such as an infra-red lamp. Typical of these machines are the devices set forth in U.S. Pat. Nos. 3,294,014 and 3,393,294. In these devices, the surface temperature I can be elevated to a relatively high temperature but they are still run at a relatively low speed of 40 feet per minute, or less, in all probability due to the rapid dissipation of the surface heat upon contacting the materialto be embossed.

Finally, a limited effort has been made to incorporate an electrical heating element into an embossing wheel. In connection with the embossing of gold leaf, inherently a relatively low temperature process, U.S. Pat. No. 3,097,592 illustrates an embossing wheel having a heating element carried by a portion of the wheel for embossing gold leaf. U.S. Pat. No. 3,269,304 illustrates a small diameter embossing wheel primarily designed for leather and plastics which may optionally include an electrical heating element at the center thereof. This device, however, is also inherently a relatively low temperature, low speed embossing machine.

Accordingly, it is an object of the present invention to provide an embossing machine which is constructed in a manner which enables wooden and plastic impregnated wooden articles to be embossed at a greatly increased feed rate while maintaining uniform penetration of the embossing die into the article.

It is another object of the present invention to provide a high speed embossing machine having a greatly improved capability to vary the embossing temperature, feed rate, and depth of penetration in accordance with the nature of the article to be embossed and the embossing pattern.

It is another object of the present invention to provide an embossing wheel for use in a high speed embossing machine which allows the easy and convenient interchanging of embossing dies.

It is still a further object of the present invention to provide an embossing machine and a high temperature embossing wheel which have improved safety, are easy to construct, and are simple and economical to operate.

Other objects and features of advantage of the embossing machine of the present invention will become apparent upon consideration of the drawings and the following description of the preferred embodiment.

SUMMARY OF THE INVENTION The embossing machine of the present invention is comprised briefly of a frame having a work supporting surface and a pair of embossing wheel mounting elements positioned on opposed sides of and extending above the surface. An elongated high strength shaft is rotatably mounted between the mounting elements, and the shaft has a variable mass gradiating from a maximum at the center thereof to a minimum adjacent mounting elements, preferably accomplished bycontinuously tapering the shaft from the embossing wheel to the mounting elements. An embossing wheel is mounted on the shaft for rotation therewith and includes a hollow body having load bearing side plate and an angular rim in which a heating element is mounted. Thermally insulating material is disposed in the hollow body. The embossing wheel has a radial height dimension from the shaft preferably substantially in excess of the radius of the shaft in order that heat transfer to the shaft and down the shaft to bearings in the mounting elements is reduced. The periphery of the embossing wheel is preferably formed as a frusto-conical surface for mounting and demounting of an embossing die having a mating inwardly facing frusto-conical surface thereon and juxtapositioning of the die over the electrical heating element carried by the wheel. Shaft and wheel tilting and shaft and wheel raising and lowering mechanisms are provided.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an end elevation'al view, partially broken away, of an embossing machine constructed in accordance with the present invention.

FIG. 2 is an enlarged, fragmentary end view, in crosssection, of an embossing wheel as shown in FIG. I and constructed in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The embossing machine of the present invention includes a frame, generally designated 21, having a work supporting surface 22 and a pair of embossing

wheel mounting elements

23 and 24 positioned on opposite sides and extending above surface 22. The frame further includes supporting leg structure 26 from which table 22 and the remaining apparatus of the machines are supported. Rotatably mounted between

elements

23 and 24 is an elongated high strength shaft 27.

Mounting elements

23 and 24 include removable

upper portions

28 and 29 which are releasably fastened by

fasteners

31 and 32 to the lower portions of the mountingelements. Positioned in

mounting elements

23 and 24 are'bearings 33 and 34 which cause ends 36 and '37 of shaft 27 to be journaled therein. As will be described more fully hereinafter, shaft 27 is provided with a further extension 38 beyond end 37 for transfer of electricity to the heated embossing wheel, generally designated 39.

It is a very important feature of the present invention that the embossing machine be constructed in a manner which enables the wheel 39 to be operated at very high temperatures, which in turn allows the machine to emboss articles at a high feed rate. In open flame heated embossing machines, the die temperature is typically 500F. or less and the feed rate 25 to 35 feet per minute. Even in electrically surface heated devices, where the die temperature on the surface may momentarily reach over a thousand degrees,the feed rate of such machines is 40 feet per minute or less. In a high speed embossing machine in the present invention, the die temperature may be as high as 1,400F. enabling feed rates as high as 200 feet per minute or five times that employed by prior art devices.

In order to maintain the embossing die at a high temperature at the embossing surface thereof and throughout the die for high speed continuous embossing, wheel 39, best seen in FlG. 2, is formed to carry an electrical heating element 41 (here shown as 2 winds 41 and 41a around the periphery of the embossing wheel) immediately adjacent to embossing die 42. Heating element 41 is connected by

electrical conductors

43 and 44 to a source of electricity. As will be seen, the immediate juxtapositioning of heating element 41 with back surface 46 of die 42 results in the die being uniformly heated so that not only the front embossing surface 47 of the die body reaches a high temperature, but the entire die is heated. Thus, pressing the die into the article to be embossed does not substantially diminish the temperature of surface 47 since the entire mass of the die is heated, rather than just the surface. Heating element 41 is preferably a resistance type of heating coil.

Heating die 47 to temperature in excess of 1,000F. by means of heating coils carried by the embossing wheel in juxtaposition to the die, however, causes serious heat transfer problems within the embossing machine. In order to insulate the embossing machine, and more particularly,

bearings

33 and 34, against the extreme heat to which die 42 is elevated, embossing wheel 39 is formed with a pair of relatively spaced apart, high strength, plate-like

annular side portions

51 and 52 which act as the load carrying members for transfer of the embossing pressure from shaft 27 to die 42.

Side portions

51 and 52 are preferably formed as annular plates having

central openings

53 and 54 for mountingon shaft 27 and the

peripheral edges

56 and 57 for receipt of die 42.

It is a feature of the present invention that the radial height of wheel 39 and

side portions

51 and 52 from the

central openings

53 and 54 be substantially in excess of the radial dimension of shaft 27 and

central openings

53 and 54. An increase in the radial height from opening 53 to peripheral edge 56 has two benefits. First, the increase in radial distance at which heated die 42 and heating elements 41 are from shaft 27 result in a diminution of the amount of heat transferred to shaft 27. Additionally, an increase in diameter of the embossing wheel results in the embossing wheel contacting the object to be embossed for a longer period of time and at a more gradual angle than is experienced when small diameter embossing'wheels are employed. The longer contact time further enables embossing to deeper depths and at higher rates of feed for a given temperature. Thus, the radial height of the wheel above shaft 27 is preferably at least about 1.5 times the diameter of the shaft at the wheel mount in order to reduce heat transfer to the shaft and increase contact time between the die and the object being embossed. Increasing the heat of the die and increasing its contact time with the object embossed in turn allows a substantial increase in the feed rate.

Side plates

51 and 52 are connected by annular rim portion 58 adjacent

peripheral edges

56 and 57. Rim member 58 is preferably adjoined to annular side portions by fasteners 59 and is formed with a radially outwardly facing heating element receiving recess,in this case two

recesses

61 and 62, extending circumferentially around the rim. The internal surface 63 of the rim and

side plates

51 and 52 define an annular cavity which extends to a second inner annular member 80 adjacent shaft 27. Positioned in this cavity is a thermally insulating material 64 which substantially fills the cavity and has the effect of directing heat in rim 58 outwardly toward die 42 and insulating shaft 27 from transfer of heat thereto. Member 80 is welded in place after positioning of the insulating material in the cavity. Thus, heat must be transferred to shaft 27 down relatively

thin die plates

51 and 52, both of which have a substantial surface area but a relatively thin cross-section (about one-fourth inch thick for 12 inch diameter wheel). The heat generated by the heating element will be dissipated to some extent by radiation and conduction from moving

surfaces

51 and 52 prior to'being conducted down these relatively thin surfaces to shaft 27. In order to further reduce the transfer to shaft 27 and

bearings

36 and 37, it is preferable that

side plates

51 and 52 are constructed of a metal having relatively low thermal conductivity. One metal that is particularly well suited for this use is stainless steel since it has high strength at elevated temperatures anda relatively low thermal conductivity. The thermal conductivity of 304 and 316 alloy stainless steels at about l,000'-F. is between 10 and 15 Btu per hour per square foot per degree F per foot. This is about one half of the thermal conductivity of most steels or irons, which could be used, and about one fourth the thermal conductivity of brass and one tenth the thermal conductivity of most aluminums, which would not be satisfactory. It should. be further noted that the insertion of thermally insulating materials such as ceramics has the disadvantage of either increasing the costs substantially or not being able to withstand the embossing pressures and impacts without cracking or fatiguing.

In order to further reduce the heat transfer to

bearings

33 and 34, high strength shaft 27 preferably has a variable mass gradating from a maxiumm mass adjacent the midpoint thereof to a minimum mass adjacent mounting

elements

23 and 24. Such a gradiation in mass is conveniently accomplished by tapering a shaft 27 in two directions from adjacent the wheel mount to the bearings, as shown in FIG. 1. Since heat will tend to seek that portion of the shaft having the most mass, tapering the shaft from the wheel mount'to the respective bearings further reduces heat transfer to the bearings. It should also be noted that in the event that excessive heat is transferred to

bearings

33 and 34, the embossing machine must be run at a slower rate. Thus, tapering the shaft and insulating the shaft from heating element 41, as above described, allows the bearings to be cool and the embossing machine to be operated at a high feed rate.

Since mounting

elements

23 and 24 span table 22, shaft 27 is also preferably formed from a steel to withstand the embossing pressures. Separation of mounting

elements

23 and 24 facilitates embossing of wide articles and further reduces heat transfer to the bearings. I I

It is a feature of the present invention that the electrically heated embossing wheel may be easily removed from the shaft and replaced by another wheel. Thus, for some tasks an embossing wheel having a thickness of one inch may be employed while for others an embossing wheel having a thickness of two inches or three inches or more may be employed. Thicker embossing wheels generally require more winds on the heating element. As shown in the drawing, a single heating element 41 is wound twice around the periphery of the embossing wheel (the element must cross once if a single element is used), which is well suited for use on a one inch wide wheel. In order to remove this wheel, shaft 27 is formed with means for releasably mounting the wheel thereto, including shoulder 67, axially extending threaded portion 68, and nut element 69 threadably mounted on portion 68 for receipt of wheels of varying width between nut element 69 and shoulder 67. As best seen in FIG. 2, the shoulder and nut engage side walls of

plates

51 and 52 to hold the wheel for rotation in a single plane. Additionally, shoulder 67 is preferably formed with a key means such as protrusion 71 which mates with a notch 72 in plate 52 of the wheel to cause the wheel to rotate with shaft 27.

In order to remove wheel 39 from the

shaft conductors

43 and 44 must be disconnected from the machine at releasable sockets 73. The

top portions

28 and 29 of the mounting

elements

23 and 24 may be removed, and nut 69 unscrewed from threaded portion 68 to allow wheel 39 to be axially displaced down over the end 36 of shaft 27. A new wheel can be mounted on shaft 27 by reversing this procedure.

It is a further important feature of the present invention that the embossing die 42 may be rapidly and easily removed from the electrically heated embossing wheel. It is highly desirable to be able to use many different embossing patterns. Accordingly, and as best may be seen in FIG. 2, embossing die 42 has a radially inwardly facing surface 46 which is frusto-conical or a slightly tapered surface which mates with a frusto-conical radially outwardly facing surface on rim member 58. Additionally, side plate 52 carries locking means, here shown as a pivoted arm 77 secured by fastener 78 to the side plate. Die 42 can be axially urged onto the

peripheral edges

56 and 57 and the outwardly facing surfaces of rim 58 and then locked in place by pivoting of arm 77 to the position shown in FIG. 2. As so locked in place, the inner surface 46 isjuxtaposed over heating element 41 for efficient heat transfer to the embossing die. Several locking arms can be positioned circumferentially around wheel 39 in order to evenly hold the die on the periphery of the wheel. The frusto-conical mating surface insures that the die seats properly with the periphery of the wheel for maximum heat transfer from the rim and heating element. The taper of the frusto-conical surface 46 and mating surface on the rim is preferably less than about 15 so that the compressive forces during embossing do not generate too high an axial force against arm 77. It has been found that a taper of about 3, as indicated by angle [3 is best suited for the embossing wheel of the present invention. It should further be noted that with this amount of taper, the tendency to thrust the die axially under the radial load is virtually eliminated, and it should be noted that the die can be readily removed by briefly turning on the heating element, causing the die to expand and then tapping the die axially, after swinging arms 77 to a position aligning removal of the die. It is preferable that the die be tapered in a direction allowing its removal over end 36 of shaft 27 in a manner similar to the removal of the wheel from the shaft, and the top

portion mounting elements

23 and 24 will have to be loosened, and in the case of element 28, removed, in order to allow the die to be removed from the wheel and the machine.

In the embossing machine of the present invention, shaft 27 is preferably not driven. Instead, a feed drum 81, which extends slightly above 22 to frictionally engage work piece 82, is provided. Drum 81 is driven through pulley 83 and chain or belt 84 by motor 86. Motor 86 is preferably a variable speed motor electrically connected to control knob 87 by conductor 88. Thus, the speed of the feed drum can be varied from about 20 to about 200 feet per minute, depending upon the material being embossed and the temperature of die 42. Also mounted on table 22 are guide fences 89 which are laterally adjustable to accommodate various sizes of work pieces in the same fashion as guide fences on table saws and the like. The interference fit of work piece 82 between feed drum 81 and wheel 39 results in rotation of the embossing wheel and progressive embossing of the work piece as the feed drum advances the work piece.

It is a further feature of the present invention to provide an embossing machine in which the embossing wheel may be tilted for embossing on surfaces which are at an angle to table 22, and raised and lowered to accommodate work pieces which are of varying width. Raising and lowering of the embossing wheel is accomplished by means of a rack 91 and pinion gear 92 forming part of both mounting

elements

23 and 24. These rack and pinion gears are interconnected by shaft 93 and simultaneously adjusted by hand wheel 94 for accurate vertical displacement of the wheel with respect to the work piece.

In order to allow tilting of the embossing wheel of the present invention, mounting

elements

23 and 24 are secured to an arcuate track or cradle 111 at ends 112 and 113 thereof. Member 114 is fixedly secured to the frame and leg supporting 26, and it carries at its lower most end a guide means 116 carrying rolling element 117, which engages upper and

lower surfaces

118 and 119 of track 1 1 l for support of the track and mounting elements with respect to the leg supporting structure 26. Guide means 116 may be formed as a generally rectangular tubular member which surrounds track or cradle 111, and the rolling elements 117 are preferably rollers which engage the upper and lower surfaces of the track over a width of several inches to prevent angular tipping of the mounting elements about the longitudinal access of track 1 l 1'.

In order to allow adjustment of the angle of tilt, adjusting means, including a worm gear (not shown) and a rack 121 on track 111, are provided, and the cradle 11 1 is advanced by means of shaft 122 and hand wheel 123. Thus, upon rotation of hand wheel 123, the worm gear engages rack 121 on cradle l 11 causing the cradle to be displaced laterally with the arcuate upper and

lower surfaces

118 and 119 of the track moving with respect to rollers 117, fixed to the frame. The result is a tipping of mounting

elements

23 and 24 and angular displacement of the shaft and embossing wheel with respect to the article being embossed and table 22. It is preferred that the arcuate track have a center of curvature following substantially on a plane passing through the center of the wheel and parallel to

side plates

51 and 52. Still further, it is preferable that the center of curvature be at about the working surface of the table in order that the embossing die will remain at about the center of the table during the tilting of the embossing wheel.

Electricity is supplied to the heating element in wheel 39 from control panel 50 through conductor 49 to brush assembly unit 48 and

dual tracks

45 and 40, which are in turn connected to

electrical conductors

43 and 44 passing through passageway 35 in shaft 27 to extension 38 thereof. Control panel 50 is provided with a knob 55 allowing manual adjustment of the heat by means ofa rheostat positioned in the'control box 50.

Although considerable variation is possible in constructing the embossing machine as the present invention, some typical specifications would include a shaft 27 or spindle which is about 30 inches long and tapers from about 3 inches at flange 67 to about 2 inches at the shaft mounts. The embossing wheel may be 12 inches in diameter and may accommodate dies varying from one-fourth inch to 2 inches wide or wider. Motor 86 may be a 2 horsepower motor to drive a inch diameter feed drum 81. The power supply to the embossing wheel may be 220 to 240 volts A.C. (single phase), witha l5 amp current if 1 inch wheels are used and a 30 amp current for 2 inch wheels having two heater elements in them. A Warner Electric Brake & Clutch Co. brush holder, Model 819-0032, may be used as brush holder 48. Bearings are preferably of the sealed type and'need lubricating only at long intervals. It is possible with an embossing machine constructed as above outlined with the temperature on the order of about 1,200F. to emboss patterns at a rate of as much as 200 feet per minute to a depth of one-fourth inch in wood. Additionally, the high strength construction and high temperature embossing wheel allows the machine to be used to emboss plastic impregnated woods. Thus, the variable feed rate and variable heated embossing wheel accommodate the use of the embossing machine on a wide variety of materials at a maximum rate of feed.

I claim:

1. In an embossing machine including a frame having a work supporting surface and a pair of embossing wheel mounting elements positioned on opposed sides of and extending above said surface, the improvement comprising:

a. an elongated high strength shaft rotatably mounted between said mounting elements adjacent opposite ends of said shaft, said shaft having a variable mass gradating from a maximum mass adjacent the midpoint thereof to a minimum mass adjacent said mounting elements; and I b. an embossing wheel mounted on said shaft for rotation therewith, said wheel including:

i. a body including annular load bearing side plates 2 and an annular rim member joining said plates adjacent the periphery of said wheel, said rim member being formed with a circumferentially extending heating element receiving recess, and said side plates and said rim member defining a cavity therebetween; ii. an electrical heating element mounted in said recess; and iii. thermally insulating material disposed in and substantially filling said cavity. 2. In an embossing machine as defined in claim 1 wherein,

said shaft is tapered in two directions from a maximum diameter adjacent said wheel to minimum diameters adjacent said mounting elements. 3. In an embossing machine as defined in claim 2 wherein,

said side plates have a radial height dimension from said shaft to said rim member of at least about 1.5 times greater than the radius of said shaft at the point of mounting of said wheel thereon, and an annular embossing die having a radially outwardly facing surface with an embossing pattern thereon and a radially inwardly facing surface dimensioned for-and mounted in sliding engagement with the periphery of said wheel and juxtaposed to said heating element. 4. In an embossing machine as defined in claim 3 wherein,

said periphery of said wheel and said inwardly facing surface of said die are formed as mating frustoconical surfaces allowing mounting and demounting of said die on said wheel by movement of said die axially along the length of said shaft, and means secured to said wheel for selectively locking said embossing die in juxtaposed relation to said heating element and releasing said embossing die for removal from said wheel. 5. In an embossing machine as defined in claim 3 wherein,

said mounting elements are formed with means for releasably mounting said shaft thereto, and

said shaft is formed with means for releasably mounting said wheel thereto. 6. In an embossing machine as defined in claim 5 wherein,

said means for releasably mounting said wheel to said shaft is comprised of a flange formed to rotate with said shaft, an axially extending threaded portion on said shaft extending to a spaced distance from said flange, and a nut element threaded on said threaded portion for receipt of wheels of varying width therebetween, said flange and nut element engaging said side plates on said wheel to hold said wheel in a single plane and formed with key means engaging said wheel and causing said wheel to rotate with said shaft.

7. In an embossing machine as defined in claim wherein,

said shaft is formed with a passageway extending from a position intermediate of said mounting elements to a position exteriorly of one of said mounting elements, and

electrical conductor means positioned in said passageway and electrically connected to said heating element at one end thereof, and

electrical brush means positioned to electrically con- 10 and carrying rolling elements engaging said track for support of said track and said mounting elements thereon, and adjustment means for displacing said track on said rolling elements selective amounts to thereby angularly tilt said mounting elements and said-shaft. .9. ln an embossing machine as defined in claim 8 wherein,

said arcuate track has a center of curvature falling substantially on a plane passing through the center of said wheel parallel to said side plates. 10. In an embossing machine as defined in claim 8, and

mounting element height adjustment means formed for simultaneous selective adjustment of the height of both said mounting elements and said shaft and wheel above said working surface.

Claims

1. In an embossing machine including a frame having a work supporting surface and a pair of embossing wheel mounting elements positioned on opposed sides of and extending above said surface, the improvement comprising: a. an elongated high strength shaft rotatably mounted between said mounting elements adjacent opposite ends of said shaft, said shaft having a variable mass gradating from a maximum mass adjacent the midpoint thereof to a minimum mass adjacent said mounting elements; and b. an embossing wheel mounted on said shaft for rotation therewith, said wheel including: i. a body including annular load bearing side plates and an annular rim member joining said plates adjacent the periphery of said wheel, said rim member being formed with a circumferentially extending heating element receiving recess, and said side plates and said rim member defining a cavity therebetween; ii. an electrical heating element mounted in said recess; and iii. thermally insulating material disposed in and substantially filling said cavity.

2. In an embossing machine as defined in claim 1 wherein, said shaft is tapered in two directions from a maximum diameter adjacent said wheel to minimum diameters adjacent said mounting elements.

3. In an embossing machine as defined in claim 2 wherein, said side plates have a radial height dimension from said shaft to said rim member of at least about 1.5 times greater than the radius of said shaft at the point of mounting of said wheel thereon, and an annular embossing die having a radially outwardly facing surface with an embossing pattern thereon and a radially inwardly facing surface dimensioned for and mounted in sliding engagement with the periphery of said wheel and juxtaposed to said heating element.

4. In an embossing machine as defined in claim 3 wherein, said periphery of said wheel and said inwardly facing surface of said die are formed as mating frusto-conical surfaces allowing mounting and demounting of said die on said wheel by movement of said die axially along the length of said shaft, and means secured to said wheel for selectively locking said embossing die in juxtaposed relation to said heating element and releasing said embossing die for removal from said wheel.

5. In an embossing machine as defined in claim 3 wherein, said mounting elements are formed with means for releasably mounting said shaft thereto, and said shaft is formed with means for releasably mounting said wheel thereto.

6. In an embossing machine as defined in claim 5 wherein, said means for releasably mounting said wheel to said shaft is comprised of a flange formed to rotate with said shaft, an axially extending threaded portion on said shaft extending to a spaced distance from said flange, and a nut element threaded on said threaded portion for receipt of wheels of varying width therebetween, said flange and nut element engaging said side plates on said wheel to hold said wheel in a single plane and formed with key means engaging said wheel and causing said wheel to rotate with said shaft.

7. In an embossing machine as defined in claim 5 wherein, said shaft is formed with a passageway extending from a position intermediate of said mounting elements to a position exteriorly of one of said mounting elements, and electrical conductor means positioned in said passageway and electrically cOnnected to said heating element at one end thereof, and electrical brush means positioned to electrically connect said electrical conductor means to a source of electricity during rotation of said shaft.

8. In an embossing machine as defined in claim 1, and shaft tilting means mounted between said mounting elements and the remainder of said frame, said shaft tilting means including an arcuate track fixedly secured at opposite ends to said mounting elements, guide means fixedly secured to said frame and carrying rolling elements engaging said track for support of said track and said mounting elements thereon, and adjustment means for displacing said track on said rolling elements selective amounts to thereby angularly tilt said mounting elements and said shaft.

9. In an embossing machine as defined in claim 8 wherein, said arcuate track has a center of curvature falling substantially on a plane passing through the center of said wheel parallel to said side plates.

10. In an embossing machine as defined in claim 8, and mounting element height adjustment means formed for simultaneous selective adjustment of the height of both said mounting elements and said shaft and wheel above said working surface.