US3082515A - Method for making face guards - Google Patents

Description

March 26, 1963 F. A. RAPPLEYEA ETAL 3,082,515

METHOD FOR MAKING FACE GUARDS Original Filed Oct. 51, 1956 s Sheets-Sheet 1 IN VEN TORS Emmi/wax H. Ra /ai s:

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March 26, 1963 F. A. RAPPLEYEA ETAL 3,

METHOD FOR MAKING FACE GUARDS Original Filed 001:. 31, 1956 3 Sheets-Sheet 2 INVENTORS Mame/(4* A. lav/Puma Gale/Mai. MORG /V JR.

n a Q March 26, 1963 F. A. RAPPLEYEA EI'AL METHOD FOR MAKING FACE GUARDS Original Filed Oct. 51, 1956 3 Sheets-Sheet 3 an/1w 5 mama/v JR.

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United States Patent 3,982,515 METHGD FUR BLAIQNG FACE GUARDd Frederick A. Rappleyea, Oak Park, and Gerard E. Morgan, 31a, Glenview, 11]., assignors to lohn 'lI. Riddeii, Inc., Chicago, 11h, a corporation of lilinois Original application Oct. 31, B56, Ser. No. 619,429, new Patent No. 2,929,1b2, dated Mar. 22, 196i}. Divided and this application Sept. 28, 1959, Ser. 1 0. 847,358 4 Ciainis. (til. 2-i22) This invention relates to an apparatus and to a method for making a face guard, particularly to an apparatus and method for making a resinous tubular face guard having flattened anchor plates at each of its ends for securing it to a helmet having a resinous shell. This application is a division of application Serial No. 619,429, filed October 31, 1956, now Patent No. 2,929,102, issued March 22, 1960, which application was filed as a continuation-in-part of application Serial No. 562,130, filed January 30, 1956, now Patent No. 2,785,406, issued March 19, 1957.

Individuals engaging in certain sports and in certain hazardous occupations are accustomed to the wearing of helmets for guarding against the possibility of accidental injury to the head. A type of helmet which is currently used widely, especially by football players and by aviators, comprises a shell made of a suitable synthetic resin which encircles the head except for the face. Such helmets are generally of such dimensions that when mounted on the head the shell is spaced at a convenient distance from the head and does not contact the head directly but only indirectly through a suspension means located inside the helmet. Various conventional suspension means have been employed, one suitable means being that of US. Patent No. 2,250,275. Such helmet shells generally extend downward at the back to cover the back of the wearers neck to a considerable extent and have dependent jaw sections at the sides which often slope downwardly toward one another to cover and protect the wearers jaws and cheeks. A chin strap which is secured to the two jaw sections and drawn snugly around the wearers chin is generally employed to assist in holding the helmet on the head.

It is apparent that such helmets ofier little protection to the face of the wearer. In the parent application there is described and claimed a face guard of tubular construction and of suitable weight which encircles the wearers face at approximately mouth level. The guard of the parent application is fabricated from a resinous tube and is especially characterized by its high resistance to impact and by having a high ratio of rigidity to weight. It has been found that such a guard offers adequate protection to a wearer of the helmet against accidental blows to the face, especially against blows which are upwardly directed such as are generally encountered in the playing of football. Such face guards are roughly semi-circular in shape and have the ends of the tubular member fiattened and contoured in such a way that when secured in face-to-face contact with the jaw sections of the helmet shell a rigid, strain-free joint is effected and the highly advantageous properties of the resinous materials from which both the helmet shell and the face guard are formed are realized to the greatest extent.

According to the method of the present invention, a face guard, such as that illustrated in FiGURE 1, is formed by first cuttin a suitable length of a suitable resinous tube and heating it at a temperature sufiicient to enable it to be bent and deformed easily but insufficiently high to cause it to soften and lose its form-stability or to decrease appreciably its strength characteristics when again allowed to cool. The degree of heating is, of course, dependent upon the particular resinous com- 3,982,515 Fatented Mar. 26, 1963 position of which the tube is composed. The heated tube is then bent around a suitable form to give its central section the desired degree of curvature and its end sections are collapsed and compressed in suitably located and shaped mold cavities to form anchor plates integral with the central curved section which are flared with respect to one another and contoured on their inner surfaces in desired fashion. The formed guard is then left in the apparatus until it has cooled sul'iiciently for the resinous composition of which it is composed to regain its rigidity and strength characteristics and then removed from the apparatus.

Since the weight of the face guard must be kept as low as possible to avoid discomfort to the wearer and since the resistance of the guard to impact must be as great as possible to afford maximum protection, it is extremely important not only that the resinous tube from which the guard is fabricated be of suitable composition and configuration but that, in the process of forming the face guard from the tube, adequate care be exercised to insure the precise de ree of heating required and the precise desired shaping of the guard without overheating and without excessive or unnecessary working of the resinous composition of which it is composed. If the resin is allowed to cool unduly during the forming operation, excessive strains are set up in the body of resin during the operation and the impact resistance of the face guard will be lowered to a dangerous degree. On the other hand, more than a slight amount of overheating of the composition to counteract cooling during the forming operation interferes seriously with the strength characteristics of the composition and face guards made from such overheated material are practically worthless. For these easons it is essential that the resinous tube be heated uniformly at an appropriate temperature such that it becomes deformable without breaking while still retaining its form-stability and that it then be formed quickly and positively into the desired shape without substantial cooling and that all subsequent deformation or stressing of the formed guard be avoided until the resin has cooled. The apparatus employed should not be complicated or costly and the process should be economical to carry out. The apparatus should also be capable of being used to form face guards in which the anchor plates are reinforced with a section of flattened metal tube as is also described and claimed in the parent application.

The method of the invention can be understood readily by reference to the accompanying drawing wherein, in the interest of clarity, certain features are shown on a somewhat exaggerated scale and wherein FIGURE 1 is a plan view of a face guard which can he made employing the method of the invention; l

FIGURE 2 is an elevation, partially in section, taken along the line Illl of FIGURE 1;

FIGURE 3 is an enlarged sectional view, slightly rotated, taken along the line llI-III of FIGURE 2;

FEGURE 4 is an elevation, partially in section, of a resinous tube ready for heating and forming into the face guard of FIGURE 1 and showing a metal tube in place in each end of the resinous tube for forming a reinforcement for parts of the guard;

FiGURE 5 is a side elevation of apparatus suitable for making the face guard of FIGURE 1;

FIGURE 6 is an elevation, partially in section, taken along the line ViVl of FEGURE 5;

FIGURE 7 is a plan view of a mold base plate of the apparatus of FIGURE 5;

IGURE 8 is an end elevation taken along the line Vlil-/lii of FIGURE 7;

PEGURE 9 is a plan view of a cavity plate of the a paratus of FiGURE 5;

FIGURE 10 is a plan'view of a male mold member of the apparatus of FIGURE FIGURE 11 is a side elevation taken along the line XIXI of FIGURE FIGURE 12 is an end elevation taken along the line XII-XII of FIGURE 10;

FIGURE 13 is a schematic oblique elevation of apparatus suitable for heating a resinous tube prior to its being formed into a face guard utilizing the apparatus of FIGURE 5; and

FIGURE 14 is a sectional elevation taken along the line XIV-XIV of FIGURE 13.

The face guard illustrated in FIGURES 1, 2 and 3 comprises a curved tubular section 24 which encircles at a suitable distance the face of a wearer of a helmet to which the face guard is secured. The curved tubular section 24 merges smoothly at each of its ends into an anchor plate 25 which, employing the apparatus and method of the invention, is formed by flattening a respective end section of the resinous tube from which the face guard is made. The anchor plates 25 are provided with means by which they can be secured to the dependent jaw sections of a resinous helmet shell, eg with holes 20 to accommodate suitable bolts. The curved tubular section 24 of the face guard is generally roughly semicircular in form with its longitudinal axis lying essentially in a single plane although its exact configuration is subject to considerable variation to satisfy different requirements of style, comfort and utility. In some instance it may even be advantageous to form the curved tubular section 24 so that it not only encircles the wearers face but so that it also curves upwardly, or downwardly, from its ends to its central section. In most instances the face guard is secured to the helmet shell in a manner such that it encircles the wearers face at approximately mouth level, although here again considerable variation is possible, depending upon the particular hazards to which the wearer is subjected. The anchor plates are generally contoured and angularly disposed with respect to. one another and to the curved section of the guard so that when properly located and secured to the helmet shell a rigid, essentially strain-free joint between the two is effected. Generally speaking, when a face guard is intended to be secured to dependent jaw sections of a resinous helmet shell which slope downwardly toward one another, the anchor plates 25 are fabricated so that their inner surfaces are flared and diverge from one another both backwardly and upwardly with respect to a wearers face to secure as strain-free a joint between the anchor plate and the jaw sections as possible. It will be apparent, however, that the particular configuration and disposition of the anchor plates can be varied as desired to provide a face guard which can be attached to a helmet shell at substantially any location desired.

Although a preferred modification of the face guard of FIGURE 1, illustrated especially in FIGURE 3, comprises a metal reinforcement for each anchor plate, it will be apparent as the description proceeds that face guards can be made with equal facility using the apparatus of the invention but without the provision of metal reinforcements for the anchor plates. Although it will be apparent that reinforcing of the anchor plates 25 can be effected in any one of several ways, a preferred way is illustrated in FIGURE 4 wherein the resinous tube 29 from which the face guard is to be made is provided at each of its ends with a snugly fitting metal tube 28 of suitable wall thickness and length. The metal tube may be of brass or other deformable metal, preferably of a metal which does not crack or break when the tube is flattened completely by pressure. When the ends of a heated resinous tube provided with tubular metal inserts, as illustrated in FIGURE 4, are flattened to form the anchor plates 25, the metal tube is likewise flattened and, as shown especially in FIGURE 3, provides along the center line of the anchor plate a pair of flat sheets of forcement in the anchor plate is not apparent from visual inspection.

The forming apparatus as shown in FIGURES 5-12, comprises a suitable support, e.g. a rigid support plate 42 of FIGURES 5 and 6 secured as by bolts 43- to permanently rigid members 44. The plate 42 is preferably mounted in a vertical position. A forming member or block 45 is secured to the front side of the support plate 42 as by bolts 46. The forming member 45 can be in the form of a suitably thick plate, the upper surface 48 of which is curved and grooved, as at 47, to provide the contour of the curved section 24 of the face guard. The groove 47, which is usually essentially semi-circular in cross-sectional outline, is dimensioned so that the resinous tube from which the face guard is being formed will lie snugly in it. The apparatus as illustrated and described is positioned so that the axis of the groove 47 lies in a vertical plane. This is of some advantage in the bending of the heated resinous tube into the groove 47 because it permits the ends of the tube to be bent directly downward with no tendency for the tube to fall or roll out of the groove 47. However, the apparatus can be positioned otherwise, if desired, and suitable means provided to prevent accidental dislocation of the resinous tube from the groove 47. In addition, it will be seen that when the curved section of the guard is to be formed with a nonplanar longitudinal axis, as mentioned previously, the longitudinal axis of the groove 47 will deviate from a single plane accordingly.

The lower corners of the forming block 45 are cut away to provide a pair of suitably sloped recessed shoulders, 49 of FIGURE 5, on which are mounted mold base plates 52: which, as will be apparent later, form the bottom surfaces of a pair of mold cavities in which the anchor plates 25 of the face guard are formed. The direction and degree of slope of the shoulders 49 are dependent to a considerable degree upon the particular desired configuration of the guard anchor plates 25. In the modification illustrated in FIGURES 5 and 6, the shoulders 49 are formed with flat surfaces which diverge from one another bot-h downwardly and rearwardly of the apparatus. The rest of the apparatus will be described with respect to such sloping shoulders, it being understood, however, that this is only by way of illustration and that the configurations and degrees and directions of slopes of the shoulders 49 are not limiting except insofar as these factors are determined by the particular face guard which it is desired to form.

The mold base plate 52, shown in detail in FIGURES 7 and 8, is of generally rectangular form, preferably with one sloping edge 5-3 so that the plate fits accurately into the angle between the shoulder 49 and the support plate 42. The mold base plate 52 is secured on the shoulder 49 as will be described presently. The outer surface 50 of the mold base plate 52 is contoured over its central region to conform to the desired contour of the inner surface of the anchor plate 25. It has been mentioned previously that in the illustration given of the face guard each anchor plate 25 is formed with a fiat inner surface. For this reason the outer surface 50 of the block 52 is illustrated as being flat, it being understood, however, that the surface can be contoured in any desirable manner to produce a correspondingly contoured inner surface of the anchor plate 25.

A cavity plate 54 is secured to the outer surface of the mold base plate 52, e.g. by bolts 55 which extend through the plate 52 and engage the shoulder 49 thereby securing both plates firmly in place. The cavity plate 54, shown more particularly in FIGURE 9, forms with the mold base plate 52 a female mold member in which the anchor plate 25 of the face guard is molded. The cavity in the cavity plate 54 is shaped to give the anchor plate 25 its desired form. It is to be noted that the parts so far mentioned are dimensioned and located so that the center of the upper edge of the outer surface of the mold base plate 52 adjoins the bottom of the groove 47 at its termination at the upper end of the plate 52. A formable resinous tube can thus be bent over the forming block 45 in the groove 47 with each of its ends projecting into the mold cavity with essentially no discontinuity in the surfaces supporting its side of shortest radius. This insures there being no roughened section or step where the inner surface of the anchor plate 25 joins and merges with the inner side of the curved tubular sections 24- of the finished face guard even though they may be disposed angularly with respect to one another. This is illustrated clearly in FIGURES ,1, 2 and 3.

The male member of the mold comprises a reciprocal member 56, shown in more detail in FIGURES 10, 11 and 12, which is in the form of a generally flat plate having on its inner surface, i.e. on its surface facing the mold base plate 52, a formed, raised member 57 dimensioned and shaped so as to enter slidably the cavity in the cavity plate 54. The thickness of the raised member 57 is somewhat less than the thickness of the cavity plate 54, the difference determining the thickness of the anchor plate 25. Suitable guide pins 51 are also preferably provided to insure proper functioning of the mold. The male mold member is reciprocated in any convenient way in a direction normal to the outer surface 5b of the mold base plate 52'. In the illustration given this is affected with a conventional hydraulic cylinder 58 fitted with a piston and :a piston rod 64 which is mounted securely on a block 59 which is in turn secured, e.g. by welding, on the surface of the support plate 42. The block 59 is dimensioned and located and its upper surface is sloped in. suitable manner to provide proper reciprocatory motion of the male mold member, which is secured at the end of the piston rod 64. It is understood, however, that operation of the male mold member can be effected in any other suitable way, either by hand or mechanically.

The upper end of the raised member 57 of FIGURES 10, ll and 12. adjacent the end of the groove 47 is contoured on its inner surface so as to have a cavity 62 which faces the mold base plate 52 and which at its extreme upper end is essentially semi-circular so as to contact the outer surface of the resinous tube without deforming it appreciably when the mold is closed. The cavtiy 62 decreases in both thickness and width in a direction toward the center of the raised member 57, preferably forming a smoothly curved surface, so that when the mold is closed the end of the curved tubular section of the face guard is reduced gradually in thickness and broadened to provide a smooth widening and merging of the tube into the fiat anchor plate, e.g. as illustrated in FIGURES 1, 2 and 3.

In operation of the apparatus of FIGURE 5, hydraulic fluid is first admitted under pressure to the hydraulic cylinder 58 through a conduit 63 to retract the piston rod 54 and the male mold member 56, thus opening the mold. A section of a suitable resinous tube of appropriate diameter and wall thickness is then cut carefully to length. If metal reinforcement of the anchor plates of the face guard which is to be formed is desired, suitable metal tubes are inserted in the ends of the resinous tube, preferably with the resinous tube projecting slightly beyond the ends of the metal tubes. The resinous tube is then heated, e.g. in an oven as will be described, to a suitable working temperature at which it can be deformed easily but at which it exhibits essentially no form-instability without the exertion of external force upon it.

One end of the heated tube is then inserted downward into the open mold cavity at one side of the apparatus and the mold closed by admitting hydraulic fluid under pressure through a conduit 65 of the adjacent hydraulic cylinder 58 to extend the piston rod 64 and close the mold. During this operation one of the anchor plates is formed and the resinous tube immediately above the upper end of the cavity plate 54 is pressed snugly without deforming into the adjacent end of the groove 47 in the block 45. The resinous tube is then bent around the forming block 45 so that it lies in the groove 47 and its other end extends into the open cavity of the mold at the opposite side of the apparatus. The second mold is then closed forming the other anchor plate. The thus formed face guard is left in the apparatus with the molds closed until it has cooled somewhat. The molds are then opened and the completely formed face guard is removed after which the anchor plates can be punched or drilled to form suitable holes by means of which they can be attached to a resinous helmet shell.

Although the resinous tube from which the face guard of FIGURE 1 can be fabricated can be heated to the desired degree in any suitable Way, an oven, such as that shown in FIGURES 13 and 14, has been used with entire satisfaction. The oven shown comprises a boxlike enclosure 71 of suitable dimensions, the walls of which are preferably insulated in suitable fashion. A suitable num ber of heating elements, conveniently electric radiant elements 72, are mounted in the upper part of the oven, the elements being energized by conventional means, not shown. In the modification illustrated, especially in FIGURE 14, the heating elements 72 are mounted at the ends of threaded adjustment rods 73 which extend through suitable holes in the top wall 74 of the oven. A pair of adjustment nuts 75 threadably engage each of the adjustment rods '73 on opposite sides of the wall 74- and thus provide means for raising or lowering the heating elements 72. The heating elements 72 can be tied together by a rigid rod 76 to eliminate the possibility of uneven adjustment of the elements upward or downward. An opening 77 is provided in one side wall of the oven to permit the insertion into the oven of tubes to be heated and the withdrawal of heated tubes therefrom.

A suitable number of rollers 78 are located in the lower part of the oven and extend between its side walls in a direction parallel with the opening 77 and at a level slightly below the lower edge of the opening. The rollers are provided with suitable spindles 79 at their ends which extend through opposite side walls of the oven and are mounted rotatively in suitable bushings 82 secured to the outer surfaces of the respective oven walls. The rollers 78 are of such a size and positioned at such a distance from one another that a resinous tube 29 lying in the hip between adjacent rollers will be rotated as the rollers are rotated and thus subjected to even heating all around by the radiant heaters 72 positioned above them.

The ends of the spindles 79 projecting through the bushings 82 on one side of the oven, not shown, are fitted with suitable collars and the other ends of the spindles projecting through the bushings on the other side of the oven are each fitted wtih a suitable sprocket 83, each collar and sprocket pair preventing longitudinal movement of the respective roller within the oven. Rotation of the rollers within the oven is effected by a suitable drive chain 84 which engages one side of each of the sprockets 83 and which is driven in suitable manner, e. g. by a driving sprocket 85 on a rotatable shaft 87 mounted on the side of the oven, the shaft 87 being riven by conventional means not shown. An idler and adjusting sprocket 86 also mounted on a shaft on the side of the oven is generally employed. When driven in this manner, the rollers 78 all rotate in the same direction and a resinous tube lying in the nip between two adjacent rollers is rotated smoothly, continuously and without injury to its surface finish.

The oven just described generally contains a sufficient number of rollers 73 and the rate of heating is adjusted so that the length of the heating cycle is synchronized with the rate of utilization of the heated tubes in forming the face guards. Often several guard-forming units are provided for each oven since it is generally possible to fabricate a guard from a heated tube in less time than it takes to heat the tube uniformly at the temperature at which it can be employed in forming the guard. Easy access to the oven can be had by way of the opening '77 so that when a heated tube is removed for forming into a face guard it can be replaced immediately with a cold tube without stopping the apparatus or interrupting the heating process. By removing the heated tubes in the order in which they were placed in the oven, a uniform heating time for each tube is assured.

Although the face guard of the parent application can be made utilizing the method of the invention from any suitable resinous material, it has been found that certain resinous materials are preferred because of the high ratio of rigidity to weight which a guard made from them possesses. An especially preferred resinous material is obtained by blending together a polyvinyl formal resin, an acrylate resin and natural or synthetic rubber. A tube of this blend having an internal diameter of about inch and an external diameter of about /2 inch had a rigidity factor (E1) of 594 square inch pounds. A face guard prepared in the apparatus and according to the method described from a length of this tube weighing 1.5 2 ounces was non-tiring to the wearer of a helmet to which it was attached and was of more than adequate strength. The ratio of the rigidity factor in inch pounds of the tube to the weight in ounces of the guard formed from it was 390. Corresponding ratios obtained in the case of other guards of nontubular character as well as of guards made from other resinous materials of relatively low impact strength are a great deal lower than this and the guards are of an unsatisfactory nature.

, Impact tests were made on face guards prepared as herein described and on other resinous face guards proposed for use with resinous helmets. The test was performed. by mounting the guard on a resinous helmet and then mounting the helmet on a form corresponding closely to the shape and weight of the human head. The form with the helmet mounted on it was then stood on a flat table below the fulcrum of a pendulum having a heavy metal weight at its lower end. The arrangement was such that when the pendulum was drawn back and allowed to swing free the weight struck the front center of the face guard while traveling essentially in the plane of the curved tubular section of the guard. The impact in foot pounds was calculated from the known mass of the pendulum and weight and from the distance through which the weight traveled before striking the guard. In repeated tests using a face guard formed as herein described from the preferred polyvinyl formal-acrylate-rubber blend, whitening of the forward surface of the guard occurred after repeated blows of 16 foot pounds each by the pendulum weight and was particularly noticeable after about 40 such blows. After a total of about 80 such blows, the guard usually failed by breaking in the center at the point of impact. Other face guards made in the same form using one of several other resinous materials and still others made in different forms using the same resinous material invariably fall after a very few blows of the pendulum weight.

We claim:

1. In a method for forming a face guard for use with a resinous helmet, the steps which include: heating a resinous tube of predetermined dimensions having a high ratio of rigidity to weight'at a temperature to cause it to become deformable without breaking while still retaining 3 its form-stability; inserting one end of the heated tube into a a first open mold; closing the first mold to flatten the end of the tube therein to form an anchor plate; bending the tube around a forming block and extending its 7 other end into the open cavity of a second mold; closing the second mold to flatten the end of the tube therein and .form it into an anchor plate; allowing the tube to cool in the molds; and subsequently removing the cooled, deformed tube from the molds and forming suitable ports therein extending through the anchor plates.

2; In a method for forming a face guard for use with :a helmet having a resinous shell, the steps which include: inserting a tightly fitting metal tube of predetermined length and wall thickness into each end of a resinous tube of predetermined dimensions having a high ratio of rigidity no weight; heating the resinous tube containing the metal :inserts at a temperature to cause the resinous tube to become deformable without breaking while still. retaining its form-stability; inserting one end of the heated tube con taining a metal insert into a first open mold; closing the first mold to flatten the end of the resinous tube and at least a portion of the metal insert containedtherein to form an anchor plate; bending the tube around a forming block and extending its other end containing a metal insert into the open cavity of a second mold; closing the second mold to flatten the other end of the resinous tube and at least a portion of the metal insert therein to form an anchor plate; allowing the resinous tube to cool while still in the molds; and subsequently removing the cooled, deformed tube from the mold and forming suitable ports therein extending through the respective anchor plates.

3. In a method for forming a face guard for use with a helmet having a resinous shell, the steps which include: inserting a tightly fitting metal tube of predetermined length and wall thickness into an end of a resinous tube of predetermined dimensions having a high ratio of rigidity to weight; heating the resinous tube containing the metal insert at a temperature to render it deformable without breaking while still retaining its form-stability; forming the central section of the heated tube into a generally arcuate member of predetermined curvature and an end section of the heated tube containing a metal insert into a generally flattened anchor plate of predetermined configuration wherein the metal insert is flattened to form a pair of joined reinforcing plates located centrally of the anchor plate in face-to-face contact with one another.

4. In a method for forming a face guard for use with a resinous helmet, the steps which include: inserting a section of a thin-walled metal tube of predetermined length into each end of a tubular resinous member of predetermined dimensions having a high ratio of rigidity to weight, heating the tubular resinous member containing the metal tubes at a temperature to cause the resinous member to become deformable without breaking While retaining its form-stability; bending the heated member to form an arcuate member of predetermined curvature; inserting an end of the still hot member into an open mold, and closing the mold to form the end of the resinous tubular member containing the metal tube into a generally flattened guard anchor plate of predetermined configuration reinforced with a centrally located pair of metal plates in face-to-face contact with one another and joined along opposite edges.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. 2. IN A METHOD FOR FORMING A FACE GUARD FOR USE WITH A HELMET HAVING A RESINOUS SHELL, THE STEPS WHICH INCLUDE: INSERTING A TIGHTLY FITTING METAL TUBE OF PREDETERMINED LENGTH AND WALL THICKNESS INTO EACH OF A RESINOUS TUBE OF PREDETERMINED DIMENSIONS HAVING A HIGH RATIO OF RIGIDITY TO WEIGHT; HEATING THE RESINOUS TUBE CONTAINING THE METAL INSERTS AT A TEMPERATURE TO CAUSE THE RESINOUS TUBE TO BECOME DEFORMABLE WITHOUT BREAKING WHILE STILL RETAINING ITS FORM-STABILITY; INSERTING ONE END OF THE HEATED TUBE CONTAINING A METAL INSERT INTO A FIRST OPEN MOLD; CLOSING THE FIRST MOLD TO FLATTEN THE END OF THE RESINOUS TUBE AND AT LEAST A PORTION OF THE METAL INSERT CONTAINED THEREIN TO FORM AN ANCHOR PLATE; BENDING THE TUBE AROUND A FORMING BLOCK AND EXTENDING ITS OTHER END CONTAINING A METAL IN-

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