US3025206A - Process of making foot cushioning devices - Google Patents

Description

March 13, 196 w. M. SCHOLL 3,025,206

PROCESS OF MAKING FOOT CUSHIONING DEVICES Original Filed Sept. 12, 1956 2 Sheets-Sheet 1 521E? MAC/AM M fay/044 March 13, 1962 w. M. SCHOLL 3,025,206

PROCESS OF MAKING FOOT CUSHIONING DEVICES Original Filed Sept. 12, 1956 2 Sheets-Sheet 2 EIE. 5

E-Zazzfm Mum/v M Scwozp 3,025,206 PROCESS OF MAKING FOOT CUfifliflNfiJG DEVICES William M. Scholl, 211-213 W. Schiller St, Chicago, lil. Original application Sept. 12, 1956, Ser. No. 609,453,

now Patent No. 2,917,842, dated Dec. 22, 1956. Divided and this application Apr. 3, H58, Ser. No.

1 Claim. Cl. 156-219) This invention relates to improvements in a process of making foot cushioning devices, the invention being highly desirable for the production of various types of foot cushioning devices or appliances including heel seats, full or partial insoles, with or without lifts at judicious or desired locations, callous or bunion treating pads and the like, and various other types of devices for alleviating afflictions of the foot, the devices not being necessarily limited to appliances of the character inserted in articles of footwear rather than attached directly to the foot of the user.

The instant application is a division of my copending application entitled Foot Cushioning Devices, filed September 12, 1956, Serial No. 609,453, now Patent No. 2,917,842, which copending application is directed to and claims the devices produced by the process of the instant application.

In the past, cushioning and corrective appliances for the feet have been produced by many and various processes and methods. In some instances, laminations of insoles or the like were joined together by heat sealing, but in no instance of which I am aware has cushioning material ever been heat sealed to anything else, the heat sealed devices heretofore made for corrective aid to the foot not embodying any cushioning means whatever. Even with such devices, the process of heat sealing was accomplished either in an objectionably expensive manner, and most frequently the heat sealing operation resulted in the provision of an oversize or awkward seam which rendered the appliances unsightly, cumbersome, and frequently ill fitting. It is well known that in a properly constructed shoe, the built-in insole acquires an upward curvature around the margin thereof in the construction of the shoe, and when it is desired to have the cushioning device present a flat surface beneath the foot of the user, some special shaping has to be made to compensate for the shape of the built-in insole, and that could not be accomplished with heat sealed devices made by processes heretofore known.

With the foregoing in mind, it is an important object of the instant invention to provide a process of making foot cushioning and corrective devices, the process embodying the step of heat sealing parts of the device together in such a manner that the resultant heat seal seam is a relatively fine line, and the method can be practiced so as to provide a heat seal seam that is substantially invisible when the device is in position for use.

It is also an object of this invention to provide a process for making foot corrective and cushioning devices, the process of embodying a step of heat sealing parts of each device together in a manner to give the resultant product a shape enabling it to compensate for the upwardly curved side edges of the structural insole of the shoe, and present a relatively flat surface to the foot of the user, in the event the device is in the form of an insole or other appliance for disposition beneath the plantar surface of the foot.

Also an object of the instant invention is the provision of a process for making foot cushioning or corrective devices, the process embodying the step of heat sealing cushioning material to some other material in the making of the device.

hired htates Patent ice Still another object of the instant invention is the provision of a process of making foot cushioning or corrective devices, in which process a plurality of sheets of cushioning material may be connected by heat sealing to a cover sheet or the like.

The invention also contemplates the provision of a process of making foot cushioning and corrective appliances, in which process a thick layer of cushioning material is heat sealed to a thin cover layer by a fine line heat seal seam defining the outer edge of the resultant article.

Another desiderattun of the instant invention is the provision of a process for making foot cushioning and corrective devices, in which process a relatively thick layer of cushioning material is heat sealed to a thin cover layer in such a manner that the cushioning layer is provided with an arcuate margin adjacent the heat seal seam; or, in other words, the cushion layer curves or gradually diminishes in thickness toward a rather fine line heat seal seam.

The process of the instant invention also embodies the novel step of providing foot cushioning or corrective appliances from stock sheets of indefinite size by heat sealing the sheets together in an intermediate location, and in the same operation providing a readily disruptible severance line at the heat seal seam, so that the waste material may readily be separated from the completed article.

The process also contemplates the step of utilizing sheets of material of different'sizes, and heat sealing these sheets together, whereby an added lift of cushioning or other material may be disposed at a judicious location in the device.

The practice of the instant method is extremely economical and results in the provision of devices or appliances that possess substantially all the advantages de sired therein, and many more advantages than were possible to incorporate in such appliances by methods heretofore known. The practice of the instant method therefore results in the provision of a better product than could heretofore be made. Among the advantages possessed by the cushioning part of the device are its light weight, softness, the fact that it conforms and molds to high points of the foot but does not mat or flatten, it gives a continuous properly balanced cushioning effect to parts of the foot at all times with uniform compression and balanced weight bearing, it possesses excellent resiliency, does not press back against the foot although it absorbs the shock from foot contact therewith to a better extent than materials heretofore used, and it is further pervious to air and so possesses ventilative properties. Since the cushioning material preferably has intel-communicating cells, it' not only provides adequate ventilation but also may be medicated with powder or the like.

Among the advantages possessed by the resultant device as a whole may be included washability without shrinkage, quick drying, excellent wearing qualities, and durability, it is non-inflammable, is non-hygroscopic, nonskid, has more than necessary strength, does not discolor, may be provided in various attractive colors, possesses excellent eye appeal, does not age or deteriorate over a considerable period of time, is not affected by perspiration, cleaning fluids, foot acids and the like, has insulating properties, has no inherent odor, is hygienic, and resists fungus and bacteria. The materials that may be used by the practice of the instant invention are also resistant to rot, mildew, oils and greases, alkalis, and most common reagents.

While some of the more salient features, characteristics and advantages of the instant invention have been above pointed out, others will become apparent from the following disclosures, taken in conjunction with the accompanying drawings in which FIGURE 1 is a bottom plan view of an electrode die that may be used in practicing the method of the instant invention;

FIGURE 2 is a fragmentary bottom plan view illustrating a pair of full size insoles made in accordance with the instant invention, with the use of the die of FIGURE 1, and an allochiral die, showing the same prior to removal from the stock material;

FIGURE 3 is an enlarged fragmentary transverse cross-sectional view illustrating the use of the die of FIGURE 1 in the making of an insole seen in FIGURE 2;

FIGURE 4 is a transverse vertical sectional view through a finished insole itself;

FIGURE 5 is a plan view of a foot cushioning appliance of different construction made also by the practice of the instant invention;

FIGURE 6 is a greatly enlarged fragmentary vertical sectional view taken substantially as indicated by the lines VIVI of FIGURE 5, looking in the direction of the arrows;

FIGURE 7 is a greatly enlarged vertical sectional view taken substantially as indicated by the lines VIIVH of FIGURE 5; and

FIGURE 8 is a fragmentary plan view of a cover sheet that may be incorporated with a product resulting from the practice of the instant invention.

As shown on the drawings:

In the practice of the instant invention, insofar as the heat sealing operation is concerned, a known type of electronic heat sealing apparatus is utilized, wherein the material to be heat sealed is placed between a pair of electrodes or dies. One of these electrodes may be shaped to define the desired outline of the resultant article, while the other may be similarly shaped if deemed necessary, or be in the form of a flat plate. The dies or electrodes are usually mounted in a suitable press capable of providing'the necessary pressure. The electrodes send a high frequency current through the material being heat sealed to heat that material above its melting point, and the pressure between the dies fuses the material in the heated regions. The entire heat sealing operation, of course, requires only an extremely short period of time, measured in seconds or fractions thereof.

In the making of a foot corrective or cushioning appliance by way of the instant invention, at least two sheets of materials are used, one being a cover sheet and the other preferably a cushioning sheet. The cushioning sheet is preferably a thermoplastic foam, having the general appearance of foam latex, but a material that not only can be heat sealed but is more shock absorbing than foam latex. While a number of thermoplastic foam materials may be suitable for the purpose, by way of specific example and not by way of limitation, I may mention that a very satisfactory substance is vinyl foam made from a liquid composition generically known as a plastisol. The plastisol is expanded preferably by the use of an inert gas, and then cured in the expanded condition to provide a lightweight structural material which is highly flexible, resilient, and possesses intercommunicating cells. The plastisol may satisfactorily be a dispersion or suspension of polyvinyl chloride resin, or a copolymer in one or more plasticizers selected from a large number of high boiling esters, for example, such as dioctyl phthalate, dioctyl adipate, dicapryl phthalate, etc.

The cushioning sheet is preferably considerably thicker than the cover sheet. The cover sheet may be of material having the same chemical constituency as the cushioning sheet, but is made under a different process to provide a relatively thin sheet or unsupported film. In this instance, the resins and plasticizers may be charged directly into a Banbury mill, and from there pass to a calender which rolls out the finished product. No expansion process is relied upon, so that the covering material will have a density of about lbs. per cubic foot as opposed to the 5 to 7 lbs. per cubic foot for the cushioning material. The covering material may be in any desired color, and may be given substantially any desired external appearance, such as artificial leather, a multi-color, a plain color, a mottled appearance, etc.

In FIGURE 1 I have illustrated one form of die which may be used in the practice of the instant method. The die shown in the drawings is of a shape to provide a full cushion insole for insertion in a shoe or the like. Obviously, the die would have the shape desired in the resultant device. The die is somewhat diagrammatically illustrated in FIGURES 1 and 3, and comprises a backing plate 1 which may be of steel or equivalent material, and a depending die element, generally indicated by numeral 2, which is preferably of brass or equivalently electrically conductive material. The die member 2 is preferably made rather wide as seen particularly in FIGURE 3, and is shaped to provide substantially a knife edge 3 with an upwardly and inwardly sloping surface 4 leading away from that knife edge. In the illustrated instance, there is a sharper slope outwardly of the knife edge 3, as indicated at 5, but the particular shape on the outer side of the knife edge is of no great importance in comparison with the shape of the sloping surface 4 inside the knife edge. The illustrated die is for the making of an insole to underlie the left foot of the user, and it will be understood that an allochiral die will be utilized to provide an insole for the right foot. In the practice of the instant invention, obviously as many dies as may be desired may be utilized in a press at one time.

In the making of the cushion insole selected as one example of a product that may be made by the instant method, it is presumed that the press has a flat platelike lower die. Numeral 6 may indicate either the lower die itself or a buffer of insulating material such as a phenolic condensation product placed upon the electrode plate, if a buffer is deemed necessary. On the top of the plate 6, a sheet 7 of cover material of the character above described is placed, and superposed on that thin cover sheet is a much thicker sheet 8 of cushioning material which, as explained above, is thermoplastic foam. It is not essential that the sheet 8 be on top the sheet 7, as illustrated.

The sheets may be of the same area, but are preferably sufiiciently large for the forming of a number of appliances therefrom, for economical reasons.

In FIGURE 3, the upper die 2 is illustrated just prior to the completion of a heat sealing operation. The developed heat in the thermoplastic sheets will of course be concentrated beneath the knife edge 3 of the die, which defines the ultimate heat seal seam, but some of the heating effect will be dissipated along the inclined face 4 of the die, so that there will be a gradually reducing effect of the heat seal upon the marginal portion of the foam layer 8 inside the knife edge 3.

When the die is pressed downwardly, the layers or sheets 7 and 8 will be fused together immediately under the knife edge 3 in a heat seal seam, which is preferably not noticeably thicker than the thin sheet 7 alone. The thick cushioning layer 8 is compressed during this operation, and a fine line heat seal seam 9 results, defining and outlining a completed cushion insole 10. This heat seal seam 9 also provides a readily disruptable line whereby the finished insole may readily and easily be removed from the scrap material or remainder of the stock sheets 7 and 8. The removal of the finished article from the balance of the stock sheets at the heat seal seam does not result in injuring the connection of the two layers forming the resultant article in any manner.

Now with reference more particularly to FIGURE 4, it will be noted that the gradual reduction of the effect of the heat sealing operation by virtue of the inclined face 4 of the die results in providing a rounded or curvate margin 11 in the cushion layer 8. In other words, the cushion layer has a marginal portion inside the heat seal seam 9 which gradually decreases in thickness toward the fine line heat seal seam. This result is obtained notwithstanding the fact that both layers of material were preferably initially flat. The rounded margin 11 is important in that it permits the resultant insole to lie in the shoe and present a flat upper surface to the foot of the user, the curvate marginal portion effectively compensating for the up ward inclination of the margin of the structural insole in a shoe. Further, this curvate marginal portion renders the actual junction between the cover layer 7 and the cushioning layer 8 substantially unnoticeable, and the heat seal seam itself is smooth and clean and does not cause any unintentional distortion of the device when placed in a shoe or the like.

Preferably, the heat sealing operation unites the two layers only at the bounding edges thereof and these layers are not secured to each other inside the heat seal seam 9. This is indicated by the exaggerated showing of a space 12 in FIGURE 4 between the cover 7 and the cushion layer 8. This arrangement prevents wrinkling of the insole when placed in a shoe, and further prevents an inward pull on the edges of the insole due to pressure on the same by the metatarsal heads or excrescences on the plantar surface of a foot. 1

The practice of the instant invention is extremely simple and economical. It is simply necessary to place the sheets 7 and 8 in position, and bring down the upper die. The heat seal seam and composite tear line are provided almost instantaneously and the layers of the resultant device are joined together positively and durably by the heat seal seam, with the curvate marginal portion on the cushion layer. In short, the complete practice of the instant invention amounts to little more than a stamping operation insofar as time and labor are concerned.

The instant invention may equally as well be practiced with more than two layers or laminations of material. It makes no difference whether the added laminations are like the thin cover layer or like the cushioning layer. Thus, a lift or the like may be added wherever desired in a foot cushioning or corrective device. By way of example and illustration, in FIGURES 5, 6 and 7 I have shown an insole of a fore-shortened type having a projecting portion to underlie at least the base of the great toe while the other toes may project entirely off the insole. This form of device is preferably made of the same materials as above described, the layers being heat sealed together in the same manner as above described, although it will be understood the upper die will have a shape in keeping with the shape of this particular article.

The form of device shown in FIGURES 5, 6 and 7 comprises a thin cover layer 13, and a relatively thick cushion layer or sheet 14 heat sealed together in the manner above described at the bounding edges, as indi-.

cated at 15. The sheets 13 and 14 are of substantially equal area, but are shaped to provide a projection 16 to underlie at least the rear portion of the great toe of the foot. In some instances, it is desirable or necessary to give an added lift to the great toe. To this end, an extra layer of cushioning material 17 may be disposed between the layers 13 and 14, as seen clearly in FIGURES and 6, this layer 17 being of suflicient size to extend within the projection 16 of the foreshortened insole. The lift 17 is of the same character as the cushioning layer 14 and may be freely disposed between the layers 13 and 14 when the heat sealing operation is performed. The lift 17 is preferably retained in position by having its edge caught in the heat seal seam 15, while the inside edge 18 of the lift 17 remains free and unsecured to either of the other sheets. The added thickness of material, such as the lift 17, provides no problem whatever in performing the heat sealing operation, although it might be necessary to increase the die pressure to some extent. The resultant heat seal seam is the same as above described, and a fine line seam is provided nothwithstanding the additional layer of material.

It will be apparent that a lift such as the insert 17 may be provided at any desired or judicious location in a cushioning or corrective appliance made by practicing the instant invention.

In FIGURE 8, I have illustrated a fragmentary section of a cover sheet 19 provided with numerous perforations therein to provide additional ventilation in the finished article; as well as to indicate that regardless of whether or not the cover sheet is perforated, the heat sealing operation is the same. A smooth, even and fine heat seal seam will result due to the fusing of the layers together, and there will be no rough edges, even though the seam passes directly through one or more perforations. Heretofore, when a perforated cover was used and a device stamped out of stock sheets, rough edges were left where perforations were cut, but that cannot happen in the practice of the instant method.

It will be understood that modifications and variations may be effected Without departing fro-m the scope of the novel concepts of the present invention.

I claim as my invention:

The method of making a cushioning appliance, including the step of superposing a thin cover sheet of flexible thermoplastic film, and a substantially thicker sheet of flexible thermoplastic synthetic resin foam, and with a die having a fine line heat sealing working edge comprising an outline of the appliance heat sealing and fusing the sheets together only where contacted by and immediately adjacent to said fine line working edge and thereby simultaneously forming a seam defining the outline of the appliance and providing a readily disruptable fine edge tear line immediately adjacent the heat seal scam, in the heat sealing of the seam gradually reducing the effect of the heat seal inwardly of the seam to provide a rounded margin on the foam sheet gradually reducing the thickness to a fine edge junction with the cover sheet substantially coinciding with said tear line, and then separating the appliance from the remainder of said sheets by tearing the appliance free along said tear line.

References Cited in the file of this patent UNITED STATES PATENTS 2,425,388 Oestricher Aug. 12, 1947 2,631,646 Gannon et al Mar. 17, 1953 2,658,288 Scholl Nov. 10, 1953 2,677,906 Reed May 11, 1954 2,702,769 Alderfer Feb. 22, 1955 2,806,812 Merz Sept. 17, 1957 2,815,306 Wasserman Dec. 3, 1957 2,878,153 Hacklander -Mar. 17, 1959 OTHER REFERENCES Modern Plastics, vol. 32, November 1954, pages 215-216.

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