US2856633A - Method of taking cast of feet in dynamic position and product thereof - Google Patents

Description

Oct. 21, 1958 MURRAY 2,856,633

METHOD OF TAKING CAST OF FEET IN DYNAMIC POSITION AND PRODUCT THEREOF Filed NOV. 9, 1956 wit! 5 INVENTOR ATTORNEYS United States Patent METHOD OF TAKING CAST OF FEET IN DYNAMIC POSITION AND PRODUCT THEREOF Alan E. Murray, Bridgeport, Conn.

Application November 9, 1956, Serial No. 621,226

9 Claims. (Cl. 18-51) This invention relates to a method of taking casts of the feet as well as to the casts produced thereby. The casts are especially adapted for use in the manufacture of shoes molded to fit the contour of the feet.

The art of manufacturing molded shoes is old and was first suggested by me in United States Letters Patent Nos. 2,177,304, 2,332,000 and 2,568,292. As there disclosed molded shoes are made by first taking casts of the feet. Shoe lasts are then made from the casts and finally the shoes are molded on the lasts to faithfully follow the contour of the feet. While molded shoes contoured to the feet have proven commercially successful, it frequently happens that the shoes are not comfortable and have to be reworked or completely remade. Most of the difficulty involves the length of the shoe but the difficulty is not always solved by merely lengthening the shoes and in some cases the toes are cramped even though the shoe is of proper length.

Heretofore casts have been taken with the foot at rest in a so-called static condition with weight supported by the heel of the foot. The difficulty with this is that the resulting cast does not truly reflect the dynamic condition of the feet while walking. For example, in walking the heel is raised to shift the weight to the toes and ball of the foot. In moving forward more and more weight is brought to bear on the toes which press down and elongate just before the foot lifts off the ground. When the foot lifts up, pressure is released and the toes contract back into the so-called static condition. A cast of the foot in static condition does not truly reflect the dynamic condition of the feet in walking and it does not provide room for elongation of the toes each time a step is taken.

In accordance with the present invention, casts are taken with the feet arranged in what is here called the dynamic position. In dynamic position, the heels are raised and held in unsupported condition with weight distributed on the toes and balls of the feet. Since the toes bear weight, they press down and are thereby slightly elongated and since the heels are unsupported, the muscles of the feet are tensed and the feet are locked in set position. Casts made of feet locked in dynamic position show great detail and the cast of the foot so closely approximates the true dynamic condition in walking that molded shoes made with the casts are extremely comfortable and the need for reworking the shoes has been virtually eliminated.

These and other advantages of the present invention may be readily understood by reference to the accompanying drawing in which,

Fig. l is a side view of a foot in position on a support.

Fig. 2 is a view similar to that of Fig. l with the foot arranged in dynami position on the support.

Fig. 3 illustrates the top portion of a cast made in accordance with the present invention.

Fig. 4 is a bottom view of the cast of Fig. 3.

'2 ice Fig. 5 illustrates the formation of the bottom portion for the cast of Fig. 3.

Fig. 6 is a front view of the completed cast of Fig. 5 illustrating how the cast is removed from the foot and Fig. 7 is a sectional view taken on line 7-7 of Fig. 5 which shows the way the top portion of the cast envelops the curved portion along each side of the foot.

In carrying out the process of the present invention foot 10 is positioned on a support 12 with heel 14 resting on a block 16 which is just about as high as an ordinary shoe heel. Block 16 may be made of a terry cloth strip which is folded over to establish the proper height for the individual at hand. With the heel resting on block 16 the weight of the leg is taken. by the heel and the foot is at rest in the so-called static condition with toes slightly contracted. Block 16 is now removed but the heel is maintained in raised unsupported condition so that all of the leg weight is shifted to the ball of the foot 18 and toes 20. In supporting this weight the toes are pressed down against the support which causes them to become slightly elongated. The muscles of the foot are tensed and the foot is thereby locked in a set position which very closely approximates the dynamic condition assumed by the foot in walking.

While a cast of the foot is being taken the individual is seated at all times preferably on the front of a chair (not shown) so that the weight of a substantial portion of the leg may be brought to bear on the front of the foot and if desired the legs may be strapped to the chair to hold them in set position. The person should not be standing up for as explained in my issued Patent No. 2,177,304 the foot in such case is deformed and the cast would be of little value in the manufacture of molded shoes.

Before a cast is taken, the surface of the support may be greased as with a suitable oil to prevent the cast from sticking to such surface. Sand 22 is preferably placed between the toes to avoid undercuts and small rods 24 may be placed in upright position in one or more of the spaces between the toes. As later described these rods provide vent holes which assist in achieving great detail in the bottom portion of the cast. In taking the cast, any convenient material adapted to conform to the contour of the feet to form an impression thereof may be employed. Best results are achieved with an aqueous slurry of plaster, preferably plaster of Paris.

A thick slurry of plaster of Paris is made up usually with cold water and the slurry is applied. to the top and around in under the foot to completely envelop all of the exposed portions of the foot which are not in actual contact with support 12 and the plaster preferably extends up to a point just above the ankle. The plaster mass is then allowed to set. However while the plaster is still soft, it is cut into with a thin blunt instrument such as a knife 25 to form a dividing line 26 so that the cast may be readily separated and removed from the foot when it is set and hard. A portion of the dividing line is obliterated by troweling so that the two halves of top portion 28 of the cast will hold together until they are subsequently removed from the foot. Since top portion 28 of the cast includes an undercut along the curved portion at each side of the foot, dividing line 26 is preferably located in a vertical plane which is parallel to the longitudinal axis of the foot. When thi is done the top portion of the cast may be separated without interference from the undercut. As shown in Fig. 6 best results are achieved by locating the dividing line in a vertical plane which includes the longitudinal axis of the foot.

While the plaster is setting the muscles of the foot are held tense to keep the foot locked in dynamic position with weight supported by the toes and ball of'the f0ot.

Referring to Fig. 4 it will be seen that the top portion 28 of the cast completely enve'lops the heel and a substantial portion of the instep and it is only the flat weight-bearing portion 29 at the bottom of the ball of the foot and toes that are not included in the top portion 28 of the cast. As a result the top portion 28 of the cast forms a positive lock for holding the foot in dynamic position and the foot may be relaxed after the plaster has set without interfering with the casting operation. After the plaster is set which only takes a few minutes, rods 24 are removed and a secand aqueous slurry of plaster is prepared for taking an impression of the weight-bearing surface at the bottom of the front of the foot.

This is most conveniently done by placing the plaster slurry in a pan 30 and by pressing the foot along with the top portion 28 of the cast firmly down into the pan. When the foot is pressed down into the soft ,plaster of pan 30the toes and ball of the foot in resisting the plaster automatically go back into the dynamic weight-bearing position with the toes elongated and the top portion of-the cast serves as a guide for this purpose. In Fig. 5 the bottom heel section of the top portion 28 of the cast is pressed down into the plaster slurry in pan 30 but this is not necessary and all that is required is to get an impression of the flat weight-bearing surfaces at the front of the foot. Any plaster that rides up beyond the rounded portion at the sides of the foot is troweled away as at 31 (Fig. '5) so that the top portion 28 of the cast may be separated alongdividing line 26 without interference from the plaster in pan 30. The mating surfaces between top portion 28 of the cast and the bottom portion 32 will readily separate after the plaster is set since the top portion of the cast will have picked up enough grease from support 12 to prevent it from sticking to the bottom portion of the cast. As before the foot is held in set position until the plaster in pan 30 has hardened to form a bottom portion 32 which completes the casting operation.

The finished cast is removed from the foot by wedging it apart along dividing line 26 as shown in Fig. 6 and as there shown the interior of the cast has great detail. In this connection it is to be noted that the cast accurately defines the curved portions along each side of the foot where the cast is continuous. The junction between the top and botom portions 28 and 32 respectively occurs under the foot where the curved portion meets the Hat weight-bearing surfaces at the front of the foot and as a result there are no undercut lines in the curve that joins the top and the bottom of the foot. As a result the cast forms a smooth and even buttress at the curve which goes all the way around the periphery of the foot and this is an important feature of the present invention which materially contributes to the comfortable fit of molded shoes. Further, since there are no undercut lines in the curved portion of the buttress the casting operation is greatly simplified. Otherwise, great skill is required toget an accurate casting of this portion of the foot especially where the top and bottom portions of the cast are divided by an undercut line positioned at the crest of the curve along the side of the foot as described in my issued Patent No. 2,177,304.

For best results some of the sand is brushed away from the bottom of the toes before an impression of the weight-bearing surfaces at the front of the foot is taken so that the plaster in pan 30 will tend to ride up between the toes and form a so-called crest 34. This crest definitely 'sets the dynamic weight-bearing position of the toes and the ball of the foot and as a result the crest appears in the molded shoes making them exceptionally comfortable to wear. The vent holes 35 in the top portion of the cast left by :rods 24 enable the plaster in pan 30 to rise up and-closely follow the detail of the weight bearing surfaces at the front of the foot.

After the cast is removed from the foot it is later reassembled in known manner to make a positive 'sho'e last which is thereafter used for the manufacture of molded shoes as described in my issued patents.

It will be understood that it is intended to cover all changes and modifications of the preferred form of invention herein chosen for the purpose of illustration which do not constitute departures from the spirit and scope of the invention.

What 'I claim is:

l. The method which comprises the steps of holding the rear portion of the foot in raised unsupported condition applying pressure to the undersurface of the front portion of the foot, applying to the opposite side of the foot and to the undersurface of the rear portion of the foot a material adapted to set into a hard mass which conforms to the contour of the foot, causing the material to harden, removing the'pressure and then pressing the undersurface of the front portion of the foot in a soft mass adapted to harden and form an impression of the undersurface of the front portion of the foot while said hardened mass of material remains on the foot.

'2. The method of taking a cast of the foot in dynamic position which comprises the steps of positioning the foot on a support with the heel in a raised and unsupported condition applying a mass of material to the foot to envelop the exposedportions of the top of the foot, the undersurface of the heel and a portion of the instep, said material being adapted to harden and conform to the contour of the exposed portions of the foot, removing the foot from the support and then applying to the bottom exposed portion of the foot a second mass of. material adapted to harden and form an impression of the bottom-exposed portion of the foot therein.

3. The method of taking a cast of the foot which comprises the steps of arranging the foot in dynamic position on a support with the front of the foot in weight-bearing condition thereon, and with the heel of the foot raised in unsupported condition, applying to the exposed portion of the foot a material adapted to harden and conform to the contour of the foot removing the foot from the support and then in a separate step applying I to the weight-bearing surfaces at the front of the foot a material adapted to harden and form an impression of such weight-bearing surface of the front of the foot' to obtain an impression thereof and complete the cast of the foot.

4. The method of taking a cast of the foot in dynamic position which comprises positioning the foot on a support, raising the heel to bring Weight to bear on the toes and ball of the foot, holding the heel in such raised unsupported condition, applying a plaster slurry. to the foot to envelop all of the foot with the exception of the weight-bearing surfaces, allowing the plaster to dry so that the foot may be lifted with the plaster cast in place thereon and then applying a plaster slurry to the weight-bearing surface at the bottom of the front of the foot to obtain an impression thereof.

5. The method specified in claim 2 which includes the step of placing dry sand in the spaces between the toes before taking a cast of the foot.

6. 'The method specified in claim 2 which includes the step of cutting into the mass of material on the top of the foot while it is still soft to provide a dividing line along a vertical plane which includes the longitudinal axis of the foot so that the cast may be separated along such line to remove 'it from the foot when hard.

7. The method specified in claim 2 which includes the step of placing small rods in upright position in the spaces between the toes in order to provide vent holes in the mass of hardened material.

8. A cast of the foot comprising a top and a bottom portion, said bottom portion having an impression therein; of the weight-bearing surface at the bottom of the front of the foot and said top portion having an impression References Cited in the file of this patent therein Of the remainder Of the fOOt. UNITED STATES PATENTS 9. A cast as specified in claim 8 in which the bottom portion of the cast includes an impression of the flat 2177304 Murray 1939 weight-bearing surface at the bottom of the toes; the 5 FOREIGN PATENTS ball of the foot, and a portion of the instep. 28,656 Great Britain Sept 3, 1908

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