US2045541A - Last - Google Patents

Description

LAST

Filed NOV. 26, 1955 J2f\ n rf STATES PATENT oFFI E LAST Francis A. Guinivan, Marblehead, Mass, assignor to United Shoe Machinery Corporation, Paterson, N. J., a corporation of New Jersey Application November 26, 1935, Serial No. 51,645

4 Claims.

This invention relates to improvements in lasts and is illustrated herein with reference tolasts for use in making shoes for correcting what is commonly known as pronation of the feet or for preventing feet from becoming p-ronated.

In the condition of the foot known as pronation, the os calcis and the other tarsal bones are displaced from their normal positions by a movement of rotation of the foot about a longitudinal axis in a direction to throw the ankle joint inward and away from a normal position of substantial vertical alinement with the outer longitudinal arch of the foot and thus to lower the inner longitudinal arch of the foot. For the purpose of relieving such a condition of pronation numerous expedients have been adopted such, for example, as the use of arch supporting plates or pads of various kinds intended to restore the foot to normal weight-bearing condition. Such expedients are generally ineffective, however, to restore proper ankle alinement and consequently they cannot be relied upon to afford permanent relief for pronated conditions of the feet. Frequently, also, the plates or pads employed have proved to be injurious to the feet.

I have discovered that pronation of the foot can be corrected or prevented by causing the foot to assume and to be positively maintained in a posture wherein not only is the above-mentioned rotational displacement of the foot and ankle bones entirely eliminated so that the os calcis is restored to an upright position and the longitudinal arch is raised to normal elevation but, in addition, the fleshy part of the lower heel portion of the foot is caused to assume a position of abnormal rotational displacement about an upright axis in a direction toward the inner side of the foot, that is, toward the left side of a right foot and the right side of a left foot. Actually the extent of this abnormal displacement of the heel of the foot is not excessive but it is effective to swing inwardly the lower rear portion of the os calcis and to shift forwardly the inner shelf-like projection thereon known as the sustentaculum tali sufficiently to lock the astragalus in normal position so as positively to insure against a condition of pronation. I have found it practicable to support and permanently retain the foot in the posture referred to by employing a shoe the interior of which is initially shaped to conform with substantial exactness to the contour of the foot in that posture. To shape the shoe as required I make it upon a last having a contour corresponding to that which is to be imparted to the 1 shoe. Such a last, as herein illustrated, has that portion of its bottom surface which corresponds to the bottom of the foot beneath the anterior tarsal bones and the forward part of the os calcis sloping gradually upward from the outer side of the last (i. e., the right side of a right last and the left side of a left last) to the inner side of the last and, in addition, the last has its lower heel portion displaced or swung laterally inward, as compared with a conventional last, relatively to its shank portion, i. e., the portion of the last which corresponds to the shank portion of a shoe. A shoe made on such a last will have, in the interior of its shank and heel portion, a sloping bottom, so constructed and arranged as to tend to support the 0s calcis in a normal weight-bearing position so that the inner longitudinal arch will be maintained in its normal elevated condition and it will also have its lower heel portion abnormally displaced or offset inwardly so as to hold the os calcis in the position of abnormal lateral displacement already described, and thus will hold or look the astragalus and the anterior tarsal bones in their normal weight-bearing positions so that it will be impossible for the foot to roll or rotate in a manner to depress the longitudinal arch and interfere with proper ankle alinement.

In a last embodying the novel features of my invention, that characteristic contour which has been referred to above as the inward lateral displacement of the heel, portion of the last may be otherwise described by reciting that the outer side of the lower heel portion of the last is reduced (as compared with a conventional last) as by cutting away the material thereof to the required extent and in the proper location and that the inner side of the lower heel portion of the last is correspondingly enlarged or built-up. Thus, in the interior of a shoe made on a last having a heel portion so shaped, the lower outer side portion of the heel of the shoe will be offset inwardly as compared with that of the corresponding portion of a normal or conventional shoe and will serve as a buttress for holding the heel of the foot in an inwardly displaced position, or at least continuously urging it toward such a position. This inwardly displaced buttress portion of the interior of the shoe will function also to offset any tendency of the bottom of the foot to slide or slip downwardly along the sloping shank portion of the shoe bottom and thus will cooperate with the latter in maintaining the foot in its proper position. It is contemplated that the heel portion of the last will be laterally displaced or offset more or less and that the shape of the bottom and the sides of the heel portion of the last will be varied more or less according to the condition of the particular foot which is to be treated and, further, that shoes made on different lasts may be employed in which the extent of inward displacement of the heel portions is made progressively less as the extent of pronation and the degree of ankle disalinement diminishes.

In order to accommodate the anterior tarsal bones of the foot in their proper positions (which are positions of outward displacement relatively to their positions in a pronated foot), my improved last is further provided with a protuberant upper surface at its outer side which, as herein illustrated, is convex heightwise as well as lengthwise of the last throughout the greater part of the area at the outer side if its waist or shank portion, i. e., the portion of the last which corresponds to the instep portion of the foot. As illustrated, also, this protuberance extends rearwarde ly into the heel portion of the last to facilitate proper positioning of the os calcis and astragalus. The inner side of the last is also characterized by having a, protuberant surface only slightly less prominent than that of the outer side of the last to provide for the accommodation, in the shoe, of the fleshy inner waist and heel portions of the foot. The forepart of my improved last is or may be normal so far as its outline is concerned but the last has less than the usual amount of toe spring, the forepart of the last bottom having an approximately flat intramarginal tread portion and sloping upwardly and forwardly only at its extreme toe portion so as to provide for natural positioning of the toes of the foot and thus to facilitate the maintenance of the foot in a properly balanced condition with the longitudinal arch elevated.

The invention will now be explained with reference to the accompanying drawing, in which Fig. 1 is a View, in side elevation, of my im proved last;

Fig. 2 is a bottom plan view thereof; and

Figs. 3, 4 and 5 are cross-sectional views taken, respectively, in the planes indicated by the lines III-III, IV-IV and VV of Fig. 1.

i 'As already explained, I provide a shoe having a sloping bottom surface and a lower heel portion which is laterally displaced inwardly, these two features cooperating in supporting a foot in a posture in which the os calcis, while occupying an upright and substantially normal weightbearing position, is urged toward or actually shifted into a position of inward lateral displacement, while the other bones of the foot are supported in substantially normal weight-bearing positions. I employ in the manufacture of such a shoe an improved last Ill which, for simplicity of illustration, is shown herein as a one-piece last, although in practice it will be made collapsible to facilitate its removal from the finished shoe. To adapt a shoe made on the last I0 to fit a foot in a normal weight-bearing position, the rear portion of the last occupies a position of displacement relatively to its forepart which corresponds to a position resulting from rotation of the rear portion of a pronated foot relatively to the forepart thereof about a longitudinal axis in a direction to elevate the longitudinal arch of the foot, i. e., in a clockwise direction viewed from the rear of a right foot and in a counterclockwise direc tion viewed from therear of a left foot. shown, the last ID has a sloping bottom surface [2 in its shank and heel portion for determining the shape of the corresponding surface of the shoe above referred to and the last also has a laterally displaced or offset lower heel portion [4 for determining the shape of the laterally displaced lower heel portion of the shoe. In that part of the bottom of the last which corresponds to the portion of the bottom of the foot that is located beneath the forward part of the os calcis, the sloping surface [2 is inclined upwardly and inwardly at a substantial angle to the horizontal from the outer marginal portion of the last bottom at I6 (where the last bottom is built up so that it is substantially lower than in a conventional last) to the inner side of the last at I8 (where the surface of the last is much higher than in a conventional last). The sloping surface in the shoe bottom which corresponds to the sloping surface l2 of the last bottom is for the purpose of supporting the os calcis in upright weight-bearing position and thus holding the longitudinal arch elevated or, if that arch has been depressed, to raise it into normal position by rotating the tarsal and metatarsal bones upwardly and outwardly or, in other words, in a clockwise direction, Viewed from the rear of a right foot, or in a counterclockwise direction, viewed from the rear of a left foot. Preferably and as illustrated, the sloping bottom surface I0 is not restricted to an area corresponding to that immediately beneath the forward portion of the os calcis but extends forwardly substantially to the vicinity of the ball of the foot to provide for the support of the anterior tarsal bones and rearwardly to a location corresponding substantially to a position of transverse alinement with the bearing or contact point at the base of the os calcis, the highest point, however, being so located as to correspond with a location on the foot which is in transverse alinement with the line of weight thrust. This location may be otherwise described as being in the vicinity of the heel breast line which, in the illustrated last, coincides substantially with the forward edge of the heel plate I 1. As illustrated, the sloping surface and transverse convexity in the heel portion of the last bottom extends approximately two-thirds of the distance across the last bottom in the vicinity of the heel breast line and the longitudinal concavity or arch of the last bottom extends rearwardly from the heel breast line approximately two-thirds the distance to the rear extremity of the heel. The outer boundary of the sloping surface of the heel portion of the last bottom is substantially as indicated at 19 in Fig. 2. It will be noted that substantially two-thirds of the area of the heel portion of the last bottom is thus left without any substantial amount of slope or convexity so that in the shoe the fleshy bottom portion of the heel of the foot will be enabled to adjust itself into proper weight-supporting position. The lower outer marginal portion of the interior of the shoe bottom which is formed by the built-up portion [6 of the last bottom constitutes, in effect, a pocket for accommodating the narrow tread. portion of the foot beneath the outer longitudinal arch or fifth metatarsal bone in the lowered position it assumes when the foot posture made of a novel shape or construction in order to provide for a correspondingly shaped heel portion in the shoe which shall be adapted to cooperate with the sloping bottom portion thereof positively to prevent the recurrence of a pronated condition. By reference particularly to Figs. 2 and 3, it will be seen that the lower heel portion 54 of the last is offset or displaced inwardly as compared with the corresponding portion of a conventional last the contour of which is indicated by dotted lines at 2E3. In other words, the lower heel portion of the last it occupies a position of displacement relatively to the rest of the last which corresponds to a position resulting from rotation of the lower heel portion of a foot relatively to the rest of the foot about a heightwise axis in a direction to swing that portion of the foot inwardly. In making the last this lateral displacement of its lower heel portion is accomplished by operations which include a reducing or cutting away of the material of the last in the lower rear portion of its outer side, as compared with that of a conventional last, and the enlarging or building up of the material of the lower rear portion of its inner side as compared with that of a conventional last. It will be noted that the inward lateral displacement of the lower heel portion of the last results in shortening the distance between the heel and ball at the inner side and lengthening it at the outer side of the last, thereby providing for the better accommodation in the shoe of the corresponding portions of the foot when the latter is postured as herein described.

As a result of using a last having its heel portion shaped or constructed as described the interior formation of the heel portion of the shoe will be such as to bend or displace the fleshy part of the heel of the foot laterally inward, or at least continuously to exert an influence tending to cramp or crowd it toward such a position, in which the os calcis will have been rotated about an upright axis extending through the astragalus, and in which the sustenaculum tali will have been swung forwardly so that its forwardly and downwardly inclined upper surface will wedge itself beneath the complemental portion of the lower surface of the astragalus which it directly supports and thus, so long as the os calcis is maintained in said rotated position, the astragalus together with the anterior tarsal bones will be positively held or locked in normal weight-bearing positions and the line of weight thrust will be substantially over the outer longitudinal arch.

,-. It will be appreciated, however, that this socalled locking action is the result not only of the described formation of the lower heel portion of the shoe but of the cooperation of that portion with the sloping bottom portions of the shank and heel of the shoe and that the shape of each of these portions of the shoe is determined by the respective and correspondingly shaped portions of my novel last upon which the shoe is made.

The illustrated last is also shaped to provide, in the shoe, ample foot-receiving space to accommodate the anterior tarsal bones and the enveloping fleshy part of the foot in the displaced positions they are forced into when the foot is caused to assume a correct posture. For this purpose the last is formed with protuberant upper surfaces which are convex heightwise of the last (as indicated at 22 and 23 in Figs. 4 and 5) as well as lengthwise of the last (as indicated in Fig. 2) throughout substantial portions of the surfaces at the outer and inner sides, respectively, of the waist or shank portions of the last and which also extend rearwardly into the heel portion of the last, as indicated at 24 and 25 in Fig. 3. These protuberant upper surfaces are shaped to correspond with substantial exactness to the contour of the waist and heel portions of the foot when the latter is in normal or correct posture and thus provide for accurate fitting of the shoe upon these portions of the foot so as to assist in securing and maintaining natural positioning of the heel and ankle bones. The shapes of these protuberant portions of the last will be appreciated by comparison with the shapes of the corresponding portions of a conventional last, as

indicated by dotted lines at 26 in Figs. 3, 4 and 5.

The forepart of the last has a conventional contour when viewed in plan, as in Fig. 2, but the last has substantially less than the usual amount of toe spring, the forepart of the last bottom having an approximately flat intramarginal tread portion 28 (see also Fig. 1) and sloping upwardly and forwardly only at its extreme toe portion as at 39. The bottom of the fore part of the last also slopes upwardly and outwardly at opposite sides of the substantially flat tread portion thereof as at 32. This construction insures that the bottom portion of the forepart of the shoe shall be shaped to support the toes of the foot in normal positions.

Having described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

l. A last having that part of its bottom surface which corresponds to the portion of the foot beneath the anterior tarsal bones sloping upward at a substantial angle from the outer to the inner side of the last so that a shoe made on said last will have a correspondingly sloping bottom portion for supporting the tarsal bones including the astragalus and the os calcis in normal weightbearing positions, and having its lower heel portion displaced relatively to its shank portion toward the inner side of the last so that the outer side of the heel portion of said shoe will tend to rotate the os calcis about an upright axis in a direction to swing the sustentaculum tali forwardly to lock the astragalus in normal position and thus to cooperate with said sloping bottom portion of the shoe in the treatment of pronation of the foot.

2. A last having that portion of its bottom surface which corresponds to the portion of the bottom of the foot beneath the forward part of the os calcis sloping gradually upward at a substantial angle from the outer marginal portion of the last bottom to the inner side of the last so that the interior of a shoe made on said last will have a correspondingly sloping bottom portion tending to support the os calcis in an upright weight-bearing position, said last also having its lower heel portion displaced inwardly relatively to the rest of the last thereby adapting the outer side of the interior of the lower heel portion of said shoe to swing the heel of the foot inwardly about an upright axis and thus to cooperate with said sloping bottom portion of the shoe in maintaining the foot in a desired posture.

3. A last having that part of its bottom surface which corresponds to the portion of the foot beneath the anterior tarsal bones sloping upward at a substantial angle from the outer to the inner side of'the last so that a shoe made on said last will have the interior of its bottom surface correspondingly shaped for supporting the longitudinal arch of the foot in raised position, said last having its lower heel portion abnormally displaced inwardly relatively to the rest of the last so that the outer side of the interior of the lower heel portion of said shoe will exert a tendency to rotate the 0s calcis about an upright axis and thereby cooperate with said bottom surface of the shoe in preventing pronation of the foot, and said last also having protuberant upper surfaces which are convex both heightwise and lengthwise of the last throughout substantial portions of the areas of the outer and inner sides of its shank and heel portions.

4. A last having its lower heel portion displaced relatively to its shank portion toward its inner side, and having the bottom surface of its shank portion longitudinally concave and transversely convex and sloping upwardly from its outer marginal portion to the inner side of the last, the highest point of said surface being located at its inner edge in the vicinity of the heel breast line and the transverse convexity of said bottom surface extending from said highest point approximately two-thirds the distance across the last bottom, the last bottom being also longitudinally concave along its inner edge from said highest point rearwardly approximately two-thirds the distance to the rear extremity of the last, and approximately two-thirds of the surface of the heel portion of the last bottom being without any substantial amount of slope or convexity.

FRANCIS A. GUINIVAN.

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