RU2546448C2 - Insole with reduced fretting wear - Google Patents

Abstract

FIELD: personal use articles.

SUBSTANCE: invention relates to footwear industry and is aimed at improvement of insole structure where in the front push phase fretting-wear conditions do not take place; such conditions negatively affect the insole and cause foot chafing. The required conditions are ensured by creation of a depression in the heel-and-waist part of the insole, the depression consisting of two combined surfaces, a spherical frustrum and an inclined plane that are smoothed away at the spot of interfacing. For nonslip effect intensification the inclined surface of the depression is agitated.

EFFECT: increase of the depression volume and its filling with a resilient friction material ensure (apart from nonslip) human body shock absorption in the front push phase.

3 cl, 2 dwg

Description

The technical field to which the invention relates is the footwear industry, namely the design of the main insole, which prevents or substantially reduces the occurrence of fretting wear in the process of wearing shoes.

The level of technology.

Fretting wear occurs between tightly set surfaces, subject to small amplitude cyclic movements of up to 2.5 mm. The wear rate increases with the work of bodies in contact in an aggressive environment, in particular during sweating, at elevated pressures and amplitudes of movement.

In shoe practice, an insole with an almost flat area in the heel is used (Shoe Reference. Mikheeva EA, Morekhodov GA Publisher: Legprombytizdat, 1989, 416 pp.).

Reliance on the heel of the insole occurs during the period of the front shock, which begins when the position of the common center of mass (GCM) of the human body is behind the leg extended forward. The foot of the leg extended forward becomes the heel on the supporting surface.

OTSM along with the forward movement also makes a vertical movement.

The kinematic characteristics of a person between the longitudinal axes of adjacent limb segments are measurable (the so-called inter-link angles). A characteristic feature of the graphs of these angles is a stable periodicity.

When walking, a person interacts with the supporting surface, and force factors arise. When placing a shod foot on a supporting surface, the angle between them is 30 ° and one would have to climb to the same angle of the heel of the foot so that the heel of the foot moves relative to the insole of the foot, while still overcoming the frictional force that arises between the heel (with or without toe) sock) and insole material.

The most dangerous moment when conditions arise for the heel (toe) to shift relative to the insole will be when the angle of heel rise along the insole is close to zero. This moment occurs when the heel part of the shoe lies flat on the supporting surface and the angle between the OTsM and the heel in contact with the supporting surface is approximately 15 °, while the horizontal force load on the supporting surface is 26% of the vertical force (Utkin V.L. Biomechanics of physical exercises. - M .: Education, 1989 - 210 p.). The same largest force, but oppositely directed, will act from the side of the supporting surface on the heel.

Based on the parallel force transfer theorem, the horizontal force moves from the contact zone of the heel with the supporting surface to the contact zone of the heel with the insole.

In order to comply with the conditions of non-slip of the heel (toe) on the insole, it is necessary to provide the friction force Ftr between them, greater than the horizontal driving force Fdv, equal to 26% of the vertical force. The friction force Ftr is found as the product of the normal force N (vertical force in the case under consideration) and the friction coefficient µ, i.e. Ftr = N * µ. The condition of non-slip of the heel (toe) on the insole is met when

Ftr> Fdv

Nµ> 0.26N

µ> 0.26

The value of the coefficient of friction is determined by the materials of the friction pairs given in the table.

Friction coefficient of friction pairs of materials Insole material Sock material foot wool cotton nylon Bakhtarma Faux Leather 0.48 0.41 0.34 Cardboard cardboard 0.36 0.35 0.22 Leather 0.17 0.21 0.11 0.17

As can be seen from the table, a number of friction pairs have a friction coefficient µ below 0.26, which means slipping of the foot relative to the insole at the considered time and the occurrence of fretting wear.

It should be noted that for a number of friction pairs with a friction coefficient p greater than 0.26, there is a certain probability of slipping conditions due to dispersion of the distribution densities of the friction coefficient and the driving horizontal force.

The possibility of slipping increases with the natural release of foot sweat. In this case, dry friction between the heel of the foot and the insole material is replaced by semi-liquid or even liquid, in which the friction coefficient decreases sharply, which ensures the heel of the foot is displaced relative to the insole.

The value of the relative displacement does not exceed several mm, since there is a constructive elastic limiter in the beam part of the shoe and the rise.

The displacement takes place with a sufficiently high pressing force of the heel of the foot and insole, approaching the force of the nose weight mg (m is the mass of the nose, g is the acceleration of gravity).

Although the relative movement of the heel along the insole is minimal, it is repeated at every step. The combination of these impact factors (load and displacement) is defined as fretting wear of the contacting pairs of bodies.

The required technical result

It is necessary in the forward push phase during walking to ensure that there is no displacement of the heel of the foot relative to the insole, which is physically achieved if the horizontal driving force throughout the considered phase of the front push is less than the friction force of the pair - the heel of the foot-insole.

The conditions must be met when the foot is in the toe, without the toe, with a dry foot and wet from sweat. If the driving force exceeds the value of the friction force, fretting wear occurs with negative consequences for both the foot and the insole.

SUMMARY OF THE INVENTION

To provide the invention with a technical result — elimination or, in any case, reduction of the possibility of creating conditions for the appearance of fretting wear, which occurs at a significant pressure between the bodies making up the friction pair and their slight displacement, within a few mm, relative to each other, it is proposed change the geometry of the insole in the area of its contact with the heel of the insole.

The reason for choosing the aforementioned zone is that in the pressure planograms in this zone the maximum pressure of the heel of the foot in the front push phase is formed and this portion of the foot carries the entire supporting load.

Insoles in the heel part from the front surface side are cut or molded in the form of a heel with the central part in the form of a truncated sphere with a radius of the upper circular surface of 0.18 D and a height h of 2-3 mm. At a distance equal to 0.27 D from the extreme point of the sphere corresponding to the beginning of the insole construction, the truncated sphere passes into an inclined plane starting at a depth of h = 2-3 mm and rising to the upper surface of the insole at an angle β = 6-10 °, partially captures not only the heel, but also the gel part. The width of the inclined plane corresponds to the footprint in the section of 0.27 D and is equal to 0.31 D.

At the moment of the most probable slipping of the heel of the foot along the insole, when the insole is almost horizontal, in the proposed design the heel of the foot with its front part will be on the inclined plane of the recess, directed to the top at an angle β = 6-10 °. To carry out the calculation, we take the average value of the angle β = 8 °. The angle between the JCM and the vertical α, where the heel is mounted on the horizontal surface of the insole, is 15 °.

The resulting force Frez is decomposed into two components - the normal force N and the driving force Fdv. From the book above B.C. Utkina is known that the ratio between the forces Fdv and N is 0.26, then the resulting force in relative units will be 1.035. When setting the heel on an inclined plane of the proposed insole design, the resulting force Fres does not change either in direction or in magnitude.

The angle between the resulting force Fres and the normal N ″ to the inclined surface is γ = α-β = 15 ° -8 ° = 7 ° and N ″ = FresCos7 ° = 1.027. Then the driving force on the inclined surface will be F ″ dv = Fresin7 ° = 1.035 * 0.122 = 0.126.

If we compare the magnitude of the frictional force that arises between the heel (toe) - insole, Ftr = N * µ with the value of F ″ dv, then we see that in all the above cases, except for a pair of capron-insole skin, slipping of the heel relative to the insole will not even occur with an average angle of inclined plane.

Changing the angle of inclination of the repulsion plane to 8 ° expands the lower limit of the coefficient of friction to µ = Fdv / N ″ = 0.126 / 1.027 = 0.122.

The technical result is enhanced if the inclined surface of the insole recess in the heel part is ruffled (roughened). In this case, the friction coefficient increases to a value of µ = 0.41. Then the frictional force between the heel of the foot and the insole will obviously be greater than the driving force, and slipping of the heel along the insole will not take place.

The proposed design of the insole with reduced fretting wear is intended for shoes made of leather, cardboard, and other materials, consisting of a flat plate with a thickness of more than 4 mm, having the configuration of the track of the shoe, characterized in that the insole in the heel and partially gel part has a recess representing the connection of a truncated sphere and an inclined plane, the truncated sphere centered at the intersection of the 0.18D section and the longitudinal axis of the heel of the insole has a circle radius in the upper plane ohm R = 0.18D, at a distance of 0.27D, the circle ends with the intersection of its frontal transverse plane at a depth of h = 2-3 mm. The spherical surface of the recess is transformed by means of the mating surface into an inclined plane, which rises to the insole surface at an angle β = 6-10 °, the inclined plane is initially located on the heel part and then may partially capture the portion of the gel part of the insole.

The inclined plane in the heel-gel part of the insole is tousled to increase the coefficient of friction, thereby creating the condition for the heel part of the foot to slip on the insole.

The insole has an enlarged 1.15-1.2 times the volume dimensions of the heel recess in comparison with the originally marked, filled with elastic friction material, which is compressed by the force of pressing the heel against the insole recess and assumes the dimensions of the initial without expansion of the recess, which ensures setting in the forward push phase heel on the insole without slipping and at the same time cushioning the front push.

Summary of the invention

The problem to which the claimed invention is directed is to exclude the phenomenon of fretting wear that occurs in the phase of the front push when the MTC of the human body is located behind the supporting foot, which is carried forward, resting on the heel with its heel part.

The working conditions of the heel of the foot without slipping relative to the upper surface of the insole is possible only if the driving force applied to the heel is less than the friction force arising between the contacting surfaces of the foot (toe) and the upper surface of the insole.

Due to the variety of materials used for socks, as well as materials and coatings on the upper surface of the insole, there are friction pairs for which the slip conditions are violated and the foot slips relative to the insole with each stop in the front push phase in the limiter lacing, vamp, etc.

Slippage with small displacement under pressure on the contacting surface by the dynamic mass of the human body causes fretting-wear of the contacted steam-abrasion on the foot and the insole surface, destruction of the sock material. The elimination of the possibility of fretting wear is carried out by making structural changes to the insole.

In the heel of the insole, a recess is cut out or molded, in shape representing a combination of two geometric figures - a truncated spherical part and an inclined plane, connected by the smooth transition surfaces of one figure to another.

The truncated spherical part is located in the heel of the insole, starts from the rear edge of the insole, has a radius of the upper plane of 0.18D; the center coincides with the center of the heel of the insole, depth 2-3 mm. At a distance of 0.27 D from the rear edge of the insole, the truncated spherical part ends with the intersection with a transverse vertical plane and from the intersection at a depth of 2-3 mm, an inclined plane located at an angle α = 6-10 ° begins, rising to the intersection with the horizontal plane of the insole, which extends on the residual heel of the insole, capturing the beginning of the gel part of the insole. The inclined plane of the recess prevents slipping of the heel of the foot relative to the insole. To enhance the non-slip effect, the inclined plane is tousled, which significantly increases the coefficient of friction of the used materials for sock and skin of the heel of the foot with the treated (tousled) inclined surface.

List of drawings

Figure 1 - The proposed design of the insole with a heel recess.

Figure 2 - Scheme of forces acting upon contact of the heel of the foot with the heel of the insole in the prototype and the proposed design of the insole.

Information confirming the possibility of carrying out the invention

The proposed recess in the heel of the insole can be performed by milling or hot molding.

Description of the construction of the invention in a static state

The proposed design of the insole is an external insole in the form of an ordinary insole, where a recess is made at the location of the heel of the foot, which is the joined surfaces of the truncated sphere 1 (Fig. 1) and the inclined plane 2, which are smoothly conjugated at the junction. The depth of the truncated sphere 1 is equal to h = 2-3 mm. The inclined plane 2 has an elevation angle α = 6-10 °, starting from the point of joining with a truncated sphere at a depth h.

The inclined plane 2 is attached to the truncated sphere 1 at a distance of 0.27D from its beginning, which coincides with the beginning of the insole. The maximum depth of the truncated sphere 1 and the junction with the beginning of the inclined plane is h = 2-3 mm. This range of depth h is selected from the condition of maintaining the stereotype of a person’s habitual walking. The inclined plane 1, located at an angle α = 6-10 °, serves to increase the force that prevents the heel of the foot from sliding in the front push phase. The selected value of the angle α of the inclined surface was determined by the condition for maintaining the heel non-slip along the insole plane.

Inclined plane 2 in order to increase the friction force is tousled.

Description of the action (work) of the insole design

In the phase of the front push of the foot, the heel rests on the insole in the heel region, while the human body MTC is located behind the contacting heel of the foot with the insole.

In the proposed design of the insole, a recess is made in the heel. The recess consists of a conjugated truncated spherical surface and an inclined plane.

The foot at the moment preceding the installation of its entire supporting surface on the insole, in the phase of the front push, gets its heel into the heel of the heel on the insole. Since the OCM is located behind the contact between the heel of the foot and the groove, the resulting force will be directed from the OCM to the inclined plane (Fig. 2). In this case, the normal force N ″ (Fig. 2), perpendicular to the inclined plane of the recess, approaches the direction of the resulting force Fres, and the driving force F ″ dv directed along the inclined plane decreases.

Since the normal force N "increases, the friction force Ftr = µN" will increase, while the driving force F ″ dw will decrease, i.e. these two factors contribute to the expansion of the range of non-slip heel on the insole indentation.

Thus, the possibility of using almost all of the applied friction pairs - the foot (toe) -insole, providing mutual contact without slipping, increases. The tousled surface of the inclined plane increases the slip effect.

In FIG. 2 also shows the decomposition of the resulting force Fres into normal to the horizontal surface N ′ for the prototype and the driving force F′dv. FIG. 2 clearly shows that F′dv> F ″ dv ′ and N ′ <N ″, i.e. with an inclined plane, the possibility of non-slip increases.

Claims (3)

1. The insole with reduced fretting wear intended for shoes, made of leather, cardboard and similar materials, which is a figured plate with a thickness of more than 4 mm, having a track trace configuration, characterized in that on the insole on the front side in the heel and fragmented gel area parts there is a recess, which is a connection of a truncated sphere and an inclined plane, and a truncated sphere with a center at the intersection of the cross section 0.18D (D-foot length) and the longitudinal axis of the heel of the insole has at a distance of 0.27 D, the circle ends with the intersection of its frontal transverse plane, at a depth of 2-3 mm, the spherical surface of the recess is transformed by means of a mating surface into an inclined surface that rises to the front surface of the insole at an angle β = 6-10 °, the inclined plane is initially located on the heel of the insole and then may partially capture the initial portion of the gel part of the insole. 2. The insole according to claim 1, characterized in that the inclined plane in the heel-gel part of the insole is tousled to increase the coefficient of friction, thereby creating conditions for the heel of the foot to slip on the insole in the forward push phase. 3. The insole according to claim 1, characterized in that it has an enlarged 1.15-1.2 times the volume dimensions of the heel-gel recess as compared with those indicated above, which is filled with elastic friction material, compressing the heel of the foot to the size of the recess without expansion, which ensures that the heel of the foot is placed on the insole in the forward push phase without slipping and at the same time depreciates the human body.

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