Method and device for determining the plantar foot shape

Abstract

The invention relates to a device and a method for determining the plantar foot shape by applying a defined spatially resolved force to the plantar foot surface. A plurality of spring elements are arranged substantially in the form of a matrix on a base plate, wherein a spring-elastic component and a measuring device for determining the indentation depth are associated with each element. The device contains a computing unit and is suitable in particular for analysing foot problems and for the individual production of orthopaedic inserts and custom-made shoes.

Description

[0001] Method and device for determining plantar foot shape >

[0002] Description

[0003] The invention relates to a device and a method for determining the plantar foot shape under defined spatially resolved force action on the plantar surface of the foot.

[0004] Traditionally, the shape of human feet is measured using foam impression material. This creates a static, three-dimensional relief of the plantar surface of the feet. Besides the considerable effort involved in performing the measurements, the foam impressions must be scanned to transfer the results to a computer for archiving and further processing.

[0005] Furthermore, there are methods to place one or both feet on a glass plate and scan them from below with a 3D scanner. Another method involves moving mechanical pins against the sole of the foot and saving the impression.

[0006] These methods only allow static measurements of the plantar surface of the foot. Furthermore, it is not possible to apply a defined force to the plantar surface, and in particular to the arches.

[0007] Patent EP 3 171 776 Bl describes an imaging device for accurate, depth-of-field imaging and 3D measurement of spatial objects. A multitude of camera units are arranged in a matrix below the object being imaged, such that the partial recording areas of all camera units combine to form a seamless three-dimensional image. The device is suitable for capturing the plantar surface shape of feet both statically and dynamically during gait. However, in addition to its complex electronic components, the entire device is not capable of applying a defined force to the planar surface of the foot and the arches while standing or walking.

[0008] The invention is based on the objective of determining the plantar surface shape of feet during standing and walking / rolling, using a device and a method of the aforementioned type, with minimal electronic, mechanical and time expenditure, while simultaneously introducing a defined variable force onto the plantar surface of the foot and the arches of the foot.

[0009] This problem is solved by a device having the features of claim 1 and a method according to claim 11. Advantageous further developments of the inventive concept are the subject of the dependent claims.

[0010] The invention proposes arranging a plurality of spring elements, essentially in a matrix, on a base plate. Each spring element is associated with a spring-elastic component and a measuring device for determining the indentation depth. All measurement results are transmitted simultaneously or sequentially to an evaluation computer. (The terms "spring element" and "spring-elastic component" are used synonymously below.) The device can be designed as either a flat and rigid measuring plate or a flexible measuring mat for insertion into shoes.

[0011] To determine the biomechanical properties of the arches of the feet, it can be advantageous if the spring stiffness of all or some parts of the spring elements can be changed from outside the device.

[0012] The spring-elastic components can consist of individual elastic and / or compressible bodies or be formed from a continuous mat-shaped body.

[0013] In one embodiment, the spring-elastic components, or at least parts thereof, can consist wholly or partially of a fluid chamber and be filled from the outside with air or a liquid to change the spring stiffness.

[0014] To determine the indentation depth of the spring elements, optical distance measuring devices can be used between the measuring surface and the base plate. For each element, a light source can be positioned in the area of ​​the measuring surface and a light receiver in the area of ​​the base plate, or vice versa. The respective spring-elastic component can be transparent or contain a recess, so that the indentation depth can be determined via the light intensity, which, as is known, decreases with the square of the distance between the light source and the receiver.

[0015] Alternatively, cameras and, if necessary, light sources can be arranged in a matrix near or beneath a transparent base plate. The spring-loaded components can have recesses, and optical marking patterns can be provided on the underside of the measuring surface, allowing the distance to the cameras to be determined using image processing.

[0016] The use of resistive measurement methods is also possible. In this method, the spring-elastic components can consist of a compressible elastomer whose conductivity changes, whereby the distance from the measuring surface to the base plate is determined via a resistance measurement, providing information about the indentation depth.

[0017] Furthermore, measurement methods for determining the indentation depth can be used with magnetic fields. Preferably, ferromagnetic foils or bodies are associated with the spring elements in the area of ​​the measuring surface, which, when the spring-elastic components are loaded, approach the Hall sensors or induction coils attached to the base plate.

[0018] In a preferred arrangement, the measuring distances are determined capacitively, with a capacitor plate positioned near the measuring surface and the corresponding capacitor plate on the base plate for each spring-elastic component. The spring-elastic component forms the dielectric. The plate spacing, changed by the application of force, alters the measurable capacitance. In a particularly preferred arrangement, the capacitor plates on the measuring surface and the base plate are arranged in a row and column configuration, with each intersection forming a measuring capacitor. This allows each measuring capacitor to be sequentially controlled externally. By continuously querying the measured values ​​of all spring elements, dynamic rolling processes can be recorded and analyzed.

[0019] The assignment of the output signals from the measuring devices to the respective indentation depth and the restoring forces of the spring elements can be carried out in a calibration procedure using a measuring punch. In this process, one or more spring elements are simultaneously pressed in at defined distances, the applied forces are measured by a force measuring device, and the values ​​are assigned to the respective measured values. The calibration values ​​determined in this way are preferably read into a storage / computer unit associated with the device.

[0020] Further evaluation then takes place, whereby both the plantar foot shape and the spatially resolved forces acting on it can be output as a three-dimensional representation and / or sections thereof and / or as a two-dimensional colored "heatmap" or a combination thereof.

[0021] The invention proposes a method in which standing tests and rolling trials are performed with different spring constants of the elastic components. For the measurements, the spring constants of a measuring device can be changed, or different devices with preset spring constants can be used. The sinkage depths of the plantar area of ​​the feet under the different spring constants provide information about the condition of the arches and valuable insights for designing the shape and hardness of therapeutic insoles. A particularly advantageous feature is the additional comparison with the results of a pressure distribution measurement device that does not apply any force to the planar arches.

[0022] In a special process, the spring stiffness under the arches of the feet is changed entirely or partially using the device while standing or walking. Continuously recorded measurements are used to determine spring stiffnesses that result in an optimal anatomical shape for the feet.

[0023] The proposed device and method have diverse applications. In particular, physicians and orthotists can use it to analyze foot problems and develop individualized solutions for orthotic insoles and custom-made shoes.

[0024] The advantages and expediencies of the invention will become apparent from the following description of exemplary embodiments with reference to the sketchy and schematic figures. These show:

[0025] Fig. 1 shows an overall view of the device according to an embodiment of the invention.

[0026] Fig. 2 shows an overall view of the device of a further embodiment with fluid chambers.

[0027] Fig. 3 shows a perspective view of the device as a measuring plate or measuring mat.

[0028] Fig. 4 shows a representation of the device with individual elastomer bodies.

[0029] Fig. 5 shows a representation of the device with the foot attached.

[0030] Fig. 6 shows a schematic circuit diagram of the control of the measuring devices.

[0031] Fig. 7 shows a representation of conductive stretchable strips

[0032] Fig. 8 shows a representation of the method with plates of different spring stiffness

[0033] Fig. 9 shows a method for determining an optimal spring rate.

[0034] Fig. 1 schematically shows the device 1 according to the invention, consisting of a measuring plate 1 with a measuring surface 2, the spring elements 3 comprising the spring-elastic components 3a, the measuring devices 5, a base plate 4, and a computing / storage unit 7. The symbolic heel of a foot 6 acts on the measuring surface 2 and presses a portion of the spring elements 3 downwards. All indentation depths are measured via the measuring devices 5, and the results are transmitted to the computing unit 7. In order to measure dynamic rolling processes, the final indentation depths of the spring-elastic components 3a are measured sequentially or simultaneously continuously and at a high measurement frequency.

[0035] Fig. 2 schematically shows the device according to the invention, consisting of a measuring plate 1 with a measuring surface 2, wherein the spring-elastic components 3a are formed from chambers containing air. In a particular embodiment, air or a liquid can be introduced into the chambers from the outside via a control unit 8, thereby allowing the spring stiffness of the elastic elements 3a to be varied. The chambers can be designed separately and connected to each other for the exchange of air or liquid.

[0036] In another embodiment, these consist of tube-like bodies 3a arranged side by side. The number of fluid chambers is not limited to the number of spring-elastic elements. A continuous, planar fluid chamber can also be provided for all spring elements and may include elastic or compressible support bodies.

[0037] Optionally, the individual fluid chambers 3a can be surrounded by an elastic and / or compressible material 3b, so that the spring-like properties result from a combination of fluid chambers 3a and the elastomer 3b. The supply of air or liquid can be controlled via a manual adjustment unit 8a and / or via a computing unit 7.

[0038] Fig. 3 shows the device according to the invention symbolically in a perspective view as a plate-shaped body 1 with a measuring surface 2 and a base plate 4. The device consists of a plurality of spring elements 3 arranged in a matrix. Directly adjacent is a second device 1a with lower height spring elements. In one embodiment, the two devices 1 and 1a can be combined in a single housing. In order for the inventive effect of the spring elements on the planar arch of the foot to occur, the possible indentation depth of the spring elements should be at least in the range of 5 to 10 mm.

[0039] Fig. 4 shows a schematic sectional view of the device 1 according to the invention with the measuring surface 2, a base plate 4, wherein the spring-elastic components 3a consist of individual bodies of a compressible material, for example, foam with low compression set. Instead of foam, structures made of elastic material can also be used.

[0040] The measuring device 9 for determining the indentation depth is shown here as an example for each element 3 as a measuring capacitor with one capacitor plate 9a on the measuring surface and one capacitor plate 9b on the base plate 4. In one embodiment, the spring elements on the upper surface can have pin-like extensions 12. These pins 12 can be guided vertically via recesses 11a in a plate 11 and are in point contact with the plantar surface during measurement. In a particular embodiment, the pins 12 on the measuring surface can be of different lengths in different areas and according to anatomical considerations.

[0041] Fig. 5 shows a schematic sectional view of the device 1 according to the invention with the measuring surface and a base plate 4, wherein the spring-elastic components 3a consist of a continuous planar compressible body, for example made of foam.

[0042] The measuring device 9 for determining the indentation depth is formed as a measuring capacitor matrix consisting of column-shaped conductive strips 9b on the base plate and row-shaped strips 9a on the measuring surface 2. The indented foot 6, shown symbolically, compresses the foam and reduces the measuring distance between the measuring capacitors. In a particular embodiment, the compressible dielectric in a device can be divided into at least two parts, so that a complete foot can be measured with only one device using both a soft and a harder dielectric. For shielding, an elastic insulating and conductive shielding layer 2a is provided on the measuring surface 2. Likewise, an insulating and conductive shielding layer 4b is provided on the base plate 4.

[0043] Fig. 6 shows a schematic circuit diagram of the measuring device for the sequential determination of the indentation depth of all spring elements. Optical, resistive, magnetic, or capacitive sensors can be controlled in a row-by-row or column-by-column configuration to determine the indentation depths. The circuit diagram shows an example of a capacitive measuring arrangement. Here, conductive strips 9b are arranged in a column-by-column configuration on the underside of the measuring surface and in a row-by-row configuration on the upper side 9a. The elastic or compressible dielectric 3 is located between them.

[0044] As an example, a line is supplied with a measurement signal 11 via an electronic switch 10b. The signal is then routed via another switch 10a across the intersecting capacitor surface 12 to the processing / evaluation unit 7. The capacitance of capacitor 12 can be correlated to the indentation depth using a calibration algorithm. By continuously switching switches 10b and 10a, the indentation depths of all measuring capacitors can be determined both statically and during dynamic rolling processes.

[0045] Fig. 7 shows exemplary conductive stretchable strips in top view and as a sectional view for use in the area of ​​the measuring surface in capacitive measuring arrangements with row and column arrangements. A continuous strip 12 preferably consists of a conductive fabric that is stretchable, especially in the longitudinal direction. In a further embodiment, a conductive thread / strand 13a is applied to a stretchable fabric 13 in a tight meandering shape.

[0046] For shielding, an elastic insulating and conductive shielding layer is provided on the measuring surface of the device according to the invention. In an advantageous arrangement, a meander shape cut from a conductive film can be designed such that a meandering conductive layer 14a is connected to an insulating layer 15 as shielding on the measuring surface, and a further meandering conductive layer 14b on the underside is exposed to the measurement signal and is connected to the compressible dielectric.

[0047] Fig. 8 schematically shows a method for determining the necessary restoring forces for the optimal biomechanical design of the plantar foot shape 6, as well as for determining the necessary spring stiffness and restoring forces in the production of orthopaedic insoles. In this method, at least two measurements are carried out with the device 1 according to the invention, using spring stiffnesses 1 and 1a that differ across the entire measuring range or in partial ranges.

[0048] The device can consist of two different devices (as shown in Fig. 3 and described above) or it can include an arrangement according to the invention for adjusting the spring stiffness externally. An additional measurement with a pressure distribution measuring system lb without spring-elastic elements is particularly advantageous. In a particular embodiment, a device includes two or three separate surfaces with different spring stiffnesses, one of which can be a pure pressure distribution measuring device lb. The measurement data from the various measuring devices or settings are read into a comparison unit 12 of a processing unit 7. This unit determines which restoring forces are necessary both when standing and when rolling / walking in order to bring the plantar arches 6 into an optimal position.

[0049] Fig. 9 schematically shows another method for determining the necessary restoring forces on the plantar foot area 6 for the optimal biomechanical design of a plantar foot shape 6a and for determining the necessary spring stiffnesses in the production of orthopaedic insoles. In this method, at least two measurements with different spring stiffnesses are carried out using the device 1 according to the invention.

[0050] The device has an arrangement by which the spring stiffness of the spring elements can be changed externally via a control unit 8. The foot 6 applied to the measuring surface is subjected to different spring stiffnesses via the computing unit 7 and the control unit 8, and the indentation depths of all spring elements io are read out by the measuring devices 5 and transmitted to the computing unit 7. Using a comparison unit 12 integrated in the computing unit 7, the indentation depths are compared, and the spring stiffnesses are determined for optimal biomechanical plantar foot shape 6a and arch support. The embodiment of the invention is not limited to these examples but is also possible in a multitude of variations that fall within the scope of professional practice.

Claims

Claims 1. Device for determining the plantar surface shape of the human foot under static or dynamic spatially resolved defined force action on the plantar surface of the foot, characterized in that the device is designed as a plate-shaped body in which spring elements are arranged in a substantially matrix-like manner under a measuring surface, which are formed from a spring-elastic component and a measuring device for determining the indentation depth, as well as a computing unit connected to the measuring device.

2. Device according to claim 1, characterized in that the spring elements are arranged in a matrix-like manner on a fixed base plate or a flexible base plate and is designed as a rigid measuring plate or flexible measuring mat.

3. Device according to claims 1 and 2, characterized in that the spring elements consist of an elastic or compressible material, which are arranged as individual bodies in a matrix-like manner, or are formed from a continuous mat-shaped body.

4. Device according to claims 1 and 2, characterized in that all or part of the spring elements consist at least partially of a fluid chamber.

5. Device according to claims 3 and 4, characterized in that a control unit is assigned to the spring elements with which their spring stiffness can be changed individually, in groups or as a whole from outside the device.

6. Device according to claims 1 to 4, characterized in that the device includes spring elements of different maximum indentation depths in different local areas.

7. Device according to claims 1 and 2, characterized in that the measuring device determines the indentation depth between the base plate and the measuring surface for each spring element by means of an optical, resistive or magnetic measuring method.

8. Device according to claims 1 and 2, characterized in that the measuring device determines the indentation depth by means of capacitive measuring technology, wherein a capacitor plate is arranged on each spring element on the measuring surface and the second capacitor plate is arranged on the base plate and the spring elements form the dielectric.

9. Device according to claim 8, characterized in that the measuring devices are formed from row-shaped tracks on the base plate and column-shaped tracks on the measuring surface, the intersection surfaces of which each form a measuring capacitor and that at least the column-shaped tracks of the measuring surface have elastic properties along their length.

10. Device according to claims 7 to 9, characterized in that the measuring device measures the indentation depth of the spring elements simultaneously or sequentially and the results are transferred to a computing / storage unit.

11. Method for determining the plantar surface shape of the human foot under static or dynamic spatially resolved defined force action on the plantar surface of the foot, characterized in that a human foot with the full or partial applied body weight stands on or rolls over the measuring surface of the device, that spring elements are pressed in with spatial resolution, and that the indentation depth of each individual spring element is measured and the measured value is transmitted to a computing / storage unit.

12. Method according to claim 11, characterized in that the measurement is carried out on a measuring device as a base plate or as an insole in a shoe.

13. Method according to claims 11 and 12, characterized in that the measurement is carried out several times while standing and / or walking / rolling over the device using different spring stiffnesses of the spring elements and the measurement data are transferred to a computing / storage unit and compared with regard to the indentation depths and spring stiffnesses.

14. Method according to claims 11 and 12, characterized in that the measurement is carried out in several partial steps while standing and / or walking / rolling on different local partial areas of a device, by having different spring stiffnesses or by not including any spring elements.

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