WO2006075941A1

WO2006075941A1 - Balance and force plate

Info

Publication number: WO2006075941A1
Application number: PCT/SE2005/001978
Authority: WO
Inventors: Stefan Andersson
Original assignee: NDT NEW DEVELOPMENTS TECHNOLOGIES AB
Current assignee: NDT NEW DEVELOPMENTS TECHNOLOGIES AB
Priority date: 2005-01-12
Filing date: 2005-12-20
Publication date: 2006-07-20
Anticipated expiration: 2007-07-12
Also published as: SE526846C2; SE0500081L

Abstract

A balance and load defining plate (1) comprising four sides that extend generally vertical in relation to one another, said sides including a bottom plate (2) and a cover member (8) fastened to the bottom plate (2) for recording movement in three directions of something placed on the cover member (8) and further including recording devices placed within the plate (1). The invention is characterised in that said devices comprise vertical load cells (3) which are placed in mutually spaced relationship on the bottom plate (2) and which are adapted to record movement in a first direction (z); in that said devices also include horizontal load cells (4) which are placed in mutually spaced relationship on the bottom plate (2); in that a bias-free circular component (5) is inscribed centrally between said horizontal load cells (4); in that the circular component (5) is fastened to the cover member (8) on a side that faces towards the bottom plate (2); and in that horizontal load cells (4) and the central circular component (5) are together adapted to record movement in a second direction (x) and a third direction (y) where the first direction (z), the second direction (x) and the third direction (y) are mutually perpendicular to one another.

Description

BALANCE AND LOAD PLATE

The present invention relates to a balance and load determining plate.

A balance and load determining plate is at present used to measure movements of something or someone that lies or stands on the plate. This may be for different purposes. For example, it may be desired to determine the balance of an individual, i.e. movement of the centre of gravity of an individual across the plate over a period of time. It may be so that people who have suffered an injury have a balance problem due to either physical injuries or nerve injuries. In this respect, the plates may be used in balance training during rehabilitation. Software is normally installed in a nearby computer so as to enable deflections on the plate to be recorded and presented on the computer screen.

Although movement can be measured in different ways, measurements are normally required in three mutually relative perpendicular directions, i.e. measurements in the x-direction, in the y-direction and in the z-direction. It is known to use magnetic sensors that utilize the Hall effect for determining plate movement when an individual stands on or moves on the plate.

A known plate of this kind measures movement by using four 3 -force-component sensors. In this case, all four sensors record movement in the x, y and z directions.

Recording the movement of something located on the plate is a complex operation. Each of all four sensors used shall record three movement directions, x, y, z precisely and, furthermore, each direction recorded by an individual sensor shall find accord between the four sensors. This requires a high degree of accuracy in the production of these balance plates, which makes the plates expensive.

Comprehensive calibration of plates that include three force component sensors is also required in order to obtain correct registration of a movement. These calibrations are carried out by a limited number of companies and consequently it is necessary to send the plate away for calibration, therewith denying those who normally use the plate the use of the plate during the time taken for calibration. Known plates are relatively heavy and are hence often placed in one particular spot and allowed to remain there. They are not considered to be readily movable.

Because of their complexity, price and difficulty to move, such plates are used solely in certain professions. The use of balance plates can be considered as being much too limited in relation to their price in order for a larger circle of customers to be interested in acquiring balance plates.

The present invention meets the above aspects.

The present invention thus relates to a balance and load measuring plate that comprises four sides which are generally vertical in relation to each other and which include a bottom plate and a cover member or lid fastened to the bottom plate for recording in three directions movement of something that is placed on the cover member, wherein the bottom plate has recording devices mounted therein. These recording devices include vertical load cells which are placed in mutually spaced relationship on the bottom plate and which are designed to record said movement in a first direction and further include horizontal load cells which are placed on the bottom plate also in mutually spaced relationship. The plate also includes a non- biased circular component positioned centrally between the horizontal load cells, wherein the central component is fastened to the cover member or lid on the side thereof facing towards the bottom plate, wherein the horizontal load cells and the central circular component are adapted to record together movement in a second and a third direction, and wherein said first, second and third directions are mutually perpendicular to one another.

The present invention will now be described in more detail partly with reference to an exemplifying embodiment thereof illustrated in the accompanying drawing in which

Fig. 1 illustrates from above the interior of an inventive balance and load determining plate comprising , inter alia, load cells and a centrally disposed circular component; and Fig. 2 is a side view of parts of the balance and load determining plate.

The present invention relates to a balance and load determining plate 1 that comprises four generally vertical sides that include a bottom plate 2 and a cover member 8 fastened to the bottom plate 2 for recording in three directions movement of something positioned on the cover member 8 with the aid of recording devices disposed within the plate 1. the plate 1 may be produced in different dimensions and sizes, depending on the intended purpose of the plate 1.

According to the invention, each of said devices includes vertical load cells 3 disposed in mutual spaced relationship on the bottom plate 2, as will be seen from figure 1. These cells record movement in a first direction z. The devices also include horizontal load cells 4 which are also disposed in mutually spaced relationships on the bottom plate 2 so as to inscribe a circular non-biased component 5 centrally between the horizontal load cells 4. The circular component 5 is fastened to the side of the cover member 8 that faces towards the bottom plate, and the horizontal load cells 4 and the component 5 together function to record movement in a second direction x and a third direction y, where the first z, second x, and third y directions are mutually perpendicular to one another.

Also fastened to the bottom plate 2 are vertical load cells 3, preferably four in number, where each vertical load cell 3 includes a tongue 12 which yields to a vertically acting load and which includes a strain gauge as shown in figure 2.

The tongues 12 of respective vertical load cells 3 extend from the corners of the plate 1 towards its side edges at an angle a. The angle a is preferably 45 degrees.

According to a preferred embodiment of the invention, the horizontal load cells 4 are preferably three in number and each horizontal load cell 4 includes a tongue 10 which yields in response to a horizontally acting load and which is provided with a strain gauge. The horizontal load cells 4 are mutually placed with a mutual angle b of 120 degrees between the tongues 10 of respective horizontal load cells 4. The central circular component 5 is placed so as to be inscribed between the tongues 10. In a non-biased state, the central circular component 5 abuts with respective tongues 10 although in the absence of any bias.

The load cells 3, 4 may consist of a material which is sufficiently yieldable for the strain gauges to obtain a registration in a response to movement of the load cells 3, 4. The load cells 3, 4 are preferably comprised of a structural steel. According to one preferred embodiment of the invention, a ball 7 is placed between the tongue of the vertical load cells 3 and the cover member 8. The vertical load cells 3 may be provided with a sheet 15 of material, preferably a hard rubber material, fastened on top of the vertical load cells 3, said sheet including a recess in which the ball 7 can rest. The ball 7 is preferably made of a metallic material and when the cover member 8 is fastened to the bottom plate 2 the cover member 8 will lie in abutment with the balls 7.

According to a further embodiment of the invention, the central component 5 is made of a polymer material. It is important that the central component 5 is made of a low-friction material, for example an oil-based nylon, so as to prevent the recording being influenced to any great extent upon movement of the load cells 4. The central component 5 will preferably be moved easily in the x and y directions. The central component is placed so that when the cover member 8 is moved in the x-direction and/or in the y-direction the central component 5 will be moved into contact with one or two of the horizontal load cells 4 causing the cell or cells to record the movement of the cover member 8.

According to another preferred embodiment of the invention, the central component 5 has the form of a ball bearing with balls situated around its periphery.

According to another preferred embodiment of the invention there is placed on the bottom plate a circuit card which functions to record movement with the aid of said load cells 3, 4, strain gauges and the central component 5 through the medium of electric signals. The circuit card will conveniently be connected to a computer for visualization and presentation of the movement.

Because registration is achieved with the aid of a plurality of mutually separate horizontal and vertical load cells 3, 4, the plate can be calibrated quickly and simply. In certain cases, calibration may solely require tarring of the plate 1. The tarring can therewith be carried out locally, i.e. in the place where the plate 1 is located.

Plates 1 according to the present invention can be produced relatively cheaply, therewith opening new marketing areas. The plates 1 can be used for different purposes, hi addition to rehabilitation after suffering an injury, other examples of said areas include training for children that have motoric injuries and in the technical and development training of sportsmen and sportswomen. The following can be added to the list of examples in this respect- registration, development and improvement of the explosiveness that is so important in some sports, and also, for instance, determining the angle of the foot of an athlete as he or she enters the down-tramping phase and the leaping phase when making a jump and where the centre of gravity lies in the foot of the athlete in a given position.

In order to establish and mark the centre of gravity of the athlete's foot or feet, the surface of the foot or the feet that is or are in contact with the plate 1 will preferably be recorded. This can be achieved, for instance, with the aid of a membrane switch that includes many cells and that generally covers the upper surface of the cover member.

A preferred use of the plate 1 is to record the balance of a person with the person standing on one foot. In this regard, the plate 1 is first connected to a computer whereafter there is started up a computer program belonging to the plate 1, from which different kinds of information can be read.

The person concerned then stands on the plate 1 on one foot. The membrane switch in the cover member 8 records the surface of the foot and information is sent to the computer via the circuit card and the computer then processes the information through the agency of a computer program wherewith the surface of the foot is presented on the computer screen. It is normally difficult to discern immediately where the centre of gravity lies in the foot in order to keep a balance, and hence the centre of gravity of the person concerned will initially be moved to some extent. For instance, let us suppose that the person sways or totters to the left and therewith causes the cover member 8 to also move to the left and also downwards, i.e. in the z-direction to some extent. The strain gauges of the vertical load cells 3 will therewith record a downward movement in the z-direction and send this information to the computer program via the circuit card in the plate 1, wherewith the movement information is presented on the computer screen.

The cover member 8 moves sideways to the left at the same time, which movement may, for instance, be both in the x and the y direction. The cover member 8 moves by sliding over the roller bearings 7 placed in the hard-rubber recesses 15 in the vertical load cells 3. As the cover member 8 moves sideways, the central circular component 5 will also move sideways since said component 5 is fastened to the cover member 8 with the aid of a bolt 14 that extends through a bolt receiving hole 6 and a corresponding hole in the cover member 8.

The central component 5 is moved towards one or two of the horizontal load cells 4, wherewith the strain gauges fastened to this horizontal load cells 4 record movement at a particular angle in relation to the horizontal load cells 4. These recordings made by the strain gauges in the x and y directions are sent to the computer program and presented on the computer screen through the medium of the circuit card, which includes an analog-digital converter. The circuit card may communicate with the computer program through wires and cables, or may have wireless communication.

Information as to how the centre of gravity of the foot moves around can be obtained through the medium of these presentations on the computer screen.

Another area of use involves recording the down tramp of the jumper onto the plate 1 and his/her leap from the plate. Assembly of the plate 1 and computer program are the same as that described with reference to the above example. Because the jumper runs up to the high jump bar prior to tramping on and leaping from,, the surface area of the plate 1 will conveniently be sufficiently large to ensure that it will not restrict the down-tramping and leaping area of the jumper.

The high jumper performs his/her normal run up to the bar and tramps down on and leaps from the plate 1. As the jump takes place, the membrane switch in the cover member 8 records the surface of the foot that is in contact with the plate 1. At the same time, movements of the cover member 8 in the x, y and z directions are recorded with the aid of the load cells 3, 4, the strain gauges and the central component 5 when the down-tramping and leaping foot of the high jumper is in contact with the cover member 8 of the plate 1. The centre of gravity can be recorded in the down-stamping phase of the jump and also the force and the angle at which the foot comes down on the plate 1. Changes in the centre of gravity of the foot are recorded from the down-stamping phase to the actual leaping phase together with the explosiveness at which the foot lifts away from the plate 1. The explosiveness of the jumper can be calculated in relation to how quickly the cover member 8 of the plate 1 moves in the leaping phase. The angle at which the foot is lifted from the plate 1 is recorded at the same time. Subsequent to the presentation of this information on the computer screen, the high jumper is able to ascertain whether or not something in his/her technique should be changed in order to maximize the possibility of higher jumps.

It will be understood that the balance and load defining plate of the type described above has many other uses than those exemplified.

Although a number of embodiments of the invention and its usages has been described, it will be understood that the balance and load defining plate 1 comprising the bottom plate 2 that includes the load cells 3, 4, the central component 5, the strain gauges and the balls 7 may be constructed in some other convenient manner without departing from the basic concept of the invention.

The present invention is therefore not restricted to the described embodiments thereof, since variations to and modifications of these embodiments can be made within the scope of the accompanying claims.

Claims

1. A balance and load defining plate (1) comprising four sides that extend generally vertical in relation to one another, said sides including a bottom plate (2) and a cover member (8) fastened to the bottom plate (2) for recording movement in three directions of something placed on the cover member (8) and further including recording devices placed within the plate (1), characterized in that said devices comprise vertical load cells (3) which are placed in mutually spaced relationship on the bottom plate (2) and which are adapted to record movement in a first direction (z); in that said devices also include horizontal load cells (4) which are placed in mutually spaced relationship on the bottom plate (2); in that a bias-free circular component (5) is inscribed centrally between said horizontal load cells (4); in that the circular component (5) is fastened to the cover member (8) on a side that faces towards the bottom plate (2); and in that horizontal load cells (4) and the central circular component (5) are together adapted to record movement in a second direction (x) and a third direction (y) where the first direction (z), the second direction (x) and the third direction (y) are mutually perpendicular to one another.

2. A balance and load defining plate (1) according to claim 1, characterized in that the vertical load cells (3) are four in number and are fastened to the bottom plate (2); and in that each vertical load cell (3) includes a tongue (12) which yields when subjected to vertical load and which includes a strain gauge.

3. A balance and load defining plate (1) according to claim 2, characterized in that the tongues (12) of respective vertical load cells (3) extend at an angle (a) towards the sides of the plate (1) from respective corners of the plate.

4. A balance and load defining plate (1) according to claim 3, characterized in that said angle (a) is 45 degrees.

5. A balance and load defining plate (1) according to claims 1, 2, 3 or 4, characterized in that the horizontal load cells (4) are three in number; and in that each horizontal load cell (4) includes a tongue (10) which will yield when subjected to a horizontal load and which includes a strain gauge.

6. A balance and load defining plate (1) according to claim 1, 2, 3, 4, or 5, characterized in that the horizontal load cells (4) are placed at a mutual angle (b) of 120 degrees between the tongues (10) of respective horizontal load cells (4) and in that said central circular component (5) is inscribed between the tongues (10).

7. A balance and load defining plate (1) according to claim 1, 2, 3, 4, 5 or 6, characterized in that the load cells (3,4) are made of structural steel.

8. A balance and load defining plate (1) according to any one of the preceding claims, characterized in that a ball (7) is placed between the tongues (12) of respective vertical load cells (3) and said cover member (8).

9. A balance and load defining plate (1) according to any one of the preceding claims, characterized in that the central circular component (5) is made of a polymer material.

10. A balance and load defining plate (1) according to any one of claims 1 to 9, characterized in that the central circular component (5) has the form of a ball bearing with balls disposed around its periphery.

11. A balance and load defining plate (1) according to any one of the preceding claims, characterized in that a circuit card is designed to record movement with the aid of said load cells (3,4) through the medium of electric signals from said cells, and in that the circuit card is connected to a computer for visualizing the recording of said movement.