Background of the invention

The most typical loading method of an exercising device is a weight stack consisting of weight plates, which moves vertically under the control of two guide rods. The load is usually selected from the weight stack with a selection pin, which is pushed through a plate and at the same time through a selection rod passing through the deck. When the selection rod is pulled up, e.g. with a cable, the selected weight plate and all the plates on top of it are included in the exercise. The total load of each plate in kilograms or pounds is marked on the weight plates or on the cover in front of them.

This technical solution has been in use for decades and although there has been an effort to develop many alternative methods, this solution is still by far the most used load selection method. The solution is easy to use, technically reliable and inexpensive to implement.

However, the solution is not optimal for rehabilitation use. In rehabilitation use it is crucial that the correct weight for the exercise is used. With the above-mentioned solution, it cannot be ensured that the user has selected the load according to the program. Selection of an incorrect weight may happen on purpose or often also by accident, because it is not always easy to see the printing of the correct plate, e.g. from the top angle.

Making a weight selection is also often difficult. Although the aim is to bring the weight stack within reach of the trainee, it is often in a place where, for example, the movement arms of the device are preventing the easy placement of the selection pin. This requires either reaching for it or the user must select it in advance before settling into the device.

Selecting the weight is also an additional procedure that must be done before the start of the exercise. This makes the training process longer per each exercise machine. The use of a selection pin requires that at least part of the weight stack is visible, which increases the risk that fingers may get caught in the weight stack, for example. The sight of the weight stack can also be embarrassing for the user if they feel that the weight they are using, is embarrassingly small.

Efforts have been made to solve these problems by means of automation, but there are very few methods that work and are in use. One of these is a system, where the weight acts as a pendulum and the weight is adjusted by moving the load further along the circumference. In this solution a beam rotates around an axis, the weight inside moves outwards and inwards in the direction of the beam, causing the magnitude of the torque to change. Although the device is convenient to use, this way of loading is not optimal. The further the load is on the circumference, the greater the inertial force of the mass and thus the nature of the exercise changes substantially. The beam also takes up a lot more space than traditional solutions.

Other automatic load selection methods are used in devices where the load is produced artificially. The most typical are compressed air and electric motors. Although these devices are convenient to use for training, based on research data, the loading methods are worse at producing an optimal loading of the neuromuscular system. So far, no other loading method has proven to be a more effective than gravity.

The present invention solves or at least alleviates all the problems mentioned above. Mass plates can be moved at a speed that is pleasant and efficient in terms of the mass's inertial force. The weight changes automatically very quickly and is available before the user is about to start the exercise.

Summary of the Invention

The present problem is solved by an automatic weight stack comprising a locking element, the locking element being based on a threaded screw, a screw motor for controlling the locking element, a locking piece mounted movably on the threaded screw, and a spindle motor for turning the locking piece. Further the automatic weight stack comprises a weight stack comprising weight plates, wherein the weight plates comprise an opening, which opening is rotated about a central normal of the plane of the weight plate, wherein the weight plates are arranged in the weight stack with the opening of the weight plate alternately rotated clockwise and counterclockwise, for every other weight plate. The weight plates in the weight stack thus forming a unitary opening through the entire weight stack, wherein the locking piece is formed to match the unitary opening of the weight stack allowing for the locking piece to pass through the weight stack and by turning clockwise or counterclockwise for every other plate in the weight stack, locking onto each individual weight plate upon selection in a locking groove formed in the weight stack by the openings of the individual weight plates.

An object of the invention is a method for for controlling weight selection of an automatic weight stack. The method comprising the steps of selecting a desired weight is selected, sending a signal to a screw motor, by means of the screw motor driving a locking piece to a correct height on a threaded screw for the selected weight. Turning the locking piece by a spindle motor or rotary actuator in order to lock on to or underneath a weight plate in a weight stack wherein the weight plates are arranged in the weight stack with the opening of the weight plate alternately tilted right and left, for every other weight plate, the weight plates in the weight stack forming a unitary opening through the entire weight stack and when the locking piece is locked underneath a weight plate releasing the selected weight of the weight stack.

Brief description of the figures

Figure 1 shows an automatic weight stack according to the invention with only one weight plate.

Figure 2 shows an embodiment of the weight plates and one example of an opening in the weight plate.

Figure 3 shows the lower end part of the automatic weight stack in detail. Detailed description of the Invention

The invention is below described in detail with references made to the figures.

The invention is based on a locking element moving along a threaded screw, or a threaded rod, which is intelligently and accurately controlled by a screw motor. After the user has selected a weight, the motor drives the locking piece to the correct height, after which a separate spindle motor or rotary actuator turns the locking piece to settle under the selected weight plate. The screw motor is then activated to pull the locking piece tightly against the upper weight plate, thus eliminating any slack in the stack of weight plates. After that, the user may begin the exercise with the desired load.

In figure 1 a preferred embodiment of the structure of the device is shown. A threaded screw or rod 1 runs down the center of the plates 2 of a weight stack. On the threaded screw a locking piece 3 is mounted on the screw. The locking piece is threaded on the inside to match the threading of the threaded screw, thus allowing for the locking piece to be moved up and down the threaded screw. A screw motor is used to drive the threaded screw, i.e. rotating it in either direction. By rotating the screw by means of the motor the locking piece either rises along the threaded screw or ascends along it. According to one embodiment the system is fast and the locking piece may be moved at a speed of about 25mm/s, in some cases at a speed of even up to 50mm/s. The threaded screw has a low enough pitch in order for it to be self-locking. In other words, during training, secured separately or held against, and the screw will stay securely in place. Guide rods 5 can be seen on both sides of the threaded screw for guiding the weight plates and supporting the structure of the weight stack.

The device may comprise a tube 4 surrounding the threaded screw. The tube comprises longitudinal openings along the length of the screw for allowing for the locking piece to move up and down along the threaded screw. Alternatively, the locking piece may have holes on both sides and stiff bars which go through the locking piece on both sides, and which is used to turn the lock piece. Also, other means for turning the locking piece are possible. According to this embodiment the tube acts as a means to turn the locking piece in order to lock onto a weight plate. A spindle motor or rotary actuator is in this embodiment used to turn the tube instead of the locking element itself.

Figure 2 shows to individual weight plates 11 according to the invention. The geometries of the openings 12 of the end plates may wary and are not restricted to the form shown in the figure, the shape in the figure is one possible form to be used. The opening of the weight plate may be selected such that when two weight plates are stacked on top of each other an opening extending through both plates is formed, but additionally a space should be formed by the opening of the individual weight plate which is not shared by the other weight plate. This allows for an opening forming between each one of the weight plates, i.e. a locking groove, wherein the locking piece 2 can lock on when turned. Optionally the opening has an elongated form. The advantage of this solution is that no gaps or grooves need to be made in the individual plates for the locking piece to lock onto. By arranging the individual weight plates alternately in alternating directions, allows for the locking piece to have a space the entire thickness of the weight plate to turn into.

Preferably the opening in the weight plate is rotated about a central normal of the plane of the weight plate. The plane of the weight plane being defined by the length and the width of the plate. The weight plates are arranged in the weight stack with the opening of the weight plate alternately rotated clockwise and counterclockwise, for every other weight plate. In this manner when the weight plates are placed alternately with the openings in opposite directions, the desired space between the weight plates if formed.

In other word, the openings of the weight plate are to be formed in such a way that they when stacked on top of each other form a uniform opening through the entire weight stack, which opening is smaller than the opening of an individual weight plate, thus allowing for a locking piece to be locked in under each individual locking plate upon selection. Figure 3 shows the lower end part of the automatic weight stack in detail. The automatic weight stack according to the invention further comprises a locking mechanism which comprises a locking piece at the lower end of the threaded screw and a locking plate fixed underneath the weight stack. The locking mechanism is used for locking the entire weight stack in place during selection of the weight and releasing the selected weight plates for exercising when the locking piece is locked onto a weight plate in the weight stack. The use of such a locking plate ensures a correct use of the weight stack as when the device selects a weight, the weight stack is locked and cannot be lifted as long as the locking piece is in motion and has not yet moved to the locking position. This is a safety measure to ensure that the weight stack is not damaged if the user tries to start the exercise before the desired load is successfully in place.

According to one embodiment the automatic weight stack further comprises a detection sensor beneath the threaded screw. The detection sensor is used for ensuring that the weight stack is in a lowered position in order for a change of the load to take place.

The screw motor is controlled by intelligent software. Upon the user selecting the desired weight, which may be selected either manually by entering the desired load at a user interface at the exercising machine in question or automatically if any means of individualization and automation is used by e.g. use of chip card or RFID or the like for each user.

According to one embodiment of the invention a RFID-card is used by the user, upon reading of the card at the exercising device, the correct weight is selected by the automatic weight stack, and the user interface indicates when the device is ready for use. For example, a red blinking light may indicate that the device is not ready, and a text Ready or a green light may indicate that the device is ready for use.

The program then controls the screw motor to find the right height according to the input by the user. After finding the correct height, the program then by use of the locking plate locks and tightens the weight stack to form a compact and clatter-free stack. The locking piece is tightened against the upper plate with a predetermined force, and the screw is thus left in a small pretension for the entire exercising period. When removing the weight selection, the pre-tension is removed, and the bottom rotary actuator can turn the locking piece into a position where the screw motor can select different weights by moving the locking piece upwards or downwards along the threaded screw.

The program also controls different situations in which the device could be misused. Also at the bottom of the weight stack a sensor may be placed to detect when the weight stack is in the down position at the end of the threaded screw. The sensor senses when the weight stack is down. When the device selects a weight, the stack is locked and cannot be lifted as long as the locking piece is in motion and has not moved to the locking position.

One object of the invention is also a method for calibration of the automatic weight stack. According to the method a computer program independently identifies the positions of the lowest and highest locking grooves in the weight stack and calculates the mutual distance of each weight plate with a high accuracy.