WO2011021921A1

WO2011021921A1 - Mechanical forearm prosthesis

Info

Publication number: WO2011021921A1
Application number: PCT/MX2009/000084
Authority: WO
Inventors: Luis Armando Bravo Castillo
Original assignee: Luis Armando Bravo Castillo
Priority date: 2009-08-19
Filing date: 2009-08-19
Publication date: 2011-02-24

Abstract

The invention relates to a mechanical forearm prosthesis connected to a hand prosthesis at one end thereof and to the user's stump or to any other element for connecting to the user's body. The prosthesis is further characterised in that it includes a gear motor and a pair of gears orbiting around one another in order to impart the rotational movement to the forearm. The elements forming the prosthesis can be assembled by removable attachment means such as screws.

Description

MECHANICAL PROSTHESIS FOR ANTEBRAZO

DESCRIPTION

Background and field of the invention

The present description relates to the field of human prostheses and more particularly it relates to a forearm prosthesis which can be attached to a hand prosthesis of amputated limbs.

The following documents are known in the state of the art, which in the opinion of the inventor of the present forearm prosthesis represent the closest state of the art.

In the state of the art, for example, Spanish patent 319995 is known, entitled "a forearm prosthesis with mylectric actuation provided with a transistorized amplifier for mylectric currents". It refers to a forearm prosthesis with myoelectric drive equipped with a transistorized amplifier for myoelectric currents. It comprises a plastic housing for fixing to the stump, provided with electrodes to derive myoelectric currents and a friction coupling; It has an amplifier, a circuit that amplifies myoelectric currents, a gear reducer, among others.

Important differences with this system are that in the present invention movements of pronation and supination by means of the forearm motor and gear transmission and which is operated by the forearm motor, while the prosthesis in question, the transmission of movement is achieved by a friction joint and manually.

The present invention comprises a motor for supination and pronation of the forearm regardless of the movement of the fingers; the Spanish patent uses a single engine for the movement of the fingers only; does not provide rotational movement of the forearm.

Another document that provides a solution for a forearm prosthesis is WO 2008155286, which consists of a forearm rotation mechanism which does not include the structural elements included in the present invention such as miniature motors, components for collecting myoelectric signals, Direct coupling gears, nor the coupled wrist in the manner in which it is achieved in the present invention.

In US Patent No. 5,800,572 to Loveall, an arm adapter and hand prosthesis attached to such an "Arm socket and attached hand prosthesis" adapter is described. This patent uses a cable, springs and serrated bars to make various movements and retain the pieces in their position; The present invention does not require such elements.

U.S. Patent Nos. 5,549,712, 4,685,928 and 4,521,924 describe forearm mechanisms. which are not inventions that affect the novelty or inventive activity by not using a technology similar to that of the present invention.

Known prostheses in general are large and complicated in terms of the number of components and their construction.

The present invention overcomes the above-mentioned drawbacks by providing a simple construction forearm with few elements; provides pronation and supination movements and can be adjusted to the length and diameters required in accordance with the missing part of the human forearm; in other words it fits the user's stump. Brief Description of the Invention

The invention provides a mechanical forearm that uses myoelectric technology to activate the forearm drive motor. The forearm for its dimensions and construction materials is a lightweight mechanical device that allows a user to carry it without representing a great effort for it.

The forearm comprises a motor and a pair of straight gears to perform the turning movement of the forearm and therefore of the wrist and mechanical hands. The forearm is used in cases in which the patient suffered the loss of his limb at the level of half of his forearm or upper, it being possible to attach the electronic forearm described here directly to a socket for amputation at the level of the forearm or to a manual or electronic elbow if it was an amputation above the elbow.

The forearm has elements that drive the electrical signals to the motor, which at all times make electrical contact with the mylectric sensors to control the rotation of the forearm. Brief description of the figures.

Figure 1 is an upper right isometric view of the forearm attached to the hand.

Figure 2 is a top plan view of the forearm attached to the hand.

Figure 3 is a right side elevation view.

Figure 4 is a rear view, where straight gears and the arrow of communication with guides are appreciated.

Figure 5 is an exploded view of the forearm of the present invention and of a hand prosthesis to which it is attached.

Figure 6 is a perspective view showing the driver-support of the forearm.

Figure 7 is an exploded view of the driver-support. Figure 8 is an exploded view of the split forearm and driver-support assembly.

Detailed description of the invention

From figure 1 it follows that the forearm 1 is a small entity which can be adjusted in length by means of an adapter (not shown), which by one end holds the forearm mechanism and on the other is attached to the user's stump .

In general, the forearm 1 comprises a motor 2, coupled to a reducer, a gear 3 coupled to the arrow of this motor 2 (Figure 4), the gear 3 has a flat EDM to fit the motor arrow, which is a round section truncated with a plane, the gear and the arrow joined by a prisoner, that is, a small notch or indentation is made on the motor shaft and a prisoner is inserted to prevent the gear from sliding horizontally. Coupled to the gear 3, the gear 4 is placed, which is mounted on the middle communication arrow 5, and is larger in diameter than the gear

3, the middle communication arrow 5 has a common longitudinal axis with the communication arrow with guides 6.

Together with arrow 6, a nylon sheath for tracks 7 is placed on which tracks 7a and their spacers 7b are placed. The motor and gearbox are shown in the different figures such as being a single piece since they are thus obtained in commerce.

As can be seen in figures 5, 7 and 8, the nylon sheath 7, the tracks 7a and the spacers 7b are contained in the divided forearm, which is divided into two parts: the inner forearm 8 and the outer forearm 9 The divided forearm is attached to the wrist 10, by 4 screws, this wrist is attached to the artificial hand 11.

An innovative development of the present invention is the way of joining the forearm and hand, it was found that the best way of holding between them was by means of two joining plates 12, the plates receive a great effort in the transmission of the turning force from the forearm to the hand, so they are fixed to the hand and wrist of the hand by means of at least 10 screws as shown in the attached figures.

Although the wrist 10 is not an anatomical part of the forearm, it will be included in the present invention because it is the part that connects the forearm 1 with the hand prosthesis 11.

It is important to note that the movement of opening and closing of the fingers of the hand is carried out by means of a motor different from that used in the forearm.

The activation of the motor 2 of the forearm is controlled by the tracks 7a, which are connected by means of cables (not shown) to the electronic board that governs the functioning of the prosthesis through the myoelectric stimulation of the patient.

The wrist 10 houses a separate motor for the hand prosthesis 11; however, both the design of this wrist and its form of hand grip are new, allowing the union with the hand 11 to be simpler by using only two plates constructed of any metallic or non-metallic material with sufficient mechanical strength such such as stainless steel, carbon or alloy steel (treated or not to prevent corrosion), aluminum, plastics, etc. and relatively simple screws. Throughout the following description, it should be understood that the use of one material or another, both in this component and in the subsequent ones, does not restrict the scope and main object of the invention which is to provide a low-weight mechanical forearm used as a prosthesis Table 1 provides examples of materials used in the described mode and some variants of them.

The wrist 10 comprises a central hole (Figure 5), sized to house a drive motor for the movement of the fingers and four non-equidistant holes distributed on the periphery of the wrist and parallel to this central hole, the object of These four holes is to hold, by means of corresponding screws, the divided forearm. Two screws will be used for the inner forearm 8 and two for the outer forearm 9. The figures illustrate an angled position of the forearm 1 with respect to wrist 10; however, this inclination or angle may not exist and the longitudinal axes of the components of both the wrist and the forearm will be collinear or they can adopt any angle at the request, taste or need of the user without significantly affecting the design and construction of the forearm or its attachment to the wrist. The connecting screws between the wrist and the divided forearm are introduced from the part of the hand, that is, the internal and external forearms 8 and 9 respectively have threaded holes to receive these screws.

The divided forearm houses inside a set of elements called conductor-support CS (figures 6, 7 and 8) comprising the middle communication arrow 5, the guide communication arrow 6, the nylon sheath 7, the sheath Nylon together with the tracks 7a and their respective spacers 7b and finally two axial bearings 13 to aid in the rotation of the forearm. The forearm can rotate 360 ° in both directions, in pronation or supination.

The divided forearm partially houses the middle communication arrow 5 because this arrow has a portion Dl and a portion D2, Dl has a length on the longitudinal axis of the arrow 5 that is less than the length of D2 in the same direction of Dl (see figures 6, 7 and 8). It is precisely the portion Dl that is housed in the divided forearm. The middle 5 communication arrow also has a internal diameter which is sized to accommodate the communication arrow with guides 6. Once in working position, arrow 5 will follow the movement of arrow 6.

The interior of the divided forearm comprises three different diameters Bl, B2 and B3 (Figure 8). In Bl the nylon sheath 7 and the tracks 7a and their spacers 7b are housed. The tracks are preferably made of copper or some similar conductive material such as bronze or silver or electrocoating thereof. Coinciding with each track, in the nylon sheath 7, and just in the middle of its perimeter, a hole (not shown) is practiced for each of them. These holes serve to introduce in them two conductive cables (not shown) that will transmit the signals coming from the electronic card (s). The cables enter through the grooves 14 (see figures 4 and 7) made in the communication arrow with guides 6, pass through the wall of the nylon sheath for tracks 7 and make electrical contact with the tracks 7a.

Each slot in the arrow 6 houses a cable and each cable passes through a hole in the nylon sheath 7 to be held by its respective track 7a, which in turn will come into electrical contact with elements placed in the corresponding holes 16, which will drive the signals to engine 2 and other components in the hand.

In previous paragraphs it was commented that the forearm divided (once armed) internally includes the diameters Bl, B2 and B3, the first has been explained, B2, that it is the one of greater magnitude, it is used to accommodate Dl and the two bearings 13. When housing the bearings and Dl, the function of B2 is to support the rotation of the forearm in both axial and longitudinal directions. A table with the construction materials used is provided below.

The third diameter B3 is sized so that the diameter D2 of the middle communication arrow 5 passes through it, D2 protrudes from the divided forearm, the object of this projection is to serve as a support for the gear 4 which will be the point of support for the rotation of the forearm-hand set. When the engine is activated, the gear 3 will rotate and, thanks to the motor being attached to the divided forearm 7, by means of the plate 3a, which in turn allows the passage of four screws that go to the motor 2 and four to the divided forearm , two to the internal 8 and two more screws to the external 9, the whole assembly 2, 3, 8, 9, and the hand 10 will rotate around the gear 4.

As mentioned above, when the engine is activated, the gear 3 will rotate, around the gear 4, since the gear 4 is integral with the projection 4a, and the projection 4a, in turn fixedly joins the orthopedic copy (no shown), the assembly will use the user's stump as a center of rotation or, if it is an upper amputation, it will revolve around a joint located on the elbow, whether manual or automatic. In other words, the activation of The motor will cause the gear 3, the forearm 1 and the hand prosthesis 11 to orbit around the gear 4.

The plate 3a is a key part in this movement since it joins, by means of screws, the motor with the external divided forearm. Obviously, the external divided forearm is attached to the internal divided arm, also by means of screws, and both forearms are joined to the hand 11 by means of the joining plates 12.

It should be noted that the gear 4 has a projection 4a (see figures 2, 3 and 5) with an internal diameter and an external diameter, the internal diameter being suitable to rotate tightly around the external diameter of the middle communication arrow 5. At its instead, the outer diameter of the projection 4a of the gear 4 has a diameter such that it fits an adapter that will be fixed to a copy that joins the socket that will contain the user's stump. In this way, and as explained above, as the stump is a fixed point in the patient's body and when it is fixedly attached to the external diameter of the projection 4a of the gear 4, the gear 4 will remain fixed while the forearm-hand assembly artificial spin around this gear 4.

The forearm of the present invention is further characterized by a weight ranging from 185 g and 197 g. This important characteristic imparts a great technical advantage to being a unit of very low weight, so that the movements that the patient carries out with his prosthesis are faster because the load of the The structure has a slight coefficient in relation to the torque developed by the forearm actuator, the power consumption of the motor is minimal and the total load that can be rotated is increased. On the other hand, the total longitudinal is reduced to only 70 mm, which means that it can be adapted to a wide variety of users who have at least 70 mm of amputation above the wrist. Fact that is not reflected in any of the state of the art documents.

Table 1

Claims

1. Mechanical prosthesis for the forearm comprising a motor, a reducer and an exit arrow with the motor being coupled to the reducer and the exit arrow, the prosthesis characterized in that it also comprises:

a gear (3) coupled to the motor arrow (2), a gear (4) that rotates around the gear (3), a middle communication arrow (5) to mount the gear (4), this arrow has an axis Longitudinal common with a communication arrow with guides (6);

a cover (7) placed around the communication arrow with guides (6), to carry the tracks (7a) and corresponding dividers (7b); Y

a divided forearm consisting of the inner forearm (8) and the outer forearm (9).

2. The forearm prosthesis according to claim 1, characterized in that it further comprises two joining plates (12) which are attached at one end to the divided forearm and in the other to a hand prosthesis (11) through of a doll (10).

3. The forearm prosthesis according to claim 2, characterized in that the divided forearm houses in its interior a set of conductor-support elements (CS), comprising the middle communication arrow (5), the communication arrow with guides (6), cover (7), tracks (7a) with their respective spacers (7b) and two axial bearings (13) to aid in the rotation of the forearm.

4. The forearm prosthesis according to claim 3, characterized in that the middle communication arrow (5) has a portion (Dl) and a portion (D2), wherein the portion (Dl) has a length in the direction of longitudinal axis of the arrow (5) which is less than the length of (D2), being (Dl) housed in the divided forearm, the middle communication arrow (5) has an internal diameter which is sized to accommodate the arrow of communication with guides (6).

5. The forearm prosthesis according to claim 4, characterized in that the divided forearm comprises three different diameters (Bl), (B2) and (B3), in (Bl) the nylon sheath (7) is housed with the tracks (7a) and its separators (7b), (B2), which is the largest, is used to accommodate (Dl) and the two bearings (13), the function of (B2) is to withstand the rotation of the Forearm both in the axial direction and in the longitudinal direction, (B3) is configured and sized to correspond to the diameter (D2) of the middle communication arrow (5).

6. The forearm prosthesis according to claim 5, characterized in that (D2) protrudes from the divided forearm, so that the gear (4) and its projection (4a) are mounted on it, this projection (4a) joins fixed form to an orthopedic copy which, in turn, joins the The user's body, both the projection (4a) and the gear (4), are non-mobile elements.

7. The forearm prosthesis according to claim 6, characterized in that the motor shaft has a flat EDM that coincides with a flat EDM in the gear (3) in order to engage one another and thus favor the dragging of the arrow through the gear (3); To prevent the sliding of the gear (3) out of the arrow, a clamping bolt is used with the gear 3 being smaller in diameter than the gear (4).

The forearm prosthesis according to claim 7, characterized in that the communication arrow with guides comprises grooves (14) which are practiced so that along them pass cables that transmit the electrical signals to and from the cards forearm control, these cables are electrically connected to the tracks (7) which in turn are electrically connected with connectors placed in corresponding holes (16) of the external forearm (9), the tracks are preferably made of copper or some conductive material similar such as bronze or silver or electrocoating of them.

9. The forearm prosthesis according to claim 8, characterized in that the motor (2) is connected by screws to the divided forearm through the plate (3a), the wrist (10) is also joined by screws to the divided forearm.

10. The forearm prosthesis according to claim 9, characterized in that the hand prosthesis can be placed at different angles with respect to the longitudinal axis of the forearm prosthesis, wherein the attachment of the joining plates (12) to the wrist (10) and the hand prosthesis (11) is made by means of removable fasteners.