Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/50—Prostheses not implantable in the body
  • A61F2/54—Artificial arms or hands or parts thereof
  • A61F2/58—Elbows; Wrists ; Other joints; Hands
  • A61F2/583—Hands; Wrist joints

Definitions

• the present invention relates to a thumb in a mechanical gripping organ intended to be secured to an amputated lower arm or an amputated hand of an amputee so as to simulate the movements of a human hand.
• the invention furthermore proposes a method for using the said thumb in order to simulate and perform the movements of a human thumb involved in the most important gripping manipulations that a human hand can execute.
• three important gripping operations that the actual hand can perform may in particular be distinguished, in which the movements of the hand and finger elements in these gripping operations become very important so they can be simulated with the help of a prosthesis, so that thereby the same movement patterns can be executed with finger elements when carrying out these gripping operations.
• the important distinguishable gripping operations may be characterised as a precision grip, a power (force) grip and a key (opening) grip.
• An important area to investigate when the human hand executes the aforementioned gripping operations are the movements of the human thumb.
• the thumb is pivoted by a certain angle about its own axis, whereupon the inside of the thumb faces the inside of the remaining fingers.
• the tip of the thumb can touch the tips of the remaining fingers, in particular the tips of the index finger and middle finger, or to touch both the tips of the index finger and middle fingers simultaneously.
• the hand can hold small objects and tools, such as for example a pen or small tools for precision work.
• the thumb is pivoted until it is opposite the remaining fingers, with the inside of the thumb facing towards the latter.
• the power grip is exerted when the fingers are forcibly bent towards the inside of the palm of the hand or towards the facing thumb, whereupon an object can be held with a strong force exerted by the fingers with or without the contribution of the thumb.
• the inward movement in this case involves a direction in which the hand is tilted so that the palm of the hand is bent towards the lower arm, i.e. so that the angle between the palm of the hand and the lower arm decreases.
• outward movements of the hand the outside of the hand is bent towards the lower arm, i.e. so that the angle between the outside of the hand and the lower arm decreases.
• a hand prosthesis should be the same size as a human hand, have a middle hand (metacarpus), fingers and thumb that resemble the corresponding elements in a real, human hand as far as possible as regards length and appearance.
• the movements of the hand elements should follow a natural movement pattern.
• the thumb can only bend from the side towards and underneath the other fingers, and accordingly the other fingers can bend towards the thumb with the side of the thumb facing towards the aforementioned fingers, with the thumb and other fingers in almost the same plane.
• no force can be exerted by the thumb on the inside of the remaining fingers.
• the inside of the aforesaid thumb cannot pivot about its own axis, so that the inside of the thumb faces towards the remaining fingers when the power grip is exerted, and accordingly it is not possible by using the hand according to the aforementioned specification to exert a firm and natural power grip with the inside of the thumb facing towards the remaining fingers around an object in a true and natural power grip.
• the hand in the aforedescribed arrangement employs fingers and a thumb that are not able to bend with the aid of joints along the fingers, which means that all the fingers are stiff and therefore creates an unnatural appearance in certain positions, since such a hand cannot be held flat for example.
• a key grip can furthermore not be exerted with this known mechanical hand.
• An object of the present invention is to provide such a mechanical hand in which the thumb belonging to the hand has been adapted so as to simulate the thumb movements of the human hand.
• One object of the present invention is to provide a thumb for a mechanical hand so as to simulate the movements in a human hand by means of a mechanical gripping arrangement that is to be secured preferably on a shortened lower arm or a shortened hand of an amputee.
• the arrangement has a supporting platform that corresponds to the metacarpus of the human hand.
• the platform has a front side for accommodating at least two finger organs, namely a first finger organ corresponding to the index finger and a second finger organ corresponding to the middle finger of a human hand.
• the said finger organs are pivotably arranged with respect to the plane of the said platform.
• the first and the second of the said finger organs can be bent around at least one finger joint.
• the gripping organ furthermore has a thumb finger corresponding to the thumb of a human hand, secured to the base of the thumb, which in turn is secured on one side of the platform adjacent to the said first finger organ.
• the base of the thumb is formed as an elongated body that is intended to simulate as regards size, position and direction the base of the thumb, i.e. the metacarpus 1 in a human hand.
• the thumb finger is furthermore arranged so that it can pivot about a thumb base axis that is inclined at an angle ⁇ that is less than 90° relative to a longitudinal axis through the lower arm.
• the thumb base axis forms the longitudinal axis of the thumb base.
• the thumb base axis projects a certain angle downwards from the lower side of the middle hand, i.e. the palm of the hand, so that the thumb base too will appear similar to that of a human hand.
• Movements in the thumb finger are achieved by using a cylinder that constitutes the thumb base and accordingly forms the elongated body that corresponds to the metacarpus 1 in a human hand.
• the pivoting of the thumb finger according to the invention largely correspond to those of the human hand for corresponding thumb movements of the human hand.
• a further characteristic feature of the thumb according to the invention is that the thumb finger has a thumb root that is secured to the thumb base so that a longitudinal axis through the thumb root forms a defined predetermined angle relative to the thumb base axis. This provides for a desired and sufficiently large gripping area between the thumb finger and index finger.
• the mounting of the thumb finger means that it now becomes possible to pivot the thumb finger underneath the remaining fingers, the inside of the thumb finger on pivoting turning upwardly so as to face the inside of the remaining fingers, as is the case with movements of the human hand when the latter is to exert a gripping action round an object.
• This is a property that has not yet been able to be achieved with the known mechanical hands.
• the prerequisite for being able to execute this pivoting movement in the thumb finger is largely determined by the fact that the cylinder acting as the thumb base can pivot about its own axis, and that the said cylinder has drive means for executing pivoting movements incorporated therein, whereby transmission means or other power transmission means between the remaining hand and base of the thumb are not required to achieve said pivoting movement.
• a further object of the invention is to provide a mechanical gripping organ that can perform the movements according to the method defined above with the gripping organ characterised according to the independent arrangement claim.
• finger is sometimes used instead of the "mechanical finger organ of the hand”
• thumb is sometimes used instead of the "thumb finger” or the “thumb finger organ” when this can be done without any risk of confusion with the natural corresponding element of the hand.
• the finger organ of the hand has drive arrangements, i.e. its drive motors and machinery turning the finger element together with the transmission means, incorporated in the respective finger organ.
• the property of having individually powered fingers gives the user in principle two functional advantages. First and foremost it allows the fingers to adapt to the shape of an object and helps to produce a more stable grip at the same time as eliminating the need for powerful squeezing forces. In addition it allows the practical power grip to be employed in order to hold different objects.
• the finger organ is flexibly secured to the palm of the hand both for cosmetic reasons and for longer durability.
• the middle hand i.e. the supporting platform, includes the control unit for the mechanical gripping means and may also include a lightweight battery pack. Since the transmission means and motors are encapsulated in the fingers, the space in the middle hand can simply be used for control units, control devices and batteries, which is not possible with arrangements according to the known technology.
• the hand i.e. the mechanical gripping device
• the hand is equipped with power and sliding sensors that are connected to the control unit of the hand.
• a light grip is first of all applied, i.e. the squeezing forces between the fingers and the opposing thumb or palm of the hand are small. If the object begins to slip from the grasp the squeezing force increases automatically. The user can however ignore this function in every case and consciously control the gripping force.
• the mechanical hand is of course intended for use with a glove made of a material that is extremely resistant to influences of various kinds.
• the glove is available in different sizes and with different pigmentation so as to create a natural appearance in combination with the hand described hereinbefore, which for its part provides natural hand movements.
• the bendable, and with respect to the middle hand, pivotable fingers have an improved function and cosmetic appearance compared to conventional hand prostheses.
• the hand described hereinbefore has a natural thumb length, which imparts a more natural appearance to the hand.
• the hand also looks more natural when its parts move.
• All finger organs can turn about a joint between the middle hand and the said finger organ.
• the said finger organ has per se only two separate finger bones, which are mutually pivotably combined, i.e. they are combined in a finger joint.
• the front end of each finger organ is slightly bent since the natural fingers on a human hand are usually held in such a position. This facilitates the use of finger organs in the aforedescribed gripping operations.
• Research has shown that there is no serious limitation on the gripping capability of a hand that does not additionally employ a finger joint in every finger, since it is not absolutely necessary to bend the outermost part of a finger in a natural hand in order to achieve a desired grip.
• a requirement, however, to be able to perform said grips without a further joint in the front part of the finger is a slight template bending of the front end of the finger organ.
• Some of the advantages of the mechanical hand according to the invention are the following : it is possible to exert different grips for different activities, it is possible to grip and handle objects of different sizes and shapes, it is possible to grip and turn a lock for example, and it is possible to exert a sufficient grip, i.e. that is not too hard or too forceful.
• the hand is equipped with five fingers and is furthermore provided with a cosmetic glove it bears a great resemblance to and is like a human hand.
• Figs, la and lb show diagrammatically in two perspective views from two different directions a complete mechanical hand according to the invention.
• Fig. 2 shows a simplified hand with the thumb finger secured to the middle hand and with the possible pivotings of the thumb clearly shown.
• Fig. 3 is a front view of thumb pivoting movements along the axis of pivoting of the base of the thumb.
• Figs. 4a and 4b illustrate in two different views the precision grip exerted by the tip of the thumb touching the tips of both the index finger and middle finger.
• Figs. 5a and 5b illustrate two different views of the power grip without the use of an opposing thumb.
• Figs. 6a and 6b show two different views of the key grip in operation.
• Figs, la and b show an example of a mechanical hand 1 according to the invention.
• the reference numeral 2 refers to a platform that simulates the middle hand of a human hand.
• the platform 2 will be referred to as the middle hand (metacarpus) 2.
• a hand joint 4 is secured to the rear end 3 of the middle hand.
• the front part of the hand joint will be referred to as the carpus 5.
• the rear part of the hand joint is in the present case termed the prosthesis connection 6, whose axis of symmetry is intended to be an extension of the longitudinal axis of an amputated human lower arm.
• Every one of the ordinary fingers is pivotably arranged at the base of the finger on an attachment to the middle hand 2 by means of a pivotable joint formed round an axis 15 that is for the most part parallel to the said front side 14 on the middle hand 2 with the said joint axis 15 in the finger base position substantially in a plane that forms an elongated section of the middle hand 2.
• the pivotable joints on the axis 15 allow the innermost finger bone on every finger 10 - 13 to bend about 90° from a substantially rectilinear direction to an angle of about 90° towards the palm of the hand, i.e. the inside 2b of the middle hand 2.
• the ordinary fingers have a second finger bone 10b - 13b that corresponds to a combination of both the second and third finger bone in a human hand.
• the second finger bone 10b -13b on each finger organ 10 - 13 is joined to the first finger bone via a pivotable finger joint 9.
• the front part of the second finger bone 10b - 13b on each finger organ 10 - 13 corresponding to the furthermost, third finger bone in a human hand is secured to the rear part of the said second finger bone 10b - 13b in a slightly downwardly bent position. This serves to simplify the mechanism since there is no need for drive arrangements for a joint in each finger organ.
• the disadvantage of such a solution is not very serious since, as has already been mentioned in connection with investigations on human hand grips, it is found that the third finger bone on each ordinary finger is scarcely bent when the human hand executes one of the gripping operations described above.
• the second finger bone 10b - 13b on each ordinary finger organ 10 - 13, with the exception of the fourth finger organ, is bent by means of a pull rod 16 secured to the finger joint 9 and, relative to the axis of the finger joint 9, towards the parallel extended axis.
• the said pull rod 16 is furthermore secured at its second, inner end, i.e.
• the thumb finger 17, hereinafter called the thumb for the sake of simplicity, is shown in more detail in Figs. 2 and 3.
• the all-round gripping capability that is provided with the aid of the new hand according to the invention is due in large part to the unique flexibility of the thumb 17. Accordingly, the configuration of the thumb and the securement of the thumb to the hand will be described in more detail.
• the unique movement pattern in the thumb 17 is primarily achieved by means of a mounting installed on a thumb base 18 formed by a cylinder located on the mechanical hand in a position corresponding to the position of the thumb base (metacarpus 1) in the human hand.
• the thumb base 18 is consequently accommodated in the lower part of one side of the middle hand 2 adjacent to the first finger organ 10.
• the axis of symmetry 19 of the cylinder that forms the thumb base 18 is fixed and forms an angle ⁇ relative to the longitudinal axis 20 of the lower arm.
• the angle ⁇ in the said axis of symmetry 19 corresponds to the angle by which the thumb base in the human hand in a normal position deviates from the longitudinal axis of the lower arm, which means that the value of the angle ⁇ is preferably in the range 0° to 45°.
• the angle ⁇ may of course be increased up to 90°, but in this case the mounting of the thumb 17 would look unnatural and anaesthetic.
• the thumb 17 is secured to the thumb base 18.
• the human hand has two finger bones. According to the invention the thumb 17 is not provided with these two separate finger bones that can be pivoted relative to one another. Instead, the two finger bones in the human thumb are simulated by a single integral thumb that projects at an angle from the circumferential surface of the cylinder that forms the thumb base 18.
• the said thumb 21 does not have any joints, but instead is bent in an arc that simulates the average curvature of a human thumb for various types of grip.
• the angle ⁇ in the thumb base 18 is such that the axis of symmetry 19, in the forward direction of the hand, is at an increasing distance from the plane of the palm of the hand.
• the axis of the base of the thumb 19 is somewhat downwardly inclined in the forward direction.
• the inner part of the thumb here called the thumb root 21
• ⁇ which may arbitrarily be chosen in the range 0° ⁇ ⁇ ⁇ 90°, but which conveniently may be in the range 30° ⁇ ⁇ ⁇ 60° so that it gives the hand a natural appearance when a glove is worn.
• the size of ⁇ depends of course on the angle that is chosen for the thumb base, i.e. the angle ⁇ .
• the cylinder 18 of the thumb base is pivotably arranged.
• the cylinder can be pivoted about its own axis of symmetry 19 by means of an electric motor installed in the cylinder.
• the thumb 17 enjoys a large degree of flexibility.
• the motor inside the thumb base 18 is activated by means of control signals and in addition a voltage from a voltage source inside the middle hand 2 is applied to the motor, the thumb 17 pivots about the axis of symmetry 19. On pivoting of the thumb in this way the tip of the thumb 17 describes a circle 22 as shown in Figs. 2 and 3.
• the thumb 17 pivots and at the same time one or both of the first finger organ 10 (index finger) and the second finger organ (middle finger) 11 is/are bent, it can be seen from the Figures that the thumb 17 and one or both of the said finger organs 10, 11 can meet one another somewhere on the periphery of the circle 22.
• the precision grip can be exerted as shown in Figs. 4a and 4b.
• the inside of the thumb together with its tip, i.e. the touch perception pad 17b of the thumb face the finger organs 10 - 13 when the thumb 17 is pivoted outwardly towards the finger organs in the same way as during the corresponding movement in a human thumb, when the same type of grip is exerted. This is important as the pattern of movements should appear natural as if performed by a human hand.
• the power grip exerted by a thumb in order to grip an object between the ordinary fingers and the thumb may also, like the precision grip, be exerted by a pivoting of the thumb 17 in the direction towards the fingers 10 - 13 along the path that is described by the circle 22, while at the same time the ordinary fingers 10 - 13 can be bent so as to touch the object, the thumb 17 acting on the object from the opposite side.
• the power grip is exerted by bending the fingers towards the inside of the palm of the hand without using the thumb 17, as can be seen in Figs. 5a and 5b.
• the key grip is illustrated in Figs. 6a and 6b. It can be seen from these Figures that the ordinary fingers 10 - 13 are bent inwardly, as a result of which the thumb 17 is pivoted towards the side of the index finger 10. In this connection the front part of the thumb 17 comes into contact with the side of the index finger 10 during pivoting of the thumb 17, so that the thumb can be held with the desired force against the side of the index finger. In this way a key or other similar object can be held by the hand with sufficient force.
• the control of the various elements of the mechanical hand 1 by means of control signals may be effected by the transmission and reception of myogram signals from muscles in for example the human arm.
• the said muscles are stimulated depending on nerve signals from the human brain, so that the muscles can exert a grip according to commands from the brain.
• Through movements of the muscles myogram signals are transmitted and received and are converted in a control unit into control signals that are used to activate the intended finger organs 10 - 13 and to actuate the appropriate motors so as to drive the said finger organs according to the desired pattern.
• the tilting and pivoting movements of the hand part may be controlled in a similar way.
• the control unit is accommodated inside a storage space in the platform 2 that forms the middle hand. Power is supplied to the motors from lightweight batteries that can likewise be accommodated in the space in the middle hand.
• the hand 1 is furthermore provided with pressure sensors and sliding sensors for detecting that sufficient forces are applied in order to exert the desired grip.

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Cited By (31)

Citations (4)

• 2001
  • 2001-08-27 SE SE0102835A patent/SE0102835D0/sv unknown
• 2002
  • 2002-08-26 WO PCT/SE2002/001529 patent/WO2003017880A1/en not_active Application Discontinuation

Patent Citations (4)

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