This invention relates to a prosthetic limb and more particularly to a functional prosthetic upper limb.

Functional prosthetic upper limbs are known for fitting to an arm stump of a user, the prosthetic limbs comprising an elongate body, a displaceable first grip (such as an artificial thumb) attached to the distal end of the body for selective displacement towards or away from a second grip (such as an artificial forefinger or other finger(s)). The grips form a jaw which can be opened and closed by the user. Such limbs are currently unavailable to below-the-elbow amputees under the age of 3.5 years in the United Kingdom under guidance issued by The National Institute for Health and Care .Excellence (NICE). To-date such users have only been offered cosmetic prosthetics under the National Health Service (NHS). At around 3.5 years of age, depending on the level of limb function, myoelectric devices and body powered mechanical devices having hooks and cables can be worn. However, for a number of reasons, the existing functional prosthetic limbs are not suitable at earlier ages because their batteries and motors are heavy and there are risks with water immersion and small parts for example. Similarly, there are issues with body powered functional prosthetic limbs which involve wearing a harness that must be constantly adjusted and is uncomfortable. Furthermore, users are often conscious of the mechanical appearance of existing functional prosthetic limbs.

Clinical research suggests that the most suitable time for functional prosthetic intervention is much earlier than current prosthetic options permit. The best time (using myoelectric prosthetics) is around 12 months of age or earlier. The latest they should be fitted, to avoid rejection of the prosthetic, is around 2.5 to 3 years i.e. 6 months before the NHS offer functional intervention. Non-functional prosthetic intervention beyond 2.5 to 3 years is most often short-lived. Without function, infants in this group stop wearing their prosthetic upper limbs (i.e. arms) for the next decade until the self-conscious teen years. Developmental^, this poses problems that could be addressed by intervening at the earliest possible age and especially with a functional limb.

With the foregoing in mind, we have now devised an improved prosthetic limb. In accordance with the present invention, as seen from a first aspect, there is provided a prosthetic limb for fitting to the stump of a user, the limb comprising an elongate body, a displaceable first grip attached to the distal end of the body for selective displacement towards or away from a second grip of the limb, a socket at the proximal end of the body for receiving the stump of a user, wherein a closing fluid displacement member is disposed within the socket is arranged to operate a fluidic actuator in the body to displace said first grip towards the second grip upon actuation of the displacement member by the stump of the user. A prosthetic limb in accordance with the present invention can be worn much earlier in infancy because it simple in construction, light in weight, has few moving parts and can be immersed in water. The grips are simply closed by the user by moving his or her stump inside the socket against the fluid displacement member. An opening fluid displacement member disposed within the socket is arranged to operate the fluidic actuator in the body to displace said first grip away from the second grip upon actuation of the displacement member by the stump of the user. The fluidic actuators are disposed remote from each other in the socket, for example such that movement of the stump in one direction displaces the first grip towards the second grip and movement in the other direction displaces the first grip away from the second grip.

The or each fluid displacement member in the socket may be a fluid-filled member such as a bladder having a deformable wall for engagement by the stump of the user, the member being fluidly connected to the fluidic actuator in the body to displace said first grip when the wall thereof is deformed by the stump of the user.

The fluidic actuator may comprise an opening fluid-filled chamber and a closing fluid- filled chamber separated by a displaceable wall, a ram extending from the wall to displace the first grip upon displacement of the wall, wherein the opening and closing chambers are respectively connected to the opening and closing displacement members such that actuation of a said displacement member by the stump of the user causes expansion of the respective fluid-filled chamber. In a first embodiment of actuator, the displaceable wall comprises a piston mounted inside a tubular body of the actuator, the piston defining the chambers at respective opposite ends of the actuator body, each chamber having a port connected to a respective displacement member. In use, the piston is moved in one direction to displace the first grip towards the second grip as the closing chamber fills with fluid and is moved in the opposite direction to displace the first grip away from the second grip as the opening chamber fills with fluid.

Means may be provided for constraining movement of the piston within the tubular body and which may seal against the piston when the closing chamber is fully expanded so that there is no loss of pressure as the first grip is urged towards the second grip.

In order to reduce friction, the diameter of the piston including any circumferential seals may be less than the internal diameter of the chambers.

The fluid may be a liquid such as a silicon based / food grade oil.

In a second embodiment of actuator, the displaceable wall comprises a partition disposed intermediate opposite ends of an elongate hollow body of the actuator, the body having a concertinaed side wall arranged to axiaily fold at a plurality of points along its length between opposite ends thereof, the partition defining the chambers at respective opposite ends of the actuator body, each chamber having a port connected to a respective displacement member. In use, the piston is moved in one direction to displace the first grip towards the second grip as the closing chamber fills with fluid and axiaily extends and is moved in the opposite direction to displace the first grip away from the second grip as the opening chamber fills with fluid and axiaily extends. This embodiment does not comprise a piston and the risk of hence frictional losses and leaks is avoided.

The concertinaed side wall may comprise a plurality of circumfererrtially extending folds disposed at discrete positions along the length of the sidewall. However, there is risk that such folds may introduce memory into the material of the sidewall. Hence, the concertinaed side wall may comprise one or more folds which extend circumferentially and axially (i.e. helically). A helical fold is more neutral and has less memory which further decreases the resistance in axially extending and retracting the chambers.

The actuator may comprise a first end wall having a port connected to the opening displacement member and a second end wall through which the ram extends, wherein a port connected to the closing displacement member extends from the side wall of the actuator body, preferably adjacent said second end wall.

In the second embodiment of actuator, a sleeve may extend between the partition and the second end wall, the ram extending through the sleeve, the sleeve having a concertinaed side wall arranged to axially fold at a plurality of points along its length between opposite ends thereof. The sleeve avoids any need for a seal in the second end wall and hence frictional losses are reduced.

In one embodiment of the second embodiment of actuator, the ram may comprise an axially extending air passageway which extends to atmosphere from inside the sleeve.

In an alternative embodiment of the second embodiment of actuator, a fluid pump is connected to chamber defined inside the sleeve so as to axially vary the length of the sleeve and thereby assist with displacement of the ram in one or both directions. In yet a further embodiment of the second embodiment of actuator, a further chamber may be provided inside the closing chamber, the further chamber extending between the partition and the first end wall and having a concertinaed side wall arranged to axially fold at a plurality of points along its length between opposite ends thereof, a fluid pump being connected to the further chamber defined so as to axially vary the length of the further chamber and thereby assist with displacement of the ram in one or both directions.

The or each fluid pump may be operated by a fluid pressure sensor or by a position sensor which senses a change in position of a part of the limb, such as the ram. The diameter of the port connected to at least the opening displacement member may be 40-60% of the diameter of chambers defined by the tubular body, so as to ensure a high fluid flow rate. The actuator operates under very low pressures at room temperature and there is no significant torque multiplication required to displace the first grip. The only mechanical advantage is the mechanical action itself by transferring energy from displaced fluid into a usable mechanical output. The design emphasises flow and reduced resistance rather than pressure and good sealing properties.

It will be appreciated that the second embodiment of actuator could be used in other applications apart from prosthetic limbs.

Hence, in accordance with the present invention, as seen from a second aspect, there is provided a f luidic actuator comprising a first fluid-filled chamber and a second fluid-filled chamber separated by a displaceable wall, a ram extending from the wall for displacing a part to be operated by the actuator, the displaceable wall comprising a partition disposed intermediate opposite ends of an elongate hollow body of the actuator, the body having a concertinaed side wall arranged to axially fold at a plurality of points along its length between opposite ends thereof, the partition defining the chambers at respective opposite ends of the actuator body, each chamber having a port adapted for connection to a respective fluid displacement member. In use, the piston is moved in one direction to displace the ram in one direction as the first chamber fills with fluid and axially extends and is moved in the opposite direction to displace the ram in the opposite direction as the second chamber fills with fluid and axially extends. The concertinaed side wall may comprise a plurality of circumferentially extending folds disposed at discrete positions along the length of the sidewall. However, there is risk that such folds may introduce memory into the material of the sidewall. Hence, the concertinaed side wall may comprise one or more folds which extend circumferentially and axially (i.e. helically). A helical fold is more neutral and has less memory which further decreases the resistance in axially extending and retracting the chambers.

The actuator may comprise a first end wall having a port adapted for connecting to one fluid displacement member and a second end wall through which the ram extends, wherein a port adapted for connecting to another fluid displacement member extends from the side wall of the actuator body, preferably adjacent said second end wall. A sleeve may extend between the partition and the second end wall, the ram extending through the sleeve, the sleeve having a concertinaed side wall arranged to axially fold at a plurality of points along its length between opposite ends thereof. The sleeve avoids any need for a seal in the second end wall and hence frictional losses are reduced.

In one embodiment, the ram may comprise an axially extending air passageway which extends to atmosphere from inside the sleeve.

In an alternative embodiment, a fluid pump is connected to chamber defined inside the sleeve so as to axially vary the length of the sleeve and thereby assist with displacement of the ram in one or both directions.

In yet a further embodiment, a further chamber may be provided inside the first chamber, the further chamber extending between the partition and the first end wall and having a concertinaed side wall arranged to axially fold at a plurality of points along its length between opposite ends thereof, a fluid pump being connected to the further chamber defined so as to axially vary the length of the further chamber and thereby assist with displacement of the ram in one or both directions. The or each fluid pump may be operated by a fluid pressure sensor or by a position sensor which senses a change in position of a part of actuator, such as the ram.

Embodiments of the present invention will now be described by way of examples only and with reference to the accompanying drawings, in which: Figure 1 is a part cut away side view of a first embodiment of functional prosthetic upper limb in accordance with the first aspect of the present invention;

Figure 2 is a perspective view of a fluidic actuator of the limb of Figure 1 ;

Figure 3 is a sectional view of through the fluidic actuator of Figure 2;

Figure 4 is a perspective view of the fluidic components of the limb of Figure 1 ; Figure 5 is a perspective cut away view of a first embodiment of fluidic actuator in accordance with the second aspect of the present invention for fitting to a second embodiment of functional prosthetic upper limb in accordance with the first aspect of the present invention; Figure 6 is a perspective cut away view of a second embodiment of fluidic actuator in accordance with the second aspect of the present invention for fitting to a third embodiment of functional prosthetic upper limb in accordance with the first aspect of the present invention; Figure 7 is a perspective cut away view of a third embodiment of fluidic actuator in accordance with the second aspect of the present invention for fitting to a fourth embodiment of functional prosthetic upper limb in accordance with the first aspect of the present invention; and Figure 8 is a part cut away side view of a fourth embodiment of functional prosthetic upper limb in accordance with the first aspect of the present invention.

Referring to Figures 1 to 4 of the drawings, there is shown a functional prosthetic limb 10 for fitting to the arm stump of a user. T e limb 10 comprises an elongate body 11 having hand fingers 12 at a distal end thereof. A displaceable thumb 13 is pivotally attached to the distal end of the body 10 for selective displacement towards or away from a forefinger of the hand fingers 12.

A socket 14 is disposed at the proximal end of the body 10 for receiving the user's arm stump. First and second fluid displacement members 15, 16 are disposed within the socket 16 for operating a flutdic actuator 17 in the body 10 to displace the thumb 13 towards or away from the forefinger of the hand fingers 12 respectively upon actuation of the respective displacement member 15, 16 by the stump of the user. The fluid is a liquid such as a silicon based / food grade oil.

The fluid displacement members 15,16 in the socket 14 comprise fluid-filled bladders having a deformable wall for engagement by the stump of the user, the members 15,16 being fluidly connected to the fluidic actuator 17 in the body 11 by respective fluid flow ducts 18,19. The fluidic actuators 15,16 are disposed remote from each other on opposite sides of the socket 14, such that movement of the user's stump in one direction displaces the thumb 13 towards the forefinger of the hand fingers 12 and movement in the other direction displaces the thumb 13 away from the forefinger of the hand fingers 12. The fluidic actuator 17 comprises a first fluid-filled chamber 20 and a second fluid- filled chamber 21 separated by a displaceable piston 22 mounted inside a tubular body 27 of the actuator 17. The actuator 17 further comprises a first end wall 30 having a port 25 connected to the first displacement member 15 and a second end 31 wall through which a ram 23 extends. A port 26 connected to the second displacement member 16 extends from the side wall 27 of the actuator 10, adjacent the second end wall 31. The 23 extends from the piston 22 to operate a linkage 24 which displaces the thumb 13 upon displacement of the piston 22.

In use, the piston 22 is moved in one direction to displace the thumb 3 towards the forefinger of the hand fingers 12 as the first chamber 20 fills with fluid and is moved in the opposite direction to displace the thumb 13 away from the forefinger of the hand fingers 12 as the second chamber 21 fills with fluid. In order to reduce friction, the diameter of the piston 22 including a circumferential seal 29 may be less than the internal diameter of the chambers 20,21.

An annular flange 28 extends around the interior surface of the tubular body 17 intermediate opposite ends thereof to constrain the movement of the piston 22 in the thumb closing direction. The piston 22 is arranged to seal against the flange 28 when the first chamber 20 is fully expanded, so that there is no loss of pressure as the thumb 13 is urged towards the forefinger of the hand fingers 12. Referring to Figure 5 of the drawings, there is shown an alternative embodiment of actuator 117 for fitting to a functional prosthetic limb of the kind shown in Figure 1. However, the actuator 117 could be used in other kinds of applications apart from functional prosthetic limbs. In this embodiment of actuator 117, a partition 122 is disposed intermediate opposite ends of an elongate hollow body 127 of the actuator 117. The body 127 comprises a concertinaed side wall arranged to axially fold at a plurality of points along its length between opposite ends thereof. The partition 122 divides the hollow interior of the body 127 into first and second chambers 120,121 at respective opposite ends of the actuator 117. Each chamber 120,121 has a port 125,126 connected to a respective displacement member of the kind shown in Figures 1 and 4. The concertinaed side wall comprises a fold 130 which extends circumferentially and axially (i.e. helically) of the body 127 between opposite ends thereof. A sleeve 131 extends between the partition 122 and a second end wall 132 of the body 117. A ram 123 from the partition 122 inside the sleeve 131 and through the second end wall 132. The sleeve 131 has a concertinaed side wall arranged to axially fold at a plurality of points along its length between opposite ends thereof. The sleeve 131 avoids any need for a seal in the second end wall 132 and hence fnctional losses are reduced. The ram 123 is tubular and comprises an axially extending air passageway 133 which extends to atmosphere from a sidewall aperture 134 disposed the sleeve 131.

In use, the actuator 117 is mounted such the first and second end walls 124,132 thereof are held in a fixed position. When fluid flows into the port 125 on the first end wall 124, the first chamber 120 axially expands to move the partition 122 in one direction to displace the thumb towards the forefinger of the hand of the limb. When fluid flows into the port 126, the second chamber 121 axially expands to move the partition 122 in the opposite direction to displace the thumb away from the forefinger of the hand of the limb. The air passageway 133 allows air to pass between the interior of the sleeve 131 and atmosphere as the sleeve 131 axially expands and contacts in use. The actuator 117 of Figure 5 does not comprise a piston or any seals and the risk of frictional losses and leaks is avoided.

Referring to Figure 6 of the drawings, there is shown an alternative embodiment of actuator 217 for fitting to a functional prosthetic limb of the kind shown in Figure 1. However, the actuator 217 could be used in other kinds of applications apart from functional prosthetic limbs. The actuator 217 is similar in construction to the actuator 117 of Figure 5 and like parts are given like reference numerals.

In this embodiment, a fluid pump (not shown) is connected via port 218 to a fluid- filled inner chamber 219 defined inside the sleeve 131. A seal 220 on the second end wall 132 seals against the ram 123. In use, when fluid flows into the port 125 on the first end wall 124, the increased fluid pressure in the first chamber 120 or the movement of the actuator 217 is sensed to trigger the pump to expel fluid from the fluid-filled inner chamber 219, thereby causing the sleeve 131 to axially contact and assist with moving the partition 122 in the direction to displace the thumb towards the forefinger of the hand of the limb. Likewise, when fluid flows into the port 126, the increased fluid pressure in the second chamber 121 or the movement of the actuator 217 may be sensed to trigger the pump to pump fluid into the fluid-filled inner chamber 219, thereby causing the sleeve 131 to axially expand and assist with moving the partition 122 in the opposite direction to displace the thumb away from the forefinger of the hand of the limb.

Referring to Figure 7 of the drawings, there is shown an alternative embodiment of actuator 317 for fitting to a functional prosthetic limb of the kind shown in Figure 1. However, the actuator 317 could be used in other kinds of applications apart from functional prosthetic limbs. The actuator 317 is similar in construction to the actuator 217 of Figure 6 and like parts are given like reference numerals.

In this embodiment, a further fluid-filled inner chamber 319 is provided inside a further sleeve 331 disposed inside the first chamber 120, the further sleeve 331 extending between the partition 122 and the first end wall 124 and having a concertinaed side wall arranged to axially fold at a plurality of points along its length between opposite ends thereof. A fluid pump (not shown) comprises an inlet port and an outlet respectively connected to ports 218, 318 extending from the inner chambers 219,319 respectively. In use, when fluid flows into the port 125 of the first chamber 120, the increased fluid pressure in the first chamber 120 or the movement of the actuator 217 is sensed to trigger the pump to pump fluid from the fluid-filled inner chamber 219 into the other fluid-filled inner chamber 319, thereby causing the sleeves 131, 331 to respectively axially contact and expand, thereby assisting with moving the partition 122 in the direction to displace the thumb towards the forefinger of the hand of the limb. Likewise, when fluid flows into the port 126, the increased fluid pressure in the second chamber 121 or the movement of the actuator 217 may be sensed to trigger the pump to pump fluid from the fluid-filled inner chamber 319 into the other fluid- filled inner chamber 219, thereby causing the sleeves 131, 331 to respectively axially expand and contact, thereby assisting with moving the partition 122 in the opposite direction to displace the thumb away from the forefinger of the hand of the limb.

An actuator in accordance with the present invention operates under very low pressures at room temperature and there is no significant torque multiplication required to displace the thumb of the hand. The only mechanical advantage is the mechanical action itself by transferring energy from displaced fluid into a usable mechanical output. The present invention utilises a good fluid flow and reduced resistance rather than pressure and good sealing properties. Referring to Figure 8 of the drawings, there is shown a functional prosthetic limb 410 for fitting to the arm stump of a user. The limb 410 comprises an elongate body 411 having hand fingers 412 at a distal end thereof. A displaceable thumb 413 is pivotally attached to the distal end of the body 410 for selective displacement towards or away from a forefinger of the hand fingers 412.

A socket 414 is disposed at the proximal end of the body 410 for receiving the user's arm stump. First and second fluid displacement members 415, 416 are disposed within the socket 416 for operating a fluidic actuator 417 in the body 410 to displace the thumb 413 towards or away from the forefinger of the hand fingers 412 respectively upon actuation of the respective displacement member 415, 416 by the stump of the user.

The fluid displacement members 415,416 in the socket 414 comprise fluid-filled bladders having a deformable wail for engagement by the stump of the user, the members 415,416 being fluidly connected to the fluidic actuator 417 in the body 411 by respective fluid flow ducts 418,419. The fluidic actuators 415,416 are disposed remote from each other on opposite sides of the socket 14, such that movement of the user's stump in one direction displaces the thumb 413 towards the forefinger of the hand fingers 412 and movement in the other direction displaces the thumb 413 away from the forefinger of the hand fingers 12.

The fluidic actuator 417 comprises a first fluid-filled chamber 420 and a second fluid- filled chamber 421 disposed on opposite sides of a lever arm 422 which extends from the thumb 413.

In use, when pressure is applied to the first fluid displacement member 415, the arm 422 is pivoted in the counter-clockwise direction to displace the thumb 413 towards the forefinger of the hand fingers 412 as the first chamber 420 fills with fluid and axially expands. Conversely, when pressure is applied to the second fluid displacement member 416, the arm 422 is pivoted in the clockwise direction to displace the thumb 413 away from the forefinger of the hand fingers 412 as the second chamber 421 fills with fluid and axially expands. It will be appreciated that axial expansion of one chamber e.g. 420 causes the other chamber e.g. 421 to axially contract, thereby forcing the fluid therein back into the fluid displacement member e.g. 416 to which it is fluidly connected.

In an alternative embodiment, the first and second fluid displacement members 415, 416 are disposed outside the socket 416 and are connected to the fluidic actuator 417 by fluid flow ducts 418,419 which are more elongate than those shown in Figure 8 and allow each displacement member 415, 416 to be disposed in another location, such as inside a shoe or under the user's armpit.

A prosthetic limb in accordance with the present invention can be worn much earlier in infancy because it simple in construction, light in weight, has few moving parts and can be immersed in water. The thumb is simply operated by the user by moving his or her stump in appropriate direction inside the socket against the respective fluid displacement member.