Abstract:
A mechanical finger comprises at least two phalanges. The phalanges have tubular bodies made of a semi-rigid material. One phalange is adapted to be secured to a base. Another phalange is connected to an adjacent phalange for pivoting movement with respect to the adjacent phalange. A skeleton member in the tubular bodies of the phalanges moves to actuate the pivoting motion of the phalanges with respect to one another. The skeleton member is connected to a degree of actuation to cause the pivoting motion of the phalanges with respect to one another. An assembly is also provided. The assembly comprises at least two of the mechanical finger, a palm actuator comprising a base for connection of the base phalange of each mechanical finger, and at least one degree of actuation connected to the skeleton member. The degree of actuation causes a grasping movement of the mechanical fingers.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application is a U.S. national stage of International Patent Appliocation No. PCT/CA2010/00910. The present application claims the benefit of U.S. Patent Application No. 61/186,497, filed Jun. 12, 2010, and U.S. Patent Application No. 61/227,511, filed Jul. 22, 2009, and incorporated herein by reference. 
    
    
     FIELD OF THE APPLICATION 
     The present application relates to mechanical fingers and more particularly to mechanical fingers used in prosthesis applications and in technical-aid applications, amongst numerous possible applications. 
     BACKGROUND OF THE ART 
     Mechanical fingers of all types have been developed as a function of various applications. One common type of mechanical finger has phalanges in an articulated configuration, to simulate the human finger. In such configurations, the articulated phalanges are displaced with respect to one another to grasp objects of all shapes. For instance, U.S. Pat. No. 5,762,390, by Gosselin et al., describes a mechanical finger performing motions similar to that of the human finger. Accordingly, a set of mechanical fingers of Gosselin et al. can be used to perform actions such as a pinch grasps. The mechanical finger taught by Gosselin et al. is more practical in industrial applications. The mechanical finger of Gosselin et al. is made of rigid phalanges that can support substantial weights. In domestic applications, such a mechanical finger may be impractical, especially in an environment with relatively fragile objects. 
     SUMMARY OF THE APPLICATION 
     It is therefore an aim of the present disclosure to provide a mechanical finger that addresses issues associated with the prior art. 
     It is a further aim of the present disclosure to provide a mechanical finger of semi-rigid material. 
     Therefore, in accordance with a first embodiment, there is provided a mechanical finger comprising: at least two phalanges, with the at least two phalanges having tubular bodies and being made of a semi-rigid material, one of the at least two phalanges being a base phalange adapted to be secured to a base; another of the at least two phalanges being an end phalange, the end phalange being pivotally connected to an adjacent one of the at least two phalanges for pivoting movement with respect to the adjacent one of the at least two phalanges; and a skeleton member received in the tubular bodies of the at least two phalanges and movable to actuate the pivoting motion of the at least two phalanges with respect to one another, the skeleton member adapted to be connected to a degree of actuation for causing the pivoting motion of the at least two phalanges with respect to one another. 
     Further in accordance with the first embodiment, the mechanical finger comprises three of the phalanges, with one of the three phalanges being a middle phalange pivotally connected to the base phalange at a first end, and pivotally connected to the end phalange at a second end. 
     Still further in accordance with the first embodiment, at least a pair of shells are interconnected to define the tubular bodies of the at least two phalanges. 
     Still further in accordance with the first embodiment, two of the shells are interconnected along a longitudinal plane of the mechanical finger, each of the two shells comprising half-phalanges pivotally interconnected, whereby the half-phalanges define the at least two phalanges when the shells are interconnected. 
     Still further in accordance with the first embodiment, the two shells are mirror images one of the other, and each are one integrally molded piece. 
     Still further in accordance with the first embodiment, each of the shells comprises a longitudinal edge ridge, with a slit defined in the longitudinal edge ridge between each adjacent pair of the at least two phalanges to form a pivot between the adjacent pair of phalanges when the shells are interconnected. 
     Still further in accordance with the first embodiment, a tail of material extends from one of the phalanges into a tubular body of an adjacent other phalanges opposite the pivot, the tail covering an interior of the tubular body when the phalanges are pivoted with respect to one another. 
     Still further in accordance with the first embodiment, the mechanical finger comprises one said tail of material between each pair of adjacent phalanges of the mechanical finger. 
     Still further in accordance with the first embodiment, the mechanical finger comprises a peripheral flange at an end of the base phalange adapted to be connected to a base, with slots in the peripheral flange adapted to receive fasteners. 
     Still further in accordance with the first embodiment, the skeleton member comprises an articulated arm extending into the tubular bodies of the at least two phalanges and interconnected to at least one of the at least two phalanges. 
     Still further in accordance with the first embodiment, the articulated arm has at least two arm segments, with each interconnected pair of the arm segments being separated by a throat portion forming a pivot connected between the arm segments of each interconnected pair. 
     Still further in accordance with the first embodiment, an actuator end of the articulated arm has an annular body adapted to be connected to the degree of actuation. 
     Still further in accordance with the first embodiment, the annular body is tapped for screwingly engaging with the degree of actuation. 
     Still further in accordance with the first embodiment, the annular body extends outside of the tubular bodies of the at least two phalanges. 
     Still further in accordance with the first embodiment, the articulated arm has an end pivot at an end thereof, further wherein the tubular bodies have a pivot housing for rotatably receiving the end pivot whereby an actuation of the skeleton member causes a rotation of the end pivot with respect to the pivot housing. 
     Still further in accordance with the first embodiment, abutment walls are adjacent to the pivot housing for delimiting a rotational movement of the articulated arm with respect to the pivot housing. 
     Still further in accordance with the first embodiment, the pivot housing is in the end phalange, and the mechanical finger further comprises a middle pivot on the articulated arm and a pivot slot in the tubular bodies for rotatably and slidingly receiving the middle pivot for transmission of the actuation of the skeleton member to the middle phalange. 
     Still further in accordance with the first embodiment, the mechanical finger comprises at least a biasing member in the tubular bodies and interconnected between the skeleton member and the at least two phalanges to bias the mechanical finger in one orientation. 
     Still further in accordance with the first embodiment, the skeleton member is one integrally molded piece. 
     Still further in accordance with the first embodiment, the skeleton member is entirely made of a semi-rigid material, whereby the mechanical finger is compliant isotropically. 
     Still further in accordance with the first embodiment, the skeleton member is made of a semi-rigid material, with rigid reinforcements thereon. 
     In accordance with a second embodiment, there is provided an assembly comprising: at least two of the mechanical finger according to the first embodiment; a palm actuator comprising a base for connection of the base phalange of each of the at least two mechanical fingers; and at least one degree of actuation connected to the skeleton member of the mechanical fingers for simultaneously causing a grasping movement of the mechanical fingers. 
     Further in accordance with the second embodiment, the assembly comprises a single one of the degree of actuation and three of the mechanical finger, with the single one of the degree of actuation simultaneously actuating all three of the mechanical fingers. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a mechanical finger constructed in accordance with an embodiment of the present disclosure; 
         FIG. 2  is a perspective view of the mechanical finger of  FIG. 1 , with a half shell of the mechanical finger removed to show an interior of the mechanical finger; 
         FIG. 3  is a perspective view of the skeleton member of the mechanical finger of  FIG. 1 ; 
         FIG. 4  is a perspective view of the skeleton member of  FIG. 3  in the half shell of  FIG. 2 ; 
         FIG. 5A to 5D  shows sequences of the assembly of  FIG. 4  as actuated in a grasping movement, with and without contact with an object; 
         FIG. 6  is a perspective view of the mechanical finger of  FIG. 1 , as mounted to a single actuator; and 
         FIG. 7  is a perspective view of the mechanical finger of  FIG. 1 , as mounted to a palm actuator. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to the drawings, and more particularly to  FIG. 1 , a mechanical finger constructed in accordance with an embodiment is generally shown at  10 . The finger  10  has a base phalange  12 , a middle phalange  13  and an end phalange  14 , although more or fewer than three phalanges may be used in the mechanical finger of the present disclosure. The three-phalange configuration illustrated in  FIG. 1  is however well suited to simulate a human finger, whereby the present disclosure will focus on the three-phalange configuration. Movements of the mechanical finger  10  are performed by actuation of a skeleton member  15 . 
     Referring concurrently to  FIGS. 1 and 2 , the phalanges  12 - 14  of the mechanical finger  10  each consist in a pair of shells made of a semi-rigid material, such as rubber, as will be described hereinafter. In  FIG. 2 , half-phalanges are shown as  12 A,  13 A and  14 A (i.e., first shells), with the plane of separation being parallel to a longitudinal axis of the finger  10 . The removed half-phalanges (i.e., second shells) are typically a mirror image of the half-phalanges  12 A- 14 A illustrated in  FIG. 2 . 
     The base phalange  12  has a tubular body  20 , at the base of which a peripheral flange  21  is provided. The flange  21  has connection slots  22 , for the base phalange  12  to be connected to a palm or actuator using fasteners such as bolts. Counterbore holes may be used amongst other possibilities. 
     The middle phalange  13  also has a tubular body  30 , with a diameter lesser than that of the base phalange  12 , such that the middle phalange  13  has an end partially accommodated in the base phalange  12 . The tubular body  30  is hinged to the tubular body  20  by slit  31 . The slit  31  is essentially a disruption in the thickness of ridges forming a periphery of the shells of the bodies  20  and  30 . As the bodies  20  and  30  are made of a semi-rigid material, the slit  31  will facilitate deformation thereat, and hence will allow a hinging movement of the middle phalange  13  with respect to the base phalange  12 . Other configurations are considered as well, such as the insertion of a pivot, as alternatives to the narrowing of the material. 
     The tubular body  30  has strengthening ribs  32 , to increase the structural integrity of the middle phalange  13 . A slot  33  is defined in each shell of the middle phalange  13 , to form a translational joint with the skeleton member  15 , as will be described hereinafter. A post  34  is also provided within the tubular body  30 . When the shells  13 A are interconnected to form the phalange  13 , the posts  34  abut against one another and therefore define a connection point for a resilient member such as a spring, as will be shown hereinafter. The tubular body  30  also features a tail  35 , accommodated in the tubular body  20 . The tail  35  ensures that an interior of the finger  10  is not exposed when the middle phalange  13  is pivoted away from the base phalange  12 , for instance as shown in  FIG. 5B . 
     Still referring to  FIGS. 1 and 2 , the end phalange  14  also has a tubular body  40 , forming the tip of the mechanical finger  10 . The tubular body  40  has a diameter lesser than that of the middle phalange  13 , such that the end phalange  14  has an end partially accommodated in the middle phalange  13 . The tubular body  40  is hinged to the tubular body  30  by slit  41 . Similar to the slit  31 , the slit  41  is essentially a disruption in the thickness of the ridges defining a periphery of the shells of the bodies  30  and  40 . As the bodies  30  and  40  are made of a semi-rigid material, the slit  41  will facilitate deformation thereat, and hence a hinging movement of the end phalange  14  with respect to the middle phalange  13 . Other configurations are considered as well, such as the insertion of a pivot, as an alternative to the narrowing of the material. 
     The tubular body  40  has strengthening ribs  42 , to increase the structural integrity of the end phalange  14 . Moreover, the tubular body  40  has a pair of pivot housings  43  (one in each shell), that will rotatably receive an end of the skeleton member  15 . A pair of abutment walls  44  are positioned adjacent to each pivot housing  43  to delimit movement of the end phalange  14  with respect to the skeleton member  15 . The tubular body  40  also features a tail  45 , accommodated in the tubular body  30 . The tail  45  ensures that an interior of the finger  10  is not exposed when the end phalange  14  is pivoted away from the middle phalange  13 . 
     The mechanical finger  10  of  FIGS. 1 and 2  has the shells  12 A- 14 A of the phalanges  12 - 14  molded integrally in one piece, with the narrowing of material allowing the pivoting movement between the phalanges. Alternatively, the phalanges  12 - 14  may be separate components, for instance interconnected by rigid pivot pins. Accordingly, in the embodiment of  FIGS. 1 and 2 , the two half-fingers (each made up of the interconnected shells  12 A- 14 A) are connected together to form the full finger of  FIG. 1 , with the skeleton member  15  inserted therein. Mating connectors (not shown), adhesives, or the like may be used to maintain the half-fingers together. 
     Moreover, the construction of the mechanical finger  10  as described above may cause a generally isotropic flexibility of the finger  10 , for instance in all directions. Alternatively, reinforcements may be used to render the flexibility anisotropic. The flexibility is due to the use of the semi-rigid material. Moreover, the use of tubular bodies for the phalanges  12 - 14  also allows some flexibility. Although the shells  12 A- 14 A are shown having a relatively thin wall thickness, it is considered to have relatively solid shells  12 A- 14 A, with a passage for the skeleton member (hence the expression tubular bodies). 
     Referring to  FIG. 3 , the skeleton member  15  has an actuator end  50 , and an elongated articulated arm  51  projecting from the actuator end  50 . The actuator end  50  may be of any shape as a function of the actuator used with the mechanical finger  10 . In  FIG. 3 , the actuator end  50  has an annular shape to be connected to an output rod of an endless screw actuator. The inner surface of the actuator end  50  may therefore be tapped to move in translation as a function of a rotation from the endless screw. The annular shape of the actuator end  50  is also well suited for connection with a rod or shaft of a translational actuator. 
     The articulated arm  51  has a first arm segment  52  and a second arm segment  53 . The first arm segment  52  is connected to the actuator end  50  by a first throat portion  54 , whereas the arm segments  52  and  53  are interconnected by a second throat portion  55 . The throat portions  54  and  55  are essentially narrowing locations in the articulated arm  51 , allowing the pivoting movement between interconnected parts. A flaring shape of the throat portions  54  and  55  ensures that the skeleton member  15  bends in the direction shown for instance in  FIGS. 5A-5D , when actuated. Alternative constructions are considered as well, such as the use of pivot pins for separated components. However, the articulated arm  51  of  FIG. 3  is an integrally molded piece. 
     Referring concurrently to  FIGS. 3 and 4 , follower  56  is provided on the first arm segment  52 , adjacent to the throat portion  54 . The ends of the follower  56  are received in the slots  33  (one shown) in the middle phalange  13 , thereby forming a translational/rotational joint. Accordingly, a translational movement of the actuator end  50  may result in a translational movement of the follower  56  in the slots  33 , and/or a rotation of the middle phalange  13  with respect to the base phalange  12 , when the follower  56  abuts against the ends of the slots  33 . 
     Pivot  57  is positioned on the second arm segment  53 , and received in the pivot housings  43  (one shown) in the end phalange  14 . Therefore, a translational movement of the actuator end  50  will result in a pivoting movement of the end phalange  14  with respect to the pivot  57 , and hence with respect to the middle phalange  13 . 
     According to an embodiment, the skeleton member  15  is made of a combination of semi-rigid material and rigid reinforcements (e.g., metal, plastic, etc). For instance, the skeleton member  15  may be a molded integral piece in the semi-rigid material, with rigid reinforcement plates on the arm segments  52  and  53 , and caps or the like on the follower  56  and the pivots  57 . As they are on portions of the skeleton member  15 , rigid reinforcements do not substantially affect the flexibility of the mechanical finger  10 . 
     Referring to  FIGS. 5A-5D , a sequence of grasping movements of the finger  10  is illustrated, without and with contact against an object X. In  FIGS. 5A-5D , a compression spring  60  is provided in the mechanical finger  10 , between the skeleton member  15  and an interior of the middle phalange  13 . Although a coil spring is illustrated, any other suitable type of resilient member can be used. The compression spring  60  maintains the end phalange  14  straight with respect to the middle phalange  13 , in the absence of an exterior restriction. In  FIG. 5A , the actuator end  50  of the skeleton member  15  is at a first position along the endless screw shaft  61  of an actuator. In this first position, the skeleton member  15  is generally straight, resulting in the phalanges  12 - 14  of the finger  10  being in a straight relation with respect to one another. 
     In  FIG. 5B , the actuator end  50  has moved along the endless screw shaft  61  to a second position, as a result of a rotation of the endless screw shaft  61 . Because of the compression spring  60  keeping the phalanges  13  and  14  in a straight relation, it is the arm segment  52  that has pivoted with respect to the actuator end  50 , resulting in the bending of the middle phalange  13  with respect to the base phalange  12 . 
     Referring to  FIGS. 5C-5D , the actuator end  50  is in the same two positions along the shaft  61  as in  FIGS. 5A and 5B , but with an object X abutting against the middle phalange  13 . The object X prevents the bending of the middle phalange  13  with respect to the base phalange  12 . Accordingly, the translation of the articulated arm  51  of the skeleton member  15  pushes the end phalange  14  into pivoting with respect to the middle phalange  13 , against the action of the compression spring  60 . The finger  10  in combination with other fingers  10  may therefore grasp the object. In the sequence of  FIGS. 5C and 5D , the follower  56  has moved in translation in the slot. 
     In  FIGS. 5A-5D , it is observed that the base phalange  12  has not moved. This is due to the fact the base phalange  12  is anchored to an actuator casing or palm, not shown for clarity purposes. 
     Referring to  FIG. 6 , the mechanical finger  10  is secured to an actuator  70 . The actuator  70  may be a endless screw actuator as described previously, or any other actuator directing the actuator end  50  ( FIG. 3 ) in a translational movement. Bolts  71  anchor the base phalange  12  to a casing of the actuator  70 , by being received in the connection slots  22 . 
     Referring to  FIG. 7 , three of the mechanical finger  10  are mounted to a palm actuator  80 . The palm actuator  80  provides actuation to all three of the mechanical fingers  10  in the manner described above. Although not shown, it is considered to provide the palm actuator  80  with orientation actuation, so as to orient the fingers  10  in view of specific tasks (e.g., pinch grasp). The fingers  10  of the palm actuator  80  may be interrelated such that the single degree of actuation of the palm actuator  80  produces the actuation of each mechanical finger  10 , making the combination of the mechanical fingers  10  and palm actuator  80  underactuated. This interrelation may be achieved by having a transmission connected to the input shaft of the palm actuator  80 , which transmission has multiple output shafts connected to the actuator ends  50  of all skeleton members  15 . 
     As discussed above, the phalanges  12 - 14  and the skeleton member  15  are preferably made of a semi-rigid material, whereby all structural members are made of the semi-rigid material, making the mechanical finger compliant in all directions in case of contacts causing a force of a given magnitude. For instance, these components are molded in a polymeric material or rubber having a hardness ranging between 50 and 98 Shore A, although a hardness outside of the range may be used as well. The hardness of the components is selected as a function of the application of the mechanical finger  10 . As an alternative to having the skeleton member  15  being made of the same or a similar material as the phalanges  12 - 14 , it is considered to fabricate the skeleton member  15  in a rigid material (e.g., metal), or to use cables or the like as skeleton member. 
     The shells of the phalanges  12 - 14  may be molded with gripping patterns, such as a knurling pattern, on the contact areas of the phalanges  12 - 14 . Such gripping patterns increase the friction surface at the contact areas. 
     Although the mechanical finger  10  is well suited for prosthesis and technical-aid applications, it is pointed out that the mechanical finger  10  may be used for any other appropriate application. For instance, robots or manipulators may be equipped with the mechanical finger  10  in white-room applications, to manipulate chemicals. This is one application among numerous others.