it shows first phalange 1 , second phalange 2 , third phalange 3 , first tendon 4 , second tendon 5 , activating rod 6 and rod &# 39 ; s guiding pin 9 . each phalange has a clevis at one end and one ear at the other end . guiding pin 9 is placed with loose in the round holes made across the ears placed on the palm structure and has a role to allow side movements of the upper part of the rod while restricting undesirable side movements of the lower part of the rod . the driving rod protrudes with the loose through the hole made across said pin 9 . this will allow for the unrestricted up and down movement of the driving rod . on the palm structure are shown two more single ears for mounting the neighboring fingers . it shows all elements and describes the mechanics of the presented invention . it shows driving rod 6 placed in the clevis of the first phalange 1 and connected to that phalange by the pin 12 which is press fitted in the clevis and loose in the rod . in the middle of the first phalange 1 there is an opening through which protrudes firs tendon 4 . said tendon 4 can be anchored to the back of the palm structure or , as shown here , can be connected to the adjustable rod 7 . the other end of the tendon 4 is firmly connected to the front of the second phalange 2 by an any means of the firm connection , and depending on the materials used , it can be glued , thermo integrated with the second phalange &# 39 ; s material , connected by a mechanical fasteners and as such . the same connection applies to the both ends of the second tendon 5 which is permanently anchored to the back of the first phalange , protrudes through the middle opening of the second phalange and is firmly connected to the front of the third phalange 3 . the similar fastening will also apply to the lower end of the flat spring 8 which is permanently connected to the back of the first phalange . the upper end of said spring 8 protrudes through the slot placed at the back of the third phalange . the role of the spring is to straighten second and third phalanges upon up movement of the rod 6 . the spring can be single flat or multiple flats depending on the version of the prosthetic hand and the flexibility of the flesh imitating material . pins 10 connect firs phalange to the palm structure and the second phalange to the first phalange . the smaller pin 11 connects phalange 3 with phalange 2 . the pins are press fitted in the devises and having a loose in the ears . upon the movement of the first phalange initiated by the down moving rod 6 the first tendon 4 will be stretched because it &# 39 ; s lower end is not attached to the pivot point of the phalange 1 but to an element behind . this tension of the tendon will initiate movement of the second phalange . similarly the movement of the third phalange will be initiated by the stretch of the second tendon upon movement of the second phalange . the length of the tendons as well as a shape of the lower back of the first and the second phalanges will determine amount of the stretch of the tendons and therefore will determine degree of the movement of the phalanges . the tension of the first tendon can be also adjusted by the down or up movement of the rod 7 and will apply mostly to the thumb finger because thumb for most of the grips , has a different timing for closing than remaining four fingers . it is believed that for all fingers the third phalanges degree of movement don &# 39 ; t need any adjustments as they are moving in the strict relation with the second phalanges except for the thumb again . but in order to accommodate for the fundamental movements steering elements for all the fingers in the arm limited space , some secondary functions are intended to be abolished as the goal of this invention is not to create perfect human prosthetic hand but rather more simple , yet practical , reliable and affordable one . it shows first and second phalanges clevises and ears configuration at the pivot point . they are shaped to make a contact in the point p and keep phalanges in the straight position when open and prevent them from over bending by the action of the spring 8 . it shows adjustable rod 7 and the lower end of tendon 4 . it shows the one of many possible connections between them throughout pin 11 which is press fitted in the rod &# 39 ; s clevis . it is the section throughout guiding pin 9 and protruding across it activating rod 6 shown and described previously on fig1 . the same mechanism is used also in the massaging device fig7 for connecting fingers 24 and 25 with disc 23 . it is the cross section of the top of the third phalange 3 . it shows slot at the back of phalange throughout which protrudes spring 8 . it shows the massaging device installed in the back of the chair . it shows all the parts used and describes mechanics of said massaging device . cylinder 21 is threaded on its outside bottom diameter and is fastened to chair &# 39 ; s structure by nuts 27 . special washers 28 are having unparallel surfaces on both sides what allows to adjust device &# 39 ; s mounting angle on the chair . inside cylinder 21 is placed piston 22 sealed with o rings 14 . the bottom boss of the piston 22 is out of round to accommodate for the gripping tool during assembly . under the bottom of the piston is placed spring 26 and washers 20 and 30 . inner wall of the lower end of the cylinder 21 has thread to connect closing plug 29 . connection is sealed by gasket 17 . in upper part of the cylinder there is threaded side hole in which is placed nozzle 19 . hose 16 is attached to the nozzle and secured by clip 18 . upper part of the cylinder 21 has a bigger diameter to accommodate for the fingers 24 and 25 as well as the driving disc 23 . said driving disc 23 is round and is guided with loose in the round opening made in the upper end of cylinder 21 . disc 23 has two slots opposite to each other and two round holes across the slots . in said across holes are placed with loose guiding pins 13 which have round holes across them . disc 23 has a threaded hole in the centre and is connected through it with the rod of the piston 22 . cylinder 21 has a hole in the centre between the lower and the upper part of the body . through this hole protrudes piston &# 39 ; s 22 rod and it is sealed with the o ring 15 . two slots opposite to each other are made in the wall of the upper body of the cylinder 21 . in those slots are placed fingers 24 and 25 which are connected to the body of said cylinder 21 with the pins press fitted in the across holes . this connection is the same one than between the finger and the palm structure and was earlier described on fig1 and fig2 . also the finger 24 is the same than earlier described on fig1 , fig2 , fig3 and fig6 . the only difference is that the clevis to connect activating rod at the front of the lower end of first phalange is eliminated and this part of the phalange is shaped into the round pin . those round pins placed at the bottom of the fingers 24 and 25 are protruding with loose through across holes of the guiding pins 13 . said guiding pins 13 are acting the same way than earlier described on fig1 and fig5 guiding pin 9 . they will turn in their round holes of the disc 23 during up and down movement of said disc what will allow for sliding in them round bottom pins of the fingers 24 and 25 and therefore allow unrestricted movement of the fingers . described above two fingers are intended to imitate pinching action of the thumb and the index or the thumb and the middle finger . one or two more slots can be added though to the upper wall of the cylinder 21 as well as to the driving disc 23 and one or two more fingers or specifically shaped claws can be accommodated into these slots . such a device can be attached to a tip of mechanical arm or a manipulator . the presented here massaging device is powered preferably by pressurized air what will allow to install multiple units in a chair or other structure and operate them by a single pump . the air supplied through hose 16 will drive piston 22 down and together with it will drive down disc 23 . down movement of the disc 23 will create closing action of the finger 24 and finger 25 together with the bending action of the finger 24 as per previous description . the opening of the fingers is done by the action of compressed spring 26 upon release of the air pressure . it shows skeleton of the finger and both tendons in the straightened inactive position as well as a bare skeleton of the finger in the closing position . this figure is intended to clarify the fingers bending mechanism . the entire finger without tendons from the first upward position to the second lower position would rotate about point a . point c of the second phalange where upper end of the first tendon attaches would move along the arc defined by radius r and in lower position would take location c 2 . point c of the upper end of the first tendon will rotate about point b along the arc defined by radius r 1 and in the lower position will take location c 1 forcing therefore point c 2 to move along the arc defined by radius r to the location c 1 where the arcs of radius r 1 and radius r intersect . the same principle applies toward rotation of the third phalange upon stretching of the second tendon and it is very characteristic to this design that top phalange will be bending spontaneously with the middle phalange just like in our human fingers where it is very difficult or impossible to bend middle digit without bending top digit at the same time .
a mechanical finger which visually and functionally resembles a human finger . the finger consists of three phalanges pivoted in their clevises . the first phalange is driven by a rod located in an arm and being connected to an actuator . the second and third phalanges are driven by tendons . the tension of the second phalange tendon is initiated by the movement of the first phalange and the tension of the third phalange tendon is initiated by the movement of the second phalange .