The present invention relates to a prosthetic foot and, more specifically to a lightweight and durable prosthetic foot.
BACKGROUND OF THE INVENTION
[2] A prosthetic foot is an artificial foot that replaces the missing foot of a user. An amputee may use the prosthetic foot for greater mobility, allowing him or her to engage in more physical activities. Prosthetics helps the amputated person to live a normal life and participate in sports and other recreation activities they could not afford earlier.
[3] Prosthetic feet are well known in the art, with several improvements made therein to enhance the comfort of the user using the prosthetic foot. The prosthetic devices these days are more advanced and closely imitate real limbs in function and appearance.
[4] Today, prosthesis are designed for maximized strength, however, the cost of added weight makes them unsuitable for users. Moreover, their prolonged usage will add to the discomfort. Also, the existing prosthetics cannot efficiently absorb the shocks/impacts generated while walking leading to jerks and causing pain in the knees and joints of the user.
[5] Furthermore, the life cycle of the existing prosthetic foot is very less. Due to the short life cycle, a user has to spend money to replace the prosthetic foot again after a short period which is very expensive.
[6] Accordingly, there is a need for an improved lightweight prosthetic foot strong enough to support its wearer and durable enough to withstand the stresses of repeated stepping motions over long periods. The prosthetic foot should also be

capable of mimicking the walking action of a human foot, should absorb impacts effectively and prevent jerks while walking.
SUMMARY OF THE INVENTION
[7] It is an object of the presently disclosed subject matter to overcome prior art sufferings and develop a novel lightweight and durable prosthetic foot that can mimic the walking action of a human foot, absorb impact effectively and prevent jerks while walking.
[8] According to another object of the presently disclosed subject matter, a novel lightweight prosthetic foot is disclosed.
[9] According to another object of the presently disclosed subject matter, it relates to a prosthetic foot comprising
a shell consisting of:
a top portion having an opening thereof;
a bottom portion having a resilient toe portion comprising a slot, and a resilient heel portion;
a hollow region extending between the bottom portion and the top portion of the shell;
a keel comprising a front end and a rear end, and is positioned inside the shell such that a gap is maintained between the rear end of the keel and the bottom portion of the shell.
wherein the keel is configured to flex upon application of load.
[10] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the resilient heel portion comprises a bore and a hollow insert positioned inside the bore.
[11] It is yet another object of the presently disclosed subject matter to provide a

group consisting of POM, Acetal, PEEK, Polyamide (All types of Nylons), Polypropylene, or any other material known in the art.
[12] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the hollow insert is inmoulded with the resilient heel portion of the shell.
[13] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the hollow insert is glued inside the bore.
[14] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the keel comprises a first portion and a second portion.
[15] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the first portion is curved.
[16] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the second portion is straight.
[17] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the second portion of the keel comprises a bore.
[18] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the keel is configured to flex about an axis parallel to the ground and pass through the keel.
[19] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the front end of the keel is positioned inside the slot of the resilient toe portion.
[20] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the front end of the keel extends up to the Metatarsals.

[21] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein a supporting element is positioned in the gap between the rear end of the keel and the bottom portion of the shell.
[22] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the supporting element is formed integrally with the keel.
[23] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the supporting element comprises a bore.
[24] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein, the supporting element is made of a material selected from a group consisting of POM, Acetal, PEEK, Polyamide (All types of Nylons), Polypropylene, ABS or any other material known in the art.
[25] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the hollow insert, the bore of the second portion and the bore of the supporting element are coaxially aligned, and a bolt passes through them.
[26] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the bolt is made of a material selected from a group consisting of SS 316, SS 410, SS 18-8, Steel Grade 2, Steel Grade 5, Steel Grade 8, Alloy steel, Silicone bronze, Brass, Aluminium, Zinc, Chrome plated, Galvanized steel or any other material known in the art.
[27] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the hollow insert, the supporting element and the bolt together forms a connecting assembly configured to rigidly secure the keel inside the shell.
[28] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein an adapter is employed at the other end of the bolt for tightly securing the connecting assembly.

[29] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the adapter is a pyramid adapter.
[30] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the bore of the second portion comprises of internal threads to fasten the bolt.
[31] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the bore of the supporting element comprises of internal threads to fasten the bolt.
[32] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the prosthetic foot is a solid ankle, cushion heel (SACH) foot.
[33] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the resilient heel portion is configured to absorb the shock/impact generated on heel strike while walking.
[34] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the keel is made of resilient material.
[35] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot further comprising a top cover.
[36] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the keel comprises slots formed on the left and right faces of the keel.
[37] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the design and material of the keel can be varied to control stiffness and toe-off deflection of the keel.
[38] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the keel is removably secured inside the shell.

[39] It is yet another object of the presently disclosed subject matter to provide a prosthetic foot, wherein the user can interchange the keel depending on activity.
BRIEF DESCRIPTION OF DRAWINGS
[40] In order to understand the invention and to see how it can be carried out in practice, non-limiting examples and embodiments will now be described with reference to the accompanying drawings, in which:
[41] FIG. 1 illustrates a prosthetic foot 10 according to an embodiment of the invention;
[42] FIG. 2A. illustrates a sectional view of a shell 20 according to another embodiment of the invention;
[43] FIG. 2B. illustrates another sectional view of the shell 20 according to another embodiment of the invention;
[44] FIG. 2C illustrates an isometric view of the shell 20 according to another embodiment of the invention;
[45] FIG. 2D illustrates a hollow insert 93 positioned inside the shell 20 according to another embodiment of the invention;
[46] FIG. 3 A illustrates a side view of a keel 50 according to another embodiment of the invention;
[47] FIG. 3B illustrates an isometric view of the keel 50 according to another embodiment of the invention;
[48] FIG. 3C illustrates a bottom view of the keel 50 according to another embodiment of the invention;
[49] FIG.4 illustrates a supporting element 91 positioned in a gap 24 according to another embodiment of the invention;

[50] FIG. 5 illustrates a bolt 92 passing through the hollow insert 93, a bore 54 and a bore of a supporting element 91 according to another embodiment of the invention;
[51] FIG. 6A illustrates a connecting assembly 90 according to another embodiment of the invention;
[52] FIG. 6B illustrates a connecting assembly 901 according to another embodiment of the invention;
[53] FIG. 7 illustrates a prosthetic foot 10 according to another embodiment of the invention;
[54] FIG. 8 illustrates a top cover 140 according to another embodiment of the invention;
[55] FIG. 9A illustrates an adapter 170 according to another embodiment of the invention;
[56] FIG. 9B illustrates an adapter 170 connected to the bolt 92 according to another embodiment of the invention;
[57] Fig. 10 illustrates a prosthetic foot 101 according to another embodiment of the invention;
[58] Fig. 11 illustrates a prosthetic foot 102 according to another embodiment of the invention;
[59] Fig. 12 illustrates a prosthetic foot 103 according to another embodiment of the invention; and
[60] Fig. 13 illustrates a prosthetic foot 104 according to another embodiment of the invention;
DETAILED DESCRIPTION

[61] Reference will be made in detail to embodiments of the present disclosure. The same or similar elements and the elements having the same or similar functions are denoted by like reference numerals throughout the descriptions. The embodiments described herein with reference to drawings are explanatory, illustrative, and used to generally understand the present disclosure. The embodiments shall not be construed to limit the present disclosure.
[62] Aspects of the present invention are best understood by reference to the figures and description set forth herein. All the aspects described herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred aspects and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope herein without departing from the spirit and scope thereof, and the present invention herein includes all such modifications.
[63] A broad framework of the principles will be presented by describing various embodiments of this invention using exemplary aspects and represented in different drawing figures. For clarity and ease of description, each aspect includes only a few embodiments. Different embodiments from different aspects may be combined or practised separately, to design a customized process depending upon application requirements. Many different combinations and sub-combinations of a few representative processes shown within the broad framework of this invention, that may be apparent to those skilled in the art but not explicitly shown or described, should not be construed as precluded.
[64] The invention relates to a lightweight and durable prosthetic foot that can mimic the walking action of a human foot, absorb shock/impact effectively and prevent jerks while walking.
[65] According to embodiments of the invention, a lightweight prosthetic foot is disclosed. As shown in FIG. 1, the novel prosthetic foot 10 comprises a shell 20 and

a keel 50 positioned inside the shell 20. The keel 50 is configured to flex upon application of the load.
[66] According to an embodiment of the invention, it relates to a prosthetic foot 10 comprising
a shell 20 consisting of:
a top portion 21 having an opening 25 thereof;
a bottom portion 22 having a resilient toe portion 30 comprising a slot 31, and a resilient heel portion 32;
a hollow region 23 extending between the bottom portion 22 and the top portion 21 of the shell 20;
a keel 50 comprising a front end 57 and a rear end 60, and is positioned inside the shell 20 such that a gap 24 is maintained between the rear end 60 of the keel 50 and the bottom portion 22 of the shell.
wherein the keel 50 is configured to flex upon application of load.
[67] According to an exemplary embodiment of the present invention, the prosthetic foot 10 is a solid Ankle, Cushioned Heel (SACH) foot.
[68] The prosthetic foot 10 of the present invention is very light compared to existing products and thereby considerably reduces the effort required by the user to walk. The prosthetic foot 10 of the present invention is configured to have a longer life and can effectively absorb shock/impact.
[69] Fig. 2A, 2B shows a sectional view of the shell. The shell 20 comprises of the top portion 21 and the bottom portion 22. The bottom portion 22 comprises a resilient toe portion 30 and a resilient heel portion 32. A slot 31 is carved at the resilient toe portion 30 and a bore 33 is carved at the resilient heel portion 32. As shown in Fig. 2C, the top portion 21 comprises an opening 25 formed at the apex which is being used to insert various components of the prosthetic foot 10 inside the shell 20.

[70] The shell 20 comprises a hollow region 23, extending between the top portion 21 and the bottom portion 22, generated by removing the material of the shell 20 from the area shown in figures and this removal of the material considerably reduces the overall weight of the prosthetic foot 10 when compared to prior art prosthetic foot.
[71] The creation of hollow region 23 forms an empty space above the resilient heel portion 32, thereby increasing the shock-absorbing capacity of the resilient heel portion 32. The hollow region 23 of the shell 20 and the bottom portion 22 are configured such that when the prosthetic foot 10 touches the ground, the shock created by the impact is completely absorbed by the resilient heel portion 32 and no shock/impact is transferred to the other parts of the prosthetic foot 10. This shock absorption increases the durability and life of the prosthetic foot 10. Also, the shock absorption at the resilient heel portion 32 makes the prosthetic foot 10 more comfortable and efficient to use and reduces jerks experienced by the user.
[72] According to another embodiment of the invention, shell 20 is made of elastomeric material. Elastomeric materials are flexible, soft and provide good cushioning when pressed.
[73] According to another embodiment of the invention, shell 20 is made of polyurethane.
[74] According to another embodiment of the invention, shell 20 is fabricated/manufactured by injection moulding.
[75] According to another embodiment of the invention, shell 20 is made of plastic, wood, polymers, metal, alloys or any other materials obvious to a person skilled in the art.
[76] According to another embodiment of the invention, a hollow insert 93 is positioned inside the bore 33 of the resilient heel portion 32 as shown in FIG. 2D.

[77] According to another embodiment of the invention, the hollow insert 93 of the resilient heel portion 32 are in-moulded with the shell 20.
[78] According to another embodiment of the invention, the hollow insert 93 is glued inside the bore 33 by adhesives.
[79] According to another embodiment of the invention, the hollow insert 93 is made of a material selected from the group consisting of POM, Acetal, PEEK, Polyamide (All types of Nylons), Polypropylene, or any other material known in the art. The hollow insert 93 can be of any shape to suit the need.
[80] Fig. 3 A, 3B and 3C show different views of the keel 50 that is placed inside the shell 20 and takes the load of the walking. The keel 50 is configured to flex upon application of load. The keel 50 provides the functionality required for smooth walking.
[81] The keel 50 comprises a first portion having a front end and a read end, and a second portion having a front end and a rear end.
[82] According to a preferred embodiment the first portion is a curved portion 51 and the second portion is a straight portion 53.
[83] The straight portion 53 comprises a front end 59 and a rear end 60 and the curved portion 51 comprises a front end 57 and a rear end 58. The front end 57 of the curved portion 51 is positioned inside the slot 31 of the resilient toe portion 30 and extends up to the Metatarsal. The rear end 58 of the curved portion 51 is connected to the front end 59 of the straight portion 53.
[84] The curved portion 51 is configured to flex about an axis XX' parallel to the ground and pass through the curved portion 51 as shown in Fig. 3B and the keel 50 is configured to deflect in the Sagittal plane.
[85] According to another embodiment of the invention, the thickness of the keel 50 increases from the front end 57 towards the rear end 58. This variation in thickness helps in providing desired flexibility to the keel 50.

[86] The straight portion 53 of the keel 50 further comprises a transverse bore 54 and the keel 50 is positioned inside the shell 20 such that the gap 24 is maintained between f the straight portion 53 and the bottom portion 22 of the shell
20.
[87] The gap 24 aids in increasing the life of the keel 50 and the prosthetic foot 10 by effective impact absorption as when the resilient heel portion 32 touches the ground, the shock/impact generated due to impact is effectively absorbed by the resilient heel portion 32 and no shock/impact is transferred to the keel 50.
[88] According to another exemplary embodiment of the invention, the straight portion 53 and the curved portion 51 are formed as a single body.
[89] According to another embodiment of the invention, the straight portion 53 and the curved portion 51 are formed as two separate bodies and the rear end 58 of the curved portion 51 is connected to the front end 59 of the straight portion 53 through bolts, adhesives, pins or any other means known in the art.
[90] According to another embodiment of the present invention, the curved portion 51 of the keel 50 can be glued to the bottom portion 22 of the shell 20 using adhesives.
[91] According to another embodiment of the invention, the keel 50 of the invention is longer than the existing keels. As the length of the keel 50 is more, the keel 50 provides a better toe-off deflection as compared to existing keels. One important aspect of the present invention is that due to the creation of the hollow region 23 inside the shell 20 the overall weight of the prosthetic foot 10 is reduced considerably and even after using longer keel 50, the prosthetic foot 10 remains lightweight.
[92] The keel 50 according to the present invention is capable of storing and releasing energy when the keel 50 flex on the application of load and unflex upon removal of load. While walking, when the leg of the user is in an inclined state and the prosthetic foot 10 is on the ground, the keel 50 undergoes the toe-off deflection

and stores energy. When the user lifts the prosthetic foot 10 from the ground, the stored energy is released thus supplementing the lift. This energy storage and release provides a spring-back effect thereby reducing the effort of the user while walking and improving the performance, fatigue resistance, and comfort. The longer keel 50 provides more toe-off deflection and thus provides more energy storage and return. Due to the lightweight of the shell 20 and the longer keel 50, the walk of the user using the present prosthetic foot is more comfortable and requires less effort.
[93] According to another embodiment of the invention, the keel 50 comprises slots 56 formed on the left and right faces of the keel 50 as shown in Fig. 3B. The formation of slots 56 reduces the overall weight and stiffness of the keel 50.
[94] The design and material of the keel 50 can be varied to control the stiffness and toe-off deflection of the keel 50 depending on the application on the user e.g. running, walking, jumping, gymming etc.
[95] According to another embodiment of the invention, the keel 50 is removably secured inside the shell 20 and the user can interchange the keel 50 depending on activity.
[96] According to another embodiment of the invention, a supporting element 91 is positioned in the gap 24 between the rear end 60 of the keel 50 and the bottom portion 22 of the shell 20 as shown in FIG. 4. According to another embodiment, the supporting element 91 comprises a bore.
[97] According to another embodiment of the invention, the hollow insert 93, the bore 54 of the straight portion 53 and the bore of the supporting element 91 are coaxially aligned, and a bolt 92 passes through them as shown in FIG. 5.
[98] According to another embodiment of the invention, the bolt 92 is made of a material selected from a group consisting of SS 316, SS 410, SS 18-8, Steel Grade 2, Steel Grade 5, Steel Grade 8, Alloy steel, Silicone bronze, Brass, Aluminium, Zinc, Chrome plated, Galvanized steel or any other material known in the art.

[99] According to another embodiment of the invention as shown in FIG. 6 A, the hollow insert 93 and the supporting element 91 together form a connecting assembly 90 configured to rigidly secure the keel 50 inside the shell 20.
[100] According to another embodiment of the invention as shown in FIG. 6B, the hollow insert 93, the supporting element 91 and the bolt 92 together forms a connecting assembly 901 configured to rigidly secure the keel 50 inside the shell 20.
[101] The hollow insert 93 is rigidly fixed inside the bore 33 of the resilient heel portion 32 such that the hollow insert 93 can take the load of the connecting assembly 90.
[102] According to another embodiment, the supporting element 91 provides support to the keel 50 and prevent it from toppling. The supporting element 91 is made of a material selected from a group consisting of POM, Acetal, PEEK, Polyamide (All types of Nylons), Polypropylene, ABS or any other material known in the art. The supporting element 91 is positioned in the gap 24 such that the bore 54 of the keel 50, the bore of the supporting element 91 and the hollow insert 93 are coaxially aligned, and the bolt 92 passes through them.
[103] As shown in Fig. 6B, YY' is the common axis of the supporting element 91, the bolt 92 and the hollow insert 93.
[104] According to another exemplary embodiment of the invention, the axis YY' is perpendicular to the floor. According to another embodiment of the present invention, the axis YY' is not perpendicular to the floor.
[105] The connecting assembly 90 enables the keel 50 to substantially remain in its position before, during, and after application of load on the keel 50 and prevents/reduces any unwanted longitudinal and lateral movement of the keel 50. This leads to the reduction in the jerks that a user may experience while using the prosthetic foot 10, and thereby, eliminates any pain in the knees of the user. Also, as the keel 50 is securely held in its position, unwanted bending stresses induced in the keel 50 are eliminated thereby increasing the life of the keel 50.

[106] According to another embodiment of the invention, the supporting element 91 is cylindrical shaped.
[107] According to another embodiment of the invention, the supporting element 91 is L shaped.
[108] According to another embodiment of the invention, the supporting element 91 is formed integrally with the keel 50.
[109] According to another embodiment of the invention, the bore of the supporting element 91 comprises internal threads to fasten the bolt 92.
[110] According to another embodiment of the invention, as shown in FIG. 7, the supporting element 91 is formed integrally with the keel 50. The bolt 92 is inserted from top such that the bolt 92 engages with the thread inside the bore of supporting element 91. Thus, it eliminates the need for the hollow insert inside 93 in the shell 20. According to another exemplary embodiment, the hollow insert 93 can be added in the shell 20 to secure the keel 50 inside the shell 20.
[Ill] The opening 25 of the top portion 21 of the shell 20 is closed by a top cover 140 as shown in FIG. 8 according to an embodiment of the invention. The top cover 140 comprises an outer surface 143, an inner surface 144 and an opening 145. The outer surface 143 aligns with the outer surface of the shell 20 and gives a smooth continuous transition. The top cover 140 adds integrity to and maintains the shape of the shell 20. Further, it also enhances the aesthetic appearance of the prosthetic foot 10 when assembled.
[112] Fig. 9A and 9B shows an adapter 170 which can be employed at the other end of the bolt 92 for tightly securing the connecting assembly 90 according to another embodiment of the invention. The adapter 170 comprises a bore 171 having internal threads that engage with the threads of the bolt 92. The adapter 170 acts as a nut for tightening the connecting assembly 90.

[113] According to a preferred embodiment of the invention, the adapter 170 is a pyramid adapter, however, other types of adapter known to a person skilled in the art can also be used.
[114] According to another embodiment of the invention, the adapter 170 is tightened on the bolt 92 such that the supporting element 91 is in a compressed state.
[115] In still another embodiment the bolt 92 is configured to engage directly with the bore 54 of the keel 50 without the need of the adapter 170.
[116] According to another exemplary embodiment of the invention, the adapter 170 is integrally formed with the top cover 140.
[117] According to another embodiment of the invention, the adapter 170 is integrally formed with the supporting element 91 and the keel 50 is connected to the integrally formed adapter 170 through bolts, pins or any other means known in the art.
[118] According to another embodiment of the invention, the adapter 170, the keel 50 and the supporting element 91 are formed integrally.
[119] According to another embodiment of the invention, the adapter 170 is a separate formed body and is placed on the top cover 140 while assembling the prosthetic foot 10.
[120] According to another embodiment of the invention, the adapter 170 is integrally formed with the keel 50.
[121] According to another embodiment of the invention, the adapter 170 is inmoulded with the keel 50.
[122] According to another embodiment of the invention, as shown in FIG. 10, a prosthetic foot 101 comprises a keel 501 supported inside a shell 201 such that the bore of the keel 501 is provided with internal threads that engage with the threads on

a bolt 921. This engagement of the threads prevents the keel 501 from toppling down and eliminates the need for any supporting element.
[123] According to another embodiment, a nut can be attached to the upper surface of the straight portion of the keel 501 and the threads of the bolt 921 engage with the threads of the nut.
[124] According to another embodiment, a nut can be attached to the lower surface of the straight portion of the keel 501 and the threads of the bolt 921 engage with the threads of the nut.
[125] FIG. 11 shows a prosthetic foot 102 wherein the rear end of straight portion of a keel 502 rests inside a slot 600 formed in the shell 202 according to another embodiment of the invention.
[126] According to another embodiment of the invention, as shown in FIG. 12, a prosthetic foot 103 comprises a keel 503 further comprising an extension 700 configured to rest on the bottom portion thus eliminating the need for any supporting element.
[127] According to another embodiment of the invention, the extension 700 is parallel to the ground.
[128] According to another embodiment of the invention, the extension 700 is inclined or at any angle with respect to the ground.
[129] FIG. 13 shows a prosthetic foot 104, wherein the straight portion of the keel 504 rests on the shell 204 and no gap is maintained in this embodiment.
[130] In an exemplary embodiment, the prosthetic as shown in FIG. 11, FIG. 12 and FIG. 13 further comprises a bolt that can pass through the keel 502, 503, 504 and the shell 202, 203,204.
[131] In another embodiment of the invention, the method to use/assemble the prosthetic foot is described. The hollow insert 93 is in-moulded in the resilient heel

portion 32. The supporting element 91 is placed coaxially with the hollow insert 93 in the hollow region 23. The keel 50 is now inserted into the shell 20 through the opening 25. The keel 50 is positioned inside the hollow region 23. The front end 57 of the keel 50 aligns in the slot 31 of the resilient toe portion 30 and the bore 54 in the rear end 60 is positioned co-axial with the supporting element 91. Now, the bolt 92 is inserted passing through the hollow insert 93, the supporting element 91 and the bore 54. The adapter 170 is now tightened on the bolt 92. The prosthetic foot 10 is now ready to use.
[132] In another embodiment of the invention, the working principle of the prosthetic foot 10 is described. The prosthetic foot 10 works in four stages. In the first stage the user puts the prosthetic foot 10 on the ground wherein, the resilient heel portion 32 of the bottom portion 22 contacts the ground first and a force is applied by the ground on the resilient heel portion 32. The resilient heel portion 32 gets compressed and absorbs the shock/impact generated due to impact. In the second stage, the resilient toe portion 30 of the shell 20 is placed on the ground and the shell 20 rests flat on the ground. In the third stage, the user lifts the resilient heel portion 32 from the ground. In the second stage and the third stage, the keel 50 undergoes flexing and stores energy. In the fourth stage, the resilient toe portion 30 of the shell 20 is being lifted off from the ground. In this condition, the keel 50 tries to unflex itself and thus releases the stored energy which compliments the lifting of the resilient toe portion 30.
[133] Although the invention has been described with regard to its embodiments, specific embodiments, and various examples, which constitute the best mode presently known to the inventors, it should be understood that various changes and modifications as would be obvious to one having the ordinary skill in this art may be made without departing from the scope of the invention. The scope of the claims should not be limited by the preferred embodiments set forth in the examples but should be given the broadest interpretation consistent with the description as a whole. All changes that come with meaning and range of equivalency of the claims are to be embraced within their scope.

Claims:
We Claim:

1. A prosthetic foot 10 comprising:
a shell 20 consisting of:
a top portion 21 having an opening 25 thereof;
a bottom portion 22 having a resilient toe portion 30 comprising a slot 31, and a resilient heel portion 32;
a hollow region 23 extending between the bottom portion 22 and the top portion 21 of the shell 20;
a keel 50 positioned inside the shell 20 comprising:
a straight portion 53 having a front end 59 and a rear end 60;
a curved portion 51 having a front end 57 and a rear end 58 such that the front end 57 of the curved portion 51 is positioned inside the slot 31 of the resilient toe portion 30 and the rear end 58 of the curved portion 51 is connected to the front end 57 of the straight portion 53;
wherein the curved portion 51 is configured to flex about an axis parallel to the ground and passing through the curved portion 51, and the straight portion 53 is configured such that a gap 24 is maintained between the rear end 60 of the straight portion 53 and the bottom portion 22 of the shell 20.
2. The prosthetic foot according to claim 1, wherein the resilient heel portion comprises a bore and a hollow insert is positioned inside the bore.
3. The prosthetic foot according to claim 1, wherein the straight portion of the keel comprises a bore.

4. The prosthetic foot according to claim 1, wherein a supporting element
having a bore is positioned in the gap.
5. The prosthetic foot according to claim 2, claim 3 and claim 4, wherein the
hollow insert, the bore of the straight portion and the bore of the supporting
element are coaxially aligned, and a bolt passes through them.
6. A prosthetic foot comprising:
a shell 20 consisting of:
a top portion 21 having an opening 25 thereof;
a bottom portion 22 having a resilient toe portion 30 comprising a slot 31 and a resilient heel portion 32 comprising a bore 33;
a hollow portion 23 extending between the bottom portion 22 and the top portion 21 of the shell 20;
a keel 50 positioned inside the shell 20 comprising a front end 57 and a rear end 60 having a bore 54;
a connecting assembly 90 for rigidly securing the keel 50 inside the shell 20 wherein the connecting assembly 90 comprises:
a hollow insert 93 positioned inside the bore 33 of the resilient heel portion 32;
a bolt 92; and
a supporting element 91 having a bore;
characterized in that the front section of the keel is positioned inside the slot of the resilient toe portion, and the rear section of the keel is configured such that a gap is formed between the rear section of the keel and the bottom portion of the shell, and

the hollow supporting element is positioned in the gap such that the bore of the keel, the bore of supporting element and the hollow insert are coaxially aligned and the bolt passes through them.
7. The prosthetic foot according to claim 6, wherein the shell is made of polyurethane.
8. The prosthetic foot according to claim 6, wherein the prosthetic foot is a solid ankle, cushion heel (sach) foot.
9. The prosthetic foot according to claim 6, wherein the resilient heel portion is configured to absorb the impact while walking.
10. The prosthetic foot according to claim 6, wherein the keel is made of resilient
material and is configured to flex/unflex and store/release energy.