Artificial foot that enables Limp-free walking

{
  "publication_number": "US5913902A",
  "country": "US",
  "kind": "A",
  "title": "Artificial foot that enables Limp-free walking",
  "abstract": "An improved energy-storing artificial foot, connectable onto a lower end of an artificial leg worn by a leg amputee, includes a ball of foot part, a main foot part, and an ankle part. The artificial foot includes first and second transversely positioned pivotal axes that are spaced longitudinally from one another. The first axis, carried in the ankle part, is positioned in vertical alignment with a longitudinal axis of an artificial leg, is about four times higher from a ground surface than is the second axis, and is positioned 78% of the length of the artificial foot as measured from the forward end of the foot. The second axis is positioned in the ball of the foot region of the artificial foot, which is about a third of the length of the foot as measured from a forward end of the foot. A pair of vertically disposed compression springs flank the first axis to simulate muscles that support an ankle. A third compression spring, disposed at a predetermined angle relative to a support surface, and which is housed so that it extends between the main foot part and the ball of foot part, provides resistance to pivoting of the ball of foot part relative to the main body part of the artificial foot and otherwise serves as the arch of the foot. The positioning of the first and second axes relative to the forward end of the articial foot, relative to each other and relative to the support surface is critical, as is the positioning of the ball of foot spring, because such positioning of parts collectively enables a user to walk without limping and to climb or descend stairs without restriction. The foot automatically adjusts, requiring no shims, to shoes of differing heel heights.",
  "claims": [
    "1. An artificial foot for an improved, more natural articulation and stride in walking use by a leg amputee, comprising: a main foot part defining a heel of said artificial foot; an ankle part pivotally connected to an upper part of said main foot part for limited pivotal fore-and-aft movement about a first axis which is oriented generally transversely to a length of said artificial foot, said ankle part including a substantially upright mounting post for connection with a lower end of an artificial leg; front and rear substantially parallel, spaced resilient ankle compression members each preloaded in compression and positioned uprightly fore and aft, respectively, of said first axis and acting between said main foot part and said ankle part whereby said mounting post is maintained in a substantially upright at rest orientation and is resiliently pivotable in either direction about said first axis first against said rear spring, and second against said front spring in walking use; a ball of foot part pivotally connected to a forward end of said main foot part for limited pivotal upward movement about a second axis that is generally parallel to said first axis, said second axis being closer to a ground-engaging surface of said artificial foot than said first axis; a resilient ball of foot flexure compression member preloaded in compression and positioned in an area of said artificial foot that substantially corresponds to an arch area of a natural foot and acting above said second axis between said main foot forward end and said ball of foot part whereby said ball of foot part is held in an at-rest position against a stop means and is gradually pivoted upwardly about said second axis against said ball of foot flexure compression member during a later stage of each stride taken during walking use; said second axis being positioned longitudinally with respect to said artificial foot at a distance about 35% of a length of said artificial foot from said forward end thereof where 100% represents a back of a heel position of said artificial foot and said second axis being positioned about half way between the ground-engaging surface and said ball of foot flexure compression member; said second axis being positioned vertically a distance of about one-quarter of a vertical distance of said first axis above the ground-engaging surface; and said first axis being positioned about 78% of a length of said artificial foot from said forward end thereof where 100% represents a back of a heel position of said artificial foot.",
    "2. An artificial foot for an improved, more natural articulation and stride in walking use by a leg amputee, comprising: a main foot part defining a heel of said artificial foot; an ankle part pivotally connected within an upwardly opening ankle cavity formed in an upper part of said main foot part for limited fore-and-aft pivotal movement about a first axis which is oriented generally transversely to a length of said artificial foot, said ankle part including an upwardly extending mounting post for connection with a lower end of an artificial leg; a pair of substantially parallel, spaced ankle compression springs each preloaded in compression and positioned uprightly each spring being formed into a lower surface of said ankle part and said ankle cavity fore and aft, respectively, of said first axis and acting between said main foot part and said ankle part whereby said mounting post is maintained in a substantially upright at-rest orientation and is forcibly pivoted in either direction against one of said ankle spring at a time in walking use; a ball of foot part connected to a forward end of said main foot part for limited pivotal movement about a second axis that is generally parallel to said first axis, said second axis being closer to, but above, a ground-engaging surface of said artificial foot than said first axis; a ball of foot flexure compression spring preloaded in compression and positioned and acting above said second axis between said main foot forward end and said ball of foot part whereby said ball of foot part is held in an at-rest position against a stop means and is gradually pivoted upwardly about said second axis against said ball of foot flexure compression spring during each step taken with said artificial foot during walking use; a first end of said ball of foot flexure compression spring seated in a mating cavity formed into said main foot forward end and a second end of said ball of foot compression spring seated in a mating cavity formed into a rearwardly facing surface of said ball of foot part; said second axis being positioned vertically a distance of about one-quarter of a vertical distance of said first axis above the ground-engaging surface; and said first axis positioned 78% of the way from the forward end of said artificial foot and said second axis positioned 35% of said way where 100% represents the positioning of a back of a heel of said artificial foot."
  ],
  "cpc": [
    "A61F 2/66",
    "A61F 2/6607",
    "A61F 2002/5043",
    "A61F 2002/5075",
    "A61F 2002/6614",
    "A61F 2002/6621"
  ],
  "filing_date": "1998-07-20",
  "publication_date": "1999-06-22",
  "grant_date": "1999-06-22",
  "priority_date": "1996-09-30",
  "application_number": "US-11938898-A",
  "family_id": "27110933",
  "citations": [
    "US1215268A",
    "US16360A",
    "US2430584A",
    "US409311A",
    "US804207A",
    "US809875A",
    "US92031A"
  ]
}