WO1997024942A1 | 1997-07-17 |
DE202005001988U1 | 2005-05-12 | |||
US4873774A | 1989-10-17 | |||
US5289647A | 1994-03-01 | |||
US6125556A | 2000-10-03 | |||
US20110047830A1 | 2011-03-03 | |||
US20080066348A1 | 2008-03-20 | |||
US20060130372A1 | 2006-06-22 |
Claims 1. A retractable stud having an outer housing for insertion in a cavity in the lowermost tread surface of a shoe sole, comprising: a piston capable of a vertically downward movement within the outer housing from a first position to a second position; and means of returning the piston from the second position to the first position; wherein an application of pressure causes the piston to move vertically downward from the first position to the second position and wherein the piston is returned from the second position to the first position upon removal of pressure; wherein an outer surface of the outer housing has screw threading for insertion in said caVity, and further wherein said outer housing comprises an internal cavity. 2. The retractable stud of claim 1 , wherein said piston in a first position is in a fully retracted position and wherein said piston in a second position is in a fully extended position. 3. The retractable stud of claim 1 , wherein said piston comprises a head portion and a tail portion. 4. The retractable stud of claim 3, wherein an outer surface of said head portion forms a tight seal with an inner surface of the outer housing. 5. The retractable stud of claim 3, further comprising a stud element attachable to said tail portion. 6. The retractable stud of claim 5, wherein said stud element is attachable to said tail portion by screw threading. 7. The retractable stud of claim , wherein said means of returning the piston from the second position to the first position comprises at least one conical spring. 8. The retractable stud of claim 1, further comprising a stop to prevent movement of said piston beyond the second position. 9. The retractable stud of claim 8, wherein an inner surface of said stop attaches to an outer surface of said outer housing by screw threading. 10. A shoe comprising: a sole having embedded therein at least one retractable stud, wherein said retractable stud comprises a piston capable of a vertically downward movement from a first position to a second position, and further wherein said piston comprises a head portion and a tail portion; said sole having an uppermost surface which supports the wearer's foot and a lowermost tread surface which is made flush with the at least one retractable stud in said first position; wherein said uppermost surface further comprises a means of applying pressure to the head portion of the piston to enable the vertically downward movement from the first position to the second position; wherein said means of applying pressure to the head portion of the piston comprises a compressible source of fluid pressure attached to the uppermost surface of the sole, and wherein said source is compressible under the body weight of the shoe's wearer; and further wherein contents of said compressible source of fluid pressure are in fluid communication with the head portion of the piston. 11. The shoe of claim 10, wherein said lowermost tread surface further comprises at least one cavity configured to receive a retractable stud. 12. The shoe of claim 10, wherein said piston in a first position is in a fully retracted position and wherein said piston in a second position is in a fully extended position. 13. The shoe of claim 10, wherein said at least one retractable stud further comprises an outer housing configured for embedding in said sole. 14. The shoe of claim 10, further comprising a means of returning the piston from the second position to the first position. 15. The shoe of claim 14, wherein said means of returning the piston from the second position to the first position comprises at least one conical spring. 16. The shoe of claim 10, further comprising a stop to prevent movement of said piston beyond the second position. 17. The shoe of claim 10, further comprising a stud element attachable to said tail portion. 18. A method of assembling a shoe having embedded in a sole at least one retractable stud capable of a vertically downward movement from a first position to a second position, comprising the steps of: i) securing a sole having at least one cavity to a lowermost tread surface of said shoe; ii) attaching a compressible source of fluid pressure to an uppermost surface of sole which supports the wearer's foot, iii) embedding the outer housing of one retractable stud in said at least one cavity, iv) inserting a piston in said outer housing, wherein said piston is capable of a vertically downward movement from a first position to a second position, v) inserting at least one means of returning the piston from the second position to the first position, and v) attaching a piston stop to prevent vertical movement of the piston beyond the second position; wherein said piston has a head portion and a tail portion; and further wherein contents of said compressible source of fluid pressure are in fluid communication with the head portion of the piston. 19. The method of claim 18, wherein the lowermost tread surface of said sole is made flush with said at least one retractable stud in said first position. 20. The method of claim18, further comprising the step of attaching a stud element to the tail portion. 21. The method of claim 18, wherein said retractable stud in a first position is in a fully retracted position and wherein said retractable stud in a second position is in a fully extended position. 22. The method of claim 18, wherein said means of returning the piston comprises at least one conical spring. |
2011, the contents of which are included herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a retractable stud for insertion in the sole of a shoe.
2. Description of the Related Art
Shoes having retractable studs are known, in which the user is required to operate the individual extending and retracting mechanism at each shoe. This requires the user to bend down to ground level for each extension and retraction of the studs. There are obvious disadvantages of such a mechanism in circumstances where the extension/retraction mechanism needs to be operated rapidly, and when the user has difficulty in bending down to ground level.
Further, shoes having retractable studs are known, in which a remote- operating means is used to conveniently actuate extension and retraction of the studs of both shoes simultaneously by remote control. This conveniently enables the user to operate the studs without bending down to ground level. The remote-operating means may, for example, be attached to a waist belt.
BRIEF SUMMARY OF THE INVENTION
According to an aspect of the present invention, there is provided a retractable stud having an outer housing for insertion in a cavity in the lowermost tread surface of a shoe sole, which comprises a piston capable of a vertically downward movement within the outer housing from a first position to a second position and means of returning the piston from the second position to the first position. An application of pressure causes the piston to move vertically downward from the first position to the second position. The piston is returned from the second position to the first position upon removal of pressure. The outer housing also comprises an internal cavity.
According to a second aspect of the present invention, there is provided a shoe comprising a sole having embedded therein at least one retractable stud. Said retractable stud comprises a piston capable of a vertically downward movement from a first position to a second position and said piston comprises a head portion and a tail portion The sole has an uppermost surface which supports the wearer's foot and a lowermost tread surface which is made flush with the at least one retractable stud in said first position. The uppermost surface further comprises a means of applying pressure to the head portion of the piston to enable the vertically downward movement from the first position to the second position. The means of applying pressure to the head portion of the piston comprises a compressible source of fluid pressure attached to the uppermost surface of the sole, and the source is compressible under the body weight of the shoe's wearer. The contents of said compressible source of fluid pressure are in fluid communication with the head portion of the piston.
According to a third aspect of the present invention, there is provided a method of assembling a shoe having embedded in a sole at least one retractable stud capable of a vertically downward movement from a first position to a second position, comprising the steps of: securing a sole having at least one cavity to a lowermost tread surface of said shoe; attaching a compressible source of fluid pressure to an uppermost surface of sole which supports the wearer's foot; embedding the outer housing of one retractable stud in said at least one cavity; inserting a piston in said outer housing, wherein said piston is capable of a vertically downward movement from a first position to a second position; inserting at least one means of returning the piston from the second position to the first position, and attaching a piston stop to prevent vertical movement of the piston beyond the second position. The piston has a head portion and a tail portion and the contents of said compressible source of fluid pressure are in fluid communication with the head portion of the piston.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
Figure 1 shows a football player wearing standard football shoes of the prior art;
Figure 2 shows a football shoe of the prior art;
Figure 3 shows a cross section of a retractable stud embodied by the present invention;
Figure 4 shows a shoe embodied by the present invention;
Figure 5 shows a shoe embodied by the present invention;
Figure 6 shows a piston embodied by the present invention;
Figure 7 shows a cross section of a retractable stud embodied by the present invention;
Figure 8 shows a shoe and a cross section of a retractable stud embodied by the present invention;
Figure 9 shows two football players wearing shoes embodied by the present invention; and
Figure 10 shows a method of assembling a shoe embodied by the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 1
Figure 1 relates to the prior art and shows a football player 101 wearing traditional football shoes 102. Such football shoes 102 have studs on the lowermost tread surface of the sole and injuries arising from these studs are common in football. Similarly, rugby shoes and boots are also studded, again leading to injuries to players. Injuries are caused not only through contact with the stud of another player's shoe, but also when a player merely turns to move position on the playing field. In the latter situation, the player's studs get stuck in the ground in a particular orientation and then the player's body continues to move while their foot is still planted in the ground. This results in strains and/or tears to the ligaments, tendons and cartilage in the hips, knees or ankles, bone dislocation and also bone fractures. Damage to any of ligament, cartilage or tendon is a serious injury and can take weeks or even months to heal. The football or rugby player will therefore be unable to participate in the sport for a prolonged period of time. Such stud injuries occur in both top-level professional players, in amateur participants and all levels in between. Time off for professional players may equate to financial losses for clubs whilst injuries in amateur participants may discourage further participation.
Figure 2
Figure 2 relates to the prior art and shows a standard football shoe 201 comprising round peg-like studs 202. The studs are in a state of permanent projection from the lowermost tread surface of the shoe sole 203. Standard football shoes comprising studs in the shape of blades are also known. Such blades may be up to three centimetres long and are shaped to contour the foot. Consequently, football shoes with blade-like studs are even more susceptible to causing direct injury to other players and to becoming stuck in the mud or grass of the playing field. When this happens, the player's body continues to move while their foot is still planted in the ground, resulting in injury to ligament, tendon and cartilage of the hips, knees and ankles, bone dislocation and also bone fractures.
Figure 3
Figure 3 shows a cross section of a retractable stud 301 embodied by the present invention. Retractable stud 301 comprises an outer housing 302. Outer housing 302 is an independent body for insertion into a preformed cavity in the lowermost tread surface of a shoe sole (not shown). In an embodiment, outer housing 302 is cylindrical in nature and comprises an internal cavity 306. Outer housing may be fabricated from a suitable plastic or aluminium.
Outer housing 302 is open at one end and at the other end comprises means for insertion 305 into a preformed cavity in the lowermost tread surface of a shoe sole (not shown). The means for insertion 305 into a preformed cavity in the sole of a shoe may comprise screw threads on the outer surface of the outer housing. As such, the preformed cavity in the sole of a shoe also comprises screw threads for mating with the outer housing.
The part of the outer housing providing the means for insertion 305 into a preformed cavity in the sole of a shoe may also be of a cylindrical nature but may have a smaller diameter than the outer housing 306. Means for insertion 305 comprises an internal cavity 307.
Outer housing 302 receives piston 303, which is inserted into outer housing 302 once outer housing 302 is inserted into a preformed cavity in the lowermost tread surface of a shoe sole. Piston 303 comprises a head portion 308 and a tail portion 309. In an embodiment, the top view of the head portion 308 is circular so that its circumference directly engages with an internal wall of the internal cavity 306 of the outer housing. The head portion 308 of piston is resistant to movement such that the head portion 308 only moves vertically downward when subject to a compressive force from a weight-bearing wearer of the shoe comprising the retractable stud. Piston 303 may be fabricated from a suitable plastic or aluminium.
The head portion 308 of the piston has a groove around its circumference. An O-ring seal 3010 nests within this groove to enhance the tight fit and direct engagement of the piston head within the internal cavity 306 of the outer housing. Any other type of seal which provides this tight fit and which enhances the engagement of the head portion 308 with the inner wall of the internal cavity 306 of the outer housing may also be used. In an embodiment, a single conical spring 304 provides a means of returning the piston from the second position (wherein piston 303 is fully extended) to the first position (wherein piston 303 is fully retracted). Single conical spring 304 is inserted into outer housing 302 once piston 303 is positioned within the cavity 306 of the outer housing and is inserted around the tail portion 309 of the piston. Single conical spring 304 thereby encircles the tail portion 309 of piston 303.
The length and wire gauge of conical spring 304 is such that conical spring 304 fully extends along its length when it is not under compression and coils fully when compressed by the weight of the wearer of the shoe comprising the retractable stud. The coils of single conical spring 304 are tapered so that when compressed by the weight of the wearer of the shoe comprising the retractable stud, the coils of the tapered spring telescope into each other, giving a shorter coil bind height. Advantageously, maximum compression of the piston can be achieved when the conical spring is subject to compressive forces as a result of the weight-bearing wearer of the shoe comprising the retractable stud. Spring 304 may be made from any suitable material having the required combination of rigidity and elasticity. In an embodiment, conical spring 304 is fabricated from spring steel.
In an alternative embodiment, the means of returning the piston from the second position to the first position may include more than one spring.
The vertically downward movement of piston 303 is restricted so that movement beyond the second position is prevented. Piston therefore is capable of moving vertically downward from the first position to the second position, but no further. The vertically downward movement of the piston is arrested at the second position by stop 3011. Stop 3011 is attached to the outer housing once piston 303 and conical spring 304 have been inserted into the internal cavity 306 of the outer housing. In an embodiment, the top view of stop 3011 is circular in nature. The diameter of the stop is greater than that of the outer housing and thereby the stop is able to attach to the external surface of the outer housing. Preferably, the external circumference of the stop has a raised lip 3012, which contains screw threads on its internal wall. Preferably, an external surface of the outer housing has screw threads for mating with the screw threads of the dp 3012 of the stop. Thereby, the stop can be securely screwed onto the outer housing 302 once the piston 303 and conical spring 304 are in place.
The outer housing 302, piston 303, conical spring 304 and stop 3011 may be fabricated as separate pieces.
Figure 4
Figure 4 shows a retractable stud 401 inserted in a preformed cavity
402 in the lowermost tread surface 403 of sole of shoe 404. The piston (not shown) of the retractable stud is in a fully retracted first position and does not protrude beyond the lowermost tread surface 403 of the shoe sole. The retractable stud is flush with the lowermost tread surface 403 of the sole of the shoe.
When the shoe wearer's body weight is not resting on the sole of the shoe, the piston of the retractable stud is in the fully retracted first position, as shown in Figure 4. This occurs when a wearer lifts their foot off the ground and there is no contact between the shoe and the ground. Therefore, when a player lifts their foot to move position on the playing field, the studs of the player's football shoes move into the fully retracted first position and do not get stuck in the ground in a particular orientation. Accordingly, the player's foot does not remain planted in the ground but instead moves in a coordinated fashion with the rest of their body. Advantageously, there is neither strain nor tears to the ligaments, tendons and cartilage in the hips, knees or ankles, and further no bone dislocation or bone fractures.
Shoe 404 may comprise an additional sole 405 to ensure that retractable stud 401 does not protrude beneath the lowermost tread surface
403 when in the fully retracted first position. Additional sole 405 may be fabricated with preformed cavities, wherein each cavity 402 accommodates one retractable stud 401. Additional sole 405 is adhered to the lowermost tread surface 403 of the shoe by stitching, gluing or by any other suitable means.
There may be any number of preformed cavities 402 in the lowermost tread surface 403 of a shoe sole. A football shoe can have anything from 8 to 16 studs on the base. Therefore, a standard number of cavities 402 would be anything from 8 to 16 in each sole. There must be one cavity for each retractable stud. The preformed cavity receives the outer housing of the retractable stud, and therefore the cavity must be appropriately shaped to tightly coordinate with the outer housing. In an embodiment, the cavity is circular in nature in order to accommodate the cylindrically shaped outer housing. The preformed cavity is of an appropriate size to accommodate a retractable stud. The stud element of the retractable stud is of a standard stud size, of between 3 and 10 millimetres along its longest length.
Preferably, the inner wall of the preformed cavity has screw threads for mating with the outer housing of the retractable stud. The means for insertion of the outer housing into a preformed cavity in the sole of a shoe preferably comprises screw threads on its outer surface.
Figure 5
Figure 5 shows a retractable stud 501 inserted in a preformed cavity 502 in the lowermost tread surface 503 of shoe 504. The piston 505 of the retractable stud is in a fully extended second position and protrudes beyond the lowermost tread surface 503 of the shoe sole. Shoe 504 comprises additional sole 506 to ensure that retractable stud 501 only protrudes beneath the lowermost tread surface 503 when in the fully extended second position. Additional sole 506 is fabricated with preformed cavities 502, wherein each cavity 502 accommodates one retractable stud 501. Additional sole 506 is adhered to the lowermost tread surface 503 of the shoe by stitching, gluing or by any other suitable means.
When the shoe wearer's body weight rests on the sole of the shoe, the piston of the retractable stud is in a fully extended second position. This occurs when a wearer's shoe is in contact with the ground. The player may, for example, be standing on the playing field. In addition, the wearer's shoe is also in contact with the ground intermittently whilst the player is running or walking on the playing field. Figure 6
Figure 6 shows the piston 601 embodied by the present invention. Piston comprises a head portion 602 and a tail portion 603. Piston 601 is inserted into the interna) cavity of the outer housing once the outer housing has been inserted into a preformed cavity in the lowermost surface of a shoe sole.
In an embodiment, the top view of the head portion 602 is circular so that its circumference directly engages with an internal wall of the main cavity of the cylindrical outer housing. The head portion 602 of piston is resistant to movement such that head portion 602 only moves vertically downward when subject to a compressive force from a weight-bearing wearer of the shoe. Piston head portion 602 and tail portion 603 may be fabricated from a suitable plastic, aluminium, or any other suitable material.
The head portion 602 of piston has a groove around its circumference. An O-ring seal 604 nests within this groove to enhance the tight fit of the piston head 602 with the wall of the internal cavity of the cylindrical outer housing. Any other type of seal which provides this tight fit and which enhances the engagement of the head portion 602 of the piston with the wall of the internal cavity of the outer housing may also be used.
The base of tail portion 602 has screw threads 605 on its outer surface. A stud element (not shown) may be attached to the base of the tail portion 602 via these screw threads.
In an embodiment, tail portion 603 is between 15 and 20 millimetres in length. The screw threads 605 on an outer surface of tail portion 603 extend between 2 and 5 millimetres. Stud element (not shown) may be attached to these screw threads. The diameter of piston head 602 is between 7 and 10 millimetres and the thickness of piston head 602 is between 2 and 5 millimetres. The groove in head portion 602 has dimensions of 1 millimetre. However, alternative dimensions may also be used.
Figure 7
Figure 7 shows a cross section of a retractable stud 701 embodied by the present invention.
Outer housing 702 is an independent body for insertion into a preformed cavity in the lowermost tread surface of a shoe sole (not shown). Screw threads 705 on an outer surface of the outer housing may be used to attach the outer housing to the cavity. Outer housing 702 has an internal cavity 7010. Once outer housing 702 is in position in the preformed cavity in the lowermost tread surface of a shoe sole, piston 703 is placed into the internal cavity 7010 of outer housing 702. Conical spring 704 is then inserted into the internal cavity 7010 of outer housing 702 and positioned around the tail portion of the piston 703. Conical spring 704 thereby encircles the tail portion of the piston 703.
Piston 703 is capable of a vertically downward movement from a fully retracted first position to a fully extended second position. Stop 708 prevents movement of piston 703 beyond the fully extended second position. Stop 708 has screw threads 709 for attachment to an outer surface of the outer housing.
Stud element 706, is attachable to the tail portion of piston 703 by screw threading 707. The outer body of stud element 706 is attachable to outer housing 702 by screw threading. The outer body of stud element 706 moves the same vertical distance as the piston (see vertical arrows) and thus acts as a secondary piston stop. The outer body of stud element 706 also prevents foreign objects obstructing the piston movement, and provides additional stability when the piston is fully extended.
Advantageously, different stud elements can be attached to the tail portion of piston 703 to suit different pitch or weather conditions. The different stud elements may be of different lengths or shapes. Moreover, a varying number of studs may be attached to the shoe, again to suit different pitch or weather conditions. Further, the retractable stud may also be used in association with athletic shoes or cross country running shoes, where attachment of different length spikes is of great importance.
Once outer housing 702 is attached to the preformed cavity in the lowermost tread surface of the shoe sole, and once the piston 703, conical spring 704 and stop 708 are in position, the stud elements 706 can easily be interchanged without detaching any of the outer housing 702, piston 703, conical spring 704 or stop 708. The stud element 706 can simply be screwed onto the tail portion of the piston and this therefore allows an easy and straight-forward mode for changing the stud element 706.
In an alternative embodiment, the tail portion of piston 703 may itself act as the stud element and make direct engagement with the surface of the playing field. In such an alternative embodiment, the tail portion of piston 703 does not have screw threads 707. Instead, the tail portion of piston 703 is tapered towards its point to simulate a stud element (not shown). In a further embodiment, wherein the retractable stud is used in association with athletic shoes or cross country running shoes, the tail portion of piston 703 is tapered towards its point to simulate a spike (not shown).
Figure 8
A shoe 801 embodied by the present invention is shown in Figure 8. Shoe 801 may be a sports shoe such as used for playing football or rugby, or a running shoe such as used for athletics or cross country running.
Shoe 801 may comprise an additional sole 802 such that retractable stud 803 is flush with the lowermost tread surface of additional sole 802 and does not protrude beneath the lowermost tread surface of additional sole 802 when in the fully retracted first position.
A cross section of a retractable stud embodied by the present invention is also shown in Figure 8. Retractable stud 803 comprises an outer housing 809 which is inserted into a cavity 808 in the lowermost tread surface of the sole of shoe 801. On the uppermost portion of sole 805, which supports the wearer's foot, is attached a compressible source of fluid pressure 807. This source of fluid pressure may be a small sack made from neoprene or other suitable material and may contain any matter which is compressible under the weight of the shoe's wearer. The source of fluid pressure may therefore contain water, any aqueous solution, a semi-solid gel-like substance or air.
The outer housing 809 of retractable stud 803 may be inserted into the cavity 808 in the lowermost tread surface of sole of shoe 801 by means of screw threading. The outer housing 809 has an internal cavity which is in fluid communication with the contents of the source of fluid pressure. The contents of the source of fluid pressure can therefore move into the internal cavity of the outer housing.
Once outer housing 809 is in position, piston 803 is inserted into the internal cavity of the outer housing 809. The piston comprises a head portion and a tail portion. In an embodiment, the top view of the head portion 803 is circular so that its circumference directly engages with the wall of the internal cavity of the outer housing 809. Head portion 803 of the piston has a groove around its circumference. An O-ring seal sits within this groove to enhance the tight fit of the piston head within the internal cavity of the outer housing.
Compressible source of fluid pressure 807 on the uppermost portion of sole 805 is compressed when the bodyweight of the wearer of the shoe rests on the sole of the shoe. This occurs when the wearer is standing, or when the shoe touches the ground when the wearer is walking or running. The compressible source of fluid pressure 807 is in fluid communication 8010 with the internal cavity of the outer housing, and compression of the source of fluid pressure 807 forces the contents into the internal cavity of the outer housing.
The head portion of the piston 803 limits movement of the contents of the source of fluid pressure within the internal cavity of the outer housing. The O-ring seal around the circumference of the head portion of the piston 803 prevents leakage of the contents past the head portion 803.
The contents of the source of fluid pressure 807 in the internal cavity of the outer housing provide pressure on the piston head 803 and cause the piston to move vertically downward. The piston moves vertically downward from a fully retracted first position until it reaches a fully extended second position.
Conical spring 806 is compressed as a result of the vertically downward movement of the piston. The coils of conical spring 806 are tapered and the coils telescope into each other.
Stop 801 which is attached to the outer housing prevents movement of the piston 803 beyond the fully extended second position.
Stud element 8012 which is attached to the tail portion of piston 803 and to outer housing 809 therefore also moves vertically downward so that it is no longer flush with the lowermost tread surface of the sole but instead protrudes below the lowermost tread surface of the sole. In this position, stud element provides traction and grip on the playing field.
When the wearer of the shoe lifts their foot such that the lowermost tread surface of the shoe sole is no longer in contact with the playing field, their bodyweight is no longer on the sole of the shoe. After removal of the bodyweight, conical spring 806 provides a means of returning the piston from the fully extended second position to the fully retracted first position. Conical spring 806 fully extends once the bodyweight is removed and urges the head portion of piston 803 vertically upwards. This upward movement of piston head 803 forces the contents of the source of fluid pressure 807 back into the sack.
Figure 9
In position A, person 901 is standing with both shoes in direct contact with the playing field. In this position, the bodyweight of person 901 is resting on the uppermost surface of the sole and the contents of the source of fluid pressure are forced into the internal cavity of the outer housing (not shown). Consequently, piston head (not shown) moves vertically downward from a fully retracted first position to a fully extended second position. Stud element protrudes below the surface of the lowermost tread surface of the shoe and provides traction and grip for the player on the playing field.
In position B, person 902 has their left leg lifted, such that the left shoe is not in direct contact with the playing field. When person 902 lifts their left leg, conical spring within the retractable stud (not shown) provides a means of returning the piston from the fully extended second position to the fully retracted first position. In the shoe on person 902 's left foot, the retractable studs are flush with the lowermost tread surface of the sole.
Figure 10
Figure 10 shows a method of assembling a shoe embodied by the present invention, comprising a number of steps.
At 1001 , a sole having at least one cavity is secured to a lowermost tread surface of a shoe. There may be any number of cavities in the sole, and in an embodiment, there are between 8 and 6 cavities. These cavities are preformed in the sole before the sole is secured to the shoe. Each individual cavity is of a size that can accommodate a retractable stud. The sole may be secured to the lowermost tread surface of the shoe by gluing, stitching, or by any other suitable means.
At 1002, a compressible source of fluid pressure is attached to an uppermost portion of the sole which supports the wearer's foot. This compressible source of fluid pressure may be secured to the uppermost surface of the sole by gluing, stitching, or by any other suitable means. This source of fluid pressure may be a small sack made from neoprene or other suitable material and may contain any matter which is compressible under the weight of the shoe's wearer. The source of fluid pressure may therefore contain water, any aqueous solution, a semi-solid gel-like substance or air.
At 003, the outer housing of a retractable stud is embedded in each one of the cavities of the sole. The outer housing of a retractable stud may be embedded in the cavity by means of screw threads or any other suitable means.
At 1004, a piston is inserted in the outer housing of each retractable stud. The piston is capable of a vertically downward movement from a fully retracted first position to a fully extended second position.
At 1005, at least one means of returning the piston from the fully extended second position to the fully retracted first position is inserted in the outer housing. In an embodiment, the at least one means of returning the piston is a tapered conical spring which coils within itself.
At 1006, a piston stop is attached to the outer housing to prevent vertical movement of the piston beyond the fully extended second position. The piston stop may be attached to the outer housing by means of screw threads or any other suitable means.