Antislip Footpiece

Abstract

An open bottom housing having a bottom tread surface mounts in its interior a circular wobble plate that is rotatable on the axis of the housing and tiltable on an axis of oscillation that is perpendicular to and intersects the housing axis. The periphery of the plate is constituted as means for penetrating a slippery surface which may underlie the housing tread surface. A spring-projected actuator carried by the wobble plate extends through the housing bottom on the axis of the housing for gripping engagement with the underlying surface. At the beginning of a slip, the actuator is displaced radially from the housing axis and correspondingly tilts the wobble plate in the direction of the slip; whereupon the low point of the plate extends through the housing bottom and penetrates the underlying surface, effectively stopping the slip immediately after it starts.

Description

BACKGROUND

1. Field of the Invention

The present invention relates to the art of devices for preventing slippage between a tread surface and an underlying slippery surface with which the tread surface is in face contact when in service. In particular, the invention is in the field of antislip footpieces for attachment to articles of footwear, overshoes, rubbers, canes, crutches, walking aids, and the like. The principle upon which this invention operates is penetration of the underlying surface by sharp-edged or pointed means associated with the tread surface.

2. The Prior Art

The prior art is replete with antislip devices designed to resist slippage in any direction, but none, so far as I am aware, is successful in stopping a slip at its beginning, immediately after it starts. The prior art has solved the problem of slowing down the progression of a slip by, in effect, braking the slide of a slipping tread surface sufficiently to allow time for reflex compensation, but it has not solved the problem of how to stop a slide substantially at the instant it starts.

The prior art presently known to me as the closest approach to my invention is epitomized in U.S. Pat. No. 1,260,142 and No. 2,383,267. Both utilize a circular plate rotatable on a vertical axis and having peripheral edge means fashioned for forcibly gripping and penetrating an underlying surface with an applied force dependent for its magnitude, and therefore its effectiveness, upon the weight of a wearer. The gripping and braking action of the rotatable plate in each patent is a function of sliding friction. No means is provided for inclining either plate whereby to cause a portion of its peripheral edge to penetrate the underlying surface.

When a person steps on a slippery surface his foot slips forwardly and laterally outward, so that his weight is concentrated at the trailing end or edge of whatever antislip device he may be wearing. This results in some inclination of the foot and throws the weight force of the foot at the rear or trailing end with respect to the direction of slip. Very little, if any, of the weight force is applied at the leading end or edge which actually is lifted from the underlying surface. In the devices of the patents hereinbefore noted the antislip plates serve only as drags for slowing the resultant slide; no part of their leading edges can penetrate the underlying surface because the low point of the plate is, in both cases, at the rear in the line of advance of the slide. Neither device can effect an immediate stop; whereas the device of this invention can and does stop a slip as soon as it starts.

SUMMARY OF THE INVENTION

The present invention is a solution of the problem of how to stop a slip-engendered slide as soon as it begins. Structurally, in the preferred embodiment herein disclosed, it is a footpiece designed for incorporation in or attachment to footwear, overshoes, rubbers, walking aids, canes, crutches, and the like. However, the generic invention, as distinguished from specific embodiments thereof, is applicable to any usage in which one of a pair of surfaces in potentially slidable face contact is to be protected against fortuitous slippage on the other.

In the footpiece here shown, the antislip mechanism is contained within an open bottom housing having a bottom tread surface which, in service, bears down upon an underlying ground surface. If the underlying surface is slippery, the danger of slippage of the tread surface is always present. A fall on an icy sidewalk, or on a wet floor, can cause serious and sometimes fatal injury, especially to the elderly and infirm. Unlike the prior art antislip devices, in which the means for penetrating the underlying surface is always in contact therewith whenever the tread surface with which it is associated is in service contact with the underlying surface, the slip stopping penetrating means of the present invention is always out of contact with the underlying surface and cannot become engaged therewith until a slip has begun. The antislip mechanism of this invention is operatively responsive only to the actual start of a slip, which therefore makes it practical to be worn indoors for walking on floors and rugs without damage thereto.

The antislip mechanism is a unit assembly of a wobble plate suspended from a support plate that is adjustable axially in the housing and an actuator (trigger) carried by the wobble plate and depending therefrom under a spring bias which maintains the bottom terminal portion of the actuator projected through the open bottom of the housing for normal gripping engagement with a surface underlying the tread surface of the housing. The wobble plate is rotatable and tiltable, and its peripheral edge provides means for penetrating an underlying surface whenever the plate is tilted out of its normal plane of revolution on the vertical axis of the housing. While the plate occupies its normal plane of revolution the penetrating means is maintained entirely within the housing and spaced vertically above the housing tread surface. At the beginning of a slip, the actuator, which is a projection of the housing axis, is displaced radially from the housing axis and correspondingly tilts the wobble plate to project its penetrating means downward and forwardly at an angle and centrally in the direction of slip advance.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diametrical sectional view through an antislip footpiece of the present invention as mounted in service position in the heel portion of an article of footwear such as a rubber or the like.

FIG. 2 is a sectional view taken on line 2--2 of FIG. 1.

FIG. 3 is a bottom plan view of the footpiece.

FIG. 4 is a fragmentary perspective view of a portion of the peripheral edge portion of the wobble plate.

DESCRIPTION OF PREFERRED EMBODIMENT

In the specific embodiment of the invention disclosed herein, the antislip footpiece, designated generally as 10, comprises a thin cylindrical shell 11 closed at its top 12 and open at its bottom. An integral, external, annular flange 13 surrounds the bottom of the shell and is bonded to the body 14 of an article of footwear into which the shell is recessed and seated against rotation or axial displacement. The shell provides a socket within which is seated a complemental metal cylindrical housing 15 closed at its top 16 and open at its bottom. An external, annular flange 17 integral with the housing underlies the shell flange 13. A ground engageable adjustable tread member 18, here shown as a ring of rubber or plastic, underlies the flange 17 and is bonded thereto. The internal diameter of the tread ring 18 is substantially the same as the internal diameter of the housing 15, and the housing and ring constitute a unit that is rotatable within the socket shell 11 but which is normally fixed against rotation or axial displacement by a setscrew 19 threaded in the housing wall and bearing against the inner face of the shell.

As best shown in FIG. 1, the body 14 of the article of footwear is formed with a conventional tread 20 for engagement with an underlying ground surface 21 of ice or snow or any slippery surface. The bottom faces of the adjustable tread ring 18 and the fixed tread 20 are flush, and the outer peripheral face of the ring abuts the complemental face of the ground tread 20 in slidable relation on the line of a circle that is concentric with the cylindrical wall of the housing 15 and at a point intermediate the inner and outer peripheries of the overlying housing bottom flange 17. Due to this arrangement, the outer marginal zone of the housing flange is firmly anchored between the body 14 of the article of footware and its ground tread 20, thus preventing axial displacement of the housing independently of the setscrew 19. Tool-engageable sockets 22 in the ring 18 opening to its bottom face are adapted to receive a suitable tool by which the entire unit comprising the ring and the housing 15 may be rotated within the shell 11 when the setscrew 19 is loosened. Bright-colored annular wear indicator strips 23 embedded in the ring become visible at the point of greatest wear and indicate when and where compensating adjustment of the ring should be made by rotating it to move the worn area and replace it with a less worn area.

A circular support plate 24 is mounted in the upper portion of chamber provided by the interior of the housing in threaded connection with the housing wall. It extends transversely across the housing interior in a plane perpendicular to the housing axis and in spaced relation to its closed top end 16. Spring means 25 in the space between the top end of the housing and the support plate 24 biases the plate to move axially downward within the housing and thus prevents loose play in the threaded connection between the peripheral face of the plate and the housing wall. Sockets 26 open to the under face of the support plate are adapted for engagement by appropriate tool means whereby the plate may be rotated for advancement or retraction axially within the housing. The support plate is provided further with a circumferential series of radial slots 27 establishing passages between spaces above and below the plate.

The slip prevention means of the present invention operates automatically and instantly at the beginning of a slip. As here shown it comprises a circular wobble plate 28 provided at its periphery with a circumferential series of downwardly angled radial teeth 29 terminating in sharp points 30. The angle of inclination of the teeth is such that immediately upon contact of their points with an ice, snow, or ground surface beneath the tread ring 18 the points presented to the surface will forcibly grip the surface and dig down into it progressively with continuity of the slip, effectively braking and stopping any slide at its beginning.

The diameter of the wobble plate is such that there is clearance space between the teeth points and the wall of the housing in any and all positions which the wobble plate may take. The wobble plate is suspended from the support plate 24 by a ball-and-socket connection comprising a stem 31 fixed on the wobble plate at its center, rising axially therefrom and terminating in a ball 32 seated in a socket 33 fixed to and depending from the support plate 24. The wobble plate is maintained normally in a plane perpendicular to the axis of the housing assembly and at such elevation above the plane of the bottom face of tread ring 18 that the teeth points 30 are fully retracted within the housing and well clear of any contact with a surface on which the tread ring 18 may seat. A conical expansion spring 34 surrounds the stem 31 between the wobble plate and the support plate and holds the wobble plate against fortuitous tilting from its normal inoperative position parallel to the support plate.

The trigger means for tilting the wobble plate at the beginning of a slip comprises a pair of bow springs 35 secured at their ends to the under face of the wobble plate and crossing each other at a right angle on the axis of the housing assembly. A crown disc 36 is welded or otherwise rigidly attached to the under one of the bow springs 35 at their point of intersection. Integrally secured to the crown disc 36 is the contact end 38, the end of which is on a plane only slightly below the crown points 37 of the crown disc 36. The contact end 38 forms the gripping engagement with the underlying surface and is specifically designed to be noninjurious to floors and rugs. The crown disc is centered on the axis of the housing assembly with its crown points 37 disposed normally in a plane parallel to and spaced beneath the plane of the bottom face of the tread ring 18. The biasing force of the bow springs maintains the crown disc and contact end 38 in projected position relative to the bottom of the housing at all times when the tread ring 18 is not in face contact with an underlying surface.

OPERATION

When the bottom wear face of the tread ring 18 bears down upon an underlying surface, the contact end and the crown disc are forced upwardly into the housing against the bias of the bow springs 35 which holds the contact end firmly against the underlying surface with a pressure sufficient to grip the surface and thus hold the contact end in its surface-engaged position until it is moved therefrom by a force greater than the grip holding force applied by the bow springs 35. In this first surface grip position of the contact end, the force applied by springs 35 is downward directly along the axis of the housing assembly, and so long as the contact end remains in its initial position of underlying surface engagement the wobble plate will not be tilted and none of its teeth points 30 will contact the underlying surface. However, immediately upon the beginning of a slip, the incident lateral movement of the housing assembly, in any direction, will be resisted by the existing surface grip of the contact end 38 which thereupon lags relative to the moving housing assembly and is dragged in the direction of the slip movement. The retarding force imposed by the drag tilts the crown disc out of its initial position so that its points will contact the underlying surface and correspondingly tilt the wobble plate 28 so that its resulting peripheral low point is disposed forwardly in the line of advance of the housing assembly, thus constituting a leading edge.

The force of the slip advance resistance imposed by the contact end and by the tilt and drag of the crown disc points forces the points of the wobble plate teeth which lie on the arc of its tilting low point into gripping and penetrating engagement with the underlying surface, as shown in dotted line in FIG. 1, thereby instantly braking the sliding housing assembly and checking its further movement. As soon as the housing assembly is lifted clear from the underlying surface the biasing force of the spring 34 returns the wobble plate to its initial position perpendicular to the axis of the housing assembly, and the biasing force of the bow springs 35 returns the contact end 38 and crown disc 36 to its initial projected position.

The contact end 38 and crown disc 36 serve as an actuator which triggers automatic operation of the slip prevention means whenever the contact end and disc are displaced radially relative to the axis of the housing assembly. The act of such displacement causes the contact end and crown disc to move bodily through an arc on a radius determined by the length of the distance between the center of the ball 32 and the planes of the contact end and the tips of the crown disc points 37. When this displacement occurs, the arcuate movement of the contact end and crown disc are reproduced exactly and simultaneously in the wobble plate 28, causing it to tilt in the direction of advance in the slide engendered by a slip. The number and circumferential spacing of the wobble plate teeth 29 is such that in any direction of slip a plurality of closely spaced tooth points 30 will grip and/or penetrate the underlying surface. The depth of their penetration is determined by the extent to which the wobble plate is tilted, and this extent is, in turn, determined by the distance between the bottom face of the support plate 24 and the top face of the wobble plate. As seen in FIG. 1, the support plate 24 provides a stop member against which the high point of the wobble plate abuts at the limit of its tilt.

It is rarely the case that the centerline of a slide will remain coincident with the radial centerline of the leading wobble plate tooth whose point first engages an underlying surface. Practically, in every slide, the direction of slide is a combined forward and lateral movement, the resultant of which is a diagonal. Because of the fact that the wobble plate 28 is freely rotatable on the axis of the stem 31 of the ball-and-socket coupling between the wobble plate and its support plate 24, an increment of lateral force will correspondingly rotate the wobble plate so that other teeth points 30 will constantly be presented to replace those moved away from the center line of the slide by the increment of lateral force. No matter how closely spaced the teeth points 30 be, if the wobble plate is fixed against rotation no more than the number of teeth points within approximately 60.degree. of arc can be in position to engage an underlying surface at the beginning of a slide, and the effectiveness of each such tooth point will decrease in proportion to its distance from the midpoint of the arc. If, then, a sudden shift in the center line direction of a slide imposes an increment of laterally directed force, the resultant centerline direction of the slide will be such that few, if any, of the stationary wobble plate teeth points will be in position to grip or penetrate an underlying surface. If, as in the present invention, the movable wobble plate shifts under the influence of laterally applied forces, the total number of teeth points 30 included in an arc of 60.degree. will always be presented in position to grip or penetrate an underlying surface in any direction or change in direction the slide may take. Due to the fact that the direction in which the contact end 38 and crown disc 36 travel during their radial displacement relative to the vertical axis of the housing assembly is always diametrically opposite to the line of advance in a slide, the arc along which the contact end and crown disc move will insure that the major bulk of the crown disc body will be disposed in opposition to slide advance of the housing assembly, thus effectively assisting the wobble plate teeth points in resisting the advance and, in fact, providing active resistance before the resistance of the wobble plate teeth points becomes fully effective.

When the tread ring 18 of the housing assembly seats on a loose snow surface, some snow may enter the housing through its open bottom and tend to pack in the space between the wobble plate and its support plate and block proper tilting of the wobble plate. In the present invention the radial passages 27 through the body of the support plate 24 permit snow lifted by the wobble plate in tilting to be moved into the space between the support plate and the closed top 12 of the housing, thus eliminating packing of the snow above the wobble plate.

A salient feature of the invention is the fact that the effectiveness of its slip prevention mechanism is in no way dependent upon the axially downward application of force to the housing assembly, so that the weight of a person wearing an article of footwear equipped with the footpiece of this invention has no effect in the operation of the slip-prevention mechanism at any time.

Claims

I claim:

1. An antislip footpiece comprising a body having a bottom tread surface, means centered on a vertical axis in the body and spring biased to a normal position for gripping a surface underlying said tread surface, a circular wobble plate in the body and tiltable on an axis of oscillation intersecting said vertical axis perpendicular thereto, the wobble plate having on its peripheral edge surface means for penetrating a surface underlying said tread surface, said gripping means being radially displaceable from said vertical axis, and a connection between the wobble plate and the gripping means operative upon radial displacement of the gripping means to tilt the wobble plate to a position in which a portion of its peripheral edge is adapted to penetrate an underlying surface in a direction opposite to the direction in which the gripping means is displaced.

2. In the footpiece of claim 1, said peripheral edge of the wobble plate being a circumferential series of radial teeth disposed downwardly at an obtuse angle relative to the plate.

3. In the footpiece of claim 1, said wobble plate being rotatable on said vertical axis.

4. In the footpiece of claim 3, said wobble plate being also rotatable on the axis of the wobble plate when it is in tilted position.

5. In the footpiece of claim 1, said wobble plate and said gripping means comprising a unit, a support in the body above the wobble plate, means suspending the unit from the support, and said suspension means including a ball-and-socket coupling.

6. In the footpiece of claim 1, said gripping means being rotatable on the axis of the wobble plate in any position thereof.

7. In the footpiece of claim 6, said gripping means being a contact end and a crown disc with downturned points.

8. In the footpiece of claim 1, the spring bias for the gripping means comprising a bow spring attached at its ends to the under face of the wobble plate and attached to the gripping means at a point coincident with said vertical axis.

9. In the footpiece of claim 5, a conical expansion spring surrounding said coupling and bearing at its ends on the support and the wobble plate, respectively.