CA1066731A

CA1066731A - Self-sharpening ice skate blade

Info

Publication number: CA1066731A
Application number: CA276,550A
Authority: CA
Inventors: Mitchell D. Charneski
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-07-12
Filing date: 1977-04-20
Publication date: 1979-11-20

Abstract

ABSTRACT OF THE INVENTION

An ice skate blade which maintains its sharpness in use by virtue of a thin hard case on the sides of the blade over a softer center core. The hard case is of de-creasing hardness inwardly to provide a concave bottom surface as a result of unequal wear.

Description

~066731 SPECIF ICAT ION

According to the present invention ice skate blades are formed from a low carbon steel which after forming the blades to the required cross-section are heat treated to form a hard case at the sides and bottom of the blades, the case being of decreasing hardness inwardly from the sides, leaving the interior relatively soft. The hard case at the bottom of the blade is ground away to expose the softer interior.
Accordingly, the self-sharpening ice skate blade designed to maintain sharp bottom edge corners as the blade wears is a one piece integral steel blade having a uniform thickness of about 125 mils and having :
parallel sides provided with hardened cases at its sides extending to a case depth of 5-20 mils, each case having a hardness directly adjacent the side surfaces of the blades of at least 40 Rc , the case hardness decreasing ~. .
j. substantially uniformly from the maximum~hardness directly ~. adjacent the side surfaces to a hardness of about 20 Rc .
adjacent the relatively soft steel core, the bottom surface ~:~ of the blade being a smooth continuous uninterr~pted :
~`i surface concave in transverse cross-section, the bottom :~
surfaces of the cases and the soft core between the hard ;
~ cases at the bottom of the blade being exposed to cause -. -I the blade bottom to wear to maintain a smoothly rounded concave transverse cross-section intersecting the sides of the blade in sharp acute corner edges~

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In use, the blade, whether initially hollow ground or flat ground quickly wears to a hollow profile at the bottom, which intersects the sides of the blade in a sharp, acute edge which is maintained without resharpening for the life of the blade.

In the drawings:
Fig. 1 is a shoe type ice skate.
Fig. 2 is an enlarged fragmentary sectional view on the line 2-2 of Figure 1.
Fig. 3 indicates the contour of the bottom of the blade after extended use.
Fig. 4 is a diagram indicating the gradual diminution of hardness from the sides of the blade.
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i~ Referring now to the drawings, a shoe type ice skate is illustrated in Figure 1, in which the shoe 10 has a steel blade 12 rigidly attached thereto by a plate 14 fixed to the shoe and integral struts 16 and 18 connected respectively to the plate 14 and the shoe heel 20.
In Figure 2, which is an enlarged fragmentary sec-~ 20 tional view on the line 2-2 of Figure 1, the lower portion of -` the blade 12 is illustratèd in the condition it attains after . ~
; a surface hardening treatment which will be described more - fully hereinafter. The full line outline illustrates a case hardening providing a case 21 having a depth suggested by dot ~, 25 and dash lines 22 and 24, both at the sides of the blade and the bottom thereof. --~
The case hardening at the bottom of the blade is removed, preferably by a hollow grind oporation to the dotted , .,~:

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line 26, thus exposing the softer metal at the interior of the blade and leaving sharp, preferably acute edge~ 28.
As the skate blade wears in use, the softer inter-ior metal wears more rapidly than the side cases, and the blade retains its sharpness without the necessity of re-sharpening. In Figure 3, the dotted line 30 indicates the contour of the bottom of the blade after extended use.
It is an essential feature of the present invention that the improved skate blade has the usual thickness of approximately .125" (125 mils) so that the skate will perform exactly like newly sharpened conventional blades throughout its life.
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The thickness of the case may vary from about 5 to 20 mils, leaving a softer blade interior or core having a `; 15 width of about 115 to 85 mils. The total blade thickness may vary as desired since this does not affect the sharpness of -the edge.
Preferably the blade is made of low carbon steel ;

~` (about 0.15 percent carbon) which is case hardened to as high -~ 20 as 60 Rc, the unhardened interior or core of the blade may -.~. -:: .
have a hardness of about 20 Rc. The case hardness preferably ~, decreases from the side surface inwardly, although some case hardening operation will produce maximum hardness àt a very small distance below the surface. For maximum hardness of course, hardness should decrease from the extreme outer or side surface of the blade inwardly.
In general, the maximum case hardness should not be less than 40 Rc, and overall case depth should be between ~
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1~66731 5 and 20 mils. Carbon content in the case will range from 0.8 to 1.2 percent at the surface to the 0.15 percent in the soft core.
The case hardening may advantageously be by commer-cially available technique.
Among those suitable for use in the present invention are gas carburizing, pack carburizing, carbonitriding, liquid carbonitriding, induction hardening and flame hardening.
carbonitriding is particularly suitable because of low coqt, control of case depth and hardness, and simplicity of operation.
Gas carburizing also has merit in that small parts such as skate blades may be case hardened by direct quenching from the furnace at the end of the heating cycle.
In Figure 4 there is shown a diagram indicating the - gradual diminution of hardness from the sides of the blade.
Here case hardness is plotted against bladè thickness. In the illustrated plot, a hardness of 45 Rc is provided at the sur- -face, decreasing substantially uniformly to a hardness of 20 Rc ;~
at a case depth of about 8 mils. The relatively soft core has ~ -a hardness of about 138 Knoop or 69 RB.
In general, the surface hardness should exceed 40 Rc, and preferably in the range of 40-65 Rc. The case depth should be 5-20 mils. The rate of change of case hardnes~ against case depth should be as nearly uniform as possible.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A self-sharpening ice skate blade designed to maintain sharp bottom corners as the blade wears comprising a one piece integral steel blade having a uniform thickness of about 125 mils and having parallel sides provided with hardened integral cases extending to a case depth of 5-20 mils, each case having a hardness directly adjacent the side surfaces of the blades of at least 40 Rc, the case hardness decreasing substantially uniformly from the maximum hardness directly adjacent the side surfaces to a hardness of about 20 Rc at the afore-said depth of 5-20 mils adjacent to the relatively soft steel core, the bottom surface of the blade being a smooth continuous uninterrupted surface concave in transverse cross-section, the bottom surfaces of the cases and the soft core between the hard cases at the bottom of the blade being exposed to cause the blade bottom to wear to maintain a smoothly rounded concave transverse cross-section intersecting the sides of the blade in sharp acute corner edges.

2. The method of making self-sharpening ice skate blades which comprises case hardening at least the lower portions of steel blades to a surface hardness of at least 40 Rc, and to a depth of 5-20 mils, and grinding the bottom edges to expose the relatively soft cores at the bottom of the blades.

3. The method as defined in Claim 2, which comprises grinding the bottom edges of the blades to a transversely concave curvature as found in hollow ground blades.