Note: Descriptions are shown in the official language in which they were submitted.
~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~
,,:, ,. - ,, , ., ,,, . ,...... .. ~
106673~
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.
. ' . .
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
, .,~:
_2_
dc/~c
.... , , . .. , .: , . . .
:1~6673~
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.
~... .
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 ~
',~ .'
-3-
. '. .
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.
', ',, ~ ,' '
.'~ : ~ .
.
,. ~ : . . : , . ,; ,
