Note: Descriptions are shown in the official language in which they were submitted.
1067530
This invention relates to ice skates of a
type which are adapted to be attached to the soles of
suitable boots for use in ice hockey and similar activities.
Designers of ice skates must meet two major
criteria. Firstly, the ice skate should be as light as
possible so that the energy expended by a skater is kept
to a minimum. This facilitates fast starts and the skater
will find lighter ice skates to be less tiring to use.
Secondly, the designer must ensure that ice skates have
~ 10 sufficient strength to withstand impacts and high side
; loading caused by a skater stopping or changing direction
suddenly.
Traditionally, ice skates are built so as
to comprise a hardened steel blade suitably secured to a
metal body or frame which includes elevated toe and heel
platforms secured to the underside of a boot. In the
., .
best quality skates made today, the blades and body or
frame are made of steel with the blade being secured to
a tubular section of the frame by spot welding.
, 20 Several difficulties exist with skates
utilizing a metal blade-supporting body or frame. First,
in fabricating a metal blade-supporting body to a blade,
it is conventional practice to use eight different steel
components which are variously spot welded together. Not
only is there a problem in insuring the integrity of such
welds, but in welding the blade to the body there is the - -
constant danger of weakening or reducing the temper of the
hardened steel blade.
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A further problem with traditional designs
is that it has become increasingly more difficult to obtain
consistently high quality steel for use in such blade-
supporting bodies. As lesser quality steel has been used,
breakage and rusting of such bodies has become more frequent.
In recent years, a number of designs have
been proposed which include a body of a synthetic plastic
material attached during moulding to a hardened steel blade. `
~anadian Patent 585,720 illustrates such a structure.
The plastic material is moulded about a series of keying , ~ `
devices which are spaced along the length of the blade and
through holes in the blade to form an integral ice skate. i~
A further example of this type of structure is shown in
Russian Patent 123,068. This structure includes a blade
, which is perforated by a series of holes spaced along its
`' length so that the body is locked to the blade by mould-
ing through these holes. Another example is to be found in
~ U.S. Patent 3,212,786.
" An ice skate having a body of synthetic
:
plastic material appears initially to have many advantages.
~, The body is light and can be attached to the blade by mould-
ing the body directly about a suitably shaped portion of
the blade. Although the initial cost of the moulds is
high, the subsequent manufacturing costs for large quanti-
ties would indicate that the process would be economic.
However, there is also a major drawback in the manufacture
of such an ice skate caused by the fact that suitable plastic
;' materials have much higher shrinkage rates than steel.
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Consequently, if the plastic is moulded about a steel blade,
the plastic material becomes highly stressed as it cools be-
cause it is locked to the steel blade and cannot shrink
freely. These resulting high stresses in the plastic material
contribute to premature failure of the ice skate and con-
sequently, the combination of a body of synthetic plastic
material moulded about a steel blade has not been an accept-
able alternative for more conventional forms of ice skates.
A further advantage of the present invention ~-
is that through the use of an extremely tough synthetic
plastic material such as a polycarbonate, the blade-supporting
body is not susceptible to denting, warping, chipping or
rusting, all of which are common with a steel body.
The present invention has been made after many
efforts to utilize a blade-supporting body of synthetic plas-
tic material in a commercially feasible composite type skate.
The original efforts resulted in a composite type skate
having greatly improved performance characteristics. More
specifically, the skates were lighter and far more respons-
ive to the skater's demands. However, as with skates made
according to prior art teachings, a serious problem developed
with respect to fracturing or cracking of the plastic body.
Such cracking either began immediately after manufacture or
developed within a reasonably short time of use. After consid-
erable experimentation, it was discovered that while com-
mercially available materials, such as those of the poly-
carbonate group, had more than enough inherent structural
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~ ~067530
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strength, the manner in which the hardened steel blade
was joined to the body was critically important. In
earlier designs, like those of the prior patented art,
when the body is initially moulded and mechanically inter-
locked with the skate blade, severe localized stresses
are set up in the plastic material. It was further found
that from these highly stressed areas cracks emanated
which eventually caused the body to fail or sufficiently ,~
disrupted its appearance as to cause the user to lose con-
fidence in its safety.
.,, , : ~
Thus, the present invention is directed to
a composite skate design utilizing a blade-supporting
body of synthetic plastic material joined to the skate
blade in such a way as to eliminate such critical stress
areas within the body therby preventing cracking or fract-
uring of the body.
Hockey players who have tested skates made
., ~: , .
in accordance with the subject invention under playing
conditions claim they sense more "life" or responsive-
20 ness in the blades. It is assumed that this reaction may
2' be attributable to the greater flexibility of the assem-
` bly as compared to its all-steel counterpart.
-, Accordingly, the invention provides ice
skates and methods of making ice skates which have a
body of a synthetic plastic material and a steel blade.
~;
The body includes an upper portion for attachment to the
sole of a suitable boot and the blade has an upper portion
enclosed in the body and a lower portion projecting from
.
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3 067530
the body. The blade has a non-interfering upper surface
so that on moulding the body about the upper portion of
the blade, the body can shrink and move longitudinally
of the blade to limit stress build-up in the body caused
by shrinking. Mechanical fastening devices are used to
hold the blade in the body.
The invention will be better understood
with reference to the following description and associated I -
drawings, in which: ~ ~
Fig. 1 is a side view of a preferred em- -
bodiment of an ice skate according to the invention; ¦
Fig. 2 is an enlarged end view on line 2-2
of Fig. l;
--~ Fig. 3 is a somewhat schematic sectional
~`; !
~ view of a mould, the view being taken on a transverse
." I:
` plane corresponding to that indicated by linè 2-2 of
Fig. 1 and illustrating a preferred method of making the
ice skate;
,, Fig. 4 is a side view of a portion of the
ice skate to an enlarged scale to illustrate the placement
of a rivet;
Fig. 5 is a side view of a portion of an
ice skate during manufacture according to another method
, of manufacture;
Fig. 6 is a composite side view of a por-
tion of an ice skate blade and illustrating three possible
embodiments of blade for incorporation into a further
method of manufacture;
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~067530
Figs. 7 to 9 are sectional views generally
on line 7-7 of Fig. 6 and illustrating the further method
of manufacture incorporating the embodiments shown in
Fig. 6;
Fig. 10 is a partially sectioned side view
of a rear portion of an ice skate illustrating yet another
embodiment of the ice skate;
Fig. 11 is a view similar to Fig. 10 and
illustrating still another embodiment of the ice skate;
Fig. 12 is a perspective view of a portion
of another ice skate blade for use in the invention;
~- Figs. 13 and 14 illustrate more embodiments
of an ice skate blade for use in the invention; and
- Fig. 15 illustrates a form of ice skate
.; ~
blade which is not acceptable in the present invention and
is illustrated for comparison purposes.
,! Reference is made firstly to Fig. 1 which
illustrates an ice skate 20 consisting of an upper body
22 of synthetic plastic material which is attached to a
lower skate blade 24 by four rivets 26 as well as by a cen-
tral anchor structure denoted generally by the numeral 28.
~, In this, the preferred embodiment, the anchor structure 28
consists of an opening 30 formed in the blade 24 and through
which the moulded body 22 extends to lock the body to the
blade 24. The purpose for this structure will be described
in more detail with reference to the method of manufacture.
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~67530
The body 22 includes a longitudinally ex-
tending main portion 32, an upwardly extending heel support
34 and an upwardly extending front support 36. The heel
support is positioned adjacent the rearward extremity of
the main portion 32 and the front support includes a heavier
rear upright portion 38 and a lighter front portion 40
which blends smoothly into a front extremity of the blade 24.
The portions 3~ and 40 blend into an enlarged flange 42
for use in attaching the ice skate to a suitable boot.
Similarly, the heel support 34 includes a flange 44 for a
- similar purpose. Both the upright portion 38 and the heel
support 34 are hollow as shown in broken outline whereas
the lighter front portion 40 is solid.
The rearward extremity of the main portion
32 blends into the rear end of blade 24 without narrowing
significantly to ensure that an adequate rearward-facing
surface area is presented as a safety precaution against
` impact between the rear extremity of the skate and a hockey
; player.
' 20 As better seen in Fig. 2, the main portion
32 of the body 22 is designed for optimum rigidity after
:! ~
assembly with the blade 24. It is evident that the cross-
sectional area of the plastic body should be kept to a mini-
mum for lightness while meeting a given strength requirement.
In this embodiment the cross-section is substantially sym-
.;, .
metrica about a vertical plane passing through the centre -~
~, ~ of the cross-section and includes upwardly converging in-
clined faces ~6, 48 which lie at about 90 degrees to one ~ -
another. These faces blend at their lower extremities into
,1 30 shorter downwardly converging faces 50, 52 which also lie
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1067530
at about 90 degrees to one another and which meet resp-
ective side flanges 54, 56 positioned about the blade 24.
The cross-section provides advantageous strength to weight
requirements after assembly using rivets 26.
Fig. 2 also illustrates a rounded upper sur-
face 58 of the blade 24. The side surfaces are substantially
parallel and are formed to blend continuously at their upper
extremities into the straight upper surface 58. As is con-
ventional in better quality skates, the lower surface 59 of
the blade 24 is hollow ground.
Description of the shape of the body 22
where it receives the rivets 26 will be incorporated into
the description of the method of manufacture.
Reference is now made to Fig. 3 which illus-
trates a portion of a mould used in the manufacture of the
ice skate shown in Fig. 1. The mould consists of respect- '
ive first and second halves 60,~62 which define recesses
64, 66 for combining to define the plastic body 22 and to
receive the blade 24 prior to moulding. Blade 24 is also
located by two pins 68 in mould half 60 which engage in
.;
corresponding front and rear ones of the openings in the
blade. Each of the pins 68 is concentric with corresponding
cylindrical portions 70, 71, 72 and 74 so that after
; moulding, cross-sections such as that shown in Fig. 3 are
, provided where the front and rear ones of the rivets 26
are to be placed. Although the same structure including
~ pin 68 could be used for the other rivet locations, the use
;~ of four pins in the mould will create tolerancing problems
~ to ensure that all four pins meet the openings in the hardened
..~
3 30 blade. To reduce this problem only two pins are used as
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1067530
described. The other two rivet locations will be formed
using forms in the mould halves which do not include pins
68. Instead, the portions 71, 72 will bear against the blade
to block the openings in the blade so that no plastic material
enters these openings. As is common practice, the portions
71, 72 can be spring-loaded outwardly for better bearing
pressure on the blade surfaces. This blocking action will -
be discussed further with reference to Fig. 6. Recesses
76, 78 and openings 77, 79 are formed in the plastic con- '
centric with the openings in the blade for receiving the
rivets as shown in Fig. 2. Also, during moulding, plastic
passes through opening 30 (Fig. 1) in the blade to lock the
blade in position in the body at the so-called "anchor
structure". It should be noted that the ends of the opening
30 are flared or chamfered to blend the wall of the opening
into the side surfaces of the blade. This blending limits
stress build-up in the plastic whlch can be caused by sudden
changes in cross-section.
After moulding, the body of synthetic plastic
; 20 material shrinks significantly, firstly as it changes from
' liquid to solid and then, secondly as it cools. Consequently,
if stress is to be avoided, the shrinkage must take place
freely along'the length of the blade. As previously described,
the straight upper surface 58 of the blade 24 is rounded
and this facilitates shrinkage because it has been found that
if the blade is not rounded, there is a tendency for inter-
ference between the plastic body and the blade. Although this
does not happen in every instance, it has been found that best
' results are achieved after rounding the upper surface. It
'' 30 will also be evident that the rounded surface 58 is desirable
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simply because sharp changes in cross-section are best
avoided in any moulded product.
The anchor structure 28 ensures that shrink-
age takes place in a controlled manner. The structure 28
is located generally centrally of the length of the skate
so that the body will shrink towards the centre from both
ends. As a result, the recesses 76, 78 and associated open-
ings 77, 79 (Fig. 23 for receiving the rivets 26 will no
longer be concentric with the corresponding openings in
the blade. Eor this reason, the recesses 76, 78 and open- -~
ings 77, 79 are proportioned such that even with the mis-
alignment caused by shrinkage, the rivets 26 can be engaged
freely and without interference with the sides of the
recesses 76, 78. The final position of the rivet may well
"
be such as that shown in Fig. 4 which demonstrates the
-~ position anticipated for the forward one of the rivets 26.
This concept allows the blade to be first fixed securely
to the body by moulding using the anchor structure, and then
the rivets to be inserted to complete the assembly without
creating significant stresses in the body. The final pro-
duct relies on the rivets 26 for strength and these rivets
are unlikely to shake loose because the blade is an extremely
good fit in the plastic and because even after free shrinkage
it is located positively by the anchor structure 28. It
has been found that ice skate 20 (Fig. 1) can be made to
~, have the necessary strength while achieving the advantages of
lightness offered by the use of a synthetic plastic material
for the body. Suitable synthetic plastic materials include
the polycarbonate group. In particular one designated by
General Electric as LEXAN. However, blends of polycarbonates
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1067530
could also be used such as CYCOLOY (Borg-Warner) as well
as any other materials such as engineered plastics provided
that the necessary strength and impact resistance are
achieved. Suitable conventional fillers can also be
used.
After moulding and inserting the rivets,
it may be necessary to dress the finished product for excess
moulding material. Otherwise the ice skate is complete and
ready for attachment to a suitable boot.
. ~
The amount of shrinkage movement at each
rivet opening will be substantially constant for a particu- '
lar skate size and for a given plastic material. Consequently,
a further improvement to the mould can be made by analysing
this movement and compensating for it in the design of the
mould. If complete compensation proves to be possible, ~ ~¦
the cylindrical portions 71 and 72 (Fig. 3) of the mould
would then have the same diameters as the openings in the
blade and the recesses 76, 78 could be just sufficiently
large to receive the rivet head and end portions respectively.
As previously discussed with reference to
Fig. 3, the pins 68 in the first half 60 of the mould must ~ -
fit in the front and rear openings in the blade. Consequently,
the tolerance between these openings must match that between
the pins. In some instances it may be preferable to avoid the
':1 .: .. .
'~ need for such accurate alignment and such a method will now
~?
be described with reference to Figs. 5 to 9.
Fig. 5 illustrates an ice skate 80 having a
blade 82 and a plastic body 84. The ice skate is illustrated
immediately after moulding and before shrinkage has taken
place. During moulding, a mould was used having two halves
` corresponding to the shape of mould half 62 shown in Fig. 3.
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1~67530
Consequently, the plastic body 84 defines recesses for the
rivets and such a recess is indicated by numeral 86. How-
ever, the method illustrated in Fig. 5 differs from that pre-
viously de`scribed in that in place of using pin 68 (Fig. 3)
in the mould, the openings in the blade are first blocked
using a plug of soft material such as aluminum. Resulting
plugs such as plug ~8 filling an opening 90 are provided
in the blade so that no plastic is injected through the
openings 90. Further, calculations and experience are used
to determine the best position for the recess 86 so that
after shrinkage takes place the opening 90 is substantially
concentric with the recess 86. -
After shrinkage has taken place, the plugs
88 are either drilled out or punche~d out of the blade 82
-~ so that the rivets can be engaged and the assembly completed.
/ The rivets then sit substantially concentrically in the
~ recesses 86 as opposed to the position of the rivet 26 shown
in Fig. 4 and forming part of the preferred embodiment.
,, The recess 86 can then be nearer to the size of the rivet
head because there is less need for clearance.
Although the Fig. 5 method has some advant-
ages from the standpoint of accuracy of tolerances between
openings in the blade, a further improvement can be made to
ensure that the tolerances are no longer of major signifi-
cance. Fig. 6 is a compound view of a blade incorporating
three embodiments which will provide this further improve-
ment. In place of the opening 90 (Fig. 5) which has a
diameter corresponding to the outside diameter of the rivet,
a larger opening 92 is used and blocked using a plug of
aluminum or the like 94. Because of the size of the plug,
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1~167530
it will be apparent that an opening for the rivet could
be drilled through this plug with quite coarse tolerances
once the blade has been received in the moulded body and
located using an anchor structure such as structure 28
shown in Fig. 1. Similarly, the opening could have any
desirable shape such as the generally rectangular opening
96 which is blocked by a corresponding plug 98.
Fig. 6 also illustrates a third possibility
in that the blade could be hardened along its outer zone 100
(indicated by ghost outline) so that a softer portion of the
- .
blade is available for drilling wherever the rivet is to go.
In general, Fig. 6 illustrates a blade having at least one
softer area for drilling to receive rivets. If the moulding I ~
is done as described with reference to Fig. 5, then the drill l -
will be placed to pass through the recess in the moulded l~
body and through the blade concentrically with this recess. 1- -
However, it will be evident that it is also possible to pro-
~- vide a moulded body having no recesses in which case one of
the embodiments illustrated with reference to Fig. 6 would 1 -
preferably be used to provide a tolerance for drilling in the
exemplary manner to be described with reference to Figs. 7 to 9.
At this point, the general use bf the term
l "blocking" will be discussed. In the preferred embodiment,
- the openings to receive rivets 26 were blocked either by a
mould pin or by a portion o~ the mould sealing off the opening
by bearing against the blade. Similarly, in other embodi-
ments, openings such as openings 92, 96 (Fig. 6) were blocked
using plugs 94, 98. Although not all of the material of
, these plugs needs to be removed to receive rivets, the term
"blocking" when applied to an opening in a blade includes such
embodiments. -
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~067530
As seen in Fig. 7, a blade 102 has been
captured in a moulded body 104 and an opening in the blade
is blocked by a plug 106. The moulded body is free of rivet
recesses and space for a rivet (or other suitable fastener)
is made by using a stepped drill 108. A jig is used to
locate the skate for drilling so that the drill will pass
through the plug within quite coarse tolerances. The first
step is to drill through the skate as indicated in Fig. 7
resulting in an opening 110 and recess 112 as shown in Fig.
8. The skate is then turned over and the same stepped drill
is entered into the opening 110 and brought down to create
a recess 114 as shown in Fig. 9.
It will be evident that the methods described
with reference to Figs. 5 to 9 allow for varying degrees
of inaccuracy in the method of manufacture. In the case
of the blade having two hardness portions, the holes could
be placed anywhere in the softer portion provided that the
body was first moulded without recesses to receive the rivets.
If recesses are provided in the mould, then they would be
used to locate the drill for drilling through the softer
part of the blade. ~owever, in all of the foregoing methods,
an anchor structure such as structure 28 shown in Fig. 1
is used to first locate the blade positively with respect
to the body so that the blade is properly located and there
is little or no likelihood that it will subsequently become
~$ loose in the body.
~' Other methods of manufacture are also pos-
sible where the accuracy of location of the blade in the
body is not as important as in the preferred embodiment.
For instance, only one of the rivet openings would be
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106~530
located by a pin in the mould and the other openings blocked
either by plugs or simply by suitable parts of the mould.
Of course the recesses (such as recess 76 as seen in Fig. 4)
must be sufficiently large to accommodate rivets after
uncontrolled shrinkage (unless an anchor structure is used).
Similarly, all of the openings could be blocked and the
shrinkage could take place at random without the control of
an anchor structure.
Reference will now be made to Figs. 10 to
12 to describe further possible forms of the anchor structure
~ 28 (Fig. 1). As seen in Fig. 10, a blade 116 is set in a
,~ moulded body of synthetic plastic material 118 and held in
place by rivets 120. An anchor structure 122 is provided
which consists of a dove-tail recess 124 in the upper sur-
face of the blade adjacent its rearward extremity and a
corresponding portion of the plastic body which is moulded
into this dove-tail recess.
;' The longitudinal extent of the dove-tail
recess 124 can be substantial from the standpoint that
2Q shrinkage within the recess will have no effect on the stresses
in the body. However, the intent of the anchor structure
!, iS to provide a positive lock at a discrete portion of the
blade so that there is controlled shrinkage of the body
;~ along the blade with reference to the positions of the rivets.
, Consequently, it is preferred that the longitudinal extent
, of the dove-tail recess be limited so that shrinkage of the -~ -
~' body will take place towards this anchor structure and be
limited within the structure.
Although the skate shown in Fig. 10 shows
the anchor structure 122 at the rear of the skate, it can
be placed anywhere along the length of the skate.
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A further embodiment of the anchor structure
is shown in Fig. 11. A blade 128 is set in a moulded body
130 and an anchor structure 132 is provided. This anchor
structure includes a keying projection 134 which extends
upwardly from a top surface of the blade 128 and includes
forward and rearward extensions which are encapsulated in
the plastic body 130. Consequently, the blade 12B is
trapped in the body and located longitudinally with reference
-, to shrinkage of the body along the blade. In this instance,
; 10 the longitudinal extent of the keying projection 134 should
` be kept to a minimum to avoid shrinkage stresses. This is
because during shrinkage, the body will tend to compress
the key projection longitudinally with the result that there
will be inherent stresses in the body. The longer the key-
ing projection, the greater the stresses and a point could be
~; reached where these stresses are intolerably large. Here
again the anchor structure is shown in an exemplary posit-
ion relative to the length of the skate.
Yet another suitable anchor structure is
illustrated in Fig. 12. In this embodiment, a blade 136
is provided with a transverse pin 138 which projects through
the blade and is an interference fit in the blade. It will
` be evident that upon moulding the body about the blade the ;~
pin 138 is trapped in the body to therefore provide yet a
further embodiment of the anchor structure originally illu-
l strated by numeral 28 in Fig. 1. -
;i In general, any anchor structure which re-
, tains the blade in position in the plastic body at a discrete
:~! location relative~to the length of the blade will be satis-
factory. The zone containing this structure will have minimal
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~067S3V
shrinkage. However, and as explained, it is essential
that such a structure does not create stress difficulties
and it is for this reason that the anchor structure 28
shown in Fig. 1 is to be preferred. Structure 28 is simple
and effective and requires a minimum of preparation.
It will be evident from the description thus
far that where an anchor structure is to be used, the rest
of the body must be free to move longitudinally on the blade
to avoid shrinkage stresses. Consequently, the blade must
have a suitable form to permit this movement. Although the
blade shown in Fig. 1 is to be preferred, there are other
possibilities which may be desirable in certain circumstances.
The term "non-interfering upper surface" will be used to
describe the upper surfaces of blades which are satisfactory
when used with anchor structures of the types already des-
cribed. Apart from the straight upper surface shown in
Fig. 1, surfaces su~h as those shown in Figs. 13 and 14 are
satisfactory. In Fig. 13, the upper surface includes a
, ,
'j long depression 140 defined by forward and rearward portions
'I 20 which extend upwardly at the extremities of the depression.
As indicated in ghost outline, the rearward upward portion
(or for that matter, the forward upward portion) could be
omitted. Also, an opening 142 is provided as part of an
;~ anchor structure, and if this opening causes an unacceptable
l reduction in cross-sectional area of the blade, the blade
i could be strengthened by an upward extension 144 above the
opening 142. Because the longitudinal shrinkage about the ~-
~! anchor structure is minimal, there will be no significant
- stress in the body caused by the upward extension 144. Also,
shrinkage of the body towards the anchor structure will not
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1067530
be limited by the shape of the blade. This blade therefore
includes some examples of many suitable non-interfering
upper surfaces.
A further suitable blade is shown in Fig. 14
which illustrates a blade having a concave upper surface
146 and an opening 148 providing part of an anchor structure
as previously described.
In general, the upper surface of the blade
will be non-interfering within the definition of the term
used in this application if the plastic body is free to
shrink longitudinally relative to the blade. Further, in
embodiments where an anchor structure is used, then the
upper surface of the blade will be non-interfering if por-
tions of the blade other than immediately adjacent the anchor
~ structure are free to shrink longitudinally towards the
;~ anchor structure. In order to further demonstrate this con- ,
cept7 Fig. 15 is included to illustrate a structure which
would not be acceptable. Upward projections 150 would limit
longitudinal shrinkage of the body towards anchor structure
152 and therefore stresses in the body would result.
: As previously illustrated with reference
to the embodiments shown in Fig. 1, the upper surface of
-~ , all of the blades is preferably rounded to limit the possi-
bility of interference between the body and the blade and
also to limit local stress concentrations in the body.
As mentioned, it may be satisfactory to manu-
facture an ice skate without controlling the direction of
the shrinkage relative to the blade. In general, the absence
of an anchor structure will result in unpredictable shrinkage
'~ 30 movement of the body on the blade and there will be a less
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1067S30
positive lock between the body and the blade. However,
an ice skate could be made without an anchor structure if
these limitations to the quality of the finished product
are acceptable.
The embodiments described with reference
to Fig. 6 can provide for tolerances so coarse that although
shrinkage movement can take place in either longitudinal
direction, the necessary rivet holes can still be drilled.
This is the case both if the recesses for the rivets are
first moulded into the body and also if the method shown in
Figs. 7 to 9 is used. An ice skate having no anchor stru-
cture can be made using the Fig. 6 blades and methods des-
cribed with reference both to this Fig. and to Figs. 7 to 9.
Yet another method of manufacture would be
to use a soft blade which is embedded in the body according
to any of the foregoing methods and then to harden the bottom
of the blade using a localized hardening technique such as
induction hardening.
; Throughout the foregoing description, rivets
have been used to attach the blade to the body. It will be
appreciated that although such a fastener is preferred, any
; other suitable mechanical fastener can be used. Also,
although the cross-section of the blade is shown to have
parallel upright sides, the cross-section could be varied
;~ provided both that the variation did not weaken the blade
significantly and provided ~hat the body would shrink freely
on the blade after moulding the body. This free shrinking
is possi~le only on blades having no cide depressions or
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1067S30
irregularities in the manner discussed with reference to
the upper surface of the blade. For convenience, suitable
blades will have the aforementioned non-interfering upper
surface as well as non-interfering sides at least in the
portion of the blade contained in the body.
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