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Sharper machine skates

Machine skates for sharpening the blade of machine skates has a vertically mounted, thin grinding wheel with a convex transverse cross-section corresponding to the concave transverse cross-section desired for the blade edge. Clamping plates on a cradle hold the blade above the wheel with their central planes coplanar and with the wheel biased against the blade. The cradle is pivotable about a horizontal axis above the machine skate so that the machine skate can be swung in an arc. Hence the movement of the blade over the wheel takes place in an arc that is curved in the same direction as the convex profile of the blade edge. This action reduces the problem of unevenness of depth of cut along the length of the blade, that has been experienced with prior machines employing straight line relative travel between the machine skate and the wheel. The tendency for the wheel to take a deeper cut at the more sharply curved toe and heel portions of the blade can be further compensated for by increasing the speed of traverse of the blade over the wheel in the vicinities of these end portions. This traversing speed can be reduced incrementally from a maximum at the extreme toe end of the blade down to a minimum over the central portion of the blade, while being increased again incrementally as the wheel approaches the heel end. Provision is also made for stopping the motor that drives the grinding wheel when the wheel is in the area of the picks of a figure skate.

In machine skates for sharpening the bottom edge of the blade of machine skates, said edge having a convex profile in side view, comprising

(a) a thin grinding wheel having a periphery with a convex transverse cross-section corresponding to a desired concave transverse cross-section of said blade edge,

(b) means for rotating said wheel about its axis,

(d) traversing means for effecting relative movement between the clamping means and the wheel in the longitudinal direction of the blade with the central longitudinal plane of the blade coplanar with the central plane of the wheel and with thewheel biassed against the blade edge to remove a cut therefrom;

the improvement wherein

(e) said traversing means includes position sensitive means for determining the location of the point of contact between the wheel and the blade edge and for regulating said relative movement to take place at a greater speed when said point is inthe vicinity of at least one end of said edge than when said point is in the vicinity of a longitudinally central portion of such edge.

2. The machine skates of claim 1, wherein the wheel is biassed against the blade edge in a direction perpendicular to the longitudinal extent of the blade.

3. The machine skates of claim 2, wherein said position sensitive means causes said relative movement to take place at the greater speed when said point is in the vicinity of both the ends of said edge.

4. In machine skates for sharpening the bottom edge of the blade of machine skates, said edge having a convex profile in side view, comprising

(a) a thin grinding wheel having a periphery with a convex transverse cross-section corresponding to a desired concave transverse cross-section of said blade edge,

(b) means for rotating said wheel about its axis,

the improvements wherein

(e) said traversing means includes means for causing said relative movement to take place in an arc that is curved in the same direction as said edge profile;

(f) the wheel is mounted in a vertical plane at a fixed location in The machine skates and said traversing means comprises a cradle assembly mounting said clamping means above the wheel, said cradle assembly being pivotally mounted about a horizontalaxis parallel to the axis of the wheel at a location above the clamping means, and said clamping means having open and closed positions;

(g) the cradle assembly is pivotable from a start position in which the clamping means is withdrawn from the wheel to grinding positions in which the clamping means is located above the wheel with a skate blade clamped therein in grinding contactwith the wheel; and

(h) skate positioning means mounted on the cradle assembly, including a pair of stops and means for moving said stops towards each other to center a skate longitudinally relative to the clamping means;

(i) wherein the machine skate positioning means has flag means movable with each said stop, and including sensor means at a fixed location in The machine skates for cooperation with said flag means for sensing the position along the blade edge of the pointthereof engaged by the wheel during pivotal movement of the cradle assembly away from its start position and for increasing the speed of such pivotal movement when said point is in the vicinity of at least one end of the edge relative to the speed whensaid point is in a longitudinally central area of such edge.

5. In machine skates for sharpening the bottom edge of the blade of machine skates, said edge having a convex profile in side view, comprising

(a) a thin grinding wheel having a periphery with a convex transverse cross-section corresponding to a desired concave transverse cross-section of said blade edge,

(b) means for rotating said wheel about its axis,

the improvements wherein

(e) said traversing means includes means for causing said relative movement to take place in an arc that is curved in the same direction as said edge profile;

(f) means are provided sensitive to the position along the blade edge of the point thereof engaged by the wheel for increasing the speed of said relative movement when said point is in the vicinity of at least one end of the edge relative to thespeed in the vicinity of the longitudinally central portion of such edge.

6. The machine skates of claim 5, wherein said arc of relative movement is a circular arc substantially coincident with a longitudinally central portion of said edge profile, end portions of such profile being more sharply curved than said centralportion, the wheel being biassed against the blade edge in a direction towards the center of curvature of said circular arc, and said position sensitive means increasing the speed of relative movement when said point is in both said end portions relativeto the speed when said point is in said central portion.

7. In machine skates for sharpening the bottom edge of the blade of machine skates, said edge having a convex profile in side view, comprising

(a) a thin grinding wheel having a periphery with a convex transverse cross-section corresponding to a desired concave transverse cross-section of said blade edge,

(b) means for rotating said wheel about its axis,

the improvement wherein

(e) said traversing means includes position sensitive means for determining the location of the point of contact between the wheel and the blade edge and for regulating said relative movement to take place at a high speed when said point is atone end of the edge, at a series of incrementally reduced speeds as said point travels towards a central portion of the edge and at a low speed as said point traverses said central portion.

8. The machine skates of claim 7, wherein said traversing means regulates the relative movement to take place at a series of incrementally increased speeds as said point travels from the central portion to the other end of the edge.

9. The machine skates of claim 8, wherein

(f) the wheel is mounted in a vertical plane at a fixed location in The machine skates,

(g) said traversing means comprises a cradle assembly pivotally mounted about a horizontal axis parallel to the axis of the wheel at a location above the clamping means,

(h) the wheel is biassed against the blade edge in a direction towards said horizontal axis,

(i) said traversing means regulates the cradle assembly to pivot in an outward pass from a start position in which the clamping means is withdrawn from the wheel, through grinding positions in which the clamping means is located above the wheelwith a skate blade clamped therein in grinding contact with the wheel, to a remote position in which the clamping means is again withdrawn from the wheel; and subsequently to pivot in a return pass from said remote position through said grindingpositions to the start position, and

(j) said traversing means so regulates such pivoting of the cradle assembly that the incremental reductions and increases of speed take place during at least one of said passes.

10. The machine skates of claim 9, wherein said incremental reductions and increases of speed take place during both said passes.

11. The machine skates of claim 9, including

(k) skate positioning means mounted on the cradle assembly, including a pair of stops and means for moving said stops towards each other to center a skate longitudinally relative to the clamping means,

(1) the machine skate positioning means having a pair of flag elements mounted to move with a respective said stop, each flag element comprising a plurality of fingers,

(m) sensor means is mounted at a fixed location in The machine skates for cooperation with said fingers for generating a series of signals corresponding to a series of longitudinal positions of said point of contact between the wheel and the blade edge,and

(n) said means for regulating the pivotting of the cradle assembly is connected to said sensor means with each of said series of signals controlling an incremental change of the speed of pivotting movement.

12. The machine skates of claim 11, including manually operable means for controlling said traversing means when the blade is that of a figure skate having picks at the toe portion thereof, whereby to disable said means for rotating the grinding wheelwhen said point of contact between the wheel and the blade edge is in the area of said picks.

13. The machine skates of claim 11, including means for locking the wheel against vertical movement.
Description
RELATED APPLICATION

Attention is directed to copending application of J. A. Consay Ser. No. 511,621 filed concurrently herewith and containing claims directed to some of the subject matter disclosed herein.

BACKGROUND

The present invention relates to machine skates for sharpening the blades of machine skatess.

As is well known, the bottom edge of machine skates blade is required to have a somewhat concave transverse cross-section so that a sharp ridge extends along each of the two side edges. This shape is maintained by grinding the blade periodicallywith a grinding wheel, the periphery of which has a corresponding convex shape in transverse cross-section. A typical machine for this purpose has been disclosed, for example, in U.S. Pat. No. 3,735,533 issued May 29, 1973 to M. Salberg (Canadianpatent No. 920,819 dated Feb. 13, 1973).

The present invention has the general objective of providing improvements in this class of machine and, in particular, seeks an improvement in the uniformity of grinding along the length of the blade. The depth of metal to be removed from theblade will vary, e.g. from about 2 thousandths of an inch, in the case of a blade requiring only minor sharpening, up to about 10 thousandths of an inch in the case of a badly deteriorated blade. Whatever the depth of cut that is selected, it isimportant that essentially the same depth of cut be maintained along the full length of the blade. If a reasonable approximation to this ideal is not maintained, after repeated sharpening operations the basic profile of the blade will becomesignificantly modified.

One of the principal difficulties with prior machines of this type has been a tendency for them to remove more metal from the ends of the blade, i.e. near the toe and the heel, than from the central portion of the blade, during each pass of thegrinding wheel along the blade. A skate blade is initially constructed with a convex profile when seen in side view. In the longitudinally central portion of the blade this convexity is comparatively slight. At the ends, the curvatures are sharper,especially at the toe. This profile is designed to maximise the performance of the machine skate and it is therefore desirable to maintain such profile throughout the life of the blade. Removal of excessive metal from either or both of the toe and heelportions will distort this profile and shorten the life of the machine skate.

The tendency towards removal of more metal from the end portions than from the center, flows from the fact that, when a grinding wheel is urged against a skate blade in a direction perpendicular to the general longitudinal direction of the bladeand the portion of the blade engaged by the wheel does not extend at right angles to such perpendicular direction due to the curvature of the blade, such portion contacts the wheel at a radius inclined to such perpendicular direction. Thus, if a uniformforce is applied to bias the wheel in the perpendicular direction throughout a complete pass of the wheel along the blade, the blade resists this applied force by a somewhat larger force acting along the inclined radius, since the action and reactionforces between the blade and the wheel can only act along a radius normal to the tangential direction of the contact between the blade and the wheel.

A proposal to compensate for this effective increase of force between the blade and the wheel (and hence increased depth of cut) at the ends of the blade by varying the perpendicular biassing force in accordance with the grinding resistance(sensed by measuring the power input to the motor driving the wheel), is disclosed in U.S. Pat. No. 4,235,050 issued Nov. 25, 1980 to J. H. Hannaford et al. (Canadian patent No. 1,118,514 issued Feb. 16, 1982). This proposed solution has, however,not been found reliable or satisfactory in practice.

There is thus a need to provide an alternative solution to the problem of ensuring substantial uniformity of depth of cut throughout the length of the blade, especially the “end effect” problem, by a system that is both simple in construction andmore accurate and reliable in practice than any machine hitherto constructed.

To this end the above referred to application of J. A. Consay provides for effecting relative movement of the blade and the wheel in an arc that is curved in the same direction as the profile of the blade edge.

In his preferred construction the wheel is mounted in a vertical plane at a fixed location in The machine skates and the machine skate is mounted blade down in a cradle assembly that is located above the wheel, the central longitudinal plane of the blade beingcoplanar with the central plane of the wheel. The cradle assembly is pivotable about an axis that extends parallel to the axis of the wheel at an upper location in The machine skates. Hence both the blade profile and the traversing arc of the blade over thewheel are curved in the same direction, i.e. convexly downwardly. If the curved profile of the blade edge were a simple circular arc, it would be possible to compensate fully for such curvature, and especially for the “end effect,” by locating thecradle assembly axis coincident with the center of curvature of the blade profile. However, only the central part of the blade profile is even approximately circular. As already mentioned, towards the ends the blade curves up relatively sharply, suchcurvature being different at the heel portion from the toe portion. In addition, a figure skate has a differently shaped toe portion from that of a hockey skate, and it is desirable that the same machine should be able to sharpen both types of skate. Hence, as a practical matter, the axis of the pivotted cradle assembly can be located to compensate reasonably well for the comparatively gentle and substantially circular curvature of the central portion of the blade profile. However, it can at thesame time compensate only partially for the more sharply curved end portions.

SUMMARY OF THE PRESENT INVENTION

For this reason, a further feature of The machine skates relates to a system for obtaining additional compensation for the “end effect.” This result is achieved by increasing the speed of relative movement between the blade and the wheel when grindingthe end portions of the blade. The depth of cut taken by the wheel is related not only to the strength of the biassing force and its direction relative to the normal to the blade edge at the point of contact, but also to the length of time that thewheel remains in contact with each part of the blade. In other words, other factors being equal, a grinding wheel that passes quickly over a workpiece will take a shallower cut than one that passes more slowly. This effect is exploited in the presentmachine by arranging for the relative motion, e.g. travel of the cradle assembly, to be speeded up when the end portions of the blades are in contact with the wheel.

More specifically, the present invention consists of providing means for accurately sensing the location of the point of contact between the wheel and the blade edge and for regulating the relative movement between them to take place at a highspeed when this point is at one end, at a series of incrementally reduced speeds as the point travels towards a central portion of the blade and at a low speed as the point moves along this central portion. Preferably the speed is then again increasedthrough a series of increments as the contact point travels from the central portion to the other end of the blade.

With this concept applied to the preferred form of machine proposed in the application of J. A. Consay, i.e. employing a pivotable cradle assembly for moving the blade in an arc over the wheel, the incremental reductions and subsequent increasesin the speed of traverse can be applied to either one or both passes, e.g. an outward pass in which the blade moves over the wheel from the toe end to the heel end or a return pass when its direction of travel is reversed.

THE MACHINE SKATE

the machine skate detector 20 is mounted beneath the clamping plates 115, as shown in FIGS. 2 and 3. Details of the machine skate detector 20 are better seen from FIGS. 4a and 4b. This detector consists of a plate 201 having ends bent up to form upstandingskate supports 202 each containing a centrally located, blade centering groove 203. Centrally of the plate 201 there is a body 204 on the upper surface of which there is a magnet 205. A portion 206 of this central body 204 projecting below the plate201 contains a known type of detecting mechanism 737, e.g. a lamp and photocell device. A pair of pins 208 project upwardly through holes in the plate 201 in alignment with the grooves 203. The pins 208 are mounted on the arms of a U-shaped member 209,the central portion of which is spring urged upwardly and passes through the detecting mechanism 737. As shown by broken lines in FIG. 4a, when both the pins 208 are depressed, the central portion of the member 209 moves to a lower position relative tothe mechanism 737. The depressed position of the member 209 is thus detected by the mechanism 737.

Alternatively, any other convenient detecting mechanism can be used that will confirm that a skate blade is in position between the clamping plates 115, e.g. a pair of spaced apart photosensors that directly sense front and rear parts of theblade without the intermediary of the pins 208 and member 209.

As shown in FIGS. 2 and 3, the machine skate detector 20 is located beneath the clamping plates 115 of the cradle assembly 10 in such a manner as to be movable between a raised and a lowered position. For this purpose, it is mounted on an arm 212 thatis freely pivoted to the frame at 902. Shown in these views in its lowered position, the detector 20 can be raised by a vertical member 211 secured to it. The member 211 carries a horizontal pin 210 that is controlled by parts of the door moving system80 in the manner described below.

the machine skate POSITIONING ASSEMBLY 30

This assembly 30 is secured to the far side of the cradle assembly 10 as seen in FIG. 1, for which reason it is largely obscured in that figure. However a fragment of the frame 301 of the assembly 30 is shown in FIG. 2 to make it clear that theassemblies 10 and 30 swing together on the shaft 101.

Details of the machine skate positioning assembly itself are shown in FIGS. 5 and 6, where it will be seen that the frame 301 supports a motor 303 that, through a chain 304, drives a threaded shaft 305 mounted in bearings 306 in a central housing. Aswill be apparent from FIG. 6, the shaft 305 has two ends that project in respective directions from the bearing housing, these ends being respectively provided with right and left hand threads. On the left hand end of the shaft 305 there is a toecarriage 307 and on the right hand end a heel carriage 308. Rotation of the shaft 305 by the motor 303 will move these carriages 307, 308 in unison either towards or away from each other. The carriages 307, 308 respectively carry laterally projectingarms 309, 310 (see also FIG. 9) that extend towards the cradle assembly. On the ends of these arms 309, 310 there are respectively an upwardly projecting toe stop 311 and a downwardly projecting heel stop 312 (also seen in FIG. 1).

Virtually all the significant parts of the frame 90 have already been described in relation to their support of the various sub-systems. However, FIG. 1 also shows a tank 935 at the foot of the frame 90 for containing coolant that is sprayedonto the grinding wheel in a known manner (not otherwise described or illustrated) and a control panel 936 for operation by the user. The housing will be completed by a door on the near side seen in FIG. 1, which door can conveniently serve to support amicrocomputer assembly (not shown) that will form part of the control system 70, and may also include a conventional coin operated mechanism (not shown) for energising The machine skates.

OPERATION OF The machine skates

Assuming that The machine skates has been turned on, either by a coin operated mechanism or the like, or by a master switch, the following sequence of steps is carried out under the control of the microcomputer.

(1) The number of passes of the cradle assembly 10 since the grinding wheel 409 was last dressed is checked and, if above a selected number, the dressing assembly motor 413 is actuated. When the dressing operation is complete, or was not carriedout, the ready status of the wheel 409 is signalled by the limit switch 734.

(2) Location of the cradle assembly 10 in its start position is detected by the limit switch 730. If it is not, the cradle cylinder 515 is retracted to bring it to this start position.

(3) The door to the opening 907 is opened by the cylinder 801 by moving the valve 704 to the position opposite to that seen in FIG. 17. This action involves the arms 807 pulling up on the pins 809 to rotate the blocks 810 to unlatch the hookedportions 812, 814, which allows the arms 811 to rotate upwards about the mountings 932. Raising of the door enables the operator to insert a skate 8 toe first, as shown in FIG. 1. The front face of the housing will contain appropriate instructions forthe operator. Opening of the door also raises the machine skate detector 20 through the members 820 to 826, 210 and 211.

(4) The blade 9 of the machine skate will pass between the clamping plates 115 to engage and be lightly held by the magnet 205 of the machine skate detector 20, while resting in the grooves 203 and depressing the pins 208 to activate the detecting mechanism 737and hence signal the presence of a skate blade to the control system.

(5) the machine skate positioning assembly 30 is then actuated, e.g. motor 303, in the direction to move the toe and heel stops 311, 312 towards each other to engage the respective ends of the machine skate. Compare FIGS. 7 and 8. The effect of this movementis to ensure centering of the machine skate blade in the longitudinal direction, regardless of how far forward or rearward it has been inserted by the operator. Firm engagement of both ends of the machine skate by the stops 311, 312 is detected by limit switches (notshown) in the toe and heel carriages 307, 308 that sense refusal of these stops to move any further.

(6) The control system then moves the valve 703 to the position shown in FIG. 17 to energise the cylinder 108 to clamp the blade tightly between the plates 115. Achievement of tight clamping is reflected in a build up of pressure in the cylinder108, which is detected by the limit switch 732. Any subsequent loss of such pressure would be detected by the switch 732 to halt the operation of The machine skates. The motor 303 is deenergised but not reversed, so the stops 311, 312 remain in engagementwith the ends of the machine skate.

(7) The door is now closed by returning the valve 704 to its FIG. 17 position to expand the cylinder 801. The downward sliding movement of the door takes place under gravity only, being merely permitted rather than forced by the return movementof the mechanism 80, so that the operator is not harmed if his hand is still inserted into the opening 907. He will, of course, have been instructed to remove his hand from The machine skates as soon as he had inserted the machine skate in step (3) above, and thesequence of steps will be controlled with appropriate delays to ensure that he has had adequate time for this purpose. In any event, while the cylinder 801 will have been fully expanded to move the arms 807 to the position shown in FIG. 16, the pins 809will only have reached the end of their slots 808 if the arms 811 have been permitted by a fully closed door to reach the position shown in FIG. 16. Until this occurs (indicating that the operator’s hand must have been removed from The machine skates), thelatches 812, 814 will not reengage. When they do, they prevent the door being raised again except by operation of the cylinder 801. At this time the limit switch 731 signals that the door is in the closed and latched condition. It also indicates thatthe machine skate detector 20 has been allowed to drop clear of the blade by lowering of the member 826. Should the magnet 205 be strong enough to prevent this, the linkage connected to the door moving system that raises the detector 20 can be modified to lowerit positively at this time.

(8) At this or some earlier stage in the operation the operator is invited, e.g. by flashing lights, to press appropriate control buttons on the panel 936 to indicate the type of skate, i.e. hockey or figure, and the depth of grinding he desires,e.g. light, medium or heavy. If a light grind is chosen, The machine skates makes one double pass (forward and back) of the machine skate over the wheel. For the medium and heavy grinds two and three double passes respectively are made.

Sharper machine skates

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