US3484997A

US3484997A - Knife sharpening machine

Info

Publication number: US3484997A
Application number: US649249A
Authority: US
Inventors: Alton K Allen
Original assignee: Individual
Current assignee: Individual
Priority date: 1967-06-27
Filing date: 1967-06-27
Publication date: 1969-12-23
Anticipated expiration: 1986-12-23

Description

Dec. 23, 1969 A. K. ALLEN KNIFE SHARPENING MACHINE 3 Sheets-Sheet l Filed June 27. 1967 I G I F i 5:51 M 4 5: H M w H yo M. M "w 1 a 5 1 M 4 5* a m??? 2 i ,b/ m F INVENTOR. ALTON K. ALLEN ATTORNEYS DEC. 23, 1969 L EN KNIFE SHARPENING MACHINE 3 Sheets-Sheet 2 Filed June 27, 1967 FIG"? FIG.4

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' INVENTO. ALTON K. A N

ATTORNEYS FIG.5

Dec. 23, 1969, A. K. ALLEN KNIFE SHARPENING MACHINE 3 Sheets-Sheet 3 Filed June 27, 1967 INVENTOR. ALTON K. ALLEN M ATTORNEYS Patented Dec. 23, 1969 US. Cl. 51-80 Claims ABSTRACT OF THE DISCLOSURE The knife sharpening machine comprises two parallel shafts geared for equal rotation in opposite direction. Each shaft has abrasive discs and spacers, with the abrasive discs on one shaft being slightly overlapped and interleaved with the abrasive discs on the other shaft. Such a construction is known, but in the present machine the discs are disposed at a slight angle to the perpendicular in order to give the same a wobble motion as they are rotated by the shaft. The angle of the discs on one shaft is equal but opposite in direction to the angle of the discs on the other shaft, so that the interleaved discs wobble in unison.

BACKGROUND OF THE INVENTION It has already been suggested to use interleaved abrasive discs for sharpening a knife which is drawn lengthwise in the crevice between the discs. Such an arrangement has the disadvantage that the knife blade must be moved steadily and continuously as it is being sharpened. The knife edge may be gouged if not handled skillfully. It has also been suggested to provide an ab rasive cylinder the periphery of which is shaped somewhat like a square thread, the helix on one cylinder resembling a right-hand thread, and that on the other cylinder resembling a left-hand thread, so that the threads may be meshed as they are rotated at equal speed in opposite direction. Such a machine has the disadvantage in that it tends to pull the knife blade lengthwise as it is being sharpened. Also the abrasive cylinders are expensive to manufacture.

SUMMARY OF THE INVENTION The present knife sharpening machine has abrasive discs which are overlapped and interleaved, but the discs are disposed at a slight angle to the perpendicular in order to give them a wobble motion as they are rotated by the shaft. The angle of the discs on one shaft is equal but opposite in direction to the angle of the discs on the other shaft. The shafts are rotated at the same speed and in opposite directions. The discs have a desirable motion lengthwise of the knife blade, and this motion is a reciprocation which is so fast that it does interfere with holding and moving the knife as it is drawn between the abrasive discs.

The foregoing and additional features are described in the following detailed specification, which is accompanied by drawings in which:

FIG. 1 is a front elevation of a knife sharpening machine embodying features of the invention;

FIG. 2 is a partially sectioned plan view thereof;

FIG. 3 is a vertical section taken approximately on the line 33 of FIG. 2;

FIG. 4 is explanatory of a modification in which the discs and spacers are cemented together;

FIG. 5 shows how the peripheries of the discs may be dressed to conform to the surface of a cylinder;

FIG. 6 is a section similar to FIG. 3, but showing another form of the invention;

FIGS. 7 and 8 show discs having two wobble cycles;

FIGS. 9 and 10 show a modified orientation; and

FIG. 11 is explanatory of the discs in FIGS. 7-10.

Referring to the drawing, and more particularly to FIGS. 1, 2 and 3, the machine comprises two

parallel shafts

12 and 14 with means gearing them for equal rotation in opposite direction. Shaft 12 has a plurality of abrasive discs 16 and spacers 18. Shaft 14 has a generally similar series of abrasive discs 20 and spacers 22. The spacers are somewhat thicker than the discs so that the discs may be slightly overlapped and interleaved, as will be clear from inspection of the drawing. The discs 16 are secured to shaft 12 in parallel relation, but with areas thereof at a slight angle to the perpendicular in order to give the same a wobble motion as they are rotated by the shaft. The same applies to the abrasive discs 20, but the angle of the discs 20 is in a different direction from the angle of the discs 16. Like areas of both sets of discs are preferably disposed at the same amount of angle or departure from the perpendicular.

The angle is preferably such that the axial motion at the periphery of a disc is greater than the axial pitch from disc to disc. The wobble of the discs produces a rapid reciprocation in a direction lengthwise of the knife blade, the latter being shown at 24 in FIG. 1. This provides a continuous grinding action along every part of the knife blade, without requiring a skilled operator to draw the knife blade through the machine. By making the reciprocation substantial, there is an allowance for reduction in diameter of the discs as they Wear, or when they are dressed to restore them to true cylindrical configuration from time to time.

As will be seen by reference to FIGS. 2 and 3,

shafts

12 and 14 have

gears

26 and 28 which are in mesh with a pair of

meshing gears

30 and 32. An even number of gears is employed so that the

abrasive wheels

16 and 20 will turn in opposite direction. This direction is preferably upward at the knife blade, as is indicated by the arrows in FIG. 1, so that there is no tendency to wedge the blade between the wheels.

Reverting to FIG. 3, the

gears

30 and 32 are disposed below the

shafts

12 and 14 in order not to interfere with a knife blade as it is drawn through the machine. Moreover, the motor 34 driving the abrasive discs is preferably operatively connected to drive one of the lower gears, in this case the gear 30, thereby keeping the body of the motor out of the path of a knife blade being sharpened.

The pairs of gears used are preferably equal because the rotative speed of the two grinding cylinders must be equal. The speed of rotation may be on the order of 1800 r.p.m.

The drawing has been simplified in certain respects. In FIG. 3 is will be understood that the

gears

26 and 28 are appropriately secured to the

shafts

12 and 14, as by means of a key or a diametrical pin or a set screw. In FIG. 2, alternate gears are shown slightly different in width from the intermediate gears in order to more clearly illustrate the gear train, but in practice the gears would have the same width. The spacing of the parts in axial direction has been exaggerated, for clarity of illustration, and in practice the knife sharpener would be much more compact than is suggested in FIG. 2. The bearings at the ends of the shaft have not been illustrated, it being known to use anti-friction bearings or'selflubricating bearings, and the bearings would be appropriate to prevent axial movement of the shafts. Such refinements would be provided in accordance with known and conventional machine design practice.

Referring to FIG. 2, the abrasive discs and the spacers may begin as simple circular discs having a center hole which is slightly oversized so that the discs can be tilted. The discs and spacers are clamped between end pieces 3 36 and 38. These end pieces have angularly disposed

inner faces

40 and 42, and they establish the desired angle of the discs. In preferred. form, the shaft 12 has a keyway and key 44 received therein. The discs have appropriate keyways, and so do the

end pieces

36 and 38, but the latter preferably have two keyways disposed 180 apart, as shown at 46 and 48. In this way the four end pieces may all be alike, but one of the keyways is used for the end piece 36 and the other keyway is used for the end piece 38, thereby reversing the angle, as is desired.

Referring to FIG. 5, after the discs have been assembled, the edges are dressed as indicated by the broken line 50, so that the edges will conform to the surface of a cylinder.

If desired, the discs and spacers may be preliminarily cemented in face to face relation to form a single unit. This is illustrated in FIG. 4 in which the adjacent faces of the abrasive discs 52 and spacers 54 are marked to suggest the use of an appropriate cement when assembling the discs and spacers to form a single unit. The cemented assembly preferably includes the end pieces 56. Such a unitary assembly may be formed on a mandrel like the keyed shaft, and may be ground or dressed to give it the desired cylindrical surface, and thereafter may be handled as a single unit when mounting the same on a shaft of the sharpening machine. Such cementing is also indicated at 58 in FIG. 5.

The ends 36 and 38 may be die cast. Moreover, under volume manufacturing conditions, the spacers also may be die-cast with their center holes at a slight angle. The abrasive wheels, if molded to final shape, would have their center holes at a slight angle, and would be slightly elliptical rather than circular, in addition to having an angular edge. This would eliminate or reduce the dressing needed to form the assembly into a grinding cylinder.

If desired, the shafts may be relatively adjustable toward or away from one another, so that a desired overlap of the abrasive disc may be maintained, even after a reduction in diameter of the disc. Such an arrangement is shown in FIG. 6, in which the

abrasive discs

60 and 62 are mounted on

shafts

64 and 66 driven by

gears

68 and 70. The latter mesh with gears 72 and 74 mounted therebeneath. The shaft 66 is carried at the upper ends of levers, one of which is shown at 76. This lever is oscillatable about the shaft 86 of gear 74, and its position may be locked by means of a locking bolt 78 received in an arcuate slot 80. By moving the lower end of levers 76 toward the right, their upper ends are moved toward the left, thereby overlapping the abrasive discs. It will be understood that other mountings may be provided to afford such relative movement of the

shafts

64 and 66.

FIG. 6 also shows that the motor 82 may be operatively connected to gear 72 through another gear 84. In this way the motor may be mounted in a lowered position as shown, or in an outwardly offset or sideward position, not shown.

However, the motor may be connected directly to the shaft 88 of gear 72, as was illustrated in FIG. 3. It is desirable that the motor be associated with gears that are not adjusted from side to side. In FIG. 6 the motor is not affected by the sideward adjustment of the shaft 66. The same would be true if the motor were connected directly to the shaft 88.

As so far described the abrasive discs have a single wobble cycle for one full rotation. By the term wobble cycle I mean one reciprocation or one complete back and forth movement. However, the discs may be designed to provide a plurality of wobble cycles for one rotation. In FIGS. 7-11, I show abrasive discs which provide two wobble cycles for one full rotation.

Referring to FIG. 11 the disc 90, when viewed in section on a diameter 9292 is concave-convex, and when viewed in section on another diameter 94-94 which is perpendicular to the diameter 9292, is straight, and is perpendicular to the shaft. With such a disc there are two wobble cycles for one full rotation. Differently expressed, the entire area of the disc of FIGS. 2, 4 and 5 slopes in one direction, so that the disc has a single wobble cycle for one full rotation, whereas in FIG- 11, half the area of the disc slopes in one direction, and the other half slopes in an opposite direction, so that the disc has two wobble cycles for one rotation. Considered more generally, the disc when viewed in section on one radius is concave-convex; when viewed in section on another radius is straight; and there are a plurality of such concavo-convex sections and a plurality of such straight sections, so that the discs have a plurality of wobble cycles for one rotation. With more than two wobble cycles per rotation the disc might be described as having a sinuous or corrugated surface.

Referring now to FIG. 9, the knife sharpening machine, as before, comprises two

parallel shafts

96 and 98 each carrying a plurality of

abrasive discs

100 and 102 which turn in opposite direction. The discs 100 are cemented around hubs 104 which act also as spacers, and the discs 102 are similarly cemented around hubs 106 which act as spacers. In FIG. 9 the orientation of the discs is such that a diametrical section is concavo-convex.

FIG. 10 shows the same parts after the

shafts

96 and 98 have turned 90. In this orientation a diametrical section is straight and perpendicular to the shaft, as shown. FIGS. 9 and 10 have been drawn with the hubs 104 horizontally aligned, and with the hubs 106 horizontally aligned, as between the two figures. It will be seen that the overlapped edges of the abrasive discs are lower in FIG. 9 than in FIG. 10, showing the axial movement or wobble of the edges of the discs as the shafts rotate. They wobble up and down in a half revolution, there being two wobble cycles for each full revolution.

On reflection it will be evident that by appropriately shaping the discs they could provide three or more wobble cycles for each full revolution.

A modified arrangement and orientation of the discs is illustrated in FIGS. 7 and 8. In FIG. 7 the shaft 108 carries discs 110 cemented on spacer hubs 112. These discs are mounted with their concave sides upward. The shaft 114 has abrasive discs 116 carried by spacer hubs 118. These discs are mounted with their concave faces downward. Moreover, the rotative orientation differs from that shown in FIG. 9, in that a section through discs 116 is curved, or differently expressed, the discs are ro ationally displaced by 90 relative to one another. The shafts rotate in opposite direction as before.

FIG. 8 shows the same parts after rotation through an angle of 90. A diametrical section through discs 110 is curved, and a diametrical section through discs 116 is straight.

Here again the hubs 112 have been drawn in horizontal alignment and the hubs 118 have been drawn in horizontal alignment. The overlapped edges in FIG. 7 are in downward position, and in FIG. 8 are in upward position, showing the desired axial reciprocation or wobble movement. The movement is upward in 90 and downward in the next 90, so that the discs have two wobble cycles for one full rotation.

In FIG. 9 it will be seen that the angle of the sloping area of disc 100 is opposite in direction to the angle of a like area of disc 102. In FIG. 7 there is a relative angle because the sloping area of disc 116 cooperates with a non-sloping area of disc 110, and vice versa in FIG. 8.

It will be understood that

shafts

96 and 98 in FIG. 9 may be driven by gearing and a motor as previously described in connection with FIGS. 1 through 6, and the same applies to

shafts

108 and 114 in FIG. 7. It will also be understood that spacers may be used between discs in FIGS. 7-10, as shown in FIGS. 16, and that conversely hubs which act also as spacers may be used inside abrasive discs in FIGS. 16, as shown in FIGS. 710.

It is believed that the construction and method of use of my improved knife sharpening machine, as well as the advantages thereof, will be apparent from the foregoing detailed description. It also will be apparent that while I have shown and described the invention in several pre fered forms, changes may be made without departing from the scope of the invention, as sought to be defined in the following claims.

I claim:

1. A knife sharpening machine comprising two parallel shafts, means gearing them for equal rotation in opposite directions, a plurality of abrasive discs and spacers mounted on each shaft, the abrasive discs on one shaft being slightly overlapped and interleaved with the abrasive discs of the other shaft, and means securing the coaxial discs on a shaft in parallel relation but with areas thereof at a slight angle to the perpendicular in order to give the discs a wobble motion as they are rotated by the shaft, the angle of said areas of the discs on one shaft being different in direction from the angle of like areas of the discs on the other shaft, in which the discs When viewed in section on one diameter are concave-convex, and when viewed in section on another diameter perpendicular to the first diameter, are straight and perpendicular to the shaft, whereby the discs have two wobble cycles for one full rotation.

2. A knife sharpening machine as defined in claim 1, in which at intervals of 90 rotation the straight diametrical sections of the discs on one shaft are parallel to the straight diametrical sections of the discs on the other shaft.

3. A knife sharpening machine as defined in claim 1, in which at intervals of 90 rotation the straight diametrical sections of the discs on one shaft are perpendicular to the straight diametrical seections of the discs on the other shaft.

4. A knife sharpening machine comprising two parallel shafts, means gearing them for equal rotation in opposite directions, a plurality of abrasive discs and spacers mounted on each shaft, the abrasive discs on one shaft being slightly overlapped and interleaved with the abrasive discs of the other shaft, and means securing the coaxial discs on a shaft in parallel relation but with areas thereof at a slight angle to the perpendicular in order to give the discs a wobble motion as they are rotated by the shaft, the angle of said areas of the discs on one shaft being different in direction from the angle of like areas of the discs on the other shaft, in which each of said shafts has a key, and in which there are end pieces with angular inner faces between which the discs and spacers are clamped in order to establish the desired angle of the discs, each of said end pieces have two keyways disposed apart, whereby the end pieces at one end may be reversed relative to the end pieces at the other end.

5. A knife sharpening machine comprising two parallel shafts, means gearing them for equal rotation in opposite directions, a plurality of abrasive discs and spacers mounted on each shaft, the abrasive discs on one shaft being slightly overlapped and interleaved with the abrasive discs of the other shaft, and means securing the co axial discs on a shaft in parallel relation but with areas thereof at a slight angle to the perpendicular in order to give the discs a wobble motion as they are rotated by the shaft, the angle of said areas of the discs on one shaft being different in direction from the angle of like areas of the discs on the other shaft, in which the discs when viewed in section on one radius are concavo-convex, and when viewed in section on another radius are straight and perpendicular to the shaft, there being a plurality of said concaxo-convex sections, and a plurality of said straight sections, whereby the discs have a plurality of wobble cycles for one full rotation.

References Cited UNITED STATES PATIENTS 1,184,517 5/1916 Burt 51-80 2,570,690 10/1951 Kilian 51-80 FOREIGN PATENTS 117,696 5/1930 Austria. 810,853 8/1951 Germany. 184,796 9/ 1935 Switzerland.

HAROLD D. WHITEHEAD, Primary Examiner US. Cl. X.R.