US2142105A

US2142105A - Knife sharpening machine

Info

Publication number: US2142105A
Application number: US49176A
Authority: US
Inventors: Blankner William
Original assignee: KEEN O MATIC MACHINE Co
Current assignee: KEEN O MATIC MACHINE Co; KEEN-O-MATIC MACHINE Co
Priority date: 1935-11-11
Filing date: 1935-11-11
Publication date: 1939-01-03
Anticipated expiration: 1956-01-03

Description

Jan. 3, 1939. w. BLANKNER KNIFE SHARPENING MACHINE 4 Sheets-Sheet 1 v Filed NOV. 11, 1935 \H lllll In Men 1%? //Z/z52n277 zzfzze'z."

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1939; w. BLANKNER 2,142,105.

KNIFE SHARPENING MACHINE Filed Nov. 11, 1935 '4 Sheets-Shed 2 Jan.3, 1939. W.BLANKNER 2,142,105

KNIFE SHARPENING MACHINE Filed NOV. 11, 1935 4 Sheefs-Sheet 3 (\P I IIQVA'IIIIIIIIIIII A Jan. 3, 1939. I LA 2,142,105

KNIFE SHARPENI NG MACHINE Filed Nov. 11, 1935 4 Sheets-Sheet 4 Patented Jan. 3, 1939 UNITED STATES PATENT OFFIQE KNIFE SHARPENING MACHINE corporation of Ohio Application November 11, 1935, Serial No. 49,176

21 Claims.

This invention relates to a knife-sharpening machine adapted to be operated by hand or by other power, and to provide guidance and control for the blade to be sharpened which shall ensure uniform and satisfactory results at all times. One object of the invention is to provide a machine adapted to utilize a straight or fiat grinding stone renewable after it has become worn, and readily removable for such renewal. Another object is to afford means for holding the knife blade at a definite angle to the stone to ensure a uniform bevel at the cutting edge. It is also an object to furnish, means for holding and guiding the knife blade designed to avoid contact with the cutting edge itself, and it is also an object of the invention to utilize substantially the full length of the stone in the grinding operation to ensure fairly uniform wear thereof. Other objects will appear from the following description. The invention thus consists in the combination of features and elements of construction as herein shown and described and as indicated by the claims.

In the drawings:

Figure 1 is a plan view of a knife-sharpening machine embodying this invention, the driving motor being only partially illustrated and broken away and a knife blade being shown in operative position.

Figure 2 is a transverse vertical section taken at convenient planes within the housing, and with certain of the exterior portions of the machine shown in elevation.

Figure 3 is a vertical section taken substantially as indicated at line 3-3 on Figure 2, the bladesupporting mechanism being shown in elevation and tilted in position for operation.

Figure 4 is a vertical section taken as indicated at line 4-4 on Figure 2, showing the blade-supporting parts in neutral horizontal position.

Figure 5 is a transverse detail section taken as indicated at line 5-5 on Figure 1.

Figure 6 is a longitudinal detail section taken as indicated at line 6-6 on Figure 1 for showing the mounting of the stone.

Figure 7 is a detail sectional view of the automatic pump taken as indicated at line 'l-l on Figure 2.

An important feature of this machine is that it is designed to utilize a fiat surfaced grinding stone or abrasive member, preferably in the form of an approximately rectangular block which may be renewed from time to time as it wears down in operation. In the design illustrating the invention I have shown such a stone mounted on a carriage connected with a suitable source of power for reciprocation, while guiding and holding means are provided for keeping the knife at a predetermined angle to the plane of movement of the grinding surface with its edge contact therewith,said holding means, however, permitting movement of the knife in the direction of its cutting edge and transversely of the direction in which the grinding stone is reciprocated. In the drawings, Figure 1 shows in plan view a sup 5 porting frame or housing whose upper surface forms a pan I, adapted to collect the grindings and drippings from the stone and the knife, and enclosing the drive gearing by which rotary motion from the shaft of a motor 2, is converted 10 into reciprocating movement of the abrasive grinding stone 3, seen in operative relation to the blade 4 of a knife. Figures 2 and 4. show the shaft of the motor 2 provided with a coupling 5 which connects it with a shaft 6 whose pinion l, with- 15 in the housing 8, meshes with a gear 9 on shaft It. The same shaft It! carries an eccentric l I encircled by a strap [2 of a pitman l3 connected to a wrist pin I4 on a rocker l5. The lower end of the rocker lever 15 is fulcrumed at It in the hous- 20 ing 8, and its upper end is a squared fork l1, bifurcated to engage a pair of blocks l8 pivotally secured at I9 to a slide or cross-head 28. The latter is shown in the form of a cylindrical rod carrying bracket arms 2| at its outer ends, which support a bed or table 22 on which the stone 3 is secured. The swinging motion of the rocker lever l5, which is produced by its connection through pitman I3 with the eccentric II, when the latter is revolved by its gear connections with the motor 30 2, operates to reciprocate the cross-head 20 and with it the abrasive stone 3 for operating upon the knife blade 4.

The cross-head 28 is carried in bearings 23 in the upper section 24 of the housing which surmounts the lower section or housing 8, and suitable stufiing boxes may be provided at 25 to retain the lubricant within the housing and exclude grindings or abrasive which may result from the operation of the machine. The brackets 2| are held upright and the cross-head rod 28 is prevented from. rotating in its bearings 23 by a flat slider 26 secured to the block 21 at the middle of the cross-head on which the blocks 8 are pivoted. Adjusting screws 28 serve to maintain sliding contact between the part 26 and the machined, downwardly facing fiat surface 29 on the under side of the top wall I.

The stone shown at 3 is retained by contact of one end with an abutment block 30 secured to the bed 22 and engagement of its opposite end by a lever at, whose spring 32 normally wedges it against the slightly inclined end surface 3 of the stone 3, but may be readily disengaged by swinging it downward against its spring, and thus rocking upward the short end 31 of the lever out of contactwith the end of the stone. The stone may be of any suitable type, such as a whet stone, with whiQh Water is commonly employed, or an oil 60 stone, or a suitable block of synthetic abrasive such as carborundum.

For holding the knife blade, such as that shown at 4, in proper relation to the stone 3, I provide a pair of rollers 33 adapted to engage the blade at or near its cutting edge, and additional rollers 34, designed to engage the back or opposite edge of the blade; each of the rollers 34 is journaled on a carrier sleeve 35 which is slidably mounted upon a tubular support 36 fixed at the middle of its length in a hollow bracket 31 upon which one of the guide rollers 33 is journaled. A spring 38 extends lengthwise within the supporting tube 36 and is anchored at its opposite ends in the two carrier sleeves 35; one of the anchorages is shown as an adjustable screw 39 for varying the tension of the spring and thus regulating the pressure with which the rollers 34 engage the back of the knife blade. Both sets of rollers are peripherally grooved for seating the edges of the blade, and the larger rollers 33 are formed with deep central channels 33, which are of less width than the total thickness of the blade 4, but prevent actual contact of the cutting edge with the rollers, the opposite and diverging faces of the blade contacting with the edges of the grooves 33 when the blade is inserted between these rollers 33 and one pair of rollers 34, as seen in Figure 1. Knife blades are either tapered to a point or rounded at their outer ends; thus the blade will act as a wedge as it is entered between the rollers 33'and the opposing rollers 34, forcing back the rollers 34 in opposition to the tension of springs 38, and shifting the carrier sleeves 35 accordingly upon the tubular support 36.

One pair of carrier sleeves 35, preferably those whose rollers 34 are first engaged by the back of the knife blade as it is inserted, are formed on their under sides with cam surfaces 36 which engage opposite sides of a cam plate 40, as seen in Figure 4, when there is no knife in the machine.

The insertion of the knife moves one of the cams 36 out of contact with the plate 40, whereupon this end of the plate rocks upward slightly, and this movement is utilized to permit the entire carriage structure which supports the knife to settle slightly toward the stone 3 so as to bring the cutting edge into operative engagement therewith. This action results from the fact that the knife carriage, consisting of the brackets 31 with the rollers 33 and rollers 34, is carried upon a stem 4| which is vertically slidable in a cylinder 42, and is drawn yieldingly downward by means of a spring 43. This spring is coiled about a stud 44 which extends downwardly from the stem 4|, and may be provided with an adjustable nut 45 at its lower end, forming a shoulder against which the spring 43 reacts. The cam plate 40 rests upon a bridge 46 which is fixed in relation to the cylinder 42 and extends through a vertical slot or rift in the stem 4|. Thus when the pressure of one cam surface 36 is removed from one end of the cam plate 40, the knife carrier assembly is drawn downward by the spring43 while the relieved end of the cam plate 40 rocks slightly upward, as seen in Figure 3. This slight shifting of the knife carriage ensures that the point of the blade may be readily inserted past the grinding surface of the stone 3 before complete control of the blade is taken over by the

rollers

33 and 34 which are to hold it with its cutting edge in contact with the stone 3.

Another adjustment which is essential for effective grinding operation is the tilting of the blade carriage to a definite angle for producing a predetermined bevel on the blade 4. The entire carriage is pivotally connected to the stem 4| by a lug 41, which is bifurcated to accommodate the cam plate 40 and which is borne upon a pivot pin 48 extending through the stem 4|, as seen in Figure 2. One of the brackets 31 carries a segment plate 5|] having a series of recesses 5| for engaging the point of a spring detent 52, which may be conveniently supported in a special bracket 53 on the guide sleeve 42 in which the stem 4| of the knife carriage is disposed. When the carriage is thus checked at the desired angle, as seen in Figure 3, the blade 4 will be inclined just enough to ensure the correct grinding of its cutting edge, and it will be understood that the series of recesses 5| will provide different positions of adjustment corresponding to various bevels which are wanted on knives intended for different uses.

When the edge has been ground or honed on one side by the action of the stone 3 it will be removed from the machine and reinserted between the rollers 33 and the other pair of rollers 34, thus presenting its other face to the stone; at the same time the carriage will be tilted in the opposite direction but at the same angle so that the correct bevel will be produced on this opposite face of the blade.

As *the stone works its grinding surface will wear down, but I have provided means for automatically keeping the blade carriage in proper relation to the stone, notwithstanding such wear. The entire carriage with its stem 4| is supported in the guide sleeve 42, which has an extension 54 overhanging the stone 3, and journaling a roller 55 which bears upon'the working face of the stone. The guide sleeve 42 is thus hung upon the stone itself; but the blade carriage assembly rests upon the cam plate 40 which, in turn, rests upon the bridge 46, which is secured in the sleeve 42. Thus, as the stone wears, and

the sleeve 42 settles in the vertical guideway 56 formed for it in the upper housing casting 24, the bridge 46 settles with it and lowers the knife carriage supported on the cam plate 40 so that the knife moves downward by exactly the same distance as the roller 55. In this way the wear of the stone is effectively compensated without attention on the part of the user until a definite limit is reached, when the guide sleeve 42 settles its lower limit in the guide pocket 56; thereafter the stone will cease to function and will be removed and replaced.

In order to ensure fairly uniform wear over the entire surface of the stone the working stroke should carry the end of the stone past the blade of the knife, because if the stroke should stop short of this there would be a small area at the end of the stone which would not wear down, and this would merge into the middle area with a rather abrupt but rounded shoulder, resulting in unsatisfactory action of the machine and requiring frequent treatment of the stone to give it a new and fiat surface. For this reason the mechanism is designed to ensure travel of the stone in the direction away from the cutting edge of the knife and by a short distance beyond that edge. Then to avoid injury to the cutting edge it becomes necessary to lift the knife slightly above the plane of the stone as the return stroke begins, and then lower it onto the stone as soon as possible. This is effected by means of a bell crank lever 60 pivoted at 6| in the lower end of the stem 4|, with its longer arm extending through clearance openings 42 and 56 in the guide sleeve 42 and the guide pocket wall 56 respectively. The lower end 'of this arm contacts a cam 62 on the shaft [0, and is held in contact by a spring 63. The short end of the lever 60 bears against the upper face of the bottom wall 42 of the guide sleeve 42, so that a slight movement of the lever away from the shaft Ill crowds the stem 4| upwardly in relation tothe guide sleeve 42, and thus lifts the knife carriage slightly with respect to the stone 3. The cam 62 has two raised portions 62 at diametrically opposite sides, so that this lifting action of the knife will occur twice in each revolution of the shaft ID in timed relation with the reciprocation of the stone 3 and just as it passes out from under the cutting edge of the knife blade in that part of the stroke in which it moves away from that edge. The length of the portion 62 is such as to keep the blade slightly elevated until after the stone has reversed its direction of movement and its extreme edge has passed under the edge of the blade. At the other end of the stroke the blade remains in contact with the stone since the cutting edge is not held exactly at the middle of the machine; but when the knife is reversed for grinding its opposite side, this other end of the stone will function in the grinding operation, thus equalizing the wear over the entire length of the stone. It will be noted that the lower end portion of the lever 60, which engages the cam 62, extends for some distance in substantially vertical direction; this ensures that throughout the range of vertical movement of the knife support which it experiences as the. surface of the stone wears down, the action of the cam and lever will be unaffected by this vertical shifting of the parts.

In grinding the extreme point of the blade the operator will tend to press the point of the knife onto the stone 3 by lifting up slightly on the handle end. In such a case the lifting action of the rollers at the end of the stroke might not be suflicient to prevent the point of the blade snagging against the end of the stone, and to guard against this possibility I provide guard members 54 extending longitudinally at each s de of the stone and formed as integral parts of the extension 54. These guards, barely below the grinding surface, will assume support of the blade as the stone leaves it in the end portion of its stroke, and the temporary lift of the.

rollers

33, 34 will still be sufiicient to raise the point of the blade and allow the stone to pass under it.

As a convenient arrangement for feeding either water or oil to the surface of the stone while in operation, I have shown a liquid supply tank In embodied in the base or housing 8, with the filler opening closed by a plug at H. and with a pump of the gear type built into the side wall of the housing at such position that one of its gears 12 may be connected directly to the shaft ill for continuous operation therewith. An inlet duct I3 leads from the tank space H! to the pump, and an outlet duct 1'4 leads upwardly to a channel 75, which may be formed in the upper edge of the casting 8 and closed by the securement of the upper housing 24 thereto. This channel. as indicated in Figure 2, leads to a length of flexible hose or tubing 15 connecting with a valve fitting 1B which is disposed directly above the roller 55 and has a small drip port Tl, controlled by an adjustable needle valve 18. The capacity of the pump will preferably be somewhat in excess of the normal demand, but to compensate-for this I provide a by-pass 19, with a check valve "80, which will permit the return of the excess of liquid to the supply tank 10. The liquid thus fed to the grinding surface of the stone 3 will be mixed with-the grindingsyandasit is "gradually flushed off from the surface of the stone, or otherwise removed, this material will drop onto the pan I which forms the top wall of the housing section 24, and it can 5 be mopped up from this surface at intervals, as necessary. To ensure clearing the cutting edge of the knife of this material I provide drain ducts 33 leading through the rollers 33 from the inner portions of their deep grooves 33 and thence v10 the full length of its cutting edge to the grinding {Q0 operation.

When the machine is driven by an electric motor, as illustrated in the drawings, it will be a relatively simple matter to provide a switch (not shown) in the motor circuit controlling its .opera- :25 .tion and arrange this switch to be closed by the outward movement of the sleeves which carry the rollers 34, at either side of the knife support,

so that the insertion of the knife between

rollers

33 and 34 will automatically initiate the opera-1.30

tion of the motor and the reciprocation of the stone 3; and withdrawal of the knife, permitting .thesleeves 35 to return toward the middle brackets 31, will automatically stop the motor. Thus the-machine will not be left inadvertently running 585 when it is not actually in use, and the use of it will be simplified for the operator.

Operation The knife blade is thrust into the DOSitiOHg-Afl shownin Figure 1, with its cutting edge disposed .in the grooves of the large rollers 33, and with the smaller rollers 34 contacting with the back edge of the blade and yieldingly held in such contact bythe springs 38. If the insertion of the a blade ie-arranged to operate the motor switch automatically, as just described, the operator need donothing further to start the machine; otherwise he'will operate any suitable control switch (not shown) for-starting the motor 2, which will a 0 cause reciprocation of the stone 3. The insertion of the blade by forcing back the rollers 34 and carrying one cam surface 36 out of contact with the cam plate 40 permits the latter to rock to the position shown in Figure 3, bringing the cut- E355 ting edge of the knife onto the surface of the stone 3 at-an angle thereto so that a beveled cutting edge will be produced. The operator will shift the knife blade 4 transversely of the movement of the stone 3, so that the entire length 01,5 the cutting edge shall be evenly sharpened; this transverse adjustment of the blade is facilitated by the

rollers

33 and 34 which rotate about their journals in'response to the movement of the blade, the yielding mounting of the rollers 34 keeping them constantly in contact with the back edge of the blade and pressing the cutting edge into the central channels of the rollers 33, so as to maintain its proper relation to the stone. When one bevel of the cutting edge has been sufiiciently o ground the knife is withdrawn and re-inserted at the opposite side of the rollers 33, with its back edge in contact with the other pair of rollers 34, and the operation is repeated.

While ,thereiis shown and described herein cer- 54 tain specific structure embodying the invention,

it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the 55 spirit and the scope of the invention, and that the same is not limited to the particular form herein shown and described, except in so far as indicated by the appended claims.

I claim:

1. A knife sharpening machine comprising a substantially fiat stone, means for reciprocating said stone, and a knife support including holding means disposed for engaging opposite edges of a knife blade with a portion of the cutting edge in contact with'the surface of said stone, and means adapted to maintain such engagement of the holding means when the blade is moved lengthwise of its cutting edge and transversely of the direction of reciprocation of the stone while the latter is in operation, in the process of sharpening the entire length of the cutting blade.

2. A knife sharpening machine comprising a substantially fiat stone, means for reciprocating said stone along a fixed path, and a knifesup- 95 port including rollers respectively disposed for rolling engagement with the cutting edge and the back edge of a knife blade with a portion of the cutting edge in contact with the surface of said stone, and yielding means adapted to presssaid -30 rollers toward each other and into engagement with the blade while the blade is moved lengthwise of its cutting edge during reciprocation of the stone in the process of sharpening said cutting edge. p Y

3. A knife sharpening machine comprising a substantially fiat stone, means for reciprocating said stone, and a knife support including rollers disposed for engaging opposite edges of a knife blade with the cutting edge in contact with the surface of said stone, and yielding means adapted to maintain said rollers in engagement with the blade, the rollers for the cutting edge of the blade having deep narrow grooves dimensioned.

so that the opposite faces of the blade adjacent the cutting edge are engaged between the edges of the grooves to avoid injurious contact with the cutting edge itself.

4. In the combination defined in claim 3, said deep-grooved rollers having ducts leading'from their grooves out through'the faces of the rollers to clear them of grindings and abrasive that is carried into the grooves from the edge of the knife blade.

5. A knife sharpening machine comprising a substantially fiat stone, means for reciprocating said. stone, and a knife support including holding means adapted to carry a knife blade with its cutting edge in contact with the surface of said stone, said knife support being movable in the machine toward and from the working face of the stone and a roller journaled on the support and resting upon the said working face of the stone which is the face in contact with the cutting edge of the knife blade, whereby said roller maintains a fixed relation between the support and said working face as the working surface of the stone wears away.

6. A knife sharpening machine comprising a substantially fiat stone; means for reciprocating said stone, a knife support including means for holding a knife blade with its cutting edge in contact with the surface of said stone-, the re ciprocating stroke of the stone being measured to carry the end of the stone past said cutting it edge of the knife and means automatically operated in timed relation to the reciprocating stone for raising the knife support in the end portion of the stroke and lowering it in the initial portion of the return stroke after the extreme end of the stone has passed under the edge of the blade.

7. A knife sharpening machine comprising a substantially fiat stone, means for reciprocating said stone including a rotary driving member, a knife support adjustable in a direction toward and from the face of the stone with means for holding a knife blade with its cutting edge nor mally in contact with said face of the stone, the stroke of the stone being measured to carry the end of said stone past said cutting edge of the knife, a lever and a part with respect to which the knife support is adjustable, said lever having an arm arranged to react between said part and the support for shifting the support in the disposed laterally adjacent the path of travel of the stone and extending longitudinally in position to support a knife blade when the stone has passed from under its cutting edge in the end portion of its stroke.

9. A knife sharpening machine comprising a substantially flat stone, means for reciprocating said stone along a fixed path, a knife support including a middle portion provided with contact means with which the knife blade is engageable at points closely adjacent its cutting edge and over which it is movable in the direction of said cutting edge to bring different portions of said edge into the path of the stone while it re ciprocates, guide means extending substantially i parallel to the'plane of the blade and in opposite directions from said middle portion and the contact means, and yieldable stops carried by said guide means at both sides of said contact means and movable in directions substantially if;

parallel to the plane of the blade, said stopsbeing adapted to engage the back edge of the blade for holding the knife against the contact means with one face or the other against the stone,

said middle portion of the knife support includ- 1'- ing a stem, 2. guide sleeve in which the stem is slidable in direction toward and from the plane of the working face of the stone, a bridge in the sleeve accommodated in a clearance 'slot in the stem, and a cam plate having a middle portion which rests on the bridge and end portions which uphold the support by engaging the slidable stop means at opposite sides of the middle portion of the knife support, whereby the outward shifting'of one of said stops upon insertion of a knife withdraws. the stop from one end of the cam plate causing the latter to tilt and permit the knife support to settle toward the stone for bringing the knife into operative contact therewith.

10. A' knife sharpening machine comprising a and rollers carried on said guides for individual yielding adjustment toward and from the first mentioned rollers, two of the latter rollers being disposed at one side of the middle portion and two at the other side so that a knife blade may be sup-ported with its cutting edge at either side of the first pair of rollers and with one of the other pairs bearing against its opposite edge.

11. A knife sharpening machine comprising a hollow base, a cross-head slidably guided in said base for reciprocation therein and having end portions extending outside the base, means for reciprocating the cross-head, brackets extending above the base from said ends of the crosshead, a table carried by said brackets, a substantially flat stone on the table and a knife support upstanding from the base including holding means disposed to engage the opposite edges of a knife blade with its cutting edge in contact with the face of the stone.

12. In the combination defined in claim 11, said support including a stem vertically adjustable on the base and a spring urging it downward to hold the edge of the knife blade to the stone.

13. In the combination defined in claim 11, said support including a stem extending upward from the base and a pivot by which the holding means is tiltably attached to the stem to permit adjusting the blade at an angle to the grinding face of the stone.

14. In the combination defined in claim 11, said means for reciprocating the cross-head comprising a rotary driving member journaled in the base and having an eccentric portion, a rocker arm fulcrumed in the base engaging the crosshead, and a pitman connecting said rocker with said eccentric portion of the rotary member.

15. A knife sharpening machine comprising a substantially flat stone, motor means for reciprocating said stone, and a knife support provided with holding means disposed for engaging the opposite edges of the knife blade with the cutting edge in contact with the surface of the stone, certain of said holding means comprising stops mounted for automatic yielding adjustment toward and from the opposite means to fit the shape of the knife blade upon insertion thereof, and a control means for said motor operable by movement of said stops toward and from the cooperating holding means.

16. A knife sharpening machine comprising a substantially fiat stone, means for reciprocating said stone along a fixed path, a knife support including contact means with which the knife blade is engageable at points on its sides closely adjacent its cutting edge and over which it is movable in the direction of said cutting edge while the stone is reciprocating, whereby different portions of said edge are shifted into the path of the stone, and yielding means acting against the back edge of the blade to urge said blade against said contact means.

17. A knife sharpening machine comprising a substantially flat stone, means for reciprocating said stone along a fixed path, a knife support including contact means with which the knife blade is engageable at points closely adjacent its cutting edge, and over which it is movable in the direction of said cutting edge to bring different portions of said edge into the path of the stone while it reciprocates, guide means, stops engageable with the back edge of the knife blade and movable upon said guide means in a direction parallel to the plane of the blade, and spring means adapted to yieldingly maintain contact of said stops with the blade for holding it against the contact means throughout its movement thereover.

18. A knife sharpening machine comprising a substantially flat stone, means for reciprocating said stone along a fixed path, a knife support including a middle portion provided with contact means with which the knife blade is engageable at points closely adjacent its cutting edge and over which it is movable in the direction of said cutting edge to bring different portions of said edge into the path of the stone while it reciprocates, guide means extending substantially parallel to the plane of the blade and in opposite directions from said middle portion and the contact means, and yieldable stops carried by said guide means at both sides of said contact means and movable in directions substantially parallel to the plane of the blade, said stops being adapted to engage the back edge of the blade for holding the knife against the contact means with one face or the other against the stone.

19. A knife sharpening machine comprising a substantially fiat stone, means for reciprocating said stone along a fixed path, a knife support including contact means with which the knife blade is engageable at points on its sides closely adjacent its cutting edge and over which it is movable in the direction of said cutting edge while the stone is reciprocating, whereby different portions of said edge are shifted into the path of the stone, and yielding means acting against the back edge of the blade to urge said blade against said contact means, said knife support being tiltably mounted for adjusting the plane of the knife blade at a predetermined angle to the flat surface of the stone for producing the desired bevel at the cutting edge.

20. A knife sharpening machine comprising a substantially fiat stone, means for reciprocating said stone along a fixed path, a knife support including contact means with which the knife blade is engageable at points closely adjacent its cutting edge and over which it is movable in the direction of said cutting edge to bring different portions of said edge into the path of the stone while the latter is reciprocating, guide means, stops engageable with the back edge of the knife blade and slidable upon said guide means in a direction parallel to the plane of the blade, together with spring means adapted to yieldingly maintain contact of said stops with the blade by urging said stops toward the contact means, and means for raising said knife support to lift the cutting edge of the blade from the surface of said stone operable by the movement of the slidable stop means toward said contact means upon the withdrawal of the knife blade.

21. A knife sharpening machine comprising a substantially flat stone, means for reciprocating said stone, and a knife support including a middle portion with bearing means positioned thereon to support the cutting edge of the blade in contact with the stone, guides extending oppositely from said middle portion approximately in the direction of said reciprocation, and stop means carried on said guides for individual yielding adjustment toward and from said bearing means, said stop means being disposed at both sides of the middle portion so that a knife blade may be supported with its cutting edge at either side of said bearing means. and with a part of said stop means pressing against its opposite edge.

WILLIAM BLANKNER.