GB2037198A - Knife sharpening mechanism - Google Patents

Abstract

A knife sharpening mechanism comprising a rotating cylinder 4, the surface of which is smooth, the rotating cylinder being mounted over a trough 3 containing a lapping compound, the arrangement being such that a knife holder 17 presents a knife blade 18 to the surface of the rotating cylinder with the longitudinal axis of the cylinder parallel to the edge of the knife blade so that the knife blade is sharpened. The knife holder can sharpen microtome knives and movement of the knife holder thereof can be controlled to move in an automatic sequence which presents the opposite sides of the knife blade to the cylinder for predetermined periods so that both sides of the knife blade are evenly ground. <IMAGE>

Description

SPECIFICATION Knife sharpening mechanism This invention relates to a knife sharpening mechanism and more particularly relates to a machine for sharpening cutting knives.

Cutting knives have in the past been sharpened in a variety of different ways on a number of different sharpening mechanisms. Some such known sharpening mechanisms suffer from disadvantages in that they do not sharpen a knife edge to the degree necessary for some special types of knife blade. For example, microtome knives which are used in laboratories for cutting sections from specimens need to be sharp enough to remove a section of as thin as 1 micron from a specimen embedded in paraffin wax. Generally a microtome knife has a blade portion about 15 cm long which blade portion is formed integrally with a base portion to form a knife which is generally of rectangular shape, a long edge of which constitutes a blade portion and the opposite edge of which forms the base portion.The base portion is shaped so that it can be supported in a microtome when it is used for cutting sections from specimens. In the past microtome knives have been sharpened on a mechanism which utilizes a flat surface on which the knife is laid and oscillated.

An object of the present invention is to provide a knife sharpening mechanism for cutting knives.

A further object of the present invention is to provide a knife sharpening mechanism which offers the public a useful alternative choice.

Further objects and advantages of the present invention will become apparent from the following description which is given by way of example only.

According to a first aspect of the present invention there is provided a knife sharpening mechanism comprising a rotating cylinder the surface of which is smooth, the rotating cylinder being mounted over a trough or bath containing a lapping compound, the arrangement being such that a knife holder presents a knife blade to the surface of the rotating cylinder with the longitudinal axis of the cylinder parallel to the edge of the knife blade so that the knife blade is ground sharp.

The cylinder can be cast from a metal alloy, the surface of which is treated to include about 10 per cent of tin before it is turned in a lathe so that the surface thereof is smooth. Alternatively the cylinder can be surfaced with diamonds which are spread thereon evenly so that a similarly smooth surface is ground by the diamonds onto the knife blade.

The knife sharpening mechanism can be used to sharpen microtome knives and the knife holder thereof can be controlled to move automatically in a sequence which presents the opposite sides of the knife blade to the cylinder for similar predetermined periods so that even grinding occurs on both sides of the knife blade until it is evenly ground.

Further aspects of the present invention which should be considered in all its novel aspects will become apparent from the following description which is given by way of example only.

An embodiment of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 is a plan view of a knife sharpening mechanism according to the present invention; Figure 2 is a side view in the direction of arrows Il-Il of the mechanism shown in Figure 1; Figure 3 is a side view in the direction of arrows Ill-Ill of part of a drive mechanism for periodically raising and lowering the knife holder; and Figure 4 is a diagrammatic view of the means for turning the knife holder th rough 1800 to allow the opposite side of the knife blade to be presented to the cylinder.

The knife sharpening mechanism according to the present invention will be described herein with reference to the use thereof to sharpen microtome knife blades. It is to be appreciated that with minor modifications thereto the mechanism can be used to sharpen a wide variety of other types of knife.

The knife sharpening mechanism according to the present invention can be mounted in or on any form or shape of housing (not shown for clarity) which includes a base 1, the outline of which is shown dotted at 2 (Figure 1). Preferably base 1 is covered by a hood (not shown) through which the operation of the knife sharpener can be viewed.

The base 1 supports a trough generally indicated by arrow 3 which can be removed for cleaning. In use the trough 3 has therein a lapping compound which may be a fine grinding paste or lubricating film which forms, in use, an even film on the surface of a cylinder 4.

The cylinder 4 is mounted on a shaft 5 which is supported in bearing means 6 which are positioned in recesses 7 in the side walls 8 of the trough 3.

The cylinder 4 is preferably cast or manufactured from a metal alloy, the surface 9 of which constitutes the grinding surface of the cylinder 4. The cylinder 4 being turned in a lathe so that the surface 9 thereof is smooth. In practice, the smooth surface 9 corresponds to the smooth surface ground onto the microtome knife.

If the cylinder 4 is cast the outer surface 9 thereof may be formed from an alloy which includes 90 percent copper and 10 percent tin.

The cylinder 4 is removable for replacement if a cylinder with a coarser orfiner surface is required or for cleaning or alternatively if the lapping compound is to be replaced by a coarser or finer lapping compound.

The cylinder 4 is rotated in the direction of arrow 10 by contact between toothed wheels 11 which in turn are driven by the drive motor 12 (shown dotted).

The speed of the drive motor 12 may be governed by any suitable means so as to rotate at about 50 r.p.m.

The cylinder 4 being driven at any predetermined speed which is selected to suit coarse or fine grinding. Advantageously the toothed wheels 11 are via Tufnol (trade mark) gears driven by the electric The drawings originally filed were informal and the print here reproduced is taken from a later filed formal copy.

motor 12.

The cylinder 4 may oscillate relative to the trough 3. This oscillation being created by forming a grooved path (not shown) in the shaft 5 in the region of the wheels 11 so that the cylinder 4 moves in the direction of arrows 20 to spread and vary the region of contact between a knife blade being sharpened and the cylinder 4. This ensures that any wear which occurs on the cylinder4 is evenly spread. This reduces the necessity for removal of the cylinder4 for resurfacing.

The base 1 has mounted thereon an upstanding frame 13 which supports a transverse shaft 14 on which is mounted an arm 15, the end 16 of which has attached thereto or formed thereon a knife holder 17.

The knife holder 17 supporting a knife 18, the position of which relative to the arm 15 can be varied by a micro head 19 which allows small adjustments to the length of the arm 15 to be made to vary the angle at which the blade of the knife 18 is presented to the surface 9 of the cylinder 4.

The knife holder 17 and arm 15 are moved periodically by a drive mechanism generally indicated by arrow 21 (shown in more detail in Figure 3). The drive mechanism 21 which controls the movement of the arm 15 is automatically controlled by a timing mechanism (not shown) which can be presetto allow grinding to occur for a set period, say ten minutes, at the end of which period the timing mechanism switches on a drive motor 29 the motion of which raises the arm 15.

The knife holder 17 can be a chuck designed to support a microtome knife 18 or may be a clamping device designed to support the knife 18 therein. The drive mechanism 21 being designed to raise and lower the arm 15 in the direction of the arrows 22. In association with a turning means 23 the arm 15 is turned through 180" so that after a predetermined period has lapsed the arm 15 is rasied and this raising and lowering movement turns the knife 18 over so that alternate sides of the knife 18 are held in contact with the cylinder 4 for sharpening.

In Figure 2 the arm 15 is shown in its first position wherein the arm 15 is lowered and the blade of the knife 18 is in contact with the surface 9 of the cylinder 4. In this first position the knife 18 is being sharpened. A second position of the arm 15 is shown dotted and in this position the arm 15 has been raised by the drive mechanism 21 in the direction of arrow 22 and has been rotated around its longitudinal axis through 90 .

This movement is created by the raising of the arm 15 causing a cam means 23' at the end 30 of the arm 15 to contact an abutment means 24. This contact causes the arm 15 to be rotated around its longitudinal axis through 90 to the position shown dotted in Figure 2.

Each downward movement of the arm 15 causes a further cam means 23" to contact another extension 24' to complete turning of the arm 15 through a further 90 .

The movement of the arm 15 around its longitudinal axis is governed by a locating means 25 which is formed by providing a locking arm 26 mounted on a pin 41. The locking arm 26 being biased by a spring 39 toward a cammed disc 27 which is mounted on the arm 15. The cammed disc 27 has four recesses 40 around the perimeter thereof within which recesses a bearing 38 on the end of the locking arm 26 can be located to firmly hold the arm 15 either with a blade 18 supported thereby horizontal (in contact with the cylinder 4) or vertical (shown dotted).

The operation of the drive mechanism 21 which is controlled by the timing mechanism (not shown) is generally preset to allow the blade 18 to be sharpened for predetermined lengths of time on each side. This can be effected by setting the interval between which the drive motor 29 is operated. When it is activated a disc or cam 28 driven thereby rotates through a reduction gearbox if necessary. The movement of the disc 28 moves the link 29 in the direction of the arrow 30 shown and this arcuate movement at A causes the tensioning link 31 to rotate the shaft 14 and rotation of this shaft 14 raises the arm 15.

The tensioning link 31 is used to adjust the pressure between the blade 18 and the surface 9 of the cylinder 4. The tensioning link 31 which is in two parts can pivot at 32 to the posititon shown dotted in Figure 3 which is the position adopted by the link 29' and tensioning link 31 during normal sharpening operation with the blade 18 bearing on the cylinder 4. The pressure between the blade 18 and surface 9 being adjusted by moving one end of the biasing means 33 to increase or decrease the downward pressure on the arm 15 which increases the pressure of the blade 18 on the cylinder 4.

The cam surface 36 contacts the microswitch 37 to switch off the drive motor 29 after a complete revolution thereof which complete revolution raises and lowers the arm 15 to enable the knife blade 18 to be turned over as hereinbefore described.

At the end of the predetermined period for which the knife sharpener has operated the timing mechanism activates the drive motor 29 and this begins the raising of the knife blade 18 from its contact with the cylinder 4. If this is the end of the full period of sharpening the timing mechanism also activates a circuit which includes a cut off switch in the form of a microswitch 34. The microswitch 34 being mounted on the upstanding portion 13 and is operated by the arcuate movement of cam disc 35 which is mounted on the shaft 14.

In this sequence when the arm 15 has been raised a short distance the microswitch 34 contacts the rebate 36' in the cam disc 35. At this point the arm 15 has been raised to a position about 3 inches above the top of the cylinder 4. In this position the knife blade 18 can be removed or the position thereof adjusted before further operation of the knife sharpener is undertaken.

The trough 3 can include an agitating or stirring means which agitates the lapping compound to ensure that the particulate grinding material therein is always suspended throughoutthe liquid. This is to ensure that the grinding material does not precipitate out and reduce the effectiveness of the lapping compound. The agitating or stirring means may be a mechanical stirrer or may be caused by blowing a gas through the liquid to disperse the grinding mat erial.

In use the knife sharpening mechanism ha a knife blade 18 mounted in the knife holder 17 thereof. The mechanism is then switched on and this rotates the cylinder 4 and is operated at its desired rate of about 50 revolutions per minute. The rotating cylinder4 collects from the trough 3 the lapping compound therein and this is spread over the surface of the rotating cylinder 4. The mechanism when switched on also activates the drive motor 29 to move downward the arm 15 and the knife holder 17 thereon, the downward movement being terminated when the cam surface 36 contacts the microswitch 37. Initially grinding occurs when a first side of the blade 18 contacts the surface 9 of the cylinder 4.After a preset period set by the timing mechanism the drive motor 29 is operated to rotate the disc 28, the rotation of which moves the link 29' and the tensioning link 31 to raise the arm 15 to remove the blade 18 from contact with the cylinder 4.

Toward the end of the raising movement the cam means 23' contacts the abutment means 24 to turn the arm 15 about its longitudinal axis through 90 .

Atthe beginning of the downward movement of the arm 15 the second cam means 23" contacts the other abutment means 24' to rotate the arm 15 through a further 90" so that when the knife blade 18 is returned to contact the cylinder 4 the opposite side is in contact therewith.

Aftertheturning of the arm 15 about its longitudinal axis it is located horizontal by the locating means 25.

This sequential operation continues until the finish of the predetermined period governed by the timing mechanism. At the end of this period the timing mechanism activates the drive motor 29 and microswitch 34. On activation of the drive motor 29 the arm 15 is again raised until the drive motor 29 is deactivated by the microswitch 34 which is operated by the rebate 36' in the cam disc 35. This switches off the mechanism and may also switch off the drive motor 21 to stop the cylinder 4 from rotating.

An override control and circuit protection fuse or fuses may be included if desired. The override control being arranged to stop grinding and raise the knife blade 18 off the cylinder4 if circumstances necessitate this.

Providing the surface 9 of the cylinder4 is smooth this ensures that the blade 18 is ground to have a similar degree of smoothness. The shape and angle of the bevels formed on the point of the blade 18 can be varied by altering the length of the arm 15. This being effected by moving the microhead 19 to change the angle of contact between the blade 18 and the surface 9 of the cylinder 4.

If necessarythe lapping compound can be changed to a coarse or fine compound to complete sharpening. If this is effected the trough 3 and cylinder 4 being removed for cleaning or an alternative trough 3 can be used which trough has a different lapping compound therein.

Thus by this invention there is provided a sharpening mechanism for cutting knives.

A particular embodiment of the present invention has been described by way of example only and it is envisaged that modifications and improvements to the invention may take place without departing from the scope of the appended claims.

Claims (17)

1. A knife sharpening mechanism comprising a rotating cylinder, the surface of which is smooth, the rotating cylinder being mounted over a trough or bath containing a lapping compound, the arrangement being such that a knife holder presents a knife blade to the surface of the rotating cylinder with the longitudinal axis of the cylinder parallel to the edge of the knife blade so that the knife blade is ground sharp.

2. A knife sharpening mechanism as claimed in claim 1 wherein the cylinder is cast from a metal alloy, the surface of which includes about 10 percent tin, the surface of the cylinder after it is cast being turned in a lathe so that it is smooth.

3. A knife sharpening mechanism as claimed in claim 2 wherein the cylinder is cast from a metal alloy the surface of which includes about 90 percent copper and about 10 percent tin.

4. A knife sharpening mechanism as claimed in claim 1 wherein the cylinder is surfaced with diamonds which are spread evenly thereon to form a substantially smooth grinding surface similar to that to be ground by the diamonds onto the blade of the knife.

5. A knife sharpening mechanism as claimed in any one of the preceding claims wherein the knife holder is moved automatically in a controlled sequence to present opposite sides of the knife blade to the cylinder for predetermined periods so that even grinding occurs on each side of the blade of the knife.

6. A knife sharpening mechanism as claimed in claim 5 wherein the controlled sequence is operated by a timing mechanism of which the predetermined period of grinding can be varied to suit a particular knife.

7. A knife sharpening mechanism as claimed in any one of the preceding claims wherein the trough and the cylinder thereof can be removed for cleaning or replacement.

8. A knife sharpening mechanism as claimed in claim 7 wherein the cylinder is mounted on a shaft extending along the longitudinal axis thereof, the shaft being supported in bearing means positioned in recesses in the side walls of the trough.

9. A knife sharpening mechanism as claimed in claim 8 wherein the cylinder oscillates relative to the shaft by forming an endless grooved path in the shaft so that the cylinder oscillates to spread and vary the region of contact between the blade of the knife and the cylinder.

10. A knife sharpening mechanism as claimed in claim 9 wherein the shaft is driven by a drive motor through toothed wheels mounted on a drive shaft of the drive motor and on the shaft.

11. A knife sharpening mechanism as claimed in claim 10 wherein the knife holder means is an arm supported by an upstanding frame, the arm extending at right-angles to the longitudinal axis of the cylinder and being arranged to move by a drive mechanism to raise and lower the knife blade, the raising and lowering movement of the arm moves turning means on the arm into contact with abutment means on the upstanding frame to rotate the arm around its longitudinal axis through 180 .

12. A knife sharpening mechanism as claimed in claim 11 wherein the arm supporting the knife holder includes a microhead which enables small adjustments to the overall length of the arm to be made to vary the angle of contact between the blade of the knife held in the knife holder and the surface of the cylinder.

13. A knife sharpening mechanism as claimed in claim 12 wherein the turning means on the end of the arm are cam means which in use contact the abutment means when the arm is raised and lowered so that as each cam means contacts its adjacent abutment means the arm is rotated around its longitudinal axis through 900 such that in a complete raising and lowering of the arm, the arm is rotated around its longitudinal axis through 180" to present the opposite side of the blade into contact with the surface of the cylinder.

14. A knife sharpening mechanism as claimed in claim 13 wherein the movement of the arm around its longitudinal axis is governed by locating means formed by providing a locking arm on a base plate on the arm, the locking arm being biased by a spring towards a cammed disc mounted on the arm, the cammed disc having four recesses around the perimeter thereof within which recesses a bearing on the end of the locking arm can be located to firmly hold the arm with the blade supported either horizontal or vertical.

15. A knife sharpening mechanism as claimed in any one of the preceding claims wherein the pressure between the knife blade and the cylinder can be increased or decreased by varying the tension in a tensioning link which assists in the raising and lowering of the arm.

16. A knife sharpening mechanism as claimed in any one of the preceding claims wherein the trough includes an agitating or stirring means which ensures that the lapping compound is an evenly spread suspension.

17. A knife sharpening mechanism substantially as hereinbefore described with reference to the accompanying drawings.