GB2061780A - Involute knife sharpener - Google Patents

Abstract

A sharpening mechanism for the knife blade 12 of a slicing machine wherein the cutting edge of the knife blade is of involute shape comprises a pinion which is co- axially securable by a hand wheel 22 to the knife blade, an elongate member 30 in driving connection with the pinion and a sharpening mechanism 31 having a grinding wheel 32 driven by a pneumatic motor 34 mounted on the elongate member. To avoid unwanted movements of the sharpening mechanism the elongate member and pinion are mounted on a support means 27 which includes an arm 44 extending in the same longitudinal direction as the elongate member, a slide block 45 being mounted on the arm and secured to the elongate member. Beyond the slide block the arm carries a handle 49 for actuating the sharpener and a mounting 51 for a guide wheel so that when the sharpener is fitted to the knife blade for sharpening purposes the guide wheel can follow a circular path 52 radially beyond the cutting edge of the knife and formed on the casing surrounding the knife blade. <IMAGE>

Description

SPECIFICATION Involute knife sharpener This invention relates to apparatus for sharpening the knife blade of a slicing machine for comestible products wherein the knife blade is of involute or non-circular shape.

In a slicing machine of this kind the knife blade perimeter is shaped such that points on the perimeter lie at varying distances from the axis of the knife blade drive shaft lying between minimum and maximum radii according to a mathematical function of the angular position of the point with respect to either the maximum or minimum radii.

We have previously proposed various forms of apparatus for sharpening such knife blades (as described in detail in U.K. Patent Application No. 7912944) all of which incorporate a first member in the form of a pinion which is co-axially securable to the knife blade drive shaft and a second member which is elongate and is in driving connection with the pinion. A sharpening mechanism is mounted at one end of the elongate member so that when the latter is moved pivotally and longitudinally with respect to the drive surface of the pinion the sharpening mechanism follows exactly the involute contour of the knife blade cutting edge during the sharpening procedure.We have now found that there is a tendency for the sharpening mechanism to move towards and away from the knife blade cutting edge during use resulting in an uneven cutting action and we have therefore devised a further form of the sharpening apparatus wherein this disadvantage is obviated or mitigated.

According to the present invention there is provided apparatus for in situ sharpening a slicing machine knife blade, comprising a first member securable co-axially to the knife blade drive shaft in a predetermined angular orientation, said first member having a peripheral drive surface, an elongate member in driving connection with the drive surface of the first member, a knife blade sharpening mechanism mounted at one end of said elongate member, means for effecting relative pivotal and longitudinal movement of the elongate member with respect to the drive surface of the first member, wherein the first member and the elongate member are dimensioned and arranged so that, in use, said relative pivotal and longitudinal movement causes said sharpening mechanism to follow a pre-determined non-circular path, the improvement comprising a support means confining the first member and the elongate member to maintain said driving connection, a rigid arm extending laterally from said support means in a direction parallel to the longitudinal axis of the elongate member and a guide member secured to the elongate member adjacent the sharpening mechanism and slidably mounted on said rigid arm, and a guide roller mounted on the rigid arm at a fixed location beyond the sharpening mechanism, whereby the guide roller may run along a fixed circular guide path radially beyond the cutting edge of the knife blade.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, in which Figure I illustrates part of a slicing machine with an involute knife blade, Figure 2 is an end view of the knife blade drive shaft shown in Fig. 1; Figure 3 is an elevational view of apparatus according to the present invention; Figure 4 is a sectional view of a detail on the line A-A in Fig. 3; Figure 5 is an underneath plan view taken in the direction of the arrow B in Fig. 3 showing a device for deburring the knife blade which can be fitted to the apparatus according to the present invention; Figure 6 is a side view of Fig. 5; Figure 7 is a top plan view of Fig. 3; Figure 8 is a sectional view of a detail on the line C-C in Fig. 7; Figure 9 is an elevational view of a detail taken in the direction of the arrow D in Fig. 7; and Figure 10 is a view similar to Fig. 7 but showing the apparatus in operative position on a slicing machine.

In the drawings a slicing machine generally denoted 10 comprises a surface 11 along which comestible products to be sliced are fed by means (not shown) to an involute knife blade 12 the edge of which is in shearing cooperation with the end face 1 a of the surface 11 to slice the product, cut slices being received in a receptable (not shown). The blade 12 is mounted on a drive shaft 13 which is journalled in a casing 14, the casing being formed in two parts which are hingedly connected together, namely part 1 4a which is rigidly secured to the surface 11 and part 1 4b which acts as a door and which is openable to gain acess to the end face 1 3a of the drive shaft 13 for the purposes of sharpening the knife blade as will be explained.A toggle latch device 15 is provided to ensure that the casing parts 1 4a, 1 4b are securely fastened together during normal use of the machine 10. To permit the product to be fed past the knife blade 12 the casing parts 1 4a, 1 4b include apertures 16a, 16b. The drive shaft 13 is rotatably driven by means of a drive motor mounted on a recessed portion of the end wall containing aperture 1 6a.

The casing 14, particularly part 14a, is made of a rigid material such as steel or aluminium or a metal alloy and is of such a strength as to withstand the significant forces imposed on the casing by the rotational motion of the knife blade 12. Although the knife blade 12 is non-circular an appropriate balancing means such as weight 9 (see Fig. 10) is secured thereto by a lock nut 8 so that no imbalance forces result during rotation of the blade 12.

In order to sharpen the cutting edge of the blade 12 the casing 1 4 is opened by releasing the toggle latch 15 and moving casing part 14b on its hinges to the position indicated in Fig. 1. This exposes the end face 1 3a of the shaft 13 and, as is shown in greater detail in Fig. 2, this end face includes a coaxially extending cylindrical recess 1 7a which leads into an internally threaded co-axially extending socket 1 7b for the purpose of receiving an externally threaded shaft forming part of the sharpener.Also, the end face 1 3a includes a radially extending groove 18 which is in a predetermined angular position with respect to the blade 12 and is for the purpose of receiving a spigot forming part of the sharpener to ensure that when the sharpener is fitted to the end face 1 3a of the drive shaft 13 it also has the correct angular orientation relative to the blade 12.

The sharpener is shown in elevational view in Fig. 3 and in a top plan view in Fig. 7 and comprises a shaft 20 which is externally threaded at 21 and is of a suitable dimension to fit the socket 1 7b. At the end of the shaft 20 remote from the threading 21 a hand wheel 22 is secured to the shaft in such a manner that rotation of the hand wheel 22 rotates shaft 20. Rotatably mounted on the shaft 20 on an unthreaded part thereof there is a cog wheel 23 which carries a co-axial spigot 24 and a non-co-axial spigot 25. Spigot 25 is dimensioned to fit the groove 18 whereas spigot 24 is dimensioned to fit the recess 1 7a. The spigots 24, 25 both project from a circular boss or bearing which is an integral part of the cog wheel 23 being coaxial with spigot 24, and on which there is rotatably mounted a plate member 26 forming part of a support means for other components of the sharpener.The plate member 26 is connected to a further plate member 27 by means of bolts 28 and spacer elements (not shown), plate member 27 also being rotatably mounted on a circular boss or bearing forming part of the cog wheel 23. The portion of the cog wheel 23 which is housed in the space between plate members 26, 27 has gear teeth around its periphery which are in driving connection with gear teeth 29 formed on an elongate member 30 which extends laterally with respect to the axis of shaft 20 through the space between plate members 26, 27. At one end of the elongate member 30 there is mounted a sharpening mechanism 31 comprising a cup shaped sharpening stone 32 mounted on a rotatable drive shaft 33 which is driven by a pneumatic motor 34.

As a safety measure a guard 32a surrounds stone 32 as shown in Fig. 7 but this is omitted from Fig. 3 in the interests of clarity.

The guard 32a also acts to collect the majority of the- grindings produced during the sharpening process. The body of the motor 34 is externally screw threaded at 35 and is threadedly received by a mounting block 36 which is secured by means of screws 37 to a flanged plate 38 the flange 39 of which is fastened by screws 40 to the elongate member 30. By virtue of the threads 35 the location of the motor 34 with respect to the block 36 is adjustable and, to lock the motor 34 in the desired position, a lock nut 41 is threaded on to threads 35 to abut the block 36 and a peg 42 made of plastics material such as PTFE is mounted in block 36 tangentially to intercept the interface between the threads 35 and the mating threads formed in block 36.The end face of the block 36 which abuts the undersurface of plate 38 is angled by about 3 so that the axis of the motor 34 is inclined by a similar amount to the undersurface of the plate 38 whereby only part of the stone 32 engages the knife edge during the sharpening operation.

The support means of the sharpener in addition to the plate members 26, 27 includes an L-shaped elongate arm 44 which is secured between plate members 26, 27 by three of the bolts 28 so that components 26, 27 and 44 are rigidly interconnected. The arm 44 extends in a direction parallel to the longitudinal axis of the elongate member 30 and acts as a guide for a guide block 45 made of nylatron which is slidably mounted thereon and which is secured by means of screws 46 to the flanged plate 38 carrying the sharpening mechanism 31.The block 45 which is shown in cross-section in Fig. 8 has two notches 45a,b respectively positioned to receive and to be a close fit with the limbs 44a,b of the arm 44 and in this way eliminates undesired movement of the sharpening mechanism 31 in two directions but permits freedom of movement of the mechanism 31 in the direction of the longitudinal axis of the elongate member 30. At its end 48 remote from the plate members 26, 27 the arm 44 carries a fixed handle 49 and a fixed mount ing 50 on which a guide roller 51 is rotatably mounted. It will therefore be appreciated that the handle 49 and guide roller 51 are each at a fixed radial distance from the axis of the shaft 20 and this distance is selected to be the same as the radial dimension of the pe ripheral wall of the casing 14 of the slicing machine 10 so that when the sharpener is fitted to the knife blade drive shaft 1 3 in the manner described above the guide roller 51 is positioned to run on the circular surface 52 of casing part 1 4a which lies at the interface between casing parts 1 4a and 1 4b as is illustrated in Fig. 10.

The elongate arm 44 provides a first con straint on the movement of the elongate mem ber 30 by virtue of the inter-connecting guide block 45 and a second constraint is imposed on the member 30 by means of a roller 54 mounted on an eccentric between the plate members 26, 27 remote from the sharpening mechanism 31. The eccentric is adjustable by screw 54a to take up any backlash which may exist between the teeth 29 of the member 30 and the teeth on the cog wheel 23. The arm 44 also acts as a support for a conduit 55 which delivers the pressurised air supply to the pneumatic motor 34.

In order to use the sharpener to sharpen the cutting edge of the knife blade 12 the casing 14 is opened and the knife blade 12 is secured in a fixed position by means of a mechanical clamp 56 located within the casing (see Fig. 1). The clamp 56 when actuated to hold the knife blade 12 also prevents the casing 14 being closed. The sharpener is then fitted to the end face 13a of the drive shaft 13 by engaging spigot 24 with recess 17a, spigot 25 with groove 18 and shaft 20 with socket 17b and the dimensions and arrangement of the components is such that guide roller 51 engages surface 52 while at the same time the cupshaped sharpening stone 32 engages the cutting edge of the knife blade. The pressure of the sharpening stone 32 on the knife blade is adjustable by means of lock nut 41 and is subject to fine adjustment by the operator.When the correct pressure has been achieved the pneumatic motor 34 is energised to rotate the sharpening stone 32 and the sharpener is moved manually by means of handle 49 in a series of to-and-fro arcuate movements during which time the guide roller 51 continuously runs on surface 52 and elongate member 30 moves longitudinally and pivotally so that the sharpening mechanism 31 exactly follows the involute contour of the knife blade cutting edge. The pivotal movement of the elongate member 30 is accompanied by pivotal movement of the plate members 26, 27 with respect to the axis of shaft 20 and this is possible, having regard to the fact that the cog wheel 23 is stationary, by virtue of the fact that both plate members 26 and 27 are mounted on annular surfaces of the cog wheel (as depicted in Fig. 4).

When the sharpening procedure has been completed the sharpener is removed from the slicing machine by manual manipulation of the hand wheel 22. The mechanical clamp 56 is released thereby freeing the knife blade 12 and the casing 14 is closed and latched in the closed position by the toggle latch 15.

It has been found that when the abovedescribed sharpening procedure has been completed, depending upon the coarseness of the stone 32, the texture of the knife blade 12, the pressure exerted on the blade 12 by the stone 32 and the rotational speed of the stone 32 (which is usually of the order of 1500 rpm), the cutting edge of the blade 12 is left with adherent metal burrs. To remove these burrs it is preferable to attach to the sharpener a deburring device and a convenient example of such a device is shown in Figs. 5 and 6 and depicted by numeral 60.

Device 60 is attached to the undersurface of plate 38 in the space between plate 38 and sharpening mechanism 31 and comprises a body 61 pivotally mounted at 62 on plate 38, the body 61 forming a guide within which is located å rod 63 one end of which carries a deburring tool 64 and the other end of which has a stop 65, a spring 66 being located between the stop 65 and the body 61 to provide a resilient loading for the tool 64. The body 61 also carries a boss 67 which is arranged to project beyond the thickness of the plate 38 and a manually operable handle 68 is secured to this boss and extends between upper surface of plate 38 and the undersurface of arm 48 whereby the device 60 can be pivoted to its in-use position for removal of burrs from the knife edge. The inuse position is determined by an abutment 69 secured to the undersurface of plate 38 against which the body 61 is urged by the operator. In this position the tool 64, which comprises a pad of highly hardened material, scrapes, rubs or otherwise removes burrs by engaging the rear face 12a (see Fig. 10) of the knife blade 12. The pivotal mounting at 62 provides a friction grip of limited strength between the plate 38 and body 61 whereby the position of the device 60 is retained after having been set by the handle 68. If so desired the body 61 may be spring urged to an out-of-use position. In Fig. 5 numeral 37A denotes the holes in plate 38 which receive the screws 37 for securing the block 36 in position.

It will be understood that the sharpener described herein is preferably fabricated from non-corrosive materials.

Claims (7)

1. Apparatus for in situ sharpening a slicing machine knife blade, comprising a first member securable co-axially to the knife blade drive shaft in a predetermined angular orientation, said first member having a peripheral drive surface, an elongate member in driving connection with the drive surface of the first member, a knife blade sharpening mechanism mounted at one end of said elongate member, means for effecting relative pivotal and longitudinal movement of the elongate member with respect to the drive surface of the first member, wherein the first member and the elongate member are dimensioned and arranged so that, in use, said relative pivotal and longitudinal movement causes said sharpening mechanism to follow a predetermined non-circular path, the improvement comprising a support means confining the first member and the elongate member to maintain said driving connection, a rigid arm extending laterally from said support means in a direction parallel to the longitudinal axis of the elongate member and a guide member secured to the elongate member adjacent the sharpening mechanism and slidably mounted on said rigid arm, and a guide roller mounted on the rigid arm at a fixed location beyond the sharpening mechanism, whereby the guide roller may run along a fixed circular guide path radially beyond the cutting edge of the knife blade.

2. Apparatus as claimed in claim 1, wherein the rigid arm is of L-section and the guide member has two notches respectively positioned to receive the limbs of the rigid arm in such a manner as to eliminate movement of the sharpening mechanism in two directions whilst permitting freedom of movement thereof in the direction of the longitudinal axis of the elongate member.

3. Apparatus as claimed in claim 1, wherein the sharpening mechanism includes a support secured to the elongate member and incorporating a threaded aperture, and a sharpening stone drive motor with a cylindrical housing which is externally threaded and mounted in the threaded aperture of the support.

4. Apparatus as claimed in claim 3, wherein said support includes a plastic peg tangentially intercepting the interface between the threads of the support and the threads of the drive motor housing.

5. Apparatus as claimed in claim 1, wherein a handle is affixed to said arm adjacent said guide roller for effecting pivotal movement of the arm with respect to said first member.

6. Apparatus as claimed in any preceding claim, including a deburring device adjacent the sharpening mechanism.

7. Apparatus substantially as hereinbefore described with reference to the accompanying drawings.