GB2392824A

GB2392824A - Slicer having upper and lower conveyors, and claw

Info

Publication number: GB2392824A
Application number: GB0223240A
Authority: GB
Inventors: John Geoffrey Phillipson
Original assignee: AEW Engineering Co Ltd
Current assignee: AEW Engineering Co Ltd
Priority date: 2002-03-13
Filing date: 2002-10-08
Publication date: 2004-03-17
Anticipated expiration: 2022-10-08
Also published as: GB0205835D0; GB0223240D0; GB0214189D0; GB2392824B

Abstract

The food 21 is gripped between upper 16, 18 and lower 14, 12 conveying means, as it is fed towards the slicing machine 20. The upper conveying means is in two sections 16, 18 and the lower conveyor is flat. A claw 34 is located in the gap between the upper conveyor sections 16, 18 a short distance upstream of a rotating blade 20. The claw 34 can be driven into the upper surface of the food 21. A sensor 30, 32 upstream of the blade 20 detects the leading 21 and trailing edge of the foodstuff. The claw 34 is controlled in response to the calculated distance travelled by the food 21 and the blade 20 position. A preferably controlled conveyor (24 figure 1) removes the sliced bacon 21. The claw 34 applies a force that resists excessive forward motion. The conveyors are resiliently and adjustably mounted. Preferably the claw 34 includes a pneumatically driven spike or prong 44, 46.

Description

Title: Improved foodstuff slicing machine Field of the invention

This invention concerns foodstuff slicing machines, particularly bacon slicing machines of the type described in US Patent 5,079,982.

Background

In conventional apparatus as described in US 5,079,982 the upper and lower conveyors grip the side of bacon from above and below, and feed it towards a rotating blade, to remove thin slices (rashers) from the leading end of the meat as it is advanced through the slicing station. Typically the cross section of a side of bacon is asymmetric throughout much of its length. The gripping force exerted on a side of bacon, and therefore the traction force exerted on the meat if the conveyors are both single and flat, will be applied to that part of the cross section which has the largest dimension (measured perpendicular to the run of the conveyors), since it is that region of the cross section which will determine the spacing between two such conveyors. Where (as is usual in the case of bacon), this is offset from the mid-way point across the width of the side of bacon, and in some cases can be virtually coincident with the left or right end of the cross section, as viewed normal to the end that is being sliced, the result is that the traction force acting on the meat is well displaced from the mid position of the cross section. This can result in a twisting action on the meat, especially as the remaining unsliced length of each side of bacon becomes smaller and smaller as more of it has been sliced into rashers.

US 5,079,982 describes an upper conveyor which is divided into four separate sections to assist in overcoming this problem. However this is relatively complex and presents difficulties when trying to clean the machine.

It is a first object of the invention to provide an improved conveyor for gripping and feeding an asymmetrical cross section length of meat and presenting the end of the uncut section of the meat squarely to a slicing station.

When using upper and lower continuous conveyors to carry a side of bacon towards the rotating blade to remove the thin slices from the leading face of the meat, the last part of each length of meat tends to become unsupported as it leaves the confines of the two conveyors. This can cause the last piece to fall into the blade and be wasted.

It is another object of the present invention to provide an improved conveyor mechanism which overcomes this problem.

In such a bacon slicing machine it is desirable to abut the leading end of the next side of bacon up to the trailing end of the side being sliced, so as to provide rear support for the latter, especially as it reduces in length towards the end of the slicing process. However this abutting of one side against the next can obscure the trailing end of the first side of bacon, since it becomes merged with the following piece of meat.

It is a further object of the present invention to provide an improved control system for a foodstuff slicing machine which overcomes this problem and allows the position of the trailing end of a length of foodstuff which is being sliced ahead of an immediately following length to be precisely known, to allow steps to be taken as it nears the slicing station, to assist in further supporting the foodstuff end of the length being sliced, as it advances into the slicing station.

Conventional slicing machines tend to mount the blade in the slicing station so that its cutting plane is approximately 20 to the vertical, and present the foodstuff at a similar angle. This can lead to problems in stacking the cut slices.

It is a further object of the present invention to provide an improved slicing station in a foodstuff slicing machine used as a bacon slicer, which assists in the stacking of slices post slicing, especially where stacks in excess of six slices are required.

Summary of the invention

According to one aspect of the present invention in a foodstuff slicing machine such as a bacon slicer the means for gripping the sides of bacon and moving them towards a slicing station comprises a generally flat lower conveyor and two upper conveyors which are resiliently urged in a direction towards the lower conveyor to grip a length of foodstuff such as a side of bacon therebetween, the two upper conveyors being spaced apart and defining a gap which will be substantially midway of the cross section of the foodstuff when located therebetween, and the two upper conveyors are displaceable relative the one to the other in at least a direction generally perpendicular to the plane of the lower conveyor, so as to accommodate different thicknesses of foodstuff on one side and the other of the gap.

Preferably separate drive means is provided for separately urging the two upper conveyors independently of each other in a direction towards the lower conveyor, with substantially the same force being exerted on the foodstuff by each of the upper conveyors, so that the foodstuff is gently squeezed between the upper and the lower conveyors by substantially the same force on each side of the said gap.

Preferably each of the upper conveyors is driven from the same drive means so that both rotate at the same linear speed so as to advance the foodstuff in a generally uniform manner towards the blade.

The conveyors may be constructed in a generally similar manner to the tracks described and illustrated in US Patent 5,079,982, although the gap between the two upper conveyors is larger than that between the separate tracks of the upper conveyor in US 5,079,982.

J According to another aspect of the invention a claw is mounted in the gap between the two upper conveyors a short distance upstream of the blade, and a drive therefor urges the claw in a downward direction to enter the upper surface of the foodstuff as the rear end of the length thereof currently being sliced approaches the blade as it is conveyed theretowards by the conveyors, and the claw is adapted to travel with the foodstuff in a direction towards the blade until the claw is just upstream of the blade at which point the drive means operates in an opposite sense to withdraw the claw from the foodstuff, to avoid entering the trajectory of the blade.

Preferably the drive for the claw is pneumatic.

Preferably the drive comprises two pneumatic drives, one to drive the claw into the foodstuff and a second to resist the forward movement of the claw as the foodstuff is advanced towards the blade, the resistance being less than the tractive force exerted by the conveyors, but being sufficient to resist any tendency of the blade to tear the foodstuff out of the grip of the conveyors and the claw.

A second similar claw may be provided on the underside of the foodstuff if desired, between the lower conveyor and the blade, and to this end the lower conveyor may also be split into left hand and right hand conveyors with a gap therebetween similar to the upper conveyor, so that the lower claw may also be moved up through the gap between the two lower conveyors, to engage the underside of the foodstuff at the same time as the upper claw moves down from above.

According to another aspect of the invention a sensor is provided upstream of the slicing station to determine the leading end of the first length of foodstuff to be moved towards the blade, and likewise to sense the position of the trailing end of that first length as it passes the position of the sensor, and an escapement is provided under the control of a control system supplied with signals from the sensor, which only allows the next length of foodstuff to move up to and abut the trailing end of the preceding length after the trailing end of that preceding length has been "seen" by the sensor.

By applying the same control over the next and each succeeding length of foodstuff to be presented to the conveyors, so the position of the trailing end of each length will be accurately determined, before the abutting occurs. Since the leading end of the next length will then coincide with the trailing end of the preceding length, the position of the leading end of that next length will also be known.

By determining the positions of the leading and trailing ends and knowing the linear advance of the length of foodstuff from the movement of the conveyors, so the operation of the blade can be synchronised to produce slices of desired thickness.

According to a further aspect of the invention the angle which the blade makes to the vertical, in the slicing station, is increased to approximately 60 relative to the vertical, and the angle of incline of the conveyors is similarly increased so that the line of travel of the foodstuff gripped therebetween is similarly inclined, albeit at 90 to the plane of the blade, so as to improve the stacking of the slices beyond the blade.

Preferably a so-called twin jump conveyor is provided beyond the blade so as to collect and remove the stacks of slices as soon as they are formed downstream of the blade.

According to a further aspect of the invention a method of slicing a length of foodstuff using a rotating blade in a slicing station, wherein a first conveyor means incrementally moves the foodstuff by applying a force Fit thereon towards the blade so as to cause successive parts of the foodstuff to protrude into the path of the blade so as to be severed therefrom as the blade passes therethrough, and second conveyor means collects the slices of foodstuff and conveys them away from the slicing station, comprises the further steps of: (1) sensing when the leading edge of the length of foodstuff passes a given position along the path of the first conveyor means upstream of the cutting station and generating a leading edge signal,

(2) sensing when the trailing edge of the same length of foodstuff also passes the said given position, and generating a trailing edge signal, to allow the length to be computed, (3) computing the length of the foodstuff being sliced from the distance travelled by the first conveyor after the leading edge signal, (4) determining from the computed length value when the trailing edge is a distance of N mm upstream of the blade trajectory, (5) driving a claw into the foodstuff at a position M mm upstream of the blade (M < N), (6) applying a force Fz to resist the forward motion of the claw towards the blade, (F: < F.) so that there is still a net force acting on the foodstuff to incrementally move it towards the blade, and (7) sensing the position of the claw in relation to the blade trajectory and retracting the claw from the foodstuff in an outward and rearward movement just before the claw reaches the blade.

Preferably in the aforementioned method the claw is introduced into the foodstuff through a gap in the first conveyor means.

Preferably the method involves pneumatically driving the claw into the foodstuff and pneumatically resisting the forward movement of the claw.

Preferably the retraction of the claw is also effected pneumatically.

Preferably the leading and trailing edge positions are detected using a laser beam and a photosensitive device.

Preferably the method further includes the step of lowering the second conveyor means as slices of foodstuff are deposited thereon so as to enable a plurality of slices to be stacked one on another on the second conveyor means without preventing the next slice from leaving the blade.

d Preferably the second conveyor means is operated to convey a stack of slices away from the region of the blade when a predetermined number of slices P. or a given weight of foodstuff W. has been accumulated thereon.

Where the criterion is the number of slices on the second conveyor, a counter counts the number of slicing cuts by the blade and resets when P is reached.

Where the criterion is weight a weighing device is associated with the second conveyor means and the conveyor is operated to move the foodstuff away from the region of the blade when the weight detected by the weighing device reaches W. Preferably the second conveyor means is in two parts and one part acts to collect slices until the P or W criterion is reached "hereafter a second part takes over to collect slices from the slicing station while the first part conveys away the slices accumulated thereon, the two parts alternating in synchronism to allow a continuous stream of slices from the slicing station to be successively stacked and conveyed away on the basis of numbers of slices, or accumulated weight, of foodstuff.

The method may involve the further step of driving a second claw into the foodstuff at the same time as the first claw is driven in to also move with the foodstuff and the second claw is also retracted from the foodstuff just before it reaches the blade.

The second claw may also be introduced into the foodstuff through a gap in the first conveyor means.

Preferably the end face of the foodstuff that is to be sliced through is viewed by at least one television camera and a video signal obtained therefrom is processed by signal processing means and logic and threshold criteria are applied to the processed signals to determine either the thickness of the next slice to be cut or whether the sliced foodstuff is of one of two or more different grades and is to be diverted to one of two or more different packaging stations downstream of the second conveyor means.

The method may also therefore include the step of directing the slices on or from the second conveyor means, to one of two or more different buffer stores for packaging separately, according to grade.

The slicing machines and methods described herein are particularly of use for slicing sides of bacon.

The claw may comprise a single spike but may to advantage comprise two spikes spaced apart across the width of the gap between the two upper conveyors so as to engage two spaced apart regions of the cross section of the foodstuff, to provide better support of the end region as it progresses towards the blade.

Where the cross section decreases in height from one side to the other, as in the case of a side of bacon, and the lengths of foodstuff are always introduced so as to have the same orientation i.e. the thicker region will always be on the same side, e.g. left hand side, then where the claw comprises two spikes, one is preferably longer than the other and the spikes are arranged so that fall off in foodstuff cross section height occurs in the direction from the shorter to the longer spike.

Whether the claw is one or two spikes as described above, advantageously it may have a second spike (or pair of spikes) upstream of the first, and thereby separated in the direction of foodstuff travel from the first spike(s) so that the downstream spike (or pair of spikes) engages the narrow tailpiece of the length being sliced, and the upstream spike (or spikes) engages the following length of foodstuff just behind the leading face thereof, thereby tying the tailpiece to the leading end of the following length of foodstuff, so as to provide even better support for the tailpiece as it progresses towards the blade.

The invention will now be described with reference to the Figs 1 and 2 of the accompanying drawings which illustrate diagrammatically one embodiment of the invention. In the drawings two sides of bacon are shown at lOA and lOB sandwiched between upper and lower conveyors formed from a lower conveyor 12 preceded by rollers 14, and an upper conveyor formed by left and right conveyors 16 and 18 which are synchronously driven but are capable of relative up and down movement in relation to the lower conveyor so as to accommodate sides of bacon of non uniform cross such that the left hand end is thicker than the right hand end (or vice versa) as viewed from the front of the conveyor path as shown in Fig 2.

The front end 21 of the leading side of bacon (see 21 in Fig 2) is pushed by the conveyors into the path of a rotating blade 20 so as to remove thin slices of bacon from the said front end, such as are shown stacked one on the other at 22 in Fig 1.

A so-called twin jump conveyor generally designated at 24 collects the cut slices and conveys them away to a weighing and packing station, not shown.

The rear of the leading side of bacon lOA is identified at 26 and the front end of the following side lOB is identified at 28 in Fig 1. The operation of the feed conveyor made up of 12,1,16 and 18 is to shunt lOB up to lOB so that 26 and 28 are in contact, as shown.

lOB thus pushes lOA into and through the slicing station even though drive to the tail end of lOA becomes progressively reduced and finally non-existent as it leaves the nip between the upper and lower conveyors and becomes supported by the stationary bridge 39 and the LH and RH rollers 40 and 42 respectively, best seen in Fig 2.

Two proximity sensors are shown at 30 and 32, the latter serving to pick up the arrival of the front end of a side of bacon, and because they are in contact, therefore also the rear end of the first and each succeeding side of bacon. This gives positional information to a control system set to advance the bacon and support the leading end of the leading side of

bacon by lowering a claw 34 into contact, and to travel forwards with the tail end of each side of bacon, until shortly before the claw reaches the cutting blade 20.

The claw 34 is mounted in front of the conveyors 16,18 and is carried by housing 36 which itself is carried by a housing 38. The housings each contain a pneumatic drive that in 36 serving to retract the claw when it has progressed sufficiently towards the blade and 38 serving to raise and lower the housing 36 and therefore the claw, to engage the latter into and out of the bacon as required.

Sensor 30 is set to detect the arrival of a flag on the plate 33 which protrudes from the rear of housing 36 and which when it registers with 30 means that the claw is just to the rear of the blade and needs to be lifted out of engagement with the bacon.

The claw is shown in Fig 2 to have two spaced apart prongs 44 and 46.

Claims

C 1082/A CLAIMS

1. A slicing machine for slicing blocks of foodstuff such as sides of bacon wherein means is provided for gripping the foodstuff blocks and moving them towards a slicing station which comprises a generally flat lower conveyor and upper conveyor means which is resiliently urged in a direction towards the lower conveyor to grip a block of foodstuff therebetween, the upper conveyor means defining a gap which will be substantially midway of the cross section of the block of foodstuff when the latter is located therebetween, and the upper conveyor means is relatively displaceable in at least a direction generally perpendicular to the plane of the lower conveyor, so as to accommodate different thicknesses of foodstuff on one side and the other of the gap.

2. A slicing machine as claimed in claim 1 wherein the upper conveyor means comprise two separate conveyors, and separate drive means is provided for separately urging the two upper conveyors independently of each other in a direction towards the lower conveyor.

3. A slicing machine as claimed in claim 2 wherein the separate drive means exerts substantially the same force on the two conveyors, so that each of the conveyors also exerts the same force on the foodstuff, so that the foodstuff is gently squeezed between the upper and the lower conveyors by substantially the same force on each side of the said gap.

4. A slicing machine as claimed in claim 2 or 3 wherein each of the upper conveyors is driven from the same drive means so that both rotate at the same linear speed so as to advance the foodstuff in a generally uniform manner towards the blade.

5. A slicing machine as claimed in nay of claims 1 to 4 wherein a claw is located in the gap in the upper conveyor means a short distance upstream of the blade, and a drive therefor urges the claw in a downward direction to enter the upper surface of the foodstuff.

6. A slicing machine as claimed in claim 5 wherein the claw drive is controlled so as to force the claw into the block as the rear end of the block currently being sliced approaches the blade as it is conveyed theretowards.

7. A slicing machine as claimed in claim 6 wherein the claw is adapted to travel with the foodstuff in a direction towards the blade until the claw is just upstream of the blade at which point the drive means is controlled to operate in an opposite sense to withdraw the claw from the foodstuff, to avoid entering the trajectory of the blade.

8. A slicing machine as claimed in any of claims 5 to 7 wherein the drive for the claw is pneumatic.

9. A slicing machine as claimed in any of claims 5 to 7 wherein the drive comprises two pneumatic drives, one to drive the claw into the foodstuff and a second to resist the forward movement of the claw as the foodstuff is advanced towards the blade, the resistance being less than the tractive force exerted by the conveyors, but sufficient to resist any tendency of the blade to tear the foodstuff out of the grip of the conveyors and the claw.

10. A slicing machine as claimed in any of claims S to 9 wherein a second similar claw is provided on the underside of the foodstuff and the lower conveyor also defines a gap through which the lower claw can protrude.

11. A slicing machine as claimed n claim 10 wherein the lower conveyor is split into left hand and right hand conveyors with a gap therebetween and a drive for the lower claw is controlled to move the lower claw up through the gap between the two lower conveyors, to engage the underside of the foodstuff, at the same time as the upper claw moves down from above.

12. A slicing machine as claimed in any of claims 1 to 11 wherein a sensor is provided upstream of the slicing station to provide a signal when the leading end of the first length

12. A slicing machine as claimed in any of claims 1 to 11 wherein a sensor is provided upstream of the slicing station to provide a signal when the leading end of the first length of foodstuff to be moved towards the blade passes the sensor, and likewise provide a signal when the trailing end of that first length passes the sensor.

13. A slicing machine as claimed in claim 12 wherein an escapement is provided under the control of a control system supplied with signals from the sensor, which only allows the next length of foodstuff to move up to and abut the trailing end of the preceding length of foodstuff after the trailing end of that preceding length has passed the sensor.

14. A slicing machine as claimed in claim 12 or 13 further comprising a control system for controlling the rotation of the blade using signals from the sensor to determine the positions of the leading and trailing ends of the block and the linear advance of the foodstuff from the movement of the conveyors, whereby the rotation of the blade can be synchronised with the forward movement of the foodstuff, to produce slices of desired thickness.

15. A slicing machine as claimed in any of claims 1 to 14 wherein the angle which the blade makes to the vertical, in the slicing station, is approximately 60 , and the conveyors are similarly inclined so that the line of travel of the foodstuff gripped therebetween is at 90 to the plane of the blade, so as to improve the stacking of the slices beyond the blade.

16. A slicing machine as claimed in any of claims 1 to 15 wherein a twin jump conveyor is provided beyond the blade so as to collect and remove stacks of slices as soon as they are formed downstream of the blade.

17. A slicing machine as claimed in any of claims 5 to 16 wherein the claw comprises a single spike.

18. A slicing machine as claimed in nay of claims 5 to 16 wherein the claw comprises two spikes spaced apart across the width of the gap so as to engage two spaced apart regions of

the cross section of the foodstuff, to provide better support of the end region as it progresses towards the blade.

19. A slicing machine as claimed in any of claims 15 to 18 wherein the claw comprises two spikes, one located upstream of the first, and thereby separated in the direction of foodstuff travel from the first spike, and the downstream spike is adapted to engage the narrow tailpiece of the length of foodstuff being sliced, and the upstream spike engages the following length of foodstuff just behind the leading face thereof, thereby tying the tailpiece of the former to the leading end of the following length of foodstuff, so as to provide even better support for the tailpiece as it progresses towards the blade.

20. A method of slicing a length of foodstuff using a rotating blade in a slicing station, wherein a first conveyor means incrementally moves the foodstuff by applying a force Fit thereon towards the blade so as to cause successive parts of the foodstuff to protrude into the path of the blade so as to be severed therefrom as the blade passes therethrough, and second conveyor means collects the slices of foodstuff and conveys them away from the slicing station, comprising the further steps of: (1) sensing when the leading edge of t'ne length of foodstuff passes a given position along t'ne path of the first conveyor means upstream of the cutting station and generating a leading edge signal, (2) sensing when the trailing edge of the same length of foodstuff also passes the said given position, and generating a trailing edge signal, to allow the length to be computed, (3) computing the length of the foodstuff being sliced from the distance travelled by the first conveyor after the leading edge signal, (4) determining from the computed length value when the trailing edge is a distance of N mm upstream of the blade trajectory, (5) driving a claw into the foodstuff at a position M mm upstream of the blade (M < N),

(6) applying a force F: to resist the forward motion of the claw towards the blade, (F: < F.) so that there is still a net force acting on the foodstuff to incrementally move it towards the blade, and (7) sensing the position of the claw in relation to the blade trajectory and retracting the claw from the foodstuff in an outward and rearward movement just before the claw reaches the blade.

21. A method as claimed in claim 20 wherein the claw is introduced into the foodstuff through a gap in the first conveyor means.

22. A method as claimed in claim 21 which involves pneumatically driving the claw into the foodstuff and pneumatically resisting the forward movement of the claw.

23. A method as claimed in claim 22 wherein the retraction of the claw is also effected pneumatically.

24. A method as claimed in any of claims 20 to 23 wherein the leading and trailing edge positions are detected using a laser beam and a photosensitive device.

25. A method as claimed in any of claims 20 to 24 which further includes the step of lowering the second conveyor means as slices of foodstuff are deposited thereon so as to enable a plurality of slices to be stacked one on another on the second conveyor means in a manner which does not prevent the next slice from leaving the blade.

26. A method as claimed in claim 25 wherein the second conveyor means is operated to convey a stack of slices away from the blade when a predetermined number of slices P. or a given weight of foodstuff W. has been accumulated thereon.

27. A method as claimed in claim 26 wherein a counter counts the number of slicing cuts by the blade and resets when P is reached.

28. A method as claimed in claim 26 wherein a weighing device is associated with the second conveyor means and the conveyor is operated to move the foodstuff away from the region of the blade when the weight detected by the weighing device reaches W.

29. A method as claimed in claim 26 wherein the second conveyor means is in two parts and one part acts to collect slices until the P or W criterion is reached "hereafter a second part takes over to collect slices from the slicing station while the first part conveys away the slices accumulated thereon, the two parts alternating in synchronism to allow a continuous stream of slices from the slicing station to be successively stacked and conveyed away on the basis of numbers of slices, or accumulated weight, of foodstuff.

30. A method as claimed in any of claims 20 to 29 which involves the further step of driving a second claw into the foodstuff at the same time as the first claw is driven in, to also move with the foodstuff, and the second claw is also retracted from the foodstuff just before it reaches the blade.

31.A method as claimed in claim 30 wherein the second claw is introduced into the foodstuff through a gap in the first conveyor means.

32. A method as claimed in any of claims 20 to 31 wherein the end face of the foodstuff that is to be sliced through, is viewed by at least one television camera and a video signal obtained therefrom is processed by signal processing means and logic and threshold criteria are applied to the processed signals to determine either the thickness of the next slice to be cut or whether the sliced foodstuff is of one of two or more different grades and is to be diverted to one of two or more different packaging stations downstream of the second conveyor means.

33. A method as claimed in claim 32 further comprising the step of directing the slices on or from the second conveyor means, to one of two or more different buffer stores for packaging separately, according to grade.

34. A slicing machine as claimed in any of claims 1 to 19 when operated to slice sides of bacon. (.. (

34. A slicing machine as claimed in any of claims 1 to 19 when operated to slice sides of bacon.

Is /! Amendments to the claims have been filed as follows CT AIMS

1. A slicing machine for slicing blocks of foodstuff such as sides of bacon wherein means is provided for gripping the foodstuff blocks and moving them towards a slicing station which comprises a generally flat lower conveyor and upper conveyor means which is resiliently urged in a direction towards the lower conveyor to grip a block of foodstuff therebetween, the upper conveyor means including two spaced apart sections defining a gap therebetween which will be substantially midway of the cross section of the block of foodstuff when the latter is located therebetween, and the upper conveyor means is relatively displaceable in at least a direction generally perpendicular to the plane of the lower conveyor, so as to accommodate different thicknesses of foodstuff on one side and the other of the gap, and a claw is located in the gap in the upper conveyor means a short distance upstream of the blade, and a drive tlerefor urges the claw in a downward direction to enter the upper suri'ace of the foodstuff.

3. A slicing machine as claimed in claim 2 wherein the separate drive means exerts substantially the same force on the two conveyors, so that each of the conveyors also exerts the same force on the foodstuff, so that the foodstuff is gently squeezed between the upper and the lower conveyors by substantially the same force on each side of the said gap. 4. A slicing machine as claimed in claim 2 or 3 wherein each of the upper conveyors is driven from the same drive means so that both rotate at the same linear speed so as to advance the foodstuff in a generally uniform manner towards the blade.

If S. A slicing machine as claimed in any of claims 1 to 4 wherein the claw drive is controlled so as to force the claw into the block as the rear end of the block currently being sliced approaches the blade as it is conveyed theretowards.

6. A slicing machine as claimed in claim 5 wherein the claw is adapted to travel with the foodstuff in a direction towards the blade until the claw is just upstream of the blade at which point the drive means is controlled to operate in an opposite sense to withdraw the claw from the foodstuff, to avoid entering the trajectory of the blade.

7. A slicing machine as claimed in any of claims 1 to 6 wherein the drive for the claw is pneumatic. 8. A slicing machine as claimed in any of claims 1 to 6 wherein the drive comprises two pneumatic drives.

9. A slicing machine as claimed in claim 8 wherein one of the drives serves to drive the claw into the foodstuff and the second serves to resist the forward movement of the claw as the foodstuff is advanced towards the blade, the resistance being less than the tractive force exerted by the conveyors but sufficient to resist any tendency of the blade to tear the foodstuff out of the grip of the conveyors and the claw.

10. A slicing machine as clairmed in any of claims 1 to 9 wherein a second similar claw is provided on the underside of the foodstuff and the lower conveyor also defines a gap through which the lower claw can protrude.

11. A slicing machine as claimed in claim 10 wherein the lower conveyor is split into left hand and right hand conveyors with a gap therebetween and a drive for the lower claw is controlled to move the lower claw up through the gap between the two lower conveyors, to engage the underside of the foodstut'f, at the same time as the upper claw moves down from above.

12. A slicing machine as claimed in any of claims I to 11 wherein a sensor is provided upstream of the slicing station to provide a signal when the leading end of the first length of foodstuff to be moved towards the blade passes the sensor, and likewise provide a signal when the trailing end of that first length passes the sensor.

14. A slicing machine as claimed in claim 12 or 13 further comprising a control system for controlling the rotation of the blade using signals from the sensor to determine the 2 positions of the leading and trailing ends of the block and the linear advance of the foodstuff from the movement of the conveyors, whereby the rotation of the blade can be synchronised with the forward movement of the foodstuff, to produce slices of desired thickness. 15. A slicing machine as claimed in any of claims 1 to 14 wherein the angle which the blade makes to the vertical, in the slicing station, is approximately 60 , and the conveyors are similarly inclined so that the line of travel of the foodstuff gripped therebctween is at 90 to the plane of the blade, so as to improve the stacking of the slices beyond the blade.

17. A slicing machine as claimed in any of claims 1 to 16 wherein the claw comprises a single spike.

18. A slicing machine as claimed in nay of claims 1 to 16 wherein the claw comprises two spikes spaced apart across the width of the gap so as to engage two spaced apart regions of

20. A method of slicing a length of foodstuff using a rotating blade in a slicing station, wherein a first conveyor means comprising upper and lower conveyor means incrementally moves the foodstuff by applying a force F. thereon towards the blade so as to cause successive parts of the foodstuff to protrude into the path of the blade so as to be severed therefrom as the blade passes therethrough, and second conveyor means collects the slices of foodstuff and conveys them away from the slicing station, comprising the further steps , of: (, (1) sensing when the leading edge of the length of foodstuff passes a given position along the path of the t'irst conveyor means upstream of the cutting station and generating a leading edge signal, (2) sensing when the trailing edge of the same length of foodstul'f also passes the said given position, and generating a trailing edge signal, to allow the length to be computed, (3) computing the length of the foodstuff being sliced from the distance travelled by the first conveyor after the leading edge signal, (4) determining from the computed length value when the trailing edge is a distance of N mm upstream of the blade trajectory, (5) driving a claw through a gap in the upper conveyor means, into the foodstuff at a position M mm upstream of the blade (M < N),

(6) applying a force I;: to resist the forward motion of the claw towards the blade, (F: < F.) so that there is still a net force acting on the foodstuff to incrementally move it towards the blade, and (7) sensing the position of the claw in relation to the blade trajectory and retracting the claw from the foodstuff in an outward and rearward movement just before the claw reaches the blade.

21. A method as claimed in claim 20 wherein the claw is pneumatically driven into the foodSLuff. 22. A method as claimed in claim 21 in which pneumatic force is employed to resist the forward movement of the claw.

23. A method as claimed in claim 22 wherein the retraction of the claw from out of the foodstuff is also effected pneumatically.

,. i 24. A method as claimed in any of claims 20 to 23 wherein the leading and trailing edge positions are detected using a laser beam and a photosensitive device.

. 25. A neLhod as claimed in any of claims 20 to 24 which further includes the step of lowering the second conveyor means as slices of foodstuff are deposited thereon so as to enable a plurality of slices to be stacked one on another on the second conveyor means in a manner which does not prevent the next slice from leaving the blade.

28. A method as claimed in claim 26 wherein a weighing device is associated with the second conveyor means and the conveyor is operated to move the foodstuff away from the region of the blade when the weight detected by the weighing device reaches W. 29. A method as claimed in claim 26 wherein the second conveyor means is in two parts and one part acts to collect slices until the P or W criterion is reached whereaftcr a second part takes over to collect slices from the slicing station while the first part conveys away the slices accumulated thereon, the two parts alternating in synchronism to allow a continuous stream of slices from the slicing station to be successively stacked and conveyed away on the basis of numbers of slices, or accumulated weight, of foodstuff.

30. A method as claimed in any of claims 20 to 29 which involves the further step of driving a second claw into the foodstuff at the same time as the first claw is driven in, to also move with the foodstuff, and the second claw is also retracted from the foodstuff just . before it reaches the blade.

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