A PRODUCT SLICING SYSTEM

Abstract: A product slicing system comprises a slicing machine (1) having a slicing blade (2) and a continuous product feeder (3,4), a product in-feed unit (5) for feeding whole logs of product (22,23) to the continuous product feeder, a detector (8) to detect the trailing end of each log (20,21) fed by the continuous product feeder, and a monitor (9) to monitor the movements of the continuous product feeder (3,4). The detector (8) triggers the product in-feed unit (5) to feed the next log (22) of product upon detection of the trailing end of the log (21) by the detector (8). Means (15) are provided to determine from the output of the detector (8) and the monitor (9) when a first location on the log (20), a predetermined distance in front of the trailing end of the log (20), is located at the slicing blade (2) and when a second location, a predetermined distance behind the trailing end of the log (20), and hence a predetermined distance behind the leading end of a following log (21), is located at the slicing blade (2). Reject means (6) are arranged to reject slices cut from each log by the slicing blade (2) after the first location and before the second location reaches it.

Description: Foodstuffs such as cold meats, bacon, meat products and cheese are often sold pre-sliced in packets. Such slices are cut from sides, legs, backs or folded middles of bacon, deboned hams, moulded blocks of meat products and prisms of cheese but all of these are subsequently referred to by the collective term of logs. The logs of product may vary in length from a few centimetres for natural products such as bacon and ham to several metres for processed meat products such as sausage. The first few and last few slices cut from such logs are not as presentable as those that are derived from the bulk of the logs and, accordingly, the initial and final slices that are cut from each log are not normally included in packs distributed to the public. Frequently the slices from the ends of the log are not of the required weight and thus packs containing them are also off-weight. However, even when the slices are of the required weight they are usually misshapen and less stable than the regular slices and tend to become displaced as they pass along the packaging line. Further, small scraps are sometimes produced from the ends which can become entangled with transfer rollers of a packaging line and disturb the arrangement of subsequent packs. Slicing machines fall into two main types. In the first a gripper grips the trailing end of each log independently to drive it forwards to control its slice thickness. As the gripper and hence the trailing end of the log approaches the slicing blade the gripper reverses its direction and pulls the butt end of the log backwards away from the slicing blade. Such an arrangement is described in our earlier specification EP-A-0127460 and this avoids the production of slices from the butt end of each log. The other main type of slicer includes a continuous product feeder. This continuous product feeder may be formed by a pair of opposed conveyor belts with the log being fed between their opposed faces towards the blade of the sling machine. A particularly preferred slicing machine with a continuous feeding device is described in our earlier International Application WO89/06588 Slicing machines including continuous product feeders have many advantages over machines including a gripper. The time taken to reload the gripper type of slicing machine is completely eliminated and this can as much as double the throughput of the slicing machine. However, perhaps more importantly, slice thickness control and hence pack weight control is greatly improved since the logs are gripped between the opposed conveyors which extend substantially up to the slicing blade which leads to the feed of the logs being positive and controlled. With the gripper type slicer the distances between the gripper and the blade varies throughout the feed and as a result of elastic and plastic deformation of the log the feed of the log is not precisely controlled, particularly during the initial stages of the slicing of each log. However the problem of the irregularities in the slices produced from the leading and trailing edges of each log is a distinct problem. At present, where the resulting packs are not of the correct weight these are detected by the downstream packaging line and are rejected. However, any packs which do happen to be the correct weight but which contain butt end portions proceed along the packaging line with all of the other correct weight portions and they are then removed manually and replaced by other, acceptable products. This not only requires extra labour and therefore incurs extra cost but is also not safe, particularly on high speed packaging lines. GB-A-2139876 discloses a product slicing system comprising a slicing machine having a slicing blade and a continuous product feeder. Means are provided to monitor the driving current which drives the blade of the slicer and the output of these means is used to discriminate whether the blade is cutting full slices of product or only part slices as occurs at the ends of logs. Upon detection of a full slice after a series of part slices the feed of the continuous product feeder is interrupted to provide a gap between part and full slices on an output conveyor so that the part slices can be removed manually from the output conveyor. According to this invention a product slicing system comprises a slicing machine having a slicing blade and a continuous product feeder, a product in-feed unit for feeding whole logs of product to the continuous product feeder, a detector to detect the trailing end of each log fed by the continuous product feeder, the detector triggering the product in-feed unit to feed the next log of product upon detection of the trailing end of the log by the detector, a monitor to monitor the movement of the continuous product feeder, means to determine from the output of the detector and the monitor when a first location on the log, a predetermined distance in front of the trailing end of the log, is located at the slicing blade and when a second location, a predetermined distance behind the trailing end of the log, and hence a predetermined distance behind the leading end of a following log, is located at the slicing blade, and reject means arranged to reject slices cut from each log by the slicing blade after the first location and before the second location reaches it. By feeding the individual logs singly from the product in-feed unit to the continuous product feeder in response to the detection of the trailing end of a log already in the feeder ensures that the trailing end of each log is always detected by the detector. There would be a risk if the logs were fed continuously towards the product feeder that two adjacent logs would appear to be a single continuous log to the detector without this arrangement of the product in-feed unit. Indeed this is the reason why GB-A-2139876 proposes the use of the blade driving current to discriminate between whole and part slices. By detecting positively and unambiguously the trailing ends of each log and controlling the reject means in accordance with the detected ends and the movement of the feeding device, this ensures that all of the slices cut from the leading and trailing end portions of each log are rejected and are not fed forwards onto the packaging line. Preferably the product slicing system includes an interleaver which feeds sheets of paper or plastic in synchronism with the slicing machine so that each sheet is fed across a drop zone of the slices so that each succeeding slice drops onto a sheet fed from the interleaver and then carries the sheet downwards onto the top of a previous slice of the stack or shingle. In this case the means to determine from the output of the detector and the monitor preferably also control the operation of the interleaver so that no sheets of paper are interleaved between slices cut from each log by the slicing blade after the first location and before the second location reaches it. The monitor to monitor the movement of the continuous product feeder may have the form of an encoder connected to the conveyors of the feeder to monitor its movement. Alternatively, when the feeder is driven by a stepper motor the monitor may merely monitor the drive pulses fed to the stepper motor and rely on no slip occurring between the drive pulses being fed to the stepper motor and the movement of the log by the continuous product feeder. The product in-feed unit for feeding whole logs of product to the continuous product feeder may be any type of automatic loader or magazine containing a number of logs and arranged to feed them singly to the continuous product feeder. Preferably however the product in-feed unit comprises a pivoted inclined ramp with an abutment formed at its downstream end. In this case the logs of product are placed one behind the other on this inclined ramp and move forwards under gravity until the leading edge of the front log engages the abutment. Upon detection of the trailing end of a preceding log the inclined ramp is lifted to lift the leading end of the leading log on the ramp over the abutment and to align the inclined ramp with the continuous product feeder of the slicing machine. The product then moves forward under gravity until its leading end abuts the preceding log in the continuous product feeder. The means responsive to the output of the detector and the monitor determine when the trailing end of the preceding log has moved sufficiently far forwards for the following log to be captured by the continuous product feeder and, once this has been achieved, actuates the lifting means so that the inclined ramp is once again lowered to ensure that the leading end of the next following log engages the abutment and is prevented from being fed to the continuous product feeder. The reject means may have the form of a separate reject conveyor forming part of the downstream packaging line with the sliced product being fed selectively forwards to the remainder of the packaging line or to the reject conveyor by a conveyor which moves sideways or pivots up and down to transfer its output from one to the other. Alternatively, the initial conveyor, usually known as a jump conveyor, which receives the slices of product as they are cut by the slicing blade of the slicing machine may be arranged to move in the reverse direction to discharge the rejected products and in the forwards direction to allow acceptable products to move forwards towards the packaging machine. Such a slicing machine and jump conveyor combination is described in detail in our co-pending application filed on the same day as this application and claiming priority from British Patent Application 8911523. The reject means may also be formed by a simple pusher which pushes slices cut from each log by the slicing blade before the first location and after the second location off a downstream conveyor. The detector may typically be formed by a photo-emitter/photo-detector pair which are preferably co-sited and have a retroreflector located on the opposite side of the path of the logs but other forms of detectors such as proximity switches, mechanical arms operating microswitches or laser or ultrasonic detectors may be included. Preferably the product slicing system includes a further detector located immediately adjacent the upstream side of the slicing blade to detect when no log is present immediately upstream of the slicing blade. As the butt end of each log approaches the slicing blade it is not held as positively by the continuous product feeding device and, accordingly, there is a risk that it will be pulled by the slicing blade further forwards than its required feed. In such circumstances the butt end of a log can be pulled out of the continuous product feeding device before it has been completely sliced. To take account of this, the output from the other detector is also preferably coupled to the reject means to ensure that such slices are rejected even if the slicing blade has not yet reached the first location on the log. A particular example of a slicing system in accordance with this system will now be described with reference to the accompanying diagrammatic side elevation. The product slicing system comprises a slicing machine 1 having a blade 2 and a continuous product feeder formed by opposed conveyors 3 and 4, an in-feed unit 5, a downstream jump conveyor 6 and an output conveyor 7 leading to a downstream packaging line. The product slicing system also includes a detector 8 to detect the trailing end of each log and an encoder 9 connected to the conveyor 4 of the continuous product feeder. The in-feed unit comprises a roller conveyor 10 which is hinged at a pivot 11 and includes a pneumatic cylinder 12 to lift and lower its downstream end. A fixed abutment 13 is located at the downstream end of the roller conveyor 10. A further detector 14 detects the absence of a log of product from immediately in front of the slicing blade 2. Logs of product 20, 21, 22 and 23 are placed on the inclined roller conveyor 10 and roll downwards under gravity until their leading ends engage the fixed abutment 13. The pneumatic cylinder is then operated under manual override control, for example, for the first log 20, to lift the downstream end 12 of the roller conveyor 10 to lift the leading end of the first log 20 over the top of the abutment 13 and to align the roller conveyor 10 with the conveyor 3 in the continuous product feeder of the slicing machine 1. A control unit 15 which typically includes a programmed computer or a programmed logic controller receives the output from the detector 8 and the encoder 9 and from this can determine the position of the trailing end of each log as it moves along the product feeder. When the trailing end of the log 20 passes the detector 8 the pneumatic cylinder 12 is again operated to lift the next log 21 over the abutment 13 so that it rolls down until it abuts the trailing end of log 20. Once the control unit 15 determines that the trailing end of log 20 has moved far enough forwards for the leading end of the log 21 to be securely engaged between the conveyors 3 and 4, the pneumatic cylinder 12 is actuated to lower the downstream end of the roller conveyor 10 so that the leading end of the following log 22 engages the abutment 13. Meanwhile the logs 20 and 21 held between the conveyors 3 and 4 are fed forwards at the required feed speed to produce slices of the required thickness and weight. Again from the output of the detector 8 detecting the trailing end of the block of product and the forwards movement of the continuous product feeder as recorded by the encoder 9 the control unit knows when a first location a predetermined distance in front of the trailing end of the log 20 reaches the slicing blade 2. Once the first location reaches the slicing blade 2 a motor 16 which drives the conveyor 6 operates in the reverse direction, i.e. feeding slices from right to left as seen in the Figure to reject the slices. The system continues in this mode until a second location a predetermined distance behind the trailing end of log 20 and hence a predetermined distance behind the leading end of the log 21 reaches the slicing blade 2. At this point the mode changes and normal product slicing continues with the jump conveyor 6 forming the slices into groups. A manual override control to introduce the first log 20 also triggers the control unit 15 to reject the first few slices cut from the leading end of the very first log. Apart from this the slices cut from the log 20 are formed into stacks or shingles on the conveyor 6 which is intermittently moved at a high jump speed in the interval between cutting adjacent slices to form separate groups of slices. When the detector 8 detects the trailing end of log 21 the process is repeated with the pneumatic cylinder 12 being operated to lift the downstream end of the roller conveyor 10 to feed the following log 22 of product onto the continuous product feeder formed by the conveyors 3 and 4. In the Figure the first log 20 is partly sliced, the second log 21 is securely held by the continuous product feeder and is being fed forwards simultaneously with the first log 20 whilst the third log 22 abuts the abutment 13 and the following fourth log 23 merely rests against the trailing end of the third log 22. During the slicing operation if the detector 14 detects the absence of a log from immediately upstream of the slicing blade 2 it causes the control unit 15 to operate the drive 16 of the conveyor 6 in the reject direction even if by calculation from the output of the detector 8 and encoder 9 the control unit 15 decides that the region between the first and second locations is not adjacent the slicing blade 2.

Claims: A product slicing system comprising a slicing machine (1) having a slicing blade (2), a continuous product feeder (3,4), and a monitor (9) to monitor the movements of the continuous product feeder (3,4), characterized by a product in-feed unit (5) for feeding whole logs of product (22,23) to the continuous product feeder (3,4), a detector (8) to detect the trailing end of each log (20,21) fed by the continuous product feeder (3,4), the detector (8) triggering the product in-feed unit (5) to feed the next log (22) of product upon detection of the trailing end of the log (21) by the detector (8), means (15) to determine from the output of the detector (8) and the monitor (9) when a first location on the log (20), a predetermined distance in front of the trailing end of the log (20), is located at the slicing blade (2) and when a second location, a predetermined distance behind the trailing end of the log (20), and hence a predetermined distance behind the leading end of a following log (21), is located at the slicing blade (2), and reject means (6) arranged to reject slices cut from each log by the slicing blade (2) after the first location and before the second location reaches it. A product slicing system according to claim 1, in which the product slicing system includes an interleaver which feeds sheets of paper or plastic in synchronism with the slicing machine (1) so that each sheet is fed across a drop zone of the slices so that each succeeding slice drops onto a sheet fed from the interleaver and then carries the sheet downwards onto the top of a previous slice of the stack or shingle. A product slicing system according to claim 2, in which the means (15) to determine from the output of the detector (8) and the monitor (9) also controls the operation of the interleaver so that no sheets of paper are interleaved between slices cut from each log by the slicing blade (2) after the first location and before the second location reaches it. A product slicing system according to any one of the preceding claims, in which the monitor (9) to monitor the movement of the continuous product feeder (3,4) has the form of an encoder (9) connected to the conveyors (3,4) of the feeder to monitor their movement. A product slicing system according to any one of the preceding claims, in which the product in-feed unit (5) comprises a pivoted inclined ramp (10) with an abutment (13) formed at its downstream end, and means (12) to lift the downstream end of the ramp and hence the leading end of the leading log (22) on the ramp over the abutment (13) and to align the inclined ramp (10) with the continuous product feeder (3) of the slicing machine (1). A product slicing system according to any one of the preceding claims, in which the reject means (6) has the form of a separate reject conveyor (6) forming part of the downstream packaging line (6,7) with the sliced product being fed selectively forwards to the remainder of the packaging line (6,7) or to the reject conveyor (6) by a conveyor which moves sideways or pivots up and down to transfer its output from one to the other. A product slicing system according to any one of claims 1 to 5, in which the initial conveyor (6) which receives the slices of product as they are cut by the slicing blade (2) of the slicing machine (1) is arranged to move in the reverse direction to discharge the rejected products and in the forwards direction to allow acceptable products to move forwards towards a packaging machine. A product slicing system according to any one of the preceding claims, which includes a further detector (14) located immediately adjacent the upstream side of the slicing blade (2) to detect when no log is present immediately upsteam of the slicing blade (2), the output from the other detector (14) being coupled to the reject means (6) to ensure that such slices are rejected even if the slicing blade (2) has not yet reached the first location on the log (20).

Inventors: SEAGER, RICHARD
Applicants: THURNE ENGINEERING CO LTD
Application year: 1990
Main classification: B26D7
IPC codes: B26D7, B26D3