HK1132709B - Method for cutting string-shaped food and cutting machine - Google Patents

Description

Method and cutting machine for cutting food bar

Technical Field

The invention relates to a method for cutting a strip-shaped food product, wherein a strip of the food product is fed by means of a feed device to a cutting device and cut into slices, strips or cubes, the strip is held during a feed movement by means of a vacuum gripper, which is fed together with the strip, and a negative pressure is created inside the interior of a contact element of the vacuum gripper, the negative pressure in the suction zone of the contact element acting on a holding zone of the strip surface.

The invention also relates to a cutting machine for cutting food bars, by means of which the food bar can be cut into slices, strips or cubes, comprising a feed device by means of which the bar can be conveyed to the cutting device during the cutting process, wherein the feed device has a vacuum gripper, with which the bar can be fixed during the feed movement, and which can be conveyed together with the bar to the cutting device, wherein a negative pressure can be created inside the interior of the contact piece of the vacuum gripper, which negative pressure in the suction zone of the contact piece acts on the fixing zone of the bar surface.

Finally, the invention also relates to a vacuum gripper for a cutting machine for cutting food bars.

Background

Methods and cutting machines of the above-mentioned type are well known. The advantage of the strip being held by means of the vacuum gripper compared with the use of a gripper hook is that the strip itself remains undamaged, since its surface is held constant by the contact elements of the vacuum gripper. In the known method and cutting machine, the generation of the underpressure is effected by means of a so-called vacuum pump. The negative pressure is transmitted from the vacuum pump to the inner cavity of the contact element through a pipeline. The contact piece itself is typically made up of a rubber cup of the type which, on account of its elastic properties, is intended to compensate for irregularities and irregularities in the surface of the strand in order to prevent air from penetrating into the suction region of the rubber cup after the application of underpressure. The vacuum pump used is typically operated continuously during the cutting operation of the known cutting machine, in order to avoid the switching-on and switching-off processes between the successive strand connections and in order to compensate for any leaks in the contact piece region and thus to generate an ambient air leakage flow from the contact piece interior, so that a sufficiently high vacuum is maintained continuously.

A cutting machine of this type is known from DE10024913a1, the feed device of which comprises at least one "suction head" which forms the boundary of a suction chamber opening into the strand. The tip has a blade-like edge which ensures a very tight connection of the tip to the product wall (Produktlaib).

The cutting machine described in US3880295A also has a suction head comprising six suction zones arranged in a straight line, which suction zones have cutting edges for cutting into the end face of the material to be cut to be fixed. Each suction zone is formed by an annular chamber between an inner cutting edge and an outer cutting edge extending concentrically thereto. There is no suction zone inside the inner blade. The circular suction zone of US3880295A is thus sealed both externally and internally by the respective knife edges.

Vacuum pumps which are in a state of continuous operation have however proven problematic from the hygiene point of view. That is to say a continuous gas flow from the vacuum gripper or from the fixed food product strand is conveyed into the pump via a suction line between the interior of the contact piece and the vacuum pump. Depending on the nature of the food, it is not possible here to prevent food particles from reaching the vacuum pump via the suction pipe and being discharged with its exhaust gases into the surroundings, i.e. into the chamber in which the cutting machine is located. Since the interior of the suction tube and the vacuum pump itself can hardly be cleaned effectively, over time, such food particles entering the suction tube and the vacuum pump will cause bacteria to develop in these areas. The bacteria which multiply there are discharged into the ambient air together with the air in the exhaust gas flow of the vacuum pump flowing past and thus cause serious bacterial problems in the known cutting machine installation. This is extremely disadvantageous particularly for cutting machines connected to fully automatic packaging machines. This bacterial problem is highly undesirable when packaging portions of cut material in a sealed, unskilled film package, since otherwise the required long minimum shelf life cannot be achieved. Typically, today the cutting and packaging process is performed in an environment, which can be said to be a clean room, where such bacterial distress caused by the known vacuum pumps is intolerable.

Disclosure of Invention

The object of the invention is to propose a method for cutting food bar and a cutting machine associated therewith, in which the bacterial problems arising during operation and due to the negative pressure that is created when using vacuum grippers are reduced compared to the prior art. The object of the invention is also to provide a corresponding vacuum gripper.

Starting from a cutting method of the type mentioned at the beginning, the above-mentioned object is achieved according to the invention in that the underpressure is generated by means of at least one piston-cylinder unit, the piston of which forms the boundary of the contact piece interior.

In contrast to vacuum pumps used in the prior art and typically in continuous operation, the piston-cylinder unit does not generate exhaust gas when a vacuum is created, since the interior space in the contact piece in which the negative pressure is created is closed to the outside. In the event of food particles falling off during the fixing process of the strand entering the interior of the piston-cylinder unit, they are no longer transported from there to a further location, for example a vacuum pump. In the method according to the invention, it is therefore sufficient to clean the interior of the vacuum gripper together with the piston-cylinder unit in addition to the contact piece. All food particles that may fall off must remain in this area and cannot be transferred further to other inaccessible areas.

Preferably, the piston of the piston-cylinder unit is moved only once in one direction in order to generate the negative pressure and only once in the opposite direction in order to cancel the negative pressure.

According to the invention, the piston of the piston-cylinder unit can be driven by means of a further piston-cylinder unit, wherein the further piston-cylinder unit itself can be operated pneumatically or hydraulically. In contrast to the two operating modes described above, the piston of this piston-cylinder unit, which generates the negative pressure, can also be driven by means of an electric motor or an electromagnet.

It is important for the normal operation of the method according to the invention that the suction area of the contact piece is sealed very effectively against the surface of the strand. This can be achieved, for example, by using a sealant which is acceptable as or for food products, for example in the form of an oil or fat or a gel or a latex with a correspondingly high viscosity which consists of oil and water. Preferably, however, at least one annular cutting edge of the contact piece surrounding the suction zone is cut into the strand, as a result of which a particularly reliable sealing of the suction zone is achieved. In particular, according to the method of the last-mentioned type, it is preferred that the piston of the piston-cylinder unit for fixing the strand is moved from a starting position in one direction into a negative pressure position, and that, in order to remove the remaining portion of the strand after the cutting operation from the contact piece of the vacuum gripper, the negative pressure position is moved in the opposite direction beyond the starting position into an overpressure position, in which an overpressure is created in the suction region, the portion is removed by means of the overpressure, and the piston is moved back into the starting position before the next fixing operation is started, in which case the contact piece does not come into close contact with the strand.

In this way, a reliable removal of the stub can be achieved, since the adhesion force, which is still present even after the removal of the underpressure, for example as a result of the cutting edge cutting into the strand, is reliably overcome by the application of the overpressure, so that the stub does not inadvertently stick to the vacuum gripper.

Starting from a cutting machine of the type mentioned at the beginning, the above-mentioned object is achieved according to the invention by a piston-cylinder unit, by means of which a negative pressure can be generated in the interior of the contact piece, wherein the piston of the piston-cylinder unit forms the boundary of the interior of the contact piece. The cutting method according to the invention can be carried out in a particularly simple manner by means of a cutting machine of the type described above.

If the piston-cylinder unit is integrated in the contact piece of the vacuum gripper, the structural costs are minimized and the cleaning costs are kept particularly low. The drive for the piston of the piston-cylinder unit can be a piston-cylinder unit, which can be actuated pneumatically or hydraulically or can also be an electric motor or an electromagnet.

It is advantageous in terms of construction if the piston of the further piston-cylinder unit has the same diameter as the piston of the piston-cylinder unit for generating the negative pressure. Here, the axis of the other piston-cylinder unit should be aligned with the axis of the piston-cylinder unit for generating the negative pressure. Preferably, a common piston rod passes slidingly and sealingly through the partition between the two axially disposed piston-cylinder units.

The partition can also be used structurally, in which channels are present for the supply of the working chambers of the two piston-cylinder units, wherein on both sides of the partition, axially aligned with one another, a cylinder tube of one piston-cylinder unit for generating the negative pressure is connected in a sealed manner on one side and a cylinder tube of the other piston-cylinder unit is connected in a sealed manner on the other side.

The above-mentioned technical problem with the vacuum gripper mentioned at the outset is solved in that the vacuum gripper is equipped with at least one piston-cylinder unit by means of which a negative pressure can be created in the interior of the contact piece, wherein the piston of the at least one piston-cylinder unit forms the boundary of the interior of the contact piece.

Drawings

The invention will be explained in more detail below with the aid of an exemplary embodiment of a vacuum gripper for a cutting machine, which is shown in the drawing. Wherein:

FIG. 1 shows a perspective view of the vacuum gripper from an oblique front;

fig. 2 shows a perspective view of the vacuum gripper according to fig. 1 from obliquely behind;

fig. 3 shows a side view of the vacuum gripper according to fig. 1 and 2;

fig. 4 shows a front view of the vacuum gripper according to fig. 1 to 3;

figure 5a shows a longitudinal section through the vacuum gripper in the starting position along the line V-V shown in figure 4;

FIG. 5b is the same as FIG. 5a, but now in a negative pressure state;

fig. 6 shows a perspective view of a gripping device comprising a base frame and three vacuum grippers according to fig. 1 to 5 mounted therein;

fig. 7 shows a side view of the gripping device according to fig. 6; and

fig. 8 shows a top view of the gripping device according to fig. 6.

Detailed Description

The vacuum gripper 1 shown in fig. 1 to 5b consists of two coaxially arranged piston-cylinder units 2 and 3, which are coupled to one another by a common piston rod 4 and are separated from one another by a partition 5, the piston rod 4 being mounted in the partition 5 in a sliding and sealing manner.

The vacuum gripper 1 has a front side 6, on which front side 6 a strand 7, indicated by a dashed line in fig. 1, for example in the form of a sausage, is fastened by means of underpressure in a manner that will be described in more detail below. The oppositely disposed vacuum gripper 1 has a rear side 8, on which rear side 8 the vacuum gripper can be fixed by means of a groove-like recess 9 to the base frame of the gripping device shown in fig. 6 to 8, which gripping device will be described in more detail below. Furthermore, the two groove-like recesses 10 on the outer surface 11 of the vacuum gripper 1 are also used for the fastening.

Connected to the diaphragm 5, the vacuum gripper 1 has a front part 12 formed by a piston-cylinder unit 2, which serves to generate the underpressure required for fixing the material strips 7. The oppositely disposed rear part 14 is essentially formed by the piston-cylinder unit 3, which serves to drive the piston of the piston-cylinder unit 2 in the front part 12.

It can be seen from fig. 5a that the piston-cylinder unit 3, which, as already mentioned, serves as a drive for generating the negative pressure, consists of a cylinder tube 16 and a piston 18 which is mounted movably and sealingly in its interior 17, the piston 18 dividing the interior 17 into a first working chamber 19 facing the partition 5 and a second working chamber 20 arranged on the other side of the piston 18. The working chamber 19 can be supplied with compressed air through a channel 21, the channel 21 being divided into a plurality of sections, first in a connecting stub 22 inserted into the partition 5 and then in the partition 5 itself. The channel has two sections which extend at right angles to one another both in the partition 5 and in the connecting piece 22, so that overall a U-shaped channel 21 results. The second working chamber 20 is passed through a channel 23 provided in an additional section 24 of the rear part 14. It likewise extends in the rear connecting piece 25.

On the opposite side of the partition 5, the piston-cylinder unit 2 is coaxial with respect to the common axis 26 to the piston-cylinder unit 3, the piston-cylinder unit 2 serving to create the negative pressure required to fix the strand 7. This piston-cylinder unit 2 also essentially consists of a cylinder 27, in which cylinder 27 a piston 28 is slidingly and sealingly supported. The piston 28 of the piston-cylinder unit 2 has the same diameter as the piston 18 of the piston-cylinder unit 3 and, due to the engagement by the piston rod 4, has the same stroke.

The other piston rod 30 is on the opposite side of the piston 28 from the piston rod 4 and guides the other piston 31 connected thereto. The piston 31 is located in a section of the cylinder 27, in which the cylinder 27 has a smaller diameter than the piston 28 and the working chamber 32 associated therewith. The unit formed by the pistons 28 and 31 (and the piston rod 30) thus relates to a stepped piston which is mounted in an axially displaceable manner in a corresponding stepped bore of the cylinder 27.

On the front side 6 of the vacuum gripper 1, a circular outer blade 33 is formed, the wall thickness of which is much smaller than the remaining wall thickness of the cylinder 27, wherein the transition from the blade 33 to the remaining wall of the cylinder 27 is realized in the form of a radial step 34. Furthermore, the front side 6 of the vacuum gripper 1 is provided with an inner blade 35, which is likewise circular in design and extends concentrically to the outer blade 33. The front edge of the inner cutting edge 35 is offset slightly rearward with respect to the front edge of the outer cutting edge 33. The inner diameter of the region of the inner blade 35 corresponds to the diameter of the front piston 31, which has a smaller diameter. The two blades 33 and 35 together with the cylinder 27 form the contact piece 29 of the vacuum gripper 1.

The circular cross-section bounded by the inner cutting edge 35 defines an inner pumping sector 36. The annular region between the inner suction sector 36 and the outer blade 33 defines an outer suction sector 37. The two suction portions 36, 37 together form the entire effective suction area of the vacuum gripper 1. The outer suction portion 37 is connected to a right working chamber 39, which is delimited by the piston 28, via two bores 38 arranged offset by 180 ° with respect to each other.

Starting from the position shown in fig. 5a, in which the two cutting edges 33 and 35 are at a distance from the end of the strand 7, the vacuum gripper 1 is moved towards the strand 7, which is supported with its opposite front end on a cutting device, not shown, for example in the form of a rotary knife. The vacuum gripper 1 is brought closer to such an extent and with sufficient force that the two cutting edges 33 and 35 cut into the strand 7 as shown in fig. 5 b. Due to the round shape of the end of the bar 7, the inner cutting edge 35 has a greater depth of cut than the outer cutting edge 33. This cutting movement is then increasingly difficult and ends when the bar 7 bears its end face in the region of the radial step 34 of the vacuum gripper 1, although the situation shown in fig. 5b is not yet the case.

After the two knife edges 33 and 35 cut into the material of the strand 7 and have thus caused the two suction zones 36 and 37 to seal, the right working chamber 40 of the piston-cylinder unit 3 is supplied with compressed air, thereby also moving the two pistons 28 and 31 to the left to the position shown in fig. 5 b. The working chamber 39 and the inner first partial chamber 41 to the right of the piston 28 and the inner second partial chamber 41' corresponding to the inner suction partial area 36 in the section of the cylinder 27 with the reduced diameter increase significantly in this way, so that a negative pressure is created in the two suction partial areas 36, 37, which fixes the strand 7 securely on the vacuum gripper 1. The inner part-chambers 41, 41' are separated from each other by a contact line K formed by the inner cutting edge 35.

Because the suction portions 36 and 37 are very effectively sealed by the blades 33 and 35, a return movement of the pistons 28 and 31, i.e. a vacuum, is sufficient to ensure a sufficiently high holding force. Since the inner suction portion 36 is completely surrounded by the outer suction portion 37, i.e. the pressure difference between the two regions is therefore small or ideally zero, there is little risk of loss of vacuum, in particular in view of the inner suction portion 36. Even when air flowing past the outer cutting edge 33 can penetrate into the outer suction portion 37, a sufficiently high underpressure is still maintained with a sufficiently effective seal by the inner cutting edge 35.

The inner suction sector 36 acts on an inner fixed sector 42 of the surface of the bar 7 and the outer suction sector 37 correspondingly acts on an outer fixed sector 43 of the surface of the bar 7. The two fastening sections 42, 43 sum in area to give the entire effective fastening area.

By selecting the diameter of the pistons 28 and 31, the diameter of the piston rod 4 and the diameter and number of the bores 38, the negative pressure which builds up in the suction partial areas 36 and 37 after a stroke of the piston 28 which is intended for driving can be influenced. It is reasonable here to choose the underpressure created in the inner suction partition 36 to be greater than the underpressure in the outer suction partition 37, since the inner suction partition 36 is arranged to be "protected" by the outer suction partition 37.

After the strand 7 has been fixed by activating the vacuum gripper 1, the strand 7 can be conveyed together with the vacuum gripper 1 to a cutting device, while the front end of the strand 7 is gradually cut into pieces. The feed movement is stopped immediately before the outer blade 33 is to enter the cutter active area of the cutting device. This achieves a reliable removal of the remnants of the strip 7 still adhering to the vacuum gripper 1, i.e. the pistons 28 and 31 are returned not only to the starting position shown in fig. 5a by the pressure exerted by the working chamber 20 via the connecting stub 25, but in addition to this an additional stroke 44 (see fig. 5a) to the right until the piston 28 rests against the step in the cylinder 27 caused by the diameter step. The pressure in the suction sub-areas 36 and 37 is therefore not only restored to the starting level, i.e. to zero, but also an overpressure is created in the two suction sub-areas 36 and 37 to such an extent that the residual portion of the strand 7 is actively expelled by the overpressure, in the process of which the frictional forces occurring in the region of the cutting edges 33 and 35 must be overcome. The pistons 18, 28 and 31 then return to the starting position shown in fig. 5a, without the front side 6 of the vacuum gripper 1 bearing tightly against the next strand 7 to be cut, so that atmospheric pressure continues to exist in the suction zones 36 and 37. Thereafter, the next cycle of gripping and cutting can be started by contacting a new strand 7.

As can be seen from fig. 6, three vacuum grippers 1, as illustrated in fig. 1 to 5b, are mounted in parallel side by side in the base frame 45 of the gripping device 46. The cross bars 47 to 49, which together with the side parts 50 and 51 form the base frame 45, secure the vacuum gripper 1 in the base frame 45 by means of the recesses 9 and 10 shown in fig. 1 to 3.

The connecting pipes 25 and 22 of the respective rear piston-cylinder unit 3 are connected in parallel via compressed air lines 52 and 53 in order to generate the negative pressure required for actuating the front piston-cylinder unit 2, so that the negative pressure required for the fastening is always generated or cancelled simultaneously for the three parallel rods 7, and the remaining residual portion is simultaneously discharged.

The base frame 45 of the gripping device 46 is known and is used in a consistent embodiment for receiving a conventional purely mechanical gripper, wherein the gripper hook cuts its gripping tooth into the rear end of the strand 7 on the basis of pneumatic actuation and, after the cutting process has ended, pulls the gripping tooth out of the stub on the basis of pneumatic actuation as well. The existing chassis 45 and the compressed air connection which is present there in any case can be used not only for the vacuum gripper 1 but also for a mechanical gripper with gripping teeth which is not shown in the figures.

Claims (14)

1. A method for cutting a strip-shaped food product, wherein a strip (7) of the food product is conveyed by means of a feed device to a cutting device and cut into slices, strips or cubes by it, the strip (7) being held during a feed movement by means of a vacuum gripper (1) which is conveyed together with the strip (7), and a negative pressure is created inside the interior of the contact member (29) of the vacuum gripper (1), the negative pressure in at least one suction zone (36, 37) of the contact member (29) acting on at least one holding zone (42, 43) of the surface of the strip (7), characterized in that: the negative pressure is generated by means of a piston-cylinder unit (2), the pistons (28, 31) of which delimit the interior of the contact piece (29).

2. Method according to claim 1, characterized in that the piston (28, 31) of the piston-cylinder unit (2) is moved only once in one direction per gripping process and only once in the opposite direction in order to cancel the underpressure.

3. Method according to claim 1 or 2, characterized in that the piston (28, 31) of the piston-cylinder unit (2) for creating the underpressure is driven by means of a further piston-cylinder unit (3), wherein the further piston-cylinder unit (3) is operated pneumatically or hydraulically.

4. Method according to claim 1 or 2, characterized in that the pistons (28, 31) of the piston-cylinder units (2) for creating the underpressure are driven by means of an electric motor or an electromagnet.

5. Method according to claim 1 or 2, characterized in that the piston (28, 31) of the piston-cylinder unit (2) for creating the underpressure is moved in one direction from a starting position for fixing the material strip (7) to an underpressure position and, for removing the remnants of the material strip (7) from the contact piece (29) of the vacuum gripper (1), is moved in the opposite direction beyond the starting position to an overpressure position, in which an overpressure is created in the at least one suction zone (35, 36), by means of which underpressure the remnants are removed, and the piston (28, 31) is moved back to the starting position before the next fixing process is started, in which the contact piece (29) is not in close contact with the next material strip.

6. A cutting machine for cutting food in strip form, comprising a cutting device by means of which a material strip (7) of food is cut into slices, strips or cubes, and comprising a feed device, by means of which the material strip (7) is conveyed to the cutting device during cutting, wherein the feed device has a vacuum gripper (1), with which the material strip (7) is held during a feed movement, and which is conveyed together with the material strip (7) to the cutting device, a negative pressure being created inside an inner cavity of a contact member (29) of the vacuum gripper, the negative pressure in at least one suction zone (36, 37) of the contact member (29) acting on at least one holding zone (42, 43) of the surface of the material strip (7), characterized by a piston-cylinder unit (2) by means of which a negative pressure is created in the inner cavity of the contact member (29), wherein a piston (28, b) of the piston-cylinder unit (2), 31) Forming the boundary of the inner cavity of the contact member (29).

7. Cutting machine according to claim 6, characterized in that the piston-cylinder unit (2) is integrated in the contact piece (29).

8. A cutting machine according to claim 6 or 7, characterized in that the piston (28, 31) of the piston-cylinder unit (2) for creating the underpressure is driven by another pneumatically or hydraulically operated piston-cylinder unit (3).

9. Cutting machine according to claim 6 or 7, characterized in that the pistons (28, 31) of the piston-cylinder unit (2) for creating the underpressure are driven by means of an electric motor or an electromagnet.

10. Cutting machine according to claim 8, characterized in that the piston of the further piston-cylinder unit (3) has the same diameter as the piston (28) of the piston-cylinder unit (2) for creating the underpressure.

11. Cutting machine as claimed in claim 8, characterized in that said further piston-cylinder unit (3) and said piston-cylinder unit (2) for creating a negative pressure are mutually aligned on an axis; and a common piston rod (4) passes slidingly and sealingly through the partition (5) between the two piston-cylinder units (2, 3).

12. Cutting machine according to claim 11, characterized in that the channel (21) for feeding the medium to the working chambers (32, 40) of the two piston-cylinder units (2, 3) extends in the partition (5).

13. Cutting machine according to claim 11 or 12, characterized in that the cylinders (16, 27) of the piston-cylinder unit (2) for creating the underpressure and the other piston-cylinder unit (3) are sealingly connected axially aligned with each other on both sides of the partition (5).

14. Vacuum gripper (1) for a cutting machine for cutting food bar-shaped items, wherein the item of food is held by means of the vacuum gripper (1) during the feed movement, and wherein a negative pressure is created inside the interior of the contact element (29) of the vacuum gripper (1), which negative pressure acts on at least one holding area (42, 43) of the surface of the item (7) in at least one suction area (36, 37) of the contact element (29), characterized by a piston-cylinder unit (2), by means of which a negative pressure is created in the interior of the contact element (29), wherein the pistons (28, 31) of the piston-cylinder unit (2) form the boundary of the interior of the contact element (29).