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The present invention relates to machines for canning tuna and the like, and in particular to a machine and method intended to minimize the damage to tuna during the canning process and to obtain cans of a substantially constant weight.

In the following, specific reference will be made to the canning of tuna yet it is clear that what is being said is also applicable to the canning of other food products having similar characteristics, such as other types of fish, meat, etc.

It is known that the main difficulties in canning tuna are obtaining cans of constant weight, so as to avoid production waste, and presenting the consumer with a good-looking product when the can is opened, since this determines the product value to a great extent. Such difficulties are not easy to overcome due to the intrinsic nature of tuna, which is a food product showing ample variations in compactness, density and shape from batch to batch where not even from loin to loin. Moreover it is obvious that the manufacturer tries to obtain the maximum quantity of finished product from the raw material, which must therefore be treated so as to avoid as much as possible crumbling and loss of liquids that lead to a decrease in weight of the raw material to be canned. Clearly, all of the above must be achieved through a machine that guarantees an adequate productivity, since machines and methods that are too slow result in excessive costs.

The main phases of the canning process are therefore the separation from the bulk of fed product of a tuna cake having a suitable weight, neither too low to risk obtaining an underweight can nor too high to reduce the yield of the raw material, and the shaping thereof into a shape suitable for the introduction into a can, typically a round cylindrical shape. In the following, specific reference will be made to the canning into conventional round cans, yet it is clear that what is being said is also applicable to the canning into cans having other shapes such as oval, rectangular with rounded corners and the like, as well as into jars or other containers.

Prior art machines and methods can be substantially divided in two categories depending on the sequence of the above-mentioned main phases, i.e. first dosing and then shaping or vice versa. In practice, in a first type of machine the product is shaped while being fed to the dosing chamber and the cake that is cut from the bulk of product already has a shape suitable for canning, whereas in a second type of machine a cake of suitable weight and generally quadrangular shape is cut from the bulk of product and subsequently shaped for the introduction into the can. A recent example of a machine of the first type can be found in WO 2004/103820 that discloses a machine for obtaining simultaneously two conventional round cans, comprising a forming mouth, with a rectangular inlet and a binoculars-shaped outlet, which is crossed by a vertical knife that reciprocates perpendicularly to the feed direction to divide the tuna loin in two portions. Said mouth connects the conveyor belt tuna feeder to two dosing chambers formed in a rotor that rotates in a plane perpendicular to said feeder to take the two dosing chambers to a second station where the round cakes are transferred into the cans. This type of machine has several drawbacks resulting from the high push on the tuna required to go from the rectangular inlet portion of the mouth to the cornerless outlet portion. A first drawback is the damage to the outer surface of the tuna that scrapes with high friction along the inner walls of the mouth to follow the great variation in shape of the cross-section; such a friction also causes a compression of the peripheral fibers of the tuna which therefore results having a non-uniform density when leaving the mouth. This compression also causes the further drawback of a "squeezing" of the tuna with loss of liquids and crumbles, which not only reduce the yield of the raw material but can also leak through the interstices of the machine causing the mechanisms to get soiled and clogged.

Still another drawback caused by such a friction is the fact that the central fibers of the tuna are more unimpeded in advancing with respect to the peripheral fibers whereby the cake that is obtained after the cut tends to be convex. This may cause problems in the steps following the canning since the central portion of the can, being higher, may get in contact with the can lid and therefore burn during the sterilization process or it may not be sufficiently covered by the control liquid (oil or other).

Finally, it should be noted that this canning method is even more sensible to the already high intrinsic variability of tuna, since the push of the conveyor belts on the tuna must be continuously adjusted and is affected by the flow of the bulk of fed product and by possible irregularities or pauses in the infeed. This also affects the precision in determining the cake weight, despite the presence of load cells that control the operation of the conveyor belts depending on the push exerted by the tuna on bottom plugs that close the dosing chambers. The most common example of the second type of machine has remained practically unchanged in the last three decades and is described in US 4116600: the tuna is cut in an approximate amount by a knife located at the end of the conveyor belt feeder, then pushed perpendicularly by a ram into a metering pocket with a semicircular concave bottom where a second knife closes the pocket and defines the exact amount. This metering pocket consists of two adjacent peripheral pockets formed in two rotating turrets between which there is arranged a third knife that divides the thus formed tuna cake in two cakes, and each turret then rotates independently towards a second station where the shaping is completed by a relevant radial plunger shaped with a concave semicircular contact surface prior to moving the cake to a third station where the transfer into the can takes place.

Although this type of machine does not subject the tuna to the high friction of a forming mouth as in the first type of machine, nonetheless it also has various drawbacks of a different kind.

In the first place, the product dosing is achieved by filling the metering pocket by means of the perpendicular ram that must compress the tuna with a pressure as uniform as possible in order to obtain a density and therefore a cake weight which is constant. However, as discussed above, the intrinsic nature of tuna and the irregularities in shape, infeed and flow make it difficult to achieve a constant weight, in particular since there are no load cells or other systems that provide a feedback to the feeder. On the other hand, increasing the ram force in order to reduce the effect of such irregularities leads to the "squeezing" of the tuna with increased damage to the product and a lower yield.

Secondarily, although the tuna is not forced through a forming mouth yet it undergoes three cuts along different surfaces and two displacements before obtaining the final shape: a first displacement by the ram scraping perpendicularly to the conveyor belt to enter the metering pocket, and a second displacement in the turret scraping against the inner surface of the machine casing between the first and second station.

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This still implies various frictions with subsequent losses of liquid and risks of crumbling, in addition to a certain degree of complexity of the machine that also has a low productivity exactly due to the several movements required to perform this canning method. Moreover, the rotating speed of the turrets can not be too high in order to prevent the centrifugal force from increasing the friction of the tuna against the casing during the rotation.

The subsequent improvements to this machine disclosed in the patent publications US 5887413 and WO 2008/109084 respectively relate to the possibility of changing the cake thickness by means of adjustable end plates and the possibility of always having the surface of the last cut facing the can lid thanks to opposite knock-out plungers, yet they do not overcome any of the above-mentioned drawbacks.

The same drawbacks, even to a higher degree, are present in the machine disclosed in EP 1448445 that performs a similar canning method but it provides the division of the cake in the metering pocket by pushing the tuna against a fixed blade and a subsequent sub-division in a second chamber by pushing it against a second fixed blade prior to shaping. It is obvious that the higher number of displacements and the use of fixed blades increase the friction, the losses and the damage to the product.

Therefore the object of the present invention is to provide a canning machine and method which overcome the above-mentioned drawbacks. This object is achieved by means of a method that provides first the dosing and then the shaping of the cake in a same first station without intermediate displacements, and of a relevant machine that performs said method with a structure that is generally similar to that disclosed in WO 2004/103820 yet without the forming mouth but with radial shaping members that act at the first station. The first important advantage of the machine and method according to the present invention is that of obtaining tuna cakes with premium quality appearance and constant weight thanks to the fact that the frictions and displacements are minimized, while the weight control is achieved through the feedback of pressure sensors (load cells or the like) as in WO 2004/103820. A second great advantage of the present method and of the relevant machine is the high productivity, much higher than prior art machines, achieved thanks to the simplifϊcation of the method and machine that allows to operate at higher speeds.

Still another significant advantage of said method and of the relevant machine stems from the fact that the general concept on which they are based can be validly applied to machines with different productivity levels depending on the needs, and this while always retaining a substantial structural simplicity.

These and other advantages and characteristics of the machine and method according to the present invention will be clear to those skilled in the art from the following detailed description of an embodiment thereof, with reference to the annexed drawings wherein: Fig.l is front perspective view diagrammatically showing the fundamental members of the machine according to the present invention;

Fig.2 is a partial enlarged view similar to the preceding one that better shows some details of said machine;

Fig.3 is a front perspective view of the mouth connecting the feeder to the dosing chambers, with the cutting means for dividing longitudinally the bulk of tuna being fed;

Fig.4 is a top plan view of the mouth of Fig.3 without the top wall;

Fig.5 is a front perspective view of the main rotor, with a portion removed for the sake of clarity, in a position between the dosing phase and the shaping phase;

Fig.6 is a lateral partially sectional view of the machine of Fig.l, in the initial step of feeding tuna to the dosing chambers;

Fig.7 is a view similar to Fig.6 showing the step of separating the tuna cakes;

Fig.8 is a view similar to Fig.6 showing the step of preparing for the shaping of the tuna cakes;

Fig.9 is a view similar to Fig.6 showing the step of shaping the tuna cakes; Fig.10 is a view similar to Fig.6 showing the step of preparing for the displacement of the shaped cakes towards the station of transfer into the cans;

Fig.11 is a front perspective view of the main rotor, with a portion removed for the sake of clarity, in the step corresponding to Fig.10.

With reference to figures 1 and 2, there is seen that a machine according to the present invention has a general structure similar to the machine described in WO

2004/103820, since it includes a main rotor 1 and secondary rotor 2 partially overlapping and rotating in planes perpendicular to a conveyor belt feeder 3 that feeds the bulk of tuna T. Said feeder 3 conventionally includes a bottom belt 3a, two shorter side belts 3b and an even shorter top belt 3c that cooperate in conveying the bulk of tuna T to a mouth 4, more visible in Fig.2 where the right side belt 3b has been removed for the sake of clarity.

This mouth 4 connects the outlet of feeder 3 to three dosing chambers formed in the main rotor 1 and aligned with said outlet. A bottom blade 5 reciprocates vertically between the outlet of mouth 4 and rotor 1 to form in the three dosing chambers three tuna cakes separate from the bulk of tuna T, as it will be better illustrated further on. It should be noted that although the figures show an exemplary embodiment suitable for the simultaneous canning of three tuna cakes, the machine and method according to the present invention can be applied to the production of a different number of cans at each cycle (one, two, four or more), three being considered the optimal compromise between the complexity and productivity of the machine. In fact, it is clear for a person skilled in the art that the size of the above-illustrated members, namely rotors 1 and 2, feeder 3, mouth 4 and blade 5 can be easily adapted to a different number of cans to be produced at each machine cycle as well as to cans of different shapes.

As previously mentioned, a first novel aspect of the present machine is given by the connecting mouth 4 that is illustrated in detail in figures 3 and 4. This mouth 4 has a cross-section of substantially constant shape so as not to perform any significant shaping of the bulk of tuna passing therethrough in order to prevent the problems mentioned in the introductory portion of the present specification, such as the friction along the perimeter, for example a rectangular shape that divides into three separate square sections of substantially equal area.

This is particularly clear from the top plan view of Fig.4 showing how the hatched area, corresponding to the tuna passage cross-section, remains unchanged for most of the length of mouth 4 up to in proximity to the outlet where a pair of chisel knives 6, provided with a vertical reciprocating motion synchronized with the movement of feeder 3, are arranged before a pair of wedge diverters 7 to divide longitudinally the bulk of tuna in three portions and to direct the two external portions to the two outer dosing chambers.

However, it should be noted that the cross-sectional area of mouth 4 may have a slight decrease between the inlet cross-section and the outlet cross-section, said decrease being suitable to achieve a slight pre-compression of the product useful to make up for possible irregularities in infeed by feeder 3. For example, the cross-section of mouth 4 may have a rectangular shape, or more generally a quadrangular shape, at the inlet cross-section and a rectangular shape with bevelled corners at the outlet cross-section, which also favours the introduction of the tuna into the dosing chambers.

Referring now to Fig.5, there is illustrated in grater detail the structure of the main rotor 1 that sequentially achieves the dosing and shaping of the tuna cakes at a same station, prior to moving them to a subsequent station where they are transferred into the cans.

Rotor 1 is substantially cross-shaped with a group of three shaping chambers Ia formed side by side in each one of the four identical arms Ib of the cross, that rotates clockwise as indicated by the arrow. The structure and operation of the machine will be described in the following with specific reference to the placement of the first dosing and shaping station in the bottom position of rotor 1, i.e. the "6 o'clock" position, and of the second cake transferring station in the following left position, i.e. the "9 o'clock" position, but this is just one of the several possible placements of the two stations. In fact it is clear that what is being said is also applicable with the two stations located in other positions, even not consecutive, being obvious that the first station must precede the second station in the direction of rotation of rotor 1. Therefore, in the following reference will be made in general to the internal/external or proximal/distal position of the members, meant with respect to the radial direction, since the above-mentioned two stations can be located at any of the positions of rotor 1.

At the first station, the three dosing chambers are defined at the distal ends of the three shaping chambers Ia by a front plug 8, that acts as back of the chambers and stops the advancing of the bulk of tuna T, by a flat internal shutter 9 and by an external shutter 10 that has an internal flat surface, in contact with the tuna, and an external surface shaped to mate with the internal shaped surface of terminal 11 of arm Ib, that acts as distal end of the shaping chambers Ia.

More specifically, said internal surface of terminal 11 preferably has two substantially semi-circular lateral profiles 11a and a central profile l ib slightly offset inwards and therefore extending along an arc of circle shorter than a half-circle, the remaining portion of the half-circle being formed in the radial baffles 12 that divide the three shaping chambers 1 a. This position offset in the radial direction allows to decrease the distance in the circumferential direction between the dosing chambers, consequently reducing the transverse displacement required to the lateral portions of tuna cut by knives 6 and guided by diverters 7 towards the lateral dosing chambers, thus resulting in a minimized damage to the product. The front plug 8 is connected to a cake dosing control system 13 comprising a pressure sensor, preferably a load cell, whose output signal is used for the feedback control of feeder 3, as already known from WO 2004/103820 yet without the problems caused by feeding the tuna through a forming mouth. The control system 13 may also include a dynamic scale (not shown) or other control system suitable to detect the weight of the cans leaving the machine and to compare it with the values detected by the pressure sensor so as to perform a dynamic feedback adjustment of said sensor.

Plug 8 and shutters 9, 10 are longitudinally mobile, by means of respective actuators not shown, between a rest position and a work position in which they define the sides of the dosing chambers, as indicated by the respective arrows in Fig.5. It is clear that for structural simplicity plug 8, and shutters 9, 10 are formed as single bodies shaped to enter the shaping chambers Ia astride the radial baffles 12, but it would also be possible to provide separate bodies for each shaping chamber which however would require multiple actuators. In any case, for an effective operation of the control system 13 as mentioned above, it is always preferable that there is a single plug 8 connected to the pressure sensor. Furthermore, the work position of said plug 8 is preferably adjustable by the control system 13 within a 2-3 mm range, in order to achieve a further possibility of adjustment of the cake weight.

To carry out the cylindrical round shaping of the tuna cakes T' having a substantially parallelepipedal shape that are obtained from the cut performed by blade 5, as shown in Fig.7, a mobile member 14 having the external surface with a semi-circular shape, called "shaper", is arranged in a radially slidable way in each shaping chamber Ia to the inside of the dosing chamber.

To take into account the adjustment range of the position of plug 8, the longitudinal thickness of shapers 14 must correspond to the maximum possible depth of the dosing chambers, therefore there is generally interference between the radial movement of shapers 14 and the work position of plug 8. Moreover, to take into account the offset position of the central profile l ib, the radial length of the central shaper 14 must be correspondingly reduced (or vice versa increased if the central profile 1 Ib were offset outwards).

The radial reciprocating motion of shapers 14, indicated in Fig.5 by the respective arrow, is performed by means of actuators generally arranged at hub 15 of rotor 1, where also the rotary motion for the whole rotor 1 is received. These actuators are not illustrated since they can be made in different ways well know to a person skilled in the art. Finally, in order to provide greater structural rigidity to rotor 1, arms Ib are preferably mutually connected through connecting rods 16 joining terminals 11. The simple and effective operation of the canning machine according to the present invention and the relevant canning method are readily understood from the following description given with reference to figures 6 to 10, in which the region within the dotted frame is depicted in vertical cross-section for the sake of clarity.

In the initial position of Fig.6, the bulk of tuna T advanced through the connecting mouth 4 until it stopped against plug 8, which together with shutters 9 and 10 defines the dosing chambers, and the pressure of tuna on plug 8 detected by the control system 13 through the pressure sensor caused feeder 3 to stop.

In the following step of separation of the tuna cakes, as shown in Fig.7, blade 5 rises to cut the bulk of tuna T and closes the front of the dosing chambers in which cakes T' of parallelepipedal shape remain. After that, as shown in Fig.8, plug 8 and the external shutter 10 move back to avoid interference with the radial movement of shapers 14, lining up so as to form the back of the shaping chambers, whereas the internal shutter 9 moves back farther stopping outside rotor 1.

In this position it is possible to perform the shaping phase of the tuna cakes T', as shown in Fig.9, in which the cakes are pushed by the radial movement of shapers 14 against the shaped internal surface of terminal 11, that shapes the outer half thereof, while the external surface of shapers 14 shapes the internal half thereof. At this moment the tuna cakes T" have taken a cylindrical round shape and are firmly retained by shapers 14 against terminal 11, while plug 8 and the external shutter 10 move back further to line up with the internal shutter 9 outside rotor 1, as shown in Fig.10. This is also the position illustrated in the perspective view of Fig.l 1, from which it is clear how the three round cakes T" can be taken through a clockwise 90° rotation to the second station where they will be transferred by known means not shown, typically plungers, into three cans B carried by the secondary rotor 2 (not shown). Since the displacement from the first station to the second station occurs with cakes T" already shaped and held by shapers 14 it is clear that it may be performed quickly and without damage to the product.

Finally, after transferring the cakes into the cans, shapers 14 return to the rest position at the proximal end of the shaping chambers Ia for the passage through the other two "12 o'clock" and "3 o'clock" positions that are mere transit stations. Obviously, since all four arms Ib are identical, each complete rotation of rotor 1 corresponds to four canning cycles and therefore to the production of 12 cans, proof of the high productivity of the present machine.

It is clear that the above-described and illustrated embodiment of the machine and method according to the invention is just an example susceptible of various modifications. In particular, in addition to the various possible changes already mentioned above, the separation of the tuna cakes T' from the bulk of tuna T and the division of the latter into a plurality of portions can be achieved by cutting means respectively different from blade 5 and knives 6 although technically equivalent (e.g. rotating blades). Similarly, the feeder of cans B to the second station could be made different from the secondary rotor 2 (e.g. rail guides) and could take cans B to the opposite side of rotor 1 with respect to what is illustrated in figures 1, 2 and 11. In this way, the smoothest side of cakes T" which was in contact with blade 5 would be on the top side of cans B upon transfer. Finally, it is obvious that rotor 1 can have a different number of arms Ib as long as they are equally spaced along the periphery thereof.