Apparatus for sealing trays.

Abstract

 This invention aims at reducing the machine width transversally of the machine, in relation to the longitudinal movement according to which the machine works, and at creating, in place of the isolated sealing unit, a machine working area completely open and closer to the operator, uninterruptedly accessible with the belt feeders and the first conveyor belt (3), upstream of the sealing unit (4), and with the second outgoing conveyor belt (5), which is positioned downstream of the sealing unit. The sealing of trays can be reached by a system which lets the movement only of lower bell (4) of sealing unit, moving to the upper bell (6) to the third step "closed die".

Description

[0001] Machines for the automatic sealing of trays are usually made up of a series of elements including, among the several parts: a belt feeder, used to convey trays already filled up with food but still open and positioned before the sealing unit; a base plane which is an intermittent-duty conveyor belt; a gripping member for the movement of the tray/s to under the sealing unit; the sealing unit itself where trays are sealed; and the following outgoing conveyor for the exit of trays positioned downstream of the aforementioned sealing unit.

[0002] The sealing unit comes with four columns that separate the lower base of the upper frame and simultaneously support the upper frame, necessary for holding the upper part of the sealing unit die-up. Therefore, the sealing unit is isolated.

[0003] The transfer of trays onto the sealing unit and going out of the same sealing unit is completed by means of gripping members.

[0004] The four support columns of the sealing unit have to be positioned externally of the working area related to the gripping members, transversally of the longitudinal motion according to which the operation of the same machine is set.

[0005] Patent EP 0334266 B2 introduces a first intermittent conveyor belt that is positioned between the belt feeder and the sealing unit in order to organise trays by number and size and also for the simultaneous sealing of a plurality of trays by the contemporary pickup, by the gripping member, of one to a plurality of trays and the following sealing of trays. This patent is for an industrial invention that has strongly increased the productive capacity of machines in this sector. In the final analysis, the increase in trays that can be sealed simultaneously has been implemented by incorporating in the most traditional base plane, which is static, a dynamic element, which moves longitudinally and, as already said, consists of the first intermittent-duty conveyor belt.

[0006] The invention in hand regarding patent EP 0334266 B2 still represents today the most widespread way of manufacturing machines for the sealing of one to a plurality of trays, depending on the change of tray sizes and the corresponding dies.

[0007] Drawbacks that can result even in the most advanced machines are related to the machine's overall dimensions. In particular, the four columns that support the sealing unit, positioned out of the working area of the gripping members, require a machine of proper width.

[0008] This invention aims at reducing the machine width transversally of the machine, in relation to the longitudinal movement according to which the machine works, and at creating, in place of the isolated sealing unit, a machine working area completely open and closer to the operator, uninterruptedly accessible with the belt feeders and the first conveyor belt, upstream of the sealing unit, and with the second outgoing conveyor belt, which is positioned downstream of the sealing unit. Although the operator works in a completely accessible open space, he is protected by safety sensors that prevent his hands touching the moving parts of the machine. So, this facilitates any check operations, any action by the operator as well as any machine cleaning operations. Of course, any operator actions can be evicted by the sealing unit operation steps as described in the lines below.

[0009] This result can be reached by positioning the columns beyond the maximum longitudinal extension, in both directions, of the operating area of the gripping members. The upper frame of the sealing unit wherein the fixed upper frame (also called upper bell) is positioned, is supported by the aforesaid columns.

[0010] The moving lower die, also called lower bell, is positioned at the base of the sealing unit.

[0011] The sealing process steps are usually four, one of which - the third - is optional.

[0012] First incoming step. Proper apparatuses ensure the correct positioning between the two bells of open trays and sealing films, also called perform tops.

[0013] Second approaching step. The lower bell wherein trays and sealing films are positioned for sealing is made up of plastic or metallic material. As it moves up, it gets in contact with the upper bell. This status is also called «closed die».

[0014] The third step is optional and regards the elimination of air and the consequent introduction of a gas mixture for preservation of the food product.

[0015] Fourth sealing step. Trays and the covering film are moved against the sealing plates or vice-versa and accordingly sealed.

[0016] As the sealing steps are completed, bells are opened and then move back to the initial position of «open die».

[0017] Only when the die is in the closing position, trays cannot be temporarily seen by the operator.

[0018] As for the approaching step, which is described as the second step in the lines above, the system in control of this movement usually consists of an electric or pneumatic handle-rod/toggle lever or one or many hydraulic or pneumatic cylinders, that is of a roll or ball screws, a mechanical cam or other positioning devices.

[0019] The movement is characterised by high speed, long stroke, dynamic thrust, high precision of positioning and low loads.

[0020] The critical factor is represented by the time required to make the movement itself, which has to be the shortest and most limited as possible.

[0021] As for the sealing step, in a traditional machine this stage is controlled by a specific device, which can basically be made up of a pneumatic cylinder, an hydraulic jack or a mechanical lever. This movement is characterised by short strokes, if compared to the previous approaching step, high precision of positioning, high loads, precise control of the sealing force. The critical factor in this step is the control over the thrust force that can also reach 10⁵N with a margin of error equal to 5%. The high and correct sealing force and immutability, cycle after cycle, make the tray film sealing perfect.

[0022] The opening step shows the same features as the approaching step: high speed, short times and low loads.

[0023] Traditional sealing machines therefore come with two different devices, one approaching device and one sealing device.

[0024] Sometime, approaching and sealing devices are built in a single group that performs both functions.

[0025] The most evolved solutions include sealing machines provided with built-in approaching and sealing units consisting of strong and fast mechanical cams, which can satisfy the operating conditions of the two approaching and sealing steps. Combined pneumatic-hydraulic cylinders exploit the proper speed of the pneumatic system for the approaching step and the hydraulic thrust force for the sealing step.

[0026] The new preferred embodiment of this invention starts from the idea of combining features of speed and accuracy of the adjusted ball screws of precision positioning machines with the features of the ball screws themselves and mechanical press rolls.

[0027] By contrast, according to the traditional solution, it is characterised by coupling a ball screw for the approaching movement with an hydraulic cylinder for the sealing step. The innovation of this invention consists in using one single ball screw built in a compact approaching and sealing group. Conditions of the two approaching and sealing steps are perfectly met thanks to a detailed study of dynamics, inertia, powers, life of the rolling elements, combined with the use of the most recent technologies of materials, mechanical processes, belts, servo motors and lubricants. The result is an approaching and sealing device that combines high speeds with high powers of a compact group, at limited costs and easily mountable in a machine for standard container sealing.

[0028] In the preferred embodiment, the machine is manufactured according to the illustrations shown in the following figures.

Claims

1. System for the sealing of trays that is made up, on the upper part, of a frame (17) supported by four columns (1) that are positioned beyond the maximum longitudinal line, in both directions, of the operation area of the gripping members (10), including the upper bell of the sealing unit (6); and, on the lower part, of a contact surface (18) wherein, so as to create a discontinuous plane positioned at the working level of the operator, it is possible to find the first intermittent-duty conveyor belt (3), followed by the lower bell of the sealing unit (4) positioned, in the open-die position, at the same level as the first conveyor belt (3) and followed by the second conveyor belt (5) for the movement of the sealed trays, which conveyor belt is also at the same level as the first conveyor belt (3) and the lower bell (4) in the open-die position, wherein the lower bell (4), when trays are positioned inside the lower bell throughout the interaction of the gripping members (2), is moved up to the upper bell (6) for tray sealing, until the die-closed position is reached, after the motion determined by a single ball-screw (15) operated by a servo motor (11) the base of which is equipped with a driving pulley (12) that, by means of a belt (13) determines the operation of the driven pulley (14) and, accordingly, of the ball screw (15) that specifically comes with axial- and radial-thrust bearings (16).

2. Apparatus as defined in claim one wherein columns (1) supporting the upper frame (17) incorporating the upper bell of the sealing unit are positioned beyond the maximum longitudinal line, in both directions, of the operation area of the gripping members (10).

3. Apparatus as defined in claim one wherein the lower contact surface of the frame (18) is positioned on the first intermittent-duty conveyor belt (3) and followed by the lower belt of the sealing unit (4) that, in the open-die position, is on the same line as the aforementioned conveyor belt (3) that, in its turn, is followed by the second continuous-duty belt feeder (5), which is also positioned on the same line as the previous two elements (3, 4).

4. Apparatus as defined in claim one wherein the operator's working area is positioned on the same discontinuous line as it is constituted by the first conveyor belt (3), the lower bell of the sealing unit (4) in the open position and the second intermittent-duty conveyor belt (5).

5. Apparatus as in claim one wherein the gripping members (2) pick up trays on the first intermittent-duty conveyor belt (3) and move them onto the lower bell (4) of the sealing unit, which is in the die-open position.

6. Apparatus as in claim one wherein the lower bell (4) of the sealing unit, after the trays are positioned into the same, moves up to the upper bell (6) of the sealing unit until reaching the closing position, throughout the motion is determined by the single ball-screw (15), powered by a servo motor (11) the base of which is positioned on a drive pulley (12) that, by means of the belt (13) create motion in the driven pulley (14) and, accordingly, the ball screw (15) that specifically comes with axial- and radial-thrust bearings (16).

Drawing