Apparatus for producing crate-like containers made of synthetic material

Abstract

 An apparatus for producing crate-like containers made of synthetic material constituted by a sheet in which die-cutting and folding lines form a bottom (2), two side walls (5,6) and two front walls (3,4) that are extended laterally at opposite ends by means of a first flap (7), a complementary flap (8) and an end flap (9) that can be folded in a tube-like fashion so as to form four corner elements (13), which can be connected on the respective sides (14) to respective end portions (5a,6a) of said side walls (5,6), forming a substantially box-like structure that is open at the top; the apparatus comprises a first station (20) and a second station (21) connected by a sliding surface (22), the first station (20) comprising a plurality of lateral units (23) for folding the complementary flaps (8) and the end flaps (9) and means (44) for the adhesion of the end flaps (9) against the front walls (3,4) in order to form the corner elements (13), the second station (21) comprising a rectangular recess (50) for the forming of the containers, a pusher (51) that can be actuated from an inactive upper position to a lower position for insertion in the recess (50) for the folding of the front walls (3,4) and side walls (5,6) in order to form the container, means (52) for fixing the sides (14) of the corner elements (13) onto the end portions (5a,6a) of the side walls (5,6), characterized in that the fixing means are constituted by thermal bonding elements (96) that comprise a plurality of thermal bonding laminas (97) that are located at the edges of the recess (50) and are associated with actuation elements (91) that are suitable to guide the thermal bonding laminas (97) from a retracted position to a protruding position, in which they are interposed temporarily between the corner elements (13) and the side walls (5,6), in order to produce the surface melting and mutual adhesion of the end portions (5a,6a) of the side walls and of the sides (14) of the corner elements (13).

Description

[0001] The present invention relates to an apparatus for producing crate-like containers made of synthetic material.

[0002] Such crate-like containers, used particularly to carry and store foodstuffs, are constituted by a sheet of synthetic material in which die-cutting and folding lines form a bottom, two front walls and two side walls. The front walls are extended laterally, at opposite ends, generally by means of three flaps, which are meant to be folded so as to form two tubular comer elements that allow connection to the side walls in order to form the container.

[0003] Crate-like containers made of synthetic material of the described type are generally produced with apparatuses that fold the walls and flaps and connect one another the comer elements and the side walls by applying adhesive.

[0004] However, these connections can often be weak and unreliable, since the side walls, mainly due to the weight of the content of the crates and to their storage and handling during transport, tend to separate easily from the comers elements.

[0005] The aim of the present invention is to provide an apparatus for producing crate-like containers made of synthetic material that is capable of connecting one another the side walls and the comer elements of the container by mutual thermal bonding of the surfaces in contact.

[0006] Within this aim, an object of the present invention is to provide an apparatus that allows to perform the thermal bonding of the side walls and comer elements of the container by simultaneous surface heating up to melting point.

[0007] Another object of the present invention is to provide an apparatus that can heat the side walls and the comer elements rapidly and reliably.

[0008] Another object of the present invention is to provide a structure that is simple, relatively easy to provide in practice, safe in use, effective in operation and relatively low in cost.

[0009] This aim and these and other objects are achieved by the present apparatus for producing crate-like containers made of synthetic material constituted by a sheet in which die-cutting and folding lines form a bottom, two side walls and two front walls that are extended laterally at opposite ends by means of a first flap, a complementary flap and an end flap that can be folded in a tube-like fashion so as to form four corner elements, which can be connected on the respective sides to respective end portions of said side walls, forming a substantially box-like structure that is open at the top, said apparatus comprising a first station and a second station which are connected by a sliding surface, said first station comprising a plurality of lateral units for folding said complementary flaps and said end flaps and means for the adhesion of said end flaps against said front walls in order to form said comer elements, said second station comprising a rectangular recess for the forming of said containers, a pusher that can be actuated from an inactive upper position to a lower position for insertion in said recess for the folding of said front walls and side walls in order to form said container, means for fixing said sides of said comer elements onto said end portions of said side walls, characterized in that said fixing means are constituted by thermal bonding elements that comprise a plurality of thermal bonding laminas that are located at the edges of said recess and are associated with actuation elements that are suitable to guide said thermal bonding laminas from a retracted position to a protruding position, in which they are interposed temporarily between said comer elements and said side walls, in order to produce the surface melting and mutual adhesion of said end portions of said side walls and of said sides of said comer elements.

[0010] Further characteristics and advantages will become better apparent from the detailed description of a preferred but not exclusive embodiment of an apparatus for forming crate-like container made of synthetic material according to the invention, illustrated by way of non-limitative example in the accompanying drawings, therein:

Figure 1 is a perspective view of the crate-like container in the several steps of its folding;

Figure 2 is a perspective view of the first station of the apparatus;

Figure 3 is a perspective view of the first station of the apparatus, in which there is a sheet on which the end flaps are fixed to the front walls;

Figures 4 and 4a are perspective views of details of the first station of the apparatus;

Figure 5 is a perspective view of the second station of the apparatus with a sheet about to be pressed by the pusher;

Figure 6 is a perspective view of the recess according to the invention;

Figure 7 is a perspective view of the means for fixing the side walls on the comer elements according to the invention;

Figure 8 is a perspective view of a detail of the second station of the apparatus;

Figure 9 is a perspective view of the pusher according to the invention;

Figure 10 is a perspective view of a detail of the pusher according to the invention.

[0011] With particular reference to Figure 1, the reference numeral 1 generally designates a sheet of synthetic material, in which die-cutting and folding lines form a bottom 2, two front walls 3 and 4 and two side walls 5 and 6, in which there are respective end portions 5a and 6a. Each one of the front walls 3 and 4 is extended laterally at opposite ends by means of a first flap 7, a complementary flap 8, and an end flap 9, which are formed by creases 10, 11 and 12. The first flap 7, the complementary flap 8 and the end flap 9, folded along the creases 10, 11 and 12, form a respective tubular comer element, generally designated by the reference numeral 13, that is provided with a corresponding side 14. In particular, each one of said end walls 9 is fixed by way of thermal bonding spots 15 to the respective front wall 3 or 4.

[0012] The front walls 3 and 4 are further extended in a longitudinal direction with respective narrower tabs 16 formed by upper creases 17. Each tab 16 is further extended laterally, at opposite ends, by means of respective wings 18 formed by lateral creases 19. The tabs 16 are folded parallel to the bottom 2, and the wings 18 are folded onto the side walls 5 and 6 and are fixed thereto, completing the forming of the container.

[0013] The apparatus for producing the containers comprises a first station 20 and a second station 21, which are crossed in succession by the sheets on a sliding surface 22. Said surface, which is considerably longer than it is wide, defines the advancement direction of the sheets. The sliding surface 22 is provided with respective shoulders 22a for the abutment of the sheets and with bands 22b that are parallel and arranged symmetrically in order to support in a vertical position the first flap 7, the complementary flap 8, and the end flap 9.

[0014] The first station 20 (Figures 2, 3, 4, 4a) comprises four lateral folding units 23, which are arranged like the comers of a rectangle and are supported by a framework 24 and are suitable to act on the respective flaps 7, complementary flaps 8 and end flaps 9 in order to fold them so as to obtain the tubular corner elements 13. Each one of the folding units 23 comprises a profiled element 25 that has a substantially C-shaped transverse cross-section and is arranged at an angle to the vertical. The profiled elements 25 face each other in pairs with their respective concavities and have opposite inclinations, converging toward the longitudinal axis of symmetry of the sliding surface 22; respective upper and lower ends 26 and 27 are formed thereon. On the side walls 28 of each profiled element 25 there is a respective pair of coaxial upper holes 29, located at the upper end 26, and a respective pair of coaxial lower holes 30, located at the lower end 27.

[0015] A pneumatic linear actuator 31 of a known type is pivoted in the pair of upper holes 29 at the end that is not provided with the stem; said linear actuator is provided with a corresponding stem 32 that ends with a head 33. A substantially L-shaped linkage element 34 is pivoted in the pair of lower holes 30 and is extended by an elongated strip 35 that is perpendicular thereto. The linkage element 34 has, proximate to the strip 35, a hub 36 that is articulated to the head 33 of the pneumatic linear actuator 31. The linkage element 34 can therefore be actuated by the actuator 31 so as to rotate about the axis of the pair of lower holes 30 from an upper parking position to a lower position for folding by means of the action of the strip 35 on the complementary flap 8.

[0016] The folding units 23 are completed by supporting rods 37, which are curved and rigidly coupled at right angles to the profiled elements 25 proximate to the lower pairs of holes 30 and are suitable to support the end flaps 9 of the sheets in a vertical position if they are large.

[0017] The first station 20 comprises a device, generally designated by the reference numeral 38, for contrasting the execution of the fold; said device is suitable to keep the first flap 7 in a vertical position when the fold is formed on the complementary flap 8 by the strip 35 of the linkage element 34. The device 38 is constituted by a post 39, which is supported vertically by the framework 24 and on which a pneumatic piston 40 is articulated at one end, said piston being provided with a corresponding stem 40a. The post 39 is provided, in a downward region, with a protrusion 41 that is shaped substantially like a parallelepiped; a substantially triangular plate 42 is pivoted to the protrusion 41 at a first comer, to the stem 40a of the piston 40 at a second comer, and a third corner is rigidly coupled to a flat elongated bar 43, which protrudes at right angles to the post 39. The plate can be guided by the piston 40 so as to rotate from a raised position to a position in which it rests against the first flap 7.

[0018] The first station 20 further comprises means, generally designated by the reference numeral 44, for the adhesion of the end flaps 9 to the front walls 3 and 4. Said means comprise four jacks 45, which are rigidly coupled to the framework 24 and are arranged vertically like the comers of a rectangle, with respective stems 45a directed toward the sliding surface 20. Each stem 45a is provided with a rigidly coupled parallelepipedal box-like body 46, which comprises two thermal bonding elements 47, constituted for example by sonotrodes, which are constituted by cylinders 48 that are extended by tangs 49 and are suitable to compress each end flap 9 in order to provide thermal bonding spots between said end flaps and the front walls 3 and 4. The tangs 49 therefore can be actuated, by virtue of the jacks 45, from an inactive upper position to a lower position for the thermal bonding of the end flaps on the front walls.

[0019] The second station 21 (Figures 5, 6, 7, 8, 9 and 10) comprises a rectangular recess for forming the containers, which is generally designated by the reference numeral 50 (see Figure 6) and is formed on the sliding surface 22. Above the recess there is a pusher 51 (see Figure 9), which can be actuated so as to perform a vertical translational motion from an inactive upper position, which is raised with respect to the sliding surface 22 in order to allow to position the sheets on the recess 50, to a lower position for insertion in said recess in order to fold the front walls 3 and 4 and the side walls 5 and 6 of the sheets, providing the substantially box-like upwardly open configuration of said containers. The recess 50 comprises means 52 for fixing the side walls 5 and 6 to the comer elements 13, devices 53 for compressing the side walls on said comer elements in order to provide a permanent connection between them, and two mutually opposite front folding units 54 for the tabs 16.

[0020] The recess 50 comprises a first bar 55 and a second bar 56, which are horizontal, parallel and arranged longitudinally with respect to the sliding surface 22, with axes that are arranged substantially at the level determined by said sliding surface, which is interrupted at the ends of said bars. The distance in a transverse direction between the first bar 55 and the second bar 56 constitutes the maximum width that can be attained by the recess. Two mutually opposite frameworks 57 are engaged slidingly on first bar 55 and on the second bar 56, transversely to the sliding surface 20, and delimit the recess 50 lengthwise. Each framework is constituted by two uprights 58 and 59, an upper cross-member 60 and a lower cross-member 61, which form a substantially frame-like structure. The uprights 58 and 59 are associated with respective female threads 62 and 63, which are coupled respectively to a first screw 64 and to a second screw 65, with axes that are parallel to those of the first bar 55 and of the second bar 56, and can be actuated by a motion transmission system. Said screws are suitable to vary the relative distance between the frameworks 57 so as to adapt the length of the recess 50 to the changing dimensions of the sheets.

[0021] Two rectangular lower plates 66 can slide freely on each one of the lower cross-members 61 transversely to the sliding surface 22. The lower plates 66 have respective female threads 67, which are mutually coaxial in pairs and have opposite threads. A threaded bar 68 engages therein and is rotatably supported on the lower cross-member 61 and actuated by motion transmission elements. The threaded bar 68 is suitable to vary the width of the recess according to the changing dimensions of the sheets: the lower plates 66 can in fact be actuated so as to slide toward or away from each other, and their relative distance constitutes the width of the recess 50. Each lower plate 66 is rigidly coupled to a respective bracket 69, which is rigidly coupled to a vertical wall 70 that is substantially trapezoidal; the respective longer parallel sides of said walls face each other in pairs. Each vertical wall 70, moreover, is connected to a fixed upper wall 71, which is perpendicular to said vertical wall and lies on an inclined plane. The inclination of the upper wall 71 is suitable to fold the side walls 5 and 6 of the sheet. The set of four upper walls 71 in fact constitutes a sort of hopper on which the side walls 5 and 6 of the sheet are meant to slide in its descent on the part of the pusher 51.

[0022] Each one of the vertical walls 70 is connected, on the outer face with respect to the recess 50, to the respective device 53 for compressing the side walls 5 and 6 on the comer elements 13. The device comprises a comer support 72, on which a respective external piston 73 is articulated; the axis of action of said piston is parallel to said vertical wall. The respective stem of said external piston 73 is in turn articulated to a movable lower wall 74, which is arranged substantially at right angles to the axis of action of said piston and therefore constitutes a downward extension of the fixed upper wall 71. Each movable lower wall 74, provided with a protrusion 74a that is pivoted to the vertical wall 70 about the axis 74b, can be actuated by the piston 73 so as to rotate about said axis 74b, and is suitable to compress the end portions 5a, 6a of the side walls 5 and 6 of the sheet 1 onto the corresponding corner elements 13, so as to achieve effective thermal bonding.

[0023] On the face of the vertical wall that lies inside the recess there are means for stopping the bottom 2 of the sheet. The stop means are constituted by an enclosure 75 that is fixed to the face of the vertical wall that lies inside the recess and contains a tooth 76; said tooth can be guided horizontally from a position that lies inside the enclosure 75 to an external position in which it constitutes an abutment for the bottom 2 of the sheet; it is in fact connected to the stem of a respective internal jack 77, whose axis of action is parallel to the vertical wall 70.

[0024] Each one of the two frameworks 57 comprises two vertically arranged beams 78 that have a flattened rectangular cross-section and face each other with their larger lateral surfaces and protrude from the lower cross-member 61 substantially at the centerline. The beams 78 constitute a vertical guide for each front folding unit 54. The front folding unit comprises a carriage 79, which can slide along the beams 78 and can be positioned according to the dimensions of the sheet. The carriage 79 is constituted by two substantially quadrangular plates 80 that are arranged externally with respect to the beams 78 on mutually opposite sides and are connected, externally with respect to the recess 50, by a box 81. Said box is substantially shaped like a parallelepiped with an inclined bottom: a central jack 82 is fixed to said bottom and its stem is consequently inclined with respect to the horizontal plane and passes through the beams 78. A pivot 83 is rotatably supported on the plates 80 at the opposite end with respect to the box 81, has a horizontal axis and passes through both of said plates. A pinion is keyed on the pivot 83, is coupled to a rack that is fixed to the stem of the central jack 82, and is associated in an upward region with a contrast roller. The portions of the pivot 83 that protrude, on opposite sides, from the plates 80 have respective arms 84 keyed to them, and respective strips 85 are rigidly coupled to them at right angles; said strips have a substantially L-shaped transverse cross-section and lie horizontally in opposite directions. The strips 85 can be actuated so as to rotate about the axis of the pivot 83 and according to the internal and external stroke limits of the central jack 82 from a raised position to a lowered position that is suitable to fold the tabs 16 of the sheet.

[0025] Two rods 86 are rigidly coupled on each upper cross-member 60, in positions that are substantially symmetrical with respect to the centerline and are longitudinally adjustable; said rods are elongated vertically within the recess 50 and are suitable to fold the wings 18 of the sheet. Moreover, each upper cross-member 60 supports additional auxiliary rods 87, which are elongated vertically inside the recess 50 and provide contrast to the front walls 3 and 4 of the sheet while folding them.

[0026] Each one of the lower plates 66 supports means, designated by the reference numeral 52, for fixing the side walls 5 and 6 to the corner elements 13. Said fixing means comprise an elongated block 88 that is rigidly coupled to the lower plate 66 and runs parallel to the lower cross-member 61, on which a rectangular upper plate 89 is arranged. Elements 91 for actuating the fixing means 52 are supported rotatably on said plate about a first pivot 90 that has a vertical axis, passes through the upper plate 89 and is associated with a locking ring 90a; said elements comprise a substantially rectangular foot 91a that can rotate freely on the horizontal plane. The foot 91a rotatably supports a second pivot 92, whose axis is horizontal and transverse with respect to the block 88. An L-shaped element 93, constituted by a base 93a and a shoulder 93b that is perpendicular thereto, acts as support for a pneumatic slider 94 whose axis of action is perpendicular to the lower cross-member 61, is articulated to the first pivot 92 along the edge formed by said base and said shoulder. The base 93a further has a hole 93c that has a vertical axis. A support 95 for thermal bonding elements 96 is fixed to the plate 94a of the pneumatic slider 94; said thermal bonding elements are constituted by a pair of heating resistors 96a, which are connected on opposite sides to a thermal bonding lamina 97 that is interposed between them and is suitable to provide the surface melting, by contact, of the corner elements 13 and of the end portions 5a and 6a of the side walls 5 and 6 of the sheets. A thermally insulating plate 98 is interposed between the pneumatic slider 94 and the support 95 of the heating resistors 96a and is suitable to prevent the transmission of heat toward said lateral jack.

[0027] Furthermore, in the fixing means 52 there is a first spring 99 and a second spring 100; said springs act in contrast with the rotation of, respectively, the foot 91a about the first pivot 90 ad of the L-shaped element 93 about the second pivot 92. In particular, the first spring 99 is engaged, at one end, to a first horizontal spring post 101 provided on the upper plate 89 and, at the other end, to a second horizontal spring post 102 that is rigidly coupled to the foot 91. The second spring 100 is engaged, at one end, to a first vertical spring post 103, which is arranged on the foot 91a at right angles to the second horizontal spring post 102, and is engaged, at its other end, to a second vertical spring post 104, which is provided on the L-shaped element 93. In this manner, the thermal bonding lamina 97 can wedge itself easily between the side walls 3 and 4 and the comer elements 13.

[0028] The fixing means 52 furthermore comprise a horizontal stroke limiter, composed of a vertical rib 105, which is rigidly coupled in a downward region with respect to the foot 91a along the side that faces the outside of the recess 50, and on which there is a slot 105a, in which a screw 106 is engaged, constituting a stop element for the rotation of said foot 91a about the first pivot 90; a nut 107 locked on a screw 107a, which is engaged in the hole 93c, instead constitutes a vertical stroke limiter, preventing the rotation of the L-shaped element 93 about the second pivot 92 from extending beyond an adjustable limit.

[0029] The pusher 51 is supported by a supporting structure 108 that is constituted by two posts 109 that are connected by a beam 110 that transversely surmounts the sliding surface 22. A support 111 is fixed on the beam 110, substantially at the centerline, has a flattened rectangular cross-section and has, on a lateral surface, a step 112 by virtue of which it engages said beam. The step 112 accordingly separates an upper thicker portion 112a from a lower thinner portion 112b; moreover, the support has a front face 113 and a rear face 114, relative to the advancement direction of the sheets 1 on the sliding surface 22.

[0030] A gearmotor 115 is rigidly coupled to the rear face 114 of the support 111 and its output shaft is perpendicular to the support and passes through it. A crank 116 is keyed at one end on said output shaft, with an end that protrudes from the front face 113 of the support 111, and can be actuated so as to rotate alternatively between two extreme angular positions about the axis of the output shaft of the gearmotor 115. At the opposite end, the crank 116 has a cylindrical tab that forms substantially an upper pivot 117, whose axis is perpendicular thereto and parallel to the sheet advancement direction. The support 111 has, on opposite sides, two pairs of guiding bearings 118 for an elongated slider 119, below which the head of the pusher, generally designated by the reference numeral 120, is rigidly coupled. The slider 119 has, substantially proximate to the head 120, a protrusion that forms a lower pivot 121 whose axis is parallel to the upper pivot 117. A linkage 122 is articulated, at its opposite ends, respectively to the upper pivot 117 and to the lower pivot 121 and is suitable to convert the alternating rotary motion of the crank 116 into an alternating rectilinear motion of the slider 119 from an inactive upper position to a lower position for insertion in the recess 50.

[0031] The head of the pusher 120 comprises a rectangular shoe 123 that substantially has the same dimensions as the bottom 2 of the sheet 1 and is rigidly connected, for example by welding, to the slider 119. Two fixing elements 124 for respective pistons with multiple stems 125 are arranged on the shoe 123. Each fixing element 124 has substantially the shape of a plate that is folded at right angles and has a respective horizontal tab 126 and a vertical tab 127; said fixing element is fixed to the shoe 123 by means of bolts 128. The respective piston 125 is rigidly coupled, by virtue of its rear end, to each vertical tab 127 and therefore its stems 129 are directed toward the outside of the shoe 123.

[0032] The stems 129 of the respective piston 125, provided with connecting plates 130, are fixed to respective contrast walls 131, which are suitable to constitute, when the pusher is in the lower position, an abutment for the corner elements 13, from the inside outward, in order to achieve their thermal bonding with the side walls 5 and 6 of the sheet. Each contrast wall 131 comprises a panel 132, which is elongated parallel to the shorter side of the shoe 123 and has, at its opposite ends, respective lugs 133 that protrude horizontally toward the centerline of said shoe. At the opposite ends of the panel 132 there are also respective horizontal slots 134 for adjusting respective comers 135 that are fixed thereto by means of peripheral screws 136; the corners 135 are substantially V-shaped, with the concavity directed toward the center of the shoe 123.

[0033] The operation of the apparatus according to the invention is as follows: each sheet moves on the sliding surface 22, being guided by the shoulders 22a. The first flaps 7, the complementary flaps 8 and the end flaps 9, folded earlier along the creases 10, are in a vertical position and are initially mutually co-planar and supported by the bands 22b. Upon arriving at the first station 20, the sheet undergoes the action of the lateral folding units 23, which induce the complementary flap 8 and the end flap 9 to fold along the creases 11 and 12, forming the tubular corner elements 13. In particular, the pneumatic actuator 31 induces the linkage element 34 to rotate about the axis formed by the two lower holes 27, moving from the upper parking position to the lower position for performing the fold; the strips 35 engage on the complementary flaps 8, making the end flaps 9 adhere to the front walls 3 and 4. Then the tangs 49 of the fixing means 44 are guided, by virtue of the jacks 45, so as to move vertically from the inactive upper position to the lower position for the thermal bonding of the end flaps to the front walls, completing the production of the tubular corner elements 13.

[0034] The sheet then moves to the second station 21, placing itself and stopping above the recess 50. The gearmotor 115 actuates the crank 116 so that it performs an angular stroke about the output shaft of said gearmotor; the linkage 122 transmits the motion to the slider 119, which induces the shoe 123 to reach the lower position for insertion in the recess 50, drawing down the sheet 1. The side walls 5 and 6 of the sheet slide on the upper walls 71, while the front walls 3 and 4 slide on the respective auxiliary rods 87; at the same time, the wings 18 slide along the rods 86, folding along the creases 19. When the lower stroke limit of the pusher 51 is reached, the means for stopping the bottom 2 of the sheet intervene: in particular, the teeth 76 are actuated by the respective jacks 77 so as to perform a translational motion from the internal position to the external position, and said bottom rests thereon.

[0035] At this point, the strips 85 rotate about the axis of the pivot 83 by means of the respective central jack 82; the strips 85 engage respective flaps 16, which are folded along the upper creases 17, arranging themselves parallel to the bottom 2 of the sheet.

[0036] Then the pistons with multiple stems 125 actuate the contrast walls 132 so that they move outward in opposite directions, moving the corners 135 into abutment against the corner elements 13.

[0037] This step is followed by the step for fixing the side walls 5 and 6 to the sides 14 of the corner elements 13 by means of the thermal bonding laminas 97, which are heated appropriately by the heating resistors 96a and are pushed by the respective pneumatic sliders 94 so that they wedge themselves between the walls and said comer elements. The lamina 97 is free to perform small rotations, which are contrasted by the first spring 99 and by the second spring 100 and are limited by the respective stroke limiters, about the axes of the first pivot 90 and of the second pivot 92, and can move therefore, in its advancement stroke, as a function of the possible obstacles provided by the positions of the side walls 5 and 6 and of the corner elements 13.

[0038] When the laminas 97 are interposed between the corner elements 13 and the side walls 5 and 6, the compression devices 53 act and place, by virtue of the thrust of the outer pistons 73 on the respective movable lower walls 74, said side walls into contact with the surfaces of the laminas 97, so as to reach a surface melting condition both on the walls and on the comer elements 13.

[0039] After surface melting has occurred, the compression devices 53 actuated by the outer pistons 73 retract toward the outside of the recess 50, allowing the laminas 97, actuated by the respective pneumatic sliders 94, to retract.

[0040] The compression devices 53 are then actuated again, with a greater delivery pressure on the outer pistons 73, in order to compact the side walls 5 and 6 and the wings 18 on the comer elements 13, providing their mutual thermal bonding.

[0041] At this point, the strips 85 perform a retrograde rotation and the panels 132 retract inward, then the pusher 51 rises vertically. Finally, the sheet leaves the recess 50 by virtue of the retraction of the teeth 76, actuated by the respective jacks 77.

[0042] The apparatus thus conceived is capable of performing the effective mutual thermal bonding of the end portions 5a, 6a of the side walls 5 and 6 and of the sides 14 of the tubular corner elements 13, particularly because the thermal bonding laminas 97 can rotate freely about the axes of the first pivot 90 and of the second pivot 92. Furthermore, the compression devices 53 that press from the outside and the contrast walls 131 on the pusher 51 that press from the inside allow safe and reliable mutual adhesion of the regions subjected to surface melting.

[0043] It has thus been shown that the invention achieves the intended aim and objects.

[0044] The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept.

[0045] All the details may further be replaced with other technically equivalent ones.

[0046] In practice, the materials used, as well as the shapes and the dimensions, may be any according to requirements without thereby abandoning the scope of the protection of the appended claims.

[0047] The disclosures in Italian Patent Application No. BO2001A000614 from which this application claims priority are incorporated herein by reference.

[0048] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims

1. An apparatus for producing crate-like containers made of synthetic material constituted by a sheet in which die-cutting and folding lines form a bottom (2), two side walls (5, 6) and two front walls (3, 4) that are extended laterally at opposite ends by means of a first flap (7), a complementary flap (8) and an end flap (9) that can be folded in a tube-like fashion so as to form four corner elements (13), which can be connected on the respective sides (14) to respective end portions (5a, 6a) of said side walls (5, 6), forming a substantially box-like structure that is open at the top, said apparatus comprising a first station (20) and a second station (21) which are connected by a sliding surface (22), said first station (20) comprising a plurality of lateral units (23) for folding said complementary flaps (8) and said end flaps (9) and means (44) for the adhesion of said end flaps (9) against said front walls (3, 4) in order to form said corner elements (13), said second station (21) comprising a rectangular recess (50) for the forming of said containers, a pusher (51) that can be actuated from an inactive upper position to a lower position for insertion in said recess (50) for the folding of said front walls (3, 4) and side walls (5, 6) in order to form said container, means (52) for fixing said sides (14) of said corner elements (13) onto said end portions (5a, 6a) of said side walls (5, 6), characterized in that said fixing means are constituted by thermal bonding elements (96) that comprise a plurality of thermal bonding laminas (97) that are located at the edges of said recess (50) and are associated with actuation elements (91) that are suitable to guide said thermal bonding laminas (97) from a retracted position to a protruding position, in which they are interposed temporarily between said comer elements (13) and said side walls (5, 6), in order to produce the surface melting and mutual adhesion of said end portions (5a, 6a) of said side walls and of said sides (14) of said corner elements (13).

2. The apparatus according to claim 1, characterized in that the longer sides of said recess (50) are constituted by respective frameworks (57) that comprise two uprights (58, 59), an upper cross-member (60) and a lower cross-member (61), which form two substantially frame-like structures, and in that said thermal bonding laminas (97) are associated with respective lower plates (66) that can be fixed in adjustable positions along the two ends of said two lower cross-members (61).

3. The apparatus according to claims 1 and 2, characterized in that a block (88) is fixed onto each one of said lower plates (66) and is surmounted by a respective upper plate (89), on which said actuation elements (91) are rotatably engaged, said actuation elements being constituted by a foot (91a) that can rotate freely about the vertical axis of a respective first pivot (90) that is rigidly coupled to said upper plate (89) and supports a pneumatic slider (94), to the plate (94a) of which said thermal bonding lamina (97) is rigidly coupled.

4. The apparatus according to claim 3, characterized in that said thermal bonding lamina (97) is interposed between two heating resistors (96a), which are supported by a support (95) that is rigidly coupled to said plate (94a) of said pneumatic slider (94), said support (95) being rigidly coupled to a thermally insulating plate (98) that is suitable to prevent the transmission of heat toward said pneumatic slider (94).

5. The apparatus according to claim 3, characterized in that said pneumatic slider (94) is fixed on an L-shaped element (93) that is rotatably supported by a second pivot (92) that has a horizontal axis and is rigidly coupled to said foot (91a), the rotation of said foot (91a) about the axis of said first pivot (90) being contrasted by a first spring (99) that is engaged respectively with one end to a first horizontal spring post (101) provided on said upper plate (89) and with the other end to a second horizontal spring post (102) that is rigidly coupled to said foot (91a), the rotation of said L-shaped element (93) about the axis of said second pivot (92) being contrasted by a second spring (100), which is engaged respectively with one end to a first vertical spring post (103) provided on said foot (91a) at right angles to said second horizontal spring post (102) and with the other end to a second vertical spring post (104) that is rigidly coupled to said L-shaped element (93), so as to allow said thermal bonding laminas (97) to wedge themselves freely between said side walls (5, 6) and said corner elements (13).

6. The apparatus according to claim 1, characterized in that said pusher (51) comprises a shoe (123) that presses on said bottom (2) of said sheet and is provided with two mutually opposite contrast walls (131), each of which comprises a panel (132) that is arranged vertically and parallel to the shorter sides of said shoe (123) and is provided, at its ends, with two corners (135) that are suitable to apply pressure to said corner elements (13), said panels (132) being associated with respective pistons with multiple stems (125) that are arranged horizontally and are suitable to move them outward in opposite directions parallel to the longer sides of said shoe (123).

7. The apparatus according to claim 2, characterized in that a respective bracket (69) is connected to each one of said lower plates (66) and is extended by a vertical wall (70) that supports a respective device (53) for the compression of said end portions (5a, 6a) of said side walls (5, 6) on said sides (14) of said corner elements (13), said device (53) comprising an outer piston (73), to the stem of which a respective movable lower wall (74) is articulated, said wall being guided by said outer piston (73) so as to rotate about a respective axis (74b) for articulation to said vertical wall (70) and being suitable to compress said end portion (5a, 6a) of said side wall onto the corresponding corner element (13).

Drawing