Tube with rectangular cross-section

Abstract: A plastics tube produced by blow moulding has a main section (1) with an essentially constant cross-section over its length, which is formed by an even number of level wall sections (2, 3, 4, 5) whose wall sections (2, 4; 3, 5) located opposite to each other each has the same width. At the front end of the main section there is a tubular opening section (15) with a smaller diameter than that of the main section (1). At the rear end the main section (1) converges to an essentially straight end edge (11) which lies in a plane extending through the central longitudinal axis of the main section (1) and which joins two longitudinal edges of the main section (1), the end edge (11) lying within the enveloping curve of the outer surfaces of the walls (2, 3, 4, 5) of the main section (1).

Description: The invention relates to a plastics tube produced by blow moulding and having a main section with an essentially constant cross-section over its length, at the front end of which there is a tubular opening section with a smaller diameter than the main section and which converges at the rear end to an essentially straight end edge, the end edge lying in a plane which extends through the central longitudinal axis of the main section and within the enveloping curve of the outer surface of the walls of the main section. Such plastics tubes are known for example for skin creams and the like. The main section of these has an oval or somewhat circular cross-section and can be relatively easily pressed together to thus discharge the contents of the tube through the tubular opening section. A deformation is also possible by pressing together the wall areas which converge to the end edge. These known plastic tubes are packaged for transport and for shop display in single cartons which, on the one hand, have printed on them all sorts of information about the contents of the carton or tube and protect the enclosed plastics tube against damage and, on the other hand, form a shape which allows a large number of plastics tubes to be combined to form a larger package in which the individual cartons can lie flat against one another and thus allow the package, e.g. a surrounding carton, to be filled exactly. Thus, whilst the usual, flat stacking of cartons each containig a tube, within a package leads to simply producible and easily handled packaging which protects the tubes satisfactorily against damage, the need to pack every single tube in a corresponding carton is a considerable cost factor. A further consequence is that the cartons thereby acquired by consumers also lead to disposal problems or to environmental pollution. Another known tube which may have a main section with a rhombic cross-section (FR-A-2 540 073) is produced from a tube-like blank and filled from the open rearward end. Thereafter the rearward end is closed by folding which generates an end edge which due to the pressing together of the rearward end projects laterally beyond the enveloping curve of the outer surface of the main section. In addition the rhombic cross-section of the main section of the tube is disadvantageous for packaging a plurality of tubes in a larger carton. The aim of the invention is to provide a tube which can be pakked well without using a carton which envelopes it and which in particular allows a substantial number of identical tubes to be combined to form a satisfactorily transportable package. To achieve this aim a plastics tube of the initially mentioned type is designed according to the invention so that the main section is formed by four level wall sections with adjacent wall sections forming a right angle in the area of the associated longitudinal edge, that the end edge joins two opposite longitudinal edges of the main section and that to the end edge two planar surfaces extend which are located opposite to each other and have the same shape. Preferably the width of all wall sections can be the same, i.e. the main section has a quadratic cross-section. Thanks to the design according to the invention of the main section of the plastics tube and the fact that the end edge does not project beyond the enveloping curve formed by the planes of the exteriors of the wall sections of the main section, it is possible to combine several plastics tubes with level or flat wall sections of the same dimensions lying against one another to form a package, so that the plastics tube can be held flat and in a defined position in the package in the same way as prior tube containing cartons. As already mentioned, the end edge of the plastics tube terminates within the enveloping curve of the main section, so that the end edge does not prevent the main sections of the plastics tubes from being placed against one another or their consequent combination to form a package. Furthermore, thanks to the arrangement of the end edge as the connection of two longitudinal edges of the main section, the plastics tube is no longer stabilized, in the area of the taper towards the end edge, by the longitudinal edges formed by adjacent wall sections, but can be easily pressed together by the user in this area tapering towards the end edge, to thus discharge the tube contents through the opening section without expending great effort on the deformation. The plastics tube according to the invention is produced by blow moulding, i.e. a heated tubular blank is inserted into a corresponding mould and then pressed by increased internal pressure against the walls of the mould so that the blank assumes the desired shape in which the end edge does not project beyond the enveloping curve of the main section of the plastic tube. In comparison, the initial step in the manufacture of normal aluminium tubes is to draw a tubular section which has a tubular opening section at the front end and is filled from the open rear end. After filling, the rear end of the tubular section is pressed together and usually folded over, so that an "end edge is formed, which, however, because of the deformation of the tubular cross-section into a straight end projects radially beyond the enveloping curve of the tubular section. The length of the end edge is thus greater than the diameter of the tubular section lying in the same plane which extends through the central longitudinal axis of the tubular section. Precisely this, however, is not the case with the tube according to the invention. Whilst conventional tubes made of aluminium, as mentioned above, are filled from the open rear end and thus a large opening cross-section is available for the filling process, filling of the tube according to the invention, which is closed at the rear end, takes place through the tubular opening cross-section formed at the front end, which also serves to discharge the tube contents. Whilst in general a relatively small opening cross-section is desired for discharging the tube contents, there should be as large as possible an opening cross-section for filling, so that the filling process can be carried out quickly, and the filler devices for filling from the rear end can be used. In order to solve this problem with the plastics tube according to the invention, the opening cross-section of the tubular opening section is designed to be relatively large so that a speedy filling with the existing filling devices can be effected. After filling, a discharge section whose opening cross-section at the free end is smaller than that of the opening section is pressed onto the opening section, so that the contents of the tube are discharged through an area with relatively small opening cross-section. It should be noted that the plastics tube according to the invention can be blow-moulded in one layer or two. With the two-layer version, where the two layers are co-extruded, a flexible, permeable plastics layer is provided on the exterior, whilst the inner layer is formed from a thick, impermeable plastics material; with the single-layer version, the tube wall is formed from a single plastics layer. The invention is further illustrated with reference to the following figures: Figure 1 is a perspective and partly exploded view of a plastics tube. Figure 2 is a diagrammatic and simplified perspective view of the two mould halves for producing a plastics tube according to Figure 1 by the blow moulding process. The plastic tube shown in Figure 1 has a main section 1 which has wall sections 2, 3, 4, 5, which are all the same width and form a quadratic cross-section. The wall sections 2 and 3 are joined to each other by a longitudinal edge 6, wall sections 4 and 5 by a longitudinal edge 8 and wall sections 2 and 5 by a longitudinal edge 9, whereas the wall sections 3 and 4 are joined together by a longitudinal edge which is not shown and is not recognizable in the drawing. At the rear end of the thus formed, tubular main section there is an end edge 11 which joins together the longitudinal edge 9 and the longitudinal edge connecting wall sections 3 and 4 and from which wedge-shaped wall sections extend, of which the wedge-shaped wall section 12 tapers forward, ending at the longitudinal edge 6. A wedge-shaped wall section of the same shape runs from the end edge 11 to the longitudinal edge 8, i.e. it lies opposite the wedge-shaped wall section 12. As can be seen, the length of the end edge 11, which seals the plastics tube at the rear end and which lies in a plane with the central longitudinal axis of the main section 1, is not greater than the distance between the longitudinal edges of the main section 1 connected by it, i.e. the end edge 11 lies within the enveloping curve of the outside surface of the main section 1. At the front end of the main section 1 there is a transverse wall 14 projecting inwards from the wall sections 2, 3, 4, 5, beyond which a tubular opening section 15 projects centrally. A circular rib 16 is formed at the outer face of the opening section 15. A forward-tapering, tubular discharge section 18 is pressed onto the tubular opening section 15 and, with an annular groove on its interior, made to engage with the circular rib 16 of the opening section 15, so that a type of snap connection is formed, which does not come apart in normal use. A sealing cap 19 which can be clamped into the front end of the discharge section 18, is swivellably secured by means of a web (not shown) on the outer edge of the discharge section 18. The plastics tube shown is produced by blow moulding, for which a mould can be used as diagrammatically shown in Figure 2. This mould consists of two identical mould halves 100 and 101, which each have a mould cavity corresponding in shape to the half of the plastics tube which lies to one side of the plane containing the end edge 11. To produce the plastics tube a heated, tubular plastics blank is introduced into the mould and the two mould halves are brought together so that the mould cavity is essentially sealed. Then the pressure in the inside of the mould blank is increased and thus its plastics material is pressed against the mould walls, mould wall 112 forming the wedge-shaped planar surface 12, mould wall 103 wall section 3, mould wall 115 one half of the opening section 15 and recess 116 in the mould wall 115 one half of the circular rib 16. At the lower end of the mould wall 112, the two thus formed wedge-shaped wall sections of the plastics tube are joined together to form a seal, thus producing the end edge 11. The plastics tube produced in this way can be filled through the relatively large opening cross-section of the tubular opening section 15, e.g. with toothpaste. The discharge section 18, likewise made of plastics material and elastically deformable for the purposes of positioning, is subsequently pressed onto the tubular opening section 15 and the sealing cap 19 is brought into the closed position. The tube thus filled can be combined, without an additional carton adapted to it, with identical tubes, say in a larger enclosure carton, to form a package, the level wall sections of adjacent tubes being placed flat against one another so that within the package an arrangement of the plastics tubes is formed which otherwise was only possible by packing each individual tube in a carton. It should be pointed out that the wall sections of the plastics tube can be labelled simultaneously with the shaping in the blow-moulding process, to which end, before introducing the plastics tube into the mould, a label is introduced into the mould cavity which carries the printed information and is securely joined to the tube body during the blowing process. This process is known as IML (in mould labelling).

Claims: A plastics tube produced by blow moulding and having a main section (1) with an essentially constant cross-section over its length, at the front end of which there is a tubular opening section (15) with a smaller diameter than the main section (1) and which converges at the rear end to an essentially straight end edge (11), the end edge (11) lying in a plane which extends through the central longitudinal axis of the main section (1) and within the enveloping curve of the outer surfaces of the walls (2, 3, 4, 5) of the main section (1), characterized in that the main section (1) is formed by four level wall sections (2, 3, 4, 5) with adjacent wall sections (2, 4; 3, 5) forming a right angle in the area of the associated longitudinal edge (6; 8), that the end edge (11) joins two opposite longitudinal edges (9) of the main section (1) and that to the end edge (11) two planar surfaces (12) extend which are located opposite to each other and have the same shape. A plastics tube according to claim 1, characterized in that the width of all wall sections (2, 3, 4, 5) is the same. A plastics tube according to one of claims 1 or 2, characterized in that onto the tubular opening section (15) a discharge section (18) is pressed whose opening diameter at the free end is smaller than that of the opening section (15).

Inventors: PRAHS HARALD, PRAHS, HARALD
Applicants: COLGATE PALMOLIVE CO, COLGATE-PALMOLIVE COMPANY
Application year: 1992
Main classification: B65D35
IPC codes: B29C49, B65D35