Device for securing a tubular heating body coaxially around a nozzle of a mould for injection moulding

The present invention relates to a device for securing a tubular heating body, which in particular is shaped in the form of a helical tube, coaxially around a nozzle of a mould for injection moulding.

In greater detail, a device of this type comprises: a strip wrapper wound around a longitudinal axis such that the inner surface of a first end edge is secured to the outer surface of a portion of the wrapper which is adjacent to a second end edge, which second edge separates a first volume, which is designed to accommodate the said heating body and the said nozzle, from a second volume which is closed by the said second edge and by a portion of the wrapper which is adjacent to the first edge; and clamping means which are located in the said second volume, and can exert a clamping force in a radial direction on the said second end edge of the wrapper.

Document DE-38 01 831 describes a securing device of the above-described type, wherein the clamping means comprise an eccentric unit which can rotate around an axis which is parallel to the longitudinal axis of winding of the wrapper. When this unit is rotated progressively in one direction, there is a gradual increase in the force which is exerted on the second end edge of the wrapper, thus compressing the tubular heating body further around the nozzle, such as to secure it around the latter.

However, a device of this type is subject to the risk of loosening, which detracts from the firmness of securing of the heating body to the nozzle.

In order to eliminate the above-described disadvantage, the subject of the present invention consists of a securing device of the type indicated at the beginning of the present description and characterized in that the portion of wrapper which is adjacent to the first edge has a projection which protrudes radially into the distal portion of the second volume, and extends in a circumferential direction, and in that the said clamping means comprise a screw, as well as a first and a second element which are disposed in the said second volume on opposite sides in relation to the projection, the said screw having a head and a threaded rod, the first element having a non-threaded through aperture, and the second element having a threaded through aperture, the said apertures being aligned and oriented parallel to the said longitudinal axis, the distal portion of the threaded rod of the screw being engaged in the said second threaded aperture, and the proximal portion of the threaded rod of the screw passing freely through the said first aperture.

When the screw is screwed into the threaded aperture, the two elements tend to draw closer to one another and are thus compressed by the projection, beneath which they are forced to be inserted. Consequently, they exert a force in a radial direction on the second end edge of the wrapper beneath. This force increases as the depth of screwing of the screw increases, and secures the heating body firmly and durably around the nozzle, since the resistance to loosening of securing of this type is guaranteed by the connection which

exists between the rod of the screw and the threaded aperture .

Other advantages and features of the present invention will become clear from the following detailed description which is given with reference to the appended drawings which are provided purely by way of non-limiting example and in which: figure 1 is a front view of a device according to the invention wound around a heating body and a nozzle; figure 2 is a lateral view of the device in figure 1 ; figure 3 is a view in lateral cross-section according to the line III-III in figure 1; and figure 4 is a plan view of the wrapper extending on the plane of the device in the preceding figures.

A device for securing a tubular heating body 10, which in particular is shaped in the form of a helical tube, coaxially around a nozzle 12 of a mould for injection moulding, comprises a strip wrapper 14. The latter is wound around a longitudinal axis 16, such that the inner surface of a first end edge 18 is secured to the outer surface of a portion 20 of the wrapper which is adjacent to a second end edge 22, which separates a first volume 24, which accommodates the heating body 10 and the nozzle 12, from a second volume 26 which is closed by the second edge 22 and by the portion 28 of the wrapper 14 which is adjacent to the first edge 18. The inner surface of the first end edge 18 is secured by means of welding spots 30 to the outer surface of the portion 20 of the wrapper 14 which is adjacent to the second end edge 22.

The first volume 24 has a substantially circular transverse cross-section, whereas the second volume 26 has a transverse cross-section which tapers, in an approximately triangular-

trapezoidal form, going towards its distal portion, this being understood as the portion which is furthest from the longitudinal axis 16.

The portion 28 of the wrapper 14 which is adjacent to the first edge 18 has a projection 32 which protrudes radially into the distal portion of the second volume 26, and extends in a circumferential direction. The projection 32 is produced in the form of an indentation which makes the corresponding surface of the wrapper 14 become indented. In embodiments of the invention which are not illustrated, this projection 32 could also consist of a part which is distinct from the wrapper 14 and is secured to the inner surface of the latter.

In the second volume 26 there are located clamping means which can exert a clamping force in the radial direction (see the arrows 34 in figure 3) on the second end edge 22 of the wrapper 14. These clamping means comprise a screw 36 as well as a first and second element 38, 40 which consist of respective pieces of reinforcing rod, and are disposed in the second volume 26, on opposite sides relative to the projection 32. The screw 36 has a head 42 with a manoeuvring cavity 44, which for example has a linear or hexagonal shape, and a threaded rod 46. The first element 38 has a non- threaded through aperture 48 and the second element 40 has a threaded through aperture 50. The apertures 48, 50 are aligned and oriented parallel to the longitudinal axis 16 around which the wrapper 14 is wound. The distal portion of the threaded rod 46 of the screw 36 is engaged in the second threaded aperture 50, whereas the proximal portion of this rod 46 passes freely through the first aperture 48. The head 42 of the screw 36 is accommodated in a hollow seat 52 which is provided in the first element 38.

The passage of the rod 46 through the aperture 48 and even partial screwing of the rod into the aperture 50, together with the interposition of the projection 32 between the two elements 38, 40, prevent the latter from being extracted in the axial direction by the wrapper 14. Consequently, the device according to the invention does not involve the presence of specific units for retention of the clamping means, unlike the device described in the prior document DE- 38 01 831 already cited. In fact, this known device comprises suitable retention units which consist of tongues which project in a radial direction from the general plane of the wrapper, into the portion adjacent to the clamping cam. From this point of view, the structure of the device according to the present invention is therefore simplified in comparison with that of the known device, and therefore makes it possible to reduce substantially the corresponding production costs .

In use, the wrapper 14 is wound around the heating body 10 and the nozzle 12, which are thus disposed coaxially in the first volume 24. When the head 42 of the screw 36 is rotated, the rod 46 is wound deeply into the second threaded aperture 50, and draws closer to one another the first and the second elements 38, 40 which are located in the second volume 26. The movement of bringing closer to one another (see the arrows 56 in figure 3) the elements 38, 40 is opposed by the protruding projection 32, beneath which they are forced to be inserted and compressed. Consequently, the elements 38, 40 exert a force in a radial direction 34 on the second end edge 22 of the wrapper 14, which in turn compresses the heating body 10 and the nozzle 12, thus guaranteeing the securing.

On the other hand, when the head 42 of the screw 36 is rotated in the opposite direction, this gives rise to moving apart of the elements 38, 40, with consequent elimination of the clamping force in the radial direction. Thus, it is possible to disengage the wrapper 14 from the heating body 10 and the nozzle 12, which can therefore be separated when required, without running the risk of accidental loosening occurring .

Naturally, the principle of the invention remaining the same, the forms of embodiment and details of construction may be varied widely with respect to those described and illustrated, which have been given purely by way of example, without thereby departing from the scope of the invention.