EP2718091A1

EP2718091A1 - Clip for stretching a film

Info

Publication number: EP2718091A1
Application number: EP11740958.1A
Authority: EP
Inventors: Gilles DUREY; François TEISSIER
Original assignee: Teissier Technique
Current assignee: Teissier Technique
Priority date: 2011-06-10
Filing date: 2011-06-10
Publication date: 2014-04-16
Also published as: WO2012168566A1; CN103687714A

Abstract

The supporting clip according to the invention comprises a main clip body (7) having an inner side flange (7a) rigidly connected to a top transverse flange (7b) that has top rollers (9, 11, 12) capable of rolling on the surfaces of a guide rail of a strip-stretching machine. A clip bottom (8) is mounted onto the main clip body (7), and has bottom rollers (15, 17, 18) capable of rolling on the side surfaces of the guide rail. A strip-clamping means (14) makes it possible to hold an edge of a strip (2) of material along an inner side (5) of the clip body (7). The top transverse flange (7b) is flat and free of outer flaps such that the cross-section of the main clip body (7) has the general shape of an inverted "L". The clip bottom (8) is flat and free of outer flaps. A lightweight clip which efficiently removes greasy residue can thus be produced.

Description

FILM STRETCHING PLIERS

TECHNICAL FIELD OF THE INVENTION

The present invention relates to transverse drawing devices for the manufacture of thin plastic films.

Thin plastic film manufacturing processes comprise a hot cross-stretching step which is carried out inside a large oven. When passing through this oven, the film is held by two sets of grippers distributed in length along the two lateral edges of the film. The clamps comprise clamping means mounted on a clamp body itself provided with sliding or bearing members bearing on a fixed guide rail. Thus, in the oven, there are two guide rails carrying two sets of clamps which hold the two lateral edges of the film. Two chains move the clamps along the rails in displacement, for the longitudinal displacement of the film in the oven.

In a first zone of the oven, the rails are parallel, until the film has reached the appropriate softening temperature. Then, the rails move away from each other symmetrically, so as to ensure transverse stretching of the film. After stretching, the guide rails become parallel again, and the film is cooled.

In a drawing device, to achieve sufficient production rates, the speed of travel of the clamps and the film exceeds 500 m / min.

During this movement, it is necessary to lubricate the sliding or rolling members at the interface between the clamp body and the rail. In particular, in the case of ball bearings, lubrication is necessary.

A gripper for holding and guiding strips of material to be stretched is described, for example, in document FR 2 686 041.

Such a clamp comprises:

a main pincer body, comprising an inner lateral wing secured to an upper transverse wing which carries upper rollers capable of rolling on an upper face and two opposite lateral faces of a guide rail of a stretching machine; bandaged,

a clamp bottom attached to the main clamp body, carrying lower rollers capable of rolling on the lateral faces of the guide rail;

- Band clamping means, in the form of two levers called valets, able to hold an edge of the material strip along an inner side of the clamp body, that is to say along the side facing the strip of material to be stretched. In this known device, the inner side wing is solid and continuous, so as to protect the strip of material to be stretched against the projections of lubricant. Indeed, during the movement of the clamp on the rail, the rollers rotate at high speed and produce radial projections of lubricant. According to the inner side of the clamp, that is to say on the side of the strip of material to be stretched, these projections are intercepted by the inner side wing of the main clamp body.

In this document, the main clamp body has a transverse "U" profile, with an outer side wing opposite and parallel to the inner side wing. This outer side wing intercepts the projections of lubricant produced to the outside by the upper rollers. Similarly, the clamp bottom has an outer side flange, which intercepts to the outside projections of lubricant produced by the lower rollers.

Thus, most radial projections of lubricant from the rollers fall into the bottom of the clamp where they are collected.

A disadvantage is that the lubricant, compatible with the high temperature of the furnace, becomes particularly viscous at a lower temperature, and tends to accumulate in the bottom of the clamp body, disrupting the operation of the lower rollers.

Another disadvantage is the relatively large mass of such a "U" clamp body clamp structure and "U" clamp bottom. Considering that a film stretching machine has several thousand such grippers, this results in wear of the guide rails, and the need for a large driving force to move the grippers and the film, especially when the clamps are moved rapidly at speeds exceeding 500 m / min.

SUMMARY OF THE INVENTION

The present invention aims to avoid the disadvantages of these known clamps, both by improving the discharge of lubricant flows in the clamp bottom, and by reducing the weight of the clamp without impairing its holding capabilities and guidance.

According to another object, the invention aims to facilitate the mounting of such a clamp, in particular the mounting of the upper roller capable of rolling on the upper face of the rail.

To achieve these objects as well as others, the present invention provides a holding clip for guiding and holding a strip of material to be stretched, said clip comprising: a main pincer body, comprising an inner lateral wing secured to an upper transverse wing which carries upper rollers capable of rolling on an upper face and two opposite lateral faces of a guide rail of a stretching machine; bandaged,

tape clamping means, mounted on the main clamp body, and able to hold an edge of the material strip along an inner side of the clamp body,

- The upper transverse wing is generally flat and devoid of outer lateral wing, so that the main body of the clip has, in cross section, the general shape of an "L" returned.

The removal of the outer side wing promotes the ejection of lubricant projections to the outside of the clamp, which reduces the flow of lubricant collected in the clamp bottom. The subsequent evacuation of the lubricant from the gripper bottom is thus facilitated.

At the same time, the removal of the outer lateral wing substantially reduces the weight of the clamp.

According to a preferred embodiment, it is also provided that:

the gripper bottom is generally flat, oriented parallel to the upper transverse flange, devoid of the outer lateral flange, and fixed to the free end of the inner lateral flange,

- The assembly formed by the gripper main body and the assembled clamp bottom thus having the general shape of a "U" lying completely open towards the outer side of the clamp.

The removal of the outer side wing also reduces the flow of lubricant directed to the bottom of the clamp, and facilitates the removal of the lubricant away from the clamp bottom, avoiding disrupting the operation of the lower rollers.

Preferably, the clamp bottom may comprise cavities open on its upper face and having passage holes for greasy residues.

This allows a direct evacuation of the lubricants collected in the clamp bottom.

More advantageously, the cavities may comprise a flat bottom or slope down to the orifices.

This arrangement further facilitates the removal of the lubricant. It has been found, on known clamps, that counterfloors produce a buildup of lubricant that prevent evacuation. To solve the problem of mounting the upper roller, it can be advantageously provided that the upper roller or rollers comprise a ball bearing having an inner ring mounted on a transverse axis engaged in lateral bores of a housing of the main body clamp.

Preferably, the transverse axis comprises:

a stepped ring whose shoulder forms a first lateral positioning stop of the inner bearing ring;

- A screw with stem and head, the rod being engaged in the shoulder ring, the head forming a second lateral positioning stop of the inner race ring.

In this way, the stepped ring is first mounted in the inner race of ball bearing, and the assembly is engaged in the housing of the main body clamp. The screw can then be axially inserted into the shoulder ring, without any risk of decentering the bearing.

According to an advantageous embodiment, it is provided that:

the screw shank is smooth, and its free end engages a small clearance in a lateral bore of the main clamp body,

- The screw head is threaded and screwed into a threaded bore of the main clamp body.

This fastening device is particularly simple and inexpensive, ensuring effective maintenance and balance of the bearing in the main body of the gripper.

SUMMARY DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention will become apparent from the following description of particular embodiments, with reference to the accompanying figures, in which:

- Figure 1 is a perspective view from above the outer side of a holding clamp according to an embodiment of the present invention;

Figure 2 is a perspective view from below of the outer side of the clip of Figure 1;

- Figure 3 is a perspective view from above the inner side of the clamp of Figure 1;

- Figure 4 is an end view of the clamp of Figure 1;

Figure 5 is a perspective view from above of the outer side of the main gripper body of Figure 1;

Figure 6 is a perspective view from below of the outer side of the gripper main body of Figure 1; - Figure 7 is a perspective view from above of the clamp bottom of Figure 1, provided with lower rollers;

FIG. 8 is a perspective view from above of the clamp bottom of FIG. 7, the rollers having been removed; and

- Figure 9 is a cross section of the main clamp body of Figure 1, in line with an upper roller axis.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the embodiment illustrated in the figures, the film stretching gripper 1 is intended to hold and guide a strip of stretching material 2. The clip 1 holds a first edge 2a of the strip of material 2, in association with other clamps which hold the same edge 2a, while a set of other opposite clamps hold the opposite edge of the strip of material to be stretched 2, not shown in the figures.

To ensure the displacement of the strip of material to be stretched 2, the gripper 1 moves along a guide rail 3 (FIG. 4), and is driven in translation along the rail 3 by a chain 4 itself guided. and driven in translation by unrepresented and conventional drive means in a film stretching machine.

In the clamp 1 is defined an inner side 5 oriented towards the strip of material to be stretched 2, and an outer side 6 facing away from the strip of material to be stretched 2.

The clamp 1 comprises a main body of clamp 7 and a clamp bottom 8 secured to one another.

The main clamp body 7 comprises an inner lateral wing 7a integral with an upper transverse wing 7b.

The inner side wing 7a is generally flat, oriented perpendicularly to the plane of the strip of material to be stretched 2 and parallel to its edge 2a, while the upper transverse wing 7b is generally flat and oriented horizontally, perpendicularly to the lateral wing inside 7a. Thus, end view, as shown in Figure 4, the main body clamp 7 has the general shape of an "L" returned, a first branch of the "L" being constituted by the inner side wing 7a vertical, the second branch of the "L" being formed by the upper transverse flange 7b horizontal.

The main gripper body 7 carries upper rollers, better visible in FIG. 2, comprising a pair of inner lateral guide upper rollers 9 and 10, a pair of lateral upper lateral guide rollers 11 and 12, and an upper roller central vertical guide 13. The upper rollers 9-13 are able to roll on an upper face and two opposite lateral faces of a guide rail 3 (FIG. 4) of a band stretching machine.

Each of the upper lateral guide rollers 9-12 is rotatably mounted on a respective vertical axis. For example, FIG. 1 shows the axis 1 1 a on which the roller 1 1 is mounted, and the axis 12 a on which the roller 12 is mounted.

The gripper main body 7 further comprises band clamping means 4, capable of holding an edge 2a of the stretching material strip 2 according to the inner side 5 of the gripper main body 7.

In practice, the band clamping means 14 comprise two pivoting levers 14a and 14b, generally called valets, pivotally mounted about a longitudinal axis 14c, comprising a respective operating arm 14d or 14e, and comprising a respective clamping arm 14f or 14g (Figure 3). The clamping arms 14f and 14g are shaped to bear against a horizontal support plate 14h (Figure 4). Thus, the edge 2a of the stretching material strip 2, as illustrated in FIG. 4, is clamped between the clamping arm such as the arm 14f and the support plate 14b. The clamping lever 14a or 14b is biased towards its clamping position illustrated in Figure 4 by elastic means such as coil springs 14i and 14j (Figure 1). In the clamping position illustrated in FIG. 4, the clamping arm 14f is braced on the support plate 14h, in an inclined position towards the outer side, so that traction exerted by the strip of material to be stretched 2 tends to rotate the clamping lever 14a in the direction of increasing clamping.

The upper central guide vertical roller 13 is mounted in a housing 13a (Figures 2, 6 and 9), and is held in this housing by a transverse axis 13b (Figures 1 and 9).

As can be seen in more detail in FIG. 9, the upper central guide roller 13 comprises a ball bearing having an inner ring 13b mounted on the transverse axis 13b itself engaged in lateral bores 3c and 13d of the housing. 13a.

The transverse axis 13b comprises a shoulder ring 13e and a screw 13f.

The shoulder of the shoulder ring 13e is engaged in the lateral bore 13c, while the head 13g of the screw 13f is threaded and is screwed into the lateral bore 3d itself threaded. The rod 13b of the screw 13f, which forms the transverse axis, is smooth, engaged with little play in the shoulder ring 13e, its free end engaging a small clearance in the lateral bore 13c of the main clamp body 7.

In the assembled position illustrated in FIG. 9, the shoulder of the shoulder ring 13e forms a first lateral positioning stop for the ring 13h inner bearing, opposing the displacement of the upper central guide vertical roller 13 towards the inner side 5 of the clamp 1. Similarly, the head 13g of the screw 13f forms a second lateral positioning stop of the inner ring of the rolling 13h, opposing the displacement of the upper central guide vertical roller 13 towards the outer side 6 of the clamp 1.

For the mounting of the upper central vertical guide roller 13, the stepped collar 13 is engaged in the inner ring 3h of the roller 13, then the assembly thus formed is engaged in the housing 13a, and then it suffices to insert the screw 13f. in the shoulder ring 13e to fix the set.

The clamp bottom 8, as illustrated in FIGS. 1 to 4, 7 and 8, carries lower rollers capable of rolling on the lateral faces of the guide rail 3 (FIG. 4). These lower rollers comprise a pair of inner lower lateral guide rollers 15 and 16, and a pair of lateral lower lateral guide rollers 17 and 18, which are all mounted on respective vertical axes such as the axis 18a of the roller 18 or the axis 17a of the roller 17.

The clamp bottom 8 is attached to the main clamp body 7, and attached to the lower end of the inner side wing 7a. A vertical screw 19 further connects the clamp bottom 8 to the upper transverse flange 7b of the main clamp body 7, to ensure the rigidity of the assembly.

Simultaneously, the vertical screw 19 connects with a link of the chain 4, to connect the chain 4 to the clamp 1.

The assembly formed by the main clamp body 7 and the gripper base 8 assembled, as illustrated in the figures, thus has the general shape of a "U" lying with total opening directed towards the outer side 6 of the 1. In other words, according to the outer side 6 of the clamp, the "U" profile is fully open, devoid of outer lateral wings coming to cover the rollers 1 1, 12, 17 and 18.

As can be seen more specifically in FIG. 8, the gripper bottom 8 comprises cavities 8a, 8b, 8c, 8d and 8e open on its upper face, and passage orifices 8f, 8g, 8h, 8i (FIG. 2). allowing the passage of fatty residues downwards. The passages 8f-8i are lined with lower annular lips, favoring the detachment of drops of greasy residues to prevent their accumulation.

The passage orifices 8f-8i of the greasy residues are formed in the bottom of the receiving cavities 8d and 8e, communicating with the open cavities 8a, 8b and 8c. The cavities 8a, 8b, 8c, 8d and 8e have a flat bottom or downward slope towards the through holes 8f-8i.

As can be seen in the figures, in particular FIG. 7, the lower rollers 15-18 are not embedded in the cavities 8a, 8b and 8c, but they overcome these cavities and lie in a plane situated above the edges of the cavities 8a, 8b and 8c.

In this way, the greasy residues possibly projected by the rotation of the lower rollers 15-18 can escape towards the outer side 6 of the clamp 1, without falling back into the clamp bottom 8.

Similarly, the upper rollers 9-12 are below the upper transverse flange 7b, and projections of greasy residues produced by the rotation of the upper rollers 9-12 can escape according to the outer side 6 of the clamp 1, without falling back into the clamp bottom 8. This reduces the accumulation of greasy residues in the clamp bottom 8.

The present invention is not limited to the embodiments which have been explicitly described, but it includes the various variants and generalizations thereof within the scope of the claims below.

Claims

1 - forceps (1) for guiding and holding a strip of material to be stretched (2), said clip comprising:

a gripper main body (7), comprising an inner lateral wing (7a) integral with an upper transverse wing (7b) which bears upper rollers (9-);

13) adapted to roll on an upper face and two opposite lateral faces of a guide rail (3) of a belt stretching machine,

- a clamp bottom (8) attached to the main clamp body (7), carrying lower rollers (15-18) capable of rolling on the lateral faces of the guide rail (3),

band clamping means (14), mounted on the main clamp body (7), and able to hold an edge of the material strip (2) along an inner side (5) of the clamp (1),

characterized in that

- The upper transverse flange (7b) is generally flat and devoid of outer lateral flange, so that the main body clamp (7) has, in cross section, the general shape of a "L" returned.

2 - Pliers (1) according to claim 1, characterized in that:

- the clamp base (8) is generally flat, oriented parallel to the upper transverse flange (7b), devoid of outer lateral flange, and fixed to the free end of the inner lateral flange (7a),

the assembly formed by the gripper main body (7) and the collet base (8) assembled thus having the general shape of a "U" lying with total opening directed towards the outer side (6) of the clamp ( 1).

3 - Pliers (1) according to one of claims 1 or 2, characterized in that the clamp base (8) comprises cavities (8a, 8b, 8c, 8d, 8e) open on its upper face and having orifices (8f-8i) passage of fatty residues.

4 - Pliers (1) according to claim 3, characterized in that the cavities (8a, 8b, 8c, 8d, 8e) have a flat bottom or slope down to the orifices

(8f-8i).

5 - Pliers (1) according to any one of claims 1 to 4, characterized in that the or the upper rollers (13) comprise a ball bearing having an inner ring (13h) mounted on a transverse axis (13b) engaged in lateral bores (13c, 13d) of a housing (13a) of the main clamp body (7). 6 - Clamp (1) according to claim 5, characterized in that the transverse axis (13b) comprises:

- a stepped ring (13e) whose shoulder forms a first lateral positioning stop of the inner race ring (13h),

- a screw (13f) with rod (13b) and head (13g), the rod (13b) being engaged in the shoulder ring (13e), the head (13g) forming a second lateral positioning stop of the inner race ring (13h).

7 - Clamp (1) according to claim 6, characterized in that:

- the rod (13b) of screw (13f) is smooth, and its free end engages a small clearance in a lateral bore (13c) of the main body of clamp (7),

- The head (13g) of screw (13f) is threaded and is screwed into a threaded bore (13d) of the main body clamp (7).