GB2176510A - Clip chain track of a stenter frame - Google Patents

Abstract

In order to avoid the polygon effect exerted on the roller chain 1 of a stenter frame by a reversing gearwheel at the locations where the direction of movement of the chain are reversed, a roller chain 1 of which the idlers 6 provided to accommodate the tension forces are ball-bearing mounted coaxially of the link pins which accommodate the longitudinal forces of the chain 1, are guided around a smooth direction changing path 8 at least at the point where the direction of the chain 1 is reversed at the intake side of the frame. To remove the polygon effect at both the intake and outlet sides a similar direction changing path (13) is disposed also at the outlet side displaced from a sprocket wheel (14) (Figure 2 not shown). <IMAGE>

Description

SPECIFICATION Clip chain track of a stenter frame The invention relates to a clip chain track of an endless roller chain of a stenter frame or the like and having a tensioning means on each chain link, and with a guide rail for the forward run of the chain with in each case a reversal arrangement at the longitudinal ends of the guide rail as a link with the return run of the chain and with a chain drive comprising an output sprocket meshing with the link pins, the guide rail being constructed as an abutment for horizontally directed transverse forces which have to be exerted on the web of fabric, each of the tensioning means being, for transmission of the transverse forces, equipped with a transverse force idler bearing on that outer face of the guide rail which is directed away from the web of fabric, the idlers being ball-bearing mounted about a vertical axis coaxial with the associated link pin accommodating the longitudinal forces of the chain.

In stenter frames of this type, such as are manufactured and marketed by the Applicants, a web of fabric to be treated is held on its longitudinal edges or selvedges and is as a rule stretched in a transverse direction and passed through a heat treatment zone. Generally what is referred to as a clip chain track is provided on each side of the machine which is referred to as a stenter frame and parallel with the selvedges of the fabric to serve as fixing and tensioning means. Running in each of these tracks is an endless roller chain carrying the tensioning means for attachment of the web of fabric. Possible tensioning means are needles or clips. The roller chains have their direction of movement reversed at the inlet and outlet from the frame.In the case of known frames, the relevant chain is driven at the outlet from the machine via a reversing wheel which is constructed as a chain sprocket.

The roller chain is mounted on at least one track accommodating the weight of the chain and at least one guide rail which accommodates the horizontal transverse forces originating from the web of fabric which is clamped in the frame. In the event of the tensioning means being equipped with at least two transverse force idlers mounted apart from the link pins, these idlers being applied against the guide rail from both its longitudinal sides, it is in DAS 14 60 640 envisaged that the guide rail extend continuously from the forward moving to reverse moving strand of the chain track at the chain reversal point at the inlet of the frame, so that at this point no direction-changing gearwheel is required. It is intended thereby to avoid any points at which jolting may occur along the clip chain track or to limit such phenomena to the degree unavoidable in a drive situation.The cost involved in the known apparatus is, however, considerable because in the first place the link pins are not used as a means of accommodating the transverse force idlers and secondly, additional idlers have to be provided on each clamping means purely for direction reversal.

This considerable complication has been provided nevertheless because it makes it possible to avoid any polygonal movement of the chain which might occur if a sprocket is present at the direction-changing point. Particularly at relatively high chain speeds, and speeds of 200 m/min are sought after, the polygonal movement exerts quite powerful jolts on the chain and in the attachment area at the intake of the frame, it makes clipping-on of the fabric selvedges difficult or even impossible, while at the outlet from the frame, disengagement or unclipping will be difficult or may in some cases actually make it impossible to cut off a marginal strip straight and hitherto one has been frequently compelled either to provide larger reversing gears to match the increasing machine speeds or to incorporate expensive damping devices which are subject to wear and tear.However, particularly, at the intake of the machine it is desirable to provide the smallest possible reversing gears so that the distance from the last reversing roller upstream of the chain to the actual point of clipping-on is kept as small as possible in order to avoid the free selvedges rolling in or being folded over. Furthermore, particularly at the higher machine speeds, the performance or the wear and tear which they involve mean that the damping devices are less than satisfactory.

The invention is based on the problem of eliminating the polygon effect of the roller chain at the machine intake and preferably also at the machine outlet without providing any special idlers on the chain and without increasing the radius at which the direction is reversed. For the clip track according to the invention, the solution resides in that the chain reversal arrangement at a longitudinal end of the guide rail at which no drive is provided consists of a reversing track constructed to have the transverse force idlers rolling on it.

Accordingly, it is made possible by the invention for the direction reversal to be achieved not by sprockets but by smooth direction-changing tracks on which the ball-bearing mounted transverse force idlers of the chain which are present in any case can roll without the disadvantageous polygon effect occurring. It is possible even to reduce the radius of direction change still further in proportion to previous chain reversing sprockets so that the distance between the draw-in roller and the clipping/ on point in the intake area of the machine can be additionally reduced. Since according to the invention the reversing tracks are smooth, there is no possibility of the polygon effect occurring.

According to a further feature of the invention, it is possible for the direction reversal point to be a smooth direction-changing track at the outlet from the frame as well, if the output sprocket of the chain drive engages the chain in the region of the return strand which is directed away from the web of fabric. Since the polygon effect is then exerted on the chain only far away from the critical parts of the machine, minimal damping means - as a rule even supporting on the working surface of the chain will be adequate - will be sufficient to obtain a smooth chain movement over the entire range of the forward strand.

Details of the invention will be explained hereinafter with reference to the diagrammatic views in the accompanying drawings; in which Figure 1 is a plan view of a chain track with an endless roller chain of a stenter frame; and Figure 2 shows a modified embodiment of chain track in a stenter frame.

The roller chains designated 1 and provided in the embodiments shown in Figures 1 and 2 consist in principle of link pins and sleeves as well as outer tie bars and inner tie bars, the link pins which are connected rigidly to the outer tie bars being carried over their entire length within the sleeves on which the inner tie bars are seated.

Fixed on each such chain link in a stenter frame or the like, in other words particularly also in a film stretching machine, is a clamping means which may be a clip or a needle member. In the forwards strand 3 of the roller chain 1 which is driven in the direction 2 of forward movement and shown on the right-hand side is Figure 1 and on the left-hand side in Figure 2, there is exerted on the tensioning means mounted on the chain links a transverse force 3 (in the direction of the clamped-in web of fabric and on the oppositely disposed chain) which has to be accommodated by a guide rail 4. To this end, there are provided on the roller chain transverse force idlers 6 which are ball-bearing mounted coaxiaily in relation to the associated link pins which accommodate the longitudinal forces of the chain.The transverse force idlers and the pins and sleeves which accommodate the longitudinal forces of the chain and which are disposed coaxially therein therefore form the only means of supporting the chain against the transverse forces exerted by the web of fabric.

In the chain track according to the invention and as shown in Figure 1, the chain's direction is reversed at the location designated 7, an inlet side comprising a clipping-on mechanism, not shown, where the smooth direction reversing track changes the reverse strand 9 into the forwards strand 3. Since no sprocket is present at this driveless intake side 7 of the roller chain 1, the much feared polygon effect cannot arise. With a preferably substantially circular curvature of the direction reversing path 8, its radius of curvature can be even smaller than with conventional direction reversing sprockets, because the essential reason for a large sprocket diameter, namely the avoidance of the polygon effect, is no longer a matter for debate.

In the example shown in Figure 1, the roller chain 1 runs at the outlet side 10 over a driving sprocket 11. By the retro-action of the sprocket 11 on the chain 1, therefore, a polygon effect can be exerted on the unclipping zone 12 adjacent the sprocket 11. To avoid this, it is in Figure 2 engisaged also to provide on the outlet side a direction reversing track 13 for the chain 1 and to drive the chain in the forwards direction 2 by a separate drive sprocket 14 which engages the reverse run 9.

Since the sprocket 14 according to Figure 2 engages the chain 1 far away from the forward strand 3 which is essential only for treatment of the web of fabric, retroaction need not be feared on either the clipping-on zone 5 nor on the unclipping zone 12.

Claims (3)

1. Clip chain track of an endless roller chain (1) of a stenter frame or the like and having a tensioning means on each chain link, and with a guide rail (5) for the forward run (3) of the chain (1) with in each case a reversal arrangement at the longitudinal ends of the guide rail as a link with the return run (9) of the chain and with a chain drive comprising an output sprocket (11,14) meshing with the link pins, the guide rail (5) being constructed as an abutment for horizontally directed transverse forces which have to be exerted on the web of fabric, each of the tensioning means being, for transmission of the transverse forces (4), equipped with a transverse force idler (6) bearing on that outer face of the guide rail (5) which is directed away from the web of fabric, the idlers being ball-bearing mounted about a vertical axis coaxial with the associated link pin accommodating the longitudinal forces of the chain, characterized in that chain reversal at one longitudinal end of the guide rail (5) at which no drive is provided consists of a direction-changing track (8, 13) constructed to have rolling on it the transverse force idlers (6) mounted on the link pins.

2. Clip chain track according to Claim 1, characterized in that the drive sprocket (14) of the chain drive engages the chain (1) in the region of the return run (9) which is directed away from the fabric and in that the reversal points are constructed adjacent to the two longitudinal ends of the guide rail (5) to serve as a direction changing track (8, 13).

3. Clip chain track as claimed in claim 1 substantially as described herein with reference to and as illustrated by the accompanying drawings.