Patent GB-1499399-A (GB)
Title: Tenter guide rail gap crossing mechanism
IPC: B29C55/04
Filed: 1975-07-16
Abstract: 1499399 Tentering apparatus MARSHALL & WILLIAMS CO 16 July 1975 [18 Nov 1974] 29934/75 Heading B5B [Also in Divisions Dl and E2] In a tentering apparatus of the kind in which a web is transversely stretched by two chains of clips, each chain gripping one edge, the chains being constrained to move along divergent paths by guide rails and in which the rails are formed of straight individual rail sections, means are provided to smooth the passage of the clips over the junctions of the rail sections. As shown in Fig. 1, a gap 5 appears at the junctions between sections 15 when these form an angle. The means provided by the invention yield under these conditions to provide a continuous path for the tenter clips. Three embodiments are disclosed. In the first, illustrated in Fig. 10, a coiled spring 150 having a flat edge to engage the tenter clips is embedded by suitable means in adjoining rails. In the second, shown in Fig. 11, two marrying half-bars 185, 186 with cuts 182 to permit flexing are used. The overlap of these half-bars permits adjustment of the angle. In the third embodiment the rails are provided with wear strips which engage the clip but which are sufficiently mobile to remain in contact when the rail sections form an angle. This is achieved by the use of bolts set in elongated slots which allow the engaging strips to move. As shown in Fig. 15, the rail sections 15C, which can pivot around pin 64C to form the required angle, provide tracks 66C, which the clips follow during stretching and 67C, the return track. These are given lateral boundaries by strips 255C and 140C provided on each rail section. The strips are made in sections L and L-L, each section overlapping the adjacent one so that the two can slide to adjust the overall strip lengths. Sections L are rigidly attached to the rail, but sections L-L are provided with elongated slots 280 and 307, through which bolts 306 and 285C slidably attach sections L-L to the rail. Rotation of rail sections 15C about pin 64C to adjust the divergence or convergence of the clip paths is compensated for by the ability of the sections L-L of strips 255C and 140C to move longitudinally by reason of these slots 280 and 307. This permits the strips to follow the movement of the rail sections 15C, pivoting about pins 364C and adjusting their length accordingly by sliding along bolts 306 and 258C and so increasing or decreasing the extent of the overlap of the adjoining strip sections. In consequence of this movement the guide clips which, in the embodiment illustrated in Fig. 19, engages strips 255C and 140C by means of rollers 171C and 170C, can pass from one rail section to another without having to cross a gap.  An additional gap crossing means may be provided with all these embodiments. In the cases where the rail is provided with a ledge 367 (see Fig. 10) along which a tenter clip roller may run, tapered ends 368 allow pivotal movement of the rail sections without a clear transverse gap arising. The rest of the apparatus defined in the claims comprises a frame 11 (see Fig. 1), having cross members 12, each of which supports a rotatable shaft 14 which has screw threads 31, 32 of opposite turn at its ends. Each screw thread engages a nut 61 (Fig. 13, not shown) each of which in turn is connected to a saddle 13. Every saddle supports a block 63 in a groove 62 and each block bears a pin 64 which is used to hinge adjacent rail sections together. The effect of this is that rotation of the shaft 14 moves the pair of saddles on it towards or away from each other and hence adjusts the dispositions of the rail sections 15. Since each rail section has flat faces to engage the tenter clips a number of possible paths for those clips is possible. Each chain of clips forms a closed loop around its rail. This type of apparatus is fully described in Specification 971,410. The Specification also discloses forms of guide rail and of tenter clips adapted to fit these rails. Thus, in Fig. 5 rail 15 has a generally U- shaped groove one face 142 of which engages the tenter clip whilst the other face is provided with a projecting ledge 141 to engage the clip from the other side. The clip straddles the projection 140 and engages the horizontal face of a ledge 367 set into the depending rib 132. The tenter clip shown in Fig. 5 is adapted to use with this rail, engaging surfaces 141 and 142 and ledge 367 by means of rollers 170, 171 and 69 respectively. The clip illustrated in Fig. 6 (not shown) may also be used with this rail. These clips and rails are preferred for use in stretching thermoplastic film webs. The rails and clips illustrated in Figs. 7 and 8 are preferred for use on woven fabrics. In this form the contact between the rails and the clips is provided by sliding flat surfaces rather than by rollers. The clip is retained in the rail by means of a top case 203 screwed to the body of the rail. Fig. 19 illustrates yet another form of guide rail, able to take the clips of Fig. 5. In this embodiment the surfaces which engage the tenter clips are bolted to the rail body and not integral with it. Further, the surface 142 is in resilient contact with the clip by means of spring washer 260 which urges the wear strip 255, having face 142A, towards roller 171A.