Seam For Paper Felts

Abstract

A clipper seam wherein the hooks for joining the ends of felts are arranged in alternating groups such that a limited number of hooks will be brought into rubbing engagement by lateral shifting or bowing of the ends of the felts.

Description

BACKGROUND OF THE INVENTION

The conventional clipper seam for joining the ends of paper makers dryer felts and the like comprises a number of wire hooks which are clinched side-by-side in spaced parallel relation to the adjacent ends of the felt or felts which are to be joined or in lengths of webbing stitched to the respective ends of the felt or felts. The hooks, which have loops at their ends, alternate from one side and then the other so that their ends intermesh. A lacing wire is threaded through the loops to connect the hooks and hence to provide a hinge. It is customary for the clipper seam to be set at right angles to the selvages of the felt so that the hooks are at right angles to the ends of the felt and so that under tension the load exerted by the hooks on the lacing wire is spread substantially equally along the length of the seam. When dryer felts are in use travelling around the cylinders and rolls in a paper or board machine at high speed, it is often found that the seam develops a configuration such that it no longer runs at right angles to the selvages across its full width. This configuration is commonly known as "bowing" or "running-out-of-square" and it is invariably accompanied by a loss of overall width of the felt and seam. Due to the longitudinal tensions applied to dryer felts during running the most natural alignment of the hooks in the seam is parallel to the selvages so that when the seam becomes misaligned the hooks strive to remain parallel to the selvages even when the seam is out of square. The hooks used in the clipper seam are capable of re-alignment by pivoting about their ends which are embedded in the felt or webbing. This re-alignment of the hooks increases the number of hooks per linear inch of the seam when considered at right angles to the selvages and decreases the amount of space between adjacent hooks. In case of severe misalignment hooks are forced against adjacent hooks at the opposite side of the seam and commence rubbing together during the continual flexing and pivoting of the hooks around the lacing wire while the felt is running. This rubbing and the increased possibility of corrosion occurring in the contacting area of the metal hooks has lead to the failure of hooks in many clipper seams. The failure of the hooks has resulted in complete failure of the clipper seam and loss of felt before its full service lift has been realized.

This probelm of short life of the clipper seam relative to the service life available from the modern dryer felts has become more acute as improved materials and workmanship have been incorporated into the felts providing for longer service life of the felts.

The object of this invention is to so space the hooks in the clipper seam that even if severe bowing or running-out-of-square occurs only a limited number of hooks stand any chance of contacting hooks on the opposite edge of the seam.

SUMMARY

As herein illustrated, the foregoing problems are minimized by providing at the adjacent ends of the dryer felt hooks set into the ends in groups of three or more which alternate first from one end and then from the other end and so that the loops of the alternating groups form a continuous passage through which a lacing wire or wires is adapted to be inserted to provide a hinge. The groups of hooks are in turn uniformly spaced and the distance between the adjacent groups is slightly greater than the distance between the adjacent hooks in a group.

The invention will now be described in greater detail with reference to the accompanying drawings wherein:

FIG. 1 is an enlarged fragmentary plan view at the adjacent ends of a dryer felt showing the seam constructed according to this invention; and

FIG. 2 is a section taken on the line 2--2 of FIG. 1

Referring to the drawings, FIG. 1 shows the adjacent ends 10 and 12 of a dryer felt or felts joined by a seam 14 which is designed especially to minimize the contact of the hooks joining the adjacent ends of the felt or felts in spite of bowing and/or misalignment of the ends by arranging the hooks in groups 16, of three hooks which alternate first from one end of the felt and then from the adjacent other end of the felt. The hooks in each group are set into the end of the felt to which they are attached in uniformly spaced parallel relation with their distal ends extending across toward the end of the felt at the other side of the seam and coextensive. Each hook comprises upper and lower limbs 22, 24 joined at one end by an integral loop 26 and provided at their opposite ends with prongs 28 and 30, the latter being set into opposite surfaces of the felt and clinched. The loops 26 at the distal ends of the hooks of the alternating groups collectively provide a transverse passage 32 through which a lacing wire or wires 34 is adapted to be inserted to thereby hingedly connect the adjacent ends of the felt.

As illustrated in the drawings, the adjacent ends of the felts may be reinforced by means of lengths of webbing fixed to the respective ends for receiving the prongs 28, 30.

As thus constructed, bowing or running-out-of-square will dispose the hooks within each group in somewhat closer relation to each other but will not change the parallelism between hooks within a group and so no rubbing between hooks in a group will take place in spite of bowing or misalignment. Between groups there is less chance of rubbing because the spacing between groups is somewhat greater than the spacing between the wires in each group and only the hooks at the outer sides in adjacent groups can possibly have contact. Since even under the most severe bowing only the outer hooks in adjacent groups can rub, the wear when groups of three hooks are employed is reduced by about one-third (1/3) which increases the life expectancy of the felt by at least 30 percent. Groups of more than three may be employed with a corresponding proportionate increase in the life expectancy of the felt, -- the maximum number of hooks being limited, of course, by the tendency for the portions of the felts between groups sagging.

By this arranging the wires in groups rather than alternating the wires from first one end to the other wear and corrosion of the hooks is minimized and thus the longevity of expensive and specially prepared felts is preserved. This grouping of the hooks also facilitates more rapid closure than with a seam employing hooks which are intermeshed singly.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents falling within the scope of the appended claims.

Claims

I claim:

1. A clipper seam for hingedly joining the adjacent ends of dryer felts comprising groups of wire connectors in which the wires in each group are closely adjacent and the groups alternate from opposite sides of the seam, each wire connector having a loop and a long and short leg terminating in hooks, said wire connectors being secured to the adjacent ends of the felt with the legs disposed in engagement with the opposite surfaces at the ends and the hooks buried in the ends and with the loops projecting from the ends in overlapping relation from opposite sides of the seam such that the centers of the loops lie along a common line transversely of the web midway between the ends and collectively define a transverse passage in which is mounted a flexible hinge element, and wherein the loops are arranged in groups of three, alternating from first one end and then the other and wherein the connector wires in each group are set in uniformly closely spaced parallel relation to each other and perpendicular to the plane of the felt.

2. A clipper seam according to claim 1, wherein the groups of wire hooks are uniformly spaced.

3. A clipper seam according to claim 1, wherein the flexible hinge element is comprised of a pair of lacing wires, the combined diameters of which do not exceed the diameter of the passage constituted by said loops.

4. A clipper seam according to claim 1, wherein the groups of hooks are uniformly spaced with the spacing between groups greater than the distance between hooks within the groups.