Weft brake for shuttleless loom

A weft brake for a loom, especially for one of the shuttleless type, comprises a stationary blade and a movable blade cantilevered in overlapping positions on respective posts rising from a supporting plate, the free end of the movable blade being spring-biased toward the stationary blade for clamping a weft thread therebetween but being periodically deflected away therefrom for releasing the weft thread to facilitate its transportation through the shed of the associated warp threads. The weft thread passes between the stationary blade and a leaf spring forming an intermediate blade, inserted between the two other blades of the brake and cantilevered on the same post as the movable blade, so as to be frictionally restrained by the elasticity of that intermediate blade in the unclamping position of the movable blade.

FIELD OF THE INVENTION 
Our present invention relates to a thread brake as used on the weft of a 
loom, particularly one of the shuttleless type in which a weft thread is 
to be transported through a shed of associated warp threads by an 
insertion lance or rapier traversing the shed, or by two such rapiers 
between which the weft thread is transferred in the middle of the shed. 
BACKGROUND OF THE INVENTION 
When a weft thread is being transported in the aforedescribed manner 
through the shed of a shuttleless loom, it is to be held taut especially 
at the instants of engagement of and disengagement from a rapier. For this 
purpose, it is already known to use weft brakes disposed laterally of a 
loom which grip the oncoming thread between two jaws and release it during 
its entrainment by the rapier. Usually one of the jaws is stationary while 
the other is movable and urged under a spring force against the first jaw; 
this second, movable jaw is intermittently deflected by a control pin, 
synchronized with the warp-engaging heddles and with the weft-transport 
mechanism, to separate it from the first jaw. 
A drawback of the known weft brake is that the thread is completely 
uncontrolled upon being unclamped. The separation of the jaws, moreover, 
enables the entry of accompanying lint into the brake where particles 
thereof may accumulate and interfere with its operation. Furthermore, the 
impact of the sudden release of the movable jaw from its unclamping 
position may be harmful to the thread if the jaw is strongly spring-loaded 
as is required for firm clamping. 
OBJECT OF THE INVENTION 
The object of our present invention, therefore, is to provide an improved 
weft brake obviating these inconveniences. 
SUMMARY OF THE INVENTION 
We realize this object, in accordance with our present invention, by 
providing such a weft brake with a leaf spring interposed between its 
stationary and movable jaws for gripping the weft thread between the leaf 
spring and the stationary jaw in a clamping position and for engaging the 
weft thread under reduced pressure in an unclamping position of the 
movable jaw. Thus, the weft thread is still frictionally restrained during 
its entrainment by a transporter such as a rapier and any accompanying 
lint is smoothed against the thread surface so as not to accumulate within 
the brake. 
When the stationary jaw is a first blade cantilevered on a first post 
rising from a supporting surface while the movable jaw is a second blade 
cantilevered on a second post rising from the same surface at a distance 
from the first post, the leaf spring is advantageously cantilevered on the 
second post to extend codirectionally with the second, movable blade 
toward the first post. This movable blade will then have a free end 
projecting beyond a free end of the leaf spring for engagement by the 
associated control means while the first blade extends toward the second 
post and closely approaches the leaf spring at an intermediate location 
between the two posts.

SPECIFIC DESCRIPTION 
The components of a shuttleless loom illustrated in the drawing include a 
stationary mounting plate 1 fastened by a bracket 33 and screws 34 to a 
beam 2 forming part of the loom frame. Mounting plate 1, disposed 
laterally of a nonillustrated set of warp threads, supports four eyes 3 
and a gate 4 establishing guidepaths for four weft threads 5 drawn off 
respective supply bobbins 6 (only one shown). A weft brake 7, associated 
with one of the threads 5 but representative of a set of four such brakes, 
comprises a stationary jaw in the form of an essentially flat blade 8, a 
movable jaw in the form of an angularly bent blade 13 and an intervening 
blade 22 designed as a leaf spring of arcuate curvature. A fixed, 
laterally bent end 12 of stationary blade 8 has two notches 30 
accommodating respective screws 9 by which that blade is secured in 
cantilever fashion to a post 10 which is fastened by a bolt 11 to mounting 
plate 1. Blade 8 has longitudinal edges 27 tapering toward its free end 
which points in the direction of the oncoming weft thread 5. Movable blade 
13 similarly has a fixed end 29 provided with notches 31 giving passage to 
a pair of screws 14 which traverse a retaining plate 23 and bracket 
tapering flanks 28 of a fixed end of leaf spring 22 while engaging a post 
15 which rises from mounting plate 1 at a distance from post 10 and is 
secured to that mounting plate by a bolt 16 further traversing a coil 
spring 17. The two blades 13 and 22 are thereby fastened, also in 
cantilever fashion, to the post 15 with their free ends extending toward 
post 10, i.e. in the direction of advance of the associated weft thread 5. 
The free end of blade 13 projects in that direction beyond the free end of 
blade 22 into the path of an associated control pin 21 rising from a 
sector 18 which is fulcrumed by a vertical shaft 19 on a journal bearing 
20. Sector 18, carrying four control pins 21 to coact with the movable 
blades of all four weft brakes, is periodically oscillated about its pivot 
19 by a nonillustrated cam synchronized with the loom drive. Sockets 24 on 
mounting plate 1 accommodate the fastening bolts (11) of the posts (10) 
for the stationary blades of the remaining three brakes whose other posts 
(15) are held in position by bolts (16) passing through bores 25 of blade 
1. The control pins 21 are received in bores 26 of the oscillating sector 
18. 
In a clamping position of brake 7, as illustrated in FIG. 2, a bend 32 of 
movable blade 13 bears upon the concave side of intermediate blade 22 
under the pressure of coil spring 17 which has a bent-over extremity 17' 
engaging behind the blade 13 as seen in FIG. 4. The point of contact 
between blades 13 and 22, defined by the bend 32, lies between the two 
posts 10, 15 at a location close to post 10. At this point the curved leaf 
spring 22 is pressed with its convex side into firm contact with 
stationary blade 8 to clamp the thread 5 therebetween. When sector 18 
swings counterclockwise from the position of FIG. 2 to that of FIG. 3, the 
movable blade 13 is separated from the associated blades 8 and 22--as are 
corresponding blades of all other brakes--whereby leaf spring 22 exerts 
only a residual pressure, due to its inherent resiliency, upon the weft 
thread 5 which is therefore entrainable in the direction of the arrow by a 
nonillustrated rapier engaging same. The free end of blade 8 diverges from 
blades 13 and 22 in the direction of the oncoming weft thread 5 so as to 
facilitate the initial insertion of that thread between the brake jaws; 
that insertion is further facilitated by the fact that the height of blade 
8 in the region of its free end is reduced, thanks to its tapering edges 
27, with reference to the height of the adjoining leaf spring 22. 
While our improved thread brake has been particularly described with 
reference to its use on a weft of a shuttleless loom, its utility is not 
limited to this mode of application.