Drive mechanism for a sub-mechanism of a weaving machine

The drive mechanism for a reciprocating sub-mechanism on a weaving machine, e.g. for a cam for raising a projectile into the picking line, comprises a dead-center type crank drive. The drive is pivoted to and fro continually through 180.degree.. The connecting rod, which drives the projectile raise cam, is kept practically completely in the standstill position in the two crank standstill positions. This rod is mounted on an eccentric section of the crank pin so that small reciprocating movements of the crank in the dead-center positions due to play in the parts driving them cannot be transmitted to the connecting rod and projectile raise cam. The eccentric section of the crank pin can also be adjusted.

This invention relates to a drive mechanism for a sub-mechanism of a 
weaving machine. More particularly, this inventon relates to a drive 
mechanism for a sub-mechanism for moving a weft picking means from a 
return line to a picking line in a weaving machine. 
Heretofore, it has been known to move a weft picking means from a return 
line to a picking line in a weaving machine by means of sub-mechanisms 
which are driven off a main drive of the weaving machine. For example, as 
described in Swiss Pat. No. 328,715, one known sub-mechanism has employed 
a cam for raising a projectile from a return line to the picking line. 
This cam has, in turn, been pivoted in a to and fro manner between two end 
positions via a cam follower and a link articulated on the follower. 
However, in this known construction, the "projectile raise cam" strikes 
against a stationary abutment in both end positions. While these abutments 
are necessary to obtain exact end positions of the "projectile raise cam" 
and hence of the weft picking projectile carried by the cam, the abutments 
do wear out after some time due to the frequent impact of the cam on the 
abutments. As a result, the cam requires replacement. Furthermore, a layer 
or cushion of flying dust from the machine can also accumulate on the cam 
such that the end positions of the cam and the projectile may become 
inaccurate. 
Accordingly, it is an object of the invention to eliminate the need for any 
fixed abutments for a projectile raise cam of a weaving machine. 
It is another object of the invention to eliminate any need for special 
guidance of a weft picking projectile of a weaving machine during picking. 
It is another object of the invention to improve the movement of a weft 
picking projectile from a return line to a picking line in a weaving 
machine. 
It is another object of the invention to provide a drive mechanism for a 
reciprocating sub-assembly of relatively long-life. 
Briefly, the invention provides a transmission which is connected between a 
main drive and a reciprocable sub-mechanism which includes a crank drive 
having a crank shaft drivingly connected to the main drive for oscillation 
thereby with at least one reversal point of the oscillation movement of 
the crank shaft in the region of a dead center position of the crank 
drive. The crank drive further includes a driving crank pin which is 
driven from the crank shaft in a reciprocating manner over an arc of 180 
degrees and a driven connecting rod which is articulated on the crank pin 
and is drivingly connected to the sub-mechanism. 
The construction is such that any slight reciprocating movement of the 
crank pin in the dead-center positions (standstill positions and reversal 
points), such as may occur due to an inevitable play in the transmission 
between the main drive and the crank drive, will extend substantially at 
right angles to the length of the connecting rod. Consequently, the 
connecting rod cannot be moved in the direction of its length. Thus, the 
two end positions of the sub-mechanism are always exactly at the same 
place during operation. 
The sub-mechanism may be constructed with a projectile raising cam which is 
pivotally mounted to move between a pair of end positions and which is 
articulated to the connecting rod. 
The crank drive is such that there is no need for any fixed abutments for 
the projectile raise cam nor any special guidance for a projectile during 
picking. The cam is kept in the exact end positions simply by the crank 
drive, i.e. a dead-center type of crank drive. There is no need to replace 
abutments due to wear nor is there any need for cleaning due to the 
formation of layers of flying dust and the like. 
The projectile raise cam and the dead-center type crank drive can operate 
in an unlimited fashion while maintaining the exact end positions of the 
cam in the dead-center positions of the crank drive.

Referring to FIG. 1, a weaving machine includes a main drive in the form of 
a rotatable shaft 1 from which a reciprocable sub-mechanism 18 is moved 
between a pair of end positions 18a, 18b (FIG. 4). To this end, a 
transmission is connected between the main drive shaft 1 and the 
sub-mechanism 18 for driving of the sub-mechanism from the shaft 1. This 
transmission includes a crank drive 10 having a crank shaft 13 as well as 
a toothed gear means for reciprocating the crank shaft 13. 
As shown in FIG. 2, the crank shaft 13 is fixedly mounted on an axis 13a 
within supports fixed to the weaving machine frame. The toothed gear means 
includes a gear wheel 12 fixedly mounted on the crank shaft 13, a lever 7 
which is pivotally mounted in fixed manner on a pivotal shaft 5, a gear 
sector 11 which is mounted on the lever 7 in meshing engagement with the 
gear wheel 12 and a cam drive for pivoting the lever 7 to and fro. As 
shown, the cam drive includes a drum 3 with a cam groove 2 which is fixed 
to the shaft 1, a roller 4 which follows the cam groove 2 and a lever 6 
which carries the roller 4 and is fixed to the shaft 5. The shaft 1 is 
rotated continuously from the main weaving machine drive (not shown) so 
that the two-armed lever 6, 7 is continuously pivoted to and fro. 
The crank shaft 13 is drivingly connected to the main drive for oscillation 
thereby with at least one reversal point of the oscillation movement of 
the shaft 13 situated near a dead-center position of the crank drive 10. 
Referring to FIGS. 2 and 7, the crank shaft 13 carries a pair of spaced 
apart crank webs 14, 14a at an intermediate point. These crank webs 14, 
14a may be fixed to the crankshaft 13 in any suitable manner or may be 
made integral therewith. In addition, a driving crank pin 15 is journalled 
in a respective bore of the webs 14, 14a and a connecting rod 16 is 
articulated to the crank pin 15 at one end and to the sub-mechanism 18 at 
the opposite end. The crank pin 15 is driven from the crank shaft 13 in a 
reciprocating manner over an arc of 180 degrees so as to be driven between 
two dead-center positions 15a, 15b of the crank drive 10 (see FIG. 3). To 
this end, the crank pin has an eccentric section 15e on which the 
connecting rod 16 is articulated. This eccentric section is adjustable as 
described below to adjust the point of articulation of the rod 16. The 
sub-mechanism 18 is in the form of a projectile raising cam 18 which is 
pivotally mounted about a pin 17 to pivot between two end positions 18a 
(FIG. 1), 18b (FIG. 4) in the direction indicated by the arrow 19. When 
the cam 18 moves from the end position 18a to the end position 18b, the 
eccentric crank pin section 15e of the crank drive 10 passes through the 
positions 15a, 15c, 15b as shown diagrammatically in FIG. 3 and the center 
line 23d of the pivot point 23, at which the rod 16 is articulated to the 
cam 18, passes through the positions 23a, 23c, 23b. The two dead-center 
positions 15a, 15b of the crank drive 10 and the corresponding end 
positions 23a, 23b and the axis 13a of the crank shaft 13 are situated in 
a common plane 48 which in the present case will be designated as the 
crank base. 
In the case of a small reciprocating movement of the levers 6, 7 and gear 
wheel 12 in the dead-center positions 15a, 15b, there is practically no 
horizontal movement transmitted to the connecting rod 16. The cam 18 thus 
remains in a complete position of rest in the two end positions 18a, 18b. 
These two end positions are thus always exactly the same during operation 
and are independent of any abutments on the machine frame or any layer of 
dirt such as flying dust which might otherwise accumulate on such 
abutments. 
As shown in FIG. 3, the arm 22 of the cam 18 is longer than the crank arm 
45 of the crank drive 10. The dimensions are such that pivoting of the 
crank drive 10 through 180 degrees produces only a 90 degrees pivoting 
movement at the arm 22 and, hence, of the cam 18. During this movement, a 
weft picking projectile 24 which is guided into the cam 18 by a return 
mechanism (not shown) on the weaving machine moves out of the position 24a 
(FIG. 1) into the position 24b (FIG. 4). This latter position 24b 
corresponds to a picking line 25. In this position, a weft yarn can be 
transferred to the projectile 24 so as to be introduced into a shed (not 
shown). After picking, the empty cam 18 is swung back into the initial 
position 18a (FIG. 1). 
As shown in FIGS. 1 and 5, the pin 17 on which the cam 18 is mounted is, in 
turn, mounted on the supports 29 on which the crank shaft 13 is mounted. 
Referring to FIGS. 6, 7 and 8, the crank pin 15 consists of three sections 
15d, 15e, 15f. The end sections 15d, 15f are disposed about a common axis 
26 coincident with axes of the bores 41, 41a in the webs 14, 14a. This 
axis 26 is offset perpendicularly from the base plane 48 (FIG. 8). The 
eccentric section 15e is disposed about an axis 47 which is eccentric to 
the axis of the pin 15 by an amount e which is substantially equal to the 
amount of offset h of the axes of the bores (sections 15d, 15f) from the 
base plane 48. As indicated in FIG. 8, the axis 26 of the bores 41, 41a 
and the pin sections 15d, 15f is offset perpendicularly from the base 
plane 48 when the crank shaft 13 is in either of the dead center positions 
15a, 15b. The amount h of this offset is equal to the distance between the 
points 50, 26 (FIG. 9), which is approximately equal to the eccentricity e 
of the eccentric section 15e. 
The crank drive 10 also has a locking means for locking the eccentric 
section 15e in a fixed position. To this end, as shown in FIGS. 6 and 7, 
at least the crank web 14a has a slot 54 so as to form a pair of free ends 
55, 56. In addition, the locking means includes a clamping screw 27 which 
is threaded into one free end 55 while passing through the other free end 
56 for selectively drawing the ends 55, 56 together in order to clamp the 
crank pin 15 in a fixed position. The crank pin 15 also has a slot 34 
(FIG. 2) which permits passage of the clamping screw 27 therethrough. This 
slot 34 is of a dimension to permit the pivoting movement of the clamping 
screw 27 between two limit positions. 
In order to adjust the eccentric section 15e, the screw 27 is first 
loosened. Thereafter, a tool (not shown) is fitted into a bore 28 in the 
pin 15 and the pin 15 rotated to the required position. The pin 15 can be 
turned until one or the other top end surfaces of the recess 34 strikes 
against the screw 27. These two stop positions correspond to the points 
47a, 47b of FIGS. 8 and 9, each of which is about 30 degrees from the 
middle point 47. The screw 27 is tightened in the required position and 
the crank pin 15 is thus locked. This locking means operates in a stepless 
manner. 
Any tolerance in the distance between a crank pin 15 and the pivot point 23 
at which the connecting rod 16 is articulated to the cam 18, can thus be 
compensated when the components of the drive mechanism are assembled. 
Further, the adjustment of the eccentric section 15e of the pin between 
the points 47a and 47b enables a relatively large area f (FIG. 9) to be 
covered in the direction of the connecting rod 16. At the same time, the 
point 47 where the connecting rod 16 is articulated to the crank pin 15 is 
prevented from shifting substantially out of the base plane 48, i.e. 
upwardly or downwardly as viewed in FIGS. 8 and 9. Consequently, the 
connecting rod 16 and, hence, the cam 18 can occupy changed positions in 
the two dead-center positions 18a, 18b due to inevitable play in the drum 
3, levers 6, 7, sector 11 and gear wheel 12. However, their end positions 
during operation are always exactly identical. 
Instead of being shifted upwardly out of the base plane 48 as shown in FIG. 
8, the axis 26 of the pin sections 15d, 15f and the bores 41, 41a can be 
shifted downwardly. The eccentricity e of the eccentric section 15e can 
also be somewhat less or more than the distance h between the points 50, 
26 by which the axis 26 is offset from the base plane 48. In this case, 
the arc 47a, 47, 47b does not touch the base plane 48 but is situated, for 
example above or below the plane 48. The eccentricity e and the distance h 
between the points 50, 26 need not be identical. However, it is 
advantageous for the two values to be substantially equal because the 
points 47a, 47, 47b are then situated substantially in the base plane 48. 
If the sub-mechanism driven by the dead-center crank drive 10 is of a 
different construction, suitable changes can be made. For example, if the 
sub-mechanism is a sley or reed (not shown) which requires only a single 
or exact reversal point in its movement program, the crank drive 10 may be 
driven so that the exact reversal point of the sub-mechanism is situated 
at only a single dead-center position, e.g. at the point 15b. The other 
reversal point of the sub-mechanism, may, for example, correspond to a 
crank point 15g (FIG. 3) which does not coincide with the other 
dead-center positions 15a. 
In modified embodiments, reciprocation of the crank drive 10 can be 
obtained in some other way than via a grooved drum 3. If required, an 
additional transmission linkage may be provided between the connecting 
rods 16 and the arm 22 of the projectile raise cam 18. 
Still further, the crank drive may be actuated by means of an eccentric 
rather than by means of crank webs 14, 14a and a crank pin 15. In this 
case, the crank shaft 13 carries an appropriate eccentric on which the 
connecting rod 16 is articulated. 
The position of the axis 47 of the section 15e of the crank pin 15 is in 
FIGS. 8 and 9 indicated by 50. Point 50 is situated exactly on base plane 
48.