Sewing machine with means for feeding a workpiece in two directions

A sewing machine capable of producing embroidery stitches on a workpiece which in general require the workpiece to be shifted relative to a needle in a lateral direction as well as a longitudinal direction. The sewing machine has first and second vertical extending presser bars provided at their lower ends with press rollers. The presser bars are spring-biased downwardly so that the press rollers exert downwardly directing pressure onto the workpiece. First and second feed rollers are arranged within a workpiece supporting table of the sewing machine, in opposition to the press rollers respectively. The first feed rollers are rotated by a first drive motor to feed the workpiece in the lateral direction, whereas the second feed rollers are rotated by a first drive motor to feed the workpiece in the longitudinal direction, thereby feeding the workpiece in any direction in a desired amount. The workpiece feeding amounts in both directions are separately controlled in response to stitch control data stored for the selected stitch pattern. Sequential control for each stitch will produce desired embroidery stitches.

FIELD OF THE INVENTION 
This invention relates to a sewing machine and more particularly to a 
sewing machine capable of producing embroidery stitches as well as 
stitching together workpieces superposed one over another. 
BACKGROUND OF THE INVENTION 
The conventional electronic zigzag sewing machines for home use has a 
laterally swingable needle, and a workpiece can be fed in forward and 
backward direction by means of a feed dog mounted on a workpiece 
supporting table of the sewing machine. The needle amplitude and the 
workpiece feeding amount will be controlled responsive to stitch control 
data of the selected stitch pattern which is read out from a memory in 
each stitch. A loop taker mounted within the workpiece supporting table is 
rotated in synchronism with vertical reciprocation of the needle to form a 
stitch composed of upper and lower threads as in a well-known manner. 
The needle amplitude will, however, be limited to the order of 7 mm in 
actual machine design since the needle must enter a thread loop formed 
around the loop taker. The workpiece feeding amount in each stitch will 
also be limited due to efficiency of the feed device. Consequently, the 
conventional sewing machine will not be suitable for producing embroidery 
stitches. 
Another type sewing machine especially adapted to produce embroidery 
stitches has also been provided, which has an embroidery frame for 
accomodating and supporting a workpiece and means for shifting the 
embroidery frame in any direction. This sewing machine will, in turn, not 
be applicable to normal stitching operation. This sewing machine will 
require a powerful torque force and thus an expensive motor for shifting 
the embroidery frame. 
SUMMARY OF THE INVENTION 
It is therefore an object of the invention to provide a sewing machine 
capable of producing embroidery stitches while not impairing functions 
inherent to the sewing machine. 
According to an aspect of the invention there is provided a sewing machine 
comprising first press means adapted to come into contact with a workpiece 
to be stitched to exert a downwardly directing pressure onto the 
workpiece; second press means adapted to come into contact with the 
workpiece to exert a downwardly directing pressure onto the workpiece; 
first drive means cooperating with said first press means being in contact 
with the workpiece for feeding the workpiece in a first direction; second 
drive means cooperating with said second press means being in contact with 
the workpiece for feeding the workpiece in a second direction 
substantially perpendicular to the first direction; and control means for 
independently controlling said first and second drive means, thereby 
feeding the workpiece in said first and second directions in independent 
and sequential manner.

DESCRIPTION OF A PREFERRED EMBODIMENT 
With reference to FIGS. 1 to 3, an electronic sewing machine embodying the 
invention includes a housing or arm 1 in which an upper drive shaft (not 
shown) is rotatably mounted. A needle 2 is supported near the projecting 
end of the arm 1 and allowed to reciprocate up and down in synchronism 
with rotation of the upper drive shaft. A first presser bar 3 extends down 
from the projecting end of the arm 1 and is moveable in up/down direction 
by means of a first solenoid 4 mounted within the arm 1. At the lower end 
of the first presser bar 3 there is provided a freely rotatable press 
roller 5. A second presser bar 6 also extends down from the projecting end 
of the arm 1 in parallel with the first presser bar 3 and is moveable in 
up/down direction by means of a second solenoid 7 mounted within the arm 
1. To the lower end of the second presser bar 6 there is connected a 
presser foot 8 for exerting a downwardly directing pressure onto a 
workpiece (not shown) placed on a needle plate 9 attached to a workpiece 
supporting table 10 of the machine housing. A pair of press rollers 11a, 
11b are rotatably supported by the presser foot 8. The presser foot 8 is 
provided with an aperture 12 for allowing the needle 2 to penetrate the 
workpiece therethrough. Springs 13 and 14 are provided for normally 
biasing the first and second press bars 3 and 6, respectively, to descend. 
In a hollow space of the workpiece supporting table 10 is rotatably 
supported a horizontal loop taker 15 which is rotated via a lower drive 
shaft (not shown) in synchronism with rotation of the upper drive shaft so 
that a thread loop hook portion (not shown) of the loop taker 15 is 
cooperated with the needle 2 to form a stitch composed of upper and lower 
threads as well known in the conventional stitching operation. In this 
embodiment, the workpiece can be shifted along the needle plate 9 in a 
direction extending in width of the machine (which will be hereinunder 
called "X direction") as well as in another direction extending in length 
of the machine, normal to the X direction (which will be hereinunder 
called "Y direction"). For shifting the workpiece in X direction, a first 
motor 16 mounted within the bed 10 is driven to rotate a feed roller 17 
located in opposition to the press roller 5, via a drive mechanism which 
comprises in this embodiment a belt 18 and pulleys 19 and 20. For shifting 
the workpiece in Y direction, a second motor 21 also mounted within the 
bed 10 is driven to rotate feed rollers 22a and 22b located in opposition 
to the press rollers 11a and 11b, respectively. The drive mechanism for 
transmitting rotation of the shaft of the motor 21 to the feed rollers 22a 
and 22b also comprises in this embodiment a belt 23 and pulleys 24 and 25. 
The machine housing 1 has a keyboard panel 26 on which are arranged a 
number of operating keys or switch buttons (not shown) including stitch 
pattern selecting keys 27. Operation of the stitch pattern select key 27 
will select a desired stitch pattern and thus read out stitch control data 
from a memory unit mounted in the housing so that the sewing machine 
becomes ready for producing the selected stitch pattern on the workpiece. 
The illustrated sewing machine will be operated as follows. The sewing 
machine is made operative when power is supplied thereto. A desired one of 
the stitch patterns is selected by operation of the corresponding stitch 
pattern select key 27 provided on the keyboard panel 26, whereby the 
stitch control data of the selected stitch pattern is sequentially read 
out from the memory unit for determining each needle dropping point. Thus, 
the amounts of feeding the workpiece in X and Y directions will be 
determined and the resulting data are temporarily stored. Similarly, the 
data for controlling the solenoids 4 and/or 17 for actuating the presser 
bars 3 and/or 6 are temporarily stored. The workpiece feeding amounts 
determining data and the solenoid controlling data both for shifting the 
workpiece in X and Y directions will determine a first needle position 
relative to the workpiece to produce a first stitch of the selected stitch 
pattern. Further stitches are sequentially produced in like manner. 
FIG. 4 is a timing chart illustrating operation of the sewing machine by 
way of example. The needle 12 is reciprocated in synchronism with rotation 
of the upper shaft. The upper drive shaft phase is detected at least each 
10.degree. interval. The needle 12 comes to the upper dead point at 
0.degree. phase and then start descending so that from 100.degree. to 
260.degree. phase its pointed end penetrates the workpiece. In this 
example shown in FIG. 4, the stitch is produced while shifting the 
workpiece both in X and Y directions. First, a controller (not shown) is 
operated to start a sewing machine motor (not shown) to rotate the upper 
drive shaft. At a timing of the upper drive shaft phase of 260.degree., at 
which time the needle has just left from the workpiece to start ascending, 
the solenoid 7 is OFF in response to the solenoid controlling data (for Y 
direction shifting) so that the presser bar 6 descends by the biasing 
force of the spring 14. Thus, the workpiece is interposed under pressure 
between the press rollers 11a and 11b and the feed rollers 22a and 22b. 
Then at 270.degree. phase, the motor 21 is driven under control in 
response to the workpiece feeding amount determining data (for Y direction 
shifting) so that the workpiece is shifted over a predetermined distance 
or pitch in Y direction. The workpiece shifting operation in Y direction 
has been completed at 350.degree. phase. Then, at 0.degree. phase the 
solenoid 7 is turned ON to attract the presser bar 6 upwardly, thereby 
releasing the press rollers 11a and 11b from contact with the workpiece. 
At the same time, the solenoid 4 is turned OFF in response to the solenoid 
controlling data (for X direction shifting) so that the presser bar 3 
descends by the biasing force of the spring 13. Thus, the workpiece is 
interposed under pressure between the press roller 5 and the feed roller 
17. Then at 10.degree. phase, the motor 16 is driven under control in 
response to the workpiece feeding amount determining data (for X direction 
shifting) so that the workpiece is shifted over a predetermined distance 
or pitch in X direction. The workpiece is therefore shifted in X direction 
during 10.degree. to 90.degree. phase. Consequently, the workpiece has 
been shifted in X and Y directions in predetermined amounts respectively, 
which will be determined in response to the stitch control data of the 
selected stitch pattern, before producing each stitch. While the needle is 
penetrating the workpiece during 100.degree. to 260.degree. phase, the 
solenoid controlling data for X and Y directions control the sewing 
machine such that the solenoids 4 and 7 remain OFF so that the press 
rollers 5, 11a and 11b are all in contact with the workpiece under 
pressure. Thus, the needle 2 penetrates the workpiece which lies between 
the press rollers and the non-driven feed rollers 17, 22a and 22b, and the 
workpiece is therefore prevented from erroneously shifting in X and Y 
directions, whereby the stitch is produced on the workpiece. During 
100.degree. to 260.degree. phase, the workpiece feeding amount determining 
data and the solenoid controlling data for producing the next stitch will 
be processed based on the stitch control data therefor. The above 
described sequential operation is repeated each stitch to produce the 
selected stitch pattern. 
According to this invention, the workpiece is fed in a substantial amount 
in each stitch by employing roller means. Since the workpiece is fed in 
one direction and then in another direction normal to the said one 
direction, the workpiece can be fed in any direction and in any desired 
amount. Thus, the embroidery stitches can easily be produced with 
beautiful appearance. The sewing machine according to this invention is 
also applicable to the normal stitching operation without disturbing any 
characteristic inherent to the sewing machine. 
while this invention has been described in conjunction with a specific 
embodiment thereof, it is to be understood that many variations and 
modifications may be made without departing the scope and spirit as 
defined in the appended claims. For example, while the illustrated 
embodiment employs the solenoids for actuating the presser bars, it may be 
replaced with linear motors capable of varying downwardly directing 
pressure exerted onto the workpiece in synchronism with the drive means 
such that the downwardly directed pressure is adjusted according to the 
speed of feeding the workpiece. This will save energy or power of the 
motor used for driving the feed rollers. More particularly, as the motor 
accelerates the torque increases by virtue of inertia so that the 
downwardly directing pressure may be decreased accordingly. When the motor 
is running at a constant high speed, in turn, the presser bar must exert a 
sufficient degree of the downwardly directing pressure onto the workpiece 
to thereby prevent slippery motion of the workpiece. Use of the linear 
motor or the like capable of controlling the downwardly directing pressure 
exerted by the presser bars onto the workpiece will minimize a loss of 
power of the driving motors without decreasing efficiency of the workpiece 
feeding operation. Further, the needle may be a laterally swingable one, 
providing improved applicability of the stitch patterns to be produced 
with the sewing machine. In the illustrated embodiment the presser foot 8 
is secured to the lower end of the presser bar 6, various presser foots 
may be selectively attached to the presser bar 6 with a fastening means. 
The press and/or feed rollers may have uneven periphery for increasing 
friction with respect to the workpiece, thereby feeding the workpiece 
without slipperiness.