JPH04348793A - Sewing machine - Google Patents

Abstract

PURPOSE:To improve workability by storing change data concerning the pressing force of a presser spring to be operated to cloth pressing in relation to the condition of advancing sewing and changing the pressing force of the presser spring corresponding to the change data read out corresponding to the condition of advancing sewing. CONSTITUTION:A sewing machine frame 1 is equipped with the pressing force changing means of a presser spring 5, and this means is constituted to apply the prescribed pressing force through a cloth presser 4 to working fabric by moving an adjusting screw 28 downward through a rack 26 and a pinion 27 and compressing the presser spring 5 when an armature 32 of a servo solenoid 31 is protruded. The servo solenoid 31 is controlled by a control means (a) corresponding to the change data concerning the pressing force of the presser spring read from the storing means, which stores the change data in relation to the condition of advancing sewing, corresponding to the condition of advancing sewing. The pressing force of the presser spring is set so as to weaken the pressure of curved line sewing rather than pressure to press the cloth in straight line sewing.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a presser foot device for a sewing machine which applies presser pressure to a workpiece cloth placed on a sewing machine bed via a presser foot based on the biasing force of a presser spring.

0002

[Prior Art] Conventionally, for example, in order to sew along the four sides of a rectangular work cloth, the number of stitches required for sewing each side is set in advance, and the set number of stitches are sewn when forming the seams. After that, the machine stops and the presser foot is raised to allow the worker to turn the workpiece cloth.Then, when the worker operates the foot pedal, the presser foot is lowered and sewing of the set number of stitches in the next process begins. There are known sewing machines that are designed to do this.

0003

[Problems to be Solved by the Invention] However, with the above-mentioned conventional device, although sewing work can be performed efficiently when each step is a straight stitch, there is a problem in that during the process, the stitching occurs in the arc-shaped corners of the fabric. If a curved stitch along which a seam is formed is included, there is a problem in that the sewing operation cannot be performed smoothly.

[0004] In other words, since cloth feeding in a sewing machine is carried out by holding the work cloth between a feed dog that protrudes and retracts from the throat plate and is fed in four movements, and a cloth presser foot, the biasing force of the presser spring is set to be strong. The feeding efficiency of the feeding teeth is increased by increasing the clamping pressure. In order to perform curve stitching in this state, when feeding the work cloth between the feed dog and the presser foot, it is necessary to forcibly shift the work cloth horizontally along the shape of the work cloth by hand. There are cases where feeding cannot be carried out easily. This means that the lateral movement of the workpiece cloth occurs when the workpiece cloth is held between the throat plate and the presser foot (
This is because the cutting is performed against the clamping pressure when the feed dog is retracted from the throat plate, and this is particularly noticeable when the fabric to be processed is thin.

The present invention has been made to solve the above-mentioned problems, and its object is to provide a presser foot device for a sewing machine that can easily perform curved stitches.

[0006]

[Means for Solving the Problems] In order to achieve this object, the present invention provides a sewing machine in which the presser foot pressure can be changed. , a sewing machine equipped with a presser spring that urges the presser foot downward toward a workpiece cloth placed on a sewing machine bed, and data on changes in the urging force of the presser spring in relation to the progress of sewing. a storage device that stores the information, a reading device that reads change data from the storage device according to the sewing progress status after sewing has started, and changes the biasing force of the pressing spring based on the read change data. and means for changing.

[0007]

[Operation] Data on changes in the urging force of the pressing spring is stored in advance in the storage means in relation to the progress of sewing. When sewing actually starts, the reading means reads out the change data from the storage means according to the sewing progress status, and the changing means changes the biasing force of the pressing spring according to the change data. For this reason, for example, when sewing a straight line for a predetermined distance, then sewing a curve for a predetermined distance, and then sewing a straight line for a predetermined distance again, the pressure of the presser foot for straight stitching is higher than that of the presser foot for curved stitching. If you set the presser foot pressure to a weak value and relate the timing of changing the presser foot pressure to the sewing progress from the start of sewing, the presser foot pressure will be changed automatically during sewing, which will greatly improve work efficiency. be.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a playback sewing machine will be described in detail below with reference to the drawings.

Now, in the sewing machine of this embodiment, as shown in FIG. 1, a presser bar 2 is supported on the head of a sewing machine frame 1 so as to be movable up and down, and a presser bar holder 3 is attached to the upper part of the presser bar 2. At the same time, a presser foot 4 is attached to the lower end. A presser spring 5 as a spring member is disposed on the presser bar 2, and always urges the presser foot 4 downward to apply presser pressure to the workpiece cloth. A first rotary lever 6 is rotatably supported within the sewing machine frame 1 adjacent to the presser bar holder 3, and is biased to rotate in the direction of engagement with the presser bar holder 3 by the action of a spring 7. ing. A second rotary lever 8 is rotatably supported within the sewing machine frame 1 in correspondence with the first rotary lever 6, and between one arm portion of the second rotary lever 8 and the first rotary lever 6. A connecting rod 9 is interposed therebetween, and an operating rod 10 is connected to the other arm.

As shown in FIGS. 1 and 2, the sewing machine frame 1
A substantially rod-shaped linking member 12 is vertically movably penetratingly supported through an oil pan 11 provided at the lower part of the oil pan 11, and the operating rod 10 is engaged with the lower end of the upper part of the linking member 12. Linking body 1
A pair of front and rear support legs 13 are protruded from the lower surface of the oil pan 11 near the lower end of the oil pan 11, and a rotation shaft 14 is supported between the support legs 13 so as to be rotatable around a horizontal axis. At the front end of the rotation shaft 14 is an operating rod 15 that is approximately L-shaped in front.
is fixed via a mounting body 16, and on the left side of its lower end is an operating body 1 that can be pressed and operated by the knee, which constitutes an operating means.
7 is installed.

An actuating member 18 is fitted to the rear end of the rotating shaft 14 and fixed with a screw 19. Actuation member 1
A pair of protrusions 18a and 18b are formed protrudingly on both the left and right sides of the connecting member 12 on the upper surface of the right side protrusion 18a.
are engaged at the lower end. A spring 20 is fitted into the rotating shaft 14 at the front of the actuating member 18, and both ends of the spring 20 are hooked to the actuating member 18 and the oil pan 11, respectively. It is biased to rotate in the direction. A stopper screw 21 is adjustably screwed into the left protruding piece 18b of the actuating member 18, and is fixed at a predetermined adjustment position by a nut 22.

As shown in FIG. 2, the tip of the stopper screw 21 is normally brought into contact with the lower surface of the oil pan 11 under the action of the spring 20, and the actuating member 18 is held in a substantially horizontal original position. When the operating body 17 is pressed by the knee, the operating member 18 is rotated counterclockwise from its original position in FIG. 2 against the action of the spring 20, and the linking member 12
The presser foot 4 is raised via the operating rod 10, the second rotating lever 8, the connecting rod 9, the first rotating lever 6, the presser bar holder 3, and the like.

As shown in FIG. 1, a needle bar 23 is supported at the head of the sewing machine frame 1 in front of the presser bar 2 so as to be movable up and down, and a needle 24 is attached to the lower end of the needle bar 23. When the sewing machine main shaft (not shown) is rotated based on the drive of a motor 25 shown in FIG. Stitches are formed on the work cloth on the bed by cooperation with a provided thread loop catcher (not shown).

As shown in FIGS. 1 and 3, a rack 26 is supported within the head of the sewing machine frame 1 above the presser bar 2 so as to be movable left and right. A pinion 27 is rotatably supported within the head of the sewing machine frame 1 so as to mesh with the rack 26, and a screw hole 27a is formed in the center of the pinion 27. An adjustment screw 28 is screwed into the screw hole 27a of the pinion 27 so as to be movable up and down, and is prevented from rotating by a key 29 engaged with a keyway 28a on one side thereof. Then, the head of the pin 30 inserted into the pressing spring 5 is connected to the adjusting screw 2.
It is in contact with the lower end of 8.

A servo solenoid 31 is disposed in the head of the sewing machine frame 1 corresponding to the rack 26, and the tip of an armature 32 of the servo solenoid 31 is fixed to the right end of the rack 26. And the armature 3 of this servo solenoid 31
When the pinion 2 is operated to protrude, the rack 26 and the pinion 2
Adjusting screw 28 is moved downward via 7, and pressing spring 5
is compressed and a predetermined presser pressure is applied to the work cloth via the presser foot 4, and the armature 3 of the servo solenoid 31
2 is turned on, the adjustment screw 28 is moved upward via the rack 26 and pinion 27, the presser spring 5 is extended, and the pressure of the presser foot 4 on the work cloth is reduced or released. ing.

A potentiometer 33 as a detector is disposed in the head of the sewing machine frame 1 corresponding to the rack 26, and a pinion 35 that meshes with the rack 26 is fixed to the tip of its operating shaft 34. There is. When the pressing pressure of the presser foot 4 on the workpiece cloth is changed due to the protruding or retracting operation of the armature 32 of the servo solenoid 31, the actuating shaft 34 of the potentiometer 33 is moved via the pinio 35 by the left and right movement of the rack 26. is rotated, and the potentiometer 34 outputs a detection signal corresponding to the amount of movement of the armature 32.

As shown in FIG. 1, a foot-operable operation pedal 36 is disposed below the sewing machine frame 1 and is equipped with a front pedal switch 71 and a rear pedal switch 72 (see FIG. 4). The rear part 36 of this operation pedal 36
When the front pedal switch 71 is turned on by pressing the a side, a start signal is output to rotate the motor 25 at a speed corresponding to the amount of pressing, and after the pressing, the operation pedal 36 returns to the neutral state. When the front pedal switch 71 is returned to the OFF position, a signal is output to stop the rotation of the motor 25 and stop the needle 24 at the bottom dead center below the throat plate, and further, the operation pedal 3 is then turned off.
When the rear pedal switch 72 is turned on by the rear pedal on the front part 36b of the needle 6, the motor 25 is slightly rotated to cut the thread, and then the needle 24 is stopped at the top dead center above the throat plate. signal is output.

As shown in FIGS. 1 and 5, an operation box 37 is provided at the bottom of the sewing machine frame 1. The operation box 37 is provided with a first presser foot pressure setting device 38 consisting of a variable resistor, etc., and is applied to the work cloth via the presser foot 4 by the protruding operation of the armature 32 of the servo solenoid 31 during sewing operation. The presser pressure of the presser spring 5 can be set in advance depending on the thickness of the work cloth. The operation box 37 is also provided with a second presser foot pressure setting device 39 consisting of a variable resistor, etc., which controls the retraction of the armature 32 of the servo solenoid 31 when performing curve sewing or the like while rotating the work cloth during sewing. The reduced presser foot pressure when the presser foot 4's presser pressure against the workpiece cloth is reduced by the operation can be set in advance according to the thickness of the workpiece cloth and the like.

Further, a key group 61 consisting of a plurality of keys with lamps is provided on the front surface of the operation box 37. Among the keys 61, the memory key 62 is used during trial sewing work.
Operated to set trial sewing mode and transfer all data. The memorization key 63 is operated to store sewing data and the like for each sewing portion of the work cloth during trial sewing work. The regeneration key 64 is operated to set the regeneration sewing mode during regeneration sewing work. Further, the four pattern keys 65 are selectively operated to select and designate different sewing patterns during trial sewing work and regeneration sewing work.

As shown in FIG. 1, a pair of front and rear support legs 40 are protruded from the lower surface of the oil pan 11 near the left side of the operating body 17, and a rotation shaft 4 is provided between the support legs 40.
1 is rotatably supported around a horizontal axis. An actuating member 42 is fitted and fixed to the front end of the rotation shaft 41, and an actuating protrusion 42a is formed projecting from one side thereof. An operating lever 43 is protruded from the lower part of the operating member 42, and the operating member 42 can be rotated to the left by operating the operating lever 43 with the knee.

An operating switch 44 is provided at the bottom of the sewing machine frame 1 in correspondence with the operating protrusion 42a of the operating member 42. When the operating member 42 is rotated to the left based on the operation of the operating lever 43 when performing curve sewing or the like while rotating the work cloth during sewing, the operating switch 44 is closed and the operating switch 44 is closed. A command signal for operating the servo solenoid 31 is output from the operation switch 44.

Next, in the sewing machine configured as described above, the configuration of the control circuit mainly for controlling the operation of the servo solenoid 31 will be explained with reference to FIG. (R
OM) 52 and random access memory (RAM) 53
is connected.

The ROM 52 stores programs and the like for controlling the entire sewing machine, and the RAM 53 stores the operating amount of the potentiometer 33 corresponding to the movement of the armature 32 of the servo solenoid 31 and the presser foot pressure of the presser spring 5. The operating amount of the servo solenoid 31 is stored.

The CPU 51 also has the key group 61,
Potentiometer 33, first presser foot pressure setting device 38, second
Presser foot pressure setting device 39, operation stitch 44, needle position detector 70 which is provided at the end of the main shaft of the sewing machine (not shown) and outputs a needle up signal and a needle down signal as the main shaft of the sewing machine rotates, and a front foot switch 71 of the operating pedal 36. , a rear pedal switch 72 are connected via the input interface 54, and various signals from them are input to the CPU 51. Further, the CPU 51 has a servo solenoid 31 and a motor 25 connected to an output interface 55 and a driver 5.
6 and 57, and a drive or stop signal is output from the CPU 51 to the servo solenoid 31 and the motor 25.

The CPU 51 also includes a stitch number counter 66 for counting the number of stitches to be sewn based on any of the needle up signals from the needle position detector 70 accompanying the rotation of the main shaft of the sewing machine during sewing operation. Furthermore, the RAM of this embodiment
53 includes sewing data such as the number of stitches and feed pitch generated during the sewing of each sewing part of the workpiece cloth during trial sewing work, and first and second presser foot pressure settings according to the opening and closing of the operation switch 44, etc. A storage area is provided for storing pressure change data and the like for applying, reducing, or canceling the pressure of the presser foot 4 based on the set values of the devices 38 and 39.

Next, the operation of the playback sewing machine constructed as described above will be explained.

Now, in this sewing machine, when performing a trial sewing operation to sew a piece of cloth W2 such as a pocket onto the surface of the work cloth W1 as shown in FIG. 8, for example, the memory key 62 is pressed after the power is turned on. When the user operates to set the storage mode and selects and operates the pattern key 65 to designate one sewing pattern, a program shown in the flowchart of FIG. 6, which will be described later, is executed under the CPU 51.

First, in step S1, the CPU 51 outputs a command signal to the servo solenoid 31, causes the armature 32 to retract, and presses the presser spring 5 against the presser foot 4.
release the pressure. Therefore, by pressing the operating body 17 with the knee in this state, the presser foot 4 can be slightly raised, and the workpiece cloth can be easily positioned when sewing starts.

In the next step S2, the operating pedal 3
6 is awaited, and when the front pedal switch 71 is turned on by the front pedal operation on the rear 36a side of the operating pedal 36 and a start signal is input to the CPU 51, the program advances to step S3. In step S3, a command signal is output to the servo solenoid 31 and its armature 32 is operated to project, and the strong presser presser pressure of the presser spring 5 preset by the first presser foot pressure setting device 38 is applied via the presser foot 4. Added to processed cloth. In this state, in the next step S4, the motor 25 is started at a rotational speed corresponding to the forward depression amount of the operating pedal 36, and the sewing operation of the sewing machine is started.

Then, in the next step S5, it is determined whether or not the operation switch 44 is turned on, and the operation switch 44 is turned on based on the operation of the operation lever 43 with the knee.
If the answer is N, the process proceeds to step S6, where a command signal is output to the servo solenoid 31, and the armature 32
By the retracting operation, the presser pressure of the presser spring 5 against the work cloth is reduced to a weak pressure preset by the second presser pressure setting device 39. Therefore, in this state, sewing can be continued while rotating the work cloth to easily perform curve stitching. In the next step S7, the operation switch 44 is turned ON again, and the operation switch 44 is turned ON again.
At the same time as n, proceed to step S8 and servo solenoid 3
The first armature 32 is moved to project, and strong pressing pressure of the pressing spring 5 is applied to the work cloth.

After the operation of step S8, or if the operation switch 44 is not turned on in step S5, the CPU 51 waits for the front depression switch 71 of the operation pedal 36 to be turned off in step S9, and the operation pedal 36 is changed from the front depression state. When the neutral state is returned, the rotation of the motor 25 is stopped and the needle 24 is stopped at the bottom dead center.
The process advances to the next step S10. In this step S10, the needle 2 is lowered by the needle lower signal from the needle position detector 70.
When the needle down position of No. 4 is confirmed, the operation of the rear pedal switch 72 is determined in the next step S11. and,
If the front part 36b side of the operation pedal 36 is not operated by the rear pedal, the process returns to step S1 and the armature 32 of the servo solenoid 31 is retracted, the presser pressure of the presser spring 5 against the work cloth is released, and in this state In the next step S2, a forward depression operation of the operation pedal 36 is awaited. Therefore, in this presser foot pressure released state, the presser foot 4 can be slightly raised by pressing the operating body 17, and during sewing, the workpiece cloth or a piece of cloth such as a patch can be rotated and attached to another edge of the piece of cloth. You can continue sewing along the line.

On the other hand, in the determination in step S11, when the rear pedal switch 72 is turned on based on the rear pedal operation on the front part 36b of the operating pedal 36, the motor 25 is slightly rotated in the next step S12 to rotate the thread. After the cut is made, the needle 24 is stopped at top dead center. Next step S
When it is confirmed in step S13 that the needle 24 is stopped at the top dead center based on the needle up signal from the needle position detector 70, the process proceeds to step S14, where the armature 32 of the servo solenoid 31 is retracted and the workpiece cloth is The presser pressure of the presser spring 5 against the presser spring 5 is released. Therefore, in this state, the operating body 17
The pressing operation allows the presser foot 4 to be slightly raised, making it easy to remove the workpiece cloth and position a new workpiece cloth upon completion of sewing.

Then, in the next step S15, it is determined whether or not the operating pedal 36 is depressed forward, and as the operating pedal 36 is depressed forward, the forward depression switch 7 is activated.
1 is turned ON and the sewing operation is restarted, the process returns from step S15 to step S3, and presser pressure is applied to the work cloth based on the operation of the servo solenoid 18.
Further, if the operating pedal 36 is not depressed forward in step S15, this is confirmed and the operation of the sewing machine is ended.

In this manner, sewing is performed from the sewing start point P1 on the piece of cloth W2 shown in FIG. When is operated, the sewing data and presser foot pressure change data for the sewing region from points P1 to P3 are stored in the working area of the RAM 53 as a storage means. Thereafter, when the memory key 62 is operated with the needle being stopped after sewing is performed from the corner point P3 to the sewing end point P5 via the second curve point P4, the sewing at the sewing area from points P3 to P5 is performed. After the data and presser foot pressure change data are stored in the working area of the RAM 53, all data in the working area is transferred to the storage area corresponding to the designated sewing pattern, and the trial sewing operation is completed.

Next, when regenerating sewing work is to be performed following the trial sewing work, the program shown in the flowchart of FIG. 7 is started under the control of the CPU 51 when the sewing machine is powered on. The CPU 51 waits for the playback key 64 to be turned on in step S16, and when the playback key 64 is turned on.
If so, the process advances to step S17 and waits for designation of a sewing pattern. When one sewing pattern is designated by the selection operation of the pattern key 65, the CPU 51 proceeds to step S18.
Then, stored data corresponding to the designated sewing pattern is read from the storage area of the RAM 53.

The next step S19 to step S22 are the same as step S in the flowchart shown in FIG.
A program similar to the operations from step S1 to step S4 is executed, and with the presser foot pressure released by the operation of the servo solenoid 31, the presser foot is raised and lowered by operating the operating body 17, and the work cloth W1 and the piece of cloth W2 are moved. Sewing start point P
After positioning the servo solenoid 3 at the needle drop point, the servo solenoid 3
1, a strong presser foot pressure is applied, and in this state, the sewing operation is started by starting the motor 25. In the next step S23, the number of stitches for each stitch is detected by the stitch number counter 66 and the number of stitches is counted, and the program proceeds to the next step S24.

In this step S24, it is determined whether or not there is a command signal to reduce the presser foot pressure in the read data, and if there is a command signal, the process proceeds to step S25.
Then, the presser foot pressure is reduced by the operation of the servo solenoid 31. In the next step S26, a command signal for restoring the presser foot pressure is waited for from the read data, and at the same time as the command signal is received, in step S25, the presser foot pressure is restored to the applied state by the operation of the servo solenoid 31, and then the next step The process advances to S28. Therefore, Figure 8
In the recycled sewing work of the work cloth W1 and the piece of cloth W2 shown in FIG. 1, when the first curve point P2 is approached, the presser foot pressure is automatically reduced and the curve stitch can be easily performed. Incidentally, in the determination in step S24,
If there is no command signal, the program returns to step S25.
From there, the process bypasses S27 and proceeds to step S28.

In this step S28, it is determined whether or not the number of sewing stitches for one sewing region counted by the stitch number counter 66 matches the number of stored stitches, and if both numbers of stitches match, as shown in FIG. When sewing up to the corner point P3 on the piece of cloth W2 is performed, the program advances to step S29, where the needle 24 is stopped at the bottom dead center, and in this state, in the next step S30, it is determined whether the pattern is finished or not. It is determined whether If the needle is stopped at corner point P3 as described above, it is in the middle of the pattern, so
The program returns from step S30 to step S19, and the presser foot pressure is released by actuation of the servo solenoid 31. Therefore, in this state, the workpiece cloth W1 and the piece of cloth W2 can be rotated about the corner point P3 while raising the presser foot 4 by operating the operating body 17. Thereafter, in step S20, the operation pedal 36 is rotated. By stepping forward on the rear part 36a side, the program progresses through steps S21, S22, etc., and sewing is performed from the corner point P3 on the cloth piece W2 through the second curve point P4 to the sewing end point P5. Can be done.

Sewing is performed in this way, and step S29
After the needle is stopped in step S30, when it is determined in step S30 that the pattern has ended, the program returns to step S.
The process proceeds to step 31, where thread cutting is performed. Then step S
At step S32, the needle 24 is stopped at the top dead center, and at the same time as the needle is stopped, the process proceeds to step S33, where the presser foot pressure is released by the operation of the servo solenoid 31, and the regenerated sewing operation ends.

It should be noted that the present invention is not limited to the structure of the above-mentioned embodiment. For example, as a structure for raising and lowering the presser foot, a servo solenoid or the like may be used instead of the knee-operable operating body of the above-mentioned embodiment. It is also possible to arbitrarily change and embody the configuration of each part without departing from the spirit of the invention, such as by providing a device and configuring the presser foot to move up and down as the drive device is driven.

[0041]

[Effects of the Invention] As described in detail above, in this invention, data on changes in the biasing force of the pressing spring is stored in advance in the storage means in relation to the progress of sewing, and sewing is actually started. The reading means reads out the change data from the storage means in accordance with the sewing progress status, and the changing means is configured to change the biasing force of the pressing spring in accordance with the change data. Therefore, for example, when straight stitching is performed for a predetermined distance, followed by curve stitching for a predetermined distance, and then straight stitching is performed again for a predetermined distance, the pressure of the presser foot for straight stitching is higher than that of the presser foot for curved stitching. By setting the pressure to a low level and relating the timing of changing the presser foot pressure to the sewing progress from the start of sewing, the presser foot pressure will be automatically changed during sewing, greatly improving work efficiency compared to conventional methods. It has the advantage of improving. Since the presser foot pressure of the presser foot can be changed automatically in this way, it has the advantage of being practical and adaptable to various sewing modes, such as when performing straight and curved stitches in succession. .

[Brief explanation of drawings]

FIG. 1 is a partial perspective view showing the mechanical configuration of a playback sewing machine according to an embodiment of the present invention.

FIG. 2 is a partially sectional view showing an enlarged configuration for raising and lowering the presser foot.

FIG. 3 is an enlarged partial cross-sectional view showing a structure for adjusting presser pressure on a cloth presser;

FIG. 4 is a control circuit diagram for controlling the operation of a servo solenoid and a motor.

FIG. 5 is a front view of the operation box.

FIG. 6 is a flowchart showing the operation of the CPU during a teaching operation.

FIG. 7 is a flowchart showing the operation of the CPU during playback operation.

FIG. 8 is a partial plan view showing an example of sewing a piece of cloth such as a pocket onto a work cloth.

[Explanation of symbols]

1 Sewing machine frame 2 Presser bar 4 Presser foot 5 If you press it 17 Operation body 31 Servo solenoid 38 First presser foot pressure setting device 39 Second presser foot pressure setting device 44 Operation switch 51 CPU 62 Memory key 63 Memorize key 64 Play key

Claims (1)

[Claims] Claim 1: A presser bar having a cloth presser at its lower end and movably supported on a sewing machine frame, and a presser spring that urges the presser bar downward toward a work cloth placed on a sewing machine bed. A sewing machine comprising: a storage means that stores change data of the biasing force of the presser spring in relation to the progress of sewing; and change data from the storage means according to the progress of the sewing after sewing is started. a reading means for reading out the
A sewing machine capable of changing presser foot pressure, comprising: changing means for changing the biasing force of the presser spring based on the read change data.