A driving device for a middle presser foot of a sewing machine

Abstract

The utility model relates to a drive arrangement of middle presser foot of sewing machine, including linear motor, connecting rod, current detector and stroke position detector, the linear motor includes motor stator and motor runner, the motor stator fixed mounting in sewing machine, the motor runner vertical linear movement, the connecting rod upper end with motor runner lower extreme direct fixed connection, lower extreme and middle presser foot direct connection, the current detector links to each other with linear motor, is used to obtain the working current of linear motor, the stroke position detector links to each other with linear motor, is used for detecting the displacement stroke of motor runner, the current detector and stroke position detector all link to each other with the control system of sewing machine, and the control system links to each other with linear motor control.

Description

Technical Field

[0001] This utility model relates to the field of sewing equipment technology, specifically to a drive device for the middle pressure foot of a sewing machine. Background Technology

[0002] The presser foot is mainly used in some special sewing machine fields, such as pattern sewing machines, bartacking machines, and template sewing machines. It is a very important moving part of the sewing machine. Currently, the presser foot is mainly driven by a motor or mechanical cam to achieve its up-and-down movement, and it has a certain synchronization relationship with the needle. When the needle leaves the fabric, the presser foot continues to press down on the fabric; when the needle rises to a certain height, the presser foot then leaves the fabric, ensuring the formation of the stitch.

[0003] Current presser foot drive mechanisms primarily utilize servo motors or similar power sources, connected to the presser foot via an intermediate transmission mechanism composed of several parts. When the servo motor rotates, the intermediate transmission mechanism facilitates the vertical linear motion of the presser foot. For example, patent application CN201110113231.X discloses a presser foot mechanism for sewing machines, comprising a transmission mechanism with multiple parts such as a connector, gear shaft, left and right support arms, bearings, and gear shafts. Existing designs suffer from complex transmission mechanisms with numerous parts, high total inertia, and require greater torque to achieve the target acceleration. This results in longer start-stop times and slower dynamic response. Consequently, even with a pre-set, precise motion trajectory curve for the servo motor, deviations between the actual displacement and the target trajectory still exist. As the spindle speed changes, the actual motion curve of the presser foot and the theoretical motion curve show different matching effects: at lower speeds, the curve matching effect is relatively good; at higher speeds, the deviation from the ideal curve increases significantly. The main reason is that due to the influence of mechanical inertia and errors, the lowest point of the actual motion curve of the presser foot fails to fully reach the theoretical lowest position of the set curve, resulting in inaccurate control of the gap between the presser foot and the fabric, which in turn leads to sewing defects such as skipped stitches and broken threads. In addition, because the presser foot stays at the bottom for too short a time, the thread loop formed after the needle pierces the fabric is often unstable, and the rotary hook cannot catch the thread. Utility Model Content

[0004] In view of the shortcomings of the prior art described above, the technical problem to be solved by this utility model is to provide a driving device for the middle presser foot of a sewing machine, which has a simple structure, low inertia, fast operation response, and precise control, and can make the actual motion curve of the middle presser foot better fit the theoretical design curve.

[0005] To achieve the above objectives, this utility model provides a driving device for the middle presser foot of a sewing machine, including a linear motor, a connecting rod, a current detector, and a stroke position detector. The linear motor includes a motor stator and a motor mover. The motor stator is fixedly installed in the sewing machine, and the motor mover moves vertically in a linear fashion. The upper end of the connecting rod is directly fixedly connected to the lower end of the motor mover, and the lower end is directly connected to the middle presser foot. The current detector is connected to the linear motor and is used to obtain the working current of the linear motor. The stroke position detector is connected to the linear motor and is used to detect the displacement stroke of the motor mover. Both the current detector and the stroke position detector are connected to the control system of the sewing machine, and the control system is connected to the linear motor control system.

[0006] Furthermore, the motor actuator and the connecting rod are integrated into one piece.

[0007] Furthermore, both the motor actuator and the connecting rod are provided with weight-reducing inner holes.

[0008] Furthermore, the lower end of the connecting rod is connected to the middle pressure foot by bolts. The connecting rod is provided with a connecting hole, and the middle pressure foot is provided with a strip-shaped hole extending in the vertical direction. The bolt passes through the strip-shaped hole and the connecting hole.

[0009] Furthermore, the stator of the linear motor is fixedly installed in the housing of the sewing machine.

[0010] Furthermore, the current detector and the travel position detector are integrated into the linear motor.

[0011] Furthermore, the travel position detector is a linear encoder.

[0012] As described above, the driving device involved in this utility model has the following beneficial effects:

[0013] 1. By using a linear motor to drive the presser foot and combining the detection signals from the current detector and the stroke position detector, high-precision closed-loop control can be achieved. It has advantages such as fast response and adaptive compensation, which can more accurately control the actual motion curve of the presser foot. It can match the set theoretical curve well at both low and high speeds, and better cooperate with the movement of the needle to improve the sewing quality.

[0014] 2. By controlling the motion of the linear motor, the time that the presser foot stays in the lowest position during normal sewing can be increased, ensuring that the fabric is fully fixed during the needle's ascent, avoiding skewing of the thread loop due to fabric displacement, and reducing the probability of missing the thread loop; the continuous pressure of the presser foot can counteract the fabric's rebound and prevent the thread loop from shrinking due to elastic deformation.

[0015] 3. The position of the presser foot is precisely controlled by a linear motor, achieving accurate positioning. In particular, the positioning of the presser foot can be adjusted according to the fabric thickness before sewing, improving work efficiency. Attached Figure Description

[0016] Figure 1 This is a schematic diagram showing the installation of the linear motor and connecting rod in this utility model.

[0017] Figure 2 for Figure 1 Enlarged view of circle A.

[0018] Figure 3 This is a schematic diagram of the structure of the motor actuator and connecting rod in this utility model.

[0019] Figure 4 This is a schematic diagram of the communication and control connection of the drive device of this utility model.

[0020] Explanation of icon numbers

[0021] 1. Medium pressure foot

[0022] 11 slotted holes

[0023] 2 needle plates

[0024] 3. Housing

[0025] 4. Linear Motor

[0026] 41 Motor stator

[0027] 42 Motor mover

[0028] 5 connecting rods

[0029] 51 Connecting hole

[0030] 6. Current detector

[0031] 7. Travel Position Detector

[0032] 8 Control System Detailed Implementation

[0033] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification.

[0034] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding. They are not intended to limit the scope of this invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, provided they do not affect the effectiveness or purpose of this invention, should still fall within the scope of the technical content disclosed herein. Furthermore, terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity and not intended to limit the scope of this invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of this invention.

[0035] See Figures 1 to 4 This utility model provides a driving device for the middle presser foot of a sewing machine, including a linear motor 4, a connecting rod 5, a current detector 6, and a stroke position detector 7. The linear motor 4 includes a motor stator 41 and a motor mover 42. The motor stator 41 is fixedly installed in the sewing machine, and the motor mover 42 moves vertically in a linear fashion. The upper end of the connecting rod 5 is directly fixedly connected to the lower end of the motor mover 42, and the lower end is directly connected to the middle presser foot 1. The current detector 6 is connected to the linear motor 4 and is used to obtain the working current of the linear motor 4. The stroke position detector 7 is connected to the linear motor 4 and is used to detect the displacement stroke of the motor mover 42. Both the current detector 6 and the stroke position detector 7 are connected to the control system 8 of the sewing machine, and the control system 8 is connected to the linear motor 4. The motor stator 41 of the linear motor 4 mainly includes an iron core, a coil, a housing, etc. The coil generates a magnetic field when energized. The motor mover 42 is generally composed of a permanent magnet or a conductor and can generate linear motion under the action of the magnetic field generated by the motor stator 41. The linear motor 4 can adopt an existing design, and its specific structure and working principle will not be described in detail.

[0036] The driving device of this utility model, when the presser foot 1 needs to move, issues a control command through the sewing machine's control system 8 to control the linear motor 4 to execute the corresponding movement. The motor mover 42 moves according to the corresponding motion curve and drives the presser foot 1 up and down through the connecting rod 5 to coordinate with the movement of the needle during normal sewing. The movement speed and stroke of the presser foot 1 are consistent with those of the motor mover 42. During the movement, the displacement stroke of the motor mover 42 is acquired in real time through the stroke position detector 7 and directly converted into the displacement stroke of the presser foot 1. Thus, the position of the presser foot 1 can be determined in real time, and it is possible to monitor whether the position of the presser foot 1 meets the requirements. Meanwhile, the current detector 6 acquires the working current of the linear motor 4 in real time, which can monitor the working status of the linear motor 4 and determine whether the middle pressure foot 1 contacts the fabric when it descends. Specifically, during the process of the motor mover 42 of the linear motor 4 driving the middle pressure foot 11 to descend, the working current of the linear motor 4 changes very little, especially during the uniform descent process, its working current can remain basically constant. However, when the lower end of the middle pressure foot 1 contacts the fabric or is released from the upper surface of the needle plate 2 located below the middle pressure foot 1, the load of the linear motor 4 increases, and its working current will increase suddenly. Therefore, by observing the change in the working current, it can be determined whether the lower end of the middle pressure foot 1 contacts the fabric or whether the middle pressure foot 1 is in contact with the fabric, which can facilitate the positioning of the middle pressure foot 1.

[0037] In this drive device, the linear motor 4 directly drives the intermediate pressure foot 1 through the connecting rod 5. The entire drive device has a simple structure, light weight, low inertia, and fast dynamic response. Combined with the current detector 6 and the stroke position detector 7, it can achieve high-precision closed-loop control, with advantages such as fast response and adaptive compensation. The motion control is more accurate, thus it can match the set theoretical motion curve well.

[0038] See Figures 1 to 4 The present invention will be further described below with reference to specific embodiments:

[0039] In this embodiment, see Figure 1 and Figure 3 As a preferred design, the motor mover 42 and the connecting rod 5 are integrated. In this case, the connecting rod 5 can be regarded as an extension of the motor mover 42. Both the motor mover 42 and the connecting rod 5 are provided with weight-reducing inner holes. The motor mover 42 and the connecting rod 5 can be made from a single hollow rod, which is convenient to manufacture and can further reduce the mass, thereby reducing inertia.

[0040] In this embodiment, see Figure 1 The motor stator 41 of the linear motor 4 is fixedly installed in the housing 3 of the sewing machine and located in the head of the machine. The installation position of the motor stator 41 is preferably as downward as possible, so as to minimize the length of the connecting rod 5 and further reduce inertia.

[0041] In this embodiment, see Figure 1 and Figure 3 As a preferred design, the lower end of the connecting rod 5 is connected to the intermediate pressure foot 1 by a bolt (not shown in the attached diagram). The connecting rod 5 has a connecting hole 51 on its side near the lower end, and the intermediate pressure foot 1 has a strip-shaped hole 11 extending in the vertical direction. The bolt passes through the strip-shaped hole 11 and the connecting hole 51, and the connecting rod 5 and the intermediate pressure foot 1 are fixedly connected by the bolt. The bolt can be used to fix the connecting rod 5 and the intermediate pressure foot 1 together, or the bolt can be threaded into the connecting hole 51. When the bolt is loosened, the fixed connection is released, and the intermediate pressure foot 1 can be adjusted to slide up and down relative to the connecting rod 5. At this time, the bolt can move up and down in the connecting hole 51, providing space for the intermediate pressure foot 1 to move up and down, thereby facilitating fine adjustment of the height of the intermediate pressure foot 1 to meet different working needs. After the intermediate pressure foot 1 is adjusted to the corresponding height, the bolt is tightened to fix the connecting rod 5 and the intermediate pressure foot 1 again.

[0042] In this embodiment, both the current detector 6 and the travel position detector 7 can be integrated into the linear motor 4, making the structure more compact. The travel position detector 7 can be a linear encoder, which typically consists of a light source, a grating, a photodetector, and a signal processing circuit. When the motor mover 42 of the linear motor 4 moves, the grating moves accordingly. The light emitted by the light source passes through the grating's etched lines, forming alternating bright and dark light signals. The photodetector converts these light signals into electrical signals, which are then processed by the signal processing circuit to obtain pulse or digital signals proportional to the displacement of the linear motor 4. The control system 8 accurately determines the position of the linear motor 4 based on these signals. The current detector 6 can be a current sensor connected to the drive circuit of the linear motor 4 to monitor the motor's operating current in real time. The controller compares and analyzes the current signal fed back by the current detector 6 with the motor's normal operating current under no-load or rated load conditions to determine the load change and whether the lower end of the pressure foot 1 is in contact with the fabric or needle plate 2. In other embodiments, the current detector 6 and the travel position detector 7 can also be other suitable existing detectors that can achieve the corresponding functions.

[0043] As can be seen from the above, the driving device of this utility model has the following beneficial effects:

[0044] 1. By using a linear motor 4 to drive the middle presser foot 1, and combining the detection signals from the current detector 6 and the stroke position detector 7, high-precision closed-loop control can be achieved. It has advantages such as fast response and adaptive compensation, which can more accurately control the actual motion curve of the middle presser foot 1. It can match the set theoretical curve well at both low speed (e.g., 1000 rpm) and high speed (e.g., 3000 rpm), and better cooperate with the movement of the needle to improve the sewing quality.

[0045] 2. By controlling the motion of the linear motor 4, the time that the middle presser foot 1 stays in the lowest position during normal sewing can be increased, ensuring that the fabric is fully fixed during the needle's rising phase, avoiding the skewing of the thread loop due to fabric displacement, and reducing the probability of missing the thread loop; the continuous pressing of the middle presser foot 1 can counteract the fabric's rebound and prevent the thread loop from shrinking due to elastic deformation.

[0046] 3. The position of the presser foot 1 is precisely controlled by the linear motor 4 to achieve accurate positioning. In particular, the positioning of the presser foot 1 can be adjusted according to the thickness of the fabric before sewing, thereby improving work efficiency.

[0047] In summary, this utility model effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0048] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. A driving device for the presser foot of a sewing machine, characterized in that: The sewing machine includes a linear motor (4), a connecting rod (5), a current detector (6), and a stroke position detector (7). The linear motor (4) includes a motor stator (41) and a motor mover (42). The motor stator (41) is fixedly installed in the sewing machine. The motor mover (42) moves vertically in a straight line. The upper end of the connecting rod (5) is directly fixedly connected to the lower end of the motor mover (42), and the lower end is directly connected to the middle pressure foot (1). The current detector (6) is connected to the linear motor (4) and is used to obtain the working current of the linear motor (4). The stroke position detector (7) is connected to the linear motor (4) and is used to detect the displacement stroke of the motor mover (42). Both the current detector (6) and the stroke position detector (7) are connected to the control system (8) of the sewing machine, and the control system (8) is connected to the linear motor (4) for control.

2. The driving device according to claim 1, characterized in that: The motor mover (42) and the connecting rod (5) are integrated.

3. The driving device according to claim 2, characterized in that: Both the motor mover (42) and the connecting rod (5) are provided with weight-reducing inner holes.

4. The driving device according to claim 1, characterized in that: The lower end of the connecting rod (5) is connected to the middle pressure foot (1) by bolts. The connecting rod (5) is provided with a connecting hole (51). The middle pressure foot (1) is provided with a strip hole (11) extending in the vertical direction. The bolt passes through the strip hole (11) and the connecting hole (51).

5. The driving device according to claim 1, characterized in that: The stator (41) of the linear motor (4) is fixedly installed in the housing (3) of the sewing machine.

6. The driving device according to claim 1, characterized in that: The current detector (6) and the travel position detector (7) are integrated in the linear motor (4).

7. The driving device according to claim 1, characterized in that: The travel position detector (7) is a linear encoder.

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