A linear drive mechanism with unlimited travel and method

Abstract

The invention discloses a linear drive mechanism with unlimited stroke and a method thereof. The linear drive mechanism with unlimited stroke comprises a moving platform, a first and a second passive screw fixedly mounted on the lower end of the moving platform, an active screw meshing with the first and the second passive screws, and a motor module for driving the active screw to rotate. The external threads of the first and the second passive screws are in the same direction, the external threads of the active screw and the first passive screw are in opposite directions, and the motor module is mounted on a machine base. After the motor module drives the active screw to rotate, the active screw moves forward and backward on the first and the second passive screws in a spiral linear manner, so as to drive the moving platform to move forward and backward in a linear manner, and the active screw can partially extend beyond the end of the first passive screw or the second passive screw, so that the stroke of the moving platform is greater than the length of the first passive screw or the second passive screw, and a large-stroke linear motion can be achieved without increasing the width of the moving platform and the machine base, thereby reducing costs and achieving the purpose of small volume and large stroke of the equipment.

Description

Technical field:

[0001] The present invention relates to the field of linear drive technology, and in particular to a linear drive mechanism and method with unlimited stroke. Background technology:

[0002] The linear drive mechanism is a mechanism that must be used in the linear movement of various mechanical equipment, such as machine tools, automation equipment (such as digital printers), robot mobile handling, etc. At present, the widely used linear drive mechanisms are ball screw pairs, gear rack pairs, and belt gear pairs.

[0003] The above-mentioned ball screw pair is widely used in various precision equipment, such as machine tools. It has many advantages such as high speed, high precision and high stability in a short distance. However, when assembling the ball screw pair, two bearing seats are installed on both sides of the ball screw, and a servo motor is used to drive the ball screw to rotate. A drive sleeve is mounted on the ball screw, and the drive sleeve drives the moving seat to move linearly. The ball screw pair of this structure can only control the moving seat to move linearly within a distance whose stroke is less than the length of the ball screw. Its stroke is limited, so when the stroke needs to be increased, the width of the moving seat and the base must be increased. This will cause the size of the entire device to become extremely large and the cost to be higher. The purpose of small size and large stroke of the equipment cannot be achieved, which causes great trouble to the user.

[0004] The gear rack pair and the belt gear pair both have the above-mentioned technical problems.

[0005] In view of this, the inventor proposes the following technical solution. Summary of the invention:

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a linear drive mechanism and method with unlimited travel.

[0007] In order to solve the above technical problems, the present invention adopts the following first technical solution: the linear drive mechanism with unlimited stroke includes a moving platform, a first passive screw and a second passive screw fixedly installed at the lower end of the moving platform, an active screw meshing with the first passive screw and the second passive screw, and a motor module for driving the active screw to rotate, the external threads of the first passive screw and the second passive screw are in the same direction, the external threads of the active screw and the first passive screw are in opposite directions, the motor module is installed on the machine base, and after the motor module drives the active screw to rotate, the active screw drives the first passive screw and the second passive screw to move forward and backward synchronously to drive the moving platform to move forward and backward, and the stroke of the moving platform is greater than the length of the first passive screw or the second passive screw.

[0008] Furthermore, in the above technical solution, the surfaces of the first passive screw and the second passive screw are respectively provided with a first countersunk hole and a second countersunk hole. After the first screw passes through the first countersunk hole, the first passive screw is locked to the lower end of the moving platform. After the second screw passes through the second countersunk hole, the second passive screw is locked to the lower end of the moving platform. A gap is formed between the first passive screw and the second passive screw, and the active screw is placed in the gap.

[0009] Furthermore, in the above technical solution, both ends of the first passive screw and the second passive screw extend to both ends of the moving platform respectively; a boss is provided on the lower end surface of the moving platform, and a first mounting groove and a second mounting groove are provided on the lower end surface of the boss in parallel; the first passive screw and the second passive screw are respectively installed in the first mounting groove and the second mounting groove; the first passive screw and the second passive screw are both made of Saigang material.

[0010] Furthermore, in the above technical solution, the motor module includes a fixed base fixedly installed on the upper end of the base, a first support plate and a second support plate rotatably installed on both sides of the fixed base, a first spring mechanism connected between the first support plate and the fixed base, a second spring mechanism connected between the second support plate and the fixed base, a motor frame installed on the first support plate, a motor installed on the motor frame, a first pulley installed on the rotating shaft of the motor, a second pulley installed on the end of the active screw and a transmission belt connected between the first pulley and the second pulley, the two ends of the active screw are respectively installed on the first support plate and the second support plate through the first bearing and the second bearing, and the first support plate and the second support plate are respectively pressed toward the first passive screw and the second passive screw under the elastic force of the first spring mechanism and the second spring mechanism, so that the active screw is always tightly matched with the first passive screw and the second passive screw.

[0011] Furthermore, in the above technical solution, a counterweight is installed on the second support plate.

[0012] Furthermore, in the above technical solution, the surface of the active screw protrudes outside the surfaces of the first support plate and the second support plate, and the surface of the active screw protrudes outside the surface of the second pulley; the first support plate is installed with a third bearing, and the first shaft body is passed through the third bearing, and the first shaft body is installed on one side of the fixed seat; the second support plate is installed with a fourth bearing, and the second shaft body is passed through the fourth bearing, and the second shaft body is installed on the other side of the fixed seat.

[0013] Furthermore, in the above technical solution, the first spring mechanism includes a first connecting plate fixed to one side of the fixed base and a first spring connected between the first connecting plate and the first support plate; the second spring mechanism includes a second connecting plate fixed to the other side of the fixed base and a second spring connected between the second connecting plate and the second support plate.

[0014] Furthermore, in the above technical solution, a drawn aluminum round shaft guide rail is provided on the machine base; a plurality of pulleys are provided at the lower end of the movable platform, the pulleys are located on both sides of the drawn aluminum round shaft guide rail, and the round shafts on both sides of the drawn aluminum round shaft guide rail are respectively placed in the slide grooves on the outer surface of the pulley.

[0015] In order to solve the above technical problems, the present invention adopts the following second technical solution: the linear driving method with unlimited stroke includes the following steps: two parallel first passive screws and second passive screws are arranged at the lower end of the moving platform, the surfaces of the first passive screw and the second passive screw are not blocked, and the external threads of the first passive screw and the second passive screw are in the same direction; an active screw and a motor module for driving the active screw to rotate are arranged on the machine base, the external threads of the active screw and the first passive screw are in opposite directions, the active screw is meshed with the first passive screw and the second passive screw, and can be spirally moved at any position on the first passive screw and the second passive screw, and can also extend out of the first passive screw and the second passive screw; after the motor module drives the active screw to rotate, the active screw drives the first passive screw and the second passive screw to move synchronously forward and backward to drive the moving platform to move forward and backward, and the stroke of the moving platform is greater than the length of the first passive screw or the second passive screw.

[0016] Furthermore, in the above technical solution, the motor module includes a fixed base fixedly installed on the upper end of the base, a first support plate and a second support plate rotatably installed on both sides of the fixed base, a first spring mechanism connected between the first support plate and the fixed base, a second spring mechanism connected between the second support plate and the fixed base, a motor frame installed on the first support plate, a motor installed on the motor frame, a first pulley installed on the rotating shaft of the motor, a second pulley installed on the end of the active screw and a transmission belt connected between the first pulley and the second pulley, the two ends of the active screw are respectively installed on the first support plate and the second support plate through the first bearing and the second bearing, and the first support plate and the second support plate are respectively pressed toward the first passive screw and the second passive screw under the elastic force of the first spring mechanism and the second spring mechanism, so that the active screw is always tightly matched with the first passive screw and the second passive screw.

[0017] After adopting the above technical scheme, the present invention has the following beneficial effects compared with the prior art: the present invention fixes the first passive screw and the second passive screw on the lower end of the moving platform, and adopts an active screw to mesh with the first passive screw and the second passive screw. After the motor module drives the active screw to rotate, since the first passive screw and the second passive screw are fixed, the active screw moves back and forth on the first passive screw and the second passive screw in a spiral linear manner, so as to drive the moving platform to move back and forth in a linear manner, and the active screw can partially extend beyond the end of the first passive screw or the second passive screw, so that the stroke of the moving platform is greater than the length of the first passive screw or the second passive screw, and the stroke of the moving platform will not be limited by the active screw and the first passive screw and the second passive screw, and a large stroke linear motion can be achieved without increasing the width of the moving platform and the base, thereby reducing costs, and achieving the purpose of small size and large stroke of the equipment, which is extremely convenient to use. Description of the drawings:

[0018] Figure 1 is a stereogram of the present invention;

[0019] Figure 2 It is a front view of the present invention;

[0020] Figure 3 It is a stereogram of another viewing angle of the present invention;

[0021] Figure 4 It is a three-dimensional diagram of the present invention after the base is disassembled;

[0022] Figure 5 It is an assembly diagram of the active screw and the motor module in the present invention;

[0023] Figure 6 It is an assembly diagram of the active screw and the motor module in the present invention from another perspective. Specific implementation method:

[0024] The present invention is further described below in conjunction with specific embodiments and drawings.

[0025] See Figure 1-6As shown, a linear drive mechanism with unlimited stroke includes a moving platform 1, a first passive screw 2 and a second passive screw 3 fixedly mounted at the lower end of the moving platform 1, an active screw 4 meshed with the first passive screw 2 and the second passive screw 3, and a motor module 5 for driving the active screw 4 to rotate. The external threads of the first passive screw 2 and the second passive screw 3 are in the same direction, and the external threads of the active screw 4 and the first passive screw 2 are in opposite directions. The motor module 5 is installed on a base 6. After the motor module 5 drives the active screw 4 to rotate, the active screw 4 drives the first passive screw 2 and the second passive screw 3 to move forward and backward synchronously, so as to drive the moving platform 1 to move forward and backward, and the stroke of the moving platform 1 is greater than the length of the first passive screw 2 or the second passive screw 3. The present invention fixes the first passive screw 2 and the second passive screw 3 on the lower end of the moving platform 1, and adopts an active screw 4 to mesh with the first passive screw 2 and the second passive screw 3. After the motor module 5 drives the active screw 4 to rotate, since the first passive screw 2 and the second passive screw 3 are fixed, the active screw 4 moves back and forth on the first passive screw 2 and the second passive screw 3 in a spiral linear manner, so as to drive the moving platform 1 to move back and forth in a linear manner, and the active screw 4 can partially extend beyond the end of the first passive screw 2 or the second passive screw 3, so that the stroke of the moving platform 1 is greater than the length of the first passive screw 2 or the second passive screw 3, and the stroke of the moving platform 1 will not be limited by the active screw 4 and the first passive screw 2 and the second passive screw 3, and a large stroke linear motion can be achieved without increasing the width of the moving platform 1 and the base 6, thereby reducing costs, and achieving the purpose of small size and large stroke of the equipment, which is extremely convenient to use.

[0026] The external threads of the first passive screw 2 and the second passive screw 3 are in the same direction, and the external threads of the active screw 4 are in the opposite direction to those of the first passive screw 2; that is, when the external threads of the first passive screw 2 and the second passive screw 3 are positive threads, the external threads of the active screw 4 are negative threads. Alternatively, when the external threads of the first passive screw 2 and the second passive screw 3 are negative threads, the external threads of the active screw 4 are positive threads.

[0027] The first passive screw 2 and the second passive screw 3 are both made of Si steel material, which is light in weight, wear-resistant, low in cost, and more convenient to use.

[0028] The surfaces of the first passive screw 2 and the second passive screw 3 are respectively provided with a first countersunk hole 21 and a second countersunk hole 31. After the first screw passes through the first countersunk hole 21, the first passive screw 2 is locked to the lower end of the mobile platform 1. After the second screw passes through the second countersunk hole 31, the second passive screw 3 is locked to the lower end of the mobile platform 1. A gap is formed between the first passive screw 2 and the second passive screw 3, and the active screw 4 is placed in the gap. The assembly structure of the first passive screw 2 and the second passive screw 3 is simple, and there is no obstruction on the surface of the first passive screw 2 and the second passive screw 3, which can realize infinite transmission and achieve the purpose of unlimited travel. Specifically, the two ends of the first passive screw 2 and the second passive screw 3 extend to the two ends of the mobile platform 1 respectively; the lower end surface of the mobile platform 1 is provided with a boss 11, and the lower end surface of the boss 11 is provided with a first mounting groove 111 and a second mounting groove 112 distributed in parallel; the first passive screw 2 and the second passive screw 3 are respectively installed in the first mounting groove 111 and the second mounting groove 112.

[0029] The motor module 5 includes a fixing seat 51 fixedly mounted on the upper end of the machine base 6, a first support plate 52 and a second support plate 53 rotatably mounted on both sides of the fixing seat 51, a first spring mechanism 54 connected between the first support plate 52 and the fixing seat 51, a second spring mechanism 55 connected between the second support plate 53 and the fixing seat 51, a motor frame 56 mounted on the first support plate 52, a motor 57 mounted on the motor frame 56, a first pulley mounted on the rotating shaft of the motor 57, a second pulley 59 mounted on the end of the active screw 4, and a connecting rod. A transmission belt 50 is connected between the first pulley and the second pulley 59, and both ends of the active screw 4 are respectively installed on the first support plate 52 and the second support plate 53 through the first bearing and the second bearing, and the first support plate 52 and the second support plate 53 are respectively pressed toward the first passive screw 2 and the second passive screw 3 under the elastic force of the first spring mechanism 54 and the second spring mechanism 55, so that the active screw 4 is always closely matched with the first passive screw 2 and the second passive screw 3, thereby ensuring the stability of the transmission between the active screw 4 and the first passive screw 2 and the second passive screw 3.

[0030] A counterweight 500 is installed on the second support plate 53 to ensure that the first support plate 52 and the second support plate 53 have equivalent load-bearing capacity, making the entire structure more stable.

[0031] The surface of the active screw 4 protrudes from the surfaces of the first support plate 52 and the second support plate 53, and the surface of the active screw 4 protrudes from the surface of the second pulley 59; the first support plate 52 is installed with a third bearing 521, and the first shaft 522 is passed through the third bearing 521, and the first shaft 522 is installed on one side of the fixed seat 51; the second support plate 53 is installed with a fourth bearing 531, and the second shaft 532 is passed through the fourth bearing 531, and the second shaft 532 is installed on the other side of the fixed seat 51.

[0032] The first spring mechanism 54 includes a first connecting piece 541 fixed to one side of the fixing seat 51 and a first spring 542 connected between the first connecting piece 541 and the first supporting plate 52; the second spring mechanism 55 includes a second connecting piece 551 fixed to the other side of the fixing seat 51 and a second spring connected between the second connecting piece 551 and the second supporting plate 53, so that the active screw 4 and the first passive screw 2 and the second passive screw 3 are always closely matched, ensuring the stability of the transmission between the active screw 4 and the first passive screw 2 and the second passive screw 3.

[0033] A drawn aluminum round shaft guide rail 61 is provided on the machine base 6; a plurality of pulleys 12 are provided at the lower end of the movable platform 1, and the pulleys 12 are located on both sides of the drawn aluminum round shaft guide rail 61, and the round shafts 611 on both sides of the drawn aluminum round shaft guide rail 61 are respectively placed in the slide grooves on the outer surfaces of the pulleys 12, so that the movable platform 1 is stably installed on the machine base 6, and the movable platform 1 can move stably on the machine base 6.

[0034] In summary, the present invention fixes the first passive screw 2 and the second passive screw 3 on the lower end of the moving platform 1, and adopts an active screw 4 to mesh with the first passive screw 2 and the second passive screw 3. After the motor module 5 drives the active screw 4 to rotate, since the first passive screw 2 and the second passive screw 3 are fixed, the active screw 4 moves back and forth on the first passive screw 2 and the second passive screw 3 in a spiral linear manner, so as to drive the moving platform 1 to move back and forth in a linear manner, and the active screw 4 can partially extend beyond the end of the first passive screw 2 or the second passive screw 3, so that the stroke of the moving platform 1 is greater than the length of the first passive screw 2 or the second passive screw 3, and the stroke of the moving platform 1 will not be limited by the active screw 4 and the first passive screw 2 and the second passive screw 3, and a large stroke linear motion can be achieved without increasing the width of the moving platform 1 and the base 6, thereby reducing costs, and achieving the purpose of small size and large stroke of the equipment, which is extremely convenient to use.

[0035] The present invention also provides a linear driving method with unlimited stroke, which comprises the following steps:

[0036] Two parallel first passive screws 2 and second passive screws 3 are arranged at the lower end of the moving platform 1, and the surfaces of the first passive screws 2 and the second passive screws 3 are not blocked; the external threads of the first passive screws 2 and the second passive screws 3 have the same direction;

[0037] An active screw 4 and a motor module 5 for driving the active screw 4 to rotate are arranged on the machine base 6. The external thread direction of the active screw 4 is opposite to that of the first passive screw 2. The active screw 4 is meshed with both the first passive screw 2 and the second passive screw 3, and can be spirally moved at any position on the first passive screw 2 and the second passive screw 3, and can also extend out of the first passive screw 2 and the second passive screw 3;

[0038] After the motor module 5 drives the active screw 4 to rotate, the active screw 4 drives the first passive screw 2 and the second passive screw 3 to move forward and backward synchronously, so as to drive the movable platform 1 to move forward and backward, and the stroke of the movable platform 1 is greater than the length of the first passive screw 2 or the second passive screw 3.

[0039] The present invention fixes the first passive screw 2 and the second passive screw 3 on the lower end of the moving platform 1, and adopts an active screw 4 to mesh with the first passive screw 2 and the second passive screw 3. After the motor module 5 drives the active screw 4 to rotate, since the first passive screw 2 and the second passive screw 3 are fixed, the active screw 4 moves back and forth on the first passive screw 2 and the second passive screw 3 in a spiral linear manner, so as to drive the moving platform 1 to move back and forth in a linear manner, and the active screw 4 can partially extend beyond the end of the first passive screw 2 or the second passive screw 3, so that the stroke of the moving platform 1 is greater than the length of the first passive screw 2 or the second passive screw 3, and the stroke of the moving platform 1 will not be limited by the active screw 4 and the first passive screw 2 and the second passive screw 3, and a large stroke linear motion can be achieved without increasing the width of the moving platform 1 and the base 6, thereby reducing costs, and achieving the purpose of small size and large stroke of the equipment, which is extremely convenient to use.

[0040] The motor module 5 includes a fixing seat 51 fixedly mounted on the upper end of the machine base 6, a first support plate 52 and a second support plate 53 rotatably mounted on both sides of the fixing seat 51, a first spring mechanism 54 connected between the first support plate 52 and the fixing seat 51, a second spring mechanism 55 connected between the second support plate 53 and the fixing seat 51, a motor frame 56 mounted on the first support plate 52, a motor 57 mounted on the motor frame 56, a first pulley mounted on the rotating shaft of the motor 57, a second pulley 59 mounted on the end of the active screw 4, and a connecting rod. A transmission belt 50 is connected between the first pulley and the second pulley 59, and both ends of the active screw 4 are respectively installed on the first support plate 52 and the second support plate 53 through the first bearing and the second bearing, and the first support plate 52 and the second support plate 53 are respectively pressed toward the first passive screw 2 and the second passive screw 3 under the elastic force of the first spring mechanism 54 and the second spring mechanism 55, so that the active screw 4 is always closely matched with the first passive screw 2 and the second passive screw 3, thereby ensuring the stability of the transmission between the active screw 4 and the first passive screw 2 and the second passive screw 3.

[0041] Of course, the above description is only a specific embodiment of the present invention and is not intended to limit the scope of implementation of the present invention. All equivalent changes or modifications made according to the structure, characteristics and principles described in the patent application scope of the present invention should be included in the patent application scope of the present invention.

Claims

1. A linear drive mechanism with unlimited travel, characterized in that: The invention comprises a moving platform (1), a first passive screw (2) and a second passive screw (3) fixedly mounted at the lower end of the moving platform (1), an active screw (4) meshing with the first passive screw (2) and the second passive screw (3), and a motor module (5) for driving the active screw (4) to rotate. The first passive screw (2) and the second passive screw (3) have external threads in the same direction, and the active screw (4) and the first passive screw (2) have external threads in opposite directions. The motor module (5) is mounted on a machine base (6). After the motor module (5) drives the active screw (4) to rotate, the active screw (4) drives the first passive screw (2) and the second passive screw (3) to move forward and backward synchronously, thereby driving the moving platform (1) to move forward and backward. The travel of the moving platform (1) is greater than the length of the first passive screw (2) or the second passive screw (3). The two ends of the first passive screw (2) and the second passive screw (3) extend to the two ends of the moving platform (1) respectively; the lower end surface of the moving platform (1) is provided with a boss (11), and the lower end surface of the boss (11) is provided with a first mounting groove (111) and a second mounting groove (112) distributed in parallel; the first passive screw (2) and the second passive screw (3) are respectively installed in the first mounting groove (111) and the second mounting groove (112); the first passive screw (2) and the second passive screw (3) are both made of Saigang material; The motor module (5) comprises a fixing seat (51) fixedly mounted on the upper end of the machine base (6), a first support plate (52) and a second support plate (53) rotatably mounted on both sides of the fixing seat (51), a first spring mechanism (54) connected between the first support plate (52) and the fixing seat (51), a second spring mechanism (55) connected between the second support plate (53) and the fixing seat (51), a motor frame (56) mounted on the first support plate (52), a motor (57) mounted on the motor frame (56), a first pulley mounted on the rotating shaft of the motor (57), and a first spring mechanism (56) mounted on the main frame (56). A second pulley (59) at the end of the active screw rod (4) and a transmission belt (50) connected between the first pulley and the second pulley (59); the two ends of the active screw rod (4) are respectively mounted on the first support plate (52) and the second support plate (53) through the first bearing and the second bearing, and the first support plate (52) and the second support plate (53) are respectively pressed against the first passive screw rod (2) and the second passive screw rod (3) under the elastic force of the first spring mechanism (54) and the second spring mechanism (55), so that the active screw rod (4) is always closely matched with the first passive screw rod (2) and the second passive screw rod (3).

2. A linear drive mechanism with unlimited stroke according to claim 1, characterized in that: The surfaces of the first passive screw rod (2) and the second passive screw rod (3) are respectively provided with a first countersunk hole (21) and a second countersunk hole (31); the first screw passes through the first countersunk hole (21) to lock the first passive screw rod (2) to the lower end of the movable platform (1); the second screw passes through the second countersunk hole (31) to lock the second passive screw rod (3) to the lower end of the movable platform (1); a gap is formed between the first passive screw rod (2) and the second passive screw rod (3); the active screw rod (4) is placed in the gap.

3. A linear drive mechanism with unlimited stroke according to claim 1, characterized in that: A counterweight block (500) is mounted on the second support plate (53).

4. The linear drive mechanism with unlimited stroke according to claim 1, characterized in that: The surface of the active screw rod (4) protrudes outside the surfaces of the first support plate (52) and the second support plate (53), and the surface of the active screw rod (4) protrudes outside the surface of the second pulley (59); the first support plate (52) is installed with a third bearing (521), a first shaft (522) is passed through the third bearing (521), and the first shaft (522) is installed on one side of the fixing seat (51); the second support plate (53) is installed with a fourth bearing (531), a second shaft (532) is passed through the fourth bearing (531), and the second shaft (532) is installed on the other side of the fixing seat (51).

5. The linear drive mechanism with unlimited stroke according to claim 1, characterized in that: The first spring mechanism (54) comprises a first connecting piece (541) fixed to one side of the fixing seat (51) and a first spring (542) connected between the first connecting piece (541) and the first support plate (52); the second spring mechanism (55) comprises a second connecting piece (551) fixed to the other side of the fixing seat (51) and a second spring connected between the second connecting piece (551) and the second support plate (53).

6. The linear drive mechanism with unlimited stroke according to claim 1, characterized in that: The machine base (6) is provided with an aluminum round shaft guide rail (61); a plurality of pulleys (12) are provided at the lower end of the movable platform (1), the pulleys (12) are located on both sides of the aluminum round shaft guide rail (61), and the round shafts (611) on both sides of the aluminum round shaft guide rail (61) are respectively placed in the slide grooves on the outer surface of the pulley (12).

7. A linear drive method with unlimited stroke, characterized in that: It includes the following steps: Two parallel first passive screws (2) and second passive screws (3) are arranged at the lower end of the moving platform (1); the surfaces of the first passive screws (2) and the second passive screws (3) are not blocked; and the external threads of the first passive screws (2) and the second passive screws (3) are in the same direction; An active screw (4) and a motor module (5) for driving the active screw (4) to rotate are arranged on the machine base (6); the active screw (4) has an external thread direction opposite to that of the first passive screw (2); the active screw (4) is meshed with both the first passive screw (2) and the second passive screw (3), and can be spirally moved at any position on the first passive screw (2) and the second passive screw (3), and can also extend outside the first passive screw (2) and the second passive screw (3); After the motor module (5) drives the active screw (4) to rotate, the active screw (4) drives the first passive screw (2) and the second passive screw (3) to move forward and backward synchronously, thereby driving the moving platform (1) to move forward and backward, and the stroke of the moving platform (1) is greater than the length of the first passive screw (2) or the second passive screw (3); The motor module (5) comprises a fixing seat (51) fixedly mounted on the upper end of the machine base (6), a first support plate (52) and a second support plate (53) rotatably mounted on both sides of the fixing seat (51), a first spring mechanism (54) connected between the first support plate (52) and the fixing seat (51), a second spring mechanism (55) connected between the second support plate (53) and the fixing seat (51), a motor frame (56) mounted on the first support plate (52), a motor (57) mounted on the motor frame (56), a first pulley mounted on the rotating shaft of the motor (57), and a first spring mechanism (56) mounted on the main frame (56). A second pulley (59) at the end of the active screw rod (4) and a transmission belt (50) connected between the first pulley and the second pulley (59); the two ends of the active screw rod (4) are respectively mounted on the first support plate (52) and the second support plate (53) through the first bearing and the second bearing, and the first support plate (52) and the second support plate (53) are respectively pressed against the first passive screw rod (2) and the second passive screw rod (3) under the elastic force of the first spring mechanism (54) and the second spring mechanism (55), so that the active screw rod (4) is always closely matched with the first passive screw rod (2) and the second passive screw rod (3).

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