A manual plane cam profile acquisition experimental teaching device and experimental method

Abstract

The present invention provides a manual plane cam profile acquisition experimental teaching device and experimental method, which can easily achieve high-pair matching between the plane cam and the follower, and can easily replace plane cams with different profiles and different types of followers. The offset distance of the follower can be adjusted according to needs. The handle and connecting rod mechanism drive the ratchet mechanism to move at a fixed angle in one direction to drive the cam to perform intermittent motion. The cam intermittent motion interval angle can be achieved by replacing ratchets with different numbers of teeth, and at the same time, the position of the crank bracket in the slide groove is changed to ensure that the accurate intermittent angle is achieved after the ratchet is replaced. The pointer on the cam follower and the scale on the follower guide are used to facilitate the acquisition of the follower displacement. The experimental device can realize manual detection of the plane cam profile.

Description

Technical Field

[0001] The invention belongs to the technical field of mechanical principle and mechanism, and particularly relates to a cam mechanism, and specifically relates to a manual plane cam profile acquisition experimental teaching device and an experimental method. Background Art

[0002] The cam mechanism is one of the most commonly used mechanisms in mechanical equipment. It is widely used in various automatic control equipment because of its simple and compact structure and the ability of the follower to achieve predetermined regular changes.

[0003] The theoretical content of cam mechanism is relatively abstract and difficult for students to learn, especially when it comes to cam profile design and analysis, as well as the comprehensive application of cam mechanism.

[0004] At present, domestic cam teaching equipment integrates motor drive and sensor acquisition, and uses computers to perform quantitative or qualitative test and analysis. These devices are highly comprehensive and are helpful for students to learn and understand cam mechanisms, but they have a mediocre effect on students' comprehensive application of cam mechanism knowledge and design analysis.

[0005] These cam mechanism experimental devices generally cannot change system parameters, are complex to operate and install, and are bulky, which is not conducive to use in cam mechanism teaching experiments. Summary of the invention

[0006] The purpose of the present invention is to provide a new manual plane cam profile acquisition experimental teaching device in view of the actual needs of the current cam mechanism experimental teaching and the shortage of current cam teaching equipment. The device has the characteristics of light and simple structure, convenient use, flexible replacement of experimental cams and followers, low cost, etc., which can well meet the needs of obtaining different types of disc cam profile curves in the cam mechanism experimental teaching. The technical solution of the present invention is:

[0007] A manual plane cam profile acquisition experimental teaching device, characterized in that it includes the following components: an equipment base, a plurality of support seats, fixing bolts, an experimental cam mounting shaft, a mounting support plate, an experimental cam, a follower, a follower guide, a reset spring, a scale pointer, a plurality of hinge bolts and locking nuts thereof, a connecting rod, a crank, a handle, a crank bracket, a rocker, a pawl, a ratchet, a locking nut, and a follower guide set screw; a ratchet positioning flat key, a ratchet positioning sleeve, a bearing, an experimental cam positioning sleeve, an experimental cam positioning flat key, a mounting shaft locking nut, and a pin on the experimental cam mounting shaft;

[0008] The equipment base and the support base of the mounting support plate are positioned by a dovetail groove, a rectangular groove is provided in the support base, the mounting support plate and the crank bracket are respectively embedded in the rectangular grooves of their respective support bases, and fixed by fixing bolts and locking nuts; the support base can be manually moved along the groove direction in the dovetail groove of the equipment base;

[0009] A horizontal dovetail slide rail is arranged on the upper part of the support plate, a follower guide is arranged on the upper part of the slide rail, the follower guide is slidably connected with the dovetail slide rail and is locked by a follower guide set screw, the follower is slidably connected with the follower guide to achieve the guide cooperation of the follower moving in the vertical direction; the reset spring is arranged on the follower; the dial pointer is arranged in the hole on the follower and contacts with the lower end of the reset spring;

[0010] A hole is provided in the middle of the support plate, which is equipped with a bearing. The bearing supports the experimental cam mounting shaft. The experimental cam mounting shaft is equipped with an experimental cam positioning sleeve and an experimental cam positioning flat key. The experimental cam is installed on the experimental cam mounting shaft, and is axially positioned by the cam positioning sleeve, and circumferentially positioned by the cam positioning flat key. The end is circumferentially positioned and locked by the mounting shaft locking nut. A ratchet is also installed on the other side of the experimental cam mounting shaft, and is axially positioned by the ratchet positioning sleeve, and circumferentially positioned by the ratchet positioning flat key. A mounting shaft locking nut is provided at the end of the ratchet mounting side for axial positioning and locking of the ratchet. The experimental cam and the ratchet form a component.

[0011] The ratchet can intermittently move in one direction under the drive of the pawl. The pawl is installed on the rocker through a hinge bolt and a hinge locking nut, and forms a revolving pair with the rocker. The rocker forms a revolving pair with the connecting rod through the hinge bolt and the hinge locking nut. The connecting rod forms a revolving pair with the crank through the hinge bolt and the hinge locking nut. The crank and the handle are fixed as a component through an interference fit via a pin shaft. The pin shaft is placed in the crank bracket hole to form a revolving pair with the crank.

[0012] Furthermore, the follower guide is provided with two upper and lower rectangular grooves, the follower is installed in the two rectangular grooves of the follower guide and is guided thereby, and the upper end of the return spring contacts the upper rectangular groove.

[0013] Furthermore, a scale indicating the lifting distance of the follower is arranged on the follower guide path, and / or a length scale is arranged along the horizontal dovetail slide rail on the mounting support plate.

[0014] The present invention also provides a planar cam profile acquisition experimental method, characterized in that it uses any one of the above-mentioned planar cam profile acquisition experimental teaching instruments and includes the following steps:

[0015] Install the experimental cam and fix it, and adjust the offset distance between the follower and the cam's rotation center; secondly, adjust the distance between the crank bracket and the cam's rotation center according to the number of ratchet teeth; then, because the angle is fixed for each turn of the handle, it is only necessary to record the corresponding follower displacement value, and finally draw the curve and perform numerical processing to obtain the follower's motion law;

[0016] By replacing the cam, the ratchet, the follower type, and moving the follower to adjust the position of the horizontal dovetail slide on the upper part of the corresponding support plate, the plane cam profile acquisition experiment can be realized under the centering / offset conditions of different followers, and the crank bracket can be moved to adjust its distance from the cam center to achieve the adjustment of the corresponding number of sampling points within one cycle of the plane cam profile.

[0017] The new cam mechanism experimental device provided by the present invention has reasonable component configuration and can be easily disassembled and assembled without professional skills. It can realize the replacement of follower type, adjustment of follower offset distance, and replacement of disc cams with different profiles, meeting teaching requirements and characteristics. The dovetail track design can facilitate disassembly and distance adjustment. The ratchet mechanism combined with the four-bar mechanism ensures the accuracy of the cam rotation angle interval. The cam mechanism rotation angle can be changed by adjusting the distance of the crank bracket. The device is simple to operate, the cam mechanism components are easy to replace, and the parameters are easy to adjust. It can meet the experimental tasks of measuring the profiles of different disc cam mechanisms, and can be combined with experimental teaching to help students understand and learn related teaching content more vividly. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 , 2 3 are respectively the front view, the rear view and the left view of the embodiment of the manual plane cam profile acquisition experimental teaching device of the present invention.

[0019] Figure 4 3D diagram of the shaft mounted for the experimental cam.

[0020] Figure 5 , 6 Three-dimensional diagrams of roller followers and flat-bottom followers respectively. DETAILED DESCRIPTION

[0021] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0022] A manual plane cam profile acquisition experimental teaching device comprises an equipment base 1, a support seat 2, a fixing bolt 3, an experimental cam installation shaft 4, an installation support plate 5, an experimental cam 6, a pointed follower 7, a follower guide 8, a reset spring 9, a scale pointer 10, a hinge bolt 11, a connecting rod 12, a crank 13, a handle 14, a crank bracket 15, a rocker 16, a pawl 17, a ratchet 18, a locking nut 19, a hinge locking nut 20, a follower guide set screw 21, a ratchet positioning flat key 22 on the experimental cam installation shaft 4, a ratchet positioning sleeve 23, a bearing 24, an experimental cam positioning sleeve 25, an experimental cam positioning flat key 26, a mounting shaft locking nut 27, and a pin 28;

[0023] The lower cavity of the equipment base 1 is hollow and the support seat 2 is positioned by a dovetail groove. The positioning can be locked by the friction generated by the transition fit between the dovetail groove and the slider in the groove of the support seat. In this way, the accuracy meets the teaching requirements and the operation is more convenient when adjusting the experimental parameters. Screw holes can also be opened at the bottom of the equipment base 1 to lock the position with screws. A rectangular groove is set in the support seat 2 for installing the support plate 5 and the crank bracket 15. The installation support plate 5 is embedded in the rectangular groove of its support seat 2, and the installation support plate 5 is fixed by the fixing bolt 3 and the locking nut 19. The support seat 2 of the crank bracket 15 is fixed by the fixing bolt 3 and the locking nut 19 to embed the crank bracket 15 in its rectangular groove. According to the experimental needs, the support seat 2 can be manually moved along the groove direction in the dovetail groove of the equipment base 1, and the friction force is used to achieve positioning.

[0024] The support plate 5 has a horizontal dovetail slide rail on the upper part, and a follower guide 8 is installed on the slide rail. The follower guide 8 can move horizontally along the dovetail slide rail on the upper part of the support plate 5 and is locked by the follower guide set screw 21. The pointed follower 7 passes through the two rectangular guide grooves 81 and 82 on the follower guide 8, so that the pointed follower 7 can move vertically. The return spring 9 is installed on the pointed follower 7, and the upper rectangular guide groove 81 of the follower guide (8) limits the highest position. The dial pointer 10 is installed in the hole on the pointed follower 7 and contacts with the lower end of the return spring 9. As the follower 7 moves upward, the return spring 9 is compressed. A dial 80 is provided on the right side of the follower guide 8, and the dial pointer 10 reads the distance moved by the pointed follower 7 through the dial.

[0025] A hole is provided in the middle of the support plate 5, which is equipped with a bearing 24. The bearing 24 supports the experimental cam mounting shaft 4. The experimental cam mounting shaft 4 is equipped with an experimental cam positioning sleeve 25 and an experimental cam positioning flat key 26. The experimental cam 6 is installed on the experimental cam mounting shaft 4, and is axially positioned by the cam positioning sleeve 25, and circumferentially positioned by the cam positioning flat key 26. The end is circumferentially positioned and locked by the mounting shaft locking nut 27. A ratchet 18 is also installed on the other side of the experimental cam mounting shaft 4, and is axially positioned by the ratchet positioning sleeve 23, and circumferentially positioned by the ratchet positioning flat key 22. A mounting shaft locking nut 27 is provided at the end of the mounting side of the ratchet 18 for axial positioning and locking of the ratchet 18. The experimental cam 6 and the ratchet 18 form a component.

[0026] The ratchet 18 can intermittently move in one direction when driven by the pawl 17. The pawl 17 is installed on the rocker 16 through the hinge bolt 11 and the hinge locking nut 20, and forms a revolving pair with the rocker 16. The rocker 16 forms a revolving pair with the connecting rod 12 through the hinge bolt 11 and the hinge locking nut 20. The connecting rod 12 forms a revolving pair with the crank 13 through the hinge bolt 11 and the hinge locking nut 20. The crank 13 and the handle 14 are fixed as a component through the pin 28 and the interference fit with the pin 28. The pin 28 is placed in the hole of the crank bracket 15 to form a revolving pair with the crank 14.

[0027] The handle 14 rotates clockwise for one circle, and the crank 13 and the connecting rod 12 drive the rocker 16 to swing back and forth once. The rocker 16 drives the ratchet 18 to rotate clockwise by an angle corresponding to the ratchet teeth through the pawl 17. At this time, the cam 6 rotates synchronously with the ratchet 18 by the same angle.

[0028] The follower guide 8 drives the top follower 7 to move along the dovetail slide rail on the upper part of the support plate 5, and the eccentric distance of the plane cam can be adjusted. Correspondingly, a scale 50 related to the eccentric distance is set along the dovetail slide rail. The top push rod follower 7 can be replaced by a roller follower 29 and a flat bottom follower 30. The inner ring of the roller 32 on the roller follower 29 is fixed to the roller follower bracket through a pin 31. The test cam 6 can replace the tested plane cam by disassembling the locking nut 27.

[0029] The profile curve of the cam in the cam mechanism is closely related to the offset distance of the cam mechanism. Different cam profiles will be designed with different offset distances for the same push rod motion law. The experimental device of the present invention can actively adjust the offset distance between the follower and the cam center, and keep the eccentricity constant after adjustment by fixing with a set screw. The offset distance adjustment in the device is adjusted in the horizontal direction by the follower guide 8, and a dovetail guide rail is adopted, which has good guiding performance. The locking method of the follower guide 8 is achieved by adopting the follower guide set screw 21. When adjustment is required, loosen the set screw for adjustment; after the adjustment is completed, tighten the set screw.

[0030] Common follower types of flat disc cam mechanisms include pointed push rods, flat bottom push rods and roller push rods. These three types of push rods have different structures and friction conditions, and are suitable for different working occasions. The cam mechanism experimental device must be able to replace different types of followers. This experimental system uses a double rectangular guide to ensure the accuracy requirements of the linear motion of the follower, and it is very convenient to replace the follower. Pull out the scale pointer 10 from the push rod, and then remove the follower and the reset spring. Install another push rod along the bottom of the double rectangular guide and put on the reset spring. Finally, compress the reset spring upwards, insert the scale pointer into the hole of the push rod, and the replacement is completed, which greatly reduces the replacement time, and the double guide rails can ensure the accuracy requirements of the follower in the running direction.

[0031] The displacement of the follower is read by the scale pointer 10 mounted on the pointed follower 7 at the scale on the right side of the follower guide 8. When reading, it is necessary to ensure that the pointer side of the scale pointer 10 is parallel to the scale plate. The displacement range of the follower can be adjusted by machining multiple mounting holes for the scale pointer 10 on the follower push rod to ensure that the requirements of different experimental cam strokes are met. The maximum displacement range is determined by the spacing between the two rectangular grooves on the follower guide.

[0032] The cam, as the object to be tested in the experimental device, meets the principle of interchangeability. The cam to be tested in the experimental device can be replaced freely. The parameters related to the cam profile, such as the base circle radius and stroke, can be calculated through the test data.

[0033] The cam movement is achieved by driving the crank rocker mechanism with the handle 14, and then the ratchet mechanism pushes the ratchet to rotate a fixed angle. At this time, the experimental cam also rotates by a corresponding angle. The designed ratchet has 30 ratchet teeth. Each rotation of a ratchet tooth records an angle and displacement, that is, (θ, s). The experimental cam rotates one circle and can record 30 sets of data. In this way, it is necessary to ensure that the lengths of the rods of the crank rocker mechanism meet a certain relationship. The relationship between the rod lengths is as follows:

[0034]

[0035]

[0036] Δφ=φ1-φ1≤2π / k

[0037] Among them: l1 is the crank length; l2 is the connecting rod length; l3 is the rocker length; l4 is the frame length (the distance between the crank rotation center and the ratchet rotation center); k is the number of ratchet teeth; Δφ is the rocker swing angle.

[0038] If more detailed records are needed, ratchets with more ratchet teeth can be installed. In order to ensure that ratchets with different ratchet teeth can achieve the angle corresponding to one tooth rotation of the ratchet when the handle rotates one circle in the same experimental device, the crank bracket 15 is constrained with the equipment base through the dovetail groove, so the length of l4 can be adjusted by moving the crank bracket 15 to meet the requirements of the cam rotation angle interval.

[0039] This experimental device can realize the test of a given cam profile and the test of the movement law of the follower. The accuracy of the cam angle is guaranteed by the ratchet mechanism, and the displacement of the push rod is manually read. The accuracy is limited, but manual operation is conducive to flexibly reflecting the test process and essence. The specific operation steps of this experimental device are: first, install the experimental cam 6 and fix it, adjust the offset distance between the follower and the rotation center of the cam, and refer to the scale when adjusting; secondly, according to the number of ratchet teeth, adjust the distance between the crank bracket and the rotation center of the cam; then, because the angle is fixed for each turn of the handle, it is only necessary to record the corresponding follower displacement value, and finally draw the curve and perform numerical processing to obtain the movement law of the follower.

[0040] The planar cam mechanism can move according to a predetermined rule mainly because of the profile curve of the cam. The movement law of the planar cam profile curve can be obtained by combining the rotation angle of the cam with the displacement of the push rod follower at the corresponding angle.

[0041] By replacing the cam, the ratchet, the follower type, and moving the follower to adjust the position of the horizontal dovetail slide on the upper part of the corresponding support plate, the plane cam profile acquisition experiment can be realized under the centering / offset conditions of different followers, and the crank bracket can be moved to adjust its distance from the cam center to achieve the adjustment of the corresponding number of sampling points within one cycle of the plane cam profile.

[0042] This specification describes the invention device by taking self-made parts as an example. Other situations in which the functions and uses of the invention are achieved by using common standard parts and corresponding combinations are within the protection scope of the invention.

Claims

1. A manual plane cam profile acquisition experimental teaching device, characterized in that: The invention comprises the following components: an equipment base (1), a plurality of support seats (2), fixing bolts (3), an experimental cam mounting shaft (4), a mounting support plate (5), an experimental cam (6), a follower, a follower guide (8), a reset spring (9), a scale pointer (10), a plurality of hinge bolts (11) and hinge locking nuts (20), a connecting rod (12), a crank (13), a handle (14), a crank bracket (15), a rocker (16), a pawl (17), a ratchet (18), a locking nut (19), a follower guide set screw (21), and a pin (28); the experimental cam mounting shaft (4) is provided with a ratchet positioning flat key (22), a ratchet positioning sleeve (23), a bearing (24), an experimental cam positioning sleeve (25), an experimental cam positioning flat key (26), and a mounting shaft locking nut (27); The device base (1) and the support base (2) of the mounting support plate (5) are positioned by means of a dovetail groove; a rectangular groove is provided in the support base (2); the mounting support plate (5) and the crank bracket (15) are respectively embedded in the rectangular grooves of the respective support bases (2) and fixed by means of fixing bolts (3) and locking nuts (19); the support base (2) is manually moved in the dovetail groove of the device base (1) along the groove direction; A horizontal dovetail slide rail is arranged on the upper part of the support plate (5), a follower guide (8) is installed above the slide rail, the follower guide (8) is slidably connected to the dovetail slide rail and is locked by a follower guide set screw (21), the follower (7) is slidably connected to the follower guide (8), and the guide cooperation of the follower (7) in the vertical direction is realized; the return spring (9) is installed on the follower (7); the scale pointer (10) is installed in a hole on the follower (7) and contacts the lower end of the return spring (9); The support plate (5) is provided with a hole in the middle thereof, on which a bearing (24) is installed. The bearing (24) supports the experimental cam mounting shaft (4). The experimental cam mounting shaft (4) is provided with an experimental cam positioning sleeve (25) and an experimental cam positioning flat key (26). The experimental cam (6) is installed on the experimental cam mounting shaft (4) and is axially positioned by the cam positioning sleeve (25), circumferentially positioned by the cam positioning flat key (26), and circumferentially positioned and locked by a mounting shaft locking nut (27) at the end. A ratchet (18) is also installed on the other side of the experimental cam mounting shaft (4) and is axially positioned by a ratchet positioning sleeve (23), circumferentially positioned by a ratchet positioning flat key (22), and a mounting shaft locking nut (27) is provided at the end of the mounting side of the ratchet (18) to axially position and lock the ratchet (18). The experimental cam (6) and the ratchet (18) form a component. The ratchet wheel (18) moves intermittently in one direction under the drive of the pawl (17); the pawl (17) is mounted on the rocker (16) through the hinge bolt (11) and the hinge locking nut (20), and forms a revolving pair with the rocker (16); the rocker (16) forms a revolving pair with the connecting rod (12) through the hinge bolt (11) and the hinge locking nut (20); the connecting rod (12) forms a revolving pair with the crank (13) through the hinge bolt (11) and the hinge locking nut (20); the crank (13) and the handle (14) are fixed to form a component through an interference fit via a pin (28); the pin (28) is placed in a hole of the crank bracket (15), and forms a revolving pair with the crank (13); The follower guide (8) is provided with two upper and lower rectangular grooves, the follower (7) is installed in the two rectangular grooves of the follower guide (8) and is guided thereby, and the upper end of the return spring (9) contacts the upper rectangular groove; The follower guide path (8) is provided with a scale indicating the lifting distance of the follower (7), and / or the support plate (5) is installed to provide a length scale along the horizontal dovetail slide rail.

2. A planar cam profile acquisition experimental method, characterized in that: It adopts the planar cam profile acquisition experimental teaching instrument described in claim 1, and includes the following steps: Install the experimental cam and fix it, and adjust the offset distance between the follower and the cam's rotation center; secondly, adjust the distance between the crank bracket and the cam's rotation center according to the number of ratchet teeth; then, because the angle is fixed for each turn of the handle, it is only necessary to record the corresponding follower displacement value, and finally draw the curve and perform numerical processing to obtain the follower's motion law; By replacing the cam, the ratchet, the follower type, and moving the follower to adjust the position of the horizontal dovetail slide on the upper part of the corresponding support plate, the plane cam profile acquisition experiment under different follower centering / offset conditions can be realized, and the crank bracket can be moved to adjust its distance from the cam center to realize the adjustment of the corresponding number of sampling points within one cycle of the plane cam profile.

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