A device for testing the axial tensile strength of a cable protection tube

Abstract

The application discloses a kind of cable protection pipe axial tensile degree testing devices in the field of cable protection member mechanics detection, base and the guide member of being fixed in base and extending along first direction;Driving mechanism, including driving carrier and the driving unit of being fixed to driving carrier;Driving carrier is slidably assembled along first direction with guide member, and can be switched between sliding state and relative guide member locking fixed state;Along the sliding fit of first direction with driving carrier, driving unit and dynamic sliding platform are transmission connection, for driving its reciprocating displacement relative to driving carrier;Clamping tool, including first clamping piece, second clamping piece, one of which is fixed to base, the other is fixed to dynamic sliding platform, to apply cyclic axial pulling load to cable protection pipe;Realize sample cyclic reciprocating stretching, simulate field alternating pulling working condition, make up the defect that traditional unidirectional stretching equipment can only test ultimate mechanical property, and obtain material fatigue related performance parameters completely.

Description

Technical Field

[0001] This invention relates to the field of mechanical testing of cable protection components, specifically a device for testing the axial tensile strength of cable protection pipes. Background Technology

[0002] Cable protection pipes, also known as cable protection sleeves, include both rigid power conduits and flexible insulating sheaths for cables. During installation and long-term use, both are subjected to axial loads caused by construction dragging, soil settlement, and environmental vibration. Under long-term alternating tension, fatigue cracking, permanent deformation, and insulation failure are likely to occur. Therefore, it is necessary to comprehensively test their axial tensile resistance performance.

[0003] Currently, the mainstream tensile testing equipment in the industry is mainly a unidirectional static tensile testing machine. This machine continuously feeds the sample in one direction until it breaks, simulating only the instantaneous ultimate tensile condition and obtaining static ultimate parameters such as ultimate tensile strength and elongation at break. However, in actual engineering scenarios, cable protection pipes / sleeves are more often subjected to cyclic violent tensile alternating loads caused by repeated dragging and high-frequency vibration. These unidirectional tensile testing machines cannot reproduce such cyclic conditions, cannot detect the product's cyclic fatigue resistance and deformation accumulation patterns, and are unable to comprehensively assess the product's long-term service reliability. Summary of the Invention

[0004] The purpose of this invention is to provide a cable protection pipe axial tensile strength testing device, which realizes cyclic tensile testing of the sample, simulates the alternating tensile conditions on site, and makes up for the deficiency of traditional unidirectional tensile equipment that can only test the ultimate mechanical properties, so as to obtain the fatigue-related performance parameters of the material.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an axial tensile strength testing device for cable protection pipes, comprising: Base; A guide member is fixed to the base and extends along a first direction; The drive mechanism includes the drive carrier and the drive unit; The driving carrier is slidably assembled with the guide member along the first direction, and can switch between a sliding state and a locked and fixed state relative to the guide member; The drive unit is fixed to the drive carrier; The movable slide is slidably engaged with the driving carrier along the first direction, and the driving unit is connected to the movable slide for driving it to move back and forth relative to the driving carrier. The clamping fixture includes a first clamping member and a second clamping member, one of which is fixed to the base and the other is fixed to the movable slide table, so as to apply a cyclic axial tensile load to the cable protection pipe.

[0006] As a further embodiment of the present invention, the drive unit is configured with a rotary reciprocating transmission mechanism, which is mounted on the drive carrier and drives the movable slide table to convert the rotational motion of the drive source into linear reciprocating displacement of the movable slide table relative to the drive carrier.

[0007] As a further aspect of the present invention, the rotary reciprocating transmission mechanism includes: The driving source is fixed to the driving carrier; The drive shaft is fixed to the movable slide. An eccentric wheel is connected to the output end of the drive source, and its outer circumference is tangentially fitted to the outer wall of the drive shaft. The drive source drives the eccentric wheel to rotate continuously, and the tangent eccentric wheel and drive shaft drive the moving slide to move back and forth relative to the drive carrier in the first direction.

[0008] As a further embodiment of the present invention, the driving carrier is provided with a stroke limiting mechanism, the position of which is adjustable, and is used to limit the reciprocating range of the moving slide relative to the driving carrier.

[0009] As a further aspect of the present invention, the travel limiting mechanism includes: The slide bar is fixed to the drive carrier and slides in conjunction with the movable slide table. A limiting element, installed on the slide rod and with an adjustable position, is used to limit the lower limit of the displacement of the movable slide.

[0010] As a further embodiment of the present invention, the movable slide table slides in a first direction in cooperation with the guide member, and the movable slide table is provided with a mounting position for assembling one of the first clamping member and the second clamping member.

[0011] As a further embodiment of the present invention, a guide rod is fixedly provided on the side wall of the driving carrier, and the guide rod slides along the first direction as a whole, with its own axis perpendicular to the first direction; The guide rod is equipped with a guide rod at its end. Adjusting the distance between the guide rod and the drive carrier can lock the guide component and the drive carrier.

[0012] As a further embodiment of the present invention, a bushing is fixedly provided on the side wall of the driving carrier, and an adjusting screw is rotatably assembled on the guide member. The adjusting screw extends along a first direction and is threadedly connected to the bushing.

[0013] As a further aspect of the present invention, the guide member is provided with a scale arranged along the first direction for intuitive reading of the adjustment position of the drive carrier.

[0014] Compared with the prior art, the beneficial effects of the present invention are: In this invention, the moving slide is driven by the drive unit to perform periodic reciprocating motion, which can apply cyclic axial tensile load to the sample, reproduce the alternating stress conditions caused by repeated dragging and environmental vibration in actual engineering, and make up for the limitation of traditional unidirectional static tensile equipment that can only detect static parameters such as ultimate tensile strength and elongation at break; it can obtain key performance data such as fatigue life and cumulative deformation law of the sample, and can more comprehensively evaluate the long-term service reliability of cable protection pipes / sleeves. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a cross-sectional structural diagram of the guide component and its connection relationship of the present invention; Figure 3 For the present invention Figure 2 Enlarged structural diagram at point A in the middle; Figure 4 This is a schematic diagram of the driving carrier and its connection structure according to the present invention; Figure 5 This is a schematic diagram of the adjusting screw and its connection structure according to the present invention; Figure 6 This is a schematic diagram of the guide rod and its connection structure according to the present invention; Figure 7 This is a schematic diagram of the limiting screw and its connection structure according to the present invention; The attached diagram lists the components represented by each number as follows: 1. Base; 11. Bushing; 12. Adjusting screw; 2. Guide component; 3. Drive carrier; 31. Guide rod; 32. Fastener; 4. Drive unit; 41. Drive source; 42. Drive shaft; 43. Eccentric wheel; 5. Moving slide; 61. First clamping component; 62. Second clamping component; 71. Slide rod; 72. Limiting component; 73. Limiting screw seat; 74. Limiting screw. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see Figures 1-7 The present invention provides a technical solution: The base 1, as the load-bearing base of the whole machine, is formed in one piece or welded to ensure the structural rigidity under test conditions; Guide member 2 along the first direction ( Figure 1 The direction of the middle arrow (i.e., the axial test direction of the cable protection pipe) is fastened to the upper surface of the base 1 by bolts. In this embodiment, the guide member 2 is a rectangular linear guide rail, which provides a long-stroke sliding reference for the drive carrier 3. The driving mechanism consists of two parts: driving carrier 3 and driving unit 4. The driving carrier 3 is a plate-type support seat with its back slidably assembled with the guide member 2. It can slide along the guide member 2 as a whole to adapt to cable protection pipe samples of different lengths. The driving carrier 3 has a locking function and can switch between a free sliding state and a locked and fixed state relative to the guide member 2. After being adjusted to the target test position, it is locked to become a rigid reference for reciprocating tensile test. The drive unit 4 is fixed to the drive carrier 3 by bolts and serves as a power output component for reciprocating pulling; the movable slide 5 is slidably fitted on the drive carrier 3 along the first direction and is connected to the drive unit 4 for transmission; when the drive unit 4 outputs power, it drives the movable slide 5 to perform short-stroke high-frequency reciprocating linear displacement relative to the drive carrier 3. The clamping fixture includes a first clamping member 61 and a second clamping member 62. One of them is fixed to the end of the base 1 as a fixed end clamp, and the other is fixed to the movable slide table 5 as a movable end clamp. During the test, both ends of the cable protection pipe are clamped and fixed by the two clamping members respectively. When the movable slide table 5 reciprocates, a cyclic tensile load is applied to the cable protection pipe sample to simulate the actual working condition of the sample being subjected to repeated external force tension.

[0019] As a further aspect of the present invention, the transmission form of the drive unit 4 is further defined; The drive unit 4 is equipped with a rotary reciprocating transmission mechanism, which is a purely mechanical transmission structure. It is installed on the drive carrier 3 and its output end is connected to the moving slide table 5. Its core function is to convert the continuous unidirectional rotational motion of the drive source 41 into the periodic linear reciprocating motion of the moving slide table 5 relative to the drive carrier 3. This eliminates the need for frequent forward and reverse switching of the drive motor. Compared with the existing servo screw reciprocating drive scheme, this rotary unidirectional reciprocating transmission mechanism only requires the drive source to rotate continuously at a constant speed in one direction to achieve periodic reciprocating pulling, without the need for frequent forward and reverse switching of the motor. On the one hand, it eliminates the need for a complex position closed-loop commutation control program, resulting in simpler control logic and lower cost of electrical control hardware. On the other hand, there is no inertial impact caused by sudden speed changes during commutation, and the moving slide table moves continuously and smoothly, resulting in less vibration and instantaneous impact loads under high-frequency fatigue testing conditions. At the same time, the motor and transmission parts only bear unidirectional rotational loads for a long time, which greatly reduces alternating impact wear, improves the stability of continuous operation of the whole machine, and also avoids premature damage to the cable protection pipe sample caused by instantaneous impact, thus improving the accuracy of test data.

[0020] See Figures 2-4 In a preferred embodiment, the rotary reciprocating transmission mechanism specifically includes a drive source 41, a drive shaft 42, and an eccentric wheel 43. The drive source 41 is a geared motor, which is fastened to the outer wall of the drive carrier 3 by bolts, and the output shaft axis is arranged perpendicular to the first direction. The mounting hole on the eccentric wheel 43 is eccentrically set and fixed to the end of the output shaft of the drive source 41, and rotates synchronously with the output shaft. The drive shaft 42 is vertically fixed to the north side of the movable slide table 5, and its own axis is parallel to the output shaft of the drive source 41. A ring is provided on the outer periphery of the eccentric wheel 43, and the inner side wall of the ring is tangentially abutted against the outer wall of the drive shaft 42. Working process: The drive source 41 drives the eccentric wheel 43 to rotate continuously in one direction. The eccentric contour of the eccentric wheel 43 periodically pushes against the drive shaft 42 on the sliding table 5, pushing the moving sliding table 5 to slide away from the fixed clamping end. When the eccentric wheel flange passes the highest point, the moving sliding table 5 moves back under the rebound force of the tube sample, thus forming a continuous cyclic axial pulling action. This structure has a short transmission link, few parts, stable operation during high-frequency reciprocating, and low maintenance cost.

[0021] In some embodiments, the tangential fit between the independent drive shaft 42 and the eccentric wheel 43 is eliminated; the output end of the drive source 41 is directly machined into an eccentric rotating shaft, and the shaft segment of the eccentric rotating shaft is rotatably fitted with the hinge hole on the back of the movable slide table 5; when the drive source 41 drives the eccentric rotating shaft to rotate continuously, the eccentric shaft segment performs a circular motion, directly pulling the movable slide table 5 to move linearly back to its original position along the first direction. This solution has fewer parts, simplifies the assembly process, and reduces transmission clearance.

[0022] As a further aspect of the present invention, the stroke control structure of the driving carrier 3 is further defined; The drive carrier 3 is equipped with a stroke limit mechanism. The installation position of this mechanism can be manually adjusted to physically limit the reciprocating range of the moving slide 5 relative to the drive carrier 3, thereby controlling the pulling stroke amplitude. By adjusting the limit position, the axial fatigue performance, deformation, and failure threshold of the cable protection pipe under different pulling strokes and different pulling amplitudes can be tested, meeting the test requirements of different test standards and working conditions. Compared with relying solely on the electrical control program to set the stroke, the mechanical limit is more reliable and can avoid equipment failure caused by program malfunction.

[0023] The preferred solution is the specific implementation of the travel limit mechanism; See Figure 4 The stroke limiting mechanism specifically includes a slide rod 71 and a limiting member 72; at least one slide rod 71 is provided along the first direction and is fixedly installed on the drive carrier 3 along the first direction through an end seat; the movable slide table 5 is provided with a corresponding guide slide hole and is sleeved on the outside of the slide rod 71 to form a sliding fit, providing precise guidance for the reciprocating motion of the movable slide table 5 and avoiding motion sway.

[0024] The limiting component 72 can be either a locking sleeve or a locking nut, both of which are fitted onto the slide rod 71. When a locking sleeve is used, the slide rod surface is locked by a radial set screw on the side. When a locking nut is used, the corresponding section of the slide rod 71 is machined with external threads, and the locking nut engages with the slide rod 71 through the threaded connection, achieving stepless adjustment and self-locking positioning through the threaded pair. The installation position of the limiting component 72 can be adjusted along the slide rod 71 by loosening the set screw or tightening the nut.

[0025] In this embodiment, the limiting component 72 is located on the side of the movable slide 5 near the fixed clamping component. It limits the retraction limit position of the movable slide 5. Its core function is to actively control the reciprocating pulling stroke amplitude of the movable slide by changing the installation position of the limiting component, thereby constructing axial tension conditions of different magnitudes. This allows for the acquisition of performance data such as fatigue life and deformation characteristics of the cable protection pipe under different tensile amplitudes. It can quickly adapt to the testing requirements of different pipe specifications and different testing standards, and can complete multi-condition testing switching without modifying the drive control program. During the test, the limiting component also serves as a reference positioning element, ensuring that the starting position of each cycle is consistent and improving the repeatability of the test data.

[0026] See Figure 7In another parallel embodiment, the movable slide 5 and the guide member 2 are slidably assembled along the first direction. A limiting screw seat 73 is fixedly installed on the drive carrier 3. The limiting screw 74 passes through the threaded hole of the limiting screw seat 73 along the first direction, with the end of the screw facing the side end face of the movable slide 5. Tightening the limiting screw 74 can change the extension length of the end, thereby limiting the retraction limit displacement position of the movable slide 5. A locking nut 76 can also be provided on the outside of the limiting screw 74. After adjustment, the locking nut is locked against the end face of the screw seat 75 to prevent the screw from loosening and shifting due to vibration during the test.

[0027] This solution utilizes a threaded connection to achieve continuous stepless adjustment, focusing more on high-precision fine-tuning compared to a sliding lever-type limiter. It achieves micro-feeding through a small-lead thread, with each rotation corresponding to a smaller displacement change, enabling micrometer-level fine-tuning of the stroke amplitude. This allows for the subdivision of multiple gradient tension conditions within a small range, accurately detecting parameters such as the critical amplitude of pipe fatigue failure and micro-deformation patterns. This solution is suitable for high-precision testing scenarios such as refined material performance testing and critical value calibration, compensating for the accuracy limitations of sliding lever-type limiters in fine-tuning minute amplitudes.

[0028] As a further aspect of the present invention, the auxiliary guide and fixture mounting structure of the movable slide table 5 is further defined.

[0029] The movable slide 5 slides and engages with the guide member 2 along the first direction, which can improve the motion stability during long stroke adjustment and avoid the drive carrier 3 being subjected to force on one side and causing uneven load. The end face of the movable slide 5 is provided with a standardized mounting position, which is a matrix of threaded holes for assembling the first clamping member 61 or the second clamping member 62. Different models of clamping members can be quickly replaced according to the sample tube diameter specifications to meet the testing needs of various specifications of cable protection pipes.

[0030] As a further embodiment of the present invention, the specific implementation of the rapid locking of the driving carrier 3 is as follows: See Figure 6 A guide rod 31 is fixedly installed on the side wall of the drive carrier 3. The axis of the guide rod 31 is perpendicular to the first direction. The guide rod 31 is embedded in the sliding groove on the side of the guide member 2 and can slide along the first direction together with the drive carrier 3. The outer end of the guide rod 31 extends out of the guide member 2 and is equipped with a guide rod 32. The guide rod 32 is a locking nut that is threadedly engaged with the end of the guide rod 31.

[0031] Locking operation: Twist the guide rod 32 so that the inner side of the guide rod 32 presses against the side wall of the guide member 2 in the direction of the drive carrier 3, and fixes the drive carrier 3 and the guide member 2 relative to each other by friction; loosen the guide rod 32 in the opposite direction to restore the sliding state, realize quick coarse adjustment positioning, simple structure and convenient operation.

[0032] As a further embodiment of the present invention, the second set of independent parallel schemes for adjusting and locking the position of the drive carrier 3 has both positioning adjustment and unidirectional tensile testing functions. See Figure 5 A bushing 11 is fixedly installed on the side wall of the drive carrier 3, and an internal thread is machined inside the bushing 11; an adjusting screw 12 is rotatably assembled at the end of the guide member 2 through a bearing seat, the adjusting screw 12 extends along the first direction, and the rod body is connected to the internal thread of the bushing 11. The extended end of the adjusting screw 12 can be connected to an external drive motor, which drives the adjusting screw 12 to rotate at a constant speed. Through threaded transmission, the bushing 11 moves along the screw axis, thereby driving the drive carrier 3 to make precise micro-displacements along the guide member 2, achieving fine adjustment of the initial test position. After adjustment, the position of the drive carrier 3 can be fixed by relying on the self-locking characteristic of the threaded pair between the adjusting screw 12 and the bushing 11, without the need for additional locking components. The positioning is stable and reliable, suitable for scenarios with high precision requirements for the initial test position.

[0033] Furthermore, by controlling the drive motor to rotate continuously in one direction, the drive carrier 3 can be driven to feed steadily along the first direction, applying a continuously increasing axial tensile force to the cable protection pipe clamped and fixed at both ends, realizing a conventional unidirectional static tensile test until the cable protection pipe breaks, thereby detecting the pipe's ultimate tensile strength, elongation at break, and other core performance parameters. This structure allows the device to simultaneously possess two test modes: cyclic fatigue tension and unidirectional tension to fracture, covering more test conditions without the need for additional mechanism replacement.

[0034] As a further embodiment of the present invention, the guide member 2 is engraved or pasted with a scale along the first direction on its side, and the scale is marked with length graduations; the drive carrier 3 is provided with an indicator arrow at the corresponding position, and the adjustment position of the drive carrier 3 can be read intuitively through the scale during debugging, which is convenient for recording the fitting position of samples of different lengths, and realizing rapid reproduction and debugging during batch testing without repeated measurement and positioning.

Claims

1. A device for testing the axial tensile strength of a cable protection pipe, characterized in that, include: Base (1); The guide member (2) is fixed to the base (1) and extends along the first direction; The driving mechanism includes a driving carrier (3) and a driving unit (4). The driving carrier (3) is slidably assembled with the guide member (2) along the first direction, and can switch between a sliding state and a locked and fixed state relative to the guide member (2); The drive unit (4) is fixed to the drive carrier (3). The movable slide (5) slides in a first direction with the driving carrier (3), and the driving unit (4) is connected to the movable slide (5) for driving it to move back and forth relative to the driving carrier (3). The clamping fixture includes a first clamping member (61) and a second clamping member (62), one of which is fixed to the base (1) and the other is fixed to the movable slide (5) to apply a cyclic axial tensile load to the cable protection pipe.

2. The axial tensile strength testing device for cable protection pipes according to claim 1, characterized in that, The drive unit (4) is equipped with a rotary reciprocating transmission mechanism, which is installed on the drive carrier (3) and drives the movable slide (5) to convert the rotational motion of the drive source (41) into the linear reciprocating motion of the movable slide (5) relative to the drive carrier (3).

3. The axial tensile strength testing device for cable protection pipes according to claim 2, characterized in that, The rotary reciprocating transmission mechanism includes: The driving source (41) is fixed to the driving carrier (3); Drive shaft (42) is fixed to the movable slide (5); An eccentric wheel (43) is connected to the output end of the drive source (41), and its outer circumference is tangentially fitted to the outer wall of the drive shaft (42); The drive source (41) drives the eccentric wheel (43) to rotate continuously, and through the tangent eccentric wheel (43) and drive shaft (42), the moving slide (5) moves back and forth relative to the drive carrier (3) in the first direction.

4. The axial tensile strength testing device for cable protection pipes according to claim 1, characterized in that, The driving carrier (3) is provided with a travel limiting mechanism. The position of the travel limiting mechanism is adjustable and is used to limit the reciprocating displacement range of the moving slide (5) relative to the driving carrier (3).

5. The axial tensile strength testing device for cable protection pipes according to claim 4, characterized in that, The travel limiting mechanism includes: The slide bar (71) is fixed to the drive carrier (3) and slides in cooperation with the movable slide table (5); The limiting element (72), which is installed on the slide bar (71) and is adjustable in position, is used to limit the lower limit of the displacement of the movable slide (5).

6. The axial tensile strength testing device for cable protection pipes according to claim 1, characterized in that, The movable slide (5) slides in a first direction with the guide member (2). The movable slide (5) is provided with a mounting position for assembling one of the first clamping member (61) and the second clamping member (62).

7. The axial tensile strength testing device for cable protection pipes according to claim 1, characterized in that, The drive carrier (3) has a guide rod (31) fixedly mounted on its side wall. The guide rod (31) slides along the first direction as a whole, and its own axis is perpendicular to the first direction. The guide rod (31) is equipped with a guide rod (32) at its end. Adjusting the distance between the guide rod (32) and the drive carrier (3) can lock the guide member (2) and the drive carrier (3).

8. The axial tensile strength testing device for cable protection pipes according to claim 1, characterized in that, The drive carrier (3) has a bushing (11) fixed on its side wall, and the guide member (2) is rotatably equipped with an adjusting screw (12), which extends along a first direction and is threadedly connected to the bushing (11).

9. The axial tensile strength testing device for cable protection pipes according to claim 1, characterized in that, The guide member (2) is provided with a scale arranged along the first direction for intuitive reading of the adjustment position of the drive carrier (3).

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