The telescopic device of self loading mixer is a special mechanism used to meet different construction requirements by changing the length of its telescopic pipe and then controlling the inclination angle or height of the discharge chute. Its structural forms include spring telescopic type, hydraulic driving type and hand screw telescopic type.
1.弹簧伸缩式伸缩装置。弹簧伸缩式伸缩装置主要由内管、外管、伸缩弹簧和限位装置等组成。该结构运用伸缩弹簧助力原理，在进行伸长作业时起到助力作用，在特定程度上降低了操控者的劳动强度；在进行收缩作业时需克服弹簧阻力，操控性降低。弹簧伸缩式具有结构简单，成本低等优点，但存在劳动强度较高，不易操作等缺点。
1. Spring telescopic device. The spring telescopic device is mainly composed of inner tube, outer tube, telescopic spring and limiting device. The structure uses the principle of telescopic spring to assist in the extension operation, which reduces the labor intensity of the operator to a certain extent; The spring resistance should be overcome during the contraction operation, and the controllability is reduced. The spring telescopic type has the advantages of simple structure and low cost, but it has the disadvantages of high labor intensity and difficult operation.
2.手摇丝杆伸缩式伸缩装置。手摇丝杆伸缩式伸缩装置主要有外管、内管、丝杠、丝母和轴承等组成。该机构运用螺旋副传递运动原理，螺母与螺杆相对位移实现结构的伸缩。与以上2种形式相比，手摇丝杆伸缩式具有结构简单、便于操作、劳动强度低等优点，故在自上料搅拌车应用较为广泛。
2. Hand screw telescopic device. Hand screw telescopic device mainly consists of outer tube, inner tube, screw, screw nut and bearing. The mechanism uses the principle of transmission motion of screw pair, and the relative displacement of nut and screw realizes the expansion and contraction of the structure. Compared with the above two forms, the hand screw telescopic type has the advantages of simple structure, easy operation and low labor intensity, so it is widely used in the self feeding mixer.
3.液压驱动式伸缩装置。液压驱动式伸缩装置通过液压能驱动液压缸伸缩完成结构的伸缩，自动化程度得到提高，降低了劳动强度，但需配备独立的液压驱动系统，提高了制造成本。
3. Hydraulic driven telescopic device. The hydraulic driven telescopic device can drive the hydraulic cylinder to expand and expand to complete the expansion and contraction of the structure. The degree of automation is improved and the labor intensity is reduced. However, it needs to be equipped with an independent hydraulic drive system to increase the manufacturing cost.
