【導讀】種新型液壓千斤頂。在這種千斤頂中，第一時間做出大小油缸和大小楔塊。同時工作并返回原點，所以可以根據(jù)載荷大小自動地改變速度，且容易操作。傳統(tǒng)的液壓千斤頂在工作行程和工作回程具有相同的速度。大多數(shù)千斤頂無法區(qū)分無載荷或者重載荷。液壓千斤頂?shù)墓ぷ餍氏喈數(shù)?，浪費能源，浪費時間，而且工作范圍狹隘。斤頂在速度與載荷之間存在沖突。典型機械千斤頂具有快慢速螺旋傳動裝置的特點，其可以通過齒輪嚙合或者分離。螺母和螺栓來提供雙倍速度。典型液壓千斤頂特點是為一種千斤頂和多速千斤頂提供多速。但是實際上使用并沒有達到預期的效果，原因是存在太多的油泵，和極大增加阻力的油缸。斤頂，其專利為液壓交換裝置。對于大量的研究和改進，我們制定了新型液壓千斤頂?shù)囊簤涸硐到y(tǒng)圖，如同1所示。油缸推動大油缸的活塞，其以最高速度到達工件。12021公斤的起重能力。

　　

【正文】 e workpiece and the piston drives the big cylinder and small cylinder to return the original position. 11 Figure 3 Appearance of sample jack This new type of hydraulic jack have solved both the structure problem and operation problem, the innovation is embodied below :(1)Internal procedure hydraulic pressure linkage: the oilinput pipeline of big pump is linked directly with the oilreturn pipeline of both the big cylinder and the small cylinder, the sequence value is not only the oilinput valve of the big cylinder and big pump, also the returning valve of the small cylinder and the big cylinder, the oilleave pipeline is also the oilenter pipeline ,the oilleave valve of the big pump is also the oilenter valve of small pump, namely a valve has multipurpose. (2) It make the seedchange system highly integrates that the big pump and small pump plus big cylinder and small cylinder. (3) The closed cycle is highly effective and reliable: the oil enters the oil cylinder directly without any medial part, so the jack has a small friction drag and very few energy loses and a flexible movement. (4) The structure is simple: the system is concise, the pipeline is short, the kind of loses is reduced, the number of parts is small. We have pared our sample jack with a traditional jack. The new jack and the traditional jack both have the same lifting capacity of 12, the moving speed of jack’s handle is , the traditional jack has a constant speed of about 5mm/s, but this new the sample jack’s speed can automatically change between return stroke, the sample jack can return to the original position automatically at a high speed(the only thing needed is turning the handle of the sequence valve),but for the traditional jack, only pushes the piston of the oil cylinder can it return to its original position. 12 4 Concluding remarks This new type of manual multispeed hydraulic jack originally use a closedcycle system which has a internal procedure hydraulic pressure linkage and use the big pump as the oil tank, it can automatically change speed by selfreturning oil flowing direction of the sequence valve. This kind of speedchange has no hydraulic loss, mechanic loss, volumetric efficiency loss and energy loss. This new type of jack ingeniously solved the condition between speed and force, the design theory can also be used for other kind of manual instrument such as vices, etc. References [1] . Research and development new type of manual instrument based on coordination with strength and speed. Master Thesis. Central South University,Changsha,Hunan,2021. [2] AIWU HU,AILUN WANG..The innovation design for clamp according to unification of force and speed. Development amp。 innovation of machinery and electrical ,Number2。. [3] CHAOLAI screw driving setup having a rapid and slow speed. China Patent,CN1094348,1994. [4] QUN FAN. Multispeed adjustment methods for a type of jack and a multispeed jack. China Patent, CN1408635,2021. [5] XUANZHE HU. Transaction device of hydraulic pressure. China Patent,CN2309453,1999. 13 指導教師評語： 簽名： 年 月 日