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液压 支架 结构 毕业设计

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矿用液压支架结构毕业设计,液压,支架,结构,毕业设计

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中文译文液压支架自动化成功的途径液压支架自动化成功的途径1. 1. 摘要摘要第一架液压顶板支护在 20 世纪 50 年代内安装在了地下，并且自那以后随着机械工程的发展已经从许多方面完善了支架。 然而，顶板支护机械设计、 水力工程学和电子学这三个主要领域的进步最终在支架运用35年后实现了自动化，并且已经普及当前。顶板支护自动化的历史介入了高技术工程学的连续综合化。将来有进一步的可能性是它们结合在一起为最终实现无人操作的新面貌提供一个可能的思想。2. 2. 介绍介绍大约 35 年前，一个变化发生在了煤炭行业，事后看来，它为煤炭产业从高劳动力密集场所演变成今天铺平了道路。这个变化便是液压顶板支护的引入。第一代支架，采用简单的液压阀控制，一开始就突飞猛进的发展，为改善工作场所的安全性和提高生产力作出了贡献。 相对支柱和气压计的用途，支护顶板的活动“实际上被自动化”，以后为获得更大自由度的挑战就要落在顶板支护设计师的肩膀上了。结果，许多改进发生在了结构和环境机械工程以及使用水为基础的流体可靠操作的液压系统的发展领域。 这被改进的工程学，加上采矿工程师们总结出不同类型岩石层适合什么样的支架安装型式的经验，知识在不断丰富，机械结构的强度也在提高。早在 1967 年，英国煤矿就试验使用电子控制支架，并且第一套遥控长壁采煤系统被用于地下。 不幸地是，无论在顶板支护还是今天的电子技术，不只是效率就能提供必需的成功。掩护式支架的发展与改善后的阀材料和流体的可及性以及“芯片”电子技术相符了。那是随着掩护式支架为电液压系统的应用提供了理想的环境后，促使自动化成功的发展因素的结合。今天，这些技术的进步，与微处理器的引入一起，为煤炭行业提供了极端可靠，灵活和高效率的系统。自动化的顶板支护不再是设计师的梦想，而是真实的，每天运作的现实。现代顶板支护的前身是木制的坑柱。所以，在 20 世纪 50 年代中期，第一架支架被设计出来时，这些仅仅是已知的技术的延伸。在第一架垛式支架中， 带有英寸长镗孔的液压油缸垂直放于箱体内作为基底，顶梁是一对工字梁。 固定在底部的液压缸起到为刮板输送机提供传动力和驱动支架上升的作用。今天的用户能很容易知道垛式支架的很多缺陷，这些缺陷有的还没设计出来，有的可能被忽略掉了。 尽管如此，相对坑柱和气压计的老方法，第一代支架向前迈了很大的一步，在安全和生产率方面做了真正的贡献。在第一次发展后，进步就更快了。一个主要的需求是为地面操作人员提供更安全的运输方式。 这就需要根据它们的支架顶梁和底版增加前柱或换成四柱。 这会大大改善顶梁的控制性能。到 20 世纪 60 年代早期，这些相互联系的支架装载容量达到了 180 吨，被直接用于改进制造和液压技术，即便在地下使用仍被限制在 1.5 米的煤层厚度。随着对获取更高煤层的需求，长壁采煤也遍及了全球。这也进一步导致对支架的装载728输送容积的要求更高了。紧接着在 1968 年引进了底版牢固的垛式支架。第二代支架能满足720 吨的容量，而且可以在 3米厚的煤层中工作。 掩护式支架是在 20 世纪 70 年代涌现的，最早的两柱式掩护梁设计在德国被广泛使用，并被引进到美国和南非。掩护式支架的效率低，但能承受很高的载荷。双纽线设计是在 20 世纪 70 年代后期引进的。掩护式支架要求在设计原理上从根本改变。 机械连接除抵抗垂直方向变形外，还有岩层侧面的力。 它提供了更有效可靠的支架，它的粗壮使它成功地应用在煤层中的长壁系统中，这在以前是不可能的。 例如，在新南威尔士和澳大利亚那极端困难的条件下以及在英国更易破裂的顶板下。现代掩护式支架的效率为自动化的成功应用提供了合适的环境。在美国更侧重于结构的掩护式支架是两柱设计，这种设计是许多自动化发展的主要平台，也是目前可使用的。这种结构正被引入英国和澳大利亚，而且在未来很长一段时间内将处于顶梁支护自动化发展的最前线。3. 203. 20世纪世纪 8080年代后的液压支架年代后的液压支架顶梁支护系统使用大量的液体装满整个系统，以弥补泄露量和其他流动损耗。此经济因素和其他如火灾和运输大量液体方面的问题带来了以水为基础的液压支护系统。以水为基础的液压技术的应用已经在工程学上占据了一个领域，顶梁支护生产者们真正利用了这项技术，甚至现在，有很少的工业液压技术设施生产者的文件夹里包含可与流体配套使用的产品。最早期的顶板支护系统使用的是根本不复杂的密封和阀门技术。简单的开关阀和带有一系列包装的皮带密封是最好的，可在比 7Mpa高的压力下工作。工程师们很快意识到为了发挥集中力的作用，需要特殊的阀齿轮确保立柱有足够的支撑度，简化操作方法。 之后为了保障工作环境和设备的安全性，方便工作人员操作，单向阀、排出阀和选择活门便应运而生了。 一直以来，制造商使用软硬不同的各种各样的材料，开发了不同的阀门座形式阀门密封技术在慢慢地得到改善。随着生产厂家逐渐使用各种硬度的橡胶和橡胶织品综合的橡胶材料时，支柱和密封技术就迅速地发生了变化。坚持不懈的工程师们梦想成真是最终的制动楔软管的发展，它们很快几乎普遍替代了螺纹联接。流体技术也是制造问题的一个领域。 开始时有乳化油和水。 但从来没有想过的是，混合使用的水可能有许多潜在的灾难性影响。 坚硬太大、 太小、 金属盐和细菌破坏了水或油形成的乳化液。造成分离物， 熔渣、过滤器堵塞。最终使设备出现了严重的问题。例外地，在乳化液里含有高水平可变的流体百分比导致了分离物和熔渣，低强度在阀门齿轮和圆筒之内导致了严重腐蚀。流体逐渐改善,英国煤矿对 Spec.18 和 Spec.19 水的公认让流体的发展明确达到了混合水的硬度。微量的垃圾制造的流体污染在地下依然是一个问题。 相对而言，最近又有了新的突破。过滤器堵塞，旁路被接受曾经是实际情形。 结果是旁通阀，在泵上的极端磨损，卸荷阀等。阀门齿轮在 20 世纪 70 年代初期朝自动化的方向发展。伴随着一系列的压力阀和销阀的引入，它们构成了应用于3 顶板支护的液压逻辑机构的基本元件。 然后它试图由操作员从简单的控制阀启蒙运动着手创造程序化的操作。 单体支护，一些包括支柱和前部的某些相当复杂体因被控制。 技术延伸到一批或边坡控制。 此设计中，一定数量的支护由液压逻辑从他们中的任意一个传递出的启蒙信号程序化。现代电液压机构的第一个 Gullick 先行者在每一个边缘的确使用了，一个主动制动器，带动电子和电磁阀和3 个从动制动器。 在过去，因为电子技术太复杂，液压逻辑元件更受欢迎。 事实上液压学是比较复杂的，阀门齿轮通常在必要的时候被掩藏在橡皮绝缘管下，特别是如果液压机构中的流体不足被维护了，对维护钳工来说是个恶梦。液压和电液压自动化的这些早期的失败导致 20 世纪 70 年代初期自动化陷入了困境，而且更简单的系统被恢复了。然而发展仍在继续。最重要的是，掩护式支架开始涌现。4. 804. 80年代的顶板支护电子学年代的顶板支护电子学早在1964年，人们就意识到电力对自动化起着举足轻重的作用。在英国煤矿螺栓企图被用来生产一个完全自动化的面孔包括在 ROLF 项目之下的创始机械。整个系统瘫痪了，不是他们付出的努力少，而是由于那时的设备和顶板支护太过简单而不适宜。然而，ROLF这个项目设想某天自动化能实现。短暂的平息直到 20 世纪 70 年代晚期，英国煤矿沉重的责任项目再次唤醒了自动化的想法。Gullich Dobson判断一个液压初始系统意味着成功的希望，虽然已经意识到早期用于ROLF的不可改变的“硬逻辑”的缺陷。所以，在控制箱内使用微处理器控制的决定和在出口处使用计算机是明智的选择。但并不是在相对想对新鲜的微处理机技术中没有指定的风险。自动连续软件放在末端计算机中，命令被传达到智慧 OFUs，激活电磁阀，依顺序驾驶操作顶板支护。三个 Gullick 电液压系统工作面在 20 世纪 70 年代晚期投入使用，发展在系统中进入了高潮，不再使用液压边缘逻辑控制液压支架和刮板输送机，支柱也得以延伸。另一发展是采煤工作面对准线，刮板输送机的平直度和网深度由微处理器基于在支架上的电路板控制，使用末端计算机连接到表面。两种安装形式都被生产，尽管遭受着各种各样的问题，包括水的流入碰撞位置传感器，它们证实了采煤工作面对准线和表面传输的原理。5. 5. 现代顶板支护控制系统现代顶板支护控制系统自动化早期的失败到当前证实了最终目标总有一天会达到，以下是得出的结论。1掩护式支架为自动化的应用提供了正确的环境。2阀齿轮需要被设计成在高压下是可靠的，容许有污染，能承受快的流动速度。3支柱和和滑枕能承受高载荷，快速操作，并且适合重流量的条件下。4微处理器是一种敏感的电学元件，要求高速度，多操作，可暴露内在安全系统的极限，使用电磁阀和更简单的硬连线逻辑电子。Gullick 开始通过寻址结论 2发展新一代的方案。 它有遮护板，微处理器，新一代的立柱和滑枕正在被开发。阀门齿轮能在大于 30Mpa 的压力下工作，低电流是关键成份，在 1984 年 Gullick引入了动力化的阀门。 这10 到 20 毫安导阀能相当愉快地运作在35 Mpa，并且仍然提供流程。 与大约消耗120 MA的电磁阀相比，由于平滑的操作和可利用的高应力，可靠性更好。动力阀和以前的螺线管系统相比,允许内在安全电源的多操作局限被克服，允许至少五倍阀门的数量同时被管理。因而电牵引系统产生了，动力化的阀门被结合了对实现最新的 CMOS 低功率芯片和技术的一个微处理器控制系统。这导致系统内部每一个支架配备以 OFU、阀门组装和相同简单的液压系统。终端计算机作为媒介控制自动化过程。1984 年电牵引系统的第一次安装在英国煤矿 Sherwood 矿区，是一次巨大的成功，可行的终端计算机控制被实现，包括短矿柱和前柱的控制。1985年此系统开始使用，安装在澳大利亚和美国。尽管如此，环境问题困扰着美国的试验，澳大利亚的设备运行得非常好，仍每天在 Baal Bone 使用着。环境问题主要是与湿度大和用软管灭火相关。一旦被认可，便恢复到正常位置，直到1988年设施才成功地安装。West Cliff在 1988年翻新改进电牵引系统。同时， 电牵引系统顶板支护的快速的速度对密封设计领域的发展发号施令。 高速经常意味着热化，这可能与半合成或合成流体润滑液的减少同时进行，然后可能产生更多的问题，这样，新一代的密封设计产生了。高压产生的地方，密封在传统的橡胶和橡胶织物间交换着。使用了塑料，现在成为耐用的准则。1988 年，对 Gullick 来讲，向下按的电钮成批成顺序的操作成为标准是显而易见的，机器初始者-关于 ROLF 的试验仍被需要。以前大多数的实验使用了计时器系统。脉冲或数据不断地把剪切轨迹输入到顶板支护控制系统中。 然而，交界面对大量剪切形式的不可靠度和需求在这次试验中呈现出极大的难度。Gullick 决定红色为执行的路径，开发了一种具有以下主要属性的系统：1可以拍打灰尘的宽大的，耀眼的红色发光体。2编码在红色传输中保证系统不被其他灯光或照明设备激活。3是一个软件，对信号的偶然丢失可容许和可编程序。这个系统是成功的，可通过增加生产和减少劳动力立即给消费者带来利益。由于Gullick 电牵引系统始终是基于生产量的微处理机，很容易扩展系统的灵活性，机器和人都可以操作，迎合了大多数消费者的需求。 看到早期软件程序的成功潜力的顾客率先开发该系统，与Gullick 软件组一起提供以下设施：1再试2反继电器气压计销轴破损3工作面末端序列4模式外的工作面选择5双重机器序列 今天的电牵引系统是多功能的，可靠的。机器启蒙经常指定，最近设备的翻新安装在West Cliff，例如，导致在机器启蒙控制之下工作面生产记录吨数。当前系统仍然使用动力化的阀门和其他基本原理，直接返回到 1984 年在 Sherwood 的系统，间接地返回到从70年代晚期最早的微处理器系统。与主要流量开关一起，小型化了的动力化的阀门被改进了并且形成整体系列的阀齿轮。电子设备使用更新的芯片，但仍然包含基本的电路连接板和通过 15 年的轮距记录加强微处理器界面用途的软件。与控制一样，监测立柱的压力可以提供，界面对准线是可利用的(虽然由于滑枕系统效率的改善，不是当前普遍的)， 由此，完整的电路最先开始在 1978年。如此，最先在 60 年代晚期设想出 ROLF 的那些工程师的梦想和客观事实-自动化，机器启蒙， 无人管理都在今天得以实现。但是未来是什么样子呢？6. 6. 未来的顶板支护自动化未来的顶板支护自动化当前有几个发展准备把液压支架自动化带入新的一代，与其他系统在长壁的结合将实现普遍。随着软件和硬件的开发使系统更具智能，顶板支护系统自身将变得更加自动化，从而能在无关紧要的情况下和固有的采煤问题上（如顶板漏洞）独立应付。例如，系统为控制 4根支柱的支架使用倾斜传感器提供平衡的机盖限制支架后部渗透到洞里，已经在发展使用了。程序的发展和新的传感器技术将使顶板支护系统继续被提高以完善它们本身， 专家系统编程，系统从它自己的错误中吸收经验，在垂直方向。然而，顶板支护系统在长壁中不再是唯一的灵巧的系统。 采煤机、刮板输送机和互换机控制以及环境监测设备全部有固有的智力。当命令发出时，将来的自动化将把这些各种各样的智能系统连接在一起，以便信息可以在系统之间传输，有利于全部。世界各地各种各样的煤炭操作员现在正在接受局部综合化方法，共同的宗旨是改进设备的可靠性和生产率，允许维护任务时更容易管理。在中期它似乎可能把分开的子系统结合在一起成为一个单元。现代微处理器和编程技术已经在向这方面发展，那是技术上可行的，而且仅仅是时间问题，不是条件问题。当综合流程被充分开发，每个界面的子系统由专家系统编程时，也许最后有机会安装第一个完全无人操作的局面。 直到那时，看到任何人为水平的主要减少是困难的。The path to Successful Roof Support Automation1 ABSTRACTThe first hydraulic roof supports were installed underground in 1950s and ever since thatengineering developments have improved the supports in many different ways.However,advancesin three main areas,the roof support mechanical design,hydraulic engineering and electronics haveultimately led to the point where ,35 years after that installation,automation has been achieved andis now commonplace.The history of roof support automation has involved the continual integration of hightechnology engineering.There are further possibilities for the future which combine to give someidea of the likelihood of there ultimately being a completely manless face.2 INTRODUCTIONAround 35 years ago,a development took place within the mining industry that,withhindsight,paved the way for this industry to change from being a highly labour intensive one,to theindustry of today.This development was the introduction of the hydraulic roof support.The first generation support,with its simplistic hydraulic tap controls,was a quantum leap inits time,contributing to improved safety of the workplace and improved productivity.Relative tothe use of props and bars,the activity of supporting the roof had actually been “automated”,andthereafter the challenge for greater degrees of automation was laid firmly at the feet of the roofsupport designers.Consequently,many improvements were made in the fields of structural and environmentalmechanical engineering and the development of hydraulic systems which would operate reliablyusing water-based fluids.This improved engineering ,coupled with the development knowledge ofthe mining engineers of the effects of and load patterns induced from different types of strata,ledto the development of competent mechanical structures.Early attempts to use electronics to control these supports were made within British Coal andthe first ROLE system (Remote Operated Longwall Face ) was installed in 1967.Unfortunatelythere was simply not the efficientcy in either the roof support or the electronics technology of theday to provide the required success.The development of the shield support coincided with the availabilities of improved valvematerials and fluids and also of “chip” electronic technology.It was the marriage of thesedevelopments that led to automation success,with the shield support providing the idealenvironment for the application of electro-hydraulics.Today,enhancements of these technologies,along with the introduction of themicroprocessor,provides the industry with extremely reliable,flexible and efficient systems.The automated roof supports are no longer a designer dream but are a true ,every-dayworking reality.The ancessor of the modern roof support is the wooden pitprop.Therefore,when,in the mid1950s,the first “roof supports”were designed,these were merely extensions of the knowntechnology.In the first chock supports,hydraulic jacks of 2inch bore were held vertical in a simple boxframe forming the base and the canopy was a pair of simple I-beam girders.A hydraulics jackmounted in the base provided for conveyor push and roof support advance.87Clearly the users of today can easily understand the multitude of shortcomings-some ofwhich still had not been designed out and some,it may be argued,which were inadvertentlydesigned in.Nonetheless,relative to the old methods of pit props and bars,the first generationsupport was a tremendous forward step and made real contributions to safety and productivity.From this first development quite rapid progress was made.A major requirement was toprovide a safer travelway through the face for the face operator and this was solved by addingone,or alternatively two,forward legs with their own roof canopies and floor bases to the four legunit.This also greatly improved the roof control characteristics.By the early 1960s,these articulated supports,with load carrying capacities of up to 180tonnes,were using substantially improved fabrications and hydraulics.although their applicationunderground was still restricted to seam heights of 1.5 metres.The worldwide expansion of longwall mining.coupled with a need to extract higher seamranges,led to a requirement for supports of higher load carrying capacities.Thus the rigid basechock was introduced in 1968.This second generation support provided for support ratings of upto 720 tonnes can seam extraction of three metres.The shield support emerged in the 1970s and the early 2 leg caliper designs were extensivelyused in Germany and introduced into the USA and South Africa.These shields were poor inefficiency and suffered from very high toe loadings.The introduction of lemniscate designs was made in the late 1970s.Shield supports requiredfundamental changes in design philosophy in that the mechanical linkage resisted strata lateralforces in addition to vertical forces.This provided for a far more efficient and reliable support andits robustness allowed for the successful application of the longwall system in strata conditionswhich had previously been impossible,for example,the extremely heavy conditions of New SouthWales,Australia and some of the more friable roof conditions in the United Kingdom.The efficiency of the modern shield support provides the suitable environment forsuccessful application of automation.The preferred configuration of shield supports in the USA is the 2 leg design,and this designhas been the major platform for many of the automation developments that are currently available.The configuration is being introduced into the UK and Australian market and will continueto be in the forefront of roof support and automation development for a long time into the future.3 ROOF SUPPORT HYDRAULICS UP TO THE 1980sRoof support systems use large volumes of fluid both to fill up the system and then tocompensate for leakage and other fluid losses.This economic factor coupled to others such as firehazard and transportation logistics of large volumes of liquids led almost immediately to roofsupport hydraulic systems becoming water-based.It is a fact that the use of water-based hydraulics has been an area of engineering in whichthe roof support manufactures have truly led the technology and even today,very fewmanufactures of industrial hydraulic equipment include products suitable for use with water-basedfluids within their portfolio.The earliest roof support systems used seal and valve technology that was not at allsophisticated.Simple tap valves and leather seals with string packings were the best that wasavailable for working at the relatively high pressure of 7MPa.Engineers soon realized that special valve gear would be needed in order to cater for effectslike convergence,to ensure that legs remained competently set and to simplify the methods ofoperation.So non-return valves,bleed valves and selector valves soon appeared in order tosafeguard the workplace and equipment and to make life easier for the operators.All thewhile,valve sealing technologies were slowly improving as manufacturers developed differentvalve seat forms using various hard and soft materials.Leg and ram seal technology also changed rapidly,with manufactures soon using rubbers ofvarious hardnesses and rubber-fabric composites.The “dream come true”of the maintenance engineer was the eventual development of thequick-release or staple lock hose fitting which very soon almost universally replaced the threadedconnection.Fluid technology was an area that also created problems.In the beginning there wasemulsifying oil and water.But it was surely never conceived that the water used for mixing couldhave so many potentially catastrophic effects.Too much hardness, too little hardness,metal saltsand bacteria played havoc with water/oil emulsions,resulting in separation,scumming,filterblockage and ultimately creating severe problems within the equipment.Abnormally high levels of fluid percentage in the emulsion caused separation andscumming,low strengths caused severe corrosion within valve gear and cylinders.Fluids gradually improved and the recognition of British Coal Spec.18 and Spec.19 watersbrought about the development of fluids specific to the hardnesses of waters with which they wereto be mixed.Fluid contamination by particles of dirt has always been a problem underground.It is againonly relatively recently that breakthroughs have been made.It used to be the case that filterblockage and bypass was accepted and the result was bypassing valves and extreme wear onpumps,unloading valves etc.Valve gear development continued down the path to automation in the early 1970s with theintroduction of sequence,striker and latching valves which formed the basis of hydraulic logicapplied to roof supports.Thus it was attempted to create sequenced operations from a simplecontrol valve initiation movement by the operator.Single supports,some quite complex involvingsprags and forepoles,were controlled thus.The technique even extended to hydraulic batch or bankcontrol.In this design,a number of supports were sequenced by hydraulic logic from an initiationsignal given on one of them.Indeed the first Gullick forerunner of the modern electro hydraulic systems used,in eachbank,an initiator chock,which housed the electronics and solenoid valves,and 3 slave chocks.Inthose days hydraulic logic was preferred because the electronics was “too complicated”.In fact thehydraulics was too complicated and the valve gear was usually,by necessity,buried beneath a massof hose spaghetti and was a nightmare for the maintenance fitter particularly if the hydraulic fluidwas poorly maintained.These early failures of hydraulic and electro hydraulic automation led to the demise ofautomation in the early 1970s,and more simpler systems were reverted to.However developmentcontinued and most important of all,the shield support was beginning to emerge.4 ROOF SUPPORT ELECTRONICS UP TO THE 1980sAs early as 1964 it was realized that electronics held the key to the automation.A bolt attempt was made within British Coal to produce a fully automated face-includingmachine initiation-under the ROLF project.The systems failed not in their endeavour but because the equipment and the roof supports ofthe day were simply not suitable.However,the ROLF project provided that one day automationshould work.A lull occurred until the late 1970s where the heavy duty programme of British Coal onceagain awakened thoughts of automation.Gullich Dobson decided that an hydraulic logic initiator system would stand a chance ofsuccess,but had recognized the earlier shortcomings of the inflexible “hard logic”used with ROLF.Therefore,the decision to use micro processor for control within the on-face controlboxes,and the use of a Gate End computer was a wise one,but not without risk given the relativenewness of microprocessor technology.Auto sequential software resided in the Gate End Computer and commands werecommunicated to the intelligent OFUs to activate solenoid valves,in sequence to pilot operate theroof supports.Three Gullick electro-hydraulic faces were installed during the late 1970s and thedevelopment culminated in a system,no longer using as much hydraulic bank logic,whichcontrolled roof support and conveyor,and also extension bars and sprages.Another development was coalface alignment,where conveyor straightness and web depthwere controlled by micro processor based electronics on the supports,with a computer in the gate-end and a link to the surface.Two installations were manufactured and although they suffered from various problemsincluding ingress of water into the ram position sensors,they proved the principles of coalfacealignment and surface transmission.5 ROOF SUPPORT CONTROL SYSTEMS UP TO THE PRESENT DAYThe early attempts at automation had proved that the ultimate goal would one day beachieved.Certain conclusions had been reached.1.The shield support provided the right environment for the application ofautomation.2.Valve gear would need to be designed that was reliable at high pressures,tolerant tocontamination and capable of hign flows.3.Legs and rams would need to be capable of high loads,rapid operation and suitablefor heavy yielding conditions where applicable.4.The micro processor was a sensible electronic approach,and that demands for highspeed and multiple operations could expose the limits of intrinsically safe systems which usedsolenoid valves and simpler hard-wired logic electronics.Gullick began is development programme for the new generation by addressing conclusions2. It already had shields,microprocessor and a new generation of legs and rams was already beingdeveloped.Valve gear capable of working at greater than 30MPa,yet low current,was the key ingredientand in 1984 Gullick introduced the motorized valve.This 10 to 20 milliamp pilot valve could workquite happily at 35 MPa and still provide flows comparable to a solenoid valve consuming perhaps120 MA.Reliability was better than a solenoid valve due to the smooth operation and high forcesavailable.The motorized valve allowed the multiple operation limitations of intrinsically safe powersupplies to be overcome,allowing at least five times the number of valves to be simultaneouslyoperated,compared with previous solenoid systems.Thus Electroflex was launched and the motorized valve was coupled to a micro processorcontrol system embodying the latest CMOS low power chips and techniques.This resulted in asystem in which each support was equipped with an OFU,a valve pack and identical simplehydraulics.The Gate End Computer was used as the medium for controlling thr automationprocess.The first installation of Electroflex in 1984,at Sherwood Colliery,British Coal,was a greatsuccess and reliable Gate End Computer control was achieved,including control of sprags andforepoles.In 1985 the system saw export use,with installations in Australia and the USA.Althoughenvironment problems bedeviled the USA attempt,the Australian installation worked extremelywell and is still in daily use at Baal Bone.The environmental problems were principally those associated with hosing down and highhumidity.Once recognized,they were put right and installations were successfully installed up to1988.West Cliff was retro-fitted with Electroflex in 1988.Meanwhile,the fast speeds of Electroflex roof supports were dictating developments in thearea of seal design.High speed often means heating,and where this might be coupled with a lowerlubricity semi synthetic or synthetic fluid,then this could be even more problematic and so a newgeneration of seal designs was created.Where high stressed could occur,seal alternatives to the traditional rubber and rubber/fabricwere developed.Plastics were used and these are now the norm for such heavy duty uses.In 1988,it was obvious to Gullick that push-button,batch,sequential operations were thenorm and that machine initiation-first attempted with ROLF was still required.Most previous attempts had employed odometer systems,with pulses or data fed dowa theshearer trailing cable,to the roof support control system.However,unreliability and the need tointerface to numerous types of shearers imposed enormous difficulties with this approach.Gullick decided that infra red was the path to take,and developed a system with thefollowing main attributes:1.A broad,powerful infra red beam capable of punching through dust.2.A coded infra red transmission to ensure that the system was not activated by cap lamps orlumimaires.3.Software,which could tolerate,and be programmable to,the occasional loss-of-signal.This system was a success and led to immediate customer benefits in terms of increasedproduction and reduced manpower.Because the Gullick Electroflex system was microprocessor based throughout,it was easy toextend the flexibility of the system,both machine and man-initiated,to cater for the multitude ofcustomer requests that followed,Customers who saw the successful potential of the early softwareprogrammes developed the system proactively,alongside the sofeware team of Gullick to providethe following facilities:1.Retries2.Anti relay-bar pin breakage3.Face end sequences4.On face selection of out mode5.Dual machine sequence The Electroflex systems of today are versatile and reliable.Machine initiation is oftenspecified,and the most recent retro-fit of such equipment at West Cliff,for example,has resulted inthe face producing record tonnages under machine initiation control.The current system still uses the motorized valve and other basic philosophies going backdirectly to the 1984 system at Sherwood,and indirectly to the earliest microprocessor systems fromthe late 1970s.Motorised valves,along with the main flow valves,have been miniaturized and improved andform the Monobloc series of valvegear.Electronic equipment uses newer chips but still embodies the basic circuit building blocksand software built up throughout a track record of 15 years use of on-face microprocessors.As well as control,monitoring of leg pressures can be provided and even face alignment isavailable(though not currently popular due to improvements in ram system efficiency),therebyfully completing a circle first embarked upon in 1978.So the dreams and objectives of those engineers who first conceived ROLF in the late 1960sautomation,machine initiation,manless operation-are achieved today.But what of the future?6 ROOF SUPPORT AUTOMATION IN THE FUTUREThere are several developments which are currently poised to take roof support autom