baber/WOPTO huggingface dataset:
Patent CN-1227526-A (CN)
Title: 安装有可充气袋囊的安全腰带及其使用方法
Inventor: LEWIS D J
IPC: B60R21/18
Filed: 1997-06-11
Abstract: 一种用于座椅上乘员的车辆约束系统，其包括一安全腰带(16)，和一安装在安全腰带(16)上的一可充气件(18)，且当充气时由安全带所约束，可充气件(18)的尺寸形状应设计得，一个可充气件表面(18a)的作用是通过与乘员膝上部和在其下的座椅的基本区域相接触来阻止和限定可充气件的转动。另一后部件表面(18b)约束乘员躯干运动。安全带(16)穿过或绕过可充气件。安全腰带系统可包含一撞击传感器和气体产生装置。
Patent CN-1194499-A (CN)
Title: 无传感器向量控制装置
Inventor: GENG YANG
IPC: H02P21/00
Filed: 1998-03-24
Abstract: 提供不需执行复杂的运算及不需安装电压检测器的无传感器向量控制装置。差频运算电路存储有关感应电动机的转子的时间常数,用来自固定/旋转坐标变换电路的磁通电流检测值及转矩电流检测值和该时间常数进行差频运算。反电动势运算电路将根据转子速度指令值和差频进行加法运算所得的换流器输出频率指令值输入,输出反电动势指令。电压指令运算电路输出电压指令值。旋转/固定坐标变换电路将电压指令值输出到电压型换流器装置。
Patent CN-1203908-A (CN)
Title: 氰醇裂解酶催化合成光学活性氰醇化合物
Inventor: LIN GUOQIANG
IPC: C07C255/32
Filed: 1998-05-04
Abstract: 本发明是以杏仁为酶源的R－氰醇裂解酶催化分子式为R 1 COR 2 的羰基化合物、分子式为R 3 CN的氰化物在有机溶剂中生成， 光学活性的氰醇化合物,反应温度为0—50℃,反应时间为0.01—120h,其中R 1 =R 4 Ph,R 4 OPh，R 4 OCH 2 Ph，   PhCH=CH，R 5 CH=CH,或R 5 ,R 2 =H或C 1－3 的烷基，R 3 =H,(CH 3 ) 2 COH或H 2 COH,R 4 =H或C 1－4 的烷基,X=O或S,R 5 =C 1－8 的烷基。所述的有机溶剂可含有微量水。反应底物和溶剂的混合物可以以流动相连续通过固定酶而获高产率、高度立体选择性的产物,尤其适于工业化生产。
Patent CN-1217483-A (CN)
Inventor: SHI NAKANO
IPC: G03D3/06
Filed: 1998-11-16
Abstract: 一种处理液的水补充方法及照明显影机,即使在照相显影机再开机时,也能适宜地维持处理液的浓度,并能充分地满足显影稳定性。在处理槽31乃至36内填充处理液的照相显影机处于开机状态时,用液位检测器61、62、63可检测出处理液由规定的液位下降到补充液位,则使水补充装置54、55、56动作,将水补充到规定的液位。还有,在照明显影停机之后再开机时,使水补充装置54、55、56动作,以补充相当于停机时处理液预测蒸发量的水。
Patent CN-1272779-A (CN)
Title: 粘合的绒毛结构及其生产方法
Inventor: GRYSKIEWICZ S M
IPC: D04H1/54
Filed: 1998-09-24
Abstract: 一种粘合绒毛结构及其生产方法,其中,将具有适用于生产绒毛的材料和可热活化纤维材料的浆粕片纤维化而产生绒毛和可热活化纤维的混合物。此混合物与热气流接触而将可热活化纤维加热到活化温度。然后将所得的加热了的混合物沉积到成形结构上,形成粘合绒毛/纤维复合基质结构。
Patent CN-1250998-A (CN)
Title: 电子交换机的用户匹配电路
Inventor: YOUNG-HO CHO
IPC: H04M7/04
Filed: 1999-08-20
Abstract: 一种用于电子交换机的混合用户匹配电路,它匹配所发送的/接收的数据,以便允许在交换机和用户之间进行呼叫通信。用户匹配电路由各单独的部件构成,而不使用变压器或SLIC,这样,可简化其外围部件,并有力地抵抗外部的脉冲冲击。
Patent CN-1318102-A (CN)
Title: 编码鸭瘟立默氏菌外膜蛋白的OmpA基因及应用方法
Inventor: FREY JOACHIM
IPC: C07K14/195
Filed: 1999-07-14
Abstract: 本发明提供了鸭瘟立默氏菌的OmpA基因及其编码的蛋白质，所述基因和蛋白质可用于疫苗生产及诊断禽类物种中对经济至关重要的疾病雁形目渗出性败血症(septicemia anserum exsudativa)。
Patent CR-20160351-A (CR)
Title: Mezclas herbicidas que comprenden imazethapyr, imazamox y fomesafen, sulfentrazone o bentazone
Inventor: SANYAL NILANJAN
IPC: A01P13/00
Filed: 2015-01-05
Abstract: La presente invención se refiere a composiciones ternarias activas como herbicidas, que comprenden a) ácido 5-etil-2-[(RS)-4-isopropil-4-metil-5-oxo-2-imidazolin-2-il]nicotínico (nombre común: imazethapyr) y ácido 2-[(RS)-4-isopropil-4-metil-5-oxo-2-imidazolin-2-il]-5-metoximetilnicotínico (nombre común: imazamox) y b) al menos un herbicida seleccionado del grupo que consiste en 5-(2-cloro-a,a,a-trifluoro-p-toliloxi)-N-mesil-2-nitrobenzamida (nombre común: fomesafen), 2',4'-dicloro-5'-(4-difluorometil-4,5-dihidro-3-metil-5-oxo-1H-1,2,4-triazol-1-il)metansulfonanilida (nombre común: sulfentrazone) y 2,2-dióxido de 3-isopropil-1H-2,1,3-benzotiadiazin-4(3H)-ona (nombre común: bentazone).
Patent CR-20160481-A (CR)
Title: Metodo y sistema para crear y manejar un anuncio combinado que usa un dispositivo móvil
Inventor: VAN DEN BERG GUY
IPC: H04W4/14
Filed: 2015-03-19
Abstract: Se proporciona un método y un sistema de recopilación de uno o más anuncios. El método incluye la recepción a través de una red de comunicaciones de una solicitud de un anunciante para publicar un anuncio.
Patent CR-20170311-A (CR)
Title: Reactor para la obtención de un producto gaseoso a partir de materia combustible
Inventor: VREUGDENHIL BEREND JOOST
IPC: C10J3/72
Filed: 2015-12-07
Abstract: Método y reactor para la elaboración de un producto gaseoso a partir de material combustible. El combustible se hace llegar a una cámara de pirólisis (6) en la que se lleva a cabo ese proceso para obtener un producto gaseoso. Parte del fluido efluente de la cámara de pirólisis (6) se recircula a una cámara de combustión (20, 23). En la cámara de combustión se efectúa un proceso de gasificación en un lecho fluidizado (20) utilizando un fluido de proceso primario, seguido de un proceso de combustión en un área (23) sobre el lecho fluidizado (20) empleando un fluido de proceso secundario
Patent CR-20220489-A (CR)
Title: Tie2-binding agents and methods of use
Inventor: ZHANG GU
IPC: C12N9/12
Filed: 2021-03-22
Abstract: The invention provides Tie-2 antibodies and fragments thereof and conjugates and methods of using the same.
Patent EC-SP003829-A (EC)
Title: Actividades trans olefinicos de glucoquinasa
Inventor: SIDDURI ACHYUTHARAO
IPC: C07C233/08
Filed: 2000-12-15
Abstract: Ureido propionamidas o propionamidas N-heteroaromáticas trans olefínicas 2,3-di-sustituidas, siendo dicha sustitución en la posición 2 un grupo fenilo y en la posición 3 un anillo cicloalquílico, siendo dichas propionamidas activadores de la glucoquinasa que aumentan la secreción de insulina en el tratamiento de la diabetes tipo II
Patent EC-SP056256-A (EC)
Title: Moduladores delta-opioides triciclicos
Inventor: CARSON JOHN R
IPC: C07D409/14
Filed: 2005-12-27
Abstract: La invención está dirigida a moduladores del receptor delta-opioide; más específicamente, la invención se refiere a moduladores d-opioides tricíclicos; también se describen composiciones farmacéuticas y veterinarias para el tratamiento del dolor leve a severo y de varias enfermedades, usando los compuestos de la invención.
Patent EC-SP972318-A (EC)
Title: Agente reductivo para alquilacion reductiva de antibioticos glicopeptidos
Inventor: ZHENG HUA
IPC: A61K38/00
Filed: 1997-11-20
Abstract: La presente invención proporciona un proceso para alquilar reductivamente un antibiótico de glicopéptido conteniendo aminas, cuyo proceso comprende la racción del antibiótico de glicopéptido con un aldehido o cetona en presencia de un agente reductor, mejora que comprende el empleo de piridina-borano como agente reductor.
Patent EC-SP992951-A (EC)
Title: Compuestos farmaceuticos
Inventor: GALLAGHER PETER THADDEUS
IPC: A61K31/39
Filed: 1999-05-12
Abstract: Compuestos farmacéuticos de la fórmula: (gráfico), en la cual n es 1 a 6, m es 1 ó 2 y p es 1 ó 2, R1 y R2, cada una de ellas, es hidrógeno, alquilo C1-4, alcoxi C1-4 HO-alquilo C1-4, alcoxi C1-4-alquilo C1-4, alquiltio-C1-4, halo, fenilo opcionalmente sustituido, fenilo opcionalmente sustituido -alquilo C1-4, o R1 y R2, junto con el átomo de carbono al que están unidas forman un grupo cicloalquilo C3-6 > C=0, C=NOR1 donde R¿es hidrógeno o alquilo C1-4, R3, R4 y R5, cada una de ellas, es hidrógeno, halo, nitro, alquilo C1-4, alcoxi C1-4, alquilo C1-4 -CO-, donde m es 0,1 o 2, R¿R¿¿N-SO2-, -COOR¿, -CONR¿R¿¿, -NR¿R¿¿, -N(OR¿)COOR¿¿, COR¿, -NHSO2R¿, donde R¿y R¿¿, cada una de ellas, es hidrógeno o alquilo C1-4, R6 y R7, cada una de ellas, es hidrógeno o alquilo C1-4 X es oxigeno o azufre, la linea punteada representa un doble enlace opcional, y el átomo de flúor esta unido en la posición 6- o 7-; y las sales de los mismos.
Patent FI-20001559-A (FI)
Inventor: SIIVONEN MIKA
IPC: B66F15/00
Filed: 2000-06-30
Abstract: The invention relates to a service stand (1), which is positioned beneath the rear part of a motorcycle and which extends from there to both sides of the motorcycle, the service stand having a lever member (2) for lifting the rear part of the motorcycle so that the rear wheel (3) is lifted off the ground (4), and members for connecting the service stand (1) to the rear part of the motorcycle. According to the invention the service stand (1) placed beneath a motorcycle leaning on its side stand has a connecting member (5), on the opposite side from the side stand, the connecting member being pre-adjustable in the height direction, whereas the height position of the connecting member (6) on the same side as the side stand can be adjusted in the height direction by the lever member (2).
Patent FR-1604463-A (FR)
IPC: G06F11/277
Filed: 1968-12-31
Granted: 1971-11-08
Abstract: 1,261,898. Testing data processors. BURROUGHS CORP. 31 Dec., 1968 [2 Jan., 1968], No. 61863/68. Heading G4A. A system and method for determining error conditions in a unit of a digital data processing system uses a programmed test routine comprising a plurality of test cases grouped into a plurality of test strings, each string including more than one test case, the cases of the routine being serially executed, there being means for detecting the failure of all the cases within any string. Preferably, the strings having larger numbers of cases precede the strings having smaller numbers of cases. In a prior art system, Fig. 3A, the error detecting system was a branching system in which the success S or failure F of a test T causes further respective tests until an appropriate error condition F1 to F16 is diagnosed. This required a random access memory. In the present system, Fig. 3B, the respective tests which result in an appropriate error condition F are performed in series for all the error conditions, e.g. if the tests T1, T2, T4, T8 which make up a string are all failures, this indicates that the error condition F1 is present. The strings are preferably executed in the series shown, larger strings first since otherwise the results of the smaller strings would be invalid, thus allowing the use of a serial memory e.g. magnetic tape. Separate routines may be provided for each unit to be tested and it is stated that routines may be sufficiently complex to diagnose errors down to the last integrated circuit chip. Operation (Fig. 1, not shown).-A magnetic tape unit holds a test routine generally for one unit e.g. a processor or a peripheral unit though one tape may be used for two identical units. Each routine comprises blocks of test cases arranged in strings (a string may extend over several blocks), each case comprising a group of 16 bit command words. The routine is transmitted a block (with parity checks) at a time to a magnetic core or thin film memory and serially executed in between receipt of blocks at the memory by a circuit connected to the unit being tested. If the system is being used for diagnosing errors, execution continues until all the test cases in a string have failed whereas if it is merely used to detect errors a halt is called after one failure. Each test case contains command words which set up pre-determined initial conditions in the unit under test, send one or more clock pulses to the unit, determine the outputs of the unit, and compare these with pre-determined correct outputs for the unit. Execution of a first test case in a string sets a flip-flop in case of failure and this is only reset if any succeeding cases in the string are successful. To detect intermittent errors the final case in a string may include a command to repeat the whole string a number of times.
Patent GB-1226278-A (GB)
IPC: H05H1/46
Filed: 1969-07-15
Abstract: 1,226,278. Microwave coupled plasma heating devices. V. P. KIRJUSHIN. 15 July, 1969, No. 35496/69. Heading H5H. A gas-discharge tube 1 is heated inside a cavity resonator 2 along its axis of symmetry and microwave energy is coupled into the resonator from a feed waveguide 5 sharing a wall 6, Fig. 2 (not shown), with the resonator, via electromagnetic coupling elements, such as slots 7, equidistantly spaced from the long axis of the tube 1 and separated from one another by a distance which provides for inphase occurrence of the oscillations produced in them. This distance is a half-wavelength of the input microwave energy, with adjacent slots on opposite sides from the long axis of waveguide 5, Fig. 1, or one wavelength, with adjacent slots on the same side of the long axis, Fig. 3. The resonator 2 is spherical, Fig. 1, or cylindrical, Fig. 3. The waveguide 5 is a ring-shaped rectangular section waveguide with a wall 8, Fig. 2 (not shown), to split up the energy equally between all the slots 7, or is toroidal, Fig. 4 (not shown). Instead of slots 7, the coupling elements may be loops or probes. The apparatus is used to carry out chemical reactions, deposit thin films, or clean powders and gases.
Patent GB-1228809-A (GB)
IPC: B21D22/02
Filed: 1968-07-15
Abstract: 1,228,809. Colour television tubes. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 15 July, 1968 [18 July, 1967], No. 33648/68. Heading H1D. A triple electron gun for a colour television tube adapted to produce beams whose axes lie at the corners of an equilateral triangle, and comprising three cathodes 6 (only one of which is shown), three common grids 8, 10 and 12 each provided with an aperture for each of the three beams, and a common fourth grid 14 of circular cross-section, is characterized in that the centres of the apertures in the third grid are less than 4 mm. from the axis and the thickness of the third grid at these apertures is no greater than this distance and is preferably less than 1 mm. The third grid may be provided with an annular protuberance 12 surrounding the apertures and of a diameter less than or equal to that of the adjacent portion 16 of the fourth grid. The fourth grid may comprise two cylindrical portions, as shown, the length of the narrower portion 16 being preferably equal to its radius, which in one example is 7 mm.; alternatively the electrode may be conical at least in part. The construction shown includes a fifth grid 15 of the same diameter as the wider portion 17 of the fourth grid.
Patent GB-1229044-A (GB)
IPC: E01D21/00
Filed: 1968-04-17
Abstract: 1,229,044. Travelling beam for bridge construction. BINDER & CO. 17 April, 1968 [24 April, 1967], No. 18127/68. Headings E1G and E1S. A "travelling beam" for use in bridge construction work, for carrying, e.g. bridge formwork, comprises a main girder 1 in combination with (a) two roller jacks 2, 4 movable along the girder, about either of which the girder can pivot in a horizontal plane, one of which jacks permits transverse displacement of the girder relative thereto; (b) a support 3 with detachable legs 3a and (c) a roller support 5, movable along the girder and having guides (as shown, holes) for the legs 3a and means for securing them thereto in different positions, the support being capable of carrying the legs 3a along the girder. The girder may have a vertical hinge 56, and a further support (57), (Figs. 21, 22, not shown) may be employed at one end. The legs 3a are attached to the supports 3 via hydraulic jacks 21 (Fig. 9) so that the legs can be moved up from resting on the pier 7, e.g. to the level of the bridge deck. The upper portions, e.g. 40, of the roller jacks, 2, 4 are designed to pivot about a transverse horizontal axis as well as to roll along the girder, and the body portion (54) of jack 4, Figs. 15, 16 (not shown) can roll on transverse tracks (59').
Patent GB-1230977-A (GB)
IPC: G09F15/00
Filed: 1967-11-27
Abstract: 1,230,977. Display panels. EMBASSY MERCHANDISING Ltd. 30 Oct., 1968 [27 Nov., 1967], No. 53784/67. Heading G5C. A collapsible display device is formed by parallel panels 13a-13d interconnected by joining panels 14a-14c which are arranged, when assembled, to be normal to the panels 13a-13d, and are pivoted intermediate the ends of the panels 13a-13c on the one hand and to the rear edges 16, 18 of the panels 13b-13d on the other. As shown, the device has two additional superposed sections, the centre section being turned upside down and end to end relative to the upper and lower sections. Pivot pins may interconnect the aligned front edges 19 of the superposed sections and similarly their aligned edges 20.
Patent GB-1231325-A (GB)
IPC: F16B15/08
Filed: 1969-03-10
Abstract: 1,231,325. Headless nails. SWINGLINE Inc. 10 March, 1969 [16 Oct., 1968], No. 12403/69. Heading B8C. [Also in Division F2] Headless nails each having ridged end portions of differing slope at opposite ends of a straight shank portion are adhered to strips 18, 22 of plastics material to form an array of nails adjacent and parallel to each other for use in a magazine of a nail-driving tool. The nails may be of steel and the strips 18, 22 may be of polyethylene terephthalate.
Patent GB-1231746-A (GB)
IPC: F02C6/00
Filed: 1969-08-07
Abstract: 1,231,746. Gas turbine plant. DAIMLERBENZ A.G. Aug.7, 1969 [Aug.7, 1968], No.39564/69. Heading F1G . The invention relates to a gas turbine engine of the kind comprising a compressor, combustion equipment and a turbine which drives the compressor, wherein an air turbine is disposed upstream of the compressor and is driven by the flow passing into the compressor. The engine shown comprises a compressor 2, an air pre-heater 3, combustion equipment 4, an HP turbine 1 which drives the compressor through shaft 5, and an LP turbine 7 which drives an output shaft 9 which is connected through gearing 10 to the drive shaft 11 of the road wheels of a vehicle. The exhuast gases from the turbine pass to the pre-heater 3. An air turbine 12 is disposed upstream of the compressor 2 and is driven by air-flow into the compressor. The turbine is provided with adjustable baffles 13 so that its expansion ratio may be varied and the turbine is connected to the compressor through an over-running clutch 14. The suction turbine may be heated by passing the exhuast gases from the turbine 7 therethrough after discharge of the gases from the air pre-heater 3, as indicated by the broken line 15. In operation of the engine at low loads the suction turbine 12 is operative so that when a sudden increase in power is required the suction turbine is rendered ineffective so that increased power in the gas generating suction of the engine is immediately available.
Patent GB-1232279-A (GB)
IPC: C08J5/08
Filed: 1968-05-27
Abstract: 1,232,279. Glass fibre-elastomer laminates. OWENS-CORNING FIBERGLAS CORP. 27 May, 1968, No. 25331/68. Addition to 1,087,904. Heading B5N. [Also in Divisions C3 and D1] An assembly comprising a matrix of elastomeric material, e.g. neoprene or chlorobutyl rubber, and a reinforcement of glass fibres is produced by coating the glass fibres with a polyfunctional organic compound which is a solvent or plasticizer for the elastomeric material in its uncured or partly cured stage, combining the coated glass fibres with the elastomeric material at this stage so that it is sufficiently free-flowing at the glass-fibre surfaces to coat and interspace the glass fibres and then curing the elastomeric material, the polyfunctional compound being monomeric and comprising one or more of (1) a thiazole having the formula in which R 1  and R 2  are hydrogen or organic radicals and X is hydrogen or a halogen atom; (2) an alkyl-or-aryl-substituted hydrazine; (3) a thiol acid or functional derivative thereof; (4) a thiol derivative of morpholine; (5) benzthiazole or a functional derivative thereof; (6) a chlorothiophenol; (7) a thioanthranol; or (8) dimethyl-2-thionyl chloride. Suitable polyfunctional compounds are phenylhydrazine and the zinc chloride salt thereof, thioglycollic acid, ethyl thioglycollate, ethyl thiosalicylate, aniline thioglycollate, dithioglycollic acid, N-morpholine methane thiol, di-N-morpholine methyl sulphide, 2-mercapto benzthiazole, dibenzthiazyl disulphide, 4,5-dimethyl-2-mercaptothiazole, thiazole - 2 - thionyl chloride, benzthiazole - 2 - thionyl chloride, ethylhydrazine, chlorothiophenol, p - methyl chlorothiophenol and thioanthranol. The polyfunctional compound which may be applied to the glass fibres after forming may be applied as such or diluted with trichloroethylene or other chlorinated solvent. The coating may also contain a divinylbenzene, diallyl benzene or ethylene dimethacrylate in partially polymerized or monomeric form. Size compositions containing partially dextrinized starch, hydrogenated vegetable oil, a cationic wetting agent and the polyfunctional compound may be applied to the filaments after forming. When the polyfunctional compound is applied to glass fibres in the form of strand, yarn, or fabric the originally applied size may be removed by washing or heating in an oxidizing atmosphere prior to application of the polyfunctional compound. Glass fibres treated with the polyfunctional compound may be laid between strips of uncured neoprene rubber containing curing agents and moulded under pressure at 300-350‹ F. to cure the elastomeric material.
Patent GB-1232345-A (GB)
IPC: E02F3/92
Filed: 1969-03-07
Abstract: 1,232,345. Endless chain excavator-suction dredge combinations. INDUSTRIEELE HANDELSCOMBINATIE HOLLAND N.V. 7 March, 1969, No. 12191/69. Heading E1F. In a suction dredger an endess chain excavating means 3-7 is so associated with the intake 1 of a suction pipe that material excavated by the means is moved thereby to the intake in substantially the same direction 11 as the direction of suction existing at the intake, which is so supported, preferably through a ball joint from the rest of the suction pipe as to be movable relative thereof as required. The longitudinal axis of the means 3-7 lies substantially in the extension of the centre line of the intake. The drive of the means 3-7 can be reversed.
Patent GB-1234115-A (GB)
IPC: B01J8/36
Filed: 1969-06-12
Abstract: 1,234,115. Reactiviating spent charcoal adsorbent. BERKWERKSVERBAND G.m.b.H. 12 June, 1969 [26 July, 1968], No. 29944/69. Heading B1L. Spent charcoal adsorbent enters inner space 4 of fluidised bed reactivator 1 through inlet 6 and is fluidised by hot gases which enter through inlet 12 and pass up through perforated base 2. The fluidised charcoal finds its way from inner space 4 to outer space 5 and eventually leaves in reactivated form for reuse through outlet 7. Generally at least 10%, and preferably 30-50%, of the surface area of base 2 is enclosed in inner space 4 by wall 3, and the perforations in this part of the base preferably have diameters 1.1-1.5 times those of the perforations in the rest of base 2.
Patent GB-1238269-A (GB)
IPC: F16K29/02
Filed: 1970-02-14
Abstract: 1,238,269. Screw-and-nut gearing; valves; one-way brakes; detents. KING OF PRUSSIA RESEARCH & DEVELOPMENT CORP. 14 Feb., 1970, No. 7196/70. Headings F2E, F2Q and F2V.  A valve actuator comprises a screw-threaded valve stem 10 which in normal operation is moved axially by rotation of an axially located nut 12, a brake 33 (Fig. 2) or 73/74 (Fig. 6) holding the stem 10 against rotation, while for scraping and cleaning, the valve seat a clutch 30 (Fig. 2) or 64/65 (Fig. 6) is engaged to rotate the valve stem 10 at substantially the same speed and in the same direction as the nut 12. The nut 12 is driven from a worm 16 via a worm wheel 15, dogs 115, 114, and a sleeve 14 in which the nut is splined. A sleeve 43 splined to the valve stem 10 carries a gear 42 meshing a gear 40 (Fig. 2) or 66 (Fig. 6). The sleeve 14 carries a gear 21 meshing a gear 22 (Fig. 2) or 62 (Fig. 6). In Fig. 2, the gear 22 is secured on a shaft 23 carrying the input member 31 of an electromagnetically engaged friction clutch 30, the output member 32 of which is rigid with the input member 132 of a no-back drive brake 33. The gear 40 is secured to the output member 34 of the brake 33. In its holding state, Fig. 3, the brake 33 prevents rotation of the output member 34 in either direction, balls 37 locking the member 34 to a fixed ring 35. When clutch 30 is engaged and the member 132 driven clockwise (Fig. 3), its initial movement takes up lost motion between members 132, 34, compressing the springs 38 and bringing recesses 39 adjacent the balls 37 (Fig. 4, not shown) so that the latter can move radially to unlock the member 34. The members 132, 34 then rotate together so that the stem 10 is also driven from the worm 16. In Fig. 6, the gear 66 is axially slidable on a stationary shaft 63 between the position shown in which dogs 73 engage fixed dogs 74 to hold the gear 66, and hence the stem 10 against rotation, and a second position in which dogs 73/74 are disengaged and dogs 65 engage dogs 64 on the gear 62 to drivingly connect the gears. A pneumatic or hydraulic actuator 175 acts via a lever 67 and a fork 68 to position the gear 66. The gear ratios are arranged so that with the clutch 30 or 64/65 engaged, the valve stem 10 either rotates without axial movement, or moves very slowly towards the valve seat as it rotates.