【正文】 mounted between an outer sleeve and an inner member having flats machined around the periphery. Driving action is obtained by wedging the rollers between the sleeve and the flats. The clutch is therefore equivalent to a pawl and ratchet with an infinite number of teeth. Magic fluid clutch or brake is a relatively new development which has two parallel magic plates. Between these plates is a lubricated magic powder mixture. An electromagic coil is inserted somewhere in the magic circuit. By varying the excitation to this coil, the shearing strength of the magic fluid mixture may be accurately controlled. Thus any condition from a full slip to a frozen lockup may be obtained. 。 that is ,a righthand driver goes with a righthand driven. In the design of crossedhelical gears, the minimum sliding velocity is obtained when the helix angle are equal. However, when the helix angle are not equal, the gear with the larger helix angle should be used as the driver if both gears have the same hand. Worm gears are similar to crossed helical gears. The pinion or worm has a small number of teeth, usually one to four, and since they pletely wrap around the pitch cylinder they are called threads. Its mating gear is called a worm gear, which is not a true helical gear. A worm and worm gear are used to provide a high angularvelocity reduction between nonintersecting shafts which are usually at right angle. The worm gear is not a helical gear because its face is made concave to fit the curvature of the worm in order to provide line contact instead of point contact. However, a disadvantage of worm gearing is the high sliding velocities across the teeth, the same as with crossed helical gears. Worm gearing are either single or double enveloping. A singleenveloping gearing is one in which the gear wraps around or partially encloses the worm.. A gearing in which each element partially encloses the other is, of course, a doubleenveloping worm gearing. The important difference between the two is that area contact exists between the teeth of doubleenveloping gears while only line contact between those of singleenveloping gears. The worm and worm gear of a set have the same hand of helix as for crossed helical gears, but the helix angles are usually quite different. The helix angle on the worm is generally quite large, and that on the gear very small. Because of this, it is usual to specify the lead angle on the worm, which is the plement of the worm helix angle, and the helix angle on the gear。Shaft In the force analysis of spur gears, the forces are assumed to act in a single plane. We shall study gears in which the forces have three dimensions. The reason for this, in the case of helical gears, is that the teeth are not parallel to the axis of rotation. And in the case of bevel gears, the rotational axes are not parallel to each other. There are also other reasons, as we shall learn. Helical gears are used to transmit motion between parallel shafts. The helix angle is the same on each gear, but one gear must have a righthand helix and the other a lefthand helix. The shape of the tooth is an involute helicoid. If a piece of paper cut in the shape of a parallelogram is wrapped around a cylinder, the angular edge of the paper bees a helix. If we unwind this paper, each point on the angular edge generates an involute curve. The surface obtained when every point on the edge generates an involute is called an involute helicoid. The initial contact of spurgear teeth is a line extending all the way across the face of the tooth. The initial contact of helical gear teeth is a point, which changes into a line as the teeth e into more engagement. In spur gears the line of contact is parallel to the axis of the rotation。 AND SHAFT INTRODUCTION Abstract: The important position of the wheel gear and shaft can39。借助激勵該線圈，磁液混合物的剪切強(qiáng)度可被精確的控制。這些磁極板之間有磁粉混合物潤滑。因此該離合器與具有一定數(shù)量齒的棘輪棘爪機(jī)構(gòu)等效。該內(nèi)軸件，在它 的周邊加工了數(shù)個平面。 超越離合器或連軸器允許機(jī)器的被動構(gòu)件“空轉(zhuǎn)”或“超越”，因為主動驅(qū)動件停頓了或者因為另一個動力源使被動構(gòu)件增加了速度。這些離合器通常用彈簧加載，以使得在達(dá)到預(yù)定的力矩時釋放。 有些裝置例如線性驅(qū)動裝置或電機(jī)操作螺桿驅(qū)動器必須運(yùn)行到一定的限度然后停頓下來。 雖然強(qiáng)制離合器不像摩擦接觸離合器用的那么廣泛，但它們