《机械原理》课程PPT教学课件（Theory of Machines and Mechanisms）Chap6 intermittent mechanisms

Chap.6 intermittent mechanisms Chap.6.1 Ratchet mechanisms Chap.6.2 Geneva mechanisms Chap.6.3 Cam-type index mechanisms Chap.6.4 Intermittent gearset

Chap.6 intermittent mechanisms Chap.6.1 Ratchet mechanisms Chap.6.2 Geneva mechanisms Chap.6.3 Cam-type index mechanisms Chap.6.4 Intermittent gearset

Chap.6.1 Ratchet mechanisms Driving pawl Working principle: Holding pawl 主动棘爪 止回棘爪 机架 Driven Frame ratchet 棘轮 弹簧

Chap.6.1 Ratchet mechanisms Working principle: Driving pawl Holding pawl Driven ratchet Frame

Type of the ratchet mechanisms Externally meshed Internally meshed Ratchet rack Tooth ratchet mechanisms Fixed direction Single function Changeable direction1,2 Double function External Silent ratchet mechanisms Internal

Type of the ratchet mechanisms Silent ratchet mechanisms Externally meshed Internally meshed Ratchet rack Fixed direction Changeable direction1,2 Single function Double function External Internal Tooth ratchet mechanisms

Externally meshed Internally meshed Ratchet rack Double function Silent ratchet mechanisms

Internally meshed Ratchet rack Externally meshed Double function Silent ratchet mechanisms

Application 1. Intermittent motion(牛头刨床的间歇送进机构) 2.Safety lifting mecjanism（卷扬机制动机 构) ·3.转位、分度（手枪盘分度机构) ·4.Clutch超越离合（钻床的自动进给机构） 卷筒 弹簧 杆2 蜗轮 手柄 皮带导板 导轨 棘爪2 滑块 外环 手枪盘 棘轮 杆1 皮带 棘爪1 棘轮 主动蜗杆 A

Application ◼ 1．Intermittent motion（牛头刨床的间歇送进机构） ◼ 2．Safety lifting mecjanism（卷扬机制动机 构） ◼ 3．转位、分度（手枪盘分度机构） ◼ 4．Clutch 超越离合（钻床的自动进给机构）

Chap.6.2 Geneva mechanisms Working principle: Driven geneva wheel 从动槽轮 机架 Driving plate 主动销轮

Chap.6.2 Geneva mechanisms Driving plate Driven geneva wheel Working principle:

Type of the geveva mechanisms external geneva mechanisms Planar geneva mechanisms internal geneva mechanisms Spherical geneva mechanisms

Type of the geveva mechanisms Planar geneva mechanisms Spherical geneva mechanisms external geneva mechanisms internal geneva mechanisms

Compared to the ratchet mechanism The Geneva mechanism has no rigid impulse and motion is smoother.Geneva mechanisms can be used to drive rotating tables with large moments of inertia. The angular velocity of a geneva mechanism should not be too high.The rotation angle of a geneva wheel for each cycle can not be adjusted

Compared to the ratchet mechanism The angular velocity of a geneva mechanism should not be too high. The rotation angle of a geneva wheel for each cycle can not be adjusted. The Geneva mechanism has no rigid impulse and motion is smoother. Geneva mechanisms can be used to drive rotating tables with large moments of inertia

Application Widely used in the Automatic machine and instruments. Projection Machine

Application ◼ Widely used in the Automatic machine and instruments. ◼ Projection Machine

Chap.6.3 Cam-type index mechanisms It is used in machines which need to transmit indexing motion or intermittent motion between two crossed shafts. ■Two types: Cylindrical-cam index mechanisms Hourglass-cam index mechanisms

Chap.6.3 Cam-type index mechanisms ◼ It is used in machines which need to transmit indexing motion or intermittent motion between two crossed shafts. ◼ Two types: Cylindrical-cam index mechanisms Hourglass –cam index mechanisms