machines and mechanisms

[...]... linkage and Figure1.39b which shows a drafting machine linkage Introduction to Mechanisms and Kinematics (a) FIGURE 1.39 23 (b) Parallelogram mechanisms 1.12.3 Quick-Return Mechanisms Quick-return mechanisms exhibit a faster stroke in one direction than the other when driven at constant speed with a rotational actuator They are commonly used on machine tools that require a slow cutting stroke and a... Introduction to Mechanisms and Kinematics 2 7 Identify All Other Links Careful observation reveals three other moving parts: Link 2: Handle Link 3: Cutting blade Link 4: Bar that connects the cutter with the handle 3 Identify the Joints Pin joints are used to connect link 1 to 2, link 2 to 3, and link 3 to 4 These joints are lettered A through C In addition, the cutter slides up and down, along the... selection of the frame is rather arbitrary The top handle is designated as the frame The motion of all other links is determined relative to the top handle The top handle is numbered as link 1 2 Identify All Other Links Careful observation reveals three other moving parts: Link 2: Bottom handle Link 3: Bottom jaw Link 4: Bar that connects the top and bottom handle 3 Identify the Joints Four pin joints are... joints) As mentioned, most linkages used in machines have one degree of freedom A single degree-of-freedom linkage is shown in Figure 1.13a Linkages with zero, or negative, degrees of freedom are termed locked mechanisms These mechanisms are unable to move and form a structure A truss is a structure composed of simple links and connected with pin joints and zero degrees of freedom A locked mechanism... multi-degree-of-freedom mechanisms are open-loop kinematic chains used for reaching and positioning, such as robotic arms and backhoes In general, multi-degree-offreedom linkages offer greater ability to precisely position a link A multi-degree-of-freedom mechanism is shown in Figure 1.13c (b) Locked mechanism (M = 0) (c) Multi-degree-of-freedom (M = 2) Mechanisms and structures with varying mobility Introduction to Mechanisms. .. provide the input motion and energy To precisely operate a mechanism, one driver is required for each degree of freedom exhibited Many different actuators are used in industrial and commercial machines and mechanisms Some of the more common ones are given below: Electric motors (AC) provide the least expensive way to generate continuous rotary motion However, they are limited to a few standard speeds that... moving parts: Link 2: Handle Link 3: Arm that connects the handle to the other arms Link 4: Arm that connects the base to the other arms Link 5: Press head Link 6: Arm that connects the head to the other arms 3 Identify the Joints Pin joints are used to connect the several different parts One connects the handle to the base and is labeled as joint A Another connects link 3 to the handle and is labeled as... actuation Figure 1.38a shows a Watt linkage and Figure 1.38b shows a Peaucellier-Lipkin linkage (b) FIGURE 1.38 Straight-line mechanisms 1.12.2 Parallelogram Mechanisms Mechanisms are often comprised of links that form parallelograms to move an object without altering its pitch These mechanisms create parallel motion for applications such as balance scales, glider swings, and jalousie windows Two types of parallelogram... cross-sectional size and material are required of the support legs so they don’t fail? A majority of mechanisms exhibit motion such that the parts move in parallel planes For the device in Figure 1.2, two identical mechanisms are used on opposite sides of the platform for stability However, the motion of these mechanisms is strictly in the vertical plane Therefore, these mechanisms are called planar mechanisms. .. diagram of the mechanism, selecting the lower handle as the frame The end of the upper handle and the cutting surface of the jaws should be identified as points of interest 1–6 Another configuration for a pair of pliers is shown in Figure P1.6 Draw a kinematic diagram of the mechanism FIGURE P1.6 FIGURE P1.2 Problems 5 and 30 Problems 2 and 27 Problems 6 and 31 1–7 A mechanism for a window is shown in . University; and Gerald Weisman, University of Vermont. Dave Myszka PREFACE iii CONTENTS 1 Introduction to Mechanisms and Kinematics 1 Objectives 1 1.1 Introduction 1 1.2 Machines and Mechanisms. the wipers and whipping tendencies. For this wiper system, like most machines, understanding and analyzing the motion is neces- sary for proper operation. These types of movement and motion analyses. analysis is a major topic in the latter portion of this text. 1.2 MACHINES AND MECHANISMS Machines are devices used to alter, transmit, and direct forces to accomplish a specific objective. A chain