Coupling and Joints P2 pps

History of Couplings FIGURE 1.4 Continued. 9 10 Chapter 1 IV. THE PERIOD 1945-1960 The late 1940s through the 1950s saw rapid technological advancement and the introduction of rotating equipment. Larger and higher horse- power equipment came into use. This brought about the need for more “power-dense” flexible couplings with greater misalignment, which had to be accommodated. Around this time the fully crowned gear spindle (Figure 1 SA) was developed and introduced into the steel industry. Also during this period, the use of the gas turbine in industrial applications (generators, compressors) was becoming popular. With increased use of the gas tur- bine came the requirement for higher speed couplings. Therefore, the gear coupling and disc coupling were upgraded and improved to handle higher speed requirements (see Figures 1.5B and I SC). Rotating equipment demands higher and higher operating speeds. With the increased speed of operation came system problems that required lighter weight couplings, and the torsional characteristics of couplings became more important. This necessitated improvements in resilient couplings (see Figure I SD), as these couplings not only had to help tune a system but in many cases had to be able to absorb (dampen) anticipated peak loads caused by torsional excitations. THE PERIOD 1960-1 985 Higher horsepower and higher speed continued to be increasing require- ments of rotating equipment. The 1960s saw the introduction of many new types of couplings. Many coupling manufacturers introduced a standard line of crowned tooth gear couplings (see Figure 1.6A). The gear coupling was probably the most widely used type of coupling on the market. A half dozen major manufacturers produced virtually inter- changeable product lines. The grid coupling and chain coupling were also very popular for general-purpose applications (see Figures I .6B and 1.6C). The rubber tire coupling (Figure 1.6D) was widely used, with many companies offering a model. More sophisticated resilient couplings (Figures 1.6E and 1.6F) were introduced during this period to help with the ever- FIGURE 1.5 Couplings of the period 1945-1 960. (A) Gear spindle cou- pling (courtesy of Renolds Industrial Contractors, Inc.). (B) High-speed gear coupling (courtesy of Kop-Flex, Inc., Emerson Power Transmis- sion Corporation). (C) High-speed disc coupling (courtesy of Coupling Division of Rexnord, Thomas Couplings). (D) Resilent coupling (cour- tesy of Kop-Flex, Inc., Emerson Power Transmission Corporation). 12 FIGURE 1.5 Continued. Chapter 1 FIGURE 1.6 (A) Crowned tooth gear coupling (courtesy of Kop-Flex, Inc., Emerson Power Transmission Corporation). (B) Grid coupling (courtesy of Kop-Flex, Inc., Emerson Power Transmission Corporation). FIGURE 1.6 Continued. (C) Chain coupling (courtesy of Morse Indus- trial, Emerson Power Transmission Corporation). (D) Rubber tire cou- pling (courtesy of Dodge Division of Reliance Electric). (E) Elastomeric coupling (courtesy of Kop-Flex, Inc., Emerson Power Transmission Cor- poration). (F) Elastomeric coupling (courtesy of Lovejoy, Inc). History of Couplings 15 increasing system problems, as were several metallic element couplings (disc or diaphragm) (Figures 1.6G-I). The application of nonlubricated couplings grew rapidly during this time period. 'The gear coupling was upgraded to meet the challenge of higher speeds (Figure 1.6J), as was the ancestor of the flexible coupling, the universal joint (Figure 1.6K). VI. THE PERIOD FROM 1985 TO THE PRESENT The advancement in couplings and joints continues today, driven by the use of improved materials, finite element analysis (FEA), and new man- ufacturing methods. Nonlubricated couplings using FEA in their design are more reliable and have greater capacities (see Figure 1.7A). Advances in computer numerical control (CNC) equipment have elim- inated the need for electron beam welding, bringing about the develop- ment of one-piece diaphragm couplings (see Figure I .7B) and also the integral filler multiple diaphragm (see Figure I .'7C). Design optimiza- tion of resilient block shapes and improvements in resilient materials allow increased capacity and longer life of resilient couplings (see Fig- ure I .7D). Through FEA optimization and material optimization, U- joints have been developed that can handle more power in the same envelope (see Figure 1.7E). The demand for more efficient rotating equipment has created the need to monitor output torque, which has in turn brought about the development of several torque-monitoring cou- plings (see Figure I .7F). VII. CONCLUSION Advances in couplings and universal joints are a continuing process as the needs of power transmission increase. In Chapter 2 we describe and discuss the types of couplings available today. Up to now we have been discussing relatively large couplings for industrial applications, gener- ally with bores larger than 1/2 in. But there is another type of flexible coupling in widespread use: the miniature coupling used to drive servo- mechanisms, office equipment, and other small mechanisms. These miniature couplings will be discussed in Chapter 2. 16 Chapter 1 FIGURE I .6 Continued. (G) Multiple convoluted diaphragm coupling (courtesy of Zurn Industries, Inc., Mechanical Drives Division). (H) Tapered contoured diaphragm coupling (courtesy of Lucas Aerospace Power Transmission Corporation). (I) Multiple diaphragm coupling (courtesy of Flexibox International, Metastream Couplings). (J) High- speed lightweight coupling (courtesy of Zurn Industries, Inc., Mechani- cal Drives Division). (K) Industrial universal joint (courtesy of Voithe Transmit GmbH). History of Couplings FIGURE 1.6 Continued. 17 FIGURE 1.7 (A) High-performance disc coupling (courtesy of Kop-Flex, Inc., Emerson Power Transmission Corporation). (B) One-piece dia- phragm coupling (courtesy of Kop-Flex, Inc., Emerson Power Transmis- sion Corporation). (C) Integral filler multiple diaphragm coupling (cour- tesy of Ameridrives International). (D) High-capacity elastomeric block coupling (courtesy of Kop-Flex, Inc., Emerson Power Transmission Cor- poration). (E) Block-type universal joint (courtesy of Kop-Flex Inc. Emerson Power Transmission Corporation). (F) Monopole torque-mea- suring coupling (courtesy of Kop-Flex, Inc., Emerson Power Transmis- sion Corporation). [...]... of Couplings FIGURE 1.7 Continued 19 20 FIGURE 1.7 Continued Chapter 1 FIGURE 1.7 Continued 22 Chapter 1 Many of the flexible couplings used today will be around for years As with the ancestor of flexible couplings, the universal joint, technological improvements in materials, design (such as FEA), and manufacturing will help upgrade couplings so they can handle the everincreasing needs and demands... at the center point of the coupling, but not in the same straight line (Figure 2.3B) 3 Combined angular and offset The axes of connected shafts do not intersect at the center point of the coupling and are not parallel (Figure 2.3C) It is important to recognize that while the equipment may see these Overview of Couplings and Joints 25 m m FIGURE 2.2 Functions of a flexible coupling: (A) Transmit torque;... equipment Overview of Couplings and Joints 1 ADVANTAGES OF USING FLEXIBLE COUPLINGS Historically, rotating equipment was first connected by means of rigid flanges (Figure 2.1) Experience indicates that this method did not accommodate the motions and excursions experienced by the equipment As discussed in Chapter 1 , F Roots was the first to thin these flanges and allow them to flex Rigid couplings are used... things can force equipment to run out of alignment The thermal effects of handling hot and cold fluids cause some movement in the vertical and axial directions, as do differentials of temperature in driver media such as gas and steam Vertical motion could be a result of support structure expansion Overview of Couplings and Joints 27 due to temperature differences, distortion due to solar heating, axial... misalignment, the coupling sees only angular misalignment The Jexible elements see only angular and axial alignment or misalignment Therefore equipment needs a coupling with more than one flexible element to accommodate offset, the exception being some elastomeric element couplings that can accommodate both parallel and angular misalignments C Accommodate End Movement Most flexible couplings are designed... to piping forces caused by poor installation practices and expansion or contraction caused by changes in the temperature or pressure of the media in the system It is a fact of life that machinery appears to live and breathe, move, grow, and change form and position; this is one of the basic reasons for using flexible couplings However, a flexible coupling is not the solution to all movement problems... failure (see Figure 2.4) FIGURE 2.4 Coupling failure Chapter 2 28 One thing to remember is that when subjected to torque and misalignment, all couplings react on the connected equipment components Some produce greater reactionary forces than others, and if these forces are overlooked they can cause vibration, shaft failure, bearing failure, and/ or other operational and early failure of other components... that experiences very small shaft excursions or with shafts made long and slender enough that they can accept forces and moments produced from flexing flanges and shafts Flexible couplings join two pieces of rotating equipment while permitting some degree of misalignment or end movement or both The three basic functions of a flexible coupling are to (Figure 2.2) 1 Transmit power (Figure 2.2A) 2 Accommodate... equipment or system designer not to confuse the term coupling misalignment capacity” with “equipment misalignment tolerance.” The capabilities of a coupling are usually substantially higher than the equipment can accept (see Figure 4.7 for coupling misalignment limits and Section 111 of Chapter 4 for guidelines for equipment misalignment tolerances) Rigid couplings produce the greatest reactions on equipment... flanged connection A Transmit Power Couplings are primarily used to transmit mechanical power from one machine to another The power is in the form of mechanical torque at some speed or work per unit of time In general, the amount of power lost by a flexible coupling is small, although some couplings are more efficient than others B Accommodate Misalignment Flexible couplings must accommodate three types . speed couplings. Therefore, the gear coupling and disc coupling were upgraded and improved to handle higher speed requirements (see Figures 1.5B and I SC). Rotating equipment demands higher and. upgrade couplings so they can handle the ever- increasing needs and demands of power transmission equipment. Overview of Couplings and Joints 1. ADVANTAGES OF USING FLEXIBLE COUPLINGS. changeable product lines. The grid coupling and chain coupling were also very popular for general-purpose applications (see Figures I .6B and 1.6C). The rubber tire coupling (Figure 1.6D) was widely