Illustrated Sourcebook of Mechanical Components Part 2 potx

1-54 6 Ways to Prevent Overloading These "safety valves" give way if machinery jams, thus preventing serious damage. Peter C. Noy r Fricfion faces Sprocket 3 m tl 1 SHEAR PIN is simple to design and reliable in service. However, after an overload, replacing the pin takes a rela- tively long time; and new pins aren't always available. 3 MECHANICAL KEYS. Spring holds ball in dimple in oppo-' site Pace until overload forces the ball out. Once slip begins, wear is rapid, BO device is poor when overload is common. 2 FRICTION CLUTCH. Adjustable spring tension that holds the two friction surfaces together sets overload limit. As soon as overload is removed the clutch reengages. One drawback is that a slipping clutch can destroy itself if unnoticed. Adjustment screw Gears & Gearing 1-55 r-i 01' I 4 RETRACTING KEY. Ramped sides of keyway force key outward against adjust- abe spring. As key moves outward, a rubber pad-or another spring-forces the key into a slot in the sheave. This holds the key out of engagement and prevents wear. To reset, push key out of slot by using hole in sheave. Load b 5 ANGLE-CUT CYLINDER. With just one tooth, this is a sim- plified version of the jaw clutch. Spring tension sets load limit. 6 DISENGAGING GEARS. Axial forces of spring and driving arm balance. Overload overcomes spring force to slide gears out of engagement. Gears can strip once overloading is removed, unless a stop holds gears out of engagement. 1-56 Torque-lim iters Protect light-Duty Drives In such drives the light parts break easily when overloaded. These eight devices disconnect them from dangerous torque surges. L. Kasper 1 2 MAGNETS transmit toraue according to their number and size. CONE CLUTCH is formed by mating taper on In-place control is limited to lowering torque capacity by remov- ing magnets. down on nut increases torque capacity. shaft to beveled hole through gear. Tightening 3 RING fights natural tendency of rollers to jump out of grooves cut in reduced end of one shaft. Slotted eiitl of hollow shaft, is like a cage. Gears & Gearing 1-57 4 5 ARMS hold rollers in slots which are cut across disks mounted on ends of butting shafts. Springs keep rollers in slots: over-torque forces them out. FLEXIBLE BELT wrapped around four pins transmits only lightest loads. Outer pins are smaller than inner pins to ensure contact. possoje 6 7 SPRINGS inside drilled block grip the shaft because SLIDING WEDGES clamp down on flattened end of they distort during mounting of gear. shaft: spread apart when torque gets too high. Strength of springs which hold wedges together sets torque limit. 8 FRICTION DISKS are compressed by adjustable spring. Square disks lock into square hole in left shaft: round ones lock onto square rod on right shaft. I L LU S T RAT E D S 0 U RC E B 0 0 K of ME C HAN I CAL C 0 M P 0 N E N T S SECTION 2 HAINS, SPROCKETS WTCHETS History of Chains Ingenious Jobs for Roller Chain Bead Chains for Light Service Types of Trolley Convey or Chain Links and Joints Method for Reducing Pulsations in Chain Drives Pave the Way for Better Chain Drives Lubrication of Roller Chains One-way Drive Chain Solves Problem of Sprocket Skip Chain Hoist for Dam’s Radial Arm Gate Portable Chain Hoist for Motors Design of Precision Sprockets Sheet Metal Gears, Sprockets, Worms & Ratchets Ratchet Layout Analyzed No Teeth Ratchets 2-2 2-4 2-8 2-10 2-12 2-14 2-15 2-17 2-18 2-19 2-20 2-23 2-25 2-27 Chains, Sprockets & Ratchets 2-3 There are eighteen American National Standards which relate to the various types of sprocket chains in general use. This family of standards is the result of over 50 years of standardization activity, which had its beginning in the work that led to the publication of American Standard B29a-Roller Chain. Smock- ets, and Cutters in as follows: ANSI B29.1 ANSI B29.2 ANSI B29.3 ANSI B29.4 ANSI B29.6 ANSI B29.7 ANSI B29.8 ANSI B29.10 ANSI B29.11 ANSI B29.12 ANSI B29.14 ANSI B29.15 ANSI B29.16 ANSI B29.17 ANSI B29.18 ANSI B29.19 ANSI B29.21 ANSI B29.22 I1 1930. The chain types covered by the current standards are Precision roller chain Inverted-tooth (or silent) chain Double-pitch roller chain for power transmission Double-pitch roller chain for conveyor usage Steel detachable chain Malleable iron detachable chain Leaf chain Heavy-duty offset-sidebar roller chain Combination chain Steel-bushed rollerless chain Mill chain (H type) Heavy-duty roller-type conveyor chain Mill chain (welded type) Hinge-type flat-top conveyor chain Drag chain (welded type) Agricultural roller chain (A and CA types) Chains for water and sewage treatment plants Drop-forged rivetless chain The basic size dimension for all types of chain is pitch-the center-to-center distance between two consecutive joints. This dimension ranges from 3/16 in (in the smallest inverted-tooth chain) to 30 in (the largest heavy-duty roller-type conveyor chain). Chains and sprockets interact with each other to convert linear motion to rotary motion or vice versa, since the chain moves in an essentially straight line between sprockets and moves in a circular path while engaged with each sprocket. A number of tooth-form designs have evolved over the years, but the prerequisite of any tooth form is that it must provide: 1. Smooth engagement and disengagement with the moving chain 2. Distribution of the transmitted load over more than one tooth of the sprocket 3. Accommodation of changes in chain length as the chain elongates as a result of wear during its service life The sprocket layout is based on the pitch circle, the diameter of which is such that the circle would pass through the center of each of the chain's joints when that joint is engaged with the sprocket. Since each chain link is rigid, the engaged chain forms a polygon whose sides are equal in length to the chain's pitch. The pitch circle of a sprocket, then, is a circle that passes through each comer, or vertex, of the pitch polygon. The calculation of the pitch diameter of a sprocket follows the basic rules of geometry as they apply to pitch and number of teeth. This relationship is simply pitch pitch diameter = sin (180"humber of teeth) The action of the moving chain as it engages with the rotating sprocket is one of consecutive engagement. Each link must articulate, or swing, through a specific angle to accommodate itself to the pitch polygon, and each link must be completely engaged, or seated, before the next in succession can begin its articulation. Source. Mechanical Components Handbook by Robert 0. Parmley 01985 Chains, Sprockets & Ratchets 2-5 4 TRANSMISSION OF TIPPING OR ROCKING MOTION. Can be combined with previous example (3) to transmit this type of motion to a remote location and around obstructions. Tipping angle should not exceed 40" approx. 5 LIFTING DEVICE is simplified by roller chain. Chain mainfains inward pressure on boards fhrough slip clulch j TWO EXAMPLES OF INDEXING AND FEEDING uses of roller chain are shown here in a setup that feeds plywood strips into EL brush-making machine. Advantages of roller chain as used here are flexibility and long feed. 2-6 Examples of how this low-cost but precision-made product can be arranged to do tasks other that transmit power. 7 SIMPLE GOVERNOR-weights can be attached by means of standard brackets to increase responze force when rotation speed is slow. A I Ao)ustrnenf boles 6 Force 8 WRENCH-pivot A can be adjusted to grip a va- riety of regularly or irregularly shaped objects. Sprocket 9SMALL PARTS CAN BE CONVEYED, fed, or oriented between spaces of roller chain. Chains, Sprockets & Ratchets 2-7 11 LIGHT-DUTY TROLLEY CONVEYORS can be made by combining standard roller- chain components with stand- ard curtain-track components. Small gearmotors are used to drive the conveyor. 10 CLAMP-toggle action is sup- plied by two chains, thus clearing pin at fulcrum. Sfondam' offochmenf frock I-beom frock fro//eys Roller lor /odderl chain I Conveyor hook 12 SLATTED BELT, made by attach- ing wood, plastic or metal slats, can serve as adjustable safety guard, conveyor belt, fast-acting security-wicket window. Chains, Sprockets & Ratchets Where torque requirements and operating speeds are low, qualified bead chains offer a quick and economical way to: Couple misaligned shafts; convert from one type of motion to another: counter-rotate shafts: obtain high ratio drives and overload protection: control switches and serve as mechanical counters. Fig. 8-Angular oscillations from ro- Fig. 9-Restricted angular motion. Fig. 10-Remote control of counter. tary input. Link makes complete revo- Pulley, rotated by knob, slips when For applications where counter can- lutions causing sprocket to oscillate. limit stop is reached; shafts A and B not be coupled directly to shaft, bead Spring maintains chain tension. remain stationary and synchronous. chain and sprockets can be used. Aoose chain Fig. 11-High-ratio drive less Fig. 12-Timing chain containing large Fig. 13-4onveyor belt composed of expensive than gear trains. beads at desired intervals operates micro- multiple chains and sprockets. Tension Qualified bead chains and switch. Chain can be lengthened to contain maintained by pivot bar and spring. sprockets will traasmit power without slippage. thousands of intervals for complex timing. Width of belt easily changed. ft L. - 1 Fig. 144ear and rack duplicated by chain and two sprockets. Converts linear motion into rotary motton. ,Idler Pig. 15 - Overload protection. Shallow sprocket gives positive drive for low loads; slips one head at a time when overloaded. Sprockef wiYh sha/fowJ recesses Fig. 16-Gear segment inexpensively made with bead chain and spring wrapped around edge of sheet metal. Retaining collars keep sheet metal sector from twisting on the shaft. 2-9 [...]... rolled on roll diameter of sprocket, 1.6667 in cos 0 = O = O = cos 9 = 9 = r2 + C2 - R ,2 2 r C + 0.50 32 2.169P - 1.7146' 2 x 0.503 x 2. 1697-0. 925 67 22 .23 02" 1.714 62 2.1697' - 0.50 32 2 X 2. 1697 X 1.7146 0.993 82 6.3 720 2", or 0.11 12 radians + Because the roller r rolls on the radius R and does not slip, they both rQlloff an equal amount of their circumference Therefore, their arcs AB and BD are equal Employing... setup as follows: 12 I - - -G DP G2 x -G3 G 4 From the selection of change gears a 16 1/3 DP is easily obtained 12 DP - 40 70 ' DP 54 42 = 16 1/3 2- 2 1 2- 22 T , = Arc tooth thickness of tooth at D , = 0.055 T , = Arc tooth thickness of tooth at D , = Pressure angle at point where the mean diameter of the film makes contact with the tooth D , = mean dia of film = 3.3333 D, = pitch dia = 3. 428 6 Computing... MODULUS OF ELASTICITY, PSI WORKING STRENGTH (MAXIMUM TENSION), PSI 0.045 0 .28 20 ,000 40,000 30,000 50,000 30,000 30 X 10” 300 TO 300 TO 300 TO 400 TO 400 TO 10,000 3 -2 1 TYPE MATERIAL COEFFICIENT OF FRICTION, (I (ON CAST IRON PULLEYS! FLAT BELT LEATHER WOVEN COTTON WOVEN HAIR BALATA RUBBER STEEL 0 .25 0 .2 0 .2 0.3 0 .2 0.15 FABRIC SET IN RUBBER 0 .25 TO 0.35 0.04 35,000 400 STRANDED COTTON 0 .2 TO 0.3 0 .28 02. .. , = 3. 428 6[-+ = 3. 428 6 - 41 = 7"30' Inv +1 = 0.00075 Inv + 2 = 0.00 622 R D = 3 .28 70 D, = 0.9639 ?r 0.055 - Inv #,z 1 1 0.00075 - 0.00 622 = 0.0343 The root diameter of the sprocket is equal to the roll diameter minus 0. 020 in as indicated in Fig 3, or 3.3073 in This figure is 0. 121 3 in less than the pitch dia of the imaginary gear Therefore, to determine the dimension for the width of the groove in the... effiHence the actual T, tension will be ciency of the tape drive is Te = T + 5 Ib s = 10 + 5 = 15 lb 110 - 0. 022 110 1 - 0.00 022 or 99.98% I Tz= TlePBA T2 = 10 e(0 .2) - p6c = In 1.5 = 0.405 BC =0.405/0 .2 = 2. 02 rad = 115 deg A wrap angle of less than 115 deg may cause slippage at pulley C Pulley B-minor load In a similar manner ,POB = 0.5 + 10 10 OB = 0 .25 = 15 deg The power loss at the driver is This... 0-600 Lubricants 24 l3- 420 20 420 - 620 30 620 -1300 40 Manual: brush, oil can Slow Drip: 4-10 drops,min Continuous: wick, wheel %-I Rapid Drip -20 drops, min Shallow Bath, Disk x 12i-p SAE No Force Feed Svstems o Note: F r ambient temperatures between SAE 50 100 to 500 Fuse Fig C H A L L O W BATH LUBRICATION uses casing as reservoir for oil Lower part of chain just skims through oil pool Levels of oil must... limit Shaft Rotation 4 -22 Friction for Damping 4 -24 15 Ways to Fasten Gears to Shafts 4 -29 14 Ways to Fasten Hubs to Shafts 4-34 Attaching Hubless Gears to Shafts 4-36 10 Different Types of Splined Connections 4-38 Typical Methods of Coupling Rotating Shafts I 4-40 Typical Methods of Coupling Rotating Shafts II 4- 42 Typical Designs of Flexible Couplings I 4-44 Typical Designs of Flexible Couplings II... belt drive One of the advantages of synchronous belts is their very high efficiency Efficiency of any power transmission system is a measure of the power loss associated with the motor, the bearings and the belt drive Any loss of power is a loss of money By minimizing the losses in the system, the cost of operating the drive is minimized Since the passage of the U.S Energy Policy Act (19 92) , higher efficiency... is P ~ o a r= P i n - Pout Piost = Ti(V1 Driving pulley = vz) TIVI - T2Vz (20 ) vl(1- C B ) (21 ) v = 2 Thus Pout Pulley B (1st driven) v = V2(l - CC) s Therefore ( 12) vs = Vl(1 - c B ) ( 1 - cc) (22 ) and (13) An ideal driving pulley will recover the power T,V, and its power output will be V” = Vl(1 - C l ) (1 - Cz) * (1 - Cn-I) (23 ) From this it can be concluded that the creep with respect to the driving... the imaginary gear No of teeth N = 56 Diametral Pitch P = 16 1/3 Pressure angle +2 = 15" 3%' Pitch diameter D:, = 3. 428 6 Circular pitch C COS +z = 15"31/i' G = - = 0.1 923 P cos Outside diameter - 2. 156 = 0.1 32 P Whole depth D Root diameter = +1 D COS $ 2 3D, N Base dia = 0.9915 x 3.3333 = 3.3048 Referring to Fig 3, the sprocket tooth shows a height of 0.051 in and an undercut of 0.10 in below roll . Layout Analyzed No Teeth Ratchets 2- 2 2- 4 2- 8 2- 10 2- 12 2- 14 2- 15 2- 17 2- 18 2- 19 2- 20 2- 23 2- 25 2- 27 Chains, Sprockets & Ratchets 2- 3 There are eighteen American National. ANSI B29.8 ANSI B29.10 ANSI B29.11 ANSI B29. 12 ANSI B29.14 ANSI B29.15 ANSI B29.16 ANSI B29.17 ANSI B29.18 ANSI B29.19 ANSI B29 .21 ANSI B29 .22 I1 1930. The chain types covered. between, 2. 1697 in. sprocket, cos 0 = O= - - O= cos 9 = - - 9= 1.6667 in. r2 + C2 - R ,2 2rC 0.50 32 + 2. 169P - 1.7146' 2 x 0.503 x 2. 1697 0. 925 67 22 .23 02& quot;