Illustrated Sourcebook of Mechanical Components Part 2 potx

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 Cha

1-54

These "safety valves" give way if machinery jams, thus preventing serious damage

S H E A R P I N i s simple to design and reliable i n service

However, after an overload, replacing the pin takes a rela-

tively long time; and new pins aren't always available

3

M E C H A N I C A L KEYS Spring holds ball in dimple in oppo-'

site Pace until overload forces the ball out Once slip begins,

wear is rapid, device is poor when overload is common

2

F R I C T I O N C L U T C H 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

R E T R A C T I N G K E Y 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 t h e sheave This holds the key out of engagement and prevents

wear To reset, push key out of slot by using hole in sheave

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

M A G N E T S transmit toraue according to their number and size C O N E C L U T C H is formed by mating taper on In-place control is limited to lowering torque capacity by remov-

shaft to beveled hole through gear Tightening

3

R I N G fights natural tendency of rollers to jump out of grooves c u t in reduced end of one shaft Slotted eiitl of hollow shaft, is like a cage

Gears & Gearing 1-57

A R M S hold rollers in slots which a r e cut across disks

mounted on ends of butting shafts Springs keep rollers

in slots: over-torque forces them out

F L E X I B L E BELT wrapped around four pins transmits only lightest loads Outer pins are smaller than inner pins t o ensure contact

possoje

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

F R I C T I O N D I S K S a r e compressed by adjustable spring

Square disks lock into square hole in left shaft: round ones lock onto square rod on right shaft

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

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 a s 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

Chains, Sprockets & Ratchets 2-5

4 TRANSMISSION O F T I P P I N G 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 L I F T I N G DEVICE is simplified by roller chain

Chain mainfains

inward pressure on

boards fhrough

slip clulch

j T W O EXAMPLES OF INDEXING AND FEEDING uses of roller chain are shown here in a setup that feeds plywood

strips into 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

Chains, Sprockets & Ratchets 2-7

11 L I G H T - D U T Y TROLLEY

combining standard roller-

chain components with stand-

ard curtain-track components

Small gearmotors a r e used

to drive the conveyor

10 CLAMP-toggle action is sup- plied by two chains, thus clearing pin a t fulcrum

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

Pig 15 - Overload protection

Shallow sprocket gives positive

drive for low loads; slips one head at a time when overloaded

Sprockef wiYh sha/fowJ

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

Chains, Sprockets & Ratchets 29- 1 1

THE SUCCESS of the overhead trolley conveyor is

largely the result of the development and use of drop-

forged, rivetless, Keystone chain The dimensions of

several sizes of Keystone chain links are shown below with two examples of pin-jointed chain Standard Keystone chain parts are shown in three views

DETAILS FOR PARTS OF STANDARD KEYSTONE CHAIN

/+ - - - ,#,A p,,ch - - - & - - 4 j n , p,fch - - I

458 Chain-Standard Center Link

458 Chain-Modified Center Link A n Improved Type Interchangeable with 450 Chain

346 C h a i n Modified C e n t e r L i n k

Chains, Sprockets & Ratchets

fnpu

1

Reduction gears *

Choin sprocket’,r

actuated lever and rollers 8 take u p slack Conveyor motion

is equalized but mechanism has limited power capacity be-

cause pitch of chain l must be kept small Capacity can

be increased by using multiple strands of fine-pitch chain

- 1 (input shot t l

Fig &Power is transmitted from shaft 2 to sprocket G

through chain 4, thus imparting a variable velocity to

shaft 3, and through it, to the conveyor sprocket 7 Since

chain 4 has small pitch and sprocket 5 is relatively large,

velocity of 4 is almost constant which induces an almost

constant conveyor velocity Mechanism requires rollers to

tighten slack side of chain and has limited power capacity

=-=

n

, Sprocket

Fig 5-Variable motion to sprocket is produced by disk 3

which supports pin and roller 4, and disk 5 which has a

radial slot and is eccentrically mounted on shaft 2 Ratio

Fig 6

of rpm of shaft 2 to sprocket equals number of teeth in

sprocket Chain velocity is not completely equalized / - - 7 - ’ -

Fig &Integrated “planetary gear” system (gears 4, 5, G

and 7 ) is activated by cam 10 and transmits through shaft

2 a variable velocity to sprocket synchronized with chain

pulsations thus completely equalizing chain velocity The

cam 10 rides on a circular idler roller 11; because of the

equilibrium of the forces the cam maintains positive contact

with the roller Unit uses standard gears, acts simultaneously

a speed reducer, and can transmit high horsepower

\

\

\

2-13

Unsatisfactory chain life is usually +he resulf of poor or ineffective lubrication M o r e

damage is caused by faulty lubrication than b y years of normal service illustrated

below are 9 methods for lubricating roller chains Selection should b e made on basis

of chain speed as shown in Table 1 Recommended lubricants are listed in Table II

Table II-Recommended Lubricants

Manual: brush, oil can Slow Drip: 4-10 drops,min Continuous: wick, wheel Rapid Drip-20 drops, min Shallow Bath, Disk

Force Feed Svstems

Pig 8-FORCE-FEED LUBRICATION for

chains running at extremely high speeds

Pump driven by motor delivers oil under

pressure to nozzles that direct spray on to

chain, Excess oil collects in reservoir which

has wide area to cool oil

SAE

No

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 be kept tangent to chain sprocket

to avoid excessive churning Should not be used at high

speeds because of tendency to generate excessive heat

Disk scoops up oil from reservoir and throws it

against baffle, Gutter catches 011 dripping down

from baffle and directs it on to chain

Chain r -Flow control valve

- - Excess oil

- - O i l

reservoir

Fig %CHAIN-DRIVEN FORCE-FEED system has pump driven

by main drive shaft Flow control valve, regulated from outride

of casing, by-passes excess oil back to reservoir Inlet hose contams filter Oil should be changed periodically-espedally when hue is

brown instead of black

Chains, Sprockets & Ratchets 2-2 1

diameter of the sprocket the tooth form will clear

the perforations in the film while the film is being

loaded or unloaded tangent to the roll diameter

To help determine the correct pressure angle, it

is necessary to establish how many degrees of rota-

tion on the sprocket are needed t o satisfy an epicy-

cloid profile tooth This information can be

established as follows (See Fig 5) and these com-

puations:

R,-Outside radii of sprocket teeth, 1.7146 in

r -Mean radii of the film rolled on 1-in dia roll-

C -Center distance between the sprocket and

R -Mean radii of film rolled on roll diameter of

2 x 0.503 x 2.1697 0.92567

22.2302"

1.71462 + 2.1697' - 0.5032

2 X 2.1697 X 1.7146 0.99382

6.37202", or 0.1112 radians Because the roller r rolls on the radius R and does

not slip, they both rQll off an equal amount of their

circumference Therefore, their arcs AB and BD are

equal Employing the theorem-radius multiplied by

the included angle expressed in radians equals the

length of arc in the included angle; then because the

two arcs are equal to each other, their equations are

also equal to each other

a =

= 6.709", or 0.1171 radians

+E = 8 - = 0.0059 radians

It is important to make certain that the pressure

angle of the teeth a t the outside diameter of the

sprocket when generated is an involute greater than

14"47', which would be the pressure angle of an in-

volute tooth whose involute function is equal to +E

Because the pitch diameter of the gear in the follow-

FIG 5

l ing computations is just about equal to the outside diameter of the sprocket, a pressure angle of 15" 3%' is selected because the base circle for this gear would then fall approximately 0.011 in below the roll diameter Furthermore, by providing a mini- mum radius of 0.004 in on the wheel, the sprocket tooth will not be undercut

This data is now converted into information similar to gear calculations in order to setup the Reishauer gear grinder, or any other gear-generat-

ing machine tool From the Reishauer manual PZA

75 a gear train can be setup as follows:

.' DP = 16 1/3

Referring to Fig 3, the sprocket tooth shows a

height of 0.051 in and an undercut of 0.10 in below

roll diameter Therefore, the wheel will penetrate

0.061 in below the outside diameter of the sprocket

Also note that the tooth has a chordal thickness of

0.055 in a t the roll diameter The arc tooth thick-

ness is 0.055 in at the point of contact with the mean

thickness of the film However, for the purpose of

dimensioning the grinding wheel the arc tooth thick-

ness must be determined at the pitch diameter of the

imaginary gear

LGrinding wheel

FIG 7

T , = Arc tooth thickness of tooth at D , = 0.055

T , = Arc tooth thickness of tooth a t D ,

= Pressure angle at point where the mean diameter of the film makes contact with

add this value to T,

.i

/

2-24

Fig 10-Sheet metal cup which Fig 11-Blanked wheel, with Fig 12-Worm wheel is sheet metal

specially formed teeth, meshes with a helical spring mounted on

a shaft, which serms as the worm

Fig 13-Blanked ratchets with one sided teeth stacked to

fit a wide, sheet metal finger when single thickness is not

adequate Ratchet gears can be spot welded

Fig 14-To avoid stacking, single ratchet is used with a

U-shaped finger also made of sheet metal

Fig 15-Wheel is a punched disk with square punched holes to selve as teeth Pawl is spring steel

Fig 17

Pig 16-Sheet metal blanked pinion,

with specially formed teeth, meshes

with windows blanked in a sheet metal

cylinder, to form a pinion and rack

2-26

Pawl in tension

has same forces acting on unit as other

arrangements Same layout principles

apply also

For steel on steel, dry, p = 0.15 Therefore, using

r/R = 0.20 to 0.25

the margin of safety is large; the pawl will slidc into

engagement easily For internal teeth with 4 of 30°,

c/b is tan 30" or 0.577 which is larger than p, and

the teeth are therefore self engaging

When laying out the ratchet wheel and pawl, locatc

points 0, A and 0, on the samc circle A 0 and AO,

will then be perpendicular to onc another; this will

insure that the smallest forces are acting on the systcm Ratchet and pawl dimensions are governed by design sizes and stress If the tooth, and thus pitch, must bc larger than required in order to be strong enough a

multiple pawl arrangcmcnt can be used The pawls

can be arranged so that one of them will cngage thc ratchet after a rotation of less than the pitch

A fine feed can be obtained by placing a numbcr

of pawls sidc by sidc, with thc corrcspoiicling I h 3 i c t whccls uniformly displaced and interconnectcd

forward stroke On return stroke, rollers

rotate backwards and release their grip

Springs keep rollers in contact with disk

5 RACK is wedge-shape so that it janis be-

tween the rolling gear and the disk, push-

ing the shaft forward When the driving

lever makes its return stroke, it carries

along the unattached rack by the cross-

7 F L A T SPRINGS expand against inside of drum when lever moves one way, but drag loosely when lever turns drum in opposite direction

during motion half of cycle Elongated holes in the levers allow cam to wedge itself inore tightly in place

I L LU S T RAT E D S 0 U RC E B 0 0 K of M E C H A N I CAL C 0 M P 0 N E N T S

S E C T I O N 3

BELTS

Mechanisms for Adjusting Tension of Belt Drives 3-16

Typical Feeders, Take-ups, Drives and Idlers for Belt Conveyors 3-22

Belts & Belting 3-3

While the supercharger drive, racing application is highly visible and glamorous, the same

polyurethane belt is used in industry to replace roller chain on a wide variety of applications

Roller chain requires lubrication and regular maintenance in order to perform at its peak level

Roller chain can stretch up to 3% of its length over the life of the chain The Kigh capacity,

polyurethane synchronous belt provides superior horsepower capacity, with virtually no stretch

Relative Center Distance Take-up Required

(100” Chain / Poly Chain GT)

.04

Stretch comparison of high performance polyurethane synchronous belt vs roller chain

Over time, stretch of flexible power transmission products may require re-tensioning for optimum performance Note that the high performance polyurethane belt system is virtually free of stretch over the life of the belt drive

Additionally, no lubrication is necessary with the synchronous belt The lack of lubrication allows

the polyurethane synchronous belt to replace roller chain on applications where cleanliness is

necessary to prevent contamination of product As an example, conveying and paper converting

applications are typically very sensitive to grease and contaminants contacting the product being

manufactured

Live roller conveyors are used for controlled movement of a great variety of regular or irregular

shaped commodities, from light and fragile to heavy and rugged unit loads The term “live roll”

indicates that the conveyor rolls are connected and driven by a power source Where roller chain

previously had to be used due to its capacity at low speeds, the latest generation of polyurethane,

modified curvilinear tooth, aramid tensile cord synchronous belt drives have horsepower capacities

in excess of similarly sized roller chain drives

3-4

The high capacity synchronous belt allows for driving live roll conveyors by an arrangement of “roll

to roll” belt drives, connecting adjacent rolls At times, idler rolls are inserted between driven rolls

Typical conveyor arrangement showing general roll to roll drive configuration

Detail showing motor and gearbox driving sets of live rolls

Note the belt drives connecting pairs of live rolls

Detail showing head shaft drive and roll to roll drive The drives can be

on opposite sides, the same side, or a combination over the length of the conveyor system

Belts & Belting

The major advantages of the polyurethane synchronous belt compared to roller chain are their high

load capacity, wide range of operating speeds, lack of lubricant contamination, and virtual elimina-

tion of maintenance The polyurethane synchronous belts can be used to replace roller chain with

performance advantages in a wide variety of industries, including lumber, pulp, and paper; packag-

ing; food processing; and sand/gravel/concrete processing A n additional conveying application for

synchronous belts is transporting product on the belt’s back

This pallet conveyor transports product on the back of a synchronous belt Typically, the belt span will be supported on a low friction surface Special high durability backings are available which will reduce wear on the back belt contact surface Special backings are also available in non-marking constructions

Another unique product which demonstrates the design flexibility available belts provide is long

length synchronous belting This is a synchronous belt which is available in a continuous length

of up to 100 feet, in a variety of pitches and constructions Rubber trapezoidal tooth profile belts

with pitches from 080” to S00” are available; as well as rubber curvilinear tooth profile belts with

pitches from 2mm to 8mm Urethane long length belting with aramid or steel tensile cords is also

available in both trapezoidal and modified curvilinear tooth profiles

Long length belting is a cost effective, efficient and low maintenance alternative to chain It is

particularly suited for linear movement applications (automatic doors, automated warehouse or

production conveying systems) and positioning applications (machine tools, x-y coordinate

machines, printers, office equipment) Synchronous long length belting offers high positioning

accuracy, length stability, low maintenance, and simple mechanical attachment using belt clamping

fixtures The clamping fixtures are easily machined, providing an effective method of attaching

the ends of the belting to the device or product being positioned

3-5

An example of a clamp groove profile which is used for attaching modified curvilinear tooth profile polyurethane long length belting to a fixture A top plate is typically used

to mechanically clamp the belt into the grooves The fixture is mechanically attached

to the component being positioned by the belt drive