PG.243-349Conveyor, Friction , Fittings

What are the four main types of conveyors mentioned?

Chain, screw, roller, and belt conveyors

What drives a chain conveyor?

A head sprocket or drive wheel

What supports a chain to prevent sagging?

Carrying idlers

What is the primary function of a screw conveyor?

Move small bulk materials and sometimes blend or meter them

Why are screw conveyors high energy users?

Due to high friction levels

What powers a gravity roller conveyor?

Gravity (no motor)

Name one powered roller conveyor method.

Motor-in-roller drive (or chain-driven, gear motor, etc.)

What drives a belt conveyor?

A head pulley (drive roller)

What is the function of the head pulley?

Drives the conveyor belt

Why are pulleys crowned?

To help center the belt (tracking)

What increases friction between belt and pulley?

Rubber lagging

What is the function of the tail pulley?

Provides belt tension

What are carrying idlers?

Rollers that support the loaded belt

What is the purpose of self-aligning idlers?

To correct belt misalignment

What do snub rollers increase?

Belt contact with drive pulley (traction)

Name three conveyor drive systems.

1. Chain and sprocket

2.Belt and pulley

3.Direct drive with speed reducer

Which drive system is strongest and most common?

Chain and sprocket

What advantage does a chain drive have?

Absorbs load shock

What is a disadvantage of belt-and-pulley drives?

Slippage under overload

What is the purpose of tensioning rollers?

Adjust belt tension

What is a gravity tensioning system?

Uses weights to maintain constant tension

What is a slider bed used for?

Supports belt at loading zones

What is a disadvantage of slider beds?

High friction

What is the best method of joining a belt?

Vulcanized splice

What percentage of belt strength does a vulcanized splice retain?

About 90%

What is a disadvantage of metal fasteners?

Noise, wear, and moisture penetration

What is the primary rule of belt tracking?

“The belt moves toward the end of the roller it contacts first.”

What happens if rollers are not parallel?

Belt misalignment

Why should belt tension not be excessive?

It can damage or stretch the belt

How should tracking adjustments be made?

In small increments

What is tolerance?

Difference between maximum and minimum size

What is the formula associated with tolerance?

Tolerance = Max Size − Min Size

What is the interval of tolerance?

Range between limits

What is the formula associated with interval of tolerance?

Interval = Upper Limit − Lower Limit

What is nominal dimension?

The target dimension

Definition of allowance.

Clearance or interference between parts

What is formula for maximum allowance?

Max Allowance = Largest Hole − Smallest Shaft

What is the formula for Formula for minimum allowance?

Min Allowance = Smallest Hole − Largest Shaft

What is a clearance fit?

Always space between parts

What sign are clearance values?

Positive

What is an interference fit?

Parts must be forced together

What sign are interference values?

Negative

What is a transition fit?

Can be clearance or interference

If:

Hole max = 4.003 in

Shaft min = 3.997 in

What is max clearance?

4.003 − 3.997 = 0.006 in

f:

Hole min = 4.000 in

Shaft max = 3.999 in

What is min clearance?

4.000 − 3.999 = 0.001 in

If allowance is negative, what type of fit is it?

Interference fit

Diagram shows a horizontal belt system with a motor on the right, a large pulley at the right end, and a smaller pulley at the left.

Which component is the head pulley

The pulley on the right (drive side near the motor)?

Diagram shows a horizontal belt system with a motor on the right, a large pulley at the right end, and a smaller pulley at the left.

Which pulley is responsible for belt tension?

The left pulley (tail pulley)

Diagram shows belt sagging slightly between rollers under load.

What are the rollers supporting the loaded belt called?

Carrying idlers

Diagram shows rollers underneath the returning empty belt.

What are these rollers called?

Return idlers

Diagram shows a belt drifting to the right side of a roller.

Which side of the roller is contacting the belt first?

The right side

Diagram shows a belt drifting to the right side of a roller.

Which side of the roller is contacting the belt first?

Which way will the belt continue to move?

Diagram shows one roller slightly angled instead of perpendicular.

What problem will this cause?

Belt misalignment (tracking issues)

Diagram shows a crowned pulley (slightly higher in the center).

What is its purpose?

To center the belt automatically

Diagram shows a motor connected to a small sprocket, linked by a chain to a larger sprocket.

What type of drive system is shown?

Chain and sprocket drive

Diagram shows two pulleys connected by a flat belt.

What drive type is this?

Belt and pulley drive

Diagram shows motor directly connected to gearbox, then to pulley.

What system is this?

Direct drive with speed reducer

Diagram shows a hanging weight connected to a pulley system pulling the belt tight.

What type of tensioning system is this?

Gravity tensioning system

Diagram shows a movable pulley adjusted by a screw mechanism.

What is this used for?

Manual belt tension adjustment

Diagram shows belt sliding over a flat metal surface instead of rollers.

What type of support is this?

Slider bed

Diagram shows belt sliding over a flat metal surface instead of rollers. What is a major disadvantage?

High friction and wear

Diagram shows belt ends fused together smoothly.

What type of splice is shown?

Vulcanized splice

Diagram shows belt ends joined with metal clips.

What type of splice is this?

Clearance fit

Diagram shows shaft slightly larger than hole and pressed in.

What type of fit is shown?

Interference fit

Diagram shows dimensions:

Hole: 2.000 – 2.005 in

Shaft: 1.998 – 2.002 in

What type of fit is this?

Transition fit (can be clearance or interference depending on sizes)