This type of conveyor is used to transport various shapes of products such as boxes or materials which extend over several rollers. This type consists of cylindrical rollers supported in frames over which materials are allowed to move. They are driven by power or gravity. These are of different varieties and can move material in horizontal direction as well as from the upper floor to lower floor.
These have a long life readily assembled and installed, easy to adjust and used for handling large variety of loads. Load with rigid and smooth base are moved on the roller conveyors. Other items can be moved after placing themon flat boards. Pitch of the the rollers should be such that minimum of 3 rollers must remain under load at all times, spacing is generally kept at 8 cm, 10cm or 15cm.
There are two main type of roller conveyors, with different sub-types:
- Gravity type or Unpowered type
- Stationary
- Mobile
- Powered type
- Chain driven
- Gear driven
- Belt driven
(Arora K.C., Shinde V.V., Aspects of Material Handling, pg.94, Kayra Ermutlu)
Automatic Welding
Traditionally, welding processes have been manually operated and are based on trial and error and/or on operator's experience. When improved control is required under manual control, an automatic welding procedure or control is established.
Automatic welding, simply means that some aspects of the welding operation is performed without the intervention of human such as welder or welding operator. In most of automatic welding operations, a welder is required to make initial preparations and then monitors the overall operation. The advantages of an automatic welding system include the following:
- Consistency in welding quality
- Increased welding production and consequent reduction of production costs
- Integration with other automatic operations of the industry
- Absence of human fatigue and/or error
- Absence of loss of human life in case of severe accidents
However, automatic welding also has some disadvantages such as listed below:
- Extensive planning of procedural steps
- Higher capital investments leading to uneconomic investment for small operations
(Naidu D.S., Özçelik S., Moore K.L., Modeling, Sensing and Control of Gas Metal Arc Welding, pg.148, Kayra Ermutlu)
Dynamometer (dynomometer)
The function of the dynamometer is to measure the torque and hence the power of the engine by applying the brake. Thus dynamometer measures the resisting force applied by the brake on the moving body.
- Absorption dynamometers
In these dynamometers, the entire energy or power produced by the engine is absorbed by the friction resistance of the brake and is transformed into heat, during the process of measurement. Under this heading the two main dynamometers are:
- Prony brake dynamometers
- Rope brake dynamometers
- Transmission dynamometers
In these dynamometers energy is not absorbed or dissipated but is used for doing useful work. In these dynamometers the poewr of the engine is measured and then transmitted through them. Important dynamometers in this category are:
- Epicyclic - train dynamometer
- Belt transmission dynamometer
- Bevis - Gibson or torsion dynamometer
(Vashist D., Mechanical Engineering:Fundamentals, pg.191-193, Kayra Ermutlu)
Photodiodes
A photodiode consists of a back-biased p-njunction which, under dark conditions, behaves as a normal back-biased diode. With these conditions the only current flowing through the diode will be the leakage current (typically 1 μA).
Absorbed light will generate electron/hole pairs, and the current through the diode will increase to a typical value of 100 μA. A photodiode has the response that it can be considered as a constant current device with the current determined by the light intensity.
The current/intensity relationship is quite linear and the response is fast; typically 0.2 μs but devices as fast as 1 ns are available. In general, photodiodes are the smallest optical sensor which, in conjunction with their high speed, makes them well suited for fibre optic data transmission and similar applications. Typical operating wavelengths are 8000Å to 11000Å (silicon) and 13000Å to 20000Å (germanium).
The relatively low level current can easily be converted to a high-level voltage using a DC amplifier. The light-dependent diode current flows through R to give an output voltage IR which is directly related to light intensity.
(Parr E.A., Industrial Control Handbook, pg.192, Kayra Ermutlu)
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