Helical Gears
Helical gears are a type of industrial gears. These gears have angled teeth
that creates a thrust load on the gears while they are meshing. They are
circular in shape. Their teeth is curved along a helical path. There is a
refinement in design, which helical gears enjoy over Spur gears. Actually
the leading edges of the teeth in Helical Gears are designed in such a way
as not to be parallel to the axis of rotation. Instead, they are set
angularly. As the gear shape is curved, the unique angle makes the tooth
shape to be like a segment of helix. The angled Helical Gear teeth is able
to engage more gradually than the spur gear teeth and makes it run in more
smoothly and quietly as well.
Power and motion transmitted by Helical-toothed gears can be between
right-angle axes (same-hand) and parallel shafts (opposite hand). There is
also scope for using non-parallel shafts.
Parallel Shaft Application
While using these gears through Parallel shaft application, there is marked
improvement that translates into a smoother action as compared to spur
gears. This happens because with successive teeth coming into action, there
is uniform and gradual transfer of load. There is also the added advantage
of reduced level of noise and vibration. In the parallel shaft engagement,
these gears need a pair of hand gears that is opposite of each other. Like
one right-hand with one left-hand helical gear.
Right Angle Shaft Application
For transmitting power and motion between shafts at a right angle (90
degree), helical gears of the same hand are put to use. Actually hand
selection is dictated by the direction of thrust. It usually is based upon
the location of thrust bearings.
Types of Helical Gears
There are different types of helical gears such as follows:
Manufacturing of Helical Gears
Materials from which helical gears can be manufactured includes all the
grades of steel, stainless, iron, brass, plastic, phenolic, rawhide, bronze
etc. Actually there are many factors that can contribute to selecting the
right material. They are design, power transmission obligations, noise, heat
generation and absence or presence of corrosive elements. For the process of
manufacture forging casting and then Hobbing are effectively used.
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Identification
of Right or Left hand Gears
To identify whether the Helix Gear you intend to use is Left Hand or
Right hand, please perform this little experiment. Place the helical
gears on a table. You will see, that the teeth is appearing to be
leaning either to the right (///) or to the left (\\\). So gear in
question is either left-hand or right-hand solely based on the direction
of leaning threads.
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| Right Hand Gears |
Left Hand Gears |
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Selection Process of Helical Gears
Important parameters that needs to be given a thought in specifying Helical
Gears are the following:
- Number of teeth
- Face or width of the tooth
- Pitch Diameter
- Outside diameter
- Gear hand direction
- Pressure angle
- Manufacturing material
- Mounting methods
- Hub
- Shaft
Application of Helical Gears
Find application in a variety of industries. They include:
- Steel industry
- Mining industry
- Packaging machinery
- Rubber industry
- Textile industry
- Specialty machinery
- OEM equipment Manufacturers
- Conveyors
- Pumps and pumping equipment
- Medical industry
- Defence industry
- Material handling conveyors
- Automotive industry
- Blower, Feeder
- Mixers and agitators
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Helical Gear Boxes: Helical gear boxes are very popular in
applications that involves high shock loads. Although Helical gear boxes
require a considerable initial investment, but they can maintain high
efficiency. This is the plus point of Helical Gear Boxes.
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Helical Gear Motors: Helical Gear motors are designed to work in
agitating applications that are subjected to high overhung, axial loads
and flexural torque.
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Cooling and lubrication of High speed
Helical Gears
It is use in checking the speed of centrifugal compressors and turbines.
That is the reason why so much importance is placed on the exact lubrication
and cooling of helical Gears. These are vital for a successful operation. As
the gears mesh, there is rolling of tooth surfaces and also sliding against
each other. This is shown in the images.
Actually improper cooling results in Gear surface distress. This can take
the forms of:
- Scuffing
Scuffing is damage of the tooth surface. The signs are characterized by
radial scratch lines. Scuffing takes place when the lubricant's oil film
thickness is typically less than the collective roughness of the pinion
and gear, and there is metal-to-metal touch.
- Wear
Ideally there should be a low rate of wear. This can happen with the
supply oil is perfectly filtered and that abrasive wear does not take
place due to suspension of hard particles in the oil.
- Micropitting
Micropitting can also take place if there is improper or insufficient
lubrication. It can lead to Gear tooth damage, noise and vibration.
- Micropatting
In case of high-speed gears, if the oil film is not thick enough to
check metal-to-metal contact then the problem of Micropatting could
occur.
- Thermal problems
In high-speed helical gears, the teeth could get easily distorted
because of uneven temperature distribution through the face width of the
gearing. This can be prevented by proper lubrication of the Gear
surfaces.
