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CYLINDERS
Pos.B
:mechanismused for thedisplacement ofmaterials onplanes of different height. Themovement takes place
“step by step” bymeans of a toothedwheel
1
, which engages a pawl
2
hinged on the crank
3
, which is controlled
by a cylinder.
For the entire length of the positive stroke of the cylinder, the pawl remains engaged always on the same tooth
(Pos. a, b) putting the toothedwheel into rotation. The stroke of the cylinder corresponds to the necessary “step”.
With the return of the cylinder, the pawl disengages (Pos. c) positioning itself in front of another tooth, once it
reaches the negative end position, the cycle is repeated.
B
A
Fig. 25
Thewedge
As noted in previous sections, the function of the cylinder is not restricted to that of moving a object, it is able
to perform numerous tasks. In this section, we analyze its use as blocking device. It is sometimes necessary to
include devices, which prevent movement in the event of air pressure failure.
The
wedge
is a simple and economic device, which is suitable for such an application. It consists of a prism, the
section of which can be:
• a right angled triangle, if used on a simple inclined plane;
• an isosceles triangle, if used on a double inclined plane.
Figure 26
The simplewedge
This device allows a large Force
F
ν
to be obtained, by applying a smaller Force value
F
s
.
By altering the ratio between the height and length of the base, the value of
F
ν
changes drastically.
Examples
:
Supposewe require a Force
F
ν
=1000
N
with awedge of height
a
= 10
mm
,
andwith a base
b
= 100
mm
. The value of the thrust Force to be applied
F
s
is given by:
F
s
=
F
ν
*
a
1000
[N]
*
10
[mm]
= 100
N
F
s
=
100
N
b
100
[mm]
By halving the height i.e. value
a
= 5
mm
, the thrust Force
F
s
becomes:
F
s
=
F
ν
*
a
1000
[N]
*
5
[mm]
= 50
N
F
s
=
50
N
b
100
[mm]
To obtain a
F
s
= 50
N
maintaining the height
a
=10
mm
wewill change the base
b
to a value of:
F
s
=
F
ν
*
a
b
=
F
ν
*
a
1000
[N]
* 10
[mm]
=200
mm
b
=
200
mm
b
F
s
50
[N]
To halve the value of
F
s
it is therefore necessary to halve the value of
a
or double the value of
b
.
3
75
CAMOZZI
>
CYLINDERS