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its axis but is prevented from moving sideways or rotating in any direction. The inner
ends of the radial flexures are attached to the moving element skeleton . The outer ends
of the radial flexures are mounted in pairs to flexure mounting blocks. The flexure mount
ing blocks are mounted on the tangential flexures
.
The tangential flexures are mounted
on the frame
.
As the moving element moves up or down, the eight radial flexures bend as a double
cantilever beam
.
The outer
ends
of the radial flexures, the flexure mounting blocks, and
the tangential flexures all move inward as the moving element moves
either
upward or
downward, and therefore vibrate at twice the frequency of the table motion
.
A side force applied to the top of the table normal to the main axis tends to deflect the
radial flexures as beams, but little deformation results since the beams are very stiff in
this direction. Motion of the outer ends of the radial flexures is resisted by the high tor
sional stiffness and high lengthwise stiffness of the tangential flexures.
Each flexure is a
sandwich
of metal and rubber bonded together
.
The design is such that
a very high degree of damping is provided for the resonant modes of the flexure
.
6,1,3, Stray Magnetic Field
Magnetic shields are provided to reduce the flux density above the table top
.
In Figs.6.4
and 6.5 are shown plots of typical steady state flux density as a function of distance
above the table top
.
The alternating flux density is negligible
.
Gauss
9
8
6
5
4
3
2
!\
\ T
yp
e48
11
~
~\
~
~
~
~
r--...
~
~"
~~
r=:;:
r----::::
t-
-I----
10
20
30
40
50
mm
Oistance
above table mounting surface
o
0,5
1,0
1,5
2,0
I~----------~I------------~I------------~I------------~I
7401
05
Fig. 6. 4. Magnetic flux density
above
table top. Types 48", 4812,
4813
with
Type 4801 Body
35
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