Tài liệu Handbook of Machine Design P46 ppt

FIGURE 39.4 Fine adjustments
II.
Fine adjustments
for
moving mecha-
nisms
are
adjusting devices which control
the
motion
of
linkages such
as
stroke, etc., while
the
mechanism
is in
motion,
(a),
(b)
Differential gear
adjustment;
(c)
adjustable-stroke engine;
(d)
adjustable stroke
of
shaper
mechanism;
(e)
ball
and
disk speed changer;
(/)
adjusting
fixed
center
of
linkage
for
changing motion properties.
FIGURE 39.5 Clamping mechanisms. These devices
are
used
to
hold items
for
machining
operations
or to
exert great forces
for
embossing
or
printing,
(a) C
clamp;
(b)
screw clamp;
(c) cam
clamp;
(d)
double
cam
clamp;
(e)
vise;
(/)
cam-operated clamp;
(g)
double
cam-
actuated clamp;
(h)
double wedge;
(i)
to
(/)
toggle press;
(m)
vise grips;
(n)
toggle clamp;
(0)
collet;
(P)
rock crusher.
FIGURE 39.6 Locating mechanisms.
These
are
devices which properly posi-
tion
a
linkage member when
the
load
is
removed,
(a) to (/)
Self-centering lin-
ear
devices;
(g) to
(n)
self-centering angular devices;
(o)
detent.
FIGURE
39.7 Escapements. These devices slowly release
the
potential energy
stored
in a
spring
to
control devices such
as
clocks,
(a)
Paddle wheel;
(b)
recoil
escapement;
(c)
dead-beat escapement;
(d)
stud escapement;
(e)
early anchor
escapement;
(/)
cylinder escapement;
(g)
double three-legged escapement
for
tower
clocks;
(h)
to
(/)
chronometer escapements;
(k)
fuse
used
to
give
uniform
torque
at
escapement
as the
spring unwinds.
FIGURE 39.8 Indexing mechanisms. These mechanical devices advance
a
body
to a
specific
position, hold
it
there
for a
period,
and
then advance
it
again.
(a)
to
(c)
Geneva stops;
(d)
four-bar
links used
to
reduce jerk;
(e)
ratchet
mechanism;
(/)
friction
ratchet;
(g)
cylindrical cam-stop mechanism;
(h) pin
gearing used
in
indexing;
(i)
dividing head.
FIGURE 39.9 Oscillating mechanisms
I.
These mechanisms cause
an
output
to
repeatedly swing
through
a
preset
angle,
(a)
Four-bar linkage;
(b)
six-bar linkage;
(c)
six-bar linkage with
pin in
slot;
(d)
inverted slide-crank quick-return linkages;
(e)
radial
cam and
follower;
(/)
cylindrical cam;
(g)
geared slider crank;
(h)
geared inverted slider crank;
(/)
slider-driven crank;
(J)
bulldozer
lift
mechanism;
(k)
oscillator
of the
Corliss valve gear.
FIGURE
39.10 Oscillating mechanisms
II.
These
all use
spatial linkages.
(a)
Spatial
pin and
yoke;
(b)
spherical four-bar linkage;
(c)
spatial RGGR
linkage;
(d)
spatial RCCC;
(e)
spatial RRGRR;
(/)
spatial RRGC.
FIGURE
39.11 Ratchets
and
latches.
These
are
mechanisms that advance
or
hold
a
machine
member,
(a)
Ratchet
and
pawl;
(b)
reversible ratchet;
(c)
cam-lock ratchet;
(d)
ball-lock ratchet;
(e)
toggle ratchet;
(/)
overrunning clutch;
(g)
high-torque ratchet;
(/*),
(i)
detents;
(/)
locking bolts.
FIGURE 39.12 Reciprocating mechanisms
I.
These mechanical devices cause
a
member
to
trans-
late
on a
straight
line,
(a)
Slider crank;
(b)
Scotch yoke;
(c)
toggle mechanism;
(d)
Zoller
engine;
(e)
V
engine;
(/)
double-stroke engine;
(g)
geared engine;
(h)
Atkinson
gas
engine;
(i)
ideal radial
engine;
(/)
practical radial engine;
(A:)
geared Nordberg radial engine;
(/)
linked Nordberg radial
engine.
FIGURE
39.13 Reciprocating mechanisms
II. (a)
Geared
cranks;
(b)
shaper mechanism;
(c)
slider
on
Whitworth
quick-return mechanisms;
(d)
slider
on
drag-link mechanism;
(e)
variable-stroke
engine;
(/)
gear-driven slider.
FIGURE 39.14
Reversing
mechanism.
These
mechanical devices change
the
direction
of
rotation
of
the
output,
(a)
Reversible prime movers;
(b)
reversing gears;
(c)
reversing belts;
(d)
transmission;
(e)
epicyclic gears
as in
Model
T
Ford.

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