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21
8.
Eccentric is a link that performs ……. movement but not around its
…….axis.
10. Match the phrases in column A with those in column B.
A B
1. If the constraint number is equal
to six…
2.
Any freely moving object in
space…
3.
All kinematic pairs are divided
into 5 classes…
4.
Links can perform five relative
movements…
5.
At the same time…
6.
Screw KP…
A. …has only one independent
motion.
B. …three rotational and two
translation
C. …links lose relative mobility
D. …has six degrees of freedom
E. …the number of conditions of
constraint cannot be less than one
F. …depending on the number of
conditions of constraint.
11. Use the words in brackets in the correct form: active or passive.
1. Crank (to perform) complete circular movement.
2. The movement of any body (can, imagine) as sliding lengthways and
rotational around axes.
3. If the constraint number is equal to six, links (lose) relative mobility.
4. The link (to perform) incomplete rotary movement (to call) rocker.
5. Motionless links of mechanisms (to design) as a frame or rack.
3. Kinematic chains
Any mechanism consists of some number of details connected with each
other. The connection of links by kinematic pairs is called a kinematic chain.
Example of a kinematic chain consisting of
four links is given in Fig. II.17.
The links 1 and 2 form rotary kinematic
pair of 5-th class, 2 and 3 form rectilinear KP
of 5-th class, 3 and 4 - rotary KP of 5-th class.
All kinematic chains (KC) are
subdivided into single-stranded KC (simple)
(Fig. II.18. b, c) and complex KC (Fig. II.18,
a).
If each link of kinematic chain enters no
more than into two kinematic pairs, such kinematic chain is called a single-
stranded (simple) KC.
Fig. II.17.
1
2
С
4
3
В
А
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