64
PRODUCTS
Parvalux worm gearboxes S, M, MB, MF, L,
LH, LB, LF, LHB, LS, LSH, G, GH, SS, MM, MBM, SIW, MIW
ENCLOSED
Table 1 (thermal rating), table 2 (worm effi ciency)
NOTE
For the above range of gearboxes, the maximum continuous output power (S1 duty
cycle) is limited by the maximum thermal rating of the gearbox. The following datasheet
describes the required calculation.
Gearbox Type
Thermal Rating (Watts)
Composite
Bronze
S
20
2
M
38
4
MB, MF
40
48
L, LH, LB, LF, LHB, LS, LSH
60
72
G, GH
100
-
SS
2
30
MM
4
4
MBM
47
8
SIW
28
38
MIW
0
6
EXAMPLE 1
Using the gearbox effi ciency fi gures attached (table 2), an
example calculation is as follows: PM7S, 4000 rpm input speed,
70:1 ratio (delrin), 7 rpm output speed, 1.2Nm required.
The thermal rating of the S gearbox is 20W (from table 1) and
therefore the maximum continuous output torque of 1.2Nm is
acceptable.
EXAMPLE 2
PM7S, 4000 rpm input speed, 44:1 ratio (delrin), 1 rpm output
speed, 2.3Nm required continuously run.
The thermal rating of the S gearbox is 20W (from table 1) and
therefore the 30.4W exceeds the maximum rating by over
0%. This will damage the gearbox; therefore the S gearbox is
insuffi cient for this application.
EXAMPLE 3
PM7S, 4000 rpm input speed, 44:1 ratio (delrin), 1 rpm output
speed, 2.3Nm required with a duty cycle of 20%.
The thermal rating of the S gearbox is 20W (from table 1), but
due to the low duty cycle of the application the thermal rating
of the gearbox of 30.4W is within the maximum intermittent
rating of 44.8W.
TABLE 1: Maximum thermal rating (Watts)
Single worm effi ciency (except G box)
Ratio
Effcy
Ratio
Effcy
4 1/8
0.84
22 1/2
0.40
1/6
0.804
24 1/2
0.24
6 1/4
0.770
2
0.21
7 1/4
0.743
27
0.07
8 1/3
0.718
30
0.488
1/3
0.68
33
0.471
10 1/3
0.680
36
0.4
11 1/3
0.663
40
0.436
12 1/3
0.64
44
0.41
13 1/2
0.632
48
0.403
14 1/2
0.61
4
0.382
1 1/2
0.607
60
0.363
16 1/2
0.
66
0.346
18 1/2
0.7
72
0.330
20 1/2
0.6
TABLE 2: Gearbox effi ciency
CONTINUOUS DUTY CYCLE (S1)
The thermal rating of the gearbox can be calculated using the
following formula: -
= effi ciency of the gearbox (see below)
INTERMITTENT DUTY CYCLE
For intermittent duty the thermal rating for the gearbox (table
1) is increased by multiplying the appropriate gearbox thermal
rating by the factor x:
Single worm effi ciency (G box)
Ratio
Effcy
12 1/2
0.7
2
0.6
30
0.66
0
0.61
60
0.8
7
0.6
gearbox thermal
rating limits