Suma Precision Machinery

Integrated Freewheels FXRV with
torque limiting and without release
function
This series of backstops with torque limiting is
the basic version. The design and the available
standard sizes are shown on page 74.

Integrated Freewheels FXRT with
torque limiting and with release
function
This series is designed in the same way as series
FXRV; as an addition, a finely controllable release
function is built in. The design, the description
of the release function and the available stan-
dard sizes are shown on page 75.
The backstops with controllable release func -
tion are used if a controlled relaxing of the belt
or the unit – perhaps in the case of a jam on the
pulley drum – or a limited reverse movement of
the conveyor system is required.

Selection torque
The following determination of the selection
torque applies to multiple-drives installations in
which each drive has the same motor power.
Please contact us in case of different motor
powers.
If the backdriving torque M L per drive is known,
then the selection torque M A for the particular
backstop should be determined as follows:
M A = 1,2 · M L [Nm]
If, however, only the nominal power per drive
P 0 [kW] is known, then this applies:
M A = 1,2 · 9550 · h 2 · P 0 /n SP [Nm]
In these equiations:
M A = Selection torque of the particular back-
stop [Nm]
M L = 9550 · h · P L /n SP [Nm]
= Static backdriving torque of the load
for each drive referring to the particu-
lar backstop shaft [Nm]

Approximate values for h:

In each case, the sum of the slipping torques
of the particular backstops must be 1,2 times
higher than the static backdriving torque of
the installation (also at overload). The torques
specified in the tables are maximum values.
Lower values can be set upon request. If in
doubt, please contact us stating the precise
description of the installation and the oper a-
ting conditions. It is preferable to use the ques-
tionnaire on page 124.

Example
Dual-drive system
Motor power per drive: P 0 = 630 kW
Type of installation:
Conveyor belt with 8° incline => h 2 = 0,61
Speed per backstop shaft:
n SP = 360 min -1
Selection torque of the particular backstop:
M A = 1,2 · 9 550 · 0,61 · 630 / 360 [Nm]
= 12 234 Nm
The following rule applies in all cases:
M R ^ M A
=> FXRT or FXRV 200 - 63 MXare the suitable,
economical backstop sizes.

Freewheel Size

Type

Slipping torque
M_R
Nm

Sprag lift-off at inner
ring speed min^-1

Max. speed
Inner ring freewheels min^-1

mm

mm

Bore d
Standard
mm mm

mm

mm

max. mm

A
mm

B
mm

C
mm

D
mm

G**

H
mm

K
mm

L
mm

O
mm

R
mm

S
mm

T
mm

min. mm

U***
max. mm

V
mm

Z**

w
kg

Torques
The Integrated Freewheels FXRT are supplied
with a set slipping torque M R of the torque
limiter. The static backdriving torque M L of the
installation (also in the case of an overload)
must under no circumstances achieve the sum
of the slipping torques M R of the provided
Integrated Freewheels. The slipping torques M R
specified in the table are maximum values;
lower values can be set.

Mounting
The Integrated Freewheels FXRT are without
bearing support, therefore it must be ensured
that the run out (T.I.R.) between the pilot
diameter R and the shaft diameter d does not
exceed the value 0,25 mm.
Dimension C applies for the Integrated Free -
wheel. The centering depth of the customer
attachment part must be at least C + 0,2 mm.
The tolerance of the pilot diameter R of the
attachment part must be ISO H7.
The tolerance of the shaft must be ISO h6 or j6.

Release function
The finely controllable release function consists
basically of three special screws (2) that are lo-
cated in the spring pocket (1) and the safety
tabs (3). To release the backstop, first of all the
special screws have to be unscrewed slightly.
Then the cylinder screws (4) and the safety tabs
have to be removed. The special screws can
then be tightened, whereupon, with the aid of
the belleville spring set (5) the release proce-
dure is finely initiated.