Integrated Freewheels FXRT

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Centimeter Equipment Trading Company Limited

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Product information

INTRODUCTION

Features

Integrated Freewheels FXRV and FXRT are sprag freewheels without bearing support and with sprag lift-off X. They consist of the Integrated Freewheels FXM (refer to pages 64 to 69) with additional torque limiter.

The sprag lift-off X ensures a wear-free free- wheeling operation when the inner ring rotates at high speed.

The freewheels FXRV and FXRT are used as:

➧Backstops

for continuous conveyor installations with multiple drives in which each drive is equipped with its own backstop. In such continuous conveyor installations with multiple drives it is important to consider the problem of the unequal distribution of backdriving torque to the individual drives and backstops. As soon as the installation comes to a standstill, the entire backdriving torque is applied primarily to a single backstop, due to differences in the play and elasticity of the drives involved. In installations equipped with backstops without torque limiters, the individual gearboxes and the corresponding backstops must be designed to accommodate the entire backdriving torque of the conveyor installation in order to ensure safety.

The problem of the unequal distribution of backdriving torque is solved by using backstops FXRV and FXRT with torque limiting. The torque limiter which is built into the backstop slips temporarily when the specified torque is exceeded until the other backstops engage in succession. In this way, the entire backdriving torque of the conveyor installation is distributed to the individual gearboxes and backstops. Furthermore, dynamic peak torques which occur during the locking process are reduced, thereby protecting the gearboxes against damaging peak torques. For this reason the use of backstops FXRV and FXRT with torque limiting in continuous conveyor installations with multiple drives enables the application of gearboxes with smaller dimensions.

Advantages

• Protection of gearboxes from overload by unequal load distribution in multiple drives

• Protection of gearboxes from dynamic peak torques during the locking process

• Smaller gearboxes can be used without n egatively effecting the safety

• Protection of the backstops, as dynamic peak torques are reduced by temporarly slipping

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]

P L = Lifting capacity per drive at full load
[kW]
= Lifting height [m] multiplied by the load
that is being conveyed per second
divided by the number of drives [kN/s]
P 0 = Nominal power of motor [kW]
n SP = Speed of backstop shaft [min -1 ]
h = Efficiency of installation
Lifting capacity
=
Lifting capacity + Power loss
After calculating M A , the size of the particular
backstop must be selected in accordance with
the catalogue tables in such a way that in all
cases this applies:
M R ^ M A
M R = Maximum slipping torque of the
particular backstop in accordance with
the table values on pages 74 and 75
[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
FXRT 85 - 40	MX	1 400	430	6 000	45	50	60	65			65	330	148	6	295	M 12	37	29	60	127	280	110	308	165	215	43	6	60
FXRT 100 - 50	MX	2 300	400	4 500	45	50	55	60	70	75	80*	350	159	6	311	M 12	39	31	70	134	300	125	328	180	240	38	6	66
FXRT 120 - 50	MX	3 400	320	4 000	60	65	70	75	80	95	95	400	159	6	360	M 16	36	31	70	134	340	145	373	200	260	38	6	87
FXRT 140 - 50	MX	4 500	320	3 000	65	90	100	110			110	430	163	6	386	M 16	36	31	70	134	375	165	403	220	280	50	6	104
FXRT 170 - 63	MX	9 000	250	2 700	70	85	90	100	120		130	500	188	6	460	M 16	43	40	80	156	425	196	473	250	340	38	6	166
FXRT 200 - 63	MX	12 500	240	2 100	130						155	555	188	6	516	M 16	49	40	80	156	495	226	528	275	390	38	6	209
FXRT 240 - 63	LX	21 200	220	3 000							185	710	210	8	630	M 20	50	50	90	170	630	290	670	355	455	45	12	355
FXRT 260 - 63	LX	30 000	210	2 500							205	750	223	8	670	M 20	50	50	105	183	670	310	710	375	500	40	12	418
FXRT 290 - 70	LX	42 500	200	2 500							230	850	243	8	755	M 24	52	50	105	190	730	335	800	405	560	48	12	574
FXRT 310 - 96	LX	53 000	195	2 100							240	900	293	10	800	M 24	63	63	120	240	775	355	850	435	600	69	12	805

Keyway according to DIN 6885, page 1 • Tolerance of keyway width JS10. * Keyway according to DIN 6885, page 3 • Tolerance of keyway width JS10. ** Z = Number of fastening holes for screws G (DIN EN ISO 4762) on pitch circle T. *** Area for O-ring sealing.

See page 73 for determination of selection torque. Other freewheel sizes upon request.

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.