205 AND 211 TRACK-TYPE EXCAVATORS Flexible Coupling Caterpillar


Flexible Coupling
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1.1. Assembly
2.1. Hydraulic Oil Reservoir

Flexible Coupling - Fig. WH 116

The essential component of the coupling is the flexible section, a molded part of heavy duty Hytrel. The metal parts are placed only in this flexible part.

The metal parts to be screwed axially are secured against the flat surface of the flywheel while those to be screwed radially are screwed on the cylindrical hub. Force flow is from the flywheel through the axially mounted metal parts to the flexible section and from there, through the radially mounted segments to the cylindrical drive hub provided on the pump shaft.

The coupling is fitted with a clamping hub so that it can be fixed absolutely without backlash on the shaft of the hydraulic pump. Assembly is straightforward, since the flexible part of the coupling is of the slip-on type, and the motor and pump are simply fitted into each other.

Assembly

1. Mount the radial segments on the hub and tighten bolts (1) to 220 N·m. If the segments are already mounted on delivery, they should not be removed again.

2. Push the hub onto pump shaft as far as possible and fix with the two locking screws (2). Tightening torque = 90 N·m.

3. Bolt the axial segments together with the flexible section to the flywheel and tighten bolts to 220 N·m.

4. Attach pump assembly to coupling.

NOTE:

1. Take care when tightening the bolts (1) that the segments are properly seated (Fig. a wrong, Fig. b right). Apply a little grease to the bolt heads before mounting in order to reduce friction between the bolt heads and segments.
2. Use only the "Inbus Plus" bolts supplied, with a colored compound (e.g. blue) on the thread. This compound contains microcapsulated adhesive which cements the bolt in the thread and helps prevent loosening.

The curing time of this adhesive after tightenting is approximately 4-5 hours at room temperature (20°C) for an adequate effect. Do not operate coupling beforehand. The adhesive is fully cured after 24 hours. Higher temperatures accelerate hardening, e.g. at 70°C (heat with hot air blower) the curing time is only 15 minutes.

"Inbus Plus" is temperature resistant from -80 to +90°C and the bolts can be used, at most, three more times. Should for some reason or other these "Inbus Plus" bolts not be available, the threaded holes and the bolts must be carefully degreased and securely cemented with a different, reliable adhesive, e.g. "Loctite". Lock washers, or suchlike are not permissible.

Hydraulic Oil Reservoir

Hydraulic Oil Reservoir - Fig. WH 206

(1) Breather filter with double check valve Response pressure of outlet valve 0.35 bar (35 kPa)

Response pressure of inlet valve -0.03 bar (-3 kPa)

(2) Check valves act as back pressure valves, opening pressure 2.5 bar (250 kPa)

(3) Integrated filter with bypass valve

(4) Sight glasses

The hydraulic oil reservoir is pressurized, i.e. the air above the oil level has an overpressure of 0.35 bar (35 kPa). This improves the intake characteristics of the hydraulic pump.

For oil quantity, type and change intervals see the topic, Lubrication and Maintenance Chart and Refill Capacities.

The breather filter, with a double check valve, has the following purpose: the build-up of pressure in the reservoir. Air can only enter the tank through the inlet valve and leave through the outlet valve. This means that air exchange with the atmosphere can take place only when considerable level and temperature changes occur in the tank. Due to the different volumes of the piston side and rod side of the cylinders, the oil level in the tank drops when the cylinders are extended and air enters the tank through the inlet valve. When the cylinders are retracted, the level rises and the air above it is compressed until the outlet valve opens.

The entrance of dirt from the atmosphere is substantially reduced by limited air exchange. Splash and drain water can not enter the tank when the machine is not in use.

To a great extent, oil leakage through the breather filter as a result of oil movement is prevented. Change breather filter at regular intervals (see "Maintenance Schedule").

The check valves, which are integrated in the two return lines, bank up the returning oil. Thus, some of this oil flows back to the tank through the oil cooler and a further return line.

The integrated filters are mounted in the return line directly on the tank. The filter outlet port is below the oil level to avoid foaming. One filter tube with two elements is fitted (205). One filter tube with three elements is fitted (211).

On the upper section of the filter tubes are the bypass valves, which open when the paper elements are badly soiled, so that unfiltered oil reaches the tank. Check the setting of the spacer screws before placing the cover over the filters. The spacer screws should cause the filter tubes to press against the O-rings slightly when the cover is fitted. Pour the oil through the hole in this cover so that it flows through the filter before reaching the tank. See "Maintenance Schedule" for filter element change.

The sight gauges are provided for oil level check. Make sure the machine is level and lower the bucket to the ground. The oil level should reach to the middle of the upper sight gauge.

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