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| Illustration 1 | g00665170 |
Location of Brake Cylinder (Boost) | |
The brake cylinder (boost) is installed on machines that are equipped with the second type of brake system. Refer to Systems Operation, "General Information". The brake cylinder (boost) is located inside the subframe in an area that is close to the rear of the cab.
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| Illustration 2 | g00664992 |
Brake Cylinder (Boost) with Fully Released Brake Pedal (1) Port (brake reservoir) (2) Valve (3) Spring (4) Port (brake line) (5) Chamber (brake line pressure) (6) Rod (7) Piston (8) Seal (9) Port (hydraulic tank) (10) Port (boost pressure) (11) Spring (12) Annular chamber (13) Passage (boost pressure) (14) Purge screw (15) Inlet port from brake cylinder (master) (16) Inlet chamber (17) Plunger (18) Chamber (boost pressure) (19) Holes (boost pressure) (20) Holes (boost pressure inlet) (21) Holes (relief for boost pressure) (22) Chamber (23) Piston (24) Spring (25) Chamber (26) Push rod | |
When the brake pedal is fully released, piston (7), piston (23), and plunger (17) are held to the right by springs (3), (24), and (11). Valve (2) is open in order to allow oil from the brake reservoir through port (1) and into chamber (5). Chamber (18) is connected to the return lines for the hydraulic tank through the following passageway: Holes (19), passage (13), holes (21), chamber (25) and port (9) .
When the engine is operating, boost pressure is transmitted to the brake cylinder (boost) from the pilot valve which is connected to the implement pilot system. When the brake cylinder (boost) is in the position that is shown in Illustration 2, the boost pressure is felt in port (10) and in annular chamber (12) which is around piston (23).
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| Illustration 3 | g00665169 |
Brake Cylinder (Boost) with the Brake Pedal Pressed. (1) Port (brake reservoir) (2) Valve (3) Spring (4) Port (brake line) (5) Chamber (brake line pressure) (6) Rod (7) Piston (8) Seal (9) Port (hydraulic tank) (10) Port (boost pressure) (11) Spring (12) Annular chamber (13) Passage (boost pressure) (14) Purge screw (15) Inlet port from brake cylinder (master) (16) Inlet chamber (17) Plunger (18) Chamber (boost pressure) (19) Holes (boost pressure) (20) Holes (boost pressure inlet) (21) Holes (relief for boost pressure) (22) Chamber (23) Piston (24) Spring (25) Chamber (26) Push rod | |
When the brake pedal is pressed, pressure from the brake cylinder (master) is transmitted through inlet port (15) to inlet chamber (16). Plunger (17) is offset against spring (11) and the plunger moves into contact with piston (23). As the plunger moves, holes (20) are opened and holes (21) are closed.
Boost pressure from the pilot valve which is connected to the implement pilot system is transmitted through port (10). The boost pressure is then transmitted through annular chamber (12) and holes (20) to chamber (18) in order to act against piston (23) .
As the plunger and the boost pressure offset piston (23) against the force of spring (24), push rod (26) offsets piston (7). Rod (6) closes valve (2) against the valve seat in order to block oil from the brake reservoir through port (1). The rod then remains stationary in order to hold the valve closed as the piston moves to the left. At the same time, oil is displaced from the cavity inside piston (7) and pressure is transmitted from port (4) to the brake lines.
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| Illustration 4 | g00665468 |
Brake Cylinder (Boost) with Constant Pressure on the Brake Pedal (1) Port (brake reservoir) (2) Valve (3) Spring (4) Port (brake line) (5) Chamber (brake line pressure) (6) Rod (7) Piston (8) Seal (9) Port (hydraulic tank) (10) Port (boost pressure) (11) Spring (12) Annular chamber (13) Passage (boost pressure) (14) Purge screw (15) Inlet port from brake cylinder (master) (16) Inlet chamber (17) Plunger (18) Chamber (boost pressure) (19) Holes (boost pressure) (20) Holes (boost pressure inlet) (21) Holes (relief for boost pressure) (22) Chamber (23) Piston (24) Spring (25) Chamber (26) Push rod | |
When the brake pedal is held down with a constant pressure, plunger (17) is moved into a position that is balanced in order to maintain pressure in the brake lines. This pressure is in proportion to the pressure that is applied to the brake pedal.
Boost pressure which is acting against piston (23) is felt in passage (13) and chamber (22) in order to act on plunger (17). When this pressure and the combined pressure of spring (11) slightly exceeds the pressure inside inlet chamber (16) which is transmitted from the brake cylinder (master), plunger (17) is moved to the right in order to gradually close holes (20) .
This action allows boost pressure in chamber (18) and the pressure inside inlet chamber (16) from the brake cylinder (master) to equalize. The pressure that is transmitted to the brake lines by piston (7) is stabilized.
When there is a reduction in the brake pedal pressure, plunger (17) moves further to the right in order to open holes (21). The pressure in chamber (22) is relieved to the tank through holes (21), chamber (25) and port (9). Spring (24) moves piston (23) to the right in order to reduce the brake line pressure in chamber (5).
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| Illustration 5 | g00665469 |
Brake Cylinder (Boost) with Initial Movement of Released Brake Pedal (1) Port (brake reservoir) (2) Valve (3) Spring (4) Port (brake line) (5) Chamber (brake line pressure) (6) Rod (7) Piston (8) Seal (9) Port (hydraulic tank) (10) Port (boost pressure) (11) Spring (12) Annular chamber (13) Passage (boost pressure) (14) Purge screw (15) Inlet port from brake cylinder (master) (16) Inlet chamber (17) Plunger (18) Chamber (boost pressure) (19) Holes (boost pressure) (20) Holes (boost pressure inlet) (21) Holes (relief for boost pressure) (22) Chamber (23) Piston (24) Spring (25) Chamber (26) Push rod | |
Illustration 5 shows the initial movement of the components in the brake cylinder (boost) when the brake pedal is released. The pressure from the brake cylinder (master) is relieved from chamber (16) and plunger (17) is offset to the right by spring (11) in order to close holes (20) and open holes (21). Boost pressure in chamber (18) which is acting on piston (23) is relieved to the hydraulic tank through the following passageway: holes (19), passage (13), holes (21), chamber (25) and port (9) .
As piston (7) and piston (23) are offset to the right by springs (3) and (24), oil is drawn into chamber (5) from the brake lines. Valve (2) is opened in order to allow oil from the brake reservoir through port (1) and into chamber (5) .
When the brake pedal is fully released, piston (7), piston (23), and plunger (17) are fully offset to the right by springs (3), (24), and (11).