INTERNALLY VENTILATED CHAMBER OF SPRING BRAKE ACTUATOR
The present invention is about diaphragm / piston spring brake actuators used in vehicles such as trucks, busses and trailers. The present invention aims to decrease actuator failures by the utilization of an internal ventilation system in the diaphragm / piston spring brake actuators.
Spring brake actuator, which provides braking power for highway vehicles such as trucks, busses and trailers used in commercial transportation, consists of a "service brake chamber" used when the vehicle is in action and a "spring chamber" used when the vehicle is parked.
The Service Brake Chamber and the Spring Chamber in spring brake actuators operate with pressurized air coming from different lines and are controlled by various valves in the cab.
The attached figures for a better understanding of the diaphragm / piston spring brake actuators developed by this invention and the brake actuators produced according to prior art are as follows:
Figure 1 - Sectional view of the internally ventilated diaphragm / piston spring brake actuator developed by this invention
Figure 2 - Sectional view of the diaphragm / piston spring brake actuator produced according to the prior art
Figure 3 - Sectional view of the plug Figure 4 - Sectional view of the valve
The parts shown in the attached figures for a better understanding of the diaphragm / piston spring brake actuator developed by this invention are given numbers. The definition for the numbered parts are as follows:
I -Aluminium piston 2 - Aluminium pipe
3 - Spring chamber
4 - Breather tube (external ventilation tube) 5 - Service chamber
6 - Piston valve
7 - Spring
8 - O-ring
9 - Ball 10 - Exhaust hole
I I - Air entry hole 12 - Air passage -
13 - Internal ventilation plug 14 - Air entry hole 15 - Sealing 16 - Exhaust bores 17 - O-Ring
18 - Piston rear area
19 - Atmospheric area
20 - Rubber elbow
21 - Rubber elbow 22 - Sealing element
23 - Guide ring
24 - Air passage
25 - Power spring
An external connection called breather tube (4) is used In the diaphragm / piston spring brake actuators produced according to prior art in order to transfer the compressed and expanded air that occurs in the piston rear area (18) due to the forward and backward movement of the piston (18) to directions (a) and (b), and in order to decrease the effect of the air.
The breather tubes (4) in the conventional diaphragm / piston spring brake actuators produced according to prior art are connected to the sheet metal body by rubber connectors called rubber elbow (20 and 21). When the piston (1) moves to direction (b) air from the atmospheric area (19) is admitted to the piston rear area via the breather tube (4). The atmospheric area (19) is opened to the external environment by a ventilation hole. Dust and moisture is allowed from the ventilation hole together with air. When the piston (1) moves to direction (b) dust and moisture are carried to the piston rear area via the breather tube (4). Moisture causes corrosion particularly in the power spring (25) and dust gradually harms the sealing (15) and guide ring (23) which are sealing elements (22).
Furthermore, the rubber elbows (20, 21) are damaged in time due to atmospheric conditions and the connection loosens. It is also common that due to vibration or to the stones on the road bouncing up, the connection gets damaged and any end of the breather tube is opened to atmosphere. If the connection is damaged, water, dust and mud are allowed in the piston rear area (18), causing abrasion of the guide ring (23) and the sealing element (22) and sealing is harmed. Moreover, water and abrasives in the vehicle causes the power spring (25), whose duty is to keep the vehicle parked, to rust and to get damaged sooner. If such a situation occurs, the spring brake actuator, which is of vital importance, needs to be repaired or replaced immediately.
In the internally ventilated diaphragm / piston spring brake actuator, which is the subject of this invention, an internal ventilation system is used to completely insulate the spring chamber of the actuator from atmosphere and the entry of the contaminants in the actuator is prevented. The ventilation of the piston rear area is provided with dry air in the ventilation system of the vehicle. Therefore, it becomes impossible for the external contaminants and moisture to damage the actuator.
The internally ventilated diaphragm / piston spring brake actuator, which is the subject of this invention, consists of main members such as aluminum piston (1), aluminum pipe (2), spring chamber (3), service chamber (5), piston valve (6), piston valve O-ring (8), piston valve steel ball (9), exhaust hole (10), air entry hole (11), air passage (12), plug (13), air entry holes (14), sealing (15), exhaust bore (16), pressurized air O-ring (17).
Piston valve (6) is made of brass to avoid rusting. It is bolted and screwed to the aluminum piston (1). O-ring (8) in the piston valve (6) is made of a rubber based material and is firmly placed in the inner surface of the piston valve (6). The piston valve steel ball has been chosen for its standard and smooth surface quality. The steel ball (9) is placed on the O-ring (8) with pressurized air, therefore the air passage (12) is closed and sealing is achieved in the piston valve. The spring (7) in the valve relocates the ball and is made of stainless spring steel. The sealing (15) in the aluminium plug (13) is made of a rubber based material which operates as a one way valve in this design. The O-ring (17) used in the plug (13) outlet serves for further safety and avoids strains in the sealing (15) that occurs by pressure in the adverse direction.
In the following explanations of the invention, the aluminium piston (1) and the aluminium pipe (2) screwed to it are guided and move freely. This system shall hereinafter be referred to as the piston.
Once air is allowed in the spring chamber (3), the spring chamber (3) starts to be filled with pressurized air from the air tanks of the vehicle. With the help of pressure the steel ball (9) of the piston valve (6) compresses the spring (7) and sits on the O-ring (8). Thus the piston blocks the valve (6) and sealing is achieved. Due to the pressure formed in the spring chamber, the piston (1) moves in direction (a), and causes the air in the piston rear area (18) to be compressed. The compressed air is transferred from the air passage (24) into the plug (13) area. Air enters the plug through the entry holes (12), opens the sealing (15) and reaches the exhaust bore (16). Pressurized air opens the O- ring (17) and is released to the service chamber (5). Meanwhile, the compressed air is released to atmosphere since the service chamber (5) is open to atmosphere through various valves, which differ according to systems.
When the air in the spring chamber (3) is released when the vehicle is parked, the piston (1) moves in direction (b) due to the force of the power spring (25) and causes a partial vacuum in the piston rear area (18). The piston valve (6) opens the vacuum to the atmosphere as follows: When the air in the spring chamber (3) is released, force acting on the ball (9) drops to atmospheric pressure; meanwhile, the ball (9) moves with the help of the compressed spring (7) and leaves the O-ring (8), on which it was sitting ; when the air is admitted through this passage (12), the piston rear area (18) reaches atmospheric pressure.
In the internally ventilated diaphragm / piston spring brake actuator, which is the subject of this invention, contaminants, dust, water, and abrasives entering in the piston rear area from the openings formed in the rubber elbows (20, 21) or due to the breather tube (4) that gets dislocated or that snaps out of place due to various reasons, and drawn inside with the motion of the piston (1) in direction (b) do not get into the actuator. Thus, corrosion and rusting in the actuator and of the power spring (25), and abrasion of the sealing element (22) and the guide ring (23) is prevented and their functionality maintained.