Abstract:
An apparatus and method for removing, flushing contaminants from and replacing vehicle brake fluid. The apparatus has storage tanks for fresh and waste hydraulic fluid, a fill pump to pump hydraulic fresh hydraulic fluid to the vehicle braking system, an adapter for sealably connecting a fill hose to the master cylinder, a suction pump to suction used hydraulic fluid from the vehicle braking system to the waste fluid tank, a suction hose for suctioning fluid out of the master cylinder and hoses for connecting the waste fluid tank to the bleeder valves located at the vehicle wheels. A by-pass valve is provided between the fill pump and master cylinder to by-pass fluid when the fill hose reaches or exceeds a predetermined level. A computer and ancillary electrical and fluid connections between the various parts of the apparatus and the hydraulic fluid system of a vehicle are also utilized. The apparatus can also be used when replacing the master cylinder or when replacing fluid in other hydraulic systems (i.e. hydraulic clutch).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/103,527 filed Oct. 8, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     A. Field of the Invention 
     The present invention relates to a system and method for removing and replacing vehicular hydraulic fluid. In particular the present invention relates to an apparatus for removing and replacing the hydraulic brake fluid used in the brake system of an automobile, truck, recreational or other vehicle which flushes the hydraulic system of contaminants such as air, water and particulates. Significantly, the present system and method can be carried out as a substantially closed system. 
     B. Background 
     Modern motor vehicles have internally-expanding, hydraulically operated brakes. Hydraulic actuation is based on the principle that a pressure exerted upon a liquid is transmitted uniformly in all directions. The typical vehicle brake system comprises a main or master cylinder with a reserve fluid tank, wheel cylinders and connecting brake lines or pipes. Application of the brakes, by depressing the brake pedal, causes a piston in the master cylinder to move and displace hydraulic brake fluid stored in the master cylinder to cause the brake fluid to move through the brake lines. The displaced brake fluid transmits pressure through the fluid filled brake lines to the wheel cylinders that actuate the brake shoe or pad. As a result, the brake shoes or pads are thrust against a brake drum to stop the vehicle&#39;s wheels. A pump can be used to increase braking capacity. 
     Brakes pads, shoes or discs apply a force to particular components, such as the brake drums or rotors that rotate with the wheels. As much as 2,000 pounds psi of hydraulic pressure may be exerted by the brakes on each of the four wheels to stop the vehicle. Brake fluid also acts as a lubricant for the pistons, cylinders, seals and valves that make up the brake system. Different brake systems use different types of brake fluid. All of the brake fluids have certain desirable characteristics and negative aspects. Desirable brake fluid characteristics of brake fluids include high boiling temperature, low freezing temperature and low tendency to bubble. The purity of the brake fluid is important, because if it becomes contaminated the piston seals, hoses and other parts of the brake system may be damaged and have to be replaced. A negative aspect of brake fluid is that it is corrosive to paint and its spillage can harm a vehicle&#39;s exterior finish. In addition, inhalation of brake fluid fumes presents a health hazard and spillage of brake fluid presents potential environmental concerns. 
     Common vehicular brake fluids have ratings such as DOT (Department of Transportation) 3, 4 or 5. DOT 3 brake fluid is recommend for normal city driving, DOT 4 for mountain, trailer towing or frequent hard braking use and silicone based DOT 5 brake fluid for performance or racing vehicles. The higher the DOT rating the higher the boiling point of the brake fluid. However, the higher the boiling point of the brake fluid, the more hygroscopic or water absorbing the brake fluid tends to be. As water is absorbed by the brake fluid its boiling point becomes lower. For instance, a brake fluid having a 3% water content can have a boiling temperature that is 25% lower than a water-free brake fluid. Additionally, at low temperatures the water absorbed by the brake fluid can form ice crystals, which impede free flow of the brake fluid. Thus, the presence of water in the brake fluid can cause a lower boiling point and ice to form, both of which can impair brake function. Even without the problems caused by extreme temperatures, water absorbed by the brake fluid can cause brake components to prematurely rust and fail. Generally, automotive brake fluid should be replaced and the brake system flushed of contaminants when the water level in the brakes fluid is about 3% by volume. 
     Most brake fluids are clear, volatile, water soluble liquids comprised of a mixture of several alcohols such as glycols. Silicone based (DOT 5) brake fluids are also known. Through use brake fluid can become discolored due to contamination from dirt and disintegrating rubber seals. Additionally, oxygen in the air can oxidize the brake fluid which also reduces its boiling point. Due to its volatile nature and easily absorbed constituents, inhalation of and/or contact with brake fluid can be hazardous. 
     A lower brake fluid boiling point can result in the brake fluid boiling during a long downhill stretch of intermittent braking. If the brake fluid boils the resulting bubbles reduce brake effectiveness and causes brake fade (“soft brakes”) due to the gas bubbles absorbing foot pressure instead of transmitting it through the brake fluid. Particulate matter, such as airborne dust and rubber seal fragments, can also collect within the fluid filled brake lines and reduce braking effectiveness. 
     To remove water and contaminants, the brake fluid is periodically replaced with new brake fluid. The drained brake fluid is not reused because once exposed to the atmosphere, even if only for a brief period, significant amounts of water, air (with the oxidizing oxygen) and contaminants such as dust can be absorbed by the brake fluid. Even new brake fluid exposed to ambient air can absorb moisture resulting in an immediate loss of the brake fluid&#39;s effectiveness. Brake fluid can be tested to determine its viability, such as determining its water content by the method and apparatus disclosed by U.S. Pat. No. 5,028,144. The &#39;144 patent, however, does not disclose an apparatus for removing or replacing spent brake fluid. 
     As described above, hydraulic brake fluid is periodically replaced due to fluid deterioration and contamination. Many brake fluids have volatile and/or toxic components which can hinder removal and replacement of the fluid. Typically, the entire hydraulic fluid is drained from the brake system and replaced with new fluid, the process being carried out in an open air environment whereby the fluid is exposed to the atmosphere as the brake system is being drained and new fluid is added. Unfortunately, this method releases pollutants into the air and exposes the operator to harmful fluids and vapors. Additionally, no attempt is made to recycle or reuse any of the hydraulic fluid resulting in economic waste and fluid disposal problems. In fact, some states have imposed a fee for the collection and disposal of used brake fluid from automotive service centers, which is typically collected into open containers. 
     Whether it is necessary to remove and replace the brake fluid is typically determined solely by examining the color of the brake fluid or by automatic replacement after a predetermined period (i.e., after 18 to 24 months or after every 30,000 miles of vehicle usage). If desired, a brake fluid water content test can be done quickly utilizing currently available technology. For instance, brake fluid test strips available from Wagner can be inserted into a vehicle&#39;s brake fluid to determine both the type of brake fluid being used and its relative water content. The test is performed much like a pH test in that the a test strip is inserted into the hydraulic fluid and visually reviewed to determine the type of brake fluid and whether the water content is too high. The test method uses samples taken from either the master cylinder or a brake cylinder. The above-described brake fluid test can be run quickly, typically taking less than 1 minute. 
     The prior art method of replacing brake fluid takes two people about 45 minutes to an hour to remove and replace the brake fluid. The prior art method also requires additional time to clean-up the resulting spillage that is essentially inherent in the prior art method. One commonly known method for removing and replacing a vehicle&#39;s hydraulic brake fluid and then removing air introduced into the brake lines by this two person, open system method is shown in FIGS. 1 and 2. Typically, about twice the volume of fluid the caliper can hold per wheel is used by the prior art method. Unfortunately, new brake fluid can become contaminated with moisture, air and particulates as soon as the brake fluid container is opened and poured into the brake system due to the typical open system method used to flush and replace used brake fluid. 
     What is needed therefore is an apparatus and method for safely removing and replacing hydraulic fluid without exposing the environment or the operator to the brake fluid. Also needed is an apparatus and method for flushing a hydraulic system of contaminants such as air, water and particulates and for safely storing and using new brake fluid while minimizing problems with the removal and disposal of waste brake fluid. 
     SUMMARY OF THE INVENTION 
     The apparatus and method for removing and replacing hydraulic fluid without exposing the environment or the operator to the hydraulic fluid of the present invention solves the problems identified above. That is to say, the present invention provides an apparatus and method for flushing fluid from a hydraulic system to remove contaminants such as air, water and particulates and for filling the system with new brake fluid while minimizing problems with the removal and disposal of the used brake fluid. 
     The present invention is based upon the concept that brake fluid can be removed and replaced and the brake system flushed of contaminants while maintaining a closed system. Because brake fluid is hygroscopic, the absorption of moisture lowers the boiling point of the brake fluid and causes premature degradation of the fluid and increased likelihood of corrosion in the brake system. Additionally, exposure of an operator to the brake fluid presents health hazards. Therefore, the apparatus of the present invention operates as a closed system. 
     An apparatus within the scope of the present invention comprises a closed system with fluid pumps, a flow meter, a computer and ancillary electrical connections between the various parts of the apparatus and fluid pipe connections between the apparatus and the hydraulic fluid system of a vehicle. The function of the computer is to control pressures and fluid levels. For safety and operational reasons, the computer should shut down the apparatus if the new fluid tank is or becomes empty and if the waste fluid tank is or becomes full. 
     The present invention is used to remove a vehicle&#39;s hydraulic brake fluid, flush and capture contaminants from the brake system and replace the brake fluid. The invention facilitates replacing brake fluid having an unacceptable level of water content with new brake fluid without exposing the new brake fluid to air and without requiring the operator to handle or be exposed to the waste brake fluid. As such, the apparatus of the present invention differs from known apparatus by use of a closed system to prevent exposure of brake fluid to the environment and to prevent exposure of air to the brake fluid system and to the new brake fluid. 
     The fresh fluid system of the invention has the following benefits: (1) provides a reliable and sealed method of pumping brake fluid; (2) connects to all major types of master cylinders &amp; reservoirs; (3) provides an automatic shutoff if reservoir is full; (4) permits the brake fluid to travel up to 25 feet with a 10 foot rise in elevation; and (5) has a working pressure of 5 to 12 psi. 
     Therefore, it is a primary objective of the present invention to provide an apparatus for easily, quickly and relatively inexpensively removing a vehicle&#39;s hydraulic brake fluid and replacing it with new brake fluid without exposing the brake fluid to the environment and the service personnel to the brake fluid. 
     It is another primary objective of the present invention to provide an apparatus for removing and replacing a vehicle&#39;s hydraulic brake fluid that utilizes a system to remove spent brake fluid from a vehicle to a closed container while re-filing the brake system with new brake fluid from a closed container. 
     It is another objective of the present invention to provide an apparatus comprising a pump, various fluid control and measuring devices, fluid tanks and an electronic control mechanism to easily and quickly remove and replace vehicle brake fluid in a closed system. 
     It is yet another objective of the present invention to provide a method for removing and replacing a vehicle&#39;s hydraulic brake fluid without exposing the old or new fluid to the environment or to persons operating the apparatus of the present invention. 
     The above and other objectives of the present invention will be explained in greater detail by reference to the attached figures and the description of the preferred embodiment which follows. As set forth herein, the present invention resides in the novel features of form, construction, mode of operation and combination of parts presently described and understood by the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings which illustrate the best modes presently contemplated for carrying out the present invention: 
     FIG. 1 is a flow chart of a prior art method for removing and replacing automotive brake fluid; 
     FIG. 2 is a flow chart of a prior art method for removing air from an automotive brake fluid system after removing and replacing the brake fluid by the method shown in FIG. 1; 
     FIG. 3 is a perspective view of an embodiment of the present invention; 
     FIG. 4 is a front side view of the embodiment of the present invention shown in FIG. 3 with the doors and cabinet top open; 
     FIG. 5 is an overall schematic of the apparatus of the present invention shown in FIG. 3; 
     FIG. 6 is a schematic of the hose system of the apparatus of the present invention shown in FIG. 3; and 
     FIG. 7 is a flow chart of a method within the scope of the present invention. 
    
    
     DETAILED DESCRIPTION 
     With reference to FIGS. 3 through 8, where like elements have been given like numerical designations to facilitate understanding of the present invention, the vehicle brake fluid removal and replacement apparatus of the present invention is designated generally  10 . Illustrated in FIG. 3 is a perspective view of an embodiment of the present invention showing a brake flushing system  10  comprising a roll-away system cart  12  forming an enclosed housing  14 , a cabinet top  16 , locking casters  18  for easy positioning and placement of the cart, and door  20 . The brake fluid flushing apparatus  10  is all contained in cart  12  to allow easy positioning in and movement around an automotive shop. A preferred cart  12  size is about three feet high by about two and one half feet wide by about sixteen inches deep. Generally, due to work conditions, the maximum comfortable height for cart  12  is about four feet. 
     Cart  12  also includes control panel  22  on cabinet top  16 , pressure gauges  24   a  and  24   b , indicator lights  26  and switches  28   a  and  28   b . In the preferred embodiment, the apparatus  10  utilizes fresh fluid tank  30  for storage of fresh (new) brake fluid and waste fluid tank  32  for the storage of waste brake fluid. For convenience purposes, cart  12  can also include storage area  34  under a raisable cabinet top  16  for the storage of master cylinder adapters and bleeder valve connectors to be used with the present invention  10  and for the power supply (i.e., a 110 volt AC or 12 volt battery). Also part of cart  12  is hose tray  38  from which the fill hose  40 , vacuum hose  42  and the four bleeder valve hoses  44   a ,  44   b ,  44   c  and  44   d  (collectively  44 ) extend. When not in use, the hoses can be stored under hose tray  38 . 
     Additional components of the present invention  10  include a master cylinder connector  46 , a peristaltic pump (or fill pump)  50 , a diaphragm or impeller pump (or vacuum pump)  52 , one air inlet valve  54  on fresh fluid tank  30 , master cylinder adapter  56 , air vent  58  on the master cylinder adapter  56 , a vacuum wand  60 , by-pass valve  62 , switch valve  64  and various control electronics, switches, hoses and indicators. 
     As set forth above and in the schematic drawing of the present invention in FIGS. 5 and 6, there are two primary components in the fluid transfer system of the present invention  10 , the fresh fluid system  66  and the scavenge/waste system  68 . The fresh fluid system  66  pumps fresh fluid into the master cylinder or reservoir of the automobile. The scavenge/waste system  68  vacuums brake fluid from the master cylinder and all four brake cylinders and transfers it to waste fluid tank  32 . The primary components of the fresh fluid system  66  are the fress fluid tank  30 , the peristaltic (fill) pump  50 , the by-pass valve  62  and fill hose  40 . The primary components of the scavenge/waste fluid system  68  are the waster fluid tank  32 , vacuum pump  32 , switch valve  64 , vacuum hose  42  and the bleeder hoses  44 . 
     Ideally, the fresh fluid tank  30  should be able to store brake fluid for long periods of time (i.e., up 3 months) without exposing it to air or moisture, resulting in deterioration of the brake fluid. Additionally, the fresh brake fluid system  66  must deliver brake fluid to the master cylinder without introducing air and contaminants into the vehicle brake system. The fresh fluid tank  30  should also easily connect to the apparatus of the present invention and be reusable for waste fluid to minimize waste and enhance safety procedures. As such, both fluid tanks  30  and  32  should be UN/DOT (United Nations/Department of Transportation) approved for shipping waste fluids to a disposal location. 
     In the preferred-embodiment, fresh fluid tank  30  is a UN/DOT approved shippable container that can, when full, contain five gallons of fresh brake fluid. The fluid tank  30  can safely store the fluid without leakage or exposure to air. The container should also have a mechanism to prevent connection of the waste fluid tank  32  to the fresh fluid inlet (i.e., fill hose  40 ). 
     The various connectors  46  and  48  and adapter  56  are the interfaces between the brake fluid stored in cart  12  and the automobile being worked on. Master cylinder adapter  56  connects to the master cylinder or fluid storage reservoir of the automobile to provide for the ingress of fresh brake fluid from fresh fluid tank  30  in cart  12  through fill hose  40 . The master cylinder connector  46 , which can be a standard quick release connector, connects to the master cylinder adapter  56 . Four bleeder valve hoses  44  are connected to the bleeder valves on the brake cylinders at each wheel. In the preferred embodiment, the end of hose  44  itself is placed onto or over the bleeder valve. Alternatively, a separate connector can be used. 
     The fluid level in the master cylinder must be maintained to eliminate air or other contaminants from getting into the system. Mounted in the master cylinder adapter  56  is a vent valve  46  for avoiding air-lock by allowing air to exit the master cylinder, but not hydraulic fluid, during filling. One type of vent valve  46  that can be used is the Maxivent™ from Aquitrol, Inc., which utilizes a polypropylene float. The master cylinder adapter  56  should be designed to be a universal adapter that can be used to connect to the master cylinder or to the brake fluid reservoir of most automobiles and provide a 25 psi seal. Adapter  56  also has a rubber protrusion in the seal that facilitates proper filling of the fluid reservoir. 
     The fresh fluid system  66  uses a peristaltic pump  50 , to help eliminate foaming of the brake fluid, connected to fresh fluid tank  30 . Tank  30  should be configured such that as fluid is pumped out air is prevented from entering the flushing system and exposing the brake fluid to the air and contaminants. Air inlet valve  54  on tank  30  allows the peristaltic pump  50  to pump out the fresh fluid without collapsing tank  30 . The air inlet valve  54  should be a desiccant valve for removing moisture from the air. The user has no direct contact with the brake fluid, which stays within the hose. 
     In the preferred embodiment, the fill pump  50  and the scavenge/waste pump  52  both operate on 12 volts or 110 volts, can withstand up to 25 psi back pressure, operate without significant frothing of the brake fluid, are chemically resistant to the brake fluid, have a 0.25 to 1 GPM (gallons per minute) flow rate and are self priming. 
     The scavenge/waster fluid system  68  removes the brake fluid from the four bleeder valves and routes it into the waste fluid tank  32 . One line of the scavenge system, the vacuum hose  42 , connects to a vacuum wand  60  to allow easy cleaning of the master cylinder reservoir. The bleeder valve hoses  44  should be transparent so as to provide visible indication of whether used or new brake fluid is exiting the bleeder valves. The bleeder valve connectors  48  should be configured to connect to the standard vehicle bleeder valves located at each wheel of a vehicle. 
     The operation of the apparatus of the present invention is illustrated in FIG.  7  and described below. After removing the cover of the master cylinder and testing the brake fluid, if desired, switch  28   b  is turned on to activate vacuum pump  52  and create a vacuum in vacuum hose  42 . Vacuum wand  60 , attached to vacuum hose  42 , is utilized to remove used brake fluid from the master cylinder and any particulate matter that has accumulated therein and dispose of it in the waste fluid tank  32 . Vacuuming out the master cylinder saves time because less fluid has to be forced through the brake system. Vacuuming out the master cylinder also avoids the potential of mixing new brake fluid with old brake fluid and of forcing particulate matter through the brake lines. After the master cylinder is vacuumed out, switch  28   b  is turned to the off position and vacuum hose  42  is returned to cart  12 . 
     Master cylinder adapter  56 , with fill hose  40  attached thereto, is installed on the master cylinder. With master cylinder adapter  56  in place, the master cylinder fill switch  28   a  is turned to the on position and the master cylinder is filled with new brake fluid from the fresh fluid tank  30 . When the pressure in the fill line reaches a pre-determined level (i.e., 10 psi) by-pass valve  62  is automatically activated in apparatus  10  to by-pass brake fluid until it is needed for filling the brake lines. While the master cylinder is filling, the vehicle can be raised for ease of vacuuming and filling the brake system. One of the four bleeder valve hoses  44  leading from the waste fluid tank  32  is connected to one of the four bleeder valves (one hose  44  for each valve) on the vehicle&#39;s wheel master cylinder. 
     After the bleeder valve hoses  44  are installed, switch  28   b  at cart  12  is turned to start vacuum pump  52  and vacuum the old fluid out of the brake lines and into waste fluid tank  32 . A sensor connected to the waste fluid tank  32  ensures that waste fluid tank  32  is not overfilled. The reduction in pressure in the brake lines releases the by-pass and new fluid begins flowing through the master cylinder into the brake lines. The bleeder valves at each of the wheels are closed when clear fluid starts passing through the bleeder valves and into the transparent bleeder valve hoses  44 . 
     When the bleeder valves are shut-off, the by-pass valve  62  in apparatus  10  will begin by-passing the new fluid again (i.e., when the pressure in reaches 10 psi). The bleeder valve hoses  44  are disconnected from the bleeder valves at each wheel, the vacuum pump  52  is shut-off and the vehicle is lowered. At the completion of the process, the master cylinder fill switch  28   a  is turned off, the master cylinder adapter  56  is removed from the master cylinder and the master cylinder cover is reinstalled. Throughout the filling and removal operation described above, a closed system is maintained. 
     The air vent/float sensor  58  incorporated into master cylinder adapter  56  vents the air to prevent air-lock. Pressure gauge  24   a  indicates the pressure of brake fluid in the master cylinder and vacuum gauge  24   b  indicates the amount of vacuum being drawn by vacuum pump  52 . 
     A typical volume of brake fluid exchange is one to two quarts. With the present invention  10  it takes approximately ten to fifteen minutes to remove the waste brake fluid and replace it with new brake fluid. Unlike the prior art method of replacing brake fluid, the present invention does not require any bleeding of the brake lines or clean-up after installing the new brake fluid. The present invention  10  can also be used when a new master cylinder has to be installed. With the present invention  10 , the need for bench bleeding of the master cylinder is eliminated. Another use for the present invention is with vehicles having a hydraulic clutch system. Because hydraulic clutch systems utilize the same hydraulic fluid, the same apparatus can be used with the same fluids. 
     While there is shown and described herein certain specific alternative forms of the invention, it will be readily apparent to those skilled in the art that the invention is not so limited, but is susceptible to various modifications and rearrangements in design and materials without departing from the spirit and scope of the invention. In particular, it should be noted that the present invention is subject to modification with regard to the dimensional relationships set forth herein and modifications in assembly, materials, size, shape, and use. For example, a wide variety of cart configurations are possible.