Patent Application
20110072962
This invention relates to hydraulic cylinder systems and in particular to hydraulic cylinders capable of purging air from the system through normal actuation of the cylinder piston.
In conventional hydraulic systems, proper operation depends on the ability to purge all compressible compounds from the system. Air is an example of a compressible compound that must be purged from a hydraulic system to ensure proper operation. The entrapment of air in the system or the dissolving of gas into hydraulic fluid may be problematic. Pressure drops, cavitation, reduced functionality, or general harm to the system may occur due to the presence of entrapped or dissolved air. As a result, air must be purged from hydraulic systems to ensure proper operation.
Current approaches rely on the positioning of system components, the use of a vacuum, or continuous operation to purge air from the system. One approach purges all air from the system through the creation a vacuum. Only once a sufficient vacuum is achieved is hydraulic fluid then added to the system. However, this approach requires specialized equipment for the creation of a vacuum. Another approach simply operates the hydraulic system for a period of time whereby the fluid moving through the system will push the air to a place in the system where it can then be purged. However, these approaches may not be feasible where the hydraulic cylinder is positioned near a high point of the hydraulic system.
Hydraulic cylinders may purge air from the system by placing hydraulic lines on top of the hydraulic cylinder. This allows the cylinder to push air that has risen to the top of the system through the ports before the hydraulic fluid. Thus, any air entrapped in the system will enter the hydraulic lines first and be pushed to a point where it can then be purged.
However, space constraints may prevent the positioning of hydraulic lines at the top of the system. As a result, the hydraulic ports and lines may need to be located on the bottom of the hydraulic cylinder. In this case, actuating the cylinder will push hydraulic fluid through the ports and lines before the air that has risen to the top of the system. As a result, air may not be sufficiently purged from the system. Because fluid was pushed through the hydraulic ports before the air, the air may remain in the hydraulic lines and return to the cylinder when the cylinder is actuated in the opposite direction. Alternatively, air may also become dissolved into the hydraulic fluid in systems where fluid is pushed from the hydraulic cylinder before air. Thus, there exists a need for a hydraulic cylinder having ports and hydraulic lines located on the bottom of the hydraulic cylinder that is also capable of purging air from the system through normal actuation of the cylinder.
A self-bleeding hydraulic cylinder system is provided. The system includes a hydraulic cylinder with an inner wall and an outer wall. A cylinder port is located in a top region of the hydraulic cylinder. A line port is located in a bottom region of the hydraulic cylinder. A sleeve covers at least a portion of the outer wall of the hydraulic cylinder, and a channel is formed between the sleeve and the outer wall of the hydraulic cylinder. The channel extends from the cylinder port to the line port such that air within the hydraulic cylinder is pushed through the cylinder port and through the channel to the line port in response to actuation of the hydraulic cylinder.
A self-bleeding, double-action hydraulic cylinder system is described herein. In particular, the hydraulic cylinder system purges air from the cylinder through normal actuation of a cylinder piston.
As shown herein, a self-bleeding hydraulic cylinder system has a hydraulic cylinder with a cylinder port located in the top region of the hydraulic cylinder. A sleeve that functions as a manifold is used to cover the cylinder port. A line port is located in a bottom region of the hydraulic cylinder system, and a channel is formed between the hydraulic cylinder and the sleeve. The channel, for example, may be a groove formed in an outer wall of the cylinder, or alternatively formed in an interior wall of the sleeve. Upon actuation of the hydraulic cylinder, air may be pushed through the cylinder port and through the channel to the line port. A hydraulic line leading to a pump and motor may also be connected to the line port of the sleeve. The hydraulic cylinder system may be mounted in a housing above pump or motor devices and beneath a top wall of the housing.
Referring to
Hydraulic cylinder 16 may be any type of hydraulic cylinder known to those skilled in the art and may include a piston 17 to move hydraulic fluid and air within the cylinder. Hydraulic cylinder 16 also includes cylinder port 20 located in top region 12 of hydraulic cylinder system 10. In one embodiment, cylinder port 20 is located proximate to the top of hydraulic cylinder 16 and is formed from inner wall 22 to outer wall 24 of the hydraulic cylinder.
Sleeve 18 functions as a manifold, providing a space through which air and hydraulic fluid may pass. Additionally, sleeve 18 may be made from the same material as outer wall 24 of hydraulic cylinder 16 or any other suitable material. In an embodiment, sleeve 18 may be made of metal and welded to hydraulic cylinder 16. Sleeve 18 includes line port 26 located in bottom region 14 of hydraulic cylinder system 10. In one embodiment, line port 26 may be located proximate to the bottom of hydraulic cylinder 16 and is formed from exterior wall 28 to interior wall 30 of sleeve 18.
Channel 32 is formed when sleeve 18 encloses cylinder port 20 of hydraulic cylinder 16. Channel 32 also extends from cylinder port 20 to line port 26. When hydraulic cylinder 16 is actuated, sleeve 18 functions as a manifold allowing air and fluid to pass through cylinder port 20 and channel 32 to line port 26 as illustrated by arrows 25. In one embodiment, channel 32 may be a groove 34 formed in outer wall 24 of hydraulic cylinder 16, as seen in
As seen in
When hydraulic cylinder system 10 is in use, hydraulic line 38 may be attached to line port 26. Line port 26 may be formed in any manner known to those skilled in the art to allow the attachment of hydraulic line 38. When hydraulic cylinder 16 is actuated (during piston movement, for example), air and fluid flowing through channel 32 to line port 26 will exit the channel through the line port and enter hydraulic line 38 as illustrated by arrows 25.
Referring now to
Hydraulic cylinder system 10 also includes sleeves 18 attached to each end of hydraulic cylinder 16 covering cylinder ports 20. Hydraulic lines 38 are attached to example hydraulic cylinder system 10 and lead to pump 42. Pump 42 is connected to vented reservoir 43 and motor 44. Pump 42 and motor 44 may be any pump and motor known to those skilled in the art to be suitable for use in a hydraulic system. Vented reservoir 43 is a fluid reservoir that is vented to the atmosphere.
Vented reservoir 43 may be used to account for the volumetric differences between either sides of hydraulic cylinder 16. Piston 17 includes piston head 45 and piston shaft 47. Head 45 divides the chamber of hydraulic cylinder 16 into two sides, one side including shaft 47. The side of hydraulic cylinder 16 lacking shaft 17 may hold a greater volume of fluid than the side that includes the shaft. Vented reservoir 43 may be used to contain excess fluid 46 as the side of hydraulic cylinder 16 that includes shaft 47 is filled to capacity.
Vented reservoir 43 is also used as the bleed site for any air present in the system. Because cylinder ports 20 are located in top region 12 of hydraulic cylinder system 10, air 48 will be pushed through cylinder ports 20 before hydraulic fluid 46. By pushing air 48 from hydraulic cylinder 16 before hydraulic fluid 46, the air ultimately be pushed to reservoir 43 at which point it will be purged from the system to the atmosphere.
As seen in
Also shown in
By way of example, the hydraulic cylinder system described herein may be installed in the housing of a vehicle door system. In an example vehicle door system, the hydraulic cylinder system may need to be positioned above the pump and motor and just below the top wall of the housing leaving little room for top-mounted hydraulic lines. In this example system, because the hydraulic cylinder is positioned at the highest point of the system, air may rise to the top of the cylinder. The hydraulic cylinder system described herein allows the installation of a hydraulic cylinder below the top wall of the housing and above the pump and motor with bottom-mounted hydraulic lines. The sleeve encloses the top-positioned cylinder ports and forms a channel to the bottom-positioned line ports. This allows air to be pushed from the hydraulic cylinder before the hydraulic fluid to a point at which it can be purged. Thus, air may be bled from the hydraulic cylinder system through normal actuation of the hydraulic cylinder without the need for special equipment or processes.
The invention illustratively disclosed herein suitably may be practiced in the absence of any element, part, step, component, or ingredient which is not specifically disclosed herein.
While in the foregoing detailed description this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purposes of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that a certain of the details described herein can be varied considerably without departing from the basic principles of the invention.
