Patent Publication Number: US-2011072962-A1

Title: Self-bleeding double action hydraulic cylinder

Description:
FIELD OF THE INVENTION 
     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. 
     BACKGROUND 
     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. 
     SUMMARY 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of an example self-bleeding hydraulic cylinder system. 
         FIG. 2  is a cross-sectional side view of an example self-bleeding hydraulic cylinder system installed in a housing and connected to a pump and motor. 
         FIG. 3  is a close-up cross-sectional view of an alternative example cylinder and sleeve configuration. 
         FIG. 4  is a close-up cross-sectional view of another alternative example cylinder and sleeve configuration. 
     
    
    
     DETAILED DESCRIPTION 
     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  FIG. 1 , a cross-section of a hydraulic cylinder system  10  is shown. Hydraulic cylinder system  10  is divided into a top region  12  and a bottom region  14  and includes hydraulic cylinder  16  and sleeve  18 . Top region  12  includes sites on the top half of the hydraulic cylinder  16 . Bottom region  14  includes sites on the bottom half of hydraulic cylinder  16 . 
     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  FIG. 2 . In another embodiment, channel  32  may be comprised of groove  34  formed in interior wall  30  of sleeve  18 , as seen in  FIG. 3 . In yet another embodiment, channel  32  may be comprised of groove  34  formed in both outer wall  24  of hydraulic cylinder  16  and interior wall  30  of sleeve  18 , as seen in  FIG. 4 . 
     As seen in  FIG. 1 , groove  34  extends along the circumference of at least one of side  36  of hydraulic cylinder  16 . In particular, in the embodiment of  FIG. 1 , groove  34  is shown extending along the circumference of both sides  36  of hydraulic cylinder  16 . Groove  34  may also be milled into outer wall  24  of hydraulic cylinder  16  or may be formed in interior wall  30  of sleeve  18 . 
     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  FIG. 2 , a hydraulic cylinder system  10  is shown positioned in a housing  40  above a pump  42 , vented reservoir  43 , and motor  44  to which the hydraulic cylinder system is attached. As seen in  FIG. 2 , example hydraulic cylinder system  10  includes cylinder ports  20  and line ports  26  at each end of hydraulic cylinder  16 . Example hydraulic cylinder  16  contains hydraulic fluid  46  and air  48 , which has risen to the top of the hydraulic cylinder. 
     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  FIG. 2 , motor  44  powers pump  42 , which pushes hydraulic fluid  46  through one of hydraulic lines  38 . Hydraulic fluid  46  exits one of hydraulic lines  38  into corresponding channel  32  where it then travels to corresponding cylinder port  20  and enters hydraulic cylinder  16  actuating piston  17 . As hydraulic cylinder  16  is actuated, air  48  is pushed through opposite cylinder port  20  followed by hydraulic fluid  46 . Air  48  leads hydraulic fluid  46  through corresponding channel  32  to corresponding line port  26  and into corresponding hydraulic line  38 . Air  48  then leads fluid  46  through pump  42  to vented reservoir  43 . Air  48  may then bubble through any fluid  46  present in vented reservoir  43  escaping to the atmosphere. 
     Also shown in  FIG. 2 , hydraulic cylinder system  10  in this example may be positioned at or just below top wall  50  of housing  40 . Top wall  50  may be an upper barrier of housing  40 , or top wall  50  may be another component also installed in housing  40 . In other embodiments, top wall  50  may be other walls or barriers of housing  40 . As seen in the example in  FIG. 2 , adequate space to allow for the attachment of hydraulic lines to the top of the hydraulic cylinder is not achieved because hydraulic cylinder  16  is placed at a high point within housing  40  adjacent to top wall  50 . Sleeve  18  functions as a manifold creating channel  32  between outer wall  24  of hydraulic cylinder  16  and interior wall  30  of the sleeve. This allows hydraulic lines  38  to be attached to the bottom of hydraulic cylinder  16  while still positioning cylinder ports  20  at the top of the hydraulic cylinder. 
     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.