Patent Application
20130014845
A portion of the disclosure of this patent document contains material, which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
This application is related to the Korea Patent Application No. 10-2006-0031762, filed Apr. 7, 2006, the disclosure of which is incorporated herein by reference in its entirety.
The presently claimed invention relates generally to hydraulic systems and more specifically relates to the sealing of mechanical parts, including control valves, of hydraulic systems.
Hydraulic actuators, including power cylinders, hydraulic motors, accumulators, and pumps are well known in the art. Typically, the actuation, or stop and go motion, of Hydraulic actuators is controlled by a sequence control system. There is a general desire in the art, along with the progress of the surrounding auxiliary technologies, to obtain faster and more accurate actuations under higher loads in hydraulic systems. Higher load, higher speed, and higher accuracy in the hydraulic systems are attainable only with higher internal pressure. A difficulty encountered with highly pressurized fluid is the sealing of mechanical parts, such as control vales, in a hydraulic system. One of the highest performance-demanded parts in a high-pressure control system is the spool type direction control valve.
Traditionally, a spool type direction control valve for high pressure hydraulic system does not have any sealing rings on the spool. The sealing of the spool relies only upon the precise dimensional fitting of the parts, which often approaches submicron level, and the fine finishing of the surface of the bore and surface of the spool for minimizing leaking There is no ideal sealing device for fitting in between the bore and the spool. Certain type of elastomeric materials such as polyamide can withstand 500 bar of pressure before it is extruded. However, elastomeric material cannot be used on the spool as sealing ring, and the reason is explained as below.
The construction spool type valve comprises at least two parts: the valve block and the spool. There must be minimum five ports on the valve block of spool type control valve: 1.) main power fluid supply port; 2.) output port A; 3.) output port B; 4.) return port of output port A; and 5.) return port of output port B. Five holes are drilled from the outer surface of the valve block into the cylinder and penetrate into the cylinder bore to connect the five ports from the outside with the cylindrical bore inside, allowing controlling fluid to flow through.
Drilling a hole that penetrates metal wall unavoidably creates burs on the opposite side of the metal wall, which are to be removed since the burs are always sharp and could damage contacting parts and cause the sticking of mating parts. Therefore, a subsequent processing is employed using, for example, chamfer tool to remove the burs. When the opposite side of the metal wall on which the hole is drilled is exposed, the burs can easily be chamfered eliminating sharp corner edge of the drilled hole. However, when the opposite side of the metal wall is the inside of a cylinder bore, the burs are not accessible to the chamfer process and the sharp corner edge of the drilled hole is left without chamfering. Furthermore, the hole inside the cylinder is not true circle but oval in shape as the drilled hole penetrates the cylindrical surface of the cylinder bore. The oval shape of the hole makes the corner edge even sharper when not chamfered.
Low pressure application spool valves such as those employed in pneumatic control systems with applicable pressure under 30 bar use elastomeric O-rings for spool sealing ring in the pneumatic spool valve since the rubber O-ring has adequate resiliency to overcome the un-chamfered sharp corner edges of the drilled holes inside of the cylinder bore of the spool valve when the internal pressure is very low.
On the other hand, it is impossible to have elastomeric sealing ring that have high enough strength to overcome 300 bar or higher internal pressure, which is the average pressure in current hydraulic systems, without being torn off at the sharp corner edges of the un-chamfered drilled holes inside of the high pressure hydraulic control spool valve. Therefore, spool type high-pressure hydraulic control valves are made without any sealing ring on the spool.
Since the sealing of the spool relies only upon the precise dimensional fitting of the parts and the fine finishing of the surface of the bore and surface of the spool, it necessitates costly and complicated manufacturing process. Using all-metal-seal rings on the spool of high-pressure hydraulic spool valve eliminate the aforementioned limitations as such metal sealing rings can withstand an applied pressure of multi-thousand bar.
It is an objective of the presently claimed invention to provide a design of a spool type hydraulic control valve that can withstand high internal pressure, has relatively low manufacturing complexity, relatively low requirement on precise dimensional fitting of the valve parts, and higher durability. It is a further objective of the presently claimed invention to provide such design with the use of all-metal-seal rings.
In accordance to various embodiments of the presently claimed invention, all-metal-seal rings are used for the sealing of the spool and the bore.
Embodiments of the invention are described in more detail hereinafter with reference to the drawings, in which:
a and
a and
In the following description, designs of hydraulic systems using all-metal-seal rings for sealing are set forth as preferred examples. It will be apparent to those skilled in the art that modifications, including additions and/or substitutions may be made without departing from the scope and spirit of the invention. Specific details may be omitted so as not to obscure the invention; however, the disclosure is written to enable one skilled in the art to practice the teachings herein without undue experimentation.
Referring to
An elongated cylindrical hole 19 is made inside of a valve block 01 in which a valve spool 02 is inserted. The valve spool 02 has six grooves 17, and on each a rubber O-ring 18 is assembled or fitted upon. The rubber O-rings 18 operate to isolate or connect the valve ports 03-07 by sliding the valve spool 02 in or out of the cylindrical hole 19, hence shifting the positions of the rubber O-rings 18 in the cylindrical hole 19, as controlled by a logic controller (not shown in the drawing) of the pneumatic system.
Supplying compressed air or pressurized fluid in the flow direction 12 into a supply port 03 causes the compressed air or pressurized fluid to flow in the flow direction 14 through the spool neck 20, port 07, and tube 09 that is connected to an actuator cylinder 10. A piston 11 is then pushed outward in the direction 16 by the compressed air or pressurized fluid in the actuator cylinder 10. By the outward movement of the piston 11, the compressed air or pressurized fluid originally inside of the actuator cylinder 10 is pushed out in the flow direction 15 through tube 08 that is connected to port 06, through spool neck 21, and discharged out as in the flow direction 13 through the port 04.
Referring to
As described in the abovementioned description, the piston 11 is moved to produce the actuation motion in either the outward direction 16 or the inward direction 25 by the sliding of the valve spool 02 position in and out of the valve block 01.
Referring to
In some instances with the rubber O-rings are shifted to the positions where the drilled holes are located, the rubber O-ring 38 returns to its original circle shaped cross section as shown by the O-ring 38 positioned at the drilled hole 34.
When the valve spool 29 slides again, shifting the rubber O-rings from their positions, the rubber O-rings can hit the sharp corner edge of the drill holes. This is illustrated by the O-ring 37 hitting the corner edge 36 of the drilled hole 35. The O-ring 37 is sheared by the sharp corner edge 36 and can be torn out, destroying the sealing function.
When the hydraulic system has a low internal pressure under 30 bar, the rubber O-rings can maintain their shape; but at an internal pressure of 300 bar or higher, the O-rings cannot maintain their shape and can be easily torn off, this is the reason why high pressure systems cannot use rubber O-ring. Consequently, sealing in high pressure system relies only upon the viscosity of the fluid used in the system, thus the clearance between the valve spool and valve bore wall must be kept as minimal as possible without causing the valve spool to be stuck.
The precision manufacturing process of the valve spool and valve bore involve boring, reaming, grinding, and honing. The alloy of the valve body is selected based on the requirement of low thermal expansion coefficient for avoiding dimensional changes due to temperature changes because of the precise clearance between the valve spool and valve bore wall. For the same reason, the valve body is to undergo extreme grade heat treatment to achieve low thermal deformation. The complex manufacturing process and quality control result in the associated high cost, and the treated alloy, having extra high strength and hardness from the treatments, makes the subsequent drilling and boring more difficult.
All-metal-seal rings in place of the rubber O-rings, on the other hand, are completely free from shearing off by the un-chamfered sharp corner edge of the drilled hole inside of the valve bore. Referring
a illustrates the isolation and/or connection of the ports under the condition in which the piston is pushed out. An elongated cylindrical hole 42 is made inside of a valve block 39 in which a valve spool 40 is inserted. Six all-metal-seal rings 60 are mounted on the valve spool 40. The all-metal-seal rings 60 are kept on their respective predetermined locations on the valve spool 40 by the separation sleeves 41. Each of the all-metal-seal rings 60 is constructed with three different functioning ring layers: a cylinder seal layer, an absorption layer, and a shaft seal layer. The layers are constructed such that they form an inseparable single piece of all-metal-seal ring.
The cylinder seal layer seals the wall of the cylindrical hole 42 and does not come into contact with the surface of the valve spool 40. The absorption layer absorbs any dimensional variations during the dynamic movement of the valve spool 40. The shaft seal layer seals the valve spool 40 and does not come into contact with the wall of the cylindrical hole 42.
Supplying compressed air or pressurized fluid in the flow direction 51 into a supply port 45 causes the compressed air or pressurized fluid to flow in the flow direction 56 through the port 50 and tube 09 that is connected to an actuator cylinder 43. A piston 44 is then pushed outward in the direction 59 by the compressed air or pressurized fluid in the actuator cylinder 43. By the outward movement of the piston 44, the compressed air or pressurized fluid originally inside of the actuator cylinder 43 is pushed out in the flow direction 57 through tube 61 that is connected to port 49, and discharged out as in the flow direction 58 through the port 46.
Referring to
As described in the abovementioned description, the piston 44 is moved to produce the actuation motion in either the outward direction 59 or the inward direction 55 by the sliding of the valve spool 02 position in and out of the valve block 01.
Referring to
The all-metal-seal rings have radial tension. As such the metal rings in an all-metal-seal ring can, by its radial tension, be expanded to have slightly bigger diameter and be contracted to have slightly smaller diameter. Each point on the ring circumference of the metal rings does not rise up or dimple down; unlike the rubber O-ring surface, which should be changed in shape as the contacting surface changes.
Therefore, even though the surface of the all-metal-seal rings 65 and 67 are situated at the locations of the un-chamfered drilled holes, they will not be torn or scratched by the meeting of any burs or sharp corner edge of the un-chamfered drilled holes. The sealing function remains effective. The durability of the valve fitted with all-metal-seal rings, thus, increases dramatically.
One embodiment of the all-metal-seal ring is the coiled felt seal (CFS). One exemplary embodiment of CFS is the helical spring tube type dynamic rotary seal. It is described in the Korea Patent Application No. 10-2006-0031762. Excerpts of its English translation are presented in the Appendix A of the present document.
The foregoing description of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations will be apparent to the practitioner skilled in the art.
The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications that are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalence.
Helical spring tube type dynamic rotary seal constructed with C-type partial rings, which are joined by dovetail joint method
1—A partial ring stamped out of thin metal sheet.
2—Male end of dovetail joint on C-type partial ring.
3—Female end of dovetail joint on C-type partial ring.
4—Dovetail Joint line, which is the result of dovetail joining of C-type partial rings.
5—Helical spring tube constructed by progressive joining of number of C-type partial rings along the helical track.
6—Shaft free circle that made slightly bigger diameter than the shaft diameter to keep it away from shaft all the time.
7—Shaft contact circle that made slightly smaller than shaft diameter to make it keep contact with shaft all the time.
8—Housing contact circle that made slightly bigger than inside diameter of the housing to make it keep contact with housing all the time.
9—Housing free circle that made slightly smaller than inside diameter of the housing to keep it away from the housing all the time.
10—Hosing seal layer whose outside diameter is housing contact circle and inside diameter is shaft free circle.
11—Displacement absorption layer whose outside diameter is housing free circle and inside diameter is shaft free circle.
12—Shaft seal layer whose outside diameter is housing free circle and inside diameter is shaft contact circle.
13—Shaft.
14—Arrow to indicate the shaft rotating direction.
15—Arrow to indicate the spreading direction of shaft seal ring when the ring spreads.
16—An imaginary pin which blocks rotating of shaft seal ring.
17—Housing.
18—Inside diameter of the housing.
19—Snap ring that inserted in snap ring groove to the hold holding ring.
20—Holding ring that holds the seal ring assembly.
21—Compression ring that pushes source rings of seal ring assembly to keep all the rings in seal ring assembly be tightly contacted one another to block leak between rings.
22—Compression spring to provide compression force of compression ring.
23—Outside diameter of the rotating shaft.
24—Completed seal assembly.
25—Snap ring groove.
Category of this invention falls in the dynamic blocking technology of the leak that inevitably arising between stationary housing and rotating shaft when pressure rises in the rotary compression system.
The dynamic rotary seal used on screw type compression system is called “mechanical seal”. A mechanical seal is composed of six parts in minimum, which are the stator block, rotor block, stator disk, rotor disk, rotor disk spring and rotor block disk seal. The entire seal function fails if any one of these parts fails. The stator disk and the rotor disk are the parts that perform the actual sealing function by contacting rubbing rotating under pressure. Those two parts must have not only high wear resistance but also low friction. They must be able to dissipate heat in possible highest speed.
Surface area can be adjusted for less contacting area for less friction heat but the less area results faster wear out. High wear resistant materials have high friction but low friction material having low wear resistance. If they are made with high wear resistant material for long life the friction heat could affect the quality of the media in contact, in some cases even bring fire.
Two contacting faces in mechanical seal are under pressure and constantly rubbing so they are wearing in all instance even submicron unit range but that submicron wear clearance always causes whole seal failure when the submicron wear is not compensated in every instance along with wear out.
In other words, one of the contacting disk, rotating disk, must move toward the mating disk, the stationary disk, to compensate wear. This means the rotating disk must travel axial direction toward the stationary disk on the rotating block while the rotating block is rotating. Rotating disk must be able to slide on the rotating block to constantly move toward the stationary disk. Thus there is another place to block leak between rotating disk and rotating block.
The axial direction movement of the rotating disk on the rotating block by wear out of disk is very little distance, within few mm in a year, so the sealing between rotating disk and rotating block could be satisfied by simple rubber O-ring for cheaper model and by metal bellows for higher performance. In short the real problem in rotary dynamic seal in prior art is in the sealing between rotating disk and rotor block, not only in contacting disks.
A rubber O-ring inserted between rotating disk and rotor block shall be burnt in high temperature media and shall be extruded under high pressure media and be attacked in the corrosive media but there are no ways to omit it.
Metal bellows are more expensive, sometimes three times of the whole mechanical seal, and the metal bellows makes complicate structure which hinders thin compact design that is very important in precision machines.
The ultimate target is to produce single piece rotary dynamic seal which is compact, higher sealing performance, cheaper and lower maintenance while the rotary dynamic sealing system of prior art which generally called mechanical seal having so many parts are inevitably inter related, complicate structure, expensive in production cost, higher maintenance cost and shorter life.
This condition is as same as the
This application claims priority under 35 U.S.C. §119 to the United States Provisional Patent Application No. 61/508,046, filed Jul. 14, 2011, the disclosure of which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61508046 | Jul 2011 | US |
