Valves and valve actuation – Mechanical movement actuator – Screw
Reexamination Certificate
2002-09-30
2004-10-12
Hirsch, Paul J. (Department: 3754)
Valves and valve actuation
Mechanical movement actuator
Screw
C251S149900
Reexamination Certificate
active
06802492
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to the operation, maintenance and servicing of machines which include hydraulic systems and, more particularly, to the connection and disconnection of hydraulic fluid conveying lines with improved safety and reduced risk of loss of hydraulic fluid.
2. Description of the Prior Art
The industrial age has been characterized by the construction and utilization of machines which provide forces beyond those which can be produced practically by one or more persons to perform work of a nature or at a rate previously far beyond human capacity. Such machines characteristically include one or more sources of power and some arrangement to transfer such power from each such source to the location in or on the machine where power is required. Hydraulic systems have become a well-known and well understood arrangement for transferring power from the power source to an arbitrary location which is often preferred, despite is relative complexity, since it offers the advantages of providing potentially precise remote control, efficient transfer of large amounts of power and freedom from constraints imposed by the geometry of the machine, which may need to be varied as the machine is used.
Therefore, hydraulic systems have been used in many applications where the machines are mobile and/or where relatively large forces may be required to provide controlled relative motion of parts of the machine. Well-recognized applications include power steering on automobiles and mechanisms for moving materials relative to the machine, such as earth-moving equipment, large snow plows, mobile cranes and the like.
It is also a common requirement, for economy, ease of maintenance or storage and the like, to provide the capacity to reconfigure the machine at will by providing folding or telescoping portions or removal of large portions of the machine such as for maintenance or seasonal storage or to provide for multiple uses of a single power source in a basic machine having a variety of interchangeable attachment mechanisms. To accommodate such arrangements and mechanisms, it is often convenient or, in some cases, necessary, to provide for disconnection of hydraulic fluid-carrying lines with convenient mechanisms such as a so-called quick-connect coupler (sometimes also referred to as a quick-disconnect coupler or simply “coupler” when the context is evident to identify the type of coupler as being of this type). These arrangements are often provided as a pair of mating fittings which can be securely attached to each other or separated by hand, ideally without the use of tools, and requiring very little force to be manually applied.
The mechanical advantage necessary to achieve such a function is generally provided by retractable metal spheres similar to ball bearings which engage a generally tapered groove in a mating part of the coupler and are held in place by a movable ring which can allow or prevent retraction of the spheres. This ring is generally spring loaded to return it to a position where retraction of the spheres is prevented when the ring is not actively moved from that position. Thus, the spheres are forced into the non-retracted or extended position when the ring is released to engage the groove and to maintain the respective parts of the coupler securely affixed together. The tapering of the groove also provides compression between the mating parts of the coupler to avoid leakage and to resist internal pressure.
Unfortunately, improper seating of the spheres in the groove to form a secure connection of the mating parts may not be fully evident from the appearance of the coupler when a connection is made. If the parts of the coupler are not properly seated together and fully engaged, the coupler may become disconnected when pressure is applied, particularly if a non-axial force is also present and sufficiently coincides with the location of improperly constrained spheres. Any fluid flow, static pressure or associated mechanical arrangements such as check valves which are manipulated as coupler parts are joined together may also increase the difficulty of achieving proper seating together of the coupler parts.
Further, such a coupler, itself, does not usually have any arrangement to prevent flow from the fluid-carrying system or ingress of contaminants into it when the coupler is disconnected. Therefore, when such a coupler is used in a system carrying a particular fluid, such as hydraulic fluid, a check valve is usually employed adjacent to the coupler or integrally formed therewith to prevent loss of fluid and/or contamination. Such a provision is particularly necessary in, for example, hydraulic systems in which the fluid, to be sufficiently non-compressible and to posses other necessary properties, cannot be made non-toxic.
Unfortunately, such check valves can also allow the hydraulic system to become pressurized while a hydraulic line or conduit is disconnected. Such pressurization can occur through operation of the machine with the line disconnected or even through environmental circumstances such as an increase in ambient temperature causing expansion of the hydraulic fluid. If a hydraulic line is connected while the system is pressurized against the check valve, the system will not be functional since the check valve will continue to resist fluid flow unless and until the pressure is overcome.
In this regard, it should be noted that most hydraulic systems use recirculating flow of fluid and two hydraulic lines are generally used to support fluid flow in opposite directions into or out of the machine and part, respectively. Check valves are generally used on both sides of each coupler to avoid both fluid loss and contamination. Fluid flow into the machine or part tends to counteract any existing pressure in the line and thus does not present a problem. However, fluid pressure corresponding to the outward direction of flow from the machine or part will maintain the check valve in a closed position, preventing flow during operation of the machine. Accordingly operation of the machine cannot provide for opening of the check valve since operation provides pressure in the same direction as any existing pressure in the hydraulic system.
Therefore, it is conventional to provide a mechanical arrangement to hold check valves open on both sides of the coupler when the coupler parts are connected. However, if the line is pressurized, any such mechanical arrangement will prevent the coupler parts from seating together to make a connection and thus pressure against the check valve must be released whenever a connection of a disconnectable line is made.
At the present state of the art, the only technique available and consistent with the operation of a quick-connect coupler is to unseat the check valve manually; generally by using a punch which is placed against the moveable portion of the valve and struck with an implement such as a hammer. Neither of these tools are generally used in other operations on the machine generally performed during operations requiring the connection of hydraulic lines; thus presenting a substantial inconvenience. Also, while the check valve is generally made of steel in a ball-shaped or pointed configuration, the punch or other tool must be a specially made of a softer material such as brass to avoid or at least minimize damage thereto resulting in a relatively non-durable tool. For this reason, use of a tool of softer material often results in particles of the punch being removed and deposited within the valve or coupler part from which they can become dislodged, circulate through the system and cause damage to pumps, control valves and hydraulic actuators or prevent proper functioning of the check valves. Valves of pointed configuration tend to increase such chipping of the punch. In practice, however, maintenance personnel will tend to use any tool available, such as an ordinary screwdriver, which is much more likely to damage the check valve and produce particles or chips of harde
Hirsch Paul J.
Whitham Curtis & Christofferson, P.C.
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