DESC:Field of invention
The present invention relates to pneumatic drive systems, and more particularly to an improved self-actuated pneumatic drive system.

Background of the invention
There are various types of pneumatic drive systems available in market that independently performs the task of moving and controlling the mechanism. Development in the pneumatic drive devices has grown beyond imagination. In general, various types of pneumatic drive systems are available in the art and each of them has its own advantages and limitations.
Currently available pneumatic drive systems particularly used in liquid pump device utilizes stroke direction change mechanism that includes spool valve with or without D-slide valves.
Conventionally, existing pneumatic drive systems includes the directional control valve which comprise a single cylindrical spool with spring loaded detent which is operated by spring loaded mechanical lever or air pilot. However, the single spool is inadequate to transfer efficient energy and complete air flow from compressor to drive unit. Further, the energy which returns from drive unit to atmosphere is in an overrunning load condition. Furthermore, conventionally, in direction change systems, the spool valve is hold by spring loaded detent and movement achieved using spring loaded lever mechanically or with sensing or poppet valves leads to actuate and control pilot force on main spool. Unfortunately, many times it causes incomplete stroke of spool which lead to stalling of self-actuated pneumatic drive system. Furthermore, if the spool valve used with D slide valve, then more pilot force is required to shift/move the spool as friction between slide valve and plate acting as additional resistance to spring loading. However, on low pressure it reduces the performance of system and it may increase the possibilities of stalling of the self-actuated drive system.
Conventionally, all these direction change systems either installed at a distance or on top of the drive or in front of the drive cylinder, therefore inlet and exhaust paths are long and narrow which results in delayed action of direction change that reduces the performance of system especially in liquid pumping devices. In liquid pumping devices high pulse is generated at stroke direction change.
In prior art during return cycle of these systems compressed air is released to atmosphere in very short period which results in cooling of outgoing air . More specifically, air inlet and outlet paths are separate and continuous cooling results in reducing temperature to form icing due to moisture contained in air. This ice is accumulated in narrow flow path and results in performance drop leaded to stalling or stopping of system to function.
Reciprocating pneumatic drive system’s capacity is determined by speed of direction change and flow rate of inlet and outlet function. The prior art systems have limitation on flow path sizes and lengths and hence are not very efficient to perform especially at high speeds and loaded condition.
Accordingly, there exists a need of an improved self-actuated pneumatic drive system that overcomes all the drawbacks of the prior art.

Objects of the invention
An object of the present invention is to provide an improved self-actuated pneumatic drive system which eliminates use of any mechanical system such as a spring in pneumatic operation.
Another object of the present invention is to provide an improved self-actuated pneumatic drive system which facilitates stall free operation with minimum movement of the pilot member in pneumatic stroke direction changeover valve systems.
Furthermore, object of the present invention is to achieve lowest pulsation on output fluid pressure at high speed and load condition shaving higher flow rate and pressure for fluid pumping apparatus.
Another object of the present invention is to provide an improved self-actuated pneumatic drive system which can be used in high humid conditions without any interruption in performance due to ice formation.
One more object of the present invention is to provide an improved self-actuated pneumatic drive system whichis useful in manual push-pull operated, pilot operated and solenoid operated direction control valves in pneumatic or similar fluid systems.
Summary of the Invention
The present invention provides an improved self-actuated pneumatic drive system that comprises a double acting pneumatic cylinder assembly configured with an inner holding tube positioned therein. The inner holding tube includes a floating member axially disposed therein. The system includes a top valve mounted on with a top end cap through the inner holding tube. The top valve has a top sliding member slidably positioned thereon. The top sliding member is slidably disposed inside a top exit manifold. The system includes a bottom valve mounted on with a bottom end cap through the inner holding tube. The bottom valve has a bottom sliding member slidably positioned thereon. The bottom sliding member is slidably disposed inside a bottom exit manifold. The bottom sliding member interconnects to the top sliding member through the floating member. The system includes a pilot member that is slidably disposed into the floating member. The pilot member is configured to be pushed or pulled by a connecting rod. The system includes another pair of rods that connect to a coupling end through the connecting rod. The rods connect to a disc that is configured to move within a cavity of the double acting pneumatic cylinder assembly during actuation thereof.

The pilot member is pulled in a bottom position when the disc is at a bottom dead position such that the floating member is pushed upward upon application of a predetermined pressure on a surface area of the sliding member through the pilot member and the floating member. In this position, the bottom sliding member closes a port defined on the bottom end cap of the bottom valve and opens a port defined on the top end cap on the top valve such that the disc starts moving in the upward direction as pressure on top side of the disc is released and applied from bottom side.

The pilot member is pushed in top position when the disc is at a top dead position such that the floating member is pushed downward upon release of the predetermined pressure on a surface area of the sliding member through openings of the pilot member and floating member. In this position, the sliding member closes the port on top valve and opens the port on bottom valve such that the disc starts moving in the downward direction as pressure on bottom side of the disc is released and applied from top side.

The pilot member moves in a reverse direction with respect to the movement of the floating member to create exponential opening on the ports of the floating member through which the compressed air (A) is passed or returned thereby causing movement of the floating member. However, even if the movement of the pilot member is stopped then the sufficient force is exerted by the opening on the floating member thereby leading to movement of the floating member.

Brief description of the drawings
FIG. 1 shows an exploded view of an improved self-actuated pneumatic drive system constructed in accordance with the present invention;
FIG. 2 is a cross sectional view of the improved self-actuated pneumatic drive system of FIG. 1;
FIG. 3 is a cross sectional view of the improved self-actuated pneumatic drive system of FIG. 1; and
FIG. 4 is a partially expanded view of the improved self-actuated pneumatic drive system of FIG. 3.

Detailed Description of the invention
The foregoing objects of the present invention are accomplished, and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
Accordingly, the present invention provides the self-actuated pneumatic drive system with the stroke direction change mechanism. The stroke direction change mechanism is also useful for pneumatic DC valve in pneumatic systems. The stroke direction change mechanism includes exponential air pilot with differential resultant force exerting area sliding valve mechanism. It facilitates stall free, rapid, full in-out flow, low pulse generating change of a stroke direction in a pneumatic drive system.
This present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.
In the following description, the terms “upward movement” and “downward movement” used in relation to the self-actuating pneumatic drive system of the present invention are for illustrative purpose. However, it is understood here that the present invention can be advantageously utilized in any direction, such as for example “horizontal movement”, “angular movement”, “upside down movement” and the like.
Referring to FIGS. 12, 3 and 4, in one preferred embodiment, an improved self-actuated pneumatic drive system (200) (hereinafter, “the system (200)”) in accordance with the present invention is shown. The system (200) comprises a double acting pneumatic cylinder assembly (10), an inner holding tube (20),a floating member (30), a top valve (40), a bottom valve (50), a top end cap (60) a bottom end cap (70), a top sliding member (80), a bottom sliding member (90), a top exit manifold (100), a bottom exit manifold (110), a pilot member (120), a connecting rod (130), a pair of rods (140), a coupling end/arrangement (150) and a disc (160).
Referring again to FIGS 1 2, 3 and 4, the self-actuated pneumatic drive system (200) is designed such that the cylinder assembly (10) is configured with the inner holding tube (20). The Floating member (30) is axially disposed inside the inner holding tube (20). The top valve (40) and the bottom valve (50) are respectively mounted on the top end cap (60) and the bottom end cap (70) using the inner holding tube (20). The top sliding member (80) and bottom sliding member (90) are slidably disposed respectively over top valve (40) and bottom valve (50) and are interconnected through floating member (30). The top sliding member (80) and bottom sliding member (90) respectively slidably disposed inside to the top exit manifold (100) and bottom exit manifold (110) respectively. The pilot member (120) is slidably disposed in to the floating member (30) that is either pushed or pulled by connecting rod (130).
The pair of rods (140) is connected to the coupling end (150) via connecting rod (130). The system (200) is coupled through the coupling arrangement (150) to any suitable apparatus such as a pumping apparatus. The disc (160) is attached with the pair of rods (140) and movably positioned within the cavity of the cylinder (10) for being capable of actuating therein. The compressed air (A) input is given through an inlet/pressure port (1) on the top exit manifold (100).The top exit manifold (100) includes a cavity, an main air inlet/ pressure port (1) and cylinder air inlet and return port (2a).The bottom exit manifold (110) includes a cavity and a cylinder air inlet and return port (2b). The pressure port (1) is on a top portion of the manifold (100) through which main air input is given to self-actuating pneumatic drive mechanism (200). The compressed air (A) is fed to drive cylinder (10) on either sides of disk (160) through cavity of sliding members (80 and 90), passage created by holding tube (20) and floating member (30) and ports on valve bodies (40 and50) .The fluid pressure acts on a surface area of the disc (160) to generate required force and displacement to do work by the self-actuating pneumatic system (200). The required force is the minimum force generated by operating air pressure at which movement of the disk (160) and floating member (30) is initiated.
Again referring to FIG. 12, 3 and 4, in operation, the pilot member (120) is pulled in bottom position when the disc (160) is at bottom dead position of the stroke. The floating member (30) is pushed upward as a pressure of at least 0.25 bar is applied on a surface area of the sliding member (90) through the openings on the members (120and 30). The direction of the disc (160) is reversed due to vertical or downward linear movement of the sliding members (80and 90). The bottom sliding member (90) closes the port on valve body (50) and opens the port on valve body (40) positioned on either caps of the cylinder (10) and the disc (160) starts moving in the upward direction as pressure on top side of the disc (160) is released and applied from bottom side.
In accordance with the present invention when the disc (160) is at top dead position of the stroke, the pilot member (120) is pushed in top position. The floating member (30) is pushed downward as pressure on a surface area of the sliding member (90) is released through the openings on the members (120and 30). The direction of the disc (160) is reversed due to movement of the sliding members (80 and 90). The sliding member (80) closes the port on top valve (40) and opens the port on bottom valve (50) positioned on either caps of the cylinder (10) and the disc (160) starts moving in the downward direction as pressure on bottom side of the disc (140) is released and applied from top side.
In the context of the present invention, the pilot member (120) moves in a reverse direction with respect to the floating member (30) movement to create exponential opening on the ports/holes (not numbered) of the floating member (30) through which the compressed air (A) is passed or returned thereby causing movement of the floating member (30). However, even if the movement of the pilot member (120) is stopped, when the sufficient force is exerted by the opening on the floating member (30) it leads to movement of the floating member (30). It is understood here that the sufficient force referred above is a minimum force generated by operating air pressure at which movement of the floating member (30) is initiated. Accordingly, a substantially very small opening due to the movement of the pilot member (120) caused by the movement of disk (160) at port crossing event results in a non-stop movement of the floating member (30) till it’s full stoke thereby facilitating stall free operation in accordance with the objectives of the present invention.
In operation, the improved self-actuated pneumatic drive system (200) facilitates stall free operation with minimum movement of the pilot member in pneumatic stroke direction changeover valve systems without using any spring or similar mechanical system.In operation, the improved self-actuated pneumatic drive system (200)facilitates rapid, quick and fastest changeover as large, adequate port openings with shortest passage length (C)in a range of 3mm to 6mm, most preferably 5mm, which are possible in this construction with direct exposure of compressed air (A) from cylinder volume to atmosphere air (B) along flow path (D) during exit cycle as well as inlet compressed air (A) to cylinder volume during inlet cycle as large valve ports are directly installed on cylinder caps. When connected to fluid pumping apparatus lowest pulsation on output fluid pressure is achieved at high speed and load condition, having higher flow rates and pressures. This is beneficial especially in spray painting applications.
In operation, the improved self-actuated pneumatic drive system prevents ice formation on exit ports of drive system as common inlet and exit port is used to inlet and exit of compressed air (A). As a zero effect of icing, uninterrupted performance is possible by drive system in high humid conditions.
In operation, the stroke direction change mechanism used is useful mainly for self-actuating reciprocating pneumatic drive system. The stroke direction change mechanism used in an improved self-actuated pneumatic drive system is also useful in manual push-pull operated, pilot operated and solenoid operated direction control valves in pneumatic or similar fluid systems.
The foregoing description of specific members of the present invention has been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The members were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others, skilled in the art to best utilize the present invention and various members with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the scope of the present invention.
,CLAIMS:1) An improved self-actuated pneumatic drive system (200) comprising:
a double acting pneumatic cylinder assembly (10) having an inner holding tube (20) positioned therein, the inner holding tube (20) having a floating member (30) axially disposed therein;
a top valve (40) mounted with a top end cap (60)through the inner holding tube (20), the top valve (40) having a top sliding member (80) slidably positioned thereon, the top sliding member (80) being slidably disposed inside a top exit manifold (100);
a bottom valve (50) mounted with a bottom end cap (70) through the inner holding tube (20), the bottom valve (50) having a bottom sliding member (90) slidably positioned thereon, the bottom sliding member (90) being slidably disposed inside a bottom exit manifold (110), the bottom sliding member (90) interconnecting to the top sliding member (80) through the floating member (30);
a pilot member (120) slidably disposed into the floating member (30), the pilot member (120) configured to be pushed or pulled by a connecting rod (130); and
a pair of rods (140) connecting to a coupling end (150) through the connecting rod (130), the pair of rods (140) connecting to,
The disc (160) configured to be move within a cavity of the double acting pneumatic cylinder assembly (10) during actuation thereof.
2) The improved self-actuated pneumatic drive system (200) as claimed in claim 1, wherein the pilot member (120) is pulled in a bottom position when the disc (160) is at a bottom dead position such that the floating member (30) is pushed upward upon application of a predetermined pressure on a surface area of the sliding member (90) through the pilot member (120) and floating member (30).
3) The improved self-actuated pneumatic drive system (200) as claimed in claim 2, wherein the bottom sliding member (90) closes a port defined on the bottom end cap (70) the bottom valve (50) and opens a port defined on the top end cap (60) on the top valve (40) such that the disc (160) starts moving in the upward direction as pressure on top side of the disc (160) is released and applied from bottom side.
4) The improved self-actuated pneumatic drive system (200) as claimed in claim 1, wherein the pilot member (120) is pushed in top position when the disc (160) is at a top dead position such that the floating member (30) is pushed downward upon application of a predetermined pressure on a surface area of the sliding member (90) is released through openings of the pilot member (120) and floating member (30).
5) The improved self-actuated pneumatic drive system (200) as claimed in claim 4, wherein the sliding member (80) closes the port on top valve (40) and opens the port on bottom valve (50) positioned on either caps of the cylinder (10) and the disc (160) starts moving in the downward direction as pressure on bottom side of the disc (140) is released and applied from top side.
6) The improved self-actuated pneumatic drive system (200) as claimed in claims 2 and 4, wherein the predetermined pressure applied on a surface area of the sliding member (90) is at least 0.25 bar.
7) The improved self-actuated pneumatic drive system (200) as claimed in claim 1, wherein direction of the movement of the disc (160) is configured to be reversed in response to linear vertical movement of the top sliding member (80) and the bottom sliding member (90).