Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01B—MACHINES OR ENGINES, IN GENERAL OR OF POSITIVE-DISPLACEMENT TYPE, e.g. STEAM ENGINES
  • F01B11/00—Reciprocating-piston machines or engines without rotary main shaft, e.g. of free-piston type
  • F01B11/004—Reciprocating-piston machines or engines without rotary main shaft, e.g. of free-piston type in which the movement in the two directions is obtained by two single acting piston motors, each acting in one direction
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L23/00—Valves controlled by impact by piston, e.g. in free-piston machines
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B9/00—Piston machines or pumps characterised by the driving or driven means to or from their working members
  • F04B9/08—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being fluid
  • F04B9/12—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being fluid the fluid being elastic, e.g. steam or air
  • F04B9/123—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being fluid the fluid being elastic, e.g. steam or air having only one pumping chamber
  • F04B9/1235—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being fluid the fluid being elastic, e.g. steam or air having only one pumping chamber the movement of the pump piston in the two directions being obtained by two single-acting piston fluid motors, each acting in one direction

Definitions

• This invention relates to reciprocable devices, and more particularly to a reciprocable device having an improved valving system for ensuring dependable switching of the reciprocable member travel direction during operation.
• Reciprocable devices typically include a reciprocable member which reciprocates to perform a useful function, such as pumping a flowable material, compressing a gas, metering a fluid or providing a reciprocating output for other purposes.
• a driving fluid under pressure which may be either a liquid or a gas, is commonly used to reciprocate the reciprocable member.
• the reciprocable member may be a piston having first and second faces which are alternately exposable to driving fluid under pressure and to exhaust.
• a valve or valving system is provided for controlling the exposure of the piston faces to the pressurized driving fluid and to exhaust.
• the valve system In order for the valve system to perform its function, it typically includes one or more valve elements which must be moved periodically from one position to another to bring about reciprocation of the piston. Movement of the reciprocable member can be used to control movement of the valve elements.
• Reciprocating devices of the type described are shown, for example, in U.S. Pat. No. 4,610,192 to Hartley et al.
• the construction disclosed therein employs a bistable toggle mechanism which is driven just over center by energy from the piston and then driven by stored spring energy.
• the toggle action reverses the pressure and exhaust valves to bring about a reversal of movement of the reciprocable member.
• the valves in this prior art system are fluid pressure biased.
• This invention provides a valving system for a reciprocable device of the type discussed, which is even easier to switch over, does not require a strong spring force to actuate, and provides for a mechanical backup in case of a valve jam, so that valve switchover and consequent dependable operation of the reciprocable device is assured.
• the invention provides a reciprocable device, in which a spool valve movable between first and second positions is employed for controlling the supply and exhaust of the driving fluid under pressure to and from the first and second driving faces of a reciprocable member.
• the reciprocable device also includes a bistable spring device having first and second states and a neutral position therebetween and a mechanism for drivingly coupling the reciprocable member and the bistable spring device so that the reciprocable member can move the bistable spring device from one of its states through the neutral position.
• the resilience of the bistable spring device at least assists in moving the bistable spring device from its neutral position to the other state thereof.
• the bistable spring device is coupled to the spool valve so that movement of the bistable spring device to the other state at least assists in driving the spool valve from one of the first and second positions to the other one thereof.
• it is the driving fluid under pressure which drives the reciprocable member in both directions.
• the reciprocable member is driven in both directions solely by the fluid under pressure.
• one or more drive springs can be employed to assist in driving the reciprocable member, none is required.
• a spool valve, and particularly a spool valve having the features described below, is relatively easy to move. This coupled with the lack of any need for a drive spring which would be compressed and therefore take energy from the system as the reciprocable member moves in one direction, reduce the likelihood of stalling due to failure of the valving system to switch over.
• bistable spring device fails for some reason to complete the switching of the valving system from one of its positions to the other one. Should this condition occur, because of a jammed valve or some other mishap, the reciprocable member continues its movement in the same axial direction, thereby eventually causing actuation of the valving system to its other position.
• This feature of the invention preferably employs, but does not require a spool valve.
• the spool valve is preferably constructed such that the valve body includes on its outer surface thereof a plurality of alternating annular lands and grooves, with the lands each including a sealing surface thereon, such as an o-ring.
• the valve body is slidable axially within a valve chamber, with alternating annular undercuts or grooves and lands being arranged on the inner wall surface defining the chamber. In both of the spool valve's operating positions, the valve body lands are sealingly engaged with corresponding lands on the valve chamber surface, and to move from one position to the other the valve body travels axially a distance equivalent to the distance between two adjacent valve chamber lands.
• the spool valve is hydraulically balanced without a substantial fluid pressure bias when in either of its first and second positions.
• the valve is held in each of its two operating positions only by virtue of a biasing force from the bistable spring device, which biases the valve body against a stop means until the initiation of valve switchover, as well as the friction generated by the sealing engagement between each o-ring and its corresponding valve chamber land. Consequently, a relatively low spring force is required to initiate movement of the spool valve between positions.
• Yet another important feature of the invention is the annular undercuts or grooves between the valve chamber lands, which serve as fluid inlet and outlet ports for the spool valve, rather than the simple drilled bores which are typically used in the prior art.
• annular undercuts provide a substantially frictionless travel path for the o-rings between adjacent valve chamber lands.
• FIG. 1 is an enlarged fragmentary sectional view through a reciprocable device constructed in accordance with the teachings of this invention, showing details of a preferred form of spool valve and bistable spring device;
• FIG. 2 is an axial sectional view of the reciprocable device illustrated in FIG. 1, showing the reciprocable member moving toward the right, and the bistable spring device about to pass through its neutral position;
• FIG. 3 is an enlarged fragmentary sectional view similar to FIG. 1, showing the bistable spring device and the spool valve just after moving into their alternative positions responsive to the rightward movement of the reciprocable member;
• FIG. 4 is an axial sectional view similar to FIG. 2, showing the reciprocable member moving toward the left;
• FIG. 5 is an enlarged fragmentary sectional view similar to FIG. 1, showing the bistable spring device and the spool valve just after moving back to their first positions responsive to the leftward movement of the reciprocable member.
• FIGS. 1 through 5 show a reciprocable device 11 (FIGS. 2 and 4) which includes a housing 13 defining a chamber or cylinder 15 in which a reciprocable member or piston 17 is slidably mounted for reciprocating movement.
• the piston 17 could also comprise a diaphragm, bellows, or the like.
• the reciprocable device is a pump; however, the reciprocable device may be a compressor, meter or serve some other purpose.
• the piston 17 can be of different constructions, in the form illustrated, it includes piston sections 19 and 21 joined together by a shaft 23 and having driving faces 25 and 27 and pumping faces 29 and 31. With this arrangement, the chamber 15 is divided into driving chambers 33 and 35 at the opposite ends of the piston 17 and pumping chambers 37 and 39 between the piston sections 19 and 21 and a partition 41.
• a spool valve 43 controls the supply of driving fluid under pressure from a supply source 45 to the driving chambers 33 and 35, and also controls the exhausting of the driving chambers 33 and 35 to atmosphere or other place of reduced pressure.
• the piston 17 is reciprocated in the chamber 15.
• fluid in the pumping chamber 37 is forced by the piston section 19 through an outlet line 47 and an outlet check valve 48 to a location where it is to be utilized, and fluid is drawn in through an inlet check valve 49 and an inlet line 50 into the pumping chamber 39.
• the spool valve 43 comprises a valve housing 55 (FIG. 1) having an inner wall surface 56 which defines a generally cylindrical valve chamber 57.
• the inner wall surface 56 of the valve housing 55 is comprised of a series of alternating annular lands 58 and annular undercuts or grooves 59.
• Slidably mounted axially about a rod 61 within the valve chamber 57 is a spool valve body 63 which has an exterior surface 65 formed of an alternating series of annular lands 67 and grooves 69.
• a plurality of o-rings 71 which are oriented so that when the valve body 63 is stopped in a position wherein the valve housing lands 58 and the valve body lands 67 are aligned, each land 58 is in sealing engagement with a respective o-ring 71.
• the rod 61 and the valve body 63 are spaced by an annular gap 72, so that the rod 61 may move axially independently of the valve body 63.
• the rod 61 extends leftwardly out of the valve chamber 57 into a driving fluid exhaust plenum 73.
• a bumper nut 75 On the leftmost end of the rod 61 is threadedly mounted a bumper nut 75 which is guided axially within the plenum 73 by a plurality of stop ribs 77 mounted longitudinally on the surface defining the plenum 73.
• the spool valve rod 61 also extends rightwardly out of the valve chamber 57 through an opening 79 in an end plate 81.
• This rod extension portion 83 includes a pair of stepped diameter increases 85 and 87 (FIG. 3) culminating in a large diameter coupling portion 89.
• the coupling portion 89 of the rod extension portion 83 is attached to the leftmost end or attachment portion 93 of the piston shaft 23, in such a manner as to ensure that there is lost motion between the two elements.
• the attachment portion 93 of the shaft 23 has a greater diameter than the remainder of the shaft and is received within a lost motion chamber 95 in the coupling portion 89 of the rod 61.
• the attachment portion 93 of the shaft 23 moves axially within the chamber 95 until it contacts one of two chamber walls 99 and 101, after which, by virtue of the contact between the coupling portion 89 and the attachment portion 93, the coupling portion 89 is either pushed or pulled to reciprocate in response to the reciprocation of the piston 17.
• the reciprocable device 11 includes a bistable spring device 102, comprising identical rigid levers 103 and 105, which may be constructed of stainless steel, and identical U-shaped springs 107 and 109 which are mounted within respective chambers 111 and 113.
• the levers 103 and 105 have tabs (not shown) on the outer ends thereof, which are received by openings (not shown) in the U-shaped springs 107 and
• the springs 107 and 109 may be integrated into one spring, interconnected by a web such as that shown in the 4,610,192 patent, or may be distinct spring elements, as shown.
• the coupling portion 89 has recesses 115 and 117 which progressively widen as they extend radially toward the periphery of the coupling portion 89 and this allows each of the levers to pivot about a pivot axis at the inner end of the associated recess. Because the levers 103 and 105 are biased toward the coupling portion 89, it forms pivot axes for the levers by virtue of the progressively widening nature of each of the recesses 115 and 117.
• the spool valve body 63 is seated against the stop ribs 77 and held in position by the spring device 102.
• Driving fluid under pressure is supplied from the supply source 45 through a fluid line 119 into an annular chamber portion 121 of the spool valve 43.
• the spool valve body 63 is in a first position at this juncture, permitting the fluid to exit the chamber portion 121 via a fluid line 123 which communicates with the driving chamber 33.
• the influx of pressurized driving fluid into the driving chamber 33 drives the piston 17 to the right, thereby causing pressurized pumping fluid to exit pumping chamber 37 through exhaust line 47 and driving fluid to be exhausted from driving chamber 35 through an exhaust line 125 which communicates with an annular chamber portion 126 of the spool valve 43. From the annular chamber portion 126, the exhaust fluid flows through an exhaust passage 127 to atmosphere, a waste sump, or some other low pressure application. With regard to the bistable spring device 102, it is apparent that the movement of the piston 17 to the right moves the attachment portion 93 to the right through the chamber 95, until it impacts the end wall 101 of the coupling portion 89.
• FIG. 3 shows the device with the piston 17 beginning its leftward travel, and the spool valve body 63 having been translated into its second axial position.
• the resilience of the springs 107 and 109 rapidly forces the levers farther over center and into their second position, pivoted to the right.
• This rapid movement of the levers 103 and 105 becomes stronger as the levers travel farther past the over center point, pushing the coupling portion 89 and the associated rod 61 equally rapidly to the right, thereby initiating movement of the spool valve body to its second axial position by virtue of a small impact of the bumper 75 on the spool valve body 63.
• the exhaust chamber 73 acts as another lost motion device, ensuring in conjunction with the lost motion chamber 95 that the spool valve 43 is not actuated to its alternate position until the piston 17 has traveled a sufficient stroke distance.
• the spring biased levers 103 and 105 are arranged to form an over center device, in order to provide the impetus necessary to move the spool valve 43 from one to another of its two positions.
• a mechanical backup to ensure the proper operation of the over center device. If for any reason switchover is not initially achieved by the bistable spring device 102, an advantage of the instant invention over the prior art is that the piston itself provides a backup means for ensuring that the bistable spring device 102 is able to switch the valve to its alternate position.
• the reciprocable device 11 is shown with the valve 43 in its second position. Consequently, because of the repositioned o-rings 71, the pressurized driving fluid from the supply line 119 is delivered into a different annular chamber portion 129.
• the flow line 123 into the driving chamber 33 is now shut off from the supply line 119 by an intervening o-ring 71, and the fluid is now redirected into the fluid line 125 which communicates with the other driving chamber 35.
• the influx of pressurized driving fluid into the driving chamber 35 reverses the travel direction of the piston, driving it to the left, thereby causing pressurized pumping fluid to exit pumping chamber 39 through exhaust line 51 and driving fluid to be exhausted from the driving chamber 33 through the fluid line 123.
• the fluid line 123 communicates with the exhaust plenum 73 through an annular chamber portion 130 of the spool valve 43, as shown.
• the movement of the piston 17 back to the left moves the attachment portion 93 to the left through the chamber 95, until it impacts the end wall 99 of the coupling portion 89. This impact begins to push the coupling portion 89 to the left, thereby pivoting the levers 103 and 105 through their neutral position, and also pushing the spool valve rod 61 to the left as shown in FIG. 5.
• FIG. 5 shows the attachment portion 93 of the piston shaft 23 beginning its rightward motion again as a result of the valve switchover, it having already moved rightwardly away from abutting contact with the end wall 99.
• the spring biased levers 103 and 105 provide the impetus necessary to move the spool valve 43 from one to another of its two positions.
• the piston 17 provides a mechanical backup to ensure that the switchover occurs. Should the spring device 102, moving from its neutral position to its over center position as disclosed above, fail to complete movement of the valve 43 from its second to its first position, because of a valve jam or the like, the piston 17 will continue to move toward the left.
• the valves are biased by the fluid pressure in the system, requiring a larger bistable spring force to overcome the fluid pressure bias in order to switch the valves.
• a strong spring must be used to assure switching of the valves.
• This relatively high spring force holds the reciprocable member in either of two positions even when the device is not in use, and as a consequence, the seating surfaces of the valves tend to take an undesirable permanent set.
• the spool valve 43 is designed to be held in either of its positions merely by virtue of the relatively small spring force created by the bistable spring, which holds the valve body 63 in position prior to initiation of valve switching, in order to eliminate the possibility of unintentional switching.
• the friction developed by the sealing engagement between the o-rings 71 and their corresponding lands 58 also serves as a secondary means for holding the valve body in position.
• the bistable spring 102 need only overcome this frictional force to initiate movement of the valve body 63 from one position to another, permitting the use of a less powerful spring.
• An additional advantage of the present invention is the use of the fully annular grooves or undercuts 59 to provide the inlet and outlet fluid flow passages for the spool valve 43, rather than simple drilled bores that are typically used in the prior art.
• the advantage of the annular undercuts is that as the valve body 63 travels axially from one of its positions to the other one, each of the o-rings 71 moving from one land 58 to the next, the o-rings encounter no friction as they travel over the annular undercuts.
• valve body 63 once a sufficient force has been applied to the valve body 63 to initiate motion thereof, overcoming the friction due to the sealing engagement between each of the o-rings 71 and its corresponding land 58, the valve body will have sufficient momentum, from the acceleration caused by the release of energy from the bistable spring, to travel an axial distance equivalent to the distance between lands 58, and thus sufficient to move into its other position. The frictionless travel of the o-rings across the undercuts 59 will not degrade that momentum.
• a spool valve is a versatile valve in that it may control the flow of a number of different fluids and fluids of different pressures simultaneously. Consequently, the inventive system may be utilized in more complex and interdependent fluid flow systems than is possible using a prior art system.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Multiple-Way Valves (AREA)
• Fluid-Driven Valves (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=22469684

Family Applications (1)

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Citations (4)

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• 1993
  • 1993-10-13 US US08/135,791 patent/US5505593A/en not_active Expired - Lifetime
• 1994
  • 1994-09-30 TW TW083109066A patent/TW285702B/zh active
  • 1994-10-05 WO PCT/US1994/011321 patent/WO1995010690A1/en not_active Ceased
  • 1994-10-05 DE DE69432594T patent/DE69432594T2/de not_active Expired - Lifetime
  • 1994-10-05 EP EP94930054A patent/EP0723624B1/en not_active Expired - Lifetime
  • 1994-10-05 EP EP01112058A patent/EP1130216A3/en not_active Withdrawn

Patent Citations (4)

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