CA2379756C - Method and apparatus for a double acting reciprocating piston assembly - Google Patents
Method and apparatus for a double acting reciprocating piston assembly Download PDFInfo
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- CA2379756C CA2379756C CA 2379756 CA2379756A CA2379756C CA 2379756 C CA2379756 C CA 2379756C CA 2379756 CA2379756 CA 2379756 CA 2379756 A CA2379756 A CA 2379756A CA 2379756 C CA2379756 C CA 2379756C
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- piston assembly
- piston
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- 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
- F04B9/10—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being fluid the fluid being liquid
- F04B9/109—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being fluid the fluid being liquid having plural pumping chambers
- F04B9/111—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being fluid the fluid being liquid having plural pumping chambers with two mechanically connected pumping members
- F04B9/115—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being fluid the fluid being liquid having plural pumping chambers with two mechanically connected pumping members reciprocating movement of the pumping members being obtained by two single-acting liquid motors, each acting in one direction
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- General Engineering & Computer Science (AREA)
- Actuator (AREA)
- Compressors, Vaccum Pumps And Other Relevant Systems (AREA)
Abstract
A method and apparatus is provided which accomodates misalignments between the components of a double-acting free-floating piston assembly and a cylinder. A divider provides a barrier between two chambers within the cylinder. The divider is held in a fixed longitudinal position and accomodates misalignment by being movable relative to the cylinder within a lateral plane perpendicular to the longitudinal axis of the cylinder.
Description
METHOD AND APPARATUS FOR A DOUBLE-ACTING
RECIPROCATING PISTON ASSEMBLY
Field of the Inveation The present :invention relates to a method and apparatus for improving an arrangement for a double-acting reciprocating piston assembly and cylinder. More particularly, the reciprocating piston is a free floating piston and the method and apparatus relate to a structure that accommodates misa:iignment between components of the double acting reciprocating piston assembly and the cylinder.
Background of the Invention A reciprocating piston assembly that employs a free floating piston comprises a piston that divides a cylinder into a drive chamber and a compression chambesr. Fluid pressure in the drive chamber is controlled to provide a differential pressure between the drive chamber and the compression chamber to cause reciprocating movement of the piston. That is, to cause a compression stroke', fluid pressure within the drive chamber is higher than the fluid pressure in the compression chamber. To reverse the direction of piston movement, fluid pressure within the drive chamber is ~__°educed so that fluid pressure within the compression chamber is higher than fluid pressure within the drive chamber.
Such assemblies may be employed to compress a gas or to pump a 7Liquid. The drive fluid may be a gas or a liquid. lBy way of example, an assembly that employs an o:il as the drive fluid is commonly referred to as being hydraulically driven, whereas an assembly that employs pressurized air as the drive fluid is commonly referred to as being pneumatically driven.
In a double-acting reciprocating piston assembly, there are at least two compression chambers and fluid is compressed when the piston moves in both directions. When a free floating piston is employed, there are two drive chambers and respective drive and compression chambers alternate and cycle between successive intake and compression strokes.
FIG. 1 depicts a conventional double-acting free floating pisi~on assembly that comprises employs cylinders 101 and 102 which are welded to central flange 105. End plates 107 and 108 are screwed into and :seal respective ends of cylinders 101 and 102. A free floating piston assembly comprises two pisi~ons 110 and 112, which are connected to each other by rod 114. Defined within cylinder 101 are first compression chamber 120 between piston 110 and end plate 107, and first drive chamber 122 between piston 110 and central flange 105. Defined within cylinder 102 are second compression chamber 124 between piston 112 and end plate 108 and second drive chamber 126 between piston 112 and central flange 105.
Fluid flows .into first and second compression chambers 120 and 124 through respective one-way valves 132 and 136 and out of the same compression chambers 120 and :124 through respective one-way valves 134 and 135. Drive fluid flows into and out of first and second drive chambers 122 and 126 through respective fluid passages 140 and 142.
The double-acting reciprocating piston assembly of FIG. :1 operates as described in the following paragraphs.
When the free floating piston assembly moves to the left in FICs. 1, piston 110 is in the midst of a compression stroke. Fluid within first compression chamber 120 is compressed and expelled therefrom through one-way valve 134 when pressure within first compression chamber 120 is greater than the pressure within the pipe connected to one-way valve 134. Drive fluid is directed to first drive chamber 122 through fluid passage 140 to propel first piston 110 towards end plate 107.
Simultaneously, piston 112 is in the midst of an intake stroke, as drive fluid flows out from second drive chamber 126 through fluid passage 142, and new fluid fills expanding second compression chamber 124 through one-way valve 136.
When piston 110 completes its compression stroke, the free floating piston assembly reverses direction, and pi:~ton 110 begins an intake stroke and piston 112 begins a compression stroke. That is, with reference. to FIG. 1, the free floating piston assembly bE~gins to move to the right, when drive fluid is directed to second drive chamber 126 and flows out from first drive chamber 122.
RECIPROCATING PISTON ASSEMBLY
Field of the Inveation The present :invention relates to a method and apparatus for improving an arrangement for a double-acting reciprocating piston assembly and cylinder. More particularly, the reciprocating piston is a free floating piston and the method and apparatus relate to a structure that accommodates misa:iignment between components of the double acting reciprocating piston assembly and the cylinder.
Background of the Invention A reciprocating piston assembly that employs a free floating piston comprises a piston that divides a cylinder into a drive chamber and a compression chambesr. Fluid pressure in the drive chamber is controlled to provide a differential pressure between the drive chamber and the compression chamber to cause reciprocating movement of the piston. That is, to cause a compression stroke', fluid pressure within the drive chamber is higher than the fluid pressure in the compression chamber. To reverse the direction of piston movement, fluid pressure within the drive chamber is ~__°educed so that fluid pressure within the compression chamber is higher than fluid pressure within the drive chamber.
Such assemblies may be employed to compress a gas or to pump a 7Liquid. The drive fluid may be a gas or a liquid. lBy way of example, an assembly that employs an o:il as the drive fluid is commonly referred to as being hydraulically driven, whereas an assembly that employs pressurized air as the drive fluid is commonly referred to as being pneumatically driven.
In a double-acting reciprocating piston assembly, there are at least two compression chambers and fluid is compressed when the piston moves in both directions. When a free floating piston is employed, there are two drive chambers and respective drive and compression chambers alternate and cycle between successive intake and compression strokes.
FIG. 1 depicts a conventional double-acting free floating pisi~on assembly that comprises employs cylinders 101 and 102 which are welded to central flange 105. End plates 107 and 108 are screwed into and :seal respective ends of cylinders 101 and 102. A free floating piston assembly comprises two pisi~ons 110 and 112, which are connected to each other by rod 114. Defined within cylinder 101 are first compression chamber 120 between piston 110 and end plate 107, and first drive chamber 122 between piston 110 and central flange 105. Defined within cylinder 102 are second compression chamber 124 between piston 112 and end plate 108 and second drive chamber 126 between piston 112 and central flange 105.
Fluid flows .into first and second compression chambers 120 and 124 through respective one-way valves 132 and 136 and out of the same compression chambers 120 and :124 through respective one-way valves 134 and 135. Drive fluid flows into and out of first and second drive chambers 122 and 126 through respective fluid passages 140 and 142.
The double-acting reciprocating piston assembly of FIG. :1 operates as described in the following paragraphs.
When the free floating piston assembly moves to the left in FICs. 1, piston 110 is in the midst of a compression stroke. Fluid within first compression chamber 120 is compressed and expelled therefrom through one-way valve 134 when pressure within first compression chamber 120 is greater than the pressure within the pipe connected to one-way valve 134. Drive fluid is directed to first drive chamber 122 through fluid passage 140 to propel first piston 110 towards end plate 107.
Simultaneously, piston 112 is in the midst of an intake stroke, as drive fluid flows out from second drive chamber 126 through fluid passage 142, and new fluid fills expanding second compression chamber 124 through one-way valve 136.
When piston 110 completes its compression stroke, the free floating piston assembly reverses direction, and pi:~ton 110 begins an intake stroke and piston 112 begins a compression stroke. That is, with reference. to FIG. 1, the free floating piston assembly bE~gins to move to the right, when drive fluid is directed to second drive chamber 126 and flows out from first drive chamber 122.
Fluid within second compression chamber 124 is compressed and eventually expelled therefrom through one-way valve 138 when pressure within second compression chamber 124 is higher than pressure within the pipe connected to one-way valve 138. Meanwhile, fluid flowing through one-way valve 132 fil:Ls expanding first compression chamber 120.
Components for assemblies such as the one shown in FIG. 1, are typically manufactured in accordance with specifications which allow such components to be manufactured within specified tolerances. However, this may result in minor misalignments between components which cooperate with one another. For example, cylinders 101 and 102 are each weldE~d to central flange 105, and there might be a small misalignment between these two cylinders. Similarly, the attachment of rod 114 to piston 110 or piston 112 might be slightly off-center, as might be the bore hole through central flange 105. Rods and cylinders may themselves not be perfectly straight. "Run out"
is a term that quantifies how far a component is from being perfectly straignt. For a reciprocating piston assembly that is aligned within a cylinder" the straightness of the components is important for good alignment, so little or no run out is preferred. However, manufacturing components to reduce or eliminate run out becomes more difficult as the length of the components increases.
Components for assemblies such as the one shown in FIG. 1, are typically manufactured in accordance with specifications which allow such components to be manufactured within specified tolerances. However, this may result in minor misalignments between components which cooperate with one another. For example, cylinders 101 and 102 are each weldE~d to central flange 105, and there might be a small misalignment between these two cylinders. Similarly, the attachment of rod 114 to piston 110 or piston 112 might be slightly off-center, as might be the bore hole through central flange 105. Rods and cylinders may themselves not be perfectly straight. "Run out"
is a term that quantifies how far a component is from being perfectly straignt. For a reciprocating piston assembly that is aligned within a cylinder" the straightness of the components is important for good alignment, so little or no run out is preferred. However, manufacturing components to reduce or eliminate run out becomes more difficult as the length of the components increases.
The misalignment of components may result in accelarated wear of seals, such as the piston ring seals or the seals that seal between central flange 205 and rod 114. Manufacturing components to higher tolerances can reduce such problems, but this approach increases the cost of manufacturing.
Accordingly, there is a need for a design that will better accomodate minor misalignments.
Summary of the Iaveatioa An apparatus is provided that comprises:
(a) an elongated cylinder;
(b) double-acting free-floating piston assembly having a longitudinal axis, the piston assembly disposed and reciprocable within the cylinder;
(c) a divider providing a barrier between two chambers within the apparatus, wherein relative to the cylinder, the divider held in a fixed longitudinal position and the divider has an outer diameter that is less than the inner diameter of an annular cavity within which the divider is disposed, whereby the divider is movable within the annular cavity in a lateral plane perpendicular to the longitudinal axis of the cylinder; and (d) a dynamic seal between the divider and the piston assembly.
__ The divider i.s preferably located at an intermediate poi.rut between the ends of the cylinder and in :=such an arrangement the divider is held between two opposing portions of the cylinder_ . 'Che aaoparatus preferably furt:her comprises a flui.~:L ~4ea.l. between tre divider and the face of at least one of the opposing cylinder portions. If th~.ere is at fl<~nge associated with the junction whe~::e~ the two portions of the cylinder are joi::iecL together, the fluid seal can be between the d:i_v.ider and at least one of the opposing flange f=aces. The flanges can be joined to each other by c;canventional means, such as bolts. Such a sEaal allows movement of the divider in the lateral pane that is perpendicular to the longitudinal axi;:~ .
The divider preferably comprises a solid body with an opening l:hroughi which a portion of the piston assembly :~~s extendable.
In a preferred embodiment, the apparatus comprises:
(a) an elorlc~ated cylinder;
(b) double--acting free-floating piston assemb:Ly comprising an elongated member disposed between two pistons, the piston assemb:Ly disposed and reciprocable within title cylinder;
(c) four c'.amber~> within the cylinder, each of the chambers f-luidly isolated from the ot':Zer_s and defined by spaces between the cylinder and the piston assembly, the four chambers consisting of, two outer chamber;, each one defineci by a space between an end of the piston assembly and an end of the cylinder;
two inner chambers, each one defined by an annular space between the piston assembly and the cylinder; and (d) a divider providing a barrier between the two inner chambers, wherein the divider comprises an opening through which the elongated member extends, the opening having a shape and size matching than of the elongated member, wherein the div:ide.r :i.s disposed within a space with lateral dimensions larger than the divider such that an open space is provided around the lateral edges of the divider whereby the divider is movable relative to the cylinder within a lateral plane perpendicular to the longitudinal axis of the cylinder.
A dynamic seal is preferably employed to seal between the divider and the elongated member. The divider has a tl-:ickness that can accommodate at least one dynamic: seal.
In preferred embodiments the two pistons each have the same diameter, al..though the invention can be applied to an apparatus that employs pistons with di__-ferent~ ci.,~meter-s.
In preferred embodiments the elongated member is cylindrical and the divider is in the shape of a ring with a central hole through which the elongated member extends. The divider preferably has parallel flat surfaces which are held between two segments of the elongated cylinder.
Another preferred embodiment of the apparatus comprises:
(a) a free-floating piston assembly that comprises:
a first piston head having a first diameter;
a second piston head having a second diameter;
an elongated body disposed between and joined to each one of the first and second piston heads, the body having a longitunal portion with a length that is at least as long as a piston stroke, the longitudinal portion having a third diameter that is less than the first and second diameters;
(b) a first cylinder comprises:
a first bore within which the first piston head is reciprocable;
a first open end, through which the elongated body is extendable; and a first flange associated with the first open end;
(c) a second cylinder comprises:
I
-a second bore within which the second piston head is reciprocable;
a second open end, through which the elongated body is extendable; and a second flange associated with the second open end;
(d) a divider with a fixed longitudinal position between the first and second cylinders, the divider dividing an annular space defined between the elongated body and the first and second cylinders and between the first and second pistons, wherein the divider has an outer diameter that is less than the inner diameter of an annular cavity within which the divider is disposed, whereby the divider is movable within the annular cavity in a direction perpendicular to the longitudinal axis of the elongated body, the divider comprising an opening through which the elongated body is reciprocable;
(e) a dynamic seal between the divider and the elongated member; and (f) connectors for joining the first and second flanges together.
A method is provided for accommodating misalignment between a free-floating piston assembly and a cylinder. The method comprises:
reciprocating a first piston head within a longitudinal bore of a first elongated cylinder;
reciprocating a second piston head within a longitudinal bore of a second elongated cylinder, which is coaxial with the first elongated cylinder;
maintaining the first and second piston heads in a fixed spatial relationship by attaching the first and second piston heads to opposite ends of an elongated rigid member that has a smaller transverse cross-sectional area than each of the first and second piston heads;
separating a space between the first and second piston heads with a divider disposed between the first and second cylinders and around the elongated rigid member; and allowing the divider to move within a plane perpendicular to the longitudinal axis of the first and second cylinders by providing an open space around the lateral edges of the divider.
The method preferably further comprises dynamically sealing between the divider and the elongated rigid member.
Another embodiment of the preferred method relates to accommodating misalignment within a reciprocating apparatus comprising a double-acting free-floating piston assembly that comprises a rigid member disposed between two pistons. This embodiment of the method comprises:
- ~~
reciprocating the free-floating piston assembly along a longitudinal axis within a bore defined by a cylinder;
dividing an annular space between the free-s floating piston assembly and the cylinder, with a divider that rides on the rigid member;
holding the divider in a fixed location along the longitudinal axis; and allowing the divider to move within a plane perpendicular to the longitudinal axis by providing an open space around the lateral edges of the divider.
Brief Description of the Drawin~~s FIG. 1 is a section view of a prior art double-acting reciprocating piston arrangement with a free floating piston;
FIG. 2 is a section view of an embodiment of an improved double-acting reciprocating piston assembly with a free-floating piston. In this embodiment, an annular collar is moveable in directions perpendicular to the longitudinal axis of the assembly to accommodate minor misalignments between component parts. While this figure illustrates a specific embodiment of the invention, it should not be considered as restricting the spirit or scope of the invention in any way; and FIG. 3 is an enlarged section view of the annular collar of FIG. 2, disposed around a piston body between two cylinders and flanges.
Detailed Descriptioa of Preferred Smbodimeatts) With reference to FIG. 2 (and also FTG.3 which is an enlarged view of portions of the apparatus of FIG. 2), apparatus 200 comprises a double-acting free-floating piston assembly that is reciprocable within a hollow cylindrical body.
The hollow cylindrical body is defined by coaxial cylinders 201 and 202 which each have respective open ends attached to flanges 203 and 204, and closed ends covered by respective end plates 207 and 208. Flanges 203 and 204 are employed to join and align the open ends of cylinders 201 and 202.
The free-floating piston assembly comprises pistons 210 and 212 and elongated body 214.
Elongated body 214 is disposed between and attached to each one of pistons 210 and 212.
Elongated body 214 has a diameter that is less than the diameters of pistons 210 and 212. The length of elongated body 214 is at least as long as a full stroke of the piston assembly.
Piston 210 is reciprocable within a bore of cylinder 201 and piston 212 is reciprocable within a bore of cylinder 202. The longitudinal axis of cylinders 201 and 202 and their respective bores are aligned with each other in addition to being aligned with the lc>ngit.ud.ir~ai axis of the free-floatinc~ piston ::assembly.
Apparatus 200 ~:omprises a pair of drive chambers anc~ a p ii r: of compression chambers . One pair of chambers i~> outer chambers 220 and 224 defined by space:: within respective cylinders 201 and 202 between :r_espect:ive pistons 210 and 212 and respective end prates 207 and 208. The other pair of chambers is inner chambers 222 and 2a?6 defined by the :respective anr~ul.ar spaces between elongated body 214 and respective cylinders 201 and 202, between divider '205 and the .back sides of respective pisto~:~~~ 2.10 and 212. The pair of chambers that act as drive chambers depends upon the function of t=he apparatus.
In one embo~:li.ment of the example illustrated by FIGS. 2 and 3,. inner chambers 222 and 226 are prefera~,ly fille~:l with liquid and cuter chambers 220 and 224 are filled with a gas. If this apparatL.s is employed to pump a liquid using gas pressure directed too outer chambers 220 and 224, then these outer chambers acts as the drive chambers. For oi=her applications, the apparatus can be conf igureci too compress a c_~as in outer chamber. 220 and 224, in which case inner chambers 222 and 226 would act as the dr~.~ve chambers.
Apparatus 200 is operable as a pump or compressor in a manner si.mi:Lar tc> known app>aratuses with double-acting free-floating piston assemblies.
As shown by F~'~:C~. 7, tree recvprocating piston assembly' and the u~~linder within wL~~ich it i reciprocates can each be elongated bodies. Minor misalignments can occur even when the individual components are manufactured in compliance with specified dimensional tolerances. Whereas conventional apparatuses employing free-floating piston assemblies have required strict alignment between the pistons, the cylinders, the connecting rod, and the opening through the divider, the present apparatus accommodates minor misalignments by an arrangement that allows divider 205 to move in a plane perpendicular to the longitudinal axis of the cylinder.
In the illustrated embodiment, divider 205 is a flat ring-shaped plate with a central opening through which elongated body 214 extends. The inner diameter of the central opening matches the diameter of elongated body 214. As shown in the enlarged section view of FIG. 3, dynamic seals 230 are disposed between divider 205 and elongated body 214 to restrict fluid flow between inner chambers 222 and 226. Divider 205 is held within an annular cavity between cylinders 201 and 202, and flanges 203 and 204, which prevent divider 205 from moving in the longitudinal direction. The inner diameter of the annular cavity is larger than the outer diameter of divider 205 such that there is an open gap therebetween whereby divider 205 is free to move transversely of the axis of elongated body 214. Lateral movement of divider 205 is guided by the position of elongated~body 214. That is, if elongated body 214 is misaligned so that it is not perfectly centered on the apparatus' longitudinal axis, divider 205 rides on elongated body 214 and is carried to the off-center position of elongated body 214. Persons skilled in the art will understand that there are limits to the amount of misalignment that can be accommodated by such an arrangement. This arrangement is not intended to accommodate large misalignments, but it will accommodate minor misalignments so that components do not have to be manufactured to higher tolerances. Seals 231 are provided to restrict fluid from flowing out of inner chambers 222 and 226 between divider 205 and the ends of cylinders 201 and 202.
As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.
Accordingly, there is a need for a design that will better accomodate minor misalignments.
Summary of the Iaveatioa An apparatus is provided that comprises:
(a) an elongated cylinder;
(b) double-acting free-floating piston assembly having a longitudinal axis, the piston assembly disposed and reciprocable within the cylinder;
(c) a divider providing a barrier between two chambers within the apparatus, wherein relative to the cylinder, the divider held in a fixed longitudinal position and the divider has an outer diameter that is less than the inner diameter of an annular cavity within which the divider is disposed, whereby the divider is movable within the annular cavity in a lateral plane perpendicular to the longitudinal axis of the cylinder; and (d) a dynamic seal between the divider and the piston assembly.
__ The divider i.s preferably located at an intermediate poi.rut between the ends of the cylinder and in :=such an arrangement the divider is held between two opposing portions of the cylinder_ . 'Che aaoparatus preferably furt:her comprises a flui.~:L ~4ea.l. between tre divider and the face of at least one of the opposing cylinder portions. If th~.ere is at fl<~nge associated with the junction whe~::e~ the two portions of the cylinder are joi::iecL together, the fluid seal can be between the d:i_v.ider and at least one of the opposing flange f=aces. The flanges can be joined to each other by c;canventional means, such as bolts. Such a sEaal allows movement of the divider in the lateral pane that is perpendicular to the longitudinal axi;:~ .
The divider preferably comprises a solid body with an opening l:hroughi which a portion of the piston assembly :~~s extendable.
In a preferred embodiment, the apparatus comprises:
(a) an elorlc~ated cylinder;
(b) double--acting free-floating piston assemb:Ly comprising an elongated member disposed between two pistons, the piston assemb:Ly disposed and reciprocable within title cylinder;
(c) four c'.amber~> within the cylinder, each of the chambers f-luidly isolated from the ot':Zer_s and defined by spaces between the cylinder and the piston assembly, the four chambers consisting of, two outer chamber;, each one defineci by a space between an end of the piston assembly and an end of the cylinder;
two inner chambers, each one defined by an annular space between the piston assembly and the cylinder; and (d) a divider providing a barrier between the two inner chambers, wherein the divider comprises an opening through which the elongated member extends, the opening having a shape and size matching than of the elongated member, wherein the div:ide.r :i.s disposed within a space with lateral dimensions larger than the divider such that an open space is provided around the lateral edges of the divider whereby the divider is movable relative to the cylinder within a lateral plane perpendicular to the longitudinal axis of the cylinder.
A dynamic seal is preferably employed to seal between the divider and the elongated member. The divider has a tl-:ickness that can accommodate at least one dynamic: seal.
In preferred embodiments the two pistons each have the same diameter, al..though the invention can be applied to an apparatus that employs pistons with di__-ferent~ ci.,~meter-s.
In preferred embodiments the elongated member is cylindrical and the divider is in the shape of a ring with a central hole through which the elongated member extends. The divider preferably has parallel flat surfaces which are held between two segments of the elongated cylinder.
Another preferred embodiment of the apparatus comprises:
(a) a free-floating piston assembly that comprises:
a first piston head having a first diameter;
a second piston head having a second diameter;
an elongated body disposed between and joined to each one of the first and second piston heads, the body having a longitunal portion with a length that is at least as long as a piston stroke, the longitudinal portion having a third diameter that is less than the first and second diameters;
(b) a first cylinder comprises:
a first bore within which the first piston head is reciprocable;
a first open end, through which the elongated body is extendable; and a first flange associated with the first open end;
(c) a second cylinder comprises:
I
-a second bore within which the second piston head is reciprocable;
a second open end, through which the elongated body is extendable; and a second flange associated with the second open end;
(d) a divider with a fixed longitudinal position between the first and second cylinders, the divider dividing an annular space defined between the elongated body and the first and second cylinders and between the first and second pistons, wherein the divider has an outer diameter that is less than the inner diameter of an annular cavity within which the divider is disposed, whereby the divider is movable within the annular cavity in a direction perpendicular to the longitudinal axis of the elongated body, the divider comprising an opening through which the elongated body is reciprocable;
(e) a dynamic seal between the divider and the elongated member; and (f) connectors for joining the first and second flanges together.
A method is provided for accommodating misalignment between a free-floating piston assembly and a cylinder. The method comprises:
reciprocating a first piston head within a longitudinal bore of a first elongated cylinder;
reciprocating a second piston head within a longitudinal bore of a second elongated cylinder, which is coaxial with the first elongated cylinder;
maintaining the first and second piston heads in a fixed spatial relationship by attaching the first and second piston heads to opposite ends of an elongated rigid member that has a smaller transverse cross-sectional area than each of the first and second piston heads;
separating a space between the first and second piston heads with a divider disposed between the first and second cylinders and around the elongated rigid member; and allowing the divider to move within a plane perpendicular to the longitudinal axis of the first and second cylinders by providing an open space around the lateral edges of the divider.
The method preferably further comprises dynamically sealing between the divider and the elongated rigid member.
Another embodiment of the preferred method relates to accommodating misalignment within a reciprocating apparatus comprising a double-acting free-floating piston assembly that comprises a rigid member disposed between two pistons. This embodiment of the method comprises:
- ~~
reciprocating the free-floating piston assembly along a longitudinal axis within a bore defined by a cylinder;
dividing an annular space between the free-s floating piston assembly and the cylinder, with a divider that rides on the rigid member;
holding the divider in a fixed location along the longitudinal axis; and allowing the divider to move within a plane perpendicular to the longitudinal axis by providing an open space around the lateral edges of the divider.
Brief Description of the Drawin~~s FIG. 1 is a section view of a prior art double-acting reciprocating piston arrangement with a free floating piston;
FIG. 2 is a section view of an embodiment of an improved double-acting reciprocating piston assembly with a free-floating piston. In this embodiment, an annular collar is moveable in directions perpendicular to the longitudinal axis of the assembly to accommodate minor misalignments between component parts. While this figure illustrates a specific embodiment of the invention, it should not be considered as restricting the spirit or scope of the invention in any way; and FIG. 3 is an enlarged section view of the annular collar of FIG. 2, disposed around a piston body between two cylinders and flanges.
Detailed Descriptioa of Preferred Smbodimeatts) With reference to FIG. 2 (and also FTG.3 which is an enlarged view of portions of the apparatus of FIG. 2), apparatus 200 comprises a double-acting free-floating piston assembly that is reciprocable within a hollow cylindrical body.
The hollow cylindrical body is defined by coaxial cylinders 201 and 202 which each have respective open ends attached to flanges 203 and 204, and closed ends covered by respective end plates 207 and 208. Flanges 203 and 204 are employed to join and align the open ends of cylinders 201 and 202.
The free-floating piston assembly comprises pistons 210 and 212 and elongated body 214.
Elongated body 214 is disposed between and attached to each one of pistons 210 and 212.
Elongated body 214 has a diameter that is less than the diameters of pistons 210 and 212. The length of elongated body 214 is at least as long as a full stroke of the piston assembly.
Piston 210 is reciprocable within a bore of cylinder 201 and piston 212 is reciprocable within a bore of cylinder 202. The longitudinal axis of cylinders 201 and 202 and their respective bores are aligned with each other in addition to being aligned with the lc>ngit.ud.ir~ai axis of the free-floatinc~ piston ::assembly.
Apparatus 200 ~:omprises a pair of drive chambers anc~ a p ii r: of compression chambers . One pair of chambers i~> outer chambers 220 and 224 defined by space:: within respective cylinders 201 and 202 between :r_espect:ive pistons 210 and 212 and respective end prates 207 and 208. The other pair of chambers is inner chambers 222 and 2a?6 defined by the :respective anr~ul.ar spaces between elongated body 214 and respective cylinders 201 and 202, between divider '205 and the .back sides of respective pisto~:~~~ 2.10 and 212. The pair of chambers that act as drive chambers depends upon the function of t=he apparatus.
In one embo~:li.ment of the example illustrated by FIGS. 2 and 3,. inner chambers 222 and 226 are prefera~,ly fille~:l with liquid and cuter chambers 220 and 224 are filled with a gas. If this apparatL.s is employed to pump a liquid using gas pressure directed too outer chambers 220 and 224, then these outer chambers acts as the drive chambers. For oi=her applications, the apparatus can be conf igureci too compress a c_~as in outer chamber. 220 and 224, in which case inner chambers 222 and 226 would act as the dr~.~ve chambers.
Apparatus 200 is operable as a pump or compressor in a manner si.mi:Lar tc> known app>aratuses with double-acting free-floating piston assemblies.
As shown by F~'~:C~. 7, tree recvprocating piston assembly' and the u~~linder within wL~~ich it i reciprocates can each be elongated bodies. Minor misalignments can occur even when the individual components are manufactured in compliance with specified dimensional tolerances. Whereas conventional apparatuses employing free-floating piston assemblies have required strict alignment between the pistons, the cylinders, the connecting rod, and the opening through the divider, the present apparatus accommodates minor misalignments by an arrangement that allows divider 205 to move in a plane perpendicular to the longitudinal axis of the cylinder.
In the illustrated embodiment, divider 205 is a flat ring-shaped plate with a central opening through which elongated body 214 extends. The inner diameter of the central opening matches the diameter of elongated body 214. As shown in the enlarged section view of FIG. 3, dynamic seals 230 are disposed between divider 205 and elongated body 214 to restrict fluid flow between inner chambers 222 and 226. Divider 205 is held within an annular cavity between cylinders 201 and 202, and flanges 203 and 204, which prevent divider 205 from moving in the longitudinal direction. The inner diameter of the annular cavity is larger than the outer diameter of divider 205 such that there is an open gap therebetween whereby divider 205 is free to move transversely of the axis of elongated body 214. Lateral movement of divider 205 is guided by the position of elongated~body 214. That is, if elongated body 214 is misaligned so that it is not perfectly centered on the apparatus' longitudinal axis, divider 205 rides on elongated body 214 and is carried to the off-center position of elongated body 214. Persons skilled in the art will understand that there are limits to the amount of misalignment that can be accommodated by such an arrangement. This arrangement is not intended to accommodate large misalignments, but it will accommodate minor misalignments so that components do not have to be manufactured to higher tolerances. Seals 231 are provided to restrict fluid from flowing out of inner chambers 222 and 226 between divider 205 and the ends of cylinders 201 and 202.
As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.
Claims (23)
1. An apparatus comprising:
(a) an elongated cylinder;
(b) double-acting free-floating piston assembly comprising an elongated member disposed between two pistons, said piston assembly disposed and reciprocable within said cylinder;
(c) four chambers within said cylinder, each of said chambers fluidly isolated from the others axed defined by spaces between said cylinder and said piston assembly, said four chambers consisting of, two outer chambers, each one defined by a space between an end of said piston assembly and an end of said cylinder;
two inner chambers, each one defined by an annular space between said piston assembly and said cylinder; and (d) a divider held in a substantially fixed position along the longitudinal axis of said elongated cylinder and providing a barrier between said two inner chambers, wherein said divider comprises an opening through which said elongated member extends, said opening having a shape and size matching that of said elongated member, wherein said divider is disposed within an open space defined by an enclosure, said enclosure having interior dimensions whereby said open space is larger than said divider such that said enclosure is laterally spaced from the lateral edges of said divider, whereby said divider is movable relative to said cylinder within a lateral plane perpendicular to the longitudinal axis of said cylinder.
(a) an elongated cylinder;
(b) double-acting free-floating piston assembly comprising an elongated member disposed between two pistons, said piston assembly disposed and reciprocable within said cylinder;
(c) four chambers within said cylinder, each of said chambers fluidly isolated from the others axed defined by spaces between said cylinder and said piston assembly, said four chambers consisting of, two outer chambers, each one defined by a space between an end of said piston assembly and an end of said cylinder;
two inner chambers, each one defined by an annular space between said piston assembly and said cylinder; and (d) a divider held in a substantially fixed position along the longitudinal axis of said elongated cylinder and providing a barrier between said two inner chambers, wherein said divider comprises an opening through which said elongated member extends, said opening having a shape and size matching that of said elongated member, wherein said divider is disposed within an open space defined by an enclosure, said enclosure having interior dimensions whereby said open space is larger than said divider such that said enclosure is laterally spaced from the lateral edges of said divider, whereby said divider is movable relative to said cylinder within a lateral plane perpendicular to the longitudinal axis of said cylinder.
2. The apparatus of claim 1 wherein said divider is held between two flanges which prevent said divider from moving in a direction parallel to said longitudinal axis of said cylinder.
3. The apparatus of claim 2 wherein said two pistons each have the same diameter.
4. The apparatus of claim 2 further comprising a dynamic seal between said divider and said elongated member.
5. The apparatus of claim 2 wherein said elongated member is cylindrical and said divider is in the shape of a ring with a central hole through which said elongated member extends.
6. The apparatus of claim 5 wherein said divider has parallel flat surfaces which are held between two segments of said elongated cylinder.
7 The apparatus of claim 1 further comprising a fluid seal between said divider and said elongated cylinder.
8. The apparatus of claim 1. further comprising:
a first flange associated with a first segment of said elongated cylinder;
a second flange associated with a second segment of said elongated cylinder; and wherein said divider is held between said first and second flanges.
a first flange associated with a first segment of said elongated cylinder;
a second flange associated with a second segment of said elongated cylinder; and wherein said divider is held between said first and second flanges.
9. The apparatus of claim 8 further comprising at least one fluid seal between said divider and at least one of said first and second flanges.
10. An apparatus comprising:
(a) a free-floating piston assembly that comprises:
a first piston head having a first diameter;
second piston head having a second diameter;
an elongated body disposed between and joined to each one of said first and second piston heads, said body having a longitunal portion with a length that is at least as long as a piston stroke, said longitudinal portion having a third diameter that is less than said first and second diameters;
(b) a first cylinder comprises:
a first bore within which said first piston head is reciprocable;
a first open end, through which said elongated body is extendable; and a first flange associated with said first open end;
(c) a second cylinder comprises:
a second bore within which said second piston head is reciprocable;
a second open end, through which said elongated body is extendable; and a second flange associated with said second open end;
(d) a divider with a fixed longitudinal position between said first and second cylinders, said divider dividing an annular space defined between said elongated body and said first and second cylinders and between said first and second pistons, wherein said divider has an outer diameter that is less than the inner diameter of an enclosure that defines an annular cavity between said divider and said enclosure, whereby said divider is movable within said enclosure in a direction perpendicular to the longitudinal axis of said elongated body, said divider comprising an opening through which said elongated body is reciprocable (e) a dynamic seal between said divider and said elongated member; and (f) connectors for joining said first and second flanges together.
(a) a free-floating piston assembly that comprises:
a first piston head having a first diameter;
second piston head having a second diameter;
an elongated body disposed between and joined to each one of said first and second piston heads, said body having a longitunal portion with a length that is at least as long as a piston stroke, said longitudinal portion having a third diameter that is less than said first and second diameters;
(b) a first cylinder comprises:
a first bore within which said first piston head is reciprocable;
a first open end, through which said elongated body is extendable; and a first flange associated with said first open end;
(c) a second cylinder comprises:
a second bore within which said second piston head is reciprocable;
a second open end, through which said elongated body is extendable; and a second flange associated with said second open end;
(d) a divider with a fixed longitudinal position between said first and second cylinders, said divider dividing an annular space defined between said elongated body and said first and second cylinders and between said first and second pistons, wherein said divider has an outer diameter that is less than the inner diameter of an enclosure that defines an annular cavity between said divider and said enclosure, whereby said divider is movable within said enclosure in a direction perpendicular to the longitudinal axis of said elongated body, said divider comprising an opening through which said elongated body is reciprocable (e) a dynamic seal between said divider and said elongated member; and (f) connectors for joining said first and second flanges together.
11. The apparatus of claim 10 wherein said first and second diameters are equal.
12.. The apparatus of claim 10 further comprising a dynamic seal between said divider and said elongated body.
13. The apparatus of claim 10 further comprising seals between said divider and said first and second cylinders.
14. The apparatus cf claim 10 wherein said first and second flanged ends are bolted together.
15. The apparatus of claim 10 wherein said divider is held between said first and second flanges in addition to being held between said first and second cylinders.
16. The apparatus or claim 10 wherein said divider is in the shape of a circular disk with parallel flat surfaces with said bore centered in the middle of said flat surfaces.
17. The apparatus of claim 16 wherein said circular disk has a thickness that can accommodate at lease one dynamic seal.
18. An apparatus comprising:
(a) an elongated cylinder;
(b) double-acting free-floating piston assembly having a longitudinal axis, said piston assembly disposed and reciprocable within said cylinder;
(c) a divider providing a barrier between two adjacent chambers further defined within said apparatus by said cylinder and said piston assembly, wherein relative to said cylinder, said divider is held in a fixed longitudinal position and said divider has are outer diameter that is less than the inner diameter of an enclosure that defines an annular cavity between said divider and said enclosure, whereby said divider is movable within said enclosure in a lateral plane perpendicular to the longitudinal axis of said cylinder; and (d) a dynamic seal between said divider and said piston assembly.
(a) an elongated cylinder;
(b) double-acting free-floating piston assembly having a longitudinal axis, said piston assembly disposed and reciprocable within said cylinder;
(c) a divider providing a barrier between two adjacent chambers further defined within said apparatus by said cylinder and said piston assembly, wherein relative to said cylinder, said divider is held in a fixed longitudinal position and said divider has are outer diameter that is less than the inner diameter of an enclosure that defines an annular cavity between said divider and said enclosure, whereby said divider is movable within said enclosure in a lateral plane perpendicular to the longitudinal axis of said cylinder; and (d) a dynamic seal between said divider and said piston assembly.
19. The apparatus of claim 18 further comprising a fluid seal between said divider and said cylinder.
20. The apparatus of claim 18 wherein said divider comprises a solid body with an opening through which a portion of said piston assembly is extendable.
21. A method of accommodating misalignment between a free-floating piston assembly and a cylinder, said method comprising:
reciprocating a first piston head within a longitudinal bore of a first elongated cylinder;
reciprocating a second piston head within a longitudinal bore of a second elongated cylinder, which is coaxial with said first elongated cylinder;
maintaining said first and second piston heads in a fixed spatial relationship by attaching said first and second piston heads to opposite ends of an elongated rigid member that has a smaller transverse cross-sectional area than each of said first and second piston heads;
separating a space between said first and second piston heads with a divider disposed between said first and second cylinders and around said elongated rigid member; and allowing said divider to move within a plane perpendicular to the longitudinal axis of said first and second cylinders by disposing said divider within an enclosure that is spaced from the lateral edges of said divider, defining an annular cavity between said divider and said enclosure, while substantially restricting said divider from moving parallel to the longitudinal axis of said first and second cylinders.
reciprocating a first piston head within a longitudinal bore of a first elongated cylinder;
reciprocating a second piston head within a longitudinal bore of a second elongated cylinder, which is coaxial with said first elongated cylinder;
maintaining said first and second piston heads in a fixed spatial relationship by attaching said first and second piston heads to opposite ends of an elongated rigid member that has a smaller transverse cross-sectional area than each of said first and second piston heads;
separating a space between said first and second piston heads with a divider disposed between said first and second cylinders and around said elongated rigid member; and allowing said divider to move within a plane perpendicular to the longitudinal axis of said first and second cylinders by disposing said divider within an enclosure that is spaced from the lateral edges of said divider, defining an annular cavity between said divider and said enclosure, while substantially restricting said divider from moving parallel to the longitudinal axis of said first and second cylinders.
22. The method of claim 21 further comprising dynamically sealing between said divider and said elongated rigid member.
23. A method of accommodating misalignment within a reciprocating apparatus comprising a double-acting free-floating piston assembly that comprises a rigid member disposed between two piston, said method comprising:
reciprocating said free-floating piston assembly along a longitudinal axis within a bore defined by a cylinder;
dividing an annular space between said free-floating piston assembly and said cylinder, with a divider that rides on said rigid member;
holding said divider in a fixed location along said longitudinal axis; and allowing said divider to move within a plane perpendicular to said longitudinal axis by disposing said divider within an enclosure that is spaced from the lateral edges of said divider, defining an annular cavity between said divider and said enclosure.
reciprocating said free-floating piston assembly along a longitudinal axis within a bore defined by a cylinder;
dividing an annular space between said free-floating piston assembly and said cylinder, with a divider that rides on said rigid member;
holding said divider in a fixed location along said longitudinal axis; and allowing said divider to move within a plane perpendicular to said longitudinal axis by disposing said divider within an enclosure that is spaced from the lateral edges of said divider, defining an annular cavity between said divider and said enclosure.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2379756 CA2379756C (en) | 2002-03-28 | 2002-03-28 | Method and apparatus for a double acting reciprocating piston assembly |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2379756 CA2379756C (en) | 2002-03-28 | 2002-03-28 | Method and apparatus for a double acting reciprocating piston assembly |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2379756A1 CA2379756A1 (en) | 2002-07-31 |
| CA2379756C true CA2379756C (en) | 2003-09-30 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2379756 Expired - Fee Related CA2379756C (en) | 2002-03-28 | 2002-03-28 | Method and apparatus for a double acting reciprocating piston assembly |
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| Country | Link |
|---|---|
| CA (1) | CA2379756C (en) |
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- 2002-03-28 CA CA 2379756 patent/CA2379756C/en not_active Expired - Fee Related
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| CA2379756A1 (en) | 2002-07-31 |
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