Fluid pressure operated piston engine assembly

• US 5,325,762 A
• Filed: 07/26/1993
• Issued: 07/05/1994
• Est. Priority Date: 10/29/1992
• Status: Expired due to Term

• Current Assignee: Nordson Corporation
• Original Assignee: Nordson Corporation
• Inventors: Woodlief, Robert J., Sloan, Patricia A., Walsh, John T.
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): Nguyen, Hoang
• Application Number:
  US08/096,862
• Time in Patent Office: 344 Days
• Field of Search: 91/361, 91/363 R, 91/363 A, 91/275, 91/459, 91/385, 91/392, 251/65
• US Class Current: 91/275
• CPC Class Codes: F01L 23/00 Valves controlled by impact by piston, e.g. in free-piston machines
• CPC Class Codes: F01L 25/08 by electric or magnetic means

Abstract

A fluid pressure operated piston engine assembly, such as a pump assembly, including a fluid pressure operated piston engine and a fluid valve for coupling fluid under pressure to alternative portions of the piston chamber of the piston engine. The fluid valve includes a valve spool which is translated to effect the alternative modes of coupling pressurized fluid to the piston chamber. The translation is accomplished by a shifter assembly having a shifter rod attached to the valve spool. The shifter rod includes a pair of diametrically opposed magnets attached thereto. A fork is attached to the piston engine drive shaft at one end and is mounted for limited movement along the shifter rod between the pair of magnets of the shifter rod. The interaction between the flux generated by a magnet carried by the fork with one of the magnets of the shifter rod causes the shifter rod, and in turn the valve spool, to shift from one position to another, thereby re-directing the flow of fluid to the piston chamber to effect the reversal of direction of travel of the piston and its associated drive shaft.

Claims

1. A fluid pressure operated piston engine assembly comprising:

a fluid pressure operated piston engine including a piston chamber, a piston reciprocable in the chamber, and a drive shaft attached to the piston and reciprocable therewith through a drive shaft stroke having a first end and a second end;

fluid valve means for coupling fluid under pressure to alternative portions of the piston chamber, including a valve spool translatable to (a) a first position in which the valve means is operable to couple fluid under pressure to a first portion of the piston chamber, tending to move the drive shaft toward the second end of its stroke and (b) a second position in which the valve means is operable to couple fluid under pressure to a second portion of the piston chamber, tending to move the drive shaft toward the first end of its stroke;

first means for coupling to the fluid valve means, mounted externally from the piston chamber, for reciprocal movement, and including a pair of diametrically opposed magnets; and

second means for mechanically coupling the first means to the piston engine drive shaft such that as the drive shaft approaches the first end of a stroke, the first means is moved to a first position relative to the valve spool and such that as the drive shaft approaches the second end of its stroke the first means is moved to its second position relative to the valve spool, wherein, as the drive shaft approaches each end of its stroke, fluid under pressure is coupled to one of said portions of the piston chamber to effect reversal of the direction of travel of the drive shaft.

2. The apparatus of claim 1 wherein as the piston engine drive shaft is moved to the end of a stroke, the second means is moved toward one of the magnets of the first means until the force of attraction becomes so great therebetween that the first means is caused to move from either the first position to the second position or from the second position to the first position.

3. The apparatus of claim 1 wherein the second means includes a ferro-magnetic portion, disposed between the pair of magnets.

4. The apparatus of claim 1 wherein the second means includes a magnet disposed between the pair of magnets of the first means.

5. The apparatus of claim 1 further comprising a detent means for retaining the first means in either the first or second position until the piston engine drive shaft reaches an end of a stroke.

6. The apparatus of claim 2 further comprising a detent means for retaining the first means in either the first or second position until the piston engine drive shaft reaches an end of a stroke.

7. The apparatus of claim 4 wherein said magnets are comprised of samarian cobalt.

8. The apparatus of claim 1 wherein the fluid valve means is capable of being manually operated, independent of the piston engine, without decoupling the second means.

9. The apparatus of claim 4 further comprising a means for compensating for magnetic misalignments between at least one of said magnets carried by said first means and the magnet of said second means.

10. The apparatus of claim 4 wherein the magnet of said second means includes a pair of parallel bar magnets.

11. The apparatus of claim 4 wherein the magnet of said second means is substantially "C" shaped in cross section.

12. An assembly comprising:

a fluid valve having an inlet for coupling to a source of fluid under pressure, first and second discharge outlets, and a valve spool translatable between a first and second position such that in the first position the inlet is coupled to the first discharge outlet and in the second position the inlet is coupled to the second discharge outlet; and

a shifter including a shifter rod coupled to the valve spool, a pair of diametrically opposed magnets carried by the shifter rod, and a means movable between said magnets and adapted for coupling to a shaft of a piston engine, for causing the shifter rod to move from either a first position relative to the valve spool to a second position or from the second position relative to the valve spool to the first position, wherein coupling of the inlet to a discharge outlet of the fluid valve is shifted from either the first to the second outlet or from the second to the first outlet.

13. The apparatus of claim 12 wherein the means includes a ferro-magnetic portion disposed between the pair of magnets.

14. The apparatus of claim 12 wherein the means includes a magnet disposed between the pair of magnets of the shifter rod.

15. The apparatus of claim 14 further comprising a means for compensating for magnetic misalignments between at least one of said magnets carried by the shifter rod and said magnet disposed between the pair of magnets of the shifter rod.

16. The apparatus of claim 15 wherein said means for compensating is a hinge means.

17. The apparatus of claim 12 further comprising a detent means for retaining the shifter rod in either the first or second position until the means causes the shifter rod to change positions.

18. The apparatus of claim 12 further comprising:

a fluid pressure operated piston engine including a piston chamber, a piston reciprocable in the chamber, a drive shaft attached to the piston and reciprocable therewith through a drive shaft stroke having a first and a second end, a means for coupling the first and second discharge outlets of the fluid valve to a first and second portion of the piston chamber, respectively, of its stroke; and

wherein said means of the shifter is coupled to the piston engine drive shaft such that as the drive shaft approaches each end of its stroke, fluid is coupled to a portion of the piston chamber to effect reversal of the direction of travel of the drive shaft.

19. The apparatus of claim 18 wherein the means of the shifter comprises:

a bar means attached at a first end to the piston drive shaft and mounted for slidable movement with respect to the shifter rod at a second end;

a magnet carried by the second end of the bar means for movement between the shifter rod magnets such that as the piston engine drive shaft reaches the end of a stroke, the force of attraction between the magnet of the bar means and that of one of the magnets of the shifter rod causes the shifter rod to shift from one position to another, which in turn causes the air valve to move from one position to another wherein the air flow to the piston chamber causes a reversal of the direction of travel of the drive shaft.

20. The apparatus of claim 19 wherein each magnet of the shifter rod has a first pole face oriented toward the magnet carried by the bar means and a second pole face distal therefrom;

and

wherein the detent means includes a ferro-magnet plate spaced from the second pole face of each of the magnets of the shifter rod.

21. The apparatus of claim 20 wherein said bar means is substantially a fork having tines;

wherein the magnet of the bar means is substantially a "C" in cross-section; and

wherein the opening of the magnet and tines of the fork straddle the shifter rod.

22. The apparatus of claim 21 wherein said fork further comprises first and second portions hingably connected together.

23. The apparatus of claim 19 wherein said magnets are comprised of samarian cobalt.

25. The assembly of claim 18 wherein the valve spool and the valve sleeve comprise hardened stainless steel and said valve sleeve being disposed within a housing of aluminum and having a means for accommodating the expansion and contraction between the housing and the sleeve.

26. The assembly of claim 19 wherein said means is substantially a fork having a pair of tines at one end spaced from the shifter rod a predetermined distance and attached at another end to the pump shaft;

said fork carrying a magnet which straddles the shifter rod;

wherein as the pump shaft reaches the end of a stroke, the force of attraction between the magnet of the fork and that of one of the magnets of the shifter spool causes the shifter spool to shift from one position to another, which in turn causes the air valve to move from one position to another such that the air flow to the piston chamber causes a reversal of the direction of travel of the drive shaft.

24. An assembly for pumping heated adhesives comprising:

a pump including a piston chamber, a piston reciprocable in the chamber, and a pump shaft attached to the piston and reciprocable therewith through a pump shaft stroke having a first end and a second end;

an air valve mounted externally from the piston chamber, capable of operating at temperatures of at least 350°

, for coupling air under pressure to alternative portions of the piston chamber, including a valve spool disposed within a valve sleeve and mounted for translatable movement between a first position in which the air valve is operable to couple air under pressure to a first portion of the piston chamber, tending to move the pump shaft toward the second end of its stroke and a second position in which the air valve is operable to couple air under pressure to a second portion of the piston chamber, tending to move the pump shaft toward the first end of its stroke, the valve spool having a stepped outer surface having a plurality of larger diameter portions, the larger diameter portions having a 1/2 inch diameter and a tolerance of about 0.0005 inches; and

a shifter mounted externally from the piston chamber, capable of operating at temperatures of at least 350°

, including a shifter rod attached to the valve spool, a pair of diametrically opposed magnets, comprising samarian cobalt, carried by the shifter rod, and a means moveable between said magnets, but spaced from said shifter rod and coupled to the pump shaft, for causing the shifter rod to move between first and second positions such that the movement of the shifter rod to the first position causes the valve spool to move to the valve spool first position, while the movement of the shifter rod to the second position causes the valve spool to move to the valve spool second position, wherein, as the pump shaft approaches each end of its stroke, fluid under pressure is coupled to one of said portions of the piston chamber to effect reversal of the direction of travel of the pump shaft.