Compressed air driven reciprocating piston hydraulic pump

Abstract

An air driven reciprocating piston hydraulic pump having a main changeover valve with a main valve body having an annular valve body portion which includes first and second annular valve faces that approach closely or contact first and second annular valve seats on valve cases which are formed on the upper and the lower ends of the annular valve body portion. An air intake chamber is defined by a piston reception hole and a drive piston portion, and an auxiliary changeover valve changes over the main changeover valve between its air supply position and its air discharge position by supplying compressed air to the air intake chamber or discharging air therefrom via a first and second valve members and a small diameter portion of a valve rod. A center side portion of the main valve body is made as a separate auxiliary valve body for facilitating up and down motion thereof.

Claims

1. A compressed air driven reciprocating piston hydraulic pump comprising a drive piston installed in a cylinder hole of a cylinder member, the drive piston being configured to be reciprocatingly driven to and fro along an axial direction of the cylinder hole, a forward motion chamber and a return motion chamber at opposite sides of the drive piston in the cylinder hole, a compression spring for return motion provided in the return motion chamber, a hydraulic pump mechanism including a plunger extending from a center portion of the piston toward the return motion chamber, a valve case having a partition wall portion that serves as an end wall of said forward motion chamber, the valve case being fixed to an end portion of the cylinder member, an air supply opening for supply of compressed air and an air discharge outlet provided in the valve case, and a changeover valve mechanism including a main changeover valve that operates to change over repeatedly between an air supply position in which the forward motion chamber is communicated with the air supply opening and an air discharge position in which the forward motion chamber is communicated with the air discharge outlet and an auxiliary changeover valve that operates in synchrony together with the main changeover valve and changes over the position of the main changeover valve between the air supply position and the air discharge position, wherein: the main changeover valve comprises a main valve body, and the main valve body comprises an annular valve body portion, and the annular valve body portion is biased toward the air supply position by compressed air in an annular air passage communicated to the air supply opening, and a piston portion defining portion is formed integrally with the annular valve body portion, and is shiftable along the axial direction; the annular valve body portion has first and second annular valve faces that are formed at respective ends of the annular valve body portion along the axial shifting direction of the annular valve body portion and that alternatively contact against first and second annular valve seats of the valve case, and the piston portion defining portion that is received in a piston reception hole formed in the valve case; and the auxiliary changeover valve comprises an air intake chamber defined by the piston reception hole and the piston portion, a valve rod that passes through and slides freely in the partition wall portion of the valve case extending from the center portion of the piston towards the forward motion chamber, the air intake chamber, and the valve main body, a small diameter portion formed on the valve rod, a first valve member that is capable of sealing between the valve rod and the main valve body, and a second valve member that is capable of sealing between the valve rod and the partition wall portion; and the auxiliary changeover valve is configured so that the auxiliary changeover valve, along with changing over the main changeover valve to its air supply position during a forward motion of the piston to enlarge the forward motion chamber, starts by releasing a seal of the first valve member between the valve rod and the main valve body by the small diameter portion and discharging compressed air from the air intake chamber, and the auxiliary changeover valve also changes over the main changeover valve to its air discharge position during a return motion of the piston to enlarge the return motion chamber, and starts by releasing a seal of the second valve member between the valve rod and the partition wall portion by the small diameter portion and intaking compressed air to the air intake chamber; wherein: a center side portion of the main valve body close to an external circumference of the valve rod is configured as an auxiliary valve body of the auxiliary changeover valve, the auxiliary valve body being separate from portions of the main valve body other than the center side portion; the auxiliary valve body comprises an auxiliary piston portion that is installed into an auxiliary piston reception hole formed in the piston portion so as to slide freely therein in an airtight manner and that faces into the air intake chamber, and a tubular portion that extends from the auxiliary piston portion toward an opposite side to the air intake chamber and that is installed in a cylindrical hole of the main valve body so as to slide freely therein; and an end portion of the tubular portion of the auxiliary valve body faces into the air discharge outlet, and a compression spring is provided that biases the auxiliary valve body toward the air intake chamber, and the first valve member is installed in the tubular portion.

2. A compressed air driven reciprocating piston hydraulic pump according to claim 1, wherein a barrel portion is provided, formed integrally with the annular valve body portion and extending from an opposite side to the piston reception hole, and fitted into a cylinder hole of the valve case so as to slide freely therein, and in that the annular air passage is formed on an external circumference of the barrel portion.

3. A compressed air driven reciprocating piston hydraulic pump according to claim 1 wherein an annular air exhaust passage is defined by the annular valve body portion of the main valve body, the piston portion defining portion, and the valve case, and an air passage that communicates the annular air exhaust passage to the air discharge outlet is formed in the main valve body.

4. A compressed air driven reciprocating piston hydraulic pump according to claim 1 wherein an air passage for intaking compressed air from the air supply opening to the air intake chamber is formed in the valve case, and an air passage capable of discharging compressed air from the air intake chamber is defined between the tubular portion of the auxiliary valve body and an outer circumferential surface of the valve rod.

5. A compressed air driven reciprocating piston hydraulic pump according to claim 1 wherein the second valve member is installed in an annular clearance between the valve rod and the partition wall portion so as to be movable in a length direction of the valve rod, and a small diameter barrel portion that receives and stops the second valve member from the air intake chamber side is provided extending from the auxiliary piston portion of the auxiliary valve body and inserted into the annular clearance.

6. A compressed air driven reciprocating piston hydraulic pump according to claim 5, wherein the auxiliary changeover valve is constituted so that when the piston has reached a forward motion limiting position to limit the forward motion of the piston, the auxiliary valve body is relatively shifted with respect to the main valve body by compressed air intaken into the air intake chamber from between an end portion of the small diameter portion of the valve rod and the second valve member so as to release the sealing of the second valve member between the valve rod and the partition wall portion.

7. A compressed air driven reciprocating piston hydraulic pump according to claim 1 wherein a compression spring is provided that biases the main valve body of the main changeover valve to the air supply position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a vertical sectional view of a compressed air driven reciprocating piston hydraulic pump (with a piston thereof in its return motion limiting position) according to an embodiment of the present invention;

(2) FIG. 2 is a vertical sectional view of the hydraulic pump (directly after its piston has reached its forward motion limiting position);

(3) FIG. 3 is a vertical sectional view of the hydraulic pump (directly before its piston starts return motion);

(4) FIG. 4 is an enlarged view of a portion A of FIG. 3;

(5) FIG. 5 is a vertical sectional view of the hydraulic pump (when its piston has started return motion); and

(6) FIG. 6 is an enlarged view of a portion B of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) The present invention will now be explained on the basis of an embodiment thereof.

(8) The compressed air driven reciprocating piston hydraulic pump P according to this embodiment is a pump that generates hydraulic pressure by means of compressed air. Moreover, in this specification, “hydraulic pressure” means hydraulic fluid under pressure.

(9) As shown in FIG. 1 and FIG. 2, this hydraulic pump P comprises a single acting type air cylinder 1, a changeover valve mechanism section 3 that changes over between supply of compressed air to a forward motion chamber 11 of this air cylinder 1 and discharge of air therefrom, a hydraulic pump mechanism section 2 that is driven by the air cylinder 1 and that includes a plunger 21, an air supply opening 4 to which compressed air is supplied from an external compressed air source, a discharge outlet 5 that discharges compressed air to the exterior, and so on.

(10) The air supply opening 4 is formed in a port fitting 4a that is fitted in a valve case 31 and in the valve case 31, and an air hose or an air conduit that supplies compressed air is coupled to this port fitting 4a. The air discharge outlet 5 is formed in the central portion of an upper end valve case 32 of the changeover valve mechanism section 3, and this air discharge outlet 5 is communicated with a noise muffling chamber 33 that contains a silencer 33a, with this noise muffling chamber 33 being opened to atmosphere. Incidentally, the silencer 33a is retained in place by a retaining ring 34.

(11) The air cylinder 1 comprises a cylinder member 13, a piston 14 that is installed in a cylinder hole 13a of the cylinder member 13 and that is repeatedly driven to and fro along the direction of the axis of the cylinder hole 13a, a piston rod 15, a forward motion chamber 11 and a return motion chamber 12 that are defined within the cylinder hole 13a on the two sides of the piston 14, a compression spring 16 that is installed in the return motion chamber 12 and that impels the piston 14 to perform return motion, shock absorption members 17a, 17b made from a synthetic resin material, and so on. Moreover, the forward motion chamber 11 is defined above the piston 14, while the return motion chamber 12 is defined below the piston 14.

(12) A valve case 31 is formed integrally at the upper end of the cylinder member 13, and the upper end of the forward motion chamber 11 is delimited by a partition wall 31a of the valve case 31 (this corresponds to an end wall of the forward motion chamber 11). The lower end of the cylinder member 13 is blocked by a pump case 22, and the pump case 22 is fixed to the cylinder member 13, for example by a plurality of bolts (not shown in the figure).

(13) The piston 14 comprises a piston main body 14a, an auxiliary piston 14b that contacts against the lower surface of the piston main body 14a, and a spring reception member 14c. The piston rod 15 extends downward from the center portion of the auxiliary piston 14b and passes through the spring reception member 14c, while a valve rod 35 (this belongs to the changeover valve mechanism section 3) extends upward from the center portion of the auxiliary piston 14b and passes through the piston main body 14a and the valve case 31. The external circumferential portion of the piston main body 14a is sealed with an O ring 14d that is made from a synthetic resin material.

(14) An annular concave portion 22a that receives the lower end portion of the compression spring 16 is formed at the upper end of the pump case 22, and the upper end of the compression spring 16 is received by the spring reception member 14c, while the lower end of the compression spring 16 is received by the wall surface of the annular concave portion 22a. The return motion chamber 12 is vented to atmosphere via a hole not shown in the figure. And a plurality of air passages 36 are formed in the valve case 31 for supplying compressed air to the forward motion chamber 11 and discharging air therefrom.

(15) The hydraulic pump mechanism section 2 comprises the pump case 22, a plunger 21 that is formed integrally at the lower end portion of the piston rod 15, a plunger hole 23 within which this plunger 21 ascends and descends, a seal member 24, an intake port 25 that admits hydraulic fluid and a non return intake valve 25a, a discharge port 26 that discharges hydraulic fluid and a non return discharge valve 26a, and so on. The plunger hole 23 is formed in a plunger hole member 23a. A port fitting 25b that defines the intake port 25 and a port fitting 26b that defines the discharge port 26 are both fitted to the pump case 22 by being screwed thereinto, and hydraulic hoses or hydraulic conduits are connected to the port fittings 25b, 26b.

(16) The changeover valve mechanism section 3 comprises: the valve case 31 and the upper end valve case 32; an annular air passage 39 that communicates to the air supply opening 4 via air passages 37, 38; an annular air exhaust passage 40 that communicates to the air discharge outlet 5 via air passages 41; and a changeover valve mechanism 42 that includes a main changeover valve 42A that operates repeatedly to change over between an air supply position (refer to FIG. 3 and FIG. 4) in which it communicates the forward motion chamber 11 to the air supply opening 4 and an air discharge position (refer to FIG. 5 and FIG. 6) in which it communicates the forward motion chamber 11 to the air discharge outlet 5, and an auxiliary changeover valve 42B that works together in synchrony with the main changeover valve 42A to change over the position of a main valve body 43 of the main changeover valve 42A.

(17) As shown in FIGS. 1 through 6, the main changeover valve 42A comprises the main valve body 43 having an annular valve body portion 43a that is biased towards an air supply position by compressed air in an annular air passage 39, a piston defining portion 43b, and a barrel portion 43c. This main valve body 43 is shiftable through, for example, 300 μm to 500 μm along the axial direction of the cylinder hole 13a (i.e. in the vertical direction), and is biased downwards by a weak compression spring 44 (i.e. towards its air supply position). The annular valve body portion 43a and the piston portion defining portion 43b are formed integrally with one another. The piston portion defining portion 43b comprises a piston portion 46 that is received in a piston reception hole 45 formed in the valve case 31 so as to slide freely in an airtight manner, and a link barrel portion 47 that extends upward from the piston portion 46 and connects to the annular valve body portion 43a.

(18) The barrel portion 43c is formed integrally with a portion of the annular valve body portion 43a that is intermediate in the radial direction and extends in the direction opposite to the piston reception hole 45 (i.e. upwards), and moreover is fitted into a cylinder hole 32a of the upper end valve case 32 so as to slide freely therein. An annular air passage 39 is defined by the annular valve body portion 43a, the barrel portion 43c, and the upper end valve case 32 around the external circumference of the barrel portion 43c. This annular air passage 39 is communicated with the air supply opening 4 by a plurality of radially extending air passages 38 and a single vertically oriented air passage 37. And an annular air passage 48 that communicates with the forward motion chamber 11 via an air passage 36 is defined at the outside of the outer circumferential surface of the annular valve body portion 43a.

(19) The annular air exhaust passage 40 is constituted by the annular valve body portion 43a, the piston portion defining portion 43b, and the valve case 31, and the plurality of air passages 41 are formed in the annular valve body portion 43a and communicate the annular air passage 40 with the air discharge outlet 5. The annular valve body portion 43a is provided with first and second annular valve faces 51, 52 that are formed at its two ends in the shifting direction (i.e. at its upper and lower ends). The first annular valve face 51 is radially outward of the barrel portion 43c, and is constituted by an annular seal member made of synthetic resin that is fitted into an annular groove on the upper end portion of the annular valve body portion 43a. And the second annular valve face 52 is below the first annular valve face 51, and is constituted by an annular seal member made of synthetic resin that is fitted into an annular groove on the lower end portion of the annular valve body portion 43a.

(20) A first annular valve seat 53 is formed on the upper end valve case 32 and closely approaches to or contacts against the first annular valve face 51, and a second annular valve seat 54 is formed on the valve case 31 and closely approaches to or contacts against the second annular valve face 52; and the structure is adapted so that the first and second annular valve faces 51, 52 contact alternatively against the first and second annular valve seats 53, 54. The state in which the first annular valve face 51 is separated from the first annular valve seat 53 and moreover the second annular valve face 52 is contacted against the second annular valve seat 54 is termed the “air supply position”. And, when the main changeover valve 42A is in the air supply position, compressed air provided from the air supply opening 4 is supplied to the forward motion chamber 11 via the air passage 37, the annular air passage 37a, the air passage 38, the annular air passages 39 and 48, and the air passage 36.

(21) Conversely to the above, the state in which the second annular valve face 52 is separated from the second annular valve seat 54 and moreover the first annular valve face 51 is contacted against the first annular valve seat 53 is termed the “air discharge position”. And, when the main changeover valve 42A is in the air discharge position, compressed air in the forward motion chamber 11 is discharged to the air discharge outlet 5 via the air passage 36, the annular air passage 48, the annular air exhaust passage 40, and the air passage 41.

(22) The auxiliary changeover valve 42B comprises an air intake chamber 55 that is defined by the piston reception hole 45 and the piston portion 46, the valve rod 35, a small diameter portion 35a that is formed on the valve rod 35, a first valve member 56 that is capable of sealing between the valve rod 35 and the main valve body 43, and a second valve member 57 that is capable of sealing between the valve rod 35 and the partition wall portion 31a. The valve rod 35 extends from the center portion of the auxiliary piston 14b toward the forward motion chamber 11, and passes through the partition wall portion 31a of the valve case 31, the air intake chamber 55, and the main body 43 so as to slide freely therein. An air passage 58 is formed in the partition wall portion 31a for intaking compressed air from the air supply opening 4 to the air intake chamber 55.

(23) A small diameter portion 35a of the valve rod 35 is formed as an annular groove of a predetermined length in the vertical direction (for example 6 to 10 mm), and the upper end portion and the lower end portion of the small diameter portion 35a are formed as tapered portions 35b that gradually decrease in diameter.

(24) As shown in FIG. 1, when the piston 14 is in its upper limit position (i.e. its return motion limiting position), the first valve member 56 is at a position corresponding to an intermediate position in the vertical direction of the small diameter portion 35a of the valve rod 35. By contrast, as shown in FIG. 2, when the piston 14 is in its lower limit position (i.e. its forward motion limiting position), the second valve member 57 is at a position corresponding to the tapered portion 35b at the lower end of the small diameter portion 35a of the valve rod 35

(25) The auxiliary changeover valve 42B is constructed so that, when forward motion of the piston 14 starts, the main valve body 43 is changed over to the air supply position by releasing the sealing of the first valve member 56 by the small diameter portion 35a so that compressed air in the air intake chamber 55 is discharged, and also is constructed so that, when return motion of the piston 14 starts, the main valve body 43 is changed over to the air discharge position by releasing the sealing of the second valve member 57 by the small diameter portion 35a of the valve rod 35 so that compressed air is intaken into the air intake chamber 55. Incidentally, a plurality of seal members a through e are provided.

(26) Next, the characteristic structure and operation of the present application will be explained.

(27) As shown in FIGS. 2 through 4, the center side portion of the main valve body 43 close to the external circumference of the valve rod 35 is built as the auxiliary valve body 43d, which is separate from the other portion than the center side portion. The auxiliary valve body 43d comprises an auxiliary piston portion 60 and a tubular portion 61 that is integral with the auxiliary piston portion 60.

(28) An air passage 62 that is capable of discharging compressed air in the air intake chamber 55 is defined between the inner circumferential surface of the tubular portion 61 and the outer circumferential surface of the valve rod 35. The auxiliary piston portion 60 is installed in an auxiliary piston reception hole 63 that is formed in the piston portion 46 so as to slide freely therein, and faces to the air intake chamber 55. The tubular portion 61 extends from the auxiliary piston portion 60 in the opposite direction from the air intake chamber 55, and passes through the cylindrical hole of the main valve body 43 so as to slide freely therein. The end portion of the tubular portion 61 of the auxiliary valve body 43d projects out toward the air discharge outlet 5, and a weak compression spring 64 is provided that biases the auxiliary valve body the air intake chamber 55. The lower half portion of the tubular portion 61 is formed to have a smaller diameter than that of 43d toward its upper half portion, and that it is built so as not to contact the inner circumferential surface of the cylindrical hole of the main valve body 43, so that the frictional force that operates on the auxiliary valve body 43d becomes small.

(29) The first valve member 56 is made of an O ring, and this first valve member 56 is installed in an annular groove formed around the internal circumferential portion of the tubular portion 61. Moreover, the second valve member 57 is made of an O ring, and is installed in an annular clearance 65 between the valve rod 35 and the partition wall portion 31a so as to be movable in the length direction of the valve rod 35 (i.e. along its axial direction). A small diameter barrel portion 60a is provided to the auxiliary piston portion 60 of the auxiliary valve body 43d, extending downward from the auxiliary piston portion 60 and inserted into the upper end side portion of the annular clearance 65, and moreover receiving and stopping the second valve member 57 from the air intake chamber 55 side. Furthermore, a plurality of sloping air passages 66 are formed in the neighborhood of the upper portion of the small diameter barrel portion 60a and communicate the valve rod through hole of the auxiliary valve body 43d to the air intake chamber 55.

(30) As shown in FIG. 4, a flanged sleeve 67 is fitted into and fixed in the lower end portion of the annular clearance 65. An O ring 68 and a spacer 69 are installed in the annular clearance 65 above the flanged sleeve 67, with this spacer 69 having a plurality of small holes 69a in a thinner intermediate stepped portion thereof; and the upper surface of the O ring 68 is pressed by the lower end surface of the spacer 69, while the second valve member 57 is received and stopped from below by the upper end surface of the spacer 69. The air passage 58 is formed so as to communicate with the plurality of small holes 69a in the intermediate stepped portion of the spacer 69.

(31) With this hydraulic pump P, by compressed air being continuously supplied to the air supply opening 4, and by the piston 14 being repeatedly caused to perform reciprocating operation at high speed due to the operation of the main changeover valve 42A and the auxiliary valve 42B of the changeover valve mechanism section 3, it is possible for hydraulic fluid to be repeatedly expelled from the hydraulic pump mechanism section 2.

(32) When the piston 14 reaches its forward motion limiting position as shown in FIG. 4, the auxiliary valve body 43d is relatively shifted upward with respect to the main valve body 43 by the gentle pressing force of compressed air that is intaken into the air intake chamber 55 from the small gap between the tapered portion 35b at the lower end of the small diameter portion 35a of the valve rod 35 and the second valve member 57, and the sealing of the second valve member 57 is reliably released due to the second valve member 57 being reliably shifted upward. At the next instant, as shown in FIG. 6, the compressed air intaken into the air intake chamber 55 operates on the piston portion 46 and the auxiliary piston portion 60, so that the main valve body 43 and the auxiliary valve body 43d are shifted upward by a small distance and the main changeover valve 42A is reliably changed over to its air discharge position.

(33) By the auxiliary valve body 43d being built in this manner so as to be shiftable upward by a small compressed air force, when the piston 14 has reached its forward motion limiting position, the sealing of the second valve member 57 is broken via the tapered portion 35b at the lower end of the small diameter portion 35a of the valve rod 35, and, due to a small amount of compressed air that flows into the air intake chamber 55, the auxiliary valve body 43d is relatively shifted upward with respect to the main valve body 43, so that, by the second valve member 57 being shifted upward, the sealing of the second valve member 57 is reliably released via the small diameter portion 35a, and thus compressed air is rapidly introduced into the air intake chamber 55, whereby the main changeover valve 42A can be rapidly changed over to its air discharge position.

(34) Even if the supply pressure of the compressed air fluctuates, the auxiliary valve body 43d does not experience any influence. Moreover, since the amount of hydraulic pressure consumed at the destination for supply of hydraulic fluid is minute, even if the piston 14 shifts at an extremely low speed, the auxiliary valve body 43d operates reliably as described above so that the main valve body 43 does not stop in a neutral position (i.e. in a state with all ports open). And it is also difficult for the main valve body 43 to stop in a neutral position, since the main valve body 43 is biased toward the air supply position by the compression spring 44.

(35) Moreover, since in this construction the valve rod 35 does not strike against any other metallic member, accordingly no clattering noise is generated, even when the piston 14 repeatedly executes reciprocating operation at high speed.

(36) The structure of the hydraulic pump P explained above is only shown by way of example; for a person skilled in the art, it would be possible to implement various partial alterations to the embodiment described above, while still not deviating from the spirit of the present invention.

(37) The present invention provides a hydraulic pump which is a compressed air driven reciprocating piston hydraulic pump that generates hydraulic pressure continuously according to supply of compressed air thereto, and that can be utilized in applications of various kinds.

DESCRIPTION OF NUMERALS

(38) P: compressed air driven reciprocating piston hydraulic pump 1: single acting type air cylinder 2: hydraulic pump mechanism section 3: changeover valve mechanism section 4: air supply opening 5: air discharge outlet 11: forward motion chamber 12: return motion chamber 13: cylinder member 13a: cylinder hole 14: piston 16: compression spring 21: plunger 31: valve case 31a: partition wall portion 32: upper end valve case 35: valve rod 35a: small diameter portion 35b: tapered portion (end portion of small diameter portion) 39: annular air passage 40: annular air exhaust passage 41: air passage 42: changeover valve mechanism 42A: main changeover valve 42B: auxiliary changeover valve 43: main valve body 43d: auxiliary valve body 43a: annular valve body portion 43b: piston portion defining portion 43c: barrel portion 44: compression spring 45: piston reception hole 46: piston portion 51, 52: first and second annular valve faces 53, 54: first and second annular valve seats 55: air intake chamber 56: first valve member 57: second valve member 58: air passage 60: auxiliary piston portion 60a: small diameter barrel portion 61: tubular portion 63: auxiliary piston reception hole 64: compression spring 65: annular clearance