GB2359342A

GB2359342A - Plastics pneumatic hydraulic pump

Info

Publication number: GB2359342A
Application number: GB0003617A
Authority: GB
Inventors: Joachim Probst
Original assignee: Schmidt & Co Kranz GmbH
Current assignee: Schmidt & Co Kranz GmbH
Priority date: 1998-12-28
Filing date: 2000-02-16
Publication date: 2001-08-22
Anticipated expiration: 2020-02-16
Also published as: GB2359342B; FR2805313B1; DE19860466C1; FR2805313A1; GB0003617D0

Abstract

Pump comprises plate 3 moulded to plastics cylinder 2 containing air piston 6 and closed by plastics cap 11. Plate and cap contain pilot valve 4, 5 stepped bores 12, 13. Removably flanged to the plate is plastics reversal casing 25 having air inlet 56 and cavity 55 containing reversal piston 48 having different area ends 58, 59 acting on cavitied 61 sliding shoe 60. Air piston to plate valve engagement links passages 12 39, 43, 44 and chamber 45 to passage 62 and inlet 56 to act on the reversal piston large area end causing the shoe to link air chamber 34 to atmosphere via 30-33,22,27,28 and shoe cavity 61. Air inlet passes through 21, to chamber 36. End cap valve actuation vents passages 40-44 and chamber 45 shifting cavity 61, linking passages 21, 22 and inlet to chamber 34. Pump may operate manually (Figs 9, 10)

Description

2359342 A pntically driven hydraulic pump

A pneumatically driven hydraulic p=p of the kind in question is prior art, e.g- in DE 26 216 954 C2. TL given good practical results, owing to its multiple Uses.

A hydraulic pump of this kind, in a standard version, comprises an air piston movable in reciprocation in a cylindrical casing and nonpositively connected to a hydraulic: piston. Thp hydraulic piston is connected a suction valve to a suction line and via a delivery valve to a delivery line. As a result of the reciprocating motion of the air piston and consequently of the hydraulic piston, the hydraulic piston intakes hydraulic medium and delivers it under pressure.

The reciprocating motion of the air piston is effected via a partly hollow sleeve valve and at least one pilot valve which is actuated by the air piston and ensures that the sleeve valve i,.,. fitoved fúc)itt unc. Le) Llic f-illiuu end position. The sleeve valve has two active end faces of different sizes- The smaller active surface is constantly 3upplied with working air, wherea5 the large active surface is supplied with working air by the pilot valve when the sleeve valve is moved in the other direction. In order to convey the workinq air into the working compartments on the two sides of the air piston and in order to discharge the exhaust air, the s1E-f-vf- valve is qtiif.icd in an cxr. )cnsivclyproduced stepped sleeve with transverse bores and peripheral slots and has a nurnber of spaced-apart peripheral sealing ringo. In addition to the complicated sleeve, one peculiarity in the known case is that the sealing 2 rings constantly move over the mouths of the bores in the sleeve and are consequently subject to considerable wear. Also the sleeve M12St be sealed and mounted in Lhe bure for receiving it in the casing.

The object of the invention, starting from the prior art, is to produce the known hydraulin pump more cheaply by large-scale manufacture and modular construction.

The solution of this problem according to the invention is in the featuies in claim 1.

One important consideration is thal Lhe easing, the valve plate integrally formed thereon, the end cap releasably associated with the cylindrical ca5ing, the casing for the reuersal valve and the sliding shoe are now made of plastic, particularly polyoxymethylene. Preferably these objects are injection-moulded. As a result, a, I mndels and types can be inexpensively massproduced.

Another iinportant point is that the 5lidinq shne serves as a flat slide valve. It also can be injectionmoulded froin plastic. Dependinq on its position in the casing, it conveys working air into one or the, other working compartment on the two sides of the air piston and, owing to the guide cavity formed in it, it also conveys exhaust air from the workinF f-oTnpartmpnts to atitosphere, more particularly via a silencer.

The sliding shoe is moved by a reversal piston dispose(i in the reversal casing and having two acti-ve end fares of different sizes. The smaller active surface is ----------------------------- - 3 always in that chamber of the reversal casing in which the sliding shoe is also situated, and is permanently supplied with working air. The reversal piston can be of a light-metal alloy. It is quided in sealingtight manner in the reversal casing. The seals however do not move over the mouths of any bores, so that they need rint be. particillarly wear-re,5i5tant- The slidinq shoe is positively guided in the chainber, but- slides on an outer side of the valve plate. Since the reversal casing is flanged on the side of the valve plate, therefore, the sliding shoe is secured in the operating position. The sliding shoe moves over the mouths of a total of three ducts. These arc in 1 ine and extend transversely to the direction of motion of the air piston. The two outer ducts are directly connected to the working chambers in thR cylindrical casing, whereas the central duct leads to atmosphere, particularly via a silencer.

According to the features in claim 2, the positive and non-positive cooperation between the reversal piston and the sliding shoe is advantaqeously facilitated in Lhat the, 1-onqitudiiial portion of the reversal piston extending into the reversal casing chamber and having the smaller active surface has a recess adapted to the lenqth of the sliding shoe and per-'pherally overlapping it. The recess is formed in the reversal piston, more particularly by turning.

According to claim 3 the chamber is permanently connected via a branch duct in the valve pate to the stepped bore receiving the first pilot valve. This enjures, deperiding on tl.i(--, positinn nf the air piston, either that the large active surface of the reversal 4 piston is supplied with working air via the first pilot valve and the ducts in the valve plate and in the reversal casing and that the tappet of the spnnnd pi.Int valve is reversed in thn working compartment between the air piston and the end cap, or that the tappet of the first pilot valve is pressed into the working compartment between the air piston and the valve plate.

In this connection, accordinq to the features in claim the stepped bore in thp valve Plate i- connected vit ducts in the valve plate and in the reversal casing to a compartment in the reversal casing quidinq the longitudinal portion of the reversal piston having the larger active surface and is also connected,;,ia ducts in the wall of the cylindrical casing and in the end cap to the stepped bore receiving the pilot valve -'In the end cap. The larger active surface is permanently disposed in a compartment in the reversal casing sealed off from the chamber. Thi5 cQmpdrtment can be supplied with working air via the first pilot valve in the valve plate and can be discharged to atmosphere via the second pilot valve in the end cap. The reversal piston and the sliding shoe are not permanently interconnected, which further simplifies production and assembly- In order to discharge air from the compartment, the stepped bore comprising the second pilot valve and the dLicts between the first pilot valve, the compartment and Lhe second pilot valve, according to claim 5, the stepped bore in the end cap is connected directly to atmosphere by a branch duct.

The foatures in claim 6 relate to an embodiment comprising two hydraulic pistons disposed coaxially relative to one another and non-positively connected to the air piston. In order to incorporate the second hydraiAlic piston, it is only necessary to provide a suitable guide bore in the valve plate. No other alterations are necessary in order to provide a doubleacting hydraulic pump.

AccQrding to the features of claim 7, the hydraulic pump according to the invention can alternatively be manually actuated. To this end the air piston, via a 1..i.nkaqe. e.xte-nciinq th-rourTh and- movable relative to the valve plate, is manually adjustable against the restoring force of a spring incorporated in the workinq compartment between the air piston and the end cap. Consequently it is only necessary to insert the spring into the cylindrical casing and to plug the duct between the chamber and the working compartment adjoining the end cap. No other alterations are necessary. The hydraulic pump can thus be operated either pneumatically or by hand as required.

According to the features in claim 8, a hand lever associated with the linkage. is -inr.kahlf.. Thi s ensures that during operation with air, the hand lever does not make any uncontrolled. movements which might cause injurV.

The invention will now be explained in further detail with reference to exemplified embodiments shown in the drawings, in which:

6 Fig. 1 is a diagrammatic vertical longitudinal section through a pneumatically driven hydraulic pump; Fig. 2 is a side view Of the hydraulic pump in Fig. along arrow II; Fig. 3 is a horizontzil section through Fig. 22 along line III-III; Fi rT, 4 i s a s e cti on through FirT. 3 a 1, on ri 1 n C TV- TV; Figs- 5 to 7 are views of Figs. 1, 3 and 4 in another nperatinq si-tuatio"n; Fig. 8 is a view corresponding to Fig. 1 in another embod-lment; Fig. 9 is a view norresponding to Fig. 5 in another embodiment, and Fig. 10 is a view of Fig.

position.

1, 9 in another operating Ficis. 1, 2 and 5 show a pnetmatically driven hydraulic pump 1 - The hydraulic pump 1 has a plastic cylindrical casing 2 comprising an air piston 6 movable via an 4ntegrally moulded valve plate 3 and reversing pilot val 4, 5 in the two end positions and also comprises a hydraulic piston 7 connected non-positively to the air piston 6. The air piston 6 has a peripheral groove 8 in which a sealing ring 9 is embedded and abuts sealitigly against the inner wall 10 of the cylindrical casing 2_ 7 A plastic end cap 11 is releasably mounted on the end of the cylindrical casing 2 remote from the valve plate 3- The hydraulic pi.ston 7 extends through and slides in the end cap 11.

The pilot valves 4, 5 are disposed in stepped bores 12, 13 in the valve plate 3 and in the end cap 11 and each coraprise a tappet 14 and a head 15. Sealing rings 16 are disposed in the eciilril longitudinal region of thn. valve tappets 14- Other Sealing rings 17 are disposed between the tappets 14 and the valve heads 15. The pilot valves 4, 5 are hi.ased by hel-Lcal pressure springs 18 towards the air piston 6. They abut helical bolts 19 screwdd into the spring compartments 20 of the stepped bores 12, 13.

Three transverse ducts 21, 22, 23 in line are provided in the valve plate 3. All three ducts 21, 22, 23 open into an outer side 24 of the valve plate 3 (see Figs, 3 and 6) on which a plaulic. rc-vf-r,,:al casing 25, shown in further detail in Figs. 3 and 4, is also flanged. The central duct 22 out of the three ducts 21, 22, 23 is connected bV a duct 28 to a connection 27 which opens into the end face 26 of the valve plate 3 aind to which a silencer can be attached. Out of the other two ducts 21 2.3, the duct 23 adjoining the first pilint- valve 4 is connected, via a longitudinal duct 30 in the wall 29 of the cylindrical casing 2 and via ducts 31 - 33 in he end cap 11, to the workinr 34 for z:he t_ T cnmnirt-me.nt L air piston 6 adjoining the end cap 11. The third duct 21 in the valve plate 3 is connected by a duct 35 to the working compcirtrRent 36 adjoininq thR valve plate 3- 8 As also shown in Figs - 1 and 5, the longitudinal portion 37 of the stepped bore 12 in the valve plate 3 guiding the valve tappet 14 is connected to the spring compartment 20 of the stepped bore 13 in Lhe und 11 via ducts 39, 40, 41, 42 in the valve plate 3, in the wall 29 of the cylindrical casing 2 and in the end cap -1 1, An additin-nal tinci- 13 in the valve plate 3 and a duct 44 in the reversal casing 25 connect the duct 39 to a compartment 45 in the casing 25, in which a longitudinal portion 47 of a reversal piston 8, de8cribed in further detail hereinafter, is movable and is provided with a sealing ring 46.

The longitudinal portion 38 between the spring compartment 20 and the longitudinal portion 37 of the stepped bore 13 in the end cap 11 is connected to atmosph c. A v i a a tr,.T)svr,-rs n cil I (-t-. 9 - The reversal piston 48 is sealingly guided in the casing 25 in the previously-.mentinnpci compartment 15 and also in a bore 50. To this end an additional sealihg ring 51 is embedded in a. peripheral groove 52 in the reversal piston 48. A longitudinal portion 54 of the reversal piston 48 formed with a recess 53 made by turning projects into a chamber 55 in the reversal casing 25. The casing 55 is permanently connected by a connection 56 to ii source of working air AL 'compressed air). The end 57 of the reversal piston 48 in the chamber 55 has an active surface 58 which is smaller than the active surface 59 on the longitudinal portion 47 of the reversal piston 48 in the compartment 15.

The length of the recess 53 at the reversal piston 40 is equal to the length of a plastic rectangular sliding 9 shoe 60 forined with a guide cavity 61. The shoe 60 slides an the outer side 24 of the valve plate 3 and moves over the mouths of the three ducts 21, 22, 23.

As also shown in rigs. 1, 4, 5 and 7, the chamber 55 is connected by a branch duct 62 to the spring compartment 20 of the stepped bore 12 in the valve plate 3.

The hydraulic piston -7 operates in a T-shaped duct 63 in a high-pressure casing 65. The duct is connected by a suction valve 64 to a suction line 66 for a hydraulic me,diiiin and is al.ri Lu a delivery va-,vc 67 connected to a delivery line 68.

The hydraulic pump 1 in Figs. 1 to 7 operates as follows:

Owing to the shape of the casing 25, driving air AL constantly arrives at the chamber 55 via the connection 56. As a result the reversal piston 48 is moved to the]E-ft-. in thp. planc. of the drawings (Figs- 3 and 4), and owing to the po sitive and non-positive coupling of the reversal piston 48 to the sliding shoe 60, the shoe is ertrained until it abut5 the end face 69 of the chamber 55. Working air AL from the chamber 55 can now flow through the ducts 23, 30, 31, 32, 33 into the workinq chamber 34 adjoining the end cap 11. When the shoe 60 is in this position, the working chamber 36 adjoining the valve plate 3 is connected to atmosphere A via the ducts 35 and 21, the guide cavity 61 in the hne 60 and the ducts 22, 28, and consequently the air piston 6 can move in the direction towards the valve plate 3_ At the same time, working air AL from chamber 55 flows through the branch duct 62 into the spring compartment --- -- -- -111..

of the first pilot valve 4, thus moving the valve tappet 14 into the working chamber 36 as shown in Fig. 5.

Shortly before reaching the top dead centre position, the air piston 6 actuates the tappet 14 of the first pilot valve 4 and Moves it against the restoring force nf tbe- helical pressure s-priii(l 18 lintil thp ring 17 is lifted off its scat in the stepped bore 12 and the working air AL arriving through the branch duct 6-2 flows through the longitudinal portion 38 of the stepped bore 12 into the duct 39 and through the duct 43 in the valve plate 3 and the duct 44 in the casing 25 into the compartment 45 guiding the longitudinal portion 47 having the larger active surface 59. At the same time, the workinq air AL flows throuqh ducts 40, 41, 43 into the spring compartment 20 of the second pilot valve 5, thus moving the valve tappet 14 into the working chamber 34 adjoining the end cap 11.

Since the active surface 59 in compartment 15 is larger than the active surface 58 of the reversal piston 48 in chamber 55, the reversal piston 48 together with the sliding shop 60 is rnoved in c 1 1 ' ' t LoWIL(Jj L11c, connection 56 for the working air AL, until the annular surface 70 on the reversal piston 48 abuts the annular surface 71 of the ca5ing 25 (Pig5. 6 and 7). Owing to this movement, the connection between the connection 56 and the working compartment 54 adjoining the end cap 11 is broken and instead the working compartment 34 i5 connected to the guide cavity 61 in the sliding shoe 60 via the ducts 31, 32, 33, 30, 72, 23 in the end cap 11, in the well 29 of the cylindrical ca5ing 2 and in the 11 valve plate 3, and is then connected to atmosphere A via the ducts 22, 28 in the valve plate 3- The working air AL now flows through the ducts 21, 35 in the valve plate 3 into the working compartment 36 adjoining the valve plate 3 and moves the air piston 6 tnwards the end cap 11- Since the tappet 14 of the first pilot valve 4 loses contact with the air piston 6, the tappet 14 is moved by the helical pressure spring 18 into the position in Fig. 5The sealing ring 17 is r)ri tn it.5.:;eAt in the stepped bore 12. The connection between the branch duct 62 and the duct 39 adjoining the longitudinal portion 38 in the stepped bore 12 in the valve plate 3 is broken- As a result, the air is enclosed in duct$ 39, 40, 41, 42, 3 and in the compartment 45 and in the spring compartment 20 of the second pilot valve 5.

Shortly before reaching the bottom dead centre position the air piston 6 comes into contact with the tappet 14 of the second pilot valve 5 and lifts the sealinq ririq 17 thereof from its seat, so that the enclosed air can now escape to atmosphere A via the spring compartment 20 in the second pilot valve 5 and the longitudinal portion 38 and through the transverse duct A9.

Since the compartment 45 in the casing 25 is now Connected to atmosphere A, the working air AL again moves the rever;5al piston 48 and consequently also moves the sliding shoe 60 in the direction towards the compartment 45 and another work cycle begins. owing to the transmission ratio of the air piston 6 relative to 12 the hydraulic piston 7, the hydraulic piston 7 when moving in one direction sucks hydraulic inedium from the suction line 66 via the suction valve 64, so that in the other direction of motion the hydraulic medium is transferred under high pressure via the delivery valve 67 to the delivery line 68. Owing to the oscillating motinn nf the air 6 und (-c.)i1L;(-,queiiLly of the hydraulic piston 7, the flow delivered in the line 68 is substantially free from pulsation.

Fig. e illustrates an embodiment of a pneumatically driven hydraulic pump la, basically corresponding to the pump previously described with reference to Figs- 1 to 7. However, the hydraillic piston 7 is associated with an additional hydraulic piston 7a- The additional hydraulic piston 7a is likewise nonpnsitively connected to the air piston 6 and slides and extends through the valve plate 3 of the cylindrical casing 2. The additional hydraulic piston 7a, like the first hydraulic piston 7, operates in a T-shaped duct 63 in a high-pressure casing 65, i.e. it intakes hydraulic medium through a suction valve 64 from the suntinn line 66 and then delivers it under high pressure through a delivery valve 67 to the delivery line 68.

Since, as stated, the embodiment in Fig. 8 is otherwise similar to that in Figs. 1 to 7, the description of this construction will not be repeated.

The embodiment of a hydraulic pump 1b shown in Figs. 9 and 10 also has basically the same construction as the hydraulic p=p 1 in Figs. 1 to 7.

In addition, however, a manual actuating system is superposed on this construction. The air Piston 6, via a linkage 73 extending through and movable relative tothe valve plate 3, can he mannally a(iji).stl.pt-3 against- the. restoring force of a helical pressure spring 74 incorporated in the working compartment 34 between the air piston 6 and the end cap 11. Tn this end the dlict23 is closed between the chamber 55 in the casing 25 and the ducts 30, 31, 32, 33 leading to the working compartment 34 between the end cap 11 and the air piston 6.

The linkage 73 is provided with a hand lever 75- BY rotating the hand lever 75 through 180' alternately around the longitudinal axis 76 of the hydraulic pump lb, the linkage 73 is moved in reciprocation by an amount equal to the stroke of the air piston 6 in the cylindrical casing 2, so that the hydraulic piston 7 non-positively connected- to the air piston 6 intakes hydraulic medium as before from a suction line 66 via a suctidn valve 64 and delivers it through a delivery valve 67 to the delivery line 68- If the construction in Figs. 9 and 10 is to be pneumatically driven, the hand lever 75 is locked in the position shown in Fig. 10. Ducts 30, 31, 32, 33 are still blocked by the plug 77 - 'I'he suction stroke is still perfomed by the spring 74.

The bottom piston Compartment 34 ij vc-,ilLilu'Ld Llirough a duct 78. A suitable filter element 79, pressed into the ventilation bore, prevents soiling of the lower piston compartment 34- 14 When operation is pneumatic as before, the hand lever romains motionless and cannot cause injury.

Claims

C L A I M S

1. A pneumatically driven hydraulic pump (1, la, lb) comprising an air piston (6) movable in a plastic cylindrical casing (2) with an integrally moulded valve plate (3) and reversing pilot valves (4, 5) in the two end positions and also comprising a hydraulic piston (7) non-positively connected to the air piston (6) and connected by a suct-inn (64) LC) L1 GLIcLion line (66) and by a delivery valve (67) to a delivery line (68) and wherein a first pilot valve (4) is provided in a <stopped bore (12) in the valve p_ate (3) and the second pilot valve (5) is provided in a stepped bore (13) in a plastic end cap (11) closing the cylindrical r.,-sincT (2) and guiding the hydraulic piston (7), wherein a plastic reversal casing (25) is releasably flanged on the side of the valve plate (3) and in it a reversal piston (18) havinq two active end faces (58, 59) of different sizes is movable in reciprocation by the working air (AL) and entrains a slidinq shoe (60) fo.r-rncd with a guide cavity (61), whereby the working air (A1) constantly arriving in a chamber (55) guiding the guiding shoe (60) in the reversal casing (25) is c n 2, nveyed via ducts (421, 22 and 23, 30, 31, 3, 33) formed in the valve plate (3), the wall (29) and the end cap (11) of the cylinder casing (2) alternately in one or the other wnrkinq compartment (26, 1214) on the two sides of the air piston (6) and on to the sealing members (17) of the pilot valves (1, 5) and whIereby -o the exhaust air from the working compartments (36, 37) can be conveyed to atmosphere (A) via the guide cavity (61) in the slidinq shoe (60).

16 2. A hydraulic pump according to claim 1, wherein the longitudinal portion (54) of the reversal piston (48), which projects into the chamber (55) of the reversal casing (25) arid lias the smaller active n-nd face (58) has a recess (53) adapted to the length of the rectangular slidinq shoe (60) and peripherally overlappinq the sliding shoe (60).

3. A hydraulic pump according to claim 1 or 2, wherein the chamber (55) is permanently connected via a branch. duct (62) in the valve plate (3) to the stepped bore (12) receiving the first pilot valve (4) - 4_ A hydraulic pump according tn any of claims 1 to 3, wherein the stepped bore (12) in the valve plate (3) is connected via ducts (39, 43, 44) in the valve plate (3) and in the reversal rasing (25) to a compRrtment (45) in the reversal casing (25) guiding the lonqitudinal portion (47) of the reversal piston (48) having the larger active surface (1)9) and is also connected via ducts (40, 41, 42) in the wall (29) of the cylindrical casing (2) and in the end cap (11) to the stepped bore (13) in the end cap (11) -receiving the pilot valve (5) - 1 tO A hydraulic Pump accOrdinq to any of claims 4, wherein the stepped bore (13) in the end cap (11) is connected to atmosphere (A) by a branch duct (49).

6_ A hydraulic pump according to any of claims 1 to 5, wherein the air piston (6) is non-positively connected in coaxial alignment with the hydraulic piston (7) to a second piston (7a) extenciinq through and movable relative to the valve plate (3) and connected to the suction line (66) via a suction valve (64) and connected to the delivery line (68) via a delivery valve (67)- 7. A hydraulic pump according to any of claims 1 to 5, wherein the air piston (6), via a linkage (73) extending through and movable relative to the valve plate (3), is manually adjustable:qcjii-ist thr force of a spring (74) incorporated in the working compartment (34) between the air piston (6) and the end :ap (11), wherein the thl-, (55) and the working compartment (34) between the end cap (11) and the air piston (6) is closed- 8- A hydraulic pump according to claim 7, wherein a hand lever (75) associated with the linkage (73) is lockable.

9. A hydraulic pump substantially as hereinbefore described with reference to the accompanying drawings.