GB2095798A

GB2095798A - Changeover device

Info

Publication number: GB2095798A
Application number: GB8209359A
Authority: GB
Original assignee: Joseph Voegele AG
Current assignee: Joseph Voegele AG
Priority date: 1981-03-31
Filing date: 1982-03-30
Publication date: 1982-10-06
Also published as: DE3112929A1; GB2095798B; DE3112929C2

Abstract

In a change-over device a block- like gate valve closure member 4 is driven by a hydraulic control circuit having a reversible pump 18 which selectively supplies pressure to pistons 13, 14 engaging the valve gate 4. The housing defines a plane control face 10 in which the mouths of consumer lines A, B and interposed supply line P terminate. On this plane control face 10 slide shearing bushes 12 which are spring-guided in the gate 4 in a U-shaped passage 9, optionally establishing communication between the supply line and a consumer line while the other consumer line is connected to tank means 24 in the hydraulic circuit prevents overloading of the pump. <IMAGE>

Description

SPECIFICATION Changeover device for a dual line central grease lubricating system The invention relates to a changeover device of the type described in the preamble to the Main Claim.

Changeover or reversal devices are known (leaflet of Messrs. De Limon Fluhme 8 Co., Dusseldorf) which are actuated either by an electric motor with a gear mechanism or pneumatically with electromagnetic anticipatory control. The amount of equipment involved thereby is considerable, since the drive means are separate assemblies which are in structural communication with the actual housing of the changeover device. For the high pressures (300 bars and more) in the grease, particularly cold grease, high actuating forces are needed for the gate valve but they must at same time be limited against overload. In addition,-it is necessary to ensure that with cold grease, too, the grease reaches the consumer in the prescribed quantity and at the prescribed pressure.The pneumatically operated reversing or changeover devices necessitate at the work site a source of compressed air and a source of current.

However, compressed air is often unavailable in such locations.

Also known is an electrically controlled reversing device (Type EM of Messrs. Lincoln Helios GMBH Heidelberg, Leaflet 7406-05) in which a gate valve is reversed via a geared motor and a cam operated drive shaft. The pulses which result in the changeover process are emitted by the lubricating system itself, e.g. by limit pressure switches. With this reversing device, too, the equipment involved is complicated and expensive.

Mounted on a chassis is an electric motor with a gear mechanism and a cam control device which has its working rhythm monitored by a microswitch. Via a push rod and, on its downstream side, a spring mechanism, a reversing gate valve is driven in the chamber of the reversing housing, the gate valve being constructed after the fashion of a piston slide valve. The housing requires complicated grease guide bores and an accurately fitted in and finely machined gate valve in the housing chamber. All in all, the known changeover devices suffer from the drawbacks of extremely complicated construction, large dimensions and complicated actuation. At the same time, no adequate sealing effect can be achieved, especially when using a piston slide valve.

The invention is based on the problem of basically simplifying a changeover device of the type mentioned at the outset in comparison with the known solutions in terms of its technical construction, of achieving a hermetic seal at the gate valve and of guaranteeing high but confined gate valve positioning forces.

According to the invention, the problem posed is resolved by the features indicated in the characterising part of the Main Claim.

A hydraulic reversing or changeover drive is small in size and ensures the necessary positioning forces at the gate valve even with cold grease. In fact in the case of a hydraulic changeover drive, load confinement is easily provided. Co-operation between the plane control face and the shearing bushes lead to a hermetic seal so that leakage losses are avoided. The housing can be constructed as a simple6lock, as can also the gate valve and the element which constitutes the control face, a factor which provides considerable advantages from the manufacturing point of view. The connections in the control face and the throughflow passage in the gate valve can be simply constructed. Dead spaces in which cold grease could deposit and then resinify are avoided.In the interaction between hydraulic changeover drive and the simple construction of the grease control system, the amount of apparatus involved can be fundamentally simplified in comparison with known solutions. The changeover device operates substantially maintenance-free and independently of the position in which it is installed and is unaffected by outside influences. Particularly favourable is the fact that it comprises a closed hydraulic system and, at the work site, requires only a supply of current to operate the pump.

Claim 2 discloses a preferred embodiment of the invention. With this development, small dimensions or a desirably compact construction are achieved.

Also important are the features indicated in Claim 3. In this way, the hydraulic changeover drive operates independently of the grease control system. The pressure limiting valves ensure reliable overload protection. The snifting nonreturn valves provide a constantly closed hydraulic circuit since when the gate is in its extreme position, the pump draws in through a snifting valve and pushes out through the pressure limiting valve.

Also expedient are the features indicated in Claim 4. The chamber and the control face can be produced with technically minimal outlay.

Nevertheless, they operate together with a high degree of reliability, despite the high pressures and also do so with cold grease.

A further important measure is stressed by Claim 5. The bore may be a simple blind hole in the side face of the housing while the gate valve may be of any desired form and be made for example from just bar material. The connection between the consumer connection which is to be relieved and the tank connection is established automatically upon movement of the gate valve without the need for any special connecting passages being provided in the gate valve.

Instead, the grease pressure then prevailing in the consumer line which is to be relieved still works towards moving the gate valve into the other position in which the other consumer connection is connected to the grease supply connection. The supply connection to be relieved provides considerable space so that hardly any reflux losses occur.

A further expedient embodiment of the invention is disclosed in Claim 6. A cylindrical gate valve may be a simple body of rotation which is correspondingly dimensioned and inserted into the chamber. So that it can perform its function perfectly, it is only necessary for it to be slidingly mounted and non-rotatably guided. The measures to be provided to this end are similarly simple and nevertheless very reliable.

Advantageously, securing of the gate valve against rotation is undertaken in the way disclosed by Claim 7.

In practice, a highly successful embodiment of gate valve securing means is disclosed in Claim 8.

Fitment on the slot in the end face is as simple as fixing a tongue or guide pins in the rear wall of the housing bore which is open at one end.

The gate valve can be displaced particularly smoothly between its two positions by the hydraulic control drive, if the measures according to Claim 9 are implemented. The medium to be controlled then provides simultaneously for lubrication of the rolling or plane-bearing mountings.

Furthermore, Claim 10 indicates an advantageous embodiment of the object underlying the invention. The shearing bushes seal whichever is the pressurised passage for the grease reliably against the ambient which may be pressureless or subject to minimal pressure. They are in fact loaded by the pressure of the grease in the direction of the control face so that the difference in diameters constitutes a force component which in the direction of application of pressure of the shearing bushes. This force of application assists the action of the springing bracing of the shearing bushes.

The springing supporting action can be achieved particularly easily from the structural point of view in accordance with Claim 11. The Oring which provides an initial pre-tension on each shearing bush provides at the same time for sealing-tightness of openings of the throughflow passage in the slide valve vis-a-vis the interior of the chamber in the housing.

Finally, the measure outlined by Claim 10 is also important, this measure making it recognisable from outside the position in which the gate valve is at any given time or which makes it possible to derive the pulses for hydraulic reversal of the position of the gate valve or to provide for it to be controlled. The gate valve device provided by the hydraulic changeover means are in this way used for automatic controlling of the device.

An embodiment of the invention will be explained in greater detail hereinafter with reference to the accompanying drawings in which: Fig. 1 is a diagrammatic partly sectional view of a changeover device according to the invention; Fig. 2 is an enlarged sectional detailed view of the housing part which contains the gate valve, and Fig. 3 is a sectional view taken on the plane Ill-Ill in Fig. 2.

The diagrammatic view in Fig. 1 shows a changeover device 1 for a dual-line greaseconsumer lubricating system. The changeover device has a solid housing 2 in which there is constructed a chamber 3 for a gate valve 4 which is guided for displacement between two positions. Leading into the chamber 4 is a supply connection P alongside which, in the direction of sliding movement of the gate valve 4, there are provided spaced-apart consumer connections A and B. The connections P, A and B have in the chamber 3 their terminations 5, 6, 7 or mouths in a control face 10 which faces an end face 11 of the gate valve. Leading out of the chamber 3 is a tank connection T which discharges into the chamber 3 at 8. Constructed in the gate valve 3 is a U-shaped throughflow passage 9 for the grease emerging from the supply connection P.Mouth parts of this throughflow passage 9 in the gate valve 4 contain shearing bushes 12, the purpose of which is to provide for perfect sealing.

As can be seen in Fig. 1, in each case one position of the gate valve 4, the throughflow passage 9 connects the supply connection P to a consumer connection A, B, while whichever is the free consumer connection A, B is connected to the tank connection T via the interior of the chamber 3. The (in the sliding direction) two end faces of the gate valve 4 are engaged by in each case an auxiliary piston 13, 14 which is displaceably guided in sealing-tight fashion in a cylinder space 15, 1 6 which is sealed in respect of the chamber 3. The cylinder spaces 15, 16 are connected to a hydraulic changeover means and can, via this latter, be alternately subjected to hydraulic pressure in order to bring about the sliding motion of the gate valve 4.The cylinder spaces 15, 16 are in flowing connection via pressure lines 1 7a, 1 7b with a hydraulic pump 18 which is reversible in each direction of conveyance and which can be actuated by a drive motor 19. The pressure lines 1 7a, 1 7b are supplied with oil from a hydraulic fluid reservoir 20 through lines 21 and snifting check valves 22 disposed therein. The pressure lines 1 7a, 1 7b are at the same time safeguarded against overload via lines 23 and adjustable pressure limiting valves 24. Instead of the pressure limiting valves 24, it is also possible to provide means of limiting the pressure in the pressure lines 1 7a, 1 7b.

The changeover device 1 according to Fig. 1 operates as follows:- In the position illustrated in which the hydraulic pump 18 is applying pressure to the cylinder space 1 5 through the pressure line 1 7a, the gate valve 3 is in its right-hand position. Via the throughflow passage 9 it connects the supply connection P to the consumer connection B so that a lubricant reaches the consumer in a consumer line not shown but connected thereto.

As a function of the time or by means not shown, the conveying direction of the hydraulic pump is then reversed so that the cylinder space 1 6 is now subject to the action of hydraulic fluid while hydraulic fluid is being drawn from the cylinder space 1 5. Thus, the gate valve 4 is moved leftwardly out of the position shown in the drawing whereby firstly the mouths 5 and 6 are sealed off before the throughflow passage 9 connects the mouths 5 and 7 to each other. The mouth 6 is exposed so that the consumer connection B is connected through the chamber 3 to the tank connection T or its mouth and so that any pressure prevailing in the grease can be dissipated. The hydraulic pump 18, via the auxiliary piston 14, displaces the slide valve 4 as far as its extreme left position.Since the gate valve 4 is then stopped, the pressure in the cylinder space 1 6 increases to a degree predetermined by the pressure limiting valve 24, whereupon the pressure limiting valve 24, upon further delivery by the hydraulic pump 18, dissipates this excess pressure into the reservoir 20. If due to leakage losses in the pressure line 1 7a or in the cylinder space 1 5 a negative pressure should arise, then the hydraulic pump 18 draws in fresh hydraulic fluid via the snifting check valve 22 so that the hydraulic control circuit remains constantly filled. The overload safeguard resulting from the pressure limiting valves 24 is also effective if the gate valve, for any unforeseeable reason, remains stationary during its movement. And thus damage to the system is avoided.As a safeguard against overload, it is possible also to associate with the hydraulic pump 1 8 a speed dependent device which, when a specific pump speed is exceeded, relieves the hydraulic control circuit pressure or shuts down the drive 19 for the hydraulic pump 1 8.

Figs. 2 and 3 show a cross-sectional view of a preferred form of embodiment which is characterised by structural and manufacturing simplicity.

Fig. 2 again shows the housing 2 in crosssection. The cylinder spaces 15, 1 6 are sealed towards the outside by screwed plugs 25. The chamber 3 is formed by a blind bore open at one end and emerging from a housing side 26, the rear wall 29 of the blind bore being flat and its side wall 27, being constructed as the shell of a cylinder. The open side of the chamber 3 is encircled by a recess 28 which serves to accommodate a sealing element, not shown. In this structurally simple construction, the control face 10 is constructed on the upper side of a connecting block 30 which, in the control face 10, comprises the mouths 5, 6, 7 of the connecting apertures A, P, B.Reference to Fig. 3 shows that the gate valve 4 has the form of a cylinder the plane end face 11 of which is directed towards the control face 10 while its other likewise plane end face has a longitudinally extending groove 36. Formed in the gate valve 4 is the throughflow passage 9 of two apertures 9a, 9b emanating at a right-angle from the end face 11 and which are connected via a passage 9c to form a U-shaped passage. The apertures 9a, 9b are expediently blind bores. Contained in each blind bore is a sleeve 31 having a lateral aperture 32 extending to the bore 9c.Resting on the end face of each sleeve 31 which is towards the control face 10 is an O-ring 33 which so springingly braces a shearing bush 12 that its edge 34 protrudes beyond the end face 11 of the gate valve 4 and is pressed in sealing-tight fashion against the control face 10. The edge 34 of each shearing bush 1 2 forms a sealing-tight fit 34 on the control face 10, the outside diameter of the edge 34 being smaller than the outside diameter of the shearing bush 12. In this way, the pressure out of the supply connection P generates at each shearing bush 12 a thrust force in the direction of the control face 10 which assists the springing action of the O-rings 33 and provides for perfect sealing in respect of the chamber 3.The auxiliary pistons 1 3, 14 are constructed as independent cylinders which protrude into cylinder spaces 15, 1 6 which are connected via pressure lines 17a, 1 7b to the hydraulic pump 18, not shown.

The rear wall 29 of the cylindrical bore forming the chamber 3 carries, extending in the sliding direction of the gate valve 4, a spring or key 35 which engages into the slot 36 in the gate valve and secures this so that it cannot rotate about its cylindrical axis. Provided between the gate valve 4 and the rear wall 29 of the chamber 3 is a rolling or plane bearing 37 which provides for easy displaceability of the gate valve even under the pressure emanating from the supply connection P.

Fig. 3 shows that the gate valve 4 has, compared with the inside diameter of the cylindrical bore wall 27, an outside diameter which is smaller by the sliding stroke so that the grease can flow unhindered out of whichever consumer connection A or B is exposed and onto the tank connection (not shown). The intermediate space between the outer periphery of the gate valve 4 and the inside wall 27 of the chamber 4 is in this way always filled with grease which helps both to iubricate the auxiliary pistons 1 3, 14 and also the slot and tongue guide 35, 36 and the bearing 37.

The bore 9c in the gate valve is expediently occluded by a plug 39 (Fig. 3).

Furthermore, a push rod 40 is displaceably and in sealing-tight fashion guided in the housing 2 and protrudes into the chamber 3, its bent-over end 41 being secured in the gate valve by means of a locking screw 42. The free end 43 of the push rod 40 projects from the housing and forms an indicator to show the position of the gate valve at any given time. As an alternative, the free end 43 of the push rod 40 may be constructed as a switching element which co-operates with a switch 44 which indicates proper actuation of the gate valve.

The block 30 which forms the control face 10 is expediently fixed to the housing 2 by fixing bores 38 and fixing screws, not shown.

Instead of a cylindrical gate valve 4, it would also be possible to use a parallelepiped gate valve which in the longitudinal and transverse direction is smaller than the chamber 3 so that whichever consumer connection A or B is exposed is reliably connected to the tank connection which discharges into the chamber 3.

Claims

1. Changeover device for a central dual line consumer lubricating system for grease, with a housing in which a gate valve guided in the longitudinal direction is provided in a chamber connected to the two consumers, one grease supply and one tank connection and displaceable between two positoins and which in each position estabiishes connection between a consumer connection and the supply connection as well as the other consumer connection and the tank connection and having a changeover drive for the gate valve, incorporating a drive means, characterised by a hydraulic changeover drive (1 5-24) with a hydraulic pump (18) which is reversible in its direction of delivery and which is safeguarded against overload, further being characterised by, provided in or on the housing (2), a plane control face (10) along which the gate valve (4) is s!idingly guided on the edges (34) of spring loaded shearing bushes (12) displaceable in mouth parts of a throughflow passage (9c, 9) connecting two apertures (9a, 9b) in the gate valve (4) and being characterised further by the gate valve (4) which is constructed as a block and which accommodates the shearing bushes (12), the consumers (A, B) and between them the supply connection (P) discharging in the direction of movement of the gate valve (4) and into the control face (10) with intermediate spacings which correspond to the distance between the apertures (9a, 9b) of the throughflow passage (9) constructed in the gate valve (4), the apertures (9a, 9b) being in the direction of displacement orientated at the mouths (5, 6, 7) in the control face (10).

2. Changeover device according to Claim 1, characterised in that the changeover drive is structurally incorporated into the housing on that side of the housing (2) which is remote from the control face (10).

3. Changeover device according to one of Claims 1 or 2, characterised in that at both ends of the gate valve (4), in cylinder spaces (15, 16) which are sealed in relation to the chamber (3) there are displaceable auxiliary pistons (13, 14) which are alternately subject to the action of the hydraulic pump (18) through control lines (17a, 17b) and in that each control line can be connected-to a hydraulic reservoir (20) via a pressure limiting valve (24) and a relief type nonreturn valve (22) connected in parallel therewith.

4. Changeover device according to one of Claims 1 to 3, characterised in that the chamber (3) consists of a cylindrical bore (27,29) open at one end and formed in a side face of the housing (2), the open side of which is closed by a control plate (30) containing the connections (A, B, P) with mouths (5, 6, 7) and on which the control face (10) is constructed.

5. Changeover device according to one of Claims 1 to 4, characterised in that the gate valve (4) is in the direction of slide and transversely thereto of smaller dimensions than the inside diameter of the bore (24,29) so that in any position the gate valve (4) exposes a consumer connection (A, P; mouth 6,7) in the control face (10) and establishes between a part of its outer surface and the inner face (27,29) of the bore a flow connection to the tank connection (P) which discharges into the chamber (4).

6. Changeover device according to one of Claims 1 to 5, characterised in that the gate valve (4) is a cylindrical block, of which one end face (11) is towards the control face (10) and in that the outside diameter of the gate valve (4) is at least by the gate valve travel smaller than the inside diameter of the bore and in that the gate valve (4) is non-rotatable about its cylindrical axis while being guided to slide in the bore (27, 29, 3) in the direction in which it is required to be operated.

7. Changeover device according to one of Claims 1 to 6, characterised in that in the end face of the gate valve (4) which is towards the back wall (29) of the bore there are engaging means for counter-engaging means provided in the rear wall (29) of the bore in order to safeguard the gate valve against rotation.

8. Changeover device according to Claim 7, characterised by a groove (36) in the end face and by a tongue (35) fixed in the rear wall (29) or by guide pins in the rear wall which engage one after another into the groove.

9. Changeover device according to one of Claims 1 to 8, characterised in that between the end face of the gate valve and the rear wall (29) of the bore there is a rolling type or plain bearing (37).

10. Changeover device according to one of Claims 1 to 9, characterised in that each shearing bush (12) has its edge (34) forming an annular fit projecting beyond the end (11) of the gate valve (4) and in that the outside diameter of the seat is smaller than the outside diameter of the shearing bush to which pressure can be applied.

11. Changeover device according to one of Claims 1 to 10, characterised in that each shearing bush (12) is springingly supported on an O-ring (33) fixed in sealing-tight fashion in the aperture (9a, 9b).

12. Changeover device according to one of Claims 1 to 11, characterised in that articulated on the gate valve (4) and parallel with the direction of slide is a push member (40), the free end (43) of which passes in sealing-tight through the cylindrical wall of the bore and is constructed as a gate valve position indicating elements or switch actuating element.

13. Changeover device substantially as hereinbefore described with reference to the accompanying drawings.