WO2015086532A1

WO2015086532A1 - Hydraulic system for automatic sequential cylinder operation

Info

Publication number: WO2015086532A1
Application number: PCT/EP2014/076895
Authority: WO
Inventors: Klaus Angleitner
Original assignee: Fella Werke Gmbh
Priority date: 2013-12-12
Filing date: 2014-12-08
Publication date: 2015-06-18
Also published as: GB201321999D0

Abstract

A hydraulic system comprising a first hydraulic cylinder (44) and a second hydraulic cylinder (56) is provided wherein a hydraulic circuit provides for automatic sequential operation of the cylinders (44,56). The second hydraulic cylinder (56) comprises a cylinder housing (150), a chamber (152) and a piston (154) having a movement range, and first and second ports (156,158) disposed on respective sides of the piston (152) for delivering pressurised fluid to move the piston (154) within the chamber. An end portion of the housing (150) accommodates a third port (160) hydraulically connected to the first hydraulic cylinder (144) and a fourth port (162) hydraulically connected to a hydraulic pressure source. The third and fourth ports are connected by a fluid passage (164) disposed in said end portion. A valve (166) located in the fluid passage (164) is biased into a closed position and is opened by a plunger (170) which is pushed by the piston (154) when at one end of said movement range.

Description

DESCRIPTION

HYDRAULIC SYSTEM FOR AUTOMATIC SEQUENTIAL CYLINDER OPERATION

TECHNICAL FIELD

The invention relates to hydraulic systems comprising first and second hydraulic cylinders which are operable in sequence. In an example application, the hydraulic systems may be embodied in agricultural machinery for folding and unfolding working tools between working and transport configurations.

BACKGROUND

Sequential operation of multiple hydraulic cylinders in any application typically requires separate spools to operate a second cylinder once a first cylinder has reached a desired extension. Furthermore, automatic systems require means to sense that the first cylinder has reached a predetermined extension.

SUMMARY OF INVENTION

It is an object of the invention to provide a hydraulic system for sequential operation of multiple cylinders with fewer components than known systems.

In accordance with the invention there is provided a hydraulic system comprising a first hydraulic cylinder and a second hydraulic cylinder, the second hydraulic cylinder comprising a cylinder housing, a chamber and a piston having a movement range, and first and second ports disposed on respective sides of the piston for delivering pressurised fluid to move the piston within the chamber, wherein an end portion of the housing accommodates a third port hydraulically connected to the first hydraulic cylinder and a fourth port hydraulically connected to a hydraulic pressure source, the third and fourth ports connected by a fluid passage disposed in said end portion, wherein a valve located in the fluid passage is biased into a closed position and is opened by a plunger which is pushed by the piston when at one end of said movement range.

Advantageously, the piston-operated plunger in one end of the second cylinder housing provides an automatic flow control for operating the first cylinder which is in direct response to a predetermined extension (or piston position) of the second cylinder. A mechanical means of automation is thus provided which saves on the need for separate sensors and spools.

The first port and the fourth port are preferably connected to a common hydraulic pressure source so that the first hydraulic cylinder is not activated until the piston of the second hydraulic cylinder has reached said one end of the movement range. Two sequentially-operated cylinders can thus be operated from a single pressure source.

The plunger preferably protrudes into the chamber when the valve is in the closed position so that the piston acts directly upon the plunger without the need for additional or complex linkages to the valve.

In a preferred arrangement the valve comprises a ball disposed in an elbow portion of the fluid passage when in the closed position, the ball being displaced into a recess when in the open position.

The ball is preferably biased out of said recess by a compressed coil spring disposed in the recess. However, other biasing means are envisaged.

The invention lends itself particularly well to agricultural working tools having a frame that folds between a working and a transport position, and more especially a frame that folds in an obligatory sequence of stages.

BRIEF DESCRIPTION OF SPECIFIC EMBODIMENTS

Further advantages of the invention will become apparent from reading the following description of a specific embodiment with reference to the appended drawings in which:-

Figure 1 is a highly schematic plan view of a agricultural tedder in a working configuration;

Figure 2 is a perspective view of an agricultural tedder comprising a hydraulic system in accordance with an embodiment of the invention shown in a working configuration;

Figure 3 is a side view of a front part of the tedder of Figure 2 in a working configuration; Figure 4 is a perspective view of the front part of the tedder of Figure 3;

Figure 5 is a side view of a front part of the tedder of Figure 2 in a transport configuration with some parts omitted for clarity;

Figure 6 is a perspective view of the front part of the tedder of Figure 5;

Figure 7 shows a hydraulic control circuit embodied in the tedder of Figure 2;

Figure 8 is a schematic view of a hydraulic system according to one embodiment and suitable for application in a hydraulic control system for the tedder of Figure 2; and,

Figure 9 is a vertical section through one hydraulic cylinder of the system shown in Figure 8.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENT

The following description will make use of directional terms which are used in relation to the forward direction of travel F. The term "longitudinal" will typically refer to a direction parallel to the forward direction of travel, whereas the term "transverse" will mean a horizontal direction perpendicular to the forward direction of travel.

With reference to Figures 1 and 2, an agricultural hay tedder 10 comprises a wheeled chassis 12 and a plurality of rotors 14 mounted to a support frame 16. The invention will be described hereinafter as embodied in the hay tedder 10. However, it should be understood that the invention could instead be embodied in other working tools, for example, a planter having a plurality of planting units.

Wheeled chassis 12 comprises at a front end a drawbar 18 for attachment to a towing hitch of a tractor (not shown). A longitudinal tongue 20 extends rearwardly from the drawbar 18 to a widened part of the chassis 12 which supports a transverse axle 22. Pivotably mounted to the rear of chassis 12 is a centre frame 24. A transverse hinge arrangement 26 permits the centre frame to rotate about the hinge axis from a deployed or working position (Figs. 1 and 2), to a raised headland position, and to a fully folded transport position. It should be understood that the hinge arrangement 26 may take several different forms and is shown in highly schematic form in Figure 1. The embodiment illustrated in Figure 3 for example includes a centre frame 24 that pivots around a transverse axis hidden from view by the wheel shown.

In the working position the centre frame 26 resides behind the chassis so as to position the rotors 14 near to the ground as required during the tedding operation.

The support frame 16 further comprises a pair of side frame assemblies 28 each being pivotably mounted to the centre frame 24 about respective hinge arrangements 30 which extend in a fore and aft (longitudinal) direction when in the working configuration. Each side frame assembly 28 includes an inner wing 32 pivotably mounted to the centre frame 24 and an outer wing 34 pivotably mounted to the inner wing 32 about respective hinge arrangements 36. Again, the hinge arrangements 30,36 may be provided with a host of alternative constructions. However, in each case, the hinge arrangement defines a longitudinal pivoting or folding axis.

In the working position the support frame 16 has an elongate axis which extends transversely and defines the working width of the tedder 10. The support frame supports the rotors 14 from above. Torque derived from a power take off (PTO) shaft 40 attached to the tractor is transmitted to the rotors 14 via a driveline including various drive shafts and gearboxes also supported by the frame 26.

Each hinged arrangement 26,30,36 has associated therewith one or more hydraulic cylinders to control movement of the pivotably connected members around the respective folding axes defined by the associated pivot joint.

With reference to Figures 3 and 4, a hydraulic cylinder arrangement 42 is connected between the chassis 12 and the centre frame 24. In the hydraulic cylinder arrangement 42, a first hydraulic cylinder 44 is connected between a pivoting joint 46 located at the front region of chassis 12 and a pivoting joint 48 provided in an upper region of a rocker arm 50 which comprises a pair of inwardly tapering arm members 52 each pivotably mounted to the chassis 12 for movement around a transverse axis defined by securing pins 54. Extension and retraction of first hydraulic cylinder 44 serves to move rocker arm 50 backward and forward respectively about pin 54.

Second and third hydraulic cylinders 56,58 are joined by a common piston rod 60, together forming a series-arranged dual hydraulic cylinder arrangement 62 which is connected between a pivotable joint 64 in the upper region of the rocker arm and a pivotable joint 66 on the centre frame 24. Despite sharing a piston rod 60, the pistons (not shown) of second and third cylinders 56,58 may have a different diameter.

Extension of one or both of the second and third cylinders 56,58 pivots the centre frame about the hinge arrangement 26 so as to unfold or lower the centre frame to the ground. Retraction of one or both of the second and third cylinders 56,58 pivots the centre frame about the hinge arrangement 26 so as to fold or raise the centre frame. The folding and unfolding sequences between the transport, headland and working configurations will be described in more detail below.

Connected between respective ones of the inner wings 32 and the centre frame 24 are dual inner wing hydraulic cylinders 70 (Fig. 2) for controlling pivoting movement of the inner wings 32 about respective hinge arrangements 30. Each dual cylinder 70 comprises a two-way main cylinder 70' which serves to fold and unfold the inner wings 32 between the transport and headland configurations, and a one-way auxiliary cylinder 71 which serves to raise and lower the inner wings 32 between the working and headland configurations.

Similarly, dual outer wing hydraulic cylinders 72 are connected between respective ones of the outer wings 34 and the respective adjacent inner wing 32 for controlling pivoting movement of the outer wings 34 relative to the inner wings 32 about respective hinge arrangements 36. Each dual cylinder 72 comprises a two-way main cylinder 72' which serves to fold and unfold the outer wings 34 between the transport and headland configurations, and a one-way auxiliary cylinder 73 which serves to raise and lower the outer wings 34 between the working and headland configurations.

All hydraulic cylinders 44,56,58,70,72 are connected hydraulically to the tractor which supplies pressurised fluid thereto in response to operator commands. A control system will be described below. Although the described embodiment includes hydraulic cylinders, other linear actuators may be used instead without deviating from the scope of the invention. For example, electric linear actuators could be used in place of the hydraulic cylinders described.

The different configurations and movement therebetween will now be described. Working configuration

In the working configuration all hydraulic cylinders 44,56,58,70,72 are fully extended and the support frame 24 is completely unfolded. In this mode, the rotors are rotateably driven around substantially vertical axes and crop-engaging tines attached thereto ted crop swaths as the machine 10 is driven across a field.

Headland configuration

Upon reaching the end of the swaths, typically on the headland of a field, the frame 26, and thus rotors 14, are lifted into a headland position so as to not disturb the headland swaths during turning. From the working configuration third cylinder 58 is retracted so as to pivot the entire support frame 24 around hinge 26 and, as a result, lift the rotors. Also, the auxiliary wing cylinders 71 ,73 are retracted to partially lift the outer sides of wings 32,34 and increase the ground clearance for the rotors 14.

It will be apparent that cylinders 58,71 ,73 serve to switch the machine between working and headland modes and, as such, are preferably controlled by a separate hydraulic line (described in more detail below). Cylinders 58,71 ,73 need only be single-acting because the weight of the lifted frame 24 and rotors 14 serves to provide a lowering force.

When returning to the working position, all cylinders 58,71 ,73 are returned to their fully extended positions.

Transport configuration

The support frame 24 is foldable about hinge axes 26,30,36 into a transport configuration which is narrower and thus suitable for movement on public highways. From either the headland position described above the process of folding the support frame comprises a sequence of folding stages. In a first stage of folding, second hydraulic cylinder 56 is fully retracted so as to pivot the support frame 24 around the transverse hinge 26. At the same time the wing cylinders 70', 72' are fully retracted to fold the wings 34,32 upwardly and inwardly with respect to the centre frame 24. By simultaneously folding the centre frame 24 and the side assemblies 28, the height obtained by the extremities of the latter is reduced, in turn reducing the risk of impacting on tree branches or overhead power cables.

Following the first stage a significant proportion of the weight of the rotors 14 and support frame 24 is supported on rocker arm 50. Advantageously, the provision of the rocker arm reduces the stress on the hydraulic cylinders 44,56,58.

In a second stage of folding, first hydraulic cylinder 44 is fully retracted to the position shown in Figures 5 and 6. This lowers the folded frame 24 with rotors 14 onto a transport tray 90 which is secured to chassis 12. The transport tray 90 serves both to support the weight of the folded frame 24 and rotors 14 and as a guard to prevent damage to the rotors 14 during transport.

When unfolding from the transport configuration, the folding sequence is reversed. Therefore, the first cylinder 44 is extended before the second cylinder 56 and wing cylinders 70',72' are extended, (to remain in headland position the third cylinder 58 remains retracted).

Hydraulic Control System

The hydraulic cylinders 44,56,58,70,72 are controlled by a hydraulic control system which may be purely hydraulic or electro-hydraulic. Figure 7 shows an example hydraulic circuit which will be described hereinafter.

First and second hydraulic lines 101 ,102 are connected to respective couplings of a two-way spool valve (not shown) of the attached tractor. Activation of the spool valve in response to a driver commands feeds pressurised fluid to one of the two hydraulic lines 101 ,102.

Starting from the transport configuration, a positive supply of pressurised fluid to first line 101 extends first hydraulic cylinder 44 in a first unfolding stage. Valve 103 opens in response to cylinder 44 reaching full extension and only then does fluid pass to second cylinder 56 and wing cylinders 70',72' to effect the second stage of the unfolding sequence.

Starting from the headland configuration, a positive supply of pressurised fluid to second line 102 retracts wing cylinders 70', 72' and second cylinder 56 in a first folding stage. Valve 104 opens in response to second cylinder 56 reaching a fully retracted position and only then does fluid pass to first cylinder 44 to effect the second stage of the folding sequence.

A further, single-acting, hydraulic line 1 10 is connected to third cylinder 58 and auxiliary wing cylinders 71 ,73 for controlling the movement of the frame 24 between headland and working configurations. A valve 1 1 1 may be provided to ensure sequential control of folding around the transverse axis 26 before the longitudinal axes 30,36.

Figures 8 and 9 illustrate an example hydraulic arrangement which can be employed in the circuit of Figure 7 wherein valve 104 is effectively integrated into the housing of second cylinder 56. In this example, second hydraulic cylinder 56 comprises a cylinder housing 150, a chamber 152, and a piston 154 having a movement range between a fully retracted position and a fully extended position. First and second ports 156,158 supply fluid to respective sides of the piston 154 to control movement thereof. First port 156 is connected to line 102 to supply a hydraulic signal that retracts cylinder 56. Second port 158 is connected to line 101 to supply a hydraulic signal that extends cylinder 56.

An end portion of the housing 150 accommodates a third port 160 hydraulically connected to one side of the first hydraulic cylinder 44. The end portion also accommodates a fourth port 162 hydraulically connected to the first port 156 and line 102. The third and fourth ports 160,162 are connected by a fluid passage or bore 164 formed in the end portion.

The fluid passage 164 is substantially z-shaped having two radially extending passages joined by an axially extending passage.

In a right-angled part of the fluid passage an in-line valve 104 is provided which comprises a displaceable ball which is biased into a closed position by a compressed coil spring 168. Valve 166 is opened by an axially-extending plunger 170 which projects into the piston chamber 152 and is pushed by the piston 154 when the cylinder 56 is fully retracted.

The plunger 170 is supported within an axial bore 171 by a seal 172 which permits the plunger 170 to move axially whilst maintaining a seal between the piston chamber 152 and the fluid passage 164.

In the context of application in the hydraulic circuit of Figure 7, valve 166 serves the function of valve 104 wherein retraction of first cylinder 44 in the folding sequence is prevented until the second cylinder 56 is fully retracted.

It should be appreciated that an integrated valve may be provided in a cylinder housing of the first hydraulic cylinder 44 to serve the function of valve 103 instead of, or in addition to, the integrated valve 166 of second hydraulic cylinder 56 described above.

Instead of directly and mechanically sensing the position of the cylinder piston, in a not-illustrated alternative embodiment, an electrical sensor may be provided to sense the position of the rocker arm 50. An electrical signal from the sensor may be exploited to control electro-hydraulic valves so that the first and second cylinders 44,56 operate in sequence as required.

It should be understood that sequential operation of the multiple cylinders is not always essential. However, in the embodiment illustrated, any operation of the second cylinder 56 and/or wing cylinders 70,72 before first cylinder 44 is fully extended would likely cause damage to the rotors 14, support frame 16 and transport tray 90.

In summary there is provided a hydraulic system comprising a first hydraulic cylinder and a second hydraulic cylinder is provided wherein a hydraulic circuit provides for automatic sequential operation of the cylinders. The second hydraulic cylinder comprises a cylinder housing, a chamber and a piston having a movement range, and first and second ports disposed on respective sides of the piston for delivering pressurised fluid to move the piston within the chamber. An end portion of the housing accommodates a third port hydraulically connected to the first hydraulic cylinder and a fourth port hydraulically connected to a hydraulic pressure source. The third and fourth ports are connected by a fluid passage disposed in said end portion. A valve located in the fluid passage is biased into a closed position and is opened by a plunger which is pushed by the piston when at one end of said movement range.

Claims

1. A hydraulic system comprising a first hydraulic cylinder and a second hydraulic cylinder, the second hydraulic cylinder comprising a cylinder housing, a chamber and a piston having a movement range, and first and second ports disposed on respective sides of the piston for delivering pressurised fluid to move the piston within the chamber, wherein an end portion of the housing accommodates a third port hydraulically connected to the first hydraulic cylinder and a fourth port hydraulically connected to a hydraulic pressure source, the third and fourth ports connected by a fluid passage disposed in said end portion, wherein a valve located in the fluid passage is biased into a closed position and is opened by a plunger which is pushed by the piston when at one end of said movement range.

2. A hydraulic system according to Claim 1 , wherein the first port and the fourth port are connected to a common hydraulic pressure source so that the first hydraulic cylinder is not activated until the piston of the second hydraulic cylinder has reached said one end of the movement range.

3. A hydraulic system according to Claim 1 or 2, wherein the plunger protrudes into the chamber when the valve is in the closed position.

4. A hydraulic system according to any preceding claim, wherein the valve comprises a ball disposed in an elbow portion of the fluid passage when in the closed position, the ball being displaced into a recess when in the open position.

5. A hydraulic system according to Claim 4, wherein the ball is biased out of said recess by a compressed coil spring disposed in the recess.

6. An agricultural working tool comprising a hydraulic system according to any preceding claim.