FRONT LIFTING DEVICE FOR A TRACTOR AND METHOD FOR OPERATING A TRACTOR'S FRONT LIFTING DEVICE

The present invention relates to a front lifting device for a tractor, which includes:

- a frame component, from which the front lifting device is arranged to be attached to the chassis of the tractor,

- a first lifting arm attached to the frame component,

- a second lifting arm attached to the frame component, - a first lift operating device for the first lifting arm,

- a second lift operating device for the second lifting arm.

The prior art describes a conventional front lifting device, such as that shown in Figure 1. A conventional front lifting device includes a frame component, a pushing arm, a lifting arm, and a cylinder for operating the lifting arms . The front lifting device is connected to the tractor from its frame component. The lifting arms are unified mechanical structures. In addition, the lifting arms are pivoted to rotate simulta- neously together around a horizontal axis. Thus the lifting arms move at the same level. Using a front lifting device according to the prior art it is difficult, for example, to attach implements that are tilted.

The invention is intended to create a front lifting device that is more versatile in use. The characteristic features of the present invention are, that the lifting arms together with the lift operating devices are separate and that the front lifting device includes an independent control system for controlling the lifting arms separately from each other. This makes it easier than before to attach implements. In addition, the invention is intended to create a method, which permits the more comprehensive control of implements. The characteristic features of the present invention are, that lifting arm is moved vertically using a lift operating device and that the

lifting arm is moved horizontally by a force transmitted by the implement between the lifting arms.

The tractor includes a chassis, to which the front lifting device is attached. The front lifting device includes a first lifting arm and a second lifting arm for attaching an implement. In addition, the first lifting arm and the second lifting arm are moved vertically independently of each other. The term vertical refers to the vertical direction of the tractor's chassis. The term horizontal in turn refers to the horizontal, i.e. transverse direction of the tractor's chassis. If the tractor tilts, the set of examination co-ordinates tilts along with it. In the set of co-ordinates of the tractor, the lifting arms move vertically independently of each other. In other words, the lifting arms are separate from each other in terms of vertical movement. The lifting arms that move independently of each other vertically permit implements to be attached to the lifting arms and further to the tractor's front lifting device more easily than previously. When the front lifting device according to the invention is used to attach an implement to a tractor, the operator can guide both lifting arms directly to the device, even though the implement may be tilted. Thus there is no need to lift the implement first of all on one lifting arm and only after that set the second lifting arm in place. In other words, the implement can be attached to both lifting arms before it is moved to any considerable extent. In addition, when the implement can be tilted when it is attached to the front lifting device.

In one embodiment, when the vertical distance of the lifting arms increases their horizontal distance decreases. The lifting arms include attachment points for attaching an implement. The embodiment in question permits the distances of the lifting arms to remain constant between the attachment points of the implement . Therefore a change in the vertical level of the

lifting arms imposes no excess strain on the implement and the lifting arms.

In a second embodiment, the first or second lifting arm is moved vertically by the lift operating device while the first or second lifting arm is moved horizontally by the force transmitted by the implement to the lifting arms. In other words, the implement transmits a force between the lifting arms, which keeps the lifting arms at the same distance from each other. In this embodiment, the vertical movement of the lifting arms is free, but the second lifting arm affects the horizontal movement of the first lifting arms. As the implement transmits a force between the lifting arms, on the basis of which the horizontal distance of the lifting arms is regulated, the embodiment is made very simple.

Figure 1 shows a front lifting device according to the prior art,

Figure 2 shows the front lifting device according to the in- vention, when the lifting arms are vertically on different levels,

Figure 3 shows the front lifting device according to the invention, with the rotating frame straight and the lifting arms at different levels, Figure 4 shows a lifting arm equipped with a spring element,

Figure 5 shows the front lifting device according to the invention, with the rotating frame turned,

Figure 6 shows a front lifting device according to the invention, Figure 7 shows a front lifting device according to the invention,

Figure 8 shows the cylinder with a sensor,

Figure 9a shows the user interface of the vertical movement of the lifting arms, Figure 9b shows the position of the lifting arms, when the user interface is in the position of Figure 9a,

Figure 10a shows the user interface of the vertical movement of the lifting arms, when then lifting arms are at the same level, and

Figure 10b shows the position of the lifting arms, when the user interface is in the position of Figure 10a.

Figure 1 shows a front lifting device 10' according to the prior art, which is arranged to be attached to the chassis of a tractor by a frame component 12'. Further, the frame compo- nent 12' includes a pushing arm 14', lifting arms 16', and cylinders 18'. The pushing arm 14' and the lifting arms 16' form together the attachment means 26' of the implement. The front lifting device 10' also includes a power-take-off 20', so that the implement will receive the power it needs . As the lifting arms 16' remain on the same vertical line, i.e. height, relative to the frame component 12 ' and further the chassis of the tractor, their operation is very restricted. Lifting arms 16' according to the prior art cannot be moved separately vertically. When the implement is attached, the lifting arms move vertically in the same level. In addition, during the operation of the implement, the implement cannot be tilted transversely to the tractor.

Figure 2 shows the front lifting device 10 according to the invention attached to the chassis 32 of a tractor 28. Further, an implement 30, which is a ploughing plate 42, is attached to the front lifting device. The front lifting device 10 is attached by is frame component 12 to the tractor 28. The front lifting device 10 includes a first lifting arm 17 and a second lifting arm 19. A first lift operating device 47 is on the first lifting arm 17 and a second lift operating device 49 is on the second lifting arm 19. The lifting arms 17, 19 are attached to a horizontal shaft 50 in the frame component 12. In addition, the lifting arms 17, 19 together with their lift operating devices 47, 49 are separate. The front lifting device 10 also includes an independent control system 75, for control-

ling the lifting arms 17, 19 separately from each other. This permits the lifting arms 17, 19 to move vertically separately from each other. The first lifting arm 17 is lower that the second lifting arm 19. Thus the first side 41 of the implement is lower than the second side 43. As the lifting arms move vertically separately from each other, the attachment points 108 of the implement 30 move vertically separately from each other. In other words, the first ends 21 of the lifting arms remain on the level of the horizontal shaft 50, but the second ends 23 of the lifting arms 16 are vertically on different levels. As the lifting arm is attached to the frame componentl2 by a horizontal shaft, the lifting arm can be attached to the frame component directly or indirectly.

The front lifting device 10 according to the invention, shown in Figure 2, is attached to a tractor 28. The tractor 28 includes a front axle 34, to which the front wheels 38 are attached. In addition, the distance e between the horizontal shaft 50 and the front axle 34 is less than 800 mm, preferably less than 500 mm. When the horizontal shaft is in the immediate vicinity of the front axle 34 of the tractor 28, the totality becomes short. Thus the length of the tractor is not increased unnecessarily and the tractor is easy to use even in tight spaces .

Figure 3 shows the front lifting device 10 according to the invention . The front li fting devi ce 10 includes firs t li ft operating devices 47 for the first lifting arm 17 and second lift operating devices 49 for the second lifting arm 19 . As both lifting arms 17 , 19 have their own lift operating devices 47 , 49 , the first lifting arms can be moved separately from the s econd li fting arm . The l i f t operat ing devi ce s 47 , 4 9 are preferably hydraulic cylinders 18 . The fact that both lifting arms have their own hydraulic cylinders is surprisingly in the light of traditional dimensioning, as traditionally the lifting cylinders have been dimensioned to lift the nominal load to-

gether. In front lifting devices according to the prior art, the cylinders form part of a mechanically unified construction, in which the lifting arms are not allowed to move relative to each other. In the front lifting device according to the inven- tion, however, the lifting arms can rotate vertically separately from each other. The lift operating devices are therefore dimensioned for the nominal load.

In the front lifting device 10 according to the invention, shown in Figure 3, a rotating frame 24 is attached by a vertical shaft 22 to the frame component 12. The rotating frame 24 is straight compared to the frame component 12 and also relative to the tractor. The lifting arms 17, 19 attached to the rotating frame 24 can be at different heights, as is Figure 3, as they are arranged to move vertically independently of each other. The lifting arms 17, 19 are attached to the shaft 50 to the rotating frame by pivots 52, which permit the lifting arms 17, 19 to move vertically relative to each other. In other words, the pivots 52 permit the lifting arms to rotate separately from each other. The lifting arms are controlled vertically separately from each other, with the aid of the sturdy totality formed by the pivots and the cylinders . As the lifting arms are not supported on each other, they can move vertically independently of each other. The term moving rela- tive to each other refers to the fact that their second ends move vertically separately relative to each other.

In the front lifting device 10 according to the invention, shown in Figure 3, there is a basic distance e between the first lifting device 17 and the second lifting device 19. In addition, the lifting arms 17, 19 are arranged to move horizontally towards each other, to keep the basic distance e constant when the lifting arms 17, 19 are moved vertically, when an implement is attached to the front lifting device. In other words, in order to keep the basic distance e constant while the vertical distance g of the lifting arms 17, 19 increases, the

horizontal distance h of the lifting arms 17, 19 decreases. In order to preserve the basis distance e when an implement 30 is attached to the attachment point 108, when the vertical distance of the lifting arms 17, 19 decreases, the horizontal distance of the lifting arms 17, 19 increases. For reasons of clarity, the attachment element 110 of the implement 30 is all that is shown of the implement 30. The attachment means 112 belonging to the attachment element 110 do not move relative to each other. Thus the attachment means 112 remain at a constant distance from each other, thus also keeping the lifting arms 17, 19 at the constant distance at the basic distance e from each other.

The front lifting device shown in Figure 3 includes a support component 104 between the lifting arms 16. In other words, the lifting arms 17, 19 are attached to the support component 104 by a shaft 50. The shaft 50 permits the lifting arms 16 to be rotated independently of each other, in such a way that the second ends 23 of the lifting arms, i.e. the ends of the lift- ing arms 17, 19 next to the implement attachment points 108, can move vertically separately from each other.

In the front lifting device shown in Figure 3, the lifting arms 17, 19 have a vertical maximum distance f, which is arranged to be the same as, or greater than the basic distance e. When the lifting arms are free, the distance between the lifting arms is the vertical maximum distance. As the basic distance e is the same as, or greater than the vertical maximum distance f, the implement will always fit between the lifting arms. When the implement 30 is attached to the attachment points 108 in the lifting arms 17, 19, the lifting arm, which is equipped with a spring element, can be pushed towards the attachment means of the implement, in order to attach the implement to the front lifting device. The basic distance e is preferably the same as the maximum distance f, in which case when the implement is on the horizontal plane the maximum distance f will be the basic

distance. This is useful when attaching implements, as the lifting arms will then go directly to the correct locations, relative to the attachment means of the implement.

Figure 4 shows the first lifting arm 17 of the front lifting device according to the invention. A corresponding lifting arm can also be used as the second lifting arm. The lifting arm 17 includes a spring element 106. The spring element 106 permits the second end 23 of the lifting arms, i.e. the attachment point 108, to move horizontally, due to the effect of the force directed between the lifting arms by the implement. The spring element, which is in the lifting arm, is used simply to implement the necessary horizontal movement.

Figure 4 shows a lifting arm 16 of the front lifting device according to the invention. The lifting arm 16 has a first end 21 and a second end 23. The second end 23 of the lifting arm 16 includes an implement attachment point 108. The lifting arm 16 is attached to the frame component 12 by a horizontal shaft 50 in connection with the first end 21 of the lifting arm (Figure 3) . The attachment of the lifting arm 16 to the frame component 12 can take place directly or indirectly, for example, through a rotating frame 24 (Figure 3) . The lifting arm is always aligned at least partly by a vertical force using a lift oper- ating device 48, which is attached between the horizontal shaft 50 and the second end of the lifting arm (Figure 3) . The lift operating device could also be attached to the other side of the shaft, in which case it would operate in the opposite direction. The horizontal shaft 50 and the lift operating device 48 form the operating arrangement 53 of the lifting arm 16. In that case, the first end 21 of the lifting arm 16 will include the operating arrangement 53 of the lifting arm 16. The spring element 106 forms part of the lifting arm 16 between the attachment point 108 and the operating arrangement 53. If the spring element 106 is between the operating arrangement 53 of the lifting arm 16 and the attachment point of the implement,

the spring element 106 will permit the implement attachment point 108 in the lifting arm 16 to move horizontally, without a force acting of the horizontal shaft 50 and the lift operating device. The spring element 106 is preferably only in the second lifting arm, as spring elements in both lifting arms would cause the implement to sway.

The spring element can also be envisaged in connection with the attachment pivot of the lifting arm, in which case the lifting arm will rotate in its entirety. The construction in question is, however, difficult to implement. In addition, it causes unnecessary strain in the lift operating device, typically a cylinder that acts as the lift operating device.

Figure 5 shows the front lifting device 10 according to the invention, which is arranged to be attached to a tractor from its frame component 12. A rotating frame 24 is attached to the frame component by means of a vertical shaft 24. The rotating frame 24 is rotated relative to the frame component 12 and also relative to the tractor. The lifting arms 17, 19 rotate together with the rotating frame 24, so that the lifting arms 17, 19 together with the lift operating devices 47, 49 too are rotated relative to the frame component 12. The rotating frame includes an attachment point 15 for a pushing arm. Thus the attachment means 26 of the implement, which include the lifting arms 17, 19, the cylinders 18, and the attachment point 15 of the pushing arm, rotate along with the rotating frame. The front lifting device includes a rotation device 44 for rotating the rotating frame 24. The rotation device 44 is preferably a hydraulic cylinder 46. In addition, the front lifting device 10 includes a power-take-off 20.

Figure 6 shows the front lifting device 10 according to the invention, which includes a rotating frame 24, supported on the frame component 12 by a vertical shaft 22, to which the lifting arms 16 and the lift operating device 28 are attached. The

rotating frame 24 is rotated relative to the frame component 12 and the lifting arms 16 are on different planes when rotated to the horizontal shaft 50.

Figure 7 shows the front lifting device 10 for a tractor, according to the invention, attached to the chassis 32 of a tractor. The front lifting device includes a frame component 12, by which the front lifting device 10 is arranged to be attached to the chassis 32 of the tractor 28. The front lifting device also includes a first lifting arm 17 attached to the frame component 12 and a second lifting arm 19 attached to the frame component 12. The attachment can be direct, as in Figure 7, or indirect, as in Figures 3, 5, and 6. The essential feature is that the lifting arms 17, 19 are pivoted to a horizon- tal shaft 50. The first lifting arm 17 includes a first lift operating device 47 and the second lifting arm 19 includes a second lift operating device 49. In addition, the first lifting arm 17 is separate from the second lifting arm 19 (Figure 5) . The first lifting arm 17 and the second lifting arm 19 are permitted to rotate separately from each other. Thus, their second ends can move separately from each other. The first lift operating device 47 is also separate from the second lift operating device 49 (Figure 5) . As there is no mechanical connection between the lift operating devices, the lift operat- ing devices are separate from each other. Thus the lift operating devices can move free independently of each other. The front lifting device 10 also includes an independent control system 75. By means of the independent control system 75 the lift operating devices 47, 49 are controlled separately from each other, so that the lifting arms 17, 19 too move separately from each other.

The independent control system 75 of the front lifting device, shown in Figure 7, includes independent control means 77. The independent control means 77 are used by the operator to control the lifting arms 17, 19. The independent control means

preferably include height-difference control means 79 and common height control means 81. The height-difference control means are used to define the desired distance between the lifting arms. The common height control means are, for their part, used to control the common movement of the lifting arms. Thus the lifting arms move for the defined distance together, until the defined distance is altered. In many work tasks, it is essential to keep the defined distance, i.e. the tilt of the implement, the same.

Of course independent control means can also be envisaged, by means of which both lift operating means could be controlled separately. However, in such an embodiment there is the problem of maintaining a constant tilt.

The independent control system 75 of the front lifting device shown in Figure 7 includes independent control data 89 transmission means 85 and vertical-position measurement data 91 transmission means 87. The independent control data 89 is transmitted from the independent control means 77 to the processing unit 93. The vertical-position measurement data 91, for its part, is transmitted from the sensor 82 to the processing unit 93. Thus the processing unit 93 receives measurement data 91 on the position of the lifting arms 17, 19 and independent control data 89 as the position to which it is desired to move the lifting arms 17, 19.

The front lifting device 10 shown in Figure 7 includes a sensor 82 in the lifting arms 17, 19 for determining the height posi- tions of the attachment points 108 of the implement 30. As a sensor is used when determining the height positions of the attachment points, the height at which an attachment point is will be known with certainty. When the vertical position is determined on the basis of the operator's visual observations, a corresponding accuracy is not achieved. It is also difficult to determine the vertical position of the attachment points

from a control signal. Using a sensor to measure the vertical position of the attachment points thus permits very accurate control .

The processing unit 93 belonging to the front lifting device shown in Figure 7 includes, among other things, proportional or servo-controlled valves . Thus the use of the valves achieves a slow, even movement in both lifting arms .

Figure 8 shows the lift operating device 48, more specifically a cylinder 18, which includes a sensor 82. The sensor 82 is arranged to determine the stroke i of the lift operating device 48. When the stroke i of the lift operating device 48 is determined, the vertical position of the lifting arms is also deter- mined indirectly. Thus the height position of the attachment point of the implement in the lifting arm is known. The sensor 82 is preferably a linear sensor 83.

Figure 9a shows the user interface 76, which includes the independent control means 77, for controlling the lifting arms 17, 19 of the front lifting device 10 in the vertical plane (Figure 9b) . The independent control means 77 include a first regulating element 78 and a second regulating element 80. The first regulating element 78 acts as a height-difference control means 79, by means of which the height difference between the lifting arms is regulated. For its part, the second regulating element 80 acts as a common height control means 81, by means of which the height position relative to the tractor is regulated.

Figure 9b shows the positions of the lifting arms 17 , 19 of the front lifting device 10 , when the user interface 76 is in the position shown in Figure 9a . Once the height-difference control means 79 has pas sed, in the clockwise direction, the half-way point in the control s cale ( Figure 9a ) , when s een from the tractor, the right-hand, i . e . first lifting arm 17 is below the

left-hand, i.e. second lifting arm 19. When the height-difference control means is in the extreme position, the height difference of the lifting arms 17, 19 is the greatest possible. If the height-difference control means is in the extreme posi- tion counterclockwise, the left-hand lifting arm will be below the right-hand lifting arm and in its extreme position. If the common height control means 81 is in the extreme counterclockwise position (Figure 9a), the lifting arms 17, 19 are in their lower position. If the common height control means were to be in the extreme clockwise position, the lifting arms would be in their upper position.

Figure 10a shows the user interface 76 and Figure 10b, for its part, the front lifting device 10, when the user interface 76 is in the state of Figure 10a. When the height-difference control means 79 is at the half-way point in the control scale (Figure 10a), the lifting arms 17, 19 are at the same height.

The lifting arm 19 is drawn with a broken line, as it is not properly visible, being behind the lifting arm 17. In addition, the common height control means 81 is in the extreme clockwise position, so that the lifting arms 17, 19 are in the upper position.

The user interface 86 shown in Figure 10a also includes a selector switch 92, by means of which the operating class of the first regulating element 78 and the second regulating element 80 is selected. In Figures 9a and 10a, the operating class 1 is selected, in which case the regulating elements 78, 80 act as the height-difference control means 79 and as the common height control means 81. The operating class 2 can also be selected, in which case the first regulating element will be used to regulate the first lifting arm and the second regulating element used to regulate the second lifting arm. The operating class in question can be used, for example, when attach- ing the implement.