Description

The present invention relates to a vehicle provided with a frame, a steering unit having a steering wheel, and a seat for a driver of the vehicle, as well as with a lifting arm device having a telescopic lifting arm, which, at a first end thereof, is connected to the frame pivotably about a horizontal pivot axis and which, at the second end situated opposite the first end, is provided with a coupling unit for being able to releasably couple an attachment to the lifting arm, wherein the lifting arm has two parallel telescopic arms, each having a fixed arm part which is connected to the frame pivotably about the horizontal pivot axis, and a telescopic arm part, which is telescopically displaceable with respect to the fixed arm part and at a distal end of which the coupling unit is provided, the lifting arm device further being provided with drive means for the telescopic displacement of the telescopic arm parts.

The invention relates especially to loaders, such as, further especially, mini loaders, which are characterized by a loading capacity of maximally 3.5 tonnes. Loaders are typically used to shift earth or to lift, and possibly move, objects. The aforementioned attachment can be chosen in dependence on the task which needs to be carried out with a loader. Typical attachments are a (closed) bucket or a hoisting mast. In order to increase the working range of a (stationary) loader, it is known to construct the lifting arm, which is also referred to as a jib, in telescopic arrangement. The telescopic lifting arm in this case comprises two tubes, whereof one tube can telescope in and out within the other tube. The telescopic arm is here located within the field of vision of the driver, who, seated on the seat of the loader, controls the loader. More specifically, the telescopic arm obstructs the view onto the coupling piece, so that the driver has no, or has only with difficulty, sight of the attachment, so that it is difficult to perform operations with the loader. It is also known to construct the lifting arm with two parallel telescopic arms. Such a vehicle is described in the above first paragraph. All kinds of provisions, such as hydraulic cylinders and pipework, for the telescoping of the telescopic arms, for the pivoting of the lifting arm as a whole, and for the operation of an attachment, are here provided between the two parallel telescopic arms, whereby the aforementioned problem of a limited view of the attachment by the driver is not solved, or at least is solved only to a limited degree. In addition, the use of two parallel telescopic arms brings with it the increased risk of tilting. This is especially caused by the fact that hydraulic cylinders which for each telescopic arm are provided for the telescoping of the relevant telescopic arm often do not, in practice, run synchronously. In order still to achieve this, it can be chosen to use a synchronizing valve which operates between the two hydraulic cylinders but, leaving aside the extra costs thereof, it turns out that a synchronizing valve also, in practice, regularly fails to offer the desired result, so that tilting does still occur.

The present invention aims to provide a vehicle having a lifting arm device according to the introduction, with which a solution, or at least an improvement, can be achieved with regard to the aforementioned drawbacks of a vehicle according to the prior art. For this purpose, each telescopic arm part is provided with a toothed rack, and each fixed arm part of a telescopic arm is provided with a gearwheel which engages with the toothed rack of this telescopic arm, wherein the two gearwheels belonging to the two telescopic arms are provided co-axially with respect to each other and are connected to each other via a shaft body for joint rotation of the two gearwheels. The use of the rack-gear transmissions for each of the two telescopic arms in combination with the mutually connected gearwheels ensures that the risk of tilting can be limited. In addition, the invention can be realized in relatively simple design and with a limited use of space, whereby the space between the two telescopic arms can be kept relatively free, so that the view between the two telescopic arms can be relatively good.

In one embodiment, the drive means comprise a single drive element. In this embodiment, the drive means is precluded from comprising two or more drive elements, such as hydraulic cylinders or hydraulic motors. Such an embodiment can have a low cost price.

In an alternative embodiment, the drive means comprise two drive elements provided in mirror symmetry. The mirror-symmetrical arrangement has the effect that the relevant drive elements can be positioned away from the middle, which is, or at least can be, favourable for the mechanical load on the lifting arm device, as well as for the view which the driver is offered.

A constructively simple embodiment can be obtained if the drive means comprise a drive element whereof the length can be varied, and which, at one end of the drive element, is connected to a fixed arm part of a telescopic arm and, at the opposite-situated end, is connected to the telescopic arm part of this telescopic arm.

In a possible embodiment, the drive element is provided on that side of this telescopic arm that is facing away from the other telescopic arm, i.e. on the outer side of the lifting arm, so that the view between the two telescopic arms is kept free.

In one embodiment, each telescopic arm is provided with a supporting roller which is rotatably connected to a fixed arm part, and wherein each telescopic arm part is provided with a running surface with which the telescopic arm part rests on the supporting roller, wherein the supporting roller is arranged to rotate during the telescopic displacement of the telescopic arm part, owing to friction between the supporting roller and the bearing surface. Thus an accurate guidance of the telescopic arm parts can be realized. Moreover, the mechanical load on the gearwheel of each telescopic arm can thus be limited.

The supporting roller and the gearwheel of each telescopic arm are preferably provided coaxially. Thus, according to a further possible embodiment, joint rotation of the supporting roller and the gearwheel can be easily achieved.

The mechanical transmission of forces acting on the toothed rack to the associated telescopic arm part can be favourably realized if the toothed rack of each telescopic arm, on a longitudinal side thereof which is facing away from the associated gearwheel, bears against a bearing edge of the telescopic arm part. The bearing edge can be, for example, an edge of a chamber in the telescopic arm part.

The invention lends itself to a slender construction of the telescopic arms, which aids the view of the driver. Within this framework, in one embodiment each telescopic arm part is formed by a metal plate having a thickness which extends in the horizontal direction and has a size of maximally 40 mm, preferably of maximally 30 mm, and/or each fixed arm part has a space in which the telescopic arm part, in a retracted state of the telescopic arm, is accommodated, and of which the width is maximally 40 mm, preferably of maximally 30 mm.

The accuracy with which the telescoping of the telescopic arms can be realized can here be enhanced if each telescopic arm is provided with a guide body which is connected to the telescopic arm part of the relevant telescopic arm on the top side and at that end of the telescopic arm that is directed towards the first end of the lifting arm, and wherein each fixed arm part is provided with a guide surface above the guide roller, against which guide surface the guide roller presses, wherein the guide roller is arranged to guidingly cooperate with the guide surface during the telescopic displacement of the telescopic arm part. The use of guide bodies limits, moreover, the mechanical friction.

A suitable embodiment can be obtained if the guide body concerns a guide roller which is rotatably connected to the telescopic arm part of the relevant telescopic arm, wherein the guide roller is arranged to rotate during the telescopic displacement of the telescopic arm part, owing to friction between the friction roller and the guide surface. Alternatively, the guide bodies could also be realized as sliding bodies, for example of Teflon.

The invention lends itself especially, but not exclusively, to use in a mini loader, also referred to as a compact loader, which is characterized by its own weight being lower than 5,000 kg, for example lower than 3,500 kg.

The invention further relates to a lifting arm device for use in a vehicle according to the invention as previously described.

The invention will be explained in greater detail below on the basis of a description of a vehicle according to the invention having a lifting arm device according to the invention, with reference to the following figures:

Figure 1 shows in side view a vehicle according to the invention;

Figures 2 and 3 show in isometric view a lifting arm device according to the invention such as forms part of the vehicle according to Figure 1 , respectively in retracted state and in extended state;

Figure 4 shows a perpendicular cross section through the lifting arm device according to Figure 2 without quick-change head; more specifically, the cross section is through the centre line 46 of the shaft body 45;

Figure 5 shows in isometric view a detail of an alternative embodiment of a lifting arm device according to the invention.

The vehicle 1 according to Figure 1 concerns a loader, more specifically a mini loader. The loader 1 has pivot steering, wherein the steering of the loader 1 by a driver 2 seated on a seat 3 who manually operates the steering wheel 4 of the vehicle 1 takes place by pivoting of the foremost frame part 5 and the rearmost frame part 6 with respect to each other about a vertical pivot axis 7 in dependence on the turning of the steering wheel 4. The loader 1 is provided with a lifting arm device 1 1 (see also Figures 2, 3 and 4), which is connected, pivotably about a horizontal pivot axis 12, to the foremost frame part 5. For the pivoting of the lifting arm device 1 1 about the pivot axis 12, the loader 1 is provided with two hydraulic cylinders 13, which are provided in mirror- symmetry with respect to a vertical mirror plane which runs through the middle of the width of the loader 1 , or at least, of the foremost frame section 5 thereof. The cylinders 13 operate between the foremost frame section 5 and the fixed arm parts 32 (yet to be described in closer detail), with which the cylinders engage at the site of the eyelets 29.

The lifting arm device 1 1 , at that end thereof which is facing away from the pivot axis 12, is provided with a quick-change head 21 , which is known per se to the person skilled in the art and with which it is possible to couple an attachment, such as a closed bucket 22, pallet forks or a hoisting mast, to the lifting arm device 1 1. The quick-change head 21 also comprises a hydraulic cylinder 23, with which it is possible to tilt the relevant attachment about a horizontal tilt axis 24.

The lifting arm device 1 1 comprises a lifting arm 31 which, at least substantially, is mirror-symmetrical with respect to the aforementioned vertical mirror plane through the middle of the width of the foremost frame section 5. The lifting arm 31 comprises two telescopic arms 32. Each of the telescopic arms 32 comprises a fixed arm part 33, which is connected pivotably with the aforementioned pivot axis 12 to the foremost frame section 5, and a telescopic arm part 34, which is telescopically displaceable with respect to the associated fixed arm part 33 between a retracted state according to Figure 2 and an extended state according to Figure 3. Each fixed arm part 33 comprises an innermost plate 35 and an outermost plate 36, which plates 35, 36 are connected to each other at a distance apart by means of bolted joints which run via a topmost strip 37 and a bottommost strip 38 (see Figure 3) of the associated fixed arm part 33. In Figure 3, in the interest of greater clarity, the outermost plate 36 and guard 39 of the, in Figure 3, foremost fixed arm part 33 is not represented. The thicknesses of the innermost plate 35, the strips 37, 38 and the outermost plate 36 are respectively 20 mm, 26 mm and 8 mm. The total width of each fixed arm part is thus 54 mm.

Each telescopic arm part 34 is, at least substantially, formed by an elongate plate 41 , which, at least in the retracted state according to Figure 2, extends in large part within the space between the topmost strip 37 and the bottommost strip 38 and between the innermost plate 35 and the outermost plate 36 of the associated fixed arm part 33. The thickness of the plate 41 is 25 mm. The clearance in the width direction of the plate 41 between the plates 35 and 36 is thus 1 mm.

Each fixed arm part 33 comprises, at that end of the fixed arm part 33 that is facing away from the pivot axis 12, a pinion 42. On the outer side the pinion 42 comprises a gearwheel 43 and on the inner side the pinion 42 comprises a running roller 44. The gearwheel 43 and the running roller 44 are formed as an integral component. The top side of the running roller 44 is situated in the extension of the top side of the bottommost strip 38. Pinions 42 are rigidly connected to the shaft body 45, for example by means of a cotter joint (not shown in detail). The shaft body 45 is accommodated, rotatably about its centre line 46, within a pipe 47, at the end of which are provided bearings 48 for the shaft body 45. The pipe 47 extends between the innermost plates 35 of both fixed arm parts 33 inside bores, provided for this purpose, in these innermost plates 35. The pipe 47 is rigidly connected, for example by means of a weld joint (not shown in detail), to the two innermost plates 35.

Each telescopic arm part 34 is provided on the outer side with a toothed rack 51 having downwardly directed teeth which engage with the teeth of the gearwheel 43. The toothed rack 51 is at various longitudinal positions fixedly bolted to the plate 41 and, on the inner side of the toothed rack 51 , accommodated in a chamber which has been milled out on the outer side of the associated telescopic arm part 34, as can especially be seen in Figure 4. The toothed rack 51 bears with the top side thereof against the top wall of this chamber, so that any forces which, in Figure 4, act upwards on the toothed rack 51 , are transmitted to the plate 41 also via the chamber and not exclusively via the said bolted joints. Each fixed arm part 32 is on the outer side provided with the guard 39, which shields the toothed rack 51 , at least in the retracted state according to Figure 2. In the outermost plate 36, a recess 49 is provided at the site of the guard 39, so that the toothed rack 51 , in the said retracted state, is afforded space.

For the telescopic extension and retraction of the telescopic arm part 34 with respect to the associated fixed arm parts 33, each telescopic arm 32 is on the outer side thereof provided with a hydraulic cylinder 52, which with one end is connected to the associated fixed arm part 33, via the outermost plate 36 thereof, and with the opposite end, is connected to the associated telescopic arm part 34.

At the rearmost end, each telescopic arm part 34 is provided with two thin welded-on plates 53, between which two running wheels 54 are rotatably accommodated. The top sides of these running wheels 54 are situated in line with the top side 55 of the plate 41 of the telescopic arm part 34. The fixed arm part is in the extension of the topmost strip 37 provided with a guide wheel 56, whereof the bottom side is situated in line with the bottom side of the topmost strip 37. During the retraction and extension of the telescopic arm parts 34, the running wheels 54 roll over the bottom side of the topmost strip 37, and guide wheels 56 are in rolling contact with the top sides 55 of the telescopic arm parts 34. The toothed racks 51 and gearwheels 43 are shaped and positioned with respect to one another such that the radial points of these teeth remain free from contact, or at least, virtually free from contact, in order to prevent a (too) high mechanical load on the teeth, and hence mechanical wearing of these same.

The lifting arm 31 as described above is constructed such that the space between the telescopic arms 32 is virtually full. The driver 2 thereby has, between the telescopic arms 32, a good view of operations which are carried out with the loader 1. Nevertheless, owing to the two pinions 42 and the associated transmission between the gearwheels 43 of pinions 42 and the associated toothed racks 51 , it is achieved in a relatively simple, mechanical manner that the telescopic arm parts 34 will telescope in and out synchronously, thus in equal measure and at the same speed, whereby the risk of tilting is limited.

Figure 5 shows a detail of the lifting arm 71 , which largely conforms to the lifting arm 31. Components of the lifting arm 71 which are equal to components of the lifting arm 31 are in Figure 5 represented with the same reference numeral as in Figures 1 to 4 inclusive. The difference between the lifting arm 71 and the lifting arm 31 lies in the fact that the two cylinders 52 are each replaced by a hydraulic motor 72, which acts directly on the shaft body to which the pinions 42 are jointly rigidly connected. For this purpose, this shaft body is lengthened at both ends with respect to the shaft body 45.

In alternative embodiments, it could also be chosen to dispense with one of the two cylinders 52, or to dispense with one of the two hydraulic motors 72. Actuation of the one remaining cylinder 52 or of the one hydraulic motor 72 will then supply the driving force for the telescoping of both telescopic arm parts 34, whereupon the associated shaft body 45, of course, will be subjected to torsion.