WO2011067470A1

WO2011067470A1 - Bogie construction

Info

Publication number: WO2011067470A1
Application number: PCT/FI2010/050991
Authority: WO
Inventors: Unto Ojala
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-12-03
Filing date: 2010-12-02
Publication date: 2011-06-09
Anticipated expiration: 2012-06-03
Also published as: FI20096281A0

Abstract

The invention relates to a bogie construction, particularly for work machines travelling by means of crawlers in forests, which bogie construction includes a body, a primary bogie (1) rotatably fastened to the body and lockable in place with locking devices (7) and secondary bogies (2) rotatably fastened to it, in which bogie wheels (3) are bearing-mounted, drive wheels (5) fastened to the body, and a crawler (4) supported by the drive wheels and the bogie wheels. According to the invention, the bogie construction includes a transfer device (9) fastened to the primary bogie (1) and the secondary bogie for adjusting the position of the secondary bogie (2) and the bogie wheels (3) fastened to it.

Description

BOGIE CONSTRUCTION

The invention relates to a bogie construction particularly for work machines travelling by means of crawlers in forests, which bogie construction includes a body and a primary bogie rotatably fastened to the body, lockable in place with locking devices and secondary bogies rotatably fastened to it, in which bogie wheels are bearing-mounted, drive wheels fastened to the body, and a crawler supported by the drive wheels and the bogie wheels.

Recent forest machines employed in usual regular and firm forest terrain are most often the so-called wheel loaders. However, e.g. many forest terrains in Finland are often very swampy and thus, particularly during frost-free seasons, too squashy for most wheel loaders. Furthermore, due to winters becoming milder, the use of wheel loaders in soft forest swamps has not recently been possible even at midwinter. Hence, the use of forest machines provided with crawlers has increased and will increase in the future. The bogie constructions of crawler forest machines usually include supporting rollers fitted between the drive wheels to support the crawlers also between the drive wheels. Crawler forest machines are also more suitable than wheel loaders in hilly and extremely irregular, e.g. stony, terrain, because their risk of getting stuck in such terrain is also smaller than that of wheel loaders. The bogie constructions employed in recently known crawler forest machines are still most often relatively rigid whereby, when crossing an obstacle, the whole bogie construction supporting the crawler climbs on top of the obstacle (e.g. a stone or a stump in the woods). Due to this, the work machine usually tilts intensively when crossing the obstacle. One has tried to solve problems related to forest machines travelling with crawlers by developing the bogie constructions supporting the crawlers elastic and thus better conforming to the terrain. However, the recently known bogie constructions conforming to the terrain are still defective in many aspects. Many of the recently known bogie constructions supporting crawlers are such that driving the forest machine over irregular terrain and crossing obstacles by means of them require plenty of power and thus their use requires much energy.

Patent specification GB2301569 describes a bogie construction having a transfer device fastened to a body and a secondary bogie for adjusting the secondary bogie and bogie wheels fastened to it. The fact that the transfer device is fastened to the body limits the versatile adjustment of the bogie wheels. An object of the invention is to provide a bogie construction which eliminates the above problems related to recent bogie constructions employed in crawler forest machines, among others. A particular object of the invention is to introduce a bogie construction which provides the work machine a better and stabler travel over irregular terrain. A further object of the invention is to introduce a bogie construction by means of which the crawler forest machine is able to cross land obstacles easier than previously and with lower energy consumption.

The object of the invention is achieved with a bogie construction which is characterised by what is presented in the characterising section of claim 1. The bogie construction according to the invention includes a transfer device fastened to a primary bogie and a secondary bogie for adjusting the position of the secondary bogie and bogie wheels fastened to it. Such a bogie construction and its bogie wheels can be adjusted in a versatile way to provide the best possible stability. They can be locked and/or let move i.e. be in the so-called floating position.

When the bogies are in the floating position, several advantages are gained. The crawler easily conforms to the irregularities of the terrain. The weight distribution is even for the whole area of the crawler. The primary/secondary bogies move simultaneously when crossing an obstacle. The negative tilting of the base has been minimised. The crawler stays in place well and endures use well.

When the bogies are locked, the base can be stabilised. When crossing ditches, travelling on swamps and snow, time is saved. Furthermore, the ground clearance can be lifted.

The secondary bogie being locked and the primary bogie being in the floating position, the secondary bogies can be braced to a long, uniform and flat bogie by means of the transfer device. Then, a flat solid base is obtained for the crawler. Such an arrangement prevents a single secondary bogie from sinlting deeper and a load-bearing surface from breaking when driving over soft terrain, a result of which could be that the machine sinks deeper, the bearing surface possibly breaks totally and the machine becomes stuck. The arrangement provides a long, solid, flat base which enables harvesting trees in all seasons on swampland and snow and the crossing of ditches in difficult harvesting conditions. The optimal position of the secondary bogie can be adjusted by electric sensors or hydraulically by means of computer programming. The arrangement can be employed in various forest machine bases. For example, excavators provided with bogie bases according to the invention are very well suited for use in swamp terrain.

When the position of the bogie wheels can be adjusted in relation to the primary bogie and the forest-machine body, it is well possible to take the terrain shapes into account when driving the forest machine. Due to such a bogie construction, the crawlers are provided to be well conforming to the terrain and still adjustable in accordance with the terrain. When crossing obstacles, such as stones and stumps, the work machine then tilts less than work machines provided with rigid bogie constructions and forces applying to the crawler are more evenly divided for the whole area of the crawler being against the ground. Hence, travelling over irregular terrain is facilitated, whereby energy is also saved. Furthermore, such a bogie construction is light, which improves the forest-machine carrying capacity, due to which, a forest machine provided with such a bogie construction can be used better than previously in forest swamps and other rough forest lands round the year.

Next, the invention will be described in more detail with reference to the enclosed drawing which shows a side view of a bogie construction according to the invention.

The bogie construction according to the drawing includes a body (not shown in the figure), drive wheels 5 fastened to it, a primary bogie 1 rotatably fastenable to the body and lockable in place with locking devices 7, secondary bogies 2 rotatably fastened to it, bogie wheels 3 bearing-mountedly fastened to the secondary bogies, being between the drive wheels, a crawler 4 supported by the drive wheels and the bogie wheels, locking cylinders 7 of the primary bogie, a tensioning cylinder 6 of the crawler, and a centre axle 8 of the primary bogie. Furthermore, the bogie construction includes a transfer device 9 fastened to the primary bogie 1 and the secondary bogie for adjusting the position of the secondary bogie 2 and the bogie wheels 3 fastened to it. As the transfer device 9, there is at least one hydraulic cylinder fitted between the primary bogie 1 and the secondary bogie 2. As the locking device 7, there is at least one hydraulic cylinder. The body of the bogie construction according to the figure can also be a part of the forest-machine body.

The drive wheels 5 are fastened on drive shafts bearing-mounted in the body. One of the drive shafts is fastened to the body with the tensioning cylinder 6 adjustably by means of a rotatable eccentric shaft. The tensioning cylinder 6 is a double- acting hydraulic cylinder which is controlled from the cabin of the forest machine e.g. by means of a solenoid valve. Due to this adjustment, the tension of the crawler 4 can be adjusted during driving. This is beneficial when travelling over soft or irregular terrain. Furthermore, the adjustment facilitates and accelerates the release and re- fitting of the crawler. The primary bogie 1 is a part consisting of two parts extending downwards from the middle at an oblique angle when seen from the side. It is fastened to the body of the bogie construction rotatably via the centre axle 8. Between the primary bogie 1 and a locking piece 10 fastened in place to the body are fastened the locking cylinders 7. In this case, the locking cylinders 7 are single-acting hydraulic cylinders by means of which the primary bogie can be locked in place by increasing the pressure of hydraulic oil entering the cylinders. In another case, it is possible to use double-acting hydraulic cylinders. The locking cylinders 7 are controlled with solenoid valves (not shown in the figures). Thus, the locking can be switched on and off from the machine cabin. In a way shown in the figures, the secondary bogies 2 consist of mainly triangular metal pieces (e.g. of a sheet structure) and of the bogie wheels 3 bearing-mounted in them by means of bogie axles 11. In this embodiment, there are two secondary bogies 2 per one primary bogie 1. In another embodiment, one secondary bogie can employ e.g. four bogie wheels. The secondary bogies 2 are bearing-mounted at the ends of the parts of the primary bogie directed obliquely downwards by intermediate axles 12 at the body-side end of which the moving ends of the locking cylinders 7 are also fastened. Between the primary bogie 1 and the secondary bogie 2 is fitted a transfer cylinder 9 operating as the transfer device. The transfer cylinder is fastened at its one end to the primary bogie close to the secondary bogie and at its other end to a fastener 13 in the secondary bogie. In this case, the transfer cylinders 9 are single-acting hydraulic cylinders, by means of which the secondary bogie can be locked in place in relation to the primary bogie by increasing the pressure of hydraulic oil entering the cylinders. In another case, it is possible to use double-acting hydraulic cylinders. The transfer cylinders 9 are controlled with solenoid valves (not shown in the figures). Thus, the locking can be switched on and off from the machine cabin.

When driving a forest machine provided with a bogie construction according to the figure e.g. over irregular terrain, the locking cylinders 7 of the primary bogie 1 and the transfer cylinders 9 of the bogie construction are released. When crossing a stone or a stump, the front side of the primary bogie then turns upwards and the first secondary bogie 2 fastened to it climbs on top of the obstacle without greatly rising the body of the bogie construction and thus also the forest machine, if the obstacle is not higher than the diameter of the bogie wheel. Immediately after having crossed the obstacle, the first primary bogie turns downwards further supporting the bogie construction without greatly rising it and thus without causing a lot of swinging and tilting of the forest machine. The first secondary bogie climbing on top of the obstacle, the second secondary bogie moves downwards tightly against the crawler, whereby it supports the bogie construction from the front of the obstacle even though there was a small hollow at this point. When further driving forward, the second secondary bogie makes a motion conforming to the obstacle, equivalent to the first secondary bogie, whereby the crawler maintains a ground contact as even as possible for the whole duration of crossing the obstacle. In other words, such a bogie construction tries to maintain the weight division as uniform as possible for the whole area of the crawler touching the ground irrespective of the irregularity of the terrain. When driving on regular ground, road or e.g. over soft regular terrain, such as an expanse swamp, the primary bogies and the secondary bogies can be locked by means of the cylinders 7 and 9 in place or only either the primary bogie or the secondary bogie can be locked in place. The secondary bogie being locked in place by means of the hydraulic cylinder 9 and the primary bogie being in a free position, the secondary bogies can be braced to a long and uniform bogie. Then, a firm and flat base is obtained for the crawler and the area of the crawlers touching the ground is as even as possible and bears well on soft ground. When crossing a one-sided obstacle (falling under only one crawler), it is possible to brace the primary bogie on the side of regular ground and the secondary bogies such that this side gives a support as good as possible when the crawler crossing the obstacle is at the point of the obstacle.

In this construction, the drive wheels are located up and they do not contact the ground. Due to a swinging motion of the primary and the secondary bogie, the secondary bogie can rise up on the crawler, the control pressure of its hydraulic cylinder turns the bogie into the horizontal position, whereby the wheel of the secondary bogie can be made to rise close to the crawler the primary bogie rising to the uppermost position. At the same time, the irregularities of the terrain are better managed with the long machine body, the drive wheels do not hit the stones and stumps first, but the secondary bogie does, whereby the primary bogie participates in the crossing of the obstacle and both bogies contribute to it. Driving the machine in terrain is improved, because the drive wheel does not stick to obstacles or irregularities when being up. Simultaneously, the strength of the construction improves when travelling with high speeds. Hydraulic crawler tensioning, a hydraulic-mechanical eccentric shaft or a hydraulic tubular telescope depending on the construction of the machine (drive wheel) keeps the tension of the crawler suitable and allows the crawler to move in accordance with the irregularity of the terrain. The locking of the primary and the secondary bogie provides a tighter support of the body to the base, whereby e.g. the use of a crane (loader) can be stabilised. Hydraulic oscillation makes the bogie motion remain vertical in relation to the body for the whole distance of the path. The terrain being irregular, the weight of the body rests on three bogies and, at the same time as one bogie hydraulically oscillates, keeps the fourth bogie construction in surface contact. Hydraulic oscillation can be varied between the front and the rear bogie in accordance with each body weight, usually the lighter bogie pair oscillates.

The bogie construction in question operates by means of hydraulic locking/suspension such that desired pressure is conveyed on the piston side of the double-acting hydraulic cylinder of the primary bogie and, in addition, hydraulic pressure is conveyed on the rod side of the hydraulic cylinder opposite the same primary rocker, whereby the primary bogie is simultaneously pulled and lifted in relation to the body. The machine being on a regular base, the pressure is adjusted such that all secondary bogies are in solid ground contact. The system is connected with a hydraulic accumulator which provides the hydraulic cylinder in question the property of a compression spring. This can be solely used in one hydraulic cylinder of the primary bogie (cross-connection) the other being in the floating position, because the opposite cylinder motion causes a counter-force which prevents the totally-operating simultaneous use of both hydraulic cylinders. The construction in question is used in a single-body four-bogie base as hydraulic oscillation which stabilises the motions of the body and the terrain, one bogie pair oscillating and the other bogie pair being in the normal drive position keeping the body closely conforming to the terrain. The lockings of the primary-secondary bogie stabilise the machine when being in place.

The bogie construction according to the invention can be implemented in many aspects different from the embodiment described here as an example. The bogie construction according to the figure only includes one primary bogie which contains two secondary bogies. In some embodiment requiring long crawlers having a better carrying capacity than described, there can be two or more primary bogies. Furthermore, it is possible to use in some embodiment instead of four bogie wheels located on the sides of the crawler only two bogie wheels located in the middle of the crawler. In such an embodiment, the drive wheels can again be supporting and pulling the crawlers from their sides. In a further embodiment, the locking cylinders can be made controllable such that, by means of them, the primary bogies can be locked in place in a desired position. Then by means of the primary bogie, it is possible to lift the ground clearance of the forest machine either one-sidedly or on both sides. This property can be utilised in many situations, e.g. when climbing or descending a steep hill.

Next, some advantageous embodiments of the invention will be presented. 1. Single-body construction with four drive bogies

In a single-body construction including four drive bogies, the irregularity of the terrain causes situations in which the base is in three-crawler contact one crawler being free of the base weight. This has been solved with hydraulic oscillation. In hydraulic oscillation, in (one) double-acting hydraulic cylinder of the primary bogie/secondary bogie is conveyed minimum pressure (1/4 of the machine weight to the oscillating crawler) and, by means of pressure, the secondary bogie (wheels) are lowered to ground contact. If no ground contact is achieved, the pressurised hydraulic cylinder of the secondary bogie transfers the secondary bogie to one- wheel ground contact. Oscillation can be varied between the front and the rear crawlers/bogies in accordance with each body weight, usually the lighter bogie pair oscillates. This operation described can vary in different cases. Hence, the base can be stabilised for all four crawlers, particularly in crane use. The locking of the primary/secondary bogie provides the stabilisation of the base and no swinging of the base is caused. The operation and pressurisation for the primary/secondary cylinder are performed automatically by electric/hydraulic control. It is substantial in the single-body arrangement that on the base below the body are fitted two rotatable rings underneath which is fitted the bogie body according to the invention. The control occurs from the rotatable ring by varying the rotation of the crawler. This can be utilised in various work machines. 2. Single-body construction with one drive bogie pair (on different sides of body)

This is a single-body, one-pair bogie/crawler with a machine construction. Then, the primary bogie of one side (e.g. left) is locked and the right bogie/crawler is in the floating position, whereby the right side conforms to the terrain shapes and the left side keeps the machine body closed in the position of the primary bogie. When stopping, the primary and the secondary bogie are locked with a hydraulic cylinder. The control occurs by varying the speed of the rotatable bogie. The arrangement in question can be used e.g. in ski-trail vehicles, ski-slope vehicles and all-terrain vehicles. 3. Front and rear body combined with rotating joint/reversal link with four drive bogies

In the model in question having two bogie pairs, the machine includes a front and a rear body. The bodies are connected horizontally with a rigid rotating joint/reversal link. The bogie pair is fastened via a primary axle with bearings at the front and the rear body, whereby the bodies are able to yield in accordance with the terrain by means of the reversal link the primary and the secondary bogie moving along with the terrain. The control occurs with a hydraulic cylinder from the rotating joint (reversal link) of the middle body. This model includes four drive crawlers. The model can be employed e.g. in forwarder and harvester forest machines. The invention is not limited to the described advantageous embodiments, but it can vary within the scope of the inventive idea presented in the claims.

Claims

1. A bogie construction, particularly for work machines travelling by means of crawlers in forests, which bogie construction includes a body, a primary bogie (1) rotatably fastened to the body and lockable in place with locking devices (7) and secondary bogies (2) rotatably fastened to it, in which bogie wheels (3) are bearing-mounted, drive wheels (5) fastened to the body, and a crawler (4) supported by the drive wheels and the bogie wheels, characterised in that the bogie construction includes a transfer device (9) fastened to the primary bogie (1) and the secondary bogie for adjusting the position of the secondary bogie (2) and the bogie wheels (3) fastened to it.

2. A bogie construction according to claim 1, characterised in that, as the transfer device (9), there is at least one hydraulic cylinder fitted between the primary bogie (1) and the secondary bogie (2).