The vehicle or the carriage, respectively, comprises in each single case a set of travelling wheels including at least two, preferably four or more, pivotal, steerable travelling wheels.

The steering gear is intended used on a vehicle/carriage hav- ing a plurality of steerable wheels, for the conveyance of long, heavy objects, such as loaded 40 feet containers. When driving on small quay and dock plants as well as within buildings, it is necessary that the carriage has several

steerable wheels with a minimum pivot radius (90° to either side).

In a set of travelling wheels of a vehicle/carriage compris- ing in all six travelling wheels: two steerable front wheels, two steerable intermediate wheels and two non-steerable rear wheels, the mutually differing angular deflections of the in- dividual travelling wheels upon turning of the vehicle may be illustrated as follows: The fixed rotational axis of the rear wheels is extended imaginarily, and an imaginary line is drawn from the rotational axis of one of the steerable wheels (e. g. the right hand front wheel) until it crosses the rota- tional axis extension of the rear wheels. Thus, a crossing point is created, the location thereof on said rotational axis extension is dependent on the radius of the turn; the more sudden turn, the closer to the rear wheels is the cross- ing point situated. This crossing point constitutes the turn- ing centre of all pivotable, steerable wheels, and this pre- supposes, of course, that all four steerable travelling wheels in the present exemplary embodiment each exhibits an angular deflection differing from the angular deflection of each of the remaining three travelling wheels.

The angle between an imaginary line parallel to the rota- tional axis of the rear wheels and the rotational axis of the various steerable wheels will differ from wheel to wheel in any turning position of the vehicle/carriage. (In one case, said angles were: right hand front wheel: al 75° ; left hand front wheel: a2; 67° ; right hand intermediate wheel: a3 3 60°; left hand intermediate wheel: a4 53°).

When following the road ahead, all angles a, OC4 are each equal to 90° (the wheels are parallel).

The above-mentioned case where the turning radius through the mid point of respective wheels of all pivotable, steerable

travelling wheels passes through a common point, represents the ideal case.

In order to secure correct angular deflection at each single pivotable, steerable wheel upon turning of the vehicle/ carriage, the steering angles (a) are synchronised by means of a steering gear always securing correct angle of the wheel axes in relation to the rolling direction of the wheels.

Correct angular deflection/steering angle for all pivotable, steerable travelling wheels is characterized in that all cen- tre lines for the wheel rotation have said common crossing point or are parallel (upon driving ahead/reversing).

Today, on loading and passenger vehicles, a synchronising mechanism comprising steering-gear levers and lateral struts is used for synchronising the turning movements of the steer- able travelling wheels. A disadvantage of this prior art syn- chronising mechanism is that the inaccuracy adjacent maximum angular deflections is all too large.

Moreover, it does not allow full swing-out of the steering wheels. Thus, said swing-out will never approach 90° to ei- ther side. For vehicles and carriages having a need for ap- proximately 90° turning possibility to either side, e. g. the above-mentioned construction where the set of travelling wheels comprises two steerable front wheels, two or more steerable intermediate wheels, as well as two rear wheels having a fixed rotational axis, this known synchronising mechanism is less fit.

In a vehicle having a 90° turning possibility to either side, the pivotable, steerable wheels must be driven; preferably hydraulic or electric operation. This has become more and more usual, e. g. in special vehicles within agriculture and industry.

Moreover, prior art comprises in the field concerned, e. g. those mechanisms disclosed in Swedish Laying-Out publication No. 343,254, British patent specification No. 1,155,469 as well as British patent applications Nos. 2,116,131 and 2,155,870.

The Swedish Laying-Out publication No. 343,254 deals with a steering gear which is intended to be used on steerable por- tal cranes. Here, the steering movement is transferred to the wheels from a rack through a toothed segment. The racks are displaced by means of cam grooves (called slideways). The shape of the cam grooves (the slideways) is configurated such that the racks, through the toothed segments, allot to the guide wheels differing steering angles in relation to the driving direction of the vehicle. The critical point of this known steering gear is the shape of the two cam grooves (the slideways). The shape of cam grooves cannot be calculated mathematically, and must be adapted by tests. This known steering gear is likely to be too inaccurate, especially in connection with large turning angles, e. g. up to 90° deflec- tion to either side. The steering mechanism has many mechani- cal parts which will probably be difficult and expensive to produce.

Moreover, the mechanism would not be usable in connection with two or more steerable intermediate wheels.

British patent specification No. 1,155,469 deals with a cam- era carriage which, in one embodiment, has four pair of wheels each allotted a vertical shaft for turning around the axis thereof in the horizontal plane. On each of the various vertical shafts, a chain wheel is mounted, two chain wheels being interconnected with an outer, driven chain wheel through a first chain, while the two chain wheels are inter- connected with another chain which, through guides, likewise engages said outer, driven chain wheel.

In this known transmission mechanism, each chain wheel is circular, and it is, therefore, unfit for use in a set of wheels wherein the steerable wheels have to be allotted mutu- ally differing angular deflections upon turning of the vehi- cle/carriage. With the known transmission mechanism, each wheel's angular deflection would be equal to the remaining deflections. Therefore, upon turning it will arise lateral sliding between the wheels.

British patent application No. 2,116,131 deals with a steer- able platform for a lawn mower. In this known device, the vertical shaft of each wheel is provided with pulley. The pulleys are motion-transmittingly interconnected by means of a belt driven by means of an outer, driven pulley. The pul- leys have the same size and will, thus, not be usable for a set of wheels comprising two steerable front wheels and at least one steerable intermediate wheel, spaced from the front wheels in the longitudinal direction of the vehicle and, pos- sibly, a pair of rear wheels without turnability.

British patent application No. 2,155,870 which is intended to be used for fork truck or harvesting vehicle for agricultural purposes, deals with two different mechanisms for the provi- sion of differing rotational movement for two wheels of a pair, each wheel's vertical shaft being provided with a non- circular, rounded body which is comma-shaped or consists of two rounded bodies consisting of upright cones, the one with the smallest base lowermost, and the other in an opposite po- sition. Both the comma mechanism and the cone mechanism are motion transmittingly connected by means of an endless, flexible rope. When a first wheel's vertical shaft is rotated for turning the vehicle, the flexible rope attends to rotate the other wheel's vertical shaft, the rotational angle of the latter shaft and, thus, of the wheel belonging thereto will differ from the rotational angle (angular deflection) of the first wheel.

On each of the comma-sign-shaped"rope sheaves", the ends must be bent up or down in order to prevent that these ends in an outer position touch the transfer belts. On the cone- shaped casters, helical grooves (coarse threads) have been made, said grooves upon turning (rotation) guide the transfer belts up or down along the cones and, thus, changes the di- ameter of the grooves.

Thus, British patent application GB No. 2,155,870 discloses two embodiments which theoretically will give two intercon- nected guide wheels a non-uniform guide angle when the car- riage turns. It is less likely that practically usable calcu- lation formulae can be developed, capable of defining dimensional criterions for the shape of the comma as well as the upward and downward bending of the ends of the comma.

(Calculation formulae based on wheel spacings, wheel angles and distance to common turning point for all wheels on the carriage).

Calculation formulae for the shape of the cone as well as the thread pitch of the helically shaped grooves, should probably be easier to develop than for the shape of the comma, but the large building height of the cones is limiting for the prac- tical use.

Comma-shaped or cone-shaped transfer means would hardly (due to inaccuracy and space considerations) be usable on a long vehicle for heavy transport, for steering a number (two rows) of steerable intermediate wheels, as the task is for the pre- sent invention.

Thus, the invention is occupied with a steering gear for steering angular deflections of the pivotable, steerable travelling wheels of a vehicle/carriage upon turning so that correct mutually differing deflections are secured on the in- dividual steerable wheels, wherein the vehicle/carriage com- prises a set of travelling wheels including at least two,

preferably four or more pivotable, steerable travelling wheels, inclusive of a pair of front wheels, and wherein each of the vertical shafts assigned to the front wheels carries at least one non-circular, rounded means, said means which are identical, are motion transmittingly interconnected by means of a movable endless means passed around the non-cir- cular means which, upon turning, allot the two front wheels different angular deflections. Upon turning, one wheel's ver- tical shaft is influenced by turning, or the influence may take place by attacking on the endless transmission means.

According to the invention, a steering gear of the kind as defined in the last section is characterized in that inter- connected chain wheels/belt pulleys which in general is to be given different angular deflections upon turning, are shaped as ellipses, the major axes thereof being disposed in a cer- tain mutual angle when the wheel axes are parallel, i. e. that the vehicle/carriage is driven straight ahead or backwards.

To the same vertical steering shafts, a non-circular means has been mounted, said means, at either side of the carriage, each is assigned an identical non-circular means on the ver- tical turning shafts for the steerable intermediate wheels.

The non-circular means of said intermediate wheels is by means of a second or a second and a third, respectively, end- less chain/ (toothed) belt, motion transferringly intercon- nected with identical non-circular means of steering wheels (front wheels/intermediate wheels) situated in front thereof (elliptical chain wheels or belt pulleys, preferably toothed belt pulleys, respectively, of front wheels or intermediate wheels situated in front thereof, respectively).

Such a steering gear comprising transmission devices where elliptical chain wheels/toothed belt pulleys are disposed on the vertical shafts assigned to the respective pivotable, steerable travelling wheels, enables the turning of each wheel about an individual vertical rotational axis, said piv-

otable, steerable wheels being interconnected in pairs by means of endless chain/toothed belt (the two front wheels be- ing interconnected as known per se; one of the front wheels and one or more intermediate wheels being interconnected at the same side of the vehicle/carriage, each front wheel and an intermedialte wheel or more on the opposite side of the side where the associated front wheel is placed, respec- tively).

Typically, the set of travelling wheels comprises in all six wheels, a pair of pivotable, steerable front wheels, a pair of pivotable, steerable intermediate wheels and a pair of rear wheels having a fixed rotational axis. Each of the two front wheels is assigned a vertical shaft to which is mounted elliptical chain wheels/ (toothed) belt pulleys. First non- circular transmission means belonging to the front wheels and positioned at the same level, are interconnected by means of a first endless chain/ (toothed) belt. Moreover, left hand front wheel's second elliptical chain wheel/ (toothed) belt pulley, at another level, is connected to left hand interme- diate wheel's elliptical chain wheel/ (toothed) belt pulley by means of a second endless chain/ (toothed) belt. Right hand front wheel's second elliptical chain wheel/ (toothed) belt pulley is connected with right hand intermediate wheel's el- liptical chain wheel/ (toothed) belt pulley, both of which are situated at the same level as the elliptical chain wheels/ belt pulleys of left hand front wheel and left hand inter- mediate wheel.

A steering gear which, according to the invention, comprises transmission devices based on elliptical chain wheels/ (toothed) belt pulleys assigned to a plurality of pivotable, steerable wheels at either side of the carriage (having one or more elliptical chain wheels/ (toothed) belt pulleys mounted on the respective vertical rotational shafts, con- nected in pairs by means of endless chains/ (toothed) belts), has be found to give more accurate angular deflections for

the pivotable wheels than achievable by means of prior art technique, especially upon sudden turns (45-90°) where steering gears shaped and designed in accordance with prior art would be quite inadequate.

Therefore, it has been a specific object of the present in- vention to provide a precision steering gear for vehicles/ carriages constructed with a view to make 90° turns. Upon such a sudden turn, the common intersection point of the turning radii of the steerable wheels on a fixed rear wheel axis (extension) will, with a set of travelling wheels com- prising e. g. six wheels, be positioned on that rear wheel's central point in vertical projection situated at that side towards which one is turning. Thus, if one turns 90° to the right, said intersection point will be positioned on the ver- tical central line of right hand rear wheel, and right hand front wheel's central vertical plane will form 90° with a vertical plane through the vertical central lines of right hand rear wheel and right hand front wheel. Right hand in- termediate wheel's vertical central plane takes the same ori- entation as right hand front wheel, while the central verti- cal planes of left hand front wheel and left hand intermedi- ate wheel form angles with the vertical plane through the vertical central line of right hand front wheel and rear wheel differing from 90°; and from each other (because their turning radii form an acute angle with each other, corre- sponding to general symmetry requirements in order to enable a 90° turn to both sides).

Also, the invention would be usable on vehicles having steer- able front wheels and rear wheels guided simultaneously, as well as on vehicles having four or more steerable intermedi- ate wheels. Then, the line for a common point of intersection for the turning centres of all wheels is an imaginary line through the central point of the carriage. (This line may also be centre line for fixed, non-steerable wheels in the middle of the carriage).

Thus, a steering gear according to the invention represents a technical progress within the field concerned, especially in vehicles/carriages the set of wheels thereof allowing 90° turns to both sides.

If the distance between the rotational axes of the front wheels and the rear wheels, upon driving straight ahead or rearwardly, respectively, is denoted C, and the corresponding distance between front wheels and intermediate wheels is de- noted B, the proportion C/B will-in order to secure correct angular deflections for the individual guiding wheels-re- quire elliptical chain wheels/toothed belt pulleys wherein the ellipsis has a certain eccentricity or proportion (Dm/dm), respectively, between the major axis (Dm) and the small axis (dm) for the respective ellipsis. It is quite sim- ple to construct chain wheels/toothed belt pulleys each hav- ing an elliptic efficient circumference and varying ellipsis eccentricity respectively varying the proportion Dm/dm for adoption to various proportions of C/B.

Non-restricting, illustrative examples of possible embodi- ments are further explained in the following, reference being made to the attached diagrammatical drawings, in which: Figure 1 shows in plan view a set of travelling wheels com- prising six wheels, arranged in pairs, two front wheels in a forward position in relation to a vehicle/carriage, only in- dicated by an outline surrounding the wheels; two intermedi- ate wheels in an intermediate position and two rear wheels in a rear position; Figure 2 corresponds to figure 1, showing the mutually dif- fering angular deflections allotted to the various pivotable, steerable wheels (front wheels and intermediate wheels) when the vehicle/carriage turns 45° to the right;

Figure 3 corresponds to figures 1 and 2, showing however the pivotable, steerable wheels in the turning positions they take when the vehicle/carriage turns 90° to the right; Figure 3b corresponds to figures 1,2 and 3, showing however the pivotable, steerable wheels in the turning positions they take when the vehicle/carriage turns around the turning cen- tre (18) halfway between the rear wheels (14a and 14b); Figure 4 shows, in a plan view, a set of travelling wheels comprising eight wheels, grouped in pairs: two front wheels in a foremost position in relation to a vehicle/carriage only indicated as an outline around the wheels; four intermediate wheels in an intermediate position as well as two rear wheels in a rearmost position; Figure 5 corresponds to figure 4, but shows the mutually dif- fering angular deflections allotted to the various pivotable, steerable wheels (the front wheels and the intermediate wheels) when the vehicle/carriage is turned 45° to the right; Figure 6 corresponds to figures 4 and 5, but shows the pivo- table, steerable wheels in the turning positions they take when the vehicle/carriage is turned 90° to the right; Figure 6b corresponds to figures 4,5 and 6, but shows the pivotable, steerable wheels in the turning positions they take when the vehicle/carriage turns with the turning point (18) halfway between the rear wheels (14a and 14b); Figure 7 shows, in a plan view, A set of wheels comprising eight wheels grouped in pairs: two front wheels in a foremost position in relation to a vehicle/carriage only indicated through an outline around the wheels, two intermediate wheels closest to the steer wheels and two intermediate wheels clos- est to the two steerable rear wheels. On the line for the

turning centres for all steerable wheels two fixed wheels are indicated; Figure 8 corresponds to figure 7, but shows the mutually dif- fering angular deflections allotted to the steerable wheels when the vehicle/carriage is turned 45° to the right; Figure 9 corresponds to figures 7 and 8, but shows the pivo- table, steerable wheels in the turning positions they take when the vehicle turns 90° to the right; Figure 9a corresponds to figures 7,8 and 9, but shows the pivotable, steerable wheels in the turning positions they take when the vehicle turns with a turning point (18) in the middle of the vehicle/carriage; Figure 10 shows a plan view of the vehicle wherein the set of travelling wheels comprises totally six wheels, of which four are pivotable, steerable wheels, each pivotable wheel being equipped with at least one elliptical chain wheel/belt pulley assigned to the vertical shaft of the respective wheel, around the axis of said shaft the wheel may turn; Figure 11 shows a plan view of the vehicle wherein the set of travelling wheels comprises totally eight wheels, of which six are pivotable, steerable wheels, each pivotable wheel be- ing provided with at least one elliptical chain wheel/belt pulley assigned to the vertical shaft of the respective wheel, around the axis of said shaft the wheel may turn; Figure 12 shows a plan view of the vehicle wherein the set of travelling wheels comprises totally ten wheels, of which eight are steerable, each pivotable wheel being provided with at least one elliptical chain wheel/belt pulley assigned to the vertical shaft of the respective wheel, around the axis of said shaft the wheel may turn. Circular turning/reversing

wheels simultaneously acting guidingly on front wheels and rear wheels; Figure 13 is a partial view as seen laterally of a steer/ guide wheel having a vertical shaft assigned thereto and car- rying two elliptical chain wheels/belt pulleys, said steer/guide wheel-in relation to figure 10-is a front wheel; Figure 14 shows the elliptical chain wheels/belt pulleys of the front wheels and their motion-transferring chain/belt on a larger scale, in order to emphasise the angle formed by the major axis of the ellipsis in relation to the associated front wheel's vertical centre plane when the vehicle/carriage drives straight ahead/rearwardly; Figure 15 is a graph in a right-angled system of co-ordinates in which varying proportions Ds/ds are placed along the ordi- nate and varying proportions C/A along the abscissa (C = dis- tance between the centre line of the front wheels and the centre line of the rear wheels; A = distance between the cen- tre lines of the front wheels); Figure 16 shows, on a larger scale, one front wheel and the intermediate wheel at the same side, on each wheel an ellip- tical chain wheel/belt pulley has been mounted on each of the assigned vertical shafts; Figure 17 is a graph where varying proportions Dm/dm are placed along the ordinate and varying proportions C/B (C = distance between the centre line of front wheels and centre line of rear wheels, B = distance between the centre line of front wheels and the centre line of intermediate wheels) placed along the abscissa;

Figure 18 indicates the influence of an angle ß on distance C (figures 1 and 10); Figure 19 shows an automatic stretching device for chains/ belts between steer/guide wheel and intermediate wheel (or two intermediate wheels) upon adjusted elliptical shape (the wheels steer straight ahead/rearwardly); Figure 20 shows the same stretching device as in figure 19, but disposed for steering about 45° to one of the sides; Figure 21 shows an automatic stretching device for the chains or belts for steer wheels used for motion-transferring inter- connection of certain"pairs"of elliptical chain wheels or belt pulleys, respectively; Figure 22 shows an automatic stretching device for chains/ belts between steer/guide wheel and intermediate wheel; Figure 23 shows a combined chain/belt stretching device also used to adjust wheel positioning; Figure 24 shows in a detail view (a part of) a carriage hav- ing three steerable/guidable wheels at the left side. The sides of the carriage are shown in dotted lines. On each wheel is shown a turning activator attached to the turning shafts of the wheels. Elliptical chain wheels/belt pulleys are turned by means of a hand wheel through chain/belt. On the belt pulleys on each wheel is shown an activating arm of an electric/hydraulic switch controlling the turning activa- tors.

First, reference is made to figures 1-3, where a pair of pivotable, steerable front wheels are denoted at 10a, lOb, a pair of pivotable, steerable intermediate wheels at 12a, 12b

and a pair of non-pivotable rear wheels at 14a, 14b. A vehi- cle/carriage is indicated by means of an outline 16 surround- ing the set of travelling wheels 10a, 10b, 12a, 12b, 14a, 14b.

Figure 1 shows the steerable wheels 10a, lOb, 12a, 12b in the parallel positions they take upon driving straight ahead/ rearwardly, figure 2 showing the steerable wheels in the mu- tually differing inclined positions they take when the vehi- cle/carriage makes a 45° turn to the right. A common turning point 18 for the four steerable wheels is positioned on a continuation 20 of the rotational axis of the rear wheels. A 90° turn to the right, in which the turning takes place around the central point of the right rear wheel 14b as com- mon turning point, is shown in figure 3. Figures 2,3 and 3b show ideal cases, in which the respective turning radii of the pivotable wheels 10a, lOb, 12a, 12b meet in a common point.

Figure 4 shows the steerable wheels 10a, lOb, 12a, 12b, 12c, 12d in the parallel positions they take upon driving straight ahead/rearwardly, figure 5 showing the steerable wheels in the mutually differing inclined positions they take when the vehicle/carriage makes a 45° turn to the right. Common turn- ing point 18 for the six steerable wheels is positioned on a continuation 20 of the rotational axis of the rear wheels. A 90° turn to the right in which the turning takes place around the central point of the right rear wheel 14b as common turn- ing point, is shown in figure 6. Figures 5,6 and 6b show ideal cases, where the respective turning radii of the pivo- table wheels 10a, 10b, 12a, 12b, 12c, 12d meet in a common point.

Figure 7 shows a carriage having ten wheels, of which eight are steerable wheels 10a, lOb, 12a, 12b and 10e, lOf, 12e, 12f which, with parallel wheels, drive straight ahead/rear- wardly. Figure 8 shows the steerable wheels in mutually dif-

fering inclined positions when the carriage makes a 45° turn to the right. Common turning point 18 for the eight steerable wheels is positioned on an extension 20 in the middle of the carriage. Fixed wheels 14a and 14b may be placed, the rota- tional axis thereof being in the extension line 20. Upon a turn of 90° to the right, the turning takes place around the centre 18 positioned in the centre of the wheel 14b in the middle of the carriage; this is shown in figure 9. In figures 8,9 and 9a, all wheels turning about a common centre 18 have been shown.

In figure 10, a set of travelling wheels comprises six wheels grouped in pairs, two steerable front wheels 10a, lOb, two steerable intermediate wheels 12a, 12b and two rear wheels 14a, 14b having a fixed rotational axis 20'. As shown, each of the two front wheels 10a, lOb is assigned two elliptical chain wheels/belt pulleys 22a, 24a, 22b, 24b. Here, the chains 28 and 30 between front wheel chain wheels/belt pul- leys and associated intermediate wheel chain wheel/belt pul- ley are approximately parallel to each other. For each of the three motion-transferring chains/belts 26,28,30, an auto- matic stretching device 40a, 40b and 40c, respectively, has been disposed; a further account of these will be given later in association with figures 21 and 22.

However, in figure 10 an activator has been drawn in the form of a pressurised fluid operated piston cylinder 42a, 42b (hy- draulic control cylinder) for each of the chains/belts 28 and 30, respectively. Displacement of the chains (or one of them) causes synchronised turning of the individual elliptical chain wheels/belt pulleys 24a and 24a'as well as 25b and 24b'transferring the turning to 22a and 22b and the chain/ belt 26.

In figure 11, a set of travelling wheels comprises eight wheels grouped in pairs: two steerable front wheels 10a and 10b, four steerable intermediate wheels 12a, 12b, 12c, 12d as

well as two rear wheels 14a and 14b having a fixed rotational axis 20b. As shown, each of the two front wheels lOa and 10b as well as each of two intermediate wheels 12a and 12b are assigned two elliptical chain wheels/belt pulleys 22a, 24a- 22b, 24b and 24a', 24c-24b', 24d.

The chain 26 interconnects the two steer wheels. The chains 28 and 30 interconnect steer wheels and intermediate wheels.

The chains 32 and 36 interconnects the two pairs of interme- diate wheels. For each of the five motion-transferring chains/belts 26,28,30,32 and 36, an automatic stretching device 40a, 40b, 40c, 40d and 40e is arranged. A further ac- count of the latter will be given later in association with figures 21 and 22.

In figure 12, a set of travelling wheels comprises eight wheels grouped in pairs, two steerable front wheels 10a and lOb and two steerable rear wheels 10e and lOf, as well as four steerable intermediate wheels 12a, 12b, 12c and 12f. To each of the vertical turning shafts of all wheels is coupled at least one elliptical chain wheel/belt pulley. The interme- diate wheels are also coupled to a circular chain wheel/belt pulley (46). The chain 26 interconnects the two steer wheels, and the chains 28 and 30 interconnect steer wheels and inter- mediate wheels. The chains 28a and 30a interconnect the two steerable rear wheels with the adjacent intermediate wheels.

In order to achieve that all wheels acquire one common turn- ing point or centre 18 situated on a line 20 through the cen- tre of the carriage (figures 8,9 and 12), circular chain wheels/belt pulleys have been mounted on each of the pairs 12a/12b and 12c/12f of intermediate wheels. Two chains/belts 38a and 38b are mounted as crossed chains/belts on the inter- mediate wheels 12a through 12e and 12b through 12f. As shown in figures 7,8 and 9, fixed, non-turnable, rotary wheels 14a and 14b may be disposed with their centres on the line 20c of the turning point. In figure 12, elliptical wheels/pulleys

22e and 22f connected to the chain 26a have been dotted on the rear wheels 10e and lOf. It is especially when this in- terconnection of wheels/pulleys is used in a servocontrol ar- rangement, that the wheels/pulleys 22a and 22f as well as the chain 26a can be used. For servocontrol, the wheels or pul- leys may have a smaller dimension than wheels or pulleys used for direct steering/guidance, see description of figure 24.

Reference is made to figure 14 where test results associated to elliptical chain wheels/belt pulleys having mutually dif- fering eccentricities or relationships between the major axis and the small axis Ds/ds are compared with the proportion be- tween the previously defined centre distances C/A (A = centre distance between front wheels/steer wheels, C = distance be- tween centre front wheels and centre rear wheels): 1) Ds 240 C 1890 --=---= 1,33 gives--=----= 4 (and when ß, 31,50°) ds 180 A 471 2) Ds 240 C 1560 --=---= 1,57 gives--=----= 2,5 (and when ß, 31, 50°) ds 153 A 625 3) Ds 240 C 800 --=---= 1,97 gives--=----= 1,7 (and when ß, 31, 50°) ds 122 A 471 For 1), 2) and 3) apply that ß is 31,50°.

The graph according to figure 15 shows Ds/ds (ordinate) as a function of C/A (abscissa).

Figures 16 and 17 illustrate test results associated with el- liptical chain wheels/belt pulleys on steer wheels/inter- mediate wheels and shows relationships between proportions Dm/dm and C/B (or C1/B1 in figure 4 and C2/B2 in figure 7).

C is the distance between the centre of steerable front wheels perpendicularly to the centre line (20) through fixed rear wheels.

B is the distance between the centre of steerable front wheels and the centre of steerable intermediate wheels.

Cl is the distance between the centre of foremost steer- able intermediate wheels and the centre line (20) through fixed rear wheels.

B1 is the distance between the centre of two steerable intermediate wheels at the same side of the carriage.

C2 is the distance between the centre of steerable rear wheels and the centre line 20c through fixed wheels in the middle of the carriage.

B2 is the distance between the centre of steerable rear wheels and the centre of closest positioned, steerable inter- mediate wheels.

1') Dm 240 C 2644 --=---= 1,57 when--=----= 3,33 dm 153 B 794

2') Dm 240 C 1844 --=---= 1,97 when--=----= 2,32 dm 122 B 794 3') Dm 240 C 1525 --=---= 2,38 when--=----= 1,90 dm 101 B 803 In figure 17, the proportion Dm/dm (ordinate) is charted as a function of the proportion C/B (abscissa).

In figure 18 is illustrated the relationship between the an- gle B, see figure 14, and the distance C as well as the di- rection of intersecting lines for the centre lines of the wheels. Proposing that the angle B is less than 31,50°, C increases and the intersecting line turns outwardly. On the other hand, proposing that the angle B is larger than 31,50°, C decreases and the intersecting line turns inwardly, see figures 14,15 and 18.

Figures 19 to 22 show various automatic stretching devices for the chains/belts as compensation for a possible slackness of a chain/belt arisen due to change of the angular adjust- ment Z of the chain/belt at different steering angles. When driving straight ahead, and upon a turn of 90° to either side, there will always exist an angle Z x 2 between chain/ belt lengths, see figure 19. Upon making a turn of about 45° laterally, the chain/belt lengths will be approximately par- allel, Z = 0°, see figure 20. The angle Z will, upon driving straight ahead and 90° laterally, increase when the differ- ence between Dm and dm increases. The angle Z will also in- crease when the distance B decreases.

This variation of the angle Z will induce a small slackness into the chain/belt lengths upon a turn of 45° when these lengths have a correct tensioning when driving straight ahead as well as upon turns of 90° laterally. When the angle Z is larger than about 2°, a compensating stretching device should be arranged which, upon a turn of 45°, automatically causes the same tensioning of the chain as when driving straight ahead and turning 90° laterally.

Figures 19 and 20 shows a compensating device where the pul- ley 24a on the steer wheel is allotted an adjusted elliptical shape (extremely exaggerated in figures 19 and 20). In order to achieve an even tensioning of the chain/belt, the length of the curved adjusted surface of the ellipsis from U to P must be equal to the length of the curved surface from U to V.

This adjustment of the shape of the ellipsis will theoreti- cally reduce the accuracy of the steering angles. Practical tests show that this inaccuracy is hard to record, and the steering accuracy with an adjusted pulley will give a steer- ing accuracy which is far better than steering by means of parallel struts.

In figure 21 is shown a stretching device for the chain/belt 26 interconnecting the elliptical chain wheels/belt pulleys 22a, 22b of the front wheels 10a, lOb. The stretching device 40b comprises two small chain wheels/belt pulleys 44a, 44b having a fixed centre distance. According to figure 21, these stretching wheels 44a, 44b are disposed on the inside of the chain/belt 26, while corresponding stretching wheels 44a', 44b'in figure 22 are disposed on the outside of the chain/ belt 28 interconnecting the pulleys 24a and 24a'between steer wheel and intermediate wheel.

Figure 23 shows a combined chain/belt stretching device and adjusting device for wheel positioning. It is used independ-

ently of the automatic stretching/compensating device as shown in figures 19 to 22.

In figure 24 is shown a coupling arrangement for servocontrol of separate steering activator on each of the wheels on a carriage. In the figure is shown three steerable wheels on the left side of a carriage, a steer wheel 10a and two steer- able intermediate wheels 12a and 12c. On each turning shaft 34a, 34c, 34e is mounted an individual turning activator con- sisting of: a worm wheel (alternative a large gear) 50a, 50c, 50e attached to the turning shaft, a worm screw 52a, 52c, 52e (alternative a small gear) for operating the worm wheel, and an electric (alternative hydraulic) motor 54a, 54c, 54e ro- tating the worm screw. Elliptical pulleys, one or two inter- connected on each shaft 34a, 34c, 34e, can be freely turned on the shaft. Through the chains 26,28 and 32, a manual steering wheel 58 can move the pulleys.

An activating arm 56a, 56c, 56e attached on the pulley unit of each turning shaft gives a pulse to an electric (hydrau- lic) switch (reverser, change-over switch) 59a, 59c, 59e in both rotational directions. The position of the manual steer- ing wheel will always take a certain angular proportion to the steering direction of the carriage. A possible error (stop) in the turning arrangement of one of the steering wheels will stop the manual steering wheel 58, as well as stop the steering of the remaining wheels. In this case, the steering mechanism gives pulses to the activators only. The forces transferred through the chains/belts of the steering mechanism are small (manual from the steering wheel 58).

Therefore, the parts of the steering mechanism can be made in small dimensions.

Again, reference is made to figure 10, showing actuators for transferring forces to the elliptical chain wheels/belt pul- leys, namely in the form of at least one hydraulic piston cylinder 42a and/or 42b or another actuator for rectilinear

transference of forces influencing at least one (e. g. 28 and/or 30) of the chains 26,28,30 directly. A large gear positioned in the turning centre of one of the wheels and driven through a small gear by means of an electric or hy- draulic motor will also be usable.

Finally, reference is made to figure 12, where a point F has been marked on each pulley (elliptical and circular). On a vehicle as indicated in figures 1 through 12, an area of the circumference of the elliptical (and circular) chain wheels/ belt pulleys will always have contact with a certain area (point) on the chain/belt. In this case, the total turning angle is less than 180°. At this area (point) the chain/belt may be attached to the wheel/pulley (be clamped or attached through toggle screw). Then, pulleys without teeth can be used. The point F marked in figure 12 shows the positioning of this attachment point.