ROLLOVER PROTECTION STRUCTURE FOR AN AGRICULTURAL TRACTOR AND METHOD OF MANUFACTURE

[01] The invention relates to rollover protection structures (ROPS) for agricultural tractors and utility vehicles and to method of manufacture.

[02] Modern utility vehicle and agricultural tractor cabs include a ROPS for safety reasons. A ROPS typically comprises a pair of front corner pillars, hereinafter termed "A-pillars" and a pair of rear corner pillars, hereinafter termed "C-piilars". Some cab designs involve a 5- or 6-pillar construction with one or two 'B-pillars' respectively.

[03] The integrity and strength of the ROPS is central to the design of the overall cab. Safety demands are balanced with operator comfort and cost. More recently, the drive to maximise operator field of view and improve aesthetic appearance has lead to the introduction of curved pillars formed from hollow structural section bent into the desired curve. Moreover, for the same reasons, the use of a 4-pillar construction is more desired.

[04] It is an object of the invention to provide a method of manufacturing a ROPS with reduced cost.

[05] In accordance with a first aspect of the invention there is provided a method of manufacturing a ROPS for an agricultural tractor, the ROPS comprising a pair of curved A-pillars, a pair of curved C-piliars and a roof frame having four roof frame members connecting the A-pi!lars and C-pillars, the method comprising bending and cutting hollow structural section to form the A-pillars and C-pillars, each pillar having a substantially continuous radius of curvature, wherein the A-pillars and C-pillars are formed from hollow structural section having the same sectional profile. By forming the front and rear corner pillars of the ROPS from the same materia!, and potentially from the same !ength, the number of different materials required is reduced thus improving economies of scale.

[06] Furthermore, by forming a cab with pillars having a continuous radius of curvature along their Iength, the step of bending the hollow structural section can be executed before cutting the pillars to length. This significantly simplifies the manufacturing process and dispenses with the need to process individual pillars thus saving on time and cost.

[07] The method may further comprise the step of welding the roof frame members to the A-pillars and C-pillars to form the roof frame.

[08] The method may further comprise stockpiling hollow structural section before cutting and bending the same to form the A-pillars and C-pillars. The requirement to store only one type of hollow structural section, rather than two or more, reduces idle inventory and further reduces production costs.

[09] The A-pillars have a radius of curvature which, preferably, is substantially equal to that of the C-pillars. Advantageously, this allows the same lengths of bent material to be cut for both sets of pillars. The bent section material may be stockpiled before cutting thus shortening the response time of the manufacturer and improving efficiency.

[10] In a preferred embodiment the hollow structural section has a cross section with a first, second and third sides, the first and third sides forming an interior obtuse angle with the adjacent second side, and wherein the second side forms an inward facing surface for the A-pilfars and C-pi!lars, and wherein the first and third sides are secured to a respective roof frame member. The angles of the cross-sectional profile are chosen to permit practical and acceptable dimensioning of the roof frame members attached thereto.

[11] Furthermore, said angles present pillars which have an increasing width moving away from the operator thus improving field of view.

[12] The hollow structural section preferably includes a hollow stiffening rib which is disposed opposite said second side and thus on the outside of the cab.

[13] In accordance with a second aspect of the invention there is provided a ROPS for an agricultural tractor comprising a pair of curved A-pillars, a pair of curved C-piliars and a roof frame having four roof frame members connecting the A-pillars and C-pillars, the A-pillars and C-pillars being formed of hollow structural section having a common sectional profile and wherein the radius of curvature is continuous for each pillar. [14] A specific embodiment of the invention will now be described with reference to the appended drawings in which:-

[15] Figure 1 is a front isometric view of a ROPS manufactured in accordance with the invention;

[16] Figure 2 is a rear isometric view of the ROPS of Figure 1 ; [17] Figure 3 is a plan view of the ROPS of Figure 1 ; [18] Figure 4 is a front view of the ROPS of Figure 1 ; and, [19] Figure 5 is a side view of the ROPS of Figure 1.

[20] In the following description, the terms 'front', 'rear', 'left', and 'right' will be used in relation to the normal forward direction of travel of an agricultural tractor fitted with the ROPS shown.

[21] It should be understood that the illustrated embodiment is given by way of example only and that the stages of manufacture and cab design can be varied whilst staying within the scope of the claimed invention.

[22] With reference to the drawings, part of a cab 10 for an agricultural tractor comprises a ROPS 12 having two front corner 'A-pillars' 14, 15, and two rear corner 'C-pillars' 16, 17. In addition to the ROPS 12, the drawings show a cab floor 18 and rear wheel arches 19, 20.

[23] The ROPS 12 has a 5-post cab construction and includes a single B-piliar 22 on the left-hand side which serves to support a hinged door (not shown) for the cab.

[24] A roof frame 24 comprises four roof frame members 25, 26, 27, 28. A first roof frame member 25 connects the top of left-hand C-pillar 17 to the top of left-hand A-pillar 14. Second roof frame member 26 connects the top of left-hand A-pillar 14 to the top of right-hand A-pillar 15. Third roof frame member 27 connects the top of right-hand A-piilar 15 to the top of right-hand C-pillar 16. Fourth roof frame member 28 connects the top of right-hand C-pillar 16 to the top of left-hand C-pillar 17. [25] The roof frame members 25, 26, 27, 28 are preferably secured to the respective A- and C-pillars 14, 15, 16, 17 by welding. Together, the roof frame members 25, 26, 27, 28 provide a supporting structure to attach a cab roof (not shown).

[26] The A-pillars 14, 15 are each formed from a single member and extend from the roof frame 24 to the floor 18. The C-pillars 16,17 are each formed from a single member and extend from the roof frame 24 to the respective wheel arch 19,20.

[27] The A- and C-pil!ars 14, 15, 16, 17 are formed from hollow structural section. In accordance with the invention, all four corner pillars 14, 15, 16, 17 are formed from hollow structural section having the same cross-sectional shape and size which is best illustrated in Figure 3. All pillars 14, 15, 16, 17 are curved inwardly and have substantially the same radius of curvature.

[28] The preferred cross sectional shape of the pillars includes an inner side 30, and two attachment sides 31 , 32 that provide the surfaces to which the roof frame members attach. The attachment sides 31, 32 each form an interior obtuse angle with the inner side 30 so as to present a surface of practical orientation for the roof frame members.

[29] The preferred profile of the pillars also includes a hollow stiffening rib, designated generally at 33 in Figure 3, on the outermost side of the hollow structural section.

[30] During construction of the ROPS 12, the hollow structural section material required for the pillars may be stockpiled before bending and cutting to the desired dimensions. Several known methods can be employed for bending and cutting the hollow structural section.

[31] Due to the like curvature of all pillars, the material may be stockpiled between the bending stage and the cutting stage wherein the required pillars can be simply cut from bulk. This reduces the lead time in manufacturing the pillars.

[32] In summary, a ROPS for an agricultural tractor and method of manufacture is provided wherein the ROPS comprises a pair of curved A-pillars, a pair of curved C- pillars and a roof frame having four roof frame members connecting the A-pillars and C-pillars. The A-pillars and C-pillars are formed from hollow structural section having the same sectional profile to allow a reduction in the number of materials required and improved economies of scale.