Lift truck mast

Abstract

A lift truck mast having extensible uprights received one within the other. Each upright includes a pair of rail members each of which has a web and flanges such that the members are I-shaped in cross section. The rail members are nested together with the web portion and end flanges of the inner overlapping the web portions and end flanges of the outer. The web portions of one rail member carry rollers which ride on the rear end flanges of the adjacent nested rail member. Each web portion, when viewed in cross section, provides a straight section of uniform thickness and a tapered portion gradually increasing in thickness toward the rear end flange. The rollers are spaced from, but mounted parallel to, the straight web portions so as to rotatably engage the rear end flanges and tangentially contact the tapered web portion. Forward mast bending loads are taken radially by the rollers and side thrust loads parallel to their axes of rotation for improved anti-friction properties and longer wear.

What is claimed is: 
     
       1. A structural member for use in a multi-sectional mast having a stationary and extensible section, one being laterally offset relative to the other and each extending longitudinally parallel to the axis of the mast and said extensible section being longitudinally parallel to the axis of the mast and said extensible section being longitudinally slidable relative to the stationary section forming therewith longitudinally extending trackways, and anti-friction rollers carried on at least one of said sections adapted to roll in said trackways when extending or retracting one section relative to the other, said structural member being adapted to form a portion of said trackways and comprising, a web portion for defining a longitudinally extending side of said trackways and having a surface inclined to .Iadd.and tangentially contactable by an edge surface of .Iaddend.the rollers in said trackways .Iadd.and then .Iaddend.diverging, in cross section, on a line from .[.a.]. .Iadd.the .Iaddend.point of tangency with said rollers and joining a straight surface at an angle of between 1° and 20° relative thereto, said straight surface extending perpendicularly to the axis of said rollers and said inclined surface and straight surface being laterally spaced from and out of contact with said .[.rollers.]. .Iadd.roller edge surface, so that a clearance is provided between said web portion and said roller .Iaddend.except at said point of tangency on the inclined surface thereby minimizing any tendency for axial loading of said rollers.   
     
     
       2. A structural member according to claim 1 wherein said inclined surface diverges at an angle of between 2° and 6°. 
     
     
       3. A structural member according to claim 2 wherein said inclined surface diverges at an angle of approximately 31/2°. 
     
     
       4. A structural member according to claim 1 wherein, viewed in cross section, said member has transversely extending end flanges on said web portion forming a generally I-shaped cross sectional configuration and one portion of one end flange joining said inclined surface of the web portion for providing a rolling surface for said rollers and adapted to transmit radial loads thereto. 
     
     
       5. A structural member according to claim 4 wherein the portion of said end flange for providing rolling engagement with the rollers is hardened during the manufacture of said structural member to a greater extent than the rest of said member. 
     
     
       6. A structural member according to claim 5 wherein said portion of the end flange for providing rolling engagement with the rollers is provided with a wear surface of greater hardness than the remainder of said structural member. 
     
     
       7. A structural member having an I-shaped cross section for use in a multi-sectional mast having fixed and extensible mast sections adapted to nest one within the other defining parallel, longitudinally extending trackways and anit-friction rollers received in said trackways for supporting the extensible mast section for movement relative to the fixed mast section, said structural member comprising a web having a tapered portion joined by a straight portion, .Iadd.said straight portion extending perpendicularly to the axes of said rollers, .Iaddend.and   a pair of end flanges, one being integrally formed with said tapered portion and the other with said straight portion and each extending transversely thereto,   the one end flange formed with the tapered portion adapted to provide a rolling surface for said rollers.Iadd., .Iaddend.and said tapered portion inclined away from said rollers .[.and.]. joining said straight portion at an angle of between 1° and 20° .[.providing a space between the rollers and said straight and tapered portions from a point of tangency on said tapered portion to said other end flange.]. .Iadd.and joined to said one end flange by an arcuate surface, said tapered and straight portions and said arcuate surface each being spaced from each of said rollers except at points of tangency between an edge surface on each one of said rollers and the tapered portion.Iaddend..   
     
     
       8. A structural member according to claim 7 wherein said tapered portion diverges at an angle of between 2° and 6°. 
     
     
       9. A structural member according to claim 8 wherein said tapered portion diverges at an angle of approximately 31/2°. 
     
     
       10. An extensible mast having collapsed and extended positions, comprising: a. inner and outer mast sections nested inner within the outer and being relatively longitudinally extensible;   b. each of said mast sections including two parallel laterally spaced rail members;   c. said rail members of at least one of said mast sections carrying a plurality of rollers mounted for rotation about parallel axes;   d. each of said rollers defining a peripheral surface and an end surface joined by a curved interconnecting surface;   e. said rail members of said other mast section defining track surfaces engageable with said peripheral surfaces, and defining inclined surfaces adjoining said track surfaces and tangentially contactable with .[.the junctures of.]. said interconnecting .[.and said end.]. surfaces of said rollers to absorb thrust loads; and,   f. said inclined surfaces being spaced from .Iadd.each of .Iaddend.said rollers except at the points of tangency with said .[.end.]. .Iadd.interconnecting .Iaddend.surfaces .Iadd.so that a clearance is provided between the interconnecting surfaces and corners of said rail members.Iaddend..   
     
     
       11. The mast of claim 10 wherein said track surfaces extend in planes paralleling said axes of said rollers, and said peripheral roller surfaces are cylindrical surfaces concentric about said axes. 
     
     
       12. The mast of claim 10 wherein said end surfaces of said rollers extend in planes perpendicular to the axes of said rollers, and said inclined surfaces are inclined at angles relative to said end surfaces within the range of about 1° to 20°. 
     
     
       13. The mast of claim 12 wherein said angles are within the range of about 2° to 6°. 
     
     
       14. The mast of claim 10 wherein said inclined surfaces are inclined at angles relative to said end surfaces within the range of about 1° to 20°. 
     
     
       15. The mast of claim 14 wherein said angles of inclination are within the range of about 2° to 6°. 
     
     
       16. The mast of claim 15 wherein said angles are about 31/2°. 
     
     
       17. The mast of claim 10 wherein: a. each of said rail members includes a pair of spaced end flanges connected by a web;   b. said webs and said end flanges of said inner section rail members overlap said webs and said end flanges of said outer section rail members;   c. said track surfaces are formed on said end flanges of said other mast section rail members; and   d. said inclined surfaces are formed on said webs of said other mast section rail members.   
     
     
       18. The mast of claim 17 wherein said points of tangency are located .[.radially inwardly on said end surfaces.]. from .[.said.]. .Iadd.the .Iaddend.junctures of said .[.peripheral.]. .Iadd.interconnecting .Iaddend.and end surfaces, whereby no contact is made between said inclined .Iadd.and connecting web .Iaddend.surfaces and said rollers.Iadd., .Iaddend.at .[.said.]. .Iadd.the .Iaddend.junctures .Iadd.of said interconnecting and end surfaces.Iaddend.. 
     
     
       19. The extensible mast of claim 17 wherein: a. said rollers include a first pair of rollers mounted on the webs of the outer section rail members, and a second pair of rollers mounted on the webs of the inner section rail members;   b. each of said rail members has an end flange defining one of said track surfaces; and   c. each of said rail members has a web defining one of said inclined surfaces.   
     
     
       20. The mast of claim 17 wherein each of said webs which define one of said inclined surfaces has, in cross section, a region of substantially uniform thickness extending toward one of the integrally formed end flanges, and a region of increasing thickness extending toward the other integrally formed end flange, said region of increasing thickness defining said one inclined surface. 
     
     
       21. The mast of claim 17 additionally including a load carriage supported on one of said mast sections and including: a. a pair of parallel, longitudinally extending load carriage support members laterally spaced from and overlapping load carriage trackways defined by the rail members of said one mast section;   b. first, second and third opposed pairs of rollers rotatably carried on said load carriage support members and received in said load carriage trackways for rolling engagement with said one mast section rail members when reciprocating said load carriage;   c. said first pair of rollers mounted above the second pair and the second pair above the third; and,   d. said first and third pairs of rollers primarily taking the dynamic fork loads during reciprocation of the load carriage throughout the length of said load carriage trackways, said first pair of rollers extending out of said load carriage trackways in the fully raised position of said load carriage free of any loading, and said second and third pair of rollers then cooperating in taking the static fork loads whereby bearing loading conditions are improved and the maximum fork height is increased.   
     
     
       22. A lift truck mast according to claim 21 wherein said load carriage support members carry side thrust rollers rotatably mounted on fore and aft extending axes to rotatably engage the webs of said one mast section rail members during reciprocation of the load carriage thereby isolating the other rollers from side thrust loads. 
     
     
       23. An extensible lift truck mast, comprising: a. inner and outer mast sections nested inner within the outer and being relatively longitudinally extensible;   b. each of said mast sections including laterally spaced rail members;   c. each of said rail members having spaced end flanges connected by a web;   d. said webs and said end flanges of said inner section rail members overlapping said webs and said end flanges of said outer section rail members to define longitudinally extending trackways;   e. said rail members of at least one of said mast sections carrying a plurality of rollers mounted for rotation about parallel axes, said rollers each having a peripheral surface and an end surface joined by a curved interconnecting surface;   f. said rail members of the other of said mast sections having track surfaces defined on its end flanges for engaging said peripheral surfaces of said rollers;   g. said webs of said other section rail members having cross sections of increased thickness near said track surfaces .Iadd.and joined to said track surfaces by a connecting surface.Iaddend., said increased thickness cross sections defining inclined surfaces that extend into tangential contact with the .Iadd.interconnecting surfaces near the .Iaddend.junctures of said interconnecting and said end surfaces at angles within the range of about 1° and 20° relative to said end surfaces.Iadd., and said web connecting surface being spaced from said rollers.Iaddend..   
     
     
       24. The mast of claim 23 wherein said angles are within the range of about 2° and 6°. 
     
     
       25. The mast of claim 24 wherein said angles are about 31/2°.