SE544646C2 - Method of producing a ladder and a ladder manufactured according to said method - Google Patents

Abstract

The present invention relates to a method of manufacturing a ladder comprising the steps of cutting away defined sections (12, 16) in a plane plate (10) of metal to form longitudinally extending sections (14) and transversally extending sections (18) between the longitudinally extending sections (14), forming the transversally extending sections (18) to generally tubular rungs (18); and forming the longitudinally extending sections (14) to profiled side profiles (14). The present invention also relates to a ladder produced by the method.

Description

METHOD OF PRODUCING A LADDER .Å s» TECHNICAL AREAThe present application relates to a method for producing a ladder in an effective way, providing a sturdy ladder.

BACKGROUND OF INVENTION Ladders have many uses and in particular ladders are used on roof instalments inorder to access certain areas and elements placed on roofs such as ventilation unitsand chimneys. ln this regard, these types of ladders are also used for securing pointsfor personal fall protection. Thus, such a ladder must be properly anchored to theroof or components thereof as well as being sturdy enough to withstand forces fromboth climbing personnel as well as someone slips and is prevented from falling off the roof by the personal fall protection.

Regarding manufacturing of ladders, there is always a strive to reach as fewproduction steps and yet provide a sturdy and safe product. One example isdisclosed in the document WO 2006/011843. lt describes a method of producing aladder from a one piece of metal-plate material. Here a workpiece is cut from a metalplate. The method comprises steps of deep-drawing of portions to form the rungs totrough-shape together with perforation and press-up for forming friction-increasingelements. A subsequent step is then to bend, for example by rolling, the sideelements to profile shape. Then the ladder is preferably corrosion treated in order towithstand the environment on a roof. The rungs are preferably provided with areaswith different inclination so that the same ladder may be used on roofs with different inclination by orienting the ladder in one or an opposite direction.

The treads work well in most instances but for heavy loads, the deep-drawing intorungs may not provide enough sturdiness. Thus, there is a constant need for improvement.

BRIEF DESCRIPTION OF INVENTION The aim of the invention is to provide an improved method for producing a ladder.The aim is solved by a method characterised by the features of the independentpatent claim. Preferable embodiments form the subject of the dependent patent claims.

According to one aspect of the invention, it comprises a method of manufacturing aladder comprising the steps of cutting away defined sections in a plane plate of metalto form longitudinally extending sections and transversally extending sectionsbetween the longitudinally extending sections. Thereafter, the method comprises forming the transversally extending sections to generally tubular rungs and forming the longitudinally extending sections to profiled side profiles.

, C _,» \ \ -"\ n* *. ~'>r^ï:: ïïšjhe method comprisegg the sub-steps of pressing the transversally extending sections in a first die, forming a generally U-shape in cross-section, and placing the lower part of the U-shape in a lower diesection of a second die and pressing on the upper part of the U-shape with an upperdie section of the second die to form the tubular rungs. Thus, the rungs of the ladder according to the method ;,>_ formed in two steps in order to obtain the tubular cross-section. ln this regard, the first die a lower die section and an upper diesection, where the lower and upper die sections complementary shape incross-section. ln particular, the lower die section of the second die a shapecorresponding to the shape of the lower die section of the first die and the upper diesection of the second die szfsaagsf--have a shape corresponding to the lower die section ofthe second die but with an opposite orientation.

Moreover, the side profiles may be formed to generally rectangular C-shape in cross-section. This shape has several advantages. The shape provides a sturdiness andstrength in directions generally transversal to the longitudinal direction of the ladder,preventing sagging of the ladder at midpoint if the ladder is mounted for instance onan inclined roof resting on support structures at each end if a person is climbing onthe ladder. The shape is also fairly easy to produce by folding the longitudinallyextending sections three times, either simultaneously or in subsequent folding steps.

Further, the method may comprise the step of providing friction enhancing elementsin the transversally extending sections and the friction enhancing elements maycomprise protrusions formed during the cutting step. These friction enhancingelements will reduce the risk of a person slipping off a rung when climbing ordescending the ladder.

Further, the ladder may comprise the step of providing a number of attachment holesalong the extension of the longitudinally extending sections. These attachment holesmay be used for different purposes such as attaching treads or steps to the ladder inorder to have a larger stepping area than just the rungs. Further, safety equipment such as rails for the anchoring of personal fall protections may be attached to theladder by the holes. Further, the ladder may comprise attachment holes in thetransversally extending sections. These holes may be used for attaching treads orsteps to the rungs. ln order to provide a weather-resistant ladder, surfaces of themanufactured ladder may be treated with anti-corrosion material.

These and other advantages and features of the present invention will becomeapparent from the following detailed description of the invention and from the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGSln the following detailed description of the invention, reference will be made to theaccompanying drawings, of which Fig. 1of forming rungs of a ladder, shows a perspective view of a plane sheet of metal with different stages Figs. 2a-d show the steps of forming the rungs of the ladder, Fig. 3profiled side sections, and shows an end view of a manufactured ladder and the steps of forming Fig.method of the invention, and shows a perspective view of a ladder manufactured according to the Fig. 5 shows a step that may be attached to the ladder of Fig.DETAILED DESCRIPTION OF THE INVENTION The method for producing a ladder according to the present application comprisesstarting with a plane plate of metal 10, preferably steel. The plate may be discreteitems or be a reel of sheet metal that is cut into the length of the ladder to beproduced. The plate 10 is placed in a stamp and certain areas are cut away. lf a reelof sheet metal is used, the stamp may cut the sheet to appropriate length of the ladder. As seen in Fig. 1, side areas 12 are first cut away adjacent sections 14 thatare to be the side profiles. Then a square area 16 is cut away leaving transversa|areas 18 that are to be the rungs. Further, a row of holes 20 may be stamped in theside profile sections 14 and friction enhancing elements 22 like corrugations orprotrusions are made in the rungs sections 18. The rungs sections 18 may also beprovided with a number of holesThe cut plate is then placed in a forming machine wherein the outer sides 18a of therungs sections are first bent upwards with a bottom curvature, forming a generally U-shaped profile as seen in Fig. 1. The forming machine may in this regard have alower die section 26, Fig. 2, having a general U-shape open upwards as seen incross-section as well as an upper die section 28 with a shape corresponding to thelower die section as seen in Fig. 2a. As an alternative, the lower die may be made ofsections along its length that are movable in order to support the plate section of the rung when forming the U-shape.

The U-shaped rungs section 18 is then placed in a second die where they are bentso that the opposite edges 18b meet each other to form a tubular and generallycircular rung as seen in a cross-sectional view. For doing this, the forming machinemay have a lower die section 30 in which the formed rung section is placed and anupper die section 32 having a general U-shape open downwards as seen in a cross-sectional view, Fig. 2c. When the upper die section 32 contacts the upper edges 18bof the upper die section 32, Fig. 2c, the upper sections are bent inwards until the edges 18b are in contact with each other, Fig. 2d.

The next step is to form the side profiles. They may be formed by bending, such asby rolling or by folding, to a generally rectangular C-shape in cross-section as seen inFigs. 3 and 4, where the folding is performed in three steps. The holes 20 along theside profiles may then be arranged generally in the center of the C. As seen in Fig. 3,the rungs and the side profiles may preferably be formed so that the rungs arepositioned inside and between the side profiles, providing a better force distribution.

Even if the manufacture of the ladder is described as being done by severalmachines, a single press may be used wherein the cutting is performed in a first section, the bending of the rungs section to a U-shape is made in a subsequentsection and the forming of the U-shaped rungs section to tubular rungs in yet asubsequent section. The plate of sheet metal is moved in steps through thesubsequent sections until all the rungs have been formed. Further, lubrication may beused in some of the steps in order to facilitate the forming of the rungs and the sideprofiles as desired.

The design makes the ladder very sturdy with the tubular rungs and the shaped sideprofiles. The finished ladder is then treated by anti-corrosion layers such as zinc andpaint. Further, the ladder may be provided with separate treads 40, Fig. 5, that maybe secured with bolts going through the holes 20 in the side profiles 14 and possiblythrough the holes 24 of the rungslt is to be understood that the embodiment described above and shown in thedrawings is to be regarded only as a non-limiting example of the invention and that itmay be modified in many ways within the scope of the patent claims.

Claims (11)

1. 1. Method of manufacturing a ladder comprising the steps of:- cutting away defined sections (12, 14) in a plane plate (10) of metal to formlongitudinally extending sections (14) and transversally extending sections(18) between the longitudinally extending sections - forming the transversally extending sections (18) to generally tubular rungs by; - pressing the transversally extending sections a first die (26, 28),forming a generally U-shape in cross-section, wherein the first die; comprises a lower die section (26) and an upper die section (28), where the lower and upper die sections “ïgfguhave complementary shape in cross-section;- placing the lower part of the U-shape in a lower die section (30) of a second die and pressing on the upper part of the U-shape with an upper die section (32) of the second die wherein the lower die section (30) of the second die die section (26) of the first die has a shape corresponding to the shape of the lower and wherein the upper die section (32) of the second die(30) of the second die wherein the edges of the transversally extending sections are “has a shape corresponding to the lower die section but with an opposite orientation to form tubular brought in contact with each other;and- forming the Iongitudinally extending sections (14) to profiled side profiles Method according to claim 1 or 2, wherein the formed rungs a generally circular cross-section. Method according to claim 1, wherein the side profiles (14) are formed to generally rectangular C-shape in cross-section. Method according to any of the preceding claims further comprising the step ofproviding friction enhancing elements (22) in the transversally extending section 5. Method according to claim 4, wherein the friction enhancing elements comprise protrusions formed during the cutting step. 6. Method according to any of the preceding claims, further comprising the stepof providing a number of attachment holes (20) along the extension of the longitudinally extending sections (14). 7. Method according to any of the preceding claims, further comprising providing attachment holes (24) in the transversally extending sections (18). 8. Method according to any of the preceding claims, further comprising the step of treating surfaces of the manufactured ladder with anti-corrosion material.9. Ladder manufactured according to any of the c|aims 1 to10. Ladder according to claim 9, further comprising treads (40) attachable to said 11.Ladder according to claim 10 when dependent on c|aims 6 or 7, wherein saidtreads attached to said rungs bolts through the attachmentholes (24) of the rungs §§j1_._§š¿§__and/or the attachment holes (20) of the side Df0fi|GS