SE2050892A1

SE2050892A1 - Method of producing a ladder

Info

Publication number: SE2050892A1
Application number: SE2050892A
Authority: SE
Inventors: Rolf Hedlund
Original assignee: Cwl Patent Ab
Priority date: 2020-07-14
Filing date: 2020-07-14
Publication date: 2022-01-15
Also published as: SE544646C2; EP3940188C0; EP3940188B1; PL3940188T3; EP3940188A1

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, forming the transversally extending sections (18) to generally tubular rungs; and forming the longitudinally extending sections (14) to profiled side profiles.

Description

METHOD OF PRODUCING A LADDER TECHNICAL AREA The 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 offthe 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 independent patent 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 comprisesforming the transversally extending sections to generally tubular rungs and formingthe longitudinally extending sections to profiled side profiles.

With such a method, a very sturdy and stable ladder is produced from a single pieceof material. No assembly is thus required and no welds, screws or rivets are necessary.

Preferably, the edges of the transversally extending sections are substantially incontact with each other after forming to rungs. Also, the formed rungs preferablyhave a generally circular cross-section. This provides sturdy rungs that can withstandhigh loads without the use of joining means such as welds.

According to one aspect, the method may comprise the sub-steps of pressing thetransversally 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 die section of a seconddie and pressing on the upper part of the U-shape with an upper die section of thesecond die to form the tubular rungs. Thus, the rungs of the ladder according to the method may be formed in two steps in order to obtain the tubular cross-section. ln this regard, the first die may comprise a lower die section and an upper diesection, where the lower and upper die sections may have complementary shape incross-section. ln particular, the lower die section of the second die may have a shapecorresponding to the shape of the lower die section of the first die and the upper diesection of the second die may have a shape corresponding to the lower die section of the second die but with an opposite orientation. l\/loreover, 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 longitudinally extending 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 or descending 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 equipmentsuch 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 DRAWINGS ln the following detailed description of the invention, reference will be made to the accompanying 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. s profiled side sections, and shows an end view of a manufactured ladder and the steps of forming Fig. 4method 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. 4.

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 theladder. 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 transversalareas 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 holes 24.

The 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 of sections along its length that are movable in order to support the plate section of therung 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 are positioned 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 firstsection, 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 rungs 18.

It is to be understood that the embodiment described above and shown in thedrawings is to be regarded only as a non-Iimiting example of the invention and that it may be modified in many ways within the scope of the patent claims.

Claims

1. 1. PATENT CLAIMS 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;and - forming the Iongitudinally extending sections (14) to profiled side profiles. l\/lethod according to claim 1, wherein the edges of the transversally extendingsections are brought substantially in contact with each other during forming to rungs. l\/lethod according to claim 1 or 2, wherein the formed rungs have a generally circular cross-section. l\/lethod according to any of the preceding claims, comprising the sub-steps of: - pressing the transversally extending sections in a first die (26, 28), forming agenerally U-shape in cross-section, - placing the lower part of the U-shape in a lower die section (30) of a seconddie and pressing on the upper part of the U-shape with an upper die section (32) of the second die to form the tubular rungs. l\/lethod according to claim 4, wherein the first die comprises a lower diesection (26) and an upper die section (28), where the lower and upper diesections have complementary shape in cross-section. l\/lethod according to claims 5, wherein the lower die section (30) of thesecond die has a shape corresponding to the shape of the lower die section(26) of the first die and wherein the upper die section (32) of the second diehas a shape corresponding to the lower die section (30) of the second die but with an opposite orientation. l\/lethod according to any of the preceding claims, wherein the side profiles (14) are formed to generally rectangular C-shape in cross-section. 8. Method according to any of the preceding c|aims further comprising the step ofproviding friction enhancing elements (22) in the transversally extendingsections. 9. l\/lethod according to c|aim 5, wherein the friction enhancing elementscomprise protrusions formed during the cutting step. 10. l\/lethod according to any of the preceding claims, further comprising the stepof providing a number of attachment holes (20) along the extension of thelongitudinally extending sections (14). 11.l\/lethod according to any of the preceding claims, further comprising providingattachment holes (24) in the transversally extending sections (18). 1

2. l\/lethod according to any of the preceding claims, further comprising the stepof treating surfaces of the manufactured ladder with anti-corrosion material. 1

3. Ladder manufactured according to any of the c|aims 1 to 12. 1

4. Ladder according to c|aim 13, further comprising treads (40) attachable to said rungs. 1

5. Ladder according to c|aim 13 when dependent on c|aims 10 or 11, whereinsaid treads are attached to said rungs with bolts through the attachment holes(24) of the rungs and/or the attachment holes (20) of the side profiles.