WO2016147109A1

WO2016147109A1 - Damper for the stiles of a telescopic ladder

Info

Publication number: WO2016147109A1
Application number: PCT/IB2016/051445
Authority: WO
Inventors: Richard Weston
Original assignee: Teletower.Com Limited
Priority date: 2015-03-13
Filing date: 2016-03-14
Publication date: 2016-09-22
Also published as: GB2536347A; GB2536297A; GB201601494D0; GB2536347B; GB2536297B; GB201504331D0

Abstract

A damper is disclosed for a ladder having telescopically collapsible stile sections. The damper operated pneumatically and comprises a plug 14 for closing off the lower end of an upper stile section 10 in each pair of adjacent stile sections, and a seal 22 projecting radially from the plug 14 so as to contact the inner wall of the lower stile section of the pair. During collapse of the stile sections of the pair, the upper style section acts as a piston to compress air present within the lower section.

Description

DAMPER FOR THE STILES OF A TELESCOPIC LADDER

Field of the invention The present invention relates to a damper for the stiles of a telescopic ladder.

damper for the stiles of a telescopic ladder.

Background of the invention

Telescopic ladders, i.e. ladders with telescopically collapsible stiles, are well known and commercially

available. Such ladders have a plurality of sections each formed of a pair of hollow tubular stile sections and a rung connected to upper ends of the two stile sections. The lower ends of the stile sections of each ladder section are slidably received within the stile sections of the next lower ladder section such that the ladder sections may slide relative to one another between an extended state in which the rungs of the ladder are spaced apart and a collapsed state in which the rungs lie adjacent one another. Suitable latches are provided within the ends of the rungs for locking the stile sections of the ladder in its extended state .

Such ladders are usually designed to collapse from the bottom up. After latches on the lowermost rung are retracted manually, the next to lowermost ladder section is freed and moves to its collapsed position. The latches of the next rung can now be released manually and the ladder collapsed one section at a time.

US 5,495,915, which is imported herein by reference, describes a telescopic ladder in greater detail and also describes how latch release mechanisms mounted on the underside of the rungs may be designed to allow the ladder to be collapsed rapidly. Once again the latches on the lowermost rung need to be retracted manually, to free the next to lowermost ladder section and allow it to move to the collapsed position. However, in this case, as the rung of the next to lowermost section comes into contact with the one beneath it, its latches are released automatically to free the next higher section and this is repeated until the entire ladder is collapsed.

The latches on the rung of the lowermost ladder section support the entire weight of the ladder and once they are released the next to lowermost rung can descend very rapidly and with considerable force. Operators are therefore warned to keep their fingers out of the way of the descending sections of the ladder for fear of their fingers becoming trapped between the runs when the ladder is collapsed.

For safety, the stiles of ladders in the past have been damped in order to reduce the speed at which they collapse when the lowermost latches are released. Typically, known collapsible ladders have relied on friction damping. Fingers mounted to the lower end of each upper stile section

frictionally engage the inner wall of the next lower stile section . Frictional damping, however suffers from certain disadvantages. In particular, the friction fingers can wear out with time reducing their effectiveness. Furthermore, if oil is applied to the stiles the damping will be impaired. Manufacturing tolerance also renders the degree of damping unpredictable.

Object of the invention

The present invention seeks therefore to provide an alternative and more consistent way of damping the stiles a telescopic ladder to avoid accidental trapping of an operator's fingers between the rungs of the ladder as it is being collapsed.

Summary of the invention

In accordance with a first aspect of the present invention, there is provided a pneumatic damper for a telescopic ladder of the type having a plurality of ladder sections each formed of a pair of hollow tubular stile sections and a rung connected to upper ends of the two stile sections, lower ends of the stile sections of each ladder section being slidably received within the stile sections of the next lower ladder section such that the ladder sections may slide relative to one another between an extended state in which the rungs of the ladder are spaced apart and a collapsed state in which the rungs lie adjacent one another, the damper comprising a plug for closing off the lower end of an upper stile section in each pair of adjacent stile sections, and a seal projecting radially from the plug so as to contact the inner wall of the lower stile section of the pair, whereby during collapse of the stile sections of the pair, the upper stile section acts as a piston to compress air present within the lower stile section; characterised in that the seal is defined by an annular strip formed

separately from the plug and mounted for axial movement with the plug, the plug is formed with a circumferential groove and the strip is formed with a radially inwardly extending flange received in the groove. In such a construction, the plug acts in a manner analogous to a piston in any internal combustion engine and the strip acts as a piston ring.

The strip may advantageously be made of a resilient material and it may be circumferentially discontinuous in order to allow some air to pass between the strip and the inner wall of the lower stile section. In this case, the skirt be made as a continuous extrusion which is cut to a desired length. In some embodiments, the seal is formed by a skirt or lip that extends axially downwards beyond the lower end of the stile section closed off by the plug, whereby air pressure in the lower section of the pair serves to press the skirt into sealing contact with the inner wall of the lower stile section.

The skirt in this case will also separate from the inner wall of the lower stile section when acted on my negative pressure as the ladder it being extended.

Consequently, the degree of damping will be reduced as the ladder is being extended compared with the damping while the ladder is being collapsed.

The gas pressures within the stile section will act to separate the plug from its stile section. To resist such forces, the plug in some embodiments is designed to fit within the lower end of the stile section and may be

retained either by use of an adhesive or by interlocking engagement, for example of an annular projecting ridge of the plug in a groove machined into the inner surface of the stile section.

In accordance with a second aspect, the invention provides a method of constructing a damper for a ladder of the type having telescopically collapsible stiles comprised of tubular stile sections of successively smaller diameter; the method comprising the steps of; securing a plug having a circumferential groove into an open end of a stile section to cap the open end and restrict air flow therethrough, cutting a strip of a linear extrusion, the strip having a length dependent upon the perimeter of the circumferential groove; inserting the strip into the circumferential groove of the plug to a form a seal; and inserting the capped stile section supporting the seal into the next larger section, the inner surface of the next larger stile section serving to retain the seal within the groove.

In accordance with a third aspect of the invention, there is provided a pneumatic damper for a telescopic ladder of the type having a plurality of ladder sections each formed of a pair of hollow tubular stile sections and a rung connected to upper ends of the two stile sections, lower ends of the stile sections of each ladder section being slidably received within the stile sections of the next lower ladder section such that the ladder sections may slide relative to one another between an extended state in which the rungs of the ladder are spaced apart and a collapsed state in which the rungs lie adjacent one another, the damper comprising a plug for closing off the lower end of an upper stile section in each pair of adjacent stile sections, and a seal projecting radially from the plug so as to contact the inner wall of the lower stile section of the pair, whereby during collapse of the stile sections of the pair, the upper stile section acts as a piston to compress air present within the lower stile section; characterised in that the seal is defined by an annular strip formed

separately from the plug and mounted for axial movement with the plug, and is a discontinuous ring formed from a linear extrusion .

Brief description of the drawings

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which :

Figure 1 shows three stiles sections of a ladder in its collapsed state,

Figure 2 is a perspective view of a damper that

comprises a plug and a separate skirt, Figure 3 is a section showing a stage during assembly of a damper after the plug has been inserted into a ladder section but before the skirt is fitted to the plug, and

Figure 4 is a view similar to Figure 3 showing the damper in its assembled state, this being the detail designated A in Figure 1, drawn to an enlarged scale.

Detailed description of the drawings. Figure 1 shows only three tubular stile sections 10a,

10b and 10c of a telescopic ladder, which typically has many more sections. As the invention is concerned only with the damping of the stile sections, the entire ladder is not shown in the drawings and will not be described herein in detail. Reference may be made to US Patent No. 5,495,915 for further details of the remaining components of the ladder, such as the rungs and the latch mechanisms for locking the ladder in its extended state. The holes designated 11 are for mounting rungs of the ladder to the stile sections and holes 13 receive latch pins to retain the stile sections in their extended position.

The lower end of each of the stile sections 10a to 10c is fitted with a respective damper 12a, 12b, 12c , which will be described in more detail below by reference to

Figures 2 to 4. Each damper 12 closes off the lower of the stile section on which it is mounted to air flow, so that the stile section then acts as a piston. Each pair of adjacent stile sections therefore act as a bicycle pump compressing air in the working chamber defined between them as the ladder is collapsed and sucking air into the working chamber as the ladder is extended.

As will be explained, each damper 12 is designed to allow air to escape at a small controlled rate as the pressure in the working chamber is increased and this is what provides the desired pneumatic damping. Air can also enter the working chamber by flowing past the damper as the ladder is being extended.

Each damper 12 is formed of a plug 14 that fits into the lower end of the tube section 10 and a strip 16 having a skirt 22 that seals against the inner wall of the next lower stile section 10.

The plug 14 is solid and dimensioned to fit into the stile section 10 so as to seal it permanently. The plug may be a tight fit in the stile section, or held in place by an adhesive. In the case of the illustrated damper, the plug 14 is formed with a tapered ridge 26 that is received within a groove 28 machined into the inner surface of the stile section 10.

The plug has a radially projecting flange 30 to limit its insertion into the stile section 10. Beneath the flange 30, the plug 14 has an annular land 18 separated from the flange 30 by a groove 20.

The groove 20 is provided for the purpose of securing to the plug 14 the strip 16, which is made of a polymeric or preferably elastomeric material. The skirt in section is L- shaped having a horizontal limb or flange 24 that is

received within the groove 20 of the plug 14 and a generally vertical limb 22 forming a generally cylindrical skirt that engages the inner surface of the next lower stile section. The strip acts in a manner analogous to a piston ring of a combustion engine with the plug 14 acting as the piston.

The strip 16 is cut to the desired length from a continuous linear extrusion and wrapped around the plug 14. It is desirable to leave a small gap between the ends of the strip, as shown in the drawings, to allow some air to pass by the damper. By varying the size of the gap, the degree of damping can be altered. This may be for reasons of preference or to account for varying levels of friction due to manufacturing tolerances of the assembled ladder.

The illustrated damper in figures 2, 3 and 4 is assembled by first pushing the plug 14 into the end of the stile section 10b until the flange 30 engages the axial end of the stile section. At this point, the shoulder of the ridge 26 engages in the groove 28 to resist the plug coming away from the stile section 10. Alternatively or

additionally, adhesive may be used to secure the plug 14.

The strip 16 is next wrapped around the projecting end of the plug 14, feeding its horizontal limb or flange 24 into the groove 20 between the land 18 and the flange 30. The next lower stile section (10c), which is of larger diameter, is then slipped over the damper to compress the skirt 22 radially inward.

As the ladder sections ( 10a, 10b, 10c) collapse, the pressure in the next lower stile section forces the skirt 22 to seal against the inner wall of the next lower stile section and allows air to escape only through the gap between the ends of the strip 16. This provides the damping needed to prevent rapid collapse of the ladder when its latches are released. Conversely, during extension of the ladder, the skirt is forced radially inwardly away from the inner wall of the next lower stile section by the reduced pressure in the expanding chamber below damper and this allows air to enter more freely into the lower stile section

Claims

1. A pneumatic damper (12) for a telescopic ladder of the type having a plurality of ladder sections each formed of a pair of hollow tubular stile sections and a rung (not shown) connected to upper ends of the two stile sections, lower ends of the stile sections of each ladder section being slidably received within the stile sections of the next lower ladder section such that the ladder sections may slide relative to one another between an extended state in which the rungs of the ladder are spaced apart and a

collapsed state in which the rungs lie adjacent one another, the damper comprising a plug (14) for closing off the lower end of an upper stile section (10b) in each pair of adjacent stile sections (10b, 10c), and a seal projecting radially from the plug (14) so as to contact the inner wall of the lower stile section (10c) of the pair, whereby during collapse of the stile sections (10b, 10c) of the pair, the upper stile section (10b) acts as a piston to compress air present within the lower stile section (10c);

characterised in that the seal is defined by an annular strip (16) formed separately from the plug (14) and mounted for axial movement with the plug,

the plug is formed with a circumferential groove (20), and

the strip is formed with a radially inwardly extending flange (24) received in the groove.

2. A pneumatic damper as claimed in claim 1, wherein the strip (16) is made of a resilient material.

3. A pneumatic damper as claimed in claim 1 or 2, wherein the strip (16) is circumferentially discontinuous in order to allow some air to pass between the strip and the inner wall of the lower stile section (10c) .

4. A pneumatic damper as claimed in any preceding claim, wherein the seal is formed by a lip that extends axially downwards beyond the lower end of the upper stile section closed off by the plug, whereby air pressure in the lower section of the pair serves to press the lip into sealing contact with the inner wall of the lower stile section .

5. A pneumatic damper as claimed in any preceding claim, wherein the plug (14) is designed to fit within the lower end of the stile section (10b) .

6. A pneumatic damper as claimed in claim 5, wherein the plug (14) is retained in the stile section (10b) by means of an adhesive.

7. A pneumatic damper as claimed in claim 5, wherein the plug (14) is retained in the stile section (10b) by means of an interlocking engagement between the plug and the stile section.

8. A pneumatic damper as claimed in claim 7, wherein the interlocking engagement is in the form of an annular ridge (26), projecting from the plug (14) and received, when in use, in a groove (28) machined into the inner surface of the stile section (10b) .

9. A method of constructing a damper (12) for a ladder of the type having telescopically collapsible stiles comprised of tubular stile sections of successively smaller diameter; the method comprising the steps of;

securing a plug (14) having a circumferential groove (20) into an open end of a stile section (10) to cap the open end and restrict air flow therethrough,

cutting a strip (16) of a linear extrusion, the strip having a length dependent upon the perimeter of the

circumferential groove (20); inserting the strip into the circumferential groove (20) of the plug (14) to a form a seal; and

inserting the capped stile section (10b) supporting the seal into the next larger section (10c), the inner surface of the next larger stile section serving to retain the seal (16) within the groove (20) .

10. A method as claimed in claim 9, wherein cutting the strip (16) includes selecting a length which is less than the perimeter of the groove (20) so as to create a gap to allow for the passage of air.

11. A method as claimed in claim 10, wherein the length of the gap is chosen in dependence upon the desired degree of damping provided by the damper ( 12a, 12b, 12c) .

12. A method as claimed in claims 9 to 11, wherein the strip (16) is dimensioned to form an interference fit with the inner surface of the next larger stile section (10c), such that the plug (14) and strip (16) are forced into the next larger stile section.

13. A method as claimed in claims 9 to 12, wherein the strip (16) is made of a resilient material and is compressed as a result of insertion into the next larger stile section.

14. A method as claimed in claims 9 to 13, wherein securing the plug (14) within the open end of a stile section (10) involves pressing the plug into the stile section (10b) until a ridge (26) engages within a groove (28) .

15. A pneumatic damper ( 12a, 12b, 12c) ) for a telescopic ladder of the type having a plurality of ladder sections each formed of a pair of hollow tubular stile sections and a rung connected to upper ends of the two stile sections, lower ends of the stile sections of each ladder section being slidably received within the stile sections of the next lower ladder section such that the ladder sections may slide relative to one another between an extended state in which the rungs of the ladder are spaced apart and a

collapsed state in which the rungs lie adjacent one another, the damper comprising a plug (14) for closing off the lower end of an upper stile (10b) section in each pair of adjacent stile sections, and a seal (16) projecting radially from the plug (14) so as to contact the inner wall of the lower stile section (10c) of the pair, whereby during collapse of the stile sections of the pair, the upper stile section (10b) acts as a piston to compress air present within the lower stile section (10c);

characterised in that the seal is defined by an annular strip (16) formed separately from the plug (14) and mounted for axial movement with the plug, and is a discontinuous ring formed from a linear extrusion.

16. A damper as claimed in claims 15, wherein the perimeter of the strip (16) is less than the perimeter of the groove (20) in order to allow air to pass between the ends of the strip (16) and the inner wall of the lower stile section (10c) .

17. A telescopic ladder of the type having a plurality of ladder sections each formed of a pair of hollow tubular stile sections and a rung connected to upper ends of the two stile sections, lower ends of the stile sections of each ladder section being slidably received within the stile sections of the next lower ladder section such that the ladder sections may slide relative to one another between a deployed state in which the rungs of the ladder are spaced apart and a collapsed state in which the rungs lie adjacent one another, wherein a damper (12) as claimed in claims 1 to 8 and 15 to 16 is provided to close off the lower end of an upper stile section (10b) in each pair of adjacent stile sections of the ladder.