WO2014059471A1

WO2014059471A1 - Automatic descender

Info

Publication number: WO2014059471A1
Application number: PCT/AU2013/001193
Authority: WO
Inventors: Richard Hugh MILLAR
Original assignee: Capital Safety Group (Australia) Pty Limited
Priority date: 2012-10-15
Filing date: 2013-10-15
Publication date: 2014-04-24
Also published as: AU2013204011A1

Abstract

The present invention relates generally to an automatic descender (10) comprising a pulley (12) rotatably mounted to a housing (14) via a shaft (16). The housing (14) includes a primary cavity (18) enclosed by a housing cover (20). The housing cover (20) includes a pair of secondary cavities (22A and 22B) enclosed by respective of a pair of brake covers (24A and 24B). The descender (10) also comprises a primary gear (32) connected coaxially to the shaft (16) and located within the housing (14). The descender (10) further comprises a pair of secondary gears (34A and 34B) each independently meshed with the primary gear (32) to rotate in conjunction with the primary gear (32). The descender (10) additionally comprises a pair of inertia brakes (36A and 36B) coupled to respective of the pair of secondary gears (34A and 34B). The secondary gears (34A and 34B) independently drive their respective inertia brakes (36A and 36B) to retard rotation of the pulley (12) and the rate of descent of a user.

Description

AUTOMATIC DESCENDER

Technical Field

[1 ] The present invention relates broadly to an automatic descender.

Background to the Invention

[2] In a conventional descender a rescue rope line passes around a rope sheave which is able to turn in either direction depending on which side the load of the rope is applied. In use a user is suspended from the descender attached to the rescue rope line. Descent is controlled via an inertia brake system which applies pressure to a brake via weight of the user. The brake system operates via inertia pressure, the higher the load the greater the pressure placed on the braking system to control the descent speed. The descender includes a main gear attached to the rope sheave which turns in tune with the rope sheave. The main gear drives a single pinion gear which is connected to the inertia brake system.

[3] During descent the descender is subject to high load and heat in a brake chamber of the inertia brake system. The descender experiences relatively high loads interacting between the main gear and pinion gear with a typical gear ratio of 10 to 1 . The conventional descender is subject to high wear on the brake system and specifically the pinion gear which can results in failure.

Summary of Invention

[4] According to the present invention there is provided an automatic descender comprising:

a pulley rotatably mounting to a housing via a shaft;

a primary gear connected to the shaft and located within the housing;

a pair of secondary gears each independently meshed with the primary gear to rotate in conjunction with the primary gear;

a pair of inertia brakes coupled to respective of the pair of secondary gears whereby rotation of the pulley effects rotation of the primary gear together with the secondary gears which independently drive their respective inertia brakes to retard rotation of the pulley. [5] Preferably the pair of inertia brakes are configured to operate independently of one another. More preferably the automatic descender is designed failsafe wherein failure of one of the independent inertia brakes does not result in failure of the other of the inertia brakes, which continues operation on its own in retarding rotation of the pulley.

[6] Preferably the pulley is exposed and is located substantially outside the housing. More preferably the housing includes a guide arranged relative to the pulley to guide a rope about at least part of a perimeter of the pulley. Even more preferably the descender also comprises a sheave cover detachably connected to the guide to retain the rope about the pulley.

[7] Preferably the housing includes a primary cavity enclosed by a housing cover, the primary gear sealed within the primary cavity. More preferably the housing cover includes a pair of secondary cavities enclosed by respective of a pair of brake covers, the pair of inertia brakes sealed within respective of the pair of secondary cavities. Alternatively the pair of secondary cavities are enclosed by a single brake cover.

[8] Preferably the pair of inertia brakes are located opposite one another wherein a rotation axis of the shaft is aligned with respective rotation axes of the secondary gears. More preferably the housing includes an anchorage arranged in alignment with the rotation axes of the shaft and the secondary gears.

[9] Preferably the pair of secondary gears are each pinion gears and the primary gear is a spur gear. More preferably the ratio of teeth on the spur gear to each of the pinion gears is set at around 10:1 .

[10] Preferably each of the pinion gears includes a coaxial pinion gear shaft connected to one of the pair of inertia brakes. More preferably each of the pinion gear shafts is keyed at one of its ends and configured to axially fit within a

corresponding keyway of the respective inertia brake to prevent rotation

therebetween. Even more preferably the pinion gear shaft includes a shoulder arranged to abut the inertia brake on its axial fitting to said brake. [1 1 ] Preferably the pair of inertia brakes are of the same construction including a centre mount having the keyway to which the respective keyed pinion gear shaft is fitted. More preferably the inertia brake also includes a pair of brake elements pivotally connected to the centre mount and designed on rotation of the pinion gear shaft under the influence of centrifugal force to pivot outwardly to frictionally engage the housing cover to retard rotation of the pulley.

[12] Preferably the pair of brake covers, or the single brake cover, include a pinion shaft bearing within which the pinion gear shaft at its keyed end rotates. More preferably the housing cover includes another pair of pinion shaft bearings within which respective of the pinion gear shafts rotate on an opposite side of the centre mount to the keyed end of the pinion gear shaft.

Brief Description of Drawings

[13] In order to achieve a better understanding of the nature of the present invention a preferred embodiment of an automatic descender will now be described, by way of example only, with reference to the accompanying drawings in which:

Figures 1 A and 1 B are front and rear perspective views of an automatic descender according to an embodiment of the present invention;

Figure 2 is a front view of the automatic descender of figure 1 ;

Figure 3 is an exploded perspective view of the automatic descender of figures 1 and 2;

Figures 4A, 4B and 4C are front, side and rear views of the automatic descender of the preceding figures with a rope fitted.

Detailed Description

[14] As shown in figures 1 A/1 B and 2 there is an embodiment of an automatic descender designated generally as 10. The automatic descender 10 comprises a pulley 12 rotatably mounted to a housing 14 via a shaft 16. The housing 14 includes a primary cavity 18 enclosed by a housing cover 20. The housing cover 20 includes a pair of secondary cavities 22A and 22B enclosed by respective of a pair of brake covers 24A and 24B. [15] In this embodiment the pulley 12 is exposed being located substantially outside the housing 14. The housing 14 includes a guide arranged about the pulley 12 which is in the form of a sheave to guide a rope 25, see figure 4. about at least part of a perimeter of the pulley 12. The guide of this embodiment includes an upper rail member 26 formed continuous with the housing 14 and curved about a perimeter portion of the pulley 12, and guide bars 28A, 28B, and 28C also formed integral with the housing 14 and disposed about a lower perimeter portion of the pulley sheave 12. The rope 25 is designed to pass between an outer and an intermediate of the guide bars 28A and 28B, around the pulley 12 and between the intermediate guide bar 28B and the other outer guide bar 28C, as shown in Figure 4. The automatic descender 10 also comprises a pulley cover 30 detachably fastened to the guide bars 28A, 28B, and 28C. The pulley cover 30 is in profile shaped semi-circular and is designed to retain the rope 25 about the pulley 12. The pulley cover 30 is for clarity removed from the drawings of Figure 4

[16] As shown in figure 3 the automatic descender 10 of this embodiment also comprises a primary gear 32 connected coaxially to the shaft 16 and located within the housing 14. The descender 10 further comprises a pair of secondary gears 34A and 34B each designed to independently mesh with the primary gear 32 to rotate in conjunction with the primary gear 32. The descender 10 additionally comprises a pair of inertia brakes designated generally as 36A and 36B coupled to respective of the pair of secondary gears 34A and 34B.

[17] In operation, a rope 25 wrapped about the pulley 12 as shown in figure 4 will, on descent of a user attached to the descender 10 via a coupling or carabiner (not shown), provide rotation of the pulley 12. The pulley 12 effects rotation of the primary gear 32 via the shaft 16. The primary gear 32 meshes with the secondary gears 34A and 34B for their rotation in an opposite direction to that of the primary gear 32. The secondary gears 34A and 34B independently drive their respective inertia brakes 36A and 36B to retard rotation of the pulley 12 and the rate of descent of the user attached to the rope 25. The pair of inertia brakes 36A and 36B thus are configured to operate independently of one another. The automatic descender 10 is therefore designed failsafe wherein failure of one of the independent inertia brakes such as 36A does not result in failure of the other of the inertia brakes 36B, which continues operation on its own in retarding rotation of the pulley 12. It will be understood that failure of one of the independent inertia brakes such as 36A may occur due to failure of linked components, for example, the meshed primary gear 32 and the associated secondary gear 34A.

[18] In this embodiment the primary gear is a spur gear 32 housed within the primary cavity 18 of the housing 14. The housing cover 20 screw mounts to the housing 14 to contain or seal the spur gear 32 within the primary cavity 18. The pair of inertia brakes 36A and 36B are housed within respective of the pair of secondary cavities 22A and 22B of the housing cover 20. The brake covers 24A and 24B screw mount to the housing cover 20 to contain or seal the inertia brakes 36A and 36B within the respective secondary cavities 22A and 22B. Each of the pinion gears such as 34A also includes a coaxial pinion gear shaft such as 38A connected to the corresponding inertia brake 36A. The pinion gear 34A meshes with the primary spur gear 32 within the primary cavity 18 of the housing 14.

[19] The automatic descender 10 of this embodiment is substantially symmetric either side of the shaft 16. That is, the pair of inertia brakes 36A and 36B together with their associated components and the secondary cavities 22A and 22B are substantially identical to one another. Furthermore, the pair of inertia brakes 36A and 36B are located opposite one another wherein a rotation axes 40 of the shaft 16 is aligned with respective rotation axes and 42A and 42B of the secondary gears 34A and 34B. The housing 14 also includes an anchorage 44 in the form of D-shaped shackle which is secured to a stationary member such as a roof anchor (not shown) or any other suitable stationary member. The anchorage 44 is also in alignment with the rotation axes of the shaft 16 and the secondary gears 34A and 34B.

[20] The pair of inertia brakes 36A and 36B of this embodiment are of the same construction including a centre mount such as 46A and a pair of brake elements such as 48A and 50A pivotally connected to the centre mount 46A. The pair of brake elements or arms 48A and 50A are coupled together at an end opposite their pivotal connection to the centre mount such as 46A via extension spring such as 52A. The pinion gear shafts such as 34A are each keyed at one of their ends and configured to axially fit within a corresponding keyway such as 54A of the centre mount 46A. This keyed connection between the pinion gear shaft such as 34A and the centre mount 46A ensures that there is not rotation between these components. The pinion gear shaft such as 34A may also include a shoulder at its keyed end arranged to abut the centre mount 46A on its axial fitting to the inertia brake 36A.

[21 ] The shaft 16 on its pulley side rotates within a pulley bearing 56 located within the housing 14. The shaft 16 on its gear side rotates within a gear bearing 58 located within the housing cover 20. The housing cover 20 also includes another pair of pinion shaft bearings 60A and 60B within which respective of the pinion gear shafts 38A and 38B rotates. The pair of brake covers 24A and 24B of this embodiment also includes a pinion shaft bearing such as 62A within which the pinion gear shaft 38A at its keyed end rotates.

[22] In use of the automatic descender 10 of this embodiment:

1 . The descender 10 is anchored to a suitable stationary member and a rope

such as 25 is passed about the pulley 12 and connected to a user in

anticipation of their descent;

2. The user descends whereupon the pulley 12 is rotated via the rope 25;

3. The pulley 12 rotates the primary gear 32 which in turn rotates the meshed

secondary gears 34A and 34B;

4. The secondary gears 34A and 34B independently drive their respective inertia brakes 36A and 36B to retard rotation of the pulley 1 2 and control the rate of descent of the user.

[23] Each of the inertia brakes such as 36A frictionally engages the housing cover 20 to retard rotation of the pulley 12. More particularly, the arms such as 48A and 50A of the inertia brake 36A are pivoted outwardly under the influence of centrifugal force. The brake arms such as 48A include friction pads such as 64A and 66A which frictionally engage or contact the housing cover 20 within the corresponding secondary cavity such as 22A.

[24] The automatic descender 10 is geared wherein a single rotation of the pulley 12 and the associated primary gear 32 effects multiple rotations of the relatively small secondary pinion gears 34A and 34B. In this example the ratio of teeth on the primary spur gear 32 to each of the pinion gears such as 34A is set at around 10:1 . It is expected that the automatic descender 10 of this embodiment will achieve a rate of descent of between 0.8 to 1 .2 metres per second. It is understood that under normal operation, the pressure or frictional engagement of the inertia brakes 36A and 36B with the housing cover 20 will be reduced. If one of the inertia brakes such as 36A fails, the automatic descender will operate in a failsafe mode with the other of the inertia brakes such as 36B functioning on its own with increased frictional engagement or pressure but nonetheless retarding rotation of the pulley 12 for safe descent.

[25] Now that a preferred embodiment of the present invention has been described in some detail it will be apparent to those skilled in the art that the automatic descender has at least the following advantages:

1 . The descender is failsafe where failure of one of the inertia brakes or their

associated components does not result in failure of the other of the inertia brakes, which continues operation in retarding descent;

2. The descender is expected to function more effectively with reduced pressure with the pair of inertia brakes acting together in normal operation;

3. The descender is relatively compact and lightweight;

4. The descender is designed so that the pulley is exposed for easy visual

inspection of the rope about the pulley during operation.

[26] Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. For example, the pair of brake covers may be replaced with a single brake cover. The specific shape and configuration of the descender may also vary from the preferred embodiment provided a pair of inertia brakes are utilised for controlled and safe descent. All such variations and modifications are to be considered within the scope of the present invention the nature of which is to be determined from the foregoing description.

Claims

The claims defining the invention are as follows

1 . An automatic descender comprising:

a pulley rotatably mounting to a housing via a shaft;

a primary gear connected to the shaft and located within the housing; a pair of secondary gears each independently meshed with the primary gear to rotate in conjunction with the primary gear;

a pair of inertia brakes coupled to respective of the pair of secondary gears whereby rotation of the pulley effects rotation of the primary gear together with the secondary gears which independently drive their respective inertia brakes to retard rotation of the pulley.

2. An automatic descender as defined in claims 1 wherein the pair of inertia

brakes are configured to operate independently of one another.

3. An automatic descender as defined in claim 2 wherein the automatic

descender is designed failsafe wherein failure of one of the independent inertia brakes does not result in failure of the other of the inertia brakes, which continues operation on its own in retarding rotation of the pulley.

4. An automatic descender as defined in any one of the preceding claims wherein the pulley is exposed being located substantially outside the housing.

5. An automatic descender as defined in claim 4 wherein the housing includes a guide arranged relative to the pulley to guide a rope about at least part of a perimeter of the pulley.

6. An automatic descender as defined in in claim 5 wherein the descender also comprising a pulley cover detachably connected to the guide to retain the rope about the pulley.

7. An automatic descender as defined in any one of the preceding claims wherein the housing includes a primary cavity enclosed by a housing cover, the primary gear sealed within the primary cavity.

8. An automatic descender as defined in claim 7 wherein the housing cover

includes a pair of secondary cavities enclosed by respective of a pair of brake covers, the pair of inertia brakes sealed within respective of the pair of secondary cavities.

9. An automatic descender as defined in any one of the preceding claims wherein the pair of inertia brakes are located opposite one another wherein a rotation axis of the shaft is aligned with respective rotation axes of the secondary gears.

10. An automatic descender as defined in claim 9 wherein the housing includes an anchorage arranged in alignment with the rotation axes of the shaft and the secondary gears.

1 1 . An automatic descender as defined in any one of the preceding claims wherein the pair of secondary gears are each pinion gears and the primary gear is a spur gear.

12. An automatic descender as defined in claim 1 1 wherein the ratio of teeth on the spur gear to each of the pinion gears is set at around 10:1 .

13. An automatic descender as defined in either of claims 1 1 or 12 wherein each of the pinion gears includes a coaxial pinion gear shaft connected to one of the pair of inertia brakes.

14. An automatic descender as defined in in claim 13 wherein each of the pinion gear shafts is keyed at one of its ends and configured to axially fit within a corresponding keyway of the respective inertia brake to prevent rotation therebetween.

15. An automatic descender as defined in claim 14 wherein the pinion gear shaft includes a shoulder arranged to abut the inertia brake on its axial fitting to said brake.

16. An automatic descender as defined in either of claims 14 or 15 wherein the pair of inertia brakes are of the same construction including a centre mount having the keyway to which the respective keyed pinion gear shaft is fitted.

17. An automatic descender as defined in claim 16 wherein the inertia brake also includes a pair of brake elements pivotally connected to the centre mount and designed on rotation of the pinion gear shaft under the influence of centrifugal force to pivot outwardly to frictionally engage the housing cover to retard rotation of the pulley.

18. An automatic descender as defined in any one of claims 14 to 17 including a pinion shaft bearing within which the pinion gear shaft at its keyed end rotates.

19. An automatic descender as defined in claim 18 wherein the housing cover includes another pair of pinion shaft bearings within which respective of the pinion gear shafts rotate.