GB2611351A

GB2611351A - Pulley blocks

Info

Publication number: GB2611351A
Application number: GB2114147.8A
Authority: GB
Inventors: Brown Kevin
Original assignee: International Safety Components Ltd
Current assignee: International Safety Components Ltd
Priority date: 2021-10-03
Filing date: 2021-10-03
Publication date: 2023-04-05
Also published as: GB202114147D0

Abstract

A snatch pulley block with a rotatable sheave mounted between relatively rotatable first 26 and second 27 side plates with a spring loaded anchor axle 21 which can extend between them to lock them in place. The anchor axle 21 has a radially extending locking pin 29 which engages an entry slot 31 in the second side plate with a closed end to limit longitudinal movement and cam rotate in an arcuate slot 34 to lock the side plates. The spring 33 may sit in grooves 35 & 36 in the first plate and on a flange 22 on the anchor axle when compressed and may be a helical spring. A spring loaded détente ball 37 may extend into a socket 39 on the anchor axle to releasably hold it in a position to allow rotation of the side plates. A secondary locking means with a button 24 which engages a notch on the flange may be used. The device can used by arborists or rock climbers.

Description

Pulley Blocks This invention relates to pulley blocks or rigging pulleys of the type used by arborists during tree pruning work or by rock-climbers when ascending or descending from a height or when hauling or lowering loads.

A known type of pulley block is sold by Intemational Safety Components Ltd ( IS CJ under the trade reference R P054 and is generally used as a rigging pulley for a rborists when working at height https://Www, is c. I e. s o rn/N1 e +Ns /B log/IS C: o rge d P ull ey/ The pulley block comprises a main pulley sheave rotatably mounted on a main pulley axle between a pair of pulley block side plates defining in combination a pulley frame comprising a fixed side plate from which extends the main pulley axle and sheave and a side plate radially movable about the axis of the main axle, the side plates being releasably connectable at a position remote from the pulley sheave by a lockable anchor axle received within co-axial bores in the side plates for collectively allowing the pulley block to be anchored when climbing or hauling with rope, the anchor axle itself being secured, in use, to its own anchor point, which may be a fixed point such as a rigid structure in the form of an overhanging tripod system installed at the top of a cliff or an anchor point in the form of a strong tree branch.. This ISC prior art device is noted for its ruggedness, ease of manufacture and ease of use, with one end of the anchor axle being in the form of a flanged and knurled knob of length and size sufficient for it to be turned by hand, thereby allowing it to be axially rotated, the flanged knob also acting as a reaction member for a helically-wound spring extending from the outside of the fixed pulley side plate to the underside of the flange, with the forward end of the anchor axle having a small locking pin extending radially therefrom with respect to the major axis of the axle and being receivable in a correspondingly sized slot in a bore in the movable side plate whereby to permit the locking pin to slide there along and out of the bore on the far side of the movable side plate, the arrangement being such that when the flanged knob at the rearward end of the anchor axle is pushed towards the fixed side plate against the bias of the spring the forward end of the anchor axle and its locking pin are able to emerge from the co-axial bore within the movable side plate, whereafter the axle can then be rotated by hand about its major axis through 1806 to a position aligned with a groove in the outer face of the movable side plate extending radially from the coaxial bore, and when hand pressure on the flanged knob is released the bias of the spring against the flange, allowing the locking pin to occupy the groove to temporarily lock the side plates together. To unlock and thus open the pulley frame the flanged knob is again pushed against the bias of the spring and rotated through 180 degrees to align the locking pin with the slot in the movable side plate, thereby allowing the axle to be returned to a position permitting the movable side plate to be rotated about the axis of the main axle relative to the first side plate for opening the pulley block frame, with the locking pin being stored within a cylindrical recess in the bollard, the recess thereby allowing the locking pin and hence the anchor axle to be freely rotatable relative to the bollard. This arrangement is generally satisfactory in that it is rugged and simple to use, although it has the disadvantage in that both the forward end of the anchor axle and the locking pin and the rearward flanged knob and spring are exposed to potential physical damage from snagging parts of a tree or rock face or contamination from dirt or grit, either of which may then be drawn into the bearing surfaces of the side plates. In addition to this potential problem, it will be appreciated that the overall length of the anchor axle must be sufficient so as to accommodate the axial length of the flanged knob and the full length of the helical spring in its uncompressed condition as well as the ability for the forward end of the axle together with the locking pin to be pushed clear of the outer surface of the movable side plate around the co-axial bore for the purpose of then allowing the axle to be rotated about its axis to a position in which the locking pin is aligned with the groove for temporarily receiving it. Accordingly, when the helical spring is in its partially compressed condition and the pulley block frame is therefore temporarily locked, the flanged knob at the rearward end of the anchor axle projects significantly beyond the co-axial bore in the first side plate along with the helically wound spring, collectively presenting an entanglement hazard for the climber and also exposing itself to physical damage and environmental contamination. In addition to the foregoing, the presence of the cylindrical recess in the bollard for receiving the locking pin necessarily represents a mechanical weakness in the overall arrangement as a result of the absence of material making up the bollard and also as a result of its necessarily smaller bearing surface area against the anchor axle, which bearing surface is also offset from the centreline of the bollard relative to its axis of rotation, leading to possible tensile forces between the two when under load being distributed unevenly along the anchor axle.

The present invention is derived from the realisation that there is a need for a more compact and unobtrusive approach to the design of this type of pulley block in which the foregoing disadvantages are obviated.

According to a first aspect of the invention there is provided a pulley block (20) for receiving climbing or hauling rope, the pulley block comprising or including at least one pulley sheave (5a) mounted for rotation on or forming part of a main pulley axle (4a) extending between first and second pulley block side plates (26, 27), the side plates collectively defining a pulley block frame when operationally aligned side-by-side, each side plate also being connected or connectable at a position remote from the main pulley axle to a common anchor axle (21) extending, in use, through co-axial anchor axle-receiving bores (28,32) in the pulley side plates, the side plates being rotatably movable with respect to each other about the major axis of the main pulley axle when the anchor axle has been removed from at least one of the co-axial bores in the side plates, whereby to permit insertion or removal of the rope into or from the pulley block frame, the anchor axle being adapted to prevent accidental opening of the pulley block frame and having a spring-loaded locking mechanism, C HARACTE RIS ED IN THAT the anchor axle locking mechanism collectively comprises a locking pin (29) extending radially outwardly from a forward part of the anchor axle (22) and a locking-pin receiving entry slot (31) extending into the co-axial bore (32) of the second side plate (27), the entry slot having a closed end whereby to limit longitudinal travel of the locking pin, the closed end of the entry slot (31) being coincident with an arcuate slot (34) within the axle-receiving bore (32) of the second side plate extending transversely to the entry slot at least partially around the co-axial bore, the arcuate slot being adapted to permit the locking pin to slide therealong and therewithin when the anchor axle is rotated about its major axis whereby to thereafter prevent removal of the anchor axle along its major axis, the rearward end of the anchor axle having a flanged knob (22) adapted to receive one end of spring means (33), the other end of the spring means being received on or in the outer surface of the first side plate around the anchor-axle receiving bore, the arrangement being such that when the forward end of the anchor axle and its locking pin are removed from the entry slot the second side plate is free to rotate about the major axis of the main axle to thereby open the pulley frame for loading or unloading rope, and when the rope is loaded into the pulley frame and the anchor axle returned to a position in which the locking pin is captured by the arcuate slot in the co-axial bore of the second side plate the forward end of the anchor axle lies within or no more than generally flush with the outer surface of the second side plate, with the spring means being compressed between the first side plate and the flanged knob.

In this patent specification the terms 'flange_ or 'flanged_ is intended to mean arrangements in which a lip or other formation capable of acting in an equivalent manner for allowing the compression of a spring and retaining it in a compressed or uncompressed condition, the flange itself being either integral with or separately connectable to the rearward end of the anchor axle. The term forward_ when used with regard to the anchor axle means that part of the axle that is inserted into the axle-receiving co-axial bore of the second side plate in order to connect both side plates together the extreme forward end of the axle means the actual end of the axle, and in connection with the term generally flush with respect to the extreme end of the axle lying generally flush with outside of the second side plate includes position not strictly flush but beyond or before the outer face of the second side plate but making no operational difference. The term rearward_ means the longitudinally opposite part of the axle to the forward part and includes the actual rearward end where the context permits. The term 'rope_ is intended to include any flexible means for hauling and lowering loads with the aid of a pulley block including, without limitation, climbing ropes, steel cables, metal chains and woven fabric slings. In addition, the term 'anchor axle_ is not intended to be limited to an axle having one or more rotatable sheaves and includes an arrangement in which the axle itself receives the rope directly if rope is used as part of the rigging in this region. The one or more sheaves on the main axle may include an arrangement in which the main axle itself also acts as a sheave or sheaves for receiving rope, thereby obviating the need for one or more separate sheaves.

With the arrangement according to this first aspect of the invention, the anchor axle and attendant spring is substantially protected from external physical damage or contamination from tree debris etc. when in its locked position because once the spring is compressed at the rearward end of the axle it is covered by the presence of the flanged knob at the rearward end of the anchor axle. This level of protection for the spring can conveniently be improved in the event that the spring is a helically wound spring by providing a circular groove of corresponding diameter to the spring in the outer surface of the first side plate around the co-axial bore and/or providing a circular groove of corresponding diameter in the flanged knob so that when the flanged knob is pushed against the outer surface of the first side plate the compressed spring is substantially enclosed. This can be contrasted with the prior art IS C device in which the locking pin and spring are always exposed to potential damage or contamination from debris because of their respective positions effectively always outside the pulley frame. Similarly, at the forward end of the anchor axle the locking pin is always protected by its position within the axle receiving bore and arcuate slot in the second side plate. When the spring is not compressed the locking pin can conveniently be received within a recess, such as a slotted recess, in the axle-receiving bore of the first side plate such that it is, again, substantially protected even when the axle is not connected to the second side plate and the pulley block is fully open.

In addition to the foregoing, because the length of the anchor axle of the invention is correspondingly shorter than that of the prior art IS C device, manufacturing cost and weight-saving advantages arise. Also, with the prior art IS C device, whether or not the anchor axle is in its locked or unlocked position, it is at greater risk of entanglement with e.g. branches of trees or with other ropes being used in the vicinity, whereas with the shorter anchor axle and internal arrangements for protecting the locking pin in the pulley design of the invention these disadvantages are largely obviated. Furthermore, because the locking pin is received directly within the arcuate slot in the axle-receiving bore of the second side plate there is no need to provide any additional axle length as in the case of the IS C prior art device in which the axle has to be sufficiently long so as to allow the locking pin to fully exit the co-axial bore on the outer face of the second side plate before being rotated and then retracted into the groove in the outer surface of the second side plate for receiving the locking pin.

Thus, in accordance with a second aspect of the invention there is provided a pulley block (20) for receiving climbing or hauling rope, the pulley block comprising at least one pulley sheave (5a) mounted for rotation on a main pulley axle (4a) extending between first (26) and second (27) pulley block side plates, the side plates being adapted to collectively define, in use, a pulley block frame, each side plate also being connected or connectable at a position remote from the main pulley axle to a common anchor axle (21) extending, in use, through coaxial anchor axle-receiving bores (28, 32) in the pulley side plates, the side plates being rotatably movable with respect to each other about the major axis of the main pulley axle when the anchor axle has been removed from at least one of the anchor-axle receiving bores in the side plates whereby to permit insertion or removal of the rope into or from the pulley block frame, the pulley block having a primary locking mechanism (29,31,34) adapted to prevent accidental rotation and removal of the anchor axle from at least one of the bores of the pulley block side plates CHARACTERISED IN THAT the pulley block (20) includes a secondary locking mechanism comprising in combination a flanged knob (22) at the rearward end of the anchor axle (21) relative to the forward end receivable in the anchor-axle receiving bore (32) in the second side plate (27) adjacent the first side plate (26)26, the flanged knob (22) including a notch (23) in the outer periphery thereof, the notch being co-operable with a spring-loaded detente button (24) extending from the outer sidewall of the first side plate whereby to prevent rotation of the anchor axle about its major axis when the button is engaged with the notch and whereby to permit rotation of the anchor axle and thus release of the primary locking mechanism when the button is depressed against the bias of the detente spring, the arrangement being such that when the side plates of the frame are aligned and the anchor axle is received within the bore of the second side plate, with the primary locking mechanism fully engaged to prevent accidental rotation and removal of the anchor axle from the second side plate, the axle can be constrained to remain in that position until the dlltente button is depressed to thereafter permit rotation of the axle from a locked to an unlocked position.

With this arrangement by preventing the anchor axle from rotating when in its primarily locked position the notch in the flange and springy-loaded detente button collectively provide a convenient and easy-to-access additional safety feature that can be operated by one hand, and if the d end of the detente button is visible it shows to the user of the pulley and others in the vicinity that the rigging pulley is safely locked. As an additional safety feature the forward end of the button is coloured, such as gree, thereby providing a simple cross-check for persons in the vicinity.

The invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a perspective view from the front and one side of a prior art device in its fully assembled and locked condition, Figure 2 is a perspective view of the prior art device of Figure 1 from the

rear and other side of the prior art device,

Figure 3 is a perspective view from the front and one side of a pulley block according to the invention, Figure 4 is a perspective view of the rear and other side of the pulley block device of Figure 3, Figure 5 is a sectional view of the upper part of the prior art device of Figures 1 & 2 in its unlocked position, Figure 6 is a sectional view of the upper part of the prior art device of Figures 1 & 2 in its locked position, Figure 7 is a sectional view of the upper part of the pulley block device of the invention in its unlocked position, and Figure 8. Is a sectional view of the upper part of the pulley block device of the invention in its locked position.

Referring firstly to Figures 1 & 2, there is shown the prior art IS C pulley block 1 discussed in the preamble hereto, comprising first and second pulley block side plates 2, 3 collectively defining a pulley block frame, a main pulley axle 4 mounted between the side plates 2, 3 and having rotatable thereon or therewith a pulley sheave 5 for receiving climbing or hauling rope (not shown). Between the side plates 2, 3 at a position remote from the main pulley axle 4 is an anchor bollard 6 mounted on an anchor axle 7, the bollard 6 allowing the pulley block 1 to be secured, in use, to an anchor point (such as a tripod frame secured at the top of a cliff or a strong upper branch of a tree), either directly or via a rope or sling such that the pulley block 1 can be used for hauling or lowering loads as required. The bollard axle 7 is slidably received within co-axial bores 8, 9 (shown more clearly in Figure 5) in the first and second side plates 2, 3 and has a flanged rearward end or knob 10 which captures in conjunction with the outer face of the first side plate 2 a helically wound spring 11, the spring 11 biasing the flanged knob 10 to the outward position shown in Figure 1 while allowing itto be selectively pushed towards the first side plate 2 against the bias of the spring 11 when locking and unlocking the side plates 2, 3 together in a manner to be described later..

As shown in Figure 2 the forward end of the anchor axle 7 has a locking pin 12 extending radially therefrom, which rests in a groove 13 in the outer surface of the second side plate 3, the locking pin 12 having originally emerged from the bore 9 in the second side plate 3 via an open-ended slot 14 extending through the entire thickness of the second side plate 3, before being rotated by hand via the flanged knob 10 through 1806 to the position shown, thereby releasably locking the bollard axle 7 to the second side plate 3. As will be appreciated, even in this locked position shown with the spring 11 only partially compressed, the rearward end of the anchor axle 7 still noticeably protrudes from the first side plate 2 and the forward end of the anchor axle 7 including its flanged end 10 protrudes significantly from the first plate 2, therefore representing a potential snag hazard or obstacle when the pulley block 1 is being used, such as during pruning of trees.

This is because the anchor axle 7 has to be of sufficient length for its forward end to be pushed through the bore 9 in the second side plate 3 before being rotated through 1806 and then released in order to allow the locking pin 12 at the forward end to engage with the groove 13 in the outer surface of the second side plate 3 and for the rearward end of the bollard axle 7 to accommodate the helically wound spring 11 in its uncompressed condition, Accordingly, not only does this arrangement present a snag hazard but it also leaves the exposed length of the rearward end of the axle bollard axle 7 and the spring 11 open to ambient conditions which may include dirt, dust leaves and other kinds of debris which may then affect the otherwise smooth operation of the pulley block..

Figures 3 & 4 show corresponding views of a pulley block 20 according to the invention having a main bollard axle 4a and main bollard 5a, the axle and bollard corresponding to the axle 4 and bollard 5 of the prior art ISC device. However, in this instance itwill be seen thatthe pulley block 20 has a much shorter anchor axle 21 (shown more clearly in Figure 7) as compared with the prior art anchor axle 7 shown in Figures 1 &2. The shorter anchor axle therefore uses less material in its manufacture, leading to cost savings, as well as having the advantage of being less obtrusive and therefore less likely to become snagged on branches of trees or with any other climbing rope in the vicinity. As with the prior art arrangement shown with reference to Figures 1 & 2, the rearward part of the anchor axle 21 is in the form of a flanged knob 22, the flange including a part-circular notch 23, co-operable with a spring-loaded detente button 24 to prevent axial rotation of the anchor axle 21 within an anchor axle bollard 25 which itself is fixed to the inside of a first side plate 26 opposite a second side plate 27, depression by hand of the dilltente button 24 therefore disengaging it from the notch 23 to allow the anchor axle 21 to be rotated about its longitudinal axis in a manner to be described. On the reverse side of the pulley block 20 as shown in Figure 4 it will be seen that the opposite, forward, end of the anchor axle 21 is generally flush with the major plane of the outer face of the second side plate 27, thereby presenting no obstuction to branches of trees or other ropes in the vicinity. Similarly, it will be seen from Figure 3 that the flanged rearward end 22 of the anchor axle 21 lies generally flush with the major plane of the outer face of the first side plate 26 other than by the presence of the knob 22 as it protrudes from the outer face such that collectively, both sides of the pulley block 20 are generally contiguous and less wider when viewed from the side orthogonal to the major axis of the axle 21 than the prior art device, thereby being less obtrusive and less likely to become snagged or to rub against unwanted surfaces that could damage or contaminate the pulley block when in its locked and operational condition.

Figure 5 shows a sectional view of the upper part of the prior art device 1 shown in Figures 1 & 2 in its unlocked condition where the locking pin 12 is initially received within a cylindrical recess 15 in the anchor bollard 6 and the bias of the spring 11 has pushed anchor axle 7 via its flanged end 10 to the fully extended position shown, thereby allowing the second side plate 3 to freely rotate about the major axis of the main axle 4 shown in Figures 1 & 2. Due to the presence of the cylindrical recess 15 in the anchor axle bollard 6 the anchor axle 7 is able to rotate the locking pin 12 through 360é. As will be explained later, the removal of material from the bollard 6 for forming the cylindrical recess 15 necessarily affects the ultimate strength of the bollard 6 and the anchor axle 7 when under tensile load.

Figure 6 shows the closed and locked position of the prior art IS C device in which the locking pin 12 has been slid along the full length of the slot 14 within the bore 9 against the bias of the spring 11 to a position beyond the bore 9 in the second side plate 3, before being rotated through 1806 and then allowed to be retracted under the bias of the spring 11 into the groove 13, leaving the extreme forward end of the axle 7 and part of the locking pin 12 slightly proud of the major plane of the outer face of the second side plate 3. In this locked position the rearward end of the axle 7 therefore still projects significantly beyond the major plane of the outside of the first side plate 2 and therefore presents a significant snag hazard as well as permitting debris to enter the spring 11 to contaminate the anchor axle 7 in this region. Even the presence of the locking pin12 in the groove 13 on the opposite side of the pulley still provides an opportunity for it to become contaminated by debris, as also the presence ofthe open end of the slot 14, which provides a channel into which unwanted dust and dirt can enter the bore 9.

Figures 7 & 8 respectively show the upper part of the pulley block 20 in its unlocked and locked positions. In the unlocked position shown in Figure 8, the flanged rearward end 22 of the anchor axle 21 is shown protruding from a bore 28 in the first side plate 26 by an amount only marginally greater than the rearward end of the anchor axle 7 of the IS C prior art device when in its fully locked position. This important difference is made possible by changing the position of the primary locking elements of the invention to those shown in the prior art ISC device, thereby leading to a much more compact and streamlined arrangement These primary locking elements include the exposed end of a locking pin 29 which extends transversely from the anchor axle 21 near to but not at its forward end, initially being received when the pulley block is open in the manner as shown in Figure 7, in a short keeper slot 30 within the bollard 25, the provision of which is the only material removed from the bollard in this region. This can be compared to the prior art bollard as shown in Figure 6 in which a relatively large amount of material is removed from the bollard 6 in order to form the cylindrical recess 15 for receiving the locking pin 12 when in its unlocked position, noting that the prior art device requires the locking pin 12 to be rotatable through 3606 relative to the major axis of the anchor axle 7. In contrast, in the more compact arrangement of the invention it will be seen that the base of the short keeper slot 30 is aligned with the base of an elongate entry slot 31 for the locking pin 29 in the lower part of an anchor-axle receiving bore 32 running through the second side plate 27, such that upon the flanged end 22 of the axle 21 being depressed by hand against the bias of a helically wound spring 33 the locking pin 29 is then slidable along the elongate slot 31 in the second side plate 27 in the manner as shown in Figure 8 in which it will be seen that the locking pin 29 is able to then engage with a transversely arranged arcuate slot 34 at the closed end of the elongate slot 31, the arcuate slot 34 extending 3606 around the bore 32 in the second side plate 27, thereby allowing the locking pin 29 to be rotated in either direction to the position shown in Figure 8, although it will be understood that the arcuate slot 34 may be of any conveniently shorter angular length. Accordingly, because the arcuate slot 34 is disposed transversely to the longitudinal axis of the axle 21 at a position short of the forward end of the axle 21, the extreme forward end of the axle 21 need only extend when fully locked in the position shown in Figure 8 up to the outer face of second side plate 27 such that they are generally flush with each other, with the locking pin never being exposed to external debris such as leaves from tree branches or tree bark, and with the elongate slot 31 never being exposed to unwanted contamination by dirt or dust As a further means of protecting the pulley 20 from external contamination or mechanical damage, the end of the helically wound spring 33 adjacent the first side plate 26 is received within a circular groove 35 and the opposite end of the spring 33 is received within a corresponding groove 36 in the flanged knob 22 such that when the knob 22 is depressed to the position shown in Figure 8 the spring 33 is effectively enclosed. As will be appreciated, although two circular grooves, 35, 36, are shown in this arrangement, there may be only a single groove in either of the first side plate 26 or in the flange of the knob 22.

In a further refinement to the invention, a spring-loaded detente ball 37 is provided in a centrally-disposed bore 38 in the bollard 25 and is co-operable with a part-spherical socket 39 in the anchor axle 21 near to its forward end. This provides a convenient arrangement in which, when the locking pin 29 is stored in the keeper slot 30 when the pulley block 20 is unlocked, it is releasably held in that position by the dilltente ball and socket arrangement, thereby ensuring that the anchor axle 21 does not interfere with rope as it is being loaded or unloaded from the pulley block.

As will be appreciated from the foregoing, the subject invention represents a much more compact and efficient arrangement to that shown in the prior art IS C device, providing minimal opportunities for the anchor axle 21 and attendant spring 33 to become snagged with e.g. branches of trees or with other ropes in the vicinity, as well as providing protection against the ingress of dirt and other debris when in its locked and operational position. The fact that the locking pin 29 is essentially always retained within and between one or other of the side plates 26, 27 whether locked or unlocked therefore represents a considerable improvement over the prior art IS C device. In addition, because the only material removed from the bollard 25 is the short keeper slot 30 for receiving the exposed end of the locking pin 29 and the small bore 38 in the bollard 25 for receiving the detente ball 37, the overall strength of the bollard 25, is greater than the bollard 6 of the prior art device because of the relatively significant amount of material removed to create the cylindrical recess 15 for temporarily receiving the locking pin 12 when the pulley block 1 is unlocked, which cylindrical recess necessarily weakens the entire pulley block 1 by decreasing the bearing surface area of the bollard 6 in contact with the outer surface of the anchor axle 7, whereas almost all of the bearing surface area of the bollard 25 of the pulley block 20 of the invention is in contact with the outer surface of the anchor axle 21. In addition, the removal of material for forming the cylindrical recess 15 in the prior art bollard 6 from one side of the bollard necessarily means tensile loads being applied to the bollard and hence the anchor axle 7 are offset from the centre of the bollard, thereby imposing undesirable unbalanced strain on both the bollard 6 and the anchor axle 7. Thus, the arrangement of the invention results in a more lightweight and compact pulley block which is also easier and cheaper to manufacture as well as being stronger and more mechanically balanced than the prior art device.

Claims

CLAIMS1) A pulley block (20) for receiving climbing or hauling rope, the pulley block comprising or including at least one pulley sheave (5a) mounted for rotation on or forming part of a main pulley axle (4a) extending between first and second pulley block side plates (26, 27), the side plates collectively defining a pulley block frame when operationally aligned side-by-side, each side plate also being connected or connectable at a position remote from the main pulley axle to a common anchor axle (21) extending, in use, through co-axial anchor axle-receiving bores (28,32) in the pulley side plates, the side plates being rotatably movable with respect to each other about the major axis of the main pulley axle when the anchor axle has been removed from at least one of the co-axial bores in the side plates, whereby to permit insertion or removal of the rope into or from the pulley block frame, the anchor axle being adapted to prevent accidental opening of the pulley block frame and having a spring-loaded locking mechanism, CHARACTERISED IN THAT the anchor axle locking mechanism collectively comprises a locking pin (29) extending radially outwardly from a forward part of the anchor axle (22) and a locking-pin receiving entry slot (31) extending into the co-axial bore (32) of the second side plate (27), the entry slot having a closed end whereby to limit longitudinal travel of the locking pin, the closed end of the entry slot (31) being coincident with an arcuate slot (34) within the axle-receiving bore (32) of the second side plate extending transversely to the entry slot at least partially around the co-axial bore, the arcuate slot being adapted to permit the locking pin to slide therealong and therewithin when the anchor axle is rotated about its major axis whereby to thereafter prevent removal of the anchor axle along its major axis, the rearward end of the anchor axle having a flanged knob (22) adapted to receive one end of spring means (33), the other end of the spring means being received on or in the outer surface of the first side plate around the anchor-axle receiving bore, the arrangement being such that when the forward end of the anchor axle and its locking pin are removed from the entry slot the second side plate is free to rotate about the major axis of the main axle to thereby open the pulley frame for loading or unloading rope, and when the rope is loaded into the pulley frame and the anchor axle returned to a position in which the locking pin is captured by the arcuate slot in the co-axial bore of the second side plate the forward end of the anchor axle lies within or no more than generally flush with the outer surface of the second side plate, with the spring means being compressed between the first side plate and the flanged knob.
2) A pulley block according to Claim 1 further characterised in that the spring means (33) between the flanged knob (22) of the anchor axle (21) and the first side plate (26) is a helically-wound spring (33).
3) A pulley block according to Claim 2 further characterised in that the spring (33) sits in a groove (35, 36) in the outer side of the first side plate and/or in the flanged knob of the anchor axle whereby to protect the spring when the flanged knob is depressed to a position against the outside of the first side plate.
4) A pulley block according to any preceding claim further characterised in that the arcuate slot (34) extends completely around the bore (32) in the second side plate (27).
5) A pulley block according to any preceding claim further characterised by including a spring-loaded dilitente ball (37) extendable from the anchor axle bollard (25) into a part-spherical socket (39) in the outer surface of the anchor axle (21) whereby to releasably hold the forward end of the axle within the axle-receiving bore (28) of the first side plate and permit the second side plate to be rotated relative to the first side plate for loading or unloading rope onto the main pulley sheave.
6) A pulley block according to any preceding Claim further characterised in including a secondary locking means in the form of a notch (23) in the outer periphery of the flanged knob (22) co-operable with a cliiitente button (24) extending from the outer side of the first side plate (26), the notch in the flanged knob being positioned to receive the cliiitente button when the locking pin (29) is received within and captured by the arcuate slot (34) in the anchor-axle receiving bore (32) of the second side plate, the arrangement being such that upon depression of the dlitente button the flanged knob and anchor axle can freely rotate to thereby unlock the locking pin and hence the second side plate from the first side plate.
7) A pulley block according to Claim 6 further characterised in that the free end of the cloiltente button (24) is marked or coloured to thereby visibly indicate the locked condition.
8) A pulley block (20) for receiving climbing or hauling rope, the pulley block comprising at least one pulley sheave (5a) mounted for rotation on a main pulley axle (4a) extending between first (26) and second (27) pulley block side plates, the side plates being adapted to collectively define, in use, a pulley block frame, each side plate also being connected or connectable at a position remote from the main pulley axle to a common anchor axle (21) extending, in use, through co-axial anchor axle-receiving bores (28, 32) in the pulley side plates, the side plates being rotatably movable with respect to each other about the major axis of the main pulley axle when the anchor axle has been removed from at least one of the anchor-axle receiving bores in the side plates whereby to permit insertion or removal of the rope into or from the pulley block frame, the pulley block having a primary locking mechanism (29,31,34) adapted to prevent accidental rotation and removal of the anchor axle from at least one of the bores of the pulley block side plates CHARACTERISED IN THAT the pulley block (20) includes a secondary locking mechanism comprising in combination a flanged knob (22) at the rearward end of the anchor axle (21) relative to the forward end receivable in the anchor-axle receiving bore (32) in the second side plate (27) adjacent the first side plate (26)26, the flanged knob (22) including a notch (23) in the outer periphery thereof, the notch being co-operable with a spring-loaded detente button (24) extending from the outer sidewall of the first side plate whereby to prevent rotation of the anchor axle about its major axis when the button is engaged with the notch and whereby to permit rotation of the anchor axle and thus release of the primary locking mechanism when the button is depressed against the bias of the detente spring, the arrangement being such that when the side plates of the frame are aligned and the anchor axle is received within the bore of the second side plate, with the primary locking mechanism fully engaged to prevent accidental rotation and removal of the anchor axle from the second side plate, the axle can be constrained to remain in that position until the dlittente button is depressed to thereafter permit rotation of the axle from a locked to an unlocked position.
9) A pulley block (20) according to Claim 8 further characterised by including a locking pin (29) extending radially from a forward part of the anchor axle (2) and being receivable in a locking pin-receiving entry slot (31) in the second side plate, the entry slot having a closed end coincident with an arcuate slot (34) in the anchor-axle receiving bore in the second side plate permitting the pin to be rotated about the major axis of the anchor axle whereby to selectively prevent removal of the axle from the bore in the second side plate.