GB2415421A

GB2415421A - Pulley block and mounting base

Info

Publication number: GB2415421A
Application number: GB0414295A
Authority: GB
Inventors: Giles Smith
Original assignee: Allen Brothers Fittings Ltd
Current assignee: Allen Brothers Fittings Ltd
Priority date: 2004-06-25
Filing date: 2004-06-25
Publication date: 2005-12-28
Anticipated expiration: 2024-06-25
Also published as: GB2415421B; GB0414295D0

Abstract

A cheek block comprises the combination of a pulley block (10, Fig 1) and a mounting base 33. The pulley block has a pair of side cheeks (11,12,) a bridging portion (13) extending between the side cheeks and an attachment projection such as a mounting swivel (21) or a U-shaped strap, as well as a sheave (16) rotatably mounted between the cheeks (11,12). The mounting base 33 has a first surface 36 adapted for cooperation with either cheek of the block and an opposed surface 35 for engaging a support surface on which the block is to be mounted. The base 33 has a housing 45 to accommodate the attachment projection (21) which housing is configured to blend with the block when mounted on the base.

Description

241 542 1

PULLEY BLOCK AND MOUNTING BASE

This invention relates to a combination of a pulley block and a mounting base therefor.

Though the combination of a pulley block and mounting base therefor may be used in a variety of circumstances, it has a particular application in relation to sailing boats and racing dinghies. As such, it will be described exclusively with reference to that use, even though the invention is not to be regarded as limited to pulley block combinations for use in connection with boats.

Pulley blocks are extensively used on the running rigging of sailing boats of all kinds, as well as on many other boats. A typical pulley block has a body which defines a pair of side cheeks between which a sheave is rotatably mounted. A pulley block of this kind is usually secured to a fixed component in order that the block may react to a load imparted thereto by a line passing around the pulley block sheave. Most pulley blocks are provided with a mounting arrangement including an opening through which a shackle may pass, in order to attach the block to a mounting point. For lighter duty applications, the block may be attached to the mounting point by means of a cord passing through the opening of the mounting arrangement. In the case of a swivel block the mounting arrangement comprises a rotatable pin projecting from the block and having a transverse opening. Other blocks may have a U- shaped strap with the arms of the strap lying alongside the outer surface of each cheek and the base of the U-shape spaced from the body of the block thereby to define the opening. r - 2

With an alternative design of pulley block, used for example to change the direction of a path along which a line is to run closely adjacent a surface such as a boat deck, the pulley block is designed for rigid attachment to that surface. Thus, one of the side cheeks of the block has a generally planar outer surface and holes are formed through the block, whereby that one side cheek may bear against the surface to which the block is to be secured by screws passing through the holes and into that surface. Such a block is usually referred to as a "cheek block", and does not have a projecting mounting arrangement which would be a potential hazard for a surface-mounted block.

Many pulley blocks include a switchable ratchet mechanism, whereby when active, rotation of the sheave is permitted in only one sense but switching off the ratchet mechanism then allows the sheave to rotate in either sense. For this purpose, a manual control projects from a central region of a cheek of the block, to control the operation of the ratchet mechanism provided internally of the block, within the periphery of the sheave. In the case of a cheek block, the manual control for the ratchet mechanism must project from the cheek opposed to the planar cheek which bears on the mounting surface, in order that the manual control may be operated as required when the block is in use. The consequence of this is that conventional ratchet cheek blocks must be handed, in order that running rigging may be laid out symmetrically on a deck to each side of the centre line and the appropriate ratchet function obtained, for blocks on both sides of the centre line.

If a manufacturer wishes to produce a range of blocks of the same basic design but which may serve as a swivel block, a ratchet block and a cheek block, the same basic design must be produced in several variants including left-handed and right-handed cheek blocks as well as a swivel block and perhaps also a conventional strap block. This increases the manufacturing costs and also increases stock levels which must be carried by wholesalers and retailers of these products. It is a principal aim of the present invention to address this problem.

According to this invention, there is provided the combination of a pulley block and a mounting base therefor, said pulley block comprising a body defining a pair of side cheeks each having an outwardly-directed surface, a bridging portion extending between the side cheeks and an attachment projection extending outwardly from the bridging portion, a sheave being rotatably mounted between the cheeks; and said mounting base has a first surface adapted for co-operation with the outwardly-directed surface of either cheek of the block, and the opposed surface of the mounting base is adapted for engaging a support surface whereby the block may be attached to that support surface with the mounting base disposed between the block and the support surface, the mounting base including a housing within which is substantially wholly accommodated the attachment projection of the block.

It will be appreciated that the mounting base allows a conventional swivel or strap block (often referred to as a bullet block), whether or not having a ratchet mechanism, to be used as a cheek block. This is achieved by the mounting base providing a housing which accommodates the projecting attachment arrangement of the block, so that the attachment arrangement whatever form it might take - is enclosed and so cannot snag a line passing around the sheave of the block. Further, the housing may provide a smooth surface that will minimise the risk of injury to sailors or damage clothing. - 4

Further, the housing may assist in transferring loads from the block to the mounting base and so to the support surface, by having the housing profiled to engage the body of the block, and preferably to engage the bridging portion of the block. The outer surfaces of the housing may substantially merge with the adjoining parts of the body and preferably the housing presents a smooth outer profile, further to reduce the likelihood of a line passing round the sheave accidentally getting wrapped a second time around the head of the block, or another line snagging on the head of the block. In addition, the profile of the greater part of the periphery of the mounting base matches that of the side cheeks of the block.

In order to increase the security of attachment of the block to the mounting base, each of the cheeks of the block may define a depression in the outwardly-directed surface thereof which depression is generally coaxial with the rotational axis of the sheave. Then, the surface of the mounting base on which the block is received tsaid first surface of the mounting base) may have a protrusion which interfits with the depression in the overlying cheek. Such an interfitting depression and protrusion may serve to prevent relative movement between the block and the mounting base, as well as assisting in the transfer of loads from the block to the mounting base. Further, the mounting base may include one or more pegs projecting from said first surface thereof, separate from the protrusion, each cheek of the block having one or more corresponding apertures for receiving the or each peg, further to enhance the mechanical interconnection of the block and a mounting base.

A preferred form of block includes an annular sheave, there being at least one through-bore provided in the block to extend within the central opening of the annular sheave generally parallel to the axis of rotation thereof, between the outwardly directed surfaces of the cheek. The mounting base may have corresponding bores to register with the or each through bore of the block when fitted to the base, whereby the block may be secured to the base by corresponding screw-threaded fasteners. Though such fasteners may thread into the mounting base, preferably the bores in the mounting base also extend therethrough whereby the fasteners may be engaged with the support surface so clamping both the mounting base and the block to that surface.

Further holes may be provided through the mounting base to permit it to be secured to the support surface by screw-threaded fasteners, before the block is fitted to the base and then secured to the support surface. This allows accurate positioning of the block on a deck surface, before final assembly.

In the case that the block includes a switchable ratchet mechanism which when active permits only uni-directional rotation of the sheave, it is preferred for the block to have a control for that ratchet mechanism which is accessible from both outwardly directed surfaces of the pair of cheeks of the block. For example, that control may comprise a shaft rotatably mounted in the cheeks to extend axially of the sheave, the shaft being provided at its two ends with respective means (such as a projecting tab) permitting the shaft to be turned from either end.

Advantageously, the cheeks of the block are provided with drainage openings to permit the draining of water from the region of the block between the cheeks. In such a case, the mounting base may also be provided with a drainage opening whereby water draining from the block may drain through the mounting base. To this end, the opposed surface of the mounting base may - 6 have a discontinuous lip upstanding from the periphery thereof such that when the base is clamped to a surface, there will be a gap between the major part of said opposed surface of the mounting base and the support surface.

By way of example only, one specific embodiment of pulley block and mounting base together arranged in accordance with this invention will now be described in detail, reference being made to the accompanying drawings in which: Figure 1 is an isometric view of the pulley block, in the form of a ratchet swivel pulley block, as used in this embodiment; Figure 2 is an isometric view of a mounting base also as used in this embodiment, in conjunction with the block of Figure 1; and Figure 3 shows the assembly of the base of Figure 2 together with the block of Figure 1.

Figure 1 shows a pulley block arranged as a ratchet swivel block, for use in this embodiment. The pulley block has a body 10 assembled from a pair of identical side cheeks 11,12, each moulded from a plastics material to include a part of a bridging member 13 disposed at one end of the body. The outer surface 15 of each side cheek has a depression 14 formed therein and internally of the body 10, the depressions form bosses (not shown) which engage each other. An annular sheave 16 is rotatably mounted between the cheeks 11,12 and is carried on ball-races (not shown) defined by outer tracks formed on the sheave and inner tracks formed on the engaging bosses of the cheeks, with balls located therebetween.

The bosses between the two cheeks are hollow and within the space defined thereby there is provided a ratchet mechanism for the sheave such that when the mechanism is active, the sheave may rotate only unidirectionally.

Such a mechanism may include a pawl which projects through an aperture in the bosses to engage teeth formed internally around the sheave 16. Further, the mechanism includes a switching arrangement such that the pawl may be urged to a position where only uni-directional rotation of the sheave is possible or where the pawl is withdrawn so that rotation of the sheave may occur in either sense. The details of the ratchet mechanism form no part of the present invention and so will not be described further here.

In order to permit switching of the ratchet mechanism between its active and inactive settings, there is provided an operating member 17 in the form of a shaft which extends through bores formed in the two cheeks, coaxially with the rotational axis of the sheave 16. That shaft has provided on its two end faces 18 a respective operating tab 19 whereby the tab may be gripped between the thumb and a finger of a user and then turned sufficiently either to engage the ratchet or to free the ratchet. As shown, the tab 19 projects into the depression 14 and the arrangement on the other side of the block corresponds precisely to that on the visible side.

The block has a swivel pin 21 which rotatably projects from one end thereof, that swivel pin having a transverse bore 22 by means of which the block may be attached to a mounting point using a shackle with the pin thereof extending through the bore 22 of the swivel pin. A metal U- shaped strap 23 extends over the bridging member 13, that strap having a hole 24 through which the swivel pin 21 projects. The strap 23 includes a pair of arms 25 (only one of which is visible in Figure 1) which extend within grooves formed in the 2s side cheeks 11,12 of the block. The free ends of the arms 25 are enlarged, the - 8 grooves being correspondingly profiled, to assist the transfer of loads between the cheeks and the strap.

The assembly described above is held together by means of two rivets 27,28. Both rivets extend through registering holes formed in the side cheeks 11,12 within the depressions, parallel to the axis of the sheave, but rivet 27 also extends through corresponding holes in the free ends of the arms 25 of the U shaped strap 23. Both rivets have a head at one end and the other ends thereof are pained over so as to prevent withdrawal of the rivets and so hold the assembly together.

Also formed within the depressions 14 are through-bores 29, the outwardlydirected ends of which are countersunk as shown. The holes for the rivets and the through-bores 29 are all on a common pitch circle centred on the axis of rotation of the sheave 16, with the holes equi-spaced on that circle.

Further, there is formed in each depression a pair of drainage holes 30 to permit the draining of any water which might enter the space within the bosses between the side cheeks when the block is in use. In addition, and between the respective depression 14 and the bridging member 13, each cheek has a pair or irregularly-shaped apertures 31, disposed symmetrically with respect to a central plane of the block passing through the swivel pin 21 and the rivets 27,28.

Figure 2 shows a mounting base 33 for use with the block described above. This base has a main portion 34 having a generally planar lower surface 35 and an upper surface 36 which is profiled to interFit with either side cheek 11,12 of the block. Thus, the upper surface includes a protrusion 37 which fits into a depression 14 of the block, that protrusion having holes 38 to - 9 - accommodate the heads of the rivets 27,28, further holes 39 to register with the through-bores 29 of the block and a central opening 40 to accommodate a projecting tab 19 of the operating member 17. In addition, the protrusion has holes 41 which register with the drainage holes 30 of the block.

Also formed in the upper surface 39 of the mounting base 33 is a groove 42 the profile of which corresponds to an arm 25 of the block, such that if the strap 23 upstands from a cheek of the block, it may be accommodated in that groove 42. To each side of the groove 42, there is a pair of pegs 43 which are suitably profiled to locate in the apertures 31 in whichever cheek of the block is presented to the mounting base 33.

At the end of the mounting base 33 there is provided a housing 45 including a circular hole 46, slightly greater in size than the diameter of the swivel pin 21. The housing 45 is profiled so as to fit against the bridging member 13 and the external walls of the housing blend into the immediately adjacent parts of the body of the block. Further, the housing has a rounded profile, generally as shown in Figures 2 and 3. Around the periphery of the mounting base there is an upstanding rim 47 the inner profile of which follows that of a side cheek 11,12 of the block so that the cheek may be positioned within that rim.

In order to permit the mounting base to be secured to a surface such as the deck of a sailing boat in the required position, there is a mounting hole 48 formed through the main portion 34 of the base. Hole 48 may be countersunk to permit the accommodation of the head of a screw passing therethrough, used to hold the base to a deck until secured in the required position following fitting of the block thereto. The lower surface 35 of the mounting base may - 1o - have a discontinuous lip upstanding from the periphery of the mounting base such that drainage grooves 49 are formed in the lower surface 35 of the base.

These grooves permit the draining away of any water between the mounting base and a mounting surface.

Figure 3 shows the assembly of the pulley block of Figure 1 with the mounting base of Figure 2. As shown, the lower side cheek 11 is a close fit within the rim 47, with the swivel pin 21 then accommodated in the circular hole 46 of the housing 45. The pegs 43 locate in the apertures 31 in cheek 11 and the through-bores 29 of the block register with the further holes 39 of the mounting base. Further, operating tab 19 projecting from side cheek 11 is accommodated in the central opening 40 of protrusion 37 in the base.

The block should be secured in the position shown in Figure 3 by means of screw-threaded fasteners which extend through the through-bores 29, the further holes 39 and into the surface on to which the base 33 has been secured. Thus, those fasteners firmly secure both the block and the mounting base to the support surface.

As will be appreciated, the ratchet operating member 17 may be operated by means of the projecting tab 19, from the upper side cheek 12 of the block. When the ratchet is active, if the sheave is pemmitted to rotate in the wrong sense, the block may be removed from the base 33, turned over and re secured in position. Of course, the permitted rotation of the sheave should be determined before the block is secured for the first time to the base but if for any reason it needs to be changed, then that can be achieved merely by releasing the block and then securing it again, after the block has been fumed over.

The block of Figure 1 may be used as a simple ratchet swivel block without the base of Figure 2. However, if that block is to be used as a cheek block, then it is merely necessary to provide the base 33 of Figure 2 and the same block may be used either as a right-handed block or as a left-handed block merely by presenting one cheek 11 of the block or the other cheek 12 to the upper surface 36 of the mounting base 33, before securing the assembly of the block and base to a deck or other mounting surface. When used as a cheek block, the housing serves to shield the swivel pin 21 and so prevent the snagging of a line passing around the sheave of the block, which otherwise would be highly likely to occur. Further, the housing protects a sailor from accidental injury by the swivel pin as well as protecting clothes from tearing.

Though described above with reference to a ratchet block, it will be appreciated that the invention is equally applicable to a non-ratchet swivel pin block. Further, by suitable modification of the housing, and in particular to the external profile thereof and the internal hole 46, the mounting base may be used with a block having a U-shaped strap for attaching the block to some other component, when used other than as a cheek block. - 1 2

Claims

1. The combination of a pulley block and a mounting base therefor, said pulley block comprising a body defining a pair of side cheeks each having an outwardly-directed surface, a bridging portion extending between the side cheeks and an attachment projection extending outwardly from the bridging portion, a sheave being rotatably mounted between the cheeks; and said mounting base has a first surface adapted for co-operation with the outwardly- directed surface of either cheek of the block, and the opposed surface of the mounting base is adapted for engaging a support surface whereby the block may be attached to that support surface with the mounting base disposed between the block and the support surface, the mounting base including a housing within which is substantially wholly accommodated the attachment projection of the block.

2. The combination of claim 1, wherein the housing is profiled to engage the body of the block.

3. The combination of claim 2, wherein the housing is profiled to engage the bridging portion of the block substantially to merge with the adjoining parts of the body.

4. The combination of any of the preceding claims, wherein the external profile of the housing is rounded.

5. The combination of any of the preceding claims, wherein the attachment projection comprises one of a cylindrical pin projecting from the bridging portion or an attachment strap having a U-shaped projection from the block body. - 1 3

6. The combination of any of the preceding claims, wherein the profile of the greater part of the periphery of the mounting base matches that of the side cheeks of the block.

7. The combination of any of the preceding claims, wherein each of the cheeks defines a depression in the outwardly-directed surface thereof which depression is generally co-axial with the rotational axis of the sheave, and the first surface of the block has a protrusion which interfits with the depression in the overlying cheek.

8. A combination as claimed in any of the preceding claims, wherein the to mounting base includes a peg projecting from the first surface thereof, and each cheek of the pulley block includes an aperture within which the peg is received, when the pulley block is mounted on the base.

9. The combination as claimed in claim 8, wherein the mounting base includes a pair of pegs projecting from the first surface thereof, and each cheek of the pulley block includes a pair of apertures for receiving the two pegs, respectively.

10. The combination as claimed in any of the preceding claims, wherein the sheave is annular and there is at least one through-bore in the block extending within the central opening of the annular sheave generally parallel to the axis of rotation between the outwardly directed surfaces of the cheeks, and the mounting base has a bore which registers with the through-bore of the block when fitted to the mounting base, whereby the block may be secured to the base by a screw-threaded fastener extending through the registering bores.

11. The combination as claimed in claim 10, wherein there are at least two through-bores in the block arranged in a diametrically-opposed relationship with - 14 respect to the axis of rotation of the sheave, and the mounting base is provided with corresponding bores whereby a plurality of screw-threaded fasteners may be used to attach the block to the mounting base.

12. The combination as claimed in claim 10 or claim 11, wherein the or each corresponding bore in the mounting base extends through the base whereby a corresponding screw-threaded fastener may extend into the support surface to attach the block thereto with the mounting base between the block and the support surface.

13. The combination as claimed in any of the preceding claims, wherein the mounting base is provided with holes extending therethrough for screw threaded fasteners to permit the attachment of the mounting base to a support surface independently of the attachment of the block thereto.

14. The combination as claimed in any of the preceding claims, wherein the block includes a switchable ratchet mechanism which when active permits only uni-directional rotation of the sheave, the block having a control for the ratchet mechanism which control is accessible from both outwardly-directed surfaces of the pair of cheeks.

15. The combination as claimed in claim 14, wherein the control for the ratchet mechanism comprises a shaft rotatably mounted in the cheeks and extending axially of the sheave.

16. The combination as claimed in claim 15, wherein the ratchet control shaft is provided at each end thereof with means permitting the shaft to be turned from either end. -

17. The combination as claimed in claim 16, wherein each end of the ratchet control shaft is provided with a respective projecting tab which may be gripped manually to effect turning movement of the shaft.

18. The combination as claimed in any of the preceding claims, wherein the cheeks of the block are provided with drainage openings, to permit the draining of water from the region of the block between the cheeks and where the sheave is rotatably mounted.

19. The combination as claimed in any of the preceding claims, wherein the opposed surface of the mounting base has a discontinuous lip upstanding around the periphery thereof, to permit the draining of water from between the opposed surface of the mounting base and a support surface on which the base is mounted.

20. The combination of a pulley block and a mounting base therefor, substantially as hereinbefore described and as illustrated in the accompanying drawings.