Elevator buffer

Abstract

In the field of elevator buffers there is a need for lighter weight buffers, as well as those useable with a wider range of working fluids An elevator buffer (10; 110; 210; 310; 410) comprises a base member (11) that defines an in-use upwardly extending base recess (12) for receiving part of a compressible energy absorber (14; 214). The elevator buffer (10; 110; 210; 310; 410) also includes a cap (16) that, in use, is located above the base member (11). The cap (16) defines one or more reaction surface (21a) for a resiliently deformable member (22) and a further, downwardly extending cap recess (15) for receiving part of a compressible energy absorber (14; 214). The elevator buffer (10; 110; 210; 310; 410) further includes a compressible energy absorber (14; 214) which has respective sections that are received in the base recess (12) and the cap recess (15). At least one wall (13, 20) extends between the base recess (12) and the cap recess (15) and defines a closed reservoir (31; 231; 331), for fluid, which extends between the base member (11) and the cap (16). An aperture (32) extends through the cap (16), and the compressible energy absorber (14; 214) includes, extending therefrom through the aperture 32, a rod (29). The rod (29) includes, or has secured thereto, a reaction member (33) that, in use, is spaced from the or each reaction surface (21a). The elevator buffer (10; 110; 210; 310; 410) still further includes, extending between the reaction member (33) and the or each reaction surface (21a), a compressible, resiliently deformable member (22). The elevator buffer (10; 110; 210; 310; 410) is characterised in that the at least one wall (13, 20) is formed of or includes a plastics material.

Description

[0001]AN ELEVATOR BUFFER The invention relates to an elevator buffer. An elevator buffer, which absorbs and dissipates energy when it is longitudinally compressed, typically is installed at the bottom of an elevator well or shaft, or at the bottom of an inclined track. Such a bottom location is some distance, such as several tens of centimetres or perhaps 1 – 2 metres, below the lowermost intended extent of travel of an associated elevator car with which the elevator buffer is configured to be used. When (as may occur as a result e.g. of component wear or a lack of adjustment) an elevator car undershoots the lowermost intended extent of travel it contacts from above and longitudinally compresses the buffer. The action of the buffer in compression then dissipates the kinetic energy in the elevator car. The aim of this is to arrest the elevator car smoothly and progressively, without jolting its occupants or any goods being carried. Elevator buffers as described have been manufactured in large numbers over many years. This is in part a consequence of the boom in the construction of multi-storey buildings in recent decades, as well as the prevalence of other moving elevator cars. According to the invention in a broad aspect there is provided an elevator buffer comprising a base member defining an in-use upwardly extending base recess for receiving part of a compressible energy absorber; a cap that in use is located above the base member, the cap defining one or more reaction surface for a resiliently deformable member and a further, downwardly extending cap recess for receiving part of a compressible energy absorber; a compressible energy absorber having respective sections received in the base recess and the cap recess; at least one wall extending between the base recess and the cap recess, the at least one wall being formed of or including a plastics material and defining a closed reservoir, for fluid, extending between the base member and the cap member, an aperture extending through the cap, the compressible energy absorber including extending therefrom through the aperture a rod, the rod including or having secured thereto a reaction member that in use is spaced from the or each reaction surface; and the elevator buffer including extending between the reaction member and the or each reaction surface a compressible, resiliently deformable member. Use of a plastics material to form the wall defining the fluid reservoir of the buffer is associated with numerous advantages. Primary among these is that the weight of the buffer is significantly less than that of a buffer of the same size and duty rating, all parts of which (including the housing defining the reservoir) are made from steel. A buffer that is lighter than the prior art product is cheaper to transport than a steel buffer. It also is easier to handle and install. Additionally, the use of a plastics material helps to reduce manufacturing costs while maintaining efficient buffer operation. This is particularly important in contrast to the use of other materials that are subject to price fluctuations in international markets. Furthermore the use of a plastics material for the wall defining the fluid reservoir in combination with a suitably designed metering device means that fluids other than oils may be used inside the buffer. In this regard it is necessary when the reservoir wall is made from, e.g. steel, to employ an oil as the working fluid since this prevents corrosion that would arise if many alternative fluids were used. When the reservoir wall is made from a plastics material however the working fluid of the buffer may be selected without concern for its effect in causing corrosion of ferrous metals. In turn this means that fluids may be selected that are both lighter and cheaper than the oils that hitherto have been used. Indeed it is possible to consider the use of a ubiquitous fluid such as water as the working fluid of the buffer when the wall defining the reservoir is made from a plastics material. This may mean it is easier than previously to install a buffer in certain circumstances; moreover a building water supply, as opposed to a container of specialist oil, may be used to fill it; and further moreover the step of filling the buffer may not need to be completed at the time of manufacturing the buffer and instead can be left until installation occurs. As a result transportation costs and the purchase prices of the buffers further are reduced. Many other non-oil fluids than water alternatively may be employed; and the features of the buffer of the invention do not preclude the use of oil if necessary. Mixtures of fluids may be employed to produce particular performance effects. As an example one may consider mixing an antifreeze with another fluid in order to produce a buffer that is useable in low-temperature environments. Other fluid mixtures also are possible. Various kinds of plastics material are suitable for forming the at least one wall. As non- limiting examples one may consider acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), polyoxymethylene (POM) or “acetal”, or polypropylenes, although any plastics material which provides ease of manufacture and corrosion resistance would be suitable. The at least one wall may surround the compressible energy absorber over at least part of its length between the base recess and the cap recess. Plastics materials may readily be formed into enveloping shapes by any of a variety of processes including but not limited to spinning, casting, pressing, moulding, additive manufacturing (i.e. so- called ”3D printing”) and related methods. All viable methods of manufacture of the plastics wall are included within the disclosure hereof. Conveniently the at least one wall includes or is constituted by respective lower and upper wall sections, the lower wall section extending upwardly from the base member, and the upper wall section extending downwardly from the cap. In such an arrangement the at least one wall section may be formed as respective upwardly extending and downwardly extending extensions of the respective base and cap recesses. When so formed as extensions of the base and cap recesses the at least one wall is a two-part construction. The two sections may be made from the same material(s) as the base and cap recesses and may be integral therewith; or they may be separate components. In the latter case the sections of the wall portions may be formed of different materials from the recesses. In some versions of the invention one of the sections of the wall portion may be formed from the same material as its associated recess; and the other may be formed from a differing material. Various material combinations are possible but in many examples of the invention the extensions defining the at least one wall are integral with, and formed from the same material as, the base member and cap. The lower wall section may define an upwardly facing, peripheral wall edge and the upper wall section may define a downwardly facing, peripheral wall edge, the upwardly and downwardly facing wall edges being of the same size and shape, and being in contact with one another about a periphery of the reservoir whereby to provide an uninterrupted wall section in the vicinity of the upwardly and downwardly facing wall edges; and the upper and lower wall sections being secured one to the other. This arrangement allows for positive location, and ready securing, of the sections of the at least one wall one to the other. Securing may be achieved by any of a wide range of means, including fasteners, clips, screw threads and other form-locking arrangements. Such means may be releasable or they may be of kinds that once secured are permanently fixed. In particularly preferred embodiments the buffer includes an adhesive material on one or both of the upwardly and downwardly facing wall edges whereby to secure the upper and lower wall sections one to the other. One of the lower and upper wall sections may include a relatively large area end section and the other of the lower and upper wall sections may include a relatively small area end section whereby the relatively small area end section is receivable within the relatively large area end section in a manner locating the upper and lower wall sections relative to one another to define the at least one wall. This aspect of the invention permits ready assembly of the sections of the wall to define a single reservoir wall. This is of benefit in for example mass-production environments where the buffers are assembled. Furthermore this aspect is compatible with the various options for securing the wall sections together as outlined above. The relatively small area end section may be a friction, press or interference fit within the relatively large area end section. This aspect when present further assists in making the reservoir wall easy, quick and reliable to assemble from discrete parts. Additionally or alternatively the base member and cap may be welded together. This may be achieved through any of a range of methods, such as friction welding and ultrasound welding. In alternative embodiments optionally the buffer includes at least one intermediate wall member extending between the base recess and the cap recess in order to define at least part of the length of the closed reservoir. The intermediate wall member may be provided in order to interconnect the lower and upper wall sections described above. To this end the intermediate wall member at its ends may be of the same cross-section as the respective lower or upper wall end section adjacent which it lies. In practice the intermediate wall member may be of constant internal cross section along its length, and more preferably may be a hollow chamber of the same internal shape as the lower and upper wall sections (assuming these in the alternative embodiments are of the same shape as one another, although this need not be the case). The intermediate wall member is made of or includes a plastics material. This can be the same material as that of the lower and upper wall sections, although this need not necessarily be the case. The lower wall section may define an upwardly facing, peripheral wall edge and the upper wall section may define a downwardly facing, peripheral wall edge. The intermediate wall member may define at each of its ends a respective intermediate wall end having a wall end edge that is, about a periphery of the reservoir, in contact with, secured to and of the same respective size and shape as at least one of the upwardly facing and downwardly facing wall edges whereby to provide uninterrupted wall sections in the respective vicinities of the wall end edges. Similarly the buffer may include an adhesive material on at least one of the upwardly facing, peripheral wall edge, the downwardly facing, peripheral wall edge and one or more said wall end edge whereby to secure elements defining the closed reservoir one to another. Hence the intermediate wall member advantageously may be secured in a manner that is similar to the securing of the lower and upper wall sections to one another as explained above. Further the shape and dimensions of the lower wall section and the intermediate wall member adjacent thereto may be such that the one is receivable within the other in a manner locating the lower wall section and the intermediate wall member relative to one another to define part of the at least one wall. Also the shape and dimensions of the upper wall section and the intermediate wall member adjacent thereto may be such that the one is receivable within the other in a manner locating the upper wall section and the intermediate wall member relative to one another to define part of the at least one wall. Again this is somewhat similar to the arrangement for locating the lower and upper wall sections as explained above, subject to interposing of the intermediate wall member. Optionally the elevator buffer includes a foot defined at or near its in-use lowermost end; and one or more rib or fillet extending between and secured to the foot and the upwardly extending base recess. The provision of a foot is one way for ensuring that the elevator buffer is stably supported from underneath on the floor of the elevator well. However other means, such as a bore extending downwardly into the material of the well and in which a stabilising downward extension of the housing is receivable, are possible within the scope of this disclosure. Conveniently the compressible energy absorber is or includes a fluidics energy absorber that in use contains an energy-dissipating fluid. However other forms of energy absorber, such as resiliently deformable elements, are not precluded. These may be provided as alternatives to a fluidics energy absorber, or in combination therewith. Desirably the fluid reservoir may contain an in-use energy dissipating fluid and the buffer may include one or more conduit via which energy dissipating fluid may be fed between the fluid reservoir and the compressible energy absorber. Conveniently the energy dissipating fluid is selected from the list including an oil; and water. Preferred oils when present include but are not limited to ISO GV 68 hydraulic oils or equivalents thereto. Further the compressible energy absorber additionally may include a hollow, metering chamber that is received over at least part of its length within the fluid reservoir and, secured to the rod, a piston that is sealingly movably received within the metering chamber, the metering chamber including one or more apertures opening into the interior of the metering chamber and on the exterior of the metering chamber thereby interconnecting the interior and exterior of the metering chamber; and the resiliently deformable member in the absence of applied force conferring a biassing force biassing the piston towards an in-use upper part of the metering chamber, the arrangement being such that on application of force to the rod longitudinally to compress the compressible energy absorber the piston moves towards an in-use lower part of the metering chamber against force generated by the resiliently deformable member while expelling fluid from the metering chamber to the fluid reservoir via the one or more apertures; and on reduction of the applied force to below the magnitude of the biassing force the resiliently deformable member biases the piston back towards the upper part of the metering chamber. Hence the energy absorber advantageously may be of a general kind. In practical yet optional embodiments the elevator buffer may include a plurality of the apertures formed spaced apart from one another about a periphery defined by the metering chamber and / or along a length defined longitudinally along the metering chamber. At least one said aperture may be of lesser cross-sectional area at its opening into the interior of the metering chamber than at its opening at the exterior of the metering chamber. The elevator buffer may include within the fluid reservoir externally of the metering chamber one or more energy dissipating elements that on longitudinal compression of the compressible energy absorber are contacted by fluid expelled via one or more said aperture in a manner dissipating energy in the energy dissipating fluid. The use of plastics materials to manufacture the one or more walls permits ready design and manufacturing of the fluid reservoir in a manner accommodating the one or more energy dissipating elements. Such elements may include one or more moveable parts that are moved on contact by the fluid expelled from the energy absorber, and such features may readily be mounted or otherwise accommodated as a result of manufacture of the at least one wall, and in many examples the entirety of the housing, from a plastics material. The one or more energy dissipating elements more particularly may be selected from the list including one or more baffles positioned to intersect and reactively reduce the energy of fluid expelled via the one or more aperture during compression of the compressible energy absorber; and one or more rings rotatably retained relative to the exterior of the metering chamber and including one or more vanes positioned to intersect and reduce through rotative acceleration of the one or more rings the energy of fluid expelled via the one or more baffles during compression of the compressible energy absorber. Further, at least one said aperture may be angled relative to the in-use horizontal whereby reactively to dissipate energy in fluid expelled via the one or more aperture during compression of the compressible energy absorber. For the avoidance of doubt the term “elevator” as used herein is a synonym for “lift” as is used in some territories. There now follows a description of preferred embodiments of the invention, by way of non-limiting example, with reference being made to the accompanying drawings in which: Figure 1 is an isometric, partly broken-away view of a first embodiment of elevator buffer according to the invention; Figure 2 is a side elevational view of the Figure 1 buffer; Figure 3 is a cross-sectional view taken on line Y-Y of Figure 2; Figure 4 is an isometric, partly broken-away view of a second embodiment of elevator buffer according to the invention; Figure 5 is a side elevational view of the Figure 4 buffer; Figure 6 is a cross-sectional view taken on line W-W of Figure 5; Figure 7 is a cross-sectional view, that is similar to Figure 3, showing an optional energy dissipating element in the Figure 1 buffer in the form of a stacked series of rotatable, vane-supporting discs; Figure 8 is an enlarged, perspective view of one form of the discs forming part of the Figure 7 embodiment; Figure 9 is a cross-sectional view that is similar to Figure 7 and shows as an alternative to the rotatable discs a jetting shield that assists to dissipate energy in fluid expelled via ports visible in the figure; and Figure 10 is a cross-sectional view that is similar to Figures 7 and 9 and shows angling of the metering ports of the energy absorber as a further means of dissipating fluid energy. Referring to the drawings and initially to Figures 1 to 3 there is shown an elevator buffer 10 according to an embodiment of the invention. Elevator buffer 10 includes a base member 11 defining an in-use upwardly extending, hollow base recess 12. In the illustrated embodiment base recess 12 is defined by an upstanding, continuous, constant thickness, inclinedly upwardly extending, cylindrical wall (lower wall section) 13 as an upright, hollow cylinder of gradually enlarging diameter along its upwardly extending length. However the recess 12 may adopt a range of other forms, including e.g. polygonal cross-sections over part or all of its length; constant or other non-constant cross-sections, non-constant wall thicknesses, formed from more than one wall and various other modifications as will be apparent to the person of skill in the art. The base recess 12 receives extending vertically upwardly therein the lower end of a compressible energy absorber 14 that is described in more detail below. The elevator buffer 10 also includes a cap 16 that as further described below is fitted onto the top of, and therefore essentially lies above, base member 11. When so fitted together the cap 16 and base member 11 define a housing. The interior of the housing functions as a container for the energy absorber 14 and as a reservoir for fluid also as described below. In the illustrated embodiment cap 16 on its exterior is formed as an upwardly extending, truncated, circular cone the lower end of which is of lesser diameter than the upper end. At its uppermost end cap 16 is formed to include a circumferential lip 17 that protrudes upwardly about the outer periphery of the upper end. In like manner to the base member 11 these design aspects of the cap 16 are not mandatory, and many construction variants (as will occur to the person of skill in the art) are possible within the scope of the invention. Radially inwardly of the lip 17 cap 16 includes an annular trough 18 that is downwardly recessed relative to the lip 17. Radially inwardly of the trough 18 the cap 16 extends upwardly beyond the height of the lip 17 to define a cylindrical housing extension 19. In the illustrated embodiment the lip 17 and trough 18 are circular by reason of the circular cross-section of the cap 16. However this need not necessarily be the case, and other shapes of the lip 17 and trough 18 are possible. The lip 17 and trough 18 do not have to be of the same shape. More generally the base member 11 and cap 16 do not need to be of circular cross-sections, although this form is advantageous because of factors such as its inherent strength and the ease with which it may be manufactured. A series of reaction surface webs 21 is arrayed around the interior of the lip so as rigidly to interconnect the lip 17 and the material of the housing extension and thereby collectively define a base member in the trough 18. The reaction surface webs 21 are spaced equiangularly about the circle defined by the interior of the trough and each present an upwardly facing, upper edge reaction surface 21a as best illustrated in Figure 3. The reaction surfaces 21a are for reacting force exerted by a resiliently deformable member that in the illustrated embodiment is a coiled spring 22. The functioning of the spring 22 is described hereinbelow. Forming the reaction surfaces by way of a series of webs 21 defining upwardly facing upper edges means that the material of the cap may be minimised while providing a design that readily may be manufactured using e.g. moulding or other mass-production techniques. However it is possible to design the one or more reaction surface 21a differently, for instance without the webs or similar features being equiangularly spaced; without the webs or similar features all being of the same design as illustrated; or as a continuous floor defining an annular bottom part of the trough 18. Other forms of reaction surface also are possible as may be devised by the person of skill in the art. The cap 16 has a hollow interior defined by a downwardly depending, essentially cylindrical wall (upper wall section) 20 and this defines a downwardly extending cap recess 15. This is intended to receive an upper part of a main body 30 of the energy absorber 14. The foregoing amounts to an apparatus in which the at least one wall is constituted by the respective lower 13 and upper 20 wall sections described above. The lower wall section 13 defines an upwardly facing, peripheral, i.e. circumferential (annular), wall edge 13a adjacent its uppermost extremity. The upper wall section 20 defines a downwardly facing, peripheral, i.e. circumferential (annular), wall edge 20a. The wall edges 13a, 20a are of the same dimensions and are positioned on the respective walls 13, 20 so as to be in contact with one another when the cap 16 is positioned above the base member 11 in order to form the housing of the elevator buffer 10. As a consequence the walls 13, 20 at least on the inside of the housing define a wall section that is in the up and down and circumferential senses uninterrupted in the vicinity of the respective wall edges 13a, 20a. As indicated, however, the lower and upper wall sections 13, 20 need not be cylindrical and may instead have a different, e.g. polygonal, cross-sectional shape, such as may correspond to the general shape of the associated base member 11 or cap 16. It follows that the wall edges 13a, 20a may similarly have a different cross-sectional shape, albeit one that is the same as the corresponding lower or upper wall section 13, 20. The lower and upper wall sections 13, 20 (and corresponding wall edges 13a, 20a) do, however, preferably have the same cross-sectional shape as one another, as is shown in the illustrated embodiment. Further, in the embodiment shown, the upper and lower wall sections 13, 20 are secured together. In the illustrated embodiment this is achieved through the presence of an adhesive material applied securing the wall edges 13a, 20a one to the other. During assembly of the elevator buffer 10 the adhesive material may be applied to one or both the wall edges 13a, 20a as may be dictated by the precise design of the buffer 10 and the assembly requirement. Various methods of applying adhesive material are possible and would be known to the person of skill in the art. As an alternative or adjunct to the use of an adhesive material the base member 11 and cap 16 may include other securing means. These non-limitingly may take the form of one or more clips, fasteners, screw threads and other form-locking arrangements. Ultrasound or heat welding of the materials of the base member 11 and cap 16 additionally or alternatively may be employed, and the applicability of these methods of securing parts together is a further unexpected advantage of the use of plastics materials in construction of the elevator buffer 10. The securing means may be releasable or they may be such as permanently to secure the base member 11 and cap 16 together. As is apparent from Figure 3 the base member 11 in the vicinity of wall edge 13a is arranged to have a relatively small diameter, and hence relatively small area, end section. The lowermost part of the cap 16 in this vicinity is of relatively large diameter and hence of relatively large area. The dimensions of these parts of the elevator buffer 10 are such that the upper end of the base member 11 is received within the lower end of the cap 16 in a manner locating the lower and upper wall sections 13, 20 one relative to the other, and defining the at least one wall referred to. The described arrangement may be such that the protruding part of the base member 11 (i.e. the relatively small area end section thereof) is a friction, interference or press fit in the relatively large area end section of the cap 16. Such arrangements may be designed so that hand assembly of the base member 11 and cap 16 together is possible. Equally, it is within the scope of the invention for the parts to be assembled together using one or more tools and / or machines. The compressible energy absorber 14 has a main body 30 which is an elongate, hollow, in-use upright cylinder having a cylindrical internal metering chamber 25 of constant internal diameter and having a cylindrical piston 23 moveably (especially slidably) received therein so as to be moveable along the length of the interior of the main body 30. Other shapes of main body, metering chamber and piston are also possible, however. The piston 23 includes one or more o-ring grooves 24, 26 formed in its external surface for receiving piston rings 27, 28, i.e. seal rings, that in combination with the outer diameter of the piston 23 and the inner diameter of the metering chamber 25 ensure a fluid-proof seal of the piston 23 relative to the inner wall of the metering chamber 25. The main body 30 of the energy absorber 14 is received within the space defined by the base recess 12 and cap recess 15, with the lower end of the main body 30 as mentioned in the base recess 12 and the upper end in the cap recess 15. This space by reason of the assembly of the cap 16 on top of the base member 11 is a single volume that in the embodiment shown is essentially cylindrical, although this need not necessarily be the case in other embodiments. In the preferred embodiment shown the lower part of the single volume, defined by the base recess 12, is of greater diameter than the upper part of the space defined by the cap recess 15, although in other embodiments this also need not necessarily be the case. The base recess 12 is defined by upwardly extending lower wall 13 and the cap recess 15 by downwardly depending upper wall 20. These walls collectively amount to at least one wall defining the aforesaid space. This functions as an essentially closed reservoir 31, for a fluid, that extends between the base member 11 and cap 16. At its upper end piston 23 is connected to a rod 29 that extends upwardly therefrom. The upper end of the reservoir 31 is essentially closed by the cap 16, but this is perforated by an aperture 32 extending therethrough. The rod 29 above its connection to the piston 23 passes through the aperture 32 so that it emerges on the upper side of the cap 16. A stabiliser bushing 35, that in the illustrated embodiment is an annulus secured to the aperture 32 but that may take other forms in other embodiments, closely encircles the rod 29 in a manner allowing movement of the rod in the aperture while ensuring a fluid-proof seal with the rod 29 during operation of the buffer 10. The rod 29 extends for a distance, beyond the upper end of the cap 16, that is determined by the design of the compressible energy absorber 14. The intended duty of the elevator buffer is important in this regard. In particular in elevator buffer design it is important to match the stroke length to the expected speed of the elevator car whose movement is to be buffered. This might suggest lengthening the rod as much as possible, but too long a rod may make the buffer laterally unstable and anyway would add unnecessary mass to the buffer 10. The rod length is optimised at the design stage with these factors in mind. Secured to the rod at its uppermost end is a reaction member in the form of a rigid, circular disc 33. Disc 33 is formed with an outer, downwardly depending, circular rim wall 34 and a downwardly depending centre boss 36 at which it is secured to the rod 29. In the radial region between the rim wall 34 and the boss 36 the disc 33 defines an upwardly extending, annular recess 37 the purpose of which is to receive, bearing against it from underneath, the upper end of spring 22. The base member 11 includes extending outwardly therefrom a flat-bottomed foot 45. In the illustrated embodiment the foot 45 is square in plan view, although a wide variety of other shapes is possible. Foot 45 is rigidly secured to, and in some embodiments formed integrally with, the base member 11 and extends outwardly from the lowermost end thereof. A series of securing holes 50 are formed extending through the material of the foot 45 at each respective corner. Optional eyelets 51 reinforce the foot 45 in the vicinities of the holes 50. The purpose of the foot 45 is to assist the elevator buffer 10 to stand stably upright on the surface of an elevator well. One or more bolts or studs may be used in a manner extending through the holes 50 in order to secure the buffer 10 in position beneath the elevator car. A series of rigid triangular fillets 52 is secured about the outer periphery of the base recess 12 and connecting to the foot 45. The fillets 52, which are optional features, assist to strengthen the housing in the vicinity of the foot 45. The parts of the elevator buffer 10 thus far described may be made of a variety of materials. The main body 30 of the compressible energy absorber 14, the piston 23, the rod 29 attached thereto and the disc 33 may be made of steel materials and may be rigidly secured one to another using per se known techniques. An important aspect of the invention however is the manufacture of at least the upwardly extending wall 13 and the downwardly depending wall 20, that between them define at least one wall in turn defining the essentially closed reservoir 31, from plastics materials. In practice in the embodiment of Figures 1 to 3 the entirety of the base member 11 and cap 16 as mentioned are manufactured from plastics materials. Advantages of such materials, exemplary, non-limiting grades of which are mentioned herein, are as stated above. In particular the use of plastics materials permits the creation of an elevator buffer that is significantly lighter than the lightest all-metal buffers presently on the market, whilst surprisingly maintaining and in some respects improving on performance levels that are comparable with those of all-metal buffers. The metering chamber 25 at least internally is an elongate, hollow cylinder of constant internal diameter, although in other embodiments the metering chamber may have a different shape. In any event, in the embodiment shown the metering chamber 25 is constituted by the main body 30 of the energy absorber 14 together with an end cap 38 sealingly fitted into the lowermost end of the chamber 25. The end cap 38 rests on the bottom of the interior of the base recess 12. The latter may be shaped as illustrated in order positively to locate the energy absorber 14 relative to the base member 11. As explained the at least one wall defined by the walls 13, 20 preferably is cylindrical at least on its interior surface, albeit that as a result of the designs of the base member 11 and cap 16 the internal diameter of the reservoir 31 reduces part-way along its length in the upward direction. Other shapes and sizes of the reservoir 31 are possible, as will occur to the person of skill in the art. As explained, the reservoir 31 surrounds the compressible energy absorber 14 over the part of its length, constituted by the main body 30, lying between the base recess 12 and cap recess 15. At the upper end of the main body 30 the space is shaped to locate the main body 30 relative to the cap 16. The locating features of the base member 11 and cap 16 assist the assembly of the elevator buffer 10 as a mass-produced item. The main body 30 includes a series of metering apertures 39 extending through it so as to interconnect the interior and exterior of the compressible energy absorber 14. The apertures 39 are in the illustrated embodiment provided as four vertical lines of four apertures per line extending along the length of the main body 30 below the piston 23 when the latter lies at the top of the metering chamber 25. The four lines of apertures 39 are mutually orthogonal in the illustrated embodiment. Other patterns and numbers of the apertures 39 are possible within the scope of the invention, but the foregoing has been found to be a highly effective arrangement. Each aperture 39 is a relatively narrow cylindrical bore where it opens on the interior of the metering chamber 25. Each of the apertures widens to become a larger diameter bore on the side opening on the exterior of the main body 30. The reason for this construction is as explained above. Other designs, e.g. cross-sectional shapes, of aperture 39 also are possible within the scope of the invention. The metering chamber 25 is filled with a working fluid that may be of the kinds exemplified herein. When an elevator car overshoots the lowermost intended extent of travel by more than a predetermined, desirable minimal amount the underside of the elevator car, or an element secured to it, contacts the rod 29 from above. This confers a downwardly acting force that is transmitted via the rod 29 to the piston 23. Assuming the force is greater than the biassing force applied by the spring 22, this causes the piston 23 to move downwardly inside the metering chamber 25. The dimensions of the metering chamber 25 and piston 23, together with the effect of the seal rings 27, 28, causes the piston 23 to press on the working fluid. The spring 22 at this time becomes compressed between the disc 33 and the cap 16. This increases the potential energy in the spring 22. The working fluid in the metering chamber 25 is incompressible. Consequently it is forced at high velocity by the movement of the piston 23 via the metering apertures 39 into the fluid reservoir 31. During this process the energy of the piston 23, and hence of the overshooting elevator car, is dissipated in the working fluid. As the piston 23 descends in the metering chamber 25 it successively covers the apertures 39 that as mentioned are formed in vertical lines in the non-limiting embodiment illustrated. This means that the volume through which working fluid may exit the metering chamber 25 reduces the further the piston 23 descends, with a concomitant increase in the resistance provided by the elevator buffer 10. In turn this means that the degree of energy attenuation provided by the buffer 10 is automatically adjusted in dependence on the energy of the impulse imparted by the elevator car to the rod 29. A more energetic impulse requires more attenuation than a less energetic one. This causes the piston 23 to descend further than in the case of a less energetic impulse, thereby causing an increase in the resistance offered by the buffer 10 that is related to the prevailing energy dissipation requirement. Once all the energy of an elevator car impulse has been dissipated the elevator car will be at rest and automatic systems forming part of the elevator installation will apply the elevator brake to ensure that while passengers, etc., leave and board the elevator car it is stable and not prone to unexpected movement. When any desired embarkation and disembarkation have occurred, a travel command has been entered, and any elevator doors or other safety barriers closed, the elevator car will ascend under the power of a motor that is an essential part of all such modern systems, lifting off from the rod 29 at this time. At this point the spring 22 decompresses, converting its potential energy to kinetic energy, and pushes the disc 33 upwards. By reason of the rigid connection represented by the rod 29 this simultaneously draws the piston 23 upwardly within the metering chamber 25, until movement of the piston 23 is arrested through contact with the bushing 35 at the top of the cap 16. Since the aperture in the bushing 35 is of smaller diameter than outer diameter of the piston 23 the latter cannot pass through the aperture 32 and it is retained at the top of the metering chamber 25 by the biassing force of the spring 22. The low fluid pressure that arises at the lower end of the piston 23 as it moves upwardly draws the working fluid via the apertures 39 back from the reservoir 31 into the metering chamber 25. By the time the piston 23 is at the top of the metering chamber 25 the elevator buffer 10 is ready to be re-stroked by a subsequent elevator car impulse. The cap 16 includes secured to one side a switch housing 41 containing an electrical switch. The switch includes a spring-biased actuator element 42 that protrudes horizontally and terminates in an engagement member. In the illustrated, non-limiting embodiment this takes the form of a cam wheel 43 (although other designs are possible). The spring biasing of the actuator element 42 urges it to a protruded position. Cam wheel 43 is mounted for rotation about a horizontal axis. A rigid (e.g. metal or other rigid material) striker rod 44 is secured to and extends downwardly from a location on the outer edge of the disc 33 towards the vicinity of the cam wheel 43. The striker rod 44 passes through a guide slot 47 formed in a guide plate 48 protruding outwardly from the cap 16 and below which the switch housing 41 is mounted. The lowermost end of striker rod 44 terminates in a chamfered cam surface 46 adjacent the cam wheel 43. The shape of the chamfer is such that when the piston 23 is at the top of the metering chamber 25 the chamfer is clear of the cam wheel 43 and the actuator element 42 is caused by its spring biasing fully to extend from the housing 41. In this configuration the connection of the switch is such that a healthy condition of the elevator buffer 10 is signalled, because the piston 23 is at the top of the metering chamber 25 such that the full stroke of the elevator buffer 10 is available for energy dissipation. When the impulse of an elevator car drives the disc 33, rod 29 and piston 23 downwardly this simultaneously causes descent of the striker rod 44 through the guide slot 47. This causes the chamfered cam surface 46 to engage the cam wheel 43 and apply a horizontal force to it. This in turn causes the actuator element 42 to be pushed against its spring biasing into the switch housing 41, thereby changing the status of the switch. The switch then signals that less than the full stroke of the buffer 10 is available. In a typical set-up the switch is configured so that it is closed when the actuator element 42 is fully extended, and open when it becomes pushed any appreciable distance into the switch housing 41. Consequently a positive signal voltage is taken as an indicator that the full buffer stroke is available for energy dissipation. However the switch may be configured in a reverse fashion so that an open switch configuration could be used to signify that the full stroke is available. The signal generated by the switch is transmitted via appropriate wiring (that is omitted from the figures for clarity) to control circuitry of the elevator installation. At times when the elevator buffer is compressed such that the status of the switch changes as described the arrangement can be such that power to the motor is temporarily disconnected. This ensures that an overshooting elevator car is not driven further to overshoot the lowermost extent of intended travel. Additionally should the elevator buffer for some reason, such as sticking of the piston 23 inside the metering chamber 25, fail to return to its fully extended length when the elevator car lifts off the rod 29 this may be a potential hazard because the energy absorbing ability of the buffer 10 may be reduced as a result. In such a situation the switch may signal the reduction in efficiency of the buffer 10 in a manner causing more permanent de-powering of the motor until repair or replacement of the buffer 10, or at least the compressible energy absorber 14, is effected. Figures 4, 5 and 6 are views similar to Figures 1, 2 and 3 of a second embodiment of elevator buffer 110 within the scope of the invention. The construction of the second embodiment is in most respects the same as that of the first embodiment. Several components of the second embodiment are similar or identical to counterpart components of the first embodiment. These are not described again in detail in relation to the second embodiment. Several such components are as necessary identified in Figures 4, 5 and 6 by the same reference numerals as in Figures 1, 2 and 3. In the Figures 4, 5 and 6 embodiment a base member 11 and a cap 16 that are the same as the counterpart components in Figures 1, 2 and 3 are provided. The elevator buffer 110 of Figures 4, 5 and 6 however is somewhat longer than the elevator buffer of Figures 1, 2 and 3. This is a consequence of a requirement for the second embodiment of the elevator buffer to accommodate higher forces than the first embodiment. This is achieved through the provision of a lengthened compressible energy absorber 114 inside a lengthened housing. Energy absorber 114 is essentially of the same construction as energy absorber 14 of Figures 1, 2 and 3 except that the main body 130, rod 129 and striker rod 144 thereof are longer. The additional length of the main body 130 is accommodated by the presence of an intermediate wall member 149. This is an elongate, constant internal diameter hollow cylinder formed of a plastics material, although other cross-sectional shapes of intermediate wall member are also possible, e.g. as required so as to correspond to the cross-sectional shape of one or more of the lower wall section 13 and the upper wall section 20.. In some embodiments the plastics material from which the intermediate wall member 149 is formed would be the same as the material of the base member 11 and cap 16. However this need not necessarily be the case; and particular performance effects (such as but not limited to insulative or heat transferring effects, radio frequency screening effects or mechanics effects such as preferred stiffness values or vibration absorption characteristics) may be achieved through selection of a material for the intermediate wall 149 that differs from that of the base 11 or cap 16. In the embodiment shown, at its lower end the intermediate wall member 149 contacts the upper wall edge 13a of wall 13 of base member 11 in a similar manner to contact of this edge by wall edge 20a in Figures 1 – 3. At its upper end the intermediate wall member 149 contacts the lower wall edge 20a of wall 20 of cap 16 in a similar manner to contact of this edge by wall edge 13a in Figures 1 – 3. The intermediate wall member 149 may be secured at its upper and lower ends through the use of adhesive material e.g. between the above-described wall ends. Options for applying the adhesive in Figures 4, 5 and 6 essentially are the same as those described above in relation to Figures 1, 2 and 3. Additionally or alternatively the other fastening means described above in relation to Figures 1, 2 and 3 may be used to secure the ends of the intermediate wall member 149 in place. As is apparent from Figure 6 the uppermost part of the base member 11 is dimensioned to be received inside the interior of the cylinder defined by the intermediate wall member 149. At its uppermost end the intermediate wall member 149 is similarly received within the lowermost part of the cap 16. Aside from the foregoing variations the elevator buffer 110 of Figures 4, 5 and 6 is essentially the same as the buffer 10 of Figures 1, 2 and 3. The buffer 110 functions in a closely similar manner to the Figures 1, 2 and 3 buffer 10. For this reason it is not necessary here to repeat a description of the operational sequence of the buffer 110. Rather, the description of the operational sequence of the first embodiment is applicable to the second embodiment, subject to any minor changes necessary to take account of the differences between the two embodiments. Referring now to Figure 7 there is shown in partly-sectioned view a variant 210 of the first embodiment of elevator buffer in which a series of rotatable baffle rings 53a, 53b, 53c, 53d, 53e is provided stacked one on another inside the base recess 12. As is best shown in the enlargement of Figure 8 each baffle ring 53 is an annulus (although other shapes are also possible) of a rigid material such as a light metal that is formed through pressing or a similar forming process into an annular series of flat- topped merlon-like upstands 54 that are spaced from one another by intermediate, flat bottomed crenels 56 also defining an annular series. The material of the baffle ring 53 interconnecting the tops of the upstands 54 and the crenels 56 extends as vertically extending walls 57 on each side of each upstand flat top. The baffle rings 53a – 53e are stacked inside the base recess 12 with the main body 230 of the energy absorber 214 extending upwardly within the resulting stack and acting as a core. The material of the baffle rings 53 is such that they are slidably rotatable one on top of another, with the lowermost ring 53a being slidably rotatable on the material of the base member 11. When the buffer 210 is compressed as a result of contact by the underside of an elevator car the working fluid expelled from the metering chamber 225 via apertures 239 impacts the baffle rings 53 adjacent the respective apertures 239 and causes them to rotate. This is chiefly a consequence of impact of the fluid on the vertically extending walls 57 acting laterally. The energy required to rotate the baffle rings 53 increases the energy dissipation in the working fluid, thereby increasing the efficiency of the elevator buffer 210. Figure 7 shows an additional optional feature that may be employed in any embodiment of the invention. This is the largely irregular pattern of the apertures 239. As is visible in Figure 7 the left-hand series of apertures 239 includes three apertures in a vertical line. The right-hand series also includes three apertures in a vertical line, but none of these is in register in the horizontal direction with any of the apertures of the left-hand series. A central series of apertures 239, that is visible end-on in Figure 7, includes four apertures in a vertical line. None of these is in register in the horizontal direction with any of the apertures 239 of the left-hand and right-hand series. A further series of apertures opposite the central series also may be provided but these are not visible in Figure 7 by reason of the sectioning in that figure. The irregularity of the apertures in Figure 7 is illustrative and is not limiting of the invention. Consequently a wide range of further variations on the numbers and positioning of the apertures 239 is possible. One reason for including the irregular pattern of Figure 7 is to ensure that a predetermined amount of working fluid force is directed towards each of the baffle rings 53. As is apparent the baffle rings 53d and 53e towards the top of the stack of rings will receive a greater flow of fluid than those lower in the stack, unless the impulse experienced by the rod 29 is sufficient to cause covering of the uppermost apertures 239. Optionally the apertures 239 in Figure 7, or in any embodiment, may be positioned in a roughly spiral arrangement so that they are cut off by the piston 23 sequentially. The cross-section of Figure 7 is taken in a different plane than for example Figures 1 to 6, and illustrates another optional feature. This is screw-in dipstick 58 that is inserted via a dipstick bore formed in the flange of cap 16. The dipstick 58 extends into the working fluid reservoir 231 and per its ready assessment of the level of fluid therein, in a manner that is familiar to the person of skill in the art. A dipstick such as dipstick 58 may be present in any embodiment of the invention, including the first embodiment elevator buffer 10, and additionally is visible in the embodiments of Figures 9 and 10 described below. The elevator buffer 310 Figure 9 embodiment is similar to the Figure 7 buffer 230 except that the baffle rings 53 are dispensed with and are replaced in this embodiment by a jetting shield 59. This is an annular hollow cylinder made from a rigid material that lines the reservoir 331 defined in base recess 12 in a manner that impedes the flow of fluid via the apertures 339 and thereby increases the energy attenuation effect, while at the same time protecting the inner wall of the reservoir 331 from jets of high pressure working fluid which might otherwise damage or puncture the material of the base member 11 and cap 16. Other shapes of jetting shield are also possible, while still providing similar energy dissipation and protection effects. In Figure 9 the pattern of the apertures 339 is the same as in the Figure 7 embodiment, but this is not mandatory and a wide variety of variations of the numbers, alignments and patterns of the apertures is possible. In Figure 10 a fourth embodiment of elevator buffer 410 omits energy attenuating features positioned externally of the main body 430 and instead enhances the energy dissipation effect through upward inclination of the apertures 439 as illustrated. The change in direction of flow of the working fluid that is needed to cause it to exit via such apertures increases the degree of attenuation. The pattern and number of apertures 439 in Figure 10 is similar to that of Figure 9, but this need not necessarily be the case and many other numbers, patterns and alignments are possible. For the avoidance of doubt, the attenuation enhancing features of Figures 7 to 10 are optional and they may be provided in any viable combination with one another if desired. Consequently for instance the angled apertures 439 of Figure 10 may be provided in combination with the jetting shield 59 of Figure 9. More generally, this disclosure extends to all reasonable combinations of features as would be apparent to the person of skill in the art. Overall the invention provides a number of unexpected advantages, as identified above. The listing or discussion of an apparently prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge. Preferences and options for a given aspect, feature or parameter of the invention should, unless the context indicates otherwise, be regarded as having been disclosed in combination with any and all preferences and options for all other aspects, features and parameters of the invention.

Claims

CLAIMS 1. An elevator buffer comprising a base member defining an in-use upwardly extending base recess for receiving part of a compressible energy absorber; a cap that in use is located above the base member, the cap defining one or more reaction surface for a resiliently deformable member and a further, downwardly extending cap recess for receiving part of a compressible energy absorber; a compressible energy absorber having respective sections received in the base recess and the cap recess; at least one wall extending between the base recess and the cap recess, the at least one wall being formed of or including a plastics material and defining a closed reservoir, for fluid, extending between the base member and the cap, an aperture extending through the cap, the compressible energy absorber including extending therefrom through the aperture a rod, the rod including or having secured thereto a reaction member that in use is spaced from the or each reaction surface; and the elevator buffer including extending between the reaction member and the or each reaction surface a compressible, resiliently deformable member.

2. An elevator buffer according to Claim 1 wherein the at least one wall surrounds the compressible energy absorber over at least part of its length between the base recess and the cap recess.

3. An elevator buffer according to Claim 1 or Claim 2 wherein the at least one wall includes or is constituted by respective lower and upper wall sections, the lower wall section extending upwardly from the base member, and the upper wall section extending downwardly from the cap.

4. An elevator buffer according to Claim 3 wherein the lower wall section defines an upwardly facing, peripheral wall edge and the upper wall section defines a downwardly facing, peripheral wall edge, the upwardly and downwardly facing wall edges being of the same size and shape, and being in contact with one another about a periphery of the reservoir whereby to provide an uninterrupted wall section in the vicinity of the upwardly and downwardly facing wall edges; and the upper and lower wall sections being secured one to the other.

5. An elevator buffer according to Claim 4 including an adhesive material on one or both of the upwardly and downwardly facing wall edges whereby to secure the upper and lower wall sections one to the other.

6. An elevator buffer according to any of Claims 3 to 5, wherein one of the lower and upper wall sections includes a relatively large area end section and the other of the lower and upper wall sections includes a relatively small area end section whereby the relatively small area end section is receivable within the relatively large area end section in a manner locating the upper and lower wall sections relative to one another to define the at least one wall.

7. An elevator buffer according to Claim 6 wherein the relatively small area end section is a friction, press, weld or interference fit within the relatively large area end section.

8. An elevator buffer according to any of Claims 1 to 4 including at least one intermediate wall member extending between the base recess and the cap recess in order to define at least part of the length of the closed reservoir.

9. An elevator buffer according to Claim 8 when depending from Claim 3 wherein the intermediate wall member interconnects the lower and upper wall sections.

10. An elevator buffer according to Claim 9 wherein the lower wall section defines an upwardly facing, peripheral wall edge and the upper wall section defines a downwardly facing, peripheral wall edge, wherein the intermediate wall member defines at each of its ends a respective intermediate wall end having a wall end edge that is, about a periphery of the reservoir, in contact with, secured to and of the same respective size and shape as at least one of the upwardly facing and downwardly facing wall edges whereby to provide uninterrupted wall sections in the respective vicinities of the wall end edges.

11. An elevator buffer according to Claim 10 including an adhesive material on at least one of the upwardly facing, peripheral wall edge, the downwardly facing, peripheral wall edge and one or more said wall end edges whereby to secure elements defining the closed reservoir one to another.

12. An elevator buffer according to Claim 10 or Claim 11 wherein the shape and dimensions of the lower wall section and the intermediate wall member adjacent thereto are such that the one is receivable within the other in a manner locating the lower wall section and the intermediate wall member relative to one another to define part of the at least one wall.

13. An elevator buffer according to any of Claims 10 to 11 wherein the shape and dimensions of the upper wall section and the intermediate wall member adjacent thereto are such that the one is receivable within the other in a manner locating the upper wall section and the intermediate wall member relative to one another to define part of the at least one wall.

14. An elevator buffer according to any preceding claim including a foot defined at or near its in-use lowermost end; and one or more rib or fillet extending between and secured to the foot and the upwardly extending base recess.

15. An elevator buffer according to any preceding claim wherein the compressible energy absorber is or includes a fluidics energy absorber that in use contains an energy-dissipating fluid.

16. An elevator buffer according to Claim 15 wherein the fluid reservoir contains an in-use energy dissipating fluid and wherein the buffer includes one or more conduit via which energy dissipating fluid may be fed between the fluid reservoir and the compressible energy absorber.

17. An elevator buffer according to Claim 15 or Claim 16 wherein the energy dissipating fluid is selected from the list including an oil; and water.

18. An elevator buffer according to any preceding claim wherein the compressible energy absorber additionally includes a hollow, metering chamber that is received over at least part of its length within the fluid reservoir and, secured to the rod, a piston that is sealingly movably received within the metering chamber, the metering chamber including one or more apertures opening into the interior of the metering chamber and on the exterior of the metering chamber thereby interconnecting the interior and exterior of the metering chamber; and the resiliently deformable member in the absence of applied force conferring a biassing force biassing the piston towards an in- use upper part of the metering chamber, the arrangement being such that on application of force to the rod longitudinally to compress the compressible energy absorber the piston moves towards an in-use lower part of the metering chamber against force generated by the resiliently deformable member while expelling fluid from the metering chamber to the fluid reservoir via the one or more apertures; and on reduction of the applied force to below the magnitude of the biassing force theresiliently deformable member biases the piston back towards the upper part of the metering chamber.

19. An elevator buffer according to Claim 18 including a plurality of the apertures formed spaced apart from one another about a periphery defined by the metering chamber and / or along a length defined longitudinally along the metering chamber.

20. An elevator buffer according to Claim 19 wherein at least one said aperture is of lesser cross-sectional area at its opening into the interior of the metering chamber than at its opening at the exterior of the metering chamber.

21. A buffer according to any of Claims 18 to 20 including within the fluid reservoir externally of the metering chamber one or more energy dissipating elements that on longitudinal compression of the compressible energy absorber are contacted by fluid expelled via one or more said aperture in a manner dissipating energy in the energy dissipating fluid.

22. A buffer according to Claim 21 wherein the one or more energy dissipating elements is selected from the list including one or more baffles positioned to intersect and reactively reduce the energy of fluid expelled via the one or more aperture during compression of the compressible energy absorber; and one or more rings rotatably retained relative to the exterior of the metering chamber and including one or more vanes positioned to intersect and reduce through rotative acceleration of the one or more rings the energy of fluid expelled via the one or more baffles during compression of the compressible energy absorber.

23. A buffer according to any of Claims 18 to 22 wherein at least one said aperture is angled relative to the in-use horizontal whereby reactively to dissipate energy in fluid expelled via the one or more aperture during compression of the compressible energy absorber.

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