Rotatable hitch for lift sheave

Abstract: A rotatable hitch (30) for securing a lift sheave to a frame element (10), including a hollow sleeve (50), first coupling means (54) for coupling the hollow sleeve to the lift sheave, second coupling means (52) for coupling the hollow sleeve to the frame element, a connecting rod (60) arranged within the hollow sleeve; third coupling means (68) for coupling the connecting rod to the lift sheave, and fourth coupling means (72) for coupling the connecting rod to the frame element, the hollow sleeve being rotatable relative to the frame element and/or the lift sheave when installed between the lift sheave and the frame element, to enable rotation of the lift sheave relative to the frame element.

Description: This invention relates to a rotatable hitch for securing a lift sheave to a frame element. Lift sheaves are rotatably connected to a frame element which may comprise car frame cross-head channels connected to a lift car or an overhead beam fixed in a lift well, to facilitate movement of the lift car in the lift well. The rotatable hitch allows the lift sheave to be orientated into a desired orientation relative to the frame member during installation and also allows a very slight amount of rotation of the lift sheave relative to the frame element during use dependent upon the load applied by a cable as the cable is wound onto and wound off the lift sheave, particularly at the extremities of the movement of the lift car. This angle of rotation may be as small as 1°. Some Government regulations also require the rotatable hitch to be secured at two locations to provide for failsafe connection in the event that one of the couplings of the sheave fails during use of the lift. A rotatable hitch for securing a lift sleave to a frame element is already known for example from US-A-5 564 530. The present invention in a first aspect provides a rotatable hitch for securing a lift sheave to a frame element, including: a hollow sleeve; first coupling means for coupling the hollow sleeve to the lift sheave; second coupling means for coupling the hollow sleeve to the frame element; a connecting rod arranged within the hollow sleeve; third coupling means for coupling the connecting rod to the lift sheave; and fourth coupling means for coupling the connecting rod to the frame element; the hollow sleeve being rotatable relative to the frame element and/or the lift sheave when installed between the lift sheave and the frame element, to enable rotation of the lift sheave relative to the frame element. In one embodiment the said first and second coupling means comprise nuts on the hollow sleeve for engaging an abutment member on the lift sheave and frame element respectively, the nuts engaging and abutting the abutment members so as to secure the hitch to the lift sheave and the frame element. In another embodiment, the first or second coupling means may comprise a screw-thread on the lift sheave or frame element and a cooperating screw-thread on the hollow sleeve for engaging the screw-thread on the lift sheave or frame element. Preferably the third and fourth coupling means comprise nuts on the connecting rod, the nuts engaging respective retaining plates and sandwiching the retaining plates between the respective nuts and respective ends of the hollow sleeve. Preferably the said retaining plates comprise washers. Preferably the lift sheave includes a pair of brackets which support a connecting plate, the connecting plate having a hole and the hollow sleeve passing through the hole to rotatably couple the lift sheave to the frame element. The invention in another aspect provides a lift system as claimed in claim 7. In one embodiment, both of the support members of the lift sheave and frame element have a hole and the hollow sleeve extends through each of the holes in the support members to that both free ends of the hollow sleeve project through the support members, and the first and second coupling members comprise nuts on the hollow sleeve for engaging the support members on the lift sheave and frame element respectively, the nuts abutting the support members so as to connect the hitch to the lift sheave and the frame element. In this embodiment of the invention, the support members may comprise abutment plates against which the nuts abut to couple the hollow sleeve to the lift sheave and frame element. In another embodiment of the invention, one free end of the hollow sleeve can be secured to the support member of the lift sheave or frame element so as to be a substantially rigid connection. In this arrangement, the substantially rigid connection can be formed by a screw-thread in a hole in the support member and a cooperating screw-thread on the free end of the hollow sleeve, the hollow sleeve being screwed into the hole to couple the hollow sleeve to the support member and thereby to the lift sheave or frame element. Preferably the third and fourth coupling members comprise nuts on the connecting rod, the nuts engaging respective retaining plates and sandwiching the retaining plates between the respective nuts and respective ends of the hollow sleeve. Preferably the retaining plates comprise washers. Preferably the lift sheave includes lift sheave brackets and the said support member of the lift sheave comprises a connecting plate connected between the lift sheave brackets. Preferably the said support member of the frame element comprises a plate connected to the frame element. Some embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a view of a rotatable hitch according to the invention applied to a car frame of a lift system; Figure 2 is a view of a rotatable hitch applied to an overhead suspended sheave of a lift system; Figure 3 is an exploded view of the rotatable hitch of Figures 1 and 2; and Figure 4 is a cross-sectional view of the rotatable hitch as used in Figure 1. With reference to Figure 1, a pair of car frame cross-head channels 10 are coupled to a lift car (not shown). A lift sheave 20 is connected to the cross-head channels 10 by a rotatable hitch 30 according to one embodiment of the invention. The lift sheave 20 includes a pair of lift sheave brackets 22 which support a connecting abutment plate 24. Top and bottom plates 26 and 28 are secured to the cross-head channels 10 and the hitch 30 passes through holes in the plates 26 and 28 as well as a hole in the connecting plate 24. In the embodiment of Figure 2, a fixed overhead beam 40 is secured in a lift well and includes a top plate 41 which supports connecting brackets 42 which in turn support a connecting plate 46. A sheave 20 is supported below the overhead beam 40 by a rotatable hitch 30 which is substantially the same as the hitch 30 described with reference to Figure 1. As in Figure 1, the sheave 20 includes brackets 22 and a connecting plate 24 between the brackets 22. The hitch 30 will be described in more detail with reference to Figures 3 and 4. As is shown in Figures 3 and 4, the hitch 30 includes a hollow outer sleeve or bolt 50 which has a nut 52 for screw-threaded engagement at one free end 51 of the sleeve 50. A nut 54 is provided for screw-engagement with the other free end 53 of the sleeve 50. A connecting rod 60 is arranged within the hollow sleeve 50 and has ends 62 and 64 which project outwardly of the free ends 51, 53 of the sleeve 50. A large washer 66 is provided on the connecting rod 60 for location adjacent end 62. A small nut 68 is screw-threaded to the end 62. A second large washer 70 is provided for location on end 64 of the rod 60 which projects from the lower free end of the sleeve 50 as shown in Figure 1 and a nut 72 is provided for screw-threaded engagement with the end 64 of the rod 60. As shown with reference to Figure 4, the connecting plate 24 is secured between the sheave brackets 22 and a rotatable sheave member 23 is rotatably mounted between the brackets 22 for receiving a cable (not shown) for allowing a lift car to be raised and lowered in a lift well. The connecting plate 24 has a hole 29. The cross-head channels 10 support upper and lower plates 26 and 28 as previously described. The plates 26 and 28 may be bolted to the channels 10 by bolts (not shown). The plates 26 and 28 have holes 31 and 33. The sleeve 50 extends through the holes 29, 31 and 33 with the ends 53 and 51 respectively projecting upwardly from the hole 29 and down below the hole 33, all as also shown in Figure 4. After the sleeve 50 has been located through the holes 29, 31 and 33, the large nut 54 is secured in place by screw-threading it onto the end 53 of the sleeve 50. The nut 54 is of larger diameter than the hole 29 and therefore engages the plate 24 and couples the sleeve 50 to the lift sheave 20 by virtue of its abutment with the connecting plate 24. The nut 54 prevents the free end 53 of the sleeve 50 from being withdrawn through the hole 29. The nut 52 is then screw-threaded onto the free end 51 of the sleeve 50 and abuts the lower plate 28. Once again, the nut 52 is of larger diameter than the hole 33 and couples the sleeve 50 to the cross-head channels 10 and prevents the free end 51 of the sleeve 50 from being withdrawn through the hole 33. As shown in Figure 4, a locknut 57 may also be located on the end 51 of the sleeve 50. A spacer sleeve 61 may be provided between the connecting plate 24 and the top plate 26 and on the sleeve 50 for spacing the sheave 20 from the cross-head channels 10. The sleeve 50 is rotatable in the holes 29, 31 and 33 so as to enable the sheave 20 to be easily rotated into a desired orientation during installation. During use of the lift system, the sheave is able to rotate slightly relative to the cross-head channels 10 if the load applied by the cable is sufficiently great, particularly at extreme ends of the lift movement. The sleeve 50 and nuts 52 and 54 provide a primary connection of the sheave 20 to the cross-head channels 10. The connecting rod 60 is arranged within the hollow sleeve 50 and the ends 64 and 62 thereof project outwardly of the sleeve 50 as is clearly shown in Figure 4. The connecting rod 60 may be a screw-threaded rod formed from high tensile material. Large washer 66 is arranged so that it abuts the end 53 of the hollow sleeve 50 and the washer 66 is retained in place by the small nut 68 which is screw-threaded onto the end 62 of the rod 60. The washer 70 is arranged on the other free end 64 of the connecting rod 60 and abuts the other end 51 of the sleeve 50. The washer 70 is located in place by the small nut 72 which is screw-threaded onto the free end 64 of the rod 60. A locking nut 75 may also be screw-threaded onto the free end 64 if desired. The washers 66 and 70 are dimensioned so that they are larger than the holes 29 and 33 and therefore cannot be pulled through those holes. The connecting rod 60 and the washer 66 and nut 68 and the washer 70 and nut 72 form a secondary connection of the sheave 20 to the cross-head channels 10. If the primary connection formed by the hollow sleeve is operating correctly, then no load is taken by the secondary connection formed by the connecting rod 60. In practice, the integrity of the primary coupling can be checked by simply determining whether the connecting rod 60 takes any load by gripping the connecting rod 60 in the vicinity of one of the nuts 68 or 72 and determining whether the connecting rod can be rotated or moved showing that it takes no load. The connecting rod 60 will only take load in the event that the primary connection formed by the hollow sleeve 50 fails for some reason. Thus, should the primary connection formed by the hollow sleeve 50 and nuts 54 and 52 fail, then the sheave 20 will remain connected to the cross-head channels 10 by the secondary connection formed from the high tensile rod 60, the washers 66 and 70 and the small nuts 68 and 72. The illustrated embodiment of the invention therefore provides primary and secondary coupling of the sheave 20 and cross-head channels 10. The hitch 30 shown in Figure 2 is of the same structure as the hitch described in detail with reference to Figures 3 and 4. The only difference is that the hitch 30 as shown in Figure 2 is arranged between the overhead beam 40 and the suspended sheave 20. In this arrangement, the connecting plate 46 supported by the brackets 42 replaces the bottom plate 38 and the hitch 30 is generally inverted from the position described with reference to Figures 1 and 4. The illustrated embodiment of the invention therefore provide a rotatable hitch and lift system which enable rotation of the hitch 30 relative to a frame member 10 as well as primary and secondary coupling of the hitch to the frame member and sheave. In another embodiment of the invention, the nut 54 can be done away with and the hollow sleeve 50 coupled to the plate 24 by providing a screw-thread in the hole 29 and a cooperating screw thread on the sleeve 50 to engage the screw-thread in the hole 29. Thus, the hollow sleeve is screw-threaded onto the plate 24 to form a substantially rigid coupling of the sleeve 50 to the lift sheave 20. This arrangement does away with the nut 54 and therefore enables the height of the system to be reduced. Rotation of the sheave 20 relative to the cross-head channels 10 takes place by virtue of the ability of the sleeve 50 to rotate in the holes 31 and 33. In this arrangement, the sleeve 50 could also be tack welded to the plate 24. In yet a further embodiment, the screw-thread engagement of the sleeve 50 could be at the lower end of the arrangement shown in Figure 4 by providing a screw-thread in the hole 33. In this arrangement, the upper end of the rotatable hitch 30 would be as per the description of Figure 4 to provide for the relative rotation of the cross- head channels 10 and the sheave 20.

Claims: A rotatable hitch (30) for securing a lift sheave (20) to a frame element (10), including: a hollow sleeve (50); first coupling means (54) for coupling the hollow sleeve to the lift sheave; second coupling means (52) for coupling the hollow sleeve to the frame element; a connecting rod (60) arranged within the hollow sleeve; third coupling means (68) for coupling the connecting rod to the lift sheave; and fourth coupling means (72) for coupling the connecting rod to the frame element; the hollow sleeve being rotatable relative to the frame element and/or the lift sheave when installed between the lift sheave and the frame element, to enable rotation of the lift sheave relative to the frame element. A hitch as claimed in claim 1, wherein the said first and second coupling means comprise nuts (54,52) on the hollow sleeve (50) for engaging an abutment member (24,28) on the lift sheave (20) and frame element (10) respectively, the nuts engaging and abutting the said abutment members so as to secure the hitch to the lift sheave and the frame element. A hitch as claimed in claim 1 or 2, wherein the said third and fourth coupling means comprise nuts (68, 72) on the connecting rod (60), the nuts engaging respective retaining plates (66,70) and sandwiching the retaining plates between the respective nuts and respective ends of the hollow sleeve (50). A hitch as claimed in claim 3, wherein the said retaining plates comprise washers (66,70). A hitch as claimed in any preceding claim, in combination with a lift sheave (20) which includes a pair of brackets (22) which support a connecting plate (24), the connecting plate having a hole (29) and the hollow sleeve (50) passing through the hole to rotatably couple the lift sheave to the frame element (10). A hitch as claimed in claim 1, wherein the said first or second coupling means comprises a screw-thread on the lift sheave (20) or frame element (10) and a cooperating screw-thread on the hollow sleeve (50) for engaging the screw-thread on the lift sheave or frame element. A lift system including: a lift sheave (20) having a support member (24); a frame element (10) having a support member (28) ; a rotatable hitch (30) as claimed in claim 1 for securing said lift sheave (20) to said frame element (10); and a hole (29,33) in at least one of the said support members of the lift sheave and frame element; wherein: said hollow sleeve (50) of said hitch (30) extends through the hole in the support member so that a free end (53,51) of the hollow sleeve projects through the hole; said first coupling means of said hitch comprises a first coupling member (54,52) on the free end of the hollow sleeve for preventing the hollow sleeve from being withdrawn through the hole and for coupling the sleeve to the lift sheave or frame element which has the hole; said second coupling means of said hitch comprises a second coupling member (54,52) on the other free end of the hollow sleeve for coupling the sleeve to the other of the lift sheave or frame element; said third coupling means (68) of said hitch is arranged at one end (62) of the connecting rod for coupling the connecting rod to the lift sheave; said fourth coupling means (72) of said hitch (30) is arranged at the other end (64) of the connecting rod for coupling the connecting rod to the frame element; and the sleeve of said hitch (30) being rotatable in the hole so as to enable the lift sheave to rotate relative to the frame element. A lift system as claimed in claim 7, wherein the said first and second coupling members comprise nuts (54,52) on the said hollow sleeve (50) for engaging the said support members (24,28) on the lift sheave (20) and frame element (10) respectively, the nuts abutting the support members so as to connect the hitch to the lift sheave and the frame element. A lift system as claimed in claim 7 or 8, wherein the said third and fourth coupling means comprise nuts (68,72) on the connecting rod (60), the nuts engaging respective retaining plates (66,70) and sandwiching the retaining plates between the respective nuts and respective ends (53,51) of the hollow sleeve (50). A lift system as claimed in claim 9, wherein the said retaining plates comprise washers (66,70). A lift system as claimed in any of claims 7 to 10, wherein the lift sheave (20) includes lift sheave brackets (22) and the said support member of the lift sheave comprises a connecting plate (24) connected between the lift sheave brackets. A lift system as claimed in any of claims 7 to 11, wherein the said support member of the frame element (10) comprises a plate (28) connected to the frame element. A lift system as claimed in claim 7, wherein one free end of the said hollow sleeve (50) is secured to the said support member (24,28) of either the lift sheave or frame element so as to be a substantially rigid connection. A lift system as claimed in claim 13, wherein the said substantially rigid connection is formed by a screw-thread in a hole (29,30) in the said support member (24,28) and a cooperating screw-thread on the end of the hollow sleeve (50), the hollow sleeve being screwed into the hole to couple the hollow sleeve to the support member and thereby to the lift sheave or frame element.

Inventors: RIDLEY STEVEN JOHN, RIDLEY, STEVEN JOHN
Applicants: OTIS ELEVATOR CO, OTIS ELEVATOR COMPANY
Application year: 1999
Main classification: B66B7
IPC codes: B66B7