Patent Description:
The present invention relates generally to lift assemblies, such as those used to raise and lower scenery, props, and lighting on a stage.

Performance venues such as theaters, arenas, concert halls, auditoriums, schools, clubs, convention centers, and television studios can employ battens or trusses to suspend, elevate, and/or lower lighting, scenery, draperies, and other equipment that can be moved relative to a stage or floor. These battens are often raised or lowered by lift systems.

Conventional lift systems commonly include an overhead pulley, or loft block, supported by an overhead building support. Ropes or cables extend from the batten and through the loft blocks to a drive mechanism that facilitates movement of the cables. Such drive mechanisms often include a motor-driven drum that winds and unwinds the cables.

In order to insure that the lift system does not exceed capacity, some lift systems include means for measuring the load on the system. In the event that the load is exceeded, the motor can be deactivated or a warning can be generated. <CIT> discloses a lift assembly with a drum rotatably mounted to a frame and linearly translatable with respect to the frame. This document discloses the preamble of claim <NUM>.

The present invention provides a lift assembly as claimed.

The present disclosure provides a lift assembly according to claim <NUM>.

Preferably, the first sheave plate is positioned at least partially directly below the second sheave plate. In this embodiment, the lift assembly can further comprise first and second sheave brackets for coupling the first and second sheaves to the first and second sheave mounts. The first sheave plate can further include an opening, and at least a portion of the second sheave bracket can be positioned in the opening.

The first sheave plate can further include an unused sheave mount adjacent the opening and substantially below the second sheave mount. The unused sheave mount is configured to allow mounting of the second sheave to the first sheave plate to thereby facilitate changing the direction of the second flexible element. Furthermore, the second sheave plate can include an unused sheave mount directly above the first sheave mount. This unused sheave mount is configured to allow mounting of the first sheave to the second sheave plate to thereby facilitate changing the direction of the first flexible element.

In another aspect, the present disclosure may provide a lift assembly comprising a base, a drive mechanism, a flexible drive element driven by the drive mechanism and extending from the drive mechanism along a fleet axis, and a sheave directing the drive element from the fleet axis to an output axis different than the fleet axis. The sheave is coupled to the base at a first sheave mount aligned with the fleet axis. For example, the sheave can be coupled to the sheave mount by a sheave bracket that positions the sheave with an edge of the sheave aligned with the fleet axis.

The present disclosure includes a second sheave mount aligned with the fleet axis. The second sheave mount is configured to be coupled to the sheave to thereby allow the sheave to be de-coupled from the first sheave mount and coupled to the second sheave mount. The second sheave mount is positioned such that coupling of the sheave to the second sheave mount results in substantially no change in a fleet angle of the fleet axis.

In the present disclosure, the sheave is positioned on a first side of the fleet axis when coupled to the first sheave mount, and the sheave is positioned on a second side of the fleet axis when coupled to the second sheave mount, the second side being substantially opposed to the first side. Preferably, the fleet axis substantially bisects the first and second sheave mounts.

The invention is not limited in its application to the details of the following drawings and embodiments of the description but limited to the scope as defined by the claims.

<FIG> illustrate a lift assembly <NUM> including a base <NUM> and a take-up mechanism <NUM> that is mounted to the base <NUM>. The base <NUM> includes a frame <NUM> and side panels <NUM> that are secured to the frame <NUM>. The frame <NUM> provides a stable location for mounting the various internal components of the assembly <NUM>, and the panels <NUM> provide a barrier for inhibiting contamination of and unauthorized access to the internal components and the panels <NUM> can also be sound deadening panels.

The base <NUM> further includes a first side <NUM>, a second side <NUM>, a first end <NUM>, and a second end <NUM> that are defined by the frame <NUM> and the panels <NUM>. The first side <NUM> and the second side <NUM> are parallel and face opposite directions and the first end <NUM> and the second end <NUM> are parallel and face opposite directions. The first and second sides <NUM>, <NUM> extend along the length of the assembly <NUM> and a longitudinal axis or centerline <NUM> of the assembly <NUM> extends midway between the sides <NUM>, <NUM> and bisecting the ends <NUM>, <NUM>. A length or longitudinal extent of the assembly <NUM> is the distance from the first end <NUM> to the second end <NUM> along the axis <NUM>.

The base <NUM> further includes a first outlet <NUM> and a second outlet <NUM>, the purpose of which will be discussed in more detail below. The first outlet <NUM> is located through the first end <NUM> of the base <NUM> and is positioned closer to the first side <NUM> than to the second side <NUM>. Alternatively stated, the first outlet <NUM> is offset from the centerline <NUM> toward the first side <NUM> of the base <NUM>. The second outlet <NUM> is located through the second end <NUM> of the base <NUM> and is positioned closer to the first side <NUM> of the base <NUM> than the second side <NUM>. Similar to the first outlet <NUM>, the second outlet <NUM> is offset from the centerline <NUM> toward the first side <NUM> of the base <NUM>.

Referring to <FIG> and <FIG>, the lift assembly <NUM> further includes flexible drive elements 40A - <NUM>. Each of the flexible drive elements 40A - <NUM> is essentially the same (the only difference being their respective length), and only one flexible drive element 40A will be described in detail. Like portions of the drive elements 40A - <NUM> have been give the same reference number with the suffix A - H, respectively. The flexible drive element 40A includes a stored portion 42A that is on the take-up mechanism <NUM> and a free portion 44A that extends from the take-up mechanism <NUM> through the outlet <NUM>. The free portion 44A that extends through the outlet <NUM> is closer to the first side <NUM> of the base <NUM> than to the second side <NUM>. That is, the free portion 44A is offset from the centerline <NUM> of the base <NUM> is a direction toward the first side <NUM>. Together the flexible drive elements 40A - <NUM> extend through the outlet <NUM> to define a cable path <NUM> having a cable path width <NUM> (see <FIG>). The cable path <NUM> is offset from the centerline <NUM> of the base <NUM> in a direction toward the first side <NUM>. In the illustrated embodiment, the entire cable path <NUM> (i.e., all of the flexible drive elements 40A - <NUM>) exiting the outlet <NUM> is located between the first side <NUM> and the centerline <NUM>. In other embodiments, a portion of the cable path <NUM> can be on the other side of the centerline <NUM> (i.e., between the centerline <NUM> and the second side <NUM>). Also, in the illustrated embodiment, all of the flexible drive elements 40A - <NUM> in the cable path are flush in a direction perpendicular to the cable path <NUM>, such that the cable path <NUM> is flat and the flexible drive elements 40A - <NUM> are co-planar. In the illustrated embodiment, the flexible drive elements 40A - <NUM> are cables, such as a twisted wire cables with multiple strands, but in other embodiment, other suitable flexible drive elements may be utilized, such as, chains, ropes, and the like.

As illustrated in <FIG>, in one application of the lift assembly <NUM>, the free portions 44A - <NUM> of the flexible drive elements 40A - <NUM> are routed to loft blocks <NUM> that change the direction of the flexible drive elements 40A - <NUM> and then routed to a batten <NUM> or the like to raise and lower an article <NUM> such as scenery, props, and lighting on a stage.

Referring to <FIG>, the take-up mechanism <NUM> includes a drive mechanism <NUM> and a drum assembly <NUM>. The drive mechanism <NUM> includes an electric motor <NUM>, a transmission <NUM>, and a drive shaft <NUM>. The transmission connects the motor <NUM> and the drive shaft <NUM> such that operation of the motor <NUM> rotates the drive shaft <NUM> in the clockwise and counterclockwise directions. The drum assembly <NUM> is coupled to the drive shaft <NUM>, such that rotation of the drive shaft <NUM> by the motor <NUM> rotates the drum assembly <NUM> in the clockwise and counterclockwise directions. In the illustrated embodiment, the drum <NUM> and the drive shaft <NUM> move axially along the longitudinal axis <NUM> of the base <NUM>, the purpose of which will discussed in more detail below.

Referring to <FIG> and <FIG>, the drum assembly <NUM> includes drum segments 60A - <NUM>. The drum segments 60A - <NUM> correspond to the flexible drive elements 40A - <NUM>. That is, the flexible drive element 40A winds around drum segment 60A, the flexible drive element 40B winds around drum segment 60B, etc. The drum segments 60A - <NUM> are substantially the same and like components have been given like reference numbers with the suffix A - H, which corresponds to the drum segments 60A - <NUM>. The drum segment 60A includes a first end 62A and a second end 64A. The first end 62A has a diameter 66A and the second end 64A has a diameter 68A that is larger than the diameter 66A. The diameter of the drum segment 60A constantly increases from the first end 62A to the second end 64A. Therefore, a large diameter portion 70A of the drum segment 60A is located adjacent the second end 64A, a small diameter portion 72A is located adjacent the first end 62A, and a tapered portion 74A is located between the small diameter portion 72A and the large diameter portion 70A.

The drum segments 60A - <NUM> are coupled to the drive shaft <NUM> as best seen in <FIG>. The first end 62B of the second drum segment 60B having the small diameter 66B abuts the second end 64A of the first drum segment 60A having the large diameter 68A. Likewise, the first end 62C of the third drum segment 60C having the small diameter 66B abuts the second end 64B of the second drum segment 60B having the large diameter 68B. The remainder of the drum segments 60D - <NUM> are similarly arranged along the drive shaft <NUM>.

The drum segments 60A - <NUM> all includes grooves 76A - <NUM>, respectively, that extend circumferentially around the drum segments 60A - <NUM>. The grooves 76A - <NUM> receive the respective flexible drive elements 40A - <NUM> to facilitate winding the flexible drive elements 40A - <NUM> around the drum assembly <NUM>.

Referring to <FIG>, the lift assembly further includes internal sheaves 80A - <NUM>. The internal sheave 80A corresponds to the drum segment 60A and the flexible drive element 40A, the internal sheave 80B corresponds to the drum segment 60B and the flexible drive element 40B, etc. The sheaves 80A - <NUM> direct the corresponding flexible drive element 40A - <NUM> from the corresponding drum segment 60A - <NUM> to the outlet <NUM>. A head block <NUM> is located adjacent the outlet <NUM>. The head block <NUM> includes a plurality of rollers <NUM> that guide the flexible drive elements 40A - <NUM>. In the illustrated embodiment, the internal sheaves 80A - <NUM> can be configured to route the flexible drive elements 80A - <NUM> through the first outlet <NUM> and the second outlet <NUM>. When any of the flexible drive elements 80A - <NUM> are routed through the second outlet <NUM> a second head block, similar to head block <NUM>, would be located adjacent the second outlet <NUM>.

With continued reference to <FIG>, the illustrated lift assembly <NUM> includes a threaded rod <NUM> located at an end of the shaft <NUM>. The rod <NUM> is fixed relative to the frame <NUM>. The shaft <NUM> is generally hollow and the threaded rob <NUM> is received in a threaded recess of the shaft <NUM>. As the shaft <NUM> rotates relative to the rod <NUM> (which is fixed relative to the frame <NUM>) the shaft <NUM> and drum assembly <NUM> (which is fixed relative to the shaft <NUM>) move relative to the internal sheaves 80A-<NUM> along the longitudinal axis <NUM> to facilitate winding and unwinding the flexible drive elements 40A - <NUM> around the drum assembly <NUM>.

In operation, the motor <NUM> rotates the drive shaft <NUM> to wind and unwind the flexible drive elements 40A - <NUM> around the drum assembly <NUM> to raise and lower the free portions 44A - <NUM> of the flexible drive elements 40A - <NUM>, which raises and lowers an article, such as scenery, props, lighting, and the like that are attached to the free portions 44A - <NUM>. As best seen in <FIG>, when raising the article, the flexible drive elements 40A - <NUM> wrap around the corresponding drum segment 60A - <NUM> in the corresponding grooves 76A - <NUM>. The first flexible drive element 40A starts wrapping around the segment 60A in the grooves 76A in the small diameter portion 72A of the segment 60A. Meanwhile, the second flexible drive element 40B starts wrapping around the drum segment 60B in the grooves 76B in the small diameter portion 72B of the drum segment 60B. The additional flexible drive elements 40C - <NUM> likewise wrap around the corresponding drum segments 60C - <NUM>.

The flexible drive element 40B is wrapped onto the small diameter portion 72B of the drum segment 60B to define an outer profile or outer diameter that is substantially flush with the large diameter portion 70A of the drum segment 60A. As the flexible drive element 40A continues to wind onto the drum segment 60A, the additional stored portion 42A moves in a direction toward the drum segment 60B because the drum assembly <NUM> moves relative to the frame <NUM> along the longitudinal axis <NUM>. Eventually, the flexible drive element 40A wraps around the drum segment 60A until it reaches the second end 64A of the drum segment 60A, and as the flexible drive element 40A continues to wind around the drum assembly <NUM>, the flexible drive element 40A overlaps onto the outer profile created by the flexible drive element 40B. As discussed above, the outer profile of the drive element 40B is flush with the second end 64A of the drum segment 60A, and therefore the drive element 40A smoothly transitions from wrapping around the segment 60A and onto the segment 60B. As illustrated in <FIG>, the other flexible drive elements 40B - <NUM> similarly overlap onto the adjacent drum segment 60B - <NUM>. Because segment <NUM> is the final drum segment there is no adjacent segment for drive element <NUM> to wrap onto and around. Therefore, drum segment <NUM> is longer and has a longer tapered portion <NUM> than the other drum segments 60A - <NUM>.

As illustrated in <FIG> and <FIG>, multiple lift assemblies <NUM>, <NUM>, and <NUM> can be mounted adjacent to each other and together the lift assemblies <NUM>, <NUM>, <NUM> can be mounted to a structure, such as a ceiling, a floor, walls, or other suitably stable component. Each of the illustrated lift assemblies <NUM>, <NUM>, and <NUM> is structurally identical to the other lift assemblies <NUM>, <NUM>, and <NUM> and identical to the lift assembly <NUM> described above with regard to <FIG> and therefore like components have been given like reference numbers plus <NUM>. Each has lift assembly <NUM>, <NUM>, and <NUM> has its own position or orientation, as described below in more detail.

With continued reference to <FIG> and <FIG>, the second side <NUM> of the first lift assembly <NUM> is positioned adjacent the first side <NUM> of the second lift assembly <NUM>. In the illustrated embodiment, the second side <NUM> of the lift assembly <NUM> abuts the first side <NUM> of the lift assembly <NUM>. Also, the ends <NUM>, <NUM> and <NUM>, <NUM> are aligned and flush as illustrated. Therefore, the cable path <NUM> and the cable path <NUM> extend in the same direction and are parallel. As illustrated in <FIG> and <FIG>, the cable path <NUM> exiting the base <NUM> of the first lift assembly <NUM> is spaced a distance <NUM> from the cable path <NUM> exiting the base <NUM> of the second lift assembly <NUM>.

The second end <NUM> of the base <NUM> of the third lift assembly <NUM> abuts the first end <NUM> of the first lift assembly <NUM> and the first end <NUM> of the second lift assembly <NUM> to define a pyramid arrangement with the third lift assembly <NUM> forming a peak of the pyramid. The third lift assembly <NUM> is positioned so that the cable path <NUM> is between in the cable paths <NUM>, <NUM> and located in the space <NUM>. The cable path <NUM> extends in the same direction as the cable paths <NUM>, <NUM> and parallel to the paths <NUM>, <NUM> and the cable paths <NUM>, <NUM>, <NUM> are co-planar. Together the cable paths <NUM>, <NUM>, <NUM> define a total cable path width <NUM>. In the illustrated embodiment that includes three lift assemblies <NUM>, <NUM>, <NUM>, the total cable path width <NUM> is only about <NUM> times greater than the width <NUM> of a single cable path <NUM>, <NUM>, <NUM>. In other embodiments, the total cable path width is between about <NUM> to <NUM> times greater than the width of a single cable path. In yet other embodiments, the total cable path width is between about <NUM> to <NUM> times greater than the width of a single cable path.

The base <NUM> of the first lift assembly <NUM> and the base <NUM> of the second lift assembly <NUM> are side-by-side to define a total width <NUM> (<FIG>) of the group of lift assemblies <NUM>, <NUM>, and <NUM>. The total cable path width <NUM> is less than the width <NUM> of the group of lift assemblies <NUM>, <NUM>, <NUM>. In some embodiments, the total cable path width <NUM> is less than <NUM> percent of the width <NUM>, and in yet other embodiments, the total cable path width <NUM> is less than <NUM> percent of the width <NUM>.

The first, second, and third lift assemblies <NUM>, <NUM>, <NUM> can be coupled using any suitable fastener or method such as bolts, welding, and the like. Also, although the illustrated third lift assembly <NUM> abuts both ends <NUM>, <NUM> of the lift assemblies <NUM>, <NUM>, respectively, in other embodiments, the end <NUM> of the third lift assembly <NUM> may abut only one of the ends <NUM>, <NUM>.

The nested arrangement of the lift assemblies <NUM>, <NUM>, <NUM>, described above, reduces the total cable path width <NUM> (compared to positioning the three lift assemblies In a side-by-side orientation). Reducing the total cable path width <NUM> is desirable because it reduces the distance required between articles lifted by the lift assemblies <NUM>, <NUM>, <NUM>. Or, if the lift assemblies <NUM>, <NUM>, <NUM> are lifting the same article, the distance between all the flexible drive elements <NUM>, <NUM>, <NUM> is reduced, which reduces the horizontal spacing required between any loft blocks that redirect the flexible drive elements <NUM>, <NUM>, <NUM> down to the article being raised and lowered.

Referring to <FIG>, the sheaves 80A-H are supported by sheave brackets 300A-H, respectively. Each sheave bracket <NUM> includes a sheave pivot <NUM> having an opening through which a sheave pin <NUM> can be positioned to allow the sheave bracket <NUM> to rotate relative to the sheave pin <NUM>. The sheave pins <NUM> are each secured to a load plate assembly <NUM>, as described below in more detail.

The load plate assembly <NUM> rests in a pocket <NUM> formed in an upper frame <NUM> that is part of the frame <NUM>. The upper frame <NUM> includes a bottom plate <NUM>, two longitudinal members <NUM>, two cross members <NUM>, and two side rails <NUM> secured to opposing outer surfaces of the longitudinal members <NUM>. The bottom plate <NUM> includes openings <NUM> through which the sheave brackets <NUM> are positioned. The side rails <NUM> include upper and lower side bearings <NUM>,<NUM> (e.g., roller bearings, <FIG>), the function of which are described below.

The load plate assembly <NUM> includes a lower bearing plate <NUM> positioned on the bottom plate <NUM>, a lower sheave plate <NUM> positioned on the lower bearing plate <NUM>, an upper bearing plate <NUM> positioned on the lower sheave plate <NUM>, and an upper sheave plate <NUM> positioned on the upper bearing plate <NUM>. In this manner, it can be seen that the lower sheave plate <NUM> is positioned directly below the upper sheave plate <NUM>. The upper and lower bearing plates <NUM>,<NUM> each includes roller bearings <NUM> positioned under each plate to facilitate longitudinal movement of the upper and lower sheave plates <NUM>,<NUM> relative to the upper frame <NUM>. The upper and lower side bearings <NUM>,<NUM> reduce friction between the upper and lower sheave plates <NUM>,<NUM> and the upper frame <NUM>.

The load plate assembly <NUM> further includes upper and lower load cells <NUM>,<NUM> and upper and lower end caps <NUM>,<NUM> sandwiched between the upper and lower sheave plates <NUM>,<NUM> and the upper and lower load cells <NUM>,<NUM>, respectively. In this manner, the upper load cell <NUM> senses a horizontal load to the right (in the Figures) on the upper sheave plate <NUM>, and the lower load cell <NUM> senses a horizontal load to the left (in the Figures) on the lower sheave plate <NUM>.

Each of the upper and lower bearing plates <NUM>,<NUM> and upper and lower sheave plates <NUM>,<NUM> includes openings <NUM> through which the upper portion of corresponding sheave brackets <NUM> can be inserted. For example, when a sheave bracket <NUM> is secured to the upper shave plate <NUM>, an upper end of the sheave bracket <NUM> will protrude through the opening <NUM> in the upper shave plate (see, e.g., <FIG> and <FIG>) and a middle portion of the shave bracket <NUM> will be positioned in the aligned openings <NUM> of the upper and lower bearing plates <NUM>,<NUM> and the lower sheave plate <NUM>.

Adjacent each opening <NUM> in the upper and lower sheave plates <NUM>,<NUM> there is provided a sheave mount (e.g., threaded holes <NUM> in the sheave plate <NUM>,<NUM> spaced from the corresponding opening <NUM>) that facilitates the securing of one of the sheave pins <NUM>. In the illustrated embodiment, the sheave mount further includes bolts <NUM> inserted through orifices <NUM> in the ends of each sheave pin <NUM> and threaded into the corresponding threaded holes <NUM> in the corresponding sheave plate <NUM>,<NUM> to secure the sheave brackets <NUM> to one of the sheave plates.

Each sheave bracket <NUM> can be secured to either the upper sheave plate <NUM> or the lower sheave plate <NUM>, depending on which direction the corresponding cable is directed. In the illustrated embodiment, four sheaves are mounted to each of the upper and lower sheave plates <NUM>,<NUM>. In particular, sheaves 80E-H that direct cables 40E-H to the right are mounted to the upper sheave plate <NUM>, and sheaves 80A-D that direct cables 40A-D to the left are mounted to the lower sheave plate <NUM>. Even though each sheave plate <NUM>,<NUM> is only supporting four sheave brackets <NUM>, each of the illustrated sheave plates <NUM>,<NUM> includes eight sheave mounts (threaded holes <NUM> in the sheave plates <NUM>, <NUM>) that are aligned vertically with the eight sheave mounts of the other sheave plate <NUM>,<NUM>. In this regard, each of the sheave brackets <NUM> can be mounted to either the upper sheave plate <NUM> or the lower sheave plate <NUM>. When switching a particular sheave bracket <NUM> from one sheave plate to the other, the sheave bracket <NUM> is rotated <NUM> degrees about a vertical axis so that the corresponding sheave <NUM> is positioned to direct the corresponding cable <NUM> in the opposite direction.

Referring to <FIG>, the mounting of each sheave <NUM> is substantially symmetrical relative to a near edge of the sheave <NUM>. In other words, rotating a sheave bracket <NUM><NUM> degrees (compare <FIG>) in order to facilitate mounting the sheave <NUM> to the other sheave plate does not substantially change the position of the corresponding cable <NUM> extending from the sheave <NUM> to the corresponding drum segment (not visible in <FIG> because the corresponding drum segment is covered with the cable <NUM>). In other words, when the sheave <NUM> is mounted on the upper sheave plate <NUM>, it is in a first orientation (<FIG>) in which the sheave <NUM> receives the cable <NUM> from the drum along a fleet axis <NUM> at a fleet angle α (angle between the fleet axis <NUM> and the axis of rotation of the drum, when view from the side, as shown in <FIG>) and redirects the cable <NUM> to an output axis <NUM>. When the sheave <NUM> is mounted on the lower sheave plate <NUM>, it is in a second orientation (<FIG>) in which the sheave <NUM> receives the cable <NUM> substantially along the same fleet axis <NUM> at substantially the same fleet angle α and redirects it to a different output axis <NUM>. This feature allows a sheave <NUM> to direct a cable <NUM> in either direction without substantially changing the position of the cable <NUM> relative to the drum segment <NUM>.

The upper and lower load cells <NUM>,<NUM> are coupled to a processor that determines the horizontal load on each of the upper and lower sheave plates <NUM>,<NUM>. These loads can be summed and/or individually monitored for a given loading arrangement in order to sense deviations from a standard or expected load profile.

Claim 1:
A lift assembly (<NUM>) comprising:
a base (<NUM>);
a drive mechanism (<NUM>);
a flexible drive element (<NUM>) driven by the drive mechanism (<NUM>) and extending from the drive mechanism (<NUM>) along a fleet axis (<NUM>); and
a sheave (<NUM>) directing the drive element (<NUM>) from the fleet axis (<NUM>) to an output axis (<NUM>) different than the fleet axis (<NUM>), wherein the sheave (<NUM>) is coupled to the base (<NUM>) at a first sheave mount (<NUM>) aligned with the fleet axis (<NUM>), characterised in that
the base (<NUM>) further includes a second sheave mount (<NUM>) aligned with the fleet axis (<NUM>), the second sheave mount (<NUM>) being configured to be coupled to the sheave (<NUM>) to thereby allow the sheave (<NUM>) to be de-coupled from the first sheave mount (<NUM>) and coupled to the second sheave mount (<NUM>), the second sheave mount (<NUM>) being positioned such that coupling of the sheave (<NUM>) to the second sheave mount (<NUM>) results in substantially no change in a fleet angle (α) of the fleet axis (<NUM>); and
the sheave (<NUM>) is positioned on a first side of the fleet axis (<NUM>) when coupled to the first sheave mount (<NUM>), and wherein the sheave (<NUM>) is positioned on a second side of the fleet axis (<NUM>) when coupled to the second sheave mount (<NUM>), the second side being substantially opposed to the first side.