Patent Description:
Document <CIT> may be construed to disclose an orthopaedic pillow for supporting a user is disclosed. The user has a head and a torso. The pillow comprises a head rest for supporting the head of the user and a wedge-shaped portion having a tapered surface. The wedge-shaped portion is attached to and extends away from the head rest. The tapered surface of the wedge-shaped portion supports portions of the torso of the user. The wedge-shaped portion has a shoulder recess depressed from the tapered surface to receive a shoulder of the user.

According to the present disclosure, there is provided a patient support system according to the independent claim. Further developments are set forth in the dependent claims.

According to the invention, there is a patient support apparatus including a support structure with a base, a support frame, and a patient support deck, the support frame extending longitudinally from a first longitudinal end to a second longitudinal end and the base having a guide. A first lift is provided to lift or lower the first longitudinal end of the support frame relative to the base. The first lift has a guided body movable longitudinally relative to the base along the guide. A second lift is provided to lift or lower the second longitudinal end of the support frame relative to the base. The first lift and the second lift being are operable to place the support frame in one or more Trendelenburg positions in which the first longitudinal end and the second longitudinal end are at different heights relative to the base. The patient support apparatus further includes a plurality of load cells, with at least one load cell coupled to the first lift to act between the first lift and the support frame, and with at least one load cell coupled to the second lift to act between the second lift and the support frame, such that a load on the support frame is transmitted to the plurality of load cells to measure the load. The guided body is arranged to move longitudinally relative to the base in response to operation of the second lift to move the support frame to the one or more Trendelenburg positions such that the first lift moves longitudinally toward the second lift to accommodate movement of the support frame to the one or more Trendelenburg positions.

In an example, a load cell including an elongate body extending longitudinally along a longitudinal axis from a mounting portion to a load application portion. The load application portion defines a pair of side openings and a pivot shaft passage extending between the side openings, with a load application region located midway through the pivot shaft passage. Each of the pair of side openings has a first diameter, and the pivot shaft passage has a second diameter at the load application region, the second diameter being smaller than the first diameter.

Referring to <FIG>, a patient support apparatus <NUM> is shown for supporting a patient in a health care setting. The patient support apparatus <NUM> illustrated in <FIG> is a hospital bed. In other versions, however, the patient support apparatus <NUM> may be a stretcher, cot, table, wheelchair, or similar apparatus utilized in the care of a patient.

A support structure <NUM> provides support for the patient. The support structure <NUM> illustrated in <FIG> includes a base <NUM> and a support frame <NUM>. The base <NUM> includes a base frame <NUM>. The support frame <NUM> is spaced above the base frame <NUM> in <FIG>. The support structure <NUM> also includes a patient support deck <NUM> disposed on the support frame <NUM>. The patient support deck <NUM> includes several sections, some of which are capable of articulating (e.g., pivoting) relative to the support frame <NUM>, such as a fowler section, a seat section, a thigh section, and a foot section. The patient support deck <NUM> provides a patient support surface <NUM> upon which the patient is supported.

A mattress <NUM> is disposed on the patient support deck <NUM> during use. The mattress <NUM> includes a secondary patient support surface upon which the patient is supported. The base <NUM>, support frame <NUM>, patient support deck <NUM>, and patient support surface <NUM> each have a head end and a foot end corresponding to designated placement of the patient's head and feet on the patient support apparatus <NUM>. The head end and the foot end may also be referred to as opposing longitudinal ends. The base <NUM> includes a longitudinal axis L1 along its length from the head end to the foot end. The base <NUM> also includes a vertical axis V arranged crosswise (e.g., perpendicularly) to the longitudinal axis L1 along which the support frame <NUM> is lifted and lowered relative to the base <NUM>. In addition, the mattress <NUM> may be omitted in certain versions, such that the patient rests directly on the patient support surface <NUM>.

Side rails <NUM>, <NUM>, <NUM>, <NUM> are coupled to the support structure <NUM>. A first side rail <NUM> is positioned at a right head end of the patient support deck <NUM>. A second side rail <NUM> is positioned at a right foot end of the support frame <NUM>. A third side rail <NUM> is positioned at a left head end of the patient support deck <NUM>. A fourth side rail <NUM> is positioned at a left foot end of the support frame <NUM>. If the patient support apparatus <NUM> is a stretcher or a cot, there may be fewer side rails. The side rails <NUM>, <NUM>, <NUM>, <NUM> are movable between a raised position in which they block ingress and egress into and out of the patient support apparatus <NUM>, one or more intermediate positions, and a lowered position in which they are not an obstacle to such ingress and egress. In some configurations, the patient support apparatus <NUM> may not include any side rails.

A headboard <NUM> and a footboard <NUM> are coupled to the support frame <NUM>. In some versions, when the headboard <NUM> and footboard <NUM> are included, the headboard <NUM> and footboard <NUM> may be coupled to other locations on the patient support apparatus <NUM>, such as the base <NUM>. In some versions, the patient support apparatus <NUM> does not include the headboard <NUM> and/or the footboard <NUM>.

Caregiver interfaces <NUM>, such as handles, are shown integrated into the footboard <NUM> and side rails <NUM>, <NUM>, <NUM>, <NUM> to facilitate movement of the patient support apparatus <NUM> over floor surfaces. Additional caregiver interfaces <NUM> may be integrated into the headboard <NUM> and/or other components of the patient support apparatus <NUM>. The caregiver interfaces <NUM> are graspable by the caregiver to manipulate the patient support apparatus <NUM> for movement.

Wheels <NUM> are coupled to the base <NUM> to facilitate transport over the floor surfaces. The wheels <NUM> are arranged in each of four quadrants of the base <NUM> adjacent to corners of the base <NUM>. In the version shown, the wheels <NUM> are caster wheels able to rotate and swivel relative to the support structure <NUM> during transport. Each of the wheels <NUM> forms part of a caster assembly <NUM>. Each caster assembly <NUM> is mounted to the base <NUM>. It should be understood that various configurations of the caster assemblies <NUM> are contemplated. In addition, in some versions, the wheels <NUM> are not caster wheels and may be non-steerable, steerable, non-powered, powered, or combinations thereof. Additional wheels are also contemplated. For example, the patient support apparatus <NUM> may include four non-powered, non-steerable wheels, along with one or more powered wheels. In some cases, the patient support apparatus <NUM> may not include any wheels. In some versions, one or more auxiliary wheels (powered or non-powered), which are movable between stowed positions and deployed positions, may be coupled to the support structure <NUM>.

The patient support apparatus <NUM> includes a lift system <NUM> that operates to lift and lower the support frame <NUM> and the patient support deck <NUM> relative to the base <NUM>. The lift system <NUM> is configured to move the support frame <NUM> from a first height (shown in <FIG>) to a second, lower height (shown in <FIG>), or to any desired position in between. The lift system <NUM> includes a head end lift <NUM> and a foot end lift <NUM>. The head end lift <NUM> is arranged to lift or lower the head end of the support frame <NUM> relative to the base <NUM>. The foot end lift <NUM> is arranged to lift or lower the foot end of the support frame <NUM> relative to the base <NUM>. Each of the head end lift <NUM> and the foot end lift <NUM> includes an actuator <NUM>, <NUM> to actuate the lifts <NUM>, <NUM>. The lifts <NUM>, <NUM> are separately and independently operable such that the support frame <NUM> and the patient support deck <NUM> can be placed in one or more Trendelenburg positions in which the head end and the foot end are at different heights relative to the base <NUM>, as shown in <FIG> and <FIG>.

The lifts <NUM>, <NUM> may be identical in form or may have different forms. For instance, one of the lifts may be a crank-type mechanism or scissor-type mechanism, while the other of the lifts may be a column lift. The head end lift <NUM> and the foot end lift <NUM> may be interchangeable such that the head end lift <NUM> is at the foot end of the patient support apparatus <NUM> and the foot end lift <NUM> is at the head end of the patient support apparatus <NUM>. <FIG> are elevational and schematic views that illustrate the lifts <NUM>, <NUM> and their operation. The mattress <NUM>, side rails <NUM>, <NUM>, <NUM>, <NUM>, headboard <NUM>, and footboard <NUM> have been removed in <FIG> for illustration purposes.

The head end lift <NUM> includes one or more head end legs <NUM> and the foot end lift <NUM> includes one or more foot end legs <NUM>. In the version shown, there are two, laterally spaced, head end legs <NUM> and two, laterally spaced, foot end legs <NUM>. Since <FIG> are elevational and schematic views, only one head end leg <NUM> and one foot end leg <NUM> are shown for ease of illustration. The other head end leg <NUM> and foot end leg <NUM> and their connections are the same as those shown, but on the opposite side of the base frame <NUM> (i.e., only one, interior side of the base frame <NUM> is shown in <FIG>). The head end legs <NUM> and the foot end legs <NUM> are similarly arranged, yet in opposing directions. All of the legs <NUM>, <NUM> can be seen in <FIG> and <FIG>.

Referring specifically to <FIG>, each of the legs <NUM>, <NUM> extends at an acute angle (relative to the longitudinal axis L1) from a first end pivotally coupled to a load cell <NUM> to a second end pivotally and slidably coupled to the base <NUM>. More specifically, the first ends are pivotally connected to the load cells <NUM> at upper pivot axes P1 and the second ends are pivotally connected to the base frame <NUM> at lower pivot axes P2. The load cells <NUM> have mounting portions fixed to the support frame <NUM>, as will be described further below (see, e.g., <FIG>).

The load cells <NUM> coupled to the head end legs <NUM> (could be only one is some versions) act between the head end lift <NUM> and the support frame <NUM>. The load cells <NUM> coupled to the foot end legs <NUM> (could be only one in some versions) act between the foot end lift <NUM> and the support frame <NUM>. Pivot connections between the legs <NUM>, <NUM> and the load cells <NUM> and/or between the legs <NUM>, <NUM> and the base frame <NUM> may be formed using any suitable brackets, pivot pins, pivot shafts, or any other suitable pivot connections. The legs <NUM>, <NUM> are operably coupled to their respective actuators <NUM>, <NUM> to be moved by their respective actuators <NUM>, <NUM> to pivot relative to the load cells <NUM> about the upper pivot axes P1 and to pivot relative to the base <NUM> about the lower pivot axes P2. In some versions, the lifts <NUM>, <NUM> may each include a single leg. In some versions, other types of lifting members capable of lifting and lowering the support frame <NUM> may be employed.

Each of the lifts <NUM>, <NUM> includes guided bodies B1, B2 that are pivotally connected to the second ends of the legs <NUM>, <NUM> via the pivot connections about the lower pivot axes P2. One guided body B1, B2 is provided for each leg <NUM>, <NUM> (only two guided bodies B1, B2 can be seen in <FIG>). In the version shown, the guided bodies B1, B2 include blocks formed of low friction materials, such as polytetrafluoroethylene (PTFE), to limit friction as the blocks translate relative to the base <NUM>. The blocks can be any shape, including box-shaped, spherical, cylindrical, or the like. In some versions, the guided bodies include rollers, pins, shafts, gears, or other movable elements that move longitudinally.

The base <NUM> includes a pair of head end guides <NUM> and a pair of foot end guides <NUM> fixed to the base frame <NUM> to receive the guided bodies B1, B2 (again, only two guides can be seen in <FIG>). The guided bodies B1, B2 are configured to translate longitudinally in the guides <NUM>, <NUM> during operation of the lifts <NUM>, <NUM>. Owing to the pivot connections of the guided bodies B1, B2 to the legs <NUM>, <NUM>, the guides <NUM>, <NUM> thereby act to guide translational movement of the second ends of the legs <NUM>, <NUM> during operation (compare <FIG> and <FIG>). The head end guides <NUM> guide movement of the guided bodies B1 pivotally connected to the head end legs <NUM>. The foot end guides <NUM> guide movement of the guided bodies B2 pivotally connected to the foot end legs <NUM>.

The head end guides <NUM> include head end guide tracks <NUM> and the foot end guides <NUM> include foot end guide tracks <NUM>. The guide tracks <NUM>, <NUM> are shaped to receive the guided bodies B1, B2. The guide tracks <NUM>, <NUM> are fixed to the base frame <NUM> and have an elongated shape. In particular, the guide tracks <NUM>, <NUM> are shown as rectangular boxes having openings facing inwardly from the base frame <NUM>. The guide tracks <NUM>, <NUM> have upper and lower walls W to vertically constrain the guided bodies B1, B2 to limit their motion to sliding within the guide tracks <NUM>, <NUM>. In some versions, the guide tracks <NUM>, <NUM> may have flanges extending from the upper and lower walls W to capture the guided bodies B1, B2 in the guide tracks <NUM>, <NUM> and prevent lateral withdrawal from the guide tracks <NUM>, <NUM>. In the version shown, the guide tracks <NUM>, <NUM> are arranged horizontally, but other arrangements are also contemplated. The guide tracks <NUM>, <NUM> may be arcuate in shape, linear, combinations thereof, and the like. The guide tracks <NUM>, <NUM> may be shaped and/or arranged to facilitate both longitudinal and vertical movement of the guided bodies B1, B2. The guide tracks <NUM>, <NUM> are slide-bearing guide tracks in which the blocks slide and may similarly be formed or coated with low friction materials, such as metal coated with PTFE and/or other low friction material.

Referring specifically to <FIG>, the legs <NUM>, <NUM> pivot relative to their respective guided bodies B1, B2 when the guided bodies B1, B2 move longitudinally in the guide tracks <NUM>, <NUM>. Thus, the legs <NUM>, <NUM> are pivotally and slidably coupled to the base frame <NUM>. The guide tracks <NUM>, <NUM> and the legs <NUM>, <NUM> are arranged so that the guided bodies B1 move toward the guided bodies B2 as the support frame <NUM> is lowered relative to the base <NUM> and move away from each other as the support frame <NUM> is lifted relative to the base <NUM> (compare <FIG> and <FIG>). In some versions, the guide tracks <NUM>, <NUM> and the legs <NUM>, <NUM> may be arranged such that the motion of the guided bodies B1, B2 during lifting and lowering is reversed. The guide tracks <NUM> and the guided bodies B1 associated with the head end legs <NUM> are best shown in <FIG> - the guide tracks <NUM> and the guided bodies B2 associated with the foot end legs <NUM> may be similar in shape, size, and arrangement with respect to the foot end legs <NUM>.

The actuators <NUM>, <NUM> may be placed at any suitable location to actuate the lifts <NUM>, <NUM>. In the version shown in <FIG>, the actuator <NUM> is a rotary actuator that has a housing 100a fixed to the head end legs <NUM> and a rotating shaft 102a fixed to at least one of a pair of links <NUM>, described further below. The rotating shaft 102a may be fixed to both of the links <NUM> through the housing 100a. The housing 100a contains a motor M (see <FIG>) and gear train operable to rotate the rotating shaft 102a about pivot axis P7. The rotating shaft 102a rotates relative to the housing 100a to rotate the links <NUM> relative to the head end legs <NUM>. Alternatively, the housing 100a could be fixed to the links <NUM> and the rotating shaft 102a fixed to the head end legs <NUM>. Other suitable locations for the rotary actuator are possible.

The actuator <NUM> could also be located as shown in <FIG> and <FIG>, to operate between the head end legs <NUM> and the links <NUM>. In this version, a first end of the actuator <NUM> is pivotally connected to the links <NUM>, e.g., directly to one of the links <NUM> or to a bracket of a cross member <NUM> (see <FIG>) fixed to and extending between the links <NUM>. A second end of the actuator <NUM> is pivotally connected to the head end legs <NUM>, e.g., directly to one of the head end legs <NUM> or to a bracket <NUM> of a head end support member <NUM> (see <FIG>) fixed to and extending between the head end legs <NUM>. In this version, the actuator <NUM> is a linear actuator that includes a housing <NUM> and a drive rod <NUM> that extends and retracts relative to the housing <NUM> to rotate the links <NUM> relative to the head end legs <NUM>. The housing <NUM> and drive rod <NUM> may be pivotally connected to the links <NUM> and the legs <NUM> via brackets and pivot pins, pivot shafts, or any other suitable pivot connections.

In the various versions shown, the actuator <NUM> is arranged without any connections to the base <NUM> or to the support frame <NUM>. In the versions shown, the first lift <NUM> is a free-standing lift. During movement to a Trendelenburg position, as described further below, the first lift <NUM> slides longitudinally relative to the second lift <NUM>. As a result, the actuator <NUM> also slides longitudinally, including both the housing 100a, <NUM> and the rotating shaft/drive rod 102a, <NUM> sliding toward the second lift <NUM>.

Referring back to <FIG>, the actuator <NUM> has a first end pivotally connected to the base frame <NUM>. More specifically, the actuator <NUM> includes a housing <NUM> and a drive rod <NUM> that extends and retracts relative to the housing <NUM>, and the housing <NUM> is pivotally connected at the first end to the base frame <NUM> via a base bracket <NUM>. The base bracket <NUM> is fixed to the base frame <NUM> (e.g., via fasteners, welding, or the like). The first end of the actuator <NUM> pivots about pivot axis P3 fixed relative to the base frame <NUM>. The pivot axis P3 is defined by the base bracket <NUM> via a pivot pin, pivot shaft, or any other suitable pivot connection. The actuator <NUM> extends from the first end to a second end that is pivotally connected to the foot end legs <NUM> via a support bracket <NUM>. The support bracket <NUM> is fixed to a foot end support member <NUM> (see <FIG>). The support bracket <NUM> is fixed to the foot end support member <NUM> via fasteners, welding, or the like. The second end of the actuator <NUM> pivots about pivot axis P4 defined by the support bracket <NUM> via a pivot pin, pivot shaft, or any other suitable pivot connection. In the version shown, the head end support member <NUM> interconnects the second ends of the pair of head end legs <NUM> and the foot end support member <NUM> interconnects the second ends of the pair of foot end legs <NUM> (see <FIG> and <FIG>). Thus, the support members <NUM>, <NUM> act as cross supports rigidly fixed to the respective legs <NUM>, <NUM> to move with the legs <NUM>, <NUM>. The support members <NUM>, <NUM>, may be fixed to their respective legs <NUM>, <NUM> in any suitable manner, such as by fasteners, welding, or the like. Thus, any forces applied to the support bracket <NUM> via the actuator <NUM> is transmitted to the foot end legs <NUM> by virtue of the rigid connection of the support bracket <NUM> to the foot end legs <NUM>.

The actuator <NUM> may also be a rotary actuator, arranged relative to the foot end legs <NUM> and links <NUM> in the same manner that the actuator <NUM> shown in <FIG> is arranged relative to the head end legs <NUM> and links <NUM>. The actuator <NUM> may also be arranged like the actuator <NUM> shown in <FIG> and <FIG>, instead acting between the foot end legs <NUM> and the links <NUM>. Numerous actuator types and arrangements are possible to operate the lifts <NUM>, <NUM> to lift and lower the support frame <NUM> relative to the base <NUM>.

The actuators <NUM>, <NUM> are operably coupled to the respective legs <NUM>, <NUM> to longitudinally move the second ends of the respective legs <NUM>, <NUM> via the guided bodies B1, B2 and guide tracks <NUM>, <NUM> and cause the respective legs <NUM>, <NUM> (by virtue of their pivot connections) to pivot about the upper and lower pivot axes P1, P2 to lift and lower the support frame <NUM> relative to the base <NUM>. The actuators <NUM>, <NUM> include linear actuators, rotary actuators, or other types of actuators. The actuators <NUM>, <NUM> may be electrically operated, hydraulic, electro-hydraulic, pneumatic, or the like. The actuators <NUM>, <NUM> may include motors, gear trains, drive screws, nuts/lead screws, and the like, for actuation. In the version shown, the actuators <NUM>, <NUM> are electric, motor-driven actuators.

Still referring to <FIG>, one or more first links <NUM> are pivotally connected at a first end to the foot end legs <NUM> and extend from the first end to a second end pivotally connected to the base <NUM>. In the version shown, two first links <NUM> are pivotally connected to the foot end legs <NUM> to pivot about a pivot axis P5 that moves with the foot end legs <NUM> (only one first link <NUM> is shown in <FIG>). Each of the first links <NUM> are pivotally connected to the base frame <NUM> to pivot about a pivot axis P6 that is fixed relative to the base frame <NUM>. The pivot connections for the first links <NUM> may be formed via pivot pins, pivot shafts, or any other suitable pivot connections. The pivot axis P5 is located in-line with and halfway between the upper pivot axis P1 and the lower pivot axis P2 for the foot end legs <NUM>.

The first links <NUM>, in some versions, control and somewhat constrain movement of the support frame <NUM> during lifting and lowering, owing to their pivot connections with the foot end legs <NUM> and the base frame <NUM>, and owing to the upper pivot axes P1 being fixed to the support frame <NUM> (some slight, relative movements may be allowed by the load cells <NUM>). Compare <FIG> and <FIG> and note that the upper pivot axes P1 remain vertically aligned with the lower pivot axes P2 during raising and lowering. Moreover, when the lifts <NUM>, <NUM> are operated independently to place the support frame <NUM> in a Trendelenburg position, as shown in <FIG> and <FIG>, the first links <NUM> act to prevent the upper pivot axis P1 at the foot end from shifting longitudinally relative to the base <NUM>. Conversely, the upper pivot axis P1 at the head end shifts longitudinally.

One or more second links <NUM> are pivotally connected at a first end to the head end legs <NUM> and extend from the first end to a second end pivotally connected to the base <NUM>. In the version shown, two second links <NUM> are pivotally connected to the head end legs <NUM> to pivot about the pivot axis P7 that moves with the head end legs <NUM> (only one second link <NUM> is shown in <FIG>). The second links <NUM> are also pivotally connected to the base frame <NUM> to pivot about a pivot axis P8. Unlike the first links <NUM> and the pivot axis P6, the pivot axis P8 is not fixed relative to the base frame <NUM> but can move longitudinally relative to the base frame <NUM>. Guided bodies B3 are pivotally connected at the second ends of the second links <NUM> about pivot axis P8 to slide in guides <NUM>. The guided bodies B3 and the guides <NUM> may be similar to those previously described to allow the second ends of the second links <NUM> to slide relative to the base <NUM> (see also <FIG>). The pivot connections for the second links <NUM> may be formed via pivot pins, pivot shafts, or any other suitable pivot connections. The pivot axis P7 is located in-line with and halfway between the upper pivot axis P1 and the lower pivot axis P2 for the head end legs <NUM>. The actuator <NUM> for the head end lift <NUM> is operably coupled to the second links <NUM>, as previously described.

As previously mentioned, when the lifts <NUM>, <NUM> are operated independently to place the support frame <NUM> in a Trendelenburg position, the first links <NUM> act on the foot end lift <NUM> to prevent the upper pivot axis P1 at the foot end from shifting longitudinally relative to the base <NUM>, but the upper pivot axis P1 at the head end does shift longitudinally. The second links <NUM> also shift longitudinally, as shown in <FIG> and <FIG>. More specifically, when either or both of the actuators <NUM>, <NUM> are operated to place the support frame <NUM> and the patient support deck <NUM> in the one or more Trendelenburg positions, the pivot axis P8 moves longitudinally to remain aligned with the upper pivot axis P1 at the head end (see the vertical line V2 shown in <FIG> compared to the vertical line V1 of <FIG> made by the pivot axes P1, P8 prior to moving to the Trendelenburg position). The guided bodies B3 thus move longitudinally in the guides <NUM> relative to the base <NUM> toward the foot end.

When moving to the Trendelenburg position, as shown in <FIG>, the horizontal, longitudinal distance between the upper pivot axes P1 and between the pivot axes P6, P8 gets smaller (see horizontal distance D2 compared to horizontal distance D1). The head end lift <NUM> slides toward the foot end lift <NUM> to accommodate movement of the support frame <NUM> to the one or more Trendelenburg positions. This occurs when placing the support frame <NUM> and the patient support deck <NUM> in either of the Trendelenburg positions shown in <FIG> and <FIG>. Thus, operation of either or both lifts <NUM>, <NUM> to place the support frame <NUM> and the patient support deck <NUM> in a Trendelenburg position causes the upper pivot axis P1 associated with the head end lift <NUM> to move longitudinally closer to the foot end. Likewise, the pivot axis P8 and associated guided bodies B3 also move longitudinally closer to the foot end. The lower pivot axis P2 and corresponding guided bodies B1 associated with the head end lift <NUM> also move longitudinally closer to the foot end. For example, comparing <FIG>, the head end lift <NUM> remains in the same configuration and fully slides toward the foot end lift <NUM> when the foot end lift <NUM> is actuated to place the support frame <NUM> and the patient support deck <NUM> in the Trendelenburg position of <FIG>. In other words, the head end legs <NUM>, the second links <NUM>, the guided bodies B1, the guided bodies B3, and the actuator <NUM> are all longitudinally displaced by a distance equal to D1-D2.

Another lift system that can be used on the patient support apparatus <NUM> is shown in <CIT>, entitled "Patient Support With Lift Assembly".

<FIG> show another lift system <NUM> that operates to lift and lower the support frame <NUM> and the patient support deck <NUM> relative to the base <NUM> in much the same way as the lift system <NUM>. The lift system <NUM> is configured to move the support frame <NUM> between various heights relative to the base <NUM>. The lift system <NUM> includes a head end lift <NUM> and a foot end lift <NUM>. The head end lift <NUM> is arranged to lift or lower the head end of the support frame <NUM> relative to the base <NUM>. The foot end lift <NUM> is arranged to lift or lower the foot end of the support frame <NUM> relative to the base <NUM>. Each of the head end lift <NUM> and the foot end lift <NUM> includes an actuator <NUM>, <NUM> to actuate the lifts <NUM>, <NUM>. The lifts <NUM>, <NUM> are separately and independently operable such that the support frame <NUM> and the patient support deck <NUM> can be placed in one or more Trendelenburg positions in which the head end and the foot end are at different heights relative to the base <NUM>, as shown in <FIG> and <FIG>.

The head end lift <NUM> and the foot end lift <NUM> may be interchangeable such that the head end lift <NUM> is at the foot end of the patient support apparatus <NUM> and the foot end lift <NUM> is at the head end of the patient support apparatus <NUM>. <FIG> are elevational and schematic views that illustrate the lifts <NUM>, <NUM> and their operation. The mattress <NUM>, side rails <NUM>, <NUM>, <NUM>, <NUM>, headboard <NUM>, and footboard <NUM> have been removed in <FIG> for illustration purposes.

In this version, the head end lift <NUM> includes a head end column lift <NUM> extending between a first pair of load cells <NUM> and the base <NUM> (only one of the pair of load cells <NUM> is shown in <FIG>). The actuator <NUM> is arranged to extend and retract the head end column lift <NUM>. The head end column lift <NUM> is fixed from sliding relative to the base <NUM> and has a base portion <NUM> fixed to the base frame <NUM>. The foot end lift <NUM> includes a foot end column lift <NUM> extending between a second pair of load cells <NUM> and the base <NUM> (only one of the pair of load cells <NUM> is shown in <FIG>). The actuator <NUM> extends and retracts the foot end column lift <NUM>. The foot end lift <NUM> is allowed to slide relative to the base <NUM> and relative to the head end lift <NUM>, as described further below, to accommodate movement of the support frame <NUM> to the one or more Trendelenburg positions.

The column lifts <NUM>, <NUM> extend and retract vertically in a telescoping manner. An end of the head end column lift <NUM> is pivotally connected to the first pair of load cells <NUM> at an upper pivot axis P1. An end of the foot end column lift <NUM> is pivotally connected to the second pair of load cells <NUM> at an upper pivot axis P1. Pivot connections between the column lifts <NUM>, <NUM> and the load cells <NUM> may be formed using any suitable brackets, pivot pins, pivot shafts, or any other suitable pivot connections. See, for example, the pivot shafts <NUM>, <NUM> connecting the column lifts <NUM>, <NUM> to the load cells <NUM> in <FIG>. In some versions, the column lifts <NUM>, <NUM> may be in the form of linear actuators such as the actuator <NUM> previously described, arranged and mounted to operate vertically. The column lifts <NUM>, <NUM> may be hydraulic jacks capable of extending and retracting. The column lifts <NUM>, <NUM> may be like those described in <CIT>, or like those described in <CIT>.

The foot end column lift <NUM> includes a guided body B4 that supports the foot end column lift <NUM> during movement to the one or more Trendelenburg positions, as shown in <FIG> and <FIG>. In the version shown, the guided body B4 includes a cart <NUM> with wheels <NUM>. The cart <NUM> is fixed to a base portion <NUM> of the foot end column lift <NUM>. The base <NUM> provides a guide <NUM> to receive the cart <NUM>. The guide <NUM> includes a guide track <NUM> that constrains movement of the cart <NUM> to within the guide track <NUM>. The guide track <NUM> may be defined by a bottom wall upon which the cart <NUM> and wheels <NUM> are supported and one or more side walls to constrain movement of the cart <NUM> so that motion is limited to being in the longitudinal direction during movement to the one or more Trendelenburg positions.

Owing to the pivot connections of the column lifts <NUM>, <NUM> at the upper pivot axes P1, which are relatively fixed to the support frame <NUM>, and owing to the head end column lift <NUM> having its base portion <NUM> fixed to the base frame <NUM>, the guided body B4 is configured to translate longitudinally in the guide <NUM> during operation of either or both of the lifts <NUM>, <NUM> to place the support frame <NUM> and the patient support deck <NUM> in a Trendelenburg position (compare <FIG> and <FIG> or <FIG>). As illustrated by arrows in <FIG> and <FIG>, when the support frame <NUM> and the patient support deck <NUM> are moved to a Trendelenburg position, the guided body B4, and by extension the foot end lift <NUM>, slide toward the head end lift <NUM>. If the lifts <NUM>, <NUM> are simultaneously operated to lift or lower the support frame <NUM> while keeping the support frame <NUM> horizontal, then the guided body B4 would remain stationary (not shown).

<FIG> show the same lift system <NUM> as shown in <FIG>, except that the load cells <NUM> connected to the head end column lift <NUM> have been rearranged to be in the same longitudinal arrangement as the other load cells <NUM> pivotally connected to the foot end column lift <NUM>. In the version shown in <FIG>, the pairs of load cells <NUM> are mounted to the support frame <NUM>, but in opposing orientations. In <FIG>, the pairs of load cells <NUM> are mounted to the support frame <NUM> in the same orientation.

<FIG> and <FIG> illustrate another alternative arrangement of the load cells <NUM> in which their mounting portions are fixed to the lifts <NUM>, <NUM> instead of the support frame <NUM>, and are pivotally connected to the support frame <NUM> at pivot connections to pivot about pivot axes P1 (compare <FIG> and <FIG> to see the pivotal motion). As a result, the load cells <NUM> remain substantially horizontally oriented, parallel to the longitudinal axis L1 of the base <NUM>, during movement of the support frame <NUM> to the one or more Trendelenburg positions (see <FIG>). Conversely, in the versions shown in <FIG>, the plurality of load cells <NUM> are arranged to tilt with the support frame <NUM> during movement of the support frame <NUM> to the one or more Trendelenburg positions.

<FIG> and <FIG> illustrate another alternative arrangement of the load cells <NUM> in which the load cells <NUM> at the foot end have their mounting portions fixed to the guided body B4 to slide relative to the foot end lift <NUM>. In this version, both of the lifts <NUM>, <NUM> are fixed from sliding longitudinally, even during movement of the support frame <NUM> to the one or more Trendelenburg positions. Instead, the load cells <NUM> at the foot end slide, with the guided body B4, relative to the foot end lift <NUM> via a sliding mechanism (shown, for example, as a plurality of rollers). In this version, all of the load cells <NUM> remain horizontal during movement of the support frame <NUM> to the one or more Trendelenburg positions.

Referring to <FIG>, a control system is shown to control operation of the actuators <NUM>, <NUM>, <NUM>, <NUM>. The control system includes a controller <NUM> having one or more processors for processing instructions or for processing algorithms stored in memory to control operation of the actuators <NUM>, <NUM>, <NUM>, <NUM> to coordinate movement of the actuators <NUM>, <NUM>, <NUM>, <NUM> to evenly lift and lower the support frame <NUM> relative to the base <NUM> or to independently operate the actuators <NUM>, <NUM>, <NUM>, <NUM> to place the support frame <NUM> in a Trendelenburg position, e.g., a normal or reverse Trendelenburg position. Additionally or alternatively, the controller <NUM> may include one or more microcontrollers, microprocessors, field programmable gate arrays, systems on a chip, discrete circuitry, and/or other suitable hardware, software, or firmware that is capable of carrying out the functions described herein. The controller <NUM> may be carried on-board the patient support apparatus <NUM> or may be remotely located. In some versions, the controller <NUM> is mounted to the base <NUM>. In some versions, the controller <NUM> is mounted to the footboard <NUM>. Power to the actuators <NUM>, <NUM>, <NUM>, <NUM> and/or the controller <NUM> may be provided by a battery power supply and/or an external power source.

The controller <NUM> is coupled to the actuators <NUM>, <NUM>, <NUM>, <NUM> in a manner that allows the controller <NUM> to control the actuators <NUM>, <NUM>, <NUM>, <NUM>. The controller <NUM> may communicate with the actuators <NUM>, <NUM>, <NUM>, <NUM> via wired or wireless connections to perform one of more desired functions. The controller <NUM> may monitor a current state of the actuators <NUM>, <NUM>, <NUM>, <NUM> via one or more sensors and determine desired states in which the actuators <NUM>, <NUM>, <NUM>, <NUM> should be placed, based on one or more input signals that the controller <NUM> receives from one or more user input devices. The state of the actuators <NUM>, <NUM>, <NUM>, <NUM> may be a position, a relative position, an angle, an energization status (e.g., on/off), or any other parameter of the actuators <NUM>, <NUM>, <NUM>, <NUM>.

A user, such as a caregiver, may actuate one or more user input devices <NUM>, which transmit corresponding input signals to the controller <NUM>, and the controller <NUM> controls operation of the actuators <NUM>, <NUM>, <NUM>, <NUM> based on the input signals. The user input devices <NUM> may include any device capable of being actuated by the user and may be provided on a control panel, touchscreen, or the like. The user input devices <NUM> may be configured to be actuated in a variety of different ways, including but not limited to, mechanical actuation (hand, foot, finger, etc.), hands-free actuation (voice, foot, etc.), and the like. The user input devices <NUM> may include buttons (such as buttons corresponding to lift, lower, normal Trendelenburg, and reverse Trendelenburg), a gesture sensing device for monitoring motion of hands, feet, or other body parts of the user (such as through a camera), a microphone for receiving voice activation commands, a foot pedal, and sensors (e.g., infrared sensor such as a light bar or light beam to sense a user's body part, ultrasonic sensors, capacitive sensors, etc.). Additionally, the buttons/pedals can be physical buttons/pedals or virtually implemented buttons/pedals such as through optical projection or on a touchscreen. The buttons/pedals may also be mechanically connected or drive-by-wire type buttons/pedals where a user applied force actuates a sensor, such as a switch or potentiometer. It should be appreciated that any combination of user input devices may also be utilized. The user input devices may be located on one of the side rails <NUM>, <NUM>, <NUM>, <NUM>, the headboard <NUM>, the footboard <NUM>, or other suitable locations. The user input devices may also be located on a portable electronic device (e.g., iWatch®, iPhone®, iPad®, or similar electronic devices).

During operation, when a user wishes to move the support frame <NUM> relative to the base <NUM>, the user actuates one or more of the user input devices <NUM>. For instance, in the event the user wishes to lower the support frame <NUM> relative to the base <NUM>, such as moving the support frame <NUM> from the position shown in <FIG> to the position shown in <FIG>, the user actuates the appropriate user input device <NUM> (see touchscreen button 202b, for example). Upon actuation, the controller <NUM> sends output signals to the actuators <NUM>, <NUM> to cause simultaneous operation of the actuators <NUM>, <NUM> in a manner that causes the support frame <NUM> to lower.

The control system may also include a scale to indicate a patient's weight and/or to detect a patient's position/movement on the patient support apparatus <NUM>, such as in conjunction with a bed exit alert system. The scale includes the load cells <NUM> connected to the controller <NUM> to provide signals associated with loads measured by each of the load cells <NUM>. For example, each load cell <NUM> may include a pair of activation leads and a pair of sensor leads. The controller <NUM> may include a circuit in electrical communication with the activation leads to supply electrical power to the load cell <NUM> via one of the activation leads with the other activation lead coupled to ground. The controller <NUM> may be in electrical communication with the sensor leads that provide output to the controller <NUM>, wherein the output correlates to how much force is being exerted on the load cell <NUM>. See, for example, the description of load cells in <CIT>.

The output signals received from the load cells <NUM> via their sensor leads are collectively processed by the controller <NUM> using scale algorithms to determine, for example, a patient's weight to output to a display <NUM>, as shown in <FIG>. See, for example, the methods described in <CIT>, entitled "Angle Calibration Using Load Cells". The scale may include a tare function <NUM> and a converter <NUM> to switch between kilograms and pounds. In some versions, by placing the load cells <NUM> between the lifts <NUM>, <NUM>, <NUM>, <NUM> and the support frame <NUM>, the lifts <NUM>, <NUM>, <NUM>, <NUM> are not part of the tare weight thereby reducing the tare weight as compared to patient support apparatuses that rely on separate weigh frames located beneath the lifts.

<FIG> illustrates one arrangement of the load cells <NUM> from the patient support apparatus <NUM> of <FIG>. In the version shown, a pair 82a of the load cells <NUM> are coupled to the head end legs <NUM> and a pair 82b of the load cells <NUM> are coupled to the foot end legs <NUM>. The load cells <NUM> are arranged such that a load on the support frame <NUM> is transmitted to the plurality of load cells <NUM> to measure the load. Portions 36a of the support frame <NUM> to which the load cells <NUM> are mounted via one or more fasteners are shown in <FIG>. The load cells <NUM> may be mounted to the support frame <NUM> via fasteners, welding, or the like. The first ends of the legs <NUM>, <NUM> are shown pivotally connected to the respective pairs of load cells <NUM> by pivot shafts <NUM>.

Each of the load cells <NUM> includes an elongate body <NUM> extending longitudinally along a longitudinal axis L2 from a mounting portion <NUM> to a load application portion <NUM>. The mounting portions <NUM> are mounted and fixed to the portions 36a of the support frame <NUM> as shown in <FIG>. In the versions shown, each of the plurality of load cells <NUM> is arranged longitudinally between the head end and the foot end of the support frame <NUM>. The lifts <NUM>, <NUM> are pivotally connected to the load application portions <NUM> of the load cells <NUM> by virtue of their corresponding legs <NUM>, <NUM> being pivotally connected to the load application portions <NUM> at the pivot axes P1. In some versions, the mounting portions <NUM> are mounted and fixed to the lifts <NUM>, <NUM>, <NUM>, <NUM> and the load application portions <NUM> are pivotally connected to the support frame <NUM> (see, e.g., <FIG> and <FIG>). In <FIG>, the pairs 82a, 82b of the load cells <NUM> are shown longitudinally aligned and oriented such that their load application portions <NUM> face in an opposite direction. In some versions, like shown in <FIG>, the pairs 82a, 82b of the load cells <NUM> are longitudinally aligned and oriented such that the load application portions <NUM> face in a common direction.

One of the load cells <NUM> is shown in more detail in <FIG>. In some versions, the load cells <NUM> are identical. In some versions, the load cells may be of different types, shapes, sizes, resolutions, etc. One type of the load cells <NUM> will be described in detail. Referring to <FIG>, a beam type load cell is shown. The mounting portion <NUM> of the load cell <NUM> includes a pair of bores <NUM> to receive fasteners to mount the mounting portion <NUM>. The load application portion <NUM> of the load cell <NUM> receives the pivot shaft <NUM> used to connect one of the legs <NUM>, <NUM>, for example, to the load cell <NUM>. The elongate body <NUM> of the load cell <NUM> also includes upper and lower beams <NUM>, <NUM> connecting the load application portion <NUM> to the mounting portion <NUM>. As best shown in <FIG>, one or more upper strain gauges <NUM> are coupled to the upper beam <NUM> and one or more lower strain gauges <NUM> are coupled to the lower beam <NUM>.

Referring to <FIG>, the beams <NUM>, <NUM> and strain gauges <NUM>, <NUM> are arranged so that the strain gauges <NUM>, <NUM> are more sensitive to loads being applied transverse to the longitudinal axis L2 as compared to loads being applied along the longitudinal axis L2. Ideally, loads are applied solely in a vertical direction, perpendicular to the longitudinal axis L2 (see "vertical load"). Under such loads, the upper and lower beams <NUM>, <NUM> are placed into tension and compression, respectively, or vice versa, depending on the direction of the vertical load. The upper strain gauge <NUM> and the lower strain gauge <NUM> have positive and negative polarities, respectively, in compression. As a result, the upper strain gauge <NUM> and the lower strain gauge <NUM> are doubly sensitive to vertical loads to suitably measure the load applied.

If during measurement of the load, there is a longitudinal load ("end load") applied along the longitudinal axis L2 exactly centered between the beams <NUM>, <NUM>, then both beams are placed into either tension or compression, equally, and due to the opposing polarities of the strain gauges <NUM>, <NUM>, the associated effects on the strain gauges <NUM>, <NUM> are substantially canceled. Thus, end loads on the load cell <NUM> may be effectively ignored by the load cell <NUM>. However, if the end load is offset vertically from the longitudinal axis L2, the associated effects on the strain gauges <NUM>, <NUM> would not effectively cancel, but could be amplified due to the opposing polarities of the strain gauges <NUM>, <NUM>. Loads applied laterally, transverse to the longitudinal axis L2 (see "side load"), may also be undesirable and difficult to compensate for during measurements. These loads cause complex shear/tensile/compressive loading at the strain gauges <NUM>, <NUM>. Twisting of the load cell <NUM> about the longitudinal axis L2 is also undesirable and causes internal shear loading at the strain gauges <NUM>, <NUM> in opposite directions in the beams <NUM>, <NUM>. Such twisting can also be difficult to compensate for during measurements and may cause inaccurate readings. For these reasons, it may be desirable to minimize side loads and twisting of the load cells <NUM>.

Referring to <FIG>, the load cell <NUM> has a bushing <NUM> that is shaped and configured to minimize side loads and twisting of the load cell <NUM> and to focus application of loads to a small, load application region R. The bushing <NUM> defines a pair of side openings <NUM> and a pivot shaft passage <NUM> extending between the side openings <NUM>. The pivot shaft passage <NUM> receives the pivot shaft <NUM>. Each of the side openings <NUM> has a first diameter D1 and the pivot shaft passage <NUM> has a second diameter D2 in the load application region R. The second diameter D2 is smaller than the first diameter D1.

The load application region R is located midway through the pivot shaft passage <NUM> and has a width W of less than <NUM>% of a length LN of the pivot shaft passage <NUM>, less than <NUM>% of the length LN of the pivot shaft passage <NUM>, or less than <NUM>% of the length LN of the pivot shaft passage <NUM>. The load application region R defines a plane with the width W along which loads are concentrated. In some versions, the load application region R has a width W of less than <NUM>,<NUM> (<NUM> inches), less than <NUM>,<NUM> (<NUM> inches), less than <NUM>,<NUM> (<NUM> inches), or less than <NUM>,<NUM> (<NUM> inches). The elongate body <NUM> defines a vertical plane VP extending midway through the elongate body <NUM> and the vertical plane VP passes through a middle of the load application region R. Accordingly, the load application region R represents a relatively narrow region within the pivot shaft passage <NUM>, that is centered in the pivot shaft passage <NUM>, and at which loads are ideally applied to the load cell <NUM>.

The pivot shaft passage <NUM> tapers down from the first diameter D1 at each of the pair of side openings <NUM> to the second diameter D2 at the load application region R. The taper may form an angle a of at least <NUM> degrees, at least <NUM> degrees, at least <NUM> degrees, or at least <NUM> degrees relative to a central axis CA of the pivot shaft passage <NUM>. The taper between the side openings <NUM> and the load application region R provides free space to receive the pivot shaft <NUM> in the event that tilting of the pivot shaft <NUM> relative to the central axis CA occurs in the pivot shaft passage <NUM>. This free space allows the pivot shaft <NUM> to tilt to at least a limited extent before causing twisting loads to be realized by the strain gauges <NUM>, <NUM>.

Referring to <FIG>, the elongate body <NUM> includes a block <NUM> and the bushing <NUM> is coupled to the block <NUM> to define the pivot shaft passage <NUM>. The block <NUM> defines a throughbore <NUM> and the bushing <NUM> is located in the throughbore <NUM>. The bushing <NUM> has a central bushing portion <NUM> and side bushing portions <NUM>. The bushing <NUM> may be insert molded in the throughbore <NUM>, press fit into the throughbore <NUM> (by first softening the bushing <NUM> and then inserting), formed in two pieces and fastened/adhered together in the throughbore <NUM>, or otherwise disposed in the throughbore <NUM>. The block <NUM> is formed at least partially of metal and the bushing <NUM> is formed at least partially of plastic. The bushing <NUM> may be formed at least partially of, and/or coated with, low friction and low wear materials, e.g., PTFE, to facilitate movement of the pivot shaft <NUM> in the bushing <NUM>.

Referring to <FIG>, an alternative block 238a and bushing 232a is shown having interlocking features <NUM>, <NUM> to facilitate connection. The interlocking features may include annular detent ribs <NUM> that fit within annual detent pockets <NUM>. Other forms of snap-fit type connections are also contemplated. In some cases, there is a single set of such interlocking features, or there may be multiple sets (as shown). The bushing 232a may be additionally, or alternatively, press fit into the block 238a. In <FIG>, the bushing 232a is shown as being two-piece with a separate cap <NUM>. The cap <NUM> may be attached about an end of the bushing 232a once the other piece of the bushing 232a is inserted through the block 238a. When the cap <NUM> is attached, the resulting bushing 232a resembles the bushing <NUM> shown in <FIG>. The cap <NUM> may be attached via welding, fasteners, adhesive, and/or press-fit, or the like.

Referring to <FIG>, the block <NUM> has sides <NUM> and the side bushing portions <NUM> extend from the sides <NUM> to abut and bear against a pivot bracket <NUM>, e.g., such as a pivot bracket of the leg <NUM>, <NUM> that is pivotally connected to the load cell <NUM> via the pivot shaft <NUM> (see <FIG> illustrates the effects of slight tilting of the pivot shaft <NUM> without causing corresponding twisting of the load cell <NUM> - owing to the tapered shape of the pivot shaft passage <NUM>. Accordingly, loads acting on the pivot shaft <NUM> are still largely applied in the load application region R and in the vertical direction and/or end direction.

In some arrangements of the load cells <NUM> previously described, the load cells <NUM> tilt with the support frame <NUM> during movement to the Trendelenburg positions (see, e.g., <FIG>). However, end loads that might otherwise occur during such tilting are minimized owing to the head end lift <NUM> (or foot end lift <NUM> in some versions) being configured to slide and compensate for such tilting movement via the guided bodies B1, B3, B4 and their translation along the base <NUM>. The load cells <NUM>, by virtue of being aligned longitudinally with respect to the support frame <NUM>, further takes advantage of the load cells <NUM> being less sensitive to end loads.

<FIG> shows such tilting of two of the load cells <NUM> (one attached to a head end leg <NUM> and the other attached to a foot end leg <NUM>). <FIG> illustrates the resulting application of loads F1, F2 acting on the load cells <NUM> through the pivot shafts <NUM>. Due to the tilt of the load cells <NUM>, the loads F1, F2 are applied at an angle to the longitudinal axis L2 of the load cells <NUM>, but the loads F1, F2 are still applied along the plane defined by the load application region R for the reasons previously discussed. Each of the loads F1, F2 has a vertical component FV directed perpendicular to the longitudinal axis L2 and a longitudinal component FL directed parallel to the longitudinal axis L2. Since the application of the longitudinal components FL are not exactly along the longitudinal axis L2, there may be some non-canceling end loading effects on the strain gauges <NUM>, <NUM> for each particular load cell <NUM>. However, because the load cells <NUM> are placed in opposing orientations, the collective effects on the load cells <NUM> tend to cancel. As a result, the measured loads are substantially based on the vertical components FV of the loads F1, F2.

A simple correction can be applied to the measurements taken by each load cell <NUM> to determine the loads F1, F2. This correction is calculated by measuring the angle of the load cells <NUM> (e.g., the Trendelenburg angle can be measured via an accelerometer, gyroscope, tilt sensor, or other suitable means connected to the controller <NUM>) and simply determining the loads F1, F2 based on a cosine function of the measured angle and applying the cosine function to the measured loads (e.g., FV). The correction factor is based on the relationship of: L = W · cos (T), where: L is the collective measurement of the load; W is a total weight of the patient; and T is the Trendelenburg angle. See, for example, the correction algorithm and associated components described in <CIT>, entitled "Angle Calibration Using Load Cells". Such correction, however, would not be needed in the arrangement of load cells <NUM> shown in <FIG> and <FIG>, since the loads F1, F2 in that arrangement would be substantially applied in the vertical direction owing to the load cells <NUM> substantially maintaining their horizontal arrangement (+/- <NUM> degrees) during tilting of the support frame <NUM> when moving the support frame <NUM> to one or more Trendelenburg positions.

Claim 1:
A patient support apparatus (<NUM>) comprising:
a support structure (<NUM>) including a base (<NUM>), a support frame (<NUM>), and a patient support deck (<NUM>), the support frame (<NUM>) extending longitudinally from a first longitudinal end to a second longitudinal end and the base (<NUM>) having a guide (<NUM>, <NUM>);
a first lift (<NUM>) to lift or lower the first longitudinal end of the support frame (<NUM>) relative to the base (<NUM>), the first lift (<NUM>) having a guided body (B1, B3) movable longitudinally relative to the base (<NUM>) along the guide (<NUM>, <NUM>);
a second lift (<NUM>) to lift or lower the second longitudinal end of the support frame (<NUM>) relative to the base (<NUM>), the first lift (<NUM>) and the second lift (<NUM>) being independently operable to place the support frame (<NUM>) in one or more Trendelenburg positions in which the first longitudinal end and the second longitudinal end are at different heights relative to the base (<NUM>); and
a plurality of load cells (<NUM>), with at least one load cell (<NUM>) coupled to the first lift (<NUM>) to act between the first lift (<NUM> and the support frame (<NUM>) and at least one load cell (<NUM>) coupled to the second lift (<NUM>) to act between the second lift (<NUM>) and the support frame (<NUM>) such that a load on the support frame (<NUM>) is transmitted to the plurality of load cells (<NUM>) to measure the load,
wherein the guided body (B1, B3) is arranged to move longitudinally relative to the base (<NUM>) in response to operation of the second lift (<NUM>) to move the support frame (<NUM>) to the one or more Trendelenburg positions such that the first lift (<NUM>) moves longitudinally toward the second lift (<NUM>) to accommodate movement of the support frame (<NUM>) to the one or more Trendelenburg positions.