Patient Support Apparatus with Lift Assembly

Abstract

The patient support apparatus includes a frame supported relative to the floor and configured to support a deck for supporting a patient thereon, and a lift assembly for raising or lowering the frame relative to the floor. The lift assembly includes lifting legs connected to the frame and an actuator having a body and an extensible member. The actuator is mounted to one of the legs, rather than the frame, and is mounted to provide linear motion for one leg and convert the linear motion to rotational motion for the other leg via a link and crank arm arrangement.

Description

[Technical Field]

[0001] This application claims the benefit of U.S. Provisional Application No. 62 / 948,540 (P-600), filed December 16, 2019, and entitled "Compliant Support Having Lift Assembly," which is incorporated herein by reference in its entirety. [Background technology]

[0002] The present disclosure relates to a patient support apparatus with a lift assembly for raising or lowering a patient support apparatus deck relative to a floor surface. More particularly, the present disclosure relates to a patient support apparatus with a lift assembly that allows the deck of the patient support apparatus to be lowered to a very low height while providing a full range of motion up to a height that allows caregivers to access the patient. Summary of the Invention

[0003] A lift mechanism is described that is very low and compact while still providing a long range of travel for raising the deck of a patient support apparatus to a height suitable for a caregiver. Further, the lift mechanism is configured to be able to raise or lower one end of the patient support deck to orient the patient in Trendelburg or reverse Trendelburg position.

[0004] In one embodiment, a patient support apparatus includes a base and a frame supported relative to the base, the frame configured to support a deck for supporting a patient thereon. The patient support apparatus further includes a lift assembly for raising or lowering the frame relative to the base. The lift assembly includes a first leg and a second leg, the first leg pivotally connected at its upper end to the frame and pivotally and slidably connected at its lower end to the base. The second leg is pivotally attached at its upper end to the first leg at its central portion so as to form an inverted Y-shaped leg assembly when deployed. The lift assembly further includes an actuator mounted within the leg assembly in a mounting configuration that generates a maximum force F1 when raising the frame, which occurs after the lift assembly is raised from its lowest configuration. For example, the maximum force F1 may occur approximately mid-stroke of the lift assembly.

[0005] In one embodiment, the actuator is mounted within the leg assembly in a mounting configuration that generates a breakthrough force SF that is within the range of 95% to 99%, or 96% to 98%, or approximately 97% of the maximum force F1.

[0006] In one aspect, the actuator is mounted in a mounting configuration to generate a minimum force F2 when raising or lowering the frame, the minimum force F2 ranging from 50% to 70% of the maximum force F1, optionally about 60% of the maximum force F1.

[0007] In another embodiment, a patient support apparatus includes a base, a frame supported relative to the base, the frame configured to support a deck for supporting a patient thereon, and a lift assembly for raising or lowering the frame relative to the base. The lift assembly is pivotally connected at its upper end to the frame and at its lower end to the base. The lift assembly includes a first leg and a second leg, the second leg pivotally attached to the first leg at a central portion thereof so as to form an inverted Y-shaped leg assembly when deployed. An actuator is mounted within the leg assembly in a mounting configuration to generate a maximum force F1 and a minimum force F2 when raising or lowering the frame, the minimum force F2 being in a range of 55% to 65% of the maximum force F1. For example, the minimum force F2 may be generated at the maximum height of the lift assembly.

[0008] In one aspect, the actuator is mounted within the leg assembly in a mounting configuration that generates a breakthrough force SF, and the minimum force F2 is within the range of 55% to 65% of the breakthrough force SF.

[0009] In another embodiment, a patient support apparatus includes a base, a frame supported relative to the base, the frame configured to support a deck for supporting a patient thereon, and a lift assembly for raising or lowering the frame relative to the base. The lift assembly is pivotally connected at its upper end to the frame and at its lower end to the base. The lift assembly includes an actuator, a first leg, and a second leg, the second leg being pivotally attached at a central portion to the first leg so as to form an inverted Y-shaped leg assembly when deployed. The actuator is attached within the leg assembly at one end to the first leg by a first connection and at its opposite end by a second sliding and pivoting connection to the first leg.

[0010] In one aspect, the second sliding and pivoting connection is coupled to the second leg, and when the actuator extends or contracts, the first leg and the second leg unfold or fold relative to each other.

[0011] In a further aspect, the first leg has an upper pivot connection to the frame and a lower pivot connection to the base, and further includes a drive link connected at one end to the actuator and at an opposite end to the first leg by a sliding link pivot connection, the drive link being eccentrically connected to the second leg.

[0012] In one aspect, the sliding link pivot connection between the drive link and the first leg comprises a non-linear sliding pivot connection.

[0013] In another aspect, the sliding link pivot connection between the drive link and the first leg extends below the lower pivot connection of the first leg when the lift assembly is in the lowermost position.

[0014] In yet another embodiment, a patient support apparatus includes a base, a frame supported relative to the base, the frame configured to support a deck for supporting a patient thereon, and a lift assembly for raising or lowering the frame relative to the base. The lift assembly is pivotally connected at its upper end to the frame and at its lower end to the base. The lift assembly includes an actuator, a first leg, and a second leg, the second leg being pivotally attached at its central portion to the first leg to form an inverted Y-shaped leg assembly when deployed. The second leg includes a crank arm. The lift assembly further includes a drive link having a first end and a second end, the first end of the drive link pivotally attached to the actuator and the second end of the drive link coupled to the crank arm and configured to move in a non-linear path so that the crank arm can be pushed or pulled through a range of angles, thereby unfolding or folding the first leg and second leg relative to each other to retract or extend the lift assembly.

[0015] In one aspect, the first leg has an upper pivot connection with the frame and a lower pivot connection with the base, and the drive link is slidably connected to the first leg by a sliding pivot connection and eccentrically connected to the crank arm.

[0016] In another aspect, the sliding and pivoting connection comprises a non-linear sliding and pivoting connection.

[0017] According to yet another embodiment, a patient support apparatus includes a base, a frame supported relative to the base, the frame configured to support a deck for supporting a patient thereon, a head-end actuator, and a foot-end actuator. The patient support further includes a lift assembly for raising or lowering the frame relative to the base, the lift assembly including a head-end leg assembly and a foot-end leg assembly. Each leg assembly includes a pair of legs, each pair including a first leg and a second leg that form an inverted Y-shape when the frame is raised and that folds substantially flat when the frame is lowered. The first leg is pivotally attached at its upper end to the frame and at its lower end to the base. Each pair of legs has a folding pivot axis, and each of the head-end actuator and foot-end actuator has a first connection with a respective first leg and a sliding lower pivot connection with a respective first leg, and the first leg and second leg of each leg assembly are connected such that extension and contraction of the respective actuators causes the leg assemblies to unfold or fold and raise or lower the frame.

[0018] In one aspect, each of the first legs is coupled to a respective second leg by a drive link that is eccentrically attached to the respective second leg.

[0019] In a further aspect, one end of each of the plurality of drive links is coupled to a respective first leg by a sliding and pivoting connection having an arcuate path.

[0020] In another aspect, the sliding and pivoting connection to the first leg of the actuator has a linear path.

[0021] According to another aspect, the head end leg assembly is separate from the foot end leg assembly.

[0022] In yet another embodiment, the lifting legs of the head-end leg assembly are pivotally mounted at or near the head-end pivot connection of the frame, and the lifting legs of the foot-end leg assembly are pivotally mounted at or near the foot-end pivot connection of the frame.

[0023] In a further aspect, the head end pivot connection and the foot end pivot connection are offset below the frame.

[0024] In another embodiment, a patient support apparatus includes a base, a support frame supported relative to the base and configured to support a deck for supporting a patient thereon, and a lift assembly, the lift assembly including a head-end leg assembly and a foot-end leg assembly, each of the leg assemblies having an actuator to form an independent assembly that can be attached between the base and the support frame as an assembled unit by simply inserting a pivot connection between the leg assembly and the base and connecting the pivot connection between the leg assembly and the support frame.

[0025] For example, in one aspect, the head-end leg assembly and the foot-end leg assembly each have an inverted Y-shape when the lift assembly moves the support frame to the raised position.

[0026] In yet another aspect, at least one of the plurality of leg assemblies has first and second lifting legs. Optionally, the first lifting leg comprises an inverted U-shaped frame. Similarly, the second lifting leg can comprise a second inverted U-shaped frame. In another embodiment, one or both lifting legs can be L-shaped.

[0027] In another embodiment, the second lifting leg forms a stop for the first lifting leg when the lift assembly is folded into its lowest configuration.

[0028] According to yet another embodiment, a patient support apparatus includes a base, a frame supported relative to the base, the frame configured to support a cushion for supporting a patient thereon, and a lift assembly for raising or lowering the frame relative to the base. The lift assembly includes a first lifting leg and a second lifting leg. A linear actuator is attached at one end to the first lifting leg and at the other end to the first lifting leg for linear movement relative to the first leg. The second lifting leg is coupled to the actuator to pivot the second lifting leg about the first lifting leg when the linear actuator is extended or retracted.

[0029] In yet another aspect, the second lifting leg has a crank arm connected to the actuator by a linkage such that extension or contraction of the actuator induces rotation of the second lifting leg.

[0030] These and other objects, advantages and features of the present disclosure will be more fully understood and appreciated by reference to the description of the present embodiments and drawings.

[0031] Before describing embodiments of the present disclosure in detail, it should be understood that the disclosure is not limited to the details of operation or the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The present disclosure can be implemented in various embodiments and can be practiced or carried out in alternative ways not expressly disclosed herein. Furthermore, it should be understood that the phraseology and terminology used herein are for descriptive purposes and should not be regarded as limiting. The use of the terms "including" and "comprising" and variations thereof is meant to encompass the subsequently listed items and equivalents thereof, as well as additional items and equivalents thereof. Furthermore, enumerations may be used in describing various embodiments. Unless otherwise expressly stated, the use of enumerations should not be construed as limiting the disclosure to any particular order or number of components. Furthermore, the use of enumerations should not be construed as excluding from the scope of the disclosure any additional steps or components that can be combined with or with the listed steps or components. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is a side elevational view of a patient support apparatus. [Figure 1A] FIG. 1A is a perspective view of the patient support apparatus of FIG. 1 with the deck, headboard, and footboard removed to show the mounting arrangement of the lift assembly. [Figure 1B] FIG. 1B is a side elevational view of the patient support apparatus of FIG. 1 with the deck, headboard, and footboard removed to show the mounting arrangement of the lift assembly. [Figure 1C] FIG. 1C is a top view of the patient support apparatus of FIG. 1 with the deck, headboard, and footboard removed to show the mounting arrangement of the lift assembly in a fully lowered position. [Figure 2]2 is a perspective view of the patient support apparatus of FIG. 1 with the deck, frame, headboard, and footboard removed to show the lift assembly in a full height position. [Figure 2A] FIG. 2A is an enlarged view of the foot end leg assembly of the lift assembly of FIG. [Figure 3] FIG. 3 is another perspective view of a patient support apparatus similar to FIG. 2, showing the lift assembly in an intermediate height position. [Figure 3A] 3A is an enlarged view of the foot end leg assembly of the lift assembly of FIG. 3. FIG. [Figure 4] FIG. 4 is another perspective view of a patient support apparatus similar to FIG. 2, showing the lift assembly in a lowered position. [Figure 4A] 4A is an enlarged view of the foot end leg assembly of the lift assembly of FIG. [Figure 5] FIG. 5 is another perspective view of a patient support apparatus similar to FIG. 2, showing the lift assembly in the Trendelenburg position. [Figure 6] FIG. 6 is a side elevational view of the patient support apparatus with the deck, frame, headboard, and footboard removed to show the lift assembly in its full height configuration. [Figure 6A] 6A is an enlarged view of the foot end leg assembly of the lift assembly of FIG. 6. FIG. [Figure 7] FIG. 7 is a side elevation view similar to FIG. 6, with the lift assembly in its mid-height position. [Figure 7A] 7A is an enlarged view of the foot end leg assembly of the lift assembly of FIG. [Figure 8] FIG. 8 is a side elevation view similar to FIG. 6, but with the lift assembly in its lowest position. [Figure 8A] 8A is an enlarged view of the foot end leg assembly of the lift assembly of FIG. 8. FIG. [Figure 9] FIG. 9 is a side elevation view similar to FIG. 6, with the lift assembly in its Trendelenburg position. [Figure 9A] FIG. 9A is an enlarged perspective view of the lift assembly. [Figure 9B]FIG. 9B is an enlarged perspective view of the lift assembly. [Figure 9C] FIG. 9C is an enlarged perspective view of the lift assembly with the actuator removed. [Figure 9D] FIG. 9D is an enlarged perspective view of the lift assembly with the actuator removed. [Figure 9E] FIG. 9E is an enlarged perspective view of the lift assembly with the actuator removed. [Figure 9F] FIG. 9F is an enlarged perspective view of the lift assembly with the actuator removed. [Figure 9G] FIG. 9G is an enlarged perspective view of the lift assembly with the actuator removed. [Figure 9H] FIG. 9H is a graph of force and force limit versus actuator stroke. [Figure 10] FIG. 10 is an enlarged fragmentary exterior elevational view of the mounting arrangement of one of several leg assemblies of the lift assembly to the base of the patient support apparatus. [Figure 10A] FIG. 10A is an enlarged cross-sectional view of the base frame member showing the sliding blocks of the lifting assembly. [Figure 10B] FIG. 10B is an enlarged perspective view of the sliding block of FIG. 10A. [Figure 10C] FIG. 10C is an enlarged elevational view of the mounting block. [Figure 11] FIG. 11 is an enlarged fragmentary interior elevational view of the mounting arrangement of one of the leg assemblies to the base of the patient support apparatus. [Figure 12] FIG. 12 is an enlarged perspective view of one of the leg assemblies and actuators of the lift assembly. [Figure 12A] FIG. 12A is an enlarged perspective view of one of the lifting legs of the lift assembly. [Figure 12B] FIG. 12B is a second enlarged perspective view of the lifting leg of FIG. 12A. [Figure 12C] FIG. 12C is a perspective view of the other lifting leg of the lift assembly. [Figure 12D]FIG. 12D is an enlarged perspective view of one of the links of the lift assembly. [Figure 12E] FIG. 12E is an enlarged perspective view of another link of the lift assembly. [Figure 12F] FIG. 12F is an enlarged perspective view of an exemplary pivot connection of the lift assembly. DETAILED DESCRIPTION OF THE INVENTION

[0033] Referring to FIG. 1 , reference numeral 10 generally designates a patient support apparatus. In the illustrated embodiment, the patient support apparatus 10 is configured as a bed, such as a hospital bed, with a headboard 10 a, a footboard 10 b, side rails (not shown), and an articulating deck 16. However, it should be understood that the patient support apparatus 10 may take other forms, including a stretcher, a folding bed, and the like. Generally, the patient support apparatus 10 is used whenever a patient is to be supported and it is desirable to raise and lower the patient relative to the floor or other support surface. As described below, the patient support apparatus 10 includes a lift assembly for raising or lowering a patient support surface, such as a mattress or other cushioning device, on which the patient is supported, between a fully raised position and a lowest position, leaving sufficient clearance to allow an overbed table or base on a patient lift to extend below the patient support apparatus.

[0034] As best shown in FIG. 2, patient support apparatus 10 includes a base 12, a support frame 14 for supporting a deck 16 (FIG. 1), and a lift assembly 18 for raising or lowering support frame 14 (and deck 16, see FIG. 1) relative to base 12. It should be understood that frame 14 may also support a load frame below deck 16, which is used to mount sensors, such as load cells, for measuring the weight of a patient supported on the deck. However, a load frame may not be necessary. Instead, load cells may be located within frame 14 to reduce forces, particularly torque, on frame 14, which is achieved by the arrangement of lift assembly components, as described more fully below.

[0035] As best shown in Figure 2, base 12 is a wheeled base with multiple caster wheels 15 to facilitate movement of the bed across a floor surface. In the illustrated embodiment, and again referring to Figure 1, deck 16 has multiple articulating deck sections 16a, 16b, 16c, 16d, and 16e. However, it should be understood that the number of deck sections may vary. For example, each deck section may be articulated by an actuator (not shown) to raise or lower the deck section so as to orient the deck section in a flat configuration or a chair configuration (and various other configurations in between). The construction of any of the base 12, support frame 14, headboard 10a, footboard 10b, and / or side rails can be of any known design, such as those disclosed in commonly owned U.S. Patient Handling Apparatus with Local Status Indication, One-Touch Fowler Angle Adjustment, and Power-On Alarm Configuration, issued to Lemire et al., the complete disclosure of which is incorporated herein by reference in its entirety, and commonly owned U.S. Patient Handling Apparatus with Local Status Indication, One-Touch Fowler Angle Adjustment, and Power-On Alarm Configuration, issued to Stryker, the complete disclosure of which is incorporated herein by reference in its entirety. The construction of any of the base 12, support frame 14, headboard 10a, footboard 10b, and / or side rails can be of any known design, such as those disclosed in commonly owned U.S. Patient Handling Apparatus with Local Status Indication, One-Touch Fowler Angle Adjustment, and Power-On Alarm Configuration, issued to Lemire et al., the complete disclosure of which is incorporated herein by reference in its entirety.

[0036] As explained more fully below, the lift assembly 18 is configured to be able to lower the deck to low height positions, such as 28 cm (11 inches) off the floor, and to full height positions, such as between 66 cm (26 inches) and 86 cm (34 inches) off the floor, while being able to use actuators with shorter strokes and consistent force limits ("actuator capacity less than applied force"). In other words, the same energy can be applied by better optimizing the force curve. In this way, lower peak loads can be applied to components, such as the weldments that form the leg assemblies. This, in turn, reduces cost and allows for the use of lighter actuators.

[0037] Optionally, the actuators may be mounted to reduce, if not eliminate, any side loads on the lifting legs by providing sufficient play in the actuator mounting arrangement, and not to create enough play at the rod mounting locations to induce side loads. Further, as noted above, the actuators are not mounted to the frame; instead, as described below, the actuators are completely contained within and mounted to the leg assemblies, thereby reducing forces on the frame so that load cells can be mounted to the frame to measure patient weight, as well as movement and patient biometrics.

[0038] 4 and 8, the lift assembly 18 can be substantially contained within the base 12 without interfering with the central space S below the base, which may be necessary, for example, to mount a drive wheel and controls for a wheel drive system (such as the Zoom system sold by Stryker Corporation). Thus, for example, when lowered, the patient support apparatus 10 can be configured such that the central space S below the base is empty over a length S1 of at least about 46 cm (about 18 inches). In this manner, the patient support apparatus 10 can provide a very low height patient support apparatus, thereby reducing the opportunity for a patient to fall without eliminating available space below the base.

[0039] 2, lift assembly 18 includes a head-end lift assembly 18a and a foot-end lift assembly 18b, which may be substantially mirror images of one another and may be mounted adjacent to the respective head and foot ends of frame 14. For ease of explanation, many of the following details are provided with reference to head-end lift assembly 18a, but it should be understood that similar details also apply to the illustrated foot-end lift assembly 18b, which is shown as a mirror image and numbered with the same numbers as the head-end lift assembly. However, it should be understood that the head-end lift assembly and foot-end lift assembly may have different configurations.

[0040] As best shown in Figure 1A, frame 14 includes a pair of longitudinal frame members 14a and a pair of transverse frame members 14b connecting longitudinal frame members 14a to form the frame. Referring to Figures 2, 2A, 3, 3A, 4, and 4A, head-end lift assembly 18a includes first and second lifting legs 20 and 22, pivotally joined by pivotal connection 30 (best seen in Figure 3A) to form folded leg assembly 21. Pivotal connection 30 is formed by pin 30a (Figure 9F) that pivotally joins first and second lifting legs 20 and 22 through openings 30b and 30c (see Figures 12A and 12C) formed in the respective legs 20 and 22.

[0041] The first lifting leg 20 is pivotally mounted at its upper end to the support frame 14 at a pivot connection 24 (FIG. 1A) formed by a pair of pins pivotally mounted to the frame 14 by pivot blocks 14d or the like, which are attached to cross frame members 14b of the frame 14 via brackets 14c. Alternatively, the pivot connection 24 may be formed by a single pivot rod 24a (shown in phantom in FIG. 2A) extending transversely below an upper cross frame member 44 (described below) and extending to the upper end of the leg 20, passing through the pivot block 14d, so that the pivot rod telescopes into the upper end of the leg 20 as the lifting assembly is lowered and folded. Alternatively, the rod 24a may be supported by an intermediate bracket 24b (FIG. 2A) attached to the underside of the frame member 44.

[0042] Lifting leg 20 is pivotally attached at its lower end to base 12 at sliding pivot connection 26, as by pivot block 60 (described more fully below). A second lifting leg 22 is pivotally attached at its lower end to base 12 at pivot connection 28 and adjacent its upper end is pivotally attached to the center of lifting leg 20 by pivot connection 30. In this manner, when legs 20 and 22 are unfolded about pivot connection 30, legs 20 and 22 form an inverted Y-shaped frame, and when folded, legs 20 and 22 are positioned in a generally flat configuration (see FIG. 4). Furthermore, as described more fully below, when legs 20 and 22 are folded, legs 20 and 22 can be positioned within base 12 such that deck 16 is lowered to a height H of less than 30 cm (12 inches) above the surface on which the base is supported. Optionally, and as will be described more fully below, the second lifting leg 22, when folded, provides an abutment surface, for example in the form of a stop 22a (see FIG. 1), for the lifting leg 20, allowing frame and deck loads to be transferred directly to the base 12 via the pivot connections 26 and 28.

[0043] As will be described more fully below, lift assembly 18a (and lift assembly 18b) includes an actuator 36 in the form of a linear actuator, such as a pneumatic, electric, or hydraulic actuator. As will be described more fully below, the upper end of head-end actuator 36 (fixed base 36d, see, e.g., FIGS. 2A and 3) is attached to the upper end of first lifting leg 20, e.g., by pivot connection 37a and bracket 37b, and is further attached at its opposite end to first lifting leg 20 via sliding pivot connection 37c. In this manner, extension of extendable rod 36a causes extendable rod 36a to extend along axis 36b, which is fixed relative to first lifting leg 20 (as will be described in further detail below). In other words, the actuator does not rotate relative to the first lifting leg 20, but instead selectively extends generally parallel to the lifting leg 20 (e.g., see at least the upper linear portion of the leg 20, described below, for details of the selective structure of the first lifting leg 20).

[0044] To convert the linear motion of the actuator 36 into rotational motion of the second lifting leg 22 (and thus, lifting motion of the lift assembly 18a), the lifting leg 22 is coupled to the actuator via a link and crank arm arrangement. Additionally, as described more fully below, the link and crank arrangement can be configured to tailor the force curve of the lift assembly to closely match the force capacity of the actuator.

[0045] For example, in one embodiment, the actuator and link and crank arm arrangement within the lift assembly is configured to generate a maximum force F1 that occurs when the lift assembly 18 raises the frame 14 after being raised from the lowest configuration. Referring to FIG. 9H, the maximum force F1 may occur approximately mid-stroke of the lift assembly. Furthermore, the actuator, link and crank arm are mounted within the leg assembly 21 in a mounting configuration that generates a breakaway force SF that is within a range of 95%-99%, 96%-98%, or approximately 97% of the maximum force F1 (see FIG. 9H). As a result, the actuator can have a shorter stroke size than would typically be used, and the force limit can have a consistent force limit that varies from approximately 1500 Newtons to approximately 3000 Newtons (see FIG. 9H).

[0046] Furthermore, by doing so, the rate of deck elevation is more uniform throughout its range of motion, which is more comfortable for a patient supported thereon. For example, the actuator speed throughout its range of motion may be more consistent and range from about 0.7 to 1.3 distances per hour. It should be understood that this rate will vary depending on the weight of the patient supported thereon and the capabilities of the selected actuator.

[0047] In the illustrated embodiment, and with reference to FIGS. 9A-9G, the second lifting leg 22 is coupled to the actuator 36 via a pair of crank arms 32 and via links 38, 40. Each crank arm 32 is fixedly attached at its upper end to the second lifting arm 22 and pivotally connected at its lower end to a respective link 40 by a pivot connection 32a. Each link 40 is, in turn, pivotally connected to a link 38 via a pivot connection 40a. In addition, the link 38 is pinned at its opposite end to the actuator 36 via a transverse pin 36c attached to the distal end of the rod 36a of the actuator 36. Thus, the distal end of the link 38 is extended along the axis 36b when the rod 36a extends or contracts along the axis 36b. Additionally, the pin 36c and the distal end of the link 38 move in a linear path P1, which will be described more fully below. Optionally, the distal end of link 38 may have a slotted opening 38a formed therein to receive pin 36c to help unload the actuator at low heights, as will be described more fully below with reference to stop 22a.

[0048] As best seen in FIGS. 9A-9C, link 38 extends rearward from pin 36c toward fixed base 36d of actuator 36. Furthermore, link 38 forms an acute angle with rod 36a throughout its entire range of motion, with its distal end moving along path P1, as described below. The opposite proximal end of link 38 is guided (at pivotal connection 40a) at least initially along nonlinear path P2 (see FIGS. 9E-9G and 1A) that branches off from linear path P1 of pin 36c, i.e., axis 36b. As noted above, actuator rod 36a extends along axis 36b, which is fixed to and generally parallel to at least a linear portion of lifting leg 20. Thus, when rod 36a is extended, link 38 becomes a tension driver link that pulls pin 40a' of pivotal connection 40a along path P2, pushing on pivot link 40. Link 40 pushes against crank arm 32, exerting a moment on second lift leg 22, causing second lift leg 22 to rotate counterclockwise (as viewed in FIG. 9A ) about pivot connection 30, unfolding leg assembly 21 until pivot connection 40a′ reaches the end of path P2. Conversely, as will be appreciated, when rod 36a is retracted, link 38 becomes a compression driver link that pushes pin 40a′ along path P2 (toward fixed base 36d of actuator 36), pulling link 40. Link 40 then pulls crank arm 32, exerting a moment on second lift leg 22, causing second lift leg 22 to rotate clockwise (as viewed in FIG. 9E ) about pivot connection 30, folding leg assembly 21 until pin connection 40a reaches the other end of path P2. As will be appreciated, path P2 can extend beyond the path of pivotal connection 40a, so that the ends of the path of pivotal connection 40a are defined by actuator 36 rather than hard stops on either end of path P2.

[0049] To hold the rod 36a of the actuator 36 along its fixed linear path, the first lifting arm 20 has a track 42 extending therefrom along the axis 36b, which guides the rod 36a of the actuator 36 as it extends or retracts. In the illustrated embodiment, the track 42 forms a pair of opposing plates 48, such as stamped plates, having elongated slots 48a for guiding the pin 36c of the rod 36 along its linear path P1 along the axis 36b. Optionally, as described more fully below, the plates 48 can be configured to provide abutment surfaces 48b along the edges of the slots 48a for the pins 36c to reduce slop and play and provide a tighter assembly. For example, the abutment surfaces 48b can be provided by lips formed in the plates 48 along at least the lower edges of the slots 48a, but can also extend around the entire periphery of the slots to reinforce the plates at the slot locations.

[0050] 9A, in the illustrated embodiment, the first lifting leg 20 is formed from an inverted U-shaped frame including an upper cross frame member 44 and two vertical frame members 46, which are joined together, such as by welding. The actuator 36 is mounted to the lifting leg 20 between the frame members 46, with its upper end attached to the cross frame member 44 by a pivotal connection 37a. The pivotal connection 37a may be formed by a bracket 37b, such as a pair of plate brackets, attached to the cross frame member 44, such as by welding.

[0051] A track 42 (which, as noted, guides the extension of rod end 36a along axis 36b) extends from an upper cross frame member 44 and is supported at one end by and rigidly attached (e.g., by welding) to cross frame member 44 (see FIGS. 9A and 2A). Track 42 is also supported by and attached to a second cross frame member 50. Cross frame member 50 is spaced from cross frame member 44 and rigidly attached, e.g., by welding, between frame members 46, providing rigidity to frame members 46 in addition to providing support for track 42.

[0052] In the illustrated embodiment, the second lifting leg 22 may also be formed from an inverted U-shaped frame with an upper cross member 56 and two vertical frame members 58 joined together, for example, by welding. The frame members 58 straddle the frame member 46 of the first lifting leg 20 and are each pivotally attached thereto by a pivot connection 30. The cross frame member 56 supports and provides a mount for the crank arm 32, which is rigidly attached to the cross frame member 56, for example, by welding, and which straddles the track 42.

[0053] As best shown in Figures 9A-9G, each plate 48 forming track 42 is supported and attached, for example by welding, to a cross member 44 and a cross member 50. In the illustrated embodiment, cross member 50 passes through an opening 48c formed in plate 48 and is welded to plate 48 around opening 48c that matches the size of cross member 50. Similarly, the upper ends of plates 48 have cutouts 48d (Figure 12B) sized to receive cross members 44, so that cross members 44 can be welded to each plate 48 around their respective cutouts. Optionally, the ends of plates 48 can be extended to form brackets 37b.

[0054] Path P2 may also be formed by a pair of slots 48e to guide pivotal connection 40a. Slot 48e may also be formed in plate 48 and have abutment surfaces 48f for pins 40a' of pivotal connection 40a, thereby reducing slack and therefore increasing tightness of movement of the lifting assembly. Similar to abutment surfaces 48b, abutment surfaces 48f may be provided by lips formed in plate 48 along at least the lower edge of slot 48e, but which may extend around the entire periphery of slot 48e to reinforce plate 48 at the slot location.

[0055] As best shown in FIG. 9E, the lips forming abutment surfaces 48b and 48f can extend in opposite directions, i.e., abutment surface 48b is formed on a lip extending from the inside of plate 48, and abutment surface 48f is formed on a lip extending from the outside of plate 48.

[0056] Each slot 48e may be non-linear to guide the pivotal connection 40a and link 38, and thus the crank arm 32, along a desired path. Each slot 48e has a first curved portion located approximately at the distal end of the slot 48e closest to the end of the rod 36. The first curved portion forms a portion of path P2 that initially diverges away from path P1 (and thus diverges away from axis 36b). A second portion of the slot 48e may be linear but angled upward toward axis 36b, extending from the first curved portion toward the proximal end of the slot 48e (the end closest to the stationary body 36c of the actuator 36).

[0057] Thus, when rod 36a is fully extended, leg assembly 21 is fully elevated, and actuator 36 is then retracted, link 38, now acting as a compression link, pushes pivot connection 40a along the first curved portion of path P2, thereby pulling link 40 and increasing the angle of link 40 with its respective crank arm 32 while pulling crank arm 32. This angle increases as pivot connection 40a moves along the curved portion due to the angle of divergence of path P2 from path P1, which increases their leverage on crank arm 32. As rod 36a continues to retract, pivot connection 40a continues to move along path P2, causing link 40 and crank arm 32 to increase their angular separation. This increasing angular separation increases the leverage of link 40, pulling crank arm 32 until the leg is fully bent and link 40 is in its lowest position, providing maximum leverage. At the lowest position, this is where maximum torque would normally be required due to maximum separation of the pivot connections 26, 28. However, in the current configuration, at this point, the force required by the actuator 36 to move the second leg 22 is not maximum, but instead is less than the maximum force due to the increased leverage of the link 40 when in those orientations corresponding to the lowest position of the lift assembly 18a. Thus, the shape of path P2 is such that maximum leverage occurs where maximum force would normally be required to lift the leg assembly 21, such as when the leg assembly 21 is at its lowest height with the pivot connections 26, 28 of the first leg 20 and second leg 22 furthest apart. However, here, the force required is not maximum due to the increased leverage provided by the link 40 on the crank arm 32, as discussed above. Instead, maximum force is required when the leg assembly 21 is raised partway, with the first and second leg pivot connections 26, 28 still significantly apart, but with the link 40 reducing leverage on the crank arm 32.

[0058] In other words, when the leg assembly 21 is fully lowered (see FIGS. 9G and 8A) and the pivot connection 40a is at the proximal end of path P2, the link 40 is substantially perpendicular to the crank arm 32 and therefore has maximum leverage, as discussed above. Additionally, as discussed above, the increased leverage results in a lesser amount of force than the maximum force required while raising or lowering the leg assembly 21. However, as the rod 36 is extended, the force required by the actuator increases as the leg assembly is moved from its lowest position to a central position where the pivot connection 40a reaches its furthest distance from path P1 (or axis 36b), corresponding to a position where the link 40 forms an acute angle and is therefore angled closer to the crank arm 32. In this orientation, the link 40 has less leverage than when it is in the lowest position. However, as the rod continues to extend, the pivot connections 26, 28 of the first and second legs are forced closer together to reduce the amount of torque required for continued deployment of the first and second legs 20, 22, such that as the distal end of path P2 is approached, the reduced leverage of link 40 coincides with the reduced amount of torque required to move the second leg 22 closer to the fully raised height of the leg assembly 21. As a result, referring to FIG. 9H, the force limit of the actuator is reduced.

[0059] Although described as a sliding pivotal connection, the pivotal connection 40 a may be formed from a single pin or rod 40 a ′ extending between the link 40 and the plate 48 .

[0060] Optionally, to provide additional support to the track 42, the crank arm 32 may be pivotally connected to the track 42 by a pin or rod 58a that passes through an opening flange 48g (FIGS. 9B and 12A) extending upward from the plate 48.

[0061] In the illustrated embodiment, to increase the rigidity and torsional resistance of the lifting legs 20, 22, each frame member forming each lifting leg may be formed from one or more closed section members, such as formed from a metal such as steel. Alternatively, each lifting leg 20, 22 may be formed from a solid member, such as a steel bar or plate. Similarly, the transverse frame members 50 and 56 may be formed from tubular members, extending into one or more transverse openings formed in the respective legs 20, 22 and welded in around one or both openings, thereby forming a rigid frame.

[0062] For example, vertical members 46 and 58 can be formed from closed tubular members or solid plates. The closed tubular members can be formed from two structural channel members or pressed plates joined together, such as by welding. For example, each plate can be pressed into a channel-shaped cross-section and then joined together in a facing relationship (with open sides facing each other, like a clamshell arrangement). Alternatively, the two plates can be slightly nested so that the flange of one channel-shaped member can be inserted into the open face of the other channel-shaped plate and then welded in place with spot welds or continuous welds along their lengths. Alternatively, the plates can be sized so that their flanges abut each other and are welded together, such as by spot welds or continuous welds along their lengths.

[0063] In addition to increasing the strength and torsional resistance of the lifting legs, their construction allows for tailoring of the leg geometry. For example, rather than having to have a relatively long pin 26b on the pivot connection 26 that spans the space between the leg 20 and the base 12, as seen in FIG. 9A , the lower portions of the legs 20 (e.g., vertical members 46) can be formed so that they are offset or angled outward. For example, starting below the pivot connection 30, the lower portions of the legs 20 (e.g., vertical members 46) can be formed so that the mounts 26a for the pivot connection 26 on the legs 20 are offset outward and aligned in the same plane as the mounts 28a for the pivot connection 28. In this way, the pivot connections 26 and 28 can be mounted within the same channel (channel 12c of frame member 12a). Thus, a single tube weldment can be used to form the base 12.

[0064] Alternatively, the cross member 44 may be formed from an open sectioned member such as a channel shaped member having channels formed from stamped plate or structural channel members.

[0065] The track 42 can be formed from a plate, which can be reinforced with braces 48h, as described above (FIG. 9A). Similarly, the links 38, 40 and crank arm 32 can also be formed from a plate and, if necessary, can have embossments or bosses around their mounting openings to enhance their strength. For example, referring to FIG. 12E, each link 40 can be formed from an elongated rectangular plate with embossments 40b to reinforce the plate. Similarly, the crank arm 32 (FIG. 12C) can be formed from a generally triangular plate with embossments 32b to reinforce the crank arm.

[0066] 12B, the links 38 are formed from two plates 38b joined at their (e.g., lower) edges by a cross plate 38c, which can be welded to or formed by the plates 38b to form a U-link assembly. The openings 38a can be reinforced by a boss or lip 38a' that surrounds the peripheral opening 38a and also forms an abutment surface for the pin 36c of the actuator 36. As mentioned above, the openings 38a can also be elongated to allow unloading from the actuator 36, for example, when the lift assembly 18a is fully lowered.

[0067] Additionally, as shown in the illustrated embodiment, the cross-sections of some components of the lift assembly may vary along their length to provide increased strength, if desired, but where loads on the lift assembly are reduced, thereby providing a more compact and lightweight assembly. Additionally, varying the cross-sections allows the components of the lift assembly to better nest when folded. In the illustrated embodiment, the frame member 46 is formed with three different cross-sections in three different elevations, which allows the lifting leg 20 to avoid interference with other components of the bed, including the legs 22, as it swings through its full range of motion.

[0068] For example, with reference to FIG. 9A, the upper ends of the legs 20, e.g., vertical frame members 46, may have the largest cross-section, provided that the forces raising or lowering the frame 14 are greatest at the upper ends of the legs 20. Furthermore, with increased cross-section, portions of the frame members 46 may have open sections at their upper ends to provide a path for the cables through the lift assembly and also to provide better nesting. As best seen in FIG. 1A, when the lift assembly is fully folded and the frame 14 is lowered, the mounting brackets 14c and mounting blocks 14d can extend and nest into the open sections of the side portions of the frame members 46, which again helps reduce the overall height of the deck when the lift assembly is in its lowest configuration.

[0069] As described above, the lower ends of the lifting legs 20, 22 are attached to the base 12 by pivot connections 26, 28. As seen in FIG. 9, the pivot connections 26 may be formed by sliding blocks 60 rotatably mounted to each of the lower ends of the lifting legs 20 by a plurality of pins 26b. The plurality of blocks 60 are guided within channels 12c formed in the base frame member 12a (FIGS. 2 and 4) between the upper and lower flanges 12b. Similarly, the pivot connections 28 may be formed by blocks 64 rotatably mounted to each of the lower ends of the lifting legs 20 by pins 28b. The blocks 64 are positioned and secured within the channels 12c by fasteners 65 extending through openings in the upper flange 12c of the frame member 12a.

[0070] To make the lift assembly more compact, the blocks 60 and 64 can be attached to and instead retained on the pins 26b, 28b using a tab and slot arrangement with the blocks 60 and 64, respectively, as described below with reference to Figures 10, 10A, 10B, and 10C, without the use of fasteners or spring clips. Also, to prevent the blocks 60, 64 from rotating off the pins 26b, 28b, each block has a tabbed connection for attaching the pins 26b, 28b to the block. Each pin 26b, 28b has one or more tabs that must be aligned with corresponding notches in the block mounting openings 60b, 64b to mount or remove the block from the pin. 3 and 10, each mounting block is square or rectangular so that pins 26b and 28b rotate freely within the block but are retained between the upper and lower flanges 12b of frame member 12a and do not rotate. The tabs (and corresponding notches) on the pins are positioned so that they do not align during normal movement of the lift mechanism, thus retaining the respective block on the pins (26b 28b) during normal operation.

[0071] As best seen in FIGS. 10A and 10B, block 60 has a rectangular body 60a with a central transverse opening 60b having one or more cutouts 60c. In the illustrated embodiment, opening 60b has a pair of opposing cutouts. Similarly, pin 26b has one or more tabs 26c for aligning with the cutouts. Once so aligned, pin 26b can be inserted into opening 60b of block 60, after which block 60 can be rotated around the pin, thereby retaining it on the block. This block is then placed within insert frame member 12a (via cutout or cutout 12e, described below) and captured between upper and lower flanges. Optionally, the upper and lower flanges may have downwardly and upwardly extending lips 12b' ( FIGS. 10 and 10A ), respectively, to further help retain blocks 60 and 64 within channel 12c.

[0072] As best shown in FIG. 10C , the block 64 similarly has a rectangular body 64a with a central transverse opening 64b having one or more cutouts 64c. In the illustrated embodiment, the opening 64b has a pair of opposing cutouts 64c. Similarly, the pin 28b has one or more tabs 28c for aligning with the cutouts. Once so aligned, the pin 28b can be inserted into the opening 64b of the block 64, after which the block 64 can rotate about the pin, thereby retaining the pin on the block. The block is then inserted into the frame member 12a (via the cutout or notch 12e, described below) and captured between the upper and lower flanges 12b. To secure the block 64 in a fixed position, the block 64 has a transverse opening through the body 64a and an offset portion 64d that is curved and aligns with the transverse opening to receive a fastener 65 through the body 64a, thereby fixing the position of the pivot connection 28 along the frame member 12a of the base 12.

[0073] 3 and 10, blocks 60 and 64 are inserted into channel 12c of frame member 12a through cutouts 12e formed in the upper flange of frame member 12a. Cutouts 12e are offset from pivot connections 28, which, when installed, are secured via fasteners 65 along the longitudinal axis of frame member 12a, removing them from the normal movement of sliding pivot connections 26. Once inserted, blocks 60, 64 are moved to their use positions and then retained therein by upper and lower flanges 12b and optional lip 12b' of frame member 12a. Thus, base 12 has multiple installation positions for pivot connections offset from their use positions.

[0074] In addition to the overall structure, this installation arrangement and mounting configuration allows the lift assembly 18a (and 18b) to be installed as a unit (with the actuators and lines (e.g., power and / or hydraulic and / or pneumatic lines) already assembled within the unit), simply requiring the lift assembly to be inserted into the base and connected at its upper end to the mounting block 14d without the need for additional brackets and fasteners for installation.

[0075] 1C and 4, when the frame 14 is in its lowest position, the frame members 14a of the frame 14 may rest on the base 12, i.e., between the base members 12a. Furthermore, the lifting legs 20, 22 and crank arm 32 are folded into the spaces defined between the base members 12a and are positioned such that most, if not all, of the legs 20 and actuator 36 are at or below the upper flanges of the base members 12a (FIG. 8). Furthermore, as discussed above, the pivot connections 26 and 28 are aligned and coplanar along the respective base frame members 12a, and the pivot connections 30 are aligned at or just below the upper flanges of the respective frame members 12a.

[0076] Thus, when the lift assembly 18 is in its lowest configuration, many of the components of the lift assembly (lifting legs, crank arms) are lowered into the spaces defined between or slightly below the base frame members 12a, as described above, but remain between the spaces S. Furthermore, when the lift assembly 18 is in its lowest configuration, the distance from the top of the deck to the floor may be less than 14 inches, less than 13 inches, and optionally less than 12 inches. Furthermore, the space below the base member 12a is sufficient to allow an overbed table or the base of the lift assembly to extend below the base. For example, the distance from the underside of the base member 12a to the floor may be at least 4 inches, at least 5 inches, or between about 5 inches and 6 inches.

[0077] As previously mentioned, the second lifting leg 22 has one or more stops 22a to provide a stop for the upper portion of the leg 20 when the leg assembly 21 is fully folded. The stops 22a are attached and positioned to extend inwardly of the leg 22 to provide a support surface for the vertical frame member 46 of the first lifting leg 20 when the first lifting leg 20 is fully folded.

[0078] In the illustrated embodiment, the stops 22a are formed by L-shaped brackets 22b attached, such as by welding, to the inner surfaces 22c of the lifting legs 22. The brackets 22b extend inwardly from the inwardly facing sides 22d of the legs 22 so as to contact the downwardly facing sides of the legs 20 when the legs 20 are folded. The brackets 22b have rubber bumpers 22c (FIG. 11) attached to them to reduce noise and absorb some vibration. Because the stops are located adjacent the pivot connections 28, when folded, the weight of the deck and frame essentially passes directly through the legs 22 to the base 12.

[0079] Referring to FIG. 9A, as described above, the actuator 36 can be mounted to reduce side loads on the lift assembly components. For example, the pin 36c of the actuator 36 can be mounted in the slot 48a of the plate 48 between the links 38 and between the pair of bushings 37e (FIG. 9D). Optionally, a gap or space is provided between the bushings 37e, e.g., plastic bushings, and the rod 36a (or between the bushings and the links 48) to provide enough play to avoid binding, but also small enough to avoid inducing side loads (e.g., to prevent the actuator from angling relative to path P1) on the lift assembly, and more specifically, on the track 42. For example, the gap on either side can be in the range of 1 / 2 inch to 1 / 1000 inch. Additionally, to help retain the pins within slots 48a, the opposing ends of each of pins 36c may be guided by rectangular bushings 37f that are taller than the height of slots 48a so that they rest on the outer surface of plate 48. Optionally, a spring may be provided in place of or in addition to bushings 37e to help maintain alignment of rod 36a along path P1.

[0080] 1A and 3, optionally, one or more of the components of the lift assembly may have a protective and / or aesthetic cover, for example, formed from plastic. For example, covers C1 and C2 may be provided to cover and selectively protect the head and foot ends of the base 12. Similarly, at least the actuator rod and track may be covered by cover C3. Cover C4 may also be provided to extend across the leg 22. However, it should be understood that many of the components of the lift assembly are of closed construction, and covers need not be provided on the leg assemblies of the lift assembly.

[0081] Although not specifically described in each example, it should be understood that all structural load-bearing members of the lift assembly may be formed from metals, including steel, and may be stamped, formed, cast, or forged members and assembled by welding. Other members, such as mounting blocks or covers, may be formed from plastic or other low-friction materials, which may be molded.

[0082] Optionally, at least some, if not all, of the pivot connections may incorporate retainers 70 (FIG. 12F) that render the pivot connections tamper-resistant and, in some cases, non-serviceable. This also facilitates inspection of the connections in the lift assembly. While pivot connection 40a of link 40 will be described in detail, it should be understood that the same or similar details apply to the other pivot connections.

[0083] As best seen in FIG. 12F, the end of pin 40a' of pivot connection 40a protrudes through an opening in link 40. Optionally, the opening may be reinforced with a raised boss 40c. A retainer 70 is attached to pin 40a' around the opening. Retainer 70 is attached to the distal end of pin 40a' via a standard pop rivet 72, which extends through retainer 70 and through a transverse opening in the distal end of pin 40a'.

[0084] In the illustrated embodiment, the retainer 70 has a cylindrical body 70a with a closed end 70b that abuts against the distal end of the pin 40a'. The cylindrical wall 70c of the body 70a is forked to facilitate installation onto the end of the pin 40a', allowing it to be manually attached to the distal end of the pin 40a', although a tool could also be used. Optionally, the body 70a has a flanged end 70d that forms an annular abutment surface 70e, which can provide a degree of thrust load when the pin 40a' pulls the washer W inward to engage it, as shown in FIG. 12F, for example. The retainer 70 is therefore tamper-resistant and provides an easily inspectable connection that is non-repairable to ensure proper assembly at the original manufacturing facility.

[0085] As will be appreciated, the head-end lifting assembly and foot-end lifting assembly are independent, allowing them to be moved independently to raise or lower the head or foot end of the support frame and move the deck into Trendelenburg or reverse Trendelenburg (see FIGS. 1A and 5). Additionally, the speed of each actuator can be independently controlled. For example, suitable actuators include Linak actuators, such as model number LA40, or Ilcon actuators. For example, the actuators can include sensors or magnets to measure the speed of the actuators, as described above, so that the actuation and speed of each actuator can be independently controlled.

[0086] Referring to FIG. 9H, in one embodiment of a standard hospital bed, the actuator force can range from approximately 5300 N to 5400 N when in the lowest position, approximately 5700 N to 5800 N when in a position approximately midway between the lowest positions, and then return to approximately 3200 N to 3300 N when in the highest position. As is commonly understood, the greatest force is required when the lift assembly is in its most compact, lowest position. However, the current arrangement of the links and crank arms maximizes the moment arm when the leg assembly is in its lowest position, and as noted above, the initial breakthrough force (SF) is less than the maximum force F1. As the lifting legs rise relative to the base, the leverage provided by the crank arms decreases, thus increasing the required force, until the lift assembly reaches an intermediate region approximately 19 inches to 24 inches from the floor. As the lift assembly continues to rise, the leverage provided by the crank arm is further reduced, albeit at a reduced rate, until the lift assembly is in the uppermost configuration, as shown in FIG. 9H.

[0087] With the above configuration, when the lift assembly 18 is in its lowest position, the distance from the top of the litter deck (shown in phantom in FIG. 30) to the floor can be less than 14 inches, less than 13 inches, or optionally less than 12 inches, and the space below the base frame members 12a is unobstructed to allow the base of an overbed table or lift assembly to extend below the base. For example, the distance from the underside of the base frame members 12a to the floor can be at least 4 inches, at least 5 inches, or between about 5 inches and about 6 inches, providing a minimum clearance of about 2 inches to 3 inches, or about 2.4 inches below the lowest member of patient support. Additionally, when the lift assembly is in its raised position, the lifting legs move outward toward the ends of the frame, thereby leaving sufficient space to allow the fluoroscope to extend between the frame and the base.

[0088] Although not illustrated in each example, it should be understood that the structural components of the frame, deck, and lift assembly may be formed from metal structural members such as steel and may be welded (as described in some cases), fastened together by, for example, bolts, rivets, pins, or screws, or simply mechanically connected (as described above in connection with some of the brackets). Furthermore, features of one embodiment may be combined with features of another embodiment. Additionally, it should be understood that the actuators may be controlled to extend or retract independently, for example, to raise or lower one end of the patient support apparatus and orient the patient support apparatus deck in Trendelenburg or reverse Trendelenburg.

[0089] Directional terms such as "vertical," "horizontal," "top," "bottom," "upper," "lower," "inner," "inwardly," "outer," and "outwardly" are used to help describe the present disclosure based on the orientation of the embodiments shown in the figures. The use of directional terms should not be construed to limit the present disclosure to any particular orientation.

[0090] Various substitutions and modifications may be made to the above-described embodiments without departing from the spirit and broader aspects of the disclosure, as defined in the appended claims, which should be interpreted in accordance with the principles of patent law, including equivalents. This disclosure is presented for illustrative purposes and should not be construed as an exhaustive description of all embodiments of the invention, nor should it be construed to limit the scope of the claims to the specific elements shown or described in connection with these embodiments. For example, but not limited to, any individual element of the invention described herein may be replaced with an alternative element that provides substantially similar functionality or otherwise provides appropriate operation. This includes currently known alternatives, such as alternatives currently known to those of ordinary skill in the art, as well as alternatives that may be developed in the future that may be recognized by those of ordinary skill in the art as such upon development. Furthermore, the disclosed embodiments comprise multiple features that are described together and that may, in combination, provide numerous benefits. The invention is not limited to only those embodiments having all of these features or providing all of some of the described benefits, except to the extent expressly set forth in the appended claims. For example, the use of the articles "a," "an," "the," or "said" to refer to an element in the claim in the singular should not be construed as limiting the element to the singular.

Claims

1. 1. A patient support apparatus comprising: the patient support apparatus comprising: A base and a frame supported relative to the base, the frame being configured to support a deck for supporting a patient thereon; a lift assembly for raising or lowering said frame relative to said base, said lift assembly being pivotally connected at its upper end to said frame and at its lower end to said base, said lift assembly having a first leg and a second leg, said second leg being pivotally attached at a central portion to said first leg so as to form an inverted Y-shaped leg assembly when deployed; and an actuator mounted in the leg assembly having a mounting configuration that generates a maximum force F1 when lifting the frame after the lift assembly is raised from its lowest configuration.

2. The patient support apparatus of claim 1 , wherein the maximum force F1 occurs approximately mid-stroke of the lift assembly.

3. 3. The patient support apparatus of claim 1, wherein the actuator is mounted within the leg assembly in a mounting configuration that generates a starting force SF that is within a range of 96% to 98% of the maximum force F1.

4. 3. The patient support apparatus of claim 1, wherein the actuator is mounted within the leg assembly in a mounting configuration that generates a breakthrough force SF that is approximately 97% of the maximum force F1.

5. 3. The patient support apparatus of claim 1, wherein the actuators are mounted in a configuration that generates a minimum force F2 when raising or lowering the frame, the minimum force F2 being in the range of 50% to 70% of the maximum force F1.

6. 3. The patient support apparatus of claim 1, wherein the actuators are mounted in a configuration that generates a minimum force F2 when raising or lowering the frame, the minimum force F2 being approximately 60% of the maximum force F1.

7. 1. A patient support apparatus comprising: the patient support apparatus comprising: A base and a frame supported relative to the base, the frame being configured to support a deck for supporting a patient thereon; a lift assembly for raising or lowering the frame relative to the base, the lift assembly being pivotally connected at its upper end to the frame and at its lower end to the base, the lift assembly having a first leg and a second leg, the second leg being pivotally attached at a central portion to the first leg so as to form an inverted Y-shaped leg assembly when deployed; and an actuator mounted within the leg assembly in a mounting configuration that generates a maximum force F1 and a minimum force F2 when raising or lowering the frame, the minimum force F2 being in a range of 55% to 65% of the maximum force F1.

8. The patient support apparatus of claim 7 , wherein the minimum force F2 occurs at a maximum height of the lift assembly.

9. 9. The patient support apparatus of claim 7, wherein the actuator is mounted within the leg assembly in a mounting configuration that generates a starting force SF, and the minimum force F2 is within a range of 55% to 65% of the starting force SF.

10. 1. A patient support apparatus comprising: the patient support apparatus comprising: A base and a frame supported relative to the base, the frame configured to support a deck for supporting a patient thereon; a lift assembly for raising or lowering the frame relative to the base, the lift assembly being pivotally connected at its upper end to the frame and at its lower end to the base; an actuator; the lift assembly having a first leg and a second leg, the second leg being pivotally attached to the first leg at a central portion thereof about a folding pivot axis to form a Y-shaped leg assembly when deployed; 10. A patient support apparatus comprising: a patient support member configured to support a patient; a patient support arm configured to support a patient; and a patient support member configured to support a patient;

11. 11. The patient support apparatus of claim 10, wherein the first leg has an upper pivot connection with the frame and a lower pivot connection with the base, the patient support apparatus further comprising a drive link slidably connected to the first leg and eccentrically connected to the second leg by a sliding link pivot connection.

12. The patient support apparatus of claim 11 , wherein the sliding link pivot connection between the drive link and the first leg comprises a non-linear sliding pivot connection.

13. 12. The patient support apparatus of claim 11, wherein when the lift assembly is in a lowermost position, the sliding link pivot connection between the drive link and the first leg extends below the lower pivot connection of the first leg.

14. 1. A patient support apparatus comprising: the patient support apparatus comprising: A base and a frame supported relative to the base, the frame being configured to support a deck for supporting a patient thereon; a lift assembly for raising or lowering the frame relative to the base, the lift assembly being pivotally connected at its upper end to the frame and at its lower end to the base; an actuator; the lift assembly having a first leg and a second leg, the second leg pivotally attached at a central portion to the first leg to form an inverted Y-shaped leg assembly when deployed; the second leg has a crank arm; the patient support apparatus further comprising a drive link having a first end and a second end; the first end of the drive link is pivotally connected to the actuator; The second end of the drive link is coupled to the crank arm and configured to move in a non-linear path to push or pull the crank arm through a range of angles, thereby causing the first leg and the second leg to unfold or fold relative to each other and the lift assembly to contract or extend.

15. 15. The patient support apparatus of claim 14, wherein the first leg has an upper pivot connection with the frame and a lower pivot connection with the base, the drive link being slidably connected to the first leg and eccentrically connected to the crank arm by a sliding pivot connection.

16. The patient support apparatus of claim 15, wherein the sliding and pivoting connection comprises a non-linear sliding and pivoting connection.

17. 1. A patient support apparatus comprising: the patient support apparatus comprising: A base and a frame supported relative to the base, the frame being configured to support a deck for supporting a patient thereon; a head end actuator; a foot end actuator; a lift assembly for raising or lowering the frame relative to the base, the lift assembly having a head-end leg assembly and a foot-end leg assembly, each of the lift assemblies having a pair of legs, the head-end leg assembly and the foot-end leg assembly having a pair of legs, each pair of legs having a first leg and a second leg that form an inverted Y-configuration when the frame is raised and that fold when the frame is lowered, the first leg being pivotally attached at its upper end to the frame and pivotally attached at its lower end to the base; and a lift assembly, wherein each pair of legs has a folding pivot axis, the head-end actuator and the foot-end actuator each having a pivot connection to a respective first leg and a sliding lower pivot connection coupled to the respective first leg, the first leg and the second leg of each of the head-end leg assembly and the foot-end leg assembly coupled such that extension and contraction of the respective actuators causes each of the head-end leg assembly and the foot-end leg assembly to unfold or fold to raise or lower the frame.

18. 18. The patient support apparatus of claim 17, wherein each of the first legs is connected to a respective second leg by a drive link, the drive link being eccentrically attached to each of the second legs.

19. 20. The patient support apparatus of claim 18, wherein one end of each of the drive links is coupled to a respective first leg by a sliding and pivoting connection having an arcuate path.

20. 20. The patient support apparatus of claim 19, wherein the sliding pivot connection of the actuator to the first leg comprises a linear path.

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