Patent Description:
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 specifically, the present disclosure relates to a patient support apparatus with a lift assembly that can lower the patient support apparatus deck to a very low height while still providing a full range of motion to a height where a caregiver can access the patient. Such an apparatus is disclosed in the <CIT>.

A lift mechanism is described that is compact at a very low height while still providing a long range of travel to raise the patient support apparatus deck to a height that is suitable for caregivers. Further, the lift mechanism is configured so that it can raise or lower one end of the patient support deck to orient the patient in a Trendelenburg or reverse Trendelenburg position.

In one form, a patient support apparatus includes a base, a frame supported relative the base, with 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, with the first leg being pivotally coupled to the frame at an upper end thereof and pivotally and slidably coupled to the base at a lower end thereof. The second leg is pivotally at its upper end mounted to the first leg at a medial portion thereof to form an inverted Y-shaped leg assembly when unfolded. The lift assembly further includes an actuator mounted in the leg assembly with a mounting configuration to produce a maximum force F1 when raising the frame occurring after the lift assembly is raised from its lowermost configuration. For example, the maximum force F1 may occur approximately at mid-stroke of the lift assembly.

In one embodiment, the actuator is mounted in the leg assembly with a mounting configuration to produce a starting force SF wherein the starting force SF is in a range of <NUM>% to <NUM> % of or <NUM>% to <NUM>% of or about <NUM>% of the maximum force F1.

The actuator is mounted with a mounting configuration to produce a minimum force F2 when raising or lowering the frame wherein the minimum force F2 is in a range of <NUM>% to <NUM>% of the maximum force F1 and, optionally, about <NUM>% of the maximum force F1.

In another embodiment, a patient support apparatus includes a base, a frame supported relative to the base, which is 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 coupled to the frame at an upper end thereof and pivotally coupled to the base at a lower end thereof. The lift assembly includes a first leg and a second leg, with the second leg being pivotally mounted to the first leg at a medial portion thereof to form an inverted Y-shaped leg assembly when unfolded. An actuator is mounted in the leg assembly with a mounting configuration to produce a maximum force F1 and a minimum force F2 when raising or lowering the frame wherein the minimum force F2 is a range of <NUM>% to <NUM>% of the maximum force F1. For example, the minimum force F2 may occur at a maximum height of the lift assembly.

In one aspect, the actuator is mounted in the leg assembly with a mounting configuration to produce a starting force SF wherein the minimum force F2 is in a range of <NUM>% to <NUM>% of the starting force SF.

In another embodiment, a patient support apparatus includes a base, a frame supported relative to the base, which is 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 coupled to the frame at an upper end thereof and pivotally coupled to the base at a lower end thereof. The lift assembly includes an actuator and a first leg and a second leg, with the second leg being pivotally mounted to the first leg at a medial portion thereof to form an inverted Y-shaped leg assembly when unfolded. The actuator is mounted in the leg assembly to the first leg on one end by a first connection and at its opposed end by a second sliding pivotal connection to the first leg.

In one aspect, the second sliding pivot connection is linked to the second leg wherein when the actuator extends or contracts, the first leg and the second leg are unfolded or folded with respect to each other.

In a further aspect, the first leg includes an upper pivot connection to the frame, a lower pivot connection to the base, and further comprises a drive link coupled on one end to the actuator and coupled at its opposed end to the first leg by a sliding link pivot connection. The drive link is eccentrically coupled to the second leg.

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

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 its lowermost position.

In yet another embodiment, a patient support apparatus includes a base, a frame supported relative to the base, which is 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 coupled to the frame at an upper end thereof and pivotally coupled to the base at a lower end thereof. The lift assembly includes an actuator and a first leg and a second leg, with the second leg being pivotally mounted to the first leg at a medial portion thereof to form an inverted Y-shaped leg assembly when unfolded. The second leg has a crank arm. The lift assembly further includes a drive link having first and second ends, with the first end of the drive link pivotally coupled to actuator and the second end of the drive link coupled to the crank arm and configured to move in a nonlinear path to thereby to push or pull on the crank arm from a range of angles and thereby unfold or fold the first leg and the second leg with respect to each other to contract or extend the lift assembly.

In one aspect, the first leg includes an upper pivot connection to the frame, a lower pivot connection to the base, and the driving link is slidingly coupled to the first leg by a sliding pivot connection and eccentrically coupled the crank arm.

In another aspect, the sliding pivot connection comprises a non-linear sliding pivot connection.

According to yet another embodiment, a patient support apparatus includes a base, a frame supported relative to the base, which is 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, which includes a head end leg assembly and a foot end leg assembly. Each of the leg assemblies has a pair of legs, with each pair of legs including a first leg and a second leg forming an inverted Y-shaped configuration when raising the frame and being folded generally flat when lowering the frame. The first legs are pivotally mounted at their upper ends to the frame and pivotally mounted at their lower ends to the base. Each pair of legs has a folding pivot axis, and each of the head end and foot end actuators has a first connection to its respective first leg and a sliding lower pivot connection to its respective first leg, wherein the first and second legs of each leg assembly are linked such that extension and contraction of their respective actuators will unfold or fold the leg assemblies to raise or lower the frame.

In one aspect, each of the first legs is linked to its respective second leg by a drive link, which are eccentrically mounted to their respective second legs.

In a further aspect, one end of each of the drive links is coupled to its respective first leg by a sliding pivot connection with an arcuate path.

In another aspect, the sliding pivot connections of the actuators to the first legs have linear paths.

According to another aspect, the head end leg assembly is independent from the foot end leg assembly.

In yet another embodiment, the lifting leg of the head end leg assembly is pivotally mounted at a head end pivot connection at or near the head end of the frame, and the lifting leg of the foot end leg assembly is pivotally mounted at a foot end pivot connection at or near the foot end of the frame.

In a further aspect, the head end and foot end pivot connections are offset below the frame.

In another embodiment, a patient support apparatus includes a base, a support frame supported relative to the base, which is configured to support a deck for supporting a patient thereon, and a lift assembly. The lift assembly includes a head end leg assembly and a foot end leg assembly. Each of the leg assemblies has an actuator and forms an independent assembly that can be mounted between the base and the support frame as an assembled unit simply inserting the pivot connections between the leg assembly and the base and coupling the pivot connections between the leg assembly and the support frame.

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

In yet further aspects, at least one of the leg assemblies includes first and second lifting legs. Optionally, the first lifting leg comprises an inverted U-shaped frame. Similarly, the second lifting leg may comprise a second inverted U-shaped frame. In another embodiment, one or both lifting legs may be L-shaped.

In another embodiment, the second lifting leg forms a stop for the first lifting leg when the lift assembly is folded to it lowermost configuration.

According to yet another embodiment, a patient support apparatus includes a base, a frame supported relative to the base, with 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 mounted to the first lifting leg on one end and mounted to the first lifting leg at another end for linear movement relative to the first leg. The second lifting leg is linked to the actuator in a manner to cause the second lifting leg to pivot about the first lifting leg when the linear actuator is extended or contracted.

In yet another aspect, the second lifting leg includes a crank arm that is coupled to the actuator by a link so that extension or retraction of the actuator induces rotation of the second lifting leg.

These and other objects, advantages, and features of the disclosure will be more fully understood and appreciated by reference to the description of the current embodiment and the drawings.

It is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of "including" and "comprising" and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. Further, enumeration may be used in the description of various embodiments. Unless otherwise expressly stated, the use of enumeration should not be construed as limiting the disclosure to any specific order or number of components. Nor should the use of enumeration be construed as excluding from the scope of the disclosure any additional steps or components that might be combined with or into the enumerated steps or components.

Referring to <FIG>, the numeral <NUM> generally designates a patient support apparatus. In the illustrated embodiment, patient support apparatus <NUM> is configured as a bed, such as a hospital bed, with head and foot boards 10a, 10b, side rails (not shown), and an articulating deck <NUM>. However, it should be understood the patient support apparatus <NUM> may take on other forms, including a stretcher, a cot, or the like. In general, patient support apparatus <NUM> is used whenever a patient is to be supported and it is desirable to raise and lower the patient relative to a floor surface or other supporting surface. As will be more fully described below, patient support apparatus <NUM> includes a lift assembly for raising and lowering the patient support apparatus surface, such as a mattress or other cushioning device, which supports a patient thereon, between a fully raised position and a lowermost position, while still leaving clearance sufficient to allow a base of an over bed table or a patient lift to be extended under the patient support apparatus.

As best seen in <FIG>, patient support apparatus <NUM> includes a base <NUM>, a support frame <NUM> for supporting deck <NUM> (<FIG>), and a lift assembly <NUM> for raising or lowering support frame <NUM> (and deck <NUM>, see <FIG>) relative to base <NUM>. It should be understood that frame <NUM> may also support a load frame beneath deck <NUM>, which is used for mounting sensors, such as load cells, to measure the weight of a patient supported on the deck. However, the load frame may be eliminated and. load cells may be placed in frame <NUM> due to the reduction of forces, especially the reduction of torque on the frame <NUM>, which is achieved the arrangement of the lift assembly components described more fully below.

As best seen in <FIG>, base <NUM> is a wheeled base with a plurality of caster wheels <NUM> to facilitate movement of the bed across a floor surface. In the illustrated embodiment, again referring to <FIG>, deck <NUM> includes a plurality of articulating deck sections 16a, 16b, 16c, 16d, and 16e. It should be understood, however, that the number of deck sections may vary. Each deck section may be articulated by an actuator (not shown) to raise or lower the deck sections, for example, to orient the deck sections in a flat configuration or in a chair configuration (and various other configurations in between). The construction of any of base <NUM>, support frame <NUM>, the headboard 10a, footboard 10b, and/or the side rails may take on any known designs, such as, for example, those disclosed in <CIT>, and entitled HOSPITAL BED, commonly assigned to Stryker Corp. , or <CIT> entitled PATIENT HANDLING DEVICE INCLUDING LOCAL STATUS INDICATION, ONE-TOUCH FOWLER ANGLE ADJUSTMENT, AND POWER-ON ALARM CONFIGURATION, also commonly assigned to Stryker Corp. , The construction of any of base <NUM>, support frame <NUM>, the headboard 10a, footboard 10b, and/or the side rails may also take on forms different from what is disclosed in the aforementioned patent and patent publication.

As will be more fully described below, lift assembly <NUM> is configured so that actuators with a shorter stroke and consistent force margin ("applied force less actuator capacity") may be used while still being able to lower the deck to a low height position, such as <NUM> inches off the floor, and to a full height position, such as in a range of <NUM> to <NUM> inches off the floor. In other words, the same energy may be applied by better optimizing the force curve. In this manner, lower maximum loads may be applied to the components, such as the weldments forming the leg assemblies. Additionally, this may reduce costs and allow use of a lighter actuator.

Optionally, the actuator may be mounted to reduce, if not eliminate, any side loading on to the lifting legs by providing sufficient play in the actuator mounting arrangement, but no so much play that will induce lateral loads at its rod mounting location. Further, as noted above, the actuators are not mounted to the frame and, instead, are fully contained and mounted in the leg assemblies, as described below, which reduces forces on the frame so that load cells may be mounted to the frame to measure patient weight, as well as movement and patient biometrics.

Additionally, when lift assembly <NUM> is moved to its lowermost configuration, such as shown in <FIG> and <FIG>, the lift assembly <NUM> may be substantially contained within base <NUM> without interfering with the central space S under the base, which may be needed, for example, for mounting a drive wheel and controls for the wheel drive system (such as the ZOOM system sold by Stryker). As such, for example, when lowered, patient support apparatus <NUM> may be configured so that the central space S under the base is clear at least over a length S1 of about <NUM> inches. In this manner, patient support apparatus <NUM> can provide a very low height patient support apparatus, which can reduce the chance of a patient fall, but without eliminating the available space under the base.

Referring again to <FIG>, lift assembly <NUM> includes a head end lift assembly 18a and a foot end lift assembly 18b, which may be substantially mirror images of each other and mounted adjacent the respective head and foot ends of the frame <NUM>. For ease of description, many of the following details are made in reference to the head end lift assembly 18a, with the understanding that the same details 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 and foot end lift assemblies may have different configurations.

As best seen in <FIG>, frame <NUM> includes a pair of longitudinal frame members 14a and a pair of transverse frame members 14b, which connect longitudinal frame members 14a to form the frame. Referring to <FIG>, <FIG>, <FIG>, <FIG>, <FIG> and <FIG>, head end lift assembly 18a includes a first lifting leg <NUM> and a second lifting leg <NUM>, which are pivotally joined by pivot connections <NUM> (best seen in <FIG>) to form a folding leg assembly <NUM>. Pivot connections <NUM> are formed by pins 30a (<FIG>) that pivotally join first lifting leg <NUM> with second lifting leg <NUM> via openings 30b, 30c (see <FIG> and <FIG>) formed in the respective legs <NUM>, <NUM>.

First lifting leg <NUM> is pivotally mounted at its upper end to support frame <NUM> at pivot connections <NUM> (<FIG>) formed by a pair of pins that are pivotally mounted to frame <NUM> such as by pivot blocks 14d, which are mounted to transverse frame members 14b of frame <NUM> via brackets 14c. Optionally, pivot connections <NUM> may be formed by a single pivot rod 24a (shown in phantom in <FIG>) that extends transversely beneath upper transverse frame member <NUM> (described below) and into the upper ends of leg <NUM> to extend through pivot blocks 14d, which as described below nest in the upper end of legs <NUM> when the lift assembly is lowered folded. Optionally, rod 26a may be supported by intermediate brackets 24b (<FIG>) mounted to the underside of frame member <NUM>.

Lifting leg <NUM> is pivotally mounted at its lower end to base <NUM> at sliding pivot connections <NUM>, such as by the pivot blocks <NUM> (described more fully below). Second lifting leg <NUM> is pivotally mounted at its lower end to base <NUM> at pivot connections <NUM> and pivotally mounted adjacent its upper end to the medial portion of lifting leg <NUM> by pivot connections <NUM>. In this manner, when legs <NUM> and <NUM> are unfolded about pivot connections <NUM> they form an inverted Y shaped frame and when folded are generally arranged in flattened configuration (see <FIG>). Further, as will be more fully described below, when folded, the legs <NUM> and <NUM> may be arranged in base <NUM> so that the deck <NUM> may be lowered to a height H of less than <NUM> inches off the surface on which the base is supported. Optionally, also more fully described below, when folded, second lifting leg <NUM> may provide a bearing surface, for example, in the form of a stop 22a (see <FIG>), for lifting leg <NUM> so that the load of the frame and deck may be directly transmitted to the base <NUM> via pivot connections <NUM> and <NUM>.

As will be more fully described below, lift assembly 18a (as well as lift assembly 18b) includes an actuator <NUM>, in the form of a linear actuator, such as a pneumatic, electric or hydraulic actuator. As will be more fully described below, upper end (fixed base 36d, e.g. <FIG> and <FIG>) of head end actuator <NUM> is mounted to the upper end of first lifting leg <NUM>, for example by a pivot connection 37a and bracket 37b, and, further, mounted at its opposed end via sliding pivot connection 37c, also to first lifting leg <NUM>. In this manner, when extensible rod 36a extends, it is extended along an axis 36b that is fixed relative to first lifting leg <NUM> (further details are provided below). In other words, the actuator does not pivot relative to the first lifting leg <NUM> and, instead, optionally extends generally parallel to lifting leg <NUM> (e.g. at least the upper linear portion of leg <NUM>, see below for further details on the optional construction of first lifting leg <NUM>).

In order to translate the linear motion of the actuator <NUM> into pivotal motion of second lifting leg <NUM> (and hence lifting motion of lift assembly 18a), lifting leg <NUM> is coupled to the actuator via a link and crank arm arrangement. Further, as will be more fully described below, the link and crank arrangement may be configured to tailor the force curve of the lift assembly to closely match the allowable force of the actuator.

For example, in one embodiment, the actuator and link and crank arm arrangements in the lift assembly are configured to produce a maximum force F1 to occur when raising the frame <NUM> after the lift assembly <NUM> has been raised from its lowermost configuration. Referring to <FIG>, the maximum force F1 may occur approximately at mid-stroke of the lift assembly. Further, the actuator, link and crank arms are mounted in the leg assembly <NUM> with a mounting configuration to produce a starting force SF wherein the starting force SF is in a range of <NUM>% to <NUM>% of, <NUM>% to <NUM>% of, or about <NUM>% of the maximum force F1 (see <FIG>). As a result, the actuator may have a shorter stroke size than normally would otherwise be used, and moreover, may have a consistent force margin, with the force margin varying from about <NUM> Newtons to about <NUM> Newtons (see <FIG>).

Further, in so doing, the speed of the lifting of the deck is more uniform throughout its range of motion, which is more comforting to a patient supported thereon. For example, the speed of the actuator over its full range of motion may be more consistent and may range from about <NUM> to <NUM> dist/time. It should be understood that the speed will vary due to the weight of the patient supported thereon and the capacity of the selected actuator.

In the illustrated embodiment, and referring to <FIG>, second lifting leg <NUM> is coupled to actuator <NUM> via a pair of crank arms <NUM> and via links <NUM>, <NUM>. Each crank arm <NUM> is fixed mounted at its upper end to second lifting arm <NUM> and pivotally coupled by a pivot connection 32a at its lower end to a respective link <NUM>. In turn, each link <NUM> is pivotally coupled to link <NUM> via a pivot connection 40a. Additionally, link <NUM> is pinned at its opposed end to actuator <NUM> via a transverse pin 36c mounted in the distal end of rod 36a of actuator <NUM>. Therefore, the distal end of link <NUM> is extended along axis 36b as rod 36a extends or retracts along axis 36b. Additionally, pin 36c and the distal end of link <NUM> move in a linear path P1, described more fully below. Optionally, the distal end of link <NUM> may have a slotted opening 38a formed therein for receiving pin 36c to help offload forces on the actuator at the low height, as more fully described below in reference to stop 22a.

As best seen in <FIG>, link <NUM> extends rearwardly from pin 36c toward the fixed based 36d of actuator <NUM>. Further, link <NUM> forms an acute angle with respect to rod 36a through its full range of motion, described below, while it distal end moves along path P1. The opposed, proximal end of link <NUM> (at pivot connection 40a) is guided along a non-linear path P2 (see <FIG> and <FIG>) that at least initially diverges away from the linear path P1 of pin 36c, or in other words away from axis 36b. As noted above the rod 36a of actuator extends along an axis 36b that is fixed and generally parallel to at least the linear portion of lifting leg <NUM>. As such, when rod 36a is extended, link <NUM> will become a tension driver link that pulls pin 40a' of pivot connection 40a along path P2, which in turn pushes on links <NUM>. Links <NUM> in turn push on crank arms <NUM>, which apply a moment to second lift legs <NUM> to cause them to rotate counter clockwise (as view in <FIG>, e.g. ) about pivot connections <NUM> and unfold leg assembly <NUM> until pin 40a' of pivot connection 40a reaches the end of path P2. In reverse, as would be understood, when rod 36a is retracted, link <NUM> will become a compression driver link that pushes pin 40a' along path P2 (toward fixed based 36d of actuator <NUM>), which in turn pulls on links <NUM>. Links <NUM> then in turn pull on crank arms <NUM>, which apply a moment to second lift legs <NUM> to cause them to rotate clockwise (as view in <FIG>) about pivot connections <NUM> and fold leg assembly <NUM> until pin connection 40a reaches the other end of path P2. As would be understood, the path P2 may extend beyond the path of the pivot connection 40a so that the end of the path of the pivot connection 40a is defined by the actuator <NUM> rather than a hard stop on either end of path P2.

To retain the rod 36a of actuator <NUM> along its fixed linear path, first lifting arm <NUM> includes a track <NUM> extending therefrom along axis 36b, which guides the rod 36a of actuator <NUM> when extending or retracting. In the illustrated embodiment, track <NUM> is formed form a pair of opposed plates <NUM>, such as stamped plates, with elongated slots 48a for guiding pin 36c of rod <NUM> along its linear path P1 along axis 36c. Optionally, as more fully described below, plates <NUM> may be configured to provide a bearing surface 48b along edges of slots 48a for pin 36c to reduce slop and play and provide a tighter assembly. For example, bearing surfaces 48b may be provided by lips formed in plates <NUM> along at least the lower edge of slot 48a, but which may extend around the full perimeter of the slot to reinforce the plate at the slot location.

In the illustrated embodiment, referring to <FIG>, first lifting leg <NUM> is formed from an inverted U-shape frame with a transverse upper frame member <NUM> and two depending frame members <NUM>, which are joined together such by as welding. Actuator <NUM> is mounted to lifting leg <NUM> between frame members <NUM> with its upper end mounted to transverse frame member <NUM> by a pivot connection 37a. Pivot connection 37a may be formed by a bracket 37b, such a pair of plate brackets attached, such as by welding, to transverse frame member <NUM>.

Tracks <NUM> (which as noted guide the extension of rod end 36a along axis 36b) extend from transverse upper frame member <NUM> and are supported and rigidly mounted (e.g. by welds) at one end to transverse frame member <NUM> (see <FIG> and <FIG>). Tracks <NUM> are also supported and mounted to a second transverse frame member <NUM>. Transverse frame member <NUM> is spaced from transverse frame member <NUM> and rigidly mounted, for example by welding, between frame members <NUM> and provides rigidity to frame members <NUM>, in addition to providing support to tracks <NUM>.

In the illustrated embodiment, second lifting leg <NUM> may also be formed from an inverted U-shaped frame with an upper transverse member <NUM> and two depending frame members <NUM>, which are joined together, for example by welding. Depending frame members <NUM> straddle frame members <NUM> of first lifting leg <NUM> and are each pivotally joined thereto by pivot connections <NUM>. Transverse frame member <NUM> supports and provides a mount for crank arms <NUM>, which are rigidly attached to transverse frame member <NUM>, for example, by welding, and which straddle tracks <NUM>.

As best seen in <FIG>, each plate <NUM> that forms tracks <NUM> is supported and mounted to transverse member <NUM> and to transverse member <NUM>, for example, by welding. In the illustrated embodiment, transverse member <NUM> passes through openings 48c formed in plates <NUM> and is welded to the plates <NUM> about openings 48c, which are commensurate in size to the transverse member <NUM>. Similarly, the upper end of plates <NUM> have notches 48d (<FIG>) formed therein sized to receive transverse member <NUM> therein so that transverse member <NUM> can be welded to the respective plates <NUM> around the respective notches. Optionally, the ends of plates <NUM> may extend to form bracket 37b.

Path P2 may also be formed by a pair of slots 48e to guide pivot connections 40a. Slots 48e may also be formed in plates <NUM> and also include bearing surfaces 48f for the pin 40a' of pivot connections 40a to thereby reduce slack and hence increase the tightness of the movement of the lift assembly. Similar to bearing surfaces 48b, bearing surfaces 48f may be provided by a lip or lips formed in plate <NUM> along at least the lower edge of slot 48e, but which may extend around the full perimeter of the slot 48e to reinforce the plate <NUM> at the slot location.

As best seen in <FIG>, the lips that form bearing surfaces 48b and 48f may extend in opposed directions from each other-that is bearing surfaces 48b are formed on a lip(s) that extend from the inner side of plates <NUM>, while bearing surfaces 48f are formed on a lip(s) that extend from the outer side of plates <NUM>.

To guide pivot connection 40a and link <NUM>, and hence crank arm <NUM>, in the desired path, each slot 48e may be non-linear. Each slot 48e includes a first curved portion that is located approximately at the distal end of the slot 48e closest to the end of the rod <NUM>. The first curved portion forms the portion of the path P2 that initially diverges away from path P1 (and hence away from axis 36b). The second portion of slot 48e may be linear but is angled upwardly toward axis 36b and extends from the first curved portion toward to the proximal end of the slot 48e (end closest to the fixed body 36c of actuator <NUM>).

In this manner, when rod 36a is fully extended and leg assembly <NUM> is fully raised, and then actuator <NUM> is retracted, links <NUM>, now acting as compression links, will push pivot connections 40a along the first curved portion of path P2, which will pull links <NUM> and cause links <NUM> to increase their angle with respective to crank arms <NUM> while pulling on crank arms <NUM>. This increase in angle increases as the pivot connections 40a move along the curved portion due to the diverging angle of path P2 from path P1, which increases their leverage on crank arms <NUM>. As the rod 36a continues to retract, pivot connections 40a will continue to move along path P2 where links <NUM> and crank arms <NUM> increase their angular separation. This increase in angular separation increases the leverage of links <NUM> to pull on crank arms <NUM> until the legs are fully folded and in their lower most positions where links <NUM> can exert their maximum leverage. At the lowermost position, this is normally where the greatest torque is required due to the greatest separation of pivot connections <NUM>, <NUM>. However, with the present configuration, at this point, the force needed by the actuator <NUM> to move second leg <NUM> is not the maximum and, instead, is less than the maximum force due to the increased leverage of links <NUM> when in their orientation that corresponds to the lower most position of lift assembly 18a. Thus, the shape of the path P2 is such that the greatest leverage occurs where the greatest force is normally needed to lift the leg assembly, which as noted is typically when leg assembly <NUM> in its lowest height where the pivot connections <NUM>, <NUM> of the first and second legs <NUM>, <NUM> are furthest apart. But here due to the increased leverage by links <NUM> on crank arms <NUM>, as noted, the force require is not the maximum force. Instead, the maximum force is required when leg assembly <NUM> is raised about halfway where the pivot connections <NUM>, <NUM> of the first and second legs are still significantly separated but links <NUM> have a reduced leverage on crank arms <NUM>.

Stated another way, when leg assembly <NUM> is fully lowered (see <FIG> and <FIG>), and pivot connections 40a are at the proximal end of path P2, links <NUM> are substantially perpendicular to crank arms <NUM> and, therefore, as noted have the greatest leverage. In addition, as noted, due to the increased leverage, the amount of force is less than the maximum force needed during raising or lowering leg assembly <NUM>. As rod <NUM> is extended, however, the force needed by the actuator increases as the leg assembly is moved from its lower most position to its medial position where pivot connection 40a reaches its furthest distance from path P1 (or axis 36b), which corresponds to where link <NUM> forms an acute angle and therefore is angled closer to crank arm <NUM>. In this orientation, link <NUM> has less leverage than when in the lower most position. As the rod continues to extend, however, the pivot connections <NUM>, <NUM> of the first and second legs are moved closer together to reduce the amount of torque needed for continued unfolding of the first and second legs <NUM>, <NUM> so that the reduced leverage of link <NUM> as it approaches the distal end of path P2 coincides with a reduce amount of torque needed to move second leg <NUM> closer to the fully raised height of leg assembly <NUM>. As a result, and referring to <FIG>, the force margins of the actuator are reduced.

Although described as sliding pivot connections, pivot connections 40a may be formed from a single pin or rod 40a' that extends between links <NUM> and plates <NUM>.

Optionally, to provide additional support to tracks <NUM>, crank arms <NUM> may be pivotally coupled to tracks <NUM> by a pin or rod 58a that passes through apertured flanges <NUM> (<FIG> and <FIG>) extending upwardly from plates <NUM>.

In the illustrated embodiment, in order to increase the rigidity and torsional resistance of lifting legs <NUM>, <NUM>, each frame member that forms the respective lifting leg may be formed from one or more closed cross-section members, such as formed from a metal, such as steel. Alternately, each lifting leg <NUM>, <NUM> may be formed from a solid member, such as steel bar or plate. Similarly, transverse frame members <NUM> and <NUM> may also be formed from tubular members and extended into one or more transverse openings formed in the respective legs <NUM>, <NUM> and welded thereto around one or both openings to thereby form a rigid frame.

For example, depending members <NUM> and <NUM> may be formed from closed tubular members or solid plates. The closed tubular members may be formed from structural channel members or two stamped plates that are joined together, such as by welding. For example, each plate may be stamped into a channel shaped cross-section, which are then joined together in a facing relationship (open sides facing each other, like a clam shell arrangement). Optionally, the two plates may be slightly nested to allow the flanges of one channel shaped member to 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 length. Alternately, the plates may be sized so their flanges abut each other and are also welded together, for example, by spot welding or continuous welds along their lengths.

In addition to increasing the strength and torsional resistance of the lifting legs, their construction allows the shape of the legs to be tailored. For example, rather than having to have longer pins 26b on pivot connections <NUM> to span the space between leg <NUM> and base (<NUM>), as seen in <FIG>, the lower portions of leg <NUM> ( e.g. depending members <NUM>) may be formed so that they are offset or angled outwardly. For example, starting below pivot connections <NUM>, the lower portions of leg <NUM> (e.g. depending members <NUM>) may be formed so that they are offset or angled outwardly so that the mounts 26a for pivot connections <NUM> on leg <NUM> are offset outwardly and can be aligned in the same plane as the mounts 28a for pivot connections <NUM>. In this manner, pivot connections <NUM> and <NUM> may be mounted in the same channel (channel 12c of frame members 12a). Consequently, a single tube weldment may be used to form base <NUM>.

Transverse member <NUM>, on the other hand, may be formed from an open sectioned member, such as a channel shaped member, including a channel formed from a stamped plate or a structural channel member.

Track <NUM>, as noted, may be formed from plates, which may be reinforced with braces <NUM> (<FIG>). Similarly, links <NUM>, <NUM> and crank arms <NUM> may also be formed from plates and when needed provided with embossments or bosses around their mounting openings to increase their strength. For example referring to <FIG>, each link <NUM> may be formed from an elongated rectangular plate with an embossment 40b to reinforce the plate. Similar, crank arms <NUM> (<FIG>) may be formed from a generally triangular shaped pate and include embossments 32b, which reinforce the crank arms.

Referring to <FIG>, links <NUM> may be formed from two plates 38b joined at their (e.g. lower) edges by a transverse plate 38c, which may be welded to or formed with plates 38b to form an U-shaped link assembly. Openings 38a to may be reinforced by bosses or lips 38a' that encircle openings 38a and which also form bearing surfaces for pin 36c of actuator <NUM>. As noted above, openings 38a may also be elongated to allow off-loading from the actuator <NUM>, for example, when lift assembly 18a is fully lowered.

Further, as shown in the illustrated embodiment, the cross-section for the components of the lift assembly may vary along their length to provide increased strength where needed, but reduced in cross-section where the loads on the lift assembly are reduced to thereby provide a more compact and reduced weight light assembly. Further, by varying the cross-sections, the components of the lift assembly may provide a better nesting arrangement when folded. In the illustrated embodiment, frame members <NUM> are formed with three different cross-sections at three different elevations, which allow the lifting leg <NUM> to avoid interference with other components of the bed, including leg <NUM>, as it swings though its full range of motion.

For example, referring to <FIG>, the upper end of leg <NUM>, for example, depending frame members <NUM> may have the largest cross-section given that the forces to raise or lower the frame <NUM> are greatest at the upper end of leg <NUM>. Further, with the increased cross-section, a portion of the frame members <NUM> may have an open section at their upper ends to provide for cable routing through lift assembly and, further, to provide better nesting. As best understood from <FIG>, when lift assembly is fully folded and frame <NUM> is lowered, the mounting brackets 14c and mounting blocks 14d may extend into and nest in the open sections of the upper portion of frame members <NUM>, which again assists in reducing the overall height of the deck when the lift assembly is in its lower most configuration.

As noted above, the lower ends of lifting legs <NUM>, <NUM> are mounted to base <NUM> by pivot connections <NUM>, <NUM>. As seen in <FIG>, pivot connections <NUM> may be formed by a sliding block <NUM> rotationally mounted to each of the lower ends of the lifting legs <NUM> by pins 26b. Blocks <NUM> are guided in channels 12c formed in base frame members 12a (<FIG> and <FIG>) between upper and lower flanges 12b. Similarly pivot connections <NUM> may be formed by blocks <NUM> rotationally mounted to each of the lower ends of the lifting legs <NUM> by pins 28b. Blocks <NUM> are located and fixed in channels 12c by fasteners <NUM>, which extend through openings in upper flange 12c of frame members 12a.

To make the lift assembly more compact, blocks <NUM> and <NUM> may be mounted to pins 26b, 28b without the use fasteners or spring clips and, instead, retained on pins 26b and 28b using a tab and slot arrangement with blocks <NUM> and <NUM>, respectively, described below in reference to <FIG>, <FIG>, <FIG>, and <FIG>. Further, in order to avoid blocks <NUM>, <NUM> being rotated off pins 26b, 28b, each block has a tabbed connection for mounting the pins 26b, 28b to the block. Each pin 26b, 28b has one or more tabs that have to align with corresponding notches provided in the block mounting opening 60b, 64b in order to mount the blocks or remove the blocks from the pins. Additionally, referring to <FIG> and <FIG>, each of the mounting blocks are square or rectangular in shape so that they can be retained between the upper and lower flanges 12b of frame members 12a and do not rotate, though pins 26b and 28b are free to rotate in the blocks. The tabs on the pins (and corresponding notches) are arranged so that they do not align during normal movement of the lift mechanism and, therefore, retain the respective blocks on the pins (26b 28b) during normal operation.

As best seen in <FIG> and <FIG>, blocks <NUM> have rectangular body 60a with a central transverse opening 60b, which includes one or more notches 60c. In the illustrated embodiment, opening 60b includes a pair of opposed notches. Similarly, pin 26b has one or more tabs 26c for aligning with the notch or notches. When so aligned, pins 26b may be inserted into the opening 60b in the block <NUM> and, thereafter, the block <NUM> rotated about the pin to thereby retain the pin on the block. The block is then inserted into the frame member 12a (via cutouts or notches 12e described below) and captured between the upper and lower flanges. Optionally, upper and low flanges may include downwardly and upwardly extending lips 12b' (<FIG> and <FIG>), respectively, to further help retain blocks <NUM> and <NUM> in channels 12c.

As best seen in <FIG>, blocks <NUM> similarly have a rectangular body 64a with a central transverse opening 64b, which includes one or more notches 64c. In the illustrated embodiment, opening 64b includes a pair of opposed notches 64c. Similarly, pin 28b has one or more tabs 28c for aligning with the notch or notches. When so aligned, pins 28b may be inserted into the opening 64b in the block <NUM> and, thereafter, the block <NUM> rotated about the pin to thereby retain the pin on the block. The block is then inserted into the frame member 12a (via cutouts or notches 12e described below) and captured between the upper and lower flanges 12b. To secure block <NUM> in a fixed location, block <NUM> includes transverse openings through body 64a and offset portions 64d that are curved and align with the transverse openings for receiving fasteners <NUM> through body 64a and thereby fix the location of the pivot connection <NUM> along frame members 12a of base <NUM>.

Referring to <FIG> and <FIG>, blocks <NUM> and <NUM> are inserted in channels 12c of frame members <NUM> via notches 12e formed in the upper flanges 12b of frame members <NUM>. Notches 12e are located offset from pivot connections <NUM>, which when installed are fixed along the longitudinal axis of frame members 12a via fasteners <NUM>, and out of the normal travel of the sliding pivot connections <NUM>. Once inserted therein, blocks <NUM>, <NUM> are moved to their in use locations and then retained therein by the upper and lower flanges 12b and optional lips 12b' of frame members 12a. Thus, base <NUM> has install locations for the pivot connections offset from their use locations.

In addition to the overall construction, this installation arrangement and mounting configuration allows for lift assembly 18a (and 18b) to be installed as a unit (with the actuator and lines (e.g. power and/or hydraulic lines and/or pneumatic lines) already assembled in the unit), simply requiring the lift assembly to be inserted into the base and connected at their upper ends to mounting blocks 14d without the need for additional brackets and fasteners for installation.

Further, referring again to <FIG> and <FIG>, when frame <NUM> is in its lowermost position, frame members 14a of frame <NUM> may rest on base <NUM>, namely on between base members 12a. Additionally, lifting legs <NUM>, <NUM> and crank arms <NUM> are arranged so that they fold into the space defined between base members 12a, with the majority, if not all of, legs <NUM> and actuator <NUM> lying at or below the upper flange of base members 12a (<FIG>). Further, as noted, pivot connections <NUM> and <NUM> are aligned along the respective base frame members 12a and lie in the same plane, with pivot connections <NUM> aligned at or just below the upper flange of the respective frame members 12a.

In this manner, when lift assembly <NUM> is in its lowermost configuration, many of the components of the lift assembly (lifting legs, crank arms) are lowered into the space defined between or slightly below base frame members 12a, but leave there between space S, as described above. Additionally, when lift assembly <NUM> is in its lowermost configuration, the distance from the top of the deck to the floor may be less than <NUM>", less than <NUM>", and optionally less than <NUM>". Further, the space below base members 12a is sufficient to allow a base of an overbed table or lift assembly to extend under base. For example, the distance from the underside of the base members 12a to the floor is at least <NUM>", at least <NUM>" or between about <NUM>"-<NUM>".

As noted about, second lifting legs <NUM> have one or more stops 22a to provide a stop for the upper portion of leg <NUM> when leg assembly <NUM> is fully folded. Stops 22a are mounted and arranged to extend inwardly of legs <NUM> so that they provide bearing surfaces for depending frame members <NUM> of first lifting leg <NUM> when it is fully folded.

In the illustrated embodiment, stops 22a are formed by L-shaped brackets 22b mounted, such as by welding, to the inner side 22c of lifting legs <NUM>. Brackets 22b extend inwardly from inwardly facing side 22d of leg <NUM> to contact downwardly facing side of leg <NUM> when leg <NUM> is folded. Brackets 22b may have a rubber bumper or rubber bumpers 22c (<FIG>) mounted thereto to reduce noise and absorb some vibration. Because the stop is located adjacent pivot connection <NUM>, when folded, the weight of the deck and frame pass essentially directly through legs <NUM> to base <NUM>.

Referring to <FIG>, as described above, actuator <NUM> may be mounted to reduce side loading on the lift assembly components. For example, pin 36c of actuator <NUM> may be mounted in slot 48a of plate <NUM> between links <NUM> and between a pair of bushings 37e (<FIG>). Optionally, gaps or spaces are provided between bushings 37e, for example plastic bushings, and rod 36a (or between the bushings and links <NUM>) to provide sufficient play to avoid binding but also play that is sufficiently small to avoid inducing side loading (e.g. to avoid actuator from angling relative to path P1) on lift assembly, and more specifically on track <NUM>. For example, the gaps on each side may fall in a range of ½ to <NUM>/<NUM>th inch. Further, to help retaining pin in slots 48a, each opposed end of the pin 36c may be guided by a rectangular bushing 37f that is taller than the height of the slots 48a so that they ride on the outside of plates <NUM>. Optionally, springs may be provided in lieu of, or in addition to bushings 37e, to help maintain the alignment of the rod 36a along path P1.

Referring to <FIG> and <FIG>, optionally one or more of the lift assembly components may include protective and/or aesthetic covers, formed, for example, from plastic. For example, covers C1 and C2 may be provided to cover and optionally protect the head end and foot ends of the base <NUM>. Similarly, at least the rods of the actuators and track may be covered by a cover C3. Covers C4 may also be provided to extend over legs <NUM>. However, it should be understood with the closed construction of many of the lift assembly components, covers need not be provided for the leg assemblies of the lift assembly.

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

Optionally, at least some, if not all, of the pivot connections may incorporate a retainer <NUM> (<FIG>) that renders the pivot connection tamper resistant, and optionally non-serviceable. It also makes the lift assembly connections easy to inspect. Although detailed in reference to pivot connection 40a of link <NUM>, it should be understood that the same or similar details apply to the other pivot connections.

As best seen in <FIG>, the end of the pin 40a' of the pivot connection (40a) projects though the opening provided in link <NUM>. Optionally, the opening may be reinforced by a raised boss 40c. Mounted on pin 40a' about opening is retainer <NUM>. Retainer <NUM> is mounted to the distal end of pin 40a' via a standard pop rivet <NUM>, which extends though retainer <NUM> and though a transverse opening provided in the distal end of pin 40a'.

In the illustrated embodiment, retainer <NUM> includes a cylindrical body 70a with a closed end 70b, which rests against the distal end of pin 40a'. The cylindrical wall 70c of body 70a is bifurcated to ease installation on the end of pin 40a' so that it can be manually mounted on the distal end of pin 40a', though a tool can be used as well. Optionally, body 70a includes a flanged end 70d that forms an annular bearing surface 70e, which can provide some thrust load when for example, when pin 40a' pulls inwardly as view in <FIG> and engages washer W. Thus, retainer <NUM> provides an easy to inspect connection, which is tamper resistant and, further, may be non-serviceable, to ensure the correct assembly at the original manufacturing facility.

As would be understood, because the head end and foot end lifting assemblies are independent, they can be independently moved to raise or lower the head or foot ends of the support frame to move the deck in a Trendelenburg or reverse Trendelenburg position (see <FIG>, and <FIG>). Additionally, the speeds of each actuator can be independently controlled. For example, suitable actuators include Linak actuators, such as model number LA <NUM>, or Ilcon actuators. For example, the actuators may include sensors or magnets to measure the speed of the actuator so that, as noted, the actuation and speed of each actuator may be independently controlled.

Referring to <FIG>, in one embodiment of a standard hospital bed, the force of the actuators may range from about <NUM>-<NUM> N when in the lowermost position, up to about <NUM>-<NUM> N when about midway between the lowermost position, and then back down to about <NUM>-<NUM> N when in the uppermost position. As would be understood normally the greatest force is needed when the lift assembly is in its most compact, lowermost position; however, with the current arrangement of links and crank arms, which maximizes the moment arm when the leg assembly is in its lowest most position, the initial starting force (SF), as noted above, is less than the maximum force F1. As the lifting legs raise up relative to the base, the leverage provided by the crank arms decreases until the lift assembly has reached the midway region, approximately <NUM>-<NUM> inches off the floor, thus increasing the required force. As the lift assembly continues to rise , the leverage provided by the crank arms furthers reduces but at a reducing rate, as shown in <FIG>, until the lift assembly is in its uppermost configuration.

With the above configuration, when lift assembly <NUM> is in its lowermost position, the distance from the top of the litter deck (shown in phantom in FIG. <NUM>) to the floor may be less than <NUM>", less than <NUM>", and optionally less than <NUM>", and the space beneath base frame members 12a is unobstructed to allow a base of an overbed table or lift assembly to extend under base. For example, the distance from the underside of the base frame members 12a to the floor is at least <NUM>", at least <NUM>" or between about <NUM>"-<NUM>" and provides a minimum clearance of about <NUM> to <NUM> inches or about <NUM> inches below the lowermost member of the patient support. Further, when lift assembly is in its raised position, the lifting legs move outwardly toward the ends of the frame to thereby leave a space sufficient to allow a fluoroscope device to extend between the frame and the base.

Though not described in each instance, it should be understood that the structural components of the frame, the deck, and the lift assembly may be formed from metal structural members, such as steel, that are either welded (as noted in some cases) or fastened together, e.g. by bolts, rivets, pins, or screws or the like, or simply mechanically interlocked (as noted above in reference to some of the brackets). Further, features on one embodiment may be combined with features of another embodiment or embodiments. Additionally, it should be understood that the actuators may be controlled to extend or contract independently, for example, so that they can raise or lower one end of the patient support apparatus to orient the patient support apparatus deck in a Trendelenburg or reverse Trendelenburg position.

Claim 1:
A patient support apparatus (<NUM>) comprising:
a base (<NUM>);
a frame (<NUM>) supported relative to said base (<NUM>), said frame (<NUM>) configured to support a deck (<NUM>) for supporting a patient thereon;
a lift assembly (<NUM>) for raising or lowering said frame (<NUM>) relative to said base (<NUM>) and being pivotally coupled to said frame (<NUM>) at an upper end thereof and pivotally coupled to said base (<NUM>) at a lower end thereof;
said lift assembly (<NUM>) including a leg assembly (<NUM>) with a first leg and a second leg, said second leg being pivotally mounted to said first leg at a medial portion thereof to form an inverted Y-shaped leg assembly when unfolded; and
an actuator (<NUM>) mounted in said leg assembly (<NUM>) with a mounting configuration to produce a maximum force F1 when raising said frame (<NUM>) occurring after said lift assembly (<NUM>) is raised from a lowermost configuration of said lift assembly (<NUM>), a minimum force F2 when lowering said frame (<NUM>) or raising said frame (<NUM>) after said lift assembly (<NUM>) is raised from said lowermost configuration of said lift assembly (<NUM>), and a starting force SF at said lowermost configuration that is less than said maximum force F1, and wherein said minimum force F2 is in a range of <NUM>% to <NUM>% of said maximum force F1.