Patent Description:
As hospital beds frames and other patient support apparatuses include more advanced and include advanced articulation to allow for better customized adjustment and positioning of patient's, the support surfaces/mattresses support on the frames are placed in ever increasingly complex positions. Relative movement of the components of the mattress relative to the frame can result in the mattress components being improperly positioned relative to the patient. In some cases, internal components are displaced within the cover of the mattress, causing a decrease in the performance of the mattress.

<CIT> describes a therapeutic mattress assembly comprising a mattress having a substrate assembly that includes a plurality of cylinders positioned side by side over the length of the mattress. Each cylinder is configured as a low air loss system to allow air to flow into the cylinder from a source and out of the cylinder through small holes located on the top of each cylinder. An overlay assembly provides a foam cushion that provides a supporting surface above the substrate assembly for the patient. A calf lift bladder operates to effectively raise or lower the patient's feet to prevent pressure related injuries. A lateral rotation assembly selectively raises and lowers a selected half of the mattress to turn patients in a lateral direction. A bolster inflates in response to the lateral rotation assembly to secure the patient within the mattress.

According to a first aspect of the present disclosure, a patient support apparatus comprises a foam frame defining a space; a bladder assembly positioned in the space, and a cover enclosing the foam frame structure and the bladder assembly. The patient support apparatus is adapted to engage an articulated frame. The patient support apparatus further includes at least one knob secured to the bladder assembly and configured to engage the articulated frame to control movement of the bladder assembly in response to movement of the articulated frame. The bladder assembly is engaged with the foam frame such that the bladder assembly has a range of movement relative to the foam frame when members of the articulated frame move. The at least one knob extends from a bottom surface of the cover.

In some embodiments, the at least one knob is adapted to be received in a receiver formed in portions of the articulated frame to secure the cover to the articulated frame at a plurality of points.

In some embodiments, the at least knob that is secured to the bladder assembly may not be secured to the cover.

In some embodiments, the bladder assembly may include a plate that secures the bladder assembly to the cover.

In some embodiments, the cover may include pockets that receive the plate of the bladder assembly to secure the bladder assembly to the cover.

In some embodiments, the bladder assembly may include a sleeve formed in a bladder assembly cover and the plate may be positioned in the sleeve and moveable relative thereto such that the plate of the bladder assembly has a range of motion relative to the remainder of the bladder assembly.

In some embodiments, the at least one knob may be fixed to the foam frame and configured to engage the articulated frame to control movement of portions of the foam frame in response to movement of the articulated frame.

In some embodiments, at least one knob may be fixed to the foam frame is connected to a plate secured to the foam frame.

In some embodiments, the plate secured to the foam frame may be secured to the foam frame by a sleeve such that the plate moves within the sleeve.

In some embodiments, the bladder assembly may include a plurality of foam-filled bladders, each of the foam filled bladders interconnected by a manifold, the manifold having an unpowered relief valve configured to release air from the bladder assembly if the pressure in the bladder assembly exceeds a predetermined limit of the relief valve, and wherein the foam-filled bladders each include a first layer and a second layer.

In some embodiments, a first group of the plurality of foam-filled bladders may have a first performance. A second group of foam-filled bladders may have a second performance, different from the first performance. In some embodiments the difference in performance may vary the support for a patient supported on the patient support apparatus between a head portion and a torso portion of the patient support apparatus.

In some embodiments, each of the bladders may include a transparent window formed in a wall of an enclosure of the bladder.

In some embodiments, the performance of a particular bladder may be color coded and the transparent window may be positioned to allow a user to identify the color of the bladder to identify the performance of the particular bladder by associating the color.

In some embodiments, the foam frame may include a perforated foot section that is variable in length.

In some embodiments, some of the plurality of foam-filled bladders may include an unpowered check valve configured to open and permit atmospheric air to enter the respective bladder if the pressure in the bladder assembly is lower than the pressure of atmospheric air.

Additional features, which alone or in combination with any other feature(s), such as those listed above and/or those listed in the claims, can comprise patentable subject matter and will become apparent to those skilled in the art upon consideration of the following detailed description of various embodiments exemplifying the best mode of carrying out the embodiments as presently perceived.

Referring to <FIG>, a patient support apparatus <NUM> is illustratively embodied as a hospital bed <NUM>. The view shown in <FIG> is generally taken from a position that is oriented at the left side, foot end of the hospital bed <NUM>. For purposes of orientation, the discussion of the hospital bed <NUM> will be based on the orientation of a patient supported on the hospital bed <NUM> in a supine position. Thus, the foot end <NUM> of the hospital bed <NUM> refers to the end nearest the patient's feet when the patient is supported on the hospital bed <NUM> in the supine position. The hospital bed <NUM> has a head end <NUM> opposite the foot end <NUM>. A left side <NUM> refers to the patient's left when the patient is lying in the hospital bed <NUM> in a supine position. The right side <NUM> refers to the patient's right. When reference is made to the longitudinal length of the hospital bed <NUM>, it refers a direction that is represented by the lines that generally extend between the head end <NUM> and foot end <NUM> of the hospital bed <NUM>. Similarly, lateral width of the hospital bed <NUM> refers to a direction that is represented by the lines that generally extend between the left side <NUM> and right side <NUM>.

The hospital bed <NUM> includes a base frame <NUM> which supports a lift system <NUM>. The lift system <NUM> engages the base and an upper frame <NUM> such that the lift system <NUM> moves the upper frame <NUM> vertically relative to the base frame <NUM>. The lift system <NUM> includes a head end linkage <NUM> and a foot end linkage <NUM>. Each of the linkages <NUM> and <NUM> are independently operable and may be operated to cause the hospital bed <NUM> to move into a tilt position which is when the head end <NUM> of the upper frame <NUM> is positioned lower than the foot end <NUM> of the upper frame <NUM>. The hospital bed <NUM> may also be moved to a reverse tilt position with the foot end <NUM> of the upper frame <NUM> is positioned lower than the head end <NUM> of the upper frame <NUM>.

The upper frame <NUM> supports a load frame <NUM>. The load frame <NUM> supports a head deck <NUM> which is movable relative to the load frame <NUM>. The load frame <NUM> also supports an articulated seat deck <NUM>, also movable relative to the load frame <NUM> and a fixed seat deck <NUM>. Also supported from the load frame <NUM> is a foot deck <NUM> that is articulated and moveable relative to the load frame <NUM>. The foot deck <NUM> in the illustrative embodiment of <FIG> provides for powered pivoting of the foot deck <NUM> and manual extension and retraction of the foot deck <NUM> to vary the length of the foot deck <NUM>. In other embodiments, powered pivoting of the foot deck <NUM> may be omitted and the related movement may be caused manually, or follow movement of the articulated seat deck <NUM>. In addition, in some embodiments, extension and retraction of the foot deck <NUM> may be powered by an actuator.

The foot deck <NUM> includes a first portion <NUM> and a second portion <NUM>, which moves relative to the first portion <NUM> to vary the size of the foot deck <NUM>. The second portion <NUM> moves generally longitudinally relative to the first portion <NUM> to vary the longitudinal length of the foot deck <NUM> and, thereby, the longitudinal length of the hospital bed <NUM>.

A foot panel <NUM> is supported from the second portion <NUM> and extends vertically from an upper surface <NUM> of the second portion <NUM> to form a barrier at the foot end <NUM> of the hospital bed <NUM>. A head panel <NUM> is positioned on an upright structure <NUM> of the base frame <NUM> and extends vertically to form a barrier at the head end <NUM> of the hospital bed <NUM>. A left head siderail <NUM> is supported from the head deck <NUM> and is moveable between a raised position shown in <FIG> and a lowered position as is known in the art. A right head siderail <NUM> is also moveable between the raised position of <FIG> and lowered position. As shown in <FIG>, in the raised position, the siderails <NUM> and <NUM> extend above an upper surface <NUM> of a mattress <NUM> of the hospital bed <NUM> when the siderails <NUM> and <NUM> are in a raised position. In a lowered position an upper edge <NUM> of the left head siderail <NUM> is below the upper surface <NUM>.

The hospital bed <NUM> also includes a left foot siderail <NUM> and a right foot siderail <NUM>, each of which is supported directly from the load frame <NUM>. Each of the siderails <NUM>, <NUM>, <NUM>, and <NUM> are operable to be lowered to a position below the upper surface <NUM>. It should be noted that when the head deck <NUM> is moved, the head siderails <NUM> and <NUM> move with the head deck <NUM> so that they maintain their relative position to the patient. This is because both of the head siderails <NUM> and <NUM> are supported by the head deck <NUM>.

Referring to <FIG> and <FIG>, the mattress <NUM> includes a core <NUM> which comprises a bladder assembly <NUM> which engages a foam frame <NUM>. The foam frame <NUM> includes a perforated foot support <NUM> which is coupled to a pair of longitudinal bolsters <NUM> and <NUM>. The longitudinal bolsters <NUM>, <NUM> are interconnected by a header <NUM> which extends laterally between the bolsters <NUM>, <NUM> at the head end <NUM> of the mattress <NUM>. The core <NUM> also includes an upper layer of foam <NUM> and a lower layer of foam <NUM> which are glued together to form an upper foam support <NUM>. The longitudinal bolsters <NUM> and <NUM> are secured to the perforated foot support <NUM> such that the foot support <NUM>, bolsters <NUM> and <NUM>, header <NUM>, and foam support <NUM> cooperate to define a space <NUM> into which the bladder assembly <NUM> is positioned to form the core <NUM>. The mattress <NUM> includes a lower cover <NUM> and an upper cover <NUM> which are secured together with a zipper as is known in the art. The mattress <NUM> further includes a fire barrier assembly <NUM> which is wrapped over the top of core <NUM> to fully enclose the core <NUM> in the fire barrier assembly <NUM>.

As shown in <FIG>, the bladder assembly <NUM> includes eight bladders <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. The bladders are arranged with bladder <NUM> positioned at the foot end <NUM> of the bladder assembly <NUM> and bladder <NUM> positioned at the head end <NUM>. Each bladder <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> comprises an outer enclosure <NUM> of urethane coated nylon which provides an air impermeable enclosure. As seen in <FIG>, inside of each enclosure <NUM> is a two layered foam structure. In <FIG>, the foam structure <NUM> includes an upper layer <NUM> and a lower layer <NUM>. The foam layers <NUM> and <NUM> are glued together. The foam structure <NUM> is deformable under load, but resiliently expands to fill the interior space of the enclosure <NUM>. Similarly, referring to <FIG>, a different foam structure <NUM> includes an upper layer <NUM> glued to a lower layer <NUM>. The foam materials used in layers <NUM> and <NUM> differs from the layers <NUM> and <NUM> so that the foam structures <NUM> and <NUM> have different performance characteristics. In the illustrative embodiment, the bladders <NUM>, <NUM>, and <NUM> include the foam structure <NUM> while the bladders <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> include the foam structure <NUM>. These differences provide for different support for the head portion of the bladder assembly <NUM>, including bladders <NUM>, <NUM>, and <NUM>, as compared to the torso portion of the bladder assembly <NUM>, which includes bladders <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>.

Referring to <FIG>, <FIG>, each of the enclosures <NUM> is formed to include a transparent window formed in wall <NUM> of the enclosure <NUM>. The window is positioned to overlie the interface between layers <NUM> and <NUM> or layers <NUM> and <NUM> so that a user may see the material within the enclosure <NUM>. This allows a user to distinguish the contents of the enclosure <NUM> to determine which of the foam structures <NUM> or <NUM> is included in the enclosure <NUM>. In the illustrative embodiment, at least one of the upper layers <NUM> or <NUM>, or one of the lower layers <NUM> or <NUM> is a different color. Thus, by comparing the colors visible through the window, an assembler can identify the characteristics of the particular enclosure <NUM> to determine whether the particular bladder should be positioned in the head portion as one of the bladders <NUM>, <NUM>, and <NUM> or the torso portion as one of the bladders <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>.

At the left side <NUM> of each enclosure <NUM> is a pressure relief or check valve <NUM>. Each of the check valves <NUM> are configured to open when the pressure applied to the valve exceeds the relief pressure of the valve <NUM>. In the arrangement of the bladder assembly <NUM>, the valves <NUM> are arranged such that when the pressure inside any one of the enclosures <NUM> is lower than the pressure of atmosphere, the corresponding valve <NUM> opens to permit air to flow from atmosphere into the respective enclosure <NUM>.

On the right side <NUM> of the bladder assembly <NUM>, each enclosure <NUM> includes a respective outlet <NUM>. Each of the outlets <NUM> are connected to a manifold tube <NUM> so that the enclosures <NUM> are all in fluid communication with one another through the outlets <NUM> and manifold tube <NUM>. The manifold tube <NUM> terminates with a pressure check valve <NUM>. The pressure check valve <NUM> is configured such that when the pressure in the manifold tube exceeds a relief pressure of the check valve <NUM>, the check valve <NUM> opens to permit the venting of the pressure to atmosphere. It should be understood that the valves <NUM>, being check valves, do not permit a flow of air from the enclosures <NUM> through the valves <NUM> to atmosphere. The only flow path for air from the enclosures to atmosphere is through the manifold tube <NUM> and pressure check valve <NUM>. Similarly, the only path for that flow into any of the enclosures <NUM> is through a respective valve <NUM>.

Thus, the mattress <NUM> is self-adjusting to maintain the pressure within each of the bladders <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> to a pressure below the relief pressure of the check valve <NUM>. The operation of the inlet valves <NUM> of any particular bladder <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, which is unloaded, provides for the rapid filling of the respective bladder <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> with air from atmosphere. This approach helps to regulate the pressure within the various bladders <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> relatively quickly to control the support pressure experienced by a patient.

In the event that the patient exceeds the weight which can be supported by the bladder assembly <NUM> pneumatically, venting of the pressure in the manifold tube <NUM> and pressure check valve <NUM> permits the patient to be supported on the foam structures <NUM> of each bladder <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. In this way, the mattress <NUM> provides the benefits of a pneumatic mattress with safety for larger patients from bottoming out against the surface of the decks of the hospital bed <NUM>. It should be understood that the foam structures <NUM> also serve the purpose of expanding the enclosures <NUM> to create the vacuum which draws air through the valves <NUM> when a particular bladder <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> is unloaded.

In the illustrative embodiment of <FIG>, foam structures <NUM> and <NUM> have similar constructions. However, in some embodiments the layers <NUM>, <NUM> or <NUM>, <NUM> of the foam structures <NUM> and <NUM>, respectively, may have different properties in different bladders <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. In addition, the foam structures <NUM>, <NUM> may be a single layer, or may include more than two layers in some embodiments.

Because the bed <NUM> has compound articulation of several members, including the movement of portion <NUM> relative to portion <NUM> of deck <NUM>, the mattress <NUM> includes several adaptations that make the mattress <NUM> suitable for use with the compound articulations. For example, each of the longitudinal bolsters <NUM>, <NUM> are formed to include a series of relief slits <NUM> positioned at the location in the longitudinal bolsters <NUM>, <NUM> which are positioned at the intersection of the head deck <NUM> and the articulated seat deck <NUM>. The relief slits <NUM> provide for expansion of the longitudinal bolsters <NUM>, <NUM> when the head deck <NUM> is raised. With the relief slits <NUM>, little material is removed, but the foam is permitted to expand at the location of the slits <NUM>. In contrast, a series of cutouts <NUM> are positioned at the interface between the articulated seat deck <NUM> and the foot deck <NUM>. The cutouts <NUM> are generally triangular with more material removed at a lower surface <NUM> of the longitudinal bolsters <NUM>, <NUM>, the cutouts <NUM> becoming narrower to a termination spaced apart from the lower surface <NUM>. The cutouts <NUM> provide for both expansion and collapsing of the length of the longitudinal bolsters <NUM>, <NUM> at the interface between the articulated seat deck <NUM> and the foot deck <NUM>. The removed material at the surface <NUM> permits the cutouts <NUM> to collapse when the foot deck <NUM> is moved downwardly relative to the articulated seat deck <NUM> such that the material of the longitudinal bolsters <NUM>, <NUM> does not bulge.

The bladders <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are each positioned in a respective sleeve <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> of a cover <NUM>. The cover <NUM> is formed of a fabric that is sewn to form the sleeves <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> as a unitary structure so that the bladders <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are permitted some relative movement, but the cover <NUM> maintains the relationship between the bladders <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> during compound articulation of the frame and deck members of the bed <NUM>. This prevents the bladders <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> from becoming dislodged and maintains an appropriate orientation.

To control movement of the mattress <NUM> relative to the moveable members of the bed <NUM>, four knobs <NUM>, <NUM>, <NUM>, and <NUM> extend from a bottom surface <NUM> of the lower cover <NUM> as shown in <FIG>. The knobs <NUM>, <NUM>, <NUM>, and <NUM> are similarly arranged and details of knob <NUM> are shown in <FIG> and the knob <NUM> includes a spherical body <NUM> that is coupled to a stem <NUM> that extends from a base <NUM>. The head deck <NUM> is formed to include a slotted opening <NUM> as shown in <FIG>. The slotted opening <NUM> is formed with a key-hole effect so that a wider portion <NUM> narrows to a thin portion <NUM>. The slotted opening <NUM> has a longitudinal axis <NUM> that extends laterally on the deck <NUM> with the slotted opening positioned with the wider portion positioned on the outboard side of the deck <NUM>. A second slotted opening that is a mirror image of the slotted opening <NUM> is positioned on the opposite outboard side of the deck so that the knob <NUM> is positioned in the slotted opening <NUM> and the knob <NUM> is positioned in the mirror image slot. The natural tendency is to have the knobs <NUM> and <NUM> to be urged into the narrow portion <NUM> of each of the slotted openings. Another configuration of key-hole opening <NUM> is positioned in the second portion <NUM> of deck <NUM> through the surface <NUM> as shown in <FIG>. A circular opening <NUM> is positioned nearer the foot end <NUM> of the second portion <NUM> and the knobs <NUM> and <NUM> are each received in a circular opening <NUM> of a respective key-hole opening <NUM> so that the stem <NUM> is urged into a slot <NUM>. When the knobs <NUM>, <NUM>, <NUM>, and <NUM> are engaged with the deck <NUM> and deck <NUM> respectively, movement of the decks <NUM>, <NUM>, and <NUM> are transferred directly to the mattress <NUM> such that the mattress <NUM> moves with the decks <NUM>, <NUM>, and <NUM>.

The knobs <NUM> and <NUM> are secured to a plate <NUM>, seen in <FIG>, that is glued to the foot end <NUM> of the perforated foot support <NUM> by a nut <NUM> and washer <NUM> (seen in <FIG>) with the nut <NUM> being received on a threaded stem <NUM> of the knobs <NUM> and <NUM>. The plate <NUM> is positioned in a sleeve <NUM> (seen in <FIG>) that is glued to the perforated foot support <NUM>. The plate <NUM> is free to move in the sleeve <NUM> in the direction of the arrow <NUM> as necessary.

The knobs <NUM> and <NUM> are secured to respective plates <NUM> and <NUM> shown in <FIG>. The cover <NUM> is formed to include a flap <NUM> with the plates <NUM> and <NUM> being secured to the flap <NUM> when the knobs <NUM> and <NUM> are secured by the respective nuts <NUM>. The plates <NUM>, <NUM> and flap <NUM> cooperate to permit controlled movement of the bladder assembly <NUM> relative to the lower cover <NUM>. The bladder assembly <NUM> is further secured to the lower cover <NUM> by a plate <NUM> positioned in a sleeve <NUM> formed on the bottom of sleeve <NUM> of the cover <NUM> of the bladder assembly <NUM>. The plate <NUM> includes two flanges <NUM>, <NUM> which are received in pockets <NUM> and <NUM> respectively. The pockets <NUM> and <NUM> are formed in the lower cover <NUM> by welding flaps of material <NUM>, <NUM> to the upper surface <NUM> of the lower cover <NUM>. The plate <NUM> is flexible so that the flanges <NUM>, <NUM> can be slipped under the flaps <NUM>, <NUM> into the pockets <NUM>, <NUM>. Thus, the bladder assembly <NUM> is secured to the lower cover <NUM> at the head end <NUM> by the plates <NUM>, <NUM> and knobs <NUM>, <NUM> and the foot end <NUM> of the bladder assembly <NUM> is secured to the lower cover <NUM> with the flanges <NUM>, <NUM> positioned in the pockets <NUM>, <NUM>.

During movement of the decks <NUM>, <NUM>, and <NUM>, the overall mattress <NUM> is secured by the knobs <NUM>, <NUM>, <NUM>, <NUM>, while the bladder assembly <NUM> is maintained in position by the flanges <NUM>, <NUM> positioned in the pockets <NUM>, <NUM> in cooperation with the plates <NUM>, <NUM> and knobs <NUM>, <NUM>. The perforated foot section <NUM> is free to expand and contract relative to the bladder assembly <NUM> when the second portion <NUM> of the deck <NUM> moves relative to the first portion <NUM>. This helps control the location of the perforated foot section <NUM> and the bladder assembly <NUM> onto the appropriate portions of the decks <NUM>, <NUM>, <NUM>, and <NUM>. Referring now to <FIG>, a flap <NUM> of fabric is welded to the surface <NUM> of cover <NUM> so that a pocket <NUM> is formed in the area of the cover <NUM> underlying a portion of the perforated foot section <NUM>. The pocket <NUM> receives a plate <NUM> that is positioned therein and serves to stiffen the portion of the lower cover <NUM> that overlies the interface between the first portion <NUM> and second portion <NUM> of the deck <NUM>. This prevents bunching of the lower cover <NUM> during movement interface between the first portion <NUM> and second portion <NUM> of the deck <NUM>.

The relative movement of deck <NUM> and deck <NUM>, the interface between the perforated foot section <NUM> and the bladder assembly <NUM> is subject to being flexed. This flexing must be accommodated without bunching of the foam members at the interface. The perforated foot section <NUM> comprises relatively soft foam that provides relief to the heels of a patient positioned on the mattress <NUM>. The foam structures <NUM> and <NUM> are relatively stiff to provide support for the patient's seat and torso. Referring to <FIG>, to accommodate the transition and limit the feeling of "sinking in" that a patient experiences as they slide toward the foot end <NUM> of the bed <NUM> to egress from the bed <NUM>, the perforated foot section <NUM> is modified to include a foam block <NUM> that is positioned under a cantilevered member <NUM> that extends from the perforated body <NUM> of the perforated foot section <NUM>. The foam block <NUM> has a density that provides a stiffness that exceeds the stiffness of the material of the body <NUM> and cantilevered member <NUM>. The foam block <NUM> is formed with material removed so that the bolsters <NUM>, <NUM> cooperate with the foam block to form a rabbet joint. The cantilevered member <NUM> overlaps the bolsters <NUM>, <NUM> to provide a uniform upper surface <NUM>.

Claim 1:
A patient support apparatus comprising:
a foam frame (<NUM>) defining a space (<NUM>);
a bladder assembly (<NUM>) positioned in the space (<NUM>); and
a cover (<NUM>) enclosing the foam frame (<NUM>) and the bladder assembly (<NUM>),
wherein the patient support apparatus is adapted to engage an articulated frame (<NUM>),
and wherein the patient support apparatus further includes at least one knob (<NUM>, <NUM>, <NUM>, <NUM>) secured to the bladder assembly (<NUM>) and configured to engage the articulated frame (<NUM>) to control movement of the bladder assembly (<NUM>) in response to movement of the articulated frame (<NUM>), the bladder assembly (<NUM>) engaged with the foam frame (<NUM>) such that the bladder assembly (<NUM>) has a range of movement relative to the foam frame (<NUM>) when members of the articulated frame (<NUM>) move,
characterised in that the at least one knob (<NUM>, <NUM>, <NUM>, <NUM>) extends from a bottom surface (<NUM>) of the cover (<NUM>).