Low profile hospital bed

[0001] This invention relates to a low profile hospital bed.

[0002] Some hospital patients have a tendency to roll out of a hospital bed. This presents a significant risk of injury. In the past, hospitals and other care facilities have used various types of restraints to secure such patients. However, patient restraints are no longer favored in the modern hospital environment. An alternate solution to this problem has been to employ a low profile bed thus locating the surface of a the bed as close to the floor as possible. Yet, such a low profile bed must also be able to raise to a higher position so that doctors and nurses may have access to the patient. The arrangement of a very low profile bed typically places the actuators for raising and lowering the bed at a relatively shallow angle when the bed is in the lowered position. The actuator vertical force component available at such relatively shallow angles can become too small to lift the bed and the patient. This has limited the minimum height of mechanically actuated low profile hospital bed frames. What is needed is an arrangement which solves this problem and permits the design of a low profile hospital bed having a minimum height which is constrained not by actuator mechanics but by such considerations the required thickness of frame members and wheel clearance.

[0003] In an embodiment of the present invention the aforementioned problem is addressed by providing a low profile hospital bed including a mattress support frame and wheel frames pivotably mounted to the mattress support frame which pivot between a folded position in which the mattress support frame is relatively close to the floor and a fully unfolded position in which the mattress support frame is at a maximum height above the floor. A leverage member for prying the wheel frame away from the mattress support frame is pivotably mounted to each wheel frame. Each leverage member is pivotably mounted to a wheel frame. A lift actuator connects between each leverage member and the mattress support frame. The leverage member is arranged to rotate relative to the wheel frame and push against the mattress support frame and thus pry the wheel frame away from the mattress support frame as the lift actuator begins extending from the its retracted position. The leverage member is also arranged to stop rotating relative to the wheel frame and thus stop pushing against the mattress support frame after the wheel frame has reached a partially unfolded position. After the leverage member has stopped rotating, it provides a simple mechanical link between the lift actuator and the wheel frame. Since the wheel frame is partially unfolded, the lift actuator has tilted sufficiently from its initial generally horizontal position to provide a sufficient amount of vertical force for powering the further unfolding of the wheel frame. As the lift actuator continues extending, the wheel frame unfolds to a fully unfolded position. Accordingly, in this embodiment of the present invention, a low profile bed is provided which can be folded into a flat configuration for providing a very low mattress elevation and yet which can be raised by lift actuators to provide a fully elevated bed.

[0024] Referring to the drawings, FIGS. 1–18 show a low profile hospital bed 10 in accordance with an embodiment of the present invention. As can be seen in the referenced figures, hospital bed 10 includes a mattress support frame 12 and opposite wheel frames 20 and 40 pivotably mounted to mattress support frame 12. Wheel frames 20 and 40 carry wheels which are shown to be in contact with floor 11 in FIGS. 4, 5A, 5B, 7, 8, 10A, 11, 14 and 17. Mattress support frame 12 includes a rigid portion 12A and an articulated portion 12B for arranging the relative angles of the various portions of a supported mattress as is well known in the art. A pair of lift actuators 22 and 42 connect between opposite ends of the rigid portion 12A of mattress support frame 12 and leverage members 26 and 46 mounted to wheel frames 20 and 40.

[0025] Low profile hospital bed 10 employs lift actuators in a mechanism which operates in two stages to pivot each of opposite wheel frames 20 and 40 from a folded position as shown in FIGS. 1–6 to a fully unfolded position as shown in FIGS. 14–18. During the first stage of motion, opposite leverage assemblies 24 and 44 operate to urge wheel frames 20 and 40 away from mattress support frame 12. During this first stage, lift actuators 22 and 42 rotate a pair of relatively short leverage members 26 and 46 which are pivotably mounted to wheel frames 20 and 40 respectively. As leverage members 26 and 46 rotate, they urge wheel frames 20 and 40 away from mattress support frame 12. Thus, during the first stage of motion, each wheel frame 20 and 40 pivots from the first folded position shown in FIGS. 1–6 to an intermediate partially unfolded position shown in FIGS. 7–9 and finally to a partially unfolded position shown in FIGS. 10A–13. At the end of the first stage of motion, wheel frames 20 and 40 are in the partially unfolded position shown in FIGS. 10A–13. As can be seen in FIG. 10A, leverage members 26 and 46 have pivoted to the end of their ranges of motion as stop blocks 26B and 46B fixed respectively to leverage members 26 and 46 engage cross members 20A and 40A of wheel frames 20 and 40. Once these components have translated to the positions shown in FIG. 10A, leverage members 26 and 46 function as simple mechanical links between the lift actuators and the wheel frames and lift actuators 26 and 46 are tilted sufficiently from horizontal such that they can apply enough vertical force to power the complete extension of wheel frames 20 and 40. FIGS. 14–18 show low profile hospital bed 10 or portions of it when it is in a fully extended and fully raised position.

[0026] Accordingly, during the first stage of motion described above, lift actuators 22 and 42 cause the rotation of leverage members 26 and 46 relative to wheel frames 20 and 40 in order to pry wheel frames 20 and 40 away from mattress support frame 12. During the second stage of motion, leverage members 26 and 46 are locked from continued rotation such that lift actuators 22 and 42 cause relative motion between mattress support frame 12 and leverage members 26 and 46 and thus further rotation of wheel frames 20 and 40 to which they are attached.

[0027] As noted above, the movement of wheel frames 20 and 40 between the folded position to the end of the first stage of motion is accomplished by the rotation of leverage members 26 and 46. Leverage members 26 and 46 are subcomponents of leverage assemblies 24 and 44 which connect between wheel frames 20 and 40 respectively and rigid frame 12A of mattress support frame 12. Because wheel frames leverage assemblies 24 and 44 are preferably symmetrical and identical assemblies, for the sake of clarity and simplicity, it is possible to discuss the detailed structure and function of one wheel frame and its associated leverage assembly. For the purposes of this detailed description, wheel frame 20 and leverage assembly 24 will be described. It should also be understood by the skilled reader that the movements of these generally symmetrical components preferably occur in a substantially symmetrical and synchronized manner so that mattress support frame 12 raises up in a uniform and level fashion.

[0028] The purpose of leverage assembly 24 is to accomplish the first stage of motion in which leverage member 26 pries wheel frame 20 away from mattress support frame 12 thus lifting mattress support frame 12 from the position shown in FIG. 5A to the position shown in FIG. 10A. Leverage assembly 24 is illustrated in FIG. 5A and FIG. 5B. FIG. 5B is an enlarged view of portion B indicated in FIG. 5A. As is shown in FIG. 5B, leverage assembly 24 includes leverage member 26 which is pivotably mounted at a fulcrum 27 to a clevis bracket 28 fixed to a cross member 20A of wheel frame 20. As can be seen in FIG. 5B, wheel frame 20 is in turn pivotably mounted by opposite devises 13C and 13D to rigid frame 12A of mattress support frame 12. As can be best seen in FIG. 16, leverage member 26 includes a clevis portion at its first end for connecting with the distal end of an actuator rod 22A. As can also be best seen in FIG. 15, leverage member 26 includes a roller 26A mounted within a second clevis portion at its opposite second end. Fixed to the side of leverage member 26 is a pair of stop blocks 26B. The function of stop blocks 26B will be described in greater detail below. A roller track member 14 for engaging roller 26A is mounted to rigid portion 12A of mattress support frame 12.

[0029] The motion of the first stage may be understood by comparing FIGS. 5B, 8 and 11. In FIGS. 5A–6, leverage assembly 24 is positioned at the beginning of the first stage. In FIGS. 5A–6, leverage member 26 is oriented such that roller 26A is in contact with roller track member 14 but may be envisioned as not applying significant force to roller track member 14. In FIGS. 5A–6, actuator rod 22A is completely retracted and wheel frame 20 is in a folded position thus allowing a very low profile for low profile bed 10. FIGS. 7–9 show leverage assembly 24 after lift actuator 22 has rotated leverage member 26 clockwise approximately 20° with respect to clevis bracket 28. When leverage assembly 24 is in this position, actuator rod 22A of lift actuator 22 is slightly extended, roller 26A has moved along roller track member 14 and is applying a significant force upon roller track member 14, stop block 26B is approaching its contact position with cross member 20A and most importantly, wheel frame 20 has been pried away from its folded position to a slightly unfolded position. During this stage of motion, the prying action of leverage member 26 against roller track member 14 amplifies the otherwise insufficient vertical force component of the nearly horizontal lift actuator 22 to provide a vertical force sufficient to pivot wheel frames 20 away from mattress support frame 12 thus lifting mattress support frame 20.

[0030] FIGS. 10–13 show low profile bed 10 and more particularly leverage assembly 24 at the end of the first stage of motion and at the beginning of the second stage of motion. In FIGS. 10–13, stop blocks 26B are in contact with cross member 20A of wheel frame 20. In FIGS. 10–13, leverage member 26 can be envisioned as having rotated from a first position shown in FIGS. 5B to a second position shown in FIG. 11. Because stop block 26B interferes with cross member 20A of wheel frame 20 when leverage member reaches the second position shown in FIG. 11, leverage member 26 can not rotate past the second position shown in FIG. 11. When leverage member 26 is in the second position shown in FIG. 11, the force applied by roller 26A to roller track member 14 shifts to stop blocks 26B as leverage member 26 is locked from further rotation away from the first position relative to leg assembly 20. Note that leverage member 26 is locked from further rotation before it reaches a top dead center position in which leverage member 26 would be generally normal to wheel frame 20 or generally normal to roller track member 14. This allows for continuous and smooth motion as wheel frame 20 is unfolding and when wheel frame 20 is folding to return to the position shown in FIGS. 1–6. After leverage member 26 is locked by contact between stop block 26B and cross member 20A, lift actuator 22 continues extending as wheel frame 20, in the second stage movement, extends into the fully unfolded position shown in FIGS. 14–18.

[0031] FIG. 16 provides a perspective view of the opposite end of low profile hospital bed 10. As can be seen in FIG. 16, the components described above are mirrored by generally opposite, symmetrical components and are given reference numbers which are twenty greater than those given to the components described above. Accordingly, lift actuator 42 and leverage assembly 44 associate between rigid frame portion 12A and wheel frame 40. Leverage assembly 44 includes a leverage member 46 having a roller 46A and a stop block 46B. Leverage member 46 is pivotably mounted to a cross member 40A by a clevis bracket 48. Wheel frame 40 is pivotably mounted to rigid portion 12A of mattress support frame 12 by a pair of clevis brackets 33C and 33D.

[0032] Accordingly, low profile hospital bed 10 described above solves the above stated problem by providing an extremely low profile bed which can raise itself and a patient to an elevation which is easily accessible for doctors and nurses attending the patient. When in the lowered position, low profile hospital bed 10 provides a safe support for a patient who is susceptible to rolling or falling out of bed.

[0033] It is to be understood that while certain forms of this invention have been illustrated and described, it is not limited thereto, except in so far as such limitations are included in the following claims and allowable equivalents thereof.