CA1170198A - Brake mechanism for an adjustable hospital bed - Google Patents

Abstract

Abstract of the Disclosure An adjustable hospital bed having a linkage system actuated by one or more drive screws for raising and lowering the bed and having a slipping brake mechanism associated with the drive screws and linkage system to provide actuation of the linkage system and, more particularly, to provide a limit stop of the linkage system when the bed is raised to its uppermost position and a similar stop when the bed is lowered to its lowermost position.

Description

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Background of the_Inventlon Thls invention relates to an adjus-table hospital bed having a lifting system including a plurality of linkages actuated by drive screws for elevating or lowering the bed in either a hori7ontal or a tilted position, and more particularly to a brake on said drive screws -to limit the movement of said linkages.
The use of one or more drive screws to actuate one or more linkages of an adjus-table hospital bed, and the use of nut/screws to permit slippage or free-wheeling of the drive screws is well known in -the prior ark as evidenced by U.S. Patents 3,277,736, 3,319,481 and 3,565,106. These prior art nut/screw combinations have ~ radially applied brakes and are not very reliable because : wear between the brake surfaces causes a change in the amount of torque required for the brake~to slip and the . brake bands must be replaced.
Summary of the Invention : Briefly stated, the present invention is an adjustable hospital bed comprising: a stationary lower : base frame, a movable upper frame, a linkage system inter-connecting the upper and lower frames and operable to adjustably elevate the upper frame, at least one drive screw mounted on the upper frame, linkage drive means threadediy coupled to, and responsive to rotation of, the drive screw for actuating the linkage system, rotation in one direction causing the upper frame to raise to an ; uppermost position, whereas rotation of the drive screw in the o-ther direction causing lowering of the upper frame to its lowermost position, means for rotating the drive screw in a selected one of its two directions, means ~-- 1 --, . ' ' . .

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associated with the drive screw for limiting the movement oE the linkage system to provide an upper limit for the uppermost position of the upper frame and -to provide a lower limit for the lowermost position comprising means including a brake mechanism having a brake nut threadedly engaging the drive screw, a radially extending brake surface on the brake nut, a brake housing surrounding -the brake nut and including a complementary radially extending brake surface yieldingly engagable with the brake surface of the brake nut, the brake housi.ng being secured to the linkage drive means, resilient means associated with the brake nut and housing adapted to urge the brake surfaces into axial engagement whereby rotation of the drive screw moves the linkage drive means, a pair of spaced stop means fixedly secured to the drive screw, one on each side of the brake mechanism, stop engaging means on the brake nut engagable with at least one of the stop means on the drive screw, whereby when the stop engaging means on the brake nu-t engages one of the drive screw stop means, the brake surfaces slip and prevent further movement of the linkage drive means.
In another aspect, the present invention relates to an adjustable bed including a relatively fixed frame, a movable frame, a mattress support structure, head and foot lift: mechanisms for raising and lowering the head and foot ends respectively of the movable frame, back and knee lift mechanisms for raising and lowering the back and knee sections respectively of the mattress support structure, and constitutes the improvement which comprises means for actuating and ~ ~ la -.., ~,.

`~ ~17(9:~9~3 driving the lift mechanisms individually or collec-tively, the means comprlsing common drive means, a plurality of drive screws opera-tively connected to the common drive means and to lift mechanisms, rotation of khe drive screws in one directlon causing the said lift mechanisms to raise toward an uppermost position, whereas rotation of the drive screws in the o-ther direction causes lowering of -the said lift mechanisms toward their lowermost position, means associated with the drive screws for limiting -the upward movements of the said lift mechanisms and to provide a lower limit for the lowermost posi-tions including brake . mechanisms associated with each drive screw and its lift mechanism each brake mechanism comprising a brake nut ,, having internal threads positively and directly engaging ~ the associated drive screw, a radially extending brake surface on the brake nut, a brake housing surrounding the brake nut and including a complementary radially extending brake surface yieldingly engageable with the brake surface of the brake nut, -the brake housing being secured to the associated lift mechanism, resilient meansassociated with the brake nut and housing adapted to urge the brake surfaces into axial engagement whereby rotation of the drive screw moves the lift mechanism, a pair of spaced stop means fixedly secured to the drive screw, one on each side of the brake mechanism, stop engaging means on the brake nut engageable with at least one of the stop means on -the drive screw, whereby when the stop engaging means on the brake nut engages one of the drive screw stop means the brake surfaces slip and prevent further movement of the associated lift mechanism while allowing continued movement of any other actuated ~ lb -?

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lift mechanism.
Consequently, the novel brake mechanism of -the present invention is constr.ucted so that the fric-tlon surfaces or "bands" are concentric to the screw and are of one piece construction, thus resul-ting in cons-tant friction on the clutch surfaces resulting in even wear.
Description of the Drawings The features of the invention which are believed to be novel are set forth with particularity in -the appended claims. The invention may best be understood, however, by reference to the following description - in conjunction with the accompanying ' ~ .i -- lc --117~13~3 drawings in whlch like reference numbers identify li,ke elements, and in which:
FIG~ 1 is a side view of an adjustable hospi-tal bed, the bed being illustrated with lifting mechanisms placing the bed in a normal horizontal position wit~ the head end.on the left and the foot end on the right;
FIG~ 2 is a view of the foot end of the bed of FIG~ 1~
FIG~ 3 is a fragmentary and partially broken away top or plan view of .the bed.of PIG~ 1 on an expanded scale;
FIG. 4 is a fragmentary view showing the means for driving the drive screws;
FIG~ 5 is a fragmentary side view of a drive screw and its.associated brake mechanism; - -FIG~ 6 is a fragmentary view, partially in section, taken on line 6-6 of FIG~ 5 and show-rng the drive screw and brake mechanism;
FIG~ 7 is a fragmentary view taken on the line 7~7 of FIG~ 5;
FIG~ 8 is a fragmentary view taken on the . line 8-8 of FIG~ 5~

:: . Descri~ti.on of the Adjustable Hospital Bed The adjustable hospital bed includes a s~ationary o~ fixed lower.base frame 10 (,see particularly FIGSo 1 and 2), a~d a movable upper frame 12 on which is mo.unted an.articulated mattress supporting structure 14.
Frame 10. has. a pair: of longitudinal bars or rails lOa with a pair of transyerse o.r cross bars lOb at the foot and head ' ends. Movable fram,e 12 is supported on and is vertically adjustable with respect ,to fixed frame 10 by means of head and foot li~ting mech:ani~sms, or elevating linkage systems ; 16,. 18~ respectively, which together provide a parallelogram lifting system. Ele~ating linkage system 18 takes the form of a lift yoke hayi,ng.a~pair of channel .

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shaped long lever or lift arms 18a rigidly affixed to a pivot or torque tube 18b (see FIG. 2~ which in turn is pivotally attached, by means of pivot studs 21, to a pair of brackets or lift support plates 22 rigidly secured to upper frame 12. The lift yoke also includes a pair of short lever arms 18c rigidly affixed to pivot tube 18b. The lower or free encl of each lever arm 18a pivotally connects to a pair of brackets 24 rigidly affixed to the cross bar lOb at the foot end of base frame 10. It should be apparent that by moving the free or upper ends of short lever arms 18c to the right, as viewed in FIG. 1, to effect clockwise rotation of yoke 18 around plvot studs 21, brackets 22 and consequently the foot end of upper frame 12 will be lowered. On the other hand, if lever arms 18c are moved to the left to rotate yoke 18 in a counterclockwise direction, brackets 22 and the foot end of frame 12 will be raised.
Although the drawings do not include an end view of the head end of the bed, it will be understood that head elevating linkage system 16 takes the form of a lift yoke of similar con-struction to yoke 18, having a pair of long lever arms 1~a rlgidly secured to frame 12. The lower or free ends of lever arms 16a are pivo~ally coupled to the upper ends of brackets 27, -~ the lower ends of the brackets being pivotally attached to ;~ frame 10 by means of pivot studs 28. In similar fashion to the operation of yoke 18, when the upper ends of lever arms 16c are moved to the right (as viewed in FIG. 1) yoke 16 rotates clock-.. ~ .
wise around pivot studs 25 causing brackets 26 and the head end of upper frame l2 to descend. Conversely, when lever arms 16c are moved to the left counterclockwise, rotation results and the head end of frame 12 moves upwardly. The lower ends of brackets 27 are pivotally coupled to base frame 10 by studs 28 to allow the bed to assume the various positions.

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_ 4 _ Articulated mattress supporting structure 14 is divided into four interconnected sections or panels, namely a back support section 31, a center or seat support section 32, an upper knee or thigh support section 33 and a lower knee or foot section 34. Seat support section 32 is rigidly affixed to frame 12, while one side or edge of back support section 31 is pivotally connected, by means of a pair of pivot studs 36 (only one of which is shown in FIG. 1), to seat support section 32.
As will be described, adjusting means are provided for tilting back section 31 upward, with respect to fixed seat sectton 32, to raise the back and head of the patient occupying the bed to maximize comfort. The tilting is achieved by a torque or pivot tube 39 (see FIG. 1) secured to back section 31 by rigid struc-tural members 41 ~and 42. A pair of lever arms 43 (only one of which is shown in FlG. 1) are rigidly affixed to tube 39 in order to facilitate turning of the tube. As the free ends of ~ lever arms 43 are moved to the left, as viewed in FIG. 1, tube 39 rotates in a clockwise direction thereby tilting back suppore section 31 upward.
The adjacent sides of knee support sections 33 and 34 are pivotally interconnected by a pair of pivot studs 47, only one I of which is shown in FIG. 1. The left side of section 33 (as viewed in FIG. 1) rigidly attaches to a torque or pivot tube 44 (see FIG. 3) which is rotatably mounted to seat support section 25 32 by pivot studs 45, only one of which is shown in FIG. 1 . A
pair of lever arms 46 (see FIGS. 1 and 3) are rigidly secured to ~orque tube 44 (see FIG. 3) so that movement of the free ends of those arms toward the right (as viewed in FIG. 1) results in counterclockwise pivoting of tube 44 around pivot studs 45.
: 30 Upper knee support section 33 therefore tilts upward and, sincethat sectlon is pivotally connected to lower knee support section 34 by studs 47, the left side of section 34 will be raised. Sections 33 and 34 will thus form an inverted V in ~7~

order to raise the pattent's knees. Adjusting means will be described for pivoting lever arms 46 to effect a desired knee adjustment to maximize the patient's comfort.
The movable members 16, 18, 31, 33 and 34 may all be actuated, either individually OI collectively, by a single reversible or bidirectional electric motor 49 (see FIGS 3 and 4~ supported on upper frame 12. When energized, motor 49 driYes gear 51 which in turn rotates four intercoupled driven gears. Each of the gears couples, via a respective one of four - 10 clutches, to a respective one of four screw-threaded drive shafts or drive screws 61-64, screws 61, 62 and 64 having left-handed threads while screw 63 has right-handed threads.
Clutches 56-59 are normally spring biased out of engagement with their respecti~e gears 52-55. The gears and clutches have dogs or lugs which interlock when engaged in order that gear rotation will be transferred to the associated drive screw.
Lugs 52a on gear 52 and lugs 56a on clutch 56 interlock when the clutch is moved to the right and into engagement with the gear.
2Q Each of clutches 56-59 is actuated into engagement with its associated gear by a respective one of four solenoids 66-69 (see FIG. 3) which actuate U-shaped yokes 71-74, respectively.
Each of yokes 71-74 is pivotally connected to support pan 75 which is mounted on frame 12. Coil springs 76 bias the free ends of yokes 71-74 so that minimal pressure i5 normally applied to the clutches by the yokes. Actuation of each yoke in response to energi~ation of its associated solenoid is achieved by means of linkages or rods 81-84 each of which connects a respective one of yokes 71-74 to a respective one of movable cores 66a-69a of solenoids 66-69, respectively. This construc-tion is clearly illustrated in FIG. 3.
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When motor 49 i5 rotating, thereby rotating all of gears 52-55, and a selected solenoid is energized, the yoke associated with the solenoid will be pulled to the right, as viewed in FIG. 4, to actuate or move its clu~ch into engagement with its associated one of gears 52-55, thereupon causing rotation of the associated drive screw in response to the gear rotation. In short, any time motor 49 ts energized, all of gears 52-55 wtll be rotating and, by energizing a selected one or more of sole-noids 66-69, a corresponding selected one or more of drive screws 10 61-64 wil1 be rotated. Of course, the rotational directions of the drive screws will depend on the direction of motor 49, but since tha. motor is reversible, it is possible to rotate each ot screws 61-64 in either of its two directions. Any appropriate electrical circuitry may be employed to control the energization 15 of motor 49 and o~ solenoids 66-69 to achieve the desired actua-tion of drive screws 61-64. A relatively simple circuit will achieve the necessary operation. The circuitry may be controlled by switches actuated by the four manually-operated switch actua-tors 86-89 (see FIG. 2) mounted at the foot end of upper ~rame 20 12. In effect, each of switch actuators 86-89 may control the energization of a respective one of solenoids 66-69, while at the same time controlling the direction of motor ~9. For example, each actuator may be a push button of the rocker type ~hich may be depressed or rocked in one direction to energize the associated solenoid and to operate the motor in one direc-tion, and which may be rocked in the other direction to energize the same solenoid, but to operate the motor in its other direc-tion. Preferably, the patient occupying the bed will have a remote control device for remotely controlling the circuitry for the motor and solenoids. Such a control device may etther be held by the patient or removably attached to the bed.

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Description of the erake Mechanism ; The rotational motion of screws 61-64 is converted to linear motion by the four drive mechanisms g1-94, respectively, the movements of which cause adjustment of the bed. Each of these four drive mechanisms includes a two-piece brake housing 121 (see FIG. 6) surrounding one of the drive screws, namely 61.
Housing piece 122 ;s made of an injection molded thermoplastic ~ resin, polyacetal, and is provided with shoulders 123, 124, an 10 opening 125 and a lip 126. While the preferred thermoplastic resin is a polyacetal, other engineering thermoplastic res7ns such as graft ABS, nylon, polycarbonate and polyphenylene oxide/
styrenic blends may be used. The other housing piece 128 is preferably made of metal and has shoulders 129, 130 and an opening 131 having a radially extending, tapered brake surface - 132 thereon. A brake nut 133 is contained in the openings 125 and 131 of the housing pieces 122, 128, respectively. The nut 133 threadedly engages the drive screw 61 and is adapted to be driven thereby. The nut 133 contains a radially extending, tapered brake surface 134. Spring means in the form of a thrust washer 135 is retained within the lip 126 and yieldingly urges the brake nut 133 to the left as seen in FIG. 6 to force the brake surfaces 132 and 134 into engagement. A stop pin 136 is secured to one end of the brake nut 133 and a stop surface 25 137 is provided on the other end of the nut. The two pieces 122 and 128 of the housing 121 are secured together by a pair of sleeves 138, 139 and cotter pins 141, 142. The bracket 96 is secured to the brake housing 121 by the sleeves 138, 139 and the cotter pins 141, 142. Stop means in the form of a collar 30 143, containing a stop pin 144, surrounds and is fixedly secured to the drive screw 61 by an allen screw 145. A second stop collar 146, containing a stop pin 147, is similarly fixedly secured to the drive screw 61 by an allen screw 148.

In operation, as the drive screw 61 rotates, the brake nut 133 and housing 121 will travel linearly and axially along the screw 61. The collars 143, 146 are provided on drive screw 61 to define the limits of travel of the associated drive mechanism 5 91, the collars rotating with the drive screw. When the drive mechanism 91 travels along the drive screw 61 to a limit of travel established by one of the collars 143, 146, the stop 136 or the stop 137 of the nut 133 will engage one of the pins 144, 147 of the collars 143, 146 and its linear travel will be 10 terminated even though the drive screw continues to rotate.
- The pin 144, for example, rotates the brake nut 133 within its housing to overcome the frictional engagement of the brake surfaces 132, 134, the nut thereby free-wheeling, as the drive screw rotates. The housing 121, and consequently the drive 15 mechanism 91, therefore remains axially stationary on the rotating drive screw 61. Thus, continued rotation of a drive screw after its driYe mechanism has reached a limit of travel results in no axial movement of the drive mechanism.
Bracket 96 is rigidly affixed to a tube 97 which in turn is 20 pivotally connected to the free ends of lever arms 43. When drive screw 61 is rotated in the direction which causes drive mechanism 91 to moYe linearly to the left (as viewed in the drawings~, arms 43 and torque tube 39 will be rotated in a clockwise direction and back support section 31 will be tilted 25 upward. Opposite rotation of drive screw 61 will lower section 31 from its tilted position. Screw 61 may thus be referred to as the "back drive screw." In similar fashion, drive mechanism 94 pivotally connects to linkage or bracket 101 which is rigidly secured to one end of a tube 102. The other end is pivotally 30 coupled to the free ends of lever arms 46 in order that rotation of drive screw 64 (which may be called the "knee drive screw") will rotate tube 44 to raise or lower the knee support sections 33 and 34.

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Movement of drive mechanism 92 results in actuation of foot elevating linkage system 18 to raise or lower the foot end of upper frame 12, depending on the rotational direction of drive screw 62, referred to as the "foot drive screw." More specifi-cally, the clutch nut housing of drive mechanism 92 is pivotallycoupled to a bracket or linkage 104 which rigidly connects to one end of a tube 105, the other end of which pivotally connects to lever arms 18co When foot drive screw 62 is rotated in the - direction to move drive mechanism 92, and consequently tube 105, to the right in the drawings, lever arms 18c will be rotated In a clockwise direction causing the foot end of frame 12 to descend.
Conversely, opposite direction rotation of screw 62 results in counterclockwise rotation of yoke 18 and raising of the upper frame's foot end.
The head elevating linkage system 16 functions in similar manner to effect independent raising and lowering of the head end of frame 12. Drive mechanism ~3 is pivotally coupled to linkage or bracket 107 which rigidly attaches to one end of a tube 108, the other end being pivotally coupled to the free ends of lever arms 16c. When drive screw 63 (called the "head drive screw") rotates in the direction required to move drive mecha-nism 93 to the right, tube 108 will cause clockwise rotation of yoke 16 with resultant lowering of the head end of frame 12.
On the other hand, opposite direction rotation of head drive screw 63 effects counterclockwise rotation of yoke 16 and raising of the frame's head end. Note that the lifting loads are divided between the two screw/nut combinations. Among other advantages, this reduces wear on the mechanical elements.
It will now be apparent that since each of lifting mecha-nisms 16 and 18 in its driving apparatus is entirely independentof the other lifting mechanism and its driving apparatus, the head and foot ends of upper frame 12 may each be positioned at any selected level or height, as a consequence of which frame 12 ~7(~1L9~3 . .
may be made horizonta1 or tilted and may be established at any desired level.
While a partTcular embodiment of the invention has been shown and described,-modiflcations may be made, and it is intended in the appended claims to cover all such modifications as may fall within the true spirit and scope of the invention.

Claims (9)

Claims

1. An adjustable hospital bed comprising: a stationary lower base frame, a movable upper frame, a linkage system inter-connecting said upper and lower frames and operable to adjustably elevate said upper frame, at least one drive screw mounted on said upper frame, linkage drive means threadedly coupled to, and responsive to rotation of, said drive screw for actuating said linkage system, rotation in one direction causing the upper frame to raise to an uppermost position, whereas rotation of said drive screw in the other direction causing lowering of the upper frame to its lowermost position, means for rotating said drive screw in a selected one of its two directions, means associated with said drive screw for limiting the movement of the linkage system to provide an upper limit for the uppermost position of the upper frame and to provide a lower limit for the lowermost position comprising means including a brake mechanism having a brake nut threadedly engaging said drive screw, a radially extending brake surface on said brake nut, a brake housing surrounding said brake nut and including a com-plementary radially extending brake surface yieldingly engagable with the brake surface of said brake nut, said brake housing being secured to said linkage drive means, resilient means asso-ciated with said brake nut and housing adapted to force said brake surfaces into axial engagement whereby rotation of said drive screw moves said linkage drive means, a pair of spaced stop means fixedly secured to said drive screw, one on each side of said brake mechanism, stop engaging means on said brake nut engageable with at least one of the stop means on said drive screw, whereby when the stop engaging means on said brake nut engages one of said drive screw stop means, the brake surfaces slip and prevent further movement of the linkage drive means.

2. An adjustable hospital bed according to claim 1 wherein said brake surface on said brake nut and said brake surface on said brake housing are tapered.

3. An adjustable hospital bed according to claim 1 wherein said brake housing is a two-piece housing and wherein at least one of the two pieces is a thermoplastic resin.

4. An adjustable hospital bed according to claim 3 wherein said thermoplastic resin is polyacetal.

5. The adjustable hospital bed of claim 1 wherein the spaced stop means are axially adjustable along the drive screw.

6. In an adjustable bed including a relatively fixed frame, a movable frame, a mattress support structure, head and foot lift mechanisms for raising and lowering the head and foot ends respectively of said movable frame, back and knee lift mechanisms for raising and lowering the back and knee sections respectively of said mattress support structure, the improvement which comprises means for actuating and driving said lift mechanisms individually or collectively, said means comprising common drive means, a plurality of drive screws operatively connected to the common drive means and to lift mechanisms, rotation of said drive screws in one direction causing the said lift mechanisms to raise toward an uppermost position, whereas rotation of said drive screws in the other direction causes lowering of the said lift mechanisms toward their lower-most position, means associated with said drive screws for limiting the upward movements of the said lift mechanisms and to provide a lower limit for the lowermost positions including brake mechanisms associated with each drive screw and its lift mechanism, each brake mechanism comprising a brake nut having internal threads positively and directly engaging said associated drive screw, a radially extending brake surface on said brake nut, a brake housing surrounding said brake nut and including a complementary radially extending brake surface yieldingly engageable with the brake surface of said brake nut, said brake housing being secured to said associated lift mechanism, resilient means associated with said brake nut and housing adapted to urge said brake surfaces into axial engagement whereby rotation of said drive screw moves said lift mechanism, a pair of spaced stop means fixedly secured to said drive screw, one on each side of said brake mechanism, stop engaging means on said brake nut engageable with at least one of the stop means on said drive screw, whereby when the stop engaging means on said brake nut engages one of said drive screw stop means the brake surfaces slip and prevent further movement of the associated lift mechanism while allowing continued movement of any other actuated lift mechanism.

7. In an adjustable bed including a relatively fixed frame, a movable frame, a mattress support structure, head and foot lift mechanisms for raising and lowering the head and foot ends respectively of said movable frame, back and knee lift mechanisms for raising and lowering the back and knee sections respectively of said mattress support structure, the improvement which comprises means for actuating and driving said lift mechanisms individually or collectively, said means comprising drive means, a drive screw operatively connected to the drive means and to a lift mechanism, rotation of said drive screws in one direction causing the said lift mechanism to raise toward an uppermost position, whereas rotation of said drive screw in the other direction causes lowering of the said lift mechanisms toward its lowermost position, means associated with said drive screw for limiting the upward movement of the said lift mechanism and to provide a lower limit for the lowermost position including a brake mechanism having a brake nut threadedly engaging said drive screw, a radially extending tapered brake surface on said brake nut, a brake housing surrounding said brake nut and including a complementary tapered radially extending brake surface yieldingly engageable with the brake surface of said brake nut, said brake housing being secured to said lift mechanism, resilient means associated with said brake nut and housing adapted to urge said brake surfaces into axial engagement whereby rotation of said drive screw moves said lift mechanism, a pair of spaced stop means fixedly secured to said drive screw, one on each side of said brake mechanism, stop engaging means on said brake nut engageable with at least one of the stop means on said drive screw, whereby when the stop engaging means on said brake nut engages one of said drive screw stop means the brake surfaces slip and prevent further movement of the lift mechanism while allowing continued movement of any other actuated lift mechanism.

8. An adjustable hospital bed according to claim 6 wherein said brake housing is a two-piece housing and wherein at least one of the two pieces is a thermoplastic resin.

9. An adjustable hospital bed according to claim 8 wherein said thermoplastic resin is polyacetal.