The subject matter described herein relates to beds having elevation adjustable frames and particularly to a bed that effects the elevation adjustment with a lift chain driven by way of a planetary gear system.
Beds of the type used in hospitals, other health care facilities and home health care settings typically have a base frame, an elevatable frame and a lift system extending between the frames for changing the elevation of the elevatable frame relative to the base frame. One type of lift system employs a lift chain. Examples of such systems are described in pending U.S. patent application Ser. No. 12/397,511 entitled “Height Adjustable Bed with a Lift Chain Assembly and Components Thereof” and Ser. No. 12/708,178 entitled “Height Adjustable Bed with a Push Chain Assembly”.
One desirable attribute of a lift system is compactness. The more compact the lift system, the more space is available for other intra-frame components or for facilitating access for cleaning, repair and maintenance. Another desirable attribute is for the resultant of the forces exerted by the lift system on the elevatable frame to be as close as possible to the lateral centerline of the bed. Such location of the resultant force helps to ensure smooth operation and reduced risk of component binding during elevation changes.
A height adjustable bed framework includes a base frame, an elevatable frame, a lift chain and a power module. The lift chain is connected to the base frame or the elevatable frame and the power module is connected to the other frame. The power module includes an energy converter such as an electric motor, a planetary gear train driven by the energy converter and a chain driver, such as a sprocket, engaged with the lift chain and driven by the planetary gear train.
The foregoing and other features of the various embodiments of the height adjustable bed frame described herein will become more apparent from the following detailed description and the accompanying drawings in which:
Referring additionally to
Lift chain 50 is comprised of links 60 designed so that the chain can flex about a laterally extending axis, such as axis S, in only one of two rotationally opposite directions. For example the lift chain of module 38F can flex in rotational sense SH (i.e. toward the head end of the framework) but not in rotational sense SF (toward the foot end of the framework). The head end lift chain is oriented so that its flex resistance is opposite that of the foot end lift chain, i.e. so that its chain can flex in rotational sense SF but not in rotational sense SH. The opposing directions of flex resistance impart stability to the elevatable frame. The lift chain also includes rollers 62 projecting laterally from the links.
Referring additionally to
The power module also includes an energy converter such as electric motor 90 having an output shaft 92 comprising a stub shaft 94 and a shaft extension 96. The motor is mounted on an exterior side of one of the housing plates, e.g. housing plate 72R with its shaft 92 extending from the motor to a planetary gear train 110 mounted on an exterior side of the other housing plate, e.g. plate 72L. The motor shaft is rotatable about axis 112.
Referring additionally to
The power module also includes a chain driver in the form of one or more sprockets 160, 162. The sprockets are rotatably mounted on the chain housing axially intermediate the housing plates 72L, 72R and therefore also axially intermediate motor 90 and gear train 110. Left sprocket 160 includes an integral hexagonal sprocket shaft 164 that mates with hexagonal opening 166 in the output carrier thereby connecting the chain driver to the output carrier. Each sprocket also includes a castellated coupler 170, 172. The couplers interlock with each other to make the sprockets corotatable. The sprocket shaft 164 is coaxial with the motor output shaft 92 (which comprises stub shaft 94 and shaft extension 96) and is rotatable about axis 112. Sprocket teeth 174, 176 project into spaces 182 (
The compactness of the above described construction conserves intra-frame space and affords the designer considerable latitude in positioning the lift system so that forces exerted by the lift chain act on the framework as close as possible to the lateral centerline of the bed.
In operation, motor output shaft 92 conveys rotary motion of motor 90 to gear train 110 in a first direction, for example direction D1, parallel to rotational axis 112. Rotation of the motor shaft 92 causes rotation of the sun gear. The sun gear, due to its engagement with large diameter portion 134 of the compound planet gears, rotates the compound planet gears about their axes 132. The meshing engagement of the small diameter portions 136 of the compound planet gears with the ring gear causes the input carrier 122 to also rotate about axis 112 and the planet gears 130C, 130S to orbit about the axis. Journals 128 convey the rotary motion of the input carrier 122 to the output carrier 124 in a second direction D2 opposite that of the first direction D1. The rotation of the output carrier is then transferred to the sprocket shaft 164 to rotate sprockets 160, 162, thereby extending chain 50 out of the housing to raise the elevatable frame or retracting the chain into the housing to lower the elevatable frame.
Although this disclosure refers to specific embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the subject matter set forth in the accompanying claims.
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