Heavy lift chair

A power-assisted heavy lift chair comprises a base assembly. A chair frame is supported on the base assembly. A lift mechanism communicates with the base assembly and the chair frame, and is operable to actuate the chair frame between first and second positions. A transformer provides electrical power to an electric motor. The electric motor provides rotational power to the lift mechanism at a first rate to lift and/or lower the chair frame. The electric motor draws current from the transformer according to a load upon the chair frame. The rate that the electric motor lifts and/or lowers the chair frame depends upon the voltage provided by the transformer. The transformer is operable to provide a generally constant voltage regardless of the current draw of the electric motor. Therefore, the electric motor lifts and/or lowers the chair at a constant rate independent of the load on the chair.

FIELD OF THE INVENTION

The present invention relates to power-assisted articles of furniture and, more particularly, to a power-assisted heavy lift chair that provides constant lift and lowering power independent of the load on the chair.

BACKGROUND OF THE INVENTION

Conventionally, power-assisted chairs include a motor-operated lift mechanism for aiding persons that require assistance in entering or exiting the chair. More particularly, motor-operated lift mechanisms are interconnected between a stationary base assembly and a moveable chair frame. Alternatively, some power-assisted chairs include separate linkage mechanisms for permitting the seat occupant to selectively extend and retract a leg rest assembly and/or produce reclining angular movement between an upright first position and a reclined second position.

Power-assisted chairs may be adapted to provide the lift and tilt function in combination with a leg rest and/or reclining function. Chairs which provide such a combination of multi-positional functions generally require the use of multiple motors for driving the separate linkages, which results in extremely large and expensive chair units. In addition, most power-assisted chairs incorporate a drive mechanism that employs both a power drive function for extending the leg rest, lifting the chair, and reclining the chair, and a power return function for returning the chair to the normal seated position.

An important characteristic of power-assisted chairs is the ability to support heavy loads during the lift and tilt functions. More specifically, power-assisted chairs are designed to support individuals of a particular weight. Typically, power-assisted chairs that are adapted to support weight above a particular threshold, such as 300 pounds, require multiple motors.

SUMMARY OF THE INVENTION

A power-assisted heavy lift chair comprises a base assembly. A chair frame is supported on the base assembly. A lift mechanism communicates with the base assembly and the chair frame, and is operable to actuate the chair frame between first and second positions. A transformer receives a first voltage from a power supply and is operable to output a second voltage that is constant. An electric motor receives the second voltage and provides rotational power to the lift mechanism at a first rate according to the second voltage to lift and/or lower the chair frame.

In another aspect of the invention, the power-assisted heavy lift chair further comprises a heating element that receives a third voltage from the transformer. The heating element is operable to provide heat to areas of the heavy lift chair in response to the third voltage. The heating element is operable to automatically discontinue providing heat during lift and/or lower operations of the heavy-lift chair.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A heavy lift chair10includes a lift base assembly12and a chair14as shown inFIG. 1. The lift base assembly12supports the chair14in a normal seated position. The lift base assembly10lifts the chair14to a tilted position that makes it easier for a person to enter or leave the chair14as shown inFIG. 2. Any of a wide variety of chair constructions can be used with the lift base assembly10. The chair14includes a frame16, side arms18, a seat back20, and a seat portion22. The seat back20may recline in response to pressure from the back of an occupant and the seat portion22may move simultaneously with the seat back20. The chair14also includes an extensible leg rest assembly24. Additionally, the seat back20and/or the seat portion22may include a heat pad26. The heat pad26may be selectively energized to provide heat to person using the chair10.

An exemplary lift base assembly12is shown inFIGS. 3 and 4. The lift base assembly12has a stationary, rectangular bottom frame member30that rests on the floor and a movable, rectangular upper frame member32on which the chair14is removably but securely attached by suitable fasteners. The bottom frame member30includes left and right hand side members34and36, respectively, that are rigid with a front cross member38. Side members34and36may have suitable pads40that engage the surface of a floor. Upper frame member32includes left and right side members42and44, respectively, that are rigid with a rear cross member46. A lift mechanism48nests inside of the bottom from member30, the upper frame member32, and the chair14.

The lift mechanism48includes a power-assist means, such as an electric motor50, a rotary screw shaft52, and an internally threaded sleeve or nut54. The motor50is selectively operable to rotate the screw shaft52in either a first direction or second direction. Both the motor50and the screw shaft52can arcuately swing up and down in a generally vertical plane about a pivot56. The screw shaft52extends through and drives the sleeve54so that the sleeve54moves forwardly or rearwardly along the length of the screw shaft52upon rotation of the screw shaft52in one of the first and second directions. In the seated or lowered position of the chair14, the sleeve54Is positioned near the front or outer end of the screw shaft52. Lifting of the chair14is accomplished by energizing the motor50to rotate the screw shaft52in a direction that pulls the sleeve54toward the motor50. To lower the chair14, rotation of the screw shaft52is reversed, which draws the sleeve54away from the motor50. The above lift base assembly12and lift mechanism48are described in more detail in U.S. Pat. No. 5,061,010, assigned to La-Z-Boy Chair Co., which is hereby incorporated by reference in its entirety. Although the above lift base assembly and lift mechanism are described for illustrative purposes, it is to be understood that other suitable lift base assemblies and lift mechanisms may be used with the present invention as it is described below.

As shown inFIG. 5, an electrical control system60for the motor50includes two-prong attachment plug62that fits into an electrical receptacle in the general proximity to where the lift base assembly12is used for providing electrical current to operate the lift assembly12. Alternatively, the attachment plug62may be a three-prong grounding plug that fits into a grounding-type receptacle. The plug62includes an insulated cable or power cord64of suitable length. The electrical control system60also includes a transformer66, an electrical controller68, a control wand70, heating pads72and74, a motor actuator76, and various male and female socket connectors for connecting the components of the electrical control system60as described below.

The transformer66includes a power cord78with three current-carrying inductors that terminate in a male socket connector80. The male socket80mates with a female socket connector82so that the transformer66is electrically connected to the electrical controller68through a power cord84. The electrical controller68further includes power cords86,88, and90. The power cord86includes four current-carrying conductors that terminate in a male socket connector92and a female socket connector94. The power cord88includes eight current-carrying conductors that terminate in a female socket connector96. The power cord90includes five current-carrying conductors that terminate in a male socket connector98. The socket connectors92,94,96, and98mate with counterpart socket connectors100,102,104, and106, respectively, to electrically connect the electrical controller68to the control wand70, the heating pads72and74, and the motor actuator76.

The transformer66receives AC power from a standard electrical receptacle via the power cord64. The transformer66steps down the input power, for example 120 volts of AC, to an output power. In the preferred embodiment, the transformer66outputs an AC voltage of 12 volts and a constant DC voltage of 27 volts. The transformer66includes batteries, such as 9 volt batteries108, which may provide backup power to the electrical system60in the event of a power failure. The heating pads72and74are powered by the 12 volts AC and the motor actuator76is powered by the 27 volts DC.

The electrical controller68receives both the 12 volts AC and the 27 volts DC from the transformer66. The electrical controller68distributes the power from the transformer66to the heating pads72and74, the motor actuator76, and the control wand70. The electrical controller68directs the 12 volts AC to the heating pads72and74and directs the 27 volts DC to the motor actuator76. The control wand70also receives power from the 27 volt DC supply.

The control wand70includes a control cord110for receiving power from the electrical controller68. The control wand110may be mounted to a side arm of the chair or, alternatively, held and operated by a person using the chair. Additionally, the control cord110communicates commands from the control wand70to the electrical controller68. For example, the control wand70includes indicator means112, such as an LED array, and one or more control switches114. The user may control the various operations of the chair with the switches114, such as lifting and lowering functions, reclining functions, and “on” or “off” status of the heating pads72and74. When the user operates the switches114to lift the chair, electrical power is supplied to the motor actuator76to rotate the screw shaft in a direction to cause the chair to lift. When the user operates the switches114to lower the chair, electrical power is supplied to the motor actuator76to rotate the screw shaft in the opposite direction for lowering the chair. The user may view status information for the chair at the indicator means112, such as “on” or “off” status or relative temperature indicators of the heating pads72and74.

The control wand70is powered by the 27 volt DC supply. However, the control wand70does not directly switch the current load of the motor actuator76. Instead, the control wand70switches relays located in the electrical controller68in order to control power to the motor actuator76. In this manner, the high current draw of the motor actuator76does not pass through the control wand70. In an alternative embodiment, the indicator means112and/or the switches114are located directly on the chair rather than on the control wand70. For example, the indicator means112and switches114may be located on a side arm of the chair.

The motor actuator76receives electrical power from the electrical controller68through the electrical connection of the power cord90, the male socket connector98, and the female socket connector106. The motor actuator76provides rotational power to the screw shaft according to the electrical power received from the electrical controller68. For example, if the user operates the switches114to lift the chair, the motor actuator76receives electrical power of a first polarity to rotate the screw shaft in a first direction. If the user operates the switches114to lower the chair, the motor actuator76receives electrical power of a second polarity to rotate the screw shaft in a second direction.

The rate at which the motor actuator76lifts and lowers the chair is directly dependent upon the DC voltage received from the transformer66through the electrical controller68. In the preferred embodiment, the DC voltage is 27 volts. The current drawn by the motor actuator76, however, is proportional to the load upon the chair. If the chair is empty, the motor actuator76requires relatively low current. If the chair is loaded with a person, the motor actuator76requires higher current. Conventionally, motor actuators receive a particular power input to control the lift and lowering functions. As the load upon the chair increases, the motor actuator draws more current. Because power is a product of voltage and current (P=VI), the voltage of the motor actuator decreases proportionately as current draw increases. As voltage decreases, the lift rate of the chair decreases proportionately. Therefore, it can be seen that the lift and/or lower rates of conventional power-assisted chairs were extremely dependent upon the load on the chair at any particular time.

In contrast, the transformer66of the present invention is operable to output a generally constant DC voltage regardless of the current draw from the motor actuator76. One such transformer available is InSeat Solutions' AC/DC adaptor, model number 15541 Class II power transformer, which outputs a 12 volt AC supply and a 27 volt DC supply. If the motor actuator76draws more current due to a heavier load upon the chair, the transformer adjusts automatically to maintain a generally constant DC voltage output of 27 volts to the motor actuator76. The motor actuator76receives a constant voltage regardless of the current draw. Therefore, the motor actuator76provides constant rotational power to the screw shaft. In this manner, the power-assisted chair of the present invention provides generally constant lift and lowering rates independent of the load on the chair. Further, the power-assisted chair of the present invention is able to provide constant lift and lowering rates for loads up to 500 hundred pounds with a single motor.

The required time to complete a full lift or lower cycle is dependent upon the lift or lower rate of the motor, and therefore is further dependent upon the voltage output of the transformer. Because the DC voltage supply of the transformer is generally constant, lift and lower cycles will be consistent regardless of the weight of the person using the chair. For example, slight voltage drops due to extremely heavy loads may cause the lift cycle to have a slightly longer duration, and the lower cycle to have a slightly shorter duration. Although cycle times may vary slightly due to factors such as increased heat due to higher current draw and other process variables, a person using the chair may expect generally uniform lift and lower cycle times.

Additionally, the electrical control system60is operable to selectively control power to the heating pads72and74during lift and lower operations of the motor actuator76, which allows the transformer66to maintain a Class II rating. For example, if the user operates the switches114to lift or lower the chair while the heating pads72and74are “on,” the electrical controller68will turn off power to the heating pads72and74. Once the lift or lower operation is complete, the electrical controller68will restore power to the heating pads7274. In this manner, the electrical controller68directs power solely to the motor actuator76during lift and lower operations, which allows the motor actuator76to receive the maximum power available.

The electrical control system60may include other electrical components, such as a vibratory massage device, an air pillow massage device, or other devices as are known in the art. The additional devices may operate on the 12 volt AC supply in a fashion similar to the heating pads72and74. Correspondingly, the electrical controller68may disable power to the additional devices during motor lift and lower operations.