CN112004510B - Lifting mechanism and lifting chair - Google Patents

Abstract

A lift mechanism has a base to which a parallelogram-shaped structure of pivots is attached. The spring extends from the first link of the parallelogram to an adjustable termination point on the second link of the parallelogram to form a lifting triangle. The spring termination point is moved away from the main pivot of the parallelogram to create an adjustable "lever arm" to vary the lifting force. The lifting force adjusting mechanism adjusts the position of the termination point of the spring. The extension is fixed relative to one of the parallelogram linkages and maintains its angle relative to the horizontal as the parallelogram is raised or lowered between the sitting mode and the standing mode. The extension thus serves as a base for the backseat portion. The front seat portion is pivotally connected to the rear seat portion so as to swing downward when the lift mechanism is raised.

Description

Lifting mechanism and lifting chair

Technical Field

The present application claims priority from: U.S. provisional application No. 62/649809 entitled "lift chair" filed on 29/3/2018; U.S. provisional application No. 62/649746 entitled "elevating walker chair, lifting mechanism and seat" filed 3/29/2018; international application No. PCT/US2017/060163 entitled "dual mode caster and method" filed on 6/11/2017; U.S. patent application serial No. 15/326113 entitled "elevating walker chair" filed on 13.1/2017, the entire contents of which are incorporated herein by reference.

Background

People's life is increasing, but people may not be able to maintain the strength of the arms, legs and core and easily sit up from a chair. Those suffering from disease and related injuries may also experience this indispensable mobility problem.

Geriatric seats are typically constructed higher than the floor, but are therefore less comfortable. Low-leg chairs, including plush armchairs, are comfortable and can be seated for long periods of time, but are difficult to sit from above. Existing lift chairs do not provide optimal support for the anatomical reality from sitting to standing.

The motorized version is typically raised and lowered by tilting the entire chair structure, which moves the body forward and tilts the chair to a point that is often frightening. Conventional spring powered seats do not provide consistent lift (iso-elasticity) or ergonomically appropriate lift geometry.

The hip joint typically shows an arc with a radius equal to the length of a person's thighs as the person's torso rises from a seated position to a standing position. This arcuate motion will of course be centered on the knee joint when the hip intersects a vertical plane above the ankle. Ideally, one's knee joint should remain substantially stationary; however, if the severe imbalance until the center of gravity reaches the standing position cannot be compensated for, great effort must be made to push down on the armrests to provide the amount of force that a successful lift-assist chair can exert without difficulty.

Therefore, in the absence of the lifting assistance, the handicapped person is instructed to rock toward the front of the seat cushion, and then to incline forward several times with increasing effort to make their center of gravity pass over their feet, and then to stand straight and stand up.

Ideally, a lift-assisted chair or seat cushion would allow the user to lift at random at a natural or human pace, as opposed to a powered lift-assisted chair that apparently slowly and noislessly advances to an awkward, inclined position.

Disclosure of Invention

An adjustable riser mechanism for use as or with a seating unit is disclosed. In the illustrative embodiment, the lift mechanism has a base to which the pivot of the parallelogram structure is connected. The parallelogram structure has four pivotally connected links. The spring extends from a first link of the parallelogram to an adjustable termination point on a second link of the parallelogram to form a lifting triangle, wherein the spring termination point is displaced from the main pivot of the parallelogram. The displacement of the spring termination point relative to the main pivot creates a "lever arm" that affects the lifting force. The lifting force adjustment mechanism adjusts the position of the spring termination point relative to the main pivot. The extension is fixed relative to one of the four parallelogram linkages and is configured to maintain its angle relative to the horizontal when the angle of the parallelogram is changed while raising or lowering the lift mechanism between the sitting mode and the standing mode. The extension may form a rear seat portion or form a base to support the rear seat portion. The front seat portion is pivotally connected to the rear seat portion to swing it downward when the mechanism is raised from the sitting mode to the standing mode.

Drawings

All figures include illustrative embodiments of the lift chair and its components, illustrative embodiments of a lift mechanism that may be incorporated into a lift chair or other device, and illustrative lift chairs and their related components and mechanisms. The illustrative embodiments are best understood from the detailed description when read with the accompanying drawing figures.

Fig. 1 is an isometric view of an illustrative lift chair transitioning between a standing mode and a sitting mode.

Figure 2 is an isometric view of the lift chair in a standing mode or transitioning from a sitting mode to a standing mode, depending on the particular design of the chair.

Figure 3 shows a cross section of the lift chair in the sitting mode taken through section 3-3 of figure 4.

Fig. 4 is a front view of the lift chair to illustrate the cross-section taken to obtain fig. 3.

Figure 5 shows a cross section of the lift chair in transition from the sitting mode to the standing mode taken through section 5-5 of figure 6.

Fig. 6 is a front view of the lift chair to illustrate the cross-section taken to obtain fig. 5.

Figure 7 shows a cross-section of the lift chair in the standing mode taken through section 7-7 of figure 8.

Fig. 8 is a front view of the lift chair to illustrate the cross-section taken to obtain fig. 7.

Fig. 9 is an isometric rear view of the lift mechanism.

Fig. 10 is a side view of the elevating mechanism.

Fig. 11 shows a side view of the lifter mechanism without the front seat part cushion or the rear seat part cushion attached.

Fig. 12 is an isometric front view of the lift mechanism without the front seat portion cushion or the rear seat portion cushion attached.

Figures 13A-B illustrate a section through section 13-13 of figure 14 showing a side view of the lift mechanism and a cross section of the front seat portion, rear seat portion and mid-seat portion in a raised position. Fig. 13B is an enlarged view of a V portion of fig. 13A.

Fig. 14 is a rear view of the lift chair to illustrate the cross-section taken to obtain fig. 13A-B.

15A-B illustrate cross-sectional views through section 15-15 of FIG. 16, showing a side view of the lift mechanism and cross-sections of the front, rear and middle seat portions in a sitting mode. Fig. 15B is an enlarged view of a J portion of fig. 15A.

Fig. 16 is a rear view of the lift chair to illustrate the cross-section taken to obtain fig. 15A-B.

Fig. 17A-B illustrate a cross-sectional view through section 17-17 of fig. 18, showing a side view of the lift mechanism and a cross-section of the front seat portion, rear seat portion, and mid-seat portion in a raised position, wherein the spring termination point is at a different slot position than fig. 15A-B. Fig. 17B is an enlarged view of a portion T of fig. 17A.

Figure 18 is a rear view of the lift chair to illustrate the cross-section taken to achieve figures 17A-B.

Fig. 19A-B show cross-sectional views through section 19-19 of fig. 20 showing a side view of the lift mechanism and cross-sections of the front seat portion, rear seat portion and mid-seat portion in a seated position with spring termination points at different slot positions than fig. 13A-B. Fig. 19B is an enlarged view of a portion G of fig. 19A.

Fig. 20 is a view for explaining a lift chair for obtaining the cross section of fig. 19A-B.

Fig. 21 is a rear isometric view of the riser mechanism without the seat cushion installed.

Fig. 22 is a side view of the lifting mechanism with the seat cushion attached.

Fig. 23 is a side view of the lifter mechanism without the seat cushion attached.

Fig. 24 is an isometric front view of the lift mechanism.

Fig. 25-29 show measurements associated with the lift mechanism 104, 350 (the latter of which will be described below) at various heights and various adjustments.

Fig. 25 shows a lift mechanism in which the parallelogram is horizontal or approximately horizontal.

Fig. 26 shows the lift mechanism at its highest parallelogram motion.

Fig. 27 shows a side view of the lift mechanism in a low or seated position.

Fig. 28 shows a side view of the lift mechanism in a high or standing position.

Fig. 29 shows a lift mechanism with a horizontal, associated parallelogram shaped link for seating position and an arcuate series of holes instead of slots for adjustment purposes.

Fig. 30 shows the lift mechanism with the spring at maximum extension for a standing position.

Fig. 31 shows the lift mechanism with the spring at maximum extension for the standing position.

Fig. 32 shows how the minimum elevation position of the spring pin in the rearmost hole position affects the elevation angle relative to the spring axis.

Fig. 33 shows a lift mechanism having a restraint plate extending between points "a" and "B".

Fig. 34 shows the restraint panel position when the lift mechanism is in its lowermost position.

Figure 35 shows an isometric view of the restraint panel when the lift mechanism is in the raised position.

FIG. 36 shows an isometric view of the riser mechanism 350 with the seat 410 in a folded mode to better view the device

Fig. 37 shows a lift mechanism with a linearly adjustable spring-terminated pivot, where the lift mechanism including the spring is disposed on the side of the seat.

Figure 38 is an isometric view of a portion of the lift mechanism shown in figure 37 with the side of the rear end block transparently presented.

FIG. 39 is an isometric view further illustrating the spring termination adjustment mechanism of FIG. 38.

Fig. 40 is an isometric view of an alternative lift geometry operating according to the same principles as the previously described embodiments, but having a spring end point adjustment mechanism at the lowermost end of the long links of the parallelogram.

Fig. 41 shows the lifting mechanism of fig. 40 with a seat cushion attached.

Fig. 42 shows a spring termination adjustment mechanism.

Fig. 43 is an isometric view of an elevating lift chair in a lower seating mode with an adjustable lift mechanism.

FIG. 44 is a rear isometric view of an elevating walker chair with an adjustable lifting mechanism.

FIG. 45 shows an isometric view of the elevating walker chair in a raised or standing position.

FIG. 46 shows a rear isometric view of the elevating walker chair in a raised position.

FIGS. 47A, 47B show front isometric views of a lift mechanism adjustment mechanism for an elevating walker chair. Fig. 47B shows detail a of fig. 47A.

FIG. 48 shows a side view of the elevating walker chair in its highest elevated position.

Fig. 49A-C show steps for adjusting the lift mechanism. FIG. 49B illustrates a side cross-sectional view of the lift chair taken along line B-B of FIG. 49A. Fig. 49C is an enlarged view of detail C of fig. 49B.

Fig. 50A-C illustrate steps for adjusting the lift mechanism. FIG. 50B illustrates a side cross-sectional view of the lift chair taken along line D-D of FIG. 50A. Fig. 50C is an enlarged view of detail E of fig. 50B.

Fig. 51A, 51B show subsequent lift adjustment steps shown in fig. 50A-C. Fig. 51B is an enlarged view of detail F of fig. 51A.

Fig. 52A, 52B show the next ascent and descent adjusting step. Fig. 52B is an enlarged view of detail G of fig. 52A.

Figures 53A, 53B show an initial elevating walker chair configuration prior to the commencement of the maximum height adjustment process. Fig. 53B is an enlarged view of detail H of fig. 53A.

Fig. 54A, 54B illustrate a first maximum height adjustment step to change the maximum height that the lift chair can reach. Fig. 54B is an enlarged view of detail H of fig. 54A.

Fig. 55A, 55B show the next maximum height adjustment step of this illustrative embodiment. Fig. 55B is an enlarged view of detail H of fig. 55A.

FIG. 56 is a side view of the elevating walker chair showing the height adjustment pin preventing the height adjustment sleeve from fully riding up the height adjustment bar.

Fig. 57A-C illustrate a support arm adjustment mechanism. FIG. 57A is a side view of an illustrative elevating walker chair with a support arm adjustment mechanism. Fig. 57B is a detail of part O of fig. 57A. Fig. 57C is a section of the arm support adjustment mechanism taken along line P-P of 57B.

FIGS. 58A-B illustrate an intermediate height adjustment mechanism. FIG. 58A shows an elevating walker chair with the intermediate height adjustment mechanism and the seat in its lowest position. Fig. 58B is a close-up of detail K of fig. 58A before seat height is selected.

Fig. 59A-B illustrate an intermediate height adjustment mechanism. FIG. 59A shows an elevating walker chair with an intermediate height adjustment mechanism and the seat secured at a selected height. Fig. 58B is a close-up of detail K of fig. 58A. Fig. 58A shows the intermediate height adjustment mechanism engaged to fix the height of the seat.

FIG. 60 is an isometric rear view of the folding elevating walker chair in a partially folded position.

FIG. 61 shows a front view of a partially folded elevating walker chair.

FIG. 62 is a rear isometric view of the elevating walker chair in a fully folded position.

FIG. 63 is a front view of the elevating walker chair in the fully collapsed mode.

Figures 64A-B illustrate another embodiment of a height adjustment mechanism for an elevating walker chair.

FIG. 65 shows an isometric view of a portion of an elevating walker chair with a seat connected to a central lifting mechanism.

Detailed Description

The illustrative embodiments of the lift chair can move the user's center of gravity in a seated position over fixed knees and feet with reduced energy consumption compared to the energy required to lift from a conventional chair.

The illustrative embodiments of the lift chair mechanism can be balanced throughout the displacement of the user's center of gravity from seated to standing, thereby reducing or eliminating the user's weight as an impediment to any portion of this movement.

Illustrative embodiments of the lift chair include an adjustable mechanism to accommodate the lifting force of various human weights.

Illustrative embodiments of the lift chair mechanism may also provide a means for withdrawing and reinserting a generally wedge-shaped or other complementary mid-seat support portion that must be removed to allow the raised seat cushion to collapse and return to a seated position without interfering with the user's standing and seating movements.

Alternatively, the mid-seat support may be stationary relative to the riser mechanism base frame so the seat moves towards and away from it for seat support or folding, respectively.

Fig. 1 is an isometric view of an illustrative lift chair 100 transitioning between a standing mode and a sitting mode. The lift chair 100 has a seat 114, the seat 114 including a front seat portion 116 and a rear seat portion 118. In the sitting mode, the front seat portion 116 and the rear seat portion 118 form surfaces adapted to sit on by, for example, abutting each other. The seat portions 116, 118 may have various contours similar to conventional chairs.

Figure 2 is an isometric view of the lift chair 100 in a standing mode or transitioning from a sitting mode to a standing mode, depending on the particular design of the chair. The rear seat portion 118 is raised from the seating position to facilitate the occupant exiting the lift chair 100 by transitioning from the seating position to the standing position. The front seat portion 116 is downwardly inclined to facilitate the transfer of weight from the seat portion 114 to the legs of the occupant. An optional flexible plate 119 has a first edge connected to the seat back 108 of the lift chair 100 and a second edge connected to the rear seat portion 118. The flexible plate 119 shields a lift mechanism included in the lift chair 100, such as the lift mechanism 104 or the lift mechanism 350 shown in fig. 29. The flexible plate 119 may be removable to allow access to the lifting mechanism 104 and its adjustment components.

Fig. 3 shows an illustrative cross section of the lift chair 100 in the sitting mode taken through section 3-3 of fig. 4. Figure 5 illustrates a cross-section of the lift chair 100 taken through section 5-5 of figure 6 for a transition from a sitting mode to a standing mode. Figure 7 illustrates a cross-section of the lift chair 100 in a standing mode taken through section 7-7 of figure 8.

The lift chair 100 has a chair frame 102 and a lift mechanism 104 coupled thereto. The chair frame 102 may have any configuration including components that together form a seating device, such as an armchair, a desk chair, a backless chair, or an elevating walker chair. In the illustrative embodiment, the frame 102 has a plurality of legs 106, a seat back 108, and a base 110. The chair frame 102 may also include a seat support 112 that provides support for a seat 114. Alternatively, the lift mechanism 104 may have a seat fully incorporated therein or connected thereto, in which case the components of the lift mechanism 104 form the seat.

Fig. 3, 5, and 7 show a seat 114 having a front seat portion 116 and a rear seat portion 118, which are directly or indirectly connected to the riser mechanism 104. In the illustrative embodiment, the seat portions 116, 118 include seat cushions. The seat cushions of the front and rear seat portions 116, 118 are connected to front and rear seat support portions 158, 160, respectively, as shown, for example, in fig. 12, 13, 21, 24. The rear seat portion 118 is hinged or otherwise pivotally connected to the front seat portion 116 at a first seat pivot 122 to allow the relative position thereof to be changed when the riser mechanism 104 is employed to raise or lower a user from or to a seated position. The seat 114 may also include a mid-seat support portion 120, the mid-seat support portion 120 reinforcing or stiffening the seat 114 in an area below the first seat pivot 122.

As shown in fig. 3, 5, and 7, the lifting mechanism 104 includes a parallelogram frame 124. The parallelogram frame 124 has a first set of parallel links 126, 128 and a second set of parallel links 130, 132 that are pivotally connected to each other at pivots 134, 136, 138, 140 to form a parallelogram. The parallelogram link 126 has an extension 150 disposed at an angle to the parallelogram link 126, as will be described in more detail below.

Fig. 9-12 are further illustrations showing the lift mechanism 104 in a standing mode or transitioning from a sitting mode to a standing mode. Fig. 9 is an isometric rear view of the lift mechanism 104. Fig. 10 is a side view of the lifting mechanism 104.

Fig. 9 and 10 show the front seat portion 116, the rear seat portion 118, and the center seat portion 120 connected to the lift mechanism 104. Fig. 11 shows a side view of the riser mechanism 104 without the seat cushion portion connecting the front seat portion 116 and the rear seat portion 118. Fig. 12 is an isometric front view of the riser mechanism 104, also without the seat cushion portion of the seat portion 116 and the rear seat portion 118. The spring 142 is connected to the spring shaft at the longitudinal center of the shaft. The spring shaft pivots relative to the parallelogram link 132 at spring pivot 144. The spring 142 is pivotally connected at the end of the extension 150 opposite the start of the extension 150 at the parallelogram link 126. The extension 150 may be connected to or integral with the parallelogram link 126. The spring pivot 144 is adjustable along a portion of the parallelogram link 132. In the illustrative embodiment shown, the spring 142 is connected to a spring shaft that extends into the slot 156 so as to be adjustable along the slot 156 and thus along the parallelogram link 132. The slot 156 may be linear or arcuate with its center at the opposite end as the spring 142 is deployed.

Note that the spring shaft is not explicitly shown in the figures, but its position is clearly seen by identifying the spring pivot 144 and noting that it extends perpendicular to the plane of the parallelogram link 132.

Returning to fig. 5, the seat 114 is transitioned from the sitting mode to the standing mode by operation of the lift mechanism 104 to assist the user while standing from the seated position. The seat 114 is raised as the parallelogram frame 124 pivots at pivots 134, 136 relative to the lift mechanism side supports 146. When the occupant stands, the weight of the occupant begins to transfer to the floor, thereby deploying the spring 142. As the extension 150 pivots about the pivot 140 relative to the parallelogram link 130, the distance from the upper spring pivot 152 to the pivot 144 increases, thereby providing the necessary distance for the deployment of the spring 142. When the lift chair 100 is in the sitting mode, the spring 142 is compressed by the weight of the occupant.

The spring 142 may be, for example, a compression spring, such as a gas spring. Other illustrative types of springs include extension springs (which will expand oppositely on a parallelogram to provide comparable lift forces). In the illustrative embodiment, the spring 142 is a gas spring having a diameter in the range of 20mm to 45mm and a rod diameter in the range of 10mm to 20 mm. The illustrative force advance range from fully expanded to fully compressed is 45% to 55%, resulting in 'p1' values in the range 2600N to 1,300N and 'p2' values in the range 1700N-4200N. In the illustrative embodiment, the range of travel of the spring 142 is 75mm to 85mm, and the uncompressed length is 200mm to 275mm.

As the parallelogram linkages 126, 128, 130, 132 of the parallelogram frame 124 pivot about pivots 134, 136, 138, 140, motion is imparted to the seat portions 116, 118, 120 of the chair 114. When the seat 114 is transitioned from the standing mode to the sitting mode, the rear seat support portion 160 remains relatively parallel to the floor, and the front seat portion 116 pivots relative to the rear seat portion 118 about the seat pivot 122, thus rotating the angle downward from the horizontal to the horizontal position or near the horizontal position. Depending on the desired design of the chair, the front seat support portion 158 and the rear seat support portion 160 may be angled from the horizontal in the sitting mode. For example, the front of the seat 114 may be higher than the rear of the seat 114. Similarly, the seat back 108 may be vertical or angled from vertical to achieve a desired position of utility or comfort. Because the parallelogram link 130 is directly or indirectly connected to the parallelogram link, the middle seat portion 120 automatically moves into position to support the seat 114 below the seat pivot 122.

In the illustrative embodiment shown in fig. 9-12, the front seat support portion 158 is connected to the mid-seat support portion 162 at a first link pivot 168 by a link 164. A second end of the pull rod 164 is pivotally connected to the front seat support portion 158 at a second pull rod pivot 172. When the lift chair 100 is transitioned from the sitting mode to the standing mode, the parallelogram links 130 of the parallelogram frame 124 rotate about the pivots 134, 140, causing the middle seat support portion 162 to move away from the front and rear seat portions 116, 118. This allows the front seat support 158 to pivot downward relative to the rear seat support 160.

Fig. 21-24 show the lift mechanism 104 in a sitting mode. Fig. 21 is an isometric rear view of the lift mechanism 104. Fig. 22 is a side view of the lifting mechanism 104. In fig. 21 and 22, the front seat portion 116, the rear seat portion 118, and the mid-seat portion 120 are shown as being connected to the lift mechanism 104. Fig. 23 shows a side view of the lifter mechanism 104 without the seat cushion. Fig. 24 is an isometric front view of the lift mechanism 104.

Fig. 22 shows the front portion 116 and the rear portion 118 forming a sitting surface in the sitting mode. The mid-seat portion 120 pivots to a position below the seat pivot 122.

In the embodiment shown in fig. 9-12 and 21-24, mid-seat support portion 162 and rear-seat support portion 160 are platforms having support springs 176 that may form a more comfortable seat than a rigid member such as a wooden platform. However, the present disclosure includes chair designs that incorporate such rigid platforms or other supports for the seat cushion.

The front seat support portion 158 is shown as a support bar 178. Other structural components may form the front seat support portion 158. The front seat portion 116 is connected to a front support bar 178, the front support bar 178 rotating at a pull bar pivot 172 such that the front seat portion 116 can fold downward about pivot 122 relative to the rear seat support portion 160 when the lift mechanism is converted from the seating mode to the standing mode (e.g., as shown in fig. 7).

The seat portions 116, 118, 120 of the seat 114 are respectively connected or integrated into the riser mechanism 104. The cushion member of the front seat portion 116 is connected to the front seat support portion 158 of the lifter mechanism 104. The seat cushion member of the rear seat portion 118 is connected to the rear seat support portion 160. The wedge portion of the mid-seat portion 120 is connected to the mid-seat support portion 162. The mid-seat support portion 162 may be a parallelogram link 130 or a fixed attachment to the parallelogram link 150. The seating portion of the seat portions 116, 118, 120 may be integral with the seat support portions 158, 160, 162 or attached to their respective seat support portions. Figures 3, 5 and 7 show the seating portion of the seat portions 116, 118, 120 having a seat cushion connected to seat support portions 158, 160, 162, respectively. When the parallelogram link 126 pivots about pivot 138, the extension 150 remains substantially parallel to the ground, and thus the seat portion 118, which is directly or indirectly connected to the extension 150, also remains substantially parallel to the floor. The extension 150 need not be integral with or directly connected to the parallelogram linkage. It only has to move in a fixed relationship. Additional components may be between the extension 150 and the parallelogram link 126 or other parallelogram link, as long as the extension 150 remains at a fixed angle to the ground when raised or lowered, it is possible to connect the seat thereto and also maintain the fixed angle. In the illustrative embodiment, the extension 150 is a seat.

The lift mechanism 104 may be adjusted to accommodate occupants of different weights. Fig. 13A-B and 15A-B show the lifting mechanism 104 adjusted to the highest occupant weight accommodation amount for this illustrative embodiment. Fig. 13A-B and 14 show the lift mechanism 104 in a standing mode. Fig. 15A-B and 16 show the lift mechanism 104 in a sitting mode. Fig. 17A-B and 19A-B show the lifting mechanism 104 adjusted to the lowest occupant weight accommodation amount for this illustrative embodiment. Fig. 17A-B and 18 show the lift mechanism 104 in a standing mode, and fig. 19A-B and 20 show the lift mechanism 104 in a sitting mode.

Fig. 13A is a sectional view through section 13-13 of fig. 14, thus showing a side view of the lift mechanism 104 and a cross section of the front seat portion 116, the rear seat portion 118 and the center seat portion 120. Fig. 13B is an enlarged view of a portion V of fig. 13A. As described above, fig. 13A, 13B, 14 show the lifter mechanism in the standing mode, which is adjusted to the maximum accommodation amount with respect to the occupant weight. In the embodiment shown in the figures, the mechanism for adjusting the lift mechanism 104 to accommodate occupants of different weights includes a pivot 144, the pivot 144 being positionally adjustable along the slot 156 to control lift efficiency. Spring pivot 144 is shown in a forwardmost or lowest position in slot 156. A "spring pivot 144" is generally used herein and may be in the form of a shaft extending through slot 156.

The spring 142 pivots on a spring pivot 152 relative to the extension 150. The position of the spring pivot 152 is fixed relative to the extension 150, but the spring 142 can rotate about the pivot 152. The position of the extension 150 is also fixed relative to the parallelogram link 126. Thus, the position of the spring pivot 152 is also fixed relative to the parallelogram link 126. This maintains the geometry regardless of the height or whether the lift chair 100 or lift mechanism 104 is in the sitting or standing mode, even if the parallelogram links 126, 128, 130, 132 pivot about the parallelogram pivots 134, 136, 138, 140. This relationship is maintained regardless of the weight of the occupant.

When the spring pivot 144 is positioned in the slot 156 toward the rear of the lift chair 100 or lift mechanism 104, as shown in fig. 19B, the actual lift lever arm will be shortened and the lift force will be minimized, and the lift action caused by the action of the parallelogram frame 124 on the spring 142 will be more equally resilient. This position will generally be more suitable for a lighter weight occupant. When the spring shaft is placed closer to the front of the lift chair 100 or lift mechanism 104 along the slot 156, the force will be maximized and the lift caused by the action of the parallelogram frame 124 on the spring 142 will be less iso-elastic. This would be beneficial for a heavier occupant. As used herein, "isoelastic" refers to an elasticity that is constant over the movement of the lift mechanism. Perfect iso-elasticity may not necessarily be achieved or desired, but the equivalent elasticity may be affected by the adjustment mechanism. Theoretically, the weight of the occupant should be balanced by the spring force throughout the travel of the lift mechanism. Although for a heavier occupant it may be desirable to vary the force at the beginning or end of the movement as compared to the rest of the lifting movement.

Spring pivot 144 can be adjusted along slot 156 by rotating adjustment knob 180. The position of the slot 156 relative to the parallelogram pivot 144 is strategically positioned on the parallelogram frame 124 to achieve optimal or beneficial iso-elasticity. The position of pivot 144 within slot 156 relative to pivot 138 determines the efficiency of the spring angle and therefore its applied force relative to parallelogram frame 124. In the illustrative embodiment, the spring pivot 144 in the slot 156 is displaced from the position of the parallelogram pivot 138. Adjustment of the spring pivot along slot 156 is generally easiest when spring 142 is perpendicular to slot 156.

In the illustrative embodiment shown in fig. 1-24, the lift mechanism 104 is symmetrical so that the components identified in side view may be repeated when viewed from the opposite side. Embodiments also include structures having a single parallelogram, spring structure, or a single support member, such as shown in fig. 65.

In the illustrative embodiment of the elevator mechanism 104, the aspect ratio of each side of the elevator parallelogram 124 is relatively low. Even when adjusted for maximum lifting force, excessive spring force is exerted on a relatively short "lever arm", which is an extension adjacent to or fixedly connected to a link or edge of parallelogram 124. In the illustrative embodiment, the aspect ratio is 6:1, or about 6:1. see fig. 25-29 for an example of an actual lever arm 402.

When adjusted to a minimum lifting force, for example by a pin and hole adjuster or a slot in which a pin or similar component can slide, these lever arms are still shorter-the length is reduced by up to 80%, and the yield width to height ratio is up to 24:1. an illustrative aspect ratio range is 6:1-24:1. the optimal aspect ratio may depend on, for example, the lifting force of the resilient member and the lever arm. The resilient member in any of the lift mechanisms described herein can be a spring, such as a gas spring. For simplicity, the resilient member may be referred to and illustrated as a spring or a gas spring, however, other resilient members may be used.

An illustrative lift angle of the lift mechanism 104 will now be described. In addition, the illustrative embodiment will show that in any lift adjustment from weakest to strongest, the seat 114 or other payload can be raised to the same height when the spring is fully deployed. This feature may be highly desirable because the raised seat presents itself at a constant height, rather than projecting higher and more forward for lighter users.

Fig. 25-29 illustrate dimensions at various heights and various adjustments associated with the lift mechanisms 104, 350 (described below), similar to the lift mechanism 602. These dimensions include the lift angle 394, the slot angle 396, the distance between the parallelogram pivots 354 and 358 or the parallelogram pivots 352 and 356 (because these distances are equal to each other), the distance between the parallelogram pivots 356 and 358 or the parallelogram pivots 352 and 354 (because these distances are equal to each other), and the distance between the lift spring end pivot 366 and the main pivot 352. Although referred to as a "slot angle," the angle may relate to a series of holes. The distance between parallelogram pivots 354 and 358 or between parallelogram pivots 352 and 356 will be referred to as parallelogram short link length 398 and the distance between parallelogram pivots 356 and 358 or between parallelogram pivots 352 and 354 will be referred to as parallelogram long link length 400. The distance between the lift spring stop pivot 366 and the main pivot 352 will be referred to as the stop pivot distance 402.

The lift angle 394 is the angle between the line connecting the upper lift spring pivot 364 and the lift spring termination pivot 366 (i.e., the spring axis 148) and the line connecting the lift spring termination pivot 366 and the main pivot 352. The line 402 between the lift spring termination pivot 366 and the main pivot 352 acts as a "virtual lever arm" or "lever arm" on the parallelogram 382. Slot angle 396 is the angle between the line connecting upper lift spring pivot 364 and lift spring termination pivot 366 and the line along which lift spring termination pivot 366 may be adjusted in slot 368. Slot angle 396 illustrates only the potential path of lift spring termination pivot 366 as a function of the length of lever arm 402.

Fig. 25 shows an illustrative embodiment in which the parallelogram is horizontal or approximately horizontal. A 2.27 "inch lever arm 402 is shown with a lift angle 394 of 115 deg.. Illustrative ranges for the lever arm length position include 1.0 inch to 4.0 inches and 2.0 inches to 3.0 inches. Illustrative adjustment amounts include 0.75 inch to 1.25 inches and 0.9 inch to 1.0 inch.

For the seating configuration of the seat cushion, as shown in fig. 25, this oblique rise and fall angle sufficiently reduces the effective spring force to cause the seat cushion to be iso-elastic or nearly iso-elastic at and near its lowest position.

As can be seen, for example, in fig. 26, the lift mechanism 104 raises the backseat portion 118 via the extension 150, which remains horizontal, while remaining substantially horizontal or at an angle to the horizontal as in the lower position. The lift mechanism 104 also moves the seat 114 forward. When transitioning to the standing mode, the front seat portion 116 tilts downward as the middle portion 120 is moved away from its position supporting the front seat portion 116 and the rear seat portion 118 in the sitting surface. The optimal lift angle may be different if the seat 114 is moved rearward. Forward lift generally requires less lifting force than when rearward lift is required, because the weight of the user of the lift chair 100 will be entirely or nearly entirely on their feet when the raised position is reached, rather than still being significantly supported, as when lifted rearward, which may cause the user to lean rearward.

In the illustrative embodiment, a lifting force of between 50% and 70% of the user's weight is used. For example, the range may be suitable for use with a lift chair having armrests on which a user may push down. Without the armrest, the optimal lifting force may be greater, for example 70% -95% or more of the occupant's weight.

Fig. 26 shows the lifting mechanism 104 at its highest parallelogram motion. Using the same 2.27 "inch lever arm, the lift angle 394 is reduced to 61 °, in this embodiment just beyond its most effective (90 °) angle. This applies to lifting the parallelogram "forward" as the lifting capacity may need to be reduced as the uppermost position is approached.

The tilt ramp angle 394 when the lifting mechanism 104 is at its uppermost position reduces the force sufficiently that the payload lifting force is equalized or nearly equalized, and thus "iso-elastic" or nearly "iso-elastic".

Fig. 26 shows a slot angle 396 of 89 degrees, which is quite different from a lever arm lift angle of 115 degrees. The slot angle 396 is selected because it depletes the travel of the fully deployed spring 142 at exactly the same height regardless of the adjustment position within the slot 156. Indeed, if the slot 156 is curved (and the lead screw is pivoted), all positions along the slot 156 may coincide with the final extension of the spring 142 and therefore produce the same height for the seat 114 at any lift adjustment.

Fig. 27 and 28 show the low and high travel of the parallelogram 382, respectively. Fig. 27 and 28 show the resultant lift angle 394 that is achieved between the lever arm 402 and the spring axis 148 when lift is adjusted to a minimum (with the spring pivot located as far to the rear of the present embodiment as possible). Note that in the seated position, spring 142 is raised and lowered at a lift angle 394 of 97 deg. against efficient lever arm 402 of approximately 90 deg..

In the high "step" position, as shown in fig. 28, noting the minimum adjustment along slot 156, lift angle 394 is 45 of low efficiency, which prevents seat 114 from being pushed forward excessively. This is important; not only is it detrimental to push the occupant away from the chair, but the force required to initiate the seat/cushion descent can also cause the entire chair to jump backwards as a potential user approaches.

The lift mechanism 104 of the illustrative embodiment (such as those shown in fig. 25-28) is below the seat 114. This same lifting geometry can be used to lift the seat/cushion, where the lifting mechanism is divided into two cooperating lifting parallelograms positioned on either or both sides of the lift chair, as shown, for example, in fig. 29-32. The lift mechanism 104 incorporates a central spring 142, or a set of adjacent springs disposed between the two parallelograms 124. While lift mechanism 350 may include two springs 362 on opposite sides of lift mechanism 350, each spring associated with a parallelogram 382, it may be configured with a single spring 362 associated with a single parallelogram 382.

The rear blocks 422 of the parallelograms 382 are interconnected by cross tubes or crossbars 426, as shown in fig. 35 and 36. Flanges may be included to support the rear seat cushion, such as component 359 shown in FIG. 35. Note that the spring 362 may be of the same type as the spring 142.

The pivots of the parallelogram 382 are designated 352, 354, 356, 358 and the main pivot is designated by reference numeral 352, but it should be understood that the configuration of the parallelogram linkage and adjustment mechanism may differ from the other lift mechanism embodiments disclosed herein.

In an embodiment of the lift mechanism 350, the base frame 406 includes a front parallelogram end block 408 on either side of the seat cushion when the seat 410 is in the seating mode. The mid-seat support portion 120 is secured to the transverse connecting floor 412 of the base frame 406. A cross-connecting bottom plate 412 connects the side walls 414, 416 to the base frame 406. Although reference is made to a seat cushion, similar lifting mechanisms having both sitting and standing modes may be constructed without the need for a seat cushion, but rather to provide sufficient surface to support the user in a reasonably comfortable manner. It should also be noted that the seat cushion may be integrated with the lifter support portion. By "integral" it is meant that the seat cushion is permanently or removably secured to the seat supporting portion of the riser mechanism.

In the unitary cushion form of the embodiment of the riser mechanism 350, the middle seat portion 120 also serves to fill the fold notches adjacent the interface of the front and rear seat portions 116, 118 in the seating position. Unlike other disclosed versions in which the riser mechanism 350 is disposed below the middle of the seat 114 and the middle section 120 must be raised as the parallelogram is raised, the riser parallelogram 382 is apparent on either side and allows the middle seat section 120 to remain fixed in position relative to the cross-linked floor 412. By "raised parallelogram 382" is meant that an assembly of parallelogram 382 may be raised, but not all portions need be raised. For example, in fig. 26, pivot 354 remains in place, and a portion of the lowermost link of parallelogram 382 may even extend below its original position.

Fig. 29 shows a lift mechanism 350 having a linkage of a horizontal parallelogram 382 (e.g., in the illustrative seating position) and having an arcuate series of holes 424 to adjust the position of spring stop 366. The radius of the aperture arc 424 is equal to the length from the spring termination point to the spring pivot 364 instead of the slot 368 when the spring 142 is fully deployed. Although the holes 424 form arcs, their centers may be used to closely approximate points to define the rays used to define the groove angle 368. Thus, the groove angle 368 is shown in fig. 29, 31, 32 for approximate comparison with a configuration having an adjustment mechanism that includes the slot 368. In the illustrative embodiment of fig. 29, the "slot angle" 396 is 150 °. The lever arm 402 has a length of 2.27 "inches and a lift angle 394 of 115 deg., where it extends between the lower parallelogram pivot 352 and the hole second to last from the rear (the farthest hole would provide additional lift). The slot angle 396 is the same regardless of which hole the lift spring termination pivot 366 is located in.

Because the spring pivot 364 is centered in the aperture arc 424 only when the spring 142 is fully deployed, the effective lifting force can only be adjusted by changing the aperture position of the lifting spring termination pivot 366 when the spring 142 is fully deployed. This is illustrated by comparing fig. 29 and fig. 30. In fig. 29, the lift mechanism 350 is in its lowest position and the spring 142 is compressed. The spring pivot 364 is not centered on the arc along which the hole 424 follows. Thus, in the lowest mode, the spring 142 cannot rotate in alignment with each of the holes 424. Fig. 30 shows the lift mechanism 350 in its uppermost position. The spring 142 is fully deployed and the spring pivot 364 is at the center of the arc along which the aperture 424 follows. In this configuration, the spring 142 can rotate about the spring pivot 364 and will align with any of the holes 424, and therefore, adjustment of the lifting force can be made.

Fig. 30 shows the lift mechanism 350 in a raised position. The rear seat portion 118 is held in a horizontal position by the horizontal-holding extensions 359. The extensions 359 may also be designed to maintain a given or selected angle with the horizontal. Extension 359 operates in a similar manner to extension 150. When the front and rear seat portions 116, 118 are removed from the fixed mid-seat portion 120, the front seat portion 116 is free to fall downward to allow the user to move to a standing position. The front seat portion 116 and the rear seat portion 118 may be connected by a hinge made of a rigid or soft material or a combination of both materials. For example, a fabric such as cloth, leather, or vinyl may connect the front portion 116 and the rear portion 118 and allow the front portion 116 to fall downward while remaining connected to the rear portion 118. Additionally or alternatively, a pivot such as pivot 122 shown in FIG. 5 may be used in the illustrative embodiments. Note that for simplicity, the front seat portion 116, the rear seat portion 118, and the center seat portion 120 include any of a seat, cushioned, or base component, but these individual components may also be separately identified. The seat 114 includes a front seat portion 116, a rear seat portion 118, and a mid-seat portion 120.

The aperture 424 may be coupled to the rear end block 422 on either side of the lift mechanism 350. Alternatively, holes 424 may be used on one end block 422 and slots and nails may be used on the opposite end block 422. An illustrative spring axle pin 432 is shown in fig. 42. Alternatively, if only one parallelogram 382 elevator mechanism is employed, then there is an arcuate series of holes 424 in the single end block 422 that is used. In this embodiment, the radius 428 of the aperture arc 424 extends from the spring (resilient member) pivot 364 to a lift spring termination pivot 366 that coincides with the selected aperture 424. In the illustrative embodiment, when parallelogram 382 is raised to its maximum height, radius 428 is equal to the distance between the center of pivot 364 of 10.5 inches of one or more fully deployed springs 362 and the center of pivot 366. An illustrative radius range is 9 inches to 12 inches.

The effective lift force can be adjusted by pulling spring pin 432 out of a selected hole 424 and swinging spring 362 up toward a more forward hole (stronger) or down toward a more rearward hole (weaker) to another hole 424. In a configuration with springs 362 on opposite sides of the riser mechanism 350, the holes 424 remain aligned to allow the spring pin 432 to be inserted into any hole, as the springs on the opposite sides still maintain the seat/cushion at the same height. The opposite side spring axle pin 432 may then be repositioned while the proximal spring axle pin maintains the seat/cushion at the maximum height. This alternative two-sided adjustment process provides a Vernier effect (Vernier effect) because adjustment through one hole on one side can only produce half the lift change when repositioning the two spring pins 432. This feature may allow for easy selection of sufficiently fine adjustments in a wide range of lift settings.

Fig. 31 illustrates how the minimum lift position (i.e., the rearmost hole position) of the spring axle pin 432 affects the lift angle 394 relative to the spring axis 148. In the rearmost position, the spring 362 powers the relatively short 1.56 "inch lever arm 402, pushing at a low efficiency lift angle 394 of only 39 degrees to offset the bias from iso-elasticity due to lowering the aspect ratio of the lift triangle. The three sides of the "lifting triangle" include: 1) the length of the spring 362, i.e., the distance from the lift spring pivot 364 to the lift spring termination pivot 366, 2) the distance from the lift spring termination pivot 366 to the main pivot 352, and 3) the distance from the main pivot 352 to the lift pivot 364. This adjustment mechanism changes the lifting force from the forward-most aperture 424 to the rearward-most aperture 424 by almost 2:1.

it should be noted that the specifications provided, for example, for the lift angle, the slot angle, and the lever arm length are for illustrative embodiments only. These specifications may be varied, for example, to accommodate users of different weights and abilities.

The effective lifting force may be selected to allow the occupant to replenish their own ability to stand up from the seated position of the chair with the lifting mechanism 350. For example, with an illustrative spring force of 3200N at 50% forward speed, this adjustment range should lift half the weight of a person between 100 pounds and 200 pounds and enable them to be easily lifted from a low arm chair or other device or furniture incorporating the lift mechanism 350. An illustrative spring force range is 3000N to 3500N. An illustrative force advance range from fully expanded to fully compressed is 45% to 55%. In the illustrative embodiment, the range of travel of the spring 362 is 75mm to 85mm, with an uncompressed length of 200mm to 275mm. The spring 362 may be, for example, a compression spring, such as a gas spring. Other illustrative types of springs include extension springs (which need to be oppositely spread out on the parallelogram to provide comparable lifting forces).

In this illustrative embodiment, a suitably small diameter gas spring, for example in the range of 23mm diameter to 28mm diameter, may fit within a narrow parallelogram mechanism on either side of the folded pad. When the rear seat portion 118 is raised, the rear seat portion 118 may be connected at its rear edge to a loose envelope (not shown) of cushion fabric that will also be connected to the lower edge of the seat back to conceal and protect the riser mechanism even in the raised condition.

Fig. 32 shows how the minimum lift position of the spring pin in the rearmost hole position affects the lift angle relative to the spring axis, providing a lift angle 394 of 98 degrees and a "slot angle" 396 of 153 degrees.

Fig. 29 shows an illustrative geometry of the lift mechanism 350 with the lift spring terminating in the forward most hole and the lift mechanism in a seated position, with an illustrative lever arm length 402 of 2.27 "inches.

As shown in fig. 33, to control or assist in controlling the position of the front seat portion 116 of the lift seat 410, a restraint plate 404 may be included. The restraint panel 404 may be connected between the lower front edge of the front seat portion 116 and a suitable point (in this illustrative case the apex of the mid-seat portion 120) such that the restraint panel 404 keeps the front seat portion folded down sufficiently and clear of the occupant's knees during upward and downward movement of the seat 410. In the illustrative embodiment, the restraint panel 404 is a non-stretch material and may be a cloth or other flexible material.

Illustrative heights 392 of the seating surface from the ground are shown in fig. 25, 29, and 31, including 13.28 inches, 5.83 inches, and 18.24 inches, respectively. The 5.83 height shown in fig. 29 corresponds to a seated height, while the height shown in fig. 31 corresponds to a raised height. Since the thickness of the seat cushion can vary and the disclosed riser mechanism can be configured for use without a seat cushion, an important distance is the variation in height of the seating surface from the lowest position to the highest elevated position. Illustrative vertical distance position changes from the sitting mode to the standing mode are 8 inches to 16 inches and 11 inches to 13 inches.

Fig. 33 shows a constraining plate 404 extending between points or edges "a" and "B". Points or edges "a" and "B" are selected so that the restraint panel 404 performs a restraining function and can remain taut and under the seat 410 in the seating position throughout movement of the lift mechanism 350.

Fig. 34 shows a diagram of the position of the restraint panel 404 when the seat is in its lowest position.

Fig. 35 shows an isometric view of the riser mechanism 350 and seat 410 in a raised position. In this illustrative embodiment, the binding plate 404 has a connection length along the lower front edge of the front seat portion 116 and along the apex of the mid-seat portion ("wedge") 120.

The opposing elevating parallelograms 382 with incremental "hole" adjustment mechanisms 430 allow the spring pin 432 to be moved away from both sides and the front 116 and rear 118 seat portions to lie flat or be designed flat with the uncompressed springs extending along the lowest holes to create a seat 410 that looks and "acts" like a conventional seat cushion when desired. The configuration may also be suitable for transporting and repositioning the lift mechanism to another chair or other device.

In the illustrative embodiment, setting and returning to its lift chair mode will only require lifting the rear seat portion 118 until one spring-loaded pin 432 can engage the spring cap 434 through any of the holes 424, and then alternately repositioning the spring-loaded pin 432 from side to obtain the desired amount of lift.

Fig. 36 shows an isometric view of the lift mechanism 350 with the seat 410 in a folded mode for additional visualization of the device. As described above, the rod 426 is shown connecting opposing lift mechanisms 350. The rods 426 may provide support for the device and maintain the position of the opposing lifting mechanisms 350 relative to each other. If only one lift mechanism 350 is present in the lift device, the rods 426 still provide structural support and maintain the integrity of the relative positions of the frame assembly or other parts on opposite sides.

Fig. 37 shows an illustrative embodiment of a lift mechanism 502 having a linearly adjustable spring-terminated pivot 504. The spring stop pivot 504 is adjustable along a slot 506. The groove angle may be increased or decreased by a conventional lead screw (e.g., a lead screw rotated by a folding crank 508). Fig. 37 shows an embodiment with a linear slot 506. The slot may also be arcuate with the remaining elevator mechanism components modified appropriately to allow the spring termination pivot 504 to be adjusted with the arcuate slot.

Similar to the extensions 150, 359, 616, the lift mechanism 502 includes an extension 524 to maintain the angle of the backseat portion 118.

Figures 38 and 42 are isometric views of the lift mechanism 502 shown in figure 37 with one side of the rear block 522 transparently presented. Fig. 39 also shows a spring termination adjustment mechanism 520 (also referred to as a "lift strength adjustment mechanism"). Fig. 38 shows the lead screw 510 disposed between two sides of the end block 522. The travel nut 512 may be moved along the lead screw 510 to adjust the position of the spring termination pivot 504. The travel nut 512 has an integral transverse shaft 514 on each side that engages a yoke 516 (to facilitate installation). Spring termination pivot 504 is also engaged in yoke 516 or a component connected thereto. A retainer screw 518 secures the integral transverse shaft 514. The folding crank 508 for adjusting the position of the travel nut 512 is shown in the folded position.

Deploying and rotating the crank 508 turns the attached lead screw 510, thereby causing the travel nut 512 and the fixed spring stop pivot 504 to travel up or down between the minimum and maximum lift strength positions. The same lift strength adjustment mechanism 520 may be employed on either side of the device. Each lift strength adjustment mechanism 520 may be individually adjusted for lifting, which may advantageously be adjusted to approximate positions along their respective slots. Thus, this version can provide vernier (continuous) rather than incremental adjustment.

The lifting geometry of those embodiments may be the same or substantially the same except for the straight slots and the series of arcuate apertures. The incremental hole adjustment mechanism 430 and the linearly adjustable spring termination pivot 504 may each be used in the lift mechanism 350. The lifting angles can be functionally identical with respect to the spring axis and the weak and strong lifting positions at the ray defining the slot angle, which effectively adjusts the aspect ratio of the lifting triangle running within the parallelogram linkage.

Alternative lifting geometries may be used for the lifting mechanism. The above-defined optimal lifting angle 394 may also be effectively implemented with respect to the spring axis 148 and the slot angle 396 to apply forces between various other links and elements inside and outside of the lifting parallelogram 124, 382. The lifting mechanisms 104, 350 and 502 exert a lifting force between the back mass 170, 422 (or an internal extension of the back mass) and the opposing lower parallelogram link.

However, the lift mechanism 602 shown in fig. 40, 41 may have alternative lift geometries that operate according to the same principles as described above. The spring applies a force between the base and the raised lower link. Fig. 40 is an isometric view of the riser mechanism 602 with no seat cushion attached, except showing the support wedge (middle seat cushion) 120 on the fixed frame base 610. Fig. 41 is a side view of the lifting mechanism 602 showing the seat cushions 116 and 118 attached. Fig. 40, 41 show a parallelogram 604 with an adjustment mechanism 606. The adjustment mechanism 606 is located at the end of the link 608 of the parallelogram 604 that remains connected to the fixed frame base 610 when the lift mechanism is raised. The angle of the extension 616 relative to or at the horizontal plane is maintained as the lift mechanism 602 is raised or lowered.

The adjustment pivot pin 612 is inserted into the lowest hole 614 on the opposing lift mechanism 602 so that the lever arm of this illustrative version is as short as possible (and thus, the lowest aspect ratio lift triangle). Other details of the lifting geometry are the same as in the illustrative embodiment described above.

Most or all of the disclosed lift mechanisms are more easily adjusted when one or more gas springs are fully deployed. The unique geometry provides adequate performance when the spring end is swung along an optimal and continuous aperture arc for incremental up-down adjustment or along a continuous adjustment mechanism.

The effect of the structure as described may be achieved in embodiments following the same design as the illustrative embodiments, but rotated, for example, such that the spring 142 or 362 protrudes toward the rear of the lift chair 100 or lift mechanism 104, 350 or 602. See, for example, fig. 40 and 41.

The disclosed lifting mechanisms 104, 350, 602 and their reverse configurations (such as those mentioned in the preceding paragraph) may be used as lifting apparatus for devices other than the illustrative chairs shown (e.g., wheelchairs or lift-type lift chairs, such as U.S. patent application 62/649,746 entitled "lift walker chair, lifting mechanism and seat" filed 3/29/2018, the contents of which are incorporated herein). It may also be used on chairs incorporated into other systems, such as vehicles or machines.

The figures show a parallelogram 124, 382, 604 with four links, but a similar lifting parallelogram can be constructed with fewer links or links of different shapes.

Fig. 43-56 show an illustrative elevating walker chair 700 into which any of the elevating mechanisms disclosed herein may be incorporated. The elevating walker chair 700 has a sitting mode with the seat or saddle 718 in a lowered position and a standing or walking mode with the seat 718 raised to allow the occupant to walk while supported by the elevating walker chair.

Fig. 43-56 show a lift mechanism similar to the lift mechanism 350 with springs on opposite right/left sides of the elevating walker chair 700. Other lift mechanisms, such as the dual spring lift mechanism 602 or the single spring lift mechanism 104, may also be incorporated into the lift chair.

As best seen in fig. 49C and 50C, lift mechanism 736 includes a parallelogram 738, which parallelogram 738 includes a link 759 that is parallel to link 756. End block 734 and frame 702 components are used for the other "links" of parallelogram 738. Parallelogram linkages 756, 759 pivot at pivots 745, 746 on end block 734. The parallelogram linkages 756, 759 are further pivoted at pivots 747, 749 on the frame 702. Although the term "parallelogram" is used for the structure 738, it should be noted that the links 756, 759 need not be straight and perfectly parallel, however, the straight lines connecting the pivots 745, 746, 747, 749 form a parallelogram.

Fig. 43 is an isometric view of the lift chair 700 in a lower seating mode. The lift chair 700 has a frame 702 to which various components are directly or indirectly connected or integrated. In the illustrative embodiment of fig. 43, the frame 702 includes a lower frame member 704 to which wheels 706 are attached. The frame 702 includes a back assembly 708 connected to the lower frame assembly 704 and extending upwardly from the lower frame assembly 704. The armrest 710 is coupled to the backrest assembly 708. Optional pedal 788 is connected to frame 702 at pedal pivot 790. The foot plate 788 may have two or more standard positions, for example, folded and pivoted 90 degrees as shown in fig. 43-46 to accommodate the feet of a user when seated. A pedal rotation mechanism may be employed to limit rotation of pedal 788 at pivot 790, such as rotation stops at the two positions. Other pedal rotation mechanisms may be included that provide additional position options.

The wheels 706 may be incorporated into the lift chair 700 via dual mode casters, such as described in international patent application PCT/US2017/060163, filed 11, 7, 2017, and incorporated herein by reference.

The frame 702 has a maximum height adjustment mechanism 712. In the illustrative embodiment shown in fig. 43, the maximum height adjustment mechanism 712 includes a height adjustment lever 714 having a series of height adjustment holes 716 for selecting the height of the seat 718. A maximum height adjustment pin 720 may be inserted into a hole in the series of height adjustment holes 716 to lock at a desired height. The maximum height adjustment mechanism 712 and process will be described in more detail below. The maximum height adjustment mechanism 712 may provide support and height adjustment functions.

As seen in fig. 43 and 48, the height adjustment rod 714 is slidably disposed within a height adjustment sleeve 754. The height adjustment sleeve 754 is connected to a parallelogram 738 at link 756. Thus, as the angle of the parallelogram 738 is changed to raise or lower the lift chair 700, the height adjustment sleeve 754 moves the height adjustment rod 714 up and down. The height adjustment pin 720 limits the movement of the height adjustment sleeve 754 along the height adjustment rod 714 when the lift chair 700 is raised. As can be seen in fig. 48, if the height adjustment pin 720 is in the highest possible hole of the height adjustment holes 716, or if the height adjustment pin 720 is not inserted into a hole, the height adjustment sleeve 754 can be raised to the highest possible position on the height adjustment bar 714 when the lift chair 700 is at its highest possible height. The lift chair 700 is limited to the lower maximum height by inserting the height-adjusting pin 720 into the lower hole.

The sleeve 754 may have an internal wheelTo facilitate sliding movement along the height adjustment bar 714. Other means to improve sliding may be used alone or in combination with the wheels, such as

Ball bearings or other conventional mechanisms.

In addition to setting the maximum height by inserting the height-adjusting pin 720, the height of the seat 718 may be set at a specific intermediate height within a range of the minimum to maximum heights. An intermediate height adjustment mechanism 760 may be employed to position the height adjustment sleeve 754 at an intermediate position along the height adjustment rod 714. For example, the height adjustment sleeve 754 may also be associated with a component that secures it along the height adjustment rod 714, such as a spring-loaded pin or a non-spring-loaded pin that may be withdrawn from one of the height adjustment holes 716 and reinserted into another hole. Other forms of intermediate height adjustment mechanism 760 may be employed. Generally, the intermediate height adjustment mechanism 760 provides a means for temporarily fixing the level of the height adjustment sleeve 754 along the height adjustment rod 714.

Fig. 58A-B and 59A-B show an illustrative intermediate height adjustment mechanism 760. FIG. 58A shows the elevating walker chair 700 with the intermediate height adjustment mechanism 760 and the seat 718 in their lowermost position. Fig. 58B is an enlarged view of detail K of fig. 58A before the height of the seat 718 is selected. Fig. 59A shows an elevating walker chair 700 with an intermediate height adjustment mechanism 760 in which the seat 718 is fixed at a selected height. Fig. 58B is an enlarged view of detail K of fig. 58A, showing the intermediate height adjustment mechanism 760 engaged to fix the height of the seat 718. The intermediate height adjustment mechanism 760 includes an intermediate height adjustment pin 770 that may be inserted into a sleeve hole 772 in the sleeve 754. The sleeve 754 can be moved along the height adjustment rod 714 until the sleeve aperture 772 aligns with a selected one of the height adjustment apertures 716 in the height adjustment rod 714. An intermediate height adjustment pin may then be inserted through the sleeve aperture 772 and into a selected one of the height adjustment apertures 716 to fix the height of the seat 718. Other conventional means for adjustably securing the parallelogram link 756 along the height adjustment rod 714 may be used as the intermediate height adjustment mechanism.

Fig. 64A-B illustrate a height adjustment sleeve 754 that is connected to end block 734 rather than to a parallelogram 738 (such as shown in fig. 56) at link 756. The height adjustment sleeve 754 may be attached to various components of the parallelogram 738. By aligning the height adjustment sleeve 754 with the riser mechanism, the height of the seat 718 may be controlled.

Although we refer to a height adjustment "sleeve," other configurations that allow the adjustment member to slide or otherwise move up and down the height adjustment rod 714 may be used. The "sleeve" need not completely surround the height adjustment rod 714. The intermediate height adjustment mechanism 760 may be configured to simultaneously adjust the right/left intermediate height mechanisms. For example, a simultaneous intermediate height adjustment component may include cables to coordinate right/left adjustments.

Note that "height adjustment" is different from the adjustment provided by the lift mechanism 736, which will be described below. The maximum height adjustment provides a maximum height that defines the degree of movement produced by the lifting mechanism from the sitting mode to the standing mode.

FIG. 44 is a rear isometric view of the elevating walker chair 700. The folding mechanism 722 is incorporated into the illustrative embodiment of fig. 43, which is described in more detail below in connection with fig. 60-63.

FIG. 45 shows an isometric view of the elevating walker chair 700 in a raised or standing position. In the raised position, the user may be supported by seat/saddle 718 while walking using leg power and motion. An upright support 732 is provided that can accommodate the user in a comfortable and supportive manner when the lift chair is in the raised position. The support arm 732 is connected to an end block 734 of the lift mechanism 736 so as to be raised when the seat 718 is raised by the lift mechanism 736. The support arms 732 may be configured to extend when the lift chair 700 is raised, or may be incorporated into the lift chair 700 for manual deployment.

Fig. 57A-C show an illustrative arm support adjustment mechanism 768. Fig. 57A is a side view of an illustrative elevating walker chair 700 with a support arm adjustment mechanism 768. Fig. 57B is a detail of a portion O of fig. 57A. Fig. 57C is a cross-section of the arm support adjustment mechanism 768 taken along line P-P of fig. 57B. An upright arm support 732 is pivotally connected to end block 734 at an arm support pivot 762. Arm support adjustment mechanism 768 locks upright arm support 732 in a selected position. Arm support adjustment mechanism 768 includes an upright arm support adjustment pin 764, which may be positioned in or withdrawn from upright arm support adjustment pin notch 766. The arm support adjustment pin 764 may be spring loaded. The upright arm support 732 may rotate about the arm support pivot 762 when the arm support pin 764 is withdrawn from the arm support pin notch 766. When arm support pin 764 is inserted into arm support pin notch 766, upright arm support 732 is locked into a rotated position. As arm support pin 764 is withdrawn from arm support pin notch 766, upright arm support 732 may rotate about arm support pivot 762. An upright arm support adjustment mechanism 768 may be included on the left and right upright arm supports 732. Other conventional means for adjusting, locking and unlocking the angular position of the upright arm support 732 may be used as the upright arm support adjustment mechanism.

The lift mechanism 736 has a parallelogram 738 with a spring 740 as shown in FIG. 49C. The spring 740 forms a lifting triangle with portions of the parallelogram 738. The lifting triangle is comprised of a first side defined by the length of the spring 740 from the spring pivot 742 to the spring termination point 744, a second side defined by a line from the spring pivot 742 to the main pivot 746, and a third side from the main pivot 746 to the spring termination point 744. The position of the spring stop pivot 744 may be adjusted along a series of spring stop holes 748 to vary the effective lifting force. Adjusting the position of the spring termination pivot 744 shortens or lengthens the third side of the lifting triangle, i.e., the distance 750 from the main pivot 746 to the spring termination point 744, or sometimes referred to as a "lever arm". The effective lifting force increases as the length of lever arm 750 increases. The lifting force can be adjusted according to the weight of the occupant.

FIG. 46 shows an isometric rear view of the elevating walker chair 700 in a raised position.

FIG. 65 shows an isometric view of a portion of an elevating walker chair with a seat 718 connected to a single central lifting mechanism 736. The seat 718 and the lift mechanism 736 may be connected to a frame similar to the frame 702. The seat 718 having the central riser 736 shown in fig. 65 may also be used in other applications. Although seat 718 is shown as a saddle, which is advantageous for an elevating walker chair, seat 718 may have other configurations compatible with the type of seating device into which it is incorporated.

Fig. 47A, 47B through 52A-52B show illustrative lift adjustment processes. If there are opposing lift and adjustment mechanisms, the steps are performed on one side of the lift chair 700 and then on the opposite side of the lift chair 700.

Fig. 47A, 47B show a first step of the elevating force adjusting process. FIG. 47A is a front isometric view of the elevating walker chair 700 in a raised position. Fig. 47B is an enlarged view of detail a showing portions of the elevation adjustment mechanism 758, which is a part of the elevation mechanism 736. The lift adjustment mechanism 758 includes a lift adjustment pin 752 and a series of spring stop holes 748 disposed in the end block 734. The lift adjustment pin 752 is first removed from one of the spring termination holes 748. This allows the lift chair 700 to be raised to its maximum height position, as shown in fig. 48, reducing or eliminating the force exerted by the spring 740 because it is in its maximum deployed mode. It also positions the spring stop holes 748 in an arc with the spring pivot 742 in the center of the arc so that the spring 740 can pivot into either of the spring stop holes 748. This is illustrated by comparing fig. 43 and 45. In FIG. 43, the elevating walker chair 700 is in its lowest seated position and the springs 740 are compressed. The spring pivot 742 is not centered on an arc along which the spring termination hole 748 is disposed. Thus, in the seated mode, the springs 740 cannot rotate in alignment with each spring stop hole 748. FIG. 45 shows the elevating walker chair 700 in its highest standing position. The spring 740 is fully deployed and the spring pivot 742 is at the center of the arc along which the spring termination hole 748 is disposed. In this configuration, the spring 740 can rotate about the spring pivot 742 and will align with either of the spring stop holes 748 so that lift adjustment can be made.

The "maximum height position" is determined by the setting of the maximum height adjustment mechanism 712. On the other hand, the lifting force adjustment mechanism 758 sets the force by which the lifting walker chair 718 will rise and fall.

Fig. 49A-C show the next step in the lift force adjustment process. Fig. 49B illustrates a side cross-sectional view of the lift chair 700 taken along line B-B of fig. 49A through the spring 740. Fig. 49C is an enlarged view of detail C of fig. 49B. Fig. 49C shows spring termination pivot 744 in one of spring termination holes 748, the spring termination pivot 744 creating the shortest lever arm 750 for this embodiment.

FIGS. 50A, 50B, 50C are similar to FIGS. 49A-C, but are taken along the cross-section D-D shown in FIG. 50A. Cross section D-D provides a side view of the spring 740 and the lift adjustment pin 752.

Fig. 51A, 51B show the next lifting force adjustment step. Fig. 51B is an enlarged view of detail F of fig. 51A. The lift adjustment pin 752 is removed from one of a series of spring stop holes 748. This allows the spring 740 to freely rotate about the spring pivot 742 into any one of the other spring stop holes 748 to adjust the lifting force.

Fig. 52A, 52B show the next step of the elevating force adjusting process. Fig. 52B is an enlarged view of detail G of fig. 52A. The spring 740 has rotated about the spring pivot 742, so the ends of the spring 740 can be positioned to form the spring stop pivot 744 at different ones of a series of spring stop holes 748. A lift adjustment pin 752 is inserted into the hole to create a spring stop pivot 744. This adjustment enlarges lever arm 750, for example, compared to the length of lever arm 750 shown in FIG. 49C. In other words, the distance between the spring stop pivot 744 and the main pivot 756 increases, and thus the effective lifting force also increases.

Fig. 53A, 53B to 56 show the height adjustment process. Fig. 53B is an enlarged view of detail H of fig. 53A. Fig. 53A, 53B illustrate an initial configuration of the lift chair 700 with the lift chair 700 at its lowest height and the height adjustment pin 720 in the highest of the height adjustment holes 716 on the height adjustment bar 714.

Fig. 53A, 53B show the lift chair 700 in its lowermost position, while the height adjustment pin 720 is in its uppermost position. Fig. 54A, 54B show a first height adjustment step for changing the maximum height achievable by the lift chair 700 of this illustrative embodiment. Fig. 54B is an enlarged view of detail H of fig. 54A. Height-adjustment pin 720 is shown removed from one of the height-adjustment holes 716 into which it has been inserted.

Fig. 55A, 55B show the next height adjustment step of this illustrative embodiment. Fig. 55B is an enlarged view of detail J of fig. 55A. Height adjustment pin 720 is reinserted into a lower one of height adjustment holes 716. Since the movement of the height-adjusting sleeve 754 along the parallelogram link 756 is restricted by the height-adjusting pin 720, the maximum height of the elevating chair 700 is set at a low level.

FIG. 56 is a side view of the elevating walker chair 700 showing the height-adjustment pins 720 preventing the height-adjustment sleeves 754 from fully rising along the height-adjustment rods 714. This resists the lifting force of the springs 740 to limit the elevating walker chair 700 to its full height.

It is noted that with the lifting walker chair 700 having the lifting adjustment mechanism 758 and height adjustment mechanisms 712, 760 on both sides, the adjustments described herein may need to be made on both sides. In further embodiments, the adjustment mechanism may be present on only one side, so long as the elevating walker chair and adjustment mechanism components are sufficiently durable for a single-sided mechanism.

Turning to fig. 60-63, a folding mechanism 722 is shown that may optionally be included in the elevating walker chair 700. FIG. 60 is an isometric rear view of a folding elevating walker chair 700. FIG. 61 shows a front view of a partially folded elevating walker chair 700. FIG. 62 is a rear isometric view of the elevating walker chair 700 in a folded position. FIG. 63 is a front view of the elevating walker chair 700 in a folded mode.

The folding mechanism 722 includes a pair of lower crossbars 724 and a pair of upper crossbars 726 that are each connected to a center column section 728 and are foldable relative to the center column section 728. A locking mechanism 730 is provided to lock the lift chair 700 structure in an open position for use and unlocked for folding. The locking mechanism 730 may also lock the elevating walker chair in the folded position. The seat 718 may also be folded upward, either manually or automatically, as the lower crossbar 724 and upper crossbar 726 are folded toward the center post 728.

In the illustrative folding mechanism 722, the elevating walker chair 700 is in a sitting mode, such as the mode shown in FIG. 44, when folded. In further embodiments, the elevating walker chair 700 may be in a standing mode when folded. The locking may be initiated by pulling the locking mechanism 730 upward. The seat 718 may be folded by lifting one side of the seat upward or lifting a handle 784 (if present) on the seat 718. A tension rod link 786 is connected at one end to the seat 718 and to the frame 702 or a component connected to the frame 702 to maintain the connection of the seat 718 to the device while allowing it to fold to accommodate the left and right sides of the elevating walker chair 700 opposite each other for folding. The tension rod 786 is slidably connected to the seat 718 and/or the frame 702.

A slot 774 in the upper cross bar 726 slidably receives an extending pin 776 of the rod 778. A guide bar 778 is pivotally secured to the center column section 728 at a center column pivot 780 as shown in fig. 61. The central pivot 780 is slidably secured to the central post member 728 in the slot 782. As the extension pin 776 moves along the slot 782, the upper cross-bar 726, the lower cross-bar 724, and the guide bar 778 pivot and move toward the center post member 728 and move the rear assemblies 708 of the frame 702 toward each other. The seat 718 folds up or down approximately 90 degrees to accommodate the lower frame member 704, the armrests 710, and other components of the elevating walker chair to fold in a folding manner toward the central post member 728.

Other conventional folding mechanisms 722 and locking mechanisms 730 may be incorporated into the elevating walker chair 700.

Figures 64A-B illustrate another embodiment of an elevating walker chair. FIG. 64A shows an isometric view of the elevating walker chair in the sitting mode. FIG. 64B shows the elevating walker chair in a standing mode. The elevating walker chair has a single central lifting mechanism with a parallelogram and spring configuration similar to that of lifting mechanism 350. The elevating walker chair may include various mechanisms described with respect to the elevating walker chair 700, such as, for example, a mid-height adjustment mechanism, a maximum height adjustment mechanism, a locking mechanism, a lifting force adjustment mechanism other than an arcuate aperture configuration, and a boom support adjustment mechanism.

Various embodiments of the invention have been described, each having a different combination of elements. The invention is not limited to the specific embodiments or combinations disclosed. The invention may include various combinations of the elements disclosed, omission of some elements, or substitution of elements with equivalents of such structures. For example, various aspects of the lift mechanisms 104, 350, and 602 may be interchanged.

Although illustrative embodiments have been described, additional advantages and modifications will occur to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details shown and described herein. Therefore, it is intended that the invention not be limited to the particular illustrative embodiments, but be interpreted within the full spirit and scope of the appended claims and their equivalents.

Claims (25)

1. An adjustable riser mechanism for or for use with a seating unit, comprising:

a base;

a parallelogram structure having four pivotally connected links, the parallelogram being connected to the base at two of the four pivots;

a spring extending from a first link of the parallelogram to an adjustable termination point on a second link of the parallelogram to form a lifting triangle, wherein the spring termination point is displaced from a first pivot of the parallelogram;

an extension fixed relative to one of the four parallelogram linkages, the extension configured to maintain its angle relative to horizontal as the angle of the parallelogram changes as the lift mechanism is raised or lowered between a sitting mode and a standing mode;

wherein the extension forms a rear seat portion having a rear edge and a front edge;

a front seat portion having a rear edge and a front edge;

the front seat portion is pivotally connected to the rear seat portion at the front seat rear edge, and the rear seat front edge is configured to allow the front seat portion to descend in the standing mode and return to the sitting mode;

a lifting force adjustment mechanism configured to adjust a position of the spring termination point relative to the first pivot; and

a mid-seat portion having a shape complementary to a space formed between the front seat portion and the rear seat portion in the sitting mode, the mid-seat portion being configured to occupy the space in the sitting mode and vacate the space when transitioning to the standing mode to allow the front seat portion to fold downward.

2. The lift mechanism of claim 1, wherein the lift force adjustment mechanism includes a pin connected to the spring and a series of holes in which the pin is selectively positionable.

3. The lift mechanism of claim 2 wherein the series of holes form an arc and the radius of the arc is the length from the spring pivot on one of the four parallelogram links to the hole when the spring is fully deployed.

4. The lift mechanism of claim 1, wherein the lift force adjustment mechanism includes a pin connected to the spring and a slot in which the pin is selectively positionable.

5. The lift mechanism of claim 1, wherein the mid-seat portion is located on the base and remains in its position on the base in the sitting mode and the standing mode.

6. The lift mechanism of claim 1, wherein the mid-seat portion is connected to and moves with one of the four parallelogram linkages to move into position when the sitting mode is achieved.

7. The lift mechanism of claim 1, wherein the lift mechanism is configured such that the spring is compressed by the weight of the occupant and expands when the user transfers weight to the user's legs.

8. The lift mechanism of claim 1, wherein the lift mechanism is configured such that the maximum height of the rear seat portion is consistent under lift force adjustment.

9. The lift mechanism of claim 1, wherein the extension moves forward as the parallelogram rises and the front seat portion falls, thereby moving a center of balance of the user toward above the user's feet.

10. The lift mechanism of claim 1, wherein the lift force of the lift mechanism is between 50% and 95% of the weight of the user.

11. The lift mechanism of claim 1, wherein the vertical displacement from the sitting mode to the standing mode is in the range of 8 inches to 16 inches.

12. The lift mechanism of claim 1, further comprising a restraint plate having a first edge connected to the front seat portion and a second edge connected to the middle seat portion.

13. The lift mechanism of claim 1, wherein the rear seat portion and the front seat portion have an integral seat cushion.

14. A chair comprising the lift mechanism of claim 1.

15. An adjustable lift mechanism comprising:

a base;

a parallelogram structure having four pivotally connected links, the parallelogram being connected to the base at two of the four pivots;

an extension having a fixed end disposed in fixed relation to a first link of the four parallelogram links and at an angle to one of the four parallelogram links, the extension configured to maintain its angle relative to horizontal as the angle of the parallelogram changes as the elevator mechanism is raised or lowered between a sitting mode and a standing mode;

a spring connected to an end of the extension opposite the fixed end of the extension and extending to an adjustable termination point on a second link of the parallelogram to form a lifting triangle, wherein the spring termination point is displaced from a first pivot of the parallelogram;

a lift force adjustment mechanism configured to adjust a position of the spring termination point relative to the first pivot.

16. The elevating mechanism according to claim 15, wherein the elevating force adjusting mechanism comprises:

a bore arc to which a first spring end is selectively alignable and securable; and

the center of the arc is located at the second end of the spring when the spring is fully deployed.

17. A seat comprising the lift mechanism of claim 16.

18. An elevating lift chair comprising:

the adjustable lifting mechanism is provided with:

a base;

a parallelogram structure having four pivotally connected links, the parallelogram being connected to the base at two of the four pivots;

a spring extending from a first link of the parallelogram to an adjustable termination point on a second link of the parallelogram to form a lifting triangle, wherein the spring termination point is displaced from a first pivot of the parallelogram;

an extension fixed relative to one of the four parallelogram linkages, the extension configured to maintain its angle relative to horizontal as the angle of the parallelogram changes as the lift mechanism is raised or lowered between a sitting mode and a standing mode;

a lifting force adjustment mechanism configured to adjust a position of the spring termination point relative to the first pivot; and

a mid-seat portion having a shape complementary to a space formed between the front seat portion and the rear seat portion in the sitting mode, the mid-seat portion being configured to occupy the space in the sitting mode and vacate the space when transitioning to the standing mode to allow the front seat portion to fold downward.

19. The elevating lift chair of claim 18, further comprising a maximum height adjustment mechanism.

20. The elevating lift chair of claim 19, wherein the maximum height adjustment mechanism comprises:

a height adjustment bar having a plurality of apertures over at least a portion of its length; and

a pin configured to be inserted into one of the plurality of holes.

21. The elevating lift chair of claim 18, further comprising a folding mechanism.

22. The elevating lift chair of claim 18, further comprising an intermediate height adjustment mechanism.

23. The elevating lift chair of claim 22, wherein the intermediate height adjustment comprises:

a height adjustment bar having a plurality of apertures over at least a portion of its length; and

a sleeve slidably mounted on the height adjustment bar and aligned with the parallelogram structure;

a pin configured to be inserted through the hole in the sleeve and into one of the plurality of holes.

24. The lift chair of claim 18, further comprising a support arm adjustment mechanism.

25. An adjustable riser mechanism for or for use with a seating unit, comprising:

a base;

a parallelogram structure having four pivotally connected links, the parallelogram being connected to the base at two of the four pivots;

an extension having a fixed end in fixed relation to and disposed at an angle to a first link of the four parallelogram linkages, the extension configured to maintain its angle relative to horizontal as the angle of the parallelogram changes as the elevator mechanism is raised or lowered between a sitting mode and a standing mode;

wherein the extension forms a rear seat portion having a rear edge and a front edge;

a spring connected to an end of the extension opposite the fixed end of the extension and extending to an adjustable termination point on a second link of the parallelogram to form a lifting triangle, wherein the spring termination point is displaced from a first pivot of the parallelogram;

a front seat portion having a rear edge and a front edge;

the front seat portion is pivotally connected to the rear seat portion at the front seat rear edge, and the rear seat front edge is configured to allow the front seat portion to descend in the standing mode and return to the sitting mode;

a lifting force adjustment mechanism configured to adjust a position of the spring termination point relative to the first pivot.

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