HK1106111B - Spring toggle furniture mechanism - Google Patents

Description

Spring toggle furniture mechanism

Technical Field

The present invention relates to furniture and more particularly to an improved leg support extension mechanism for articles of furniture such as chairs, sofas and loveseats.

Background

Traditionally, back-to-back furniture items (i.e., chairs, sofas, loveseats, and the like) require a mechanism to bias the leg rest assemblies in the extended and stowed (stowed) positions. The mechanisms provided by the prior art include a large number of moving parts that tend to increase the manufacturing time and costs associated with furniture.

Furthermore, because these components move to extend and retract the leg support assembly, the components need to be aligned with each other to ensure proper operation. In addition, the large number of components adds weight to the furniture, thereby making the furniture difficult to move and transport. In addition, the occupant of the seat must overcome this biasing force in order to begin extending the leg rest assembly. Since one of the objectives of providing a leg rest assembly is to increase user comfort, overcoming a large biasing force tends to detract from the user's enjoyment of the furniture.

Once the occupant does overcome the biasing force of the mechanism, however, the large number of moving parts tend to generate noise as the user extends (or retracts) the assembly. Also, as the assembly approaches its fully extended (or retracted) position, the prior art mechanism suddenly accelerates (or jerks) to the fully extended position. These drawbacks of the prior art mechanisms again detract from occupant comfort and enjoyment of the furniture.

Finally, the large number of components also subjects the furniture to an increased risk of mechanical failure, particularly those components that are subjected to cyclic stresses (i.e., fatigue). Thus, there is a need to simplify and improve the prior art leg support mechanisms.

Disclosure of Invention

The present invention provides a biasing assembly for an article of furniture having a seat assembly supported by a chair frame and a drive mechanism for enabling a leg rest assembly to move between a stowed position and an extended position. The mechanism includes a support shaft, a drive rod spaced apart from the support shaft, and a toggle link coupled to the support shaft. The biasing assembly includes a spring having first and second ends. The spring is adapted to be attached to the toggle link at a first end. The spring also includes an engagement member at the second end adapted to engage the support shaft while remaining free to slide along the axis of the support shaft. Thus, the spring aligns itself to the bracket axis.

In another embodiment, the present invention provides a drive mechanism for an article of furniture having a seat assembly supported by a chair frame and a leg rest assembly. The leg rest assembly is movable between a stowed position and an extended position. The transmission mechanism enables movement of the leg rest assembly and includes a support shaft, a drive rod spaced apart from the support shaft, a toggle link coupled to the support shaft, and a biasing assembly. The biasing assembly includes a spring having first and second ends. The spring is attached at a first end to the toggle link and includes an engagement member at a second end that engages the support shaft while remaining free to slide along the axis of the support shaft. Thus, the spring aligns itself to the bracket axis. In yet another embodiment, the invention provides an article of furniture including such a mechanism.

In another form, the invention provides a method of assembling an article of furniture. An article of assembled furniture has a seat assembly supported by a chair frame and a drive mechanism for enabling movement of a leg rest assembly between a stowed position and an extended position. In addition, the assembled mechanism includes a support shaft, a drive rod spaced apart from the support shaft, and a toggle link coupled to the support shaft. Additionally, the method includes attaching a spring in a spring assembly to the toggle link at a first end of the spring and engaging a member in the spring assembly at a second end of the spring to the carriage shaft while remaining free to slide along an axis of the carriage shaft. Thus, the spring aligns itself on the bracket axis.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

Drawings

The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. 1 is an exploded perspective view of the chair with trim material, springs and other components removed from the preassembled components to show an improved drive mechanism;

FIG. 2 is a top plan view of the leg support mechanism of the chair of FIG. 1 in accordance with a preferred embodiment of the present invention;

FIG. 3 is a front view of the leg support mechanism of the chair of FIG. 1 in accordance with a preferred embodiment of the present invention;

FIG. 4 is an exploded perspective view of a spring toggle assembly of the mechanism of FIG. 1;

FIG. 5 is an elevation view of the spring toggle assembly of the mechanism of FIG. 4 in a folded-back position; and

FIG. 6 is a front view of the spring toggle subassembly of the mechanism of FIG. 4 in an extended position.

Detailed Description

In accordance with the teachings of the present invention, an improved transmission 10 for use in single and multi-person articles of furniture 12 (i.e., chairs, sofas, or loveseats) is disclosed. In addition, the present invention is directed to a method of assembling an improved drive mechanism for an article of furniture having a leg rest assembly (e.g., a recliner or similar furniture). As will be described, the transmission 10 contains fewer components and is therefore simpler, lighter and more reliable than prior art transmissions. Consequently, the present invention facilitates efficient manufacturing and application of assembly processes.

The transmission mechanism 10 of the present invention includes a single spring mechanism 14 to bias the leg rest assembly 16 into the stowed and extended positions. Furthermore, the single spring mechanism 14 simplifies the assembly process and improves the reliability of the transmission mechanism 10. In the disclosed embodiment, the article of furniture 12 includes a preassembled drive mechanism 10 and various trim frame components (not shown). In addition, because the drive mechanism 10 of the present invention is relatively compact in size, loose upholstery pads may also be used, an important feature in selling various fashion chairs, sofas, or love seat furniture.

Referring now to the drawings in particular, functional and structural aspects of the transmission mechanism 10 will be described, the transmission mechanism 10 being shown as various pre-decorated box-shaped frame members operatively suspended from a chair 12 (partially shown). For the sake of clarity, fig. 1 shows various pre-assembled frame parts with their decorative material, fillers, springs, etc. parts removed, in order to better show the interdependence of the frame parts that can be quickly and rigidly assembled in a relatively easy and efficient way. Thus, all of the frame components can be individually manufactured or component assembled to include the necessary brackets, springs, padding and upholstery on an "off-line" batch-type base. Thus, various pre-assembled and decorated frame components are assembled to fully integrate the transmission 10 therein.

As seen in fig. 1-3, the drive mechanism 10 of the chair 12 is integrated into and operatively suspended from left and right side frame assemblies 18. In addition to the side frame assemblies 18, the chair 12 also includes front and rear crossbar assemblies 20, 22, respectively, which, when interconnected, define a rigid "box-shaped" frame. The seat assembly 24 is supported within the side frame assembly 18 and the drive mechanism 10. As described in greater detail below, the transmission 10 is preassembled to include the drive rod 26 and the front carrier shaft 28, both spatially oriented for precise positioning and "suspension" from the left and right side frame assemblies 18.

The drive mechanism 10 is shown supporting a leg rest assembly 16 thereon. More specifically, leg rest assembly 16 includes left and right pantograph linkages 30 and a single spring assisted toggle mechanism 14, which toggle mechanism 14 is operatively associated with drive rod 26 and front carrier shaft 28 for selectively actuating leg rest assembly 16. Rigid cross-braces 32 are secured between the drive rods 26 and the carrier shaft 28 to provide structural rigidity within the transmission 10. One end of cross-brace 32 is journaled on drive bar 26, while the opposite end is configured as a bracket 34 fixedly secured to the inner surface of front rail assembly 20 (e.g., by suitable threaded fasteners). In addition, the bracket shaft 28 is fixed to a middle portion of the cross-brace 32 so as to restrain the bracket shaft 28 from rotating with the rotation of the drive lever 26. In a preferred construction, the drive bar 26 is an elongated square shaft having a handle portion (not shown) disposed adjacent the upholstered exterior of one of the side frame assemblies 18 that is easily accessible by a person seated in the chair 10 to facilitate actuation thereof.

As best shown in FIG. 1, most of the structural frame components, such as the side frame assemblies 18, the front crossbar assembly 20, the rear crossbar assembly 22, the seat assembly 24, and the leg rest frame plates 36, are each constructed in a manner that enables them to support springs, padding, upholstery, etc., in order to complete the ornamental and stylish chair 12. Preferably, the frame members are made of one or more wooden boards and/or rails which are fixedly fastened together in a known manner by means of suitable fasteners, such as dowel pins, staples, nails or screws, and reinforced at the critical joints by metal reinforcing plates or brackets and/or wooden corner blocks. As previously mentioned, each frame component is individually pre-assembled for subsequent assembly into the chair 12. However, it is to be understood that the particular structure shown for each frame member is merely exemplary in nature.

The leg rest assembly 16 is shown as including a frame panel 36 having an outer surface that is padded and upholstered. The frame plate 36 is supported and moved by the same left and right hand pantograph linkages 30. Pantograph linkage 30 is similar in function and structure to the pantograph linkage shown in fig. 3 of U.S. No.3,096,121, assigned to the common assignee of the present invention, except that pantograph linkage 30 is operatively suspended adjacent a second set of "fixed" suspension points defined by carriage axles 28.

As best shown in fig. 2 and 3, a single spring assisted toggle assembly 14 is provided in cooperation with a leg support pantograph linkage 30. Toggle assembly 14 provides a means for securely supporting frame plate 36 of leg rest assembly 16 in a fully retracted position relative to front rail assembly 20. Toggle assembly 14 is also operable to supply a spring force for biasing actuating leg rest assembly 16 toward one of its extended and retracted positions. More specifically, toggle assembly 14 includes a toggle lever 38 having a square aperture 40, and toggle lever 38 is mounted to square drive rod 26 through square aperture 40 for rotation therewith. The toggle lever 38 is pivotally connected at pivot 42 to the rear leg 44 of a C-shaped toggle link 46, the toggle link 46 being bent around behind the drive rod 26 below the drive rod 26. Wherein the front leg 48 of the toggle link has an opening 50 and an attachment means 56 in the form of a hook at one end of the helical coil spring 52 is attached to the opening 50. The toggle lever 38 of toggle assembly 14 is forcibly positioned on drive bar 26 by fastener 58 to hold toggle assembly 14 in place on drive bar 26. The configuration of the aperture 40 in conjunction with the use of the fastener 58 has the advantage of integrally coupling the toggle lever 38 with the drive bar 26. Thus, spring 52 will not cause toggle lever 38 to jump as toggle assembly 14 rotates over center.

The opposite end of the spring 52 includes an engagement member 54 that slidably engages the support shaft 28. More specifically, the engagement member 54 is configured to couple the spring 52 to the carriage shaft 28 while remaining free to slide along the axis of the carriage shaft 28. When combined together, the spring 52, the engagement member 54, and the attachment device 56 at the other end of the spring 52 may be referred to as a biasing element, which may also be formed as a continuous member, such as by forming the biasing assembly from a suitable wire. However, the biasing element may be formed from multiple components. A tension adjustment device (not shown) may optionally be provided to adjust the tension in the spring 52. For example, the tension in the spring 52 is adjusted by relatively increasing or decreasing the length, and thus the preload, within the spring.

The operation of toggle assembly 14 will now be described in detail. The positioning of pivot 42 on drive rod 26 and the line of action of spring 52 are such that when in the retracted position of leg rest assembly 16, the spring action acts to directionally support or "hold" leg rest assembly 16. After a slight rotation of drive rod 26, as leg support 16 begins to extend, pivot 42 moves downward and above the center of an imaginary line between approximately the center of engagement member 54 (e.g., a hook) and the axis of drive rod 26. Once pivot 42 is over center, the tension loaded on spring 52 helps drivingly rotate drive rod 26 to extend leg rest assembly 16 as forward leg 48 of link 46 is pulled toward engagement member 54. In addition, the spring 52 assists the seat occupant in pivoting the handle (not shown) through a desired actuation angle. In a similar manner, toggle assembly 14 is adapted to utilize the spring-biasing force of spring 52 to assist in returning leg rest assembly 16 to its stowed position upon reverse rotation of drive rod 26.

Referring now to fig. 5 and 6, further differences between the stowed and folded back positions of the leg rest assembly 16 are shown. First, the C-shaped toggle link 46 has rotated about the drive shaft 26 from a retracted position (see FIG. 5) to an extended position (see FIG. 6). As can be seen, in the retracted position, approximately half of the C-shaped toggle link 46 is shown on the side of the drive shaft 26 opposite the spring 52, whereas in the extended position, substantially all of the C-shaped toggle link 46 is on the same side of the drive shaft 26 as the spring 52. Thus, the spring 52 is stretched less in the extended position than in the retracted position. Thus, the biasing force created by the spring in the retracted position exceeds the biasing force created in the extended position. However, in another embodiment, the extension bias force exceeds the retraction bias force.

From a comparison of fig. 5 and 6, it can be seen that toggle assembly 14 and in particular toggle lever 28 is rotated approximately 145 ° from the retracted position to the extended position and spans an over center position after approximately 50 ° of rotation. In this manner, the motion of the toggle assembly is timed to provide a balanced force (i.e., flexion-back extension and its reverse) over the range of motion, which results in a smoothly operating leg rest assembly.

Referring now next to fig. 5 and 6, there is also shown a spring 52 having a member 54 slidably engaged on the support shaft 28. In particular, a portion 60 of the support shaft 28 is shown in fig. 3 and 4. The portion 60 is generally unobstructed so that the engagement member 54 is otherwise prevented from sliding along the portion 60. Generally, the portion 60 is positioned on the bracket shaft relative to the position of the fastener 58 on the drive bar 26.

Thus, the spring 52 acting in tension tends to pull the engagement member 54 towards the centre of the portion 60. Thus, the spring 52 will slide along the length of the carriage shaft 28 and align itself between the drive rod 26 and the carriage shaft 28 at the spring's minimum installed length. In other words, the spring 52 may be considered a self-aligning member of the mechanism 10. A lubricant, such as wax or oil, is provided locally on the portion 60 of the support shaft 28 to promote self-alignment. Due to the self-alignment of the spring 52, the spring 52 will experience lower and more predictable cyclic stress levels during operation. Thus, the spring 52 (and similarly stressed components) lasts longer than a non-self-aligning spring that experiences a similarly stressed environment. Of course, although the individual springs 52 are generally sized to provide the desired biasing force without the need for a second and subsequent springs.

In comparison, prior art devices typically use one or more wires, spacers, springs, retaining clips, and the like to maintain the plurality of spring toggles in alignment with other components of the recliner 12. Thus, movement of the prior art spring toggle moves and vibrates all of these various components. Thus, operation of the prior art lounge chair produces more noise than the chair 12 of the present invention. In contrast, the spring toggle assembly 14 provided by the present invention does not require an auxiliary element to align the individual spring toggles 14. Thus, the present invention provides quieter operation. Furthermore, the present invention significantly reduces the number of components of the chair 12 by eliminating the alignment aid and reducing the number of spring toggles to one (and only one spring toggle in the preferred embodiment). Thus, the chair 12 is simpler, lighter, less expensive, and more reliable than prior art recliners.

Turning now to a detailed discussion of the load points of the springs 52, those skilled in the art will appreciate that the upholstery and padding applied to the leg rest assembly 16 may generate a relatively slight force to act on the transmission mechanism 16. Some of these forces tend to move the leg rest assembly 16 toward the folded or extended position. Thus, it should be noted in this application that unless explicitly stated otherwise, the term "biasing force" refers to the force specifically developed by the spring 52.

With respect to the load point of the spring 52, it has been found that occupants of the chair 12 prefer the drive mechanism 10 that they feel operating smoothly (e.g., without sudden additions or jerks to the leg rest assembly 16). Thus, in a preferred embodiment, the spring is 5.8 inches long in the fully neutral state and the spring rate is 30 pounds per inch and the initial preload is 17 pounds. In addition, the spring 52 is positioned relative to the drive rod 26 and the support shaft 28 such that the spring is stretched approximately 7.75 inches in the extended position. Thus, the preferred extension bias force is about 83 pounds. In the retracted position, the spring may be stretched approximately 7.0 inches in the same manner to provide a biasing force of approximately 54 pounds. Currently, the spring 52 is designed to extend a maximum of 8.5 inches.

Meanwhile, in the over-center position (relative to the drive rod axis), the spring 52 may be preloaded to 17 pounds. Note that in the current embodiment, the over center position corresponds to approximately 67% of the extension of the leg rest assembly 16. Thus, when the spring 52 is over-center, the preload tends to act through the axis of the drive shaft 26, thereby tending to not move the leg rest assembly 16 in either direction. As the drive shaft 26 rotates from a centered upper point, it causes a spring force to act on one end of the toggle lever 38 with a short moment arm from the axis of the drive shaft 26 (i.e., a distance perpendicular to the spring force). Thus, the torque applied by the spring 52 to the drive shaft 20 near the over-center position is relatively small due to the relatively short moment arm. As the drive shaft 20 continues to rotate, the moment arm increases from a centered position in proportion to the sine of the increasing angle of the drive shaft 26. Thus, as the drive shaft 26 rotates toward the extended or retracted position, the spring 52 smoothly develops an increasingly large biasing force.

While the preferred embodiment has been described as having particular spring parameters and force generation, those skilled in the art will appreciate that the specifications for a given toggle assembly may be dictated by the parameters of a given chair. For example, the spring rate may be increased to accommodate reclining chair type leg support mechanisms that tend to be heavier than non-reclining chair (chaise) type leg supports. Likewise, movement of the toggle assembly may be such that in the extended position (I)_e) And a folded-back position (I)_r) The moment arm provides different force balances, thereby requiring modification of the spring parameters.

In addition, the spring tends to draw the drive rod 26, carriage shaft 28, and components of the spring toggle assembly 14 firmly together due to the loading of the spring 52 at all times (even at an over center point). Thus, this preloading reduces relative movement and backlash between the components. Thus, the present invention provides a quieter, smoother transmission 10 than the prior art. It should also be noted that the preferred biasing force and preselected loading (discussed below) may be determined empirically for a given article of furniture 12.

In another embodiment, the engagement member 54 includes a hook to slidably engage the support shaft 28. While hooks 54 having a diameter d1 equal to the diameter d2 of the stent shaft 28 may be employed, a diameter d1 exceeding the diameter d2 is preferred. More specifically, it has been found that a hook having a diameter d1 equal to diameter d2 tends to fail at a portion 62 of spring 52 adjacent hook 54 (i.e., adjacent support shaft 28). Conversely, hooks 54 having a diameter d1 greater than d2 provide a reliable and predictable service life when subjected to a designed cyclic stress level. It is desirable that the diameter d1 be between about 130% and about 170% of the diameter d 2. As presently preferred, a 3/4 inch diameter hook is used on a 1/2 inch diameter stent shaft.

The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

Claims (21)

1. A spring assembly for use in an article of furniture having a seat assembly supported by a frame and a drive mechanism for enabling a leg rest assembly to move between a stowed position and an extended position, the mechanism including a support shaft, a drive rod spaced away from the support shaft, and a toggle assembly including the spring assembly, a toggle link and a toggle lever coupled to the drive rod, the toggle lever pivotally connected to a rear leg of the toggle link at a pivot, the spring assembly comprising:

a spring having a first end attached to said toggle link and a second end directly and slidably engaging said carriage shaft, whereby said second end is slidable on a substantially cylindrical unobstructed portion of said carriage shaft along an axis defined by said carriage shaft to align said spring thereon.

2. The spring assembly of claim 1, wherein: further comprising a member formed on the second end, the member having an inner diameter greater than the diameter of the support shaft, the member being slidable over an unobstructed portion of the support shaft, thereby allowing the stress of the spring to be reduced.

3. The spring assembly of claim 2, wherein: the member further comprises a hook.

4. The spring assembly of claim 1, wherein: the spring is comprised of a single spring sized to provide the full extension biasing force that holds the leg rest assembly in the extended position when the leg rest assembly is in the extended position, whereby the single spring biases the leg rest assembly in the extended position.

5. The spring assembly of claim 4, wherein: the single spring is sized to provide the full stow biasing force that holds the leg rest assembly in the stowed position when the leg rest assembly is in the stowed position, whereby the single spring biases the leg rest assembly in the stowed position.

6. The spring assembly of claim 5, wherein: the single spring is positioned relative to the carriage shaft position such that the retraction biasing force is less than the extension biasing force.

7. A mechanism for use in an article of furniture of the type having a seat assembly supported by a chair frame and a transmission mechanism for enabling a leg rest assembly to move between a stowed position and an extended position, the mechanism comprising:

a support shaft;

a drive rod spaced apart from the support shaft; and

a toggle assembly including a biasing assembly, a toggle link, and a toggle lever coupled to the drive rod, the toggle lever pivotally connected to a rear leg of the toggle link at a pivot; the biasing assembly includes a spring having a first end attached to the toggle link and a second end directly and slidably engaging the support shaft, whereby the second end is slidable along an axis defined by the support shaft over a substantially cylindrical unobstructed portion of the support shaft to align the spring thereon.

8. The mechanism of claim 7, wherein: further comprising a member formed on the second end, the member having an inner diameter greater than a diameter of the support shaft, thereby reducing stress on a portion of the biasing assembly adjacent the support shaft.

9. The mechanism of claim 8, wherein: the member further comprises a hook.

10. The mechanism of claim 7, wherein: the spring is comprised of a single spring sized to provide the full extension biasing force that holds the leg rest assembly in the extended position when the leg rest assembly is in the extended position, whereby the single spring biases the leg rest assembly in the extended position.

11. The mechanism of claim 10, wherein: the single spring is sized to provide the full stow biasing force that holds the leg rest assembly in the stowed position when the leg rest assembly is in the stowed position, whereby the single spring biases the leg rest assembly in the stowed position.

12. The mechanism of claim 11, wherein: the single spring is positioned relative to the carriage shaft position such that the retraction biasing force is less than the extension biasing force.

13. The mechanism of claim 7, wherein: the toggle lever is rigidly secured to the drive rod.

14. The mechanism of claim 13, wherein: the drive rod is received through an aperture formed in the toggle lever.

15. The mechanism of claim 7, wherein: the unobstructed portion of the support shaft further comprises a smooth surface.

16. A method of assembling an article of furniture of the type having a seat assembly supported by a frame and a transmission mechanism for enabling a leg rest assembly to move between a stowed position and an extended position, the mechanism including a support shaft, a drive rod spaced away from the support shaft, and a toggle assembly including a spring, a toggle link and a toggle lever coupled to the drive rod, the toggle lever pivotally connected to a rear leg of the toggle link at a pivot, the method comprising:

attaching a first end of the spring to the toggle link; and

slidably engaging a second end of the spring directly to the substantially cylindrical unobstructed portion of the support shaft, whereby the second end is slidable on the substantially cylindrical unobstructed portion of the support shaft along an axis defined by the support shaft to align the spring thereon.

17. The method of claim 16, wherein: further comprising reducing stress on the spring by sizing an inner diameter of the second end to be larger than a diameter of the stent shaft to operatively allow self-alignment of the spring along an unobstructed portion of the stent shaft.

18. The method of claim 17, wherein: the second end further comprises a hook.

19. The method of claim 16, wherein: further comprising sizing a single spring to provide a full extension biasing force that holds the leg rest assembly in the extended position when the leg rest assembly is in the extended position, whereby the single spring biases the leg rest assembly in the extended position.

20. The method of claim 19, wherein: further comprising sizing the single spring to provide the full stowed biasing force that holds the leg rest assembly in the stowed position when the leg rest assembly is in the stowed position, whereby the single spring biases the leg rest assembly in the stowed position.

21. The method of claim 20, further comprising positioning the single spring relative to the support shaft such that the stow bias force is less than the extend bias force.