INSERT MOLDED TORSION BAR HINGE

One aspect is an insert molded torsion bar hinge including a cylindrical metal torsion bar with a main bar body, a portion of which extends along a torsion bar axis, a first contoured bar end and a second contoured bar end on opposite ends of the main bar body. A first hinged element of molded plastic and with a first knuckle, is molded directly over and encompasses the first contoured bar end such that the first contoured bar end is fixed within and not rotatable relative to the first hinged element. The first knuckle is molded directly over and encompassing a portion of the main bar body. A second hinged element of molded plastic and with a second knuckle is molded directly over and encompasses the second contoured bar end such that the second contoured bar end is fixed within and not rotatable relative to the second hinged element. The second knuckle is molded directly over and encompassing a portion of the main bar body. The first and second hinged elements rotate and produce a torsional spring torque.

BACKGROUND

Torsion hinges are commonly used for many applications and come in many varieties throughout industry. One example is a piano hinge with coiled torsion springs inserted on the hinge axis. These hinges are commonly made with stamped and formed sheet metal brackets where the coil spring includes neutral angle tolerance and remains visible with cosmetic and exposure impacts to the product. Another example is a torsion bar hinge designs that also typically require stamping the hinge leaves separately and forming a torsion bar and crimping the hinge leaf after assembly, potentially adding free play, adding neutral angle tolerance and again complicating assembly. Other metal torsion spring hinges are also made with coiled torsion springs inside of a hinge barrel, which leads to larger diameter requirements. Some of these hinges are commonly made with stamped and formed sheet metal brackets that have to be attached to the larger plastic molded hinge leaves. This requires multiple additional parts and additional assembly steps. Because of these shortcomings, there is a need for a compact torsion spring hinge design that provides torsional spring torque without the addition of sleeves or bushings. There is also a need to eliminate riveting and forming operations and have the functional and cosmetic benefits. For these and other reasons, there is a need for the present invention.

DETAILED DESCRIPTION

FIGS.1a-1billustrate insert molded torsion bar hinge10in accordance with one embodiment.FIG.1cillustrates an exploded view of insert molded torsion bar hinge10in accordance with one embodiment. In one embodiment, insert molded torsion bar hinge10includes first hinged element12, second hinged element14, torsion bar16, and knuckles18. Torsion bar16includes main bar body16a, first end16b, and second end16c. In one embodiment, first and second hinged elements12and14are rotated relative to each other along main torsion hinge axis X, and torsion bar16provides torsional spring torque for insert molded torsion bar hinge10.

In one embodiment, first end16bof torsion bar16is completely embedded within first hinged element12and second end16cof torsion bar16is completely embedded within second hinged element14, while alternating knuckles18from first and second hinged elements12and14extend about sections of main bar body16a. As such, when first and second hinged elements12and14are rotated relative to each other, such as when first hinged element12is rotated from its “flat” position inFIG.1ato a “near vertical” position inFIG.1b, first end16bof torsion bar16is rotated with first hinged element12, while second end16cis held in place. This rotation of the ends of torsion bar16produces the torsional spring torque for insert molded torsion bar hinge10.

In one embodiment, the position of first and second hinged elements12and14inFIG.1ais a neutral spring position. In that position, first and second ends16band16cof torsion bar16are not flexed, but are in a relaxed state. As second hinged element12, and accordingly second end16b, are rotated to the near vertical position illustrated inFIG.1b, torsion bar16moves from its neutral relaxed state to a flexed state.

In embodiment, first and second ends16band16care contoured such that they are respectively fixed to first and second hinged elements12and14. In one embodiment, while main bar body16aextends along main torsion hinge axis X, first and second ends16band16care contoured to extend in non-parallel directions from main torsion hinge axis X such that when respectively embedded within first and second hinged elements12and14, they will be fixed to and rotate with the first and second hinged elements12and14. Other configurations for contouring first and second ends16band16cin order to secure them to first and second hinged elements12and14are possible, as will be discussed further below.

In one embodiment, insert molded torsion bar hinge10is formed in an injection molding process in which molten material is injecting into a mold cavity. Injection molding can be performed with a host of materials, including thermoplastic and thermosetting polymers. Material for the mold part is fed into a heated barrel, mixed, and injected into a mold cavity, where it cools and hardens to the configuration of the cavity.

FIG.1dillustrates a mold cavity20used for forming insert molded torsion bar hinge10. First, torsion bar16is placed into a mold cavity20. In one embodiment, the mold cavity has first and second mold cavity parts22and24, which are respectively negative images of the first and second hinge elements12and14illustrated inFIG.1b. The first end16bof torsion bar16is placed within the first mold cavity part22, which forms first hinged element12, while second end16cis placed within the second mold cavity part24, which forms second hinged element14. Within the mold cavity22, torsion bar main bar body16aalternates between the first and second mold cavity parts22and24, where knuckles18are formed over the main bar body16a. In one embodiment, half of knuckles18formed over of torsion bar16are part of first hinge element12and formed in first mold cavity part22, and the other half of knuckles18formed over of torsion bar16are part of second hinge element14and formed in second mold cavity part24. Other combinations are also possible, where one of the hinged elements have more knuckles18than the other.

In one embodiment, first and second hinge elements12and14can include a wide variety of attachment features without added cost to the parts by simply including them into the mold cavity. These features can include screw clearance holes, snap fits, adhesive pads, studs and other common methods. Each hinge element can also include cosmetic contours and shapes along with chosen rib/thickness for structural support, various plastic colors or textures to avoid extra parts or processing currently required to make a torsion spring hinge product.

In one embodiment, insert molded torsion bar hinge10is formed in a single shot of molding material into first and second mold cavity parts22and24of the mold cavity20. A main runner21supplies hot molding material, which is then diverted into both first and second mold cavity parts22and24via runners21aand21b. Formation of insert molded torsion bar hinge10with a single shot into first and second mold cavity parts22and24and over torsion bar16greatly simplifies the manufacturing process, limits the part count and creates a stable and consistent performing torsion hinge device. As mold material flows into each of first and second mold cavity parts22and24, it completely surrounds and encapsulates first end16bin first hinged element12and completely surrounds and encapsulates second end16cin second hinged element14. The mold material then freezes in place with cooling and isolates the torsion bar first and second ends16band16c, such that there is no free play between first hinged element12and first end16bor between second hinged element14and second end16c. In one embodiment, torsion bar16is secured exclusively with the molded material forming first and second hinged elements12and14. In this way, insert molded torsion bar hinge10is a simpler hinge with no need for attaching additional parts or needing to secure other devices.

For previous configurations of torsion hinges, where hinge parts are stamped and formed sheet metal brackets, a torsion bar is bent into position with the hinge parts, and a gap needs to be left in the hinge parts in order to accommodate bending and then placing the bar into the hinge part. However, since first and second hinged elements12and14are molded around torsion bar16, no gap or opening is needed, and instead, the mold material completely surrounds and encompasses first and second ends16band16cfor insert molded torsion bar hinge10.

Furthermore, molding directly around torsion bar16dictates that the mold position sets the neutral angle of the spring hinge. This removes product variation that is typical with prior systems, which bend the torsion bar into its neutral position or use wound coil springs, thereby causing some level of variation from product to product. Mold22is configured with a desired neutral angle and some allowance is included for the ends16band16c. Accordingly, when the molten plastic encompasses ends16band16c, it fills in any gaps from the torsion bar tolerance, providing a consistent outcome from product to product.

FIG.1eis a partially ghosted sectional side view of the insert molded torsion bar hinge10in accordance with one embodiment. First hinged element12is partially ghosted so that first end16bis visible extending within first hinged element12. Also, knuckle18is illustrated in an area between first and second hinged elements12and14. In one embodiment, torsion bar16has an outer diameter D16of 0.080 inches and made of a metal. In one embodiment, knuckle18is a molded plastic material and has an outer diameter D18of 8 mm. In order to ensure that insert molded torsion bar hinge10has consistent performance and withstands strains of use, in one embodiment, the outer diameter D18of knuckle18is between 2 to 6 times the outer diameter D16of torsion bar16. In another embodiment, the outer diameter D18of knuckle18is 1 mm to 8 mm larger than outer diameter D16of torsion bar16.

In addition,FIG.1eillustrates how insert molded torsion bar hinge10provides tolerance for torsion bar16during its manufacturing. First end16bis illustrated with a variance D20for its angular position. Because of imperfections in the formation process, torsion bar16may not be perfectly straight. Depending on its formation, torsion bar may be angled slightly down, mostly horizontal or may be angled slightly up as it is positioned in the mold cavity during formation. However, once molding material is flowed in and encases first end16b, its relative angular position does not affect the performance of insert molded torsion bar hinge10, since its neutral position is set by the relative positions of first and second hinged elements12and14. The same is true for the relative angular position of second end16c.

FIG.1fillustrates a partially ghosted detailed view of a portion of insert molded torsion bar hinge10in accordance with one embodiment. Second end16cof torsion bar16is fully secured in the molded material that forms second hinged element14and main bar body16aextends through molded material that forms knuckles18(in both first and second hinged elements12and14). Main bar body16ais cylindrically shaped, such that as first and second hinged elements12and14are rotated about main torsion hinge axis X, main bar body16arotates relatively freely within knuckles18. However, because second end16cextends in a non-parallel direction relative to main torsion hinge axis X, and because it is completely embedded within the molded material of second hinged element14, second end16cremains fixed within second hinged element14as first and second hinged elements12and14are rotated about main torsion hinge axis X. As will be further illustrated, torsion bar ends16band16cmay be deformed or modified by a variety of methods to allow the molding process to secure them in hinged elements12and14.

As is also visible inFIG.1f, there is also a build in tolerance as to the length of torsion bar16. Just as angular position may not always be exact as mentioned above, so too may the length of torsion bar16vary slightly along D20. Again, however, mold cavity20will accommodate these slight variations and when mold material flows in and around second end16c, it will be secured within second housing14.

FIG.1gillustrates a detailed view of a portion of insert molded torsion bar hinge10. In one embodiment, alternating knuckles18are formed in each of first and second hinged elements12and14, with main bar body16aof torsion bar16secured in the molding material of each knuckle18.FIG.1gillustrates knuckles18formed by the molding process of first and second hinged elements12and14. In one embodiment, the number of knuckles18provided in first and second hinged elements12and14to support torsion bar16is dependent on the torque and motion requirements of torsion bar16. In one embodiment, there are at least two knuckles18for each torsion bar16.

In one embodiment, torsion bar16is configured to slip within each knuckle18in order to allow hinge motion and torsional spring energy to be stored in the torsion bar16of insert molded torsion bar hinge10. The knuckles18that are nearest first end16bwithin hinge element12will have less relative motion relative to the torsion bar surface than will knuckle18positioned toward the middle of main bar16a. The knuckles18furthest from the end16bwithin hinge element12will have more relative motion. The same is true for second end16cwithin hinge element14. The plastic of the knuckles18that is in contact with the torsion bar16surface is typically configured to have a low friction coefficient, a low radius, and a low pressure from the plastic molding shrinkage. While there is some frictional torque between the knuckle18and the torsion bar16, it is typically configured to be much lower than the spring torque generated in the torsion bar16due to its twisting rotation.

In one embodiment, it may be desirable to adjust the frictional torque between the knuckle18and the torsion bar16. This may be done in several configurations according to alternative embodiments. In one embodiment, frictional torque between the knuckle18and the torsion bar16is adjusted by providing notch out18ain knuckle18. In one embodiment, molded plastic material is removed to form notch out18ain knuckle18. In another, the mold cavity is adjusted so that notch out18ais formed as part of forming knuckle18. In either case, there is less frictional torque between the knuckle18and the torsion bar16where notch out18ais provided, compared to a solid-filled18bknuckle18. In addition, the surface finish of torsion bar16can be adjusted to increase or decrease friction. Also, plastic material choices, plastic additives and torsion bar coatings may be used to adjust friction torque as well.

FIGS.2a-2billustrate insert molded torsion bar hinge40in accordance with one embodiment.FIG.2cillustrates an exploded view of insert molded torsion bar hinge40in accordance with one embodiment. In one embodiment, insert molded torsion bar hinge40includes first hinged element42, second hinged element44, first torsion bar46, and knuckles48(only a few of which are labeled for simplification of the figure). In one embodiment, insert molded torsion bar hinge40further includes second, third and fourth torsion bars56,66, and76. In one embodiment, additional torsion bars56,66, and76are axially spaced on the same main torsion hinge axis X. In one embodiment, the additional torsion bars are configured to accommodate longer hinges and/or higher torque requirements for some applications. Furthermore, additional torsion bars provide improved torque consistency for insert molded torsion bar hinge40.

As with hinge10above, a first end46cof torsion bar46is completely embedded within first hinged element42and a second end46bof torsion bar46is completely embedded within second hinged element44, while alternating knuckles48from first and second hinged elements42and44extend about sections of the main bar body46aof torsion bar46. Second, third and fourth torsion bars56,66, and76are similarly embedded. As such, when first and second hinged elements42and44are rotated relative to each other, the first ends of the torsion bars46-76are rotated with first hinged element42, while the second ends of the torsion bars46-76are held in place. This rotation of the ends of torsion bars46-76produces the torsional spring torque for insert molded torsion bar hinge40.

Although four torsion bars are illustrated inFIGS.2a-2c, more or less can be used. Furthermore, the length of each torsion bar, and the number of torsion bars in each, may be selected in order to control of the spring rate of the hinge10. Because all of the torsion bars are molding together at once, however, this embodiment eliminates the freeplay and tolerance stack of bending and assembling that occurs in known hinges.

In one embodiment, first-fourth torsion bars46,56,66and76can be translated or mirrored to the additional locations as needed to provide leg forces in the locations desired on the moving first and second hinged elements42and44relative to each other. In one embodiment, insert molded torsion bar hinge40is formed by injection molding in a mold cavity similar to that described above with respect toFIG.1d. Torsion bars46-76are placed into the mold prior to injecting material into the cavity, such that the mold material of first and second hinged elements42and44directly contacts and completely surrounds the ends of the torsion bars46-76.

FIGS.3a-3billustrate insert molded torsion bar hinge80in accordance with one embodiment.FIG.3cillustrates an exploded view of insert molded torsion bar hinge80in accordance with one embodiment. In one embodiment, insert molded torsion bar hinge80includes first hinged element82, second hinged element84, first torsion bar86, and knuckles88(only a few of which are labeled for simplification of the figure).

In one embodiment, insert molded torsion bar hinge80further includes first and second toe support and impact bars90and92. In one embodiment, first and second toe support and impact bars90and92distribute the force from the ends of torsion bar86further along the first and second hinged elements82and84, and also provides some resistance to impact for misuse requirements that could damage knuckles88or hinge elements82and84. In one embodiment, first and second toe support and impact bars90and92also include notches90aand92aconfigured to extend partially around torsion bar86in order to add more support.

As is visible inFIG.3b, first and second toe support and impact bars90and92are spaced away from torsion bar86such that the molding material of first and second hinged elements82and84completely surrounds torsion bar86. In one embodiment, insert molded torsion bar hinge80is formed by injection molding in a mold cavity similar to that described above with respect toFIG.1d. Torsion bar86and first and second toe support and impact bars90and92are placed in to the mold prior to injecting material into the cavity. Within the cavity, first and second toe support and impact bars90and92are positioned away from torsion bar86such that the mold material forms directly around torsion bar86completely enclosing around its ends, without impact bars90and92, or anything else, intervening between the mold material of first and second hinged elements82and84and torsion bar86.

FIGS.4a-4billustrate insert molded torsion bar hinge110in accordance with one embodiment.FIG.4cillustrates an exploded view of insert molded torsion bar hinge110in accordance with one embodiment. In one embodiment, insert molded torsion bar hinge110includes first hinged element112, second hinged element114, first torsion bar115, second torsion bar116, and knuckles118. First torsion bar115includes main bar body115a, first end115b, and second end115c. Second torsion bar116includes main bar body116a, first end116b, and second end116c. In one embodiment, first and second hinged elements112and114are rotated relative to each other along main torsion hinge axis X, and first and second torsion bars115and116provide torsional spring torque for insert molded torsion bar hinge110. In one embodiment, providing two torsion bars115,116in parallel within a single insert molded torsion bar hinge110as shown can create two times the spring force than can be achieved in known designs of similar size configurations.

In one embodiment, first end115bof first torsion bar115is completely embedded within first hinged element112and second end115cof first torsion bar115is completely embedded within second hinged element114, while alternating knuckles118from first and second hinged elements112and114extend about sections of main bar body115aof first torsion bar115. Similarly, first end116bof second torsion bar116is completely embedded within first hinged element112and second end116cof second torsion bar116is completely embedded within second hinged element114, while alternating knuckles118from first and second hinged elements112and114extend about sections of main bar body116aof second torsion bar116. As such, when first and second hinged elements112and114are rotated relative to each other, first ends115band116bof torsions bars115and116are rotated with first hinged element112, while second ends115cand116care rotated with second hinged element114. This relative rotation of the ends of torsion bars115and116produces the torsional spring torque for insert molded torsion bar hinge110.

In one embodiment, first and second torsion bars115and116are molded into insert molded torsion bar hinge110with injection molded plastic similar to that described above with respect toFIG.1d. In one embodiment, insert molded torsion bar hinge110is molded over first and second torsion bars115and116in one shot. Each of first and second torsion bars115and116align with main torsion hinge axis X at one end (115con one side and116bon the other) and is connected off axis at the other end (115band116c). This configuration gives twice as much torque as previously described single bar designs for a given length.

In one embodiment, more complex hinge geometries and features may be desired. In such case, it may be preferred to mold first and second hinge elements112and114is in multiple steps or shots.

In one embodiment, first and second ends115band116band115cand116cof torsions bars115and116are contoured such that they are respectively fixed to first and second hinged elements112and114. As with embodiments above, main bar body115aof first torsion bar115is cylindrical and portions of main bar body115aextend along main torsion hinge axis X, while first and second ends115band115cof first torsion bar115are contoured to extend in non-parallel directions from main torsion hinge axis X. As such, when respectively embedded within first and second hinged elements112and114, they will be fixed to and rotate with the first and second hinged elements112and114.

While main bar body116aof second torsion bar116is also cylindrical, first and second ends116band116cof second torsion bar116are contoured such that they are non-cylindrical and at least partially flattened. As such, when respectively embedded within first and second hinged elements112and114, first end116bis fixed to, and cannot move relative to, first hinged element112and second end116cis fixed to, and cannot move relative to, second hinged element114. Other contours are possible to ensure respective torsion bar ends are secured within first and second hinged elements112and114. For example, headed shapes for the ends, such as squares, hexes and splines can be used. When first and second hinged elements112and114are molded directly over these shapes, they will be fixed to the hinged elements.

Insert molded torsion bar hinges10,40,80and110have a variety of useful applications where it is desired to have a torsional spring torque between two or more hinged elements.FIG.5aillustrates one such exemplary application in hinged device200in accordance with one embodiment. In one embodiment, hinged device200includes hinged cover202, container housing204and insert molded torsion bar hinge240. In one embodiment, hinged device200is a center console in an automobile. In one embodiment, insert molded torsion bar hinge240provides consistent and predictable torsional spring torque for opening and closing hinged cover202on container housing204. In one embodiment, insert molded torsion bar hinge240allows the console hinged cover202to pop up upon release of a latch or other control device (not shown).

FIG.5billustrates an exploded view of hinged device200andFIGS.5c-5eare detailed, side and sectional views of insert molded torsion bar hinge240. In one embodiment, hinged cover202includes first and second slots206(only one is visible inFIG.5band the other is identical on the opposite side) and container housing204similarly includes first and second slots208on either side of the container housing204. Slots206and208are positioned to align insert molded torsion bar hinge240at the desired neutral angle which along with the spring rate provides the hinge preload when fully closed. Insert molded torsion bar hinge240includes first, second, third and fourth hinged elements242,244,246and248and further includes first and second torsion bars250and252.

In one embodiment, a first end of first torsion bar250is embedded within first hinged element242and a second end of first torsion bar250is embedded within third hinged element246. A first end of second torsion bar252is embedded within second hinged element244and a second end of second torsion bar252is embedded within fourth hinged element248. Insert molded torsion bar hinge240can be manufactured with a one-shot molding process as described above with the other embodiments. Just like the prior embodiments, the molding material of the hinged elements completely surround and directly encapsulate the torsion bar ends, which each includes a contoured features, such that there is no relative movement between the torsion bar ends and the hinged elements.

In operation, insert molded torsion bar hinge240is coupled into hinged device200in that first hinged element242is placed into first slot206of hinged cover202and fourth hinged element248is placed into second slot206of hinged cover202, while second hinged element244is placed into first slot208of container housing204and third hinged element246is placed into second slot208of container housing204. First and second torsion bars250and252provide torsional spring torque for opening and closing hinged cover202on container housing204.

FIG.6a-6billustrate another exemplary application in hinged device200in accordance with one embodiment. In one embodiment, hinged device200includes hinged cover202, container housing204and insert molded torsion bar hinge280. In one embodiment, hinged device200is a center console in an automobile. In one embodiment, insert molded torsion bar hinge280provides consistent and predictable torsional spring torque for opening and closing hinged cover202on container housing204.

FIGS.6c-6dillustrate insert molded torsion bar hinge280in accordance with one embodiment. In one embodiment, insert molded torsion bar hinge280provides an alternative for hinging hinged cover202and container housing204. In one embodiment, insert molded torsion bar hinge280includes first and second hinged elements282and284, and further includes torsion bar290. For example, in one embodiment, first hinged element282is placed into first slot206of hinged cover202, while second hinged element284is placed into first slot208of container housing204. Insert molded torsion bar hinge280provides torsional spring torque for opening and closing hinged cover202on container housing204. In one embodiment, an insert molded torsion bar hinge280can be placed into both sides of hinged device200. In another embodiment, insert molded torsion bar hinge280can be placed into one side of the hinged device200, while a plain pivot or friction hinge295can be placed on the other side as desired.

In one embodiment, a first end of first torsion bar290is embedded within first hinged element282and a second end of torsion bar290is embedded within second hinged element284. Insert molded torsion bar hinge280can be manufactured with a one-shot molding process as described above with the other embodiments. Just like the prior embodiments, the molding material of the hinged elements completely surround and directly encapsulate the ends of each of the torsion bar ends, which each include contoured features, such that there is no relative movement between the torsion bar ends and the hinged elements. Also, as with prior embodiments, a circular cross section torsion bar is used as the pivot axis. When the first and second hinged elements282,284are rotated relative to each other, torsion bar290pivots along the main torsion hinge axis providing torsional spring torque.

FIGS.7a-7cillustrate fold down system300in accordance with one embodiment. In one embodiment, fold down system300includes base310, folding member312, and insert molded torsion bar hinge340. In one embodiment, insert molded torsion bar hinge340includes fixed hinge side344and spring loaded side342. In operation, folding member312has an open position (illustrated inFIGS.7aand7c) and a folded position (illustrated inFIG.7b). When folding member312is folded down against base310, it leaves a gap315. In one embodiment, insert molded torsion bar hinge340is positioned to automatically cover gap315when folding member312is folded down against base310, due to its torsional spring torque, allowing for a smooth flat surface when folding member312is folded down.

Such a gap hider can be useful in a variety of applications, such as in a pick-up truck, where folding member312could be a tailgate on a truck, a mid-gate on a truck with the option to extend the bed into the cab, a common back row seat that folds down, or any of a variety of other dividing panels.

In one embodiment, insert molded torsion bar hinge340is injection molded in a single shot mold over one or more torsion bars, as described above with respect to insert molded torsion bar hinges10,40and80. It can have one or more torsion bars, which include ends that are contoured and embedded on one end within the fixed hinge side344and on the other end within the spring loaded side342. By attaching the fixed hinge side344against base310and then loading the embedded torsion bars to press spring loaded side342against folding member312, torsion bar hinge340will fold down over gap315as folding member312is folded down to base310.

Fixed hinge side344can have any number of attachment options to secure it to base310, such as screw clearance holes, glue down, snap fits, studs, etc. The spring loaded side342can include a variety of cosmetic contours and shapes, along with rib thickness for structural support.

Insert molded torsion bar hinge340has a smaller barrel size than traditional hinges, and it eliminates separate coil springs often used in traditional hinges. This has superior visual appearance and also eliminates potential entanglement associated with coil springs. Insert molded torsion bar hinge340is made in a single shot injection mold as described above, it can also readily include various plastic colors or textures and will avoid extra parts or processing currently required to make a finished product known in the art.

FIGS.8a-8billustrate multi-axis insert molded torsion bar hinge380in accordance with one embodiment.FIG.8cillustrates an exploded view of multi-axis insert molded torsion bar hinge380in accordance with one embodiment. In one embodiment, multi-axis insert molded torsion bar hinge380includes first, second and third hinged elements382,384and386and first and second torsion bars390and392. Multi-axis insert molded torsion bar hinge380is similar to the above-described torsion hinges, but has two axes of rotation (X1and X2), rather than one.

In one embodiment, each of first and second torsion bars390and392include a main bar body390a,392a, first end390b,392band a second end390c,392c. Main bar body390aof first torsion bar390lies in a first axis X1, and main bar body392aof second torsion bar392lies in a second axis X2. In one embodiment, first and second ends390b,392band390c,392care contoured to extend in non-parallel direction to the axes X1and X2. In other embodiments, other contours, such as flattened sections, can be used.

In one embodiment, first end of first torsion bar390bis embedded within second hinged element384, second end of first torsion bar390cis embedded within first hinged element382, first end of second torsion bar392bis embedded within third hinged element386, and second end of second torsion bar392cis embedded within second hinged element384. Insert molded torsion bar hinge380can be manufactured with a one-shot molding process as described above with the other embodiments. Just like the prior embodiments, the molding material of the hinged elements completely surround and directly encapsulate the ends of each of the torsion bar ends, which each includes the contoured features, such that there is no relative movement between the torsion bar ends and the hinged elements.

Furthermore, knuckles388(only a few are labeled for simplicity) are formed in each of first, second and third hinged elements382,384and386such that knuckles388from first and second hinged elements382and384are formed directly over the main bar body390aof first torsion bar390and such that knuckles388from second and third hinged elements384and386are formed directly over the main bar body392aof second torsion bar392. Since main bar body390a,392aof torsion bars390,392are cylindrical, torsion bar390rotates within knuckles388as first and second hinged elements382and384rotate relative to each other along first axis X1, and torsion bar392rotates within knuckles388as second and third hinged elements384and386rotate relative to each other along second axis X2. Additional hinged elements and torsion bars can be added to have additional hinged parts as needed.