Foldable elliptical fitness machine

Abstract

A foldable elliptical fitness machine comprises a first frame securely supported on a floor and a second frame for installing an elliptical structure, and the second frame is pivotally coupled to the first frame by a pivoting device, such that the second frame can be rotated with respect to the first frame, wherein the elliptical structure comprises a rotating member having two eccentric pivotal points, and two pedal arms. A central penetrating axle of the rotating member is pivotally coupled onto the second frame, and each eccentric pivotal point is pivotally coupled to the first end of the pedal arm, and each pedal arm includes a footrest for a user to step. If the first end of the pedal arm rotates with the crank, the footrest will move in an elliptic path. With the foregoing structural design, the elliptical structure can be fully folded to improve the convenience of use.

Description

FIELD OF THE INVENTION

The present invention relates to a foldable elliptical fitness machine, and more particularly to an elliptical fitness machine structure that includes a first frame and a second frame, and wherein the second frame installed an elliptical mechanism, and the second frame can be turned and folded upright with respect to the first frame and supported securely by the first frame to achieve the purposes of effectively folding and using the elliptical fitness machine.

BACKGROUND OF THE INVENTION

In general, the basic structure of a prior art elliptical fitness machine includes a flywheel, two cranks, and two pedal arms, and a first end of each crank is coaxially connected to the flywheel, and a second end of each crank is pivotally connected to a first end of each corresponding pedal arm, and each pedal arm has a footrest, such that a user can step on the footrest. If the first end of the pedal arm rotates with the crank, the footrest will move in an elliptic path.

Since the elliptical fitness machine provides the function of a striding exercise, the elliptical fitness machine becomes one of the fitness equipments as popular as the treadmill. If the elliptical fitness machine and the treadmill are placed flatly on a floor for their use, the footprint of these fitness equipments occupy much area. To reduce the footprint of the fitness machines when the machines are not in use, some treadmills are designed to have a belt that can be folded upward, and it is not easy to design a foldable elliptical fitness machine because many mechanisms are disposed on the link rod, and the elliptical fitness machines are usually designed as a partial foldable structure. All of the present elliptical fitness machines do not come with a structure having a variable inclined body. For example, U.S. Pat. No. 6,149,551 only disclosed a foldable elliptical exercise machine that includes one frame, and the frame includes the main components such as a flywheel and a crank to operate with a pedal arm and the track is designed to have a free end which can be turned and folded upright with respect to a second frame. The elliptical exercise machine is partially folded, and the footprint is still large after the machine is folded. Furthermore, such foldable exercise machine does not come with a function of changing the inclination of the machine, and thus users cannot change the level of difficulty of their exercise by changing the inclination of the elliptical fitness machine. U.S. Pat. No. 6,146,313 disclosed a cross training exercise device, and the end of a pedal arm is connected to a guide track for adjusting the height and changing the exercise path of the pedal arm. However, the structure of this machine is not stable enough.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide a fully foldable elliptical fitness machine to improve the convenience of its use, and the foldable elliptical fitness machine comprises a first frame and a second frame, wherein the first frame securely supported on a floor and the second frame installed an elliptical structure, and the second frame is pivotally coupled to the first frame by a pivoting device, such that the second frame can be rotated with respect to the first frame, wherein the elliptical structure comprises a rotating member having two eccentric pivotal points, and two pedal arms. A central penetrating axle of the rotating member is pivotally coupled onto the second frame, and each eccentric pivotal point of the rotating member is pivotally coupled to a first end of the corresponding pedal arm, and each pedal arm includes a footrest, such that a user can step on the footrest. If the first end of the pedal arm rotates with the crank, the footrest will move in an elliptic path. With the foregoing structural design, the elliptical structure of the invention has the functions of being fully folded upright and improving the convenience of using the elliptical fitness machine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a basic structure and a structure having a smaller inclination and a usable status according to a first preferred embodiment of the present invention:

FIG. 2 is a schematic view of a second preferred embodiment of the present invention;

FIG. 3 is a schematic view of a third preferred embodiment of the present invention;

FIG. 4 is a schematic view of a structure as depicted in FIG. 3 which is adjusted to have a larger inclination;

FIG. 5 is a schematic view of a structure as depicted in FIG. 3, which is folded;

FIG. 6 is an exploded view of a portion of the first preferred embodiment as depicted in FIG. 1;

FIG. 7 is a schematic view of an assembled structure as depicted in FIG. 6;

FIG. 8 is a schematic view of a structure as depicted in FIG. 1 which has a larger inclination and a usable status;

FIG. 9 is a schematic planar diagram of FIG. 1;

FIG. 10 is a schematic planar diagram of FIG. 8;

FIG. 11 is a schematic view of a partially folded structure of the present invention;

FIG. 12 is a schematic view of a fully folded structure of the present invention;

FIG. 13 is a schematic view of a fourth preferred embodiment of the present invention;

FIG. 14 is a schematic view of the movements with respect to FIG. 13; and

FIG. 15 is a schematic view of a second frame together with an elliptical structure being folded upright according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 to 3, a foldable elliptic fitness machine according to a preferred embodiment of the present invention comprises a first frame 10 and a second frame 20, wherein the first frame 10 securely supported on a floor and the second frame 20 installed an elliptical structure, and the second frame 20 is pivotally coupled with the first frame 10 by a pivoting device 30, such that the second frame 20 and the elliptical structure 2 can be fully rotated and folded upright with respect to the first frame 10, and the first frame 10 stably supports the second frame 20, wherein the elliptical structure 2 is like a general prior art structure comprising a rotating member 22 having two eccentric pivotal point 220a, 220b, and two pedal arms 23a, 23b, and a central penetrating axle 220 of the rotating member 22 is pivotally coupled to the second frame 20, and the two pivotal points 220a, 220b of the rotating member 22 are separately and pivotally coupled to the corresponding first end of a pedal arm 23a, 23b, and each pedal arm 23a, 23b includes a footrest 24a, 24b, such that a user can step on the footrest 24a, 24b. When the first end of the pedal arm 23a, 23b rotates with the rotating member 22, the footrest 24a, 24b can move in an elliptic path. With the foregoing structural design, the elliptical structure 2 of the invention can be folded upright to improve the convenience of using the elliptical fitness machine. In the foregoing basic structure, the rotating member 22 is coaxially coupled with two cranks 22a, 22b to form a rigid body, and the axle 220 is pivotally coupled onto the second frame 20.

The present invention installs a pivoting device 30 for pivotally connecting the second frame 20 with the first frame 10 of the elliptical structure 2. Many preferred embodiments are feasible for the invention and three of them as shown in FIGS. 1 to 3 are used for illustrations. The second preferred embodiment as shown in FIG. 2 can use a simple pivotal axle 300 to pass through the second frame 20 and the first frame 10, such that the second frame 20 can be rotated to an angle with respect to the first frame 10. As to an enabling assembly 4 for enabling the second frame 20 to rotate with respect to the first frame 10, a support rod 70 is pivotally coupled to a rear end of the second frame 20, and an actuating device 71 is connected between the support rod 70 and the second frame 20. The actuating device 71 includes a body 72 and a contractible rod 73, and the contractible rod 73 can be contracted with respect to the body 72, such that the support rod 70 can be swung to an angle to support a rear end of the second frame 20 to define positions of different heights and achieve the function of changing the inclination of the second frame 20. The third preferred embodiment as shown in FIGS. 3 to 5, a link rod 80 and a swinging rod 81 are pivotally coupled to the same pivotal point at the front end of the second frame 20, and another end of the link rod 80 is pivotally coupled to the first frame 10, and a roller 82 is pivotally coupled to a free end of the swinging rod 81, and the first frame 10 includes a track 83, and the roller 82 of the swinging rod 81 is in contact with the track 83, and the enabling assembly 4 has an actuating device 84 connected between the first frame 10 and the swinging rod 81, and the actuating device 84 includes a body 85 and a contractible rod 86, and the contractible rod 86 can be contracted with respect to the body 85, such that the swinging rod 81 is swung to an angle to support the front end of the second frame 20 to define positions of different heights, so as to achieve the function of changing the inclination of the second frame 20.

Since the structure of the present invention includes a structure as illustrated by a complete set of drawings of the first preferred embodiment, therefore the following movements are illustrated by using the first preferred embodiment as shown in FIGS. 1, 6, and 7. The pivoting device 30 according to the first preferred embodiment comprises:

two side panels 11a, 11b, disposed on a first frame 10, and each of the two side panels 11a, 11b includes a first pivotal connecting portion 12a, 12b and a second pivotal connecting portion 13a, 13b;

two side rods 200a, 200b, disposed on the second frame 20, and each of the two side rods 200a, 200b includes a pivotal connecting portion 201a, 201b proximate to a distal end;

two first link rods 31a, 31b, and each first link rods 31a, 31b includes a first pivotal connecting portion 310a, 310b, a second pivotal connecting portion 311a, 311b and a third pivotal connecting portion 312a, 312b, and the third pivotal connecting portion 312a, 312b on each first link rod 31a, 31b and a pivotal connecting portion 201a, 201b corresponding to a side rod 200a, 200b on the second frame 20 are passed through a pivotal axle (not shown in the figure) for the pivotal connection;

two second link rods 32a, 32b, and a first end of each second link rod 32a, 32b is passed through a pivotal axle and pivotally coupled to a first pivotal connecting portion 12a, 12b corresponding to a side panel 11a, 11b of the first frame 10, and a second end is passed through a pivotal axle (not shown in the figure) and pivotally coupled to a corresponding first pivotal connecting portion 310a, 310b of a first link rod 31a, 31b; and

two third link rods 33a, 33b, and a first end of each third link rod 33a, 33b is passed through a pivotal axis (not shown in the figure) and pivotally coupled to a second pivotal connecting portion 13a, 13b corresponding to a side panel 11a, 11b of the first frame 10, and a second end is passed through a pivotal axle (not shown in the figure) and pivotally coupled to a corresponding second pivotal connecting portion 311a, 311 b of a first link rod 31a, 31 b, wherein the enabling assembly 4 according to a preferred embodiment comprises:

a fixed rod 34, fixed between the two first link rods 31a, 31b and extended to a lateral side of a connecting rod 35; and

an actuating device 40, including a motor 41 for supplying a motive power, and a moving element 42 driven by the motor 41 for moving flexibly, and the moving element 42 is pivotally coupled to the connecting rod 35 of the fixed rod 34;

such that each set of the corresponding first link rod 31a, 31b, second link rod 32a, 32b, third link rod 33a, 33b, and side panel 11a, 11b constitutes a structure of four link mechanism (11a, 31a, 32a, 33a/ 11b, 31b, 32b, 33b).

Since the first link rods 31a, 31b can be rotated with respect to the second link rod 32a, 32b and the third link rod 33a, 33b, and the second link rod 32a, 32b and the third link rod 33a, 33b will rotate in opposite directions, and thus the first link rod 31a, 31b can rotate with respect to the frame 10, and the second frame 20 is fixed with the first link rods 31a, 31b by an actuating device 40, such that the second frame 20 and the elliptical structure 2 also can be rotated with respect to the first frame 10 and folded upright. In other words, when the foregoing structure of four link mechanism (11a, 31a, 32a, 33a/ 11b, 31 b, 32b, 33b) operated with the actuating device 40 and the second frame 20 is secured on a floor, the actuating device 40 is enabled to push or pull the first link rods 31a, 31b to rotate with respect to the second frame 20, and the first link rod 31a, 31b, the second link rod 32a, 32b, and the third link rod 33a, 33b are operated to ascend or descend the front end of the second frame 20, so as to change the inclination of the second frame 20 (as shown in FIGS. 1, 8, 9, and 10). Further, when the elliptical fitness machine is not in use, the free end at the rear of the second frame 20 is lifted upright, so that the second frame 20 can be rotated and folded upright with respect to the first frame 10 (as shown in FIGS. 1, 6, 7, 11, and 12).

Referring to FIG. 1 for the preferred embodiment of the present invention, an output end of the actuating device 40 is a rotate rod 43 screwed to the moving element 42, such that when the rotate rod 43 is rotated, the moving element 42 can move on the rotate rod 43.

In FIG. 12, an actuating device 60 is installed and connected between the first frame 10 and the second frame 20 for providing a subsidiary force when the second frame 20 is rotated and folded upright with respect to the first frame 10.

In the elliptical structure on the second frame 20 as shown in FIG. 1, the second frame 20 includes two sliding tracks 25a, 25b, and the second end of each pedal arm 23a, 23b includes a roller 230a, 230b, and the second end of each pedal arm 23a, 23b is embedded into a corresponding sliding track 25a, 25b, such that the roller 230a, 230b can be rolled on the corresponding sliding track 25a, 25b. In a further preferred embodiment of the present invention, the sliding track 25a, 25b includes a recessive guide groove 250a, 250b separately on both sides of the sliding track 25a, 25b, and the second end of the pedal arm 23a, 23b is pivotally coupled to a wheel base 26a, 26b, and each wheel base 26a, 26b includes a plate 260a, 260b extended downward from the wheel base 26a, 26b, and the internal surface of each plate 260a, 260b is pivotally coupled to two rollers 230a, 230b, and the roller 230a, 230b of each plate 260a, 260b is embedded into a corresponding guide groove 250a, 250b.

In FIG. 1, the first frame 10 includes a pillar 110a, 110b extended upward from and disposed separately on both sides of the first frame 10, and each pillar 110a, 110b includes a handgrip 12a, 12b.

In FIG. 1, the first frame 10 includes a pillar 110a, 110b extended upward from and disposed on both sides of the first frame 10, and each pillar 110a, 110b is pivotally to a shaking rod 13a, 13b extended vertically up and down, and each pedal arm 23a, 23b of the second frame 20 is pivotally to the first end of a link rod 14a, 14b, and the second end of the link rod 14a, 14b is coupled to the bottom of a corresponding shaking rod 13a, 13b, and the top of each shaking rod 13a, 13b has a handle 130a, 130b. In a further preferred embodiment, the lower half of each shaking rod 13a, 13b includes a C-shape cross section extended along the shaking rod 13a, 13b to the first guide groove 131a, 131b, and the second frame 20 includes two corresponding link rods 14a, 14b separately installed in a guide track 15a, 15b, and each lateral side of the guide track 15a, 15b has a C-shape cross section extended axially along the first guide track 15a, 15b to the second guide groove 150a, 150b, and each link rod 14a, 14b includes a first roller 16a, 16b and a second roller 17a, 17b separately disposed proximate to the ends of the link rod 14a, 14b. The first roller 16a, 16b is embedded and limited in the corresponding first guide groove 131a, 131b and rolled in the first guide groove 131a, 131b, and the second roller 17a, 17b is embedded and limited in the corresponding second guide groove 150a, 150b and rolled in the second guide groove 150a, 150b. With such design, the second frame 20 can be rotated and folded upright with respect to the first frame 10 to avoid any interference to the shaking rod 13a, 13b and the second frame 20.

Referring to FIGS. 1, 13, 14 for a preferred embodiment of the present invention, the first frame 10 further comprises a sliding track 50, and the axis of the sliding track 50 is extended along the direction of the front and rear ends of the first frame 10, and the sliding track 50 is sheathed onto a sliding rod 51, and the sliding rod 51 can be moved and contracted with respect to the sliding track 50. The sliding rod 51 includes a second pivotal connecting portion 510 pivotally coupled to a first end of a link rod 52, and the second end of the link rod 52 is pivotally coupled to the second frame 20. The sliding rod 51 includes a latch 53 pivotally coupled thereon, and a first end of the latch 53 includes a hook portion 530, and a spring 54 is installed between the second end of the latch 53 and the sliding rod 51. The first frame 10 includes a hooked portion 100 corresponding to the hook portion 530 of the latch 53, such that when the second frame 20 is rotated and folded upright with respect to the first frame 10, the sliding rod 51 is contracted with respect to the sliding track 50, and the hook portion 530 of the latch 53 will be hooked and fixed to the hooked portion 100 of the first frame 10, such that the second frame 20 is securely fixed and supported with respect to the first frame 10. If the second frame 20 is set down for the use of the elliptical fitness machine, the sliding rod 51 will be linked and extended backward to increase the area of the supporting plane to give a better stability when a user is doing exercises on the second frame 20.

In FIG. 1, the second frame further includes a flywheel 21 pivotally coupled thereon, and the flywheel 21 and the rotating member 22 are coaxially and pivotally coupled to the second frame 20, and the flywheel 21 includes a magnetic resisting device 27, such that when the flywheel 21 rotates, the magnetic lines of the magnet on the magnetic resisting device 27 is cut off, and the flywheel 21 produces a magnetic resistance to improve the exercise performance.

In FIG. 15, the bottom of the first frame 10 supported on a floor constitutes a supporting plane. When the second frame 20 with the elliptical structure 2 is folded fully upright with respect to the first frame 10, the second frame 20 and the elliptical structure 2 have a center of gravity G falling within the range of the supporting plane of the first frame 10.

While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.

Claims

1. A foldable elliptical fitness machine, comprising a first frame and a second frame, wherein the first frame securely supported on a floor and the second frame installed an elliptical structure, and the second frame being pivotally coupled to the first frame by a pivoting device, such that the second frame and the elliptical structure can be rotated and folded upright with respect to the first frame, and the first frame supports the second frame, and the elliptical structure comprises a rotating member having two eccentric pivotal points, and two pedal arms, and the middle of the rotating member is pivotally coupled with the second frame, and the two pivotal points of the rotating member are separately and pivotally coupled to a first end of a corresponding pedal arm, and the each pedal arm includes a footrest capable of moving in an elliptic path.

2. The elliptical fitness machine as claimed in claim 1, wherein the rotating member is coaxially coupled to two cranks to define a rigid body and the axle is pivotally coupled to the second frame.

3. The elliptical fitness machine as claimed in claim 1, wherein the pivoting device is passed through the second frame and the first frame by a pivotal axle, such that the second frame can be rotated to an angle with respect to the first frame.

4. The elliptical fitness machine as claimed in claim 1, wherein the pivoting device is passed through the second frame and the first frame by a pivotal axle, such that the second frame can be rotated to an angle with respect to the first frame, and a enabling assembly includes a support rod and an actuating device, the support rod pivotally coupled to the rear end of the second frame, and the actuating device is coupled between the support rod and the second frame, and the actuating device includes a body and a contractible rod, and the contractible rod can be contracted with respect to the body to swing the support rod to an angle.

5. The elliptical fitness machine as claimed in claim 1, wherein the pivoting device is pivotally coupled to a link rod and a swinging rod at the same pivotal point at the front end of the second frame, and another end of the link rod is pivotally coupled to the first frame, and the swinging rod includes a roller pivotally coupled to a free end of the swinging rod, and the first frame has a track thereon, and the roller of the swinging rod is in contact with the track, and a enabling assembly connected between the swinging rod and the first frame, the enabling assembly includes an actuating device connected between the first frame and the swinging rod, and the actuating device includes a body and a contractible rod, and the contractible rod can be contracted with respect to the body to swing the swinging rod to an angle.

6. The elliptical fitness machine as claimed in claim 1, wherein the pivoting device comprises:

two side panels, disposed at the first frame, the each side panel includes a first pivotal connecting portion and a second pivotal connecting portion; two side rods, disposed at the second frame, and the each side rod includes a pivotal connecting portion disposed proximate to an end of the second frame; two first link rods, each having a first pivotal connecting portion, a second pivotal connecting portion, and a third pivotal connecting portion, and the third pivotal connecting portion on the each first link rod and the pivotal connecting portion corresponding to the rod on the second frame are passed by a pivotal axle for defining a pivotal connection;

two second link rod, and a first end of the each second link rod having a pivotal axle and being pivotally coupled to a first pivotal connecting portion corresponding to the side panel of the first frame, and the second end includes a pivotal axle pivotally coupled to a corresponding first pivotal connecting portion of the first link rod; and

two third link rods, and a first end of the each third link rod includes a pivotal axle pivotally coupled to a second pivotal connecting portion corresponding to the side panel of the first frame, and a second end includes a pivotal axle pivotally coupled to the second pivotal connecting portion corresponding to the first link rod; and

an enabling assembly comprises: a fixed rod, fixed to the two first link rods, and a lateral side of the fixed rod is extended to a connecting rod; and an actuating device, including a motor and a moving element driven by the motor to move and contract, and the moving element is pivotally coupled to the connecting rod of the fixed rod;

each set of the first link rod, the second link rod, the third link rod, and the side panel constitutes a structure of four link mechanism, such that when the actuating device drives the moving element, the structure of four link mechanism will move to drive an end of the second frame to ascend to change the inclination of the second frame.

7. The elliptical fitness machine as claimed in claim 6, wherein the second link rod and the third link rod are rotated in opposite directions with respect to the first frame.

8. The elliptical fitness machine as claimed in claim 6, wherein the actuating device has an output end being a rotate rod, and the rotate rod is screwed with the moving element, such that when the rotate rod is rotated, the moving element can move on the rotate rod.

9. The elliptical fitness machine as claimed in claim 6, further comprising an actuating device coupled between the first frame and the second frame for providing a subsidiary force to rotate and fold the second frame upright with respect to the first frame.

10. The elliptical fitness machine as claimed in claim 1, wherein the second frame includes two sliding tracks, and a second end of the two pedal arms separately have a roller, and a second end of the each pedal arm is embedded into the sliding track, such that the roller can roll on the corresponding sliding track.

11. The elliptical fitness machine as claimed in claim 10, wherein the sliding track includes a recessive guide groove disposed separately on both sides of the sliding track, and a second end of the pedal arm is pivotally coupled to a wheel base, and the wheel base includes a plate extended down separately from both sides of the wheel base, and the internal surface of the each plate is pivotally coupled to two of the rollers, and the roller of the each plate is embedded in the corresponding guide groove.

12. The elliptical fitness machine as claimed in claim 1, wherein the first frame includes a pillar extended downward separately from both sides of the first frame, and the each pillar includes a handgrip.

13. The elliptical fitness machine as claimed in claim 1, wherein the first frame includes a pillar extended upward separately from both sides of the first frame, and the each pillar is pivotally coupled to a shaking rod extended vertically up and down, and the each pedal arm on the second frame is pivotally coupled to a first end of a link rod, and a second end of the each link rod is coupled to the bottom of a corresponding shaking rod, and the each shaking rod includes a handle at the top of the shaking rod.

14. The elliptical fitness machine as claimed in claim 13, wherein the each shaking rod includes a C-shape cross section disposed at its lower half and a first guide groove extended axially along the shaking rod, and the second frame includes a guide track disposed separately on the two link rods, and the each guide track includes a C-shape cross section at a lateral side of the guide track and a second guide groove extended axially along the guide track, and the each link rod includes a first roller and a second roller disposed separately on the distal ends of the link rod, and the first roller is embedded and limited in the corresponding first guide groove and rolled in the first guide groove, and the second roller is embedded and limited in the corresponding second guide groove and rolled in the second guide groove.

15. The elliptical fitness machine as claimed in claim 1, wherein the first frame further comprising a sliding track, and the axial line of the sliding track is extended along the direction of the front and rear ends of the first frame, and the sliding track is sheathed onto the sliding rod, such that the sliding rod can move with respect to the sliding track for a contraction, and the sliding rod includes a second pivotal connecting portion, and the second pivotal connecting portion is pivotally coupled to a first end of a link rod, and the link rod second end is pivotally coupled to the second frame, and the sliding rod includes a latch pivotally coupled thereon, and a first end of the latch includes a hook portion, and a spring is installed between a second end of the latch and the sliding rod, and the first frame includes a hooked portion corresponding to the hook portion of the latch, such that when the second frame is rotated and folded upright with respect to the first frame, the sliding rod is contracted with respect to the sliding track, and the hook portion of the latch is hooked and fixed by the hooked portion of the first frame for fixing the second frame with the corresponding first frame.

16. The elliptical fitness machine as claimed in claim 1, wherein the second frame further comprises a flywheel, and the flywheel and the rotating member are coaxially and pivotally coupled to the second frame, and the flywheel includes a magnetic resisting device, such that when the flywheel is rotated to cut off a magnetic line of a magnet on the magnetic resisting device, the flywheel produces a magnetic resistance.

17. The elliptical fitness machine as claimed in claim 1, wherein the first frame having a bottom supported on a floor constitutes a supporting plane, such that when the second frame and the elliptical structure are folded fully upright with respect to the first frame, the center of gravity of a structure comprised of the second frame and the elliptical structure falls within the range of the supporting plane.