Crank structure for treadmills

Abstract

An improved crank structure for treadmills, each of the treadmills has two pedals for a user to step, the pedals respectively connect on one of their ends with the periphery of a rotary wheel, and are linked with cranks respectively on the front and the rear sides of the rotary wheel, the cranks are connected on their internal end portions with the center of the rotary wheel, the cranks are provided each with a first section which has an included angle with the vertical diametric line of the rotary wheel, at the tailing end of the first section, there is a bent section for connecting with the center of the rotary wheel. A user using such a treadmill needs only to exert a small force at the uppermost position of the rotary wheel for stepping; this can prevent probable damage of exercising.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention is related to an improved crank structure for treadmills, and especially to such a structure of which the cranks can allow people to step pedals more conveniently with smaller force when they get to the top point within a circular motion.

[0003] 2. Description of the Prior Art

[0004] People nowadays live busily and the spaces they live are more and more smaller; it is quite difficult to keep appropriate amount of exercising. In view of this situation, there have been various indoor sporting instruments in the markets, such sporting instruments can be used in a limited space without influence by time and weather; therefore, they are very suitable as sporting instruments for health for modern people.

[0005] Treadmills are of one kind of popularized indoor sporting instruments, basically, they are provided each with two pedals for people to step with their feet, when the feet act in running or stepping mode thereon, the pedals is moved up and down alternately; in this way, a function of exercising simulating running or jogging outdoors can be obtained.

[0006] The basic principles for such treadmills are expressed as shown in FIG. 1, wherein, a treadmill of such is provided with a first pedal 10 and a second pedal 20, the left foot “L” of a user can step on the first pedal 10, while the right foot “R” can step on the second pedal 20. The pedals 10, 20 respectively connect on their front ends with a first crank 11 and a second crank 22 mutually oppositely directing. The cranks 11, 22 respectively connect on their external end portions in the mode of linking with peripheral points 13, 24 on a rotary wheel 30. In such a crank mechanism of the treadmill, when the user runs or steps at the fixed position, the cranks 11, 22 will respectively run circular motions about the center “O” of the rotary wheel 30. This makes the ends of the pedals 10, 20 move up and down successively to give the desired function of exercising.

[0007] Referring to FIGS. 1-3, by virtue that the cranks 11, 22 are straight and are given with predetermined lengths to connect each from the peripheral points 13, 24 on the rotary wheel 30 to the center “O” of the rotary wheel 30, the lengths for motion thereof are both approximately equal to the radius “r” of the rotary wheel 30. For example, when the first pedal 10 is at the uppermost position (dead point) as shown in FIGS. 1 and 2, this is the position which exhaust force the most, here the action force completely vertically gets through the center “O” of the rotary wheel 30 with an arm of force of merely zero, the required torque will not be created. This is why the stage for the first pedal 10 to move from the uppermost position 13 to a neighboring peripheral position 13a is most difficult.

[0008] The source of power for running the rotary wheel 30 of such a treadmill is mainly the down pressing weight “W” of the user plus a horizontal pushing force “P”. For example, as shown in FIG. 1, when the user moves the crank 11 to the uppermost position 13 of the rotary wheel 30, the force that the weight “W” of the user applying to this position is ½ W assuming that the weight is averagely loaded; the force completely vertically gets through the center “O” of the rotary wheel 30, it does not have any tangential component to drive the rotary wheel 30 to rotate. The main driving force at this time is the horizontal action force “P” of the user. Assuming in an exercising case, the horizontal component “f” (the vertical component “g” is functionless) of the half weight “W/2” through one leg of the user is extremely small, when the first crank 11 or the second crank 22 is rotated to the aforesaid uppermost position 13 or an area nearby the position, the user must exert very hardly a horizontal action force “P” for further moving.

[0009] The rotating mechanism as shown in FIG. 4 is frequently seen on the instruments such as a bicycle, the main chain wheel 35 thereof is provided on the two sides thereof with a left pedal 15, a right pedal 25 and cranks 17, 27; both the pedals 15, 25 are movable. In the drawing shown, when the right pedal 25 is moved to the uppermost position 13, an inclining stepping force P′ is exerted onto the main chain wheel 35 to prevent the above stated exhaustion situation at the uppermost position. However, as shown in FIG. 5, both the pedals 11, 22 of such a conventional treadmill are fixed, this forms a limitation, when the first pedal 11 has its end located at the uppermost position, the thighs and shins of the legs 181 of the user 18 must bend about the knee 182 as an axis to give a horizontal action force “P”. This not only makes an extreme large burden against physical strength of the user in exercising, but also repeatedly gives sudden adding of loading on the knee 182 during exercising. Inadvertent damage of sporting thereby may be induced.

SUMMARY OF THE INVENTION

[0010] The present invention provides an improved crank structure for a treadmill, whereby, when the pedals and the linked ends of the cranks are moved to the uppermost position of the rotary wheel, a pushing force can be easily formed, this can prevent inadvertent damage of sporting.

[0011] To get the above stated object, the present invention mainly makes the cranks thereof bent, the first section of each of them is set to form a angle with the vertical diametric line of a rotary wheel; at the tailing end of the first section, there is a bent section for connecting with the center of the rotary wheel. With this, the inclining component of the weight “W” along the first section times the arm of force, namely, the distance from the center line of the first section to the center of the rotary wheel, to form a torque to push the crank away from the uppermost position of the rotary wheel.

[0012] The present invention will be apparent in its novelty and features after reading the detailed description of the preferred embodiment thereof in reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a schematic view showing the crank mechanism of a conventional treadmill and its motion in operation;

[0014] FIG. 2 is a schematic view showing the mechanism on one side and its motion in operation of the treadmill as shown in FIG. 1;

[0015] FIG. 3 is a schematic view showing the forces exerting for the treadmill as shown in FIG. 1 and 2;

[0016] FIG. 4 is a schematic view showing the related mechanisms of the conventional chain wheel and pedals of a bicycle and their motions in operation;

[0017] FIG. 5 is a schematic view showing a man steps on the conventional treadmill as shown in FIG. 1;

[0018] FIG. 6 is a schematic view showing the mechanism and its motions in operation of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] Referring to FIG. 6, the present invention likewise has two pedals 100, 200 for stepping respectively of the left foot “L” and the right foot “R” of a user, the pedals 100, 200 respectively have one of their ends connected to the two sides of a rotary wheel 300 with a set diameter. The connecting ends of the pedals 100, 200 are respectively connected with one of the ends of each of two cranks 110, 220, the other of the ends of each of the two cranks 110, 220 are both connected with the center of the rotary wheel 300.

[0020] The present invention is characterized by that: the length of each of the cranks 110, 220 measuring vertically on the rotary wheel 300 equals to the radius “r” of the rotary wheel 300, and each of the cranks 110, 220 can be bent for a suitable angle. In the embodiment of the crank 110 shown in the drawing as an example, a first section 110a of the crank 110 connecting movably to the pedal 100 makes an included angle &thgr; with a vertical diametric line Cv of the rotary wheel 300, the tailing end of the first section 110a is bent to form a bent section 110b which connects with the center of the rotary wheel 300.

[0021] Such an improved design of crank will make generation of an inclining component “b” and another inclining component “c” perpendicular to the former component of a half of the weight “W/2” assuming the force provided by the user is the half of the weight “W/2”. For example, with the bending angle of the crank 110 shown in the drawing, the distance between the centerline of the first section 110a and the center “O” of the rotary wheel 300 is “d”, the inclining component “b” will get a torque b×d.

[0022] Assuming an angle &thgr; between the first section 110a and the vertical diametric line Cv of the rotary wheel 300 is 45 degrees, the weight of the user is “W”, the abovementioned torque should be:

∵b=cos45°×W/2=25(kg)

∴the torque M=25×d(the set length)=25d(kg-cm)

[0023] Thereby, the torque produced when the user stands on the pedal 100 or 200 is decided by the angle &thgr; between the first section 110a and the vertical diametric line Cv of the rotary wheel 300 as well as the distance “d” between the centerline of the first section 110a and the center “O” of the rotary wheel 300. By setting of the values &thgr; and “d” for the torque produced by the weight of the user at the uppermost position of the rotary wheel, &thgr; can be within 90 degrees, and are suitably within 30° to 60° and is most preferably 45° as shown in the drawing. And the first section 110a is orthogonal to the bent section 110b (when the included angle between the two is 90°, the longest arm of force can be obtained).

[0024] With the above stated improved design of the cranks 110, 220, when the crank 110 or 220 arrives at the uppermost position of the rotary wheel 300, the torque produced by the weight “W” of the user will render the rotary wheel 300 very easy to rotate away from the uppermost position to a neighboring area thereof. In stepping, only an extreme small horizontal action force “P” is needed from the user to make the rotary wheel 300 get away from the uppermost position to go on rotate. The user needs only to exert a small force at the uppermost position for stepping; this can prevent probable damage of exercising with such a treadmill.

[0025] The embodiment cited above is only for illustrating a preferred embodiment of the present invention. It will be apparent to those skilled in this art that various modifications or changes can be made to the elements of the present invention without departing from the spirit and scope of this invention. Accordingly, all such modifications and changes also fall within the scope of the appended claims and are intended to form part of this invention.

Claims

1. An improved crank structure for treadmills, each of said treadmills has two pedals for a user to step, said pedals respectively connect on one of their ends with the periphery of a rotary wheel, and are linked with cranks respectively on the front and the rear sides of said rotary wheel, said cranks are connected on their internal end portions with the center of said rotary wheel, said crank structure is characterized by that: said cranks are provided each with a first section which has an included angle with the vertical diametric line of said rotary wheel, at the tailing end of said first section, there is a bent section for connecting with the center of said rotary wheel.

2. An improved crank structure for treadmills as claimed in claim 1, wherein, said first sections of said cranks each has an included angle of within 90° with said vertical diametric line of said rotary wheel.

3. An improved crank structure for treadmills as claimed in claim 1, wherein, said first sections of said cranks each is perpendicular to the corresponding one of said bent sections.