ES2617959A1 - Loading means for weight machines (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Load medium of the type used in weight machines. The load means incorporates two curved guides (1a, 1b) arranged symmetrically and whose outer faces define respective raceways (11a, 11b) on which two rollers (3a, 3b) can move. The axes (4a, 4b) of said rollers (3a, 3b) are joined together by an extension spring (5). Two tie rods (6a, 6b) join the axes (4a, 4b) of respective rollers (3a, 3b) with a charging cable (8). The geometry of the curve defined by the raceways (11a, 11b) is such that the external force applied on the load cable (8) is the same regardless of the position in which the rollers are (3a, 3b). (Machine-translation by Google Translate, not legally binding)

Description

CARGO MEDIA FOR MUSCLE MAIN

SECTOR OF THE TECHNIQUE

The present invention generally relates to weight training machines and, more particularly, to the loading means incorporated by said machines.

BACKGROUND OF THE INVENTION

Weight training machines typically have loading means based on the lifting of masses (weights). The movement of the user's arms or legs is usually transmitted by some mechanism to a cable, the

which, redirected by one or several pulleys, allows the lifting of one or several weights fixed to its end. Thus, in order to perform the movement, the user must exert the necessary force to lift the total weight supported by the cable

This type of machines, based on the use of weights as a means of loading, allow the connection of a variable number of them to modify the level of force necessary to perform the exercise. Some machines have a number of weights that add up to a total mass of more than 100 kg, which can be inconvenient if you need to transport or change the location of the machine.

A consequence of the use of these weights as a means of loading is that the force exerted by the user when performing the exercise will depend on the speed with which it is performed and, more specifically, on the acceleration acquired by the weight at each moment . This is due to the inertial component that has a mass that does not move at constant speed, that is, that has acceleration. Thus, for example, to start the movement it is necessary to accelerate the weight and therefore a greater force is required than at a later time when the weight can be moved at a constant speed. In the same way, in the final part of the exercise, the weight will decrease its speed until it stops, which means a negative acceleration and a lower force exerted by the user. Consequently, the force exerted by the

user will be variable throughout the exercise since the speed of the weight will not be

constant.

This described behavior may not be desirable in some cases, with a load medium where the force to be applied by the user is constant throughout the entire movement, regardless of the speed at which the exercise is executed. A solution to this problem is to eliminate moving weights or masses from the loading medium. In this sense, solutions have been proposed that replace the weights with other devices that ensure that the force exerted by the user is constant throughout the entire exercise, although they are usually quite complex. Most solutions are based on the use of springs, such as US patents 6685602, US 4231568, US 6958032 and US 2005/0181915. US 7677540 gives various solutions to the problem of obtaining a constant force from a linear extension spring, all based on the use of variable radius pulleys. Other loading means for weight training machines that achieve approximately constant force are based on pneumatic systems.

The present invention is proposed as an alternative to the loading means for existing weight training machines and aims to give a new solution to the technical problem of achieving a constant force. In this case, the loading means object of the present invention incorporates a mechanism with a linear extension spring, arranged so that the level of constant loading is achieved regardless of the speed at which the exercise is performed.

EXPLANATION OF THE INVENTION

Loading medium for weight training machines. The invention object of the present specification refers to a charging means, between those loading means intended to be used in weight training machines and that allow to maintain a constant load level during the exercise.

This invention characterizes a special means of loading that allows to maintain constant the level of load in the weight training machine, regardless of the speed and acceleration at which the user makes the movements during the exercise.

The loading means object of the present invention comprises a flat and symmetrical mechanism with respect to its middle axis, consists of two rigid and equal curved guides, facing each other and placed one on each side of the axis of symmetry. Both guides are in solidarity with a fixed base, which will be firmly anchored to the weight training machine. The outer face of both curved guides is smooth and serves as a track for two rollers in rolling contact with said guides. The axes of both rollers are coupled to each other through an extension spring. This spring is arranged perpendicular to the axis of symmetry and keeps the rollers in contact with individual raceways. In addition, two cables are attached to the axis of both rollers as braces, which join together at a point contained in the axis of symmetry of the mechanism. Both braces are pulled by a charging cable coinciding with the axis of symmetry. This charging cable will be operated by the user of the weight training machine on which the charging medium will be mounted.

The curvature and arrangement of the curved guides are such that the separation between the two knees increases as they are displaced by the action of the straps, while the force exerted by the spring opposes the movement. For a spring and a given length of braces, a geometry for the curved guides can be determined for which it is fulfilled that the force applied on the load cable, necessary to maintain the static balance, is the same for any point in the that the rollers are located on said curved guides; where the greater the elongation of the spring, the smaller the slope of the curved guides should be, said slope taken with respect to the axis of symmetry of the mechanism. The geometry of the curved guides can be determined by resolving the balance of forces shown in Figure 4, and imposing that the force F applied on the charging cable be kept constant

Figure 4 shows the force diagram for any position of the rollers on the curved guides. The force F applied on the load cable in the direction of the y-axis (the y-axis is defined coincident with the axis of symmetry of the mechanism) will give rise to a force F¡ on each value rod:

F

(')

F [= 02 -.- c-os-a

where a is the angle formed by each brace, of length ll 'with the y-axis.

Next, the static balance of forces acting on the axis of one of the rollers is proposed; the same result will be obtained for the other knee. Three forces will act on the axis of the roller: that exerted by the tie rod (Ft), that exerted by the spring (F «), and the normal force to the contact surface between the roller and the guide

5 curve (N). The force exerted by the linear extension spring will be FK = 2 · K ·! J.x (2)

K being the spring stiffness constant and 2. you the total elongation of the spring, this measured as the difference between the solid length of the spring (2 · xo) and the current length (2 · x); being therefore:

I! Jx = X-Xo (3)

Posing the balance of forces according to the direction of the x-axis (perpendicular to the axis of symmetry) you get:

N. cos (i = FK + F,. without a (4)

Substituting in this expression the values of F, and FK given by Equations (1) and 15 (2), you arrive at: 1

N. cos f3 = 2. K. I! Jx + _. F. so to (5)

Where p is the slope of the curve that describes the axis of the roller ({3 = dxfdy). Posing now the balance of forces according to the direction of the y axis. N · sin, O = Faith · thing (6)

20 And replacing in this expression the value of F "is obtained: 1 F

N = - "- (7)

2 sinp

From the two equilibrium equations, substituting the value of the normal force N given by Equation (7) in Equation (5), we obtain:

1 F 1

-

"- = 2 · K · lJ.x + _. F · tan a (8)

2 tan p 2

Where clearing is reached the expression that determines the force F, which depends on the elongation of the spring (8X) and the slope p of the curve described by the axis of the roller: 1 -, F = 4 'K' l: Jx '(--- so a) (9)

so f3

5 Rearranging,

F 1 -} - = you '(--- tana) (10)

4 'K \ tan J1

Therefore, for a linear spring of constant stiffness, the force F applied on the charging cable will remain constant as long as the second term of Equation (10) is kept constant:

1 -, I> x '(--- tan a) == cte (11)

Tanp 10 being:

I1x = x

xo

dx

p ~

dy

x

a = arcsin 1;

Thus, for given values of F and K, the sequence of values of x and y that give

15 solution to Equation (10) define the curve (x, y) that the roller axis must describe so that said force F, applied on the load cable, remains constant Finally, the geometry of the curved guide on which wheel the roller can be deduced from the curve (x, y) described by the roller axis

On the other hand, given a curve (x, y) that complies with Equation (11), of the first member of Equation (10) it is established that the value of the constant force F will be directly proportional to the value of the constant of rigidity of the spring K. In this way, the load level (force F) can be modified by replacing the spring with another of equal solid length but with different stiffness constant. Having a

25 set of interchangeable springs with different stiffness constants, you can select the load that best suits the needs of each user.

Traction springs are usually present at the beginning of their elongation a small section in which the stiffness is not exactly constant. to later enter a wide stretch of elongation in which said stiffness does remain constant. To prevent the spring from working on this initial stretch of the extension, stops are provided on the curved guides, which prevent the free movement of the rollers and provide the spring with a small initial extension or preload.

The present invention is preferably oriented to its use in weight training machines, but it also has application in other machines or mechanisms that incorporate some means of loading based on counterweights, such as some garage doors.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood with reference to the following drawings illustrating preferred embodiments of the invention, provided by way of example, and which should not be construed as limiting the invention in any way.

Figure 1 shows a schematic view with a possible embodiment of the charging means according to the present invention; Figure 2 shows a section according to line A-A of Figure 1: Figure 3 shows a schematic view of the charging means when it has been put into operation; Figure 4 shows the force diagram when the loading medium has entered into operation.

PREFERRED EMBODIMENT OF THE INVENTION

In view of the foregoing, the present invention relates to a means of loading from among those used in weight training machines. It is essentially characterized by incorporating two equal curved guides (1 a, 1 b), facing each other and placed in a manner symmetric The load medium is symmetric with respect to an axis of symmetry y-y '. The curved guides (1a, 1b) are rigid and in solidarity with a base piece (2) that will be firmly fixed to the weight training machine. The outer faces of both curved guides (1 a, 1 b) define each raceways (11 a, 11 b) on which two rollers (3a, 3b) are arranged in rolling contact. The shafts (4a, 4b) of both rollers (3a, 3b) are linked together by means of an extension spring (5), so that the rollers (3a, 3b) are pressed against the raceways (11a, 11b) . To the axes (4a, 4b) are also attached two braces (6a, 6b), which are joined together at a point of attachment

(7) contained in the axis of symmetry y-y '. To said junction point (7) a charging cable (8) is also fixed, which is at all times coinciding with the axis of symmetry Yy '. When the charging cable (8) is operated by an external force, it causes the rollers (3a, 3b) to move on the raceways (11 a, 11 b) and therefore the extension of the extension spring (5), where the separation between both rollers (3a, 3b) grows as they move on the raceways (11 a, 11 b).

The curved guides (la, 1 b) have two stops (12a, 12b) for the rollers (3a, 3b), so that the extension spring (5) maintains a small elongation when no force is exerted on the cable load (8).

The raceways (11a, 11b) of two curved guides (the, lb) have a variable curvature, their geometry being defined so that the force exerted on the load cable (8), necessary to keep the mechanism in balance, It is always the same for any point where the rollers (3a, 3b) are located on said raceways (11a, 11b). It is true that the value of the slope

at a point on the curve defined by the raceways (11 a, 11 b), said slope relative to the axis of symmetry y-y ', is smaller the greater the elongation experienced by the spring (5).

It does not alter the essentiality of this invention, variations in materials, pharma, size and arrangement of the component elements, described in a non-limiting manner, it being sufficient to proceed to its reproduction by an expert

Claims (2)

one.

Loading medium, of the type used in weight training machines, essentially characterized by incorporating two curved guides (1 a, 1 b) placed symmetrically with respect to an axis of symmetry y-y '. The curved guides (la, 1b) san solidarity with a base piece (2) that will be fixed to the weight training machine. The outer faces of the curved guides (the, lb) define each raceways (11a, 11b) on which two rollers (33, 3b) can move. The axes (4a, 4b) of said rollers (3a, 3b) are joined together by an extension spring (5). To the axes (4a, 4b) an end of two braces (6a, 6b) is attached, the other two ends are joined together at a junction point (7) contained in the axis of symmetry y-y ', A cable The load (8) coincides at all times with the axis of symmetry Y-Y ', one of its ends being fixed to the point of attachment (7). By exerting force on the other end of the charging cable (8), the charging means becomes operational, the rollers (3a, 3b) moving. The geometry of the curve defined by the raceways (11a, 11b) of curved guideways (1a, 1b), is such that the external force applied on the load cable (8) to maintain the balance is the same regardless of the position in which the rollers are located (3a, 3b).

2.

Loading means according to claim 1, characterized in that the curved guides (1a, 1b) have two stops (12a, 12b) that limit the movement of the rollers (3a, 3b), such that the extension spring (5) they maintain a small elongation when no force is exerted on the charging cable (8).