CN108992080B

CN108992080B - Gravity balance mechanism

Info

Publication number: CN108992080B
Application number: CN201810551822.7A
Authority: CN
Inventors: 孙俊杰
Original assignee: Neusoft Medical Systems Co Ltd
Current assignee: Neusoft Medical Systems Co Ltd
Priority date: 2018-05-31
Filing date: 2018-05-31
Publication date: 2022-05-10
Anticipated expiration: 2038-05-31
Also published as: CN108992080A

Abstract

The invention provides a gravity balance mechanism which comprises a base, a fixed pulley and a reversing pulley which are fixed on the base, a sliding block which slides relative to the base, an elastic part which is abutted against the sliding block, a moving pulley which is fixed to the sliding block, a pair of connecting rods which are connected with the moving pulley, a pair of side pulleys which are respectively connected with the connecting rods, and a steel wire rope which is wound around the reversing pulley, the side pulleys, the moving pulley and the fixed pulley.

Description

Gravity balance mechanism

Technical Field

The invention relates to the technical field of medical machinery, in particular to a gravity balance mechanism in DR equipment.

Background

DR (digital radio) equipment is a short name of a digital direct imaging system, and has the advantages of clearer image, lower radiant quantity, higher inspection speed, higher inspection success rate and the like compared with the traditional X-ray imaging. The image receiver on the bulb or the upright of the general DR equipment needs to move up and down along a straight line. In order to achieve labor-saving and stable manual lifting or electric lifting, a gravity balance mechanism is usually used for offsetting the gravity of the bulb or the image receiver, so that the movement is more labor-saving and the control is more convenient.

The general gravity balance mechanism can counteract gravity in the following ways:

firstly, the counter weight is balanced, offsets the gravity of bulb image receiver with the counter weight of same quality or multiple quality, and the advantage is that vertical state gravity can offset accurately, and the shortcoming is that the counter weight quality itself is great, and the counter weight need with lift object simultaneous movement, the complicated and stroke of structure is restricted.

Secondly, adopt the reducing pulley, convert extension spring's power into relatively steady output power, the shortcoming is when extension spring's output power is great, and own structure size can follow grow, and the structure receives very big restriction, leads to output power to be restricted.

Thirdly, a spring balancer is adopted, and the spring balancer is used for outputting relatively stable force by utilizing the curling and loosening of the coil spring and matching with the diameter-variable pulley, so that the spring balancer has the advantages of compact structure, short service life and limited output force, and is generally only used for counteracting the condition of small gravity.

Disclosure of Invention

The invention provides a gravity balance mechanism with long stroke and stable output force value.

Further, the gravity balance mechanism comprises a plurality of elastic pieces which are arranged in series or in parallel.

Further, the elastic member is a general linear spring.

Further, the elastic member is a gas spring.

Further, opposite ends of the gas spring are fixed to the slider and the base, respectively.

Further, the base is provided with a vertically extending recessed groove, the gravity balance mechanism is provided with a slide rail located in the recessed groove, and the slide block slides along the slide rail.

Further, the moving sheave and the side sheave have the same diameter.

Furthermore, the reversing pulley, the side pulley, the moving pulley and the fixed pulley comprise a plurality of grooves.

Furthermore, the steel wire rope is accommodated in the groove, and the number of turns of the steel wire rope wound on the reversing pulley, the side pulley, the moving pulley and the fixed pulley is more than or equal to 1.

Furthermore, the base is provided with an accommodating groove for accommodating the reversing pulley, and the accommodating groove is close to the fixed pulley.

The gravity balance mechanism of the invention converts the output force and the movement stroke of the elastic part changing along with the compression amount into the output force with stable force value and doubled stroke through a group of dynamic pulley mechanisms, and is used for balancing the gravity of the lifting object.

Drawings

Fig. 1 is a perspective view of a gravity balance mechanism according to an embodiment of the present invention.

Fig. 2 is a perspective view of the moving pulley of the gravity balance mechanism shown in fig. 1 in a first position.

Fig. 3 is a perspective view of the moving pulley of the gravity balance mechanism shown in fig. 1 in a second position.

Detailed Description

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the invention, as detailed in the appended claims.

The gravity balance mechanism of the present invention will be described in detail with reference to the accompanying drawings.

Referring to fig. 1 to 3, the gravity balance mechanism of the present invention includes a base 1, a fixed pulley 2 fixed on the base 1, a diverting pulley 3 and a linear slide rail 4, a slide block 5 sliding on the linear slide rail 4, an elastic member 6 abutting against the slide block 5, a moving pulley 7 fixed to the slide block 5, a pair of connecting rods 70 connected to the moving pulley 7, a pair of side pulleys 8 connected to the connecting rods 70, and a wire rope 9 winding the diverting pulley 3, the side pulleys 8, the moving pulley 7 and the fixed pulley 2. The elastic element 6 is used for outputting force and stroke. In this embodiment, the elastic member 6 is a gas spring, and opposite ends of the gas spring are fixed to the slider 5 and the base 1, respectively, but the invention is not limited thereto, and the elastic member 6 may also be a common linear spring. In the present embodiment, only one elastic member 6 is provided, but the present invention is not limited thereto, and the gravity balance mechanism of the present invention may be provided with a plurality of elastic members 6 connected in series or in parallel.

The base 1 is provided with a recessed groove 10 extending in a vertical direction, a pair of guide grooves 11 located at both sides of the recessed groove 10, and a receiving groove 12 adjacent to the fixed pulley 2. The linear slide rail 4 is positioned in the concave groove 10. The diverting sheave 3 is accommodated in the accommodating groove 12 to change the direction of the wire rope 9.

The fixed pulley 2 is fixed to the base 1 by a first shaft 21, the moving pulley 7 is fixed to the slider 5 by a second shaft 71, and the pair of side pulleys 8 are fixed to the connecting rod 8 by third shafts 81, respectively. The fixed sheave 2 is rotatable about the first shaft 21. The fixed pulley 2 is located directly below the moving pulley 7. The moving pulley 7 can move on the linear slide 4 along with the sliding block 5 and can rotate around the second shaft 71. The pair of guide grooves 11 is symmetrically arranged with respect to the gas spring. The pair of side pulleys 8 is rotatable about the third shaft 81, and the third shaft 81 slides in the guide groove 11 and contacts the side wall of the guide groove 11. The connecting rod 70 is rotatable about the second shaft 71 and the third shaft 81, ensuring that the distance between the moving pulley 7 and the side pulley 8 is constant. The reversing pulley 3, the side pulleys 8, the moving pulley 7 and the fixed pulley 2 are provided with a plurality of grooves 31 for accommodating the steel wire rope 9. The moving pulley 7 and the side pulley 8 have the same diameter.

The principle of the gravity balance mechanism of the invention is as follows:

the moving pulley 7 moves linearly together with the gas spring, and the pair of side pulleys 8 are connected to the moving pulley 7 through the connecting rod 70 and move along the guide groove 11. The distance l (ab) between the moving pulley 7 and the side pulley 8 is a set constant value, and the distance l (ac) between the moving pulley 7 and the fixed pulley 2 is a variable value, and an initial value is determined.

A connection line between the first shaft 21 and the second shaft 71 is defined as a first connection line, a connection line between the third shaft 81 and the second shaft 71 is defined as a second connection line, and a connection line between the first shaft 21 and the third shaft 81 is defined as a third connection line, wherein an included angle between the first connection line and the third connection line is defined as α, an included angle between the first connection line and the second connection line is defined as β, an angle value of α and β changes with movement of the moving pulley 7, and a magnitude of the angle value of α and β is determined by the guide groove 11.

It is defined that the contact angle coefficient of the third shaft 81 of the side pulley 8 with the side wall of the guide groove 11 at a certain position is K. K is defined as a ratio of a moving speed in a direction perpendicular to the first connecting line to a moving speed in a direction parallel to the first connecting line when the side pulley 8 moves along the guide groove 11 at a certain position, and is a variable amount; k is the slope of the contact of the side wall of the guide groove 11 with the third shaft 81 of the side pulley 8. The reaction force of the side wall of the guide groove 11 against the contact surface of the third shaft 81 of the side pulley 8 is determined.

Assuming a stable force F (wire rope) output by the wire rope 9, the size of each position of the wire rope 9 is uniform. The movable pulley 7 receives a force F (a) ═ 2 × F (wire rope) × COS β from the wire rope 9, and the direction is parallel to the direction of the first connection line; the side sheave 8 receives a resultant force F (b) of the forces of the wire rope 9 and the side wall of the guide groove 11 in the direction of the first connection line, which is 2 (F (wire rope) · COS α -F (wire rope) · COS β) + (F (wire rope) · SIN β + F (wire rope) · SIN α) ·. The combination of the movable sheave 7 and the side sheave 8 receives a resultant force F (a + B resultant force) parallel to the direction of the first connection line, which is 2 × F (wire rope) COS β +2 × F (wire rope) COS α -F (wire rope) COS β) +2 × F (wire rope) SIN β + F (wire rope) SIN α), which is 2 × F (wire rope) (COS α + K SIN β + K SIN α).

The force F (gas spring) of the gas spring can be approximated as F1+ kS, where F1 is the initial force of the gas spring, is the set value, lower case k is the calculated spring coefficient of the gas spring, is the specified value for a certain type of gas spring, and S is the compression length, depending on the characteristics of the gas spring. The resultant force of F (a + B) is made to be F (gas spring), that is, 2 × F (wire rope) (COS α + K + SIN β + K + SIN α) is made to be F1+ kS, to obtain F (wire rope) ═ F1+ kS)/(COS α + K SIN β + K + SIN α)/2. For each position, α angle (ATAN) (l (ab) · SIN β/(l (ac) — l (ab) · COS β)), and β corresponds to α when l (ac) value is constant, according to trigonometric function α being a correlation function using β as a variable.

Meanwhile, L (AC) ═ L (AC initial length value) -S, it is possible to obtain F (wire rope) ═ F1+ kS)/(COS (ATAN (L (ab) × SIN β/(L (AC) -L (ab) × COS β))) + K × SIN β + K × SIN (ATAN (L) (ab) × SIN β/(L (AC) -L (ab)))/COS β)))/2, that is, F (wire rope) corresponds to angle β at a certain amount of compression S of the air spring. That is, in each S value, the force of the F (steel wire rope) can be substantially consistent by adjusting the magnitude of β, so as to achieve the purpose of stable output force. The movement locus of the side pulley 8 can be obtained from β obtained by the above correspondence.

As shown in fig. 3, as the gas spring is compressed, the distance l (ac) between the fixed sheave 2 and the moving sheave 7 becomes shorter, and the angle β also changes. The value of β is ensured by the movement of a pair of side wheels 8 along the guide grooves 11. So that the requirement of F (steel wire rope) is a stable force value.

The gas spring of the gravity balance mechanism of the invention can also be a linear spring with the initial force of F1 and the constant elastic coefficient k.

The following describes the conversion of the changing linear force output by the gas spring into a stable output force by the gravity balance mechanism according to the present invention through calculation data.

Assuming that the output force of the steel wire rope 9 is required to be 418N, the initial force F1 of a linear spring is selected to be 800N; the stroke is 200 mm. The characteristic value of the selected gas spring is 1.35 in a stroke of 200mm, and in the case of a general linear spring, the elastic coefficient k is 1.15, the distance L (AC initial) between the moving sheave 7 and the fixed sheave 2 is 600mm at the beginning, and the distance L (ab) between the moving sheave 7 and the side sheave 8 is 200 mm. The number of turns of the steel wire rope 9 wound on the reversing pulley 3, the side pulley 8, the moving pulley 7 and the fixed pulley 2 is 1. The value of F (wire rope) is calculated from the above formula of F (wire rope), as shown in the following table, corresponding to β from 40 ° to 21 °, F (wire rope) can be guaranteed to be approximately 403.5 (the first number is ignored, the contact angle coefficient K value is an estimate), the force changes from 800 to 1030 over a 200mm stroke relative to the gas spring, the output force change rate is small, and the output distance becomes 400 mm.

The calculation accuracy is influenced by the number of the points and the value taking precision, and the more the number of the points is taken, the more the value is taken, and the more accurate the calculation is. Therefore, various desired stable output forces can be obtained by different types and designs. The movement track of the side pulley 8 ensures that the changed linear force output by the gas spring is converted into the output force with stable size.

In this embodiment, the steel wire rope 9 wound around the reversing pulley 3, the side pulley 8, the moving pulley 7 and the fixed pulley 2 is a circle, but the invention is not limited to this, and the gravity balance mechanism of the invention can be provided with n circles (n >1) of the steel wire rope 9, so that the output force is reduced by n times, and the movement length of the steel wire rope is increased by n times.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A gravity balance mechanism is characterized by comprising a base, a fixed pulley and a reversing pulley which are fixed on the base, a sliding block which slides relative to the base, an elastic part which is abutted against the sliding block, a moving pulley which is fixed to the sliding block, a pair of connecting rods which are connected with the moving pulley, a pair of side slipping wheels which are respectively connected with the connecting rods, and a steel wire rope which is wound on the reversing pulley, the side slipping wheels, the moving pulley and the fixed pulley, the fixed pulley, the moving pulley and the side pulley are respectively fixed through a first shaft, a second shaft and a third shaft and can respectively rotate around the first shaft, the second shaft and the third shaft, the base is provided with a pair of guide grooves which are symmetrically arranged relative to the elastic piece, the third shaft is in rolling contact with the side wall of the guide groove, and the connecting rod can rotate around the second shaft and the third shaft.

2. The gravity balance mechanism according to claim 1, wherein the gravity balance mechanism comprises a plurality of elastic members arranged in series or in parallel.

3. A gravity balance mechanism according to claim 1 or 2, wherein the resilient member is a generally linear spring.

4. A gravity balance mechanism according to claim 1 or 2, wherein the resilient member is a gas spring.

5. The gravity balance mechanism according to claim 4, wherein opposite ends of said gas spring are fixed to said slider and said base, respectively.

6. The gravity balance mechanism according to claim 5, wherein the base is provided with a vertically extending recessed groove, the gravity balance mechanism is provided with a slide rail located in the recessed groove, and the slide block slides along the slide rail.

7. The gravity balance mechanism of claim 1, wherein the moving sheave and the side sheave are the same diameter.

8. The gravity balance mechanism according to claim 1, wherein the diverting pulleys, side pulleys, moving pulleys and fixed pulleys comprise grooves.

9. The gravity balance mechanism according to claim 8, wherein the wire rope is accommodated in the groove, and the number of turns of the wire rope wound around the reversing pulley, the side pulley, the moving pulley and the fixed pulley is greater than or equal to 1.

10. The gravity balance mechanism according to claim 1, wherein said base is provided with a receiving groove for receiving said diverting pulley, said receiving groove being adjacent to said fixed pulley.