HINGE MECHANISMS

Abstract: A hinge mechanism for allowing relative pivotal movements between first and second members (5, 3), of the hinge mechan­ ism comprising a third hinge element (13) pivotally attached to said first member (5) at a first point (15), a second hinge element (27) pivotally attached to the second member (3) at a second point (29), said second hinge element also being pivotally attached to said first hinge element at a third point (25), and there being provided means (21) for applying a force to a fourth point (17) lying on such first hinge element (13) said third point lying between said first and fourth points between one-third and two-­ thirds of the distance between the two. The hinge is capable of maintaining a substantially constant output torque over 180° of operation and is useful in artiticial or prosthetic or robot limbs, elevated platforms, mechanical excavators, diggers or loaders.

Description: HINGE MECHANISM The present invention relates to hinge mechanisms, especially powered hinge mechanisms. There are applications where it may be desired for two members to be hinged in such a manner that relative pivotal movement of the two members may be actuated by means of a single force applied to one or both of the members. Examples of such applications are in industrial robot arms, artificial limbs, and arms of, for instance, mechanical diggers or excavators, loaders, and elevator platforms used, for example, for lifting workmen into normally inaccessible places. Common hinge mechanisms of this type may use either a linear actuator or a rotary actuator. The rotary actuator is capable of allowing a large degree of relative pivotal motion between the two members with substantially equal torque over the whole of the pivotal range. However, such rotary actuators are generally expensive and are often more complex than the linear actuators. The known hinge mechanisms using linear actuators such as hydraulic piston and cylinder arrangements, allow a relatively limited range of pivotal movement between the two members, with the torque provided at the hinge varying considerably with the angle between the two members According to the present invention there is provided a hinge mechanism for allowing relative pivotal movement between a first and second member, the hinge mechanism comprising a first hinge element pivotally attached to said first member at a first point, a second hinge element pivotally attached to the second member at a second point, said second hinge element also being pivotally attached to said first hinge element at a third point, and there being provided means for applying a force to a fourth point lying on said first hinge element, said third point lying between said first and fourth point between one third and two thirds of the distance between the two. Preferably said force is applied to said second hinge element by means of a linear actuator mounted on said second member. More preferably said actuator is hydraulically, pneumatically or electrically operated. Most preferably said linear actuator is a piston and cylinder arrangement. Preferably said hinge elements are substantially elongate bars. Preferably said first, third and fourth points lie on a substantially straight line. Said third point lies between positions from one-third to two-thirds along a line between said first point and said fourth point and preferably said third point lies at half way along the line between said first point and said fourth point. The first and second members are pivotally attached to one another at a fifth point, either directly or, for example, through a third hinge element pivotally connected to said second member at a fifth point and rigidly attached to said first member at a sixth point. Preferably said means for applying the force to the fourth point are such that said force is applied in a direction substantially parallel to a line interconnecting the pivot centre between the first and second members (the fifth point) and the pivot centre between the second member and the second hinge element (the second point). Preferably the distance A between said first and fourth points on said first element is from two to six times the distance 3 between the fifth and first points. More preferably the distance A on said first element is between three and five times the distance 3. Most preferably the distance A is three, four or five times the distance 3. Preferably the distance C between the second and third points on the second hinge element is from one to three times the distance 3. More preferably the distance C is from 1.5 to 2.5 times the distance 3. Most preferably the distance C is 1.5, 2.0 or 2.5 times the distance 3. Preferably the distance D between the fifth point on the second member and the second point on said second member is from one to three times the distance 3. Preferably the distance D is from approximately from 1.414 to 2.0 times the distance 3. Most preferably the distance D is 1.414, 1.732, or 2.0 times the distance 3. Preferably the distance H perpendicularly from the plan in which the linear force is applied to the first hinge element to the second point on said second member is from one to five times the distance 3. More preferably said distance H is from 1.5 to four times the distance 3. Most preferably the distance H is 1.9, three or four times the distance 3. A hinge mechanism according to the present invention allows a range of pivotal movements between two members up to or greater than 180 , with a substantially uniform torque output over the whole range of movement. Alternatively dimensions can be selected as indicated later to give maxaam torque either at mid-range or at t 900 measured from the mid-position Preferably the distance ; ; relative to said second member, of which said fourth point may be displaced by said substantially linear force is from two to five times the distance 3. More preferably the distance F is from 2.828 to 4.0 times the distance 3. Most preferably the distance F is 2.826, 3.464 or 4.00 times the distance 3. Preferably said first and second members form parts of artificial or prosthetic or robot limbs, elevator platforms, or mechanical excavators, diggers or loaders. The invention will be described further by way of example with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic representation of a hinge mechanism in accordance with the invention; Figure 2 is a diagrammatic representation of an elevated platform equipped with hinge mechanisms in accordance with the invention; Figure 3 is a diagram showing S possible linkages for a hinge mechanism of the invention; Figure 4 is a graph of torque against angle for the linkages of figure 3; Figure 5 is a diagrammatic representation of another embodiment of elevated platform equipped with hinge mechanisms in accordance with the invention; and Figure 6 is a view of a robot arm incorporating hinges according to the invention. Referring now to figure 1, a hinge mechanism indicated generally by 1 in accordance with the present invention comprises a first member 5 and a second member 3 pivotally attached together by means of a third element 7 fixedly attached at 9 to the member 5 and pivotally attached at 11 to the member 3. The first member 5 is thus able to pivot relative to the second member 3 about the pivot point 11. A first hinge element 13, hexinafter referred to as a 'coupler', is pivotally attached by pivot pin 15 to the first member 5 and by pivot point 17 to the end of a piston 19 of a hydraulic linear actuator 21. The end of the actuator 21 remote from the piston 19 is connected to a projection struck up from the second member 3 by means of a pivot pin 23 passing through the end of the actuator 21. At the mid point of the first hinge element 13 is connected by means of a pivot pin 25 one end of a second hinge element 27, hereinafter referred to as a 1rockery. Eheother end of the rocker 27 is pivotally connected by means of a pivot pin 29 to the second member 3. Tn use, the relative dispositions and dimensions of the elements of the hinge mechanism 1, as described more fully hereinafter,are such that the movement of the piston 19 of the linear actuator 21 causes pivotal movemement of the elongate member 5 relative to the elongate member 3 about the pivot point 11. The range of the pivotal movement is from 0o to 1800 between the first and second members 5 and 3 respectively illustrated in figure 1 as positions 5a and Sb respectively. A hinge mechanism such as that shown in figure 1 may be used in many applications with variations of materials, sizes and actuators. A suitable application may be, for instance, for industrial robot arms, or similarly for artificial or prosthetic limbs for humans. However, in the latter application it may be adventageous for the linear actuator to be situated within the outer surface of the elongate members so as not to be conspicuous. With suitably strengthened components, a hinge mechanism according to the present invention could be used in heavier industrial situations such as, for instance, for elevator platforms. Such an elevator platform is shown in Figure 2 of the accompanying drawings. The elevator platform comprises a rotatable base 31, the base being rotatable in a horizontal plane, to which is pivotally connected at pivot 43 a first elongate member 33. At the end of the first elongate member 33 is pivotally connected a second elongate member 35. At the remaining end of the second elongate member 35 is pivotally connected a support platform 37 which may, for instance, carry men or other apparatus. All the pivots in the elevator platform arrangement are disposed so as to allow the platform to be pivoted in a vertical plane. Thus various heights and positions can be achieved by the combined rotation of the base 31 and the relative pivoting of the elongate members between the member 35 and 33 and 35, the support platform 37. The pivots 43 and 41 could in such an arrangement advantageously utilise hinge mechanisms according to the;present invention, where the increased pivotal movement allowed by such hinges would allow the elevator platform arrangement to be more flexible and to have a greater range of operation, The pivot controlling the support platform 37 is also controlled by a hinge mechanism according to the present invention or, in an alternative embodiment, is related to the movement of the remaining pivots 43 and 41 by means of a series of parallelogram linkages. Figure 5 of the accompanying drawings shows an elevator platform arrangement using the parallelogram linkages mentioned above. The arrangement is mounted on a substantially flat, circular base plate 151, which is rotatable about a vertical axis passing through the centre of the base 151. Projecting upwardly from the upper surface of the base 151 are two substantially parallel ears 153 and 155. The ears 153 and 155 are of different heights, ear 155 being taller than ear 153. Lying between the ears 153 and 155 is a substantially horizontal pivot 157, positioned near the top of the shorter ear 153. An elongate arm 159 is pivotally connected by one of its ends 161 to the pivot 157, so that the arm 159 is free to move in a vertical plane. A power hinge mechanism 163 is arranged between the ears 153 and 155 so as to be capable of pivoting the arm 159 about the pivot 157 over a range of approximately 1800 from the horizontal Extending from, and pivotally connected to, the upstanding ears 153 and 155 are elongate arms 165 and 167. The arms 165 and 167 are of substantially equal length to the arm 159, and'lie parallel to the arm 159. The arms 165 and 167 are pivotable in the same vertical plane as the ar,m 159, about pivots 169 and 171 respectively. The pivots 169 and 171 lie in the same vertical plane, and are positioned on the ears 153 and 155, such that the planes passing through pivots 171 and 157, and through pivots 169 and 157, lie at an angle of 90 to one another. Angle s is preferably 90 but in alternative embodiments, angle B may be any desired angle, although small valves of angle B are not desirable when a range of arm movement of greater than approximately 1600. In addition, the plane passing through the pivots 169 and 157 lies at an angle A of 450 from the vertical, but in alternative embodiments angle A may be altered to any desired angle. The ends of the elongate arms 159, 65 and 167 remote from the base 151 are pivotally connected to an intermediate member 173. The member 173 comprises a pivot pin 177 substantially horizontally between the ends of two struts 173 and 175. The struts 179 and 175 are fixed substantially at right angles to each other and may be fixed to the pivot pin 177 although in alternative embodiments the angle B may be an angle other than gO , and the angle between the struts 179 and 175, is equal to angle 3, The end of the arm 159 is pivotally connected to the pivot pin 177, whilst the end of the arm 165 is pivotally connected at 181, near to the end of the strut 175 which is remote from the pivot pin 177, and the end of the arm 167 is similarly connected at 183 near to the corresponding end of the strut 179. Pivotally connected to the pivots 181, 177 and 183 are also ends of elongate arms 187, 189 and 191 respectively. The arms 187, 189 and 191 are of equal length and extend parallel Bel to one another. Associated with the member 159 and 189 is a power hinge mechanism according to the present invention arranged so that the angle between the corresponding arms 159 and 189 may be varied over a range of approximately 0o to 1800. Attached to the ends of the arms 187, 189 and 191,remote from the member 173, is a platform 193 upon which a man or other objects may stand. Projecting from the platform 193 are two substantially triangular ears 195 and 197 lying in substantially parallel vertical planes. Pivotally attached to the ear 197 at 203 is the end of the arm 187. and pivotally attached to the ear 195 at 199 is the end of the arm 191. Extending substantially horizontally between the ears 195 and 197 is a pivot pin 201, to which is pivotally attached the end of the arm 189. The pivots 199, 201 and 203 are arranged so that the plane passing through the pivots 199 and 201 lies at angle B, in this embodiment 90 , to the plane passing through pivots 203 and 201. In addition, the plane passing through pivots 203 and 201 lies at angle A to the vertical, angle A in this embodiment being 45 . In use the combination of the movements of the arms 159, 165 and 167, and 189, 187 and 191, actuated by the power hinge mechanisms 163 aid 185, allow a large degree of movement of the platform 193, whilst retaining the floor of the platform 193 in a horizontal orientation. In figure 6 there is illustrated the application of hinges in accordance with the invention to an industrial robot arm. The robot arm comprises a primary support member 10 mounted on a rotatable base 12;the support member 10 is connected to a first extension member 14 which is in turn connected to a second extension member 16 which is itself connected to a grip or tool member 20 in each case by a power hinge mechanism in accordance with the invention generally designated 22, 24, and 26 respectively. The operation of the hinge mechanism 22, 24 and 26 is substantially as previously described in relation to figure 1 and, by appropriate selection of the hinge parameters, as will be described more fully hereinafter in relation to configuration VIII in figure 3, relative displacement of adjacent members of up to 2700 is possible. Referring now to figures 3 and 4 of the drawings, figure 3 shows diagramatically eight alternative arrangements of a hinge mechanism in accordance with the invention. The lengths of the coupler and rocker elements are varied as well as the relative dispositions of the second and fifth points, In each case the third point is situated mid-way between the first and fourth points. Referring to both figures 1 and 3, for each of the cases I to VIII the distance A represents the length of the coupler, the distance 3 represents the separation of pivot points 11 and 15 which is maintained constant and set equal to unity. The length of the rocker 27 is indicated by C and the distance of the rocker pivot 29 frpm the pivot 11 is indicated by D. Finally, the height of the actuator pivot 17 above the rocker pivot 29, measured at values of 9 of + 90 , is indicated by E¯ The angle & is the angle between the first and second members 5 and 3 and is set at zero at the mid- point of the range of movement of the two members. Figure 4 then shows graphically the output torque for constant actuator torque plotted against output angle compared with the conventional hinge mechanism in which the actuator is merely connected across the two members pivotally attached together. In the table given below the various parameters are listed for the eight arrangements and these correspond with the eight curves shown figure 4. It can be seen from figure 4 that the output torque EMI11.1 <tb> <SEP> Crank <SEP> (3) <SEP> <SEP> = <SEP> 1 <SEP> <SEP> unit <SEP> <tb> <SEP> Rocker <SEP> Frame <SEP> Coupler <SEP> Height <SEP> Deviation <tb> <SEP> (C) <SEP> (D) <SEP> <SEP> (A) <SEP> (H) <SEP> (#H) <SEP> <tb> <SEP> I <SEP> 3 <SEP> 2.236 <SEP> 6 <SEP> 5 <SEP> + <SEP> 0.053 <tb> <SEP> II <SEP> <SEP> 2.75 <SEP> 2.121 <SEP> 5.5 <SEP> 4.5 <SEP> + <SEP> 0.029 <tb> <SEP> III <SEP> <SEP> 2.5 <SEP> 2 <SEP> 5 <SEP> 4 <SEP> + <SEP> 0.010 <tb> <SEP> 2.25 <SEP> <SEP> 1.871 <SEP> 4.5 <SEP> 3.5 <SEP> - <SEP> 0.035 <tb> <SEP> V <SEP> 2 <SEP> 1.732 <SEP> 4 <SEP> 3 <SEP> - <SEP> 0.078 <tb> <SEP> VI <SEP> 1.75 <SEP> 1.581 <SEP> 3.5 <SEP> <SEP> 2.5 <SEP> - <SEP> 0.136 <tb> <SEP> VII <SEP> 1.5 <SEP> 1.414 <SEP> 3 <SEP> <SEP> 2 <SEP> --0.218 <tb> VIII <SEP> <SEP> 1.25 <SEP> 1.225 <SEP> 2.5 <SEP> 1.5 <SEP> - <SEP> 0.359 <SEP> <tb> may be kept substantially constant throughout the operating range by suitable selection of parameters in, for example, configurations III, IV and V, or may be made to peak towards the extreme ends of its range as in, for example, VII and VIII. It will be seen that with the arrangement illustrated in VIII the range of operation of the device of the invention is approximately 270 , and a device having substantially these parameters may be employed at each of the hinge mechanism 22, 24 and 26 illustrated in the robot arm of figure 6. Hinge mechanisms in accordance with the present invention may thus have varying properties for different applications, whilst retaining the advantage of pivotal movements of 180 or more. Thus, as already mentioned, for some uses such as robotic arms the configuration having a wide range of movement may be advantageous while for other uses a more uniform torque against angle curve may be preferable. All of the components of hinge mechanism according to the invention may be of any suitable material such as metal and/or plastics material, and the linear actuator of the hinge mechanism may be electrical, pneumatic, hydraulic or of any other suitable form. As can be seen from the table above the deviation AH from the height H is relatively small and the actuator operates substantially parallel to a line drawn between the pivots 11 and 29 throughout the whole of its cycle. There is, of course, some deviation from this, and it is preferred to fix the height of the actuator pivot 23 at a height of the pivot EMI12.1 For man# torque at p = 0o the height of H - A H, whereas for maximmm torque at 9 = + 900 the height should be H.

Claims: CLAIMS: 1. A hinge mechanism for allowing relative pivotal movement between a first and second member, the hinge mechanism comprising a first hinge element pivotally attached to sail first member at a first point, a second hinge element pivotally attached to a second member at a second point, said second hinge element also being pivotally attached to said first hinge element at a third point, and there being provided means for applying a force to a fourth point lying on said first hinge element, said third point lying between said first and fourth points between one-third and two-thirds of the distance between the two. 2. A hinge mechanism as claimed in claim 1 in which said third point lies half way between the first and fourth points. 3. A hinge mechanism as claimed in either of claims 1 or 2 in which the third point lies on a straight line joining the first and fourtpoints. 4. A hinge mechanism as claimed in any of claims 1 to 3 in which the means for applying force is a linear actuator mounted on said second member. 5. A hinge mechanism as claimed in claim 4 in which the linear actuafior is hydraulically, pneumatically or electrically operated. 6. A hinge mechanism as claimed in any one of claims 1 to 5 in which said first and second members are pivotally attached to one another at a fifth point either directly or through a third hinge element pivotally connected to such second member at the fifth point and rigidly attached to said first member at a sixth point. 7. A hinge mechanism as claimed in claim 6 in which the means for applying the force to the fourth point are such that the force is applied in a direction substantially parallel to a -line interconnecting the said fifth point and the said second point. 8. A hinge mechanism as claimed in claim 6 or 7 in which the distance A between said first and fourth points is from two to six times the distance 3 between the said fifth and first points. 9. A hinge mechanism as claimed in any of claims 6 to 8 in whirl the distance C between the said second and third points is from one to three times the distance 3 between the said fifth and first points. 10. A hinge mechanism as claimed in any one of claims 6 to 9 in which the distance D between the said fifth and second points is from one to three times the distance 3 between the said fifth and first points. 11. A hinge mechanism as claimed in any one of claims 6 to 10 in which the distance H perpendicularly from the plane in which the linear force is applied to the first hinge element to the second point on the said second member is from one to five times the distance 3 between the said fifth and first points. 12. A hinge mechanism as claimed in claim 10 in which the stroke of the means for applying force is twice the distance D for a displacement of 1800. 13. An artificial, prosthetic or robot limb embodying one or more hinge mechanisms a claimed in any one of claims 1 to 12. 14. An elevated platform, mechanical excavator, digger or loader embodying one or more hinge mechanisms as claimed in any one of claims 1 to 12.

Inventors: BAKER, ALAN
Applicants: UNIVERSITY OF BRADFORD
Application year: 1982
Main classification: F16C11
IPC codes: B66F11, F16C11, B25J17, E02F3, B25J9