US3900113A - Apparatus for adjusting the relative inclinations of pivotable members - Google Patents

Abstract

This invention relates to apparatus for controlling the inclination of a pivotable member relative to a fixed structure, in particular the inclination of the jib of a crane. Control is effected by two jacks, each being connected by one end to the jib and by the other end to the body of the crane. The points of attachment of the jacks to the jib and the pivot axis of the jib define the vertices of two deformable triangles, one preferably being right-angled when the other has been flattened to a straight line. The lifting torque of a crane can thereby be substantially constant for all values of jib inclination.

Description

nite States Patent 11 1 Bourges 1 1 APPARATUS FOR ADJUSTING THE RELATIVE INCLINATIONS OF PIVOTABLE MEMBERS Bernard M. Bourges, Lagny Le Sec, France [75] Invento 173] Assignee: Societa Anonyme Poclain, Oise,

France 22 Filed: July 17, 1974 21 Appl.No :489,099

214/130 R, 77 R; 212/8 R, 8 A, 9, 35 R, 35 HC, 58 R, 58 A, 59 R, 59 A, 66; 91/210, 411 R, 413; 180/792 B; 254/124; 74/36, 128, 42,

[56] References Cited UNITED STATES PATENTS 2,841,231 7/1958 Armington ISO/79,2 B

[4 1 Aug. 19, 1975 Primary E.\'anzinerAlbert J. Makay Assistant ExuminerLawrence J. Oresky Attorney, Agent, or Firm-Fitzpatrick, Cella, Harper & Scinto [57] ABSTRACT This invention relates to apparatus for controlling the inclination of a pivotable member relative to a fixed structure, in particular the inclination of the jib of a crane. Control is effected by two jacks, each being connected by one end to the jib and by the other end to the body of the crane. The points of attachment of the jacks to the jib and the pivot axis of the jib define the vertices of two deformable triangles, one preferably being right-angled when the other has been flattened to a straight line. The lifting torque of a crane can thereby be substantially constant for all values of jib inclination.

PATENTEI] Am; 1 9197s SE'IET E OF 2 APPARATUS FOR ADJUSTING TI-IE RELATIVE INCLINATIONS OF PIVOTABLE IVIEMBERS This invention relates to apparatus for controlling the inclination ofa pivotal member on a fixed structure, for instance the jib of a lifting machine or a Public Works machine.

The jib of a hydraulic shovel is usually pivoted to a frame or turret thereof, and changes in the inclination of the jib are effected by a hydraulic jack connected be tween the jib and the turret. This jack is usually in the acute angle which the jib makes with the horizontal. The disadvantage of apparatus of this kind is that the torque applied at the foot of the jib, that is the point about which the jib is pivoted to the turret, is not constant. If the hydraulic pressure acting on the jack is constant, this torque is proportional to the length of the lever arm to the end of which a force is applied. This lever arm is equal to the distance between the point about which the foot of the jib is pivoted to the frame and the line of action of the jack. It is therefore variable by reason of movement of the jack with respect to this point. The variation in torque is substantially sinusoidal, which is a disadvantage as it limits the possible uses of the machine. It is in fact always more profitable to make a machine operate at the limits of its capabilities, and these are determined by its design and are represented more particularly by the rocking torque. The rocking torque is substantially constant, and with hith erto proposed machines it is impossible to operate very close to this torque at all positions of the jib.

According to the present invention there is provided apparatus for changing the inclination of a pivotal element, the element being pivotal about an axis with re spect to a fixed structure, the apparatus comprising a main jack connected between the structure and the element, and a secondary jack connected between the structure and the element, the main jack always being on the same side of said pivotal axis, the points of connection of the respective jacks to said structure and said element, and said pivotal axis constituting the vertices of two deformable triangles, the defonnable triangle of which one side is defined by the secondary jack being flattened to form a straight line when the deformable triangle of which one side is defined by the main jack is substantially right-angled at its vertex defined by the point of attachment of said main jack to said structure.

In a preferred embodiment of the invention said jacks are hydraulic and double-acting, and each chamber thereof communicates with a circuit for distributing and returning a fluid under pressure, the communication being direct in the case of the main jack and through distribution and reversing means in the case of the secondary jack, said distribution and reversing means being controlled by detector means responsive to the position of the secondary jack with respect to said pivotal element.

In accordance with a further preferred embodiment of the present invention, said detector means comprises a lug rigid on an end portion of the secondary jack the lug being arranged to cooperate with a cam connected to the slide valve of the said distributing and reversing means, said cam being capable of assuming two stable positions under the action of said lug, the stable positions being maintained by resilient return means, the two stable positions corresponding respectively to positions of the secondary jack on one or other side of the line defined by the said flattened triangle.

One embodiment of the present invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 shows a hitherto proposed machine;

FIG. 2 shows graphically the variations in characteristic torques of a machine as shown in FIG. 1;

FIG. 3 shows an embodiment in accordance with the invention; and

FIG. 4 graphically shows the variations in characteristic torques of a machine including an embodiment as shown in FIG. 3. I

FIG. 1 shows a hydraulic shovel with a structure 1 consisting of a turret 1b rotatable on a frame la. A jib 2 on structure 1 is pivotal about an axis 3. Between jib 2 and structure 1 is ajack 4 which is connected to two pivot points 5 and 6, each of which being secured to one of the elements 2 and 1. In FIG. 1, the jib 2 is shown inclined at an angle A to the horizontal. A thrust force F, or a traction force F, applied to the jib 2 by the jack 4 causes the jib 2 to rotate about axis 3. The torque producing this rotation is equal to the product of the force F (or F) and the length l, which is the distance between axis 3 and the line of action of jack 4 (i.e. the direction of the force F or F).

Rotation of jib 2 about axis 3 causes rotation of jack 4 about pivot point 6, and this results in a change in the length l. The torque applied to the jib 2 by jack 4 is therefore variable, and FIG. 2 illustrates the manner in which it varies.

FIG. 2 has the angle A as abscissa and the value C of the moment of the force F with respect to the pivotal axis which is assumed to be constant, as ordinate. Curve 7 shows how this moment varies as a function of the angle A. It can be seen that this moment passes through a maximum value Cm for an angle of inclination A0 corresponding to a position of jib 2 such that the line of action of jack 4 is at right angles to the straight line joining axes 3 and 6. In this position, the length l is at a maximum. The curve 7 is limited to a maximum value Am for the angle A beyond which the jib cannot travel by reason of its construction. However, curve 7 extends into the region of negative values of A, because jib 2 can be inclined below the horizontal.

Curve 8 illustrates the variation in rocking torque Cb of the machine, applied to axis 3, as a function of the angle A. This torque can be regarded as constant.

FIG. 2 shows that with hitherto proposed machines as shown in FIG. 1, the potential maximum work permitted by its construction is not achieved, except when the inclination of the jib is close to A0. By increasing the hydraulic pressure in jack 4, that is to say the force -F, a curve such as 9 is obtained in which the central portion thereof is situated beyond the rocking torque Cb of the machine, and this is not allowable. The problem is therefore, not to increase the power of the jack 4 but to raise the extreme portions 7a and 7b of curve 7 which correspond to extreme angles of inclination of jib 2.

The embodiment shown in FIG. 3 causes a flattening of the curve 7. The foot of jib 2 is pivotal about shaft 3 which is rigid on structure 1. Jack 4 is connected at 5 and 6 between jib 2 and structure 1. A second jack 10 is connected between jib 2 and structure 1 at points 11 and 12 which constitute pivot points. Axes 5, 6 and 3 on the one hand, and 11, 12 and 3 on the other hand, constitute the vertices of two deformable triangles. Their positions with respect to each other are such that when jib 2 moves so that axis 11 takes up position 110, thus making the triangle 11, 12, 3 flat, the axis 5 takes up position 50 so that the triangle 5, 6, 3 becomes triangle 5a, 6, 3, which is rightangled at vertex 6. In other words, when the line of action of the jack passes through axis 3 ofjib 2, so that the torque exerted on jib 2 by jack 10 is zero, the line of action of jack 4 is at right angles to the straight line passing through axes 3 and 6. Jib 2 is then at an angle of inclination A0 corresponding to the maximum moment of force from jack 4 with respect to axis 3, and the distance I of this axis from the line of action of jack is a maximum and equal to 1m. Because of the hereinbefore described relative arrangement of the various axes 3, 5, 6, 11 and 12, supplementary torque from the second jack 10 is zero when the torque from jack 4 is a maximum.

Jacks 4 and 10 are double-acting, and they have two chambers, 4a and 4b in the case of the jack 4, and 10a and 10b in the case of the jack 10. Chambers 4a and 4b are connected to a circuit for supplying and returning a fluid under pressure through ducts 13 and 14, and chambers 10a and 10b are likewise connected to ducts 15 and 16. Each of ducts 15 and 16 communicates with a respective one of the two ducts 13 and 14 to form two main supply ducts 17 and 18 which can be made to communicate selectively with a pump 19 or with a return circuit symbolised by a reservoir 20 through a distributor 21. Distributor 21 has two routes and three positions, and it is shown in an inoperative position in FIG. 3. A distributing and reversing device 22 has two routes and two stable positions, and it is interposed in the ducts 15 and 16. Device 22 defines two sections 150 and 15b in the case ofthe duct 15, and 16a and 16b in the case of the duct 16. Device 22 has a slide valve connected to a cam 23 through a rod 24. Cam 23 consists of a disc rotatable about a shaft 26, the disc having a recess with edges 25a and 25b adapted to cooperate with a lug 27 rigid on an end portion 12 of the jack 10. Rod 24 is connected to cam 23 by an eccentric finger 28 which is opposite recess 25 with respect to shaft 26. A resilient member 29, including a spring abutment, is also connected to the finger 28, this abutment being mounted for pivotal movement about a fixed shaft and tending to create a torque retaining cam 23 to one or other side of the abutment.

Operation of this embodiment will now be described with reference to a lifting cycle for the jib 2. The jib 2 initially assumed to be in a position below the straight line defining the angle A0 shown in FIG. 3. The line of action of jack 10 extends below axis 3. In order to lift the jib 2 fluid is supplied under pressure to chamber 4b of jack 4, and to chamber 10b of jack 10. This is effected by setting distributor 21 to the position where duct 17 communicates with pump 19. Pump 19 delivers fluid to chamber 4b of jack 4 through duct 14. In the same way duct 16b is pressurized, and the distributing and reversing device 22 is in a position in which the duct 16b communicates with duct 160. This position is ensured by rocking cam 23 about shaft 26 when lug 27 engaged edge 25b of recess 25 as triangle l1, 3, 12 became flat. The position is maintained by spring abutment 29 having rocked about shaft 30 on rocking cam 23.

Fluid under pressure tends to extend jack 4 outwardly, and thereby push jib 2 upwardly. Chambers 40 and are, of course, in communication with reservoir 20. When jib 2 is at an inclination A0, the pivot points 11 and 12 ofjack 10 are aligned with pivot axis 3. Lug 27 then pushes edge 25a of recess 25 in cam 23 sufficiently to ensure that the effect of spring abutment 29 is no longer nullified by alignment of shafts 26 and 30 with finger 28. The spring in the abutment is then able to expand, and rotate cam 23 about shaft 26. The resultant rotation drives rod 24 and moves the slide valve of the distributing and reversing device 22 to a position in which fluid communication occurs between duct 16b and duct 15a. Fluid is then admitted under pressure into chamber 100 of jack 10, and chamber 10b is brought into communication with reservoir 20.

Jack 10 then co-operates in lifting jib 2 by pulling on the jib, and the action of jack 4 remains as hereinbefore described.

Lowering the jib is effected in the reverse way, a change in the position of the distributor 21 establishing communication between pump 19 and duct 18. This admits fluid under pressure into chambers 4a and 10b when the angle of inclination of the jib 2 is greater than the angle A0, and into the chambers 40 and 100 when the angle of inclination is less than A0.

The embodiment shown in FIG. 3 has torque characteristics as shown in FIG. 4, the co-ordinates being the same as in FIG. 2. Curve 7 as shown in FIG. 2 is also shown in FIG. 4, curve 8 corresponding to the rocking torque. The maximum torque Cm is obtained when the inclination of the jib is A0. Curve 31 shows the variation in torque applied to the foot ofjib 2 by jack 10. In the direction of increasing values of A, this torque decreases, becoming zero at A0, and then increasing beyond A0, jack 10 operating under thrust for lifting the jib. The consequent torque is then of the same sign as the torque from jack 4. As the angle A0 is approached, the distance from the line of action of jack 10 to the axis 3 decreases, and consequently its torque decreases. When the angle is A0, the torque of the lifting force of jack 10 is zero because the line of action of the jack then passes through axis 3. Beyond A0, jack 10 operates under traction because of changes in the position of the distributing and reversing device 22. The torque of the consequent traction force is still of the same sign as the force developed by jack 4, and its strength increases because the line of action of jack 10 moves away from axis 3. The discontinuity in curve 31 at A0 is due to the change in direction of the lifting force applied to jib 2 by jack 10.

Curve 31 added to curve 7 gives curve 32, which shows the variation in the total lifting torque on a pivoted element including an embodiment of apparatus in accordance with the invention. The total torque applied to the foot ofjib 2 of a lifting or Public Works machine is therefore substantially constant in the range of use of its jib. By correctly adjusting the strengths of the torques of which it is composed, by adjustment of the dimensions of the jacks 4 and 10, or by adjustment of the pressure of the fluid admitted into each of the jacks, a curve 32 is obtained which can be located close to curve 8, which represents the rocking torque of the ma chine. It is then possible to use the machine to its maximum potential while remaining within the safety limits imposed by its construction, irrespective of the shape and movement of the jib.

It will be noted that in the hereinbefore described embodiment in accordance with the invention, the maximum torque from jack 4 coincides with zero torque from jack 10.

In other words, the deformable triangle 3, 11, 12 is fiat (H6. 3) when triangle 3, 5, 6 is right-angled at its vertex 6. The torque from jack 4 is reduced by about 30% when the angle at 6 of triangle 3, 5, 6 changes from 90 to 45. For example, when the angle of the vertex 6 of triangle 3, 5, 6 is 60, the torque from jack 4 is 86% of its maximum value.

In view of this, an increase in the torque lifting jib 2 which is developed by a jack such as 4 can still be satisfactory if a jack such as 10 is positioned such that the triangle 3, 11, 12 is flat when the angle at 6 of triangle 3, 5, 6 is between 60 and 90 or even 120. However, curve 32 (FIG. 4) will be flatter when the angle at 6 is closer to 90, the desired effect then being at a maximum.

The preceding description has been given with reference to a hydraulic jacks. However, alternative forms using mechanical, electrical or other lifting means can be used. Apparatus in accordance with the invention can be used in the handling and Public Works machine industries.

The hereinbefore described embodiment of the present invention enables the inclination of a jib to be altered, using a substantially constant lifting torque. The magnitude of this torque can be adjusted to be very close to the rocking torque, and this makes it possible to improve the profitability and increase the performance of machines equipped with such apparatus.

I Claim:

1. Apparatus for changing the inclination of a pivotal element, the element being pivotal about an axis with respect to a fixed structure, the apparatus comprising a main jack connected between the structure and the element, and a secondary jack connected between the structure and the element, the main jack always being on the same side of said pivotal axis, the points of connection of the respective jacks to said structure and said element, and said pivotal axis constituting the vertices of two deformable triangles, the deformable triangle of which one side is defined by the secondary jack being flattened to form a straight line when the deformable triangle of which one side is defined by the main jack is substantially right-angled at its vertex defined by the point of attachment of said main jack to said structure. I

2. Apparatus according to claim 1, having a circuit for distributing and returning fluid under pressure, dis tribution and reversing means, and detector means, and said jacks are hydraulic and double-acting jacks with two chambers, each chamber communicating with the said circuit, the communication being direct in the case of the main jack and through said distribution and reversing means in the case of the secondary jack, said distributing and reversing means being controlled by said detector means responsive to the position of the secondary jack with respect to said pivotal element.

3. Apparatus according to claim 2, having a cam connected to the slide valve of the said distributing and reversing means and said detector means comprises a lug rigid on an end portion of the secondary jack, the lug being arranged to co-operate with said cam, said cam being capable of assuming two stable positions under the action of said lug, the stable positions being maintained by resilient return means, the two stable positions corresponding respectively to positions of the secondary jack on one or other side of the line defined by the said flattened triangle.

Claims (3)

1. Apparatus for changing the inclination of a pivotal element, the element being pivotal about an axis with respect to a fixed structure, the apparatus comprising a main jack connected between the structure and the element, and a secondary jack connected between the structure and the element, the main jack always being on the same side of said pivotal axis, the points of connection of the respective jacks to said structure and said element, and said pivotal axis constituting the vertices of two deformable triangles, the deformable triangle of which one side is defined by the secondary jack being flattened to form a straight line when the deformable triangle of which one side is defined by the main jack is substantially right-angled at its vertex defined by the point of attachment of said main jack to said structure.

2. Apparatus according to claim 1, having a circuit for distributing and returning fluid under pressure, distribution and reversing means, and detector means, and said jacks are hydraulic and double-acting jacks with two chambers, each chamber communicating with the said circuit, the communication being direct in the case of the main jack and through said distribution and reversing means in the case of the secondary jack, said distributing and reversing means being controlled by said detector means responsive to the position of the secondary jack with respect to said pivotal element.

3. Apparatus according to claim 2, having a cam connected to the slide valve of the said distributing and reversing means and said detector means comprises a lug rigid on an end portion of the secondary jack, the lug being arranged to co-operate with said cam, said cam being capable of assuming two stable positions under the action of said lug, the stable positions being maintained by resilient return means, the two stable positions corresponding respectively to positions of the secondary jack on one or other side of the line defined by the said flattened triangle.

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