UTILITY ARM

Abstract

A utility arm includes a first arm, terminating in first universal joint, locked by a first piston, and a second arm, terminating in second universal joint, locked by a second piston. These are joined by an intermediate joint positioned between the first universal joint and second universal joint, and there is a locking means on the intermediate joint. The intermediate joint has a first housing, with a first pressure piece having an inclined surface which abuts the first piston, the first pressure piece having a conical or frustoconical surface a second housing, with a second pressure piece having an inclined surface which abuts the second piston, the second pressure piece having a conical or frustoconical surface. The first pressure piece and second pressure piece interlocks with corresponding conical or frustoconical surfaces, so that pressure exerted by the locking means presses the first pressure piece and second pressure piece together, such that the inclined surface of the first pressure piece acts on the first piston to lock the first universal joint, the inclined surface of the second pressure piece acts on the second piston to lock the second universal joint, and the corresponding conical or frustoconical surfaces lock the intermediate joint.

Claims

1. A utility arm comprising a first arm, terminating in first universal joint, locked by a first piston a second arm, terminating in second universal joint, locked by a second piston an intermediate joint positioned between the first universal joint and second universal joint a locking means on the intermediate joint the intermediate joint including a first housing, with a first pressure piece having an inclined surface which abuts the first piston, the first pressure piece having a conical or frustoconical surface a second housing, with a second pressure piece having an inclined surface which abuts the second piston, the second pressure piece having a conical or frustoconical surface the first pressure piece and second pressure piece interlocking with corresponding conical or frustoconical surfaces, so that pressure exerted by the locking means presses the first pressure piece and second pressure piece together, such that the inclined surface of the first pressure piece acts on the first piston to lock the first universal joint, the inclined surface of the second pressure piece acts on the second piston to lock the second universal joint, and the corresponding conical or frustoconical surfaces lock the intermediate joint.

2. A utility arm according to claim 1 wherein the first pressure piece is a unitary component.

3. A utility arm according to either claim 1 wherein the first piston includes a roller which abuts the inclined surface of the first pressure piece.

4. A utility arm according to claim 3 wherein the second piston includes a roller which abuts the inclined surface of the first pressure piece.

5. A utility arm according to claim 1 wherein the first housing and the second housing are spaced apart when the intermediate joint is unlocked, and come together when the intermediate joint is locked to give a visual indication of the state of the intermediate joint.

6. A utility arm according to claim 1 wherein at least one of the pistons includes a resilient compression member.

7. A utility arm according to claim 1 wherein the first universal joint has a first torque resistance, the intermediate joint has a second torque resistance, and the second universal joint has a third torque resistance, the ratio of the first, second and third torque resistances being substantially in proportional to the ratio of the distances from the payload.

8. A utility arm comprising a first arm, terminating in first universal joint, locked by a first piston a second arm, terminating in second universal joint, locked by a second piston an intermediate joint positioned between the first universal joint and second universal joint a locking means on the intermediate joint the intermediate joint including the intermediate join acting on the first piston to lock the first universal joint the intermediate join acting on the second piston to lock the second universal joint; wherein at least one of the pistons includes a resilient compression member.

9. A utility arm according to claim 8 wherein the first universal joint has a first torque resistance, the intermediate joint has a second torque resistance, and the second universal joint has a third torque resistance, the ratio of the first, second and third torque resistances being substantially in proportional to the ratio of the distances from a payload.

10. A utility arm according to claim 9 wherein the difference in torque resistance is provided at least in part by resilient compression members having different spring strengths.

11. A utility arm comprising a first arm, terminating in first universal joint, locked by a first piston a second arm, terminating in second universal joint, locked by a second piston an intermediate joint positioned between the first universal joint and second universal joint a locking means on intermediate joint the intermediate joint including a first housing, with first pressure piece having an inclined surface which abuts the first piston a second housing, with second pressure piece having an inclined surface which abuts the second piston wherein the first housing and the second housing are spaced apart when the intermediate joint is unlocked, and come together when the intermediate joint is locked to give a visual indication of the state of the intermediate joint.

12. A utility arm according to claim 11 wherein the visual indication includes a gradation or scale or other indication that an intermediate point has been reached.

13. A utility arm comprising a first arm, terminating in first universal joint, locked by a first piston a second arm, terminating in second universal joint, locked by a second piston an intermediate joint positioned between the first universal joint and second universal joint a locking means on intermediate joint the intermediate joint including a first housing, with first pressure piece having an inclined surface which abuts the first piston a second housing, with second pressure piece having an inclined surface which abuts the second piston the first pressure piece and second pressure piece interfering with the application of pressure by the action of the locking means, such that the inclined surface of the first pressure piece acts on the first piston to lock the first universal joint, the inclined surface of the second pressure piece acts on the second piston to lock the second universal joint, the first pressure piece having a rotationally asymmetric shape and sliding within a substantially corresponding channel in the first housing so as to be constrained the first pressure piece from relative rotation

14. A utility arm according to claim 13 wherein the second pressure piece being constrained from rotation relative to the second housing.

15. A utility arm comprising a first arm, terminating in first universal joint, carrying a payload a second arm, terminating in second universal joint an intermediate joint positioned between the first universal joint and second universal joint wherein the first universal joint has a first torque resistance, the intermediate joint has a second torque resistance, and the second universal joint has a third torque resistance, the ratio of the first, second and third torque resistances being substantially in proportional to the ratio of the distances from the payload.

16. A utility arm according to claim 15 wherein the first arm is locked by a first piston having a first resilient compression member, and the second arm is locked by a second piston having a second resilient compression member, the first and second resilient compression members having different spring strengths.

Description

[0025] The invention will now be described, by way of example, with reference to the drawings, of which

[0026] FIG. 1 a is a perspective view of a known utility arm;

[0027] FIG. 1b and 1c are perspective views of known utility arms in use;

[0028] FIG. 2 is a sectional view of the known utility arm;

[0029] FIG. 3 is a sectional view of an embodiment of the new utility arm in an unlocked state;

[0030] FIG. 4 is a sectional perspective view of part of the new utility arm;

[0031] FIG. 5 is a perspective view of part of the new utility arm; and

[0032] FIG. 6 is sectional view of the new utility arm in a locked state.

[0033] FIG. 7 is perspective view showing partial sections of the new utility arm in use.

[0034] FIG. 8 is perspective view of the new utility arm in use.

[0035] Referring to FIG. 3, the utility arm comprises a first arm 51 and a second arm 53 which are pivotable about a pivoting joint 54. As for known utility arms, each arm 51, 53 may conveniently terminate with ball and socket joints 57, 58 having threaded attachment studs 55, 56, though of course some other termination could be provided.

[0036] The first arm 51 and second arm 53 are secured together by a central bolt 63 which runs through bores 82, 83 provided in the first arm 51 and second arm 53. The central bolt 63 terminates at its lower end with a thickened head 64, which engages with the arm housing 75 of the second arm 53. An operating knob 61 is attached to the upper end of the central bolt 63 with a thread. The lower surface of the operating knob 61 abuts the arm housing 74.

[0037] An upper pressure wedge 65 and lower pressure wedge 66 are mounted on the central bolt 63. Referring to FIGS. 4 and 5, the upper pressure wedge 65 has a frustoconical male surface 107 which engages with a corresponding frustoconical female surface 108. The upper pressure wedge 65 can slide inwards and outwards of the arm housing 74 through an aperture in an upper cover plate 84, the upper pressure wedge 65 and aperture in the upper cover plate 84 both having an corresponding square shape so that the upper pressure wedge 65 cannot rotate relative to the arm housing 74. Likewise, the lower pressure wedge 66 can slide inwards and outwards of the arm housing 75 through an aperture 111 in a lower cover plate 85, the lower pressure wedge 66 and aperture in the lower cover plate 85 both being square so as to prevent rotation of the lower pressure wedge 66 relative to the arm housing 75.

[0038] A first piston 68 extends along arm housing 74, and a second piston 69 extends along arm housing 75. Each piston is split, so that the first piston 68 has a roller bearing end 87 and a ball joint end 88 which are separated by a compression spring 92. The second piston 69 is similarly arranged, with a roller bearing end 89 separated from a ball joint end 90 by a compression spring 93. The compression springs may for example be coil springs, Belleville springs or other compression members known in the art.

[0039] Referring also to FIG. 5, the roller bearing end 87 of the first piston 68 has a roller 95 supported on a roller bearing 98. The upper pressure wedge 65 has an inclined surface 101 that bears against the roller 95. When the operating knob 61 is tightened, the arm housing 74 and arm housing 75 are drawn together, so that the upper pressure wedge 65 moves upwards relative to the arm housing 74. The inclined surface 101 of the upper pressure wedge 65 urges the roller 95 away from the central bolt 63, so that the first piston 68 is urged outwards towards the ball and socket joint 57. An inclined surface 104 on the upper inside surface of the arm housing 74 also bears on the roller 95 as the operating knob 61 is tightened during the initial tightening.

[0040] Referring to FIG. 6, as the operating knob 61 is progressively tightened, the inclined surface 101 of the upper pressure wedge 65 rides up the roller 95, and the force is transmitted through the compression spring 92 to the ball and socket joint 57. The ball and socket joint 57 is arranged generally as in the known manner, with the distal end of the first piston 68 having a conical notch 77 which bears against a ball 79; however, the force applied by tightening the operating knob 61 is now regulated by the compression spring 92, allowing an explicit variable and repeatable clamping force applied to be applied to the ball and socket joint 57, and the spring also applying a reactive force back to the pivoting joint 54.

[0041] Referring back to FIG. 3, the lower pressure wedge 66 and second piston 69 are arranged in a similar way to the upper pressure wedge 65 and first piston 68. The lower pressure wedge 66 has an inclined surface 102 facing downwards which abuts a roller 96 mounted on a roller bearing end 89 of the second piston 69. As the operating knob 61 is tightened, the lower pressure wedge 66 moves downwards relative to the arm housing 75, so that roller 96 rides up the inclined surface 102 of the lower pressure wedge 66 and is forced outwards away from the central bolt 63. An upward facing inclined surface 105 on the lower inside portion of the arm housing 75 also initially acts on the roller 96 as the arm housing 75 and lower pressure wedge 66 are drawn together. The roller bearing end 89 moves distally outwards, energising a compression spring 93 which in turn acts on ball joint end 90 of the second piston 69, so that a conical notch 78 presses against ball 80 to lock the ball and socket joint 58.

[0042] The line of contact between roller 95 and inclined surface 101 is perpendicular to the axis of the first piston 68; the force moves gradually along a plane rather than being concentrated along a line (and the same applies to the roller 96 of the second piston 69 and inclined surface 102 of the lower pressure wedge 66). This in conjunction with the use of a rolling element rather than a sliding contact makes the contact elements much less prone to wear. The inclined surfaces of the pressure wedges can be given low incline angles, allowing for finer adjustment and less sensitivity to wear.

[0043] Though the inclined surfaces are here shown as planer side of the pressure wedge, the area of the inclined surface could be more limited, and need not be planar, and the incline need not be constant. For example, the inclined surface could provide by a ramp occupying a notch or hollow in the surface of the parts here termed pressure wedges, with a ball bearing or other cam follower engaging with the inclined surface provided in the hollow instead of a roller illustrated in this embodiment.

[0044] It will be noted that in a fully unlocked state, the arm housing 74 and arm housing 75 are separated by a distance X. As the operating knob 61 is tightened, the arm housing 74 and arm housing 75 are drawn together, until in the fully locked state of the utility arm 50, the upper cover plate 84 of the arm housing 74 and the lower cover plate 85 of the arm housing 75 abut and there is no separation between the arm housing 74 and arm housing 75. This separation may be utilised by including some visually indication means on the utility arm 50 that allows a user to see the locking state. Further, as the upper pressure wedge 65 and lower pressure wedge 66 are urged together (via the reactive force from the compression springs 92, 93 and rollers 95, 96 respectively) with the tightening of the operating knob 61, the friction between the mating frustoconical surfaces of the pressure wedges 65, 66 increases and resists pivoting of the pivoting joint 54, so that the operating knob 61 may be tightened to a value between fully locked and fully unlocked, the resistance to pivoting (i.e. the torque resistance) being dependent on how closely the arm housing 74 and arm housing 75 have been drawn together by the operating knob 61. The clamping force is continuously variable between the maximum and minimum values, and the joint is fully locked when the maximum clamping force exists between the components. Since the value of the separation distance X is proportional to the degree of tightening of the operating knob 61 and the clamping force, and is predictable and repeatable, the user may adjust the joint to give a pre-selected desired degree of lock or resistance to the arm. In this, any indication, scale or legend provided may be used to help, and means may be included to indicate to the user, by sight or by feel, that such an intermediate point between the maximum and minimum clamping force has been arrived at.

[0045] When the operating knob 61 is fully tightened and the arm housing 74 and arm housing 75 have been drawn fully together, both the ball and socket joint 57 and ball and socket joint 58 are locked, and the pivoting joint 54 itself is locked.

[0046] FIG. 6 also shows a possible modification of the design, where a counter screw 110 engages with a threaded bore provided in the bolt shaft 63. The knob 61 is provided with a countersunk bore 113, which the head of the counter screw 110 abuts when the knob is displaced a set distance along the bolt shaft 63 (just beyond the point when the joint is fully unlocked), thereby preventing the knob 61 from being over loosened. This stops the joint being accidentally dismantled, and also stops the frustoconical surfaces 101, 102 from separating; since the frustoconical surfaces are in contact at all times, ingress of contaminants is prevented. The stop arrangement could be arranged in alternative ways, such as having the counterscrew extend outwards, or even arranging a counterscrew or other stop means on the other end of the shaft 64 or along the shaft's length.

[0047] By choosing the incline (and/or other characteristics, such as the surface area, material etc) of the mating frustoconical surfaces of the pressure wedges 65, 66, and the characteristics of the compression springs 92, 93 and the characteristics of the conical notches 77, 78 and the ball and socket joints 57, 58, the torque resistance of the first ball and socket joint 57, second ball and socket joint 58 and pivoting joint 54 for a particularly degree of actuation of the utility arm 50 as a whole can be chosen.

[0048] Advantageously, the utility arm 50 may be configured so that the operating knob 61 can be set to semi-actuate the utility arm 50—that is, to set the resistances of the first ball and socket joint 57, second ball and socket joint 58 and pivoting joint 54 to some point between being fully unlocked (having little resistance to any pivoting or rotational force) and fully locked (having a high resistance to any pivoting force).

[0049] Further, the torque resistance of the first ball and socket joint 57, second ball and socket joint 58 and pivoting joint 54 may be chosen to be unequal for a given degree of semi-actuation. If the torque resistance for each joint is chosen to be proportional to the distance from the payload, so that the torque resistance of the ball and socket joint 57 is greater than the torque resistance of the pivoting joint 54, which is in turn greater than the torque resistance of the ball and socket joint 58, a payload attached to the ball and socket joint 58 may be moved from point to point along a desired line within the hemisphere of reach, since each joint offers the same subjective torque resistance to a force applied at the payload point.

[0050] Referring to FIG. 7, a number of factors affect the torque resistance of a joint, including the strengths of the compression spring 92 and/or compression spring 93, the radii of the ball 79 and/or ball 80 (and the geometry of the conical notch 77 and conical notch 78 respectively), and the cone angle of the frustoconical male surface and frustoconical female surface between the upper and lower pressure wedges 65, 66. Increasing the size of the ball 79 and ball 80 increases the respective torque resistance in those joints, as does increasing the spring strength in each arm 51, 53, The torque resistance of the pivoting joint 54 may is dependant (amongst other things) on the conical angle α between the two conical surfaces 108, 109 the upper pressure wedge 65 and lower pressure wedge 66 (the torque resistance being inversely proportional to the sine of angle α, so that a more acute cone increases the torque resistance). Other factors, such as the length of the first arm 51 and second arm 53, and the material used for the components, will also affect the joints' torque resistance.

[0051] With the appropriate selection of ball diameter, spring dimension and cone angle an equal reaction movement in each joint may be provided independent of length of lever arm: Larger balls, heavier springs, and smaller (more acute) cone angle all result in higher torque resistance (the torque resistance of the cone clutch being inverse proportion to sin α).

[0052] Referring also to FIG. 8, the payload here is to be secured to ball 79 at the distal end of the first arm 51, while the second arm 53 is secured by ball 80 to an anchor point. Accordingly, the radius of the ball 79 is chosen to be smaller than the radius of the ball 80. Similarly, the compression spring 92 in the first arm 51 is chosen to be weaker than the compression spring 93 located in the second arm 53. The ratio of the torque resistance of the ball and socket joint 57 to the torque resistance of the ball and socket joint 58 is ideally close to the ratio of the distance between the payload and the ball and socket joint 58 to the distance between the payload and ball and socket joint 57. The torque resistance of the pivoting joint 54 is similarly chosen to have the same ratio to the ball and socket joint 57 and to the ball and socket joint 58 as the ratio of its reciprocal of its distance from the payload to the reciprocals of other joints' payload distance.

[0053] Again, ideally this relative torque resistance is particularly chosen to apply at a semi-actuation point that is just sufficient to support the weight of the payload, so that the payload will remain stationary when not deliberately moved, but when the user applies a force to move the payload the torque resistance of each joint is overcome to allow the payload to be moved in a free-floating manner, ideally with a single hand, the payload again being securely supported when the pressure from the user is removed. The utility arm can then be used allow a payload to be freely supported at different re-positioned points without having to adjust the operating knob 61. The joint may then be in a state between being fully locked and fully unlocked, where the arm position and configuration is spatially fixed unless a force (depending on the setting, this may be a relatively small force) is applied. The user may adjust the pivoting joint to vary the force necessary to overcome the clamping force; since the distance X is proportional to the clamping force, the user may note the particular distance or distances X that he finds most convenient, and reproduce them by adjusting the pivoting joint to a particular value of X. The user may be aided by a visual scale or other indicia that allows the value of distance X to be judged.

[0054] Although a knob 61 is shown here, the joint could equally be controlled by a lever turning the thread.