Friction control for articulating arm joint

This invention relates generally to articulating arms for movably connecting a first body to a second body, specifically to a friction control mechanism for permitting close control of the friction at a joint of an articulating arm, allowing the articulating arm to hold the second body in a set position with respect to the first body after movement.

Articulating arms that extend between a first body and a second body are well known in the art. Dental x-ray machines, for example, often use such articulating arms. The dental x-ray machine often has an x-ray machine head that must be located next to the patient's jaw while in use. Further, it must maintain that position without being held there by an operator, so that the operator can move behind a screen so as to be protected from the x-rays when the machine is operating. When the x-ray machine is not in use, the x-ray machine head must be moved to a location that will not interfere with the rest of the dentist's duties. An articulating arm allows the x-ray machine head to be easily moved between these locations.

Another usage for such articulating arms is to moveably attach a machine to a remote input/output station while maintaining the orientation of the input/output station without being held by an operator. For example, an x-ray machine often has an output screen for providing information to the operator. The operator must be able to see the screen from a remote position where he or she is behind a shield and protected from the effects of the x-rays. The articulating arm maintains the orientation of the screen without being held there by the operator, while allowing the operator use both hands to operate x-ray controls. The operator can move the screen horizontally and vertically to a position where he or she can view it from the remote location. U.S. Pat. No. 6,315,259 issued to Kolb is an example of such an articulating arm.

One problem with existing articulating arms is that they tend to permit drift, so that the piece of equipment being held by the arm loses its set position after the operator moves the equipment to the desired location and releases it. This is a particular problem with articulating arms used with dental x-ray machines. To take dental x-rays, the operator moves the x-ray machine head, attached to an articulating arm, to the desired location next to the patient's jaw, and then must leave the room to activate the x-ray machine. Before the operator is able to activate the x-ray machine, the articulating arm attached to the x-ray machine may lose its set position, causing the x-ray machine head to be in a different position than the operator intended. As a result, an unintended area of the patient's jaw may have been x-rayed, and the operator may have to repeat the x-ray. This wastes both the operator's and the patient's time, as well as potentially exposing the patient to unnecessary x-rays.

This invention relates to improvements to the products described above, and to solutions to some of the problems raised or not solved thereby.

The present invention provides a friction control mechanism for the connecting joints in an articulating arm, so as to stop the piece of equipment held by the articulating arm from drifting away from its set position. The friction control mechanism includes a pivot connector attached to an arm with a pivot pin, an axial washer placed around the pivot pin and between the arm and the pivot connector, and two set screws threaded through the arm. The set screws are positioned and oriented so that they bite into the axial washer, generally preventing relative movement between the set screws and the axial washer, and creating a friction force between the axial washer and the pivot connector. This friction force is sufficient to hold the arm in its set position, preventing any drift. The set screws can be adjusted to control the level of the friction force between the axial washer and the pivot connector.

As part of an articulating arm, the pivot connector may be connected to another device, such as another part of the arm, a machine such as an x-ray machine, or another pivot connector for connection to another arm. Each joint in the articulating arm may have such a friction control mechanism.

Various other features, objects, and advantages of the invention will be made apparent to those skilled in the art from the following detailed description, claims, and accompanying drawings.

FIG. 1 is a perspective view of an articulating arm constructed according to a preferred embodiment of the invention, applied to hold the x-ray head of a dental x-ray machine.

FIG. 2 is an exploded view of one joint of the articulating arm shown in FIG. 1 , illustrating the relationship of the component parts.

FIG. 3 is a cross-sectional view of the joint shown in FIG. 2 , taken along line 3 — 3 thereof.

FIG. 4 is an exploded view of a joint of an articulating arm, constructed according to an alternative embodiment of the invention. 1 .

FIG. 5 is a sectional view of the embodiment of the invention shown in FIG. 4 , taken along line 5 — 5 thereof.

The invention is used to prevent drift in an articulating arm assembly 20 used in connection with a dental x-ray machine 12 as shown in FIG. 1 . One or more of the joints 16 in the articulating arm assembly 20 may include the structure provided by the invention, improving the ability of the joints 16 to maintain a set position. As a result, the x-ray machine head 24 will stay in the proper position and x-ray the correct area of the patient's jaw.

As shown in FIG. 2 , a preferred embodiment of the invention includes an arm 10 , generally hollow, at least at the end where the joint is to be formed. One preferred cross-sectional shape for the arm 10 , as shown in FIG. 2 , is that of a U-shape. In that form, the arm 10 includes two sides 38 . A pivot connector 14 is positioned between the sides 38 . The pivot connector 14 has a center aperture 42 and is fastened to the arm 10 by means of a pivot pin 18 . The pivot pin 18 is positioned through aligned holes 30 in sides 38 , and the center aperture 42 of the pivot connector 14 . Axial washers 22 are applied around each end of the pivot pin 18 , between the sides 38 of the arm 10 , and outside the pivot connector 14 . Set screws 26 are threaded through threaded holes 34 formed in the sides 38 , which threaded holes are offset from the aligned holes 30 . As each set screw 26 is threaded into the threaded holes 34 , it bites into the axial washer 22 , thereby substantially preventing relative motion between the arm 10 and the washer, and exerting an inward force on the washer, increasing the pressure by which the washer contacts a flat surface 40 provided for that purpose. The pressure between the washer 22 and the flat surface 40 creates a friction force between the pivot connector 14 and the arm 10 . This friction force controls how easily the arm 10 moves relative to the pivot connector 14 . The pivot connector 14 has an attachment portion 48 to facilitate attachment to other parts, such as another arm 50 ( FIG. 1 ) or a an x-ray head 24 (FIG. 1 ).

The benefit of the invention can be more clearly seen by reference to FIG. 3 . As there shown, the pivot pin 18 is placed through the center aperture 42 . The axial washers 22 are fitted around each end of the pivot pin 18 and between the sides 38 of the arm 10 and the flat surface 40 of pivot connector 14 . The set screws 26 are shown making contact with the axial washers The contact between the set screws 26 and the axial washer 22 prevents relative movement therebetween, and creates a friction force between the pivot connector flat surface 40 and the axial washer 22 . The set screws 26 can then be adjusted to control the degree of friction force necessary to prevent drift.

A second embodiment of the invention may be used with joints requiring two pivot connectors as illustrated in FIGS. 4 and 5 , FIG. 4 being an exploded view and FIG. 5 being a cross-sectional view. As there shown, the pivot connector 14 is connected to a second pivot connector 14 by a coupler 46 . The second pivot connector 14 is connected to a second arm 10 by a second pivot pin 18 . An axial washer 22 is applied about each end of the pivot pin 18 , between the sides 38 of the second arm 10 and the flat surface 40 of the second pivot connector 14 . Two set screws 26 are threaded through two threaded holes 34 , contacting the axial washer 22 .

The pivot connector is preferably formed of cast aluminum and the axial washers are preferably formed of stainless steel. Other material combinations are possible, but many do not work as well. For example, both aluminum-on-aluminum and aluminum-on-brass tend to bond and score or result in excessive wear.

While the invention has been described with reference to preferred embodiments, it is to be understood that the invention is not intended to be limited to the specific embodiments set forth above. It is recognized that those skilled in the art will appreciate certain substitutions, alterations, modifications, and omissions may be made without parting from the spirit or intent of the invention. Accordingly, the foregoing description is meant to be exemplary only, the invention is to be taken as including all reasonable equivalents to the subject matter of the invention, and should not limit the scope of the invention set forth in the following claims.