US3436046A - Infinite positioning mechanism for a movable arm - Google Patents

Description

A ril 1, 1969 F- 3,436,046

INFINITE POSITIONING MECHANISM FDR A MOVABLE ARM Filed Sept. 1, 1967 7 J I I 6285 63- 6-1 I INVENTOR.

JOHN J. VALESKA ATTORNEY States ABSTRACT OF THE DISCLOSURE A movable arm, for use in combination with a dental console, supports an instrument tray outwardly spaced from the console. The arm, movable in both horizontal and vertical planes carries a friction lock, which permits free upward movement of the arm but locks instantly when the upward movement is stopped and the arm begins to fall by gravity. The lock has a manual release for disengaging the lock to move the arm to a lower level. The lock is operable over the entire range of vertical movement of the arm so that the arm can be positioned at any point within the range of vertical movement.

The present invention relates to a movable arm for supporting a platform outwardly spaced from an upright structure, and more specifically to such an arm as may be attached to a dental console to hold an instrument tray within reach of the dentist. In particular, the invention relates to an arm of the type described having a lock mechanism which automatically locks whenever the arm is subjected to the force of gravity and automatically unlocks Whenever upward pressure is applied to the arm.

Movable arm supports for dental consoles are well known in the art. These arms are usually hinged and pivoted to the console so that the arm can swing in both vertical and horizontal planes. The arm usually carries at its outer limit some sort of platform or tray on which the dentist can place, within easy reach, his picks, mirrors or other handtools, extra burrs for the power operated drills, materials for mixing the amalgam fillings and other small items. The flexibility of the arm permits the tray to swing over the patient to the position most convenient to the dentist.

The movable arms in the prior art lock against downward movement at several ditferent heights so that the instrument tray will be reasonably close to the patient and within reach of the dentist regardless of whether the patient is seated upright or reclining. However, several drawbacks inherent in prior art arm members can be attributed to the construction of the locking mechanism used to hold the arm at different levels. For example, the locking mechanisms are designed to lock at several set intervals so that the instrument tray could be positioned only at a limited number of vertical height positions. These locks are also designed to hold the arm in position against both upward and downward movement. In such a case, the dentist must be sure to raise or pivot the arm away from the patient before elevating him. Otherwise the patient might become jammed against the unyielding arm as he is elevated in the dental chair causing possible injury to both the patient and the arm.

Other movable arms which yield upwardly to safeguard equipment and patient return to the original lock position when released. With this type of arm the dentist must reset the locking mechanism each time he wishes to reposition the arm at a higher level.

atent O Patented Apr. 1, 1 969 SUMMARY OF THE INVENTION In the present invention a friction lock is adapted to lock automatically whenever downward pressure is exerted on the movable arm, which prevents the arm from lowering and to unlock automatically to permit free unimpeded movement of the arm under the influence of an upwardly directed force. To this end, the movable arm comprises a parallel motion linkage wherein the parallel members move axially, one relative to another, when the arm is raised or lowered. A plurality of locking discs and a latch slidably carried by one of the parallel members are springurged against a stop carried by the other parallel member, the stop being set at an angle to tilt the locking discs and the latch which in turn binds and prevents the relative axial motion of the parallel members when the members attempt to move downwardly. Applying upper pressure to the parallel members to move the members upwardly, carries the locking discs and latch away from the stop and permits the parallel members to move upwardly.

Since there are no ratchets or stations to engage, the friction lock also has the advantage of locking the arm at an infinite number of levels over the entire vertical movement range of the arm. This feature allows the dentist to position the arm and tray at the level most convenient for the performance of his work.

Accordingly, it is an object of my invention to provide a movable arm for dental units and the like which will lock the arm at any level over the entire vertical range of arm movement to permit the dentist to position the instrument tray at the most convenient level.

Another object of my invention is to provide a lock mechanism in combination with a movable arm of the type described which locks only when the arm is subjected to downward pressure.

Still another object of my invention is to provide a locking mechanism in combination with an arm for dental units and the like which will prevent injury to the patient or to the arm itself resulting from the patient being jammed upwardly against the arm.

A further object of my invention is to provide a movable arm for dental units and the like which can be raised without disengaging the lock mechanism.

These and other objects, advantages, and characterizing features of my invention will become more apparent upon consideration of the following detailed description thereof when taken in conjunction with the accompanying drawings depicting the same in which:

FIGURE 1 is an elevation view of the movable arm assembly of my invention with the phantom line representing the upper limit of vertical movement and the solid line representing the lower limit of vertical movement; and

FIGURE 2 is an enlarged cross sectional view of the lock mechanism of my invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT My invention can be characterized in one aspect thereof by the provision of a movable arm having a pair of elongated parallel members pivotally supported at one end and pivotally connected to a platform at their other end, the members being adapted to move axially one relative to another as they are pivoted vertically about the pivotally supported end. One of the parallel members slidably carries a friction lock and the other member carries a stop. The friction lock is adapted to engage the stop to prevent the members from moving axially one relative to the other as the parallel members attempt to pivot downwardly about the pivotally supported end to prevent downward movement of the arm. The lock is,

however, carried away from the stop when upward pressure is applied to the arm so that the arm can be moved upwardly.

Referring now to the drawings, FIGURE 1 shows the arm assembly and the lock mechanism of my invention generally designated at 10. The arm assembly includes a pair of parallel members 12 and 14, both pivotally supported at one end by a pivot member 16 and pivotally connected at their other end to a knuckle 18. Pivot member 16 in turn connects the arm assembly to a dental console 20 and knuckle 18 connects the arm assembly to an instrument tray 22 on which the dentist places his hand tools and other like equipment. The pivot action of pivot member 16 and knuckle 18 permits the instrument tray to swing in both a horizontal or vertical plane over the seated or reclining patient.

Member 12 is generally U-shaped in cross section and forms a casing for member 14, the member 14 being disposed entirely within member 12 as shown in FIGURES 1 and 2. Members 12 and 14 together define a parallel motion linkage which in and of itself is well known and old in the art. Since parallel motion linkages are well known in the art, the operation of such a linkage will be described only briefly to clarify the present invention.

In order for the parallel motion linkage to function it is essential that the distance between the points of connection of member 12 to pivot 16 and knuckle 18 is substantially equal to the distance between the points of connection of member 14 to pivot 16 and knuckle 18. With this arrangement, pivoting parallel members 12 and 14 downwardly about pivot member 16 causes the parallel members to move axially one relative to another as indicated by arrows 26 in FIGURE 1. In like respect pivoting parallel members 12 and 14 upwardly about pivot member 16 causes the parallel members to move axially one relative to another as indicated by arrows 28 in FIG- URE 1. The relative axial movement of the parallel members acts to maintain knuckle 18 and thereby instrument tray 22 in a substantially level position regardless of the inclination of members 12 and 14 as the arm assembly is swung upwardly or downwardly about pivot member 16.

Arm assembly 10 further includes a locking mechanism generally designated at 30 (FIGURE 2) which is designed to prevent arm assembly 10' from pivoting downwardly about pivot member 16 by preventing the relative axial movement between members 12 and 14 which normally would occur when downward pressure is: exerted on the arm assembly. As shown in FIGURE 2, locking mechanism 30 includes a spring retainer 32 fixed to parallel member 12 by any suitable means, such as screws 34. The retainer has a pair of downwardly depending legs 36 which straddle member 14. A coil spring 38 disposed about member 14 has one end 40 seated in a spring guide 42 which in turn is supported against the downward depending legs 36 of spring retainer 32. The coil spring has its other end 44 seated in a spring guide 46 which is thereby resiliently urged toward a stop 48 fixed to member 12 by any suitable means such as screws 50. Stop 48 includes a pair of downwardly depending legs 52 which straddle member 14, each leg having an inclined cam surface 55 thereon for purposes set out hereinbelow.

Slidably carried by parallel member 14 are one or more locking discs 54 and a latch '56. Each locking disc 54 and the latch 56 has a sharp edged opening 62 therethrough to permit the passage of member 14. As viewed in FIGURE 2, the letters A, A and A" are used to designate the rearward or left hand edges of openings 62 and the letters B, B and B" are used to designate the forward or right hand edges. In addition, latch 56 is counterbored at which makes the latch and locking discs 54 movable into either of two positions; a first or upright position wherein the latch and locking discs are slidable with respect to member 14 and a second or inclined position (as shown in FIGURE 2) wherein the latch and locking discs are inclined on member 14 so that sharp edges A, A, A", and B, B, B" frictionally engage parallel member 14. It should be apparent that when locking discs 54 and latch 56 are in the first position, members 14 can move axially with respect to member 12 by sliding through openings 62. However, with locking discs 54 and latch 56 in the second or inclined position and sharp edges A, A, A, and B, B, B" frictionally engaged with member 14, member 14 is prevented from moving axially with respect to member 12 in a manner and for purposes set out hereinbelow.

Moving locking discs 54 and latch 56 into the second or inclined position is accomplished by coil spring 38 which urges the discs and latch against inclined cam surface 55 of stop 48. As set forth hereinabove, when arm assembly 10 is moved downwardly, parallel members 12 and 14 will move axially one relative to the other. For example, as shown in FIGURE 2, member 14 will tend to move axially with respect to member 12 in the direction indicated by arrow 63. Since locking discs 54 and latch 56 have their sharp rearward or left hand edges A, A and A" frictionally engaged with member 14, the locking discs and latch are also carried in the direction indicated by arrow 63. Stop 48, however, prevents forward movement of locking discs 54 and latch 56, which in turn prevents further movement of member 14 in the direction indicated by arrow 63. In this manner, member 14 is prevented from moving axially with respect to member 12 which in turn prevents arm assembly 10 from pivoting downwardly about pivot member 16. The greater the downward pressure exerted on arm assembly 10, the more forceful will be the engagement between sharp edges A, A and A and member 14 to keep the assembly from lowering. However, when upward pressure is applied to assembly 10, member 14 tends to move axially away from stop 48 in the direction indicated by arrow 65, and toward the resilient support of coil spring 38. Since locking discs 54 and latch 56 have their sharp forward or right hand edges B, B and B" frictionally engaged to member 14, the locking discs and latch are also carried toward the resilient support of coil spring 38. By moving against the resilient support of the coil spring, the locking discs and latch are carried to the first or upright position on member 14 which restores the sliding relationship between locking discs 54, latch 56 and member 14. Thus, as upward pressure is applied, member 14 is able to move axially in the direction indicated by arrow 65 with respect to member 14 which in turn allows the arm assembly 10 to pivot upwardly about pivot support 16. Arm assembly 10 will continue to move upwardly until it is released. At this point the assembly will begin to fall by gravity causing sharp edges A, A and A of looking discs '54 and latch 56 to re-engage member 14 which prevents arm assembly from pivoting downwardly in a manner as set out hereinabove.

In order to disengage locking mechanism 30 for moving the arm assembly downwardly, latch 56 is provided with an upper portion 66 which extends through member 12 terminating in a knob 68. Using the downward depending legs 52 of stop 48 as a fulcrum, depressing knob 68 causes the latch and locking discs to pivot to the first or upright position on member 14. This restores the sliding relationship between the locking discs, latch and member 14 which permits member 14 to move axially with respect to member 12 in the direction indicated by arrow '63. This in turn allows the arm assembly to pivot downwardly about pivot support 16. When the desired lower level is reached, knob 68 is released which instantly activates locking mechanism 30 to prevent the arm assembly from further downward movement as set forth hereinabove.

Therefore, it will be appreciated that the present in vention accomplishes its intended objects. The parallel motion or linkage of members 12 and 14 provides a simple low cost arrangement for maintaining instrument tray 22 in a horizontal position regardless of: the inclination of arm assembly 10. Furthermore, locking mechanism 30 prevents downward movement of the arm assembly while permitting the assembly to swing upwardly at the slightest upward pressure.

This one way action of the locking mechanism acts as a safety feature to prevent possible injury to the patient or equipment when the dental chair is elevated with the arm and instrument tray extended over the patient. In this respect, the arm will yield and ride up with the patient under the influence of upward pressure exerted by the patient on the arm. The arm will continue to ride up with the patient until the upward pressure is removed at which point the arm will automatically lock against downward movement. Furthermore, if the dentist desires to raise the arm, he can do so without unlocking the friction lock simply by lifting the arm to the desired level. The arm when released, will then automatically lock at this level. Moreover, since the surface of parallel member 14 is free of any obstruction, there being no set stations for sharp edges A, A, A" or B, B, B" to engage, the latch and locking discs can engage member 14 at any point along the length of the member so that the arm assembly can be positioned and maintained at any level.

While I have described the preferred embodiment of my invention, it will be readily apparent that various modifications can be made therein without changing the spirit and scope of the invention. Having thus described my invention in detail, what I claim as new is:

1. A movable supporting structure for supporting an object in adjusted position comprising:

(a) a parallel motion linkage having first and second parallel members movable axially, one relative to one another, the parallel members being pivotally supported at one end and pivotally connected to said object at their other end;

(b) a plurality of sharp edged elements slidably mounted on said first parallel member;

(0) means for causing said sharp edged elements to frictionally engage said first parallel member including a stop attached to said second parallel member and having a surface inclined at an angle to said parallel members for tilting said sharp edged elements causing the sharp edges thereof to frictionally engage said first parallel member; and

(d) means for releasing the frictional engagement of said sharp edged elements and said first parallel member.

2. A movable supporting structure as set forth in claim 1 further comprising means resiliently urging said sharp edged elements into contact with the inclined surface of said stop means for tilting said sharp edged elements.

3. In combination with a parallel motion linkage hav ing two parallel members movable axially one relative to another, the parallel members being pivotally supported at one end and pivotally connected to an object at their other end, a friction locking device for maintaining the object in a vertically adjusted position comprising:

(a) a member having a surface inclined with respect to one of said parallel members rigidly mounted on a second of said parallel members;

(b) locking elements slidably mounted on said one parallel member, each of said locking elements having a sharp edged opening therethrough to permit the passage of said one parallel member; and

(c) resilient means urging said locking elements against said inclined surface for tilting said locking elements on said one parallel member and frictionally engaging said one parallel member with the sharp edges of said openings to prevent said parallel members from moving axially one relative to another whereby said parallel members are prevented from pivoting downwardly for maintaining said object in a vertically adjusted position.

4. The combination as set forth in claim 3 in which said resilient means comprises:

(a) a spring retainer rigidly fixed to said second parallel member; and

(b) a spring biased against said spring retainer and toward the inclined surface of said member.

5. The combination as set forth in claim 4 in which said spring is disposed about said one parallel member.

6. The combination as set forth in claim 3 in whic said locking members comprise:

' (a) a plurality of disc-shaped elements each having a sharp edged opening therethrough and each slidably carried by said one parallel member; and

(b) a latch disposed between the inclined surface of said member and said discs, said latch having a sharp edged opening therein counterbored to permit said latch to tilt with respect to said one parallel member for moving said latch and disc shaped elements into said tilt position.

7. The combination as set forth in claim 6 in which said latch has a handle portion for manually moving said latch and therefore said disc-shaped elements against said resilient means and away from the inclined surface of said member to permit said parallel members to move one relative to another, whereby said parallel members pivot downwardly.

References Cited UNITED STATES PATENTS ROY D. FRAZIER, Primary Examiner.

U. FRANKLIN FOSS, Assistant Examiner.

US. Cl. X.R. 21 1-100

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