Patent Description:
Medical device support systems, also referred to as suspension systems and carry systems, are used in health treatment settings such as hospital examination rooms, clinics, surgery rooms and emergency rooms. These systems may suspend or support any variety of medical devices or components including surgical lights, supply consoles, patient monitors, camera detector heads, medical instruments, ventilator systems, suction devices, among others. The support systems typically include a central shaft or support column that is suspended from the ceiling or mounted to a wall, one or more generally horizontal extension arms mounted for rotational movement about the shaft, and one or more load balancing arms, also known as counterbalancing arms, that enable positioning of a medical device to a proper orientation relative to for example a patient operating table and healthcare professionals in the operating room. The extension arms and load balancing arms each include a support arm structure or housing, or more generally a support arm.

For load balancing arms in some medical device support systems or carry systems, there is a need to improve the force transmission and increase the load bearing capacity and range of control of the load balancing arm with minimal or no corresponding increase in the size of the load balancing arm. In some applications a load balancing arm may have insufficient capacity to adequately balance a load, whether due to the arm's spring lacking a sufficient counterbalancing effect or due to the arm's inability to otherwise provide a stable and natural handling for the operator. Simply increasing the spring force of the arm's spring may not be practicable as it may require increasing the spring constant and thus increasing the cross sectional area of the spring and consequently the cross sectional area of the load balancing arm. In many health treatment settings, increasing the cross sectional area of the load balancing arm translates into less available space for healthcare personnel, particularly because the load balancing arm may require space for a variety of rotations and pivots for a single medical procedure and/or space to accommodate numerous different medical procedures.

Accordingly, there remains a need for further contributions in this area of technology. <CIT> and <CIT> disclose known load balancing arms.

The application relates to a load balancing arm for a medical device support system, in which a link connects at its proximal end to a link bearing element and at its distal end to a distal end of a first spring and a proximal end of a second spring, where both of the springs are within a cavity of the load balancing arm and contribute to the counterbalancing biasing forces of the load balancing arm. The inventor has found that a load balancing arm configured in this way improves the force transmission and increases the load bearing capacity of the load balancing arm with minimal or no corresponding increase in the size of the load balancing arm.

According to one aspect of the invention, a load balancing arm for a medical device support system includes a proximal hub including a main bearing element defining a main pivot axis; a link bearing element defining a link pivot axis; a support arm having a proximal end and a distal end, wherein the distal end is configured to support a medical device load and the proximal end is pivotably mounted to the main bearing element for pivotable movement about the main pivot axis; a first spring extending within a cavity of the support arm and mounted to exert a biasing force between the main pivot axis and a distal end of the first spring; a second spring extending within the cavity of the support arm and mounted to exert a biasing force between a proximal end of the second spring and a wall at the distal end of the support arm; and, at least one link having a proximal end pivotably mounted to the link bearing element for pivotable movement about the link pivot axis, and a distal end pivotably mounted to the distal end of the first spring and the proximal end of the second spring such that the biasing forces exerted by the first and second springs are transmitted through the link to the link bearing element thereby to generate a moment about the main pivot axis of the proximal hub that counters a moment generated by the medical device load at the distal end of the support arm.

Embodiments of the invention may include one or more of the following additional features separately or in combination.

The first spring and the second spring may be connected functionally in series.

The first and second springs may be oriented along an axis that extends radially from and perpendicular to the main pivot axis.

The first spring may be configured to expand and contract along a first axis and the second spring may be configured to expand and contract along a second axis, and the first and second axes may coincide with one another.

The biasing force of the first spring may be configured to bias the distal end of the at least one link toward the main pivot axis at the proximal end of the support arm and the biasing force of the second spring may be configured to bias the distal end of the at least one link toward the wall at the distal end of the support arm.

The link pivot axis may be axially spaced from the main pivot axis.

The link bearing element may be an adjustable bearing element, and the link pivot axis may be adjustable axially relative to the main pivot axis.

The first spring may be a compression spring and the second spring may be a tension spring.

The load balancing arm may further include a carriage slide that is slidable relative to the support arm, and the distal end of the link may be pivotably mounted to the distal end of the first spring and the proximal end of the second spring via the carriage slide.

The proximal end of the second spring and the distal end of the first spring may be connected to axially opposite ends of the carriage slide.

The proximal end of the second spring, the carriage slide, and the distal end of the first spring may be configured to move together in unison as the carriage slide moves relative to the support arm.

The carriage slide may be slidable within at least one groove in the support arm.

The groove may be oriented along an axis that extends radially from and perpendicular to the main pivot axis.

The wall may be an internal wall that is supported by and projects inward from a perimeter wall of the support arm that surrounds the first and second springs.

The first and second springs may be gas springs having a cylinder and a rod, and the rod of the first spring and the cylinder of the second spring may be pivotably mounted to the distal end of the at least one link.

The at least one link may comprise a pair of links that straddle the first spring on laterally opposite sides of the first spring.

The support arm may include an intermediate portion between the proximal end and distal end of the support arm, and the intermediate portion may have a relatively narrower height span than the proximal end of the support arm, and the at least one link may have at least one bend that corresponds to the difference in height span between the intermediate portion and the proximal end of the support arm.

The support arm may have an angle of rotation about the main pivot axis of about <NUM> degrees upward from horizontal to about <NUM> degrees downward from horizontal.

The load balancing arm may further include a parallel link that is pivotably connected at its proximal end to a pin supported by the proximal hub and at its distal end to a pin supported by a distal hub pivotably connected to the distal end of the support arm.

The parallel link may include a pair of laterally spaced side walls that straddle a vertically lower portion of the first and second springs on laterally opposite sides of the first and second springs.

The parallel link may include a pair of laterally spaced side walls that straddle the at least one link on laterally opposite sides of the at least one link over at least a portion of a pivotable range of the load adjustment arm.

The following description and the annexed drawings set forth certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features according to aspects of the invention will become apparent from the following detailed description when considered in conjunction with the drawings.

The annexed drawings, which are not necessarily to scale, show various aspects of the disclosure.

While the present invention can take many different forms, for the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of modifications of the described embodiments, and any further applications of the principles of the invention as described herein, are contemplated as would normally occur to one skilled in the art to which the invention relates.

<FIG> shows a medical device support system <NUM>. The medical device support system <NUM> includes a central shaft or support column <NUM> that is suspended from the ceiling, and three generally horizontal extension arms <NUM> mounted to the shaft <NUM> for rotational movement about the shaft <NUM>. The central shaft <NUM> could be mounted to a wall or stand rather than the ceiling. Three load balancing arms <NUM>, which are also referred to as counterbalancing arms, are mounted to the respective extension arms <NUM>. The extension arms <NUM> and load balancing arms <NUM> each include a support arm structure or housing, or more generally a support arm. In the <FIG> embodiment, a proximal hub <NUM> of the load balancing arm <NUM> includes a support structure <NUM>, for example the illustrative drop tube <NUM>, that is rotatably connectable to a receptacle at the distal end <NUM> of the extension arm <NUM>. The distal end of each load balancing arm <NUM> is configured with a suitable support hub <NUM> to support a medical device load <NUM>. The medical device load <NUM> may include a surgical light as shown, or a supply console, a patient monitor, a camera detector head, a medical instrument, a ventilator system, a suction device, among others. A control console, if provided, may provide controls for navigation of a medical instrument that is either coupled to or remote from the load balancing arm <NUM>. The load balancing arm <NUM> enables positioning of the medical device <NUM> to a proper orientation relative to for example a patient operating table and healthcare professionals in the operating room.

Turning now to <FIG>, there is shown a load balancing arm <NUM> of the medical device support system <NUM> not in accordance with the invention. The load balancing arm <NUM> includes a proximal hub <NUM>, an adjustable bearing element <NUM>, a support arm <NUM>, a spring <NUM>, and one or more links, two such links <NUM>, <NUM> in the illustrative embodiment, as shown in <FIG> and <FIG>. The proximal hub <NUM> may include a support structure <NUM> such as the drop tube <NUM> (see <FIG>). The proximal hub <NUM> includes a main bearing element <NUM> that defines a main pivot axis <NUM>. The adjustable bearing element <NUM> defines an adjustable pivot axis <NUM> that is adjustable relative to the main pivot axis <NUM>. The support arm <NUM> has a proximal end <NUM> and a distal end <NUM>. The distal end <NUM> is configured to support a medical device load <NUM> (see <FIG>) and the proximal end <NUM> is pivotably mounted to the main bearing element <NUM> for pivotable movement about the main pivot axis <NUM>. Pivotable movement about the main pivot axis <NUM> raises and lowers the height of the medical device load <NUM> at the distal end <NUM>.

The spring <NUM> extends within a cavity <NUM> of the support arm <NUM> and is mounted to exert a biasing force between the main pivot axis <NUM> and a distal end <NUM> of the spring <NUM>. The links <NUM>, <NUM> each have a proximal end <NUM> and a distal end <NUM>. The proximal end <NUM> is pivotably mounted to the adjustable bearing element <NUM> for pivotable movement about the adjustable pivot axis <NUM>. The distal ends <NUM> of the links <NUM>, <NUM> are pivotably mounted to the distal end <NUM> of the spring <NUM> such that the biasing force exerted by the spring <NUM> is transmitted through the links <NUM>, <NUM> to the adjustable bearing element <NUM> thereby to generate a moment about the main pivot axis <NUM> of the proximal hub <NUM> that counters a moment generated by the medical device load <NUM> at the distal end <NUM> of the support arm <NUM>, thereby balancing the medical device load <NUM>.

Thus, in the load balancing arm <NUM>, the links <NUM>, <NUM> connect at their proximal ends <NUM> to an adjustment bearing element <NUM> and at their distal ends <NUM> to the distal end <NUM> of the spring <NUM>. As will be described in greater detail below, the attachment at the distal end <NUM> of the spring <NUM> allows for a relatively longer link than if connected to the proximal end of the spring <NUM>. This allows for a better force transmission and less spring travel resulting in a more balanced load balancing arm <NUM> throughout the pivotable range of travel of the arm <NUM>.

Reference is now made to <FIG> and <FIG> which show greater detail of the support arm <NUM>, the proximal hub <NUM>, and the interface between the support arm <NUM> and proximal hub <NUM>. As shown in <FIG>, <FIG> and <FIG>, the proximal end <NUM> of the support arm <NUM> has a relatively smaller width than the proximal hub <NUM> and fits within the proximal hub <NUM>. In the illustrated embodiment, the proximal end <NUM> of the support arm <NUM> includes a pair of vertically oriented laterally spaced protrusions or tongue portions <NUM> and a circular portion <NUM> substantially surrounding the tongue portions <NUM>. As shown in <FIG> and <FIG>, the proximal hub <NUM> includes a mounting surface <NUM> for mounting the proximal hub <NUM> and thus the load balancing arm <NUM> to, for example, the distal end of an extension arm <NUM>. The proximal hub <NUM> includes a pair of vertically oriented side walls <NUM> alongside which the tongue portions <NUM> of the support arm <NUM> slide during adjusting of the support arm <NUM>. In side profile, the side walls <NUM> have a circular shape that corresponds in diameter to the circular portion <NUM> of the proximal end <NUM> of the support arm <NUM>.

The proximal hub <NUM> also includes a load adjustment base <NUM> that extends width-wise between the pair of vertically oriented side walls <NUM> and that, as shown in <FIG>, extends vertically downward from a location just below the vertically uppermost portion of the circular portion <NUM> of the proximal end <NUM> of the support arm <NUM> downward approximately three fourths the distance across the circular portion <NUM>. Details of one example of the load adjustment base <NUM> are shown in <FIG>, <FIG>, <FIG> and <FIG>. As shown in <FIG>, the load adjustment base <NUM> may be fastened to the side walls <NUM> by fasteners <NUM>. As shown in <FIG>, the load adjustment base <NUM> has a pair of laterally spaced flanges <NUM> that are recessed inward from the outer width of the load adjustment base <NUM>. Referring to <FIG>, the recessed flanges <NUM> form respective gaps <NUM> with the side walls <NUM> within which the tongue portions <NUM> of the support arm <NUM> are received. As shown in <FIG>, <FIG> and <FIG>, the tongue portions <NUM> of the proximal end <NUM> of the support arm <NUM> have through holes <NUM> and the main bearing element <NUM> of the proximal hub <NUM> includes a pair of laterally spaced pins <NUM>. The central axis of these pins <NUM> defines or coincides with the main pivot axis <NUM>. The through holes <NUM> receive the pins <NUM> thereby to pivotably mount the proximal end <NUM> of the support arm <NUM> to the main bearing element <NUM> of the proximal hub <NUM> for pivotable movement of the support arm <NUM> about the main pivot axis <NUM>.

In the illustrative example, bushings <NUM> are provided on the pins <NUM> to promote smooth pivotable operation and serviceability. As shown in <FIG>, <FIG> and <FIG>, the pins <NUM> are fixedly connected, for example by welding, to a retainer plate <NUM>, which, in turn, is fastened to the side walls <NUM> of the proximal hub <NUM> by fasteners <NUM>.

As shown in <FIG> and <FIG>, a load adjustment screw <NUM> is rotatably mounted in a bottom wall <NUM> of the load adjustment base <NUM>. The load adjustment screw <NUM> is fixed in a vertical orientation in the proximal hub <NUM> and rotates about its own central axis <NUM>. Referring to <FIG> and <FIG>, in the present embodiment, the axis <NUM> of the load adjustment screw <NUM> is parallel to an axis <NUM> of rotation of the load balancing arm <NUM> extending centrally through the support structure <NUM> and perpendicular to horizontal. As shown in <FIG> and <FIG>, the adjustable bearing element <NUM> includes a load adjustment nut <NUM> that threadably engages the load adjustment screw <NUM> to adjust the adjustable pivot axis <NUM> relative to the main pivot axis <NUM>. The load adjustment nut <NUM> moves in the vertical direction as the load adjustment screw <NUM> is rotated, which vertical movement adjusts the adjustable pivot axis <NUM> relative to the main pivot axis <NUM>. As shown in <FIG>, the adjustable bearing element <NUM> includes a pin <NUM> that is carried by the load adjustment nut <NUM>. The central axis of the pin <NUM> defines or coincides with the adjustable pivot axis <NUM>. As shown in <FIG> and <FIG>, the proximal ends <NUM> of the links <NUM>, <NUM> are pivotably mounted to the pin <NUM> at respective opposite ends of the pin <NUM>. The adjustable pivot axis <NUM> is adjustable relative to the main pivot axis <NUM> over a range of adjustment <NUM>, defined in the illustrative embodiment by the uppermost and lowermost vertical position of the load adjustment nut <NUM>.

The vertical movement of the load adjustment nut <NUM> adjusts the load capacity of the load balancing arm <NUM>. As will be appreciated, the distance between the adjustable pivot axis <NUM> of the pin <NUM> and the main pivot axis <NUM> of the proximal hub <NUM> provides the mechanical advantage, or moment, that allows the load balancing arm <NUM> to balance a medical device load <NUM> at the distal end <NUM> of the arm <NUM>.

With reference to <FIG>, the laterally spaced pins <NUM> split the main pivot axis <NUM> thereby enabling the adjustable bearing element <NUM> to be moved vertically across the main pivot axis <NUM> into a position between the laterally spaced pins <NUM>. Accordingly, the adjustable bearing element <NUM> and the proximal ends <NUM> of the respective pair of links <NUM>, <NUM> are movable between the pair of pins <NUM> over a portion of the range of adjustment <NUM>. As will be appreciated, this provides greater adjustment range in the proximal ends <NUM> of the links <NUM>, <NUM> pivotably mounted to the pin <NUM> of the adjustable bearing element <NUM> than if the pins <NUM> were a single pin member and the main pivot axis <NUM> was not split. As shown in <FIG> and <FIG>, the split main pivot axis <NUM>, i.e. laterally spaced pins <NUM>, also enables the proximal ends <NUM> of the links <NUM>, <NUM> to move between the pins <NUM> for example when the load balancing arm <NUM> is pivoted to lower positions.

Referring to <FIG>, the adjustable pivot axis <NUM> of the adjustable bearing element <NUM> is horizontally offset from the main pivot axis <NUM> of the main bearing element <NUM> in a direction toward the portion of the proximal hub <NUM> that includes the support structure <NUM>, in the illustrative embodiment toward the axis <NUM> of rotation of the load balancing arm <NUM> extending centrally through the support structure <NUM> and perpendicular to horizontal. In <FIG>, the offset is the gap between the plane <NUM>-<NUM> and the axis <NUM>. This offset allows for better balancing of the spring arm when a lighthead or other medical device is attached. It also slightly changes the dynamics of the load balancing arm <NUM> so that when above horizontal there is slightly more mechanical advantage about the main pivot axis <NUM> and when below horizontal there is slightly less mechanical advantage about the main pivot axis <NUM>. As such, this allows the load balancing arm <NUM> to compensate for the spring force increasing as the arm <NUM> is moved to lower vertical positions, for example.

Turning now to <FIG>, <FIG> and <FIG>, the support arm <NUM> includes an intermediate portion <NUM> between the proximal end <NUM> and distal end <NUM> of the support arm <NUM>. The intermediate portion <NUM> has a relatively narrower height span than the circular portion <NUM> of the proximal end <NUM> of the support arm <NUM>. The links <NUM>, <NUM> (only link <NUM> is in view in <FIG>) have at least one bend that corresponds to the difference in height span between the intermediate portion <NUM> and the circular portion <NUM> of the proximal end <NUM> of the support arm <NUM>. In the illustrative embodiment, the links <NUM>, <NUM> have one bend and consequently have a J-shape in side view. Other shapes such as S-shape (two bends) are also contemplated. The bend in the links <NUM>, <NUM> aids in the load balancing arm <NUM> having a smaller size and lower overall cross section profile than if the links <NUM>, <NUM> were straight. The smaller size and lower overall cross section profile make the load balancing arm <NUM> less obstructive in the operating room and improve the laminar airflow around the surface of the load balancing arm <NUM>.

The distal ends <NUM> of the links <NUM>, <NUM> are pivotably mounted to the distal end <NUM> of the spring <NUM> via a carriage slide <NUM> that is slidable relative to the support arm <NUM>. The pivotable connection may be facilitated by, for example, a pin <NUM> mounted within the carriage slide <NUM>. As shown in <FIG>, the carriage slide <NUM> is slidable within at least one groove <NUM> in the support arm <NUM>, wherein in the illustrative embodiment there are two such grooves <NUM> at laterally opposite sides of the support arm <NUM>. The grooves <NUM> are oriented along an axis that extends radially from and perpendicular to the main pivot axis <NUM>. The grooves <NUM> are formed by parallel ribs <NUM> in the inward facing walls of the support arm <NUM>. The ribs <NUM>, along with a box shape member in the lower portion of the support arm <NUM>, also serve as stiffening members.

The spring <NUM> of the load balancing arm <NUM> may be any type of counterbalancing member, and in the illustrative embodiment is a compression gas spring <NUM>. Like the grooves <NUM>, the spring <NUM> is oriented along an axis that extends radially from and perpendicular to the main pivot axis <NUM>. The spring <NUM> has a cylinder <NUM> and a rod <NUM>. Referring to <FIG>, <FIG> and <FIG>, the cylinder <NUM> has a proximal end wall <NUM> that is coupled to a vertical beam <NUM> of the support arm <NUM>. As shown in <FIG>, the vertical beam <NUM> extends from a top wall <NUM> to a bottom wall <NUM> of the support arm <NUM> and is sufficiently narrow that the links <NUM>, <NUM> straddle the vertical beam <NUM> on opposite lateral sides thereof throughout the pivotable range of the load balancing arm <NUM>. The proximal end wall <NUM> of the cylinder <NUM> may be coupled to the vertical beam <NUM> in any suitable manner, for example as by a protrusion <NUM>, shown in <FIG>, that fits within an opening <NUM> in the vertical beam <NUM>, shown in <FIG>. The rod <NUM> is pivotably mounted to the distal ends <NUM> of the links <NUM>, <NUM> via the pin <NUM> of the afore described carriage slide <NUM>. In operation, the links <NUM>, <NUM> straddle the spring <NUM> on laterally opposite sides of the spring <NUM> throughout the pivotable range of the load balancing arm <NUM>.

Reference is now made to <FIG>, which show the load balancing arm <NUM> in three different vertical positions, and <FIG>, which show the links <NUM>, <NUM> and the proximal end <NUM> of the support arm <NUM> relative to the proximal hub <NUM> in the three respective vertical positions. The links <NUM>, <NUM> are shown adjusted to their maximum height in <FIG>, thereby maximizing the moment, or mechanical advantage, of the load balancing arm <NUM>. In <FIG> and <FIG>, the support arm <NUM> is in a substantially horizontal position. In <FIG> and <FIG>, the support arm <NUM> is shown pivoted about the main pivot axis <NUM> about <NUM> degrees upward relative to horizontal. In <FIG> and <FIG>, the support arm <NUM> is shown pivoted about the main pivot axis <NUM> about <NUM> degrees downward from horizontal. As will be appreciated, then, the support arm <NUM> has an angle of rotation about the main pivot axis <NUM> of about <NUM> degrees upward from horizontal to about <NUM> degrees downward from horizontal.

The load balancing arm <NUM> is in many respects similar to the above-referenced load balancing arm <NUM>, and consequently the same reference numerals are used to denote structures corresponding to similar structures in the load balancing arm <NUM>. In addition, the foregoing description of the load balancing arm <NUM> is equally applicable to the load balancing arm <NUM> except as noted below. Moreover, it will be appreciated upon reading and understanding the specification that aspects of the load balancing arms <NUM>, <NUM> may be substituted for one another or used in conjunction with one another where applicable.

Turning then to <FIG>, there is shown a load balancing arm <NUM> of the medical device support system <NUM>. The load balancing arm <NUM> includes a proximal hub <NUM>, an adjustable bearing element <NUM>, a support arm <NUM>, a spring <NUM>, and one or more links, two such links <NUM>, <NUM> in the illustrative embodiment, as shown in <FIG> and <FIG>. The load balancing arm <NUM> also includes a distal hub <NUM> shown in <FIG>, <FIG>, <FIG> and <FIG>, a parallel link <NUM> shown in <FIG>, <FIG>, <FIG> and <FIG>, and a load adjustment base <NUM> shown in <FIG> and <FIG>. The proximal hub <NUM> may include a support structure <NUM> such as the drop tube <NUM> (see <FIG>). The proximal hub <NUM> includes a main bearing element <NUM> that defines a main pivot axis <NUM>. The adjustable bearing element <NUM> defines an adjustable pivot axis <NUM> that is adjustable relative to the main pivot axis <NUM>. The support arm <NUM> has a proximal end <NUM> and a distal end <NUM>. The distal end <NUM> is pivotably mounted to the distal hub <NUM>, which, in turn, is configured to support a medical device load <NUM> (see <FIG>). The proximal end <NUM> is pivotably mounted to the main bearing element <NUM> for pivotable movement about the main pivot axis <NUM>. The pivotable movement raises and lowers the height of the medical device load <NUM> at the distal end <NUM>.

Thus, in the load balancing arm <NUM> , the links <NUM>, <NUM> connect at their proximal ends <NUM> to an adjustment bearing element <NUM> and at their distal ends <NUM> to the distal end <NUM> of the spring <NUM>. As will be described in greater detail below, the attachment at the distal end <NUM> of the spring <NUM> allows for a relatively longer link than if connected to the proximal end of the spring <NUM>. This allows for a better force transmission and less spring travel resulting in a more balanced load balancing arm <NUM> throughout the pivotable range of travel of the arm <NUM>.

Reference is now made to <FIG>, <FIG> and <FIG>, which show greater detail of the support arm <NUM>, the proximal hub <NUM>, and the interface between the support arm <NUM> and proximal hub <NUM>. As shown in <FIG> and <FIG>, the proximal end <NUM> of the support arm <NUM> has a relatively smaller width than the proximal hub <NUM> and fits within the proximal hub <NUM>. In the illustrated embodiment, the proximal end <NUM> of the support arm <NUM> includes a pair of vertically oriented laterally spaced protrusions or tongue portions <NUM> and a circular portion <NUM> substantially surrounding the tongue portions <NUM>. As shown in <FIG>, <FIG> and <FIG>, the proximal hub <NUM> includes a mounting surface <NUM> for mounting the proximal hub <NUM> and thus the load balancing arm <NUM> to, for example, the distal end of an extension arm <NUM>. The proximal hub <NUM> includes a pair of vertically oriented side walls <NUM> alongside which the tongue portions <NUM> of the support arm <NUM> slide during adjusting of the support arm <NUM>. In side profile, the side walls <NUM> have a circular shape that corresponds in diameter to the circular portion <NUM> of the proximal end <NUM> of the support arm <NUM>.

The proximal hub <NUM> also includes a load adjustment base <NUM> that extends width-wise between the pair of vertically oriented side walls <NUM> and that, as shown in <FIG>, <FIG> and <FIG> extends vertically downward from a location just below the vertically uppermost portion of the circular portion <NUM> of the proximal end <NUM> of the support arm <NUM> downward approximately three fourths the distance across the circular portion <NUM>. Details of one example of the load adjustment base <NUM> are shown in <FIG>, <FIG> and <FIG>. As shown in <FIG> and <FIG>, the load adjustment base <NUM> may be fastened to the side walls <NUM> by fasteners <NUM>. As shown in <FIG> and <FIG>, the load adjustment base <NUM> has a pair of laterally spaced flanges <NUM> that are recessed inward from the outer width of the load adjustment base <NUM>. Referring to <FIG>, the recessed flanges <NUM> form respective gaps <NUM> with the side walls <NUM> within which the tongue portions <NUM> of the support arm <NUM> are received. As shown in <FIG>, the tongue portions <NUM> of the proximal end <NUM> of the support arm <NUM> have through holes <NUM> and the main bearing element <NUM> of the proximal hub <NUM> includes a pair of laterally spaced pins <NUM>. The central axis of these pins <NUM> defines or coincides with the main pivot axis <NUM>. The through holes <NUM> receive the pins <NUM> thereby to pivotably mount the proximal end <NUM> of the support arm <NUM> to the main bearing element <NUM> of the proximal hub <NUM> for pivotable movement of the support arm <NUM> about the main pivot axis <NUM>.

Bushings <NUM> are provided on the pins <NUM> to promote smooth pivotable operation and serviceability. As shown in <FIG>, <FIG> and <FIG>, the pins <NUM> are fixedly connected, for example by welding, to a retainer plate <NUM>, which, in turn, is fastened to the side walls <NUM> of the proximal hub <NUM> by fasteners <NUM>.

As shown in <FIG>, <FIG>, <FIG> and <FIG>, a load adjustment screw <NUM> is rotatably mounted in a bottom wall <NUM> of the load adjustment base <NUM>. The load adjustment screw <NUM> is fixed in a vertical orientation in the proximal hub <NUM> and rotates about its own central axis <NUM>. Referring to <FIG> and <FIG>, in the present embodiment, the axis <NUM> of the load adjustment screw <NUM> is parallel to an axis <NUM> of rotation of the load balancing arm <NUM> extending centrally through the support structure <NUM> and perpendicular to horizontal. As shown in <FIG> and <NUM>, the adjustable bearing element <NUM> includes a load adjustment nut <NUM> that threadably engages the load adjustment screw <NUM> to adjust the adjustable pivot axis <NUM> relative to the main pivot axis <NUM>. The load adjustment nut <NUM> moves in the vertical direction as the load adjustment screw <NUM> is rotated, which vertical movement adjusts the adjustable pivot axis <NUM> relative to the main pivot axis <NUM>. As shown in <FIG> and <FIG>, the adjustable bearing element <NUM> includes a pin <NUM> that is carried by the load adjustment nut <NUM>. The central axis of the pin <NUM> defines or coincides with the adjustable pivot axis <NUM>. As shown in <FIG>, <FIG> and <FIG>, the proximal ends <NUM> of the links <NUM>, <NUM> are pivotably mounted to the pin <NUM> at respective opposite ends of the pin <NUM>. The adjustable pivot axis <NUM> is adjustable relative to the main pivot axis <NUM> over a range of adjustment <NUM>, defined in the illustrative embodiment by the uppermost and lowermost vertical position of the load adjustment nut <NUM>, as shown in <FIG>.

With reference to <FIG>, the laterally spaced pins <NUM> split the main pivot axis <NUM> thereby enabling the adjustable bearing element <NUM> to be moved vertically across the main pivot axis <NUM> into a position between the laterally spaced pins <NUM>. Accordingly, the adjustable bearing element <NUM> and the proximal ends <NUM> of the respective pair of links <NUM>, <NUM> are movable between the pair of pins <NUM> over a portion of the range of adjustment <NUM>. As will be appreciated, this provides greater adjustment range in the proximal ends <NUM> of the links <NUM>, <NUM> pivotably mounted to the pin <NUM> of the adjustable bearing element <NUM> than if the pins <NUM> were a single pin member and the main pivot axis <NUM> was not split.

Referring to <FIG> and <FIG>, the adjustable pivot axis <NUM> of the adjustable bearing element <NUM> and the main pivot axis <NUM> of the main bearing element <NUM> are horizontally offset the same distance from the axis <NUM> of rotation of the load balancing arm <NUM> extending centrally through the support structure <NUM>.

The distal ends <NUM> of the links <NUM>, <NUM> are pivotably mounted to the distal end <NUM> of the spring <NUM> via a carriage slide <NUM> that is slidable relative to the support arm <NUM>. The pivotable connection may be facilitated by, for example, a pin <NUM> mounted within the carriage slide <NUM>. As shown in <FIG>, the carriage slide <NUM> is slidable within at least one groove <NUM> in the support arm <NUM>, wherein in the illustrative embodiment there are two such grooves <NUM> at laterally opposite sides of the support arm <NUM>. The grooves <NUM> are oriented along an axis that extends radially from and perpendicular to the main pivot axis <NUM>. The grooves <NUM> are formed by parallel ribs <NUM> in the inward facing walls of the support arm <NUM>. The ribs <NUM>, along with a horizontal cross beam in the bottom portion of the support arm <NUM>, also serve as stiffening members.

The spring <NUM> of the load balancing arm <NUM> may be any type of counterbalancing member, and in the illustrative embodiment is a compression gas spring <NUM>. Like the grooves <NUM>, the spring <NUM> is oriented along an axis that extends radially from and perpendicular to the main pivot axis <NUM>. The spring <NUM> has a cylinder <NUM> and a rod <NUM>. Referring to <FIG>, <FIG>, <FIG> and <FIG>, the cylinder <NUM> has a proximal end wall <NUM> that is coupled to a vertical beam <NUM> of the support arm <NUM>. As shown in <FIG>, the vertical beam <NUM> extends from a top wall <NUM> to a bottom wall <NUM> of the support arm <NUM> and is sufficiently narrow that the links <NUM>, <NUM> straddle the vertical beam <NUM> on opposite lateral sides thereof throughout the pivotable range of the load balancing arm <NUM>. The proximal end wall <NUM> of the cylinder <NUM> may be coupled to the vertical beam <NUM> in any suitable manner, for example as by a protrusion <NUM>, shown in <FIG>, that fits within an opening <NUM> in the vertical beam <NUM>, shown in <FIG>. The rod <NUM> is pivotably mounted to the distal ends <NUM> of the links <NUM>, <NUM> via the pin <NUM> of the afore described carriage slide <NUM>. In operation, the links <NUM>, <NUM> straddle the spring <NUM> on laterally opposite sides of the spring <NUM> throughout the pivotable range of the load balancing arm <NUM>.

<FIG>, <FIG>, <FIG> and <FIG> show detail of the distal hub <NUM> of the load balancing arm <NUM>. The distal hub <NUM> is pivotably connected to the distal end <NUM> of the support arm <NUM> via a pair of laterally spaced pins <NUM> held in flanges of a vertical block <NUM> of the distal hub <NUM>. The vertical block <NUM> can be fixedly connected to a pair of vertically oriented side walls <NUM> of the distal hub <NUM> in a similar manner that the load adjustment base <NUM> is connected to the side walls <NUM> of the proximal hub <NUM>. Likewise, the distal end <NUM> of the support arm <NUM> can include laterally spaced protrusions <NUM> that pivotably connect to the respective laterally spaced pins <NUM> in a similar manner that the proximal end protrusions <NUM> pivotably connect to the laterally spaced pins <NUM> of the proximal hub <NUM>.

<FIG>, <FIG>, <FIG> and <FIG> show detail of the parallel link <NUM> of the load balancing arm <NUM>. The illustrative parallel link <NUM> is a single U-shape link with two vertically oriented laterally spaced parallel side walls <NUM> and a lower bridge member <NUM> connecting the bottom edges of the side walls <NUM>. It will be appreciated that the parallel link <NUM> may comprise two parallel links in the form of the two parallel side walls <NUM> with the lower bridge member <NUM> omitted. Referring to <FIG>, in the present embodiment, the parallel link <NUM> is made up of two pieces, a U-shape stainless steel member <NUM> and a pair of relatively harder stainless steel side braces <NUM> tack welded to the U-shape stainless steel member <NUM>.

The parallel link <NUM> is pivotably connected at its proximal end <NUM> to a pin <NUM> supported by the load adjustment base <NUM> of the proximal hub <NUM> and at its distal end <NUM> to a pin <NUM> supported by the vertical block <NUM> of the distal hub <NUM>. As shown in <FIG>, the split main pivot axis <NUM>, i.e. the laterally spaced pins <NUM>, enable the proximal end <NUM> of the parallel link <NUM> to move between the pins <NUM> for example when the load balancing arm <NUM> is pivoted to upper positions. Likewise, as shown in <FIG> and <FIG>, the split pivot axis <NUM>, i.e. the laterally spaced pins <NUM>, enable the distal end <NUM> of the parallel link <NUM> to move between the pins <NUM> for example when the load balancing arm <NUM> is pivoted to lower positions.

As shown in <FIG>, the pin <NUM> is oriented vertically below the pins <NUM> a distance <NUM> and the pin <NUM> is oriented vertically below the pins <NUM> by the same distance <NUM>. Also, the horizontal distance between the pins <NUM> and the pins <NUM> at opposite ends of the support arm <NUM> is equal to the horizontal distance between the pin <NUM> and the pin <NUM> at opposite ends of the parallel link <NUM>. In this way, a parallelogram is formed by the structure of the support arm <NUM> between the pins <NUM> and the pins <NUM>, the portion of the load adjustment base <NUM> between the pins <NUM> and the pin <NUM>, the parallel link <NUM> between the pin <NUM> and the pin <NUM>, and the portion of the vertical block <NUM> between the pin <NUM> and the pins <NUM>. Referring to <FIG>, owing to this parallelogram linkage, the vertically aligned pins <NUM>, <NUM> at the distal end <NUM> remain parallel to the vertically aligned pins <NUM>, <NUM> at the proximal end <NUM> throughout the pivotable range of the load balancing arm <NUM> about the main pivot axis <NUM>. This permits a medical device load <NUM> such as a monitor to remain properly oriented regardless of its vertical displacement from the ceiling of the operating room.

Referring now to <FIG>, <FIG>, <FIG>, <FIG> and <FIG>, the side walls <NUM> of the parallel link <NUM> straddle the vertically lower portion of the gas spring <NUM> on laterally opposite sides thereof. The side walls <NUM> also straddle the links <NUM>, <NUM> on laterally opposite sides of the links <NUM>, <NUM> over at least a portion of the pivotable range of the load adjustment arm <NUM>, particularly when the adjustable bearing element <NUM> is in lower positions as shown in <FIG>.

Reference is now made to <FIG>, which show the load balancing arm <NUM> in three different vertical positions, and <FIG>, which show the parallel link <NUM> and the distal end <NUM> of the support arm <NUM> relative to the distal hub <NUM> in the respective uppermost and lowermost vertical positions. The links <NUM>, <NUM> are shown adjusted to their maximum height in <FIG>, thereby maximizing the moment, or mechanical advantage, of the load balancing arm <NUM>. In <FIG>, the support arm <NUM> is in a substantially horizontal position. In <FIG> and <FIG>, the support arm <NUM> is shown pivoted about the main pivot axis <NUM> about <NUM> degrees upward relative to horizontal. In <FIG> and <FIG>, the support arm <NUM> is shown pivoted about the main pivot axis <NUM> about <NUM> degrees downward from horizontal. As will be appreciated, then, the support arm <NUM> has an angle of rotation about the main pivot axis <NUM> of about <NUM> degrees upward from horizontal to about <NUM> degrees downward from horizontal.

<FIG> show a load adjustment base <NUM> and an adjustable bearing element <NUM>. The load adjustment base <NUM> and adjustable bearing element <NUM> are in many respects similar to the above-referenced load adjustment bases <NUM>, <NUM> and adjustable bearing elements <NUM> shown for example in <FIG>, <FIG>, <FIG> and <FIG>, and consequently the same reference numerals are used in <FIG> to denote structures corresponding to similar structures in the load adjustment bases <NUM>, <NUM> and adjustable bearing elements <NUM>. In addition, the foregoing description of the load adjustment bases <NUM>, <NUM> and adjustable bearing elements <NUM> is equally applicable to the load adjustment base <NUM> and the adjustable bearing element <NUM> except as noted below. Moreover, it will be appreciated upon reading and understanding the specification that aspects of the load adjustment bases <NUM>, <NUM>, <NUM> may be substituted for one another or used in conjunction with one another where applicable, and aspects of the adjustable bearing elements <NUM>, <NUM> may be substituted for one another or used in conjunction with one another where applicable.

Turning to <FIG>, the load adjustment base <NUM> and the adjustable bearing element <NUM> are configured to enable a specific range of adjustment of the adjustable pivot axis <NUM> of the adjustable bearing element <NUM> relative to the main pivot axis <NUM> of the proximal hub <NUM>. As shown in <FIG>, <FIG> and <FIG>, a pair of socket head cap screws <NUM>, <NUM> are provided in respective threaded openings in a rear wall <NUM> of the load adjustment base <NUM>. As shown in <FIG> and <FIG>, the centers of the screws <NUM>, <NUM> are laterally spaced apart a distance X in a direction parallel to the main pivot axis <NUM>, and vertically spaced apart a distance Y in a direction perpendicular to the main pivot axis <NUM>. As shown in <FIG> and <FIG>, a pair of vertically extending slots <NUM>, <NUM> are provided in a load adjustment nut <NUM> of the adjustable bearing element <NUM>. The lateral spacing between the vertically extending slots <NUM>, <NUM> is equal to the lateral spacing Y between the centers of the screws <NUM>, <NUM>. In the illustrative embodiment, the screws <NUM>, <NUM> and slots <NUM>, <NUM> are on laterally opposite sides of the central axis <NUM> of the load adjustment screw <NUM>.

The tips <NUM>, <NUM> of the respective socket head cap screws <NUM>, <NUM> protrude forward from the rear wall <NUM> and are sized to fit within the respective slots <NUM>, <NUM>. One slot <NUM> has a lower abutment wall <NUM> and opens upward at a top surface <NUM> of the load adjustment nut <NUM> to define a vertical entranceway <NUM> for the screw <NUM>. The other slot <NUM> has an upper abutment wall <NUM> and opens downward at a bottom surface <NUM> of the load adjustment nut <NUM> to define a vertical entranceway <NUM> for the screw <NUM>. The lower and upper abutment walls <NUM>, <NUM> of the load adjustment nut <NUM> define the respective upper and lower limits on the range of adjustment of the load adjustment nut <NUM>, and thus, in reference to <FIG>, <FIG>, <FIG>, <FIG> and <FIG>, the upper and lower limits on the range of adjustment of the pin <NUM> to which the proximal ends <NUM> of the links <NUM>, <NUM> are pivotably mounted. This contrasts with the upper limit of the range of adjustment <NUM> being defined by a top wall of the load adjustment base <NUM>, <NUM> or an end-of-thread of the load adjustment screw <NUM>, and the lower limit being defined by the bottom wall <NUM> of the load adjustment base <NUM>, <NUM>.

Thus, as the load adjustment nut <NUM> moves up and down in the vertical direction as the load adjustment screw <NUM> is rotated respectively clockwise and counterclockwise, the adjustable pivot axis <NUM> moves vertically up and down relative to the main pivot axis <NUM> bound by the respective upper and lower limits on the adjustment range provided by the abutment walls <NUM>, <NUM> of the load adjustment nut <NUM>. <FIG> and <FIG> show an example of the lower limit. As will appreciated with reference to <FIG>, as the load adjustment nut <NUM> is urged downward, the upper abutment wall <NUM> of slot <NUM> eventually abuts the tip <NUM> of the socket head cap screw <NUM> thereby preventing further downward movement of the load adjustment nut <NUM>. As will be appreciated, in a similar manner, as the load adjustment nut <NUM> is urged upward, the lower abutment wall <NUM> of the slot <NUM> eventually abuts the tip <NUM> of the screw <NUM> to prevent further upward movement of the load adjustment nut <NUM>.

The <FIG> embodiment enables a specific range of adjustment of the adjustable pivot axis <NUM> relative to the main pivot axis <NUM>. For example, by adjusting the lengths of the slots <NUM>, <NUM> and/or the positions of the upper and lower abutment walls <NUM>, <NUM>, the range of adjustment can be changed without having to change the structure of the load adjustment base <NUM>. In the illustrative embodiment, for example, the lower abutment location, L, is vertically above the topmost portions of the diameters of the openings <NUM> that accommodate the laterally spaced pins <NUM> that form the main bearing element <NUM> (see <FIG> and <FIG>) that defines the main pivot axis <NUM>. When the upper abutment wall <NUM> has abutted the socket head cap screw <NUM>, the load adjustment nut <NUM> has reached its lowermost position or "bottomed out" but a clearance gap, C, remains between the bottom surface <NUM> of the load adjustment nut <NUM> and the bottom wall <NUM> of the load adjustment base <NUM>.

It will be appreciated that the quantity of socket head cap screws <NUM>, <NUM> and corresponding quantity of slots <NUM>, <NUM> need not be limited to two as shown. For example, a second pair of socket head cap screws and a second pair of slots further laterally spaced apart than the first pair of socket head cap screws <NUM>, <NUM> and the first pair of slots <NUM>, <NUM>, for a total of four socket head cap screws and four slots, can be provided, where the second pair of socket head cap screws and second pair of slots define a different upper and lower limit on the range of adjustment than that of the first pair of socket head cap screws <NUM>, <NUM> and first pair of slots <NUM>, <NUM>. It will also be appreciated that the rear wall <NUM> of the load adjustment base <NUM> may include a plurality of vertically staggered threaded openings to allow the vertical height of the screws <NUM>, <NUM> to be changed, thus allowing the corresponding range of adjustment of the adjustable pivot axis <NUM> relative to the main pivot axis <NUM> to be changed. It will also be appreciated that either the upper adjustment limit mechanism <NUM>, <NUM>, <NUM> or the lower adjustment limit mechanism <NUM>, <NUM>, <NUM> may be omitted and a different limit mechanism substituted therefor; for example, substituting a top wall of the load adjustment base <NUM>, <NUM> or an end-of-thread of the load adjustment screw <NUM> for the upper adjustment limit mechanism <NUM>, <NUM>, <NUM>, and/or substituting the bottom wall <NUM> of the load adjustment base <NUM>, <NUM> for the lower adjustment limit mechanism <NUM>, <NUM>, <NUM>. Other combinations are also contemplated. It will further be appreciated that protruding elements other than socket head cap screws <NUM>, <NUM> may be used to fit within the slots <NUM>, <NUM> to act as limits to the respective abutment walls <NUM>, <NUM> of the adjustable bearing element <NUM>. For example, rather than socket head cap screws <NUM>, <NUM> being inserted in respective threaded openings in the rear wall <NUM> of the load adjustment base <NUM>, clips may be inserted through respective through holes in the rear wall <NUM>, wherein the tips of the clips act as the limits to the respective abutment walls <NUM>, <NUM>.

<FIG> show a load balancing arm <NUM> according to an embodiment of the invention. The load balancing arm <NUM> is in many respects similar to the above-referenced load balancing arms <NUM>, <NUM> and consequently the same reference numerals are used to denote structures corresponding to similar structures in the load balancing arms <NUM>, <NUM>. In addition, the foregoing description of the load balancing arms <NUM>, <NUM> is equally applicable to the load balancing arm <NUM> except as noted below.

Turning then to <FIG>, there is shown a load balancing arm <NUM> of the medical device support system <NUM> in accordance with an embodiment of the invention. The load balancing arm <NUM> includes a proximal hub <NUM>, an adjustable bearing element <NUM>, a support arm <NUM>, first and second springs <NUM>, <NUM> and one or more links, two such links <NUM>, <NUM> in the illustrative embodiment, as shown in <FIG>. The proximal hub <NUM> may include a support structure <NUM> such as the drop tube <NUM> (see <FIG>). The proximal hub <NUM> includes a main bearing element <NUM> that defines a main pivot axis <NUM> (see <FIG> and <FIG>). The adjustable bearing element <NUM> defines an adjustable pivot axis <NUM> that is adjustable relative to the main pivot axis <NUM>. It is contemplated that the pivot axis <NUM> need not be adjustable relative to the main pivot axis <NUM> and, accordingly, the adjustable bearing element <NUM> and the adjustable pivot axis <NUM> may be referred to herein respectively as a link bearing element <NUM> and link pivot axis <NUM>. The support arm <NUM> has a proximal end <NUM> and a distal end <NUM>. The distal end <NUM> is configured to support a medical device load <NUM> (see <FIG>) and the proximal end <NUM> is pivotably mounted to the main bearing element <NUM> for pivotable movement about the main pivot axis <NUM>. Pivotable movement about the main pivot axis <NUM> raises and lowers the height of the medical device load <NUM> at the distal end <NUM>.

The first and second springs <NUM>, <NUM> extend within a cavity <NUM> (see <FIG>) of the support arm <NUM>. The first spring <NUM> is mounted to exert a biasing force between the main pivot axis <NUM> and a distal end <NUM> of the first spring <NUM>, and the second spring <NUM> is mounted to exert a biasing force between a proximal end <NUM> of the second spring <NUM> and a wall <NUM> at the distal end <NUM> of the support arm <NUM>. The links <NUM>, <NUM> each have a proximal end <NUM> and a distal end <NUM>. The proximal end <NUM> is pivotably mounted to the link bearing element <NUM> for pivotable movement about the link pivot axis <NUM> (or, where an adjustable bearing element <NUM> is provided, pivotably mounted to the adjustable bearing element <NUM> for pivotable movement about the adjustable pivot axis <NUM>). The distal ends <NUM> of the links <NUM>, <NUM> are pivotably mounted to the distal end <NUM> of the first spring <NUM> and the proximal end <NUM> of the second spring <NUM> such that the biasing forces exerted by the first and second springs <NUM>, <NUM> are transmitted through the links <NUM>, <NUM> to the link bearing element <NUM> thereby to generate a moment about the main pivot axis <NUM> of the proximal hub <NUM> that counters a moment generated by the medical device load <NUM> at the distal end <NUM> of the support arm <NUM>, thereby balancing the medical device load <NUM>.

Thus, in the load balancing arm <NUM> according to the present embodiment, there are two springs <NUM>, <NUM>, connected functionally in series, that together provide the load balancing arm <NUM> with an improved force transmission and a greater load bearing capacity, and thus a greater range of control than if the load balancing arm <NUM> had only a single spring; and these improvements are realized with minimal or no corresponding increase in the size of the load balancing arm <NUM>. In this regard, it is noted that the <FIG> dual spring load balancing arm <NUM> has the same cross sectional area as that of the <FIG> single spring load balancing arm <NUM>. Moreover, the links <NUM>, <NUM> connect at their proximal ends <NUM> to the bearing element <NUM> and at their distal ends <NUM> to the distal end <NUM> of the first spring <NUM>. The attachment at the distal end <NUM> of the first spring <NUM> allows for a relatively longer link than if connected to the proximal end of the first spring <NUM>, which has been found to allow for a better force transmission and less spring travel resulting in a more balanced load balancing arm <NUM> throughout the pivotable range of travel of the arm <NUM>.

The proximal end <NUM> of the support arm <NUM> of the load balancing arm <NUM> is identical in structure and function to that of the afore described load balancing arm <NUM> and thus for brevity further description thereof is omitted.

Turning now to <FIG> and <FIG>, the support arm <NUM> includes an intermediate portion <NUM> between the proximal end <NUM> and distal end <NUM> of the support arm <NUM>. The intermediate portion <NUM> has a relatively narrower height span than the circular portion <NUM> of the proximal end <NUM> of the support arm <NUM>. The links <NUM>, <NUM> (only link <NUM> is in view in <FIG>) have at least one bend that corresponds to the difference in height span between the intermediate portion <NUM> and the circular portion <NUM> (see <FIG>) of the proximal end <NUM> of the support arm <NUM>. In the illustrative embodiment, the links <NUM>, <NUM> have one bend and consequently have a J-shape in side view. Other shapes such as S-shape (two bends) are also contemplated. The bend in the links <NUM>, <NUM> aids in the load balancing arm <NUM> having a smaller size and lower overall cross section profile than if the links <NUM>, <NUM> were straight. The smaller size and lower overall cross section profile make the load balancing arm <NUM> less obstructive in the operating room and improve the laminar airflow around the surface of the load balancing arm <NUM>.

Referring to <FIG>, like the afore described load balancing arm <NUM>, the load balancing arm <NUM> includes a carriage slide <NUM> that is slidable relative to the support arm <NUM>. The distal ends <NUM> of the links <NUM>, <NUM> are pivotably mounted to the distal end <NUM> of the first spring <NUM> via the carriage slide <NUM>. The pivotable connection may be facilitated by, for example, a pin <NUM> mounted within the carriage slide <NUM>. The sliding connection between the carriage slide <NUM> and the support arm <NUM> for the load balancing arm <NUM> is identical to that of the carriage slide <NUM> and support arm <NUM> for the load balancing arm <NUM>; as such, reference is made again to <FIG>. As shown in <FIG>, the carriage slide <NUM> is slidable within at least one groove <NUM> in the support arm <NUM>, wherein in the illustrative embodiment there are two such grooves <NUM> at laterally opposite sides of the support arm <NUM>. The grooves <NUM> are oriented along an axis that extends radially from and perpendicular to the main pivot axis <NUM> (see <FIG> and <FIG>). The grooves <NUM> are formed by parallel ribs <NUM> in the inward facing walls of the support arm <NUM>. The ribs <NUM>, along with a box shape member in the lower portion of the support arm <NUM>, also serve as stiffening members.

The first and second springs <NUM>, <NUM> of the load balancing arm <NUM> may be any type of counterbalancing member, and in the illustrative embodiment are, respectively, a compression gas spring <NUM> and a tension gas spring <NUM>. Like the grooves <NUM>, the first and second springs <NUM>, <NUM> are oriented along an axis that extends radially from and perpendicular to the main pivot axis <NUM>. In the illustrated embodiment, the first spring <NUM> is configured to expand and contract along a first axis and the second spring <NUM> is configured to expand and contract along a second axis, and the first and second axes coincide with one another. Of course, in other embodiments, the first and second springs <NUM>, <NUM> may expand and contract along respective axes that do not coincide with one another, for example, where other components within the support arm <NUM> may impede the expansion and contraction of one or both of the first and second springs <NUM>, <NUM>, , in which case the first and second axes may be slightly offset from one another or at non-zero angles relative to one another.

The first spring <NUM> of the load balancing arm <NUM> is similar in structure and function as the spring <NUM> of the load balancing arm <NUM> and, accordingly, reference is made to <FIG>, <FIG> and <FIG> and the corresponding description of the spring <NUM> of the load balancing arm <NUM>. The first spring <NUM> has a cylinder <NUM> and a rod <NUM>. The cylinder <NUM> has a proximal end wall <NUM> at a proximal end <NUM> of the first spring <NUM> that is coupled to a vertical beam <NUM> of the support arm <NUM>. As shown in <FIG>, the vertical beam <NUM> extends from a top wall <NUM> to a bottom wall <NUM> of the support arm <NUM> and is sufficiently narrow that the links <NUM>, <NUM> straddle the vertical beam <NUM> on opposite lateral sides thereof throughout the pivotable range of the load balancing arm <NUM>. The proximal end wall <NUM> of the cylinder <NUM> may be coupled to the vertical beam <NUM> in any suitable manner, for example as by a protrusion <NUM>, shown in <FIG>, that fits within an opening <NUM> in the vertical beam <NUM>, shown in <FIG>. The rod <NUM> is pivotably mounted to the distal ends <NUM> of the links <NUM>, <NUM> via the pin <NUM> of the afore described carriage slide <NUM>. In operation, the links <NUM>, <NUM> straddle the first spring <NUM> on laterally opposite sides of the first spring <NUM> throughout the pivotable range of the load balancing arm <NUM>.

Details of the second spring <NUM> are shown in <FIG>. The second spring <NUM> has a cylinder <NUM> and a rod <NUM>. The cylinder <NUM> is connected to the carriage slide <NUM> and the rod <NUM> is connected to the wall <NUM> of the support arm <NUM> so that the second spring <NUM> exerts a biasing force that biases the carriage slide <NUM> and thus the distal ends <NUM> of the links <NUM>, <NUM> toward the distal end <NUM> of the support arm <NUM>. The cylinder <NUM> of the second spring <NUM> has a proximal end wall <NUM> at the proximal end <NUM> of the second spring <NUM> that is connected to the carriage slide <NUM> such that the proximal end wall <NUM> and the carriage slide <NUM> do not separate due to the biasing force. In this way, the proximal end <NUM> of the second spring <NUM>, the carriage slide <NUM>, and the distal end <NUM> of the first spring <NUM> are configured to move together in unison as the carriage slide <NUM> moves relative to the support arm <NUM>. In the illustrated embodiment, the cylinder <NUM> and the proximal end wall <NUM> of the second spring <NUM>, the carriage slide <NUM>, and the rod <NUM> of the first spring <NUM> are connected relative to each other and move together in unison as the carriage slide <NUM> moves relative to the support arm <NUM>. As will be described in greater detail below, the rod <NUM> of the second spring <NUM>, or more generally a distal end <NUM> of the second spring <NUM>, is connected to the wall <NUM> of the support arm <NUM> such that the rod <NUM> and the wall <NUM> do not separate due to the afore described biasing force.

The proximal end wall <NUM> of the cylinder <NUM> may be connected to the carriage slide <NUM> to prevent separation therebetween in any suitable manner. Referring to <FIG>, the proximal end wall <NUM> of the cylinder <NUM> is connected to the carriage slide <NUM> by spot welding although it will be appreciated that brazing, riveting, soldering and/or adhesive glue may additionally or alternately be used. In another form, the proximal end wall <NUM> may be connected to the carriage slide <NUM> by an axially extending threaded protrusion of the proximal end wall <NUM> threadedly engaging a corresponding axially extending threaded opening in the carriage slide <NUM>, or by a protrusion at the proximal end wall <NUM> being fitted within an opening in the carriage slide <NUM> in an interference-fit manner. In yet another form, the proximal end wall <NUM> may be connected to the carriage slide <NUM> by means of a pivotable connection, for example, by means of a transverse pin mounted within the carriage slide <NUM> pivotably received in a transverse bore in the proximal end wall <NUM>. In this way, the proximal end <NUM> of the second spring <NUM> is pivotably connected to the carriage slide <NUM> to prevent separation between the proximal end <NUM> of the second spring <NUM> and the carriage slide <NUM> and also to provide tolerance for misalignment among the first and second springs <NUM>, <NUM> and the carriage slide <NUM> axially relative to each another.

In the illustrated embodiment, the cylinder <NUM> of the second spring <NUM> and the rod <NUM> of the first spring <NUM> are connected to axially opposite ends of the carriage slide <NUM> in the slide direction of the carriage slide <NUM>. Thus, the proximal end <NUM> of the second spring <NUM> and the distal end <NUM> of the first spring <NUM> are connected to axially opposite ends of the carriage slide <NUM> in the slide direction of the carriage slide <NUM>. This aids the support arm <NUM> of the load balancing arm <NUM> in accommodating the second spring <NUM> within the cavity <NUM> (see <FIG>) of the support arm <NUM> without a corresponding increase in the cross sectional area (perpendicular to the slide direction) of the support arm <NUM>. As with the rod <NUM> of the first spring <NUM>, the cylinder <NUM> of the second spring <NUM> is pivotably mounted to the distal ends <NUM> of the links <NUM>, <NUM> via the pin <NUM> of the carriage slide <NUM>.

The wall <NUM> of the support arm <NUM> may take any suitable form to provide support for the second spring <NUM> at the distal end <NUM> of the support arm <NUM>. Referring to <FIG>, the wall <NUM> is an internal wall that is supported by and projects inward from a perimeter wall <NUM> of the support arm <NUM> that surrounds the first and second springs <NUM>, <NUM>. Laterally opposite convex portions <NUM> of the wall <NUM> are slidably fit within laterally opposite internal flanges <NUM> of the support arm <NUM>. The internal flanges <NUM> prevent the convex portions <NUM> and thus the wall <NUM> from twisting during operation or during assembly of the load balancing arm <NUM>. In the illustrated embodiment, the internal flanges <NUM> are an axial extension of the ribs <NUM> that form the grooves <NUM> (see <FIG>) within which the carriage slide <NUM> slides during operation. Thus, the internal flanges <NUM> of the support arm <NUM> are oriented along an axis that extends radially from and perpendicular to the main pivot axis <NUM>. In the illustrated embodiment, the internal flanges <NUM> of the support arm <NUM> are formed from the same extruded portion of the support arm <NUM> as the ribs <NUM> and grooves <NUM> that slidingly support the carriage slide <NUM>.

The wall <NUM> also includes axially facing bearing surfaces <NUM> that abut opposite facing axially facing bearing surfaces <NUM> of the internal flanges <NUM>. Referring to <FIG>, <FIG>, <FIG>, the axially facing bearing surfaces <NUM> of the wall <NUM> face axially inward toward the main pivot axis <NUM>, and the axially facing bearing surfaces <NUM> of the internal flanges <NUM> face axially outward away from the main pivot axis <NUM>. The bearing surfaces <NUM> of the wall <NUM> abut the bearing surfaces <NUM> of the internal flanges <NUM> to prevent the wall <NUM>, and thus the rod <NUM> and the distal end <NUM> of the second spring <NUM>, from moving toward the main pivot axis <NUM> of the proximal hub <NUM> or the proximal end <NUM> of the support arm <NUM>, due to the biasing force exerted by the second spring <NUM>. Thus, the second spring <NUM> biases the carriage slide <NUM> toward the wall <NUM> of the support arm <NUM> and, in so doing, biases the carriage slide <NUM> and thus the distal ends <NUM> of the links <NUM>, <NUM> toward the distal end <NUM> of the support arm <NUM> and correspondingly away from the proximal end <NUM> of the support arm <NUM>. In another form, the wall <NUM> may be cast integrally with the support arm <NUM> as a monolithic structure, or the wall <NUM> may be fixed to, for example by fasteners, an internal projection of the support arm <NUM>.

The rod <NUM> of the second spring <NUM>, or the distal end <NUM> of the second spring <NUM>, may be connected to the wall <NUM> to prevent separation therebetween in any suitable manner. Referring to <FIG>, the rod <NUM> of the second spring <NUM>, in the illustrated embodiment also the distal end <NUM> of the second spring <NUM>, is connected to the wall <NUM> by spot welding although it will be appreciated that brazing, riveting, soldering and/or adhesive glue may additionally or alternately be used. In another form, the rod <NUM> of the second spring <NUM> may be connected to the wall <NUM> by a threaded portion of the distal end of the rod <NUM> threadedly engaging a corresponding axially extending threaded opening in the wall <NUM>, or by the distal end of the rod <NUM> being fitted within an opening in the wall <NUM> in an interference-fit manner. In yet another form, the rod <NUM> may be connected to the wall <NUM> by means of a pivotable connection, for example, by means of a transverse pin mounted within the wall <NUM> pivotably received in a transverse bore in the rod <NUM>. In this way, the distal end <NUM> of the second spring <NUM> is pivotably connected to the wall <NUM> to prevent separation between the distal end <NUM> of the second spring <NUM> and the wall <NUM> and also to provide tolerance for misalignment among the first and second springs <NUM>, <NUM>, the carriage slide <NUM>, and the wall <NUM> axially relative to each another.

Reference is now made to <FIG>, which show the load balancing arm <NUM> in three different vertical positions, and <FIG>, which show the distal ends <NUM> of the links <NUM>, <NUM> relative to the distal end <NUM> of the support arm <NUM> in the three respective vertical positions, as well as the corresponding biasing effects of the first and second springs <NUM>, <NUM> in the three respective vertical positions. The links <NUM>, <NUM> are shown adjusted to their maximum height in <FIG> (the height from axis <NUM> to axis <NUM> in <FIG>), thereby maximizing the moment, or mechanical advantage, of the load balancing arm <NUM>.

In <FIG> and <FIG>, the support arm <NUM> is in a substantially horizontal position. Here, the first spring <NUM> is shown exerting a biasing force between the main pivot axis <NUM> and the distal end <NUM> of the first spring <NUM>, and the second spring <NUM> is shown exerting a biasing force between the proximal end <NUM> of the second spring <NUM> and the wall <NUM> at the distal end <NUM> of the support arm <NUM>. In the present embodiment, as the first spring <NUM> is a tension spring, the first spring <NUM> biases the distal ends <NUM> of the links <NUM>, <NUM> toward the distal end <NUM> of the support arm <NUM> and thus away from the proximal end <NUM> of the support arm <NUM> and away from the main pivot axis <NUM>. Also, as the second spring <NUM> is a compression spring <NUM> in the present embodiment, the second spring <NUM> likewise biases the distal ends <NUM> of the links <NUM>, <NUM> away from the proximal end <NUM> of the support arm <NUM> and away from the main pivot axis <NUM>. Thus, both the first spring <NUM> and the second spring <NUM> contribute to the biasing force that biases the distal ends <NUM> of the links <NUM>, <NUM> away from the proximal end <NUM> of the support arm <NUM> and away from the main pivot axis <NUM>. As the distal ends <NUM> of the links <NUM>, <NUM> are pivotably mounted to the distal end <NUM> of the first spring <NUM> and the proximal end <NUM> of the second spring <NUM>, the biasing forces exerted by the first and second springs <NUM>, <NUM> are transmitted through the links <NUM>, <NUM> to the link bearing element <NUM> thereby to generate a moment about the main pivot axis <NUM> of the proximal hub <NUM> that counters a moment generated by the medical device load at the distal end <NUM> of the support arm <NUM>.

In <FIG> and <FIG>, the support arm <NUM> is shown pivoted about the main pivot axis <NUM> about <NUM> degrees upward relative to horizontal. As compared to <FIG> and <FIG>, the first spring <NUM> in <FIG> and <FIG> is shorter in length from its proximal end <NUM> to its distal end <NUM> and the second spring <NUM> is greater in length from its proximal end <NUM> to its distal end <NUM>. Accordingly, in this position, the biasing force that the first spring <NUM> exerts to bias the distal ends <NUM> of the links <NUM>, <NUM> toward the distal end <NUM> of the support arm <NUM> is less than that shown in <FIG> and <FIG>, and the biasing force that the second spring <NUM> exerts to bias the distal ends of the links <NUM>, <NUM> toward the distal end <NUM> of the support arm <NUM> is less than that shown in <FIG> and <FIG>.

In <FIG> and <FIG>, the support arm <NUM> is shown pivoted about the main pivot axis <NUM> about <NUM> degrees downward from horizontal. As compared to <FIG> and <FIG>, the first spring <NUM> in <FIG> and <FIG> is greater in length from its proximal end <NUM> to its distal end <NUM> and the second spring <NUM> is shorter in length from its proximal end <NUM> to its distal end <NUM>. Accordingly, in this position, the biasing force that the first spring <NUM> exerts to bias the distal ends <NUM> of the links <NUM>, <NUM> toward the distal end <NUM> of the support arm <NUM> is greater than that shown in <FIG> and <FIG>, and the biasing force that the second spring <NUM> exerts to bias the distal ends of the links <NUM>, <NUM> toward the distal end <NUM> of the support arm <NUM> is greater than that shown in <FIG> and <FIG>.

As will be appreciated, then, the support arm <NUM> has an angle of rotation about the main pivot axis <NUM> of about <NUM> degrees upward from horizontal to about <NUM> degrees downward from horizontal.

In the <FIG> embodiment, the first spring <NUM> includes a compression spring having the cylinder <NUM> and the rod <NUM> wherein the cylinder <NUM> includes the proximal end <NUM> of the first spring <NUM> and the rod <NUM> includes the distal end <NUM> of the first spring <NUM>. This need not be the case and other embodiments are contemplated. For example, the cylinder <NUM> and rod <NUM> may be switched so that the cylinder <NUM> includes the distal end <NUM> of the first spring <NUM> and the rod <NUM> includes the proximal end <NUM> of the first spring <NUM>. Also, in the <FIG> embodiment, the second spring <NUM> includes a tension spring having the cylinder <NUM> and the rod <NUM> wherein the cylinder <NUM> includes the proximal end <NUM> of the second spring <NUM> and the rod <NUM> includes the distal end <NUM> of the second spring <NUM>. This too need not be the case and other embodiments are contemplated. For example, the cylinder <NUM> and rod <NUM> may be switched so that the cylinder <NUM> includes the distal end <NUM> of the second spring <NUM> and the rod <NUM> includes the proximal end <NUM> of the second spring <NUM>.

<FIG> show a load balancing arm <NUM> according to another embodiment of the invention. The load balancing arm <NUM> is in many respects similar to the above-referenced load balancing arms <NUM>, <NUM>, <NUM> and consequently the same reference numerals are used to denote structures corresponding to similar structures in the load balancing arms <NUM>, <NUM>, <NUM>. In addition, the foregoing description of the load balancing arms <NUM>, <NUM>, <NUM> is equally applicable to the load balancing arm <NUM> except as noted below.

Turning then to <FIG>, there is shown a load balancing arm <NUM> of the medical device support system <NUM> in accordance with an embodiment of the invention. The load balancing arm <NUM> includes a proximal hub <NUM>, an adjustable bearing element <NUM>, a support arm <NUM>, first and second springs <NUM>, <NUM> and one or more links, two such links <NUM>, <NUM> in the illustrative embodiment, as shown in <FIG>. The proximal hub <NUM> may include a support structure <NUM> such as the drop tube <NUM> (see <FIG>). The proximal hub <NUM> includes a main bearing element <NUM> that defines a main pivot axis <NUM> (see <FIG> and <FIG>). The adjustable bearing element <NUM> defines an adjustable pivot axis <NUM> that is adjustable relative to the main pivot axis <NUM>. It is contemplated that the pivot axis <NUM> need not be adjustable relative to the main pivot axis <NUM> and the adjustable bearing element <NUM> defines an adjustable pivot axis <NUM> that is adjustable relative to the main pivot axis <NUM>. It is contemplated that the pivot axis <NUM> need not be adjustable relative to the main pivot axis <NUM> and, accordingly, the adjustable bearing element <NUM> and the adjustable pivot axis <NUM> may be referred to herein respectively as a link bearing element <NUM> and link pivot axis <NUM>. The support arm <NUM> has a proximal end <NUM> and a distal end <NUM>. The distal end <NUM> is pivotably mounted to the distal hub <NUM>, which, in turn, is configured to support a medical device load <NUM> (see <FIG>). The proximal end <NUM> is pivotably mounted to the main bearing element <NUM> for pivotable movement about the main pivot axis <NUM>. The pivotable movement about the main pivot axis <NUM> raises and lowers the height of the medical device load <NUM> at the distal end <NUM>.

Turning now to <FIG> and <FIG>, the support arm <NUM> includes an intermediate portion <NUM> between the proximal end <NUM> and distal end <NUM> of the support arm <NUM>. The intermediate portion <NUM> has a relatively narrower height span than the circular portion <NUM> of the proximal end <NUM> of the support arm <NUM>. The links <NUM>, <NUM> (only link <NUM> is shown in <FIG>) have at least one bend that corresponds to the difference in height span between the intermediate portion <NUM> and the circular portion <NUM> (see <FIG>) of the proximal end <NUM> of the support arm <NUM>. In the illustrative embodiment, the links <NUM>, <NUM> have one bend and consequently have a J-shape in side view. Other shapes such as S-shape (two bends) are also contemplated. The bend in the links <NUM>, <NUM> aids in the load balancing arm <NUM> having a smaller size and lower overall cross section profile than if the links <NUM>, <NUM> were straight. The smaller size and lower overall cross section profile make the load balancing arm <NUM> less obstructive in the operating room and improve the laminar airflow around the surface of the load balancing arm <NUM>.

Referring to <FIG>, like the afore described load balancing arm <NUM>, the load balancing arm <NUM> includes a carriage slide <NUM> that is slidable relative to the support arm <NUM>. The distal ends <NUM> of the links <NUM>, <NUM> are pivotably mounted to the distal end <NUM> of the first spring <NUM> via the carriage slide <NUM>. The pivotable connection may be facilitated by, for example, a pin <NUM> mounted within the carriage slide <NUM>. The sliding connection between the carriage slide <NUM> and the support arm <NUM> for the load balancing arm <NUM> is identical to that of the carriage slide <NUM> and support arm <NUM> for the load balancing arm <NUM>; as such, reference is made again to <FIG>. As shown in <FIG>, the carriage slide <NUM> is slidable within at least one groove <NUM> in the support arm <NUM>, wherein in the illustrative embodiment there are two such grooves <NUM> at laterally opposite sides of the support arm <NUM>. The grooves <NUM> are oriented along an axis that extends radially from and perpendicular to the main pivot axis <NUM> (see <FIG> and <FIG>). The grooves <NUM> are formed by parallel ribs <NUM> in the inward facing walls of the support arm <NUM>. The ribs <NUM>, along with a horizontal cross beam the bottom portion of the support arm <NUM>, also serve as stiffening members.

The first and second springs <NUM>, <NUM> of the load balancing arm <NUM> may be any type of counterbalancing member, and in the illustrative embodiment are, respectively, a compression gas spring <NUM> and a tension gas spring <NUM>. Like the grooves <NUM>, the first and second springs <NUM>, <NUM> are oriented along an axis that extends radially from and perpendicular to the main pivot axis <NUM>. In the illustrated embodiment, the first spring <NUM> is configured to expand and contract along a first axis and the second spring <NUM> is configured to expand and contract along a second axis, and the first and second axes coincide with one another. Of course, in other embodiments, the first and second springs <NUM>, <NUM> may expand and contract along respective axes that do not coincide with one another, for example, where other components within the support arm <NUM> may impede the expansion and contraction of one or both of the first and second springs <NUM>, <NUM>, in which case the first and second axes may be slightly offset from one another or at non-zero angles relative to one another.

The first spring <NUM> of the load balancing arm <NUM> is similar in structure and function as the spring <NUM> of the load balancing arm <NUM> and, accordingly, reference is made to <FIG>, <FIG>, <FIG>, and <FIG> and the corresponding description of the spring <NUM> of the load balancing arm <NUM>. The first spring <NUM> has a cylinder <NUM> and a rod <NUM>. The cylinder <NUM> has a proximal end wall <NUM> at a proximal end <NUM> of the first spring <NUM> that is coupled to a vertical beam <NUM> of the support arm <NUM>. As shown in <FIG>, the vertical beam <NUM> extends from a top wall <NUM> to a bottom wall <NUM> of the support arm <NUM> and is sufficiently narrow that the links <NUM>, <NUM> straddle the vertical beam <NUM> on opposite lateral sides thereof throughout the pivotable range of the load balancing arm <NUM>. The proximal end wall <NUM> of the cylinder <NUM> may be coupled to the vertical beam <NUM> in any suitable manner, for example as by a protrusion <NUM>, shown in <FIG>, that fits within an opening <NUM> in the vertical beam <NUM>, shown in <FIG>. The rod <NUM> is pivotably mounted to the distal ends <NUM> of the links <NUM>, <NUM> via the pin <NUM> of the afore described carriage slide <NUM>. In operation, the links <NUM>, <NUM> straddle the first spring <NUM> on laterally opposite sides of the first spring <NUM> throughout the pivotable range of the load balancing arm <NUM>.

Details of the second spring <NUM> are shown in <FIG> and <FIG>. The second spring <NUM> has a rod <NUM> and a cylinder <NUM>. The rod <NUM> is connected to the carriage slide <NUM> and the cylinder <NUM> is connected to the wall <NUM> of the support arm <NUM> so that the second spring <NUM> exerts a biasing force that biases the carriage slide <NUM> and thus the distal ends <NUM> of the links <NUM>, <NUM> toward the distal end <NUM> of the support arm <NUM>. The rod <NUM> of the second spring <NUM>, in the illustrated embodiment also the proximal end <NUM> of the second spring <NUM>, is connected to the carriage slide <NUM> such that the rod <NUM> and the carriage slide <NUM> do not separate due to the biasing force. In this way, the proximal end <NUM> of the second spring <NUM>, the carriage slide <NUM>, and the distal end <NUM> of the first spring <NUM> are configured to move together in unison as the carriage slide <NUM> moves relative to the support arm <NUM>. In the illustrated embodiment, the rod <NUM> of the second spring <NUM>, the carriage slide <NUM>, and the rod <NUM> of the first spring <NUM> are connected relative to each other and move together in unison as the carriage slide <NUM> moves relative to the support arm <NUM>. As will be described in greater detail below, the cylinder <NUM> of the second spring <NUM>, or more generally a distal end <NUM> of the second spring <NUM>, is connected to the wall <NUM> of the support arm <NUM> such that the cylinder <NUM> and the wall <NUM> do not separate due to the afore described biasing force.

The rod <NUM> of the second spring <NUM>, or the proximal end <NUM> of the second spring <NUM>, may be connected to the carriage slide <NUM> to prevent separation therebetween in any suitable manner. Referring to <FIG>, the rod <NUM> of the second spring <NUM> is connected to the carriage slide <NUM> by spot welding although it will be appreciated that brazing, riveting, soldering and/or adhesive glue may additionally or alternately be used. In another form, the rod <NUM> may be connected to the carriage slide <NUM> by a threaded portion of the proximal end of the rod <NUM> threadedly engaging a corresponding axially extending threaded opening in the carriage slide <NUM>, or by the proximal end of the rod <NUM> being fitted within an opening in the carriage slide <NUM> in an interference-fit manner. In yet another form, the rod <NUM> may be connected to the carriage slide <NUM> by means of a pivotable connection, for example, by means of a transverse pin mounted within the carriage slide <NUM> pivotably received in a transverse bore in the carriage slide <NUM>. In this way, the proximal end <NUM> of the second spring <NUM> is pivotably connected to the carriage slide <NUM> to prevent separation between the proximal end <NUM> of the second spring <NUM> and the carriage slide <NUM> and also to provide tolerance for misalignment among the first and second springs <NUM>, <NUM> and the carriage slide <NUM> axially relative to each another.

In the illustrated embodiment, the rod <NUM> of the second spring <NUM> and the rod <NUM> of the first spring <NUM> are connected to axially opposite ends of the carriage slide <NUM> in the slide direction of the carriage slide <NUM>. Thus, the proximal end <NUM> of the second spring <NUM> and the distal end <NUM> of the first spring <NUM> are connected to axially opposite ends of the carriage slide <NUM> in the slide direction of the carriage slide <NUM>. This aids the support arm <NUM> of the load balancing arm <NUM> in accommodating the second spring <NUM> within the cavity <NUM> (see <FIG>) of the support arm <NUM> without a corresponding increase in the cross sectional area (perpendicular to the slide direction) of the support arm <NUM>. As with the rod <NUM> of the first spring <NUM>, the rod <NUM> of the second spring <NUM> is pivotably mounted to the distal ends <NUM> of the links <NUM>, <NUM> via the pin <NUM> of the carriage slide <NUM>.

The wall <NUM> of the support arm <NUM> may take any suitable form to provide support for the second spring <NUM> at the distal end <NUM> of the support arm <NUM>. Referring to <FIG> and <FIG>, the wall <NUM> is an internal wall that is supported by and projects inward from a perimeter wall <NUM> of the support arm <NUM> that surrounds the first and second springs <NUM>, <NUM>. In the present embodiment, the wall <NUM> is cast integrally with the support arm <NUM> as a monolithic structure. The cylinder <NUM> of the second spring <NUM> has a distal end wall <NUM> at the distal end <NUM> of the second spring <NUM> that is connected to the wall <NUM>. The connection between the wall <NUM> and the cylinder <NUM> of the second spring <NUM> prevents the cylinder <NUM> and the distal end <NUM> of the second spring <NUM> from moving toward the main pivot axis <NUM> of the proximal hub <NUM> or the proximal end <NUM> of the support arm <NUM>, due to the biasing force exerted by the second spring <NUM>. Thus, the second spring <NUM> biases the carriage slide <NUM> toward the wall <NUM> of the support arm <NUM> and, in so doing, biases the carriage slide <NUM> and thus the distal ends <NUM> of the links <NUM>, <NUM> toward the distal end <NUM> of the support arm <NUM> and correspondingly away from the proximal end <NUM> of the support arm <NUM>. In another form, the wall <NUM> may be a different structure from the remainder of the support arm <NUM> and be fixed to, for example by fasteners, an internal projection of the support arm <NUM>. In another form, the wall <NUM> may be structured and function in a manner similar to the wall <NUM> of the support arm <NUM> of the load balancing arm <NUM>.

The distal end wall <NUM> of the cylinder <NUM> may be connected to the wall <NUM> to prevent separation therebetween in any suitable manner. Referring to <FIG> and <FIG>, the distal end wall <NUM> of the cylinder <NUM> is connected to the wall <NUM> by spot welding although it will be appreciated that brazing, riveting, soldering and/or adhesive glue may additionally or alternately be used. In another form, the distal end wall <NUM> of the cylinder <NUM> may be connected to the wall <NUM> by an axially extending threaded protrusion of the distal end wall <NUM> threadedly engaging a corresponding axially extending threaded opening in the wall <NUM>, or by a protrusion of the distal end wall <NUM> being fitted within an opening in the wall <NUM> in an interference-fit manner. In yet another form, the distal end wall <NUM> may be connected to the wall <NUM> by means of a pivotable connection, for example, by means of a transverse pin mounted within the wall <NUM> pivotably received in a transverse bore in the distal end wall <NUM>. In this way, the distal end <NUM> of the second spring <NUM> is pivotably connected to the wall <NUM> to prevent separation between the distal end <NUM> of the second spring <NUM> and the wall <NUM> and also to provide tolerance for misalignment among the first and second springs <NUM>, <NUM>, the carriage slide <NUM>, and the wall <NUM> axially relative to each another.

Reference is now made to <FIG>, which show the load balancing arm <NUM> in three different vertical positions, and <FIG>, which show the distal ends <NUM> of the links <NUM>, <NUM> relative to the distal end <NUM> of the support arm <NUM> in the three respective vertical positions, as well as the corresponding biasing effects of the first and second springs <NUM>, <NUM> in the three respective vertical positions. The links <NUM>, <NUM> are shown adjusted to their maximum height in <FIG> (the height from axis <NUM> to axis <NUM> in <FIG> and <FIG>), thereby maximizing the moment, or mechanical advantage, of the load balancing arm <NUM>.

In the <FIG> embodiment, the first spring <NUM> includes a compression spring having the cylinder <NUM> and the rod <NUM> wherein the cylinder <NUM> includes the proximal end <NUM> of the first spring <NUM> and the rod <NUM> includes the distal end <NUM> of the first spring <NUM>. This need not be the case and other embodiments are contemplated. For example, the cylinder <NUM> and rod <NUM> may be switched so that the cylinder <NUM> includes the distal end <NUM> of the first spring <NUM> and the rod <NUM> includes the proximal end <NUM> of the first spring <NUM>. Also, in the <FIG> embodiment, the second spring <NUM> includes a tension spring having the rod <NUM> and the cylinder <NUM> wherein the rod <NUM> includes the proximal end <NUM> of the second spring <NUM> and the cylinder <NUM> includes the distal end <NUM> of the second spring <NUM>. This too need not be the case and other embodiments are contemplated. For example, the rod <NUM> and cylinder <NUM> may be switched so that the rod <NUM> includes the distal end <NUM> of the second spring <NUM> and the cylinder <NUM> includes the proximal end <NUM> of the second spring <NUM>.

Claim 1:
A load balancing arm (<NUM>) for a medical device support system (<NUM>), comprising:
a proximal hub (<NUM>) including a main bearing element (<NUM>) defining a main pivot axis (<NUM>);
a link bearing element (<NUM>) defining a link pivot axis (<NUM>);
a support arm (<NUM>) having a proximal end (<NUM>) and a distal end (<NUM>),
wherein the distal end (<NUM>) is configured to support a medical device load (<NUM>) and the proximal end (<NUM>) is pivotably mounted to the main bearing element (<NUM>) for pivotable movement about the main pivot axis (<NUM>); characterized by
a first spring (<NUM>) extending within a cavity (<NUM>) of the support arm (<NUM>) and mounted to exert a biasing force between the main pivot axis (<NUM>) and a distal end (<NUM>) of the first spring (<NUM>);
a second spring (<NUM>) extending within the cavity (<NUM>) of the support arm (<NUM>) and mounted to exert a biasing force between a proximal end (<NUM>) of the second spring (<NUM>) and a wall (<NUM>) at the distal end (<NUM>) of the support arm (<NUM>); and,
at least one link (<NUM>,<NUM>) having a proximal end (<NUM>) pivotably mounted to the link bearing element (<NUM>) for pivotable movement about the link pivot axis (<NUM>), and a distal end (<NUM>) pivotably mounted to the distal end (<NUM>) of the first spring (<NUM>) and the proximal end (<NUM>) of the second spring (<NUM>) such that the biasing forces exerted by the first and second springs (<NUM>,<NUM>) are transmitted through the link (<NUM>,<NUM>) to the link bearing element (<NUM>) thereby to generate a moment about the main pivot axis (<NUM>) of the proximal hub (<NUM>) that counters a moment generated by the medical device load (<NUM>) at the distal end of the support arm (<NUM>).