Patent Description:
The present disclosure generally relates to positioning apparatuses for holding and positioning objects, and more particularly to medical positioning apparatuses.

Positioning apparatuses are currently used for multiple applications, including medical applications where they are used for maintaining limbs or other body parts, or holding surgical tools during surgical procedure for example. Positioning apparatuses may also have industrial applications where they may be used to hold tools or objects being manufactured.

Some medical positioning apparatuses comprise joints which are locked using hydraulic pressure and then released when this hydraulic pressure is removed. Such systems may require bulky hydraulic systems for maintaining a constant hydraulic pressure. Furthermore, such systems may not be fail-safe: in case of malfunction, for example when electrical power loss or a leakage causes a loss of hydraulic pressure, such positioning apparatuses may collapse.

Therefore, there is a need for an improved positioning apparatus.

<CIT>, <CIT>, <CIT> and <CIT> each disclose a positioning apparatus with features of claim <NUM>.

The invention provides a medical positioning apparatus according to claim <NUM>. Further embodiments of the invention are provided in the dependent claims.

According to a first broad aspect, there is provided a medical positioning apparatus for positioning and holding an object, comprising: a telescopic member extending between a first end and a second end and having an adjustable length; a support member for receiving the object; a base member securable to a base; a first joint mechanism movably securing the support member to the first end of the telescopic member; a second joint mechanism movably securing the base member to the second end of the telescopic member, the first and second joint mechanisms each having at least two rotational degrees of freedom; a locking device operatively connected to the first and second joint mechanisms and the telescopic member, the locking device operable between a locked position in which the support member, the base member, and the telescopic member are lockingly interconnected together and the length of the telescopic member is fixed, and a released position in which the support and base members are free to pivotally move with respect to the telescopic member and the length of the telescopic member is adjustable, the locking device being passively biased in the locked state; and a lock activation device to unlock the locking device biased in the locked position in order to adjust the length of the telescopic member and a relative position of the support member, the base member, and the telescopic member.

In one embodiment, the locking device comprises a first, second, and third locking units operatively connected to the first joint mechanism, the second joint mechanism, and the telescopic member, respectively, and each passively biased in the locked position.

In one embodiment, each one of the first, second, and third locking units comprises an elastic member, a piston, and a brake pad operatively connected together, the elastic member being passively compressed when the first, second, and third locking units are in the locked position, and being further actively compressed when the first, second, and third locking units are in the released position upon activation of the lock activation device.

In one embodiment, the lock activation device is a pump fluidly connected to the first, second, and third locking units to define a closed-circuit containing a fluid in contact with the piston for the first, second, and third locking units, an activation of the pump causing an increase in a pressure of the fluid for further compressing the elastic member via the piston and unlocking the first, second, and third locking units.

The first and second joint mechanisms may each comprise a ball and a socket operatively connected together. In this case, the brake pad abuts the ball against the socket for preventing any relative motion between the ball and the socket when the first and second locking units are in the locked position, and is away/disengaged from the ball when the first and second locking units are in the released position.

In one embodiment, the first and second locking units are integrated into the socket of the first and second joint mechanisms, respectively.

In one embodiment, the ball comprises a first and a second hemispherical portions moveably connected together, the first hemispherical portion being fixedly secured to the telescopic member, the piston abutting the second hemispherical portion against the socket for preventing any relative motion between the ball and the socket when the first and second locking units are in the locked position, and the piston being away from the second hemispherical portion when the first and second locking units are in the released position.

In one embodiment, the telescopic member comprises a first elongated and hollow member and a second elongated member having a given end slidably engaged within the first elongated and hollow member, the third locking unit being secured at the given end of the second elongated member.

The brake pad of the third locking unit engages an internal surface of the first elongated and hollow member for fixing the length of the telescopic member when the third locking unit is in the locked position, the brake pad being away from the internal surface when the third locking unit is in the released position.

In one embodiment, the pump is a foot pump to be manually operable. In
one embodiment, the elastic member is at least one Belleville spring.

In one embodiment, the lock activation device is adapted to substantially concurrently unlock the first, second, and third locking units.

In one embodiment, the lock activation device comprises one of a cable and push/pull/torsion rods.

In one embodiment, the support member comprises one of a limb support.

In one embodiment, the support member is a tool holder.

In one embodiment, the base member is securable to one of a bed, a chair, and a table.

According to a second broad aspect, there is provided a joint mechanism for a medical positioning apparatus, comprising: a first joint member; a second joint member movable with respect to the first joint according to at least one degree of freedom; a locking device operatively connected to at least one of the first and second joint members, the locking device operable between a locked position in which the first and second joint members are lockingly interconnected together, and a released position in which the first and second joint members are free to move with respect to each other, the locking device being passively biased in the locked state and connectable to a lock activation device, the lock activation device for unlocking the locking device biased in the locked state in order to adjust a relative position of the first and second joint members.

In one embodiment, the locking device comprises an elastic member, a piston, and a brake pad operatively connected together, the elastic member being passively compressed when the locking device is in the locked position, and being actively further compressed when the locking device is in the released position upon activation of the lock activation device.

In one embodiment, the first joint member comprises a joint ball and the second joint member comprises a joint socket operatively connected to the joint ball, the brake pad abutting the joint ball against the joint socket for preventing any relative motion therebetween when the locking device is in the locked position, and the brake pad being away from the joint ball when the locking device in the released position.

In one embodiment, the first joint member is a first elongated and hollow member and the second joint member is a second elongated member having a given end slidably engaged within the first elongated and hollow member, the locking device being secured at the given end of the second elongated member, the brake pad of the locking device engaging an internal surface of the first elongated and hollow member for releasably securing the first and second elongated members together when the locking device is in the locked position, and the brake pad being away from the internal surface when the locking device is in the released position.

In the present description, an object should be understood as an inanimate object, such as a medical or surgical tool for example, or a living being or a part of living being, such as a human being limb for example.

The terms "resilient" and "elastic" are interchangeably used in the following description and used for characterizing a material capable reversible deformation.

The expressions "joint" or "joint mechanism" refers to a connection between two body members which allows relative movement between the two body members with one or more degrees of freedom between them.

The foregoing and other objects, advantages and features of the present disclosure will become more apparent upon reading of the following non-restrictive description of illustrative embodiments thereof, given by way of examples only with reference to the accompanying drawings.

Generally stated, the positioning apparatus described herein is concerned with a releasable lockable telescopic arm having two joint mechanisms at its ends. The joint mechanisms have each three rotational degrees of freedom. These joints and the telescopic arm may be locked and released using a locking mechanism described below. The locking mechanism is passively biased in a locked position and an external intervention is required for unlocking the locking mechanism in order to change the configuration of the positioning apparatus. The positioning apparatus offers a very wide range of adjustment over several degrees of freedom.

Lockable and releasable mechanisms are used for releasably locking the joint mechanisms in a desired position and the telescopic arm at a desired length. The joint mechanisms are passively locked using elastic energy, or potential energy, stored as pressure in a resilient member, for example a spring. Releasing the joint mechanisms is made using hydraulic pressure, pneumatic pressure, tension from a cable, push/pull rods, or a similar force that overcomes pressure from the resilient member.

Likewise, the telescopic arm may comprise a locking mechanism. The locking mechanism may be attached at an extremity of a first segment of the telescopic arm and is lockable on a second segment of the telescopic arm. The locking mechanism is locked using elastic energy stored as pressure in a resilient member, for example a spring. Releasing the locking mechanism is made using hydraulic pressure, pneumatic pressure, tension from a cable, push/pull rods, or a similar force that overcomes pressure from the resilient member.

In case of malfunction, for example when leakage causes a loss of hydraulic pressure, the positioning apparatus maintains its position at the joint mechanisms and at the arm locking mechanism because the elastic energy stored as pressure in the resilient member is not affected.

In one embodiment, a first intended use of the positioning apparatus is as a limb positioner for medical use. For example, the positioning apparatus may be used for surgery such as orthopaedic surgery, shoulder arthroscopic surgery, abdominal surgery, laparoscopic surgery, and/or the like. A second intended use of the positioning apparatus may be as a medical/surgical tool holder. These suggested uses are not limiting and are provided solely for illustration purposes.

In one embodiment, for a use as a reusable medical device, a limb interface for receiving a limb may be attached to a first joint mechanism of the positioning apparatus. The interface may then be in direct contact with a patient's limb. Alternatively, a tool interface for receiving a surgical or medical tool may be secured to the first joint mechanism. A second joint mechanism may be attached to a base interface or member which is securable to a base such as a surgical table for example.

<FIG> illustrates one embodiment of a positioning apparatus <NUM> to be mounted to a base. The positioning apparatus <NUM> comprises a support or base member <NUM> which forms a securing device for attachment to the base such as a surgical table (not shown) for example. The positioning apparatus <NUM> comprises a telescopic arm <NUM> having three segments 3a, 3b and 3c, an upper spherical joint mechanism (not shown), a housing <NUM> covering the upper spherical joint mechanism, and a lower spherical joint mechanism <NUM>. An accessory coupling <NUM> allows connection of the positioning apparatus <NUM> to various accessories, depending on its intended use. For example, the accessory coupling <NUM> may be used for securing a receiving member (not shown) adapted to receive an object such as a patient limb or a surgical tool. The spherical joint mechanisms each comprise a ball jointed to the telescopic arm, only the lower ball <NUM> is visible on <FIG>. The lower spherical joint mechanism <NUM> is connected to an arm holder <NUM> of the support <NUM> via an arm <NUM>. The support <NUM> further comprises height adjustment guides <NUM> and a table clamp <NUM>. The positioning apparatus <NUM> is thus an arm-like mechanism used as a means to position, and to maintain in a desired position, a limb during a medical intervention, or a tool for various industrial applications. In an embodiment, the support <NUM> allows a position adjustment of the positioning apparatus <NUM>, at its bottom-end, along a side of a surgical table. Various bases may be designed for various applications. The spherical joint mechanisms <NUM> and <NUM> allow a wide range of positions of an object attached to the accessory coupling <NUM>.

The positioning apparatus <NUM> further comprises a locking device (not shown) operatively connected to the upper and lower joint mechanisms and the telescopic arm, and a lock activation device (not shown) for locking and releasing the locking device. When locked, the locking device lockingly interconnects the upper and lower joint mechanisms to the telescopic arm <NUM> so that no motion of the upper and lower joint mechanisms relative to the arm <NUM> is possible, and lockingly interconnects the arm segments 3a, 3b, and 3c together so that the length of the telescopic arm is fixed. Therefore, the positioning apparatus <NUM> is fixed in a given configuration. When the locking device is released, the telescopic arm <NUM> is free to move with respect to the upper and lower joint mechanisms and the arm segments 3a, 3b, and 3c are free to move the ones with respect to the others in order to adjust the positioning apparatus <NUM> from one configuration to another.

The locking device is passively biased in the locked position, i.e. in the absence of external intervention (when the lock activation device is not actuated) the configuration of the positioning apparatus is fixed and cannot be changed. In order to change the configuration of the positioning apparatus <NUM>, the lock activation device must be activated.

In one embodiment, the locking device comprises a first locking unit operatively connected to the upper joint mechanism, a second locking unit operatively connected to the lower joint mechanism <NUM>, a third locking unit secured to the arm segment 3b and operatively connected to the arm segment 3a, and a fourth locking unit secured to the arm segment 3c and operatively connected to the arm segment 3b. Each locking unit is passively biased in a locked position and may comprise a compressed elastic device and a piston operatively connected together. For the first and second locking units in the locked position and since the elastic device is in compression, the piston exerts a force on its respective joint mechanism which is prevented to move. For the third and fourth locking units in the locked position and since the elastic device is in compression, the piston exerts a force on the arm segment 3a and the arm segment 3b, respectively, in order to prevent any relative motion between the arm segments 3a, 3b, and 3c.

<FIG> is an example of use of the positioning apparatus of <FIG> as a limb support. The positioning apparatus <NUM>, and the support <NUM> forming its base, are mounted on a surgical table <NUM>. The table <NUM> is shown in a so-called "beach chair" position, but the positioning apparatus <NUM> could also be attached to most types of surgical chairs or beds, including dental chairs. A limb support <NUM>, or limb interface, is connected to the positioning apparatus <NUM> via the accessory coupling <NUM>. A patient <NUM> is shown to illustrate a possible use of the positioning apparatus <NUM> for orthopaedic surgery.

In one embodiment, the lock activation device comprises a pedal or foot pump <NUM> and fluidic connections filled with fluid such as oil for example. The fluidic connections fluidly connect the foot pump <NUM> to the locking units which each comprise an adjustable oil chamber of which one wall is formed by the piston. When a user depresses the foot pump, the force exerted by the user is transferred to the oil contained in the oil chambers. As a result, the oil contained in the oil chambers exerts a force on the pistons. For a given force exerted by the user on the foot pump <NUM>, the force exerted by the oil contained in each oil chamber on its respective piston becomes greater than the force exerted by its respective elastic device on the respective piston. The locking units are then in the released position and the configuration of the positioning apparatus may be changed. When he has positioned the positioning apparatus <NUM> in a desired position, the user stops exerting the force on the foot pump <NUM> and the locking units return in the locked position, thereby maintaining the positioning apparatus <NUM> in the desired configuration.

Therefore, depressing the foot pump <NUM> with a foot may cause a release of the various locking mechanisms of the positioning apparatus <NUM>, allowing for example a surgeon to effortlessly position a limb for surgery. Releasing the pedal removes all hydraulic pressure, whereafter resilient members within the various locking mechanisms maintain the positioning apparatus <NUM>, and the patient's limb, in a desired position.

Those of ordinary skills in the art will readily appreciate that the positioning apparatus <NUM> may be used for various medical, veterinarian, or other applications. The positioning apparatus <NUM> may be attached to any base and to any accessory (not shown) attached to the accessory coupling <NUM>. Non limiting examples of accessories may include tools, tool holders, computer displays, robots or robot components, and the like.

<FIG> illustrates another embodiment of a positioning apparatus <NUM>'. Some parts of the upper and lower spherical joint mechanisms are omitted in <FIG> in order to show upper ball <NUM>, the lower ball <NUM>, connecting tubes <NUM> and <NUM>, and covers <NUM> and <NUM>. The balls <NUM> and <NUM> and their respective connecting tubes <NUM> and <NUM> are permanently joined, for example by adhesive or welding, and are fixedly attached to respective ends of the telescopic arm <NUM>'. The covers <NUM> and <NUM> are put in place prior to bonding the lower ball <NUM> to the connecting tube <NUM> and to the segment <NUM> using adhesives, and prior to securing the upper ball <NUM> to the connecting tube <NUM> to the segment <NUM>. The covers <NUM> and <NUM> as well as other parts of the spherical joint mechanisms <NUM>' and <NUM>' (shown on next Figures) may move around the balls <NUM> and <NUM>, when in unlocked position. The telescopic arm <NUM>' comprises an upper segment <NUM> and a lower segment <NUM>. The upper segment <NUM> shows a telescopic arm locking mechanism <NUM>, which will be described in details hereinbelow. While the present description refers to a telescopic arm <NUM>' comprising two segments <NUM> and <NUM>, it should be understood that the telescopic arm <NUM>' may comprise more than two segments. Similarly, while the arm segment <NUM> fits and slides into the hollow arm member <NUM>, other configurations are possible. For example, the arm segment <NUM> may comprise a rail on its outer surface in which the arm segment <NUM> may slide. It should also be understood that the shape, dimensions, and/or materials for the arm segments may vary and are chosen according to the needs of an intended application.

Of course, for use in some applications, the positioning apparatus <NUM>' may be attached to a base located at an elevated point such as a ceiling for example, and an object supported by the positioning apparatus <NUM>' may be located at a lower point. Those of ordinary skills in the art will appreciate that terms such as "upper", "lower", and the like are used for illustration purposes and are not meant to limit the present disclosure.

<FIG> is a side cutaway view of a movable spherical joint mechanism operatively connected to a locking device in an unlocked position, the locking device comprising a spring and a piston. <FIG> is a side cutaway view of the movable spherical joint mechanism and the locking device in a locked position. Considering at once <FIG> and <FIG>, the upper spherical joint mechanism <NUM>' is shown in parts. It should be observed that its operating principles,are the same as those of the lower spherical joint mechanism <NUM> and the following description of those principles applies to both spherical joint mechanisms. The upper spherical joint mechanism <NUM>' comprises the cover <NUM>, the ball <NUM> (omitted from <FIG> and <FIG>), a piston <NUM> having a hollow spherical portion <NUM> for positioning the ball <NUM> and a hollow cylindrical portion <NUM> for passage of hydraulic tubes (not shown) and like ancillary devices. The cover <NUM> is attached to a housing <NUM> that contains the piston <NUM>, the housing <NUM> further attached to a coupling attachment <NUM> using various screws <NUM>. The coupling attachment <NUM> is for attaching to an accessory coupling interface. The piston <NUM> abuts on springs <NUM>, for example Belleville springs. Belleville springs are compact and minimize a length of the housing <NUM>. Other types of springs, such as coil springs, or other types of resilient members, such as a compressible foam pad, may be used for some applications. Seals <NUM>, such as o-rings gaskets for example, maintain a tight seal between the piston <NUM> and the housing <NUM>. One or more shims 28A, or spacers, may be inserted between the coupling attachment <NUM> and the springs <NUM>, being used as spacers in order to adjust a pressure applied by the springs <NUM> on the piston <NUM> and further on the ball <NUM>. Additionally, one or more shims <NUM>, or spacers, may be used to limit an upper movement of the piston <NUM>. A screw (not shown) allows the piston <NUM> to move up and down, within the housing <NUM>, while preventing its rotation within the housing <NUM>. Most of the components of the upper spherical joint mechanism <NUM>' are circular and a cutaway view will be similar in most angles. However the screws and an oil inlet <NUM> are located at discrete points around a diameter of the housing <NUM>.

As shown on <FIG>, the upper spherical joint mechanism <NUM>' is in the locked position. The springs <NUM> push on the piston <NUM>, which further pushes on the ball <NUM> (not shown), firmly keeping the ball <NUM> in position against the cover <NUM>. The piston <NUM> and the cover <NUM> thus act as brake pads for the ball <NUM>. A small gap <NUM> is created above the piston <NUM>, between the piston <NUM> and the coupling attachment <NUM> or, if the shims <NUM> are present, between the shims <NUM> and the coupling attachment <NUM>. A circular oil chamber <NUM> contains oil at a low pressure and has a minimized depth D1. As shown on <FIG>, the upper spherical joint mechanism <NUM>' is in the unlocked position. A higher oil pressure is induced via the oil inlet <NUM> within the oil chamber <NUM>, inflating the oil chamber <NUM> until it reaches a maximized depth D2, pushing the piston <NUM> upward against the pressure of the springs <NUM>. As the oil pressure creates a force to overcome pressure from the springs <NUM>, the gap <NUM> disappears. At the same time, the piston <NUM> is no longer pushing on the ball <NUM>, which is free to rotate, for example within a range of plus or minus <NUM> degrees around a central axis of the housing <NUM>. It may be observed that zero, one or more shims 28A may be used to adjust the level of resistance for the upper spherical joint mechanism <NUM>' in order to set the predefined oil pressure at which the upper spherical joint mechanism will unlock.

In an embodiment, pneumatic pressure could be used instead of hydraulic pressure within the upper spherical joint mechanism <NUM>. Those of ordinary skills in the art will appreciate that the upper spherical joint mechanism's operating principles will not be essentially modified. They will be able to adapt tolerances and sealing means within the joint to use pneumatic pressure.

In another embodiment, a cable, for example a Bowden cable comprising an inner flexible wire within an outer hollow cable housing, similar to cables used for ordinary bicycle brakes, may be used to pull on the piston <NUM>, pulling force being applied from the top of the piston <NUM> so to overcome pressure from the springs <NUM>.

<FIG> is a side cutaway view of a movable spherical joint mechanism attached to a telescopic arm and to a base. The lower spherical joint mechanism <NUM> differs from the upper spherical joint mechanism <NUM> in some details, but not in its operating principles. The lower spherical joint mechanism <NUM> comprises the ball <NUM>, which is attached to the lower segment <NUM> via the connecting tube <NUM>. Also shown are the cover <NUM>, a housing <NUM>, a base attachment <NUM> comprising the arm <NUM> connected to the arm holder <NUM> of the support <NUM>, various screws <NUM>, a piston <NUM>, springs <NUM> maintained in place by spring holders <NUM>, and an oil chamber <NUM>. Oil enters the oil chamber <NUM> via an oil inlet <NUM> connected to a hydraulic fitting <NUM>, which is itself connected to a hydraulic pump (not shown). It may be observed that the upper spherical joint mechanism <NUM>' of <FIG> and <FIG> comprises an oil inlet <NUM> connected to a hydraulic fitting (not shown) similar to the oil inlet <NUM> and to the hydraulic fitting <NUM> of <FIG>. A bleeding plug <NUM> and a base plug 39A allow maintenance of the lower spherical joint mechanism <NUM>. An oil tube <NUM>, cables (not shown) or similar ancillary devices may pass through passages of the springs <NUM>, a ball <NUM>, a connecting tube <NUM>, and a lower segment <NUM>. Oil pressure entering via the hydraulic fitting <NUM> may be applied to release the lower spherical joint mechanism <NUM>, allowing a wide range of adjustment of a position of the telescopic arm <NUM>. When the oil pressure is removed, pressure applied by the springs <NUM> on the piston <NUM> and further on the ball <NUM> maintains the ball <NUM> against the cover <NUM>, locking the position of the telescopic arm <NUM>.

A length of the telescopic arm <NUM> is defined by a desired position of an object attached to the accessory coupling <NUM>. The telescopic arm <NUM>' comprises two (<NUM>) segments <NUM> and <NUM>, one sliding within the other one, so that the telescopic arm <NUM> may be elongated or retracted to the desired length. The desired position is maintained by friction between the segments <NUM> and the arm locking mechanism <NUM> attached to the segment <NUM>. In an embodiment, the telescopic arm <NUM>' may comprise more segments and a plurality of arm locking mechanisms.

Energy stored in a resilient member mechanism forces the telescopic arm <NUM> to maintain a fixed length until an opposite force overcomes pressure from the resilient member mechanism. <FIG> is a side cutaway view of a telescopic arm locking mechanism in locked position. <FIG> is a side cutaway view of a telescopic arm locking mechanism in unlocked position. The arm locking mechanism <NUM> comprises a housing <NUM>, a cap <NUM>, a piston <NUM> that maintains a tight seal against the housing <NUM> by use of o-rings <NUM>, one or more rollers <NUM> positioned on a circumference of a support <NUM>, brake pads <NUM>, which may be metallic pads, a resilient member such as springs <NUM>, which in an embodiment may be Belleville springs, shims <NUM>, an oil inlet <NUM> and a hydraulic fitting <NUM>.

The arm locking mechanism <NUM> may be attached at the top of the segment <NUM>, which as shown on <FIG>, has a smaller diameter compared to the segment <NUM>. Attachment of the arm locking mechanism <NUM> to the segment <NUM> may be by bonding, welding, gluing, tight insertion, or any suitable means. The segment <NUM> and the arm locking mechanism <NUM> are thus inserted within the segment <NUM>. As shown on <FIG>, the arm locking mechanism <NUM> is in locked position. Pressure from the springs <NUM> push on the support <NUM>, creating a gap <NUM> between the support <NUM> and the cap <NUM>. As the support <NUM> is pushed down, the rollers <NUM> push on the brake pads <NUM>, which rotate about respective axis <NUM>, a tip <NUM> of each brake pad <NUM> moving outwardly and applying pressure on an inner surface of the segment <NUM>. Pressure from the brake pads <NUM> on the inner surface of the segment <NUM> maintains a relative position between the two segments <NUM> and <NUM>, thereby maintaining a length of the telescopic arm <NUM>'. The support <NUM> also applies pressure on the piston <NUM>. An oil chamber <NUM> has a minimized depth D3 and has a low hydraulic pressure.

In one embodiment, the arm locking mechanism <NUM> may be mounted within the segment <NUM> in various positions. When the segment <NUM>, which has a wider diameter, is located above the narrower segment <NUM> and when the arm locking mechanism <NUM> is mounted vertically as shown on <FIG> - the cap <NUM> being in a higher position above the piston <NUM> - weight on the telescopic arm <NUM>' may tend to push down the segment <NUM>. Because of the configuration of the brake pad <NUM>, which applies pressure on the inner surface of the segment <NUM> at its tip <NUM>, this weight applies an added friction force of the brake pad <NUM> on the segment <NUM>.

<FIG> shows that the oil chamber <NUM> has extended to a maximized depth D4 when high hydraulic pressure from the hydraulic fitting <NUM> enters the oil chamber <NUM> through the oil inlet <NUM>. This oil pressure creates a force that pushes the piston <NUM> against the support <NUM>, the support <NUM> pushing against the springs <NUM>, overcoming their pressure. The gap <NUM> disappears. As the support <NUM> moves up, the rollers <NUM> no longer push the brake pads <NUM>, which may move inwardly and which no longer apply pressure on the inner surface of the segment <NUM>. This removes any restriction to the length of the telescopic arm <NUM>', which may then be extended or shortened as desired. In an embodiment, application of the oil pressure may be controlled by the pedal <NUM>.

<FIG> is an exploded view of a telescopic arm locking mechanism. It may be observed that the arm locking mechanism <NUM> comprises generally circular members having inner passages for the oil tubes <NUM>, cables (not shown) and like devices. Various parts of the arm locking mechanism <NUM> are held together using screws <NUM>.

<FIG> is a side cutaway view of another example of telescopic arm locking mechanism. An arm locking mechanism <NUM> is attached, for example by gluing or welding, at the top of the segment <NUM> and is located, with the top of the segment <NUM>, within the segment <NUM>. The arm locking mechanism <NUM> comprises a generally frusto-pyramidal base <NUM>, a cap <NUM> screwed onto the base <NUM>, a piston <NUM> abutting on springs <NUM> which further abut on the cap <NUM>, and one or more deformable polymeric brake pads <NUM>. One brake pad <NUM> may fill a full circumference of the arm locking mechanism <NUM> or, alternatively, several brake pads <NUM> may be positioned around the circumference. When in a resting position, the springs <NUM> push down on the piston <NUM>, thereby elastically deforming the brake pads <NUM> which in turn push against an internal surface of the segment <NUM>. In order to release the arm locking mechanism <NUM>, hydraulic pressure may be applied in an oil chamber <NUM>, confined by o-rings <NUM>, via a hydraulic inlet <NUM>. The hydraulic pressure creates a force that pushes the piston <NUM> upward against the springs <NUM>, overcoming their downward pressure. As the piston <NUM> moves upwards, the one or more brake pads <NUM> regain a somewhat circular sectional shape, thereby no longer pushing against the internal surface of the segment <NUM>. Relative movement of the segments <NUM> and <NUM> is then possible. A stop <NUM> may prevent the arm locking mechanism <NUM> and the segment <NUM> from becoming disengaged from the segment <NUM>.

Variations of the arm locking mechanisms <NUM> or <NUM> will come to mind to those of ordinary skill in the art. For example, in an embodiment, coil springs or a compressible foam pad may substitute for the Belleville springs. The type of resilient member and the presence and number of shims may vary according to expected weight applied on the telescopic arm <NUM>', materials used, and the like. In an embodiment, pneumatic pressure could be used instead of hydraulic pressure within the arm locking mechanisms <NUM> or <NUM>. In another embodiment, a Bowden cable may be used to pull on the pistons <NUM> or <NUM>. In another embodiment, an equivalent arm locking mechanism, fixedly attached to the segment <NUM>, may comprise a bore for insertion of the segment <NUM>. This arm locking mechanism may thus have brake pads that push inwardly on an outer surface of the segment <NUM>, when in locked position.

Considering any one of <FIG>, and <FIG>, each one of the spherical joint mechanisms and each one the arm locking mechanisms comprises a support (<NUM>, <NUM>, <NUM>, <NUM>), a movable member (<NUM>, <NUM>, <NUM>) or a deformable member (<NUM>), a piston (<NUM>, <NUM>, <NUM>, <NUM>) capable of moving along an axis of the support, a resilient member (<NUM>, <NUM>, <NUM>, <NUM>) applying pressure on the piston for transmitting the pressure to the movable or deformable member in order to lock the movable or deformable member, and oil enclosed in a chamber (<NUM>, <NUM>, <NUM>, <NUM>) for exerting on the piston a force opposing the pressure from the resilient member, the oil pressure being controlled by a pump. Applying the force on the piston overcomes the pressure from the resilient member and releases the movable or deformable member.

<FIG> is another example of use of a positioning apparatus as a limb support, showing another base. The positioning apparatus <NUM> is mounted on a base <NUM> attached to the surgical table <NUM>.

<FIG> illustrate a further embodiment of a positioning apparatus <NUM>. The positioning apparatus <NUM> comprises a telescopic member or arm <NUM> having a first or upper end 102a and a second or lower end 102b. A first or upper joint mechanism <NUM> and a second or lower joint mechanism <NUM> are secured at the ends 102a and 102b of the telescopic arm <NUM>, respectively. The positioning apparatus <NUM> further comprises an interface member <NUM> secured to the upper joint mechanism <NUM> for receiving an object thereon, and a base member <NUM> for removably securing the positioning apparatus <NUM> to a base.

While in the illustrated embodiment the interface member <NUM> is adapted to receive an arm, it should be understood that any adequate interface member for receiving an object may be used. For example, the interface member may be adapted to receive a limb other than an arm such as a leg for example. In another example, the interface member may be adapted to receive a surgical or medical tool.

While in the illustrated embodiment the base member <NUM> comprises an elongated member <NUM> having one end secured to the lower joint mechanism <NUM> and an adjustable clamp <NUM> secured at the other end of the elongated member <NUM> for removably securing the positioning apparatus <NUM> to a surgical table for example, it should be understood that other configurations for the base member <NUM> may be used. For example, the base member <NUM> can be adapted for being removably or permanently secured to any adequate base such as a floor, a wall, a ceiling, a bed, a chair, or the like.

As illustrated in <FIG>, the telescopic arm <NUM> comprises two hollow elongated members <NUM> and <NUM> which are adapted so that the hollow member fits and slides into the hollow member <NUM>. The telescopic arm <NUM> comprises a third hollow elongated member <NUM> connected at one end of the hollow member <NUM> via a connector <NUM>, thereby providing the telescopic arm <NUM> with a substantially L-shape. The hollow member <NUM> is further connected to the lower joint mechanism <NUM>.

Three locking devices <NUM>, <NUM>, and <NUM> are operatively connected to the upper joint mechanism <NUM>, the lower joint mechanism <NUM>, and the hollow member <NUM>, respectively. The locking devices <NUM> and <NUM> are used for selectively locking the joint mechanisms <NUM> and <NUM>, respectively, in a desired position while the locking device <NUM> is used for fixing the length of the telescopic member <NUM> at a desired length. As described below, the locking devices <NUM>, <NUM>, and <NUM> are passively locked in a locked position, thereby preventing any position adjustment of the joint mechanisms <NUM> and <NUM> and any length adjustment for the telescopic member <NUM> without external intervention.

The external intervention is provided via a lock activation device <NUM>, as illustrated in <FIG>. In the illustrated embodiment, the lock activation device <NUM> is a pump fluidly connected to the locking devices <NUM>, <NUM>, and <NUM>. A fluidic connection <NUM> fluidly connects the pump <NUM> to a T-shaped fluidic manifold <NUM>. The fluidic connector <NUM> is inserted into the connector <NUM> and comprises an inlet fluidly connected to the fluidic connection <NUM> and two outlets. The first outlet is fluidly connected to the locking unit <NUM> via a fluidic connection <NUM> extending through the hollow member <NUM>, and the second outlet is fluidly connected to the locking unit <NUM> via a fluidic connection <NUM> extending inside the hollow arm member <NUM>. The locking unit <NUM> is further connected to the locking unit <NUM> via a fluidic connection <NUM> extending inside the hollow arm member <NUM>. The fluidic connections <NUM>-<NUM>, the pump <NUM>, and the chambers described below are filled with oil, and form a substantially hermetical closed-circuit from which oil cannot substantially leak.

<FIG> illustrate the upper joint mechanism <NUM> in a locked position and a released or unlocked position, respectively. The joint mechanism <NUM> comprises a ball <NUM>, a connecting tube <NUM> for connection to an interface connector <NUM> of the interface member <NUM>, and a casing <NUM>. The connecting tube <NUM> interconnects the ball <NUM> and the interface connector <NUM> which is used for connecting the interface member <NUM> to the upper joint mechanism <NUM>. The casing <NUM> comprises a first recess portion <NUM> for receiving the ball <NUM> and a cover <NUM> comprising a central aperture partially encloses the ball <NUM> within the recess portion <NUM>. The casing <NUM> further comprises a second recess portion <NUM> for receiving the locking device <NUM> and a cover <NUM> for enclosing the locking device <NUM> within the recess portion <NUM>.

The locking unit <NUM> comprises two Belleville springs <NUM> and a piston assembly formed of a piston <NUM>, a set screw <NUM>, and a brake pad <NUM>. The set screw is used for adjusting the resistance of the Belleville springs, and therefore the force required for unlocking the locking unit <NUM>. The brake pad <NUM> has a substantially cylindrical shape and its internal shape substantially matches that of the ball <NUM> so that the ball seats into the brake pad <NUM>. The set screw <NUM> connects the piston <NUM> to the brake pad <NUM>. Guides <NUM> are used to guide the translation of the brake pad <NUM> and prevent the brake pad <NUM> from rotating. The Belleville springs <NUM>, while in compression, are enclosed between the cover <NUM> and the piston <NUM>. The piston assembly is used for transferring the pressure force exerted by the Belleville springs <NUM> to the ball <NUM>. A space between the piston <NUM> and the casing <NUM> defines an oil chamber <NUM> for receiving oil therein. The oil chamber <NUM> is fluidly connected to the fluidic connection <NUM> via a manifold <NUM> extending through the piston member <NUM> and the cover <NUM>. Seals <NUM> are used for preventing the oil contained in the oil chamber <NUM> from leaking out thereof.

The locking unit <NUM> is passively biased in the locked position illustrated in <FIG>. In the locked position, the force exerted by the oil present in the oil chamber <NUM>, if any, on the piston <NUM> is less than the force exerted by the springs <NUM> on the piston <NUM>. Therefore, the resulting force is transferred to the ball <NUM> via the piston assembly and the ball <NUM> abuts against the cover <NUM>, thereby being prevented from moving via friction and/or deformation forces. The joint mechanism <NUM> is then locked. Since no external intervention is required for maintaining the locking device <NUM> in the locked position and locking the joint mechanism <NUM>, the locking device <NUM> is passively biased in the locked position.

Upon activation of the pump <NUM>, the pressure of the oil within the oil chamber <NUM> increases. When the force exerted by the oil contained in the oil chamber <NUM> on the piston <NUM> becomes greater than the force exerted by the springs <NUM> on the piston <NUM>, the height of the oil chamber increases and the springs <NUM> is further compressed. The brake pad <NUM> is then disengaged from the ball <NUM> which is free to move in the recess <NUM>, as illustrated in <FIG>.

<FIG> illustrate the lower joint mechanism <NUM> in a locked position and a released or unlocked position, respectively. The joint mechanism <NUM> comprises a ball <NUM>', a base member connector <NUM>', a connecting tube <NUM>', and a casing <NUM>'. The connecting tube <NUM>' interconnects the ball <NUM>' and the base member connector <NUM>' which is used for connecting the base member <NUM> to the lower joint mechanism <NUM>. The casing <NUM>' comprises a first recess portion <NUM>' for receiving the ball <NUM>' and a cover <NUM>' comprising a central aperture partially encloses the ball <NUM>' within the recess portion <NUM>'. The casing <NUM>' further comprises a second recess portion <NUM>' for receiving the locking device <NUM> and a cover <NUM>' for enclosing the locking device <NUM> within the recess portion <NUM>'.

The locking unit <NUM> comprises two Belleville springs <NUM>' and a piston assembly formed of a piston <NUM>' and a brake pad <NUM>'. The brake pad <NUM>' has a substantially cylindrical shape and its internal shape substantially matches that of the ball <NUM>' so that the ball partially seats into the brake pad <NUM>'. The piston members <NUM>' and <NUM>' are connected together. Guides <NUM>' are used to guide the translation of the brake pad <NUM>' and prevent the brake pad <NUM>' from rotating. The Belleville springs <NUM>', while in compression, are enclosed between the cover <NUM>' and the piston <NUM>'. The piston assembly is used for transferring the pressure force exerted by the Belleville spring <NUM>' to the ball <NUM>'. A space between the piston <NUM>' and the casing <NUM>' defines an oil chamber <NUM>' for receiving oil therein. The oil chamber <NUM>' is fluidly connected to the fluidic connection <NUM> via an aperture <NUM>' extending through the piston member <NUM>' and the cover <NUM>'. Seals <NUM>' are used for preventing the oil contained in the oil chamber <NUM>' from leaking out thereof.

The locking unit <NUM> is passively biased in the locked position illustrated in <FIG>. In the locked position, the force exerted by the oil present in the oil chamber <NUM>', if any, on the piston <NUM>' is less than the force exerted by the springs <NUM>' on the piston <NUM>'. Therefore, the resulting force is transferred to the ball <NUM>' via the piston assembly and the ball <NUM>' abuts against the cover <NUM>', thereby being prevented from moving via friction and/or deformation forces. The joint mechanism <NUM> is then locked. Since no external intervention is required for maintaining the locking device <NUM> in the locked position and locking the joint mechanism <NUM>, the locking device <NUM> is passively biased in the locked position.

Upon activation of the pump <NUM>, the pressure of the oil within the oil chamber <NUM>' increases. When the force exerted by the oil contained in the oil chamber <NUM>' on the piston <NUM>' becomes greater than the force exerted by the springs <NUM>' on the piston <NUM>', the height of the oil chamber <NUM>' increases and the springs <NUM>' are further compressed. The brake pad <NUM>' is then disengaged from the ball <NUM>' which is free to move in the recess <NUM>', as illustrated in <FIG>. The locking unit <NUM> is then in the unlocked or released position.

<FIG> illustrate the locking unit <NUM> in a locked position and an unlocked or released position, respectively. The locking unit <NUM> is secured at one end of the arm member <NUM> and is located within the arm member <NUM>. The locking unit <NUM> comprises a casing <NUM>, a cover <NUM>, two Belleville springs <NUM>, and a piston assembly comprising a piston <NUM>, a set screw <NUM>, and a brake pad <NUM>. The casing <NUM> comprises a first recess portion <NUM> for receiving the brake pad <NUM> and a second recess portion <NUM> for receiving the piston <NUM> and the springs <NUM>. The cover <NUM> is used for enclosing the piston member <NUM> and the springs <NUM> in the second recess portion <NUM>. The springs <NUM>, while in compression, are sandwiched between the cover <NUM> and the piston member <NUM>. An aperture is present through the casing <NUM> for connecting the first and second recess portions <NUM> and <NUM>. A portion of the piston <NUM> extends through the aperture to connect with the brake pad <NUM> via the set screw <NUM>. The set screw is further used for adjusting the compression of the springs <NUM>, and therefore setting the force at which the locking unit <NUM> will unlock. Guides <NUM> are used to guide the translation of the brake pad <NUM> and prevent the brake pad <NUM> from rotating.

The piston assembly is used for transferring the pressure force exerted by the Belleville springs <NUM> to the brake pad <NUM>. A space between the piston member <NUM> and the casing <NUM> defines an oil chamber <NUM> for receiving oil therein. The oil chamber <NUM> is fluidly connected to the fluidic connection <NUM> via a first aperture <NUM> extending through the casing <NUM>. The oil chamber <NUM> is further fluidly connected to the fluidic connection <NUM> via a second aperture <NUM> extending through the casing <NUM>. Seals <NUM> are used for preventing the oil contained in the oil chamber <NUM> from leaking out thereof.

The locking unit <NUM> is passively biased in the locked position illustrated in <FIG>. In the locked position, the force exerted by the oil present in the oil chamber <NUM>, if any, on the piston <NUM> is less than the force exerted by the springs <NUM> on the piston <NUM>. Therefore, the resulting force is transferred to the brake pad <NUM> via the piston <NUM> which firmly abuts against the arm member <NUM>. The cover <NUM> also firmly abuts against the internal surface of the arm member <NUM>, thereby preventing any relative motion between the two arm members <NUM> and <NUM> via friction and/or deformation forces. The telescopic arm <NUM> is then locked, and its length is fixed. Since no external intervention is required for maintaining the locking device <NUM> in the locked position and locking the telescopic arm <NUM>, the locking device <NUM> is passively biased in the locked position.

Upon activation of the pump <NUM>, the pressure of the oil within the oil chamber <NUM> increases. When the force exerted by the oil contained in the oil chamber <NUM> on the piston member <NUM> becomes greater than the force exerted by the springs <NUM> on the piston <NUM>, the width of the oil chamber <NUM> increases and the springs <NUM> is further compressed. The brake pad <NUM> is then disengaged from the internal surface of the arm member <NUM>, as illustrated in <FIG>. The arm member <NUM> may slide within the arm member <NUM>, and the length of the telescopic arm <NUM> may be adjusted to a desired length. The locking unit <NUM> is then in the unlocked or released position.

In one embodiment, a single activation of the pump <NUM> allows for the concurrent releasing of the three locking units <NUM>, <NUM>, and <NUM>, and therefore the adjustment of the configuration of the joint mechanisms <NUM> and <NUM> and the length of the telescopic arm <NUM>. Since the oil chambers <NUM>, <NUM>', and <NUM> are fluidly connected together, the activation of the pump <NUM> causes a pressure increase for the oil contained in the oil chambers <NUM>, <NUM>', and <NUM>. In one embodiment, the springs <NUM>, <NUM>', and <NUM> and their respective compression are chosen so that the locking units <NUM>, <NUM>, and <NUM> are substantially concurrently released when the oil pressure reaches a given pressure. In another embodiment, the locking units may be released sequentially. For example, the springs <NUM>, <NUM>', and <NUM> and their respective compression are chosen so that the locking unit <NUM> is first released when the oil pressure reaches a first given pressure, and the locking units <NUM> and <NUM> are substantially concurrently released when the oil pressure reaches a second and greater pressure.

It should be understood that the length of the fluidic connections <NUM>, <NUM>, and <NUM> is chosen so as to allow the piston assemblies for the locking units <NUM>, <NUM>, and <NUM> to move and the arm member <NUM> to slide within the arm member <NUM>.

In one embodiment, the pump <NUM> is a foot pump to be manually activated by a user. In another embodiment, the pump is electrically or pneumatically driven.

While the present description refers to a hydraulic/pneumatic lock activation device using a fluid such as oil, water, air, and the like for unlocking the locking units, it should be understood that any adequate lock activation device which allows for further compression the elastic/resilient member of the locking device in order to unlock the joint mechanism may be used. For example, a cable may be secured to the elastic/resilient member of the locking device and the further compression of the elastic/resilient member can result from a tension exerted on the cable. In another example, push/pull/torsion rods may be used for further compressing the elastic/resilient member in order to overcome pressure from the resilient member.

<FIG> illustrates a further embodiment of a positioning apparatus <NUM>. The positioning apparatus <NUM> comprises a telescopic member or arm <NUM> having a first or upper end 302a and a second or lower end 302b. A first or upper joint mechanism <NUM> and a second or lower joint mechanism <NUM> are secured at the ends 302a and 302b of the telescopic arm <NUM>, respectively. The positioning apparatus <NUM> further comprises an interface member <NUM> secured to the upper joint mechanism <NUM> for receiving an object thereon, and a base member <NUM> for removably securing the positioning apparatus <NUM> to a base.

The telescopic arm <NUM> comprises two hollow elongated members <NUM> and <NUM> which are adapted so that the hollow member <NUM> fits and slides into the hollow member <NUM>. The telescopic arm <NUM> is further connected to the L-shaped base member <NUM> via the joint mechanism <NUM>.

Three locking devices <NUM>, <NUM>, and <NUM> are operatively connected to the upper joint mechanism <NUM>, the lower joint mechanism <NUM>, and the hollow member <NUM>, respectively. The locking devices <NUM> and <NUM> are used for selectively locking the joint mechanisms <NUM> and <NUM>, respectively, in a desired configuration while the locking device <NUM> is used for fixing the length of the telescopic member <NUM> at a desired length. As described below, the locking devices <NUM>, <NUM>, and <NUM> are passively biased in a locked position, thereby preventing any position adjustment of the joint mechanisms <NUM> and <NUM> and any length adjustment for the telescopic member <NUM> without external intervention.

The external intervention is provided via a lock activation device (not shown), such as a pump fluidly connected to the locking devices <NUM>, <NUM>, and <NUM>. A fluidic connection <NUM> fluidly connects the pump <NUM> to the locking unit <NUM>. A second fluidic connection <NUM> extending within the arm member <NUM> fluidly connects the locking unit <NUM> to the locking unit <NUM>, and a third fluidic connection <NUM> extending within the arm member <NUM> fluidly connects the locking unit <NUM> to the locking unit <NUM>.

The fluidic connections <NUM>, <NUM>, and <NUM>, the pump, and the chambers described below are filled with oil, and form a substantially hermetical closed-circuit from which oil cannot substantially leak.

<FIG> illustrate the lower joint mechanism <NUM> in a locked position and a released or unlocked position, respectively. The joint mechanism <NUM> comprises a ball <NUM>, a socket <NUM>, a connecting tube <NUM>, and a casing <NUM>. The ball <NUM> comprises a first hemispherical portion 350a fixedly secured to the casing <NUM> via the connecting tube <NUM>, and a second hemispherical portion 350b movable with respect to the first hemispherical portion 350a. Guides <NUM> are used for guiding the translation of the second hemispherical portion 350b with respect to the first hemispherical portion 350a, and preventing any rotational motion of the second hemispherical portion 350b with respect to the first hemispherical portion 350a. The socket <NUM> comprises a socket casing 352a and a socket cover 352b. The socket casing 352a is provided with a recess portion <NUM> for receiving at least a part of the ball <NUM>. The socket cover 352b is provided with an aperture <NUM> through which a part of the ball <NUM> extends. The socket cover 352b is used for enclosing the ball <NUM> within the socket <NUM>, while allowing motion of the ball <NUM> within the socket <NUM>.

The casing <NUM> comprises a casing recess portion <NUM> for receiving the locking device <NUM> and a cover <NUM> for enclosing the locking device <NUM> within the recess portion <NUM>.

The locking unit <NUM> comprises two Belleville springs <NUM> and a piston <NUM>. The piston <NUM> is operatively connected to the Belleville springs <NUM> at one end, and to the second hemispherical portion 350b at the other end. The piston receiving aperture extends through the casing <NUM>, the connecting tube <NUM>, and the first hemispherical portion 350a. The piston <NUM> extends through the piston receiving aperture to connect the Belleville spring <NUM> to the second hemispherical portion 350b. The piston <NUM> is used for transferring the compression force exerted by the Belleville springs <NUM> to the second hemispherical portion 350b. For example, the piston <NUM> may abut against the second hemispherical portion 350b for transferring the Belleville spring force thereto. In another embodiment, the piston <NUM> is fixedly secured to the second hemispherical portion 350b.

The Belleville springs <NUM>, while in compression, are enclosed between the cover <NUM> and the piston member <NUM>. The cover is further secured to the arm member <NUM> in order to secure the joint mechanism <NUM> thereto. A space between the piston <NUM> and the casing <NUM> defines an oil chamber <NUM> for receiving oil therein. The oil chamber <NUM> is fluidly connected to the fluidic connection <NUM> via an aperture <NUM> extending through the casing <NUM>. Seals <NUM> are used for preventing the oil contained in the oil chamber <NUM> from leaking out thereof.

The locking unit <NUM> is passively biased in the locked position illustrated in <FIG>. In the locked position, the force exerted by the oil present in the oil chamber <NUM>, if any, on the piston <NUM> is less than the force exerted by the Belleville springs <NUM> on the piston <NUM>. Therefore, the resulting force is transferred to the second hemispherical portion 350b via the piston <NUM>. The second hemispherical portion 350b moves away from the first hemispherical portion 350a and abuts at least partially against the socket casing 352a while the first hemispherical portion 350a abuts at least partially against the socket cover 352b, thereby preventing the ball <NUM> from moving within the socket <NUM> via friction and/or deformation forces. The joint mechanism <NUM> is then locked. Since no external intervention is required for maintaining the locking unit <NUM> in the locked position and locking the joint mechanism <NUM>, the locking device <NUM> is passively biased in the locked position.

Upon activation of the pump, the pressure of the oil within the oil chamber <NUM> increases. When the force exerted by the oil contained in the oil chamber <NUM> on the piston <NUM> becomes greater than the force exerted by the spring <NUM> on the piston <NUM>, the height of the oil chamber increases and the spring <NUM> is further compressed. The ball <NUM> is then free to move within the socket <NUM>, as illustrated in <FIG>.

<FIG> illustrate the upper joint mechanism <NUM> in a locked position and a released or unlocked position, respectively. The joint mechanism <NUM> comprises a ball <NUM>', a socket <NUM>', a connecting tube <NUM>', and a casing <NUM>'. The ball <NUM>' comprises a first hemispherical portion 350a' fixedly secured to the casing <NUM>' via the connecting tube <NUM>', and a second hemispherical portion 350b' movable with respect to the first hemispherical portion 350a'. Guides <NUM>' are used for guiding the translation of the second hemispherical portion 350b' with respect to the first hemispherical portion 350a', and preventing any rotational motion of the second hemispherical portion 350b' with respect to the first hemispherical portion 350a'. The socket <NUM>' comprises a socket casing 352a' and a socket cover 352b'. The socket casing 352a' is provided with a recess portion <NUM>' for receiving at least a part of the ball <NUM>'. The socket cover 352b' is provided with an aperture <NUM>' through which part of the ball <NUM>' extends. The socket cover 352b' is used for enclosing the ball <NUM>' within the socket <NUM>', while allowing motion of the ball <NUM>' within the socket <NUM>'.

The casing <NUM>' comprises a casing recess portion <NUM>' for receiving the locking device <NUM> and a cover <NUM>' for enclosing the locking device <NUM> within the recess portion <NUM>'.

The locking unit <NUM> comprises two Belleville springs <NUM>' and a piston <NUM>'. The piston <NUM>' is operatively connected to the Belleville springs <NUM>' at one end and the second hemispherical portion 350b' at the other end. The piston receiving aperture extends through the casing <NUM>', the connecting tube <NUM>', and the first hemispherical portion 350a'. The piston <NUM>' extends through the piston receiving aperture to connect the Belleville spring <NUM>' to the second hemispherical portion 350b'. The piston <NUM>' is used for transferring the compression force exerted by the Belleville springs <NUM>' to the second hemispherical portion 350b'. For example, the piston <NUM>' may abut against the second hemispherical portion 350b' for transferring the Belleville spring force thereto. In another embodiment, the piston <NUM>' is fixedly secured to the second hemispherical portion 350b'.

The Belleville springs <NUM>', while in compression, are enclosed between the cover <NUM>' and the piston <NUM>'. The cover <NUM>' is further secured to the arm member <NUM> in order to secure the joint mechanism <NUM> thereto. A space between the piston <NUM>' and the casing <NUM>' defines an oil chamber <NUM>' for receiving oil therein. The oil chamber <NUM>' is fluidly connected to the fluidic connection <NUM> via an aperture <NUM>' extending through the piston <NUM>' and the cover <NUM>'. Seals <NUM>' are used for preventing the oil contained in the oil chamber <NUM>' from leaking out thereof.

The locking unit <NUM> is passively biased in the locked position illustrated in <FIG>. In the locked position, the force exerted by the oil present in the oil chamber <NUM>', if any, on the piston <NUM>' is less than the force exerted by the Belleville springs <NUM>' on the piston <NUM>'. Therefore, the resulting force is transferred to the second hemispherical portion 350b' via the piston <NUM>'. The second hemispherical portion 350b' moves away from the first hemispherical portion 350a' and abuts at least partially against the socket casing 352a' while the first hemispherical portion 350a' abuts at least partially against the socket cover 352b', thereby preventing the ball <NUM>' from moving within the socket <NUM>' via friction and/or deformation forces. The joint mechanism <NUM> is then locked. Since no external intervention is required for maintaining the locking device <NUM> in the locked position and locking the joint mechanism <NUM>, the locking unit <NUM> is passively biased in the locked position.

Upon activation of the pump, the pressure of the oil within the oil chamber <NUM>' increases. When the force exerted by the oil contained in the oil chamber <NUM>' on the piston <NUM>' becomes greater than the force exerted by the spring <NUM>' on the piston <NUM>', the height of the oil chamber <NUM>' increases and the springs <NUM>' are further compressed. The ball <NUM>' is then free to move within the socket <NUM>', as illustrated in <FIG>.

The operation of the locking device <NUM> for removably securing the arm members <NUM> and <NUM> together is similar to that of the locking unit <NUM> illustrated in <FIG>.

While the present description refers to a three-rotational degree of freedom joint mechanism in the form of a ball and socket joint mechanism, it should be understood that any adequate joint mechanism having three rotational degrees of freedom may be used. For example, a ball joint mechanism may be replaced by three rotary joints each having a single rotational degree of freedom. The three rotary joints are connected so that their axes of rotation be orthogonal or perpendicular. The ball and socket joint mechanism may also be replaced by an ellipsoid or condyloid joint, a pivot joint, or the like.

It should also be understood that, while it has a spherical shape, the ball described in the present application may have any other adequate shape. For example, the ball may have a substantially cylindrical shape or an ellipsoidal shape as long as the socket in which the ball moves comprises a substantially spherical chamber or cavity for receiving the ball.

It should be understood that the above-described locking device which is passively biased in a locked position may be used for selectively locking any adequate joint mechanism having at least one degree of freedom and comprising at least two joint members movable the one with respect to the other.

In one embodiment, the use of a telescopic arm allows for having a suspended mass which is lower with respect to positioning apparatuses having arm members interconnected via pivots for not biasing the user's perception.

While the present description refers to upper/lower joint mechanisms having three rotational degrees of freedom, it should be understood that the joint mechanisms may each only have two degrees of freedom. In this case, the third rotational degree of freedom may be provided by the telescopic arm. For example, at least one given arm member may rotate with respect to the other arm members about an axis extending along the length of the telescopic arm. The locking device for fixing the length of the telescopic arm may also be used for locking the angular position of the given arm members with respect to the other arm members.

While the present description refers to a locking device comprising a piston and a brake pad for transferring the force exerted by an elastic/resilient member to a joint member, it should be understood that the brake pad may be omitted or integral with the piston. In this case, the piston may be in direct contact with the joint member and act as a brake pad. In another embodiment, the locking device may further comprise no piston or the piston and the brake pad may be integral with the elastic/resilient member. For example, the elastic/resilient member may be adapted to be in direct contact with the joint member and act as a paddle brake. In this case, the elastic/resilient member may be integral with the casing of the joint mechanism or be a part of the casing.

Claim 1:
A medical positioning apparatus (<NUM>) for positioning and holding an object, comprising:
a telescopic member (<NUM>) extending between a first end (102a) and a second end (102b) and having an adjustable length;
an interface member (<NUM>) for receiving the object;
a first joint mechanism (<NUM>) movably securing the interface member (<NUM>) to the first end (102a) of the telescopic member (<NUM>);
a second joint mechanism (<NUM>) connected to the second end (102b) of the telescopic member (<NUM>);
a base member (<NUM>) movably connected to the second joint mechanism (<NUM>), wherein the base member (<NUM>) comprises an elongated arm (<NUM>);
wherein the second joint mechanism (<NUM>) is directly rotationally connected to the base member (<NUM>) and movably secures the base member (<NUM>) to the second end (102b) of the telescopic member (<NUM>); and
wherein the first and second joint mechanisms (<NUM>, <NUM>) each having at least two rotational degrees of freedom,
a locking device (<NUM>, <NUM>, <NUM>) operatively connected to the first and second joint mechanisms (<NUM>, <NUM>) and the telescopic member (<NUM>), the locking device (<NUM>, <NUM>, <NUM>) operable between a locked position in which the interface member (<NUM>), the base member (<NUM>), and the telescopic member (<NUM>) are lockingly interconnected together and the length of the telescopic member (<NUM>) is fixed, and a released position in which the interface and base members (<NUM>, <NUM>) are free to pivotally move with respect to the telescopic member (<NUM>) and the length of the telescopic member (<NUM>) is adjustable, the locking device (<NUM>, <NUM>, <NUM>) being passively biased in the locked position; and
a lock activation device (<NUM>) to unlock the locking device (<NUM>, <NUM>, <NUM>) biased in the locked position in order to adjust the length of the telescopic member (<NUM>) and a relative position of the interface member (<NUM>), the base member (<NUM>), and the telescopic member (<NUM>),
wherein the base member (<NUM>) or the telescopic member (<NUM>) is L-shaped, so that the base member (<NUM>) can be positioned parallel to the telescopic member (<NUM>).