DESCRIPTION

Technical field

The present invention relates to a balanced support head for video-photographic equipment of the type including the features mentioned in the preamble of the main claim .

Technological background

In the field of video-photographic recordings , and particularly cinematographic recordings , both of the amateur type and of the professional type , it is known to provide for the positioning of the video-photographic equipment and/or the movement thereof by using suitable support heads .

In particular, there are known support heads which comprise a base and a platform, to which there is coupled the equipment , in which the platform is connected to the base in such a manner that it can tilt about one or more pivot axes which extend through the base .

The movement of the platform and consequently of the equipment secured thereto about a hori zontal pivot axis which is perpendicular to the optical axis of the equipment and which is known as the "tilt" axis allows , for example , adj ustment of the orientation of the equipment with respect to the hori zontal plane , allowing the obj ective to be directed upwards or downwards . However, this tilting movement generally brings about a movement of the centre of gravity of the assembly of the equipment and platform which, once moved out of the vertical plane containing the pivot axis , causes an unbalancing of the system which tends to cause the equipment to fall .

This unbalancing is more correctly described by identi fying the moment of the gravitational force of the equipment/plat f orm system with respect to the pivot axis .

This moment (M) is proportional to the own weight ( P ) of the assembly comprising the platform and equipment at the distance (H) of the centre of gravity of this assembly from the pivot axis and to the sine of the tilting angle (a) of the above- mentioned centre of gravity according to the relationship :

M = P -H • sin (a)

The tilting angle (a) is defined as the angle between the vertical plane comprising the pivot axis and the plane which comprises the pivot axis and which extends through the centre of gravity of the assembly comprising the platform and equipment . Therefore , when the centre of gravity of the assembly comprising the platform and equipment is placed at the vertical of the pivot axis , the tilting angle is 0 ° (balanced position) .

The relationship set out above means that , when the equipment items are particularly heavy, for example , cameras , the tilting movement about the tilt axis is di f ficult and laborious to control by the operator, with a risk of the equipment items falling dangerously .

In order to prevent such undesirable disadvantages , it is known to construct support heads which comprise balancing devices which are capable of acting counter to the uncontrolled tilting of the platform from the balanced position .

Among the known balancing devices , some comprise mechanisms which provide a balancing moment ( opposing torque ) which is counter to the unbalancing moment ( falling torque ) in a manner proportional to the tilting angle .

The patent US 10465837 in the name of the same Applicant describes a support head which is balanced with a pneumatic spring which is fixed to the base of the head and which extends vertically towards the platform and an abutment element which is fixed to the platform and which is placed against an end of the spring at a predetermined distance from the pivot axis . When the platform is tilted with respect to the base from the balanced position, the abutment element moves along the end of the spring so that the force applied thereby to the abutment element generates a balancing torque with a sign opposite to the torque generated by the weight of the equipment and the platform .

This solution, although providing optimum performance levels in terms of balancing and compactness , has some limitations in terms of conditions of use . In particular, in environments with an excessively severe temperature , the resilient properties of the pneumatic spring are liable to change and, furthermore , the correct operation thereof over time can be impaired by possible losses of gas from the pneumatic spring .

The patent US 6328487 describes a support head, in which the balancing moment is applied by cables which, when subj ected to traction by means of compression springs , act on the platform by passing over respective pulleys which are fixedly j oined to the base .

The main disadvantage of this solution is constituted by the fact that a device constructed according to US 6328487 involves a large number of additional components which af fect the spatial requirement and the complexity of the device .

Another example of a balanced support head is described in US 20050230576 . In this case , there are also provided cables which, when subj ected to traction by means of compression springs , act on the platform by passing over respective pulleys which are fixedly j oined to the base . Furthermore , there are provided additional pulleys for deflecting the cables parallel with the tilt axis . The additional pulleys are supported in an idle state about respective shafts which are parallel with the tilt axis so as to allow the alignment of the additional pulleys with the progression of the respective cables in the various tilting positions of the head . However, it is evident that the presence of additional pulleys makes the support head even more bulky . In fact , it must be observed that each of the additional pulleys has a dimension equal to the volume passed over by the rotation of the pulley about the individual shaft . Furthermore , so that the additional pulleys can become aligned with the course of the respective cables in the various positions of the head, it is necessary for the shafts of the pulleys to be provided with bearings which maintain the shafts parallel with the tilt axis and which reduce the friction during the alignment . Therefore , the support structure of the additional pulleys is structurally complex and bulky .

Statement of invention The problem addressed by the present invention is to provide a balanced support head which is structurally and functionally configured to at least partially overcome the disadvantages set out with reference to the cited prior art .

In particular, a first obj ective of the invention is to provide a balanced support head comprising a balancing device which is capable of acting counter to the falling torque with changes to the tilting angle following the sinusoidal law of variation of the balancing torque without any discontinuities .

A second obj ective of the invention is to provide a balanced support head comprising a balancing device which is capable of acting counter to the falling torque over a wide range of weight values of the video-photographic equipment item supported .

Another obj ective of the invention is to provide a balanced support head, in which the balancing device is provided in a protected position and does not cause a substantial increase to the dimensions of the support head .

Another obj ective of the invention is to provide a balanced support head at low cost and with a simple construction .

The present invention further has the obj ective of providing a balanced support head which maintains the balancing characteristics over time and without any alterations as a result of the ambient temperature .

This problem is solved and these obj ectives are achieved by the present invention by means of a balanced support head which is constructed according to one or more of the appended claims .

Brief description of the drawings

The features and advantages of the invention will be better appreciated from the detailed description of a preferred embodiment thereof which is illustrated by way of non-limiting example with reference to the appended drawings , in which :

- Figure 1 is a schematic, perspective front view of a balanced support head which is constructed according to the present invention, Figure 2 is a schematic, perspective rear view of the head of

Figure 1 ,

- Figure 3 is a schematic plan view of the head of Figure 1 ,

- Figure 4 and Figure 5 are cross-sections along the plane IV- IV and along the plane V-V of the head of Figure 3 , respectively,

- Figures 6a and 6b are sectional views of the head of Figure 4 in two di f ferent operating positions ,

- Figures 7 to 9 are schematic sectional views of additional embodiments of a balanced support head according to the present invention .

Preferred embodiment of the invention

With reference to the Figures set out above , there is generally designated 1 a balanced support head which is constructed according to the present invention .

The head 1 is preferably a head with two rotation axes and comprises a base 2 and a platform 3 which is secured to the base 2 with the ability to tilt about a corresponding pivot axis X, which is substantially hori zontal and which is capable of allowing the so-called "tilt" movement of a video-photographic equipment item 100 .

The base 2 comprises a lower member 2a and an upper member 2b which is connected to the lower member 2a with a capacity for rotation about a panoramic axis Z which is substantially vertical and perpendicular to the pivot axis X . There is further interposed between the lower member 2a and the upper member 2b of the base 2 a fluid cartridge 2c, which is known per se in the sector and which is able to make the relative rotational movement about the panoramic axis Z fluid and uni form .

The base 2 is further provided to be secured to a suitable support , such as , for example , a tripod, and, to this end, there is formed in the lower member 2a a threaded hole 2d for a screw type attachment of the standard type .

The relative rotation between the lower member 2a and the upper member 2b is advantageously blockable by means of a blocking pin 2e .

The video-photographic equipment item 100 , for example , a camera, is able to be removably secured to the top of the platform 3 at the side opposite the base 2 .

In particular, there is formed at the top of the platform 3 a seat 4 which preferably has a cross-section which is provided with an undercut which is provided to receive with the ability to slide , in a longitudinal direction Y thereof , an attachment plate (not shown) which can in turn be fixed to the base of the video-photographic equipment item 100 .

The longitudinal direction Y is spaced apart from and orientated perpendicularly to the pivot axis X . Preferably, the attachment plate is fixed to the videophotographic equipment item 100 in such a manner that the longitudinal direction Y in which the attachment plate can slide inside the seat 4 is parallel with an optical axis T of the video-photographic equipment item 100 and can be fixed in the preselected position by means of a blocking lever 4a .

There is further provided on the platform 3 a pair of attachments 5 which extend from the sides of the seat 4 and which proj ect towards a rear side of the platform 3 .

The attachments 5 are preferably couplings with front teeth which can allow one or more control levers ( so-called pan bars ) to be fixed to the platform 3 and to be able to be used by the operator to move the video-photographic equipment item 100 in terms of rotation about the axis X and/or the axis Z and, where applicable , to control the main functions of the videophotographic equipment item 100 by remote control operations .

The platform 3 comprises two faces 6a and 6b which extend towards the base 2 and which are rotatably fixed to respective counter- faces 7a and 7b, which extend from the upper member 2b of the base 2 towards the platform 3 , by means of a pin 8 which defines the pivot axis X .

At the side opposite the pin 8 , there is further provided a fluid cartridge 9 which is coaxial with the pivot axis X and which is fixed to the platform 3 and the upper member 2b of the base 2 in order to make the relative rotational movement about the pivot axis X fluid and uni form .

The support head 1 further comprises a balancing device 10 which can act counter to the tilting of the platform 3 about the pivot axis X as a result of the weight of the video-photographic equipment item 100 and the platform 3 .

The balancing device 10 comprises a flexible traction member 11 which cooperates with a pre-tensioned spring 12 in order to apply a balancing moment to the platform 3 .

In some preferred embodiments , the flexible traction member 11 includes a rope made from metal or textile material . It will be understood that the rope can be replaced by a transmission chain .

Preferably, the flexible traction member 11 is substantially non-extensible . It will be understood that , in some embodiments , the flexible traction member 11 may be resiliently extensible . In this case , the flexible traction member 11 can contribute to or replace the resilient action applied by the spring 12 .

The spring 12 which is part of the balancing device 10 is fixed, in a preferred embodiment , to the upper member 2b of the base 2 in a fixedly j oined manner at one side and, at the other side , to a first end 11c of the flexible traction member 11 . Preferably, the spring 12 extends along a substantially hori zontal axis of the base 2 in a radial direction with respect to the panoramic axis Z . It must be observed that the hori zontal axis along which the spring 12 extends and consequently along which the spring 12 applies its own action is fixed and does not depend on the tilting of the platform 3 with respect to the base 2 .

In one embodiment , the spring 12 is a linear spring . In the greatly preferred embodiment of the invention, the spring 12 is a helical compression spring with a steel thread, even i f there may be provis ion for using a spring o f a di f ferent type , such as , for example , a traction spring or a torsion spring .

The spring 12 is received in a cylinder 12a which extends along the hori zontal axis of the spring 12 and which is fixedly j oined to the upper member 2b of the base 2 . An end of the cylinder 12a proj ects from the base 2 in a radial direction with respect to the panoramic axis Z so as to facilitate the adj ustment of the pre-tensioning of the spring 12 , while maintaining a compact structure .

There is engaged in the cylinder 12a, through a hole 12b, a piston 12c which connects the first end 11c of the flexible traction member 11 to a free end of the spring 12 .

The piston 12c, preferably with a circular cross-section, extends along the hori zontal axis of the spring 12 , coaxially with the cylinder 12a .

At the side opposite the hole 12b, the piston 12c ends with a nut 12d, against which there abuts the free end of the spring 12 which is therefore urged in terms of compression between the base of the cylinder 12a at one side and the nut 12d at the other side . Preferably, the nut 12d, at the side directed towards the spring 12 , has a planar surface which is substantially perpendicular to the hori zontal axis of the spring 12 .

The flexible traction member 11 is fixed in a fixedly j oined manner to the piston 12c and is subj ected to traction by the pre-tensioned spring 12 . In one preferred embodiment , it is possible to adj ust the pre-tensioning of the spring 12 by rotating the nut 12d which is axially screw- fitted to the piston 12c so as to move the flexible traction member 11 away from and towards the nut 12d, against which the free end of the spring 12 abuts .

The balancing device 10 further includes a deflection pulley 13 which is fixed to the component of the head 1 to which the spring 12 is connected and which is , in the greatly preferred embodiment , the upper member 2b of the base 2 by means of a pin 13a which is rotatably supported on the upper member 2b and which extends parallel with the pivot axis X . The deflection pulley 13 is configured to deflect the longitudinal extent of the flexible traction member 11 away from the spring 12 about a deflection axis A which is parallel with the pivot axis X .

It may be noted that the deflection axis A is parallel with the axis of the deflection pulley 13 but - unless as an approximation - does not coincide therewith . In fact , the deflection axis A is located on the cylindrical surface of the deflection pulley 13 in the region of the location at which the flexible traction member 11 moving away from the spring 12 becomes detached from the deflection pulley 13 and leaves it .

The flexible traction member 11 leaving the deflection pulley 13 is connected in the region of a second end l id thereof to a lever location 14 which, in this preferred embodiment , is de fined on the platform 3 , at a distance E from the pivot axis X .

The flexible traction member 11 which is engaged on the deflection pulley 13 defines a first branch I la of the flexible traction member 11 which is comprised between the spring 12 and the deflection pulley 13 and a second branch 11b of the flexible traction member 11 which is comprised between the deflection pulley 13 and the lever location 14 . It may be noted that the first branch I la and the second branch 11b are located in a plane perpendicular to the pivot axis X .

It must be observed that the balancing device 10 preferably comprises a single deflection pulley 13 which is configured to deflect the longitudinal extent of the flexible traction member 11 from the spring 12 towards the lever location 14 with an advantage in terms of compactness and structural simplicity of the head 1 .

Advantageously, the lever location 14 is defined on the platform 3 at the side opposite the seat 4 with respect to the pivot axis X with the ability to slide away from and towards the pivot axis X so as to be able to adj ust the distance E between the lever location 14 and the pivot axis X .

To this end, the balancing device 10 comprises a mechanism 15 for adj usting the distance E between the lever location 14 and the pivot axis X .

The adj ustment mechanism 15 in turn comprises a pin 16 and an adj ustment wheel 17 which are mounted on the platform 3 .

In a preferred embodiment , the pin 16 is received with the ability to slide along a guide channel which extends inside the platform 3 towards the base 2 along an adj ustment axis R which j oins the platform 3 to the base 2 and which is directed radially with respect to the pivot axis X .

It will be noted that , when the platform 3 is in a balanced position, as shown in Figure 4 , the adj ustment axis R is substantially vertical and coincides with the panoramic axis Z .

The pin 16 has a first end 16a which is directed towards the seat 4 of the platform 3 and a second end 16b on which there is defined the lever location 14 which is directed towards the base

2 .

In a preferred embodiment , the second end 16b of the pin 16 directed towards the base 2 has a fork-like structure 21 , on the opposite tines of which there are formed respective holes for a plug 22 , about which, between the two tines , a slot of the second end l id of the flexible traction member 11 is fixed . The plug 22 therefore defines the lever location 14 .

The pin 16 is movable along the adj ustment axis R so as to approach or move away from the lever location 14 with respect to the pivot axis X by means of the adj ustment wheel 17 which proj ects from the platform 3 and which is rotatable about its own axis .

The pin 16 and the adj ustment wheel 17 are in fact connected to each other by means of a gear mechanism so as to allow a movement of the pin 16 along the adj ustment axis R following the rotation of the adj ustment wheel 17 .

As shown in Figure 5 , the gear mechanism comprises a first gearwheel 18 which is secured coaxially to the adj ustment wheel 17 , a second gearwheel 19 which is axially screw- fitted to the pin 16 in the region of a threaded axial hole , through which the pin 16 extends , between which gearwheels there is provided a third gearwheel 20 which is idle and which is engaged at a portion with the first gearwheel 18 and at another portion with the second gearwheel 19 .

In this manner, when the adj ustment wheel 17 is rotated about its own axis , there is also rotated the second gearwheel 19 which, as a result of the engagement with mutual screwing, brings about the movement of the pin 16 along the adj ustment axis R by moving the lever location 14 away from or towards the pivot axis X .

The operation of the support head 1 is described below .

The head 1 is initially positioned with the base 2 arranged in such a manner that the pivot axis X is in a hori zontal plane and the platform 3 is orientated vertically above the base 2 in such a manner that the seat 4 is substantially perpendicular to the panoramic axis Z .

The video-photographic equipment item 100 , for example , a camera, is therefore engaged with an attachment plate which is connected to the platform 3 in the region of the seat 4 . The attachment plate is therefore moved in the longitudinal direction Y of the seat 4 as long as the centre of gravity G of the assembly formed by the platform 3 and the equipment item 100 is positioned vertically above the pivot axis X . The attachment plate is therefore blocked in position inside the seat 4 by the blocking lever 4a .

In this balanced position which is illustrated in Figure 4 , the seat 4 is located in a hori zontal plane (which typically includes the fact that the optical axis T of the videophotographic equipment item 100 also is ) and the centre of gravity G of the assembly formed by the equipment item 100 and the platform 3 is located in a vertical plane which contains the pivot axis X .

In this balanced position, the tilting angle a which is defined as the angle between the vertical plane comprising the pivot axis X and the plane comprising the pivot axis X and which extends through the centre of gravity G of the assembly of the platform 3 and the equipment item 100 , is zero .

In this position, the lever location 14 is located in a plane which extends through the deflection axis A and the pivot axis X and is interposed between these axes .

In this position, the second branch 11b of the flexible traction member 11 between the deflection pulley 13 and the lever location 14 belongs to the vertical plane which contains the pivot axis X so that the force applied by the spring 12 by means of the flexible traction member 11 to the lever location 14 has a zero moment with respect to the pivot axis X .

Furthermore , in the balanced position, the pin 16 which defines the movement direction of the lever location 14 away from and towards the pivot axis X is aligned with the vertical panoramic axis Z . When the video-photographic equipment item 100 and the platform 3 therewith is tilted through an angle a about the pivot axis X ( see Figures 6a and 6b ) , the centre of gravity G, by moving from the balanced position described above , brings about a falling torque Cd which tends to rotate the assembly of the equipment item 100 and the platform 3 downwards .

The falling torque Cd is represented by the following expression :

Cd = P -H • sin (a) , where P is the weight of the assembly of the equipment item 100 and the platform 3 , H is the distance of the centre of gravity G from the pivot axis X and a is the tilting angle defined above .

The tilting of the platform 3 involves the simultaneous movement along a centered circular traj ectory of the lever location 14 which is raised by moving away from the pulley 13 and from the vertical plane which is tangent to the pulley 13 and which extends through the deflection axis A and the pivot axis X . As a result of this movement , the flexible traction member 11 which has the second end l id fixed in a fixedly j oined manner to the lever location 14 , moves the piston 12c along the cylinder 12a, urging the spring 12 in terms of compression . The force applied by the spring 12 to the flexible traction member 11 produces on the platform 3 a balancing torque Cb (with a direction counter to the falling torque Cd) which may be expressed as follows : where K is the spring constant of the spring 12 , B is the distance between the pivot axis X and the deflection axis A, E is the distance between the pivot axis X and the lever location 14 , Xp is the pre-tensioning of the spring 12 , X _o is the distance between the deflection axis A and the lever location 14 in the balanced position, and a is the tilting angle defined above .

It must be observed that the analytical treatment provides for the deflection axis A to be fixed . In reality, the flexible traction member 11 engages about a cylindrical surface of the deflection pulley 13 and, therefore , when the flexible traction member 11 follows the movement of the lever location 14 , it is possible for the deflection axis A to move , though in a very limited manner, on the cylindrical surface of the deflection pulley 13 . However, the deflection pulley 13 has such dimensions that the movement of the deflection axis A generated by the movement of the lever location 14 is negligible . Consequently, it is possible to assume with a good approximation that the position of the deflection axis A does not vary substantially as a result of the ef fect of the movement of the lever location 14 and that the distance B between the pivot axis X and the deflection axis A can be considered to be constant for our purposes .

The head 1 is speci fically configured to ensure the balancing of the assembly comprising the platform 3 and equipment item 100 with a weight between 0 and a maximum weight Pmax . In order to comply with this speci fication, the manufacturer of the head 1 adequately selects the value of the spring constant K of the spring 12 and the maximum value Emax which the distance E can assume between the pivot axis X and the lever location 14 .

At the same time , the values of K and Emax are selected so as to allow the spring 12 to be able to be adequately pre-tensioned during the assembly step of the head 1 . In this step, the platform 3 is in the balanced position, with the distance E brought to the maximum value Emax thereof in order to balance the maximum weight Pmax . Under these conditions , the nut 12d rotates in order to assign to the spring 12 the pre-tensioning Xp corresponding to the distance X _o between the deflection axis A and the lever location 14 in the balanced position .

Once the pre-tensioning Xp of the spring 12 has been set , the adj ustment mechanism 15 allows during use the simultaneous adj ustment of the distance X _o and the pre-tensioning Xp in a mutually identical manner as a result of the ef fect of the nonextensibility of the flexible traction member 11 .

Given that X _p = X _o as described above , the equation which expresses the balancing torque Cb is :

Cb = K B E sin(a).

The torques Cd and Cb are equal when the following relationship is veri fied :

P H = K B E which, as can be seen, is independent of the tilting angle a . As set out above , the distance E is advantageously adj ustable by acting on the adj ustment mechanism 15 .

In fact , rotating the adj ustment wheel 17 about its own axis rotates the first , second and third gearwheels which, as a result of the threaded connection with the pin 16 , bring about the movement of the pin 16 along the adj ustment axis R away from and towards the base 2 .

It will be noted that the adj ustment mechanism described above allows the position of the lever location 14 defined at the end of the pin 16 to be varied in a very simple and precise manner .

Therefore , by moving in a suitable manner the lever location 14 with respect to the pivot axis X, it is possible for the balancing torque to balance the falling torque for any value of the tilting angle a so that the assembly formed by the equipment item 100 and the platform 3 is balanced for any angular position obtained by tilting about the axis X .

As a result of this characteristic, i f the operator had to veri fy that the falling torque resulting from the equipment item 100 being tilted about the pivot axis X is not adequately balanced by the balancing device 10 , the operator can act on the adj ustment wheel 17 in order to vary the distance E between the lever location 14 and the pivot axis X so as to obtain the balance between the falling torque and the balancing torque , also making the system definitively balanced for any other tilting angle .

It is thereby possible to ensure the balancing of equipment items 100 with di f ferent weights and dimensions on the support head 1 simply by varying in a suitable manner the distance E . In particular, the distance E between the lever location 14 and the pivot axis X is adj ustable between a minimum value of 0 mm, at which there is no balancing action, and the maximum value Emax, at which the balancing action is at a maximum .

In a preferred embodiment , given the technical and structural characteristics of the head 1 , the platform 3 is able to tilt with respect to the base 2 through a tilting angle a between a maximum value of + 90 ° ( see Figure 6a ) and a minimum value of - 60 ° ( see Figure 6b ) .

In some embodiments of the invention, as shown in Figure 7 , the spring 12 is fixed in a fixedly j oined manner at one side to the first end 11c of the flexible traction member 11 and, at the other side , to the platform 3 instead of the upper member 2b of the base 2 .

In this case , the deflection pulley 13 is secured to the platform 3 while the end of the pin 16 with the lever location 14 and the adj ustment mechanism 15 are fixed to the upper member

2b of the base 2 . In a preferred embodiment , the platform 3 comprises a control lever 23 (pan bar ) which proj ects from the platform 3 and which extends longitudinally so as to define a hollow structure inside the control lever 23 , as depicted in Figure 8 .

In this case , the spring 12 may be at least partially received inside the hollow structure of the control lever 23 and connected, at one side , to the flexible traction member 11 and, at the other side , to the interior of the hollow structure of the control lever 23 . This embodiment allows protection of the spring 12 inside the control lever 23 by minimi zing the dimensions and reducing the number of additional components .

In another embodiment , the spring 12 can be arranged coaxially relative to the panoramic axis Z and fixed at one side to the first end 11c of the flexible traction member 11 and, at the other side , to the lower member 2a of the base 2 at the side opposite the platform 3 , as shown in Figure 9 . This configuration further reduces the spatial requirement of the head 1 about the panoramic axis Z , further allowing the tilting angle a to be extended up to 90 ° in both rotation directions .

It may be noted that , in this embodiment , the cylinder 12a which extends with the spring 12 extends from the lower member 2a of the base 2 in the direction opposite the platform 3 . In order to further reduce the spatial requirement of the head 1 along the panoramic axis Z , the base 2 can be secured to a tripod which is provided with a cross-member group 24 which is arranged to receive the cylinder 12a therein .

Advantageously, the embodiment of Figure 9 provides for two opposite deflection pulleys 13 between which there is interposed the flexible traction member 11 . It will be noted that one of the deflection pulleys 12 serves to deflect the longitudinal extent of the flexible traction member 11 through positive tilting angles a and the other serves to deflect the longitudinal extent of the flexible traction member 11 through negative tilting angles a .

The two deflection pulleys 13 are fixed to the upper member 2b of the base 2 by means of respective pins 13a which are rotatably supported on the upper member 2b and which extend parallel with the pivot axis X . During the rotation of the platform 3 about the axis X, the deflection axis A is located on the cylindrical surface of one or the other pulley in accordance with the fact that the tilting angle a is positive or negative . As a result of this configuration, the first branch I la of the flexible traction member 11 which is comprised between the spring 12 and the deflection pulleys 13 is kept coaxial with respect to the panoramic axis Z for any tilting angle a .

By ensuring the possibility of obtaining a stable positioning for the equipment item which is supported by the platform, i f desired also in a manner independent of the tilting angle , the invention solves the problem set out with reference to the cited prior art , at the same time achieving a number of advantages . These include the fact of being able to construct a compact balancing device which is capable of providing high forces in a restricted space , with a limited number of components .

As a result of these characteristics , the balancing device is contained within the overall dimensions of the head, in a position protected and without potentially dangerous proj ecting members .

Furthermore , the balancing device maintains the balancing characteristics without any changes as a result of the ambient temperature or the passage of time .

According to another advantageous aspect , the balancing device provides a balancing moment which changes in accordance with the tilting angle without any discontinuity about the balanced position .

Furthermore , the support head can be correctly adj usted in a simple and precise manner for a wide range of video-photographic equipment items , also ensuring continuous adj ustment of the balancing in the face of modest changes of weight and/or position of the video-photographic equipment items as a result , for example , of the addition or the movement of accessories , such as batteries , microphones , screens and so on .