Patent Description:
A great variety of tripods are used in photography and they have an upper substantially circular bracket to which the three legs are fixed and these brackets have mostly a central opening in which a top plate or top platform can be fixed. The top plate is provided with more or less standardized support elements which provide releasable connection to a ball head or to different connection means like an I-plate or L-plate to which the camera can be fixed in different positions. Owing to its special shape top brackets are often referred to as "spider" or "chassis".

The fastening and release of the top plate is solved generally by providing a narrow vertical gap across the top bracket, and using an adjusting bolt with a large button head to tighten thereby the gap or to allow the gap open under the effect of the flexibility of the material of the top bracket.

The inner wall of the central opening of the top bracket is generally cylindrical or cylindrical at least at the upper and lower end regions, and the upper surface adjacent the opening serves as a support for the top plate. The diameter of the cylindrical opening follows standard sizes, and sizes <NUM> and <NUM> in diameter are the most frequent but other diameters like <NUM> are also used.

Several types of tripods and accessories can be found at different manufacturer's websites, like http://www. com/accessories-systematic or http://www. com/products/photo-tripod-heads/.

For fastening and releasing the top plate in the opening of the top bracket it need not have a slot and a gap but the use of an adjustable pressing member can solve the same task. A tripod designed without a slot is published at the website https://shop. uk/products/<NUM> that shows the picture of the Sirui R-42133X reporter tripod in which the top bracket has no gap but a short adjustment bolt presses a curved member to the cylindrical side face of the top plate when inserted in the top bracket.

A different type of camera supports includes adjustable center columns which can be inserted and fixed in the top bracket, whereby the height of the camera can be adjusted. A special type of tripods with center column are called "leveling tripods", wherein a spherical member surrounds the center column, and in that case in the opening of the top bracket a spherical nest is provided. This nest co-operates with the spherical member around the center column, whereby the angular position of the column can be adjusted within a given range. Because in case of a sphere any upper or lower diameter is smaller than the equator, the insertion of the sphere in the nest requires disassembly of the bracket which can be made in specialized workshops only. With such leveling tripods the vertical position of the center column can be easily adjusted even if the top plane of the tripod is not horizontal.

German patent publication <CIT> shows an example of a leveling tripod with adjustable center column. The publication is silent about the way how the sphere can be inserted in the conforming nest.

There are several accessories that can be attached to the top plate which are capable of level adjustments. An example is shown in <CIT> that relates to an adjustable ballhead and has a housing being an upright cylinder and the bottom of the housing can be connected to a top plate of a tripod. In the housing there is a cylindrical shell with an upper rim in which a leveling bubble is arranged. The shell can be adjusted in any position in the housing and the leveling bubble allows adjustment of the rim to the horizontal plane without regard the position of the top plate.

In <CIT> the tripod's three legs have respective ball joints at their upper ends that are connected to a central top bracket in which a fourth ball joint is arranged that holds the camera support. This is a complicated structure with four ball joints, wherein adjustment takes a long time, and the camera holder cannot be removed from the upper ball joint.

<CIT> describes a top bracket mounted on the top of a tripod which receives a cylindrical support that can receive a column in a first opening. On the top of the column a camera holder can be arranged, and the cylindrical support has a second opening into which the column can be inserted in a normal position with respect to the first opening, and the position of the camera can be adjusted by a separate ball head. Here the top bracket has a single function of holding the cylindrical support. <CIT> describes a top bracket according to the preamble of claim <NUM>.

<CIT> relates to a tripod with a top part that has a specific multi-part ball joint by which the camera holder and the camera can be adjusted within a limited angular range in every direction, and the fixing of the position takes place from below by a bolt arranged between the three legs of the tripod. The assembly cannot be removed in an easy way and has a complicated handling.

The use of a special shell with leveling properties could be spared if the top plate was designed as the top of a level adjusting sphere. In case the opening of the top bracket is not an upright cylinder, a number of standard top plates cannot be used to such tripods, therefore this would limit the different uses of such a tripod.

The task of the present invention is to provide a universal tripod top bracket in which a standard top plate with cylindrical side surface can be inserted, fixed and in case of need it can be removed, and a leveling support with a spherical side surface can be inserted therein to enable leveling in a simple way.

This task has been solved by the tripod top bracket designed as defined in the attached claims.

The invention will now be described in connection with preferable embodiments thereof, in which reference will be made to the accompanying drawings. In the drawing:.

<FIG> shows the perspective view of a first embodiment of the top bracket <NUM> designed according to the present invention which has a flat body <NUM> made preferably of a cast aluminum alloy, and along its outer portion three radial projections as leg supports <NUM>, <NUM> and <NUM> are provided which serve as attachment to the upper ends of the three legs of the tripod (not shown). The leg supports <NUM> to <NUM> are angularly offset from each other by <NUM>°. The connection to the legs is provided through respective horizontal through bores in the leg supports <NUM> - <NUM>. Opposite to the leg support <NUM> a narrow vertical gap <NUM> is provided across the body <NUM> and at the two faces of the gap the otherwise circular body has two radially extending projections <NUM>, <NUM> and respective tangential bores are provided in them. One of the bores has an inner thread in which a threaded adjustment bolt <NUM> can be turned. At the head of the bolt <NUM> an elongated adjustment button <NUM> is provided whereby the width of the gap <NUM> can be adjusted. The body has a central opening <NUM> which is symmetrical to the central vertical axis of the body <NUM>. Around the upper end of the opening a narrow horizontal ring <NUM> is provided on the top surface of the body <NUM>, and beyond the ring <NUM> the upper surface of the body has a conical portion <NUM>.

In the upper part of the leg support <NUM> a small circular leveling bubble <NUM> is arranged by which the leveling of the tripod can be checked, if one wishes to level the upper plane of the top bracket <NUM> adjust to horizontal position.

The design of the interior surface of the opening <NUM> is very essential from the point of view of the present invention and will be explained in detail.

<FIG> shows a cylindrical top plate <NUM> which has a more or less standard cylindrical shape around a vertical axis <NUM>. The top plate <NUM> has a cylindrical body that has an upper and a lower part <NUM>, <NUM>, and a step <NUM> with smaller diameter is provided between the two parts <NUM>, <NUM>. Above the upper part <NUM> the top plate has a flat head which has a rim <NUM> with a diameter larger than that of the upper part <NUM>, and the lower ring-like surface of the rim <NUM> provides a definite abutment and support for the top plate <NUM> when inserted in the opening <NUM> of the top bracket. When the top plate <NUM> is inserted in the opening <NUM> of the top bracket <NUM> (see <FIG>) the cylindrical upper and lower parts <NUM>, <NUM> of the top plate <NUM> are guided and held by an upper and lower cylindrical portion of the opening, and the rim <NUM> sits on and supported by the ring <NUM>. The top plate has a central vertical threaded bore <NUM> for connection to a ball head or different accessories required for holding a camera (not shown). In <FIG> a leveling support <NUM> is shown in perspective view, which has a flat upper surface <NUM> and a threaded central bolt <NUM> which has the task of providing a releasable connection to the device held by the leveling support <NUM>. The leveling support <NUM> has a spherical side <NUM> and this allows adjusting the angle of inclination of the upper surface <NUM>. In use the leveling support <NUM> should be inserted and fitted in the central opening <NUM> of the top bracket <NUM>. In the upper surface <NUM> a leveling bubble <NUM> is arranged that is used to adjust he horizontal position of the leveling support <NUM>.

Reference is made now to <FIG> shows a simplified sectional view of the top bracket <NUM> when the top plate <NUM> is inserted and fitted in the central opening <NUM>. <FIG> shows the enlarged profile of the opening <NUM>. The opening <NUM> has a cylindrical upper section <NUM> and a spaced cylindrical lower section <NUM> and a spherical cavity <NUM> that extends between the upper and lower sections <NUM>, <NUM>. The upper section <NUM> has the same diameter as that of the upper part <NUM> of the top plate <NUM> and its height can be smaller but in any case sufficient for squeezing and holding the top plate <NUM> when the gap <NUM> is tightened. It is advantageous but not always necessary that the lower cylindrical section <NUM> has the same diameter as the lower part <NUM> of the top plate <NUM>, but in such a design the positioning of the top plate <NUM> in the opening <NUM> is more definite. The lower cylindrical part <NUM> can even be omitted and the spherical cavity <NUM> can extend till the bottom face of the opening <NUM>, since the support between the ring <NUM> on the top bracket <NUM> and the lower face of the rim <NUM> of the top plate <NUM> together with the matching diameters of the upper part <NUM> of the top plate <NUM> and the cylindrical upper section <NUM> of the top bracket <NUM> can provide a stable positioning of the top plate <NUM> in the top bracket <NUM>.

<FIG> is a similar sectional view to <FIG> but here the leveling support <NUM> is inserted in the central opening <NUM> of the top bracket <NUM>. The shape of the spherical cavity <NUM> in the opening <NUM> fits to the shape of the spherical side <NUM> of the leveling support <NUM>. <FIG> shows also the inner design of the leveling support <NUM> wherein a screw projects out of a central bore that connects the devices held by the leveling support <NUM>. A hook <NUM> project out from the bottom of the leveling support <NUM> that facilitates handling.

Reference is made now to <FIG> which shows a first way of placing the leveling support <NUM> with its spherical side <NUM> in the central opening <NUM> of the top bracket. The normal width of the gap <NUM> on the body <NUM> of the top bracket <NUM> is much smaller than the difference in the equatorial diameter D (shown in <FIG>) of the spherical cavity <NUM> of the opening <NUM> and the diameter of the cylindrical upper section <NUM>. The leveling support <NUM> can be inserted in the opening <NUM> if the gap <NUM> is increased to the extent to be able to receive the diameter D. <FIG> show that a flat plate <NUM> which can be a coin as well is inserted in the gap <NUM> after the bolt <NUM> has been removed from the threaded bore in the projection <NUM> so that the plate <NUM> covers the connection between the bores in the two projections <NUM>, <NUM>. Then the bolt <NUM> with its large button <NUM> is screwed from the other projection <NUM> in the threaded bore as shown in <FIG> as long as its inner end abuts the plate <NUM>. When the bolt <NUM> is forced further in the same direction, the projection <NUM> is forced to open the gap <NUM>, and this operation can be continued as the central opening <NUM> will be sufficiently wide to receive the leveling support <NUM>. After this the bolt <NUM> can be loosen, whereby the flexibility of the material of the body <NUM> of the top bracket <NUM> closes the gap, and that fixes the leveling support <NUM> in the spherical cavity <NUM>. Then the plate <NUM> can be removed, and the bolt <NUM> can be removed and inserted in the bore of the other projection <NUM> as shown in <FIG>, and by tightening the bolt <NUM> the position of the leveling support <NUM> can be fixed. This operation requires that the material of the alloy from which the top bracket <NUM> is made has a sufficient extent of flexibility. Using the aforementioned standard diameters of the opening <NUM> this condition can be fulfilled with several alloy materials, however, a few preferred alloy compositions for this purpose are the AlZn5Mg3Cu (that has a type name EN AW <NUM> - and a commercial name: CERTAL) and the composition AlZn5,5MgCu (having the type name: EN AW <NUM> - and commercial name PERUNAL).

While the here described way of forced opening the gap <NUM> provides a solution to allow insertion of the leveling support <NUM> in the central opening <NUM>, this is connected with some additional effort. In <FIG> a different way is shown that allows easy and fast insertion of the leveling support <NUM> in the top bracket <NUM>. In the bottom view of <FIG> that shows the top bracket <NUM> from below it is shown that the previously described design of the central opening <NUM> has a pair of diametrically opposite and identical cuts <NUM>, <NUM> which have a width L. The cuts <NUM>, <NUM> have a cylindrical surface and the diameter of the cylinder corresponds to the equatorial diameter D of the spherical cavity <NUM>. It is preferred if the cuts <NUM>, <NUM> extend only till the halving plane <NUM> of the spherical cavity <NUM> illustrated by the chain line in <FIG>. The width L is at least as high as the height L1 of the leveling support where its outer diameter is the same as the diameter of the cylindrical upper section <NUM> of the opening <NUM> (see <FIG>) and illustrated by a thin line on <FIG>. To find the position of the cuts <NUM>, <NUM> it is preferred if they are symmetrically arranged to one of the three leg supports <NUM> to <NUM>. In <FIG> they are position symmetrically to the leg support <NUM>.

<FIG> shows the perspective view of the top bracket <NUM> view from the bottom. The insertion of the leveling support <NUM> in the opening <NUM> of this embodiment is illustrated in <FIG>. The leveling support <NUM> has to be turned by <NUM>° so that the upper surface <NUM> which is normally horizontal should become vertical, and in this position the leveling support <NUM> has to be inserted in the opening from below where the cuts <NUM>, <NUM> are provided. This can be easily recognized from the position of the leg support <NUM>. <FIG> shows the initial position of the insertion. <FIG> shows when the leveling support <NUM> is in central position within the opening. At this central position the leveling support <NUM> should be turned by <NUM>° so that its upper surface <NUM> becomes again horizontal and faces upward. This turning movement can be done easily, as the presence of the cuts <NUM>, <NUM> has removed all parts which would prevent such a rotation. In the moment the leveling support <NUM> has been turned, the spherical side <NUM> thereof fits in the spherical cavity <NUM> of the opening <NUM> and the leveling support <NUM> can now be turned in any position.

The removal of the leveling support <NUM> occurs in reverse direction, and when it has been removed the top plate <NUM> with cylindrical side surfaces can be inserted.

<FIG> is a perspective view showing the top bracket <NUM> holding the leveling support <NUM> in the opening <NUM>. The upper surface <NUM> of the leveling support <NUM> is higher than the upper surface of the top bracket <NUM> because in that case any accessory connected place on the upper surface will not get abutted to the top bracket <NUM> even if the plane of the upper surface <NUM> is inclined to the upper plane of the top bracket <NUM>. In this way after the tripod has been positioned anywhere in the field and its upper surface is not quite horizontal, by loosening the bolt <NUM> the leveling support <NUM> can be adjusted easily so that its upper surface <NUM> becomes horizontal. This is made possible by the presence of the leveling bubble <NUM> in the leveling support <NUM>.

The adjusted position can be fixed by tightening the bolt <NUM>. In the embodiment there is no need to provide the gap <NUM> because a continuous top bracket design is possible; where the fixing of the inserted leveling support <NUM> can take place by a lateral pressure means like in case of the previously mentioned Sirui reporter studio tripod type R-4213X.

The top bracket <NUM> designed according to the present invention is very similar to conventional top brackets, however owing to the special design of the interior of the central opening <NUM>, it can receive and fix standard top plates with cylindrical side surface, and after removal of the top plate one can insert the leveling support <NUM> which performs the same function as the top plate but allows easy, simple and fast leveling rendering the use of expensive and large leveling systems unnecessary.

Claim 1:
A top bracket (<NUM>) for tripods having a substantially flat body (<NUM>) provided with a center opening (<NUM>) and an outer region comprising respective leg supports (<NUM>, <NUM>, <NUM>) angularly spaced from each other, the opening (<NUM>) has a symmetric design around a central axis (<NUM>) and a cylindrical upper section (<NUM>) for receiving and holding a cylindrical top plate (<NUM>) inserted therein, and an adjustable fastening means that fixes the position of said top plate (<NUM>) when inserted and allows removal of the top plate (<NUM>) when loosened, characterized in that a spherical cavity (<NUM>) is provided in the opening (<NUM>) starting under the cylindrical upper section (<NUM>) which has a height measured in the direction of said central axis (<NUM>) much smaller than the height of the spherical cavity (<NUM>) under it, and the diameter of the spherical cavity (<NUM>) increases under the cylindrical upper section (<NUM>) in axial direction until at a central height region of the body (<NUM>) it takes the highest equatorial diameter (D) and narrows down in downward direction along the axis (<NUM>), and the opening (<NUM>) is designed to receive either the cylindrical top plate (<NUM>) or to receive a leveling support (<NUM>) that has a spherical side (<NUM>) that fits in the spherical cavity (<NUM>), and the top bracket (<NUM>) comprises a mechanism that allows insertion and removal of the leveling support (<NUM>) in the opening (<NUM>).