Head clamp

Details Head clamp Head clamp

2001-03-01

2002-05-07

Trettel, Michael F. (Department: 3628)

Beds

Invalid bed or surgical support

With body member support or restrainer

C005S637000, C005S640000, C005S643000

Reexamination Certificate

active

06381783

ABSTRACT:

The invention concerns a head clamp for positioning a head, with a frame formed from two frame elements, which respectively have first ends which are movably joined together and second ends which carry pins for fixing the head in position.
In the case of the already known head clamps of the type initially described, the head is clamped between the two frame elements, i.e., by a linear movement of the two frame elements relative to one another. For the purpose of positioning the head, it is first brought between the two frame elements and the two frame elements are then moved axially towards one another by means of a side arm of each of the frame elements. The frame elements are locked relative to one another for the purpose of initial fixing in position. The head is finally clamped by means of a fine adjustment of the pins in which the latter are moved yet further on to the head.
The disadvantages of these head clamps are to be seen primarily in the large amount of mechanical play of the frame elements relative to one another; the longer the side arms that are in contact with one another, the greater is this play. Moreover, the adjustment and retightening of the pins by screwing is demanding and awkward. Also disadvantageous is the increased risk of breakage with increased loading, particularly through the attachment of additional appliances. These head clamps are also unsuitable for additional neuroradiological examinations, since they substantially restrict the beam path.
Accordingly, the object of the present invention is to develop a head clamp of the generic type in such a way that a greater mechanical stability is achieved.
This object is achieved, in the case of a head clamp of the type initially described, according to the invention in that the frame elements are pivoted relative to one another about a common axis of rotation.
For the purpose of clamping the head, the two frame elements are swivelled relative to one another, about a common axis of rotation. This enables the frame elements to be dimensioned as small as possible since, unlike those of head clamps which are adjustable in the axial direction, the side arms of the frame elements do not have to be made longer in order to permit opening of the head clamp. Due to the relative swivelling of the frame elements, a maximum opening angle can consequently be set with a very small structural size. This facilitates the handling and the application of the head clamp. In addition, the weight of the head clamp is drastically reduced, since the frame elements can be made substantially smaller and shorter. Due to a smaller structural form of the head clamp achieved thus, its mechanical stability is increased substantially in comparison with those already known in the art.
According to a preferred embodiment of the present invention, provision can be made such that the frame comprises a swivel position fixing device with at least one fixing component, on one of the two frame elements, which has at least one projection, and with corresponding recesses, disposed on the other frame element, in which the projection engages in a fixing position and fixes the frame elements in their position relative to one another, and that the fixing component can be brought relative to the recesses from the fixing position into a release position in which the frame elements can be swivelled relative to one another.
This design of the head clamp enables the frame elements to be fixed in a defined position relative to one another. It is thus possible to define the relative swivelling of the frame elements solely through the interaction of the fixing component with the recesses, for example, solely through the movement of the projection of the fixing component into the recess. As soon as the fixing component is withdrawn from the recesses, the frame elements can be swivelled again as required.
It is then advantageous if the recesses are connected non-rotatably to the other frame element. The non-rotatable connection has the advantage, firstly, of making the position fixing as free of play as possible, since a relative degree of freedom for a movement between the recesses and the frame element of the head clamp is thus eliminated. In addition, there is no need for a further, complicated, locking mechanism since the projections of the fixing components of the one frame element engage directly in the recesses and, in this way, are joined directly to the other frame element.
It is particularly advantageous if the fixing component is movable relative to both frame elements. The fixing component that is movably joined to the one frame element can thus engage in the recesses of the other frame element and remain invariably joined to the one frame element.
According to an advantageous embodiment, there can be provision such that the fixing component can be moved by means of an actuating component joined to it with a positive fit. The advantage lies in the fact that the fixing component can be concealed. Only the actuating component need be accessible to a person operating the head clamp. In addition, to facilitate actuation of the fixing component, an appropriate lever is provided on the actuating component. Furthermore, it is conceivable that one or more fixing components can be moved by a single actuating component. A quick-action mechanism is thus achieved for the head clamp.
In the case of another preferred embodiment of the invention, provision can be made such that the fixing component is mounted on a frame element in such a way that it can be moved towards the recesses. The swivelled head clamp can thus be fixed in its position solely by the fixing component being pushed into the recess. This renders possible particularly fast and easy handling of the head clamp.
In the case of another embodiment of the invention, provision can be made such that the fixing component is mounted on the one frame part in such a way that it can be swivelled towards the recesses. A pivoted mounting of the fixing component allows levers, resulting from this type of mounting, to be used on the fixing component, rendering possible a particularly force-efficient locking or release by means of the fixing component.
It is particularly advantageous if the recesses are formed by the teeth of a toothed wheel whose circumference extends maximally over an angular range of 360°. Toothed wheels can be produced very simply and cost-effectively by machine. In addition, it can be sufficient to provide only a limited angular range of the toothed wheel with teeth for which fixing of the head clamp in its position is required. This also reduces the production expenditure.
It is then advantageous if the teeth are undercut on at least one side. This has the advantage that when the fixing component is engaged between the teeth of the toothed wheel, inadvertent removal of the fixing component from the recess becomes impossible if the head clamp is pretensioned. An additional safeguard is thus provided against unintentional release of the fixing position.
According to a preferred embodiment of the invention, provision can be made such that only one of the fixing components can be brought into the fixing position in each case. A more precise subdivision for possible swivel positions of the head clamp can thus be predefined with appropriate arrangement of the fixing components relative to the recesses. This means, firstly, that the number of fixing positions can be increased and, secondly, that the fixing components and the corresponding recesses can be made sufficiently large to permit an optimal transfer of force. In addition, the play of the frame elements in relation to one another is reduced and the mechanical stability of the head clamp is coincidentally increased.
It is advantageous if the projections on the fixing components are in each case offset, according to the number of fixing components by a fraction, which is the reciprocal of this number, of a tooth division of this toothed wheel. The number of teeth of the tooth wheel is thus in effect multiplied by a factor corresponding to

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