Bearings – Linear bearing – Roller bearing
Reexamination Certificate
2002-02-15
2003-07-29
Footland, Lenard A. (Department: 3682)
Bearings
Linear bearing
Roller bearing
Reexamination Certificate
active
06599017
ABSTRACT:
The present invention relates to a device that is provided with a C-arm for the mounting of medical equipment, which C-arm is attached to a carrier so as to be adjustable along its circumference, said carrier being provided with a bearing block that is provided with at least one row of roller elements on both sides, the C-arm being constructed so as to be hollow and being provided on both sides with at least two oppositely situated internal running surfaces for the roller elements.
Devices of this kind set forth are used in practice for medical examination of a patient. To this end, an emitter of, for example, X-rays is attached to one end of the C-arm whereas a corresponding receiver is attached to the opposite end. The C-arm is adjustable inter alia along its circumference and hence can be accurately positioned relative to the patient who is accommodated on a table, for example, during a surgical intervention.
In order to ensure safe operation in all circumstances, the design of a device of this kind should satisfy a number of design requirements that are contradictory in some cases. First of all, the beam from the emitter to the receiver should remain within predetermined boundaries in all circumstances. This means that the C-arm should have a high bending strength. Furthermore, the construction of the device should be as light as possible so as to achieve an as high as possible degree of moeuvrability. This is of importance, for example, for the displacement of the device and for the adjustment of the C-arm that can be performed manually as well as with the aid of a motor. Furthermore, the device should be capable of withstanding large temperature differences that may occur, for example, during transport. In order to satisfy the above requirements, the operation of the bearing for the C-arm should be smooth and light with a minimum amount of play.
A device of the kind set forth is known from DE 298 02 014. The cited document describes a device for medical diagnostic applications that is provided with a C-arm on which a radiation source is mounted at one side while a corresponding receiver is mounted at another side. The C-arm is journaled on a carrier. The bearing block is provided on both sides with two rows of wheels that are situated one above the other. The C-arm is constructed so as to be hollow and is provided with internal running surfaces for the wheels. The running surfaces are provided with guide rails that have a semi-circular cross-section. The wheels are provided with corresponding recesses. This construction minimizes the play in the lateral direction and prevents the C-arm from performing undesirable lateral pivotal motions during its movement along its circumference.
The known device has the drawback that the guide rails must be attached to the C-arm with a bias, for example, by means of a construction involving tension springs and compression springs. A construction of this kind has a negative effect on inter alia the weight of the C-arm and it also disturbs the delicate balance between weight and bending strength that is realized under the influence of the design requirements imposed on the C-arm.
The object of the invention is different, that is, it aims to provide a device of the kind set forth that offers a higher mechanical loadability of the bearing surfaces in combination with a low weight and a high bending strength.
To achieve this, the device in accordance with the invention is characterized in that the running surfaces are provided with reinforcement elements.
The running surfaces thus reinforced are suitable for co-operation with a bearing block that is provided with reinforced roller elements. Because reinforced roller elements are capable of taking up a higher load, the number of roller elements in each row can be advantageously reduced. This results in a shorter bearing block which in its turn enables a larger angulation angle for the C-arm.
The reinforcement elements in a first preferred embodiment of the device in accordance with the invention are strip-shaped. Choosing a shape in the form of a strip offers several advantages. The additional weight of the reinforcement elements is thus minimized minimum, so that the delicate balance between weight and bending strength for the C-arm is hardly disturbed. Moreover, the strips expand mainly in the longitudinal direction under the influence of temperature fluctuations. This expansion can be simply taken up by allowing some play in the longitudinal direction.
The running surfaces in a practical preferred embodiment are provided with recesses for receiving the reinforcement elements. The reinforcement elements can thus be quickly and efficiently fitted in the correct position on the running surfaces.
The recesses in an elegant preferred embodiment are form-locking. The reinforcement elements are preferably arranged loosely in the recesses. Bias constructions of the kind described above in relation to the guide elements of the known device can thus be dispensed with. Moreover, any expansion and contraction of the reinforcement elements due to temperature fluctuations can be taken up without special steps being required.
The reinforcement elements preferably contain a metal such as hardened steel. The roller elements may be reinforced by using a hardened metal. As a result of the use of the reinforcement elements, the C-arm may contain aluminum or a composite material in known manner. Thanks to the use of the metal reinforcement elements, such a softer material is effectively protected against damaging by the reinforced roller elements during use.
Each row of the bearing block in another preferred embodiment comprises no more than six roller elements. This advantageous reduction of the number of roller elements is possible because of the use of the reinforced roller elements that are individually capable of withstanding a higher load.
The invention also relates to a bearing block as described as part of the device in accordance with the invention.
REFERENCES:
patent: 4722150 (1988-02-01), Jacobs et al.
patent: 6347887 (2002-02-01), Bolzonaro et al.
patent: 29802014 (1998-06-01), None
De Vries Hendrik Wijbe Johannes
Geelhoed Frans Eduard Nicolaas
Footland Lenard A.
Koninklijke Philips Electronics , N.V.
Vodopia John
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