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[ EN ]

Field of invention
The present invention relates to an improvement in holders for X-ray cassettes or some other receiver of X- ray or like radiation, said holders being oveable, preferably in a vertical plane, between two terminal positions in relation to a frame or stand part, namely a position in which a change of cassette or receiver can take place and a position in which the cassette or receiver can be exposed to radiation, and also being provided with pairs of dogging or centering devices for centering the cassette or receiver.

' A holder of this kind is often referred to as a "Potter spade" or "Bucky". The unit or assembly comprising the holder and stand part is referred to as a "Potter Box" , "Bucky Box" or "Potter-Bucky-Box".

Such units, or "Potter-boxes" are often placed beneath a table on which a patient to be X-rayed is positioned, the holder or "spade" being moved horizontally to a cassette-change position on one side of the table. When the patient is in a standing or sitting position, the Potter box is, instead, normally located in the vertical plane, in which case the holder or spade is displaced vertically to a position on one side of the patient and a cassette change effected.

In the case of other types of X-ray equipment, the holder is pivotal about an axis and - similar to various ' types of rectilinearly displaceable holders - can be moved in relation to a Potter box, which may be horizontal or vertical and which in some cases may also be able to take different angular positions relative to the horizontal .

The invention relates primarily to X-ray film cassettes. It can also be applied, however, to cassette holders for other types of receivers ; e.g. so-called image plates for instance.

Background prior art
Subsequent to inserting an X-ray film cassette or the like into the holder in the cassette-change position, it is necessary to centre the cassette, which can present certain, problems, owing to the fact that the cassettes used vary in size, depending on the part of the body which is to be photographed. For instance, there are normally 23 different standard cassette dimensions, in centimeters or imperial inches.

The cassettes are normally centered through the agency of separate dogging or centering devices, which are usually arranged in pairs.

The dogging devices are normally moved by a link- mechanism which forms part of a separate auxiliary operating device carried by the holder.

GB-B-1 358 660 (Philips Electronic) describes a cassette holder which can be swung relative to a box and which is provided with an auxiliary operating device in the form of a handle.

Other, similar arrangements are described in, for instance, US-A-4 128 767 (Stodberg et al), EP-A1_0 068 212 (Siemens) and US-A-4 246 488 (Hura) . WO86/01311 (Ohlson) describes a cassette holder of the aforesaid kind in which movement of the holder in conjunction with a change of cassette or receiver iε utilized in automatically decentering and centering the cassette in two perpendicular directions. This obviates the need to manipulate separate auxiliary operating devices for centering or decentering the cassette.

When inserting a cassette into the holder, and particularly in the case of vertical holders , there is a risk that in the initial stages the cassette will fall from the holder before it can be gripped for centering purposes, which means that the operator must concentrate on holding the the cassette in position until the centering devices grip the cassette and therewith relieve him of this task.

In addition to the risk of a cassette falling from the holder, there is also the risk that the cassette will be wrongly positioned, e.g. placed on its edge, particularly in the case of certain types of centering devices, thereby preventing the cassette from being centered correctly. This can result in an exposure being made with the cassette wrongly positioned, meaning that the exposure must be taken again and therewith subjecting the patient to an otherwise unnecessary dose of radiation.

Corresponding problems exist subsequent to moving the holder from the exposure position to the cassette-change position and the centering devices no longer engage the cassette. There is also a risk that a cassette will fall from the holder in this position, with subsequent injury to personnel and damage to equipment.

Object of the invention.
The object of the invention is to eliminate these drawbacks.

The invention is characterised in that the frame part has mounted thereon a sprung abutment device which engages the cassette and urges the same against the holder subsequent to the cassette being inserted into the holder in the cassette-change position.

The inventive arrangement ensures that the cassette is held in position from the time of inserting the cassette into the holder, irrespective of the type of centering means used.

Consequently, the operator need not concentrate on holding the cassette in position, but may instead concentrate on the task of centering the cassette and moving the same to the exposure position.

When the centering devices are in engagement with the cassette there is no longer need for the abutment device to be in engagement with the cassette, and consequently, in accordance with one embodiment of the invention, the abutment device is arranged to be free from engagement with the cassette in the exposure position.

This will ensure that the abutment device does not take part in the exposure effected at the exposure position.

In practice, the abutment device is preferably postioned in the region of one corner of the stand or frame part. This will enable the abutment device to br brought readily into engagement with the cassette as the cassette is inserted into the holder, while at the same time also ensuring that the abutment device is out of engagement with the cassette in the exposure position. In the case of one preferred embodiment, the abutment device is intended to engage the cassette during a part of the movement of the holder towards and away from the exposure position.

This embodiment finds particular application in the case of holders with which the cassette iε centered auto- matically as it moves towards the exposure position. The abutment device will namely ensure that the cassette iε held in place until the caεsette is engaged by the centering device, irrespective of the size of the cassette.

When the caεsette is returned from the exposure position, the abutment device will come into abutment contact vith the cassette as the centering device releases its engagement therewith.

According to another preferred embodiment of the invention, the abutment device is located on one end of a sprung arm which can be pivoted about an axis extending at right angles to the plane of the casεette, εuitably against the action of a spring.

This embodiment affords a given extent of flexibility between abutment device and cassette, i.e. the abutment device is allowed to move to some extent together with the cassette towards and away from the exposure position while exercising its cassette abutment function.

In the case of this embodiment, a stop device will be conveniently located to restrict rotation of the arm in one direction.

In accordance with one preferred embodiment of the invention, the abutment device has a bevelled edge sur-face which facilitates insertion of a cassette into the holder in the cassette-change position.

An abutment device of this kind will preferably have located opposite the bevelled edge surface a straight abutment surface which engages the cassette during movement of the cassette holder from the exposure position, wherewith the arm swings against the action of said spring, until the abutment device snaps outwards into abutment with the outer flat surface of the cas-sette, said arm in its outwardly swung position urging the cassette against the cassette holder.

As a rule, the friction acting between the cassette and the abutment device will be sufficient to prevent the abutment device from swinging back to its initial position. This affords the advantage that when the cassette reaches the cassette-change position, the cassette will be securely held in place, such as to ensure that the cassette will not fall from the holder before the operator is able to grip the cassette and effect a cassette change.

The arm of the abutment device is preferably made of spring steel.

An exe plifyng embodiment of the invention will now be deεcribed in more detail with referrence to the accompanying drawings.

Brief Description of the Drawings
Figure 1 is a perspective view of a "Bucky" or "Potter Box" provided with an arrangement according to the invention;

Figure 2 ilustrates the abutment device in larger scale and in perspective;

Figure 3 is a sectional view taken on the line III-III in Figure 2;

Figure 4 is a perεpective view of the Bucky with the caεsette located in the exposure position;

Figure 5 illustrates in perspective movement of the cassette holder towards the cassette-change position, wherewith the casεette strikes against the abutment device; and

Figure 6 illustrates in perspective the cassette holder subsequent to its return the cassette-change position.

Description of a preferred embodiment.

The reference numeral 1 identifies a unit in the form of a "Bucky" or "Potter-box" which is equipped with a rectilinearly moveable holder or Potter spade 2 and a stationary part 3, in the form of a frame 3. The frame is provided with guides for guiding the movement of the holder 2 between a cassette-change position, shown in Figure 1, in which a cassette containing an exposed X-ray film is exchanged for another cassette containing an unexposed film, 'and a film exposure position, εhown in Figure 4.

The holder may be provided with a handle (not shown) for moving the holder between said positionε. Alternatively, the holder may be driven by a motor, e.g. an electric, pneumatic or hydraulic motor. The caεsette holder iε conεtructed to centre the caεsette 4 automatically, as the casεette is moved to the exposure position, irrespective of the size of the cassette. To this end, the holder is provided with two dogging devices 5 for centering the cassette horizontally, and two dogging de-vices 6 for centering the casεette vertically. This automatic centering of the cassette is achieved with the aid of a linkage mechanism, not shown, mounted within the holder.

Arranged in the lower left hand corner of the frame part 3 iε an abutment device 10 which is effective in holding a casεette 4 in place in the holder 2, εo aε to prevent the caεεette from falling from the holder before the centering deviceε 5 and 6 are able to engage the caε-εette. The abutment device, which is shown in Figures 2 and 3, may be made of a plasticε material and iε carried on an arn 11, made of εpring εteel, which can be rotated about an axiε 13 againεt the action of a spring 12. The arm is prevented from rotation in a counter-clockwise direction, by means of a stop means 14.

The abutment device 10 has a bevelled εurface 10a which facilitateε insertion of the cassette in the casεette-change poεition, Figure 1, and an oppositely located straight surface 10b againεt which a cassette 4 will engage during movement of the caεεette from the film expoεure position, illustrated in Figure 5.

The inventive arrangement functions in the following manner:

When the cassette 4 is inserted into the cassette holder 2 in the casεette-change poεition, the cassette will be held in place by the abutment device 10 in the afore- described manner.

The holder is then displaced to the exposure position shown in Figure 4, while being automatically centered horizontally and vertically by the coacting dogging devices 5 and 6.

The film iε expoεed in the expoεure poεition, whereafter the holder 2 iε drawn from the frame 3. During this movement, the two dogging devices 5 and the upper dogging device 6 are released from the casεette, which therewith reεtε on the lower dogging device 6.

During movement of the caεsette 4 towards the cassette-change poεition, the caεεette engages the abutment device 10, which is swung counter-clockwise through an angle of about 45°, against the action of the spring 12. During this movement, the cassette is in engagement with the straight edge 10b of the abutment device 10.

The abutment device 10 on the sprung arm 11 will therewith snap outwards into abutment with the outer flat εurface of the caεεette, aε illuεtrated in Figure 6, and in thiε outwardly εwung poεition, will urge the cassette 4 against the holder 2. The friction acting between the cassette and the abutment device is sufficient to prevent the arm from swinging inwardly to a vertical position.

When the casεette haε reached the caεεette-change poεition illuεtrated in Figure 6, the cassette 4 can be removed readily from the holder 2, wherewith the abutment device will swing back to its initial position shown in Figure 1 and a new cassette containing an unexposed film can be iserted into the holder 2.

In the aforegoing, the invention has been deεcribed with reference to a cassette holder with which the casεette is centered automatically in conjunction with movement of the holder to the film exposure position. The invention, however, can be applied also to other kinds of cassette holders, for instance holders of the kind in which centering of a casεette iε effected prior to moving the holder to the expoεure poεition. The invention will enable the operator to concentrate his attention on centering the cassette even with holders of thiε kind, without needing to fear that the caεεette might fall unintentionally from the holder. As an alternative to the deεcribed poεitioning of the abutment device, said device may be located in the upper corner of the frame part 3, or an abutment device may be provided in both the upper and the lower corner. Thiε alternative arrangement is particularly beneficial in the case of top-centered casεette holderε.

One particular advantage afforded by the inventive arrangement iε that manipulationε can be carried out with one hand, i.e. a caεεette can be removed with one hand and a new caεεette inεerted with the other.