A DEVICE FOR REGULATING THE FLOW AREA IN A FLEXIBLE TUBE

Abstract: A flow regulator especially for infusion and transfusion assemblies. The flow regulator comprises a clamp housing (11) through which the tube (16) is passed, and a clamping member axially displaceable in the clamp housing (11), e.g. a roller (12), intended to compress the tube against a clamping surface. In order to reduce stresses in the tube material at the compression and obtain an exact adjustment of the drop rate, which should not be changed with the time, the clamp housing (11) has a groove (15) in which the tube (16) rests. The groove has at the inlet of the clamp housing a width and a depth which substantially corresponds to the cross-sectional area of the tube in unloaded condition and has a decreasing depth and increasing width towards the outlet and corresponding to the cross-sectional size of the tube in gradually compressed condition. In connection to the upper edge of the groove (15) rest surfaces (17) are arranged against which the roller (12) runs.

Description: A device for regulating the flow area in a flexible tube The present invention relates to a device for regulating the flow area in a tube, particularly for infusion and transfusion assemblies, and comprising a clamp housing through which the tube is passed and which has a clamping surface in the form of an axial groove with a depth decreasing along its length, and a clamping member in the form of a roller which is axially displaceable in longitudinal guides in the clamp housing. Background of the invention Flow regulators, so called drop regulators are previously known i.e. through the US patent specification No. 3,900, 18 , which refers to a regulator in the form of a roller clamp, the supporting member of which has a longitudinal groove with a decreasing depth and width towards the outlet opening. The tube rests on said groove and when the tube by means of the roller is compressed the central portion will be pressed down into the groove and leave a passage, while the end portions are compressed. By the fact that both the width and depth of the groove are decreasing, the free flow passage will be gradually reduced by displacing the roller in the direction towards the outlet opening of the supporting member until the tube is completely closed off. Such a device causes considerable stresses in the plastic material in the tube at high degrees of compression and so called cold flow will easily occur in the material. Oue to the redistributions in the material caused by that the area of the flow passage will be changed and by that also the adjusted drop rate. Because of the high deformation of the tube caused by the compression it can take a long time before it reverts to a lower degree of compression if the drop rate is to be increased and sometimes the deformation is even permanent, at which the drop rate can not be increased. This is of course a serious drawback in infusion and transfusion assemblies in medical treatment, where it is very important that the drop rate can be set and adjusted with a high accuracy. In other types of known roller clamps the central portion of the tube is compressed first while one or both outer portions are left free as flow passages, which are gradually compressed when the roller is displaced towards the outlet opening of the clamp housing. According to another known roller clamp a groove is arranged just opposite one side portion of the tube, the width and depth of the tube being gradually reduced towards the outlet opening of the clamp housing. However both these devices have the same drawbacks as the one described above. The ob-iect and most important features of the invention The object of the present invention is to provide a flow regulator of the kind mentioned above, which minimizes the Influence of cold flow on the flow regulation. A more exact adjustment of the drop rate will by that be possible, which should be constant and not be changed with the time. This has according to the invention been provided by the fact that said groove is arranged to receive substantially the whole cross-section of the tube, at which it at the inlet end of the clamp housing has a width and the depth which substantailly corresponds to the cross-sectional size of the tube in unloaded condition and has an increasing width and a decreasing depth towards the outlet end of the clamp housing corresponding to the cross-sectional size of the tube in gradually compressed condition. Description of the drawings The invention will now be described more in details with reference to some embodiments shown in the accompanying drawings. Fig. 1 is a vertical longitudinal section through a flow regulator according to the invention. Fig. 2 shows the regulator in a view from above. Fig. 3a-3c show vertical cross-sections through a part of the regulator with the roller in three different positions, Fig. 4 is a vertical logitidunal section through a flow regulator according to a modified embodiment of the invention, Fig. 5a-5b are cross-sections through a regulator according to fig. 4 showing the tube in unloaded and compressed conditions respectively, Fig. 6 is a cross-section through a regulator according to a further modified embodiment. Descriptions of some embodiments The flow regulator 10 is of a type commonly used for infusion and transfusion assemblies in medical care and comprises a clamp housing 11 and a clamping member displaceably arranged therein, which in the shown embodiment consists of a roller 12. The roller 12 is on both side provided with axle hubs 13, which are guided in two tracks 14 in the clamp housing 11. The bottom surface of the clamp housing 11 is provided with a groove 15, in which the tube 16 is placed. The groove has at the inlet end of the clamp housing a depth and a width which substantially corresponds to the cross-sectional size of the tube 16 in unloaded condition and has an increasing width and a decreasing depth towards the outlet end of the clamp housing corresponding to the cross-sectional size of the tube 16 in gradually compressed condition as is illustrated in figs. 3a-3c. In connection to the upper edge of the groove 15 rest surfaces 17 are arranged against which the roller 12 runs. The roller 12 will by that never completely press against the tube 16, at which the stresses therein are reduced. By the fact that the tube 16 during the whole compression process will have support at all sides of the groove 15, which is designed after the cross-sectional size of the tube, a" compression which is gentle to the material is obtained and the risk for cold flow is considerably reduced. A constant drop rate is obtained immediately after each new adjustent. OM In the embodiment according to fig. 4 the track 14 is somewhat inclined downward towards the outlet end of the regulator. In the clamp housing 11 there is further arranged a pad 18 of a resilient material, for example rubber. which in the embodiment shown in fig. 4 and 5 has a groove 15 designed for the tube 16, which is placed in said groove. The upper surface of the pad 18 makes the clamping surface for the roller 12 and when displacing the roller, which is guided by the inclined tracks 14, towards the outlet end of the clamp housing the tube 16 as well as the pad 18 will be gradually compressed. If the drop rate then is to be increased and the roller 12 is brought backwards the part of the pad 18 which has been compressed will by its resilience revert to its original shape, at which it will press on the tube 16 from the sides and force this to revert to the shape it had before the compression. As it is shown in fig. 6 the pad 18 can have an almost closed groove 15 or even a through hole, through which the tube 16 can be passed. In this embodiment the roller 12 can be considerably thinner than the pad 18, which by that can have the same height over its whole cross-section. At the compression the material in the pad 18 can be redistributed to the spaces beside the roller 12. The pad 18 can appropriately be firmly fixed in the clamp housing 11. The invention is not limited to the embodiments shown but can be modified within the scope of the following claims. It would of course be possible to design the clamp housing 11 with a bottom inclined uppwards towards the outlet and/or make the pad 18 so that its upper surface is inclined instead of making the tracks 14 in the side walls of the clamp housing inclined. It would further be possible to have the clamping member other than a roller 12, e.g. a displaceable element having a plane surface towards the tube.

Claims: s CLAIMS 1. A device for regulating the rate of a flow in a flexible tube, particularly for infusion and transfusion assemblies, and comprising a clamp housing (11) through which the flexible tube (16) is passed and which has a clamping surface in the form of an axial groove (15) with a decreasing depth along its length and a clamping member, e.g. a roller (12), which is axially displaceable in the clamp housing along guides (14), c h a r a c t e r i z e d i n. that said groove (15) is arrranged to receive substantially the whole cross section of the flexible tube (16), at which it at the inlet end of the clamp housing (11) has a width and a depth substantially corresponding to the cross-sectional size of the tube in unloaded condition and has an increasing width and decreasing depth towards the outlet end of the clamp housing corresponding to the cross-sectional size of the tube in gradually compressed condition. 2. A device according to claim 1, c h a r a c t e r i z e d i n, that the clamping member (12) is arranged to run against rest surfaces (17) arranged in connection to the upper edge of the groove ( 15 ) . 3. A device according to claim 1 or 2 , c h a r a c t e r i z e d i n, that the groove (15) is arranged in a resilient pad (18) extending over a substantial part of the length of the clamp housing (11) and that when compressing the tube (16) by means of the clamping member (12) the resilient pad (18) is exerted to a compression, at which the pad is intended to exert a lateral pressure to the tube (16) which forces it to resumes its original shape when the pressure from the clamp member is ceased and the pad reverts to its original shape. 4. A device according to claim 3, c h a r a c t e r i z e d i n, that the pad (18) is designed to enclose an essential part of the circumference of the part of the tube (17) which is located in the clamp housing. 5. A device according to claim 3 or 4 , c h a r a c t e r i z e d i n, that the pad (18) is firmly fixed in the clamp housing. 6. A device according to claim 3, 4 or 5, c h a r a c t e r i z e d i n, that the groove (15) consists of a through passage in the pad (18). __ CM

Inventors: ANDERSSON INGVAR, STACKELL JOHAN, ANDERSSON, INGVAR, STACKELL, JOHAN
Applicants: MEDIPLAST AB
Application year: 1984
Main classification: F16K7
IPC codes: A61M39