1.  Field of the Invention
The invention relates to an apparatus for skinning double fillets of fish having a highly sensitive skin, for example, due to cooking, e.g. herb-seasoned fillets, the apparatus comprising a fillet-conveying driving or entraining roller driven in rotary manner and having a gripping circumferential surface, a resiliently displaceable skinning knife facing the entraining roller at an adjustable spacing, and a presser surface extending below the skinning knife. 
2.  Prior Art
A skinning apparatus provided for the aforementioned skinning purposes is disclosed in German Pat.  No.  30 21 151.  In this apparatus, the entraining roller, which is termed skinning roller, is provided with grooves extending along the axially extending surface lines of the cylindrical roller, which grooves are interrupted by a groove region surrounding the circumference of the entraining roller and having a pitch of grooves which is larger than that of the remaining regions of the circumferential surface.  The function of this apparatus is not satisfactory because faults made evident by, in particular, recurrent, persistent blockages occur comparatively often.  The reason for this is the inadequate capacity of the larger pitch groove zones, so that the dorsal fin strip coming to rest in this area is engaged and the gristly fin holders run against the cutting edge of the skinning knife, which, apart from the fact that the skinning knife may cut into the fin holders which may then remain in the final product, will mainly lead to skin patches remaining on the skinned fillets. 
3.  Objects of the Invention
The main object of the invention is to obviate these shortcomings.  In particular, it is an object of the present invention to improve a skinning apparatus for double fillets of the type set out above with regard to its function such that the products obtained are satisfactory to the consumers concerned. 
According to the invention, these objects are achieved in an apparatus comprising an entraining roller driven to rotate and defining a gripping surface for engaging the fillets to be processed, a resiliently displaceable skinning knife having a cutting edge and facing the entraining roller at a settable spacing, and a presser surface extending below the skinning knife in that the entraining roller has at least one radial groove with an auxiliary conveyer arranged therein, the auxiliary conveyor being provided with elastic vanes projecting approximately up to the external diameter of the entraining roller, and that a resilient hold-down device is positioned over the radial groove and upstream of the cutting edge of the skinning knife, when seen in the processing or conveying direction of the fillets.  The advantages of these features are in particular that, as a result of their elasticity, the vanes can, if necessary, be displaced by the dorsal fin strip and, as a result of their resilience, will have a cleaning effect on the cutting edge of the skinning knife in this area. 
In order to achieve a particularly efficient hold-down action of the hold-down device, this may be, at least in its portion facing the radial groove and cooperating therewith, roughly of the same width as the radial groove. 
Advantageously, the radial groove receiving the auxiliary conveyor in the case of a single-path construction of the apparatus should be located in the centre of the entraining roller, whereas in the case of a two-path construction it should be located in the outer quarter points of the length dimension of the entraining roller.  The radial groove can, advantageously, be designed to have a width of between 5 and 12 millimeters, preferably of 8 millimeters. 
A safety-controllable apparatus which can be integrated into an automatic fish processing line expediently may be obtained if, upstream of the entraining roller, there is provided a belt conveyor rotating in the same direction as and at a lower circumferential speed than the entraining roller.  It is advantageous for manual feeding purposes if the belt conveyor has line-up marks directed towards the radial grooves of the entraining roller.