the value u03b4r as opposed to the construction previously described here the two membranes 10 and 11 are held and secured in the frame 15 or equivalent structure by means of the thicker dimensioned rims safety pins are therefore not necessary in a further embodiment as shown in fig6 in order to increase the insulation effect the animal gate is provided with three membranes with overlapping flaps membranes 16 and 18 are again convex while the intermediate membrane 17 is flat the clamping in the frame 19 depending upon requirements may be accomplished according to the teachings described and shown in fig3 a or as described and shown with reference to fig2 a fig7 shows an alternative constructional form of a gate a membrane 20 is originally formed as a closed disc and individual membrane flaps 21 are produced by means of incisions 22 in order to guarantee the complete freedom of movement between the membrane flaps 21 the strengthened or reinforced rim 23 of the membrane 20 is subjected to a radial outwards tension or pull z the incision 22 is thereby increased in size to a small gap or slot which is changeable within limits as described below a special shaped rim or marginal lip 24 fig8 serves this purpose its inside recess or cavity 25 has a diameter d which is smaller than the outside diameter d of a ring 26 by the amount u03b4d and which ring forms the inside part of a frame for the membranes 20 the radius of curvature of the recess or cavity.