hereafter different embodiments are described according to the figures . the same elements , similar elements or elements with the same effect are identified with the same reference signs . in order to avoid redundancies there is partially no repeated description of these elements in the following description . fig1 shows a perspective view of a heel unit 1 . the heel unit 1 comprises a base plate 30 , which is attached to the surface of a ski . usually , the base plate 30 is screwed onto the surface of the ski . alternatively , the base plate 30 can also be adhered to the surface of the ski . a base plate 30 is attached to the heel member 10 by means of two brackets 18 . the heel member 10 has the purpose to receive the heel part of a ski boot and to bias the ski boot against the front unit . accordingly , the heel member 10 comprises a reception bowl 12 , which is suitable to receive the heel part of a ski boot . the heel unit 1 shown in fig1 is in the starting position , in which the heel member 10 is ready to receive the heel part of the ski boot . at a lower edge of the reception bowl 12 a flange 16 is disposed , onto which the heel part of the ski boot can be set down . a ski boot that is set down on the flange 16 can transfer the heel unit 1 to the snap - in position shown in fig3 by means of a further downward movement . in this position the ski boot is snapped - in in the touring ski - binding , wherein the heel member 10 biases the ski boot against the front unit . the touring ski - binding is in the downhill mode . the heel unit 1 further comprises a blocking means 20 , which is disposed on the base plate 30 . the blocking means 20 can be displaced between the non - blocking position shown in fig1 and the blocking position shown in fig2 . the displacement of the blocking means 20 occurs in the longitudinal direction l of the ski . in the non - blocking position shown in fig1 the blocking means 20 is inactive , so that the heel unit 1 can be transferred from the starting position shown in fig1 to the snap - in position shown in fig3 by means of the reception of the heel part of a ski boot . fig2 a shows the heel unit 1 of fig1 with the difference that the blocking means 20 is in the blocking position . the blocking means 20 is closer to the stopper plate 40 with respect to the non - blocking position , so that it is disposed directly below the flange 16 of the heel member 10 . the flange 16 contacts the surface 24 of the blocking means 20 . thereby , the blocking means 20 prevents that the flange 16 can move towards the base plate 30 when a force , which for example originates from the heel part of a ski boot , acts on the flange 16 . accordingly , in the blocking position the blocking means 20 prevents that the heel unit is being transferred to the snap - in position . thus , a ski boot can be set down on the flange 16 without the heel unit 1 and , thus , the touring ski - binding snapping - in . the fig1 a and 2b further show a stopper plate 40 , which is disposed in the front area of the base plate 30 . the stopper plate 40 is biased against the base plate 30 by means of a torsion spring . as can be taken from fig1 , two stopper arms 42 extend almost perpendicular to the longitudinal direction of the ski l when the stopper plate 40 is freely pushed away by means of the spring force of the base plate 30 . if a force is applied to the stopper plate 40 , so that the stopper plate 40 presses on the base plate , the coupling between the stopper plate 40 and the stopper arms 42 causes the stopper arms 42 to run almost parallel to the longitudinal direction of the ski . fig1 and 2a further show that the blocking means 20 comprises retaining members 26 . if the blocking means is in the blocking position as shown in fig2 , the retaining members 26 are partially displaced over the stopper plate 40 and hold the latter on the base plate 30 against the spring force acting on the stopper plate . accordingly , the retaining members 26 in the blocking position of the blocking means 20 shown in fig2 cause the stopper arms 42 to run almost parallel to the longitudinal direction of the ski l without a ski boot being on the stopper plate 40 . if the blocking means 20 is in the blocking position shown in fig2 a and 2b , the reception bowl 12 together with the flange 16 can be stressed , wherein the heel unit 1 remains in the starting position . thereby , the heel part of a ski boot can be lowered onto the flange 16 and can be lifted from the flange 16 so that the flange 16 functions as climbing aid when the touring ski - binding is in the climbing mode . fig2 b shows a side - view of the heel unit of fig2 a . the flange 16 of the heel member 10 contacts the blocking means 20 . thereby , the flange 16 provides a climbing aid onto which the heel part of a ski boot can be lowered and from which the heel part of a ski boot can be lifted . the climbing aid increases the walking comfort in steep terrain . fig3 shows a perspective view of the heel unit 1 of fig1 . the heel unit 1 takes - up this position when the heel part of a ski boot is biased against the base plate 30 . i . e ., the touring ski - binding is in the downhill mode , wherein a ski boot is firmly clamped in the touring ski - binding . fig3 shows the blocking means 20 in a non - blocking position . the stopper plate 40 is held in the adjacent position by means of the sole of a ski boot clamped in the touring ski - binding . if the ski boot is being released from the binding , for example by means of a fall , the stopper plate 40 can take - up a protruding position as it is not blocked by the blocking means 20 . thereby , the stopper arms 42 are being moved into the direction of the riding surface , so that the loosened ski can be slowed down . fig4 a shows the cut b - b of fig4 b through a detailed view of a blocking means 20 and a base plate 30 . the blocking means 20 can be displaced in the longitudinal direction of the ski l . the blocking means 20 has a groove 28 by means of which it can slide on a guiding 32 of the base plate 30 . alternatively , the groove can be disposed in the base plate and the guiding can be disposed on the blocking means . fig4 b shows a cross - sectional view along cutting line a - a of fig4 a . the lateral walls of the groove 28 have undercuts viewed from the base plate 30 . the base plate comprises a guiding 32 configured complementary to the profile of the groove 28 . the guiding 32 ensures that the blocking means 20 is retained on the base plate 30 . fig5 a shows the cut d - d of fig5 b through a detailed view of a blocking means 20 and a base plate 30 . fig5 b shows a cross sectional view along cutting line c - c of fig5 a . the blocking means 20 comprises a snap - in means 22 . the snap - in means 22 comprises a hole on a surface of the blocking means 20 facing the base plate 30 . the snap - in means 22 further comprises a ball 23 biased by means of a spring , the ball 23 being disposed in the hole . the spring biases the ball 23 against the base plate 30 . the base plate 30 has shapings 34 , 35 into which the ball 23 can be pressed by means of the spring . the fig5 a and 5b show the blocking means 20 in a non - snapped - in position . if the ball 23 snaps into the shaping 34 , the blocking means is in the non - blocking position . if the ball 23 snaps into the shaping 35 as shown in fig5 c , the blocking means is in the blocking position . the spring force defines the force that is necessary to release the blocking means 20 from a snapped - in position . the single components of the touring ski - binding are made of plastic and / or metal . the plastic components may comprise injection molded components . generally , light - weight materials like polypropylene , fiber reinforced plastics and / or aluminum may be used . as far as applicable , single features shown in the embodiments can be combined and / or replaced with each other without departing the field of the invention .
the present invention relates to a heel unit for a touring ski - binding , comprising , a heel member , wherein the heel member comprises a reception bowl for receiving the heel part of a ski boot and a biasing device for biasing the heel unit against a ski boot , and wherein the heel unit is switchable between a starting position for receiving or releasing the ski boot and a snap - in position for holding the ski boot , wherein the heel unit comprises a blocking means by means of which the heel unit can be blocked in the starting position , wherein the blocking means is switchable between a blocking position and a non - blocking position .