according to the current state of the art , the conventional chain brake 1 is triggered only in the event of a blow to the hand - guard frame towards the front ( direction a in fig3 and 7 ). no protection is provided against a lateral slipping of the handle ( direction d and e ) ( fig6 and 7 ). mounted on the hand - guard frame 4 on the left and right sides are flanges 5 which point towards the rear . a lower ball joint or cross joint 32 is provided as the articulation for the hand - guard frame . the lower ball joint 32 is attached to the handle 3 . a spring 27 is mounted at one end to the frame 4 and at the opposite end to the handle 3 , and pulls the hand - guard frame 4 against the interposed countersupport 33 , which is connected to the handle via an upper ball joint or cross joint 31 . the countersupport 33 is of t - shaped construction and gives the hand - guard frame the necessary stability , in conjunction with the spring 27 . the countersupport 33 seats against the rear of the hand - guard frame 4 between the stop 30 at the top , side stop 29 on the left and side stop 28 on the right . the hand - guard frame 4 is connected to the triggering lever 12 of the chain brake 1 ( of fig2 ) via the wire of the bowden cable 16 . in the case of a chain brake which is switched electrically ( not illustrated ), an electrical switch and an electrical cable connection are fitted , instead of the mechanical bowden cable , as the triggering system for the chain brake . in the event of lateral slipping of the handle ( direction d or e in fig6 ), the hand knocks against one of the two flanges 5 . the countersupport 33 prevents the hand - guard frame 4 from folding back to the handle 3 . when the hand - guard frame 4 is deflected laterally , it locks the chain brake by means of the bowden cable 16 actuating the connected triggering lever 12 in a conventional manner . a further system for increasing safety is shown in fig1 to 5 . a spring 13 , which is attached to the triggering lever 12 of the chain brake , holds the latter in the locked condition . a weight 113 , as shown attached to the lever 112 in fig8 can be substituted for the spring 13 . in order to achieve unlocking , it is necessary to pull the hand lever 8 mounted on the front handle 3 against the grip part of the handle . this function can be carried out by grasping the handle 3 and the hand lever 8 with the hand and then clenching the hand . during this process of pulling the hand lever 8 against the handle 3 , the metal pin 26 connected to the lever 8 displaces one of the mechanisms 100 or 100 &# 39 ; ( shown as examples in fig4 or 5 ) downwards . the mechanism 100 , for example , is connected to the casing 10 of the bowden cable . as the hand lever 8 is displaced , the pin 26 in the mechanism 100 forces the triggering lever 12 of the chain brake into the ordinary rearward position ( described above ) via the casing of the bowden cable being displaced longitudinally and the intermediate piece 11 operating in a conventional manner to displace the triggering lever 12 . this function unlocks the chain brake 1 and allows the saw to be started and run . after the chain brake 1 has been unlocked , the mechanism 100 travels slightly further until an inclined edge 102 slides against a stop 24 . the stop 24 causes the part 25 to be displaced leftwardly , thereby switching the mechanism 100 over . ( in fig4 the mechanism 100 &# 39 ; folds up as the lower link 23 hinges upwardly relative to the upper link 21 along the arrows and the bar 22 rotates 180 °. in fig5 the stop 24 pushes the part 25 in the direction b and the spring force of the spring 13 pushes the part 25 in the direction c up to the end of the longitudinal groove .) as a result of the switching - over of the mechanism 100 or 100 &# 39 ;, the spring 13 of fig2 pulls the triggering lever 12 of the chain brake into the central position discussed above . the chain brake is unlocked and pre - tensioned and therefore ready for operation . in order to continue to obtain readiness for operation , the hand must grasp the grip part of the handle 3 and the lever 8 and press the lever 8 and press the lever continuously against the grip part . releasing the lever 8 locks the chain brake . this safety arrangement is also linked to the hand - guard as shown in fig1 and 3 . one end of the wire 16 of the bowden cable is attached to the part 14 , which is pivotably connected to the hand - guard 4 . in the event of a blow to the hand - guard frame 4 in the direction a , the hand - guard 4 pulls the part 14 ( fig3 ) out of its abutment with the finger 15 and along the long leg 118 of the l - shaped groove 120 . at the rightward end of the groove 120 , the part 14 drops down under a force applied to it by the wire 16 , and releases the wire 16 of the bowden cable . this simultaneously causes an easing of the pressure of the bowden cable casing on the triggering lever 12 of the chain brake . the spring force of the spring 13 , which is attached to the triggering lever 12 , then locks the chain brake .