referring to fig1 the indicator 1 is mounted on a grass mower 2 comprising , a rotating mower head 3 , a container 4 for receiving and storing the mower clippings , and a duct 5 through which the clippings are transported to the container 4 . in fig2 and 4 the indicator 1 is shown in the first position under conditions of no air flow . the indicator 1 is a single molded piece which is composed of a number of features ; a flap member 6 , a flag member 7 , an triangular sealing flange 8 , a pin 9 . referring to fig2 and 4 the flap member 6 is inside the duct 5 and is biased in the first position such that when in the first position it is generally perpendicular to an interior wall of the duct 5 . the flap member 6 has a front surface 10 that when viewed from the front is generally circular and is shaped so that it is curved inward towards a centre line b -- b from each side 11 , 12 and inwards and upwards from a bottom end 13 forming thereby a generally concave surface . a back surface 14 of the flap member follows the shape of the front surface 10 terminating at the top at a point 15 where it intersects with the flag member 7 forming thereby a generally convex surface when viewed from behind . the flap member in cross section is part circular such that it lies flat against the interior surface of the duct 5 when in the second position ( see fig3 and 5 ). referring to fig2 the flag member 7 of the indicator 1 is located on the outside of the duct 5 and is generally rectangular in cross section and on each side . when in the first position the flag member 7 is generally parallel to the outer surface of the duct 5 such that it has ; a bottom surface 16 which begins at the point 15 at the top of the back of the flap member 6 and extends perpendicular to the flap member 6 parallel to the outer surface of the duct 5 along the longitudinal axis of the duct , an end surface 17 pointing upwards perpendicular to the bottom surface 16 , and a top surface 18 which runs from the end surface 17 to an intersection point 19 where it joins with the triangular sealing flange 8 . from the intersection point 19 a triangular sealing flange 8 projects upwards on a angle to an apex 20 forming thereby an inclined surface 21 , and then downwards in line with the back surface 14 of the flap member 6 to a point 22 in line with the top surface of the flag member 7 forming a sealing surface 23 . a radius 27 extends from point 22 on the sealing surface 23 of the triangular sealing flange to the front surface 10 of the flap member 6 joining the front surface to the triangular sealing flange 8 . the sealing flange has a cross section with the same width as that of the flag member ( see fig6 ). a pin 9 or similar member projects through and is perpendicular to the triangular sealing flange 8 such that it forms a pivot around which the whole of the indicator 1 may rotate . referring to fig4 and 6 on the duct 5 at the location where the indicator 1 is mounted is a rectangular slot shaped opening 24 and on each side of the slot shaped opening is a support member 25 , 26 . the indicator 1 is mounted so that it passes through the rectangular slot shaped opening 24 such that the flag member 7 is on the outside of the duct 5 and the flap member 6 is on the inside of the duct 5 . a support member 25 , 26 on each side of the slot shaped opening 24 accepts the pin 9 to which the indicator 1 is fixed such that it allows rotation of the indicator 1 about the longitudinal axis of the pin . the indicator 1 will be in position 1 when there is no air flow through the duct . this occurs due to the fact that the weight of the flap member 6 exceeds the weight of the flag member 7 causing the flap member to fall into a vertical position . when in use air flows through the duct 5 caused by pressure generated by the mower head 3 carrying grass clippings through the duct 5 to the container 4 . referring to fig3 the pressure of the air flowing against the flap member 6 in the duct 5 causes the indicator 1 to rotate about the longitudinal axis of the pin 9 so that the flap member 6 rotates into a generally parallel position with respect to the inner surface of the duct ( position 2 ), the flag member 7 is raised into a generally perpendicular position with respect to the outer surface of the duct , and sealing surface 13 of the triangular sealing flange 8 rotates into contact with the outer surface of the duct thereby closing off any opening that was left unsealed when the flap member rotated into the second position . the flag member when in a position 2 indicates that there is normal air flow , while the flag member in when in position 1 indicates that there is no air flow and that a complete blockage may have occurred . when in a position intermediate of position 1 and 2 the flag member indicates that normal air flow is being impeded and that a blockage may be occurring thereby allowing the driver to take appropriate actions . since various modifications can be made in my invention as herein above described , and many apparently widely different embodiments of same made within the spirit and scope of the claims without departing from such spirit and scope , it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense .
this invention provides an indicator means for a grass mower to detect blockages of a duct used to transport clippings from a mower head to a storage container . the indicator is mounted on the duct and is responsive to air flow rate in the duct thereby indicating any reduction of air flow rate from a predetermined normal flow rate and therefore when a blockage is occurring so that the operator can take actions to prevent it .