High load descender with adaptive release linkage
A high load descender for rope access and rescue has a ratcheting sheave mounted to a pivoting arm, which translate with rope tension against a fixed shoe. The ratcheting sheave has a groove that grips rope during descent while allowing free rotation for ascent and progress capture. An adaptive release linkage enhances ease of operation and control while maintaining convenient handle position in a variety of conditions.
1. A descender for controlling descent of a load along a rope; the descender comprising:
a chassis with a first end of a pivot arm pivotably attached thereto, wherein a control ring and control ring aperture are integrally formed into the chassis;
an opening plate movably attached to the chassis, the opening plate movable between an open and a closed position;
a generally circular sheave, the sheave having a circumference, the circumference including a groove;
the generally circular sheave rotatably attached to a second end of the pivot arm;
a guide and a shoe, each of the guide and the shoe attached to the chassis and positioned on substantially opposite sides of the sheave, the sheave positioned a variable distance between the guide and the shoe, such that when the opening plate is in the open position, the rope is installed by inserting the rope past the guide, around at least a substantial portion of the circumference of the sheave, and past the shoe;
when the opening plate is in the closed position, a secure path for the rope is formed, the secure path allowing the rope to slide against the guide and the shoe, and to be selectively forced into the groove;
the second end of the pivot arm biased away from the shoe;
a handle including a pawl having teeth and a tail;
a cam rotatably mounted to the chassis;
the teeth selectively engaged with the cam;
the cam engaged with the pivot arm;
the handle configured to move to control the variable distance between the sheave and the shoe; and
the handle configured to rotate to a stowed position such that the tail contacts the control ring, which causes the pawl to rotate and disengage from the cam.
2. The descender of claim 1 , wherein the sheave can freely rotate in only one direction.
3. The descender of claim 1 , further comprising:
a cam spring forcing the cam toward a pivot arm roller.
4. The descender of claim 1 , wherein the guide is a roller that can freely rotate.
5. The descender of claim 1 , wherein the shoe is a roller that can freely rotate.
6. The descender of claim 1 , wherein a spring biases the pivot arm away from the shoe.
7. The descender of claim 1 , wherein the sheave does not rotate during descent, but can freely rotate during ascent.
8. The descender of claim 1 , further including an attachment hole passing through the chassis and opening plate such that when the opening plate is in the closed position, an operator can lock the descender in the closed position.