Fluid reaction surfaces (i.e. – impellers) – Specific working member mount – Blade received in well or slot
Reexamination Certificate
1999-12-03
2001-09-11
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Specific working member mount
Blade received in well or slot
C416S248000
Reexamination Certificate
active
06287079
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to rotors for compressors and turbines and, more specifically, to shear pins mounted between the disks which form the rotor.
2. Background Information
The hub of a compressor or turbine rotor is comprised of a plurality of stacked disks. Each disk provides a means for attaching a plurality of blades. The combination of blades and disks form the bulk of the rotor. The disks are situated one next to another forming a stack with an interface between each pair of disks. The disks may be attached to each other by various means such as a threaded fastener passing axially through each disk. Such fasteners hold the disks axially and assist in creating friction at each interface between the disks. The friction at the interface between each disk transmits engine torque throughout the rotor stack. Additionally, it is known to provide radial shear pins at each disk interface to assist in transmitting engine torque.
Prior art shear pins included a pin body with an expanded portion at both ends. The pins were positioned in holes bored into the rotor stack. The holes extend between the outer surface of the rotor stack and a cavity which is formed between each pair of disks. The holes are counter-bored on each end. Thus, after a pin was installed in a hole, the expanded ends of the pin fit into the counter-bores, preventing the pins from moving radially and securing the pins within the holes during operation or the rotor.
The installation of the prior art shear pins was a time consuming operation. The process entailed a total of two disk stacking and one de-stacking operations. The first stacking operation was required to position the disks to allow the holes to be bored at the interface between each disk. After the holes were bored, the ends were counter-bored, and back counter-bored. Because the pin holes extended into an inner cavity in the rotor, debris from the drilling operation fell into the cavity. The rotor had to be de-stacked to allow removal of the cutting debris and to allow placement of the pins between each rotor disk. Additionally, the bore holes needed to be cleaned and de-burred prior to insertion of the pins between the disks. As each disk was being re-stacked, a plurality of pins were set, one each, in the bore holes on the exposed interface. As the next disk in the stack was put in place, the pins became trapped in the bore holes by virtue of the expanded ends.
There is, therefore, a need for a rotor shear pin that may be installed without requiring the rotor stack to be de-stacked.
There is a further need for a rotor shear pin that may be installed in a blind pin hole.
SUMMARY OF THE INVENTION
These needs and others are satisfied by the present invention which relates to a shear pin having a pivoting cam. The shear pin includes a cylindrical body having a cavity located adjacent to the upper end of the shear pin. A cam is pivotally disposed within the cavity. The shear pin further includes a hole passing through the upper end and into the cavity. As the shear pin is being inserted in its hole the cam is positioned entirely within the cavity. Once the shear pin is in place, the cam is rotated so that a portion of the cam engages the slot in the rotor disk. The cam is held in the slot by the self-locking fastener which is inserted in the hole in the upper end of the shear pin. The cam holds the shear pin in place by cooperating with a slot that is machined into a rotor disk.
The assembly of the rotor using the shear pins of the present invention can be accomplished without de-stacking the rotor. To assembly the rotor, the disks are stacked, the holes and slots are machined, cleaned and de-burred, and the shear pins installed in the holes. Because shear pins of the present invention do not require a hole that is drilled into the inner cavity of the rotor stack there is no opportunity for debris to enter the cavity. Accordingly, the bore holes for shear pins of the present invention can be cleaned and de-burred without the rotor being de-stacked.
REFERENCES:
patent: 2753149 (1956-07-01), Kurti
patent: 4050850 (1977-09-01), Beckershoff
patent: 4400137 (1983-08-01), Miller et al.
patent: 5720596 (1998-02-01), Pepperman
patent: 5727927 (1998-03-01), Luxenburger
patent: 5749706 (1998-05-01), Maar
Chune R. C.
Gosling Martin Charles
Moles Kevin
Look Edward K.
McAleenan James M
Siemens Westinghouse Power Corporation
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