Emergency Shutdown Mechanism For Centrifugal Compressor

Abstract

A switch is mounted on a bracket fixed in the compressor casing and has contacts connected in a control circuit means for the impeller driver. Upon actuation, the contacts of the switch are cooperable with the circuit means to deenergize the driver. A lever is pivotally mounted on the bracket and in normal position restrains actuation of the switch contacts. Upon the impeller driving shaft shifting from normal operating position, a projection on the shaft moves the lever from normal position permitting actuation of the switch contacts to effect stoppage of the impeller driver.

Description

BACKGROUND OF THE INVENTION

Various forms of automatic shutdown mechanisms have been proposed to stop centrifugal gas compressors in the event the shaft carrying the impeller shifts from normal operating position. Certain of said mechanisms function satisfactorily. However, they are expensive to manufacture and assemble into the compressor structures. This invention has as an object an automatic emergency shutdown mechanism for a centrifugal gas compressor embodying a structural arrangement, particularly economical to manufacture and assemble into the compressor structure and which is rugged and durable in use.

SUMMARY OF THE INVENTION

A commercially available switch having a spring actuated plunger for automatically actuating the contacts, such as a Microswitch, is fixed on a bracket in the compressor casing. A lever pivotally mounted on the bracket is arranged with one end portion for engagement by a projection on the impeller shaft as it shifts from normal operating position. Upon such engagement, the lever is swung out of contact with the actuating plunger of the switch, deenergizing the impeller driver through a control circuit means in which the contacts of the switch are connected. Upon movement of the lever by the shaft, the switch contact plunger maintains the end of the lever spaced from the path of movement of the projection on the shaft.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a lengthwise sectional view of a centrifugal compressor embodying our invention with a portion of the casing shown in elevation and including a schematic representation of the driver.

FIG. 2 is an enlarged view of the safety shutdown mechanism as shown in FIG. 1.

FIG. 3 is a view taken on line 3--3, FIG. 2, and

FIG. 4 is a view taken on line 4--4, FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The impellers 10, 11 are mounted on an impeller drive shaft 12. The shaft 12 is journaled in bearings mounted in a casing having upper and lower sections 13, 14 detachably secured together as by bolts 15, see FIG. 1. A driver 17 as an electric motor, steam turbine or the like is operatively connected to the impeller shaft 12 to effect rotation thereof.

Control circuitry is provided for the driver 17 and includes a control element 20 connected by line 21 to the contacts of a switch 23. When the contacts of the switch 23 are actuated, the control element functions to deenergize the driver 17.

A lug 26 is formed on the inner surface of the top casing section 13. A bracket 27 is mounted on the lug 26 as by bolts 29. The bracket 27 is of right angle form in cross section having side flanges 30, 31. The flange 31 is formed with elongated apertures 35 through which the mounting bolts 29 extend. With this arrangement, the bracket 27 may be adjusted toward and from the impeller drive shaft 12.

The switch 23 is fixed to the flange 31 of the bracket, as by screws 40, and is constructed with a contact actuating plunger 43 extending through an aperture 44 in the flange 30 of the bracket 27.

A lever 45 is pivotally mounted intermediate its ends to the flange 30 by bolt 47. As the lever 45 is moved about its pivot 47, one end of the driver is moved in to and out of engagement with the plunger 43. The surface of the lever contacting the plunger 43 is formed with a depression 50. The plunger 43 is spring pressed outwardly and when the outer end of the plunger is seated in the recess 50, the lever 45 is yieldingly restrained against movement about the pivot 47. In this position, shown in full line in FIG. 2 and in dotted line in FIG. 3, the opposite end of the lever is located in proximity to the impeller shaft 12.

The impeller shaft 12 is provided with a projection 51 located to engage the free end of the lever 45 upon the impeller shaft shifting axially or radially from normal operating position. Upon the projection 51 engaging the lever 45, it is moved from the dotted line position in FIG. 3 to the full line position. Accordingly, the opposite end of the lever 45 is moved out of engagement with the plunger 43. The movement of the spring press plunger is such that a substantial end portion of the plunger extends outwardly from the flange 30 of the bracket, as shown in FIG. 4, and serves to prevent return movement of the lever 45. That is, when the lever 45 has been tripped, it is held in trip position shown in full line, FIG. 3, with the free end of the lever spaced from the path in which the projection 51 moves, the path being indicated by the line 53. This is advantageous in that it prevents the projection 51 from engaging with the free end of the lever during reverse rotation of the compressor. During the coast down period of the centrifugal compressor, there is a time when the high pressure gas will backflow through the machine and effect reverse rotation of the impellers and the shaft 12.

The shutdown mechanism described embodies a low cost structure which is conveniently mounted in the compressor casing, and which functions to deenergize the compressor driver prior to the movement of the impellers and impeller drive shaft from normal operating position, prior to the engagement of the rotating parts with the frame structure or casing of the machine.

Claims

We claim:

1. A centrifugal refrigeration compressor including a casing, an impeller drive shaft journaled in said casing, a driver operatively connected to said shaft for effecting rotation thereof, said shaft having a radially extending projection, a safety shutdown mechanism for deenergizing said driver upon said impeller shaft shifting from normal operating position, said mechanism comprising a control circuit means for said driver, a bracket fixedly mounted in said casing, a switch mounted on said bracket and having contacts connected in said control circuit and operable when actuated to cause deenergization of said driver, said contacts being mounted in an enclosure, an axially movable contact actuating plunger, means yieldingly urging said plunger outwardly out of said enclosure for actuation of said contacts, a lever pivotally mounted on said bracket for movement in to and out of engagement with said plunger, said lever normally engaging said plunger and restraining outward movement thereof, said lever having an end portion terminating in close adjacency to the path of revolution of said projection, said lever being movable about said pivotal mounting out of engagement with said plunger upon contact by said projection.

2. A centrifugal refrigeration compressor as set forth in claim 1, wherein said lever is formed with a depression for the reception of the outer end of said plunger.

3. A centrifugal refrigeration compressor as set forth in claim 1, wherein upon movement of said lever out of engagement with said plunger for outward movement thereof, said plunger is effective to maintain said lever out of normal position.

4. A centrifugal refrigeration compressor as set forth in claim 1, wherein the axis of the pivotal mount for said lever is located in spaced parallel relation to the axis of said plunger and said impeller drive shaft.