Hydraulically-operated control system for a screw compressor

Abstract

A power system includes a power unit, a screw compressor, a hydraulic pump, and a hydraulic control system. The screw compressor is connected to the power unit to be driven thereby for compressing air. The screw compressor has an air intake opening and an adjustable air intake valve mechanism for opening and closing the air intake opening. The hydraulic pump pressurizes hydraulic fluid, and the hydraulic control system is operably connected to the pump and to the air intake valve mechanism for utilizing the pressurized hydraulic fluid to adjust the air intake valve mechanism. The compressed air is delivered to an air reservoir which returns lubrication oil back to the compressor in quantities commensurate with the degree of openness of the air intake opening.

What is claimed is:  
     
         1 . A power system comprising: 
 a power unit;    a screw compressor connected to the power unit to be driven thereby for compressing air, the screw compressor having an air intake opening and an adjustable air intake valve mechanism for opening and closing the air intake opening;    a hydraulic pump for pressurizing hydraulic fluid; and    a hydraulic control system operably connected to the pump and to the air intake valve mechanism for utilizing the pressurized hydraulic fluid to adjust the air intake valve mechanism of the screw compressor.    
     
     
         2 . The power system according to  claim 1  wherein the hydraulic pump is connected to the power unit to be driven thereby simultaneously with the screw compressor.  
     
     
         3 . The power system according to  claim 1  wherein the hydraulic control system is operable to maintain the air intake valve mechanism in a selected one of numerous open states in which the air intake opening is open by various degrees.  
     
     
         4 . The power system according to  claim 3  further including a source of lubrication oil communicating with the screw compressor, and an oil injection valve for controlling the amount of lubrication oil admitted into the screw compressor; the hydraulic control mechanism connected to the oil injection valve for opening the oil injection valve by selected amounts proportional to the degree that the air intake opening has been opened by the air intake valve mechanism.  
     
     
         5 . The power system according to  claim 1  wherein the air intake valve mechanism includes a closure element movably mounted at the air intake opening, and a valve actuator connected to the closure element; the hydraulic control system connected to the valve actuator for utilizing the pressurized hydraulic fluid to adjust the air intake valve.  
     
     
         6 . The power system according to  claim 1 , further comprising an air reservoir connected to an air outlet of the screw compressor for receiving and storing compressed air received from the screw compressor; the air reservoir including an oil accumulation section for accumulating lubrication oil entrained in compressed air received from the screw compressor; the oil accumulation section connected to the screw compressor for delivering lubrication oil to the compressor; the air reservoir including an air outlet for discharging compressed air, and a minimum pressure valve for maintaining a selected minimum air pressure in the air reservoir; the minimum pressure valve including a valve element arranged to be pressurized by hydraulic fluid from the hydraulic control mechanism; the valve element arranged to close the air outlet of the reservoir in response to the air intake valve mechanism being positioned in a state closing the air intake opening, and to open the air outlet in response to the air intake valve mechanism being positioned in a state opening the air intake opening.  
     
     
         7 . The power system according to  claim 1  wherein the hydraulic control system is arranged to receive a first supply of hydraulic fluid at a first pressure, and a second supply of hydraulic fluid at a second pressure; the first pressure being greater than the second pressure; the hydraulic control system arranged to control the intake valve mechanism with the first supply of hydraulic fluid for opening the air intake opening, and to control the intake valve mechanism with the second supply of hydraulic fluid for closing the air intake opening.  
     
     
         8 . The power system according to  claim 4  wherein the source of lubrication oil comprises an air reservoir to which oil-containing air is supplied from the compressor; the reservoir including an oil accumulation section to which the oil gravitates; the oil accumulation section connected to the compressor for recycling oil back to the compressor; the air reservoir including an air outlet for discharging compressed air, and a minimum pressure valve for maintaining a selected minimum air pressure in the reservoir; the minimum pressure valve mechanism including a valve element arranged to be pressurized by hydraulic fluid from the hydraulic control mechanism; the valve element arranged to close the air outlet of the reservoir in response to the air intake valve mechanism being positioned in a state closing the air intake opening, and to open the air outlet in response to the air intake valve mechanism being positioned in a state opening air intake opening.  
     
     
         9 . The power system according to  claim 8  wherein the hydraulic pump comprises a first hydraulic pump, and further comprising a second hydraulic pump; the hydraulic control system arranged to receive a first supply of hydraulic fluid at a first pressure from the first hydraulic pump, and a second supply of hydraulic fluid at a second pressure from the second hydraulic pump; the first pressure being greater than the second pressure; the hydraulic control system arranged to control the intake valve mechanism with the first supply of hydraulic fluid for opening the air intake opening, and to control the intake valve mechanism with the second supply of hydraulic fluid for closing the air intake opening.  
     
     
         10 . The power system according to  claim 9  wherein the hydraulic pumps are connected to the power unit to be driven thereby simultaneously with the screw compressor.  
     
     
         11 . The power system according to  claim 3  further comprising an air reservoir connected to an air outlet of the screw compressor for receiving and storing compressed air received from the screw compressor; the air reservoir including an oil accumulation section for accumulating lubrication oil entrained in compressed air received from the screw compressor; the oil accumulation section connected to the screw compressor for delivering lubrication oil to the compressor; the air reservoir including an air outlet for discharging compressed air, and a minimum pressure valve for maintaining a selected minimum air pressure in the air reservoir; the minimum pressure valve mechanism including a valve element arranged to be pressurized by hydraulic fluid from the hydraulic control mechanism; the valve element arranged to close the air outlet of the reservoir in response to the air intake valve mechanism being positioned in a state closing the air intake opening, and to open the air outlet in response to the air intake valve mechanism being positioned in a state opening the air intake opening.  
     
     
         12 . The power system according to  claim 11  wherein the hydraulic pump comprises a first hydraulic pump, and further comprising a second hydraulic pump; the hydraulic control system arranged to receive a first supply of hydraulic fluid at a first pressure from the first pump, and a second supply of hydraulic fluid at a second pressure from the second hydraulic pump; the first pressure being greater than the second pressure; the hydraulic control system arranged to control the intake valve mechanism with the first supply of hydraulic fluid for opening the air intake opening, and to control the intake valve mechanism with the second supply of hydraulic fluid for closing the air intake opening.  
     
     
         13 . The power system according to  claim 12  wherein the hydraulic pumps are connected to the power unit to be driven thereby simultaneously with the screw compressor.  
     
     
         14 . The power system according to  claim 4  wherein the hydraulic pump comprises a first hydraulic pump, and further comprising a second hydraulic pump; the hydraulic control system arranged to receive a first supply of hydraulic fluid at a first pressure from the first pump, and a second supply of hydraulic fluid at a second pressure from the second hydraulic pump; the first pressure being greater than the second pressure; the hydraulic control system arranged to control the intake valve mechanism with the first supply of hydraulic fluid for opening the air intake opening, and to control the intake valve mechanism with the second supply of hydraulic fluid for closing the air intake opening.  
     
     
         15 . The power system according to  claim 3  wherein the hydraulic pump comprises a first hydraulic pump, and further comprising a second hydraulic pump; the hydraulic control system arranged to receive a first supply of hydraulic fluid at a first pressure from the first pump, and a second supply of hydraulic fluid at a second pressure from the second hydraulic pump; the first pressure being greater than the second pressure; the hydraulic control system arranged to control the intake valve mechanism with the first supply of hydraulic fluid for opening the air intake opening, and to control the intake valve mechanism with the second supply of hydraulic fluid for closing the air intake opening.  
     
     
         16 . A mobile drilling rig comprising: 
 a mobile platform;    a drill string;    a mast on the platform for supporting the drill string;    a hydraulic motor for rotating the drill string;    a hydraulic pump for supplying pressurized hydraulic fluid to power the hydraulic motor;    a screw compressor for supplying compressed air to the drill string, the screw compressor having an air intake opening and an adjustable air intake valve mechanism for opening and closing the air intake opening; and    a hydraulic control system operably connected to the pump and to the air intake valve mechanism for utilizing pressurized hydraulic fluid to adjust the air intake valve mechanism.    
     
     
         17 . The mobile drilling rig according to  claim 16  wherein the hydraulic pump is connected to the power unit to be driven thereby simultaneously with the screw compressor.  
     
     
         18 . The mobile drilling rig according to  claim 16  wherein the hydraulic control system is operable to maintain the air intake valve mechanism in a selected one of numerous open states in which the air intake opening is open by various degrees.  
     
     
         19 . The mobile drilling rig according to  claim 18  further including a source of lubrication oil communicating with the screw compressor, and an oil injection valve for controlling the amount of lubrication oil admitted into the screw compressor; the hydraulic control mechanism connected to the oil injection valve for opening the oil injection valve by selected amounts proportional to the degree that the air intake opening has been opened by the air intake valve mechanism.  
     
     
         20 . The mobile drilling rig according to  claim 16  wherein the air intake valve mechanism includes a closure element movably mounted at the air intake opening, and a valve actuator connected to the closure element; the hydraulic control system connected to the valve actuator for utilizing the pressurized hydraulic fluid to adjust the air intake valve.  
     
     
         21 . The mobile drilling rig according to  claim 16 , further comprising an air reservoir connected to an air outlet of the screw compressor for receiving and storing compressed air received from the screw compressor; the air reservoir including an oil accumulation section for accumulating lubrication oil entrained in compressed air received from the screw compressor; the oil accumulation section connected to the screw compressor for delivering lubrication oil to the compressor; the air reservoir including an air outlet for discharging compressed air, and a minimum pressure valve for maintaining a selected minimum air pressure in the air reservoir; the minimum pressure valve including a valve element arranged to be pressurized by hydraulic fluid from the hydraulic control mechanism; the valve element arranged to close the air outlet of the reservoir in response to the air intake valve mechanism being positioned in a state closing the air intake opening, and to open the air outlet in response to the air intake valve mechanism being positioned in a state opening the air intake opening.  
     
     
         22 . The mobile drilling rig according to  claim 16  wherein the hydraulic pump comprises a first hydraulic pump, and further comprising a second hydraulic pump; the hydraulic control system arranged to receive a first supply of hydraulic fluid at a first pressure from the first pump, and a second supply of hydraulic fluid at a second pressure from the second hydraulic pump; the first pressure being greater than the second pressure; the hydraulic control system arranged to control the intake valve mechanism with the first supply of hydraulic fluid for opening the air intake opening, and to control the intake valve mechanism with the second supply of hydraulic fluid for closing the air intake opening.  
     
     
         23 . In a method of initiating the drilling of a hole in the ground wherein a drill bit is rotated by a hydraulically driven mechanism to cut through the ground, a flow of compressed air from a screw compressor to the drill bit is established for removing cuttings, and a dust hood is positioned against a ground surface in surrounding relationship to the drill bit to capture dust; the improvement wherein a hydraulic control mechanism is actuated to control an air intake valve mechanism of the screw compressor to regulate the compressed air flow and pressure such that the flow of compressed air is supplied at a first volume for minimizing cavitation of the ground surface during the cutting of an initial portion of the hole at the ground surface, and thereafter is supplied at a greater volume.