EP0573144A1 - Compressor unloader - Google Patents

Compressor unloader Download PDF

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Publication number
EP0573144A1
EP0573144A1 EP93303142A EP93303142A EP0573144A1 EP 0573144 A1 EP0573144 A1 EP 0573144A1 EP 93303142 A EP93303142 A EP 93303142A EP 93303142 A EP93303142 A EP 93303142A EP 0573144 A1 EP0573144 A1 EP 0573144A1
Authority
EP
European Patent Office
Prior art keywords
compressor
vane
valve
unloader
motor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP93303142A
Other languages
German (de)
English (en)
French (fr)
Inventor
Mark W. Wood
Michael J. Kosmyna
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
DeVilbiss Air Power Co
Original Assignee
DeVilbiss Air Power Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by DeVilbiss Air Power Co filed Critical DeVilbiss Air Power Co
Publication of EP0573144A1 publication Critical patent/EP0573144A1/en
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/22—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by means of valves
    • F04B49/24—Bypassing
    • F04B49/243—Bypassing by keeping open the inlet valve
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B35/00—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for
    • F04B35/04—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for the means being electric
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
    • F04B39/06—Cooling; Heating; Prevention of freezing
    • F04B39/066—Cooling by ventilation

Definitions

  • the invention relates to air compressors and more particularly to an unloader for an air compressor which is responsive to a compressor motor reaching a predetermined minimum speed before leading the compressor.
  • Air compressors are commonly used, for example, for operating pneumatic tools, for inflating tires, etc.
  • a common type of air compressor has a motor connected to reciprocate a piston in a cylinder.
  • the piston reciprocates alternately between a suction stroke and a compression stroke.
  • One or more intake valves direct a flow of ambient air into the cylinder during the suction stroke and one or more outlet valves direct pressurized air from the cylinder to an air tank or through a hose to a tool, for example, during the compression stroke.
  • the electric motor is strained when the motor is started while the compressor is subject to a load.
  • a switch turns the motor off when the tank pressure reaches a preset maximum pressure and turns the motor on when the tank pressure drops to a preset minimum pressure.
  • the motor will be subjected to a high starting torque if it is started against the load of the preset minimum tank pressure on the compressor.
  • Starting problems are especially of concern under low voltage conditions, as might occur, for example, at a construction site where long extension cords are often used to connect the compressor motor to the power source.
  • engine starting is more difficult while the compressor is subject to a load.
  • valves are often used to unload the compressor motor when the motor is stopped.
  • Various designs are known for unloader valves.
  • One type of unloader valve operates m response to the motor speed through a mechanism activated by centrifugal force. Electric timers also have been used to unload a compressor for a predetermined time while the motor comes up to speed.
  • the motor output is coupled through a magnet to a cam. The cam opens a valve to unload the compressor when the motor is stopped. When the motor speed is sufficiently high, the magnet rotates the cam to close an unloader valve.
  • a compressor unloader is designed to respond to the flow of cooling air from a fan driven by the compressor motor.
  • the suction or inlet valve is held open during both the intake and the compression strokes of the piston to unload the compressor while the motor is stopped or operating at a low speed during startup and idle.
  • the motor speed is sufficiently high, the flow of cooling air from the fan moves a vane and a connected mechanism which allows the suction valve to close. Once the suction valve can close during the compression stroke, the compressor will have a normal compressed air output.
  • a vent passage is connected either to the compression chamber or to the outlet side of a valve head on the compressor.
  • the passage is open to vent high pressure.
  • cooling air from a fan driven by the motor moves a vane to close the vent passage.
  • the vent passage is closed, the compressor and connected drive motor become fully loaded.
  • the air compressor 10 generally includes an electric motor 12 or an internal combustion engine (not shown) having an output shaft 13.
  • the term "motor” as used herein shall mean either an electric motor or an internal combustion engine.
  • the output shaft 13 is connected to drive an eccentric plate 14 having an eccentric shaft 15 which is offset from the axis of the output shaft 13.
  • the eccentric shaft 15 is connected through a bearing 16 to a free end 17 of a connecting rod 18.
  • the connecting rod 18 and a piston head 19 connected to an opposite end 20 of the connecting rod 18 form a wobble piston 21.
  • the piston head 19 reciprocates in a cylinder 22.
  • the piston head 19 wobbles or rocks back and forth because it is rigidly connected to the connecting rod end 20.
  • a piston seal 23 establishes a sliding seal between the piston head 19 and the cylinder 22 as the piston reciprocates and rocks.
  • An end 24 of the cylinder 22 is closed by a valve plate 25.
  • the valve plate 25 has one or more inlet or suction ports 26 and one or more outlet ports 27.
  • a resilient reed 28 covers the inlet port 26 to form a suction valve 29 and a resilient reed 30 covers the outlet port 27 to form an outlet valve 31.
  • a fan 35 is mounted on the motor shaft 13. During operation of the compressor 10, the fan 35 draws cooling air over the motor 12 and blows the cooling air around the exposed exterior portions of the cylinder 22 and the piston 21.
  • a suitable housing (not shown) for the compressor 10 and baffles within the housing (not shown) may be provided to direct the cooling air from the fan 35 to the locations needing cooling.
  • an improved unloader 11 is provided for holding open the suction valve 29 while the motor 12 is stopped, just starting or idling.
  • a rocker arm 36 is mounted to rock within the inlet chamber 32.
  • a push rod 37 extends from one end 38 of the rocker arm 36 through the inlet port 26 to the valve reed 28.
  • a spring 39 tends to rock the arm 36 until the push rod 37 contacts and holds the valve reeds 28 away from the inlet port 26, as shown. Consequently, the suction valve 29 is held open and air is free to flow through the inlet port 26 during both the intake and the compression strokes of the piston 21. So long as the suction valve 29 is held open, the load and the starting torque requirements for the motor 12 are at a minimum.
  • a second end 40 of the rocker arm 36 is connected through a rod 41 to a vane 42.
  • the vane 42 is mounted to pivot about an axis 43.
  • the vane 42 is mounted where it is subjected to air flow from the fan 35.
  • the motor 12 When the motor 12 is started and the fan speed increases to a sufficient level, the air discharged by the fan acts on the vane 42.
  • the air flow causes the vane 42 to pivot about the axis 43 in the direction of the arrow to pull on the rod 41.
  • the suction valve 29 is held open by the rod 37 both when the motor 12 is stopped and during startup for the motor 12.
  • air flow from the fan 35 causes the rod 37 to be drawn away from the valve reed 28 and the suction valve 29 becomes operational to load the compressor motor 12.
  • FIGs. 2-4 are fragmentary views showing a modified embodiment of a compressor unloader 48 according to the invention.
  • a valve plate 49 is mounted to close a cylinder 50 in which a piston 51 reciprocates.
  • the valve plate 49 defines a plurality of inlet or suction ports 52 and a plurality of outlet ports 53.
  • the inlet ports 52 are closed by resilient valve reeds 54 and the outlet ports 53 are closed by resilient valve reeds 55.
  • a resilient flat spring 56 is secured to the valve plate 49.
  • the spring 56 has at least one finger 57 (two shown) which extends through at least one of the inlet ports 52 and contacts the adjacent reed 54.
  • the spring 56 is stronger than the resilient reed 54 and, consequently, the fingers 57 can deflect the adjacent reeds 54 away from the valve plate 49, as shown in Fig. 4. So long as the fingers 57 hold one or more of the inlet valve reeds 54 away from the valve plate 49, the compressor will be unloaded and minimum torque is required to start the compressor motor.
  • a rigid wire 58 is secured by suitable mounts 59 to rotate about an axis 60.
  • the wire 58 has an S-shaped end 61 which extends between a tab 62 on the spring 56 and the valve plate 49.
  • the wire 58 is generally U-shaped and has a side 63 which is spaced from an edge 64 of the valve plate 49 and is generally parallel to the axis 60.
  • a vane 65 is secured to the wire side 63. If the cylinder 50 is generally vertically oriented, the vane 65 will fall through gravity to the position shown in dashed lines in Fig. 3. A finger 66 extending from the vane 65 will contact the cylinder 50 to limit travel of the vane 65.
  • Figs. 5-8 are fragmentary views showing a further modified embodiment of a compressor unloader 70 according to the invention.
  • a piston 71 is reciprocated in a cylinder 72.
  • the cylinder 72 is closed by a valve plate 73 having a plurality of inlet ports 74 and a plurality of outlet ports 75.
  • Resilient valve reeds 76 normally close the inlet ports 74 and resilient valve reeds 77 normally close the outlet ports 75.
  • the unloader 70 includes a rigid wire 78 attached to rotate in mounts 79 about an axis 80.
  • the wire 78 has an end 81 which is bent to extend into one of the inlet ports 74.
  • the wire 78 has a second end 82 which is spaced from an edge 83 of the valve plate 73 and extends substantially parallel to the axis 80.
  • a vane 84 is attached to the wire end 82.
  • the vane 84 is located to be moved in response to a predetermined flow of air from a fan driven by the compressor motor (such as the fan 35 driven by the motor 12 in Fig. 1). When the motor is off, gravity moves the vane 84 to the position shown in dashed lines in Fig. 6.
  • the vane 84 While the vane 84 is in this position, the bent wire end 81 pushes an adjacent inlet valve reed 76 open, as shown in Fig. 8, to unload the compressor motor. While any of the inlet valve reeds 76 is held open, air will flow through the inlet port 74 on both suction and compression strokes of the piston 71. Consequently, the motor is subjected to only a minimum torque during startup. When the motor reaches a sufficient speed during startup, the air flow moves the vane 84 to the position shown in solid in Fig. 6 and the wire end 81 is moved away from the adjacent inlet valve reed 76, as shown in Fig. 7. At this speed and at higher motor speeds, the inlet valve reeds 76 are all allowed to close during the compression stroke of the piston 71 and the compressor will operate.
  • the vanes 65 and 84 move through the action of gravity to open one or more of the inlet valves when the motor is stopped.
  • gravity has been found sufficient to move the vane and unload the compressor with the cylinders arranged from a vertical orientation to tilted up to about 45°. If the cylinder is tipped too far from the vertical, a spring may be needed to move the vane to assure positive action of the unloader.
  • Fig. 9 is a fragmentary cross sectional view of a modified embodiment of an air compressor 90 according to the invention.
  • the compressor 90 includes an electric motor 91 having an output shaft 92 which rotates both a cooling air fan 93 and an eccentric plate 94.
  • An end 95 of a wobble piston 96 is connected to an eccentric pin 97 on the eccentric plate 94.
  • the piston 96 is caused to reciprocate in a cylinder 98.
  • a valve plate 99 and a head 100 are secured to a top 101 of the cylinder 98.
  • An inlet chamber 102 in the head 100 is connected through a port 103 in the valve plate 99 and a intake check valve 104 to a compression chamber 105.
  • the compression chamber 105 is connected through an outlet port 106 in the valve plate 99 and an outlet check valve 107 to an outlet chamber 108.
  • a tube or hose 109 receives compressed air from the chamber 108.
  • the compressor 90 is unloaded during starting either by venting the outlet chamber 108 (as shown) or by venting the compression chamber 105 (not shown) through a normally open small vent hole 110.
  • a vane 111 is mounted to pivot on a bracket 112 which is illustrated as being secured to the head 100.
  • the vane 111 is influenced by air flow from the fan 93. Either through gravity or through the action of a spring (not shown), the vane will be in the position illustrated by the solid lines in Fig. 9 when the motor 91 is stopped or operating at a low startup or idle speed. When the motor speed reaches a predetermined level, the flow of cooling air from the fan 93 will be sufficient to pivot the vane 111 to the position 113 shown in dashed lines.
  • a stopper 114 is secured to the vane at a location to plug the vent hole 110 when the vane 111 pivots to the position 113. Consequently, when the compressor motor reaches a predetermined minimum speed, the vent hole 110 will be plugged and the compressor 90 will supply compressed air to the tube 109. At lower motor speeds, the compressed air will be vented to atmosphere through the open hole 110.
  • the flow of cooling air required to close the vent hole 110 is determined by various factors. If, for example, the vent hole is 0.05 inch (1.27 mm) in diameter and the maximum output pressure from the compressor is 100 psi (0.0703 Kg/mm2), a maximum force of 0.2 pounds (0.00089 Kg) is required to stop the vent hole 110. This force is significantly reduced by the leverage exerted by the vane 111 due to the difference in distances between the pivotal connection of the vane 111 to the bracket 112 and the stopper 114 and between the pivotal connection of the vane 111 to the bracket 112 and an end 115 of the vane 111 on which the cooling air flow acts. The required air flow for stopping the vent hole 110 may be further reduced by increasing the area of the vane 111 impinged by the air flow. Thus, the motor speed at which the vent hole 110 will be closed will be set by adjusting various design factors for the vane 111.
  • the compressors shown and described above are of a type sometimes called oilless compressors because the wobble piston does not require an oil sump for continuous lubrication. It will be appreciated that the compressor unloader of the invention will be equally applicable to a compressor having a purely reciprocating piston of the type which is hinged to a connecting rod by a wrist pin. The invention is also applicable to other known compressor designs, such as rotating piston compressors. Various modifications and changes may be made to the above described preferred embodiments of the invention without departing from the spirit and the scope of the following claims.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Compressor (AREA)
EP93303142A 1992-06-01 1993-04-22 Compressor unloader Withdrawn EP0573144A1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US891719 1986-07-29
US89171992A 1992-06-01 1992-06-01
US145293A 1993-01-07 1993-01-07
US1452 1997-12-31

Publications (1)

Publication Number Publication Date
EP0573144A1 true EP0573144A1 (en) 1993-12-08

Family

ID=26669045

Family Applications (1)

Application Number Title Priority Date Filing Date
EP93303142A Withdrawn EP0573144A1 (en) 1992-06-01 1993-04-22 Compressor unloader

Country Status (4)

Country Link
EP (1) EP0573144A1 (forum.php)
AU (1) AU3837493A (forum.php)
CA (1) CA2095772A1 (forum.php)
TW (1) TW223140B (forum.php)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113236528A (zh) * 2021-06-02 2021-08-10 广东民鑫机械设备科技有限公司 一种工业用空压机

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3718844B1 (en) * 2019-04-05 2023-02-08 KNORR-BREMSE Systeme für Nutzfahrzeuge GmbH Piston assembly for an unloader valve of an air compressor

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4519752A (en) * 1982-09-03 1985-05-28 Applied Power Inc. Control system for a variable displacement pump

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4519752A (en) * 1982-09-03 1985-05-28 Applied Power Inc. Control system for a variable displacement pump

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 7, no. 44 (M-195)(1189) 22 February 1983 & JP-A-57 193 786 ( SANWA ) 29 November 1982 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113236528A (zh) * 2021-06-02 2021-08-10 广东民鑫机械设备科技有限公司 一种工业用空压机

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TW223140B (forum.php) 1994-05-01
CA2095772A1 (en) 1993-12-02
AU3837493A (en) 1993-12-02

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