Pressure fluid motor having a power regulator

Abstract: A pressure fluid motor (1) having a regulator (30, 37) for regulation of output power of the motor, the regulator including a bypass of a selected portion of the supplied pressure fluid to the motor exhaust as a means of effectively reducing the available pressure drop across the motor and thereby its power output.

Description: This invention relates to a pneumatic pressure fluid motor for a power tool having a power regulator and more particularly to an apparatus for the control of pressure fluid supplied to a pneumatically-operated, hand-held power tool for power output regulation. In the past, power regulation for pressure fluid driven power tools have been accomplished by restricting the flow of pressure fluid supplied to the power tool or restricting the exhaust to back pressure the tool for reduced power. The restricting devices in general reduce power output of the tool even in the minimum restriction settings because the supply pressure fluid must still pass through the device on "full" power settings. US-A-4 740 144 discloses a pneumatic pressure fluid motor assembly in accordance with the pre-characterising portion of claim 1. US-A-3 951 217 also discloses a pneumatically powered impact wrench having a pressure regulator between a reverse valve and a reversible air driven motor. According to one aspect of the present invention, there is provided a pneumatic pressure fluid motor assembly comprising a reversible, pneumatic motor and a pressure fluid regulator for the motor, there being an inlet for supplying pressure fluid to said motor and an exhaust for exhausting expanded pressure fluid from said motor to atmosphere, said pressure regulator having a bypass passageway interconnecting said inlet and said exhaust to reduce the output power of the motor, characterised in that said pressure fluid regulator is so constructed that, in a forward operational condition of said motor, a selected portion of the supplied pressure fluid is bypassed through said bypass passageway directly to the exhaust, thereby achieving both a bleeding of the air pressure supplied to the motor and back pressurising the exhaust, and in that a secondary exhaust from said motor is provided, said pressure fluid regulator being constructed to bypass said secondary exhaust in a reverse operational condition of said motor. According to another aspect of the present invention, there is provided a power regulator for a pneumatic pressure fluid motor assembly as just defined, the regulator being characterised in that it is so constructed that, in a forward operational condition of said motor, a selected portion of the supplied pressure fluid is bypassed through said bypass passageway directly to the exhaust, thereby achieving both a bleeding of the air pressure supplied to the motor and back pressurising the exhaust, and in that a secondary exhaust from said motor is provided, said pressure fluid regulator being constructed to bypass said secondary exhaust in a reverse operational condition of said motor. For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:- Figure 1 is a sectional side view of a power regulated power tool; Figure 2 is a rear view showing the power regulators' convenient location on the back end of the tool; Figure 3 is a side view of the regulator; Figure 4 is a rear view of the regulator; Figure 5 is a cross-section of the regulator taken along line B-B of Figure 4; Figure 6 is a cross-section of the regulator taken along line A-A of Figure 5; Figure 7 is an end view of the regulator showing a rotary step indexing of a power regulator index finger in co-operation with indexing indentations in a housing; Figure 8 is a partial component/partial schematic depiction of a power regulator cycle in a forward or tightening mode; and Figure 9 is a partial component/partial schematic depiction of the power regulator cycle in the reverse or untightened mode. Referring to Figure 1, part of a power tool 1 is shown in partial section. The power tool 1 is provided with a handle 2 having a pneumatic fluid or air inlet 3 for providing motive fluid to a pneumatic motor 13. Air is supplied to the motor through an air inlet passageway 4. A tilt valve 5 is operated by means of a trigger 6 to admit pressure fluid to a chamber 9. Disposed within chamber 9 is a rotary spool 10 performing as a reversing valve for selectively distributing pressure fluid to a forward supply port 20 or optionally to a reverse port 21 (hidden behind the forward port 20 at a position approximately opposite the forward port in a valve plate 12). The reversing valve spool 10 is provided with a planar segmented end which slidably co-operates with the planar surface of the plate 12. The spool 10 contains forward and reverse passages 22 and 23 (hidden), and a notched area 29 which handles secondary exhaust, as will be described later. Air entering the forward or reverse ports 20 or 21 selectively proceeds to drive the motor 13 in forward or reverse direction as the air is expanded against motor vanes 14 in a motor cylinder 15. The motor rotates on bearings 16 and 16' to drive an output shaft 17 which in turn drives a rotating shaft 18 of the working output device 19. Referring now to Figures 8 and 9 for operation, air passing the spool 10 from the air passage 4 in the chamber 9 is directed to one of two face termination passageways 22 or 23 depending on the selected orientation of a partition 24. The ports 22, 23 selectively register with either the forward port 20 or reverse port 21 in the valve plate 12. The notched area 29 registers with corresponding ports 20 or 21 to bleed secondary exhaust which prevents recompression. The notched area 29 allows the secondary exhaust to enter the main exhaust cavity 7. Since the passageways 22 and 23 are located approximately 90 degrees apart and the forward and reversing ports 20, 21 are located approximately 180 degrees apart, it will be appreciated that rotating the reversing valve spool 10 approximately 90 degrees by depressing either a forward pushbutton 40 or a reverse pushbutton 25 will bring one or the other of the passageways 22 or 23 in communication with one of the ports 20 or 21 leading to either the forward or reverse chambers of the motor. Thus, the rotation of the reversing valve spool 10 will accomplish direction of motive fluid to drive the motor either forwards or in reverse. As previously described, earlier attempts to regulate the supply of pressure fluid to the motor have throttled the pressure fluid being supplied to the motor or restricted the exhaust to back pressure the motor, thereby reducing power output. With the present apparatus pressure fluid regulation is achieved which does not involve restricting the supplied pressure fluid or restricting the exhaust, thereby permitting, in at least one selected operating position, full power application without the need for passing the pressure fluid through a restricting device. This is accomplished in the preferred embodiment by bypassing a selected portion of the supplied pressure fluid directly to the exhaust thereby effectively back pressuring the exhaust while bleeding off a portion of the available pressure fluid. The dual action of the present construction effectively reduces power output and the apparatus for accomplishing it may be best understood by referring back to Figure 1, in which a bypass regulator 30 is shown installed at the back end of the power tool in line with the motor. The regulator, best seen in Figures 3 to 6 may be described as an irregular cylinder closed at one end having a knob 31 formed in the closed end to facilitate rotation of the regulator. Towards one end of the periphery of the cylinder is formed a bearing ring 32 which co-operates with a shoulder 33 formed in the end of the tool housing to retain the bypass regulator and permit its rotation about its cylindrical axis in tool bore 37. A groove 33 is also formed in the periphery near the closed end of the cylinder which receives an "O" ring 34. The "O" ring 34 prevents the escape of pressure fluid from the housing. As best seen in Figure 6, the periphery of the regulator 30 towards the open end is provided with a series of power regulating steps designated A, B, C and D in descending order from the periphery of the cylinder. As will be later described in more detail, these steps co-operate with a pressure fluid supply port to permit a greater degree of pressure fluid bypass from essentially zero (when step A co-operates with the port) to a maximum (when the pressure fluid port is positioned adjacent to step D). The regulator cylinder is also provided with an axially extending indexing finger 35 which co-operates with a series of indexing indentations 36, 36', 36'' and 36''', formed in the rear of the tool housing as best seen in form in Figure 7. Each of the four indexed positions 36 et seq. shown corresponds to a position placement of the steps A-D with the reaction to the pressure fluid supply port previously mentioned. Maximum power output being achieved when step A is in register with the port to minimum power when step D is adjacent the pressure fluid port. The regulator 30 is installed in a cylindrical bore 37 and is free to rotate therein. The rotary position of the regulator may be selected by turning knob 31 to the desired position as indicated by the degree of power output dots best seen on Figure 2. The selected position is retained by the index finger 35 co-operating with the index positioning grooves 36 et seq. as previously described. An inlet pressure fluid port 38 is disposed in the periphery of the bore to co-operate with the periphery of the regulator. An exhaust bore 39 on the periphery of the bore 37 and spaced apart from the pressure fluid inlet port 38 permits the bypass pressure fluid to enter the exhaust of the power tool motor. Operation of the tool is best understood as previously introduced by referring to Figures 8 and 9, which depict the major components in form while schematically interconnecting them for ease of understanding. It should be understood that the porting provided in the casing of the power tool utilises formed interspaced channels within the housing and are difficult to depict in planar presentation. For this reason the schematic presentation of the fluid channels were chosen so that the flow patterns within the power tool might be readily understood. Figure 8 shows the forward operation of the power tool during a typical tightening mode in, for example, an impact wrench. As previously described, the inlet pressure fluid which may be air, is selectively supplied to the chamber 9 wherein it further enters the reversing valve 10. When the trigger 6 is depressed, air enters the pressure fluid supply passageway 20 leading to the forward motor port from whence the pressure fluid or air enters the vane motor 13. Expanded air exhausts the motor via the exhaust passageway or port 7 which eventually exits through the handle exhaust passageway 41 and exhaust screen or muffler 42 to atmosphere. A portion of the pressure fluid supplied to the motor is directed to the regulator 30 by means of the passage 43 and escapes through the regulator past the regulator step (B in the depicted case) and exits the regulator through the exit port 39 to the exhaust cavity 7 to be merged with the primary exhaust, thereby accomplishing both a bleeding of the air pressure supplied to the motor and back pressuring the exhaust as a means of regulating the motor power. Secondary recompression and exhaust of the pressure fluid in the motor exits the port 21 and is passed through the notch 29 into the exhaust cavity 7 to be exhausted eventually to atmosphere as previously described. Reverse operation of the tool is depicted in Figure 9, where depression of the pushbutton 40 rotates the reverse valve 10 to the position shown. The valve partition 24 closes off the forward supply port and redirects the air or pressure fluid to the reverse port 21 of the motor. The pressure fluid is expanded against the motor vanes 14 to rotate the motor in the reverse direction, again exhausting through the exhaust cavity 7 as previously described. Secondary reverse recompression and exhaust is passed in reverse direction through the forward port 20 and is passed through the notch 29 into the exhaust cavity 7 and eventually to atmosphere, as previously described, and is also free to flow through the power regulator 30 through the passageway 43, exit port 39 and finally the exhaust cavity 7 to atmosphere.

Claims: A pneumatic pressure fluid motor assembly (1) comprising a reversible, pneumatic motor (13) and a pressure fluid regulator (30) for the motor, there being an inlet (3) for supplying pressure fluid to said motor and an exhaust (42) for exhausting expanded pressure fluid from said motor to atmosphere, said pressure regulator (30) having a bypass passageway (43, 39) interconnecting said inlet and said exhaust to reduce the output power of the motor, characterised in that said pressure fluid regulator (30) is so constructed that, in a forward operational condition of said motor, a selected portion of the supplied pressure fluid is bypassed through said bypass passageway (43, 39) directly to the exhaust, thereby achieving both a bleeding of the air pressure supplied to the motor and back pressurising the exhaust, and in that a secondary exhaust from said motor is provided, said pressure fluid regulator being constructed to bypass said secondary exhaust in a reverse operational condition of said motor. A motor assembly according to claim 1, in which said motor is a rotary vane air motor. A motor assembly according to claim 1 or 2, wherein said inlet (3) includes a passageway (4) including a valve means (10) for controlling the flow of pressure fluid to said motor. A motor assembly according to claim 1, 2 or 3, wherein said exhaust includes a passageway (41) extending from said motor to a muffler (42) and thereafter to atmosphere. A motor assembly according to any one of the preceding claims, wherein said pressure fluid regulator (30) includes a rotatable cylinder (30) disposed in a bore (37), interspaced in said bypass passageway (43, 39). A motor assembly according to claim 5, wherein said rotatable cylinder is provided with progressive step relief means (A, B, C, D) on its periphery which cooperate with one part (43) of said bypass passageway for regulating the amount of pressure fluid passing along the periphery of said rotatable cylinder to another part (39) of said bypass passageway addressing said bore (37). A motor assembly according to any one of the preceding claims, wherein said bypass passageway (43) includes a flow regulating means (30, 37) for controlling the amount of pressure fluid bypassed in said bypass passageway. A power regulator (30) for a pneumatic pressure fluid motor assembly (1) according to any one of the preceding claims, the regulator being characterised in that it is so constructed that, in a forward operational condition of said motor (13), a selected portion of the supplied pressure fluid is bypassed through said bypass passageway (43, 39) directly to the exhaust (42), thereby achieving both a bleeding of the air pressure supplied to the motor and back pressurising the exhaust, and in that a secondary exhaust from said motor is provided, said pressure fluid regulator being constructed to bypass said secondary exhaust in a reverse operational condition of said motor.

Inventors: GEIGER ROBERT E, GEIGER, ROBERT E.
Applicants: INGERSOLL RAND CO, INGERSOLL-RAND COMPANY
Application year: 1993
Main classification: B25F5
IPC codes: F01C13, F01C1, B25F5, B25B21, F01C20