Motor speed controller for a pressure fluid-operated motor

Abstract: A motor speed controller (1) for a pressure fluid-operated motor having a controller body (26) with generally frustoconical cap (35), rotatable in proportion to the speed of rotation of the motor, the cap housing balls (30) which act centrifugally to cause axial translation of a controller stem (32). The cap (35) is surrounded by a housing (20), which co-operate with one another to provide a face seal valve and protects the controller against entry of particulate matter.

Description: This invention relates to a motor speed controller for a pressure fluid-operated motor. In the past, centrifugal governors have been extensively used to control the speed of rotary, pneumatic, or pressure fluid driven high speed grinders and other tools. Typically, these flyweight, ball and ring type controlled devices have been revolved about a pivot point or displaced radially as the speed of the grinder increased. The movement of the flyweights working against a spring as a speed reference force was converted into a movement of a valve means to modulate the supply of pressure fluid. Numerous ingenious devices have been developed to accomplish what appears to be this relatively simple task. JP-A-55-149181 discloses a safety device of a pneumatic tool where a rotor rotates by means of allowing air introduced into a governor chamber to be supplied to a cylinder chamber. When the rotor exceeds a set maximum speed of rotation, a governor is actuated and reduces the rotation by controlling the quantity of air supply. If the governor does not act normally, however, a plurality of balls are run radially outwardly by centrifugal force and if the speed of rotation of the rotor exceeds a certain point, the balls run out completely from underneath a hollow cone part of the ball cage, thereby overlaying holes through which air is otherwise supplied, thereby sealing the air supply holes to shut the rotor down. US-A-2,733,690 also discloses a hydraulic governor and pressure regulating valve structure which has a hollow cone arrangement housing centrifugally operated balls, the interaction between the speed of rotation of the rotor and the centrifugal force required to move the balls to govern the speed of the rotor being controlled by spring force. According to one aspect of the present invention, there is provided a motor speed controller for a pressure fluid operated motor comprising a controller body rotating in proportion to the speed of said motor; a plurality of balls disposed on said controller body for radial displacement upon increase of rotation speed, a control means surrounding said controller body and mounted thereon for resilient resisted axial extension in response to the radial displacement of said balls; and a face seal means on said control means for co-operation with a face seat means for controlling fluid flow to said pressure fluid motor in response to motor speed, and said control means being a hollow cone which overlays said controller body, characterised in that said control means forms a sealed cover over said controller body at low speed. The invention also extends to a pressure fluid motor incorporating a motor speed controller which is essentially as defined in the preceding paragraph. 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 side elevation of a pressure fluid operated rotary grinder having a motor speed controller, Figure 2 is a plan section taken through the controller at section 2-2 of Figure 1, and Figure 3 is a side elevation of the controller of Figure 1 in its overtravel/lockout position. A portion of a rotary high speed grinder commonly referred to as a horizontal grinder is generally designated as reference numeral 1. The grinder is provided with a housing 10, a handle 20 (partly shown), and a grinding wheel (not shown). The housing contains a rotary pressure fluid motor 15 (partly shown) which has its power output on a spindle which is adapted at its outer end to receive the grinding wheel. In the device as shown in Fig. 1, air is supplied to the grinder through a passageway 21, formed in the handle 20. The on/off flow of air is controlled by a lever operated valve (not shown). The supply of air to the motor is controlled in flow as a function of rotor 11 speed by a cone and ball centrifugal controller 25. The centrifugal governor or controller 25 is comprised, in the following preferred embodiment, of a controller body 26, roughly in the shape of a solid cone having a central bore 27, running from its apex to it base. The controller body 26 has an extended base in the form of a hollow shaft 28, which supports the controller body 26, for rotation with the rotor 11 of motor 15, in bearing 16. The controller body 26 has formed therein six arcurate formed pockets 29, which receive and position a number of controller balls 30. The central bore 27 is of hexagonal cross section and receives therein an adjusting bolt or controller stem 31 having a hex head 32, found thereon. The hex head 32, cooperates with the hexagonal bore 27, to prevent rotation of the controller stem while allowing its axial translation within the bore. The axial translation to the right as shown in Fig. 1 is resisted by controller spring 33. Surrounding the controller body towards the air inlet 21 is a cup like, or cone having a substantially flattened tip, controller cap 35. The substantially flattened tip of the cap 35 forms a face annulus 36, which cooperates with controller seat 37, to restrict air inflow to the circumferential air passages 40, which in turn direct air or pressure fluid to the motor 15, by way of distributor passage 41, and plenum 42. The controller cap 35 is connected by means of threaded connection 44, to controller stem 31. This permits adjustment of the controller spring 33 preload. Once the appropriate preload is set, the cap 35 is secured rotationally relative to controller body by pin stakes 45, which cooperate with holes 36, provided on the cap 35, and slots or notches 46, in the body 26, to prevent further rotation of the cap 35, relative to the controller stem 31. This in combination with the number of governor balls selected sets the controller speed. Once set, the pin stakes 45 are inserted and secured by means of cover 51. The cover is crimped in place to prevent disassembly and unauthorized service of the assembled controller. The governor balls 30 cooperate with cam surface 50, provided in the cone 35, to provide the force necessary on rotation to displace the cone in an axial direction to the right as viewed in Fig. 1. Fig. 2 shows the disposition of six balls 30, in the pockets 29. It should be understood that two, three, four or six balls may be used and result in a dynamically balanced controller. The number of balls effect the displacement force and in combination with the controller spring 33, set the controlled speed with appropriately adjusted preload. Bleed holes (100) are provided for dynamic stabilization to prevent hunting and instability due to internal volume changes during operation. In other words, to reduce the air spring effect. Fig. 3 shows the controller in its overtravel/lock-out position. In this position lock pin 52 extends radially outward by centrifugal force to engage a ridge 53 in the cap 35. Once this occurs on overtravel the controller assembly cannot be disassembled and repaired as it is a sealed, crimped , unit. However, it can be reset from the lockout position by applying extension force to the cap to receive the load on the lock pin and then tapping on the side opposite the pin to force the pin back into its hole (below the ridge on the cap). Once this is done, the controller is reset, reassembled and tested. This is a safety feature of the present device. In operation, an additional failsafe design concept involves the support of rotor shaft 5, within the controller body shaft 28 and bearing 16. Should the speed controller be accidently left out or intentionally removed during assembly, loss of radial support of the rear rotor shaft 25 would permit the rotor to cock and bind between motor end plates 55 thereby preventing the rotor from accelerating to unsafe speeds. Retaining screws 101 function as a safeguard to assure proper positioning of the controller cap with the nozzle face. Should someone operate the tool without the housing pieces properly clamped and positioned, the controller nozzle gap would be larger than designed (and the tool could be operated this way) and as the controller cap travel is limited, it may be insufficient to control in the oversize nozzle gap. The screws 101 assure the nozzle gap is as designed whether the housing pieces are properly clamped or not. If the screws are left out them supply air will blow out of the screw holes - a circumferential channel 102 about the end plate provides a locking groove for the screws as well as an air channel to distribute supply air to the screw holes. The controller unit is virtually sealed against contamination when operating at speeds up to approximately 70% of the designed free speed because of rim seal 103. At speeds above the 70% point up to the controlled free speed RPM the controller cap is displaced axially to the right to regulate the air flow and the rim seal 103 is separated. To prevent contamination from entering the controller, the cap 35 and housing 20 are constructed to form a nozzle 104 at the tip of the cap thereby accelerating the air and contaminants beyond the separated rim seal area. The particles pass into the annular region 105 about the rear end plate and are prevented from returning to the separated seal area because of the high air flow velocity created by the nozzle 104. The centrifugal action of the controller cap acting against the particles tends to keep the contaminants against the housing 20. Without the face seal 103, nozzle 104, annulus 105, and centrifugal action, particles could enter the controller and contaminate the inside. It will be appreciated that the present controller has a capability of speed control satisfactory for normal grinder usage and other applications where ultra precise speed control is not required.

Claims: A motor speed controller (1) for a pressure fluid operated motor (15) comprising a controller body (26) rotating in proportion to the speed of said motor; a plurality of balls (30) disposed on said controller body for radial displacement upon increase of rotation speed, a control means (33, 35) surrounding said controller body and mounted thereon for resilient resisted axial extension in response to the radial displacement of said balls; and a face seal means (36) on said control means for co-operation with a face seat means (37) for controlling fluid flow to said pressure fluid motor (15) in response to motor speed, and said control means being a hollow cone (35) which overlays said controller body, characterised in that said control means forms a sealed cover over said controller body (26) at low speed. A motor speed controller according to claim 1, wherein said controller body (26) is in the form of a cone having ball pockets (29) formed in its peripheral surface. A motor speed controller according to claim 1 or 2, wherein said control means forms a deflector nozzle (104) to deflect contaminant particles past said controller during operation. A motor speed controller according to claim 1, 2 or 3, wherein said control means is arranged to form a sealed cover over said controller body up to approximately 70 percent of the normal maximum operating speed and an effective annular nozzle to accelerate particles past its open seal at operating speed. A motor speed controller according to any one of the preceding claims, wherein said controller body is provided with a rim seal (103) which co-operates with said control means to prevent contaminants from entering said controller body. A motor speed controller according to any one of the preceding claims, wherein said controller body is provided with at least one radially displaceable pin (52) as a means for locking out said speed controller on overtravel. A motor speed controller according to claim 6, wherein said pin (52) intercepts a ridge (53) in said control means to hold said control means in its overtravel position. A motor speed controller according to any one of the preceding claims and being mounted in bearing means (16) which also provide bearing means for said pressure fluid motor (15), whereby removal of said controller will disable said bearing means for said motor means as a safety device. A motor speed controller according to any one of the preceding claims, and being encased in a housing (20) and valve seat means (37) are provided in said housing which co-operate with said control means to effect speed control and said housing and said valve seat means are each provided with means (45, 46, 36, 51) for securing their relative position. A motor speed controller according to claim 9, wherein said means for securing said housing further comprise means (101, 102) for retaining pressure fluid as a safety device to assure proper housing position relative to said control means. A pressure fluid motor incorporating a motor speed controller according to any one of the preceding claims.

Inventors: ALBERT GREGORY P, ALBERT, GREGORY P.
Applicants: INGERSOLL RAND CO, INGERSOLL-RAND COMPANY
Application year: 1988
Main classification: G05D13
IPC codes: G05D13, F01D17, F16K17, F02D9, B23Q5, F02D31, B24B55, B24B47, F03B15, F02D1