US3749530A

US3749530A - Governor for pneumatic motor

Info

Publication number: US3749530A
Application number: US00220252A
Authority: US
Inventors: G Amador
Original assignee: Dresser Industries Inc
Current assignee: Dresser Industries Inc
Priority date: 1972-01-24
Filing date: 1972-01-24
Publication date: 1973-07-31
Anticipated expiration: 1990-07-31
Also published as: GB1411034A; JPS5645163B2; JPS4883235A; CA969821A; DE2303942A1; DE2303942C2; IT974131B; AR199890A1; SE394014B

Abstract

A safety governor operable on failure of the primary governor to arrest operation of the motor with which it is associated. An annular spring-washer, that includes weights supported peripherally distributed about its face, is secured to the drive spindle proximately displaced opposite inlet air passages to the motor. In response to centrifugal forces of rotation, the weights bend or deflect the spring-washer in an axial direction increasingly toward the inlet air passages until, at a predetermined overspeed, passage closure is effected interrupting air supply to the motor.

Description

United States atent 1 1 Amador 1 July 31, 1973 German Amador, Houston, Tex.

52 us. or. 418/41, 137/53 51 1111.01. F016 21/12 [58] Field 61 Search 418/41, 42, 43; 137/53 [56] References Cited UNITED STATES PATENTS 2,586,968 2/1952 Maclay 418/43 2,422,733 6/1947 Jimerson..... 3,043,273 7/1962 Schott 3,071,115 1/1963 Schott 3,257,913 6/1966 Broom et al. 418/43 as 43 44 Q J l J 3,279,485 10/1966 Alexander 418/43 3,421,414 1/1969 Peale 1 418/43 3,519,372 7/1970 Peale 418/43 Primary ExaminerC. J Husar Attorney-Robert W. Mayer, Daniel Rubin et a1.

[57] ABSTRACT A safety governor operable on failure of the primary governor to arrest operation of the motor with which it is associated. An annular spring-washer, that includes weights supported peripherally distributed about its face, is secured to the drive spindle proximately displaced opposite inlet air passages to the motor. In response to centrifugal forces of rotation, the weights bend or deflect the spring-washer in an axial direction increasingly toward the inlet air passages until, at a predetermined overspeed, passage closure is effected interrupting air supply to the motor.

14 Claims, 6 Drawing Figures Patented July 31, 1973 v 3,749,530

2 Sheets-Sheet 1 76 I: I I/ 44 43 53 4- I FIG. 3

Patented July 31, 1973 2 Sheets-Sheet 13 FIG.4

GOVERNOR FOR PNEUMATIC MOTOR BACKGROUND OF THE INVENTION 1. The field of art to which the invention pertains includes the art of pneumatic motors and more particu larly to component apparatus for limiting speed of such motors.

2. In pneumatic tools of various types, it is common to employ a governor for limiting motor speed in order to prevent a runaway speed condition that might otherwise occur. Devices being driven by the motor, such as grinding wheels or the like, frequently have a critical speed limit above which they are subject to rupture or fragmenting. Similarly, a drill bit or the like may encounter excessive heat at overspeed deleteriously affecting its cutting edge. Consequently, failure to limit speed within safe operating ranges not only impairs efficient operation of the tool, but represents a substantial hazard to operating personnel should the driven member shatter at the overspeed conditions. Under normal operating conditions, the primary governor effects adequate speed limitation to avoid overspeed conditions. However, the primary governors are themselves occasionally subject to malfunction from corrosion, particle interference, or the like causing one or more components to bind or freeze. This has occasioned use of a backup or safety governor employed in conjunction with or independent of the primary governor to provide overriding safety should failure of the latter occur.

Such safety governors in accordance with the prior art achieve their overriding objectives in various structural arrangements. Some operate combined with the primary governor and are known to occasionally become ineffective from the same malfunction affecting the latter. Others operate on the principle of a shearing or similar destruction of one or more components to reduce or eliminate speed by rendering the tool inoperable. Still others act to arrest rotation by a mechanical braking interference applied to the drive shaft in one form or other. Whatever technique is employed, safety governor devices of the prior art are characterized by a general lack of reliability, complexity and/or undesirable destruction of components. This has caused them to be reliably ineffectual for the purposes intended or excessively expensive to fabricate and/or maintain. Despite recognition of these inherent drawbacks, it has not been previously possible to effect their elimination by a safety governor construction that is more simple, reliable and relatively inexpensive to manufacture and maintain as compared to such similar purpose constructions of the prior art.

SUMMARY This invention relates to a governor and particularly to a safety governor for preventing overspeed of a pneumatic motor. More specifically, the invention relates to a safety governor operably able to interrupt the air supply to the motor of a pneumatic tool at any predetermined overspeed relative to the operating speed intended to be limited by the primary governor. In accordance herewith the safety governor is frictionless in its operation and is operably independent of the primary governor as not to be rendered ineffectual by failure of the latter. Nor does the safety governor hereof impose any form of destruction or mechanical braking interference as has been common with such similar purpose devices of the prior art. By contrast, novelty in the safety governor hereof resides in its simplicity, reliability and a relatively inexpensive manufacture of a frictionless device for interrupting motor operation at any desired predetermined overspeed condition.

In accordance with the invention hereof, the foregoing is achieved by means of an annular, disc-like springwasher axially secured to the motor drive spindle proximately displaced opposite inlet air passages to the motor. Weights secured on the washer face respond to centrifugal forces of rotation to deflect or bend the washer axially rearward on itself in a sort of foldover toward a superposed relation with the inlet air passages. Washer deflection increases with speed until at a predetermined overspeed condition, the foldover shuts or sufficiently throttles the passages to effect either motor stoppage or sufficient speed reduction respectively to within safe operating levels. Once the latter has occurred, restarting of the tool is prevented until the original operating relation of the springwasher is restored. While restoration is a simple matter, preferably a tool disassembly is required to afford an inspection opportunity for determining the malfunction cause of the primary governor.

It is therefore an object of the invention to provide a novel governor apparatus for preventing overspeed of a pneumatic motor. I

It is a further object of the invention to provide a pneumatic motor governor apparatus characterized by frictionless operation in preventing motor overspeed.

It is a further object of the invention to provide a pneumatic motor safety governor apparatus that is operably independent of the primary governor as not to be rendered ineffectual by a malfunction failure of the latter.

It is yet a further object of the invention to provide a novel safety governor for pneumatic motors capable of interrupting motor operation without mechanical braking or component destruction in the manner of such similar. purpose safety governors of the prior art.

It is a still further object of the invention to provide a novel safety governor in accordance with the aforementioned objects that is more simple, reliable and relatively less expensive to manufacture than similar purpose safety governors of the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a pictorial representation of a hand-held grinder employing a safety governor in accordance herewith;

FIG. 2 is a longitudinal section through the grinder of FIG. 1;

FIG. 3 is an enlarged section through the primary and safety governors with the air motor inoperative;

FIG. 4 is a view similar to FIG. 3 generally representing normal operating relation of the motor;

FIG. 5 is a section as viewed substantially along the lines 55 of FIG. 3; and

FIG. 6 is a fragmentary view of the safety governor in its shutoff or operative relation.

Reference is now made to FIGS. 1 and 2 of the drawings in which for purposes of description there is illustrated a hand-held grinder designated 10 exemplifying a type of pneumatic tool with which a safety governor is frequently utilized. Other tools also using such gover nors include sanders, polishers, drills, etc.

Grinder I is comprised of a generally cylindrical housing 11 from which radially extends a pair of angularly displaced

elongated gripping handles

12 and 13. Gripping handle 13 includes an air inlet 14 normally connected to a hose or the like (not shown) delivering compressed operating air from a remote source to the grinder in a well known manner. Actuating the grinder for operation is by means of a depressable thumb throttle lever 18 whereby operating air is delivered from the inlet to a motor 22 for rotating abrasive cup 19.

Throttle lever 18 controls throttle 20 for opening port 21 to air supplied at inlet 14. From port 21, entering air is admitted into a cavity 24 from which it flows to a through passage 25 of housing 11 and then upward through cavity 26. From that point, the air being delivered passes through port 27 in middle cap 28 into chamber 29 formed between the middle cap and a top cap 33.

Compressed air in chamber 29 enters an aperture 34 in the middle cap to a chamber 36 at which location flow is regulated by a main governor 35 as will be later described. From chamber 36 flow is delivered through a plurality of angularly displaced ports or passages 37 (see also FIG. 3) formed in a seal plate 38. Passages 37 connect to a chamber 42 surrounding a rear bearing plate 43 which in turn defines a through-port 44 leading to the inlet of air motor 22. The air motor is of a conventional construction comprising the usual cylinder S0, rotor 51, blades 52, spindle 53, rear bearing plate 43 and front bearing plate 54. Secured to the outboard end of spindle S3 is the grinding wheel including abrasive cup 19.

The governors can be best understood from FIGS. 3-6 to which reference is now made. Briefly, primary governor 35 includes a spider 58 threadedly secured to the rear of spindle 53 for conjoint rotation therewith. A pair of

weights

59 and 60 pivotally supported by pivot pins 61 on opposite sides of the spider respond to centrifugal forces of rotation to force governor valve 62 slideably toward middle cap aperture 34 in opposite air flow. Movement of valve 62 toward the aperture reduces the effective flow area therethrough whereby under usual operating conditions motor speed is both regulated and uniformly limited. Opposing the centrifugal force action of the weights in addition to air flow is a compressed spring 66 coiled about the lower end of screw 67 between an adjusting nut 68 and a radial spider flange 69. Via a cross pin 70 supported in open slots 71 the biasing force of spring 66 is transmitted to valve 62 urging increased flow area through aperture 34.

Operation of main governor 35 can be best understood by comparing the normally inoperative and operative relations of the governor contrasted in FIGS. 3 and 4 respectively. Should a malfunction occur in any governor component such as binding occasioned by corrosion or the like that prevents the intended forward movement of valve 62, an overspeed or runaway speed condition can occur. Marketed grinding wheels for example are characteristically unable to withstand the increase forces associated with speeds much beyond rated operation, tending to fragment or explode at about 50 percent over rated speed. To preclude the latter, there is provided a safety governor 75 in accor' dance herewith as will now be described with continuing reference to FIGS. 3-6.

Safety governor is comprised of a dish-like annular spring washer 76, shaped conically concave on its upper surface facing toward aperture 34. The washer is centrally bored for coaxial mounting onto the exterior of spindle 53. An annular spacer 78 provides a somewhat critical spacing from the top face plane of bearing 77 to place the rear or bottom washer face proximate passages 37 for reasons as will be understood. Drag thin rubber grommet 79 maintains the washer secured to the spindle and seated against under spacer 78. Supported on the washer top face are a plurality of cylindrical weights 80 uniformly distributed near the periphery thereof and each secured to the washer by means of a mounting screw 81. While for purposes of disclosure, eight weights 80 are illustrated, the exact quantity and size of each to be employed are a function of their intended operating level as will likewise be understood.

On startup prior to energizing motor 22, the weight axes are angularly diverging in the manner illustrated in FIG. 3. Tripping throttle lever 18 energizes the motor and initiates rotation of spindle 53. In response to the centrifugal forces of rotation, weights 80 oppose the directionally inherent spring forces of spring washer 76 to bend, pivot or deflect the washer axially downward about a pivot axis defined by spacer 78 from its concave relation in FIG. 3 toward its radially flat normal operating relation of FIG. 4. This places the weight axes substantially parallel to the spindle axis in a relation representing normal operating conditions with all components including primary governor 35 functioning in the manner intended. Should however, the primary governor bind, freeze or otherwise incur malfunction that prevents sleeve 62 from advancing toward aperture 34 to limit motor speed, an overspeed will be incurred almost instantaneously.

Accelerating beyond the normally limited operating speed increases the centrifugal forces of rotation reacting against weights 80. In response, the weights react to increasingly bend, pivot or deflect spring washer 76 axially downward beyond its normal operating relation. As a result, the washer shape is altered from its radially flat relationship shown solid in FIG. 4 to a convex popover relation phantom outlined in FIG. 4 and shown solid in FIG. 6. On achieving the latter, the spring washer is peripherally positioned overlaying seal plate 38 and may extend within annular groove or recess communicating with air inlet passages 37.

At such time as the spring washer begins to seat in recess 85, ports 37 are increasingly throttled against delivery of operating air to motor 22. when fully or substantially fully seated with the washer positioned superposed with respect to the passages, further delivery of air How to motor 22 is prevented or substantially curtailed. In either event, the effect is to completely shut off or at least substantially reduce motor speed. Once 'in the shutoff position, the spring-washer will not self revert thereby preventing motor restarting without disassembly of the apparatus. The latter purpose is to force determination of the malfunction cause which prompted operation of the safety governor. Obviously, external leverage or the like could be provided, if preferred, to restore the spring-washer to its normal relation of FIG. 3 without tool disassembly.

To effect operation in the foregoing manner, springwasher 76 should be selected of physical properties characterized to give the appropriate response. It has been found that materials such as spring steel, beryllium copper or other common spring materials of appropriate thickness available from various commercial sources are suitable for these purposes. For one such application, the washer was of heat treated beryllium copper on the order of about 2-3/16 inches in diameter, of 1/64 inche thickness and with an original cone height of about three sixty-fourth inche. Another important factor is a matching of annular washer seal plate space area with the area of aperture 34 in middle cap 28 in order to maintain flow quantity necessary for maximum horsepower. Likewise, the quantity and magnitude of weights 80 secured to the spring-washer face should be closely matched with the spring characteristics to effect motor shutoff at a desired predetermined overspeed. Moreover, thickness of spacer 78 is critical in that it governs the proximate washer displacement from seal plate 38 to ensure washer seating on being actuated to its shutoff position.

In operation, normal operating speed of motor 22 causes weights 80 secured to the spring-washer to bend, pivot or deflect the washer from its concave relation of FIG. 3 to its radially flat relation of FIG. 4. Should an overspeed condition be encountered, the increased magnitude of centrifugal forces reacting against weights 80 causes further bending, pivoting or deflection of the spring-washer to a popover convex orientation effecting a seating relation within seal plate 38. On seating, air inlet ports 37 are instantly blocked against further air delivery to the motor effecting shutoff or substantial slowdown thereof. With the springwasher in the latter relation, the motor cannot be restarted until the spring-washer is intentionally deflected upward and restored to its normal startup configuration.

By the above description there has been disclosed a novel safety governor for preventing overspeed of a pneumatic motor in the event of a malfunction in the primary governor. It operates completely independent of the primary governor as not to be affected by factors producing malfunction in the latter. At the same time operation does not rely nor utilize shearing or other form of component destruction for effecting stoppage at any predetermined condition. By appropriate selection and matching of components, the operating level can be accurately predetermined. Unlike prior art devices, the safety governor hereof enjoys frictionless operation in being highly simple in construction yet reliable and effective while relatively inexpensive compared to such similar purpose governors of the prior art. Whereas the governor hereof has been principally described in its safety function in a backup safety capacity with an associated primary governor, the invention is not intended to be so limited. To the contrary, it should be apparent that the governor of the invention can itself be readily adapted to function as a primary governor or as a safety governor without association with a primary governor of any sort.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the drawings and specification shall be interpreted as illustrative and not in a limiting sense.

The embodiments of the invention in which an exclu- I sive property or privilege is claimed are defined as follows:

l. The combination of:

a. a pneumatic motor having a drive spindle for providing a rotational output;

b. inlet means to receive operating air from a supply source for delivery to said motor; and

c. governor means located in the delivery path of the air between said inlet means and said motor for limiting operating speed of said motor;

d. said governor means being responsive to the rotational speed of said motor to frictionlessly move toward interrupting said delivery path concomitantly with increases in said rotational speed.

2. The combination according to claim 1 in which said governor means frictionlessly moves to a position effectively shutting said delivery path at a predetermined rotational speed of said motor.

3. The combination according to claim 1 in which said governor means is secured to the drive spindle of said motor for conjoint rotation therewith and is operatively responsive to the centrifugal forces imposed by the rotational speed rate of said spindle.

4. The combination according to claim 3 in which said governor means comprises an annular springwasher proximately displaced from at least the inlet of one air passage to said motor and weight means secured uniformly distributed about the face of said washer, said weights means being responsive to the centrifugal forces of rotation to effect said frictionless movement by deflecting said washer from its proximate displaced relation with said one passage toward a superposed transverse relation therewith at a predetermined rate correlated with the rotational speed of said motor.

5. The combination according to claim 4 in which said deflection rate is effective for said washer to close said one passage at a predetermined speed of said motor for effecting shutoff thereof.

6. The combination according to claim 5 in which said annular spring-washer is of frusto-conical cross section and said deflection thereof efi'ects a directional reversal of apex in being deflected from speedless to the shutoff speed of said motor.

7. The combination according to claim 4 in which said deflection in response to increases in rotational speed directionally corresponds with the flow direction of operating air being delivered to said one passage.

8. The combination of:

a. a pneumatic motor having a drive spindle for providing a rotational output;

b. inlet means to receive operating air from a supply source for delivery to said motor;

c. a main governor for modulating the flow of said delivered air to effectively limit the operating speed of said motor; and

d. a safety governor operative independent of said main governor at a predetermined motor speed exceeding the limit speed to be effected by said main governor;

e. said safety governor including operative means frictionlessly effective at said predetermined motor speed to interrupt delivery of operating air to said motor.

9. The combination according to claim 8 in which the operative means of said safety governor is located in the delivery path of the air between said inlet means and said motor and is responsive to the rotational speed of said motor to frictionlessly move toward interrupting said delivery path concomitantly with increases in said rotational speed.

10. The combination according to claim 9 in which said safety governor operative means is secured to the drive spindle of said motor for conjoint rotation therewith and is operatively responsive to the centrifugal forces imposed by the rotational speed rate of said spindle.

1 l. The combination according to claim 10 in which said safety governor operative means comprises an annular spring-washer proximately displaced from at least the inlet of one air passage to said motor and weight means secured uniformly distributed about the face of said washer, said weights means being responsive to the centrifugal forces of rotation to effect said frictionless speed to said predetermined motor.

14. The combination according to claim 11 in which said deflection in response to increases in rotational speed directionally corresponds with the flow direction of operating air being delivered to said one passage.

Claims

1. The combination of: a. a pneumatic motor having a drive spindle for providing a rotational output; b. inlet means to receive operating air from a supply source for delivery to said motor; and c. governor means located in the delivery path of the air between said inlet means and said motor for limiting operating speed of said motor; d. said governor means being responsive to the rotational speed of said motor to frictionlessly move toward interrupting said delivery path concomitantly with increases in said rotational speed.

4. The combination according to claim 3 in which said governor means comprises an annular spring-washer proximately displaced from at least the inlet of one air passage to said motor and weight means secured uniformly distributed about the face of said washer, said weights means being responsive to the centrifugal forces of rotation to effect said frictionless movement by deflecting said washer from its proximate displaced relation with said one passage toward a superposed transverse relation therewith at a predetermined rate correlated with the rotational speed of said motor.

6. The combinaTion according to claim 5 in which said annular spring-washer is of frusto-conical cross section and said deflection thereof effects a directional reversal of apex in being deflected from speedless to the shutoff speed of said motor.

8. The combination of: a. a pneumatic motor having a drive spindle for providing a rotational output; b. inlet means to receive operating air from a supply source for delivery to said motor; c. a main governor for modulating the flow of said delivered air to effectively limit the operating speed of said motor; and d. a safety governor operative independent of said main governor at a predetermined motor speed exceeding the limit speed to be effected by said main governor; e. said safety governor including operative means frictionlessly effective at said predetermined motor speed to interrupt delivery of operating air to said motor.

11. The combination according to claim 10 in which said safety governor operative means comprises an annular spring-washer proximately displaced from at least the inlet of one air passage to said motor and weight means secured uniformly distributed about the face of said washer, said weights means being responsive to the centrifugal forces of rotation to effect said frictionless movement by deflecting said washer from its proximate displaced relation with said one passage toward a superposed transverse relation therewith at a predetermined rate correlated with the rotational speed of said motor.

12. The combination according to claim 11 in which said deflection rate is effective for said washer to close said one passage at said predetermined motor speed.

13. The combination according to claim 12 in which said annular spring-washer is of frusto-conical cross section and said deflection thereof effects a directional reversal of apex in being deflected from zero motor speed to said predetermined motor.