US 3924693 A
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Description (OCR text may contain errors)
United States Patent [1 1 1 3,924,693
Whitehouse Dec. 9, 1975 FLUID OPERATED TOOL HAVING 2,661,765 12/1953 Troy 251/80 x SELECQMPENSATING THROTTLE VALVE 2,740,507 4/1956 Shaff 173/169 X 3,037,740 6/1962 Sheps et al.... 25l/285 X 5] Inventor: g Wlntehnnse, Lyndhurst, 3,086,501 4/1963 Nielsen 251/285 x OhlO 3,373,824 3/1968 whit/31161156 91/59 x  Assignee: The Stanley Works, New Britain, FOREIGN PATENTS OR APPLICAT O S Conn- 1 372,325 3/1923 Germany 173/169  Filed: July 11, 1973 Primary Examinerlrwm C. Cohen PP N05 378,154 Attorney, Agent, or FirmPrutzman, Hayes, Kalb &
Related US. Application Data Chllton  gsanntiirguxaettijon of Ser. No. 208,217, Dec. 15, 1971, ABSTRACT V A tool housing having a fluid supply passage leading to  US. Cl. 173/169; 91/59; 91 /46g; a fluid motor, a throttle valve received for movement 137/529 in the passage between an open flow control position  Int. Cl. B23B 45/04; F15B 13/04 and a Closed position, and a throttle control luding  Field of Search 251/77, 28 5 322, 32 83; a positively operated throttle actuator and a spring be- 91/59, 413, 468; 173/12 169; 137/529 tween the throttle valve and its actuator, the spring being preloaded upon operation of the actuator for ef-  References Ci fecting movement of the throttle valve independently UNTED STATES PATENTS of its actuator for automatically controlling fluid flow in the passage. l,623,431 4/1927 McVoy 137/529 1,681,044 8/1928 Malik 173/169 x Claims, 1 Drawing Figure I g dl 4 US. Patent Dec. 9, 1975 3,924,693
FLUID OPERATED TOOL HAVING SELF-COMPENSATING THROTTLE VALVE This is a continuation of application Ser. No. 208,217, filed Dec. 15, 1971, and now abandoned.
This invention generally relates to power tools and particularly concerns a fluid operated power tool having a so-called self-compensating throttle valve.
A primary object of this invention is to provide a fluid operated tool having a new and improved self-compensating throttle valve which is positively actuated by a manually operable trigger and which then automatically varies fluid flow to afluid motor responsive to change in the operating speed of the tool to effect a controlled torque output while the trigger remains fully actuated.
Another object of this invention is to provide a selfcompensating throttle valve of the type described which is quick and easy to manufacture and install on a fluid operated tool and which is readily adjustable for desired tool performance over a broad range of operating requirements.
A further object of this invention is to provide a new and improved self-compensating throttle valve for use with fluid operated tools and which is of simplified but rugged construction for reliable service over an extended period of time.
Other objects will be in part obvious and in part pointed out in more detail hereinafter.
A better understanding of the objects, advantages, features, properties and relationships of the invention will be obtained from the following detailed description and accompanying drawing which set forth an illustrative embodiment indicative of the way in which the principle of this invention is employed.
The drawing shows a fragmentary view, partly in section and partly broken away, of a fluid operated power tool incorporating a preferred embodiment of this invention.
Referring to the drawing in detail, a fluid operated power tool such as a pneumatic drill is shown for illustrative purposes, although it is to be understood that this invention may be used in a variety of different types of fluid operated power tools. The drill 10 has a housing 12 with a contoured depending pistol grip l4, and a fluid motor, such as a conventional rotary vane type air motor 16, is mounted in the housing 12 for driving a work engaging element of the tool, not shown. Compressed air for driving the motor 16 is supplied through a coupling, not shown, at the bottom of the pisto] grip 14 and flows through a passage 18 comprising a series of passageways, leading to the air motor 16.
An inlet supply line 20 and a motor outlet line 30 (depicted by broken lines) of the passage 18 are interconnected through a valve chamber 24, defined by a cylindrical valve body 26 suitably secured in a bore 28 extending across the housing 12. The valve bore 28 has a multiple diameter inner end providing a pair of coaxial compartments 32 and 34 which connect the valve chamber 24 with the supply line 20. Compartment 32 is of an intermediate size relative to the full diameter portion of the valve bore 28 and its reduced terminal compartment 34, and a concentric annular shoulder 36 is formed in the housing 12 at the juncture of the intermediate compartment 32 with the full diameter portion of the valve bore 28.
The elongated axially extending valve chamber 24 of the valve body 26 terminates in a concentric compartment 38 of enlarged diameter within a cupshaped inner end of the valve body 26. An O ring seal 40 is disposed between a shoulder 42 adjacent the inner end of the valve body 26 and shoulder 36 of the housing 12 to prevent undesired air leakage past the valve body 26 and the surrounding portions of the housing 12. The valve chamber 24 is accordingly suited to serve as a part of the fluid supply passage 18 to communicate its inlet supply line 20 with the motor outlet line 30 via a port shown in broken lines at 44 which will be understood to extend radially outwardly through the valve body 26 to interconnect its valve chamber 24 with the motor outlet line 30.
For controlling air flow through the passage 18, a valve member 46 is provided on a throttle valve 48 reciprocably mounted within the chamber 24. In the specifically illustrated embodiment, the valve member 46 is provided by an O ring seal disposed within an annular groove 50 on a rearwardly extending coaxial stem 52 of the throttle valve 48. The main body of the valve 48 is enlarged relative to its stem 52 which is provided with an annular flange 54 on one side of which is formed the groove 50 on the stem 52, within which the O ring seal is mounted, and the other side of which seats a valve closure compression spring 56. The spring 56 is biased between the flange 54 and a housing portion defining an end wall 58 for the bore 28 to hold the throttle valve 48 in its illustrated normally closed position with the valve body surrounding the inner end of the chamber 24 and providing a valve seat for member 46.
The throttle valve 48 is shown having its full diameter main body suitably contoured with a symetrically fluted construction to permit fluid flow past the valve 48 within its chamber 24 responsive to its being moved in a valve opening direction from left to right as viewed in the drawing. The inner end of the main valve body is tapered as at 60 from its juncture with the stem 52 in a direction away from the valve member 46 to provide a graduated reduced intermediate portion for metering inlet airflow to the motor 16 upon opening the throttle valve 48.
For positively actuating the throttle valve, a manually operable trigger 62 is shown suitably secured, e.g., by a roll pin 64, to an actuating shaft 66 axially extending into the valve chamber 24 and having an integral concentric throttle pin 68 of reduced diameter extending rearwardly of the shaft 66 for positively actuating the throttle valve 48. The actuating shaft 66 has an intermediate portion of reduced size forming a longitudinally extending notch 70 through which is extended a second roll pin 72 to retain the shaft 66 and its trigger 62 in assembly with the valve body 26 while yet permitting limited freedom of longitudinal reciprocating movement of the actuating shaft 66 within the valve chamber 24. In its illustrated normal rest position, the throttle pin 68 of the actuating shaft 66 is spaced apart a preselected distance from the throttle valve 48 in its normally closed position.
From the foregoing description, it will be seen that upon squeezing the trigger 62, the actuating shaft 66 will be depressed rearwardly into the valve chamber 24, from left to right, as viewed in the drawing, and its integral throttle pin 68 will positively engage the throttle valve 48 to unseat its valve member 46 and permit air to flow through the passage 18 to actuate the motor 16.
To preselect a desired motor operating speed under free running conditions, an adjustment nut 74 isthreadably mounted on an externally threaded, forwardly projecting, reduced end portion 76 on the valve body 26. The nut 74 has a forward abutment stop face 78 for engagement with surface 80 of the trigger 62. Accordingly, the abutment stop surface 78 may be axially adjusted relative to the valve body 26, and thus to the trigger 62 and its actuating shaft 66, by simply rotating a knurled shoulder 84 of the adjustment nut 74 such that the maximum rearward trigger displacement from its normal rest position may be selectively limited to a desired throttle valve opening upon initial actuation of the air motor and, accordingly, set its speed of operation during idling under no load conditions.
To maintain the adjustment nut 74 in a selected position, an annular series of detent recesses such as at 86 will be understood to be formed around the inside wall of the adjustment nut 74 confronting the valve body 26. A detent pin 88 is received in an opening 90 formed in a lower portion of valve body 26 and a suitable spring 92 is fitted within the opening 90 to urge the detent pin 88 axially outwardly for registration with the annular series of detent recesses 86 and to maintain the adjustment nut 74 in a selected angular position. The angular position of the adjustment nut 74 relative to the valve body 26 is readily established by an operator for a desired idling speed by suitable indicia 94 marked on the adjustment nut 74, it being understood that the indicia 94 is calibrated to different motor idling speeds as determined by the extent of the throttle valve opening displacement for a given air supply pressure and a given size air motor.
With a conventional throttle valve having a solid integral shaft connected to the trigger, as normally associates with such power tools, a change in throttle valve opening displacement would not only change the idling speed but also the available torque. To maintain torque characteristics at slower idling speeds, the valve must open further in response to torque loading. A force is available for this in that as an air motor is loaded, its speed decreases, its airflow demand decreases, and its operating pressure downstream of the restricting speed controlling throttle valve rises.
As noted above, upon squeezing the trigger 62, the throttle pin 68 positively engages the throttle valve to unseat the valve member 46 and move it to an open flow control position as established by the extent of actuator movement permitted by the adjustment nut 74 to allow air flow through the passage 18 to the motor under idle or free running conditions. Actuation of the throttle valve 48, however, simultaneously compresses a compensating spring 96 located in valve chamber 24 between actuating shaft 66 and throttle valve 48. As the tool is loaded and the motor operating speed decreases, the preloaded resilient force of the compressed compensating spring 96, together with the increased downstream motor operating pressure within the valve chamber 24, jointly act upon the throttle valve 48 to move it further in a valve opening direction from left to right, as viewed in the drawing, against the opposing upstream line pressure and biasing force of the valve closure spring 56 to automatically provide increased air flow through the valve chamber 24 past the throttle valve 48 to increase the motor operating speed and the output force of the motor 16 during increased loading of the tool 10.
Upon trigger release, the bias effected by the compensation spring 96 is also released, and the biasing force of the valve closure spring 56 is sufficient to overcome the motor operating pressure in the valve chamber 24 and to close the valve member 46 into sealing engagement with its valve seat and through the compensating spring 96, to return the actuating shaft 66 and operating trigger 62 to their illustrated normal rest position.
It will be seen that the self-compensating throttle valve 48 of this invention effects a controlled fluid flow to the motor 16 responsive to the torque loading on the tool 10 as reflected by changes in motor operating speed, due to the combination of opposed spring forces and the opposed pneumatic forces on the throttle valve 48 to provide for opening it further as the downstream motor operating pressure increases, even when the trigger 62 is squeezed and retained in a fully retracted, actuated position.
The above described self-compensating throttle valve is particularly useful with grinders, various fastener tools and similar tools such as the illustrated pneumatic drill. For example, in the use of the pneumatic drill, a proper speed may be selected for the material of the workpeice and the type and diameter drill bit which is to be used. The feed in hand drilling, e.g., is accomplished by arm thrust against the tool. A drill incorporating the disclosed self-compensating throttle valve will normally drill holes easily in a variety of materials with normal arm thrust without burning or snapping the drill bits and without glazing or hardening the workpiece while ensuring that full torque is available at the time the drill bit breaks through the workpiece. The disclosed construction is simplified but rugged and easily manufactured and assembled while at the same time providing reliable performance over an extended period of time with minimum service requirements.
As will be apparent to persons skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing from the teachings of the present invention.
1. In a power tool having a pneumatically operated drive motor, a control valve having a fluid inlet adapted to be connected to a pneumatic pressure source and a fluid outlet connected to the drive motor, a valve bore interconnecting the valve inlet and valve outlet providing a fluid passageway therebetween, a valve seat surrounding the bore intermediate the valve bore inlet and outlet, a valve member mounted in the bore shiftable in first and second opposite axial directions therein respectively to and from a respective closed position thereof for selectively seating on said valve seat and closing said fluid passageway and providing a variable and decreasing fluid restriction between the valve inlet and outlet as the valve member is shifted in said second opening direction from its closed position, the valve member being mounted to be biased in the first closing direction by the valve inlet pressure and in the second opening direction by the valve outlet pressure, the valve member being mounted in the bore such that the net fluid pressure force on the valve member is in said first closing direction and is a function of the pressure drop from the valve inlet to the valve outlet and therefore the fluid restriction therebetween, first spring means biasing the valve member in said closing direction and manually operated valve control means for selectively-shifting the valve in said opening direction for controlling the pneumatic operation of the drive motor, the improvement wherein the manually operated valve control means comprises second spring means biasing the valve member in the opening direction and manual actuator means for manually actuating the valve member in said opening direction from its closed position, said manual actuator means closing the bore at an end thereof and continuously sealing the bore from atmosphere, said second spring means being mounted between said valve member and said manual actuator means, said manual actuator means manually selectively varying the opening spring bias on the valve member in excess of the opposing closing spring bias on the valve member such that the open axial position of the valve member is dependent on the relative opening and closing spring bias on the valve member and on the pressure drop and therefore the fluid restriction between the valve inlet and valve outlet and the valve member automatically compensates for drive motor speed and therefore drive motor load for varying the valve opening in accordance with the drive motor load.
2. A power tool according to claim 1 wherein the second spring means is a compression spring.
3. A power tool according to claim 1 wherein the manual actuator means is selectively operable from a first position to a second position for engaging and initially shifting the valve member in said opening direction from its closed position, and wherein the second spring means, with the actuator means in its second position, has sufficient bias to shift the valve member further in said opening direction so that the valve member thereupon automatically compensates for drive motor speed.