US3580285A

US3580285A - Work control device for fluid driven apparatus

Info

Publication number: US3580285A
Authority: US
Inventors: Karl A Brandenberg
Original assignee: Aro Corp
Current assignee: Aro Corp
Priority date: 1969-08-28
Filing date: 1969-08-28
Publication date: 1971-05-25
Anticipated expiration: 1988-05-25

Abstract

A device for controlling the amount of work performed by a pneumatic tool including a pair of sensors adapted to sense the pressure drop caused by a restriction in a pneumatic line to the tool. The sensors produce signals that are summed thereby providing a pressure supply through a metered orifice whenever the tool begins work output. The metered orifice delays the pressure supply signal to a valve in the pneumatic line downstream from the restrictor in that line. The valve closes upon receipt of the pressure supply signal thereby stopping the tool. The sensors and orifices the device are adjustable in order to compensate for various work tools, workloads and time of operation of the device.

Description

United States Patent [72] Inventor Karl A. Brandenberg Hayward, Calif.

[21] Appl No. 853,632

22 1 Filed Aug. 28, 1969 [45] Patented May 25,1971

[73] Assignee The Aro Corporation Bryan, Ohio [54] WORK CONTROL DEVICE FOR FLUID DRIVEN Primary Examiner-Alan Cohan Attorney-Molinare, Allegretti, Newitt & Witcoff ABSTRACT: A device for controlling the amount of work performed by a pneumatic tool including a pair of sensors adapted to sense the pressure drop caused by a restriction in a pneumatic line to the tool. The sensors produce signals that are summed thereby providing a pressure supply through a metered orifice whenever the tool begins work output. The metered orifice delays the pressure supply signal to a valve in the pneumatic line downstream from the restrictor in that line. The valve closes upon receipt of the pressure supply signal thereby stopping the tool. The sensors and orifices the device are adjustable in order to compensate for various work tools, workloads and time of operation of the device.

Patented May 25, 1971 4 Sheets-Sheet 1 Mays.

Patented May 25, 1971 4 Sheets-Sheet 2 Iii/ 67110?" wzic. $9355 Pu s: o

.BEZ O j a! @Zfirandenbery (figs.-

Patented May 25, 1971 4 Sheets-Sheet 3 66 w ll MIMI WORK CONTROL DEVICE FOR FLUID DRIVEN APPARATUS CROSS REFERENCE TO RELATED APPLICATION This application is related to Ser. No. 766,202 filed Oct. 9, I968, by Gemian and Short for a Work Control System, this application being directed to a species of the generic work control device set forth in the identified application.

BACKGROUND OF THE INVENTION In the above-cited German and Short application, the general theory and operation of a work control system is disclosed. This novel system is adapted to be connected in line with a fluid operated tool and to provide a predetermined work output by that tool. The theory of operation and the embodiments disclosed in the earlier application are quite sound and workable. Pressure in the line to a work tool is sensed by the device made in accordance with the invention and the relationship of the operation of the work tool is then correlated with the feedback pressures from the tool to enable control of the work output of the tool.

SUMMARY OF THE INVENTION In the principal aspect then, the present invention comprises a work control device for a fluid driven apparatus which is placed in a fluid flow line having a fluid inlet and outlet, the outlet leading to the work tool. A restrictor is positioned between the inlet and outlet with a control valve in the fluid line downstream from the restrictor. Start and impact sensors sense the pressure drop across the restrictor. The signals from the sensors are summed to provide a control output for the control valve in the fluid line.

It is thus an object of the present invention to provide a work control device of reduced size and weight, having fewer parts than previously manufactured devices, Such a device is far easier to assemble and has a reduced manufacturing cost. It is reduced in weight and in size and yet operates on standard pneumatic line pressures.

These and other objects, advantages and features of the present invention will be set forth in greater detail in the description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS In the detailed description which follows reference will be made to the drawing comprised of the following figures:

FIG. 1 is a schematic circuit diagram representing the construction of a device comprising the invention;

FIG. 2 is a cutaway perspective view of a typical device comprising the invention;

FIG. 3 is a top plan view of the front cover plate of the device;

FIG. 4 is a top plan view of the control body of the device;

FIG. 5 is a bottom plan view of the control body of the device;

FIG. 6 is a top plan view of the control base of the device;

FIG. 7 is a bottom plan view of the control base of the device;

FIG. 8 is a top plan view of the rear cover plate of the device; I

FIG. 9 is a cross-sectional view of the diaphragm valve of the device, which, in conjunction with a volume and metering orifice, acts also as a timing device; and

FIG. 10 is a cross-sectional view of a sensor, a restrictor and a timing needle of the device.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the following detailed description reference is first directed to the schematic circuit diagram of FIG. 1. The operation and typical characteristics of the device will be explained in relation to this diagram. Then there will be described in specific detail the construction of a device made in accordance with the invention as illustrated in FIGS. 2 through 10.

Referring to FIG. 1, a fluid operated tool, for example, an impact wrench 10, which includes a trigger 12 is connected to a pressurized fluid supply line 14 which leads from the outlet 13 of the work control device 15 of the invention denoted by the dotted lines-A fluid pressure supply is provided to the work control device through an input supply line 16 via inlet 17. Quite importantly, the work control device 15 of the invention operates to control the work output by the tool 10 by sensing the pressure drop across a restrictor 18 in the main fluid supply line 20 through the work control device 15.

Downstream from the restrictor 18 is a diaphragm control valve 22. The diaphragm valve 22 is a pilot operated valve including a diaphragm 23 biased by a spring 25 adapted to open or close by engaging or disengaging from a seat 27 to provide fluid power to the tool 10 depending upon the control signal provided through a valve control line 24 to chamber 240 of valve 22.

A start sensor 26 senses the pressure drop through the restrictor 18 as fluid passes through the line 20. Sensing lines 28 and 30 connect with

chambers

29 and 31 defined on opposite sides of a diaphragm 34 of sensor 26. The start sensor 26 is in a normally closed position due to the bias of a spring 32 on diaphragm 34. When the force of the pressure through line 28 exerted on the diaphragm 34 exceeds the force exerted through the line 39 on the opposite side of the diaphragm 34, the diaphragm 34 unseats from an orifice 36 to a line 38 allowing fluid flow passage into the inhibitor line 38.

Impact sensor 40 has a construction similar to start sensor 26. It includes a diaphragm 42 biased by a spring 39 defining two

chambers

41 and 43. The force on one side of the diaphragm 42 is directed through line 28 and the force on the opposite side of diaphragm 42 is directed through a line 44. An orifice 46 permits fluid flow from chamber 43 through the orifice 46 into a second inhibitor line 48.

The inhibitor lines 38 and 40 direct fluid flow pressure to

opposite chambers

47 and 72 respectively on opposite sides of a diaphragm 52 of an inhibitor valve 50. Whenever the force against the diaphragm 52 as provided through the line 38 exceeds the force as provided through the line 48, the diaphragm 52 opens from a seat 76 over cavity 49 and an output signal is provided through output line 54. Output line 54 connects through an adjustable metering orifice or impact timer 56 to the control line 24 which, as explained before, controls the control valve 22. A control valve exhaust line 58 permits exhaust from the control valve 22 through another adjustable metering orifice or off timer 60.

The operation of the work control device is as follows. An impact wrench 12 having an associated work control device 15 is initially not being operated. The supply line 16 is at that time pressurized. Likewise

lines

28, 30, 32 and 14 are pres surized by the supply of pressure. The start sensor 26 and impact sensor 40 are in closed position due to the bias of springs 32 and 39 respectively.

Upon triggering the tool 10, fluid, such as air, flows through the

supply passage

16, 20 and 14 to the tool 10. A pressure drop occurs across the restrictor 18 upon this initial fluid flow. This pressure drop is sensed by the pressure differential sensors or start sensor 26 and impact sensor 40. The start sensor 26 manifests the sensing in pressure drop by permitting the diaphragm 34 to rise off the orifice 36 so that the line 38 becomes pressurized. The impact sensor 40 likewise opens to permit the line 48 to become pressurized. The sensor 26 must open slightly after that time which the impact sensor 40 opens. This delay is provided by the reservoir of volume 62 in combination with the delay restrictor 64. Pressure thus drops at a slower rate in line 30 than it does in line 44, thereby opening start sensor 26 after impact sensor 40 opens.

Initially, the

lines

38 and 48 are pressurized and the wrench or tool 10 is running free. The orifice 46 of the impact sensor 40 is much larger than a bleed restrictor 66. This enables the pressure in the upper cavity 47 of the inhibitor 50 to remain as close as possible to the pressure in the lower cavity 72 of the inhibitor 50 even though fluid is bleeding to the atmosphere through restrictor 66.

When impacting or work by the tool 10 occurs, pressure in the supply line rises causing pressure in line 44 to rise. Consequently, the impact sensor 40 closes. The pressure at which sensor 40 will close may be adjusted by varying the position or bias force of the spring 39. The bias of the start sensor spring 32 is adjusted such that the start sensor 26 will remain open during impacting or work by the tool 10.

The pressure patterns expected during the work cycle performed by the tool are the same as those set forth in the previously referenced German and Short application. When the impact sensor 40 closes, the line 48 is closed to the pressure supply from the line 28. The fluid in the cavity 47 thus exhausts through the bleed restrictor 66 so that the diaphragm 52 of the inhibitor 50 rises from the seat 76 thereby permitting fluid flow into the line 54.

Fluid flow through the line 54 may pass through either the impact timer 56 or ultimately out an exhaust restrictor 78. The amount passing through the restrictor 78 is, however, of small consequence. After pressure rises and fluid passes through the impact timer 56, pressure then rises in the line 80 to a sufficient level and a reservoir of volume 82 is filled. Ultimately, fluid passes through the line 24 to impinge on the diaphragm 23 which is biased by the spring 25. The diaphragm 23 engages a seat 27 of the valve 22 closing the valve 22. The period of time during which the pressure in volume 82 and line 24 increases to a sufiicient level to close valve 22 can be adjusted by means of the variable timing needle or orifice 56. Of course, the volume 82 may be varied also to control the characteristics of the control valve 22.

Closing the valve 22 shuts off the fluid flow through the

supply line

16, 20 and 14. At that time pressure equalizes on both sides of the restrictor l8 and thus on both sides of the

diaphragms

34 and 41 of the sensors 26 and 40 respectively. Sensor 40 is already in the closed position, however, sensor 26 then assumes a closed position. Thus, no additional fluid is supplied through the

lines

38 and 54 and the air utilized to bias the diaphragm 23 against seat 27 is exhausted through the timer 56, a timer 60 and an exhaust restrictor 78. After the pressure in the line 24 has decreased sufficiently, the diaphragm 23 is released from the seat 27. If the operator holds the trigger 12 open during this entire process, then a new impact cycle starts as soon as the control valve 22 is open. This is followed by another off cycle and so on. If, on the other hand, the operator releases the trigger of the tool 10 during the off delay, the line 14 to the tool will merely be pressurized and available for another work cycle once the trigger is actuated.

The remainder of this description refers to FIGS. 2l0 which illustrate a preferred embodiment of the device of the present invention. In FIG. 2 there is shown a perspective view of this embodiment. The device has dimensions of approximately 3 inches by 4 inches with a thickness of approximately 2% inches. The device is comprised of four substantially rigid or solid plate members: a front cover plate 84, a control body 85, a control base 86 and a rear cover plate 87. These

plates

84, 85, 86 and 87 may be cast or machined from a suitable rigid material such as aluminum stock.

Sandwiched between each pair of

plates

84, 85, 86 and 87 are gaskets or a diaphragm having openings which match appropriately the channels and openings in the faces of the

plates

84, 85, 86 and 87. For example, a gasket 90 is positioned between the front cover plate 84 and the control body 85. A diaphragm 91 is situated between control body 85 and control base 86, and another gasket 92 is situated between control base 86 and rear cover plate 87.

Inlet 17 enters the control base 86 and outlet 13 exits from the control base 86. The various passages, cavities and chambers in FIGS. 3-10 are labeled to correspond with the schematic diagram, FIG. 1. It will be recognized that FIGS. 3-8 represent plan views of the faces of the various plates or

members

84, 85, 86 and 87; whereas, FIG. 9 is a cross-sectional view of the control valve 22 and FIG. 10 is a cross-sectional view of a sensor, a metering orifice for timing, and a restrictor of the device.

The restrictor 18 as shown in FIG. 10 is comprised of a threaded pin which may be removed and interchanged with threaded pins of difierent dimensions to provide for different restricted openings depending upon the characteristics of the tool with which the device of the invention is to be used. The sensor 26 is comprised of an adjustable threaded head 94 which cooperates with a spring 32 that engages a metal flange 96 resting against the diaphragm 34. The opposite side of the diaphragm 34 is biased by means of the difference in spring force to close the orifice 36. The timer 56 includes an adjustable restriction 101 having O-

ring seals

102 and 103 to ensure that there will be no leakage of fluid.

In FIG. 3, the plan view of the top of the assembled device illustrates graphically how the device may be adjusted. The sensors and timing orifices may all be adjusted with a screwdriver for desired operation as may the restrictor, R, which is designated as 18 in FIG. 1.

For the purposes of information and comparison typical dimensions for the device illustrated in FIGS. 310 are set forth in tabulated form below. Such a device has been tested with an impact wrench having an 8 foot length of 5/ 1 6-inch internal diameter hose leading from a pressure source of approximately p.s.i. The work control device is positioned between the impact wrench and a regulator at approximately 8-feet distance from the impact wrench.

Control valve diaphragm... 1.652 in. diameter exposed to cavity 24a.

0.506 in. diameter exposed to seat 27.

By varying the adjustment of the needle orifices or timers 56 and 60 for such a device, the period of impact can be adjusted from approximately l/ 10 to 10 seconds. Thus, the amount of work by the wrench is controlled.

What I claim is:

1. A work control device for fluid driven apparatus comprising, in combination, a fluid flow line with a fluid inlet and a fluid outlet, a restrictor between said inlet and said outlet to provide a pressure drop between said inlet and outlet, a control valve in said line downstream from said restrictor, a start sensor for sensing said pressure drop, and an impact sensor for sensing said pressure drop, said start and impact sensors providing opposing signals, means for summing said opposing signals to provide an output signal to said control valve to terminate fluid flow through said valve, and means to control the period of time for said output signal to activate said control valve.

2. The device of claim 1 including means for removing said signal from control valve after a predetermined time.

3. The device of claim 2 including means for adjusting said period of predetermined time.

4. The device of claim 1 including means to delay the pressure drop signal to said start sensor.

5. The device of claim 1 including adjustable means to control the period of time for said output signal to activate said control valve.

6. The device of claim 1 including means for adjusting the response pressure of said sensors.

7. The device of claim 1 wherein at least one of said sensors is a diaphragm valve having biasing means against at least one side of said diaphragm and having signal producing characteristics dependent upon the product of surface area and pressure against the opposite sides of the diaphragm and the force of the biasing means.

8. The device of claim 1 wherein said sensors provide fluid signal outputs respectively against opposite sides of a diaphragm inhibitor, the force of said signals dependent upon the area of said diaphragm being impinged, and wherein the signal from said start sensor is directed to said control valve whenever said impact sensor signal is less than said start sensor signal.