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Publication numberUS3691902 A
Publication typeGrant
Publication dateSep 19, 1972
Filing dateJul 13, 1971
Priority dateJul 13, 1971
Publication numberUS 3691902 A, US 3691902A, US-A-3691902, US3691902 A, US3691902A
InventorsLebzelter Joseph
Original AssigneeUs Army
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Monitoring system for pneumatic cylinder
US 3691902 A
Abstract
A pneumatic cylinder for a power piston is provided with a cushion bore at one end and a cushion plug on the piston which is adapted to enter and cut off said cushion bore at the end of the piston stroke and provide a cushioning pressure area between the piston and said end of the cylinder. A pressure leakage path with a cushion adjusting screw therefor is provided between the cushioning area of the cylinder and the cushion bore. A spring-biased plunger-type control valve is connected at one end with the cushioning area of the cylinder and at the other end with the cushion bore, and responds to a pressure differential therebetween at the end of the piston stroke to provide a pulse output through the valve as a monitoring signal for the cylinder operation.
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Description  (OCR text may contain errors)

United States Patent Lebzelter 1 Sept. 19, 1972 [54] MONITORING SYSTEM FOR PNEUMATIC CYLINDER Primary Examiner-Edgar W. Geoghegan Assistant Examiner-A. M. Zupcic [72] Inventor. Joseph Lebzelter, Sparta, NJ. Attorney Ha"y M Saragovitz at a. [73] Assignee: The United States of America as represented by the Secretary of the [57] ABSTRACT Army A pneumatic cylinder for a power piston is provided [22] Filed: July 13, 1971 with a cushion bore at one end and a cushion plug on the piston which is adapted to enter and cut off said [21] Appl' L069 cushion bore at the end of the piston stroke and provide a cushioning pressure area between the piston 52 us. c1. ..91/1, 91/394, 91/396, and said end of the cylinder- A Pressure leakage P 92 5 with a cushion adjusting screw therefor is provided 51 Int. Cl. ..F0lb 25/26, FlSh 15/22 between the cushimliflg area cylinder and the 58 Field of Search ..91/1, 26, 394, 396; 92/5 cushiO" A sprmg-blased Plunger-type valve is connected at one end with the cushioning area [56] References Cited of the cylinder and at the other end with the cushion bore, and responds to a pressure differential UNITED STATES PATENTS therebetween at the end of the piston stroke to provide a pulse output through the valve as a monitoring 5%; 1;; gag: 9 3? signal for the cylinder operation. 3,541,925 I 1 [I970 Guinot ..91/1 11 Claims, 7 Drawing Figures w l 4 IIIIIIIIIIIIIIIIIIIIIIIIIIIIIJ 2 PATENTED E l 9 I973 3.691. 902

sum 2 or 4 Fig. 2 01/7 //v 65 20 PSI INVENTOR. Joseph Lebzelter MONITORING SYSTEM FOR PNEUMATIC CYLINDER GOVERNMENT RIGHTS The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

SUMMARY OF THE INVENTION output or control signal at the limit of the piston travel.

The first requires the use of limit valves and physical contact with the piston rod or connected part. It has the disadvantage that it may be damaged by overtravel if improperly adjusted, gives a maintained output signal of a pulse signal which is desired for most control purposes, and must often be located in a crowded mechanical environment. The second system involves the use of sequencing valves and the monitoring of the internal pressure of the cylinder to determine the travel limits of the piston and provide a signal output. It has the disadvantage that if the piston becomes jammed and does not complete its normal travel, pressure conditions for full travel may be duplicated and an output signal may be given, and it gives a maintained signal instead of the desired pulse signal. 7

7 It is, therefore, an object of this invention to provide an improved and simplified monitoring system for pneumatic cylinders which generates an output control signal of the desired pulse type without utilizing the control features or being subject to the disadvantages of the presently used systems referred to.

It is also an object of this invention to provide an improved monitoring system for pneumatic cylinders which may effectively derive and utilize the cylinder pressure developed in cushioning or decelerating the piston at the end of its travel or stroke to generate an output signal of the desired pulse type for control purposes and in isolation from the pneumatic or other operating media of the cylinder.

It is a further object of this invention to provide an improved monitoring system for pneumatic cylinders which generates an output pulse signal only in response to piston travel above a minimum speed and at the limit or end thereof.

It is a still further and important object of this invention to provide an improved monitoring system of the type referred to which is particularly adapted for monitoring the travel of the piston and piston rod of a pneumatic cylinder in connection with a work load, such as a drill or other tool, and in a remote or relatively inaccessible location, such as a deep well for example, without attachment to any moving parts thereof and with a single pressure monitoring connection with the cylinder.

In the monitoring system of the present invention, the operating medium for the cylinder may be any fluid pressure, although pneumatic or air-pressure operation is more general and for that reason is referred to herein as the preferred medium. In any case, the monitoring system'of the present invention provides, as one of its features, for using thepressure developed in cushioning or deceleration the piston at the end or limit of its travel or stroke to produce a pulse output as a monitoring signal for control purposes, and as a further feature, that the medium through which the output signal is transmitted may be independent of and different from the operating medium for the cylinder.

In the system of the present invention, a pneumatic cylinder with a movable power piston therein is .provided with operating pressure connections, one directly into the cylinder at the rear end and the other indirectly into the cylinder through a smaller coaxial cushion bore at the forward end. A power or operating valve is provided for applying operating pressure through said connections to either end of the cylinder selectively to move the piston through its travel or stroke and to retract it. The cushion bore is adapted to receive a cushion plug on the piston and be cut off from the forward end of the cylinder, thereby entrapping air and providing a compression or cushioning area ahead of the piston at or near the end of its forward travel or stroke. A pressure leakage path is provided between the cushioning area and the cushion bore and includes an orifice controlled by a cushion adjusting screw to gradually release the cushioning pressure at a controlled rate and bring the piston to rest.

In accordance with the invention, the pressure developed in cushioning or decelerating the piston at the end of its stroke or travel is used to generate a monitoring output pulse or signal and indicate the limit or completion of the piston travel or stroke. The piston is generally connected with a work load which may be provided, for example, in moving a work tool, such as a drill, in a well or other remote location. It is important, therefore, that the end or limit of the piston travel or stroke be signalled back for control purposes. The power valve may then be operated either manually or automatically in response to the pulse or signal, to retract the piston for the next operation in connection with the work load. The pulse signal may otherwise be used for any control purpose.

In the system of the present invention,; the foregoing monitoring operation in response to the 'cushioning pressure is accomplished through the use of a pulse generating device or valve connected with the cylinder at the cushioning area and at the cushion bore to receive operating or controlling pressures therefrom. The pulse valve includes a valve element which moves as a plunger to open and close a passageway and pulse fluid flow therethrough between inlet and outlet chambers. The valve element is spring-biased to the closed position and moves momentarily to the open position in response to a momentary differential between the pressures received from the cushioning area of the cylinder and the cushion bore at the end of the piston travel or stroke. The pulsed fluid flow through the valve provides a monitoring pulse signal which may be used for any control purpose.

The monitoring signal thus. provided is preferred over the maintained type signal, as it gives an accurate indication of the piston travel limit and is better adapted for automatic control purposes. In this system the output pulse signal comes directly at the end or limit of the piston travel or'stroke and thus cannot occur prematurely, and requires no physical contact with the moving piston or piston rod.

The invention will, however, be-further understood from the followingdescription, when considered with reference to the accompanying drawings, and its scope is pointed-out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS 1 In the drawings:

FIG. 1 is a schematic diagram, with certain elements in cross-section, showing a monitoring system for a pneumatic cylinder embodying the invention;

FIGS/2, 3, 4, 5 and 6 are partial diagrams of the system of FIG. 1 showing the sequence of operations thereof in accordance with the invention; and

FIG. 7 is a schematic diagram, similar to FIG. 1, showing a modification in' accordance with the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawings, wherein like reference numerals refer to like parts throughout, and referring more particularly to FIG. 1, a pneumatic cylinder 10 in an elongated cylinder housing or casing 11 is provided with a power piston 12 movable therein between the rear end 13 and the forward end 14 and having a pressure seal with the cylinder wall as indicated at 15. The piston is connected with a piston rod 16 having a bearing 17 at the forward end of the cylinder casing and is provided with a cushion plug 18 on the forward face thereof surrounding the piston rod. A complementary cushion bore 19 is provided in the cylinder casing coaxial with and in extension of the cylinder 10 at the forward end 14 for receiving the cushion plug at the end of the piston stroke, thereby to cut off the cylinder and entrap air in a short compression or cushioning area 20 ahead of the piston at the cylinder end.

The degree of cushioning of. the piston is adjustable by means of a cushion adjusting screw 22 threaded into a radial cavity 23 in the side of the cylinder casing near the forward end and having a tapered end 24 controlling an orifice opening 25 into the cushion bore 19. The adjusting screw cavity opens at oneside into the cushioning area 20 of the cylinder through achannel 26 in the cylinder casing to complete a leakage path for the cushioning pressure from the cushioning area 20 to the cushion bore 19 under control of the cushion adjusting screw.

Pressurized air or other pneumatic operating fluid for moving the piston is applied to the cylinder through a rear port 27 in the casing 11 directly into the cylinder in rear of the piston and through a forward port 28 opening into the forward end of the cushion bore and thence indirectly into the cylinder at the cushioning area. The pressurized air or other pneumatic operating fluid for the cylinder is controlled by a power or operating valve 29 having valve openings 30 therethrough, for conduction in the directions indicated, between a pneumatic pressure inlet or supply line 31 and an outlet or exhaust line 32 on one side thereof and two cylinder operating or supply lines 33 and 34 on the opposite side thereof, leading respectively to the rear cylinder port 27 and the forward cylinder port 28 as shown.

In this position, which may be called the retract position, the valve applies pressure from the supply line 31 to the forward end of the cylinder through the port 28 and the cushion bore 19 to hold the piston in the retracted or rest position shown, while the rear port 27 is connected through the valve to the exhaust line 32. This is the piston holding position of the valve. For moving the piston forward to drive or move a work load connected with the piston rod, as indicated by the legend, the valve is moved to the operating position,to the right as viewed in the drawing, to bring two crossed valve openings 35 into registration with the supply connections for the cylinder and connect the cylinder rear port 27 with the pressure inlet or supply line 31 while the cylinder forward port 28 is connected with the outlet or exhaust line 32, conduction through the valve being in the directions indicated.

The supply lines 33 and 34 to the cylinder, at a point adjacent to the valve 29, are each provided with a throttling valve 36 and a one-way valve 37, the valves 36 adjustably restricting flow in either direction and the valve 37 permitting flow only in one direction, as indicatedby the arrowed lines, which in this case is the inlet direction. By this means the exhaust from one end of the cylinder is restricted while the other end receives full operating pressure against controlled back pressure. It has been found that it is better thus to limit the outflow rather than the inflow to the cylinder, that is, to put the full operating pressure on and restrict the outflow, thereby to provide better control and faster motion of the piston and better cushioning action.

Thus in the foregoing pneumatic cylinder construction, the power or operating valve, which may be manually or automatically controlled, provides for applying operating pressure to either end of the cylinder selectively to move the piston through its travel or stroke or to retract it, and the adjustable cushioning pressure means effectively provides controlled deceleration for the piston at the end of the stroke. This construction is typical of pneumatic cylinders for power purposed and is shown by way of example as a preferred type for use in connection with the monitoring system of the invention. 7 a

In this system, the pneumatic pressure developed ahead of the piston at the cushioning area 20 is used in a pulse generating device or valve 38 to provide a monitoring output pulse or signal and indicate the limit or completion of the piston travel or stroke for control purposes.

The valve comprises a valve casing 39 and a longitudinally movable cylindrical valve element or plunger 40 controlling an annular passageway 41 between respective coaxial annular inlet and outlet chambers 42 and 43 therein. These are provided with inlet and outlet ports 44 and 45 respectively, opening through the side of the valve casing for external control connections as will be described.

The valve element 40 has an intermediate section 46 of reduced diameter and moves longitudinally as a plunger to open and close the passageway 41 and pulse fluid flow therethrough between said chambers and the inlet and outlet ports 44 and 45. The valve plunger is normally moved to and held in the closed position shown, to block the passageway, bya coiled biasing spring 47 bearing against the forward end thereof in an annular spring cavity 48 in the forward end of the valve casing. The valve is thus normally self-closing under control of the spring bias.

A pilot or pressure inlet chamber 49 in the valve casing, in coaxial continuation of the spring cavity at the forward end, is connected with the cushion bore 19 through a pressure supply line 50 leading into and connected with the cylinder operating or supply line-34 and the forward port 28 at the cushion bore, thereby to receive and applythe cushion bore pressure to the forward end of the valve plunger and tend to hold the valve in the closed position in aiding relation to the spring bias.

A second pilot or pressure inlet chamber 51 in the valve casing at the rear end, is connected with the cushioning area of the cylinder through a pressure supply line 52 and an added pressure outlet port 53 drilled or otherwise provided in the forward end of the cylinder at the cushioning area and an added outlet connection 54therewith for said line drilled or otherwise provided on the side of the cylinder casing, thereby to receive and apply the cushioning area pressure to the rear end of the valve plunger. This pressure thus tends to move the valve plunger forward and open or operate the valve in opposition to the closing force of the spring bias and the cushion bore pressure.

Thus with this arrangement, it will be seen that the rear or operating end of the valve plunger is subject at all times to the pressure at the cushioning area 20 of the cylinder while the forward or holding end of the valve plunger is likewise subject to the pressure at the cushion bore 19. These pressures are equal at all times and thus balanced at the ends of the valve plunger, so that the valve remains closed under the force of the biasing spring as the piston moves in either direction,

due to the cushion bore being open directly into the cushioning area, except when cut off by the cushion plug at the end of the piston travel or stroke. The piston cushioning pressure then creates a pressure differential to pulse'the valve open briefly and produce a pulse output therethrough and thus indicate the limit or completion of the piston movement, as is desired from monitoring the cylinder operation.

For control purposes, the pulse output from the valve 38 may be applied to any device or system adapted to respond to pulsed fluid flow therethrough or the blocking and unblocking of the passageway between the valve chambers. In the present example, this is a back pressure switch or valve 55, which is a fluidic device, as indicated, having a control port 56 connected through a fluid pressure or control line 57 with the inlet port 44 on the pulse valve and, through the valve, with the vent or outlet port and an outlet line 58 connected therewith.

The back pressure switch or valve has a fluid pressure inlet connection or port 59 at one end and two fluid outlet connections. or ports 60 and 61 at the opposite end. As a fluidic device, it operates to direct fluid flow from the inlet port 59 to the outlet port 60 when the control port 56 is vented by the opening of the pulse valve in response to the cushioning pressure, and to direct fluid flow from the inlet port 59 to the outlet port 61 when the pulse valve is closed, as normally, and the control port 56 is blocked. Thus when the valve 38 is pulsed open by the cushioning pressure at the end of the piston travel or stroke, a monitoring pulse signal is emitted from the outlet port 60.

The pulse generating device or valve 38 may be used in connection with other pulse operated devices and control meanswhich may be of the hydraulic, pneumatic, or electrical type and may be connected with the outlet line 58 to receive pulsed fluid pressure applied through the valve from the inlet line 57, as will hereinafter be described.

It will also be seen that with this system, using the plunger-type, differential-pressure-operated pulse valve in connection with the cushioning of the cylinder area and the cushion bore as shown and described herein, the medium through which the output pulse is transmitted may be independent of and different from the pneumatic operating medium for the cylinder. Thus the pulse output may be fluid pressure'relief or transmittal through the pulse valve'as described above, or a pneumatic or hydraulic fluid pressure medium pulsed by the valve for similar control purposes.

' The operation of the pneumatic cylinder monitoring system of the present invention may now be considered with further reference to FIG. 1, along with the diagrams of FIGS. 2 to 6, inclusive, showing the sequence of operations and the relative operating pressure on the pulse valve and the piston from the retracted position forward through the power stroke.

In each of those diagrams, the operating pressure on the piston at the rear is indicated by a pressure gauge 63 shown in connection with the cylinder supply line 33. The operating pressure at the cushion bore and at the forward or holding end of the pulse valve 38 is in dicated by a pressure gauge 64 shown in connection with the pressure supply line'50. The pressure at the cushioning area 20 and at the rear or operating end of the pulse valve 38 is indicated by a pressure gauge 65 shown in connection with the pressure supply line 52. In' each of the diagrams of FIGS. 2 and 3, the supply or operating pressure for the cylinder at the pneumatic pressure inlet or supply line 31 is indicated by a pressure gauge 66 shown in connection with said line at the power or operating valve 29. In each figure, the pressure at each gauge is indicated by the legend adjacent thereto.

In FIG. 2, the first of the sequence, the piston is in the retracted position and the power valve 29 is in the retracted position, as in FIG. 1, to apply the operating pressure to the cylinder and the forward side of the piston through the cushion bore 19 and the cushioning area 20. This may be pounds per square inch, for example, as indicated by the gauge 66. The cushion bore 19 and the cushioning area 20 are thus at the operating pressure and equal, as indicated by the gauges 64 and 65, so that the spring-biased pulse valve 38 is maintained in the inactive or closed position with the equalized pressures applied at its holding and operating ends, as described hereinbefore. Thus it will be seen that as the piston is retracted from the power stroke, the valve 38 will not be pulsed to provide a false monitoring signal and will remain closed while the piston is in the retracted position shown in FIGS. 1 and 2. In this position, the pressure at the rear or operating end of the cylinder is at 0 pounds per square inch, as indicated by the gauge 63, as the supply line 33 is then open to the outlet or exhaust line 32 as shown.

In FIG. 3, the start of the power stoke of the piston is shown, as the power valve 29 is moved to the operating position, thereby applying the supply or operating pressure to the rear or operating end of the cylinder and 7 piston through the supply line 33, while theforward end of the cylinder ahead of the piston is connected at the cushioning area and cushion bore with the outlet or exhaust line 32. Thus the pressure rises at the rear end of the cylinder through the supply line 33, as indicated by the gauge 63, to nearly the full operating pressure. This pressure is applied against the piston to move it forward against the falling pressure ahead of it as the cylinder exhausts and the pressures at the cushioning area and the cushion bore, and hence on the ends of the pulse valve, fall to low and equal values such as indicated by the gauges 64 and 65, whereby the pulsed valve continues to remain closed and inoperative and the relatively wide pressure differential starts the piston forward rapidly against the work load.

As the piston moves forward, as indicated in FIG. 4, the pressure in rear of the piston falls slightly as indicated by the gauge 63, while, as indicated by the gauges 64 and 65, the pressures ahead of the piston and at thecushioning area and cushion bore begin to rise due to the compression created by the advancing piston. The cushioning area and the cushion bore 19 remain in direct communication and therefore the pulse valve remains closed and inoperative since the pressures applied thereto remain equal. This condition continues until the cushion plug 18 enters the cushion bore 19, as indicated in FIG. 5.The operating pressure in rear of the piston remains substantially the same as the piston moves but the cushion bore is cut off from the cushioning area 20 in which the pressure rises rapidly to a higher value than the cushion bore pressure, as indicated by the gauges 64 and 65.

These opposing pressures at the ends of the pulse valve create a pressure differential thereon sufficient to overcome the spring bias and pulse the valve open briefly as the piston comes to rest, as shown in FIG. 6, at'the end of its travel or stroke. The pulse valve then recloses due to the pressure levels at its ends quickly equalizing to zero as indicated by the gauges 64 and 65. The monitoring pulse thus derived from the pulse valve may then be used for any control purpose as described hereinbefore and to signal for the retraction of the piston to the position shown in FIGS. 1 and 2 for the start of the next operation. As noted in connection with FIG. 2, this operation does not affect the pulse valve which remains closed as the piston is retracted. It may also be noted that the piston must travel above a predetermined minimum speed in order to create a relatively high cushioning pressure and thus operate the pulse valve. Therefore, in this system, failure of the pulse valve to operate may thus signal a faulty piston operation.

In the embodiment of the invention shown in FIG. 1, the pressure at the cushioning area 20 of the cylinder is derived for application to the pulse valve, through the port 53 in the end of the cylinder and the outlet connection 54 in the side of the cylinder casing, both of which must be drilled or otherwise provided by an added and often complicated operation in the construction of the cylinder casing. In a modification of the cylinder construction in accordance with the invention, this added operation is avoided while attaining the same desired access to the cushioning to derive operating pressure for the pulse valve as before. This modification is shown in FIG. 7, to which attention is now 8 directed, along with FIG. 1, and which is the same as FIG. 1 except that the operating valve is omitted to simplify' the showing in connection with the modified cylinder construction, and an electrical switching device is provided for operation in response to the pulse output. All other elements of FIG. 7 are the same and operate in the same manner as. shown and described in connection with FIG. I and the other preceding figures of the drawing.

In the modified cylinder construction, no additional drilling or machining is required. A substitute for the cushion adjusting screw 22 of FIG. 1 is made'in the form-of an adapter plug 67 which is of the same size and directly interchangeable therewith in the screw cavity 23, being screw-threaded as indicated, to fit tightly therein. The adapter plug has a transverse slot 68 at its inner end opening into the screw cavity and'a hollow tubular core 69 connecting therewith provides an external pressure outlet from the cushioning area 20 through the passage 26 and the screw cavity 23, and

' thus access to the cushioning area for connection with the pulse valve through the pressure supply line 52 as before. The connection with the line 52 is provided by a tubularexternal extension on the adapter plug, and through which the core 69 extends, although other suitable connecting means may be provided.

In this modification, the leakage path provided through the orifice 25, from the cushioning area to the cushion bore, is closed or sealed off by a ball or like closure element 71 at the inner end of the adapter plug and forced to a seat thereby in the orifice as shown. The closure element is thus part of the plug and may be integral therewith. In this construction, therefore, the

leakage path from the cushioning area to thejcushion bore must be provided in other ways as'by a greater leakage past the cushion plug 18 in the cushion bore or, as in the present example, it may be provided and more exactly controlled by an adjustable throttling or flow restricting valve 72in a bypass line 73 connecting the pressure supply line 52 and the cushioning area 20 with the pressure supply line 50, and thus the cushion bore 19 through the supply line 34 and the cylinder forward port 28.

Thus access to the cushioning area 20, to derive operating pressure for the pulse valve, may be obtained directly through a port provided by drilling or other operation on the cylinder casing, as in FIG. 1, or indirectly and without any added operation, through a hollow adapter plug threaded into the cushion adjusting screw cavity to seal the leakage path therethrough and provide a pressure outlet therefrom and the cushioning area as in FIG. 7. In the latter case, the cushion adjustment is preferably provided, as indicated, through throttling or controlling valve means in a bypass line between the cushioning area 20 of the cylinder and the cushion bore 19.

As referred to hereinbefore, the pulse valve 38 may be used in connection with various pressure operated devices or control means, such as the pneumatic or fluidic type of FIG. 1. In the present example, the pulse valve is connected to control the pressure operated electrical switch device 74. This may be of the pneue matic or hydraulic pressure operated type having an inlet connection through the line 58 from the pulse valve and receiving operating pressure through thevalve from the pressure supply line 57 which in this case may be connected with any suitable pressure supply source (not shown). The switch has terminals 75 in any number to meet the internal contact arrangement, and is connected with external controlcircuit leads 76 attached to the terminal. As the valve 38 is pulsed at the end of the piston travel or stroke, a fluid pressure pulse through the valve momentarily operates the switch in response thereto.

From the foregoing description, it will be seen that in accordance with the invention there may be provided an improved monitoring system for pneumatic cylinders which may effectively derive and utilize the cylinder pressure developed in cushioning or decelerating the piston at the end of its travel or stroke to generate an output signal of the desired pulse type for control purposes, without attachment to any moving parts, and in which the medium through which the output signal is transmitted may be independent of and different from the operating medium for the cylinder.

What is claimed is:

1. A pneumatic cylinder monitoring system' comprising in combination:

a pneumatic cylinder having a coaxial cushion bore at the forward end thereof and a piston movable therein from a retracted position to said forward end in a power stroke;

said piston having a coaxial cushion plug thereon adapted to enter and cut off the cushion bore from the cylinder at the end of the piston stroke and thereby provide a cushioning area between the piston and said end of the cylinder;

a plunger-type fluid pressure control valve connected at one end with the cushioning area of the cylinder and at the other end 'withthe cushion bore to receive pressure therefrom at opposite ends and operate in response to a pressure differential therebetween at the end of the piston stroke to provide a fluid pressure pulse output through the valve as a monitoring signal for the cylinder operation; and

control means connected with said valve for operation in response to said-pulse output.

2. A pneumatic cylinder monitoring system as defined in claim 1, wherein said control valve comprises a valve casing and a longitudinally movable cylindrical valve plunger therein controlling an annular passageway between coaxial fluid-pressure inlet and outlet chambers in connection with said control means and being spring-biased at one end to move to the closed position and block said passageway, and wherein the pressure connections therefor with the cushioning area of the cylinder and the cushion bore.

are through a pilot or inlet chamber in the valve casing at each end of the valve plunger to apply pressure thereto, the connections being such that the pressure from the cushion bore is applied at said one end of the valve plunger tending to hold the passageway blocked and the valve closed in aiding relation to the spring bias, and that the pressure from the cushioning area is applied at the opposite end of the valve plunger tending to open the passageway and the valve in opposition to the spring bias and the cushion bore pressure.

3. A pneumatic cylinder monitoring system comprising in combination:

g a pneumatic cylinder in an elongated cylinder casing with a coaxial cushion bore at the forward end thereof and a forward operating port for the cylinder'in the casing at the cushion bore; a piston movable in said cylinder from a retracted position to said forward end in a power stroke and having a coaxial cushion plug thereon adapted to enter and cut off the cushion bore from the cylinder at the end of said stroke, thereby to provide a compression or cushioning area between the piston and said end of the cylinder;

means providing a pressure leadage path in the cylinder casing between the cushioning area and the cushion bore;

a pulse generating control valve comprising a valve casing and a longitudinally movable cylindrical valve plunger therein controlling an annular passageway between coaxial fluid pressure inlet and outlet chambers and being spring-biased at one end to move to the closed position and block said passageway;

said valve being connected with the cushioning area and the cushion bore to receive pressure therefrom at opposite ends of the plunger and operate in response to a pressure differential therebetween at the end of the piston stroke and provide a fluid pressure pulse output through the valve as a monitoring signal for the cylinder operation, and

said pressure connections being such that the pressure from the cushion bore is applied at said one fend of the valve plunger tending to hold the passageway blocked and the valve closed in aiding relation to the spring bias, and the pressure from the cushioning area is applied at the opposite end of said plunger tending to open the passageway and the valve in opposition to the spring bias and the cushion bore pressureiand v control means connected with one of said valve chambers for operation in response to said pulse output.

4. A pneumatic cylinder monitoring system as defined in claim 3, wherein the operating pressure connection for the pulse valve to the cushion bore is through said forward operating port of the cylinder, and wherein the operating pressure connection from the pulse valve to the cushioning area is through a port provided at the forward end of the cylinder and an external connection therefor in the cylinder casing.

5. A pneumatic cylinder monitoring system as defined in claim 3, wherein means are provided for sealing off said pressure leakage path from the cushion bore and providing a pressure outlet for the cushioning area and connection to said pulse valve from said leakage path.

6. A pneumatic cylinder monitoring system as defined in claim 3, wherein the pressure leakage path includes a threaded cushion-adjusting screw cavity communicating with the cushioning area and an orifice opening therefrom into the cushion bore, and wherein the valve connection to the cushioning area is through a hollow adapterplug screw-threaded into said cushion-adjusting screw cavity and providing means for closing said orifice and a pressure outlet therethrough from the cushioning area for said connection with said pulse valve.

7. The combination with a pneumatic cylinder having a cushion bore at the forward end thereof and a movable piston therein having a cushion plug adapted to enter and cut off the cushion bore from the cylinder and provide a cushioning area for the piston at the end of its stroke; of 7 means for deriving and utilizing the cushioning pressure from said area to generate a cylinder monitoring output signal of the pulse type;

said means comprising a pressure-operated plungertypepulse valve connected with the cushioning area and the-cushion bore to receive operating pressures therefrom in opposition, and includinga passageway between two valve chambers and a valve element responsive to said pressures and movable as a plunger to open and close said passageway and pulse fluid pressure therethrough between said chambers;

a said valve element being spring-biased to the closed position and movable momentarily to the open position in response to a momentary differential in the pressurefrom the cushioning area above the cushion bore pressure at the end of thevpiston stroke, thereby to provide said pulsed fluid pressure as an output monitoringsignal and indicate completion of the cylinder operation; and

.control means connected with one of said valve chambers for operation in response to said pulsed fluid pressure.

8. The combination as defined in claim 7, wherein the cylinder is provided with a forward operating port at the cushion bore and the operating pressure connection' for the pulse valve with the cushion bore is provided through said operating port, and wherein the operating pressure connection for the'pulse valve with the cushioning area is provided through an outlet port and an outlet connection therewith at the forward end ofthecylinder. 1 a

9. The combination as defined in claim 7, wherein a pressure leakage path is provided between the cushioning area and the cushion bore comprising athreaded cushion adjusting screw cavity, a passageway therefrom into thecushioning area of the cylinder and an orifice opening therefrom into the cushion bore, and the pulse valve connection with the cushioning area is through a hollow adapter plug screw-threaded into said cavity and having a ball closure element for said orifice and providing a pressure outlet through a tubular core therein from the said cavity and the cushioning area for said pulse valve connection, and wherein a bypass pressure line connection with throttling valve means therein is provided between the cushioning area and the cushion bore.

10. A pneumatic cylinder monitoring system comprising in combination:

a pneumatic cylinder in an elongated cylinder casing with a coaxial cushion bore at the forward end thereof,

a piston movable in said cylinder froma retracted position through its travel or stroke to the forward end and having a coaxial cushion plug thereon adapted to enter and cut off said cushion bore from the cylinder at the end of said stroke, thereby to provide a cushioning area between the piston it said en f the c linder; 2 piston ro xtendiiig forwardly from said piston and cushion plug coaxially therewith through the cushion bore and externally of the casing for connection with a work load movable by the piston; V means providing two operating pressure connections with the cylinder, one directly into the cylinder through a port in the casing at the rear end and the other indirectly into the cylinder through a forward port in the casing at the cushion bore; an operating valve for the cylinder for applying pneumatic operating pressure through said connections to either end of the cylinder selectively to move the piston through its travel or stroke or to retract it; control valve means in said cylinder connections for limiting V the outflow therethrough from the cylinder while permitting full inflow therethrough to the cylinder, thereby to control the operating movement of the piston; m'eans providing a pressure leakage path in the cylinder casing between the cushioning area and the cushion bore including a threaded cushion-adjusting screw cavity, a passageway therefrom into the cushioning area of the cylinder and an orifice opening therefrom into the cushion bore; a pulse generating valve comprising a valve casing and a longitudinally movable cylindrical valve plunger therein having an intermediate section of reduced cross-section controlling an annular passageway between coaxial fluid" pressure inlet and outlet chambers and being spring-biased at one end to move to the closed position andblock said passageway; said valve being connected with the cushioning area and the cushion bore to receive operatingpressure therefrom through pressure inlet chambers in the valve casing at opposite ends of the plunger and operate in response to a pressure differential in the cushioning-area pressure above the cushion-bore pressure at the end of the piston stroke and provide a fluid pressure pulse output through the valve as a monitoring signal for the cylinder operation; and control means connected with one of said valve chambers for operation in response to said pulse output. 11. A pneumatic cylinder monitoring system as defined in claim 10, wherein the operating pressure connection for the pulse valve with cushion bore is through the forward port in the cylinder casing, and

wherein the operating pressure connection for the pulse valve with the cushioning area of the cylinder is through a hollow adapter plug screw-threaded into the cushion adjusting screw cavity and providing ball closure means for the orifice and a pressure outlet therethrough from the cushioning area and said cavity for said connection with said pulse valve.

* II I I!

Patent Citations
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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3895560 *Nov 12, 1973Jul 22, 1975Leesona CorpCylinder motion sensing
US4002103 *Jul 1, 1974Jan 11, 1977The West CompanyReciprocating apparatus with a controllable dwell time at each end of the stroke
US4006666 *May 22, 1975Feb 8, 1977Towmotor CorporationCushioning device for a hydraulic jack
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CN101675254BFeb 28, 2008Apr 10, 2013伊利诺斯工具制品有限公司Pneumatically self-regulating valve
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WO2008124215A1 *Feb 26, 2008Oct 16, 2008Illinois Tool WorksValve with magnetic detents
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WO2008124220A1 *Feb 28, 2008Oct 16, 2008Illinois Tool WorksPneumatically self-regulating valve
Classifications
U.S. Classification91/1, 92/5.00R, 91/394, 91/396
International ClassificationF15B15/00, F15B15/22
Cooperative ClassificationF15B15/223
European ClassificationF15B15/22C