US3408465A - Pneumatic timing device having straight through operation - Google Patents

Description

Oct. 29, 1968 E. F. DUNCAN 3,408,465

PNEUMATIC TIMING DEVICE HAVING STRAIGHT THROUGH OPERATION Filed July 25, 1966 3 Sheets-Sheet 2 Inna 1||m "II I 6 /5 /7 3- 53 g /8 54 T m) 59 26 r 9 20 "2/ 43 I 29a 4 23\ II I I II I I 4 Oct. 29, 1968 E. F. DUNCAN 3,408,465

PNEUMATIC TIMING DEVICE HAVING STRAIGHT THROUGH OPERATION Filed July 25, 1966 5 Sheets-Sheet 5 34\ I 2/ v I 1l||l 1 5 14: 3 as 37 llllz i T ll --7a "HT T TLII HI ag. I I Z I HI United States Patent 3,408,465 PNEUMATIC TIMING DEVICE HAVING STRAIGHT THROUGH OPERATION Eugene F. Duncan, Milwaukee, Wis., assignor to Cutler- Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Filed July 25, 1966, Ser. No. 567,569 8 Claims. (Cl. 20034) This invention relates to adjustable pneumatic time delay devices and particularly to such devices to be used in conjunction with electrical switches such as limit switches.

Electrical limit swtches generally comprise a switch housing containing a precision snap action switch, and a multi-position operating head having either a rotary lever or top or side push type operator for actuating the switch contacts. The operating head assembly may be provided with optional features such as overtravel means for the operator, rotary and linear adjustment for the lever and various modified forms of levers as may be required according to the desired use of the switch.

In certain limit switch installations it is desirable to have a time delay period between the operator movement and the controlling contact function. This may be accomplished through an auxiliary device such as a time delay relay mounted on a central control panel. However, the panel may be some distance from the location of the limit switch and possibly out of view of the switch. In this instance, an individual must make blind adjustments to the timer and subsequently traverse the distance from the panel to the switch location to check his results, perhaps necessitating several such adjustments and trips.

It is therefore an object of this invention to provide a timing device which may be mounted to and function directly with a limit switch.

It is a further object of this invention to provide an adjustable timing device to be mounted to and function directly with a limit switch whereby adjustments to the timing device may be made at the switch location.

It is a further object of this invention to provide an adjustable timing device for a limit switch which is mounted between the switch base and the operating head of a standard limit switch whereby the timing feature may be added to a switch having any or all of the other features designed therefor.

Another object of this invention is to provide an adjustable timing device which may be operated from one side to cause actuation of a device on the opposite side thereof.

These and other objects will be more fully understood in the following specification and claims when read in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a front elevational view of the timing device of this invention mounted to a limit switch which is shown in dotted lines;

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1 showing an adjusting mechanism for the device;

FIG. 3 is a sectional view of the device taken along line 33 of FIG. 1 showing the device in one operating condition;

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FIG. 8 is an enlarged fragmentary sectional view of a portion of the mechanism shown in FIG. 2 drawn to an enlarged scale and taken along the line 8-8 of FIG. 9;

FIG. 9 is a fragmentary sectional view taken along line 99 of FIG. 8 showing a feature of the adjusting mechanism and drawn to an enlarged scale;

FIG. 10 is a fragmentary sectional view taken generally along the rotated line 1010 of FIG. 5; and

FIG. 11 is a sectional view similar to FIG. 3 showing a second preferred embodiment of the device.

As seen in FIG. 1, a timing device 2 is mounted between an operating head 3 and the base portion 4 of a standard limit switch having a rotary lever operator. The operating head 3 has a rotatable shaft 5 extending outwardly through one side to which is attached the operating lever 6. The operator 6 is adjusted to extend into the path of travel of a moving object which will rotate the operator out of its path as it passes by.

Rotation of the shaft 5 by operator 6 causes a camming member within the head to move a plunger 7a (FIG. 3), which extends into the timing device, toward the switch base 4. In the standard limit switch used without the timing device the plunger 7a is in direct engagement with a contact carrier means as indicated by the dotted line 8 in FIG. 7 and the described movement causes contact actuation of the switch 9 against the bias of return spring 10. Upon return of operator 6 to its original position the camming mechanism releases the plunger 7a and the spring 10 causes the plunger to return to its initial position. When the timing device 2 is incorporated into the switch, the plunger 7a extends into the device as shown in FIG. 3 and a second identical plunger 7b is provided with the device to extend into the switch base 4 to engage carrier means 8.

The joint between the operating head 3 and the base portion 4 of the standard limit switch is provided with a diaphragm type of seal to prevent foreign material from entering the switch. In the switch of this invention a similar seal 11 is provided at the joint between the operating head 3 and the timing device 2 and an identical seal 12 is provided between the timing device and the base portion 4. The upper surface of timing device 2 has an annular groove formed therein identically to the upper surface of the existing limit switch base portion and these grooves receive the peripheral portions of seals 11 and 12. A central aperture in each of the seals is received by a groove formed in the respective plungers 7a and 7b to provide a sealed joint therebetween. A small slit 11a and 12a is formed in seals 11 and 12, respectively, to prevent any build-up in air pressure on the outer sides of the timing structure as will be seen later.

The timing device 2 comprises two housing portions, a cover member 13 and a base member or valve body 14. The cover 13 has a central circular opening extending between' its upper and lower surfaces into which is pressed a bearing sleeve 15 to receive and guide plunger 7a. A pair of frusto- conical spring pockets 16 and 17 are formed in cover 13 which open to the bottom surface thereof. A transverse groove 18 (FIG. 4) is cut into the wall structures between the central opening and each of the spring pockets 16 and 17 and alined pairs of round ended slots 19 and 20 are formed on opposite walls of the groove 18, the slots being open to the bottom surface of cover 13 as shown most clearly in FIG. 10. A circular recess 21 is also formed in the bottom surface of the cover member.

The base member 14 has a circular recess 22 formed in its upper surfaces, which will become one surface and the sides of the timing chamber in later description, and another circular recess 23 formed in its lower surface. A circular central aperture extends between the recesses 22 3 and 23 and a bearing sleeve 24 is pressed into place within the aperture to receive and guide an intermediate plunger 25.

A diaphragm 26 is sealed along its peripheral flange between the lower surface of cover 13 and the upper surface of base 14. With particular reference to FIG. wherein the diaphragm 26 is shown in its relaxed position, the latter is provided with an annular oflset portion which lies adjacent the periphery of recess 22 to provide flexure for movement of the central portion of the diaphragm which overlies the recess 22 to become the remaining surface of the timing chamber. A pair of large washers 27 are provided on either side of the central portion of the diaphragm to provide that portion with a required rigidity. A central clearance opening is provided in the diaphragm 26 and the washers 27 to receive a screw 28 which takes into a threaded opening in plunger to secure the plunger to the underside of the diaphragm assembly. An annular ridge surrounding the central opening in diaphragm 26 is compressed by the plunger 25 to provide an air tight seal between the two members.

The lower end of plunger 25 has an annular groove which receives a sealing ridge surrounding a central opening in a flexible bellows 29 made of rubber or the like. Bellows 29 has a flat, outwardly extending annular flange portion 29a which is biased into and against a dished area in the upper surface of recess 23 by a closed-end helical compression spring 30 which bears against the flange 29a at approximately its mean diameter and seals at its other end in a spring retainer 31 pressed into the recess 23. Retainer 31 has a central opening through which the plungers 25 and 7b may extend, the latter being maintained in engagement with plunger 25 by the bias of the switch return spring 10.

A lateral slot 32 extends along the opening for plunger 25 in base 14 to communicate with recesses 22 and 23 as seen specifically in FIGS. 5 and 9. Slot 32 merges with a C-shaped groove 33 formed in the dished portion of recess 23 which is covered by the outer flange of bellows 29. When air is forced from the timing chamber due to a downward movement of the diaphragm 26 it passes through the slot 32 into the groove 33 and from there it is forced out between the flange 29a and the dished portion of recess 23. The flange 29a in this way functions as a one-way check valve allowing air flow in the above described direction and preventing air from returning into the timing chamber through the reverse path since a reverse air flow at the outermost portion of the flange 29a would tend to increase the pressure of the flange against the dished area.

In order to provide equal air pressure above and below the timing chamber for achieving greater timing accuracy, a passageway is provided which communicates between recesses 21 and 23, shown specifically in FIG. 9. Cover 13 and base 14 are provided with alined holes 34 and 35, respectively, and a similarly alined hole is provided in the sealing flange of diaphragm 26. A hole 36 connects recess 21 to hole 34 and a similar hole 37 connects recess 23 to hole 35, thereby providing a direct air passage between the two recesses.

The metering assembly to allow air to return into the timing chamber at a preset timed rate is shown specifically in FIGS. 2, 8 and 9. A square hole 38 is formed in the base 14 open to one exterior side of the base and terminating at the interior end in a minutely tapered frusto-conical hole 39. An air intake opening 40 is formed in the base 14 to connect hole 38 with recess 23 and a similar opening 41 connects hole 39 with the recess 22, or timing chamber. The side of base 14 through which hole 38 extends is further provided with a circular recess 42 formed concentric to the center of square hole 38. The recess 42 is in turn equally surrounded by a larger rectangular recess 43.

A metering pin 44, having a cylindrical body portion with an internally threaded opening at one end, is pro- 4 vided at the other end with a conical end portion44a which is concentric with the hole 39. The cylindrical body of pin 44 is further provided with a pair of offset transverse slots, each of which receives a triangular bearing wedge 45. As seen in FIGS. 8 and 9, the wedges 45 are held outward against the opposite corners of hole 38 by the threaded shank of an adjusting screw 46 which takes into the opening of metering pin 44. The shank of screw 46 is exposed to the hypotenuse of eachwedge 45 by the slots in pin 44 so that threads of the screw cut into each wedge to force the wedges into the opposite corners with sufiicient pressure to prevent the pin from rotating, yet allow the assembly to slide linearly along the holes 38 and 39. The width of the slots and the wedges are held to a very close tolerance to provide extremely small clearance therebetween. Since the threads of the screw cut into the wedges, an immediate directional response is afforded the pin upon rotation of the screw in either direction to thus eliminate any lost motion as would be present through the backlash of the ordinary thread engagement. A washer 47 placed in the circular recess 42 provides support for the free end of screw '46. 'A cover plate 48 is placed in the rectangular recess 43 and held there by screws 49. An 0 ring seal 50 is also placed in the recess 42 and is compressed between the walls of the recess, the head of screw 46 and the cover plate 48 when the latter is secured in place, to prevent foreign material from entering the timing chamber therethrough. Access to the head of screw 46 is had through an'alined opening in cover plate 48, this opening further being covered by a pivotable member 51 held by one of the screws 49.

Rotation of adjusting screw 46 in one direction causes the metering pin 44 to thread itself upon the screw through the aforedescribed slot and wedge arrangement, thereby causing the conical end 44a thereof to slide linearly outward with respect to the conical hole 39 and thus increase the clearance between the hole 39 and the end 44a to allow a greater passage of air into the timing chamber. The reverse rotation of screw 46 causes immediate reverse linear travel of end 44a with respect to hole 39 to thereby decrease the clearance between the two and decrease the passage of air into the timing chamber.

The seals 11 and 12 provide an eifective re-circulating air arrangement for the timing device 2 upon its assembly to the limit switch. The slots 11a and l2a allow for some air passage therethrough to prevent any great pressure differential on opposite sides of the seals as may build up within the operating head 3 or switch base 4, while preventing foreign material from passingtherethrough to interfere with the timing mechanism. In this regard, no extra air filtering assemblies are required since the air to be utilized for timing purposes remains within the timing device.

The operation of the device insofar as described may be seen with respect to FIG. 10 wherein the device is shown in its inoperated position, there being a spacer sleeve 52 disposed around the screw 28 between its head and the upper washer 27 of the diaphragm to raise the screw into engagement with theplunger 7a in the latter inoperative position. Upon movement of the lever 6, the camming mechanism of operating head 3 causes plunger 7a to drive the central portion of the diaphragm assembly to a point very near the lower surface of recess 22 to collapse the timing chamber and thereby exhaust the air therein through the slot 32, groove 33 and out between the flange 29a of bellows 29 and the dished portion of recess 23 as before described. The above movement also causes plunger 25 todrive plunger 7b toward thevswitch mechanism to simultaneouslyactuatethe switchcontagts 9. v I

p The return movement of the lever 6 to its original position causes the camming mechanism to remove its force from the plunger 7a and hence the diaphragm 26.

The return spring of the switch mechanism then biases the diaphragm to its original relaxed position through plungers 7b and 25 against the vacuum created within the timing chamber. The diaphragm returns to its original position at a controlled rate due to the metered air intake to the chamber through holes 40, 38, restricted hole 39 and opening 41, thereby affecting a time delay period between the release of the operating lever 6 and the deactuation of the switch contacts 9.

When used as described above, the timing device is described in the art as off delay device. An on delay device may be provided within the same basic timing device structure by the addition of certain parts as hereinafter described.

The pairs of alined slots 19 and of cover 13 receive pivot pins 53 and 54, respectively. The pins are held against the closed ends of the respective slots by pairs of flathead screws 55 as shown in FIG. 4, the tapered heads of which engage conical end portions formed on the pins 53 and 54. A pair of levers 56 and 57 straddle the pins 53 and 54, respectively, within the slot 18 at substantially their midportions to pivot about the pins, the lever 57 being positioned reversely to the lever 56. The adjacent ends of the levers extend into the central opening of cover 13 to engage the interior end of plunger 7a. The opposite ends of the levers bear against the surface of the upper washer 27 of the diaphragm. Helical compression springs 58 are placed in the spring pockets 16 and 17 to bias the levers against the washer 27 through spring caps 59.

The timing device as just described is shown in FIG. 3 in its inoperated position, the lever 6 of the operating head and hence plunger 7a, being in their normal position. In this position the springs 58 bias the levers 56 and 57 to the position shown wherein the timing chamber is collapsed and the adjacent ends of the levers engage the interior end of the plunger 7a in its inoperated position. The plunger applies a constant force to the plunger 7b against the bias of spring 10 to maintain the contacts 9 actuated.

Rotation of the lever 6 by a passing object operates the camming mechanism to force plunger 7a inward, driving the adjacent ends of the levers 56 and 57 downward which raises their opposite ends free of the diaphragm assembly and against the bias of springs 58. The bias of return spring 10 urges the diaphragm to its relaxed position through the plungers 7b and 25 against the vacuum in the timing chamber. Air is metered into the timing chamber through the metering pin assembly as before described to provide in this instance a controlled time delay between the operation of the operating lever and the deactuation of the switch mechanism, known in the art as an on delay.

From the foregoing it may be seen that there is provided a timing device which is adjustable, is capable of having either of two types of time delay operations within identical superstructure, and which is relatively inexpensive to manufacture and supply. In addition there is provided a timing device having a centrally located straight through operating actuating mechanism which allows the superstructure to take on various forms to comply to the product to which it may be associated with to permit a building block, or modular structure. The device also uses a substantially captive recirculating air supply which requires no external filtering assemblies for an outside air source.

It should be understood that the device as described and shown in the foregoing is merely exemplary of certain preferred embodiments and is not intended to limit the scope of the appended claims.

I claim:

1. A pneumatic timing device comprising, in combination, a housing having a cavity therein, a flexible diaphragm secured along its periphery to said housing in sealed relation thereto and having a central portion forming a chamber with a portion of said cavity in a normal position of said diaphragm, means biasing said central portion of said diaphragm to said normal position, first and second openings in said housing extending from said cavity to exterior surfaces of said housing and being on opposite sides of said diaphragm, a plunger member secured to said central portion of said diaphragm within said chamber and extending through the first one of said openings, flexible sealing means providing an air-tight seal between said plunger and said first opening and permitting reciprocable movement of said plunger within said first opening, means extending through said second opening for causing movement of said central portion of said diaphragm in one direction to eifect movement of said plunger within said first opening, one-way valve means permitting substantially unrestricted passage of air out of said chamber upon movement of said central portion away from said normal position, and metering means permitting air to enter said chamber at a controlled rate upon movement of said central portion to said normal position.

2. The combination according to claim 1, wherein said first and second openings in said housing are in axial alinement and movement of said central portion of said diaphragm by said means extending through said second opening in one side of said housing effects responsive movement of said plunger through said first opening in the opposite side of said housing.

3. The combination according to claim 2, together with lever means mounted to said housing to engage said central portion of said diaphragm at one end thereof and said means extending through said second opening at the other end thereof, a second biasing means acting upon said lever means for biasing said central portion of said diaphragm in one direction, and wherein movement in one direction of said means extending through said second opening causes movement of said lever means against the bias of said second biasing means to eflFect movement of said central portion of said diaphragm and said plunger in a reverse direction.

4. The combination according to claim 2, wherein said one-way valve means in said flexible sealing means comprise a resilient bellows member having a centarl opening to receive the outer end of said plunger in sealed relation thereto and further having a peripheral flange which lies along and closely conforms to a surface of said housing adjacent said first opening, together with a third biasing means to hold said flange against said surface. s

'5. The combination according to claim 4, together with a switch operating structure secured to said one side of said housing in sealed relation thereto, a switch housing structure secured to said opposite side of said housing in sealed relation thereto, and a passageway within said housing extending between the areas on either side of said chamber for providing equal air pressure on either side of said chamber.

6. The combination according to claim 5, wherein said metering means comprises a pasageway extending between said chamber and one of said areas, and a tapered pin within a correspondingly tapered portion of said passageway, said pin being adjustable within said portion to provide a variable restriction in the air flow from said area into said chamber.

7. The combination according to claim 6, wherein said metering means further comprises an elongated opening of rectangular cross section open at one end to an exterior surface of said housing and terminating at its other end in a frustoconical portion, a metering pin having a cylindrical body portion terminating at one end in a tapered pin formed to be complemental to and concentric with said frusto-conical opening, a threaded opening in the other end of said cylindrical body portion to receive an adjusting screw therein, the head of said screw being assemble within said opening to said exterior surface, sealing means for providing a seal between said screw and said opening, a plurality of transverse grooves formed in said body portion, a plurality of wedge members seated within said grooves and having portions extending outwardly of said body portion to engage the walls of said rectangular opening for preventing rotation of said body portion within said opening, whereupon rotation of said adjusting screw in one direction causes said tapered pin to move -1inearly and non-rotatably into said frusto-conical opening toincrease the restriction of air flow into said chamber.

8. The combination according to claim 7, wherein said wedge members are triangular in shape, the hypotenuse 10 of which seats upon said screw within said groove and engages a bottom portion of said groove and the remaining edges thereof engage respective sides of said rectangular opening, and wherein there is provided at least 8 two of said wedge members oppositely disposed on said body portion, the apeces of which engage vdiagonally opposite corners of said rectangular opening.

References Cited v UNITED STATES PATENTS' 3,246,094 4/1966 Zaske et a1 ZOO-34 X 3,261,958 7/1966 Bittner 20034X ROBERT K. SCHAEFER, Primary Examiner.

HERMAN O. JONES, Assistant Examiner.

Claims (1)

1. A PNEUMATIC TIMING DEVICE COMPRISING, IN COMBINATION, A HOUSING HAVING A CAVITY THEREIN, A FLEXIBLE DIAPHRAGM SECURED ALONG ITS PERIPHERY TO SAID HOUSING IN SEALED RELATION THERETO AND HAVING A CENTRAL PORTION FORMING A CHAMBER WITH A PORTION OF SAID CAVITY IN A NORMAL POSITION OF SAID DIAPHRAGM, MEANS BIASING SAID CENTRAL PORTION OF SAID DIAPHRAGM TO SAID NORMAL POSITION, FIRST AND SECOND OPENINGS IN SAID HOUSING EXTENDING FROM SAID CAVITY TO EXTERIOR SURFACES OF SAID HOUSING AND BEING ON OPPOSITE SIDES OF SAID DIAPHRAGM, A PLUNGER MEMBER SECURED TO SAID CENTRAL PORTION OF SAID DIAPHRAGM WITHIN SAID CHAMBER AND EXTENDING THROUGH THE FIRST ONE OF SAID OPENINGS, FLEXIBLE SEALING MEANS PROVIDING AN AIR-TIGHT SEAL BETWEEN SAID PLUNGER AND SAID FIRST OPENING AND PERMITTING RECIPROCABLE MOVEMENT OF SAID PLUNGER WITHIN SAID FIRST OPENING, MEANS EXTENDING THROUGH SAID SECOND OPENING FOR CAUSING MOVEMENT OF SAID CENTRAL PORTION OF SAID DIAPHRAGM IN ONE DIRECTION OF EFFECT MOVEMENT

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