US2839929A - Solenoid operated trip mechanism - Google Patents

Description

n 1958 w. F. HURLBURT, JR 2,839,929

SOLENOID OPERATED TRIP MECHANISM Filed Aug. '14, 1953 4 Sheets-Sheet 1 INVENTOR W/LBUR E HURLBURT. JR.

ORNEY7 June 24, 1958 w. F. II-IURLBURT, JR 2,839,929

I SOLENOID OPERATED TRIP MECHANISM Filed Aug. 14. 1955 4 Sheets-Sheet s 50 5 T1|: ."7.z 5;; 5a

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une 4, 1958 w. F. HURLBURT, JR 2,839,929

SOLENOID OPERATED TRIP'MECHANISM Filed Aug. 14. 1953 I 4 Sheets-Sheet 4 INVENTOR: M451? A #024 30/??- Me.

United States Patent ()fiice SOLENOID OPERATED TRIP MECHANISM Wilbur F. Hurlburt, In, West Orange, N. J., assignor t Automatic Switch C0., Orange, N. J., a corporation of New York Application August 14, 1953, Serial No. 374,283

Claims. (Cl. 74-2) My present invention relates generally to operating mechanisms for valve stems or the like, and has particular reference to operating mechanisms suitable for free-handle manual-reset valves.

In an installation of the character referred to, the setting of the valve into and out of various positions is under the manual control of an operator only so long as a certain condition, or a selected set of conditions, is maintained; and in the event that any of the conditions is or becomes different from What it should be, the valve automatically closes (or opens, as the case may be) and the manual control is rendered completely inefit'ective, and remains so, until the desired conditionsare re-established.

The existence or establishment of the desired condi tions is usually caused to manifest itself by the energization of an electromagnetic means such as a solenoid, and no manipulation whatsoever of the valve handle or other control is effective to re-open or otherwise reset the valve until the contemplated energization of the solenoid. occurs. 7

While the invention is primarily directed to the opening and closing, or other setting, of valves, it will be understood that certain phases of the invention are of broader scope and may beapplicable to the setting of other mechanisms or devices where it is desired that there be manual control under a pattern of predetermined conditions and an automatic rendering of the manual control ineffective wheneverthere is a deviation from such pattern.

While mechanisms of this type are of general utility, they are especially useful for the operation of .valves that are to function automatically under predetermined faulty conditions to interrupt the flow of liquids or, gases, such as fuel, or to initiate flow, as in sprinkler systems. This automatic operation functions to disengage manual operating means in a manner that requires manual reengagement thereof to return the valve to its normal position when the faulty conditions no longer obtain. The automatic operation may be caused to be in response to pressure or temperature changes, the presence or ab.- sence of water vapor or other impurities in a gas, electrical failure, or the happening of other events that may or may not be directly associated with the system being controlled.

Prior mechanisms of this nature have often involved relatively expensive and complicated structures which generally limited their use. Moreover many of the prior mechanisms required careful and delicate adjustment in order to insure stability and dependability, thus adding to the cost and complication of manufacture. Accordingly it is one object of this invention to provide an improved, relatively inexpensive, staunch and reliable free-handle reset valve that can be readily tripped in response to a departure from a normal or predetermined condition and which may be simply and easily restored to manual control upon the re-establishment of such-70 Another object of the invention is to provide-a new condition. 1

2,839,929. Patented June 24, 1958 the handle releasing and valve operating means may be fabricated by relatively inexpensive procedures such as punch press operations and the like and yet provide a highly sensitive and stable mechanism virtually unaffected by frequent actuation and extended use.

Still another object of the invention is to provide a structure characterized by its simplicity and positive response to departures from predetermined or normal conditions.

A further object is to provide a releasable holding means or latch mechanism wherein very small pressures may be used to maintain engagement of the handle and valve to hold the valve in one position and wherein the absence of such slight pressure will effect positive and immediate disengagement of the handle and permit the:

valve to be instantly moved to another position.

A particular feature of the invention, involving a:

special time-delay mechanism, is applicable not only to.-

their short duration are adequate in magnitude to activate a the electromagnetic control instrument. For example,'if the latter is arranged to hold the valve in a predetermined. setting so long as electric power is maintained, and to release or trip it on power failure, any momentary power'failure of even one second duration or less is a source of annoyance. An instance of this would be, for example, the needless shutting off of gas furnaces with a resultant undesirable cooling before the safety valve can be reset and the furnaces restarted. It is one of the objects of the present invention to obviate this disadvantage by means of a time-delay arrangement that bridges over such momentary power fluctuations or' failures by delaying the activation of the electromagnetic instrument whenever it is conditioned to become operativeto close or open or otherwise operate the valve. 7

The above and other'objects and advantages will become more apparent. in the following description and accompanying drawings forming part of this application.

In the drawings:

Figure l is a perspective view of a valve constructed in accordance with the invention, the operating handle being of the wheel type;

Figure 2 is an enlarged cross-sectional view of the line 66 of Figure 8 with the operating mechanism in position;

and improved valve of the free-handle type whereinthe engaged position; 1

Figure 7 is a cross-sectional view taken along the line' 7.7 of Figure 2;

Figure 8 is a partial-cross-sectional view similar to Figure .2 with the operating mechanism in the engaged vFigure 9 is-a side elevation of the valve shown in Figure '7taken along the line cover plate removed;

Figures: 10 and l1';are diagrammaticperspective views a 9-9 thereof and with the' 3' of the operating mechanism in the engaged and disengaged positions respectively; a

Figure 12 is one embodiment of an electrical circuit for operating the valve in accordance with the invention;

Figure 13 is a fragmentary view similar to Figure 2, illustrating a modified construction iniwhich the operating handle is of the pivoted lever type; a I

Figures-l4, and 16 are fragmentary views showing the parts in the various relative positions they assume during manual control of the valve; and

Figure 17 is a cross-sectionalview along the line 17-17 of Figure 16. 1

The valve operating mechanism of this invention provides a simple and positive structure for the attainment of desired safety features and has the advantage that only slight pressure is required to maintain operative engagement of the operating handle with the valve mechanism, a release of this slight pressure resulting in an instantaneous and positive disengagement of the handle. This operation involves the use of a collapsible link assembly between the valve handle and valve disc so that the major force exerted by the handle to open (or close) the valve against the pressure of a valve spring is carried by the links when in a folded or heated position; The links can be maintained in this nested relation by only a slight transverse pressure which when released permits the links to collapse and enables the valve to be operated instantaneously in response to the valve spring notwithstanding the position of the operating handle. Furthermore, positive disengagement of the handle is effected since the force of the valve spring which functions to close (or open) the valve also causes collapse of the linksout of nested relation when the transverse pressure is released.

A perspective view ofone embodiment of the invention is shown in Figure 1. In this figure, the valve body is denoted by the numeral 10, and immediately above the body is the mechanism unit 11. The unit 11 houses the handle engaging andydisengaging apparatus which I have shown associated .with a handle of the hand wheel type. The wheel 14 carries a threaded part 13 and cooperates with mechanisms within the cylindrical housing part 12. While the illustrated embodiment of the invention is a hand wheel operated Y valve it is to be understood that theinvention 'is equally applicable to other types of globe and gate valves, such as those operated by a lever type handle" (Figure .13.) or wherein the valve and stem assembly are at right angles or otherwise ar ranged with respect to the fluid flow.

Referring more specifically to Figures 2 and 7, the

valve body I have chosen to show includes a fluid condiiit 15 having threaded end sections 16 and 17 for connection with a system to be controlled. Joined with the conduit 15 at an angle of about 45 is the valve housing 18 having a cylindrical opening 19 for receiving certain elements of the valve operating structure. The valve housing 18 is formed integrally with the conduit 15 and comprises part of the supporting structure for the valve and operating mechanism.

Within the fluid conduit 15 is a valve seat 20 formed in the conventional manner for cooperating with the valve 21. The latter has a cylindrical body 22 containing a circular seat 23 of resilient material retained in position by a circular washer 24 threaded to the cylindrical center 4 ing 32 which has a flanged bottom section 33 secured to a corresponding flanged part 34 of the valve body 10 by means of bolts 35. These flanges 33 and 34 are sealed one to the other by means of an O ring 36 retained within a groove 37 in the valve body 10 by a downwardly extending circular flange 38 formed integrally with the flange 33. The valve stem 26 is journaled within a 4 cylindrical bearing 39 having a flange 40 secured to the bottom wall 41 of housing part 32 by bolts 42. An enlarged cylindrical section 43 of bearing 39 cooperates with a corresponding opening in housing 32, and a downwardly extending part of reduced diameter 44 holds the spring 31 in alignment with the stem 26. This spring 31 is interposed between the flange 40 and valve body 21 and the lower end of the spring is held in alignment by the head of plug 27.

The valve operating parts 14 and 13 are operatively supported within the housing 12 extending from the top side of the mechanism unit 11-. The part 13 is provided with single or multiple threads 45 which cooperate with an internally threaded rectangular sleeve or element 46 slidably mounted for longitudinal movement within a flanged guide bearing 47. This bearing is locked in an opening 48 in the upper end of housing 32 by means of a sleeve 49 and screws 50. The lower end 51 of the element 46 is rigidly secured by rivets 59 to an extension 56 that extends downwardly for cooperation with the link assembly. If desired, parts 46 and 56 may be 'formed of a single piece. I

The hand wheel and operating assembly are retained in position on the housing 32 by a flanged plug 52, closing the upper end of sleeve 49 and having a central opening 53 for receiving the hand wheel part 13. With this arrangement rotation of the hand wheel 14 rotates the part 13 relative to the rectangular element 46, moving the latter upwardly or downwardly depending on the direction of rotation of the wheel. tamed against longitudinal movement by lock rings 54 The part 13 is rebearing against the plug 52; and the downward movement of the element 46 is limited by a lock ring 55 which cooperates with the upper side of the bearing 47.

Inoperation, when the link assemblywithin the unit 11 operates to couple the end 51 of element 46 with the upper end. 26"of valve stem 26, rotation of the hand wheel will function to open and close the valve 21 in the normal manner. The valve may be fully or partially opened, as may be desired. Under conditions when the link assembly 'is'collapsed, however, the valve stem 26 is free to move downwardly'under the influence of spring 31 to close valve 21, and operation of the hand wheel Mwill have no effect whatever on the stem 26.

iThe'link assembly coupling the element 46 with the valve stem26 comprises two links 57 and 58. They are shownin the collapsed or disengaged relationship in Fig u'res '2, 5, 7, 11 and 13. The upper or first link 57 is pivotally coupled to the lower end of extension 56 by a pivot pin 60. The part 56 is in the form of a channel to accommodate the link 57 (Figures 6 and 10), and the latter isalso preferably of channel cross-section so as to piece 25 of the valve body 22. The valve stem 26 is coupled to the valve body 22 by means of a threaded plug 27 slidably surrounding the stem 26 and threaded into an opening 28 withinthe piece 25. A flange 29 retains the stem in the plug 27 and cooperates withthe plug to open the valve 21 when thestem is lifted; A small spring 30 is interposed between the flanged end of the valve stem 26 and the bottom of the'cavity 28 and will give under the action of the stem to limit the pressure between the valve body 21 and the seat 20 to that provided by the main valve spring 31.

.;'Ihe.va1ve and stem assembly is supported the housaccommodate the second or lower link 58. The link 58 is pivoted to link 57 by a pin 61 and is pivoted at its outer end" by a pm or bolt 62 (Figure 7) to the slotted upper part 26' ofvalve stem 26.

The pivot pin 61 is somewhat longer than the width of the llIlk 57 so that it can enter a pair of slots 63 in the 'sides of part 56. The link 53 is also provided with arecess 64' toreceive the piir when the linksare in the folded or nested position.

The pivot pin 60 lies and always remainsin the line of valve movementwhich in this case is coincident with the axis of:the'valve stem 26. Actuation of the handle moves the pin60 up. and down along the line of valve movement but these movements are transmitted to the valve itself With the links in the open position as shown in Figures 2 and 11, it is apparent that vertical displacement of the element 46 by operation of the hand wheel 14 will not function to control the valve. The handle is therefore completely free and ineffective and it cannot be operatively engaged with the valve until the operating links 57 and 58 are moved to and retained in the nested position as shown in Figures '6, 8 and 10. 7

To place the liiiks 57 and 58 in the nested position the hand wheel 14 is operated to move the element 46 to its downward position. This action will cause the links to assume the nested relation, with the ends of the pivot pin 61 engaging the bottom of the slots 63. The depth of these slots 63 is preferably such that the pin 61 will move to a position just approaching and closely adjacent to (but not in line with) the center line of the valve stem 26 and hand wheel element 46. If desired, the slots 63 may be deep enough to allow the pin 61 to come into full alignment with the center line axis, but in that case provision should be made for some auxiliary force, such as that afforded by a light spring or the like, to push the linkage out of the dead in-line position when the solenoid is de-energized.

The links are retained in the nested position by a lateral pressure exerted upon them, preferably upon the connecting pivot 61. I have shown a triangularly shaped cam or rocker element 65 secured to the wall 66 of housing 32 by a rocker pin 67. The pin 67 is carried by cars 68 formed on the rocker 65 and supported by a bracket 69 fastened to the wall 66 by screws 70 (Figures and 6). The broad end of the cam plate 65 is bent to provide a sloping surface or cam 71 extending generally in line with the folded link assembly. This surface 71 cooperates with a roller 72 (Figures 5, 6, and 11) carried on one end of the pivot pin 61 so that when the links are in the nested relation and the sloping surface 71 is raised as shown in Figures 6 and 10, it will bear transversely against the pin 61 to hold the links in the nested positionand against the action of the main valve spring 31. The sloping surface 71 is made long enough to maintain sliding contact with the roller 72 through its entire travel from a closed valve position to a fully open valve position. When the plate 65 is rotated in a clockwise direction as viewed in Figures 5 and 6, the transverse pressure on roller 72 and pin 61 is released whereupon the links will fly to an open position as shown in Figure 11 under the action of valve spring 31.

Operation of the cam plate 65 is controlled by an electromagnet contained within a housing 73 on the side of the mechanism unit 11 as shown in Figures 5 and 6. The magnet includes a coil or winding 74 having a central pole piece 75 terminating at one end within the coil and having its other end threaded for engagement with and support by the housing 73. A nut 76 may be used to secure this pole'piece in place. The plunger 77 extends through an opening 78 in the wall 66 and through a corresponding opening in the housing 73 in line with the center pole piece 75 and the central opening of the coil 74. The outer end of the armature or. plunger 77 is provided with a circular groove 79 for engagement'with a recess. 80 in the rocker 65, and isheld in the upward position as shown in Figure 5 by a collar 81 and a spring 82 encircling the plunger and held between the collar and the spacer 83 between the housing 73 and wall 66. Thus when the coil 74 is not energized the plunger 77 moves upwardly, lowering the sloping surface or cam 71 and permitting. the links 57 and 58 to fly open. When the coil is energized the cam 71 is raised as shown in Figure 6 to hold the links in the nested or engaged position.

This" embodiment of the invention includes visual means for indicating theposition of the..valve 21 relative to the seat 20. This is accomplished bymeans of a bracket member 84 (Figure 7 carried by the valve stem 26. The upwardly extending arm 84' of this bracket lies behind a window 85 in the cover plate 86 of housing 32 6 as seen in Figures 3 and 7. The window may be provided with markings 87 which cooperate with means on the bracket arm 84 to indicate the amount the valve is opened.

In order also to provide a remote indication or signal of opening and closing of the valve, means are provided in the form of a bell-crank comprising a shaft 88 (Figures 7 and 9) and a pair of arms 89 and 90 The shaft 88 is iournaled in the wall 66 of housing 32 and carries on its inner end the lever arm 89 which cooperates with one end of the pivot pin 62. The outer end of shaft 88 carries the arm 90 which cooperates with a microswitch 91 within the housing 92 carried on one side of housing 32. When the valve stem 26 is in its lowermost position as shown in Figure 7, the pin 62 contacts the recess 89' in arm 89 to move it in a counter-clockwise direction as viewed in Figure 9. This moves the arm 90 to actuate the microswitch. When the valve stem 26 is lifted even a few thousandths of an inch the switch is disengaged by arm 90 and returns to a position indicating that the valve is open. Any suitable signaling system such as lights,- buzzers and the like, well known in the art, may be op-' erated by the switch in any desired manner.

As pointed out above, the solenoid 74, 77 functions to control the engagement and disengagement of the valve handle 14 with the valve 21 and usually it is desirable to have engagement effected when the magnet is in the energized condition. Experience has indicated that disengagement of the handle and closure (or opening) of the valve often results from brief temporary interruptions of the energizing current. In most cases it is therefore desirable to interpose a delay system so that transient effects like these will not operate to actuate the valve. While this may be accomplished in a variety of ways (as for instance the use of a dash pot mechanically coupled with the solenoid plunger 77), it has been found that electronic procedures provide the greatest latitude in attaining the desired delay time fora given valve. For this purpose a direct current magnet is employed and means in the form of a condenser is bridged across the coil. In view of the prevalence of alternating current a typical circuit for attaining this is shown in Figure 12. An alternating current is connected to terminals 93 and 94 and the latter is connected to one terminal 99 of the coil 74. The other terminal 93 is connected to terminal 98 through the series-connected switch 95, resistor 96 and rectifier 97. When switch is closed, coil 74 will be energized by the rectified current which is limited by the resistor 96. Delay is eifected by bridging a condenser 100 across coil 74, and the extent of the delay is a direct terminals 93 and 94 can be interconnected directly with such power source.

. To illustrate the applicability of the features of the in vention to. valves of varying kinds, I have shown in Figures 13-17 how the basic linkagecan be employed with ahandle of the pivoted lever type;

The links, 101 and 102 are pivoted to each other at 103. The outer end of the upper or first link 101 carries a pin 104 by means of which it is articulated to the operating handle 105. The outer end of the lower or second link 102 is pivoted at 106 to the valve stem to be moved. Except for the mode, of articulation of the linkage to the handle, .it may beassumed for the purpose of this description that the valve and all its parts are essentially the same as hereinbefore described.

The pin 104 lies and is maintained in the line of move mentof the valve which is, as'before, coincident with the axis of the valve stem 107. When nested in overlying relation the links 101, 102 overlap, as shown in Figures 14-16, and the connecting pivot pin 103 lies in, or: almost in, the line of valve movement. If absolute-alignment, is provided for, a smallauxiliary spring or other force,'as hereinbefore mentioned, is needed to push the pin 103 out of the deadcenter position when collapse of the linksis to be effected.)

The releasable holding means is the same as that hereinbefore described, comprising a pivoted cam plate 108 having a dimension of adequate magnitude inthje direction of'valve movement. A cam follower 109 (here shown as a rounded end on the pin 103) remains in contact with the cam plate in all settings of thevalve, so long as the cam is held by the electromagnetic instrument, such'as a solenoid, in the effective position in which it bears laterally against the follower 109.. Whenever the cam plate 108 isshifted aside (e. g., by dp-energization of the solenoid) the lateral, pressure on the nestedlinks isremoved and they fly open into the collapsed relation of Figure 13 in which the handle is completely ineffective. As in the structure shown in Figures 1-11, the movement of the holding means, viz., the cam plate, from a linkholding to a link-releasing position, is along a direction transverse to its effective direction of .pressure against the links so that it withdraws immediately from the path of linkage collapse.

The handle 105 is pivoted to thehousing at 110 and is adapted to move between the fullline and dotted posi I tions indicated in Figure 13. In the construction illustrated a spring 111 (Figure 17) constantly urges the handle into the full-line position, but the use of such a spring is not essential. I

The inner lever arm of the handle 105 is provided with a slot with which the pin 104 engages. In'the illustrated embodiment of the invention the innerarmof the handle is forked, consisting of two spaced arms 112 (Figure 17) and each of these arms is provided with the slot referred to, but since the slots are identical and in alignment, and the arms 112 move and function as a unit, the,

inner part of the lever is referred to hereinafter as a single arm" 112 having a slot 113 formed in it.

In. order that the pin 104 shall always remainin the line of valve movement its ends are providedwith rolling parts or elements 11.4 that are caused to ride along fixed guide rails 115, the slot 113 being curved, as shown, so as to urge the elements 114 constantly against theserails.

When the parts are in the relationship shown in Figure 13 and the conditions required to be met by the particular'installation are faulty or unfulfilled, the handle 105 is ineffective to control movements of the valve stem 107, and the latter will remain under the influence of a valve spring (not shown) or other forces to hold it in the position illustrated. The handle 105 can be moved, but this merely shifts the links 101, 102 back and forth between the collapsed and nested positions and imparts no lifting forceto the valve stem 107. I

Once the required conditions have been established, the cam plate 108 will be pivoted from the dotted to the full line position shown in Figure 17, this being accomplished by a solenoid or other electromagnetic instrument as hereinbefore described. ,The handle is then moved to the dotted position shown in'Figu re 13, and during this manipulation the links 101, 102 fold up into nested overlying relationship and the follower 109 snaps into a position behind the hump in the cam plate (Figure 17). The oblique extended margin of the latter is a holding means that now bears lightly against thefollower 1'09 and thusmaintains the links, in nested relation. This condition obtains so long as the solenoid keeps'the holding means effective. in this relationship of the parts the handle can'be moved downwardlytFigures 14, 15, 16) and this will transmit an eifective force to the valve stem 107 to lift in into the desired position.

A release of the holding means to shiftit to dotted position of Figure 17 will immediately result and adapted to swing into and out of link holding postnically; designated valves and has theimportant advantages of simplicity of structure, complete dependability, and low cost; Moreover the holding mechanism may be readily set and reset without the application of large forces and the'only stresses supported by the mechanism in the case of the valve shown, for instance, are those produced by the valve operating spring.

While the manually operable handle has been shown in one case in the form of a hand wheel, and in another case in the form of a lever, it will be understood that the valve may be caused to move by other well-known manually operated elements or devices. The term handle as used herein and in the appended claims is intended to include all such instrumentalities within its scope.

While only two embodiments of the invention have been illustrated and described it is apparent that many changes and modifications may be made without necessarily departing from the true scope and spirit of the invention as expressed in the appended claims.

. Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. In a mechanism for moving a valve stem or the like along a predetermined line, a handle, a linkage between the handle and stem comprising a pair of links joined end to end by an intermediate pivot, one of said links having its outer end articulated to the handle and the other link having its outer end pivoted to the stern, said links being movable into and out of an overlying relation in which said intermediate pivot is substantially aligned with the line of stem movement, a housing enclosing said linkage, and releasable holding means within said housing and independent of said handle and linkage and adapted to bear laterally against said intermediate pivot to hold the links in overlying relation and therebyr render said handle effective to move said stem.

2. In a mechanism of the character described, the combination of elements set forth in claim 1, said holding means comprising 'a cam having an operative surface of substantial dimension parallel to said line of stem movement.

3. In a mechanism of the character described, the combination of elements set forth in claim 1, said holding means comprising a cam mounted for pivotal movement on an axis parallel to said line of stem movement and adapted to swing into and out of link'holding position.

14. In a mechanism of the character described, the combination of elements set forth in claim 1, said holding means comprising a cam mounted for pivotal movement on an axis parallel to said line of stem movement tion, said cam having an operative surface of substantial V dimension parallel to said line of stem movement.

r5. In a mechanism of the character described, the combination of elements set forth in claim 1, said hold- 7 ing means comprising a cam mounted for movement into and out of link holding position, and an electromagnet.

having an armature coupled to said cam to control its movement. V

6. In a mechanism for operating a valve stem or the like by movementof the stem along a predetermined line, a handle, a pair of links pivoted to each other end to end, the first link'having its outer end articulated to the handle and lying in the line of movement'of the valve stem, the second link having its outer end pivoted I to the valve stem, said links being movable into and'out of an overlying relation in which their 'outer ends are in proximity and the links are substantially in alignment with said line of valve stem movement, and releasable holding means adapted to bear laterally against said links 9 to retain them in their overlying relation and thereby render the handle effective to operate the valve stem, said holding means having a substantial dimension parallel to the line of stem movement so that said holding means so long as it is unreleased .remains eifective in all positions of the stem.

7. A stem operating mechanism as set forth in claim 6, said handle comprising a lever mounted for pivotal movement and provided with a slot, said articulation with said first link comprising a pin carried by said link and engaging Within said slot.

8. A stem operating mechanism as set forth in claim 7, in combination With guide means constraining said pin to remain constantly in the line of stem movement.

9. A stem operating mechanism as set forth in claim 8, said guide means comprising a rail against which said pin bears.

10 10. A stem operating mechanism as set forth in claim 9, said lever slot being contoured to press the pin against said rail in all positions of the handle.

References Cited in the file of this patent UNITED STATES PATENTS 925,673 Zook June 22, 1909 1,644,171 Caldwell Oct. 4, 1927 1,672,049 Almquist June 5, 1928 2,014,101 Bryan Sept. 10, 1935 2,218,606 Foster Oct. 22, 1940 2,301,876 Hurlburt Nov. 10, 1942 2,456,078 Paille Dec. 14, 1948 2,630,832 Lutherer Mar. 10, 1953 FOREIGN PATENTS 191,599 Great Britain Jan. 18, 1923

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