US2703117A

US2703117A - Power-actuated sawmill carriage dogging apparatus

Info

Publication number: US2703117A
Application number: US332667A
Authority: US
Inventors: Elenbaas George
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-01-22
Filing date: 1953-01-22
Publication date: 1955-03-01
Anticipated expiration: 1972-03-01

Description

March 1, 1955 G. ELENBAAS 2,703,117

POWER-ACTUATED SAWMILL CARRIAGE noccmc; APPARATUS Filed Jan. 22, 1953 aim: 4 l

\\Ill (350265 BLIENBAAS INVENTOR.

, V BY l. 22 29 A? 3 Q5 United States Patent ,POWER-A'CTUATED ISAWMHLL CARRIAGE LDOGGING ABPARATUS "George Elenbaas, Ocean "Falls, British Columbia, Canada Application 'January22, 1953, Serial No. 332,667

11 Claims. -(Cl. -143125) power consumption thereof.

Another object is to provide 'a dogging mechanism that continually exerts the maximum clamping 'force while in operation and "consequently automatically maintains the'holdof the'tong'armson the log'ortimbereant.

Still another object of the invention'is to provide a clampingmechanism for the tong arms including pneumatic or hydraulically operated motors wherein torsional and bending stresses are not exerted on the cylindersand piston rods'of said motors.

It is a further object -to provide an improved sawmill dog which has advantages over those constructedheretofore inrespect to ease and 'econorny'of manufacture, ease and simplicity of operationaridfiexibility of operation.

"In accordance with the illustrated embodimentrof my invention 1 'have'provided inlcombination witha sawmill :carriage knee a 'pair. an elongated tong members :pivotally mounted intermediate theirsen'ds "on :a' horizontallyreciprocable cross-head located rearwardly of athe knee. Aaverticalrguidewayrisrarranged adjacenttthe aknee, the 111131361 and lower: tongs'eachrhaving: means ttOfCOaCiWVith T the guideway whereby the itongs iaretconstrained 'to"follow r-the zguideway in a verticalaplane perpendicular fto the :face of rthesknee.

Mounted :on each .of the r tongs f is .a :fiuid rpressure 1 mo- 1 tor:having a :piston :reciprocally. movable: longitudinally; of sthe ttong. Connected ate the pistons *and running rover sheaves: rotatably: mounted: on the tongs between ithetmotors and: the log-engaging ends isua flexible: element where- :by,:upon movementiof thezpistonsxofthe respective :mo- .tors "rearwardlyaof .the (ton gs, :the 'forward, logsen-g-aging ends thereof will aberdrawn together. :A--- second: flexible :element is arranged at:the rearward ends: :of theitong'lnembers, one end bein-g secured .tothe:pistonofnthe motor 10f the uppentong:andrpassing over-aasheave on the-rear- -ward=end .thereof :and the other end-.beingwsecureda to the rearward: end .ofthe lower tong,"- whereby upon movement aof the piston ofathe-motoron the uppervtongttowardthe forward end 1 thereof the forward wends of Y the tongs "will be drawn apart.

Other objects :and advantages of the PICSQHIZiIWBHfiOII will:be more readily ascertained t-frorn. inspection @of :the following specification taken 7 connection with the accompanying drawing-wherein:like-numerals:refer to like parts throughout, while 1 the features of :novelty will be more distinctly, pointed .out in the-appended claims.

In the drawing,

Fig. 1 is a side elevation of-a-portion of a -sawmill carriage equipped with Y the& present invention;

Fig- 2 is.a fragmentary'top. plan view showing the man- .ner.-in which the flexibletelements-are'coupled .to .the motor. mounted on the upper tong; and

:Fig. .-3 is .ra-sectional =view-along 1j116.I-3,3- of. Fig. 1.

.-The invention herein: disclosed is; shown associated with .a-.-sa-wmill.carriage .-knee llmountedt on .a carriage head 2,703,117 Patented Mar. 1, 1955 "ice .2 7 block 11. The knee -'10may be'adjustably mounted in the conventionalmanner, 'thedevices-for obtaining such adjustment forming .no part of the present invention. Pivotally mounted 'on a .crosshea'd 12 which is .slidably mounted on the knee frame inia manner to be subsequently explained is an .uppertong armor member .13 and a'lower tongarm or member 14.

'Tong members 13,14 are restrained to movement in a vertical plane perpendicular to .theface of a knee by a connection to the guideway '19 formed with :a substantially vertical lower-section and an upper'section curvingrearwardly at an arc, the center of which is approxinaat'ely the -pivot point'of the upper tong member 13 t in its most usual position. "The guideway 19 is of U- shaped cross-section and is provided with'a longitudinally extending slot'2'0 in the web thereof in which, areslidably engaged the guide pins 21, 22 pivotally afiixe'dto upper tong guide'shoe 23 and lower tong guide shoe '24, respectively. The guide p'ins 21,22 are each provided with an enlarged head 25 forming shoulders to engage the surfaces 'of'the guideway web oneither side-of the slot "20 whereby the guide shoes"2-3, "24 areconstrained to'follow the path of the slot. The side channels of the guideway may be braced at suitable intervals-bysleeves 3i) welded at their ends to the opposite side channels and through which pass the bolts3l.

"The forward-part of each of the tongmembers13,14 comprises a 'cylin'clric'al tong"holder 27, 28, respectively, each of which'is slidably engaged in a tong holder guide -bushing-29'pivotally afiixed to 'the 'r'espective guide shoes 23, 2'4 by suitable :means, herein shown as the guide pins 21, 22. A back board dog 33 may be afiixed-to the upperiguideishoe 523, the purpose of which is well known. The tong "holders i extend forwardly: of the "face *of the knee and have'removably aflixe'd -at their forward ends *by :suitable "means, Ithe work gripping tong elezments :32.

The rearward :port-ion of reach of "the tong members 1' 1'3, '14 comprises=atframe assembly *35, 36, respectively,

toiwhichthe tong'holderszlyisr are secured. The frame '-assemblies :55, :36 :are substantially identical and com- 'priset'apairof -substantiallysparallelisideipla-tes 37, "38,

'' theu-sidea plates of :the upperfframe assembly. 35"be'rng tied together at their opposite tends eby r sprocket "bushings 39, "-42 rsecured: thereto ,iaS I.by-"W1 diIig, :the: side plates 0f the :bottom *frame assembly :38 being [tied :together in :like

zmanner'at "their forwardrends'cby the zsprocket bushing t (not shown) in whichithe'ssprocketfishafl 63 is -journaled and at their rearward vends by :an end'z plate 41 :secured thereto by welding ior"otheruconventionalzmeans. :The

t upper and .lower :tong -tmembersare pivotally *rsupported intermediate their: ends a vertically spaced :relation' to ROBE anotherat :a point ;:substantially:rearwardly of the \face of thetknee. As shown, .therupperandzlower frame assemblies are pivotally mounted on cross-head filthy :upper iand l lower -pivot 1 shafts 45, T46 suitably supported on the-cross-head--andusuitably r'journa-led in abushings rarranged between the 'side plates r37, 38.

The motor ;15 is preferablysarreversible motor "having .a first fixed:elementvand--a asecond element reciprocally 1movablelongitudinally.ofrthezupper'tong-member-13. .=As ShOWIl,.IIlIOI v is a: double: acting, I fluid pressure-motor having a cylinder-50 afiixed=to.thenupper frame assembly 1bycylinderasupporting frame :51, the bore of the cylinder ibeinglongitudinally--aligned with thenupper 1 tong member :13-.-and,containing a conventional piston :(not fshown) attached 1 to 'the i extending ;piston rod 52, :to ;the outer end of whichis securedthechain clamp-53. ."Suit- #ablefiuid inlets (not-shown) are-provided -at;either=end ofthe cylinder 50.

The motor. 161.may .be:a'single.=acting motorrhaving a rfirst 'fixed element and :a.-second ':element movable upon --actuat-ion of the motorin a longitudinal direction rearwardly=of the :lower'ton-g member :14. ASiShOWD, the smotor :16 may .comprise a-single acting, fluid .pressure motorhaving 'zacylinder 54 a-ffixed'to thetlower dog :assembly. 3fi-byra-frame 55, r the: borerof thev cylinder; being longitudinally aligned with the \lower tong :member 114.

. A conventional ,piston-i(not a.shown) is provided intthe A suitable fluid inlet (not shown) is provided at the rod end of the cylinder. The control means for the

motors

15, 16 may be of conventional types and form no part of the present invention.

Closing means are provided coacting between points spaced near the forward ends of the upper and lower tongs 13, 14 operable to draw the forward ends together. The closing means include a first flexible element connected at its ends to the pistons of the motors and passing over a first sheave rotatably mounted on the upper tong member 13 at a point intermediate the face of the knee and the upper motor 15, and a second sheave rotatably mounted on the lower tong member 14 at a point intermediate the face of the knee and the lower motor 16 and substantially vertically below the first sheave of the upper tong member. As shown in the drawing in Fig. 2, secured to the chain clamps 53, 57 are the opposite ends of the pair of closing chains 17. Means are provided on the upper and lower tong members cooperable with the closing chains 17 to cause them to have a substantially vertical run between the members at a point near the forward ends of the tongs and runs from the vertical run to each of the chain clamps in a direction substantially aligned with the direction of movement of the pistons. Mounted on the opposite ends of a pivot shaft 60 rotatably journaled in sprocket bushing 39 in the forward end of the upper dog assembly is a pair of sprockets 61. Similarly, a pair of sprockets 62 is mounted on the pivot shaft 63 rotatably journaled in the sprocket bushing in the forward end of the lower dog assembly 36 and substantially vertically below the sprockets 61. As may be seen, the sprockets 61, 63 cooperatively engage the closing chains 17 to provide the aforementioned means and form the desired chain runs.

Opening means are provided to draw the forward ends apart, the opening means including means coacting between points spaced near the rearward ends of the upper and lower tongs 13, 14 operable to draw the rearward ends together and thus the forward ends apart. The opening means include a second flexible element connected at one of its ends to the piston of upper motor and passing over a third sheave rotatably mounted at the rearward end of the upper tong member to the rearward end of the lower tong member 14 to which the other end thereof is connected. As shown, secured to chain clamp 53 is one end of each of the pair of opening chains 18, the other ends of each chain being secured by a suitable clamp 65 at the rearward end of the lower dog assembly 36. Means in the form of sprockets 66 mounted in a pivot shaft 67 rotatably journaled in the sprocket bushing 42 are provided cooperative with the opening chains 18 to cause them to have a first run leading from the rearward end of the lower tong member 14 to the rearward end of the upper tong member 13 and a second run from said first run to the chain clamp 53 substantially aligned with the direction of movement thereof.

The cross-head 12 is slidably mounted on the crosshead guide bars 70 in a conventional manner and is adapted to be reciprocally moved thereon by a suitable motor such as the double-acting, fluid pressure motor 71, the cylinder of which is secured to the frame of the knee in a conventional manner, the piston of the motor being connected to the cross-head by the piston rod 72.

The operation of the device should be readily apparent. To draw the forward, log-engaging ends of the tong members 13, 14 together, actuating fluid is admitted to the rod ends of each of the

motors

15 and 16 whereupon the pistons thereof will be urged toward the rearward end of the respective tong members drawing the closing chains 17 over the sprockets and decreasing the length of the bight thereof whereby the forward ends of the tong members will be drawn together. Since the sprockets 61, 62 are located close to the logengaging tong elements 32, a very favorable mechanical advantage is realized as to the amount of force exerted by the long ends as compared to the power consumption of the motors. Thus motors of relatively small bore may be utilized which require relatively small amounts of compressed air or fluid and consequently have a relatively low amount of power consumption as compared with other types of dogging mechanisms. So long as actuating fluid is applied under pressure to the motors, the tong members will be urged together and the clamping force will be applied to the log-engaging tong elements 32. Thus the hold on the log or timber cant engaged on the knee will be held firm and any give in the wood will be taken up automatically.

To release the grip of the tong elements 32 on a log and draw the forward ends of the tong members apart, the application of fluid under pressure to the motor 16 and the forward end of the motor 15 is terminated and pressure fluid supplied instead to the rearward end of motor 15 whereby the piston thereof will be urged toward the forward end of the upper tong member 13. This causes the chains 18 to be drawn over the sprockets 66 at the rearward end of the upper tong member so that the rearward ends of the upper and lower tong members are drawn together and the forward ends thereof are drawn apart.

Horizontal movement of the cross-head 12 and consequently the tong members 13, 14 is attained by actuation of the cross-head motor 71. As before stated, the tong holders 27, 28 are slidably engaged in the pivotally mounted guide bushings 29, 30 so they may freely move reciprocally in respect to the face of the knee.

In the illustrated arrangement of the

motors

15, 16 and chains 17, 18 it may be observed that cylinder bodies and piston rods are never subjected to any bending or torsional stresses at any phase of the operation. Consequently it is possible to utilize members of relatively slight structural weight and the piston rod glands are subjected to relatively slight wear.

It should be apparent that a flexible element such as a cable could be utilized in place of chains 17, 18 in which case the sprockets 61, 62 and 66 would be replaced with suitable sheaves or pulleys. As used in the claims, therefore, the term sheave is to be understood to include sprockets, pulleys and their equivalents. Obviously a single flexible element or multiple elements could be used in place of the pairs of illustrated chains 17 and 18; thus, the singular expressions sheave and flexible element as used in the claims are to be understood to include the single and multiple forms of the same.

Having illustrated and described a preferred embodiment of the invention, it should be apparent to those skilled in the art that the same permits of modification in arrangement and detail. I claim as my invention all such modifications as come within the true spirit and scope of the appended claims.

I claim:

1. In a sawmill carriage in combination; a knee, a guideway having a vertical lower portion and a rearwardly curving upper portion, upper and lower elongated tong members, means coacting with the tong members and the guideway to constrain the tong members to follow the guideway, the log engaging ends of said tong members extending beyond the face of said knee, means reciprocally movable in a perpendicular direction in respect to the face of said knee for pivotally supporting said tong members intermediate their ends at a point substantially rearwardly of said knee in a vertically spaced relation to one another, a double-acting fluid pressure first motor supported on said upper tong member, a single-acting fluid pressure second motor supported on said lower tong member, each of said motors having a piston movable in the longitudinal direction of said tong members, the piston of said second motor being responsive to admitted fluid to move in a direction rearwardly of said knee, a first flexible element having its ends connected to said pistons, a first sheave rotatably mounted on said upper tong member at a point intermediate the knee and said first motor, a second sheave rotatably mounted on said lower tong member at a point intermediate said knee and said second motor and substantially vertically below said first sheave, said first flexible element coacting with said first and second sheaves whereby, upon operation of said motors to move said pistons away from said knees, said log engaging ends will be drawn together, a second flexible element having one of its ends connected to the piston of said first motor and its other end connected to the rearward end of said lower tong member, a third sheave rotatably mounted at the rearward end of said upper tong member and coacting with said second flexible element whereby upon movement of said piston of said first motor away from the rearward end of said first tong member said log engaging ends will be drawn apart.

a vertically spacedrelation to oneanother, said means being reciprocallymova ble in a horizontal direction in respect to saidfknee, '-a double acting fluid pressure first motor supported on said upper tong member, a singleacting fluid pressure second motor supported on said lower tong member, eachof saidmotors having a piston movable in the longitudinal direction of said tong members, the piston'of said second'motor being responsive to admitted fluid to move in a direction rearwardlyof said knee, a first flexible element having its ends connected tosaid, pistons, a first sheavev rotatably mounted on said top tong member at apoint intermediate'said knee and said first motor, a second sheave rotatably mounted on said lower tong member at a point intermediate said knee and said second motor; said first flexible element coacting with said first'and-second sheaves whereby, upon operation of said motors to-move said pistons away from said knees, the forward ends of said tong members will be drawn'togethena second flexible element having one of its ends connected to the piston of said first motor and its other end connected to the rearward end of said lower tong member, a third'sheave rotatably mounted at the rearward end of said upper tong member and coacting with said second flexible element whereby, upon movement of said'piston of said first motor away from the rearward end of said'first tong member, the forward ends of said tong members will be drawn apart.

3. In a sawnfillcarriage in combination; a knee, upper and lower elongated tong members, means pivotally supporting said tong members in a vertically spaced relation intermediate "their ends ="at a point substantially rearwardly of said knee, a fluid pressure first motor supported on said upper tong member, a-fluidpressure second motor supportedon-said-lower tong member, each of said motors having-a pistonmovable-inthe longitudinal direction'of said tongmembers, a first flexible element having 'its ends connectedto saidpistons,-a first sheave rotatably mounted on 'said'upper tong-member at a, pointinter mediatesaid-knee and-said first motor, a second-sheave rotatably mounted on saidlower tong member at a point intermediate said knee and said second motor, said first flexible element coacting with said first and second sheaves whereby, upon operation of said motors to move said pistons away from said knees, the forward ends of said tong members will be drawn together, a second flexible element having one of its ends connected to the piston of said first motor and its other end connected to the rearward end of said lower tong member, a third sheave rotatably mounted at the rearward end of said upper tong member and coacting with said second flexible element whereby, upon movement of said piston of said first motor away from the rearward end of said first tong member, the forward ends of said tong members will be drawn a art.

4. A dogging device for a sawmill carriage knee comprising upper and lower elongated tong members, means pivotally supporting said tong members intermediate their ends in a vertically spaced relation, a double-acting fluid pressure first motor supported on said upper tong member, a single-acting fluid pressure second motor supported on said lower tong member, each of said motors having a piston movable in the longitudinal direction of said tong members, the piston of said second motor being actuated toward the rearward end of said lower tong, a first flexible element having its ends connected to said pistons, a first sheave rotatably mounted on said top tong member at a point intermediate the forward end thereof and said first motor, a second sheave rotatably mounted on said lower tong member at a point intermediate the forward end thereof and said second motor and substantially vertically below said first sheave, said first flexible element coacting with said first and second sheaves whereby, upon operation of said motors to move said pistons toward the rearward end of said tong members, the forward ends of said tong members will be drawn together, a second flexible element having one of its ends connected to the piston of said first motor and its other end connected to the rearward end of said lower tong member, and a third sheave rotatably mounted at the rearward end .of said upper tong member and coacting with said secondflexible'element whereby, "upon move- "ment of said plston of said first *rnotor away fromthe rearward end of said first tong.member,"the forwardends of-said tong members will be drawnapart.

"5. A dogging device for a sawmill'carriage knee comprising upper and lower elongated-tong members, means pivotally supporting vsaid tong members intermediate their ends in 'a vertically spaced relation, afirstfluid pressure motor supported on said uppertong'member, a second fluid pressure motor supported on said lower tongmember, each of said motors having a piston movable in the longitudinal direction of said tong members, the piston of said second motor being actuated toward the rearward end of said lower tong member, a first flexible element having its ends connected to said; pistons,

ja first sheaverotatably mounted on-said top tong member at a point intermediate theforward endthereof and said first motor, a second sheave rotatably mounted on said lower tong member at a,point intermediate the forward end thereof and said second motor, said first element coacting with'said first-and second sheaves whereby, upon operation of said motors to move said pistons toward the rearward end-of said tong members, the forward ends of said tong members will be drawn together, and means operatively arranged between said tong 'menibers'for drawing said forward ends apart.

6. A dogging device for a sawmill carriage knee .com-

prising upper and'lower-elongated tong members, means pivotally supporting said tong members in a vertically spaced 'relation,'a first fluid pressure motor supported on said upper tong member, a second fluid pressure motor supported-on'saidlower tong member, each of said motors having a-piston movable in the'longitudinal direction of said tong members, the piston of said second motor being actuated toward the'rearward end of said lower tong member, a'first flexible element havingits ends connected to said pistons, a first-sheave rotatably mounted on said top tong member at a point intermediate the'forward end thereof and said first motor, and a second 'sheave rotatably 'mounte'd'on said lower tong member'at a point intermediate-the forward end thereof and said second motor, said fir'st'flexible element coacting with said first and second sheaves whereby, upon operation of said motors tornove said pistons toward the rearward erid'of'said tongmembers, the forward ends of said tong members willfbe drawn together.

7. In a sawmill dogging apparatus, the combination comprising upper and lower elongated tong members pivotally supported in a vertically spaced relation at a point intermediate their ends, a first fluid pressure motor mounted on said upper tong member and having a piston movable longitudinally in respect thereto, a second fluid pressure motor mounted on said lower tong member and having a piston movable longitudinally in respect thereto, a first flexible element having its ends operatively connected to said pistons, means on said upper and lower tong members cooperable with said first flexible element to cause the same to have a substantially vertical run between said upper and lower tong members at a point near the forward ends of said tong members, and runs from said vertical run to said pistons substantially aligned with the direction of movement thereof, a second flexible element having one end connected with said piston of said first motor and the other end connected to the rearward end of said lower tong member, and means on said upper tong member cooperable with said second flexible element to cause the same to have a first run leading from the rearward end of said upper tong member to the rearward end of said lower tong member, and a second run leading from said first run to the piston of said first motor and substantially aligned with the direction of movement thereof.

8. In a sawmill dogging apparatus, the combination comprising upper and lower elongated tong members pivotally supported in a vertically spaced relation, a first fluid pressure motor mounted on said upper tong member and having a piston movable longitudinally in respect thereto, a second fluid pressure motor mounted on said lower tong member and having a piston movable longitudinally in respect thereto, a first flexible element having its ends connected to said pistons, and means on said upper and lower tong members cooperable with said first flexible element to cause the same to have a run between said upper and lower tong members at a point near the forward ends of 7 said tong members, and runs from said vertical run to said pistons substantially aligned with the direction of movement thereof.

9. A dogging device for sawmill carriage knees comprising upper and lower tong members, means pivotally supporting said tong members intermediate their ends in a vertical spaced relation, a reversible first motor mounted on said upper tong member having a first fixed element and a second element reciprocally movable longitudinally of said upper tong member, a single-acting second motor mounted on said lower tong member having a fixed first element and a second element movable upon actuation in a longitudinal direction toward the rearward end of said second tong member, a first flexible element having its ends connected to said second elements of said motors, a first sheave rotatably mounted on said upper tong member at a point intermediate the forward end thereof and said first motor, a second sheave rotatably mounted on said lower tong member at a point intermediate the forward end thereof and said second motor, a first flexible element having its ends connected to said second elements of said motors and being trained over said first and second sheaves, a third sheave rotatably mounted on the rearward end of said upper tong member, a second flexible element having one of its ends connected to the movable element of said first motor and its other end connected to the rearward end of said lower tong member and being trained over said third sheave, whereby, upon operation of said first and second motors to move said second elements rearwardly of said tong members, the forward ends of said tong members will be drawn together, and, upon operation of said first motor to move the second element thereof forwardly of said first tong member, the forward ends of said tong members will be drawn apart.

10. A dogging device for sawmill carriage knees comprising upper and lower tong members, means pivotally supporting said tong members intermediate their ends in a vertical spaced relation, a reversible first motor mounted in said upper tong member having a first fixed element and a second element reciprocally movable longitudinally of said upper tong member, a second motor mounted on said lower tong member having a fixed first element and a second element movable upon actuation in a direction toward the rearward end of said second tong member, a flexible element having its ends connected to said second elements of said motors, a first sheave rotatably mounted on said upper tong member at a point intermediate the forward end thereof and said first motor, a second sheave rotatably mounted on said lower tong member at a point intermediate the forward end thereof and said second motor, said flexible element being trained over said sheaves whereby, upon actuation of said first and second motors to move said second elements rearwardly of said tong members, the forward ends of said tong members will be drawn together, and means cooperatively arranged with the rearward ends of said tong members operative to draw them together so as to draw the forward ends apart.

11. A dogging device for sawmill carriage knees comprising upper and lower tong members, means pivotally supporting said tong members intermediate their ends in a vertical spaced relation, a reversible first motor mounted on said upper tong member having a first fixed element and a second element reciprocally movable longitudinally of said upper tong member, a second motor mounted on said lower tong member having a fixed first element and a second element movable upon actuation in a direction toward the rearward end of said second tong member, a first flexible element having its ends respectively connected to said second elements of said motors, a first sheave rotatably mounted on said upper tong member at a point intermediate the forward end thereof and said first motor, a second sheave rotatably mounted on said lower tong member at a point intermediate the forward end thereof and said second motor, said flexible element being trained over said sheaves whereby, upon operation of said first and second motors to move said second elements rearwardly of said tong members, the forward ends of said tong members will be drawn together.

References Cited in the file of this patent UNITED STATES PATENTS 414,994 Perkins Nov. 12, 1889 1,637,907 Langill et al Aug. 2, 1927 1,774,311 Bidwell et a1. Aug. 26, 1930 1,822,116 Thompson Sept. 8, 1931 1,838,948 Langill et al. Dec. 29, 1931 1,840,846 Martin Ian. 12, 1932 1,944,285 Haase Jan. 23, 1934 2,633,879 Andrus Apr. 7, 1953