US2904301A - Chock release - Google Patents

Description

Sept. 15, 1959 DUNC'A-N caocx RELEASE s Sheets-Sheet 1 Filed Oct, 7-, 1955 Sept. 15, 1959 A. w. DUNCAN CHOCK RELEASE 3 Sheets-Sheet 2 Filed Oct. 7. 1955 Au 0 s #545641: v Java: 4

Sept. 15, 1959 A. DUNCAN 2,904,301

CHOCK RELEASE Filed 001:. 7, 1955 3 SheetsSheet 3 fltent 2,904,301 Patented Sept. 15, 1959 CHOCK RELEASE Angus Wellesley Duncan, Leigh Sinton, near Malvern,

England, assiguor to The Mining Engineering Company Limited, Worcester, England, a British company Application October 7, 1955, Serial No. 539,254 7 Claims. (Cl. 248-651) This invention relates to a new or improved chock release for use in conjunction with roof supports in coal mines and other underground workings.

Chocks as used for roof support are commonly built up from timber baulks in the form of a hollow square with or without a fabricated steel base. The chock is tightened between the floor and the roof by means of wedges driven in near the roof, and to allow the chock to be withdrawn one layer of the structure is formed by chock releases which can be released to collapse the whole chock. Such chock releases commonly comprise four pairs of wedge members located at the corners of the chock' structure and retained in operative relationship by quickly releasable catches. The angle of the wedge members is normally such that there is a tendency to collapse of about 10% of the roof weight supported by the chock, and that is the load taken by the catches.

In one known form of chock release the catch is a latch member pivoted'in the lower wedge member of a pair and having a T head which passes through a slot in and bears against the vertical face of the upper wedge member. To release the chock the operator strikes the heads of the latches for each of the pairs of wedges upwardly with a long handled hammer so that the upper wedges are released and are free to slide downwardly and outwardly over the lower wedges, the upper wedges being attached by chains to the assembly to retain them when collapsed.

There are various other forms of chock release but all of them incorporate double wedges with some form of catch which has to be moved under high and progressively increasing load per unit area to effect release.

Amongst the practical disadvantages of known forms of chock release are that the effort required to release the latches may be diflicult to apply in thin seams and may require the operator to be in a dangerous position, that when wear of the cooperating faces of the wedges and latches takes place the wedges may self-release unless very carefully set and the release of one pair of wedge members may cause the others to self-release with the operator in a dangerous position, and under heavy load ing the very high bearing pressure on the latch face may cause sparking on release with consequent risk of an explosion.

According to the invention a chock release comprises at least one pair of co-operating wedge members which are normally retained in the load-carrying position by a' tension member connected between one wedge member and the crank pin of a crankshaft journalled in the other wedge member or in an associated part with its axis at right angles to the line of movement of the movable wedge member, and a releasable locking device is provided to hold the crankshaft normally in a position in which the crank extends in a direction away from the first wedge member and at a small angle to thetension member.

The wedge members have an angle above the friction angle, that is, there is a component of the vertical load on the chock tending to cause the one wedge to slide on the other, and the major part of this force is taken by the crankshaft journals, a minor part represented by the torque on the crankshaft due to its angular displacement from the dead-centre position being taken by the releasable locking device which normally prevents angular movement of the crankshaft.

The proportion of the force taken by'the releasable locking device can be made as small as desired by reducing the angular displacement of the crankshaft from dead-centre in the locked position, provided it is sufficient to cause the crankshaft to rotate when the locking device is released. 7'

When it is desired to collapse the chock the locking device for the crankshaft is released and the crankshaft is then free to rotate through an angle of approximately so that the first wedge member can move into .its released position through a distance substantiallyequal to twice the crank throw, the wedge member being retained in the released position by the tension member connecting it to the crank-pin.

The tension member may be a rigid link or it may be a chain or other flexible member. If it is a rigid link it will be pivotally connected at its ends to the first wedge member and to the crank-pin.

Where two spaced pairs of wedge members are associated in a structure replacing one chock piece, sustaining tension-members for the movable wedges of the two pairs may conveniently be connected to the diametrically opposed crank-pins of a common double crankshaft mounted in journals in the structure substantially midway between the wedge members. 1

Any convenient locking device may be employed for holding the crankshaft in the operative position, and as the loading on the locking device is relatively small it can readily be released from a remote point by means of a chain or cable temporarily coupled to it and operated manually or by a light pulling jack. Supplementary or safety locking means may be provided for the locking device.

It will be appreciated that on release the loading on the crank journals disappears and the only load on the tension member or members is that required to accelerate the crank mechanism. 7 I

As there are no parts moving under heavy bearing loads during release the risk of sparking is eliminated and as the release can be elfected from a distance risk-to the operator is reduced to a minimum.

At the same time the improved chock release is free from any danger of self-release as a positive locking device for the crankshaft can be employed.

One practical chock release in accordance with the invention is illustrated by way of example in the accompanying drawings in which: 1

Figure 1 is an end view of the chock release.

Figure 2 is a longitudinal section on the line 2-2 of Figure 1.

Figure 3 is a horizontal section on the line 33-of Figure 2.

Figure 4- is a diagrammatic side elevation on a small scale of a chock release incorporating two spaced pairs of wedge members.

The chock release illustrated comprises a lower wedge member 10 having a substantially horizontal base and a co-operating upper wedge member 11 having a substantially horizontal upper surface. The wedges are shown in the normal load-carrying position in which they are held against relative sliding movementby the means forming the subject of our invention.

A transverse horizontal pin 12 mounted in the upper wedge member adjacent to its outer end is coupled tothe crank-pin 13 of a parallel crankshaft 14 journalled in the lower wedge member by a tension member comprising a pair of chain side plates 16 mounted on the pin 12 and a link 17 mounted on the crank-pin 13 between the crank we'bs 15, the side plates and link being pivotallyconnected by a pin 18.

\ In the load-supporting position of the chock release as illustrated the crank extends in a direction away from the pinlqt the axis of the crank-pin 13 lies below the plane containing the axis of the chankshaft '14 and of the pin 12, theiplane containing the axes of the crank-pin 13 and of the crankshaft 14 being inclined at a small angle to the plane containing the axes of the crankshaft and the The wedge rnembers have an angle above the friction angle so that the vertical load on the chock release when it is supporting a mine roof has a component tending to use the upper wedge member to slide outwardly on the lower member.

;As't he crank is close to dead-centre the major part of this force is taken by the journals of the crankshaft 14 and a minor part applies a torque to the crankshaft tending to rotate it in an anti-clockwise direction in Figure 2 owing 'to the angular displacement of the crankshaft below dead-centre.

lifis torque 'is prevented from rotating the crankshaft by tlieengagement of the lower edge of the inner end ofthe link 17 with a flat 19 machined on a locking shaft 20 journalled in the lower wedge member adjacent to its "i""er end. The shaft is cut away at the centre of its lengthffor half its diameter to provide the flat 19 with which the end of the link 17 engages at a point spaced a short distance from the axis of the shaft 20 so that the torque tending to rotate the crankshaft 14 in an anticlockwise direction tends to rotate the shaft 20 in a clockwise direction. In a modification the ends of the crank webs instead of the end of the link 17 may enga'ge'the fiat 19.

'One end 'of the shaft projects from the side of the lower wedge member and is hexagonal in cross-sectionas -shown at 21. The projecting hexagonal portion of the shaft'is received in an hexagonal sleeve 22 of which the inner end is normally engaged in an hexagonal recess 40 in the side of the wedge member to hold the shaft against angular movement.

The sleeve is retained in the locking position by the bolt 23 of a D link 24, the bolt passing transversely through the sleeve and shaft.

The central part of the bolt is formed with opposed flats and is 'received in the wide inner end of a longitudinal keyhole -slort 25in the shaft so that when the link is hanging vertically as shown in the drawing the sleeve is held against axial movement on the shaft, the link being maintained in this position by its -own weight.

To release the chock the D link is swung up into a horizontal position and pulled outwardly so that the bolt passes into the 'outer portion of the slot in the shaft 20 and the locking sleeve 22 is withdrawn from the hexagonal recess 40 in the wedge member. The shaft 21) is their "free to rotate under the torque applied to it by the link 17, the shaft moving angularly until the fiat 19 is substantially vertical and the end'c'f the link 17 can move downwardly past it. The crankshaft is thus released and isfree to rotate through approximately 180 and allow the upper wedge member '10 to slide downwardly and outwardly through a distance substantially totwice the crank throw, the wedgemember being retained in the released position by its connection to crank pin *through the tension member.

The D link can be withdrawn by a chain or cable hooked on to it "and actuated ifrom a distance so that the eperator can remain out ofthe danger zone while the chock is being released. V gl'l wo chock releases as illustrated in Figures 1, '2 and 3 will 'usuallybe associated in a structure replacing one 4 chock piece in a built-up chock, two opposed spaced chock releases being connected by parallel plates 45 bolted to the lower wedge members.

In that case the arrangement shown diagrammatically in Figure 4 can be employed. The lower wedge members 30, 30 are rigidly connected by spaced parallel plates 31. The movable upper wedge members 32, 32 are connected by tension members 33, 34 to the diametrically opposed crank-pins of a common double crankshaft 35 mounted in journals in the plates 31. Any convenient locking means e.g. means 19 to 25 shown in Figs l to 3 and in general denoted by 36 in Fig. 4 may be provided for holding the crankshaft normally in the angular position shown in which the cranks are closed to dead-centre with respect to the tension members, one above and one below dead-centre. Thus the sustaining loads on the tension members are opposed and are substantially balanced and the loadon -the crankshaft is-reduced to a minimum. When the locking device is released both the movable upper wedge members are released simultaneously and move in opposite directions.

In both forms of the invention, there are certain common characteristics which are worthy of note at this point. Considering the form shown to particular advantagein Fig. 2, it will be noted that the .pin 12 can appropri ately be termed a first pivotal connection, the crank shaft 14 can be termed a second pivotal connection, and the crank pin 13 comprises a third pivotal connection.

Links 16,17 comprise a link means, accordingly, which extendsin crossing relation to the complementary, inclined, slidably contacting faces of the upper and lower wedge members 11, 10 respectively. The inclined faces are so arranged that when the upper and lower wedge members are in their operative, wedging'positions shown in Fig. 2, and are under a downwardly exerted load, the downward pressure exerted on the upper Wedge member would normally tend to shift the wedge members outwardly from one another, that is, they would tend to shift wedge member 11 to the right in Fig. 2 with wedge member 10 tending to move to the left in Fig. .2.

The link means is kept under tension to prevent this movement in the operative position of the components, and when under tension in this manner, obviously tends to exert a turning moment on the crank arm- 15, such that thecrank arm and the linkrneans both .tend to swing downwardly in a counterclockwise direction about the axis of shaft :14 and pin .12,-respectively.

In the form shown in Fig. 4, of course, the identical .characteristicsobtain. In this form, there is once again a linkmeans 33, extending incrossing relation to the complementary, inclined faces of the upper wedge member 32 shown at the right in Fig. 4 and the lower wedge member '31. .In this casethe first pivotal connection is the pivotal connection at the right .hand'end of the link means 33, the second pivotal connection is the axis about which the double crank 35 turns, and the third pivotal connection is the connection between the linkmeans 33 and said double crank 35. V

It will be appreciated that the locking means illustrated for holding the crank-shaft in the load-sustaining position is one example only and thatany other convenient locking means maybe employed. For instance an arm of substantialilength may be keyed on-one end of the locking shaft 20 for engagement with apin which is located in the lower Wedge member or :in the associated structure and is withdrawn .to release the chock.

When the chock .is released the movement of the upper wedge meniber or members is :substantially instantaneous without any initiaLcontr'olledmovement, and this ensures the desired break of strata in the .roof supported bythe chock.

I claim:

-1. A chock release comprising a lower wedge member having an inclined upper surface, an upper wedge men;- ber having an inclinedlower surface adapted to slide on the inclined surface of the lower member for release, means for holding the wedge members normally against relative sliding movement, said means comprising a crankshaft journalled in the lower wedge member with its axis at right angles to the direction of sliding of the upper wedge member, a crank-pin associated with said crankshaft, another pin in said upper wedge member parallel to said crankshaft, a tension member connecting said other pin and said crank-pin, and releasable means for holding the crankshaft in an angular position in which the crankpin lies on the opposite side of the crank-shaft axis from the connection of the tension member to said other pin and a plane containing the axes of the crank-pin and of the crank-shaft is inclined at a small angle to a plane containing the axes of said crank-shaft and of said other pin, said inclination being in a direction such that a force tending to cause relative sliding movement between the Wedge members exerts a turning moment on the crankshaft in a direction permitting such sliding movement.

2. A chock release comprising upper and lower wedge members having co-operating inclined surfaces, the upper wedge member being adapted to slide on the lower member for release, a crank-shaft journalled in the lower wedge member with its axis at right angles to the direction of sliding of the upper wedge member, a crank-pin associated with said crank-shaft, another pin in said upper wedge member parallel to said crank-shaft, a tension member connecting said other pin and the crank-pin, and releasable means for holding the crank-shaft in a predetermined angular position for preventing sliding movement of the upper wedge member on the lower wedge member, said releasable means comprising a locking shaft journalled in the lower wedge member with its axis parallel to the crankshaft, a portion of said locking shaft of semicylindrical cross-section having a flat face containing the axis of the shaft, a part of the tension member engaging said flat face on a line spaced from the axis of the locking shaft, and releasable means for holding the locking shaft against angular movement.

3. A chock release as in claim 2 wherein the releasable means for holding the locking shaft against angular movement comprises a non-circular end on said shaft, a sleeve of corresponding cross-section slidably keyed on said end, a complementary locking recess in the lower wedge member in which the inner end of said sleeve is normally engaged, opposed openings in said sleeve, a longitudinal keyhole slot in said shaft end having its larger inner end registering with said holes, a bolt passing transversely through said holes and the larger end of said keyhole slot, opposed flats on said bolt over the portion within the keyhole slot, the width over the flats being less than that of the narrower end of said keyhole slot, and a D link mounted on said bolt and normally hanging therefrom to maintain said flats vertical, movement of said D link into a horizontal position rotating said bolt and bringing said flats into a horizontal position in which the bolt can pass into the narrower end of the keyhole slot and withdraw the sleeve from engagement with the locking recess.

4. A chock release comprising at least one upper and one lower wedge member having complementary, inclined, slidably contacting faces arranged to effect move- 1 ment of said wedge members outwardly from each other when undera downwardly exerted load in an operative, wedging position thereof, link means extending in crossing relation to the inclined faces and having a pivotal connection to the upper wedge member, an arm having a pivotal connection to the lower wedge member and having a pivotal connection at a location spaced from the axis of its connection to the lower wedge member, to the link means, the second pivotal connection being disposed between the first and third pivotal connections, the axes of the first and second pivotal connections lying in a plane disposed above the axis of the third pivotal connection in said operative position of the wedge members, the link means being under tension in said operative position of the wedge members and exerting a turning moment on the arm tending to swing the arm and link means downwardly about the first and second axes, respectively, and locking means on the lower wedge member operable between an operative position in which it restrains the link means and arm against said downward swinging movement, and a releasing position in which it frees the link means and arm for downward swinging movement about the first and second axes, respectively.

5. A chock release as in claim 4 wherein said link means comprises a pair of links pivotally connected to each other at one end, the first and third pivotal connections being disposed at the other ends of the respective links of said pair.

6. A chock release as in claim 4 wherein said link means comprises a single link, the first pivotal connection being disposed at one end of said link and the third pivotal connection being disposed at the other end thereof.

7. A chock release as in claim 4 wherein the axes of the second and third pivotal connections lie in a plane disposed at a wide, downwardly opening, obtuse angle to the first named plane in said operative position of the wedging members.

References Cited in the file of this patent UNITED STATES PATENTS 1,331,715 Lindfors Feb. 24, 1920 1,361,856 Heininger Dec. 14, 1920 FOREIGN PATENTS 495,781 Great Britain Nov. 18, 1938 732,412 Germany Mar. 4, 1943 737,698 Great Britain Sept. 28, 1955 777,866 France Dec. 5, 1934

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