US3295814A - Control means of mine roof supports - Google Patents

Description

Jan. 3, 1967 F. TOWN CONTROL MEANS OF MINE ROOF SUPPORTS 2 Sheets-Sheet 1 Filed Jan. 13, 1965 5240! H 5 3 9 22222 8 m 7 2 Z V07 K N 2 I g 4/ k: 4 a \W D zmpwwfl A M 2 B I FKGJ.

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if 1511 11% 1mm? an. 3, W67 F. TOWN 3 CONTROL MEANS OF MINE ROOF SUPPORTS Filed Jan. 13, 1965 2 Sheets-Sheet 2 l/VVENTOR United States l atent ()filice 3,2 95,8l4 Patented Jan. 3, 1967 3,295,814 CONTROL MEANS OF MINE R081 SUPPORT Frank Town, Burton .loyce, England, assignor to W. E. & F. Dolbson Limited Filed Jan. 13, 1965, Ser. No. 425,123 Claims priority, application Great Britain, Jan. 18, 1964, 2,314/ 64 11 Claims. (Cl. Mitt-35d) This invention is for improvements in control means of mine roof supports primarily of the kind comprising hydraulic props interconnected by a horizontal advancing cylinder and ram.

It has been heretofore proposed to provide for control of the different operations necessary with the above type of support to be instigated by operation of electric switch means. Specifically it has been proposed for the extending movement of a prop to cause operation of an electric switch for instigating the next operation to be performed. However this arrangement is such that the switch would be operated even if the roof were so high as not to be engaged by the prop in its fully extended condition.

An object of the invention is to provide for operation of the switch in such improved manner that it will be operated only when the prop is actually supporting the roof.

The invention provides a hydraulic prop having a control device for controlling another hydraulic device, an operating device movably mounted at an end of the prop for operating the control device, and means whereby relative movement between the operating device and said end of the prop to operate the control device is eflected only when a predetermined pressure is exerted by the prop against the roof. Conveniently the prop has an operating cap slidable on the outer end of the ram and adapted for operating the control device consequent upon relative sliding movement between the cap and the ram, and wherein the ram, its pressure cylinder, and the cap form a diiferential piston and cylinder arrangement whereby prop-extending pressures below a predetermined pressure act in the cap to prevent said relative movement and a predetermined prop-setting pressure in the pressure cylinder overcomes the pressure in the cap to effect said relative movement and the control device is consequently operated. Conveniently also the operating cap is biased in projecting direction by spring means and the mode termined prop pressure is sufficient to overcome the force of this spring in addition to the fluid pressure in the cap before the control device is operated.

The control device may be an electric switch, or a hydraulic pilot valve and it may be operable by the operating device through the intermediary of a cam slide movable by the operating device. Conveniently the con trol device is operable through a plunger and a cam slide mounted in the ram, and the cam slide is operable by a spigot carried by the operating device. Conveniently also the upper end of the ram is in the form of a piston, the operating device is an end cap forming a cylinder for the rams upper piston, and this cylinder and ram is of less diameter than that of the rams lower piston and its pressure cylinder.

More specifically the ram has a central bore communicating between a fluid connection and an annulus between the ram and its cylinder, a pipe is mounted in the bore to connect a second fluid connection to the rams cylinder, and the cam slide is mounted in the bore above the inlet and is formed with fluid ducts: connecting the inlet to the upper cam cylinder.

The invention also provides a hydraulic prop comprising a ram and pressure cylinder therefor, first and second fluid connections communicating with an annulus etween the ram and its cylinder and with the rams cylinder respectively, a control switch mounted on the ram with an operating plunger directed to a central bore in the ram which communicates with the second fluid connection, a cam slide in said bore engaging said plunger and formed with ducts for fluid from said second fluid connection, a piston formed on the top end of the ram and through which the cam slide is directed, a top end cap on the ram and forming a cylinder for the rams top piston, a spring in the cap biasing it upwardly, and a spigot directed downwardly from the cap and engaging the upper end of the cam slide.

The above and other features of the invention set out in the appended claims are incorporated in the construction which will now be described as a specific embodiment with reference to the accompanying drawings in which:

FIGURE 1 is a sectional view of a hydraulic prop according to the invention.

FIGURE 2 is a side view thereof.

FIGURE 3 is a sectional view of a part of the hydraulic prop shown in FIG. 1 according to an. alternative embodiment of the invention.

Referring to FIGURE 1 the hydraulic prop is in this instance one of two similar hydraulic props which are interconnected by a horizontal advancing cylinder and ram providing a step by step advancing roof support of which there is a series employed along a coal face. The necessary operations of extending and contracting the digerent props and in advancing the different props in a required cycle of operations is desirably achieved automatically by each operation being accompanied by operation of an electric switch to instigate the next operation and so on.

For this purpose in connection with the hydraulic props, each is provided with an electric switch as indicated at 1 in FIGURE 1.

The prop is in this instance of the type comprising a cylinder 2 forming a pressure chamber 3 in which operates a piston 4 on a ram 5.

For extending the ram 5 a pipe 6 extends through the ram 5' from a lower location where it communicates with the pressure chamber 3 and an upper location where it communicates with a chamber 7 at the position of a fluid connection 8 to which there can be alternatively fitted a suitable fluid charging unit connected to a pressure fluid supply or a return line. A second fluid connection for a return line or a charging unit, is indicated at 9 in FIGURE 2 and this is in communication with a chamber 10 which is itself a communication, via a bore 11 in the ram 5 and a transverse duct 12 with the annulus 13 between the ram 5 and the cylinder 2.

For operation of the electric switch 1 there is a plunger 1.4 which is operable, through a ball 15 by a cam slide 16 disposed in the chamber 7 and having a cam face 17 engaging the ball 15.

This cam slide 16 has sealing rings 18, 19 for sealing against the fluid in the chamber 7, and the upper end of the cam slide 16 projects through a chamber 20 which houses a biasing spring 21 for biasing the cam slide 16 in an upward direction.

The upper end of the ram 5 is in the form of a piston 22 which is of less diameter than that of the piston 4.

On the upper end of the ram 5 there is fitted an end cap slide 23 which at its lower end forms a cylinder 24 for the piston 22, there being a pressure chamber 25 between the end slide 23 and the piston 22, this chamber 25 being in communication with the pressure chamber 3 through the pipe 6, the chamber 7, and a duct 26 in the cam slide 16 and connecting the chamber 7 with the chamber 29 which is open to the pressure chamber 25. The end slide 23 has a central spigot 27 for engaging the cam slide 6 and mounted on this spigot there is a thrust member 28 which is biased downwardly by resilient means 29 which in the illustration consists of Belvedere washers, but which may consist of a spring or of a rubber block or the like.

In use of the prop, the end slide 23 is normally biased in extending direction from the ram 5 by the resilient means 29 acting between the end slide 23 and the thrust member 28 which bears on the piston 22.

In this position of the parts the cam slide is in such a position relative to the ball 15 that the latter engages the lowest part of the cam 17 so that the switch 1 is not operated by the cam 17.

When the prop is next extended by applying a charging unit to the connection 8 and a return line to connection 9, fluid pressure in the chamber 3 extends the ram 5 until the end slide 23 engages the roof (assuming the roof to be sufficiently low for this purpose). On continuance of fluid pressure in the chamber 3 this is accompanied by a separating fluid pressure being applied from the connection 8 to the cylinder 24 between the end slide 23, and the ram 5, and this in addition to the pressure of the spring 29 prevents the ram 5 from rising relative to the end slide 23 so that the switch 1 remains unoperated by the cam 17.

Not until the pressure in the chamber 3 overcomes both the fluid pressure in the chamber 25 and the pressure of the spring 29 will the ram 5 rise relative to the end slide 23, at which time the prop is actually supporting the roof, and it is only at this time that the cam slide 16 in ram 5, in raising relative to the end slide 23 raises the switch of the end plunger to engage the high part of the cam face 17 as held stationary by the end slide 23, so that the cam face 17 acts on the ball 15 and causes the plunger 14 to operate the switch 1.

The switch 1 is of course suitably associated with the mechanism next to be operated and operates, for example, a solenoid operated control valve for controlling the operation of a successive hydraulic prop in the manner hereinbefore described of a further section of a hydraulic sequence.

An important advantage of the arrangement is that the switch 1 is not only prevented from operation when the prop engages the roof without actually supporting the roof but it is also prevented from operation if the roof happens to be so high that the prop in its fully extended condition does not reach the roof. In other words the switch 1 cannot be operated to instigate the next operation under any circumstances other than when the prop is actually supporting the roof.

Instead of the electric switch there may be a hydraulic pilot valve 30, which, as seen in FIG. 3, will operate a hydraulically-operated control valve for controlling the operation of a successive hydraulic prop or a further section of a hydraulic sequence. A valve member 32 is hydraulically actuated through inlet 34 and outlet 36 against a return spring 38 to be actuated by plunger 14 to operate the props in the manner of switch 1 in the previous embodiment.

What I claim is:

1. A cylinder and ram assembly comprising a ram, a ram piston thereon, a ram cylinder in which the ram piston is slidable, an inlet for leading pressure fluid into said ram cylinder, a control device mounted on said ram and operable for instigating a separate operation other than that of the cylinder and ram assembly, operating means including an end member axially slidable on said ram so as to operate said control device upon relative contraction between said end member and said ram, and pressure applying means providing a predetermined pressure less than the loading pressure of the ram piston and ram cylinder and disposed in separating association with said end member and said ram, whereby said ram piston and ram cylinder must be pressure loaded in excess of said predetermined pressure before said control device is operated.

2. In a hydraulic mine roof support system comprising at least one hydraulic device, operation of which is required to be instigated by operation of a control device, a hydraulic prop comprising (a) a cylinder,

(b) a ram slidable in said cylinder,

(c) said control device being mounted on said ram,

((1) an operating device movably mounted in said ram and operatively associated with said control device,

(e) an end member axially slidable on the outer end of said ram, and

(f) means for causing relative movement between the operating device and the control device for operating the latter only upon predetermined load being applied to said prop.

3. A hydraulic prop according to claim 2, wherein the operating device comprises an operating member slidable in said ram under control of the hydraulic fluid in the prop, said member engaging a spigot biased against said end member, said end member being slidable on the outer end of said ram and forming an auxiliary piston and cylinder in operative association with said operating device.

4. A hydraulic prop according to claim 2, wherein said end member forms a cap axially slidable on the outer end of said ram forming an auxiliary piston and cylinder, a fluid duct communicating between said ram cylinder and said auxiliary cylinder.

5. A hydraulic prop according to claim 2, wherein the end member and the outer end of said ram comprise an auxiliary piston and cylinder forming an auxiliary pressure chamber therebetween, the cross-sectional area of said auxiliary piston and chamber being less than that of the main piston and pressure chamber, whereby the control device is operated only upon a predetermined load being applied to the prop.

6. A hydraulic prop according to claim 2, wherein the operating device comprises an operating member slidable in said ram under control of the hydraulic fluid in the prop, said member engaging a spigot biased against said end member, said end member being slidable on the outer end of said ram and forming an auxiliary piston and cylinder in operative association with said operating device.

7. A hydraulic prop according to claim 2, wherein the operating means includes an operating member slidable in said ram under cotnrol of the hydraulic fluid in the prop, said member engaging a spigot biased against said end member, said end member being slidable on the outer end of said ram and forming an auxiliary piston and cylinder in operative association with said operating device, the cross sectional area of said auxiliary piston and chamber being less than that of the main piston and pressure chamber, whereby the control device is operated only upon a predetermined load being applied to the prop.

8. A hydraulic prop according to claim 2, wherein said end member forms a cap axially slidable on the outer end of said ram forming an auxiliary piston and cylinder, a fluid duct communicating between said ram cylinder and said auxiliary cylinder, the cross sectional area of said auxiliary piston and chamber being less than that of the main piston and pressure chamber, whereby the control device is operated only upon a predetermined load being applied to the prop.

9. A hydraulic prop according to claim 2, wherein the operating device comprises an operating member slidable in said ram under control of the hydraulic fluid in the prop, said member engaging a spigot biased against said end member, said end member being slidable on the outer end of said ram and forming an auxiliary piston and cylinder in operative association with said operating device and having a fluid duct communicating between said ram cylinder and said auxiliary cylinder, the cross sectional area of said auxiliary piston and chamber being less than that of the main piston and pressure chamber, whereby the control device is operated only upon a predetermined load being applied to the prop.

10. A hydraulic prop according to claim 2, wherein said control device is an electric switch.

11. A hydraulic prop according to claim 2, wherein said control device is a hydraulically operated pilot valve.

No references cited.

CLAUDE A. LE ROY, Primary Examiner.

Claims (1)

1. A CYLINDER AND RAM ASSEMBLY COMPRISING A RAM, A RAM PISTON THEREON, A RAM CYLINDER IN WHICH THE RAM PISTON IS SLIDABLE, AN INLET FOR LEADING PRESSURE FLUID INTO SAID RAM CYLINDER, A CONTROL DEVICE MOUNTED ON SAID RAM AND OPERABLE FOR INSTIGATING A SEPARATE OPERATION OTHER THAN THAT OF THE CYLINDER AND RAM ASSEMBLY, OPERATING MEANS INCLUDING AN END MEMBER AXIALLY SLIDABLE ON SAID RAM SO AS TO OPERATE SAID CONTROL DEVICE UPON RELATIVE CONTRACTION BETWEEN SAID END MEMBER AND SAID RAM, AND PRESSURE APPLYING MEANS PROVIDING A PREDETERMINED PRESSURE LESS THAN THE LOADING PRESSURE OF THE RAM PISTON AND RAM CYLINDER AND DISPOSED IN SEPARATING ASSOCIATION WITH SAID END MEMBER AND SAID RAM, WHEREBY SAID RAM PISTON AND RAM CYLINDER MUST BE PRESSURE LOADED IN EXCESS OF SAID PREDETERMINED PRESSURE BEFORE SAID CONTROL DEVICE IS OPERATED.

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