US2959922A - Hydraulic supports - Google Patents

Description

Nov. 15, 1960 11555 ETAL 2,959,922

HYDRAULIC SUPPORTS Filed July 28, 1958 2 Shgets-Sheet 1 lnvenlor! 6:10 88 cumgw l /211;" My

Nov. 15, 1960 B. TEBB ET AL 2,959,922

HYDRAULIC SUPPORTS Filed July 28, 1958 2 Sheets-Sheet 2 Z a/1 9 1 can/cs 1mm) United States Patent HYDRAULIC SUPPORTS Bernard Tebb, Staddlestones Garth, Swanland, and Clarence Herbert Perry, Hull, England, assignors to Mastabar Mining Equipment Company Limited, Hull, Yorkshire, England, a British company Filed July 28, 1958, Ser. No. 751,475 Claims priority, application Great Britain July 30, 1957 2 Claims. (Cl. 60-52) This invention concerns hydraulic supports, that is to say supports in which a pair of relatively movable members are telescopically extendible and collapsible due to the flow of hydraulic fluid between a reservoir and a hydraulic pressure chamber associated with said members; and relates particularly to supports of this type which constitute roof supports or pit props for use in mining operation, and wherein the fluid flow for collapse of the support is via ports, tubes, channels or the like passing through a ram or piston between the relatively movable members.

It is not an uncommon experience with such hydraulic supports that the rate of collapse is not adequate for rapid withdrawal of a support from one position and quick resetting thereof for use in another position, primarily due to the small cross-sectional areas of the ports, tubes, channels or the like as compared with the crosssectional areas of the relatively movable members, resulting in restriction of the fluid flow from one side of the piston or ram to the other.

According to the present invention, therefore, the ram or piston between the two relatively movable members comprises two mutually separable parts, and manually operable means accessible externally of the support are provided to enable said parts to be mutually displaced to create therebetween a fluid flow passage providing for substantially unrestricted fluid flow from one side of the ram or piston to the other side thereof.

The invention may conveniently be employed with that type of telescopic hydraulic support wherein one of the relatively movable members serves as a hydraulic pressure chamber and the other member, which carries or acts as the ram or piston, serves as a hydraulic reser voir and is slidable within the pressure chamber in dependence upon the flow of fluid therein.

The invention will be decribed further, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a vertical longitudinal section through a pit prop embodying the invention, and showing a twopart ram in closed condition; and

Fig. 2 is a similar section with certain parts broken away and showing the ram in open condition.

In the embodiment of the invention shown in the drawings, a pit prop includes a first hollow elongated cylindrical member which at one end presents the base 12 of the prop, and which at its opposite end slidingly receives a second, similar member 14, the upper end of which presents the supporting head as at 14a of the prop. The cylindrical member 10 is employed as a hydraulic pressure chamber, and the second cylindrical member 14 as a fluid reservoir; and hydraulic fluid is pumped from the reservoir space 16 of the member 14 into the working space 18 of member 10 by means of a hydraulic pump generally designated 20 and located at the inner end of the member 14. This inner end of member 14 is constructed to constitute a hydraulic ram against which acts the fluid pressure generated in the working space 18.

The ram carries a peripheral oil sealing ring 22 hydraulically isolating the reservoir space from the working space, and the pump 20, which is operable by manual means accessible externally of the prop, may conveniently be mounted on the ram itself.

In accordance with the proposal made by the invention, this ram is constructed substantially in two main parts, an outer part 24 carrying the aforementioned sealing ring 22 and slidable within the first cylindrical member 10, and an inner part 26 carrying the pump 20 and displaceable from the outer part 24 in order to create (Fig. 2) a fluid flow passage 28 when hydraulic fluid under pressure in the working space 18 is to be rapidly allowed to return to the reservoir space 16 for the purpose of collapsing the prop from an extended condition. The outer ram part 24 is hollow and is provided towards one and region of its internal cylindrical wall with an annular recess 30, and the inner ram part 26, which is solid, has an annular flange 32 adapted to operate in but ofless axial depth than the said recess 30. This annular flange 32 carries an upper hydraulic fluid sealing ring 34, and the annular recess 30 in the outer ram part houses spring means 36 arranged resiliently to urge the said annular flange together with the sealing ring, 34, into abutment against the upper wall of the recess.

At the top of the inner part 26 of the ram is carried a pump cylinder 38 wherein is slidingly arranged a pump piston 40 carrying a clevis 42 to which is pivotally secured a connecting rod 44 arranged axially within the reservoir space 16 and adapted for operative connection, at its end remote from the pump piston 40, with a handle (not shown) positioned externally of the support, the handle being arranged for reciprocation between a pair of limiting positions, which typically may be some 45 above the horizontal to 45 below the horizontal. By way of example, the connecting rod 44 is shown diagrammatically as being engaged at its upper end with a crank pin 46 of a crank 48 pivotally mounted in the cylindrical wall of the member 14, the crank being formed externally of the member 14 with a square recess 50 adapted to receive a co-operating key presented by the said handle. At its lower position, shown in dotted lines in Fig. 1, the pump piston 40 abuts against the bottom of the pump cylinder 38 which is, of course, constituted by the top of the inner part 26 of the two-part hydraulic ram, and

considerable resistance to further depression of the handle is experienced due to the springs 36 which urge the two ram parts 24 and 26 together, this resistance being all the greater if the prop is supporting a load and hence there is pressure in the working space 18. If, however, there is no load on the prop, further depression of the handle beyond its normal 45 lower limit causes the piston 38 to depress the inner ram part 26 so as to separate the same from the outer part 24 and create the fluid flow passage 28, thereby enabling hydraulic fluid to pass with a minimum of resistance from the working space 18 to the reservoir space 16, and in consequence, due to the weight of the second cylindrical member 14 and its ram, permitting a rapid drop of the latter within the first cylindrical member 10. Thus a prop from which a load has been removed, but which is still in an extended condition, may rapidly be collapsed and made ready for resetting in a new position.

If convenient in any particular construction of hydraulic support embodying the invention, the inner part of the ram 26 may include suction and delivery ports 52 and 54 with valves 56 and 58 for the pump, and an excess pressure relief valve (not shown) allowing the support to yield under a predetermined maximum load.

We claim:

1. In a hydraulic support of the type having a hollow outer member defining a pressure chamber, an elongate Patented Nov. 15, 1,960

hollow inner member telescopically received within one end of said outer member and having an inner end projecting into said pressure chamber, and means for controlling the flow of pressure fluid between the interior of said hollow inner member and said pressure chamber; the improvement wherein said means for controlling flow comprises a housing defining a piston chamber opening at one end into the interior of said inner member and having a first valve controlled flow passage for conducting fluid from the other end of said piston chamber through said housing into said pressure chamber, said housing having a second valve controlled flow passage therein for conducting fluid from the interior of said inner member to said other end of said piston chamber, means supporting said housing within an opening in said inner end of said inner member for relative sliding movement longitudinally of said inner member, shoulder means on said housing engageable with said inner member to limit sliding movement of said housing into said inner member and operable when engaged with said inner member to seal said opening from said pressure chamber, means normally maintaining said shoulder means in engagement with said inner member, a piston mounted within said piston chamber for reciprocating movement longitudinally of said inner member to pump pressure fluid from the interior of said inner member into said pressure chamber via said flow passages, means for reciprocating said piston in a normal working stroke between the ends of said piston chamber, said reciprocating means being movable to an abnormal position to engage said piston with said other end of said piston chamber to drive said housing outwardly of said inner member to thereby disengage said shoulder means from said inner member and place said pressure chamber in direct fluid communication with the opening in said inner member.

2. A hydraulic support as defined in claim 1 wherein said means normally maintaining said shoulder means in engagement with said inner end of said inner member comprises an extension on the inner end of said inner member, and spring means seated in compression between said extension and said shoulder means to resiliently maintain said shoulder means seated against said inner member.

References Cited in the file of this patent UNITED STATES PATENTS

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