US2955574A - Hydraulic actuator having cooling fluid circulation - Google Patents

Description

2,955,574 HYDRAULIC ACTUATOR HAVING COOLING FLUID CIRCULATION Filed Jan. 13, 1958 H. M. GEYER Oct. 11, 1960 4 Sheets-$heet 1 INVENTOR. flowaea M Game Ms firms/m 2,955,574 HYDRAULIC ACTUATOR HAVING COOLING FLUID CIRCULATION Filed Jan. 15, 1958 I H. M. GEYER 4 Sheets-Sh et 2 Oct. 11, 1960 I-NVENTOR. f/awaea M 65% 5 AWAJ C, 5% Ms flrroem'f N A r .R mm u H. M. GEYER Oct. 11 1960 HYDRAULIC ACTUATOR HAVING COOLING FLUID CIRCULATION Filed Jan. 15, 1958 4 Sheets-Sheet 3 INVENTOR. Hon/41w M 665458 J m I M5 firraezvir UnitedStates Patent Ofiice 2,955,574 Patented Oct. 11, 1960 HYDRAULIC ACTUATOR HAVING COOLING FLUID CIRCULATION Filed Jan. 13, 1958, Ser. No. 708,490

Claims. (Cl. 12138) This invention pertains to actuators, and particularly to synchronized hydraulic actuators designed for use in high ambient temperatures.

It is well recognized that hydraulic actuators which are subjected to high ambient temperatures in the range of 1000 F. must include means for circulating hydraulic fluid throughout the parts exposed to such ambient temperatures to effect cooling thereof. The. present invention relates to a linear actuator assembly designed for synchronous operation with other like actuators including self-cleaning orifice means for controlling the metered flow of circulating hydraulic cooling fluid. Accordingly, among my objects are theprovision of a hydraulic actuator assembly including means for circulating cooling fluid throughout substantially the entire length of the piston rod; the further provision of a hydraulic actuator including metallic piston rings constituting a metering orifice for the circulation of cooling fluid; and the still further provision of an actuator assembly including tandem arranged pistons and means for circulating cooling fluid through the exposed piston rod thereof.

The aforementioned and other objects are accomplished in the present invention by incorporating an oil circulation tube in the actuator assembly and pressure drop orifice means for the circulation of cooling oil through the tube. Specifically, the actuator assemblies of this invention constitute improvements over the actuator assembly disclosed in my copending application Serial No. 681,033, filed August 29, 1957. Moreover, two embodiments of an improved actuator assembly are disclosed, the first embodiment including a cylinder having a reciprocable piston disposed therein. The piston includes a rod which extends without the cylinder for attachment to a movable load device, the cylinder being attached to a fixed support. The piston carries a nut which engages a screw shaft, or rotatable member, such that piston reciprocation is dependent upon rotation of the screw shaft. The screw shaft is adapted for connection through gearing to a rotary synchronizing shaft which interconnects adjacent like actuators. The piston rod carries a pair of metallic piston rings, which are assembled with the actuator by first placing a sleeve thereover, the sleeve constituting an assembly tool, and thereafter remaining within the actuator cylinder. The piston rings constitute pressure drop orifice means, and the rod has disposed therein a coaxial tube such that oil flowing between the piston rings and the cylinder can flow through a rod opening to the space between the tube and the inner surface of the rod.

The oil circulation cooling tube terminates short of the outer end of the rod such that cooling fluid can pass through the tube and back through the piston to the other actuator chamber. In addition, the rod end of the cylinder includes a pressure drop bushing as well as low pressuremetallic seals, the outlet side of the pressure drop bushing being connected to a drain circulation line.

In the second embodiment the actuator assembly includes a pair of pressure drop bushings, a pair of pistons arranged in tandem and a piston rod which extends Without the cylinder. One of the pistons is operatively connected to a screw shaft such that pistonreciprocation is again dependent upon rotation of the screw shaft. The external piston rod likewise has an oil circulation tube coaxially disposed therein whereby oil leakage past the pressure drop bushing passes throughout substantially the entire length of the rod before returning to the actuator chamber having the lower pressure potential.

Further objects and advantages of the present inven tion will be apparent from the following description, reference being had to the accompanying drawings, wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

Figure 1 is a perspective view, partly in section and partly in elevation, of an actuator assembly constructed according to one embodiment of this invention.

Figure 2 is a fragmentary view, partly in section and partly in elevation, of an actuator constructed according to the second embodiment of this invention.

Figure 3 is a fragmentary sectional view of'the actuator assembly constructed according to the second embodiment of this invention.

Figures 4 and 5 are enlarged fragmentary sectional views of the pressure drop bushings 98 and 82, respectively, of Figure 3.

With particular reference to Figure 1, an actuator assembly is shown including a cylinder 10 having an integral axially extending skirt portion 11 at the rod end thereof. The head end of the cylinder is closed by a cap 12 having a fixture 13 by which means the actuator can be attached to a fixed support, not shown. The cylinder 10 has disposed therein a reciprocable piston 14 having a pair of metallic piston ring seals 15, the piston 14 dividing the cylinder 10 into an extend chamber 16 and a retract chamber 17. The piston carries a nut 18 which threadedly engages a screw shaft 19 attached to a worm gear 20. The worm gear 20 is rotatably journalled with the cylinder 10 by ball bearing assemblies 21, and reciprocation of the piston 14 is dependent upon and effects rotation of the screw shaft 19.

In accordance with the teachings of my Patent 2,657,- 639, the worm gear 20 meshes with a worm 22 attached to a rotary synchronizing shaft 23, which may be of the flexible type. The synchronizing shaft 23 is utilized to interconnect the rotatable members, or screw shafts, of adjacent like actuators so as to synchronize their movements. In addition, synchronizing shaft 23 is enclosed by a conduit 24 through which hydraulic fiuid under pressure can be admitted or drained from the extend chamber 16.-

The piston 14 has an integral hollow rod 25 that extends wi-thout the cylinder. The rod has a closed outer end and can be connected to any suitable movable load device, not shown. The actuator is installed so that neither the cylinder nor the piston can rotate, and hence, it is termed a linear actuator. The piston rod carries a pair of piston ring type seals 26, which constitute selfcleaning orifice means since they permit a metered amount of fluid flow between the rod and the cylinder due to a pressure differential thereacross. The orifice means are termed self-cleaning since any foreign ma terial which may become lodged between the piston rings 26 and the skirt 11 will be automatically removed during reciprocation of the piston rod relative to the cylinder. The piston rings are maintained in assembled relation with the rod 25 by a sleeve 27 prior to insertion of the piston and rod assembly into the cylinder. However, after assembly of the piston rod in the skirt 11 of the cylinder, the sleeve 27'remains in the retract chamber, as shown in Figure 1. The retract chamber 17 is connected through a porting block 28 to a retract conduit 29 through which fluid under pressure may be applied or drained from the retract chamber 17.

The piston rod 25 has an oil circulation tube 30 press fitted therein, the major portion of the oil circulation tube 30 being of a lesser diameter than the hollow piston rod so as to form an annular channel 31 between the tube and the inner surface of the hollow piston rod. The annular channel 31 connects with the right hand side of the piston ring seal 26 through a radial passage 32. The circulation tube 31 terminates short of the closed outer end of the hollow piston rod, and the inner end of the tube 30 connects with the extend chamber 16 through passage means in the piston similar to those disclosed in the aforementioned copending application.

In addition, the rod end of the cylinder is fitted with a pressure drop bushing 33 as well as metallic low pressure seals 34 and 35 which are retained in position by a nut 36. The outlet side of the pressure drop bushing 33 communicates with an annular groove 37 which connects with a porting block 38 and a drain conduit 39. The porting block 38 is attached to the rod end of the cylinder by a U-shaped clamp 40, the ends of which are threaded to receive nuts, such as indicated by numeral 41.

Operation of the actuator aforedescribed is as follows.

Upon application of pressure to the extend chamber 16 while the retract chamber 17 is connected to drain, the piston 14 will move outwardly as viewed in Figure 1 thereby eflecting rotation of the screw shaft 19. A predetermined amount of fluid from the extend chamber 16 will flow into the hollow rod 25 through passages 18a formed by longitudinal serrations in the nut as seen in Figure la, through the tube 30, to the outer end of the rod 25 and thence through the annular channel 31 thereby cooling substantially the entire length of the piston rod. This cooling fluid will flow to drain through the passage 32, past the piston ring type orifice means 26 which control the amount of circulating cooling fluid, and thence to the retract chamber 17 which is connected to drain. Any cooling fluid which does not pass through the orifice means 26 will flow outwardly to the annular groove 37 and thence through the porting block 38 to the drain conduit 39.

Conversely, when the retract chamber is subjected to pressure while the extend chamber is connected to drain, a predetermined quantity of oil will flow past the pressure drop bushing piston ring type sealing means 26 through the passage 32, to the annular groove 31 and thence through the tube 30 and back to the extend chamber 16. Some fluid will also flow between the rod 25 and the skirt 11 to the annular groove 37 and thence to the drain line 39.

With particular reference to Figures 2 and 3, a second embodiment of a hydraulically cooled synchronized actuator will be described. In the second embodiment, the actuator includes a cylinder 50 having a head end cap 51 secured thereto by means of a nut 52. The cylinder 50 has a pair of porting blocks 53 and 54 attached thereto by U-shaped clamps 55, having threaded ends which receive nuts 56. As seen particularly in Figure 3, the head cap 51 has a fixture 57 attached thereto whereby the cylinder may be attached to a fixed support, not shown. In addition, a Worm gear 58 is rotatably journalled within the head cap 51 by means of a ball bearing 59 and 60. The worm gear 58 meshes with a worm 61 which may be attached to a flexible synchronizing shaft enclosed Within a conduit 62. The conduit 62 is used to supply and drain oil to the actuator extend chambers, as will be described hereinafter.

In the actuator assembly of the second embodiment, a tandem piston arrangement is utilized enabling the use of a smaller diameter cylinder. Thus, the cylinder 50 has disposed therein a pair of pistons 63 and 64 having metallic pinion ring seals 65 and 65', respectively. The

piston 63 is integral with a hollow rod 66 which is threadedly connected at 67 to the piston 64. In addition, the piston 63 carries a nut 68 which threadedly engages a rotatable screw shaft 69 connected to the worm gear 58. Accordingly, reciprocation of the piston 63 and the piston 64 is dependent upon rotation of the screw shaft 69. The nut 68 is formed with external serrations so as to form passages 70 for the flow of circulating cooling fluid through the piston 63.

The piston 63 divides its portion of the cylinder into an extend chamber 71 and a retract chamber 72, the cylinder being divided into two portions by a pressure drop bushing 98. Likewise, the piston 64 divides its portion of the cylinder into an extend chamber 73 and a retract chamber 74. The extend chambers 71 and 73 are interconnected by a conduit 75, and the retract chambers 72 and 74 are interconnected by a conduit 76. One end of the conduit 75 connects with the conduit 62 and the other end of the conduit 75 connects with the porting block 53 and thence through a passage 77 to the extend chamber 73. Conduit 62 is connected to extend chamber 71 through passage 97. One end of the conduit 76 connects with the porting block 53 and through a passage 78 to the retract chamber 72. The conduit 76 also connects to a conduit 79 in the porting block 53. The other end of the conduit 76 connects through a passage 80 in the porting block 54 to the retract chamber 74. In addition, the porting block 54 is connected to a drain line 81.

The pressure drop bushing 98 slidably supports the piston rod 66, it being understood that there is a slight annular clearance 98a, as seen in Figure 4, between the inner diameter of the pressure drop bushing and the piston rod 66 constituting a self-cleaning orifice. The latter orifice is termed self-cleaning since any foreign material which may become lodged between the pressure drop bushing 98 and the piston rod 66 will be automatically removed upon reciprocation of the piston rod relative to the cylinder and the pressure drop bushing 98. The rod end of the cylinder likewise includes a pressure drop bushing 82, the outlet side of which connects with a radial passage 83 and the drain line 81. There is also a slight annular clearance 82a between the rod 84 and the pressure drop bushing 82, as seen in Figure 5, constituting a self-cleaning orifice.

The piston 64 also includes an integral hollow rod 84 having a closed outer end. The piston rod 84 is adapted for connection to a movable load device and extends outside of the cylinder. In addition, the piston rod 84 has attached thereto a sleeve 85. with a flanged end 86 telescopically disposed within a reciprocable sleeve 87 having flanged ends 88 and 89. The slidable sleeve 87 is disposed within an outer heat shield 90 having a flanged end 91. During outward movement of the piston rod 84, as viewed in Figure 3, the flange 86 will engage the flange 88 with sleeve 87 and thereby move the sleeve 87 out- Wardly until the flange 89 engages the flange 91 of the heat shield 90. The heat shield 90 is attached to the cylinder 50 by a threaded coupling 92. In addition, the rod end of the cylinder 50 includes three metallic low pressure seals 93.

The hollow rod 84 has disposed therein an oil circulation tube 94, the inner end of which is snugly received wittnn the hollow piston rod 66. The outer end of the rod 94 has a plurality of radial ports 95 therein, the rod 94 terminating short of the closed outer end of the rod 84. The tube 94 is utilized to circulate cooling fluid throughout substantially the entire length of the piston rod 84 to eflect cooling thereof.

Operation of the tandem piston actuator is as follows. When the extend chambers 71 and 73 are subjected to fluid under pressure while the retract chambers 72 and 74 are connected to drain, a predetermined quantity of oil will flow from the extend chamber 71 through the passage 70, the hollow rod 66 to the tube 94 so as to cool the rod 84. The return flow of the cooling oil is through holes 95, and the annular space 96 between the tube 94 and the hollow rod 84. This cooling oil will flow through groove 99 between the tube 94 and the outer end of rod 66 through radial passages 100 in the rod 66 and thence through the annular clearance between the pressure drop bushing 98 and the rod 66 to retract chamber 72 which is connected to drain. During application of pressure fluid to the extend chambers, pisgons and 64 will move to the right as viewed in Figures When pressure is applied to retract chambers 72 and 74 while the extend chambers 71 and 73 are connected to drain, oil will flow from the retract chamber 72 through the orifice means to passages 100 and thence through the passage 99 to the channel 96. This cooling oil will flow to the outer end of the rod through passages 95 and thence through the tube 94 to the hollow piston rod 66 to the extend chamber 71 through the passage 70. At this time, a predetermined quantity of oil will also flow past the pressure drop bushing 82 to the annular groove 83 and thence to the drain line 81. During the application of pressure to the retract chambers, of course, the pistons 63 and 64 will move to the left as viewed in Figure 3.

While the embodiments of the invention as herein disclosed constitute a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. An actuator assembly including, a cylinder, a pair of tandem arranged reciprocable pistons disposed in said cylinder capable of fluid pressure actuation in both directions, one of said pistons having a hollow rod with a closed outer end extending from said cylinder, the other of said pistons having a rod connected to said one piston, self-cleaning orifice means between one of said rods and said cylinder, and means directing the flow of fluid through said orifice means throughout substantially the entire length of said hollow piston rod to effect cooling thereof.

2. An actuator assembly including, a cylinder, a pair of tandem arranged reciprocable pistons disposed in said cylinder capable of fluid pressure actuation in both directions, one of said pistons having a hollow rod with a closed outer end extending from said cylinder, the other of said pistons having a hollow rod attached to said one piston, a member rotatably journalled in said cylinder and operatively connected with one of said pistons whereby piston reciprocation effects rotation of said member, selfcleaning orifice means between said cylinder and one of said rods, and means directing the flow offluid through said orifice means throughout substantially the entire length of the hollow piston rod to effect cooling thereof.

3. A fluid pressure operated actuator, including, a cylinder, a pair of tandem arranged reciprocable pistons disposed in the cylinder, one of said pistons having a hollow rod extending from the cylinder with a closed outer end, the other piston having a hollow rod attached to said one piston, a member rotatably supported in said cylinder and operatively connected to said other piston so as to rotate upon piston movement, a pair of spaced self-cleaning orifice means between the cylinder and said rods permitting a metered flow of fluid therebetween due to a pressure differential across said orifice means, said pistons dividing the cylinder into pairs of opposed chambers, one end of each orifice means connecting with one pair of said chambers, means connecting the other end of one of said orifice means to the interior of one of said hollow rods, and means including a tube disposed within one of said hollow rods for connecting the outer end of said extending hollow piston rod with one of said other pair of actuator chambers.

4. An actuator assembly including, a cylinder, a pair of tandem arranged reciprocable pistons disposed in the cylinder capable of fluid pressure actuation in both directions, means dividing said cylinder in two parts, each piston dividing its part of the cylinder into an extend chamber and a retract chamber, one of said pistons having a hollow rod extending from said cylinder with a closed outer end, the other piston having a hollow piston rod attached to said one piston, said means dividing said cylinder into two parts comprising self-cleaning orifice means between said cylinder and the rod attached to the other piston, one end of said orifice means connecting with the retract chamber of one cylinder part and the other end of the orifice means connecting with the extend chamber of the other cylinder part, passage means connecting the other end of the said orifice means with the interior of said hollow rod having a closed outer end, a tube disposed within said hollow rod and having an end spaced from the closed outer end of said rod, and through which fluid passing through said orifice means to the outer end of the rod can flow, and passage means connecting the interior of said tube with the extend chamber of one of said cylinder parts, said orifice means permitting metered flow of fluid due to a pressure differential thereacross which flow of fluid cools substantially the entire length of said hollow rod having the closed outer end.

5. A fluid pressure operated actuator including, a cylinder, a reciprocable piston in the cylinder having a hollow rod extending therefrom with a closed outer end, a member rotatably supported in said cylinder and operatively connected to said piston so as to rotate upon piston movement, self-cleaning piston ring type orifice means between the cylinder and the rod permitting metered flow of fluid therebetween due to a pressure diflerential across said orifice means, said piston dividing said cylinder into opposed chambers, one end of said orifice means communicating with one of said chambers, means connecting the other end of the orifice means to the interior of said hollow rod, means including a tube disposed within said hollow rod connecting the outer end of said hollow rod with the other actuator chamber, and a sleeve slidably engaging said piston rod and disposed within one of said actuator chambers, said sleeve being utilized during assembly of the rod with the cylinder for retaining the piston ring type orifice means in position.

References Cited in the file of this patent UNITED STATES PATENTS 2,217,239 Smith Oct. 8, 1940 2,688,313 Bauer Sept. 7, 1954 2,806,450 Geyer Sept. 17, 1957

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