US3003471A - Actuator with stroke end locking means and stroke adjusting means - Google Patents

Description

Oct. 10, 1961 R. c. BODEM ETAL ACTUATOR WITH STROKE END LOCKING MEANS AND STROKE ADJUSTING MEANS 2 Sheets-Sheet 1 Filed June 23, 1958 INVENTORS. Ray 6. Bodem. Howard M. Geyer.

Their Attorney.

Oct. 10, 1961 Filed June 25, 1958 R. c. BODEM ETAL ACTUATOR WITH STROKE END LOCKING MEANS AND STROKE ADJUSTING MEANS 2 Sheets-Sheet 2 INVENTORS. Ray C. Bodem. Howard M. Geyer.

Th'eir Attorney.

United States This invention pertains to fluid pressure operated actuators, and particularly to a linear actuator having stroke end locking means and means for adjusting the stroke of the actuator.

In order to use the same actuator in different installations, it is necessary to incorporate means for adjusting the stroke of the actuator without varying the physical dimensions of the actuator cylinder. In addition, in some installations it is only necessary to lock the actuator against movement in one position, for instance, at one end of the stroke. Moreover, where fluid pressure operated actuators are subjected to high ambient temperatures, it is necessary to provide means for circulating fluid through the actuator chambers to prevent congealing thereof and to cool the actuator. The present invention relates to a linear actuator including releasable means for locking the actuator piston against movement at one stroke end position thereof; externally adjustable means for varying the stroke of the actuator; and means permitting the circulation of fluid in metered quantities to prevent congealing thereof due to high ambient temperatures. Accordingly, among our objects are the provision of a fluid pressure actuator including stroke end locking means; the further provision of a fluid pressure operated actuator including stroke end locking means and means for automatically releasing the locking means upon application of pressure fluid so as to effect actuator movement away from the stroke end locking position; the further provision of fluid pressure operated actuator including means for adjusting the stroke of the actuator piston; and the still further provision of an actuator of the aforesaid type including means for circulating fluid through the actuator chambers to effect cooling thereof.

The aforementioned and other objects are accomplished in the present invention by incorporating fingertype locking means in an actuator in combination with an adjustable drain tube, the position of which determines the stroke of the actuator piston. Specifically, the unit comprises a cylinder having a reciprocable piston therein capable of fluid pressure actuation in both directions. The piston divides the cylinder into an extend chamber and a retract chamber, and includes an integral rod which extends outside of the cylinder for attachment to a movable load device. The cylinder is adapted to be connected to a fixed support.

In order to facilitate circulation of fluid through the retract chamber, a pressure drop bushing is incorporated in therod end of the cylinder, and the piston rod is slideably supported by the pressure drop bushing and extends therethrough. The pressure drop bushing functions in the manner set forth in copending application Serial No. 648,361 filed March 25, 1957, now Patent No. 2,953,119, inthe name of Howard M. Geyer and assigned to the assignee of this invention, such that whenever there is a pressure differential across the pressure drop bushing, a metered amount of fluid will flow between the pressure drop bushing and the piston rod to a drain conduit. A second pressure drop bushing is subjected to the pressure existent in the extend chamber for permitting the circulation of cooling fluid therethrough to a drain tube.

The drain tube is coaxially disposed within the cylinder and extends into the hollow piston rod. The drain tube has a closed inner end having a plurality of radial pasatent 'ice sages therethrough adjacent the end thereof, which pas sages communicate with an annular groove in a bushing fixedly attached to the tube. The bushing has a plurality of radial ports therein which are normally closed by the piston rod or the piston head. By adjusting the position of the drain tube relative to the cylinder, the ports in the bushing will be uncovered during extending movement of the piston, and when the ports are uncovered the extend chamber will be connected to drain thereby limiting the stroke of the actuator piston and determining the extend stroke end position of the piston.

The piston also carries a pair of pivotally mounted locking fingers or jaws which are engageable with a fixed locking cam attached to the head end of the cylinder. When the actuator piston is moved to the fully retracted stroke end position, the locking fingers engage the locking cam and a spring biased piston, and thereby prevent extending movement of the actuator piston under the influence of the load device attached thereto. In order to release the stroke end locking means upon the application of pressure fluid to the extend chamber, the spring biased piston is moved out of engagement with the locking fingers whereby the locking means are disengaged so as to permit extending movement of the actuator piston.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred embodiment of the present invention is clearly shown.

in the drawings:

FIGURE 1 is a fragmentary longitudinal sectional view of an actuator constructed according to this invention with the stroke end locking means engaged.

FIGURE 2 is a fragmentary longitudinal sectional view of the actuator with the stroke end locking means disengaged depicting the stroke of the piston as limited by the adjustable drain tube.

FIGURE 3 is a fragmentary sectional View depicting the limits of adjustment of the drain tube for varying the stroke of the actuator.

FIGURE 4 is an enlarged sectional view taken along line -4-4 of FIGURE 2.

With particular reference to FIGURE 1, the actuator includes a cylinder 10 having a head end cap 12 attached thereto by means of a nut 14. A reciprocable piston 16 having an integral hollow rod 18 with a closed outer end is disposed within the cylinder 10. The piston 16 divides the cylinder into an extend chamber 20 and a retract chamber 22. The bore of the cylinder 10 adjacent the head end thereof is slightly larger as indicated by numeral 24, than the bore of the cylinder traversed by the piston 16, and the enlarged bore 24 is formed with a shoulder 26.

The hollow piston rod 18. extends through the rod end of the cylinder 10 and slideably engages a pressure drop bushing 28. The pressure drop bushing is formed with an external annular groove 30 and a plurality of axial passages 32 which connect the groove 30 with the retract chamber 22. The cylinder 10 is formed with a retract port 34 that communicates with the annular groove 30. The inner diameter of the pressure drop bushing is spaced slightly from the outer periphery of the piston rod 18 so as to form an annular orifice whereby a metered amount of fluid will flow from the retract chamber 22 to an annular groove 36 formed between the rod end of the cylinder and the piston rod 18 due to a pressure differential across the bushing 23. The annular groove 36 is connected to a drain conduit 38. A plurality of low pressure metallic sealing rings 40 are retained in sealing engagement with the piston rod 18 and the rod end of the cylinder by a nut 42 which threadedly engages the cylinder 10. The retract stroke end position of the piston 16 relative to the cylinder 10 is determined by engagement between the nut 42 and a nut 44 which threadedly engages the piston rod 18 and abuts the nut 42 as shown in FIGURE 1 when the actuator is fully retracted.

The piston 16, as seen particularly in FIGURES l and 4, has a pair of diametrically opposed arcuate fingers, or jaws, 46 pivotally attached thereto by means of pins 48. The fingers 46 are formed with curved ends 50 having beveled, or tapered, inner surfaces 52. The fingers 46 are engageable with a fixed cam member 54 having a complementary frusto conical surface 56 engageable with the surfaces of the fingers. The cam 54 is fixedly attached to the head end cap 12 by means of a nut 58. The cam 54 also has a second frusto conical surface portion 59 which intersects the surface 56.

'In order to maintain the fingers 46 in locking engagement with the cam 54, an auxiliary reciproc-able sleeve piston 69 is disposed within the enlarged portion adjacent the head end of the cylinder 16. The piston 66 is normally urged into engagement with the shoulder 26 by a compression spring 62, one end of which engages the head end cap 12 and the other end of which engages the piston 60. The piston 60 is formed with a frusto conical surface 64 and a cylindrical surface portion 66. When the actuator piston 16 is in the fully retracted stroke end position as shown in FIG- URE l, the cylindrical portion 66 of the piston engages the outer peripher of the fingers 46 so as to preclude disengaging movement the locking fingers 46 from the cam 54 due to an external load acting on the piston rod 18.

The piston 66 carries a pressure drop bushing 68 which slidably engages a cylindrical portion 70 of the cam 54. The slight annular clearance between the pressure drop bushing 68 and the cylindrical periphery 70 0f the cam 54 constitutes an orifice permitting a metered flow of fluid from the extend chamber 20 to the space 72 to the left of the piston 60 as seen in FIGURE 1. The space '72 is connected by one or more passages 74 in the cam member 54 to the hollow interior thereof. The cylinder 16 is formed with an extend port 76 which communicates with the extend chamber 20. In addition, the cylinder has a trunnion 78 attached thereto, as seen in FIGURE 4, by which means the cylinder can be attached to a fixed support.

In order to release the stroke end lockingmeans, fluid under pressure is applied to the extend chamber 20 through the port 76 while the retract chamber 22 is connected to drain through port 34. This pressure fluid will act on the piston 60 and effect movement of the piston 60 to the left thereby compressing the spring 62. When the piston 60 has been moved to the left throughout a sufficient distance so that the cylindrical periphery 66 thereof is disengaged from the locking fingers 46, the pressure fluid acting on the piston 16 will effect movement of the piston 16 to the right, as viewed in FIGURE 1. Thus, the piston 69 constitutes means for releasing the stroke end locking means, since as soon as the cylindrical periphery portion 66 of the piston 69 is disengaged from the fingers 46, relative movement between the coacting inclined surfaces 52 and 56 will result in outward pivotal movement of the fingers 46 so as to disengage the fingers 46 from the cam 54.

Assuming the actuator piston to be in an extended position, as shown in FIGURE 2, upon application of pressure fluid to the retract chamber 22 while the extend chamber 20 is connected to drain, the piston I6 will move to the left, as viewed in FIGURE 2. As the piston 16 approaches the retract stroke end limit p0- sition the curved ends of the fingers will ride up the frusto conical portion 59 of the cam and engage the frusto conical portion 64 of the piston 60 so as to move the piston 69 to the left, as viewed in FIGURE 1. As soon as the locking fingers move out of engagement with the frusto conical portion 59 and into engagement with the frusto conical portion 56, the spring 62 will move the piston 66 to the position of FIGURE 1 there by locking the actuator piston in the fully retracted stroke end position.

The cam 54 is also formed with an internally threaded portion '79. A drain tube 89 having a closed inner end and an open outer end is coaxially disposed within the cylinder Lid and extends into the hollow piston rod 18. The tube St has a plurality of circumferentially spaced radial ports 82 formed therein adjacent the closed inner end thereof and supports a bushing 84 having an internal annular groove 86 and a plurality of circumferentially spaced radial ports 88. The closed outer end of the tube St) is tapered, as indicated by numeral 90 and threaded at 92, and the bushing 84 is securely held in fixed relation relative to the tube 8%) by a nut 94. The open end of the tube is connected to drain, and in addition the tube is formed with a plurality of circumferentially spaced radial ports 96 that communicate with an annular groove 98 formed between the cam 54 and the outer periphery of the tube 30.

The tube 80 is formed with axially spaced threaded portions 1% and 162, the threads 1410 engaging the threads 79 on the cam 54, and the threads 1432 receiving a out 184 having a sealing edge 106 that engages the end of the cam 54 and the outer periphery of the tube St The drain tube 80 is longitudinally adjustable relative to the cylinder 10 for determining the extend stroke end limit position of the piston 16. Normally, the extend stroke end limit position of an actuator piston is determined by engagement of the piston with the rod end of the cylinder. However, in the instant actuator, the extend stroke end limit position can be varied by adjusting the longitudinal position of the drain tube 80 relative to the cylinder 1 3. Thus, as seen in FIGURE 2 when the piston 16 is moved to the right throughout a predetermined distance, the ports 88 in the bushing 84 will be uncovered by the piston. When the ports 83 in the bushing are uncovered, the extend chamber 20 is connected to drain through the ports 88, the groove 86, the ports 82 and the drain tube 80. Accordingly, further movement of the piston 16 to the right under the urge of fluid pressure cannot be effected, and thus the extend stroke end limit position of the actuator is determined by the position of the drain tube 80.

With reference to FIGURE 3, in order to adjust the longitudinal position of the drain tube 80 relative to the cylinder 10, the nut 104 is loosened, whereupon the drain tube 80 can be rotated relative to the cam 54 so as to adjust the longitudinal position thereof relative to the cylinder 10. The limits of adjustment of the tube 80 relative to the cylinder 10 are shown in full and dotted lines in FIGURE 3, and these limits are determined by the length of the annular groove 98 between the cam 54 and the tube 80, since in order to maintain the circulation of cooling fluid through the extend chamber, the ports 96 in the tube must always communicate with the annular groove 98. After the drain tube 80 has been adjusted relative to the cylinder, the nut 104 is tightened to maintain the drain in the adjusted position.

When the extend chamber 20 is subjected to fluid under pressure, the orifice means constituted by the slight annular clearance between the pressure drop bushing 68 and the cam 54 will permit a metered amount of fluid to flow from the extend chamber 20 to the space 72. This fluid will flow through the passage 74 to the groove 98, and from the groove 98 through ports 96 to the drain tube 86. Likewise, when retract chamber is subjected to fluid under pressure, a metered amount of fluid will circulate through the orifice means between the pressure drop bushing 28 and the piston rod 18 through an annular groove 36 and the drain tube 38. Accordingly, when either actuator chamber is subjected to fluid under pressure, the fluid will be maintained in a state of continuous circulation by reason of the pressure drop bushings and the drain tubes.

While the embodiment of the invention has herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A fluid pressure operated actuator assembly including, a cylinder, a reciprocable piston disposed in said cylinder capable of fluid pressure actuation in both directions, said piston having a hollow rod with a closed outer end extending outside of said cylinder and dividing said cylinder into an extend chamber and a retract chamber, a pressure drop bushing disposed between the rod end wall of said cylinder and the outer periphery of said piston rod, the inner surface of said pressure drop bush ing being radially spaced from the outer periphery of said rod so as to form an orifice through which a metered amount of fluid can flow due to a pressure differential across said bushing, a drain conduit connected with the low pressure side of said pressure drop bushing, a drain tube assembly coaxi'ally disposed within said cylinder and having a closed inner end disposed within said piston rod, port means in said drain tube assembly adjacent the closed inner end thereof cooperating with said piston so as to be uncovered and thus connect the extend chamber to drain for determining the extend stroke end limit position of said piston, means for adjusting the position of said drain 6 tube assembly relative to said cylinder to vary the extend stroke end limit position, and means constituting an orifice connecting the extend chamber to said drain tube assembly whereby a metered amount of fluid can flow from said extend chamber to drain due to a pressure differential across said last recited orifice.

2. The fluid pressure operated actuator assembly set forth in claim 1 wherein said last recited means comprises a second pressure drop bushing located adjacent the head end of said cylinder, and means connecting the low pressure side of said second pressure drop bushing with the interior of said drain tube assembly.

References Cited in the file of this patent UNITED STATES PATENTS 1,834,773 Fellmann et a1. Dec. 1, 1931 2,333,274 Schannell Nov. 2, 1943 2,478,790 Stephens Aug. 9, 1949 2,494,752 Gambell Jan. 17, 1950 2,547,029 Loungway Apr. 3, 1951 2,634,709 Fageol Apr. 14, 1953 2,685,275 Caldwell Aug. 3, 1954 2,771,060 Allbright Nov. 20, 1956 2,787,254 Rhoades Apr. 2, 1957 2,851,995 Westcott Sept. 16, 1958 FOREIGN PATENTS 551,207 Germany Oct. 21, 1930

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