This invention relates to magnetic coupling pneumatic linear motion actuators. More particularly, this invention relates to such linear motion actuators which incorporate a hollow bored tube, a magnetic piston slidably mounted within the tube, and a magnetic sleeve slidably mounted over such tube.
Commonly known and commonly configured magnetic coupling pneumatic linear motion actuators lack any means for accessing the actuator's interior magnet adapted piston in the event such piston becomes seized in place or is in need of repair or replacement.
The instant inventive magnetic coupling pneumatic linear motion actuator solves or ameliorates such problems and deficiencies of commonly known magnetic coupling pneumatic linear motion actuators by providing specially configured shoulders and end caps at opposite ends of the actuator. Such shoulders extend oppositely with respect to each other, with one shoulder extending radially outwardly, and with the other shoulder extending radially inwardly.
The invention's radially outwardly extending shoulder facilitates mounting of an end cap whose removal exposes the entire inside diameter of the tube to facilitate piston insertions and extractions. The invention's radially inwardly extending shoulder allows the formation at the opposite end of the actuator of a push rod passage port which is closed by a removable end cap. Such radially inwardly extending shoulder eliminates any radially outwardly protruding structure which would interfere with sliding installations and deinstallations of the actuator's magnetic sleeve.
A first structural component of the instant inventive magnetic coupling pneumatic linear motion actuator comprises a substantially ridged tube having a longitudinal end and having an oppositely longitudinal end. To facilitate magnetic coupling via radially emanating magnetic flux, the tube's wall is preferably both thin and non-magnetic. The non-magnetic character of the invention's tube component advantageously establishes the radial thickness dimension of the tube's wall as a magnetically neutral or non-magnetic “air gap”.
To maximize the magnetic attraction between an interior magnetic piston and an exterior magnetic slide sleeve, the tube's wall thickness is preferably minimized. While tube wall materials such as plastic, copper, brass, and aluminum may satisfy the required non-magnetic “air-gap” characteristic of the tube, utilization of such materials to form the thin wall of the tube undesirably results in insufficient structural rigidity, causing the tube to bow or buckle.
Satisfaction of both the thin wall characteristic and non-magnetic wall characteristic of the actuator's tube often requires that the tube be composed of durable and strong non-magnetic stainless steel. However, a follow-on problem associated with the provision of a thin-walled stainless-steel tube is recognized upon a fabricator's attempt to cut female or male helical screw threads at the ends of the tube for the purpose of installation of a removably attachable end caps. The formation of such screw threads at the ends of such stainless steel tubes often fails because the thin wall character of such tube interferes with proper tap and die thread cutting. “V” channel helical threads cut at the ends of such thin walled stainless-steel tubes extends multiple channels through a major portion of the tube's wall thickness, undesirably degrading the structural integrity of the tube.
The inability of thin-walled stainless-steel pneumatic actuator tubes to receive sufficiently deep and strong helical threads tends to complicate a needed adaptation of prior art magnetic coupling pneumatic linear motion actuators to include releasably attached end caps. Such defect interferes with provision of mechanical access to the tube's interior magnetic piston when repairs are needed. As a result of such design challenges, known magnetic coupling pneumatic linear motion actuators commonly permanently seal their magnetic pistons within their tubes, and provide no means of access to the magnetic piston for repairs. Such defects undesirably require wasteful replacements of an entire tube when the interior magnetic piston is in need of maintenance or repair.
The instant invention advantageously and beneficially solves and ameliorates such problems by facilitating an insertion of a push rod through an end cap and into the actuator's tube for dislodging a stuck or seized magnetic piston. The instant invention enables such push rod insertions by providing specially configured shoulders and specially configured end caps associated with the shoulders at opposite ends of the actuator's pneumatic tube.
The instant invention recognizes that extraction of the actuator's magnetic piston from one of the ends of the actuator's tube requires that that end of the tube's bore be unobstructed. However, the tube's piston extraction end must be removably capped, requiring the provision of a cap mounting surface which extends radially outwardly from the tube's bore.
The instant invention also recognizes that a sliding deinstallation of the actuator's magnetic sleeve cannot be performed at the actuator's magnetic piston extraction end because the radially outwardly extending cap mounting surface at that end of the tube mechanically interferes with sliding deinstallation of the magnetic sleeve. Accordingly, the sliding deinstallation of the magnetic sleeve must occur at the opposite end of the actuator's tube.
The instant invention also recognizes that provision of such another removable cap at the sleeve deinstallation end of the tube will allow, upon cap removal, a push rod to be inserted into the tube to drive the magnetic piston toward the tube's piston extraction end. However, the mounting surface upon which such another removable cap is mounted cannot extend radially outwardly from the tube's bore, because any radially outward extension of the such mounting surface would mechanically interfere with sliding deinstallation of the magnetic sleeve.
The instant invention avoids the above-described mechanical interferences with magnetic piston extraction and with magnetic sleeve deinstallation by providing a pair of annularly extending shoulders which are fixedly attached to or formed wholly with the tube's ends. One of such shoulders extends radially inwardly from the tube's longitudinal end, while the other shoulder extends radially outwardly from the tube's oppositely longitudinal end. Removable end caps which are mounted upon such shoulders advantageously permit magnetic piston extraction at the tube's oppositely longitudinal end while permitting both a push rod insertions and magnetic sleeve deinstallations at the tube's longitudinal end.
Accordingly, objects of the instant include the provision of a magnetic coupling pneumatic linear motion actuator which incorporates structures as described above and which arranges those structures in relation to each other in the manners described above for the performance of useful functions as described above, other and further objects, benefits, and advantages of the instant invention will become known to those skilled in the art upon review of the detailed description which follows, and upon review of the appended drawings.
Referring now to the drawings, and in particular to
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A further structural component of the instant inventive actuator comprises a magnetic sleeve which is slidably mounted about and extends annularly over the tube 2. As shown in
The preferred magnetic sleeve 14 comprises longitudinal and oppositely longitudinal sleeve halves 16 and 18 which are rigidly interconnected by longitudinally extending bolt fasteners 20. Longitudinal and oppositely longitudinal wiper seals 24 extend annularly about the tube 2, while inwardly mounded longitudinal and oppositely longitudinal hydraulic seals 25 facilitate continuous lubrication for the prevention of fouling and jamming of the sleeve 14. The hydraulic seals 25 hermetically seal an annulus or reservoir 30 which surrounds the tube 2, such annulus 30 retaining a volume of hydraulic fluid which continuously lubricates sliding contact points between the magnetic sleeve 14 and the tube 2.
A longitudinally extending series of radially outer ring magnets 26 and magnetically permeable pole pieces 28 is supported at the radially inner periphery of the sleeve. In the preferred embodiment the sleeve's magnets and pole pieces are arranged similarly with the piston's magnets and pole pieces 10 and 12.
Intense magnetic fields emanating radially inwardly from magnets and pole pieces 26 and 28 and emanating radially outwardly from magnets and pole pieces 10 and 12 establish a non-mechanical locked juncture between the magnetic sleeve 14 and the magnetic piston 6. As the piston 6 is driven longitudinally or oppositely longitudinally along the hollow bore 4 of the tube 2, such magnetically locked connection between the sleeve 14 and the piston 6 required that the sleeve travel along the tube 2 with the magnetic piston 6. An equipment mounting bracket or fastener such as a threadedly mounted eye 29 attached to the undersurface of the sleeve 14 may be operatively connected to a workpiece which is operatively moved by the actuator 1. A typical example of such workpiece is a garage door (not depicted within views).
In the preferred embodiment, the outside diameter of the tube 2 is substantially equal to the effective inside diameter of the magnetic sleeve 14 at the inner peripheries of its wipers 24 and hydraulic seals 25. Correspondingly, the effective outside diameter of the magnetic piston 6 at the radially outer peripheries of the “O” ring seals 8 is substantially equal to the inside diameter of the tube 2.
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The inventive linear motion actuator further comprises a longitudinal end cap which is referred to generally by reference arrow 73. In the preferred embodiment, the longitudinal end cap 73 is positioned at the longitudinal end of the tube 2, such cap being adapted for releasable attachment to the tube's longitudinal shoulder 62. In a preferred embodiment, such releasable attachment comprises a combination of male 66 helical threads which extend radially outwardly from the end cap 73 in mating combination with female helical threads 64 which extend radially inwardly from the radially inner periphery of the longitudinal shoulder 62.
In a preferred embodiment, the longitudinal end cap 73 presents an annular flange 68, which supports an air sealing “O” ring 70. Upon application of a wrench to the longitudinal end cap's hexagonal head 76, wrench actuated turning and counter turning may install or deinstall the end cap 73 upon and from the longitudinal shoulder 62.
While the longitudinal end of the longitudinal shoulder 62 is adapted to facilitate releasable attachment of the longitudinal end cap 73, the oppositely longitudinal end of such shoulder preferably forms a hollow push rod receiving port or channel 78, the function of which is described below.
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In operation of the instant inventive magnetic coupling pneumatic linear motion actuator 1, and referring simultaneously to
The magnetic piston may, upon occasion, become mechanically seized or stuck within the hollow bore of the tube 2. Upon such seizure of the magnetic piston 6, an operator may apply a wrench to the hexagonal head 76 of the longitudinal end cap 73, and may turn such end cap counter clock wise to unscrew and uninstall the longitudinal end cap 73. Thereafter, as indicated in
To facilitate similar maintenance of the magnetic sleeve 14, the air line attachment adapter 82 may be threadedly removed from port 80. Thereafter, one of the hydraulic fluid plugs 32 may be unscrewed and removed from the sleeve 14, allowing the hydraulic fluid within sleeve annulus 30 may be drained. Thereafter, the magnetic sleeve may be slidably moved longitudinally along the tube 2 until such sleeve reaches the tube's extreme longitudinal end. The exclusively radially inward extension of the longitudinal shoulder 62 assures that no end cap mounting structure interferes with sliding removal of the magnetic sleeve 14. The exclusively radially inward extension of the longitudinal shoulder 62 effectively forms a radially outwardly extending annulus 63 through which the magnetic sleeve 14 may freely pass. In the preferred embodiment, the inside diameter of the annulus 63 is less than the outside diameter of the tube 2, such differential in diameters assuring that the entirety of the magnetic sleeve 14 may pass longitudinally through such annulus 63.
Upon a sliding longitudinal removal of the magnetic sleeve 14, maintenance and repairs may be performed. Thereafter, the magnetic sleeve may be reinstalled by oppositely longitudinally sliding the magnetic sleeve 14 over the outer periphery of the longitudinal shoulder 62 and over the longitudinal end of the tube 2.
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While the principles of the invention have been made clear in the above illustrative embodiment, those skilled in the art may make modifications to the structure, arrangement, portions, components, and method steps of the invention without departing from those principles. Accordingly, it is intended that the description and drawings be interpreted as illustrative and not in the limiting sense, and that the invention be given a scope commensurate with the appended claims.