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United States Patent  mi Patent Number: 5,031,510
Krauter  Date of Patent: Jul. 16, 1991
 EVACUATION SPRING FOR
 Inventor: Allan I. Krauter, Syracuse, N.Y.
 Assignee: Welch Allyn, Inc., Skaneateles Falls, N.Y.
 Appl. No.: 497,602
 Filed: Mar. 22, 1990
 Int. C1.5 F01B 19/04
 U.S. CI 92/92; 92/94;
92/132; 92/130 A; 128/4; 403/316; 403/341
 Field of Search 92/90, 91, 92, 94, 247,
92/130 R, 130 C, 132, 130 A, 40; 403/316, 317,
341, 353; 128/4
 References Cited
U.S. PATENT DOCUMENTS
1,107,889 8/1914 Burns 403/353
2,399,133 4/1946 Midling 403/316
2,483,088 9/1946 DeHaven 92/90
3,861,814 1/1975 Fisher 403/316 X
4,571,788 2/1986 Bruengger 403/316 X
4,645,373- 2/1987 Purdy 403/341
4,664,232 5/1987 Takagi et al 92/90 X
4,678,360 7/1987 Miller 403/353
4,762,118 8/1988 Lia et al 128/4
4,793,726 12/1988 Sword 403/353 X
4,794,912 1/1989 Lia 92/92 X
4,841,845 6/1989 Beullens 92/90 X
4,865,017 9/1989 Shinozuka 128/4
4,962,751 10/1990 Krauter 128/4
FOREIGN PATENT DOCUMENTS 58-81205 5/1983 Japan 92/90
Primary Examiner—John T. Kwon
Assistant Examiner—John Ryznic
Attorney, Agent, or Firm—Wall and Roehrig
A hydraulically or pneumatically actuated muscle has an elongated elastomeric bladder that is covered by a tubular sheath. A fluid conduit is coupled to the bladder to supply hydraulic or pneumatic pressure. A coil tension spring is attached to a distal terminator of the muscle and extends to the distal end of a compression tube covering the bladder and braid. The evacuation spring draws the braid and bladder towards their fully extended state when fluid pressure is relieved and ellshaped retaining pin in the muscle terminator has one end that extends radially outward to lodge between turns of the evacuation spring. Split shoulder washers secure the proximal and distal ends of the compression tube.
12 Claims, 2 Drawing Sheets
EVACUATION SPRING FOR
BACKGROUND OF THE INVENTION 5
This invention relates to hydraulically or pneumatically actuated muscles, that is, devices which convert a fluid pressure into a tensive force. The invention is more specifically directed to structure for biasing the muscle to its elongated or extended state. The invention is also 10 directed to the serviceable attachment of the distal muscle terminator to its associated control cable.
Hydraulic muscles can be favorably employed in an elongated flexible probe such as a borescope or endoscope for actuating its articulation or steering section. 15 With the use of hydraulic muscles, the conventional long steering cables can be eliminated. This use of a hydraulic muscle in a borescope or endoscope is described in U.S. patent application Ser. No. 357,806, now U.S. Pat. No. 4,962,751 filed May 30, 1989, and having 20 a common assigned herewith. Another fluid dynamic muscle in a borescope or endoscope is described in U.S. Pat. No. 4,794,912, granted Jan. 3, 1989. Fluid dynamic articulation and steering for a borescope or endoscope offers a distinct improvement over the conventional 25 system of steering cables, permitting much more accurate and precise positioning of the viewing end of the instrument within the cavity to be inspected.
The hydraulic or fluid dynamic muscle is made of an elongated tubular bladder which is encased in an elon- 30 gated tubular braid member disposed over it. Terminators are provided at the proximal and distal ends of the muscle to seal the ends of the bladder and to provide a place for mechanical attachment between the ends of the braid member and the mechanical members to 35 which they are to transfer force, e.g., a cable or a muscle sheath. The braid permits the bladder within the muscle to expand laterally when hydraulic pressure is applied to it. However, as the braid and bladder expand radially, the braid contracts axially and generates an 40 axial tensive force.
The fluid dynamic muscles are used in pairs, with one of the muscles being actuated to deflect the borescope steering section in one direction (i.e. to the left) and the other muscle being actuated to deflect the steering sec- 45 tion in the other direction (i.e. to the right). With this arrangement the tension from the muscle that is actuated extends the muscle that is not being actuated and expels the fluid from it. The bladder and braid alone typically are not effective to stretch the muscle back to 50 an elongated state when the hydraulic or pneumatic pressure is relieved. Therefore, there is a constant tension on both steering cables of each pair of cables. This can make steering somewhat difficult, can reduce the amount of articulation of the steering section, and can 55 require higher pressures to be employed than is desirable in view of the need to avoid leakage of hydraulic fluid from the muscles.
Also, under current techniques, access to the muscle terminator that connects to the cable terminator is diffi- 60 cult, once the muscle is installed. Further, it is difficult to detach and reattach the cables to the muscle terminators, and special tools may be required to do so.
OBJECTS AND SUMMARY OF THE 65
It is an object of this invention to provide an improved hydraulic or pneumatic muscle having an inter
nal bladder, an external braid, and a terminator disposed at the distal end to connect with a control cable, and which avoids the drawbacks of the prior art.
It is another object of this invention to provide a hydraulic muscle with a stretching force to bias the same towards its elongated or extended condition.
It is still another object of this invention to provide a retainer mechanism to facilitate assembly and disassembly of the muscle and associated control cable.
According to one aspect of this invention, the fluid dynamic muscle is provided with a coil tension spring for drawing the braid and bladder toward their fullyextended state when fluid pressure is relieved from the bladder. The muscle itself comprises an elongated elastomeric bladder, a fluid conduit coupled to the proximal end of the bladder to supply hydraulic or pneumatic pressure to the interior of the bladder, and a tubular braid disposed over the bladder. The braid is made up of substantially inextensible filaments that cover the bladder. The braid increases in diameter when fluid pressure is applied to the bladder within it, but is self-restrained to contract axially and creates a tensile force that is transmitted to an associated control cable.
A muscle terminator is fitted into the distal ends of the bladder and braid, to seal the distal ends of the bladder and to transmit tensile force between the braid and the proximal end of the control cable, which has a cable sheath disposed over it.
To support the cable sheath, a compression tube is disposed radially outside the braid and extends from the proximal end of the braid, where it is attached to the braid, to a point beyond the distal end of the braid as considered when the braid and bladder are in their fully extended state. At the distal end of the compression tube is supported a cap, in the form of, e.g. a shoulder washer with internal threads, and a threaded nipple supported therein. The control cable passes through this nipple and the proximal end of the cable sheath is held against it.
A coil spring is attached to the distal end of the compression tube, e.g., by screwing one end of it onto the threaded nipple, and is also attached at its other end onto the muscle distal terminator. The evacuation spring is favorably attached to the terminator by means of an ell-shaped retainer pin that also retains the cable terminator within an axial bore of the muscle terminator.
The evacuation spring serves to elongate the muscle and to evacuate any remaining air or hydraulic fluid when the fluid pressure is relieved. This hastens the return of the muscle to its elongated condition and reduces frictional forces in the slack cable, e.g. between the cable and sheath and also within the associated steering section.
This means that frictional buildup of the relaxed muscle and cable does not occur in the cable sheaths or in the bending or steering section. The opposed or active muscle does not have to overcome that frictional force, but only needs to meet the additional force of its own evacuation spring, which is typically about ten percent of the muscle force.
Borescopes which employ a hydraulic muscle with evacuation spring have exhibited an increase of at least 20 degrees in the range of steering deflection obtainable without any increase in hydraulic capacity or pressure.
The use of the evacuation spring in combination with a cable retention pin permits easy serviceability of the