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Publication numberUS3146592 A
Publication typeGrant
Publication dateSep 1, 1964
Filing dateMay 20, 1959
Priority dateMay 20, 1959
Publication numberUS 3146592 A, US 3146592A, US-A-3146592, US3146592 A, US3146592A
InventorsJohnson Philip C
Original AssigneeF & F Koenigkramer Company
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Hydraulic lift with rotation lock for beauty chair
US 3146592 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

Sept 1, 1964 P. c. JOHNSON 3,146,592

HYDRAULIC LIFT WITH ROTATION LOCK FOR BEAUTY CHAIR Filed May 20, 1959 2 Sheets-Sheet l ATTORNEYS.

Sept 1, 1964 P. c. JOHNSON 3,146,592

HYDRAULIC LIFT WITH ROTATION LOCK FOR BEAUTY CHAIR Filed May 2Q, 1959 2 Sheets-.Sheet 2 lil n INVENTOR. ""PHluP c. JOHNSON.

FlG. 4

ATTORNEYS United States Patent O 3,146,592 HYDRAULIC LIFT WITH RTATIN LOCK FR BEAUTY CH Philip C. .Iohnsom Cincinnati, Ghia, assigner to F. 8l F.

Koenigkramer Company, Cincinnati, h10, a corporation of (Ehio Filed May 20, 1959, Ser. No. 814,500 11 Claims. (Cl. 613-52) This invention relates to an hydraulic lift with rotation lock for us in beautician or medical chairs or the like.

An object of this invention is to provide for beauty chairs and the like, a lift adapted to support, raise and lower the seat portion thereof for swinging into desired orientation and having means for locking the seat in fixed orientation as desired.

Another object of this invention is to provide a device of the foregoing character in which a single lever serves to actuate and control raising, lowering, and locking of said seat in fixed orientation.

A further object of this invention is to provide a device of the above character in which said lift and lock means are interconnected to preclude raising or lowering of the seat while said seat is locked in fixed orientation.

Another object of this invention is to provide a device of the above character in which said single lever control is pivoted about an axis in predetermined relation to stationary portions of said chair and does not travel with the movable seat thereof.

Another object of this invention is to provide an hydraulic lift with rotation lock for beauty chairs and the like, which is sturdy, reliable, easy and simple to operate, and which may be made at moderate cost.

The above and other objects and features of this invention will in part be obvious and will in part be apparent to those having ordinary skill in the art to which this invention pertains.

In the accompanying drawings and the following description of the embodiment disclosed therein, like reference characters indicate like parts.

yIn the drawing:

FIG. 1 is a view in side elevation of an hydraulic lift with rotation lock which presently appears to be a preferred embodiment of this invention associated with fragmentary portions of other parts of a beauty chair;

FIG. 2 is a top plan view of an hydraulic lift with rotation lock shown in FIG. 1, portions thereof being broken away;

FIG. 3 is a fragmentary view in side elevation of the structure illustrated in FIGS. 1 and 2, taken from the right hand side of those views;

FIG. 4 is a View in vertical section taken generally along the line 4-4 in FIG. 2, portions thereof being broken away to show details of construction, the parts thereof being shown in positions corresponding to conditions in which both the outlet valve and the lowering valve are seated;

FIG. 5 is a fragmentary view in vertical section taken generally along a line 4 4 and similar to the lower portion of FIG. 4, but showing the lowering valve open;

and'

FIG. 6 is a fragmentary view in vertical section taken along the line 6 6 in FIG. 2.

FIG. 7 is taken on line 7-7 of FIG. 1 and shows the manner in which the lock is supported.

The illustrative embodiment shown in the drawings comprises an hydraulic lift 11 with rotation lock, which, as shown in FIG. l, is secured in co-operating engagement with a base 12 and seat mounting bracket 13 of a ice beauticians or barbers chair. The hydraulic lift 11 includes a base casting 14 adapted to be mounted in fixed relation on base 12 by means such as bolts 15, each of which extends through an aperture 14-2 into lug 14-3 into threaded engagement with base 12.

Base column 16, a cylindrical shell member, is disposed between and spans the distance between base casting 14, and top or head 17. Tie bolts 19 cooperate with base casting 14 and nuts 21, to firmly clamp base casting 14, head 17, and base column 16 together to form a suitable fluid reservoir and housing. A cylinder 22 is secured in co-operative relation to base casting 14 and head 17. A piston 24, received in cylinder 22 for reciprocation, is secured to piston rod 28 by piston pin 27. Piston packing ring 26 provides a seal between piston 24 and the wall of cylinder 22. Piston rod 2S extends upwardly through cylinder 22 to a projecting tapered free end portion 31. As shown in FIG. 4, a pair of spaced, annular snap retainer rings 32 and 33 cooperate with cylinder 22. Between upper snap retainer ring 32 and lower snap retainer ring 33, piston rod Wiper retainer 34, piston rod wiper 35, piston rod seal 36, upper piston rod bushing 37, bushing spacer 38 and lower piston rod bushing 39, are provided in succession. Pump cylinder 41 is secured to base casting 14 in fluidtight relation. As shown in FIGS. 4 and 5, a pump stroke stop spring 43 is disposed in spring well 44. Pump plunger 47 is reciprocable in pump cylinder 41 between the retracted position, shown in FIG. 4, and the fully advanced position of FIG. 5. Advancement of pump plunger 47 is resisted by pump stroke stop spring 43. Pump piston 47 is biased toward the position of FIG. 4 by pump piston spring 48, under compression between iiange 14-1 and ange 5i); Hydraulic uid inlet passage 52 extends from hydraulic fluid reservoir 59 to well 44, and, as shown in FIG. 6, inlet valve 55 therein limits hydraulic fluid to unidirectional flow through fluid inlet passage 52 into well 44 when pump piston 47 moves upwardly in the direction of arrow A in FIG. 4. Upward movement of pump piston 47 also tends to seat outlet valve ball 61. Pump piston rod 62 is secured to and moves in unison with pump piston 47 and extends through an aperture provided in top or head 17. A suitable seal (not shown) may be provided in cooperation with top 17 and pump piston rod 62. When pump piston 47 is moved downwardly, in the direction of arrow B, inlet valve 55 is closed and outlet valve 61 is opened and hydraulic iiuid flows through passage 63 into cylinder 22, forcing piston 24 and piston rod 2S in the direction of arrow A. When travel of pump plunger 47 in the direction B ceases, valve 61 closes and precludes back ow of fluid from cylinder 22. into spring well 44. Repetitive reciprocatory movement of piston 47 serves to effect movement of piston rod 28 and piston 24 in the direction A to any desired position between that shown in FIG. 4 and that in which piston 24 engages retainer ring 33. To lower piston rod 2S, outlet valve actuating lug Sil-1, an integral part of plunger 47, is advanced from the position of FIG. 4, substantially to that of FIG. 5, to engage and displace plunger 72 in the direction of arrow B to open valve 67. When valve 67 is opened, hydraulic uid is expelled from cylinder 22, past Valve 67, into reservoir 59. When piston 24 is in engagement with retainer ring 33, advancement of plunger 47 is the direction of arrow B, effects hydraulic lifting of relief valve plug 77 until hydraulic'fluid may continuously escape through plug 77 and cavity 79, into reservoir 59 until valve 67 is opened, whereupon plug valve 77 is closed by spring 7S. Imposition of overload forces upon retainer ring 33 is also precluded thereby.

An hydraulic lift such as it described above, is operable to effect raising and lowering of piston rod 2S by appropriate reciprocative movement of pump piston rod 62.

Actuating linkage suitable for effecting such movement of piston rod 62, is illustrated in FIGS. 1, 2, 3, and 4. In the drawings, a pair of integral pedestal lugs 81 and S2 project upwardly from top 17 adjacent the portion of cylinder 22 which projects above top 17. Rocker arm hinge pin 03 extends through and is supported by pedestal lugs 81 and 82. Hinge pin 83 supports lever stops 84 and 86 together with U-shaped rocket arms 87 in pivotal relation to the pedestal lugs. Pivot pin 8S is supported in rocker arm 87 and supports roller 89 between the parallel extending portions or arms of rocker arm 87 for oscillatory rotation when in engagement with pump piston rod 62 as shown in FIG. 4.

Pump piston spring 48 biases pump piston rod 62 to advance in the direction of arrow A (FIG. 4) and cooperation of end face 62-1 with roller S9 serves to bias rocker arm 87 toward the position of FIG. 4, which corresponds to the position N, shown in full lines in FIG. 1. The full line position of rocker arm 57, FIGS. 1, 4, and 5, is the limit of clockwise pivoting in which its faces 91 and 92, respectively, contact stop abutments 93 and 94, integral parts of top 17. Resilient spring cup washers 96, 97 are disposed annularly of hinge pin 83 and respectively between lever stop S4 and pedestal 81, and pedestal 82 and lever stop 56. Portions of retainer rings 98 and 99 are respectively received in annular grooves provided in hinge pin 83 and cooperate with rocker arm 87. The lever 101, a pedal of a generally U-shaped form, pivots on pivot pin 08 (FIGS. 1, 2 and 3) and has portions 101-2 and 101-3 which extend alongside the straight arm-like portions of rocker arm S7 and co-operate with lever stops 84 and 86, respectively, while the lever is in position N or in a position of counterclockwise displacement from position N as viewed in FIG. 1. Thus, lever 101 and rocker arm S7 swing in unison about pin 83, downwardly and to the right of position N of FIG. l. Counterclockwise swinging of lever 101 from position N moves pump piston rod 62 in the direction indicated by arrow B in FIG. 4 to pump hydraulic fluid into cylinder 22 raising piston rod 28. When pump piston 47 engages pump stroke stop spring 43 additional resistance is imparted by spring 43 to further advance of piston 47 and is readily sensible to the manipulator of lever 101. As lever 101, swinging from position N, reaches position P, FIG. 1, then outlet valve actuating lug 50-1 engages lowering valve plunger 72. Further movement of lever 101 toward position L opens lowering valve 67. Thus, swinging of lever 101 between positions N and P, results in pumping action moving piston rod 28 in the direction of arrow A in FIG. 4. As lever 101 swings from adjacent position P toward position N, outlet ball valve 61 seats preventing back flow of hydraulic uid into pump cylinder 41 and pump piston 47 moves in the direction of arrow A in FIG. 4, opening inlet valve S and hydraulic fluid flows into cylinder 41 from reservoir 59, so long as lever 101 is moving from adjacent position P toward position N. When lever 101 is stopped or moves through position N toward position RL, spring 54 seats inlet valve 55. Piston rod 28 is permitted to move in the direction of arrow B in FIG. 4 when lever 101 is depressed through position P toward position L, opening lowering valve 67, the degree of opening regulating fluid flow and rate of descent. The position L is the limit position of counter-clockwise movement of lever 101 and rocker arm 87 about pin 83 and corresponds to the full open position of lowering valve 67, FIG. 5. If lever 101 is in position N and piston 24 in engagement with retaining ring 33, movement of the lever 101 hydraulically opens relief valve plug 77 so hydraulic fiuid escapes as piston 47 moves to the position in which lowering valve 67 is opened. Thus, raising and lowering may be effected by swinging of lever 101 and rocker arm 37 in unison about pin 83 between positions N and L.

A rotation lock 103 has its arm portion 103-1 secured to integral pedestal lug 31 by bolt 104 which extends through an aperture provided in arm 103-1 into threaded engagement with pedestal 81. Rotation lock 103 has substantially parallel arm portions 103-1 and 103-2 connected by a central portion annularly of piston rod 2S adjacent the upper end of cylinder 22. Piston rod wiper 102 encirclingly engages piston rod 28 and is supported by rotation lock 103 and piston rod wiper retainer 100 which also co-operates with lock 103. Wiper 102 protects the clampingly engageable surfaces of rod 28 and lock 103 by excluding foreign matter. Lock screw 105 has threads 106, on shoulder portion 105-1, which co-operate with mating threads provided in arm portion 103-1 and portion 10S-2 of reduced diameter extending through an aperture in arm 103-2 into co-operative engagement with nut 109 secured in xed relation to lock screw 105. Lock screw 105 has a radial lever arm 107. Lock link of generally U-shape, shown in FIGS. 1, 2, 3, and 4, has an arm portion 10S-1 extending in pivotal relation through arm portion 101-2 of lever 101 and an arm portion 10S-2 co-operating in similar manner with lock screw lever arm 107. Lock link 103 links lever 101 and lock screw lever arm 107. By rotation of nut 109 relative to lock screw the effective length of its portion 105-2 may be adjusted so that when lock screw lever arm 107 is in the position illustrated in full lines in FIG. 1, piston rod 28 may move freely in axial and rotational directions. Threads 109 are of the character that swinging of lever 107 from the full line position of FIG. 1 to the position 1071s, position of L of lever 101, effects advancement of lock screw 105 axially to move nut 109 further away from arm portion 103-1. As previously described, the faces 91 and 92 of rocker arm 87 co-operate with stop abutments 93 and 94, respectively, to preclude swinging of rocker arm 87 in a clockwise direction about hinge pin 83 from the position in which it is shown in full lines in FIGS. 1, 2, 3, and 4. Lever 101 is supported in pivotal relation to rocker arm 87 by pivot pin 88 and such relative pivotal movement is limited to positions of lever 101 on the same side of position N as position RL. Lever stops 84 and 86 limit lever 101 and rocker arm 37 to unison movement between positions N and L. Movement of lever 101 from the position N toward the position RL correspondingly swings lock screw lever arm 107 toward the position 107RL effecting axial movement of lock screw 105 and nut 109 to reduce the spacing of arms 103-1 and 103-2 and move rotation lock 103 into binding relation to piston rod 28, locking same in non-rotating relation to top or head 17, which is supported in fixed relation to base 12 by the structure previously described. Rotation lock 103 is released by movement of lever 101 into the position N. The hydraulic means for shifting piston rod 28 axially, cannot be operated until the lock is released and the lock cannot be reapplied until lever 101 has been moved into a position in which it does not operate the hydraulic means.

Thus, the hydraulic lift with rotation lock may be operated to secure piston rod 2S in a desired position of axial and rotational displacement to support a seat or the like 13 at an elevation and in orientation desired through simple manipulation of lever 101.

Having thus described what presently appears to be a preferred embodiment of the invention, it will be apparent to those having ordinary skill in the art to which this invention pertains, that various modifications and changes may be made in the illustrative embodiment without departing from the spirit or the scope of the appended claims.

Therefore, what is claimed as new, and is desired to be secured by Letters Patent, is:

1. An hydraulic lift with rotation lock comprising an hydraulic lift means including a piston rod supported for rotation and movable axially between extended and retracted limit positions and a rocker arm pivotally secured to said lift means for actuating same, a clamp lock secured to said hydraulic lift and adapted to lock said piston rod against rotation, a lever coupled to said clamp lock and pivotally secured to said rocker arm, said lever swinging in unison with said rocker arm to actuate said hydraulic lift means, and to swing pivotally relative to said rocker arm to actuate said clamp lock to lock said piston rod against rotation, said lock being released when said lever and said rocker arm swing in unison.

2. In a device for supporting a human, the combination comprising a column, means supporting said column for rotation and for advancing same longitudinally between upper and lower limits of movement, a split-clamp encircling said column and secured to said column-supporting means, a rocker arm pivotally secured to said column support means and biased toward a neutral limit position for actuating said column support means to advance said column, a pedal pivotally secured to said rocker arm, split-clamp actuating means coupled to said pedal, said pedal swinging in unison with said rocker arm in one direction from neutral position to actuate said columnsupporting means to raise and lower said column and swingable in a second direction and relative to said rocker arm when said arm is in said neutral position into a clamp set position to actuate said split-clamp to secure said column in non-rotating relation to said means supporting said column and swingable from a clamp set position to said neutral position and relative to said rocker arm to release said clamp.

3. An hydraulic lift with rotation lock comprising in combination an hydraulic lifting and lowering means including a piston rod supported for rotation and movable axially thereby, means supported by said hydraulic lifting and lowering means for clampingly securing said piston rod against rotation, a hinged lever having a first portion secured in pivotal relation to said piston supporting means and in cooperating relation thereto and a second portion pivotally secured to said first portion and in cooperative relation to said clamping means, said first portion being biased to a neutral position and swingable in unison with said second portion in one direction from said neutral position to actuate said hydraulic lifting and lowering means and said second portion thereof being swingable relative to said first portion thereof and in an opposite direction from neutral position to actuate said means for clamping said piston rod against rotation to clamp said piston rod and being swingable toward said neutral position to unclamp said piston rod, whereby a device supported on said piston rod may be axially moved, and locked against rotation and released for rotation by manipulation of said single second lever portion.

4. An hydraulic lift with rotation lock comprising an hydraulic lift means including a piston rod supported for rotation and movable axially between extended and retracted limit positions and a rocker arm pivotally secured to said lift means and biased toward a neutral limit position, a clamp lock secured to said hydraulic lift and adapted to lock said piston rod against rotation, a lever pivotally secured to said rocker arm and operatively connected to said clamp lock, said lever being swingable in unison with said rocker arm in one direction from said neutral limit position to actuate said hydraulic lift means and swingable in an opposite direction from said neutral position and pivotally relative to said rocker arm when said rocker arm is in neutral limit position to actuate said clamp lock to lockingly engage said piston rod against rotation, said lock being released when said lever and rocker arm swing in unison.

5. An hydraulic lift with rotation lock comprising an hydraulic lift means including a piston rod supported for rotation and movable axially between extended and retracted limit positions, a split clamp lock secured to said hydraulic lift means and actuatable to grippingly lock said piston rod against rotation, a lift and lock actuating lever coupled to said lock and coupled to said lift for pivotal movement about a first axis in fixed relation to said lift and about a second axis related to the first axis and biased toward a neutral position from which said lever may be swung in one direction about said first axis to actuate said lift means while said lock is released and which may be swung in a second direction from said neutral position and about a said second axis to actuate said lock to secure said piston rod against rotation Without actuating said lift means.

6. In a beauty or medical chair having a base, a seat, an hydraulic lift mounted on said base and supporting said seat mounted on a movable and rotatable piston rod of said lift in the elevation desired between predetermined upper and lower limits, the combination comprising a clamp supported in fixed relation to said base on said hydraulic lift to grippingly co-operate with said piston rod, clamp operating means operable to set and release said clamp, a lever pivotally secured to said hydraulic lift for swinging about an axis fixed relative to said base to actuate said lift and swingable about a second axis, and a link connecting said lever and said clamp-setting means whereby said lever may be pivoted relative to said second axis to set said clamp member to lock said piston rod against rotation and to release said clamp before said lift is actuated by movement of said lever about said first axis for effecting axial movement of said piston rod.

7. An hydraulic lift with rotation lock comprising in combination an hydraulic lift means including a piston rod supported for Irotation and axial movement, means supported by said hydraulic lift and adapted for clamping said piston rod against rotation, a centrally hinged lever having a free end portion and a rocker portion, said rocker portion being pivotally connected to said free end portion on the central hinge axis and pivoted to said lift on a first axis parallel to said central hinge axis and swingable in unbroken condition with the free end portion and rocker portion in fixed relation to each other and about said first axis within predetermined limits of movement fixed in relation to said hydraulic lift to actuate said lift means, said rocker portion being biased to a limit position of swing corresponding to one limit of swinging in unbroken condition, the free end portion of said hinged lever being hingedly swingable past said limit position and about the central hinge axis and relative to the rocker portion to actuate said means for clamping said piston rod against rotation, whereby a device supported on said piston rod may be moved axially, and may be locked against rotation by manipulation of said single free end portion of said lever within respective predetermined portions of its predetermined limits of movement fixed in relation to said hydraulic lift.

8. An hydraulic lift with rotation lock comprising in combination an hydraulic lift means including a piston rod supported for rotation and for axial movement, means supported in fixed relation to the piston rod supporting portion of said hydraulic lift for clamping said piston rod against rotation, a hinged lever having a free end portion connected to said clamping means and pivotally secured to a rocker portion on a first axis and swingable in unison therewith within predetermined limits of movement about a second axis fixed in relation to said hydraulic lift, said rocker portion being biased to a limit position of unison swingability about said second axis to actuate said hydraulic lift means and the rocker portion of said lever remaining in said limit position when the free end portion of the lever hinged thereto is swung beyond said limit position and about said iirst axis to actuate said means for clamping said piston rod against rotation, whereby said piston rod may be moved axially, and locked against rotation by manipulation of said single lever within its predetermined limits of movement fixed in relation to said hydraulic lift.

9. In a beauty or medical chair the combination cornprising a base, an hydraulic lift having a portion thereof mounted in fixed relation on said base and having a piston rod vertically movable and axially rotatable relative to said base, a clamp supported on said lift at a fixed distance from said base and adjacent said piston rod, clamp actuating means, a lever pivotally secured to said xedly mounted portion of said hydraulic lift and adapted to actuate said lift to vertically position said piston rod as desired, and means connecting said lever and clampactuating means, said lever being swingable into nonoperating relation to said hydraulic lift to actuate said clamp-actuating means to set said clamp to secure said piston rod against rotation relative to said base and swingable from said clamp-set position to succesively release said clamp and move into operating relation to said hydraulic lift whereby said piston rod may be vertically moved only while said clamp is released.

10, In a beauty or medical chair having a base, an hydraulic lift xedly mounted on said base and having a rotatable piston rod extendable between predetermined upper and lower limits, the combination comprising a split clamp mounted on said hydraulic lift for gripping co-operation with said piston rod and supported by said hydraulic lift against movement having direction like said piston rod movements, and linking means spanning the split in said clamp and actuatable to alter the width of said split by moving the one end of said split clamp toward and away from the other end thereof for setting and releasing said clamp, a lever connected to said linking means and pivotally secured to said hydraulic lift for actuating said lift by swinging movement to one side of a neutral position and setting said clamp member to lock on and secure said piston rod against rotation by swinging movement in non-operating relation to said lift 8 and to an opposite side of said neutral position into a locking position and releasing said clamp when said lever is moved in non-operating relation to said lift from a locking position to said neutral position, whereby said clamp is released during lift operating movements of said lever and is set and released by movement of said lever while said lever is in non-operating relation to said lift.

1l. In an elevatable chair having a base, an hydraulic lift fixedly mounted on said base and having a rotatable piston rod extendable relative to said lift and between predetermined upper and lower limits, the combination comprising a split member secured to said hydraulic lift against movement with said piston rod and encircling said piston rod, means linking the end portions of said split member, a lever coupled to said means linking the end portions of said split member and supported for limited actuating cooperation with said hydraulic limit and for pivoting about an axis and biased toward a neutral position, said piston rod being moved relative to said split member and between said upper and lower limits by actuation of said hydraulic lift by swinging of the lever in cooperating relation thereto and to one side of said neutral position and said lever actuating said means linking the end portions of said split member to advance said ends toward each other and secure the piston rod when the lever is oppositely displaced from said neutral position and is out of actuating cooperation with said lift.

References Cited in the file of this patent UNITED STATES PATENTS 885,843 Fischer et al Apr. 28, 1908 1,951,375 Schwarzkopf et al Mar. 20, 1934 1,999,848 Ries Apr. 30, 1935 2,296,954 Schneider Sept. 29, 1942 2,854,061 Romito Sept. 30, 1958 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No., 3,146,592 vSeptember l, 1964 Philip C. Johnson It is hereby certifiedl that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Signeo'l and sealed this 22nd day of December 1964'.

(SEAL) Attest:

ERNEST vW. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3260051 *Mar 17, 1964Jul 12, 1966Takara CompanyChair raising and lowering mechanism
US3296935 *Aug 17, 1964Jan 10, 1967F & F Koenigkramer CompanyHydraulic lift with rotation lock for beauty chair
US3345039 *Jul 21, 1966Oct 3, 1967Gray Mfg Company IncOverhead hoist
US3347594 *Sep 8, 1966Oct 17, 1967Werner Herbert EHydraulic mechanism
US4852941 *Jul 22, 1988Aug 1, 1989Midmark CorporationAdjustable debris tray assembly for podiatry chairs
US5213295 *May 31, 1991May 25, 1993Steelcase Inc.Two-way actuator for a chair height adjustment mechanism
US5601284 *Feb 12, 1996Feb 11, 1997Blackwell; ScottAdjustable basketball goal
US5630647 *May 26, 1995May 20, 1997Steelcase Inc.Tension adjustment mechanism for chairs
US5630649 *May 26, 1995May 20, 1997Steelcase Inc.Modular chair construction and method of assembly
US5782536 *Feb 17, 1995Jul 21, 1998Steelcase Inc.Modular chair construction and method of assembly
US5873634 *Jan 8, 1998Feb 23, 1999Steelcase Inc.Modular chair construction and method of assembly
US5979988 *Dec 31, 1998Nov 9, 1999Steelcase Development Inc.Modular chair construction and method of assembly
US6993905 *May 14, 2003Feb 7, 2006Kyung-Han MinOil hydraulic cylinder
USRE35805 *May 18, 1995May 26, 1998Steelcase Inc.Two-way actuator for a chair height adjustment mechanism
EP0416606A1 *Sep 6, 1990Mar 13, 1991Wilhelm LupoldHydraulic lifting device
EP1623653A1 *Jul 26, 2005Feb 8, 2006Andreas Lupold Hydrotechnik GmbHHydraulic apparatus
Classifications
U.S. Classification60/442, 248/404, 92/15
International ClassificationA47C3/30, A47C3/20
Cooperative ClassificationA47C3/30
European ClassificationA47C3/30