Ground- Or Floor-engaging Patents (Class 182/39)
  • Patent number: 9408461
    Abstract: A storage system includes a plurality of shelves, an aisle and a plurality of ladders. The plurality of shelves includes a pair of fixed shelves and at least one mobile shelf located between the pair of fixed shelves. The aisle is selectively configured to be located between two of the plurality of shelves. The plurality of ladders are spaced apart from and stored at an end of the at least one mobile shelf for slidable access into the aisle. Each ladder engages with a pair of fixed rails that span at least a length of the fixed shelves. A number of ladders correspond with a number of selectively defined aisles.
    Type: Grant
    Filed: November 15, 2012
    Date of Patent: August 9, 2016
    Assignee: Target Brands, Inc.
    Inventor: Mitchell Knoll
  • Patent number: 8882067
    Abstract: A guide track system and a bracket assembly thereof for supporting guide tracks thereof are provided. The guide track system comprises a first guide track piece, a second guide track piece, and a bracket assembly configured to support the first and second guide track pieces. The bracket assembly comprises a mounting feature configured to be mounted to a support structure, and a guide track supporting feature connected to the mounting feature and configured to support a portion of the guide track mounted thereon. The guide track supporting feature, in turn, comprises a body having a first end, a second end, and a longitudinal axis extending through the first and second ends, wherein the first end is configured to be coupled with an end of the first guide track piece, and the second end is configured to be coupled with an end of the second guide track piece.
    Type: Grant
    Filed: May 5, 2011
    Date of Patent: November 11, 2014
    Assignee: Material Control, Inc.
    Inventor: James F. Kerr
  • Patent number: 8881866
    Abstract: A self-rescue device that features an escape ladder, having one or more spaced steps, a base to hold the escape ladder in an open or closed position, a locking mechanism to keep the escape ladder in the open position, and a release mechanism to release the escape ladder from the open position.
    Type: Grant
    Filed: March 25, 2014
    Date of Patent: November 11, 2014
    Inventor: Diana Costello
  • Patent number: 8807280
    Abstract: A multi-directional scaffold transport device, which may be attached to each base of a scaffold's legs, provides increased mobility in relation to movement atop corrugated floor decking with vertical anchor studs used in conventional steel I-beam superstructures. The device comprises an elongated flat plate with angled extensions. The angled extensions may form a trapezoidal shape, or more preferably a triangular shape, and may be curved or have compound curvature to enable deflection of the device to either side of any anchor stud encountered, rather than jamming thereon. The elongated flat plate may have minimal length sufficient to normally receive support from at least two peaks of the corrugated decking. The device may incorporate threaded studs protruding from the elongated flat plate, which may be received by holes in the base of the scaffold, and be removeably fastened thereto using nuts. The device may also incorporate vertical walls for increased stiffness.
    Type: Grant
    Filed: October 13, 2009
    Date of Patent: August 19, 2014
    Inventor: John Jackman
  • Patent number: 8733502
    Abstract: The disclosed ladder system may be disposed in a store, warehouse, library, or similar facility where two storage shelves form an aisle. The ladder can be pivotally attached to a roller structure that moves along a length of the aisle on a guide track. The guide track may be disposed along sides of the storage shelves. The roller structure may be formed by a lateral rod extending between and coupled to two roller carriages. Further, because the ladder is pivotally attached to the roller structure, the ladder may fold substantially out of the aisle when the ladder is not in use.
    Type: Grant
    Filed: May 17, 2012
    Date of Patent: May 27, 2014
    Assignee: Material Control, Inc.
    Inventor: Roger Larson
  • Publication number: 20140097039
    Abstract: A ladder system includes an overhead track system, a ladder, a latch and a carriage. The overhead track system includes a first guide track and a second guide track. The carriage is operatively configured to move longitudinally along the first and second guide tracks and to move laterally between the first and second guide tracks. The ladder is pivotally mounted to the overhead track system. A lateral carriage brake is provided which prevents lateral movement of the ladder, and a longitudinal carriage brake is provided to prevent longitudinal movement of the ladder. The latch is operatively configured to affix the ladder to the carriage.
    Type: Application
    Filed: December 16, 2013
    Publication date: April 10, 2014
    Inventor: James F. Kerr
  • Patent number: 8622171
    Abstract: A ladder system includes an overhead track system, a ladder, a latch and a carriage. The overhead track system includes a first guide track and a second guide track. The carriage is operatively configured to move longitudinally along the first and second guide tracks and to move laterally between the first and second guide tracks. The ladder is pivotally mounted to the overhead track system. A lateral carriage brake is provided which prevents lateral movement of the ladder, and a longitudinal carriage brake is provided to prevent longitudinal movement of the ladder. The latch is operatively configured to affix the ladder to the carriage.
    Type: Grant
    Filed: June 14, 2010
    Date of Patent: January 7, 2014
    Assignee: Material Control, Inc.
    Inventor: James F. Kerr
  • Publication number: 20120312634
    Abstract: A work platform on which a worker can ride includes a suspended portion supported above a floor surface, the suspended portion being movable by a movement rail provided upwardly of a movement path, and a platform portion provided in the form of a plate on which the worker can ride, the platform portion having a base end connected to a lower end portion of the suspended portion to be pivotable about an axis along the direction of lateral width of the movement path. With pivotal movements about the axis, the platform portion can selectively assume a riding posture wherein the platform portion extends along the movement path so that the worker riding on this platform portion can move along the longitudinal direction of the movement path and a folded posture wherein the platform portion is folded toward the suspended portion to extend along the vertical direction.
    Type: Application
    Filed: October 22, 2010
    Publication date: December 13, 2012
    Applicant: DAIFUKU CO., LTD.
    Inventors: Yasushi Morikawa, Hideo Yoshioka
  • Publication number: 20120292130
    Abstract: The disclosed ladder system may be disposed in a store, warehouse, library, or similar facility where two storage shelves form an aisle. The ladder can be pivotally attached to a roller structure that moves along a length of the aisle on a guide track. The guide track may be disposed along sides of the storage shelves. The roller structure may be formed by a lateral rod extending between and coupled to two roller carriages. Further, because the ladder is pivotally attached to the roller structure, the ladder may fold substantially out of the aisle when the ladder is not in use.
    Type: Application
    Filed: May 17, 2012
    Publication date: November 22, 2012
    Inventor: Roger Larson
  • Patent number: 8276713
    Abstract: Disclosed is a scaffold installed within a large structure such as a pressure vessel or a tank of a ship, and an insulation system construction method using the same. The scaffold for use in performing desired work within a large structure includes a supporting structure installed adjacent to both side surfaces and a top surface of the large structure, and a carrying unit installed movable along the supporting structure to allow materials to be carried or to provide a working space for a worker thereon, wherein the supporting structure is installed to be movable along a wall surface of the large structure.
    Type: Grant
    Filed: March 5, 2007
    Date of Patent: October 2, 2012
    Assignee: Korea Gas Corporation
    Inventors: Young Myung Yang, Seong Ho Hong, Ihn Soo Yoon, Young Chul Yang, Heung Seok Seo, Ji Hun Kim, Byoung Taek Oh, Young Kyun Kim
  • Patent number: 8261879
    Abstract: Disclosed is a scaffold installed within a large structure such as a pressure vessel or a tank of a ship, and an insulation system construction method using the same. The scaffold for use in performing desired work within a large structure includes a supporting structure installed adjacent to both side surfaces and a top surface of the large structure, and a carrying unit installed movable along the supporting structure to allow materials to be carried or to provide a working space for a worker thereon, wherein the supporting structure is installed to be movable along a wall surface of the large structure.
    Type: Grant
    Filed: March 5, 2007
    Date of Patent: September 11, 2012
    Assignee: Korea Gas Corporation
    Inventors: Young Myung Yang, Seong Ho Hong, Ihn Soo Yoon, Young Chul Yang, Heung Seok Seo, Ji Hun Kim, Byoung Taek Oh, Young Kyun Kim
  • Patent number: 8051951
    Abstract: An apparatus for providing access to vehicles and containers on a pair of railways or thoroughfares. The apparatus is comprised of a raised walkway between the pair of thoroughfares having a tracking platform movable thereon. Pivotally attached to and carried by the tracking platform is a turret. Carried on the turret and hinged thereto is a bridge that is rotatable in a vertical plane. At the end of the bridge is a cage pivotally attached to the bridge so that the cage remains horizontal when the bridge is rotated vertically on the turret. The bridge and cage are dimensioned so that, when the turret is rotated such that the bridge is directed between and parallel to the thoroughfares and the bridge and cage are raised, the apparatus is entirely out of the clearance envelopes of the thoroughfares.
    Type: Grant
    Filed: June 4, 2009
    Date of Patent: November 8, 2011
    Assignee: Aluminum Ladder Company
    Inventors: Ronald W. Bennett, Ellie H. MacDonald
  • Publication number: 20110036662
    Abstract: A movable platform system for performing workover tasks on a wellhead includes a platform base with a base wellhead access gap at its front end. At least one track is fixed to the upper surface of the platform base and extends from the rear of the platform base to a position near the rearward edge of the base wellhead access gap. A platform support frame with a wellhead access gap at its front end is coupled to the track and configured for movement along the length of the track. An upper platform is connected to the platform support frame and also has a platform wellhead access gap at its front end. The three wellhead access gaps at the three levels of the platform system are substantially aligned when the movable platform support frame is disposed and locked in the working position above the wellhead. Workers on the upper platform have access to equipment surrounding the wellhead.
    Type: Application
    Filed: April 16, 2009
    Publication date: February 17, 2011
    Applicant: LAMBS WELLSITE SERVICES, INC.
    Inventor: Paul Richard Smith
  • Publication number: 20100252362
    Abstract: A ladder system includes an overhead track system, a ladder, a latch and a carriage. The overhead track system includes a first guide track and a second guide track. The carriage is operatively configured to move longitudinally along the first and second guide tracks and to move laterally between the first and second guide tracks. The ladder is pivotally mounted to the overhead track system. A lateral carriage brake is provided which prevents lateral movement of the ladder, and a longitudinal carriage brake is provided to prevent longitudinal movement of the ladder. The latch is operatively configured to affix the ladder to the carriage.
    Type: Application
    Filed: June 14, 2010
    Publication date: October 7, 2010
    Inventor: James F. Kerr
  • Patent number: 7802652
    Abstract: A servicing station for flatbeds includes a workers platform which is driven along one lateral side of the flatbed by an electric motor driving a spur gear in mesh with a rack on an overhead beam positioned sufficiently high to not interfere with lift truck loading and unloading of the flatbed. The electric motor is supplied electrical power through a power chain positioned on the overhead beam.
    Type: Grant
    Filed: March 13, 2006
    Date of Patent: September 28, 2010
    Assignee: Aluminum Ladder Company
    Inventors: Ronald W. Bennett, Ellie H. MacDonald, James A. Ackerman
  • Patent number: 7757813
    Abstract: The ladder system is disposed between two spaced storage shelves of the types found in crowded warehouses. The ladder is mounted on overhead guide tracks and may be moved longitudinally along the shelves and laterally between the shelves. Locating means are provided for immobilizing the ladder against movement laterally and longitudinally. The locating means includes a pair of spring-loaded casters and rubber pads at the lower end of the ladder and a pair of braking mechanisms overlying and engageable with the guide tracks when subjected to the weight of the user to prevent movement of the ladder at the top thereof either intentionally or unintentionally. Finally, a lateral brake is carried by the ladder which prevents the roller carriage from moving laterally. The brake is applied when the ladder is in use.
    Type: Grant
    Filed: June 9, 2008
    Date of Patent: July 20, 2010
    Assignee: Material Control, Inc.
    Inventor: James F. Kerr
  • Publication number: 20090301812
    Abstract: The ladder system is disposed between two spaced storage shelves of the types found in crowded warehouses. The ladder is mounted on overhead guide tracks and may be moved longitudinally along the shelves and laterally between the shelves. Locating means are provided for immobilizing the ladder against movement laterally and longitudinally. The locating means includes a pair of spring-loaded casters and rubber pads at the lower end of the ladder and a pair of braking mechanisms overlying and engageable with the guide tracks when subjected to the weight of the user to prevent movement of the ladder at the top thereof either intentionally or unintentionally. Finally, a lateral brake is carried by the ladder which prevents the roller carriage from moving laterally. The brake is applied when the ladder is in use.
    Type: Application
    Filed: June 9, 2008
    Publication date: December 10, 2009
    Inventor: James F. Kerr
  • Patent number: 7370725
    Abstract: A device supported by a ground surface and a structure for at least one of elevating and descending a user. The device includes a first guide rail having a first channel extending along a length thereof and a second guide rail having a second channel extending along the length thereof. At least one connector connects the first guide rail with the second guide rail at a predetermined location along a length thereof so that said first channel and said second channel face inwards towards each other. A platform for supporting the user having a predetermined amount of weight is connected within each of the first and second channels and between the first guide rail and second guide rail. The device further includes means for moving the platform along the length of each of the first channel and the second channel.
    Type: Grant
    Filed: January 3, 2005
    Date of Patent: May 13, 2008
    Inventor: Gary R Dornfeld
  • Patent number: 6619427
    Abstract: The ladder system is disposed between two spaced storage shelves of the types found in crowded warehouse-type retail outlets. The ladder is mounted on an overhead track system and may be moved longitudinally along the shelves and laterally between the shelves. The ladder is pivotly connected on one side to the overhead track system whereby the ladder may be moved from a latched position to a folded position about the pivot means against one of the storage shelves to thereby minimize the ladder as an obstruction in the aisle between the storage shelves.
    Type: Grant
    Filed: April 9, 2002
    Date of Patent: September 16, 2003
    Assignee: Material Control, Inc.
    Inventor: James F. Kerr
  • Patent number: 6523640
    Abstract: An undercarriage for a mobile ladder stand or other similar warehouse apparatus includes a pair of retractable wheels located at the rear of the undercarriage frame and a pair of retractable wheels located at the middle of the undercarriage frame. When the wheels are retracted, the structure is supported by a pair of legs and foot pads located at the front of the undercarriage frame and another pair of legs and foot pads located at the rear of the undercarriage frame. When the wheels are extended, the structure is supported on the ground surface for rolling by the middle and rear wheels. The rear wheels are preferably mounted on swivel casters and the diameter of the middle pair of wheels is preferably greater than the diameter of the rear pair of wheels.
    Type: Grant
    Filed: May 21, 2001
    Date of Patent: February 25, 2003
    Assignee: EGA Products, Inc.
    Inventors: David T. Young, Scott E. Kaczor
  • Patent number: 6315078
    Abstract: A multi-position ladder includes a ladder, a longitudinally extending support member for supporting the ladder, and a tightening mechanism associated with the ladder or the support member. The tightening mechanism is operable to secure the ladder to the support member, thereby prohibiting movement of the ladder along the support member.
    Type: Grant
    Filed: June 28, 2000
    Date of Patent: November 13, 2001
    Inventors: Don A. Kumher, Boyd S. Kumher
  • Publication number: 20010032435
    Abstract: A portable fall-arrest system is designed for convenient attachment and/or removal relative to a concrete beam. The system includes stanchions which are preferably secured to respective anchorages embedded within a reinforced concrete beam. The anchorages may alternatively be used to support other types of personnel safety devices. The preferred embodiment anchorage may be described as a flared coil loop insert having a threaded neck. The loop is disposed inside the concrete beam and the neck extends to the outer surface of the concrete beam. The neck is sized and configured to receive and retain a threaded shaft associated with a safety device. The anchorage provides a convenient and reliable anchor point in a concrete beam without drilling into the beam and/or potentially weakening its structural integrity.
    Type: Application
    Filed: February 16, 2001
    Publication date: October 25, 2001
    Inventor: Barry J. Austin
  • Patent number: 6230841
    Abstract: A track ladder that includes a ladder frame, plurality of steps secured to the ladder frame and a carriage assembly secured to the ladder frame. The ladder frame rides on an upper track and a lower track and adapted to move in a horizontal direction and pivot about a vertical axis.
    Type: Grant
    Filed: July 9, 1999
    Date of Patent: May 15, 2001
    Assignee: Melfred Inc.
    Inventor: Nicholas J. Valore
  • Patent number: 6131869
    Abstract: A device for deflecting ladders and other moving structures away from sensitive and readily damageable stationary equipment. More particularly, disclosed is a device in the form of a wedge-shaped ramp structure which is mounted at the end of a guard rail located at the bottom of the stationary equipment which is arranged in an uneven lineup and presenting protruding end edges which the ramp structure will prevent from being struck by moving aisle ladders or the like through deflecting the latter. Pursuant to a specific aspect, the device is a wedge-shaped deflector ramp structure mounted at the end of the guard rail which is located to extend along the lower end of a forward surface of unequal flange cable duct (UFCD) racks which are frequently employed in telephone or communication equipment central offices.
    Type: Grant
    Filed: August 3, 1998
    Date of Patent: October 17, 2000
    Assignee: Hubbell Incorporated
    Inventors: James H. Durham, Charles W. Cramp
  • Patent number: 6105720
    Abstract: A multi-position ladder includes a ladder, a longitudinally extending support member for supporting the ladder, and a connecting member connecting the support member and the ladder. The connecting member includes a sliding bar, a pivot bar, and a rotating arm, the sliding bar being in sliding engagement with the support member for permitting lateral shifting movement of the ladder along the support member to one of multiple generally vertical use positions, the pivot bar extending laterally outwardly from the sliding bar for permitting pivotable movement of the ladder about the pivot bar between a generally vertical use position and one of multiple storage positions, and the rotating arm providing tilting movement of the ladder towards or away from a wall to which the support member is attached. The ends of the rotating arm are slidably received in elongated slots in the uprights of the ladder for permitting sliding movement of the ladder relative to the rotating arm.
    Type: Grant
    Filed: May 28, 1999
    Date of Patent: August 22, 2000
    Inventors: Don A. Kumher, Boyd S. Kumher
  • Patent number: 6073725
    Abstract: A multi-position ladder includes a ladder, a longitudinally extending support member for supporting the ladder, and a connecting member connecting the support member and the ladder. The connecting member includes a sliding bar, a pivot bar, and a rotating arm, the sliding bar being in sliding engagement with the support member for permitting lateral shifting movement of the ladder along the support member to one of multiple generally vertical use positions, the pivot bar extending laterally outwardly from the sliding bar for permitting pivotable movement of the ladder about the pivot bar between a generally vertical use position and one of multiple storage positions, and the rotating arm providing tilting movement of the ladder towards or away from a wall to which the support member is attached.
    Type: Grant
    Filed: November 5, 1998
    Date of Patent: June 13, 2000
    Inventors: Don A. Kumher, Boyd S. Kumher
  • Patent number: 5653307
    Abstract: The ladder system is located adjacent the front face of a storage rack. The ladder is carried by a cantilever supported carriage assembly having a pair of pivotally mounted frames. The ladder is connected to one frame and may move longitudinally along the front face of the storage rack. The ladder and its frame may also be moved laterally in an arc up to 90.degree. in a direction extending perpendicular to the front face of the storage rack. The carriage assembly includes a horizontal ladder support arm on the first frame upon which the ladder is mounted. A user can quickly and easily position the ladder at any position along the storage rack for accessing items stored on the shelves. This ladder system is particularly useful in crowded warehouse-type retail outlets which are now in popular use across the country.
    Type: Grant
    Filed: September 26, 1995
    Date of Patent: August 5, 1997
    Assignee: Material Control, Inc.
    Inventor: James F. Kerr
  • Patent number: 5480002
    Abstract: The ladder system is located adjacent the front face of a storage rack. The ladder is carried by a cantilever supported carriage assembly. The ladder may move longitudinally along the front face of the storage rack and may also be moved laterally in a direction extending perpendicular to the front face of the storage rack. The carriage assembly includes a horizontal ladder support track upon which the ladder is mounted by means of two sets of rollers. With such a construction, the ladder may pivot about the support track to avoid obstructions in the aisle or projecting from the storage rack. In this way, a user can quickly and easily position the ladder at any position along the storage rack for accessing items stored on the shelves. This ladder system is particularly useful in crowded warehouse-type retail outlets which are now in popular use across the United States of America.
    Type: Grant
    Filed: December 13, 1994
    Date of Patent: January 2, 1996
    Assignee: James F. Kerr
    Inventor: James F. Kerr
  • Patent number: 5413191
    Abstract: A ladder system is disposed between two spaced storage shelves. The ladder may move longitudinally along the shelves, and may also be moved laterally between the shelves. Further, the ladder may pivot about a lateral axis such that the ladder may be picked up over obstructions in an aisle between the shelves. In this way, one can quickly and easily position the ladder at any position along or between the two storage shelves for accessing items stored on the shelves. This ladder system is particularly useful in the crowded warehouse-type retail outlets which are now gaining popularity.
    Type: Grant
    Filed: August 29, 1994
    Date of Patent: May 9, 1995
    Assignee: Material Control, Inc.
    Inventor: James F. Kerr
  • Patent number: 5148889
    Abstract: A new and improved overhead package retrieval system, including a series of C-shaped tracks which are mounted onto storage shelf units, a platform that has rollers that fit within these C-shaped tracks and allow the platform to move, a special jointed retractable axle system which allows the platform to move along the tracks even if they are not completely parallel, a fold-up ladder for a user to get from ground to platform level, a special brake that operates when fold-up ladder is down to prevent movement of the platform, a package platform that allows a user to easily move packages from the platform to the ground, and a series of guard rails and hand rails to make the overhead package retrieval system safe.
    Type: Grant
    Filed: September 30, 1991
    Date of Patent: September 22, 1992
    Assignee: Joyce/Streater Inc.
    Inventors: Jay G. Fenwick, Jay R. Stemler, Jr.
  • Patent number: 4899847
    Abstract: This invention is directed at a mobile ladder which has a two pairs of rollers. One pair of rollers moves in a first metal trough and the other pair moves in another metal trough. The metal trough are positioned close to a building wall, for example, and are in parallel relation to each other. The ladder can be moved in the troughs when a workman in on the ladder through use of a pulley system.This invention is also directed at a mobile scaffold which has a two pairs of rollers. One pair of rollers moves in a first metal trough and the other pair moves in another metal trough. The metal trough are positioned close to a building wall, for example, and are in parallel relation to each other. The scaffold can be moved in the troughs when a workman in on the scaffold through use of a pulley system.This invention is also directed at a work bucket that is mounted to a ladder by a pair of bracket members.
    Type: Grant
    Filed: April 24, 1989
    Date of Patent: February 13, 1990
    Inventor: Elmer S. Lufkin
  • Patent number: 4753321
    Abstract: A worker platform for sandblasting a cylindrical fuel storage tank includes a lookout frame section secured to the tank top that has an arm extending radially outward beyond the tank wall and a roller assembly supporting the arm for circumferential movement about the tank. A stage is suspended by a winch from the arm, and a square cross-sectioned standpipe is captured within upper and lower square guide channels formed at the center of the stage and by a yoke at the outer extent of the arm. The standpipe has a base plate with projections or spikes to penetrate the ground. The winch moves the stage up and down with the standpipe passing vertically through the guide channels and providing stability against swinging, twisting and tilting. For circumferential movement, a pin temporarily locks the standpipe for lifting with the stage. Lookout frame embodiments are given for both solid and floating tank tops.
    Type: Grant
    Filed: May 18, 1987
    Date of Patent: June 28, 1988
    Assignee: Benjamin E. Price
    Inventor: Lee B. Winslow
  • Patent number: 4660677
    Abstract: Personnel evacuation apparatus for use with an offshore platform. A launching ramp that is mounted to the platform by a gimbal is stowed in a vertical position with a survival vessel secured in the entry end of the ramp. A release mechanism activatable from the deck of the platform enables flotation members secured to the exit end of the ramp, to pivot the ramp about the gimbal to its deployed position. The gimbal further permits the ramp to maintain a usable orientation in spite of inclination of the deck of the platform by 25.degree. due to pitch, roll or yaw. The exit end will pivot under wave action so as to gravity launch the survival vessel downwind and, upon release of the boat securement, carry the vessel safely away from the platform.
    Type: Grant
    Filed: July 28, 1986
    Date of Patent: April 28, 1987
    Assignee: Conoco Inc.
    Inventor: Andrew F. Hunter
  • Patent number: 4311208
    Abstract: A warning light assembly for use on ladders having a plurality of rungs to indicate the presence of someone on the ladder. The warning light assembly has a switch activated by a person's foot placed on one of the lower rungs of the ladder. When first activated, the switch turns on a flashing light positioned about eye level. As the person disembarks from the ladder, his foot on the lower rung again activates the switch turning off the flashing light.
    Type: Grant
    Filed: July 18, 1980
    Date of Patent: January 19, 1982
    Inventors: Patrick L. Macrorie, Ronald C. Rohrenbacher, Stephen B. Austin
  • Patent number: 4232759
    Abstract: A track supported mobile ladder-scaffolding system with self-adjusting lateral supporting structure at the top for engaging a roof by means of a vehicle which engages track structure attachable to a roof by clamping: safety hook structure prevents support failure at the top at roof-engaging and ladder engaging points of the mobile portion of the system.
    Type: Grant
    Filed: August 2, 1979
    Date of Patent: November 11, 1980
    Inventor: Ronald S. Jacobs