Powered hand truck for climbing steps
OwnerJames L. Melsoninventor
Life of this patent
Estimating the term…
Abstract
A hand truck powered by pressurized gas for transporting a load up one or more steps, having a unique mechanical design permitting it to execute a smooth climbing motion up nosed or unnosed steps, and further having a power control system implementing several novel safety and convenience features.
Claims28
A powered hand truck capable of climbing stair steps comprising:
- a frame extending in a longitudinal direction from a lower end to an upper end and extending laterally from a left side to a right side, having a front side for retaining a load and a back side, and having a pair of runners extending in the longitudinal direction along the lower portion of the back of said frame;
- a pair of support wheels attached for rotation about a common lateral axis to the lower end of said frame;
- powered means pivotally connected to said frame for limited rotational swinging movement about a lateral axis, said powered means having a powered ram and being selectively operable to extend said ram in a generally longitudinal direction below said wheels, and to maintain said ram held at an attained extension, and to retract said ram;
- manually actuable means for operating said powered means to extend said ram for elevating the hand truck to an upper stair step;
- and
- neutralizing means connected between said frame and said powered means and responsive during extension of said ram in climbing a stair step to predetermined pivotal rotation of said powered means toward said front side of said frame as the elevated hand truck begins to roll onto the stair step for automatically operating said powered means to terminate further extension of said ram and maintain the then-attained extension of said ram.
For attachment to a hand truck having a frame extending in a longitudinal direction from a lower end to an upper end and extending laterally from a left side to a right side, having a front side for retaining a load and a back side, having a pair of runners extending in the longitudinal direction along the lower portion of the back of the frame and having a pair of wheels attached for rotation about a common lateral axis to the lower end of the frame, a stair-climbing power unit comprising:
- powered means pivotally connected to said frame for limited rotational swinging movement about a lateral axis, said powered means having a powered ram and being selectively operable to extend said ram in a generally longitudinal direction below said wheels, and to maintain said ram held at an attained extension, and to retract said ram;
- manually actuable means for operating said powered means to extend said ram for elevating the hand truck to an upper stair step;
- and
- neutralizing means connected between said frame and said powered means and responsive during extension of said ram in ascending the stair step to predetermined pivotal rotation of said powered means about said lateral axis toward said front side of said frame as the elevated hand truck begins to roll onto the stair step for automatically operating said powered means to terminate further extension of said ram and maintain the then attained extension of said ram.
In a powered hand truck adapted for climbing stair steps, having a frame extending in a longitudinal direction from a lower end to an upper end and extending laterally from a left side to a right side, having a front side for retaining a load and a back side, having a pair of runners extending in the longitudinal direction along the lower portion of the back of the frame, having a pair of wheels attached for rotation about a common lateral axis to the lower end of the frame, and having powered means pivotally connected to the frame for limited rotational swinging movement about a lateral axis and having a powered ram controllably extensible in a generally longitudinal direction below the wheels and controllably retractable, the improvement comprising:
- neutralizing means connected between said frame and said powered means and responsive during extension of said ram in ascending a stair step to predetermined pivotal rotation of said powered means toward the front side of said frame as the hand truck begins to roll onto the stair step for automatically operating said powered means to terminate further extension of said ram and maintain the then attained extension of said ram.
In a powered hand truck having a frame extending in a longitudinal direction from a lower end to an upper end and extending laterally from a left side to a right side and having a front side for retaining a load and a back side, having a pair of runners extending in the longitudinal direction along the lower portion of the back of the frame having a pair of wheels attached for rotation about a common lateral axis to the lower end of the frame, having powered means pivotally connected to the frame for limited movement about a lateral axis and having a ram controllably extensible in a generally longitudinal direction below the wheels and controllably retractable, the improvement comprising:
- a guard, extensible below the wheels and retractable with the ram, and pivotable with the powered means, disposed to the rear of the powered means and frontward of said runners, whereby when the hand truck rolls onto a step the guard shields the ram from contacting the edge of the step and limits the rearward roll of the hand truck onto the step until the ram is retracted.
In a powered hand truck having a frame extending in a longitudinal direction from a lower end to an upper end and extending laterally from a left side to a right side and having a front side for retaining a load and a back side, having a pair of runners extending in the longitudinal direction along the lower portion of the back of the frame, having a pair of wheels attached for rotation about a common lateral axis at the lower end of the frame, having powered means pivotally connected to the frame for limited movement about a lateral axis and having a ram controllably extensible in a generally longitudinal direction below the wheels and controllably retractable, the improvement comprising:
- mechanical shifting means connected to said powered means and said frame and having a portion thereof in the path of the ram when it retracts and directly and solely mechanically responsive to pressure exerted on said portion by said ram during its retracting motion for pivoting said powered means to its rearmost pivotal position.
In a powered hand truck having a frame extending in a longitudinal direction from a lower end to an upper end and extending laterally from a left side to a right side and having a front side for retaining a load and a back side, having a pair of runners extending in the longitudinal direction along the lower portion of the back of the frame, having a pair of wheels attached for rotation about a common lateral axis to the lower end of the frame, having powered means pivotally connected to the frame for limited movement about a lateral axis and having a ram controllably extensible in a generally longitudinal direction below the wheels and controllably retractable, the improvement comprising:
- a ram detent for yieldably holding the ram in its extreme retracted position whereby the ram can be extended from its extreme retracted position only by application of force exceeding a predetermined limit, said ram being thereafter controllably extensible over a wide continuous range of extensions.
In a powered hand truck having a frame extending in a longitudinal direction from a lower end to an upper end and extending laterally from a left side to a right side and having a front side for retaining a load and a back side, having a pair of runners extending in the longitudinal direction along the lower portion of the back of the frame, having a pair of wheels attached for rotation about a common lateral axis to the lower end of the frame, having powered means pivotally connected to the frame for limited movement about a lateral axis and having a ram controllably extensible in a generally longitudinal direction below the wheels and controllably retractable, the improvement comprising:
- powered means detents for resiliently and yieldably holding the powered means at predetermined front and back limits of its pivotal swinging motion at which front and back limits the longitudinal axis of said ram is directed respectively slightly forward and slightly back of the common axis of said wheels whereby it can be moved from the limit pivotal positions only by application of forces exceeding predetermined limits.
In a powered hand truck having a frame extending in a longitudinal direction from a lower end to an upper end and extending laterally from a left side to a right side and having a front side for retaining a load and a back side, having a pair of runners extending in the longitudinal direction along the lower portion of the back of the frame having a pair of wheels attached for rotation about a common lateral axis to the lower end of the frame, said wheels including selectively engageable ratchets, having powered means pivotally connected to the frame for limited movement about a lateral axis and having a ram controllably extensible in response to actuation of an extension trigger by the operator in a generally longitudinal direction below the wheels and controllably retractable, and having neutralizing means connected between the frame and the powered means and responsive to predetermined motion of said powered means relative to said frame for automatically operating said powered means to terminate further extension of said ram and maintain the then attained extension of said ram, the improvement comprising:
- a tripping mechanism interconnected between the extension trigger and the ratchets of the wheels for engaging the wheel ratchets when the extension trigger is actuated.
In a powered hand truck having a frame extending in a longitudinal direction from a lower end to an upper end and extending laterally from a left side to a right side and having a front side for retaining a load and a back side, having a pair of runners extending in the longitudinal direction along the lower portion of the back of the frame, having a pair of wheels attached for rotation about a common lateral axis to the lower end of the frame, said wheels including selectively engageable ratchets, having powered means pivotally connected to the frame for limited movement about a lateral axis and having a ram controllably extensible in response to actuation of an extension trigger by the operator in a generally longitudinal direction below the wheels and controllably retractable, the improvement comprising:
- a tripping mechanism interconnected between the extension trigger and the ratchets of the wheels for engaging the wheel ratchets when the extension trigger is actuated.
Dependencies are inferred from the claim text.