# US 10,118,450 B2 · Tow bar assembly and dolly comprising the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,118,450 B2 - Document ID: US10118450B2 - Status: Granted - Kind: B2 - Application number: 15/528,471 - Filed: 2015-11-10 - Published: 2017-12-07 - Granted: 2018-11-06 - Earliest claimed: 2014-11-21 - Assignees: K. Hartwell Oy Ab - Applicants: K. Hartwall Oy Ab - Inventors: Jack Grönholm - Web page: https://patentgrep.com/patent/US10118450B2 ## CPC - B60D 1/155: comprising telescopic or foldable parts - B62D 63/08: Component parts or accessories - B60D 2001/005: {for carts, scooters or the like} - B62B 5/0079: {Towing by connecting to another vehicle} - B62B 2207/00: Joining hand-propelled vehicles or sledges together - B60D: VEHICLE CONNECTIONS - B62D: MOTOR VEHICLES; TRAILERS (steering, or guiding on a desired track, of agricultural machines or implements A01B69/00; wheels, castors, axles, increasing wheel adhesion B60B; vehicle tyres, tyre inflation or tyre changing B60C; connections between vehicles of a train or the like B60D; vehicles for use on rail and road, amphibious or convertible vehicles B60F; suspension arrangements B60G; heating, cooling, ventilating or other air treating devices B60H; windows, windscreens, non-fixed roofs, doors or similar devices, protective coverings for vehicles not in use B60J; propulsion plant arrangements, auxiliary drives, transmissions, controls, instrumentation or dashboards B60K; electric equipment or propulsion of electrically-propelled vehicles B60L; power supply for electrically-propelled vehicles B60M; passenger accommodation not otherwise provided for B60N; adaptations for load transportation or to carry special loads or objects B60P; arrangement of signalling or lighting devices, the mounting or supporting thereof or circuits therefor, for vehicles in general B60Q; vehicles, vehicle fittings or vehicle parts not otherwise provided for B60R; servicing, cleaning, repairing, supporting, lifting, or manoeuvring, not otherwise provided for, B60S; brake arrangements, brake control systems or parts thereof B60T; air-cushion vehicles B60V; motor-cycles, accessories therefor B62J, B62K; testing of vehicles G01M) - B62B: HAND-PROPELLED VEHICLES, e.g. HAND CARTS OR PERAMBULATORS; SLEDGES (characterised by animal propulsion B62C; propulsion of sledges by driver or engine B62M) ## Abstract The present invention provides a tow bar assembly, which may be retrofitted to a dolly while maintaining convenient space saving properties of permanently fitted tow bars. The novel tow bar assembly includes a tow bar, a shaft and a biasing member, such as a spring, biasing the tow bar towards an upright orientation about an axis of revolution. The shaft has a first end and a second end, which opposes the first end. The shaft connects the tow bar to the dolly from the ends so as to provide rotation of the tow bar in respect to the dolly about the axis of revolution. The shaft features an inner cavity, which extends along the axis of revolution. The biasing member is arranged into the cavity of the shaft and rotationally secured thereto. The shaft also features a first end plug at the first end of the shaft for enclosing the biasing member to the cavity. The first end plug rotationally locks the biasing member to the dolly. ## Claims ### Claim 1 A tow bar assembly for a dolly, the tow bar assembly comprising: a tow bar, a shaft having a first end and a second end opposing the first end, from which ends the shaft is configured to connect the tow bar to the dolly so as to provide rotation of the tow bar in respect to the dolly about an axis of revolution, and a biasing member, configured to bias the tow bar towards an upright orientation about the axis of revolution, wherein: the shaft comprises an inner cavity extending along the axis of revolution, the biasing member is arranged into the cavity of the shaft and rotationally secured thereto, and in that the shaft comprises a first end plug at the first end of the shaft for enclosing the biasing member to the cavity, the first end plug is configured to rotationally lock the biasing member to the dolly. ### Claim 2 (depends on 1) The tow bar assembly according to claim 1, wherein the shaft is fixed to the tow bar. ### Claim 3 (depends on 1) The tow bar assembly according to claim 1, wherein the first end plug comprises a form locking shape, for engaging the biasing member. ### Claim 4 (depends on 1) The tow bar assembly according to claim 1, wherein an end of the first end plug distal to the biasing member comprises a rotationally symmetrical shape. ### Claim 5 (depends on 1) The tow bar assembly according to claim 1, wherein the first end plug comprises a rotationally non-symmetrical shape, for engaging to the dolly. ### Claim 6 (depends on 5) The tow bar assembly according to claim 5, wherein the rotationally non-symmetrical shape for engaging to the dolly is shaped to be engaged with a tool. ### Claim 7 (depends on 1) The tow bar assembly according to claim 1, wherein the first end plug comprises: a form locking shape for engaging the biasing member formed to the surface proximal to the biasing member, a rotationally symmetrical body portion extending from the surface proximal to the biasing member along the axis of revolution, a rotationally non-symmetrical shape extending from the body portion along the axis of revolution and a rotationally symmetrical shape extending from the rotationally nonsymmetrical shape. ### Claim 8 (depends on 1) The tow bar assembly according to claim 1, wherein the first end of the shaft is configured to be rotationally locked in respect to the dolly, whereas the second end of the shaft is configured to be rotated in respect to the dolly. ### Claim 9 (depends on 1) The tow bar assembly according to claim 1, wherein the first end plug is arranged in the cavity of the shaft through a sliding fit. ### Claim 10 (depends on 1) The tow bar assembly according to claim 1, wherein the biasing member is configured to resist winding and compression. ### Claim 11 (depends on 1) The tow bar assembly according to claim 1, wherein the biasing member is a spring. ### Claim 12 (depends on 1) The tow bar assembly according to claim 1 included in a dolly. ### Claim 13 (depends on 1) The tow bar assembly according to claim 1, wherein the shaft comprises a second end plug fixed to the second end of the shaft for enclosing the biasing member to the cavity, the second end plug is configured to rotationally lock the biasing member to the shaft. ### Claim 14 (depends on 13) The tow bar assembly according to claim 13, wherein the second end plug comprises: a form locking shape for engaging to the biasing member and a rotationally symmetrical shape for engaging to the dolly in a rotatable manner, the rotationally symmetrical shape distal from the form locking shape for engaging to the biasing member. ### Claim 15 (depends on 13) The tow bar assembly of claim 13 included in a dolly, wherein the dolly comprises a chassis with at least two mutually parallel beams arranged at a distance from each other, wherein one of said beams comprises a rotationally nonsymmetrical opening for receiving the rotationally non-symmetrical shape of the first end plug and the other one of said beams comprises a rotationally symmetrical opening for receiving the rotationally symmetrical shape of the second end plug. ### Claim 16 (depends on 15) The tow bar assembly according to claim 15, wherein the rotationally non-symmetrical opening of the dolly is dimensioned to: receive the rotationally symmetrical shape of the first end plug in a rotatable manner in a retracted axial position of the first end plug, and to receive the rotationally non-symmetrical shape of the first end plug in a non-rotatable manner in an extended axial position of the first end plug. ### Claim 17 (depends on 15) The tow bar assembly according to claim 15, wherein the chassis of the dolly comprises: two mutually parallel longitudinal peripheral supports, two mutually parallel transversal peripheral supports connected by the longitudinal peripheral supports to form a rectangular frame, wherein: said beams are longitudinal cross beams and the shaft is configured to span the longitudinal cross beams within the periphery of the frame of the chassis and is protected by at least one of the transversal peripheral supports.