GEAR MECHANISM

Abstract: A gear mechanism, incorporating a driving input shaft (11), an output shaft (12) arranged coaxially thereto, a first gear rim (21) arranged in a bearing housing (15) and being coaxial relative to said shafts, a second gear rim (22) provided on the output shaft (12) and a ring (18) having double gear rings (19,20) and being excentrically supported on the input shaft (11), one of which gear rings (19) is partially in gear engage­ ment with the gear rim (21) facing inwards and the other gear ring (20) of which is partially in gear engagement with the gear rim (22) facing outwards. The purpose is to provide a gear mechanism having a big gear ratio in a compact design and at a low price. This has been obtained in that the ring (18) is constituted by the outer race ring of a rolling bearing (17), the inner race ring of which is excentrically arranged upon the input shaft (11).

Description: The present invention refers to a gear mechanism incorporating a driving input shaft, an output shaft arranged coaxially thereto, a first gear rim arranged in a bearing housing and being coaxial relative to said shafts, a second gear rim provided on the output shaft and a unitary, one piece ring, having double gear rings integral with said ring and being eccentrically supported on the input shaft, one of which gear rings is partially in gear engagement with the first gear rim which faces inwards and the other gear ring of which is partially in gear engagement with the second gear rim which faces outwards. BACKGROUND OF THE INVENTION Speed reducing gear wheel transmissions of the above mentioned type are earlier known in several different embodiments. Common to them all is that they require quite a large space and are comparatively expensive to manufacture. In FR-A-2592121 there is shown another type of a gear mechanism. Instead of a unitary, one piece ring there is provided two gears which are rotatably on outer portions of a ring which is rotatably arranged on the input shaft. PURPOSE AND MOST ESSENTIAL FEATURES OF THE INVENION The purpose of the invention is to provide a gear mechanism having a big gear ratio in a compact design and at a low price. This has been obtained in that the ring is constituted by the outer race ring of a rolling bearing, the inner race ring of which is eccentrically arranged upon the input shaft. DESCRIPTION OF THE DRAWING The invention hereinafter will be further described wich reference to the accompanying drawings, which show some embodiments. Fig. 1 shows a section through a gear mechanism according to the invention. Fig. 2 shows a section along line II-II in Fig. 1. Figs. 3 and 4 show sections through parts of modified gear mechanisms according to the invention. DESCRIPTION OF THE EMBODIMENTS The gear mechanism according to the invention consists of a driving input shaft 11, e.g. shaped as a tubular shaft, and an output shaft 12 arranged coaxially in relation thereto, and which is preferably also a tubular shaft. The input driving shaft 11 may e.g. be the rotor shaft of an electric motor. Both shaft ends 11 and 12 are supported in one bearing 13 and 14 each in a bearing housing 15. At the free end of the input shaft 11 there is provided excentrically to the longitudinal axis 16 of the input shaft 15, a further rolling bearing 17, the excentricity in relation to the longitudinal axis 16 is designated e. The outer race ring 18 of the rolling bearing 17 is designed as a transmission member, provided with two gear rings 19 and 20 arranged axially displaced relative to each other. One of the gear rings 19 is provided with outwardly projecting teeth and the other gear ring with inwardly projecting teeth. The gear ring 19 is partially in gear engagement with a first gear rim 21 provided coaxially to the shafts 11, 12, and being fixedly attached to the bearing housing 15 and having its teeth directed radially inwardly towards the gear ring 19. This has a sligthly lower number of teeth than the first gear rim 21, the ratio thereby being e.g. 98 to 100. At the outer free end of the output shaft 12 is designed or provided a second gear rim 22, coaxially to the output shaft 12, which second gear rim is also in partial gear engagement with the excentrically arranged gear ring 20 of the outer race ring 18. At rotation of the shaft 11, the outer race ring of the rolling bearing 17 will rotate at a low speed relative to the shaft. This speed is transferred via the ring 18 and further via the introverted gear ring 20, which cooperates with the second gear rim 22 to the concentrically supported output shaft 12. The embodiment according to Fig. 3 differs from the one shown in Fig. 1 therein that both gear rims of the outer race ring are displaced radially relative to each other contrary to the embodiment according to Fig. 1 and 2, wherein the gear rings are arranged to be axially displaced relative to each other. In the embodiment according to Fig. 4 the simplification of the design has been driven still further, in that the input and output tubular shafts of the gear mechanism have been equipped with race tracks for the rolling bearings, whereby the tubular shafts also constitute the inner race rings for the rolling bearings.

Claims: 1. A gear mechanism incorporating a driving input shaft (11), an output shaft (12) arranged coaxially thereto, a first gear rim (21) arranged in a bearing housing (15) and being coaxial relative to said shafts, a second gear rim (22) provided on the output shaft (12), and a unitary, one piece ring (18) having double gear rings (19, 20) integral with said ring (18) and being eccentrically supported on the input shaft (11), one of which gear rings (19) is partially in gear engagement with the first gear rim (21) which faces inwards and the other gear ring (20) of which is partially in gear engagement with the second gear rim (12) which faces outwards, said input shaft (11) being rotatably journalled in the bearing housing (15) by means of a rolling bearing (17), the inner race ring of said rolling bearing being arranged eccentrically upon the input shaft (11), characterized in that said ring (18) spans the input and output shafts (11, 12) and forms the outer race ring of said rolling bearing (17), the inner race ring of said bearing (17) being arranged eccentrically on the input shaft (11), and the outer race ring of said bearing (17) being the sole transmission means between said input shaft (11) and said output shaft (12). 2. A gear mechanism according to claim 1, wherein the two gear rings (19, 20) of the outer race ring (18) are axially displaced relative to each other. 3. A gear mechanism according to claim 1, wherein the two gear rings (19, 20) of the outer race ring (18) are radially displaced relative to each other. 4. A gear mechanism according to claim 1, wherein the input shaft and/or the output shaft (11 and 12 resp.) are tubular shafts which is/are designed as inner race ring(s) for rolling bearing(s) arranged thereupon.

Inventors: ADOLFSSON, RUNE
Applicants: SKF NOVA AB
Application year: 1988
Main classification: F16H1
IPC codes: F16H1