SWIVEL CASTER

Abstract: The castor-wheels concerned are applied "up-side-­ down" in an apron (air-field)-conveyer whereover havy crates can be transported. Practice has learned that the bearing arrangements failed mainly because of insufficient sealing due to which dirt, water and mud can penetrate into the bearings. According to the improved castor-wheel all bearing arrangements comprise standard (for life lubricated and sealed) ball bearings (44, 45 and 32-35) whereby the support part (31, 36) at the upper side and at the bottom is closed by special shaped covers (47 and 38 resp.).

Description: Swivel caster The invention concerns a swivel caster, in particular for application in a so-called roller platform, including a swivel fork with a body and two legs extending from it and forming one unit with it, which legs extend into an upward rim around the body, and a caster running on bearings between these legs, which rotates by means of pivot bearing constructions around an axle through the legs, and a base plate with openings for attaching the swivel caster, which plate is connected to the body of the swivel fork by means of a truncated pin mounted perpendicular to the body, which pin is attached to one of these components, and at least one pivot bearing construction whose inner race is attached around the truncated pin and whose outer race is connected to the other component, in such manner that the swivel fork can swivel around the cardioid line of the truncated pin with regard to the base plate, and the caster can rotate around the cardioid line of the axle through the legs, whereby the latter cardioid line cuts the extension of the cardioid line of the truncated pin perpendicularly. In airfreight, extensive use is made of special, relatively large shipping pallets and shipping crates. In order to movie these shipping pallets and crates easily in all horizontal directions when loading and unloading cargo planes, airport services use, amongst others, so-called roller platforms. These devices consist mainly of a large number of swivel casters which are mounted, casters upward, in a number of parallel rows on an essentially horizontal support structure, so that a shipping crate placed on the roller platform is supported by these swivel casters and can be easily moved in all directions over the platform, whereby the swivel casters rotate and adapt automatically to any given direction of displacement due to the swivelling of the swivel forks. In the known swivel caster the truncated pin is attached with its bottom end to the base plate, and the outer race of the pivot bearing construction is attached to the body of the swivel fork because this outer race is contained in a downward bent rim of an opening cut into the body. Because, as a result, the top part of this pivot bearing construction is entirely unprotected so that water and dirt can freely enter the pivot bearing construction, a sealing hood covering entirely the opening in the body has been attached to the top part of the body. Because the pivot bearing construction formed in this manner has a relatively limited rigidity, a second pivot bearing construction is provided whose inner race is formed by an upward bent annular section of the base plate, and the outer race by the downward bent outer surface section of a special annular plate attached to the bottom of the body. The known swivel caster is relatively expensive to manufacture while it does not give full satisfaction in practical applications, mainly because water and dirt can penetrate into the pivot bearing constructions from below. Moreover, it is necessary, in order to give sufficient rigidity to the fork whose body has an opening, that the legs of the swivel fork extend, on both sides, into the upward rim surrounding the body, so that an annular gutter is formed which is open at the top and in which water and dirt can accumulate. A drain hole has been provided, but this is easily clogged. The purpose of the invention is to create a swivel caster of the aforementioned type, which does not possess these disadvantages. This purpose is reached on account of-the fact that in the swivel caster according to the invention, the body of the swivel fork consists of a closed plate-shaped section and the legs extend only on one side into the upward rim, so that this rim runs only along the surface section of the body between the legs, which section lies, with regard to the rotation cardioid line of the caster, on the opposite side of the cardioid line of the truncated pin, and the truncated pin is attached to the bottom of the body, on the side away from the legs, and the pivot bearing construction is formed by one sealed standard pivot bearing whose outer race is attached to an annular casing which rises upward from the base plate with which it forms one unit or to which it is connected. In this manner, a swivel caster is obtained which can be manufactured in a relatively simple and cheap manner and which, through the application of a standard bearing, i.e., a sealed and permanently lubricated bearing, prevents the penetration of dirt and/or water in the bearing. In addition, any water dripping on the body of the swivel fork is immediately evacuated by way of the flat section of the body which extends between the legs, on the same side - beside the truncated pin - as the axis of rotation of the caster. In order to increase the protection of the pivot bearing against dirt and moisture even further, a preferably annular dust hood has been mounted over the top part of the pivot bearing directed toward the caster, and over the free top rim of the aforementioned casing, whereby this hood has an outer rim, bent downward in the direction of the casing, while a sealing plate has been mounted against the bottom of the base plate, whereby the entire bottom of the pivot bearing is sealed against outside influences. In an advantageous model, the sealing plate has essentially the same outline and dimensions as the base plate, and it has corresponding openings with vertical collars, which fall within the openings in the base plate. To simplify the manufacture of the swivel caster even further, it is preferable that the pivot bearing constructions supporting the caster each consist of standard pivot bearings as well. The invention is described in detail with reference to the drawing in which: Figure 1 shows, to the left, a cross-section and, to the right, an elevation of the known swivel caster, Figure 2 is a schematic rendering of a roller platform, Figure 3 shows, to the left, an elevation and, to the right, a cross-section of a swivel caster according to the invention, and Figure 4 shows a side view of the swivel caster according to Figure 3. As shown in Figure 2, a so-called roller platform includes a generally horizontal support 1 on which a number of swivel casters 2 are mounted in parallel rows, with the casters 3 pointing upward. At a distance above the support 1 a cover plate 4 is placed which has a number of openings 5 through which the casters 3 of the swivel casters 2 protrude slightly, so that a shipping crate placed on the cover plate is supported by a number of casters 3, which make it possible to move the crate easily in all directions over the cover plate 4. Figure 1 shows the known swivel caster. This swivel caster includes a swivel fork 6 with the legs 7 and 7' and the body 8. The legs 7 and 7' extend on both sides into the upward rims 9 and 9' of the body 8. The base plate 10 has openings 11 for attaching the swivel caster and, in its center, it has an opening for attaching the truncated pin 12 which runs through an opening formed in the center of the body 8. The inner race 13 of a first pivot bearing construction is attached around the truncated pin 12, and the outer race 14 is contained in the downward bent rim section 8' of the opening in the base plate 8. A number of ball bearings 15 are placed between the races 13 and 14. The second pivot bearing construction has an inner race which is formed by an upward bent section 10' of the base plate 10, whereas the outer race is formed by a downward bent outside section 16 of an annular plate attached to the bottom of the body 8. A number of ball bearings 17 are contained between the races 16 and 10'. Furthermore, a hood 18 is attached to the body 8, covering entirely the truncated pin 12 and the adjacent pivot bearing 13, 14, 15. The body has a weep hole 19 through which water, accumulated in the gutter formed by the body 8, the upward rim sections 9 and 9' and the connecting legs 7 and 7', can flow out. An axle 20 runs between the legs 7 and 7' which is attached by means of the nut 21 and which is equipped with a bushing 22. The surface of the bushing 22 contains the inner races 22' of two pivot bearing constructions, whose outer races, for the ball bearings 23, are formed by the outer races 24. The caster 25, for example made of a synthetic material, is equipped with a bore which fits around the outer races 24. Furthermore, the caster 25 is equipped on both sides with a groove 26 in which the bent rim section of the sealing plate 27 fits; the sealing plate is placed over the axle 20. The sealing plates serve to prevent blockage of the wheel, for example, through pieces of rope or paper. As shown in Figures 3 and 4, the swivel caster according to the invention includes a swivel fork 28 with the legs 29 and 29', and the fully sealed body 30. The legs 29 and 29' extend into the upward rim section 30' of the body 30 on one side only. The truncated pin 31 is attached to the bottom of the body 30 by means of a weld 31a. The inner race 32 of a standard ball bearing is attached around this truncated pin 31. A standard ball bearing includes always an outer race 33, a series of balls 34 in a cage, and the sealing rings 35 and 35'. In addition, this ball bearing is permanently lubricated, i.e., provided with a suitable lubricant. The outer race 33 is contained in an annular casing 36' which forms one unit with the base plate 36. Over the top part of the ball bearing 32, 33, 34, a dust hood 37 is placed whose outer rim is bent downward toward the casing 36'. Against the bottom of the base plate 36 a sealing plate 38 is placed, of the same size and outline as the base plate 36. The sealing plate 38 is equipped with openings 39 which are surrounded by upward collars 39' which fall within the openings in the base plate 36. Furthermore, the sealing plate 38 is provided with an annular protrusion 38' for the containment of a sealing ring -40 which, as a result, is squeezed between the protrusion 38' and the base plate 36. Between the legs 29 and 29', a bolt 41 is mounted with a bolt head 41' and a threaded end, on which thread a nut 42 is screwed. The bolt 41 is surrounded by a bushing 43 to which the inner races 44 of two standard ball bearings are attached. Around the outer races 45 of these ball bearings, the caster 47 is mounted which is equipped on both sides with a continuous groove 48 in which the rims of the sealing plates 49, 49' fit. It appears clearly from the Figures 3 and 4 that, with the application of a sealed standard ball bearing 32, 33, 34, 35, 35', no dirt and/or moisture can penetrate the bearing while, in addition, the dust hood 37 and the sealing plate 38 give extra protection to the top and bottom of the bearing against penetrating dirt and/or moisture. Any water landing on the body 30 can immediately flow away over the flat edge 30" of the body 30.

Claims: Conclusions 1. Swivel caster, in particular for application in a so-called roller platform, including a swivel fork with a body and two legs extending from it and forming one unit with it, which legs extend into an upward rim around the body, and a caster running on bearings between these legs, which rotates by means of pivot bearing constructions around an axle through the legs, and a base plate with openings for attaching the swivel caster, which plate is connected to the body of the swivel fork by means of a truncated pin mounted perpendicular to the body, which pin is attached to one of these components, and at least one pivot bearing construction whose inner race is attached around the truncated pin and whose outer race is connected to the other component, in such manner that the swivel fork can swivel around the cardioid line of the truncated pin with regard to the base plate, and the caster can rotate around the cardioid line of the axle through the legs, whereby the latter cardioid line cuts the extension of the cardioid line of the truncated pin perpendicularly, characterized by the fact that the body (30) of the swivel fork consists of a closed plate-shaped section and the legs (29, 29') extend into the upward rim (30') on one side only, so that this rim (30') runs only along the surface section of the body (30) between the legs (29, 29') which, with regard to the axis of rotation of the caster (47), lies on the opposite side of the cardioid line of the truncated pin (31), and the truncated pin (31) is attached to the bottom of the body (30) away from the legs (29, 29'), and the pivot bearing construction is formed by one standard pivot bearing (32, 33, 34, 35), whose outer race (33) is attached to an annular casing (36') which rises upward from the base plate (36) with which it forms one unit or to which it is connected. 2. Swivel caster according to Conclusion l, character- ized by the fact that an annular dust hood (37) is mounted over the top part of the pivot bearing (32, 33, 34, 35, 35') directed toward the caster (47), and over the free upper rim of the casing (36'), whereby this hood has an outer rim bent downward, in the direction of the casing. 3. Swivel caster according to Conclusions 1 or 2, characterized by the fact that a sealing plate (38) is mounted against the bottom of the base plate (36), whereby the entire bottom of the pivot bearing (32, 33, 34) is sealed against outside influences. 4. Swivel caster according to Conclusion 3, characterized by the fact that the sealing plate (38) has essentially the same size and outline as the base plate (36), and is equipped with corresponding openings (39) surrounded by upward collars (39') which fall within the openings in the base plate (36). 5. Swivel caster according to Conclusions 1 - 4, characterized by the fact that the caster (47) runs on bearings by means of two standard ball bearings (44, 45) around an axle (41, 43) supported by the legs (29, 29') of the swivel fork (28).

Inventors: TIMMER, HENDRIKUS JACOBUS MARIA
Applicants: SKF TRANSPORTWIELEN B.V.
Application year: 1985
Main classification: B60B33
IPC codes: B60B33