A castor, or articulated or swivel wheel, has a rolling body freely rotatable around a substantially horizontal axis of rotation carried by a support freely rotatable around a substantially vertical axis.

A swivel castor of said type therefore comprises a wheel body mounted freely rotatable around an axis carried by a fork-type support in turn freely rotatable around a vertical pin through interposition of a ball bearing or similar means.

As far as fixed, that is not swivel, wheels are concerned, the fork-type support is mounted fixedly around a vertical pin.

The fork-type supports according to the known art are provided with a cover such as to close the ball bearing or bearing assembly or similar means housed in special circumferential seats provided in the upper surface of the body of the fork. A through hole for coupling is made in a central position in the cover and is made to coincide with another through hole, made in the body of the fork, in such a way as to be able to insert a pin in these two coinciding through holes.

The part of the pin protruding from the top of the cover is destined to couple inside a hollow tube, integral with the frame of a trolley or a bed or any other means to which castors must be applied. The part of the pin protruding from the bottom of the fork body, on the other hand, is caulked or riveted by means of a further mechanical process, in order to prevent the pin from coming out of its engagement holes.

Said system for securing a pin to the bearing or bearing assembly of the fork of a swivel castor for trolleys or the like, according to the prior art, has some drawbacks. In fact, the process of riveting the pin makes this system somewhat slow, highly complex and

excessively expensive. Furthermore, it requires an excessive number of pieces to be assembled.

The object of the invention is to eliminate these drawbacks by providing a system for securing a bearing or bearing assembly of a fork particularly for swivel castors for trolleys, hospital beds and the like that is rapid, economical and easy to achieve.

This object is achieved according to the invention with the characteristics listed in appended independent claim 1.

Preferred embodiments of the invention are apparent from the dependent claims.

In the system for securing a bearing or bearing assembly for swivel castors, according to the invention, a cover for the fork is provided that has a bottom pin, integral therewith and protruding downward from the lower surface of the cover. Said bottom pin is shaped in such a way as to be able to be coupled by pressure with a corresponding through hole provided in the fork.

The fork cover according to the invention preferably carries, integral therewith, a top pin protruding upward from the upper surface of the cover and destined to couple inside a hollow tube integral with the frame of a trolley or the like.

Assembly of a wheel for trolleys and the like, according to the invention, is instant. In fact it is sufficient to simply press the bottom pin of the cover inside the special hole made in the body of the fork, then insert the top pin of the cover inside the supporting tube of the frame of a trolley or the like.

Production of the system according to the invention is economical and fully automated ; in fact it is sufficient to provide a single piece, obtained by moulding, consisting of the bottom pin and the top pin integral with the cover of the fork.

Further characteristics of the invention will be made clearer by the detailed description that follows, referring to a purely exemplary and therefore non-limiting embodiment thereof, illustrated in the appended drawings in which :

Figure 1 is a side view. in part section, of a castor provided with a system for securing a ball bearing of a fork, according to a first embodiment of the present invention ; Figure 2 is a side view. in part section, of the fork of Figure 1 ; Figure 3 is a side view of the device for securing the bearing of the fork according to the embodiment in Figure 1 ; Figure 4 is a cross sectional view of the device for securing the bearing of the fork, taken along the line IV-IV in Figure 3 ; Figure 5 is a plan view from above of the fork securing device in Figure 3 ; Figure 6 is a plan view from below of the device for securing the bearing of the fork in Figure 3 ; Figure 7 is a side view in part section of a swivel castor provided with the system for securing a bearing assembly of a fork, according to a further embodiment of the invention ; Figure 8 is an exploded side view, in part section, of the device for securing the bearing assembly of the fork in Figure 7 ; Figure 9 is a side view in part section of a further embodiment of the device for securing the ball bearing of a fork ; Figure 10 is a plan view from above of the device for securing the bearing in Figure 9.

The device for securing the bearing of a fork particularly for swivel castors according to the invention will be described with the aid of the figures.

As shown in Figure 1, a rolling body or wheel body 1 is supported by a fork 2. The wheel 1 is pivoted on the fork 2, by means of a pin 3, in such a way as to be able to rotate freely around a substantially horizontal axis X, coinciding with the axis of the pin 3.

As shown in Figure 2, the top part of the fork 2 comprises a substantially cylindrical hollow body 4. In the central part of the hollow body 4 there is a cavity 7. substantially

cylindrical in shape, having a slightly re-entering seat 5, able to house a ball bearing 6, in such a way that the inner race 100 of said ball bearing 6 can rotate freely around the vertical axis Y of the fork. A circular ring-shaped seat 8 is formed in the top end of the cylindrical body 4.

Figures 3-6 show the device for securing a ball-bearing of a fork according to the invention, denoted as a whole with reference numeral 10. The ball-bearing securing device 10 comprises a cover 11, substantially circular in shape and with a diameter about equal to the diameter of the cylindrical body 4. In the inner surface of the cover 11 an annular protrusion 12 is provided, such as to engage inside the seat 8 of the body 4 of the fork, giving rise to a labyrinth structure such as to prevent dust and liquids from entering the bearing.

A discoid projection 13 is provided on the upper surface of the cover 11 and can have a profile of any shape, such as circular or polygonal, for example. A top pin 14 with a substantially cylindrical shape protrudes vertically from the upper surface of the flange 13. The top pin 14 is destined to engage inside a hollow tube (not shown) connected to the frame of the means to which the wheel 1 is to be applied. A through hole 16 is made transversally in the top pin 14 to house locking means for securing the top pin 14 in the hollow tube. The top pin 14 can have a flat surface 15 which, made to coincide with a respective flat surface inside the hollow tube, ensures centering of the hole 16 with the securing means.

A cylindrical shank 17 is made in the lower surface of the cover 11. After closure of the cover 11 on the cylindrical body 4 of the fork, the lower surface of the cylindrical shank 17 abuts against the upper surface of the inner race 100 of the ball bearing 6 (Figure 1).

A bottom pin 18 protrudes vertically downward from the lower surface of the cylindrical shank 17. The bottom pin 18 is inserted in the inner race 100 of the ball bearing 6 through the cavity 7 of the cylindrical body 4 of the fork. The bottom pin 18 has radial notches 19 (as shown in Figure 6, four in number arranged in a cross) which increase its elastic grip, so that it can easily be inserted by pressing inside the inner race 100 of the ball bearing 6. Near the free end of the bottom pin 18, teeth 20 are provided that abut against the lower surface of the inner race 100 of the ball bearing 6 (Figure 1) thus ensuring that the bottom pin 18 is secured.

The top pin 14 has a hole 21 longitudinally, along the vertical axis Y. The hole 21 is in communication with a hole 22 of smaller diameter, made in the body of the cover 11 and extending into a hole 24 formed axially in the bottom pin 18. Between the hole 21 and the hole 22 there is a tapered seat 23.

In this manner, as shown in Figure 1, once the ball-bearing securing device 10 has been mounted on the fork 2, a lockpin 25 can be inserted from the upper end of the hole 21 of the top pin 14. The lockpin 25 has a head 26 with a greater diameter than the stem which stops in the tapered seat 23. The stem of the pin 25 has a slightly larger diameter than the diameter of the hole 24 of the bottom pin 18 and therefore forces the pin 18 radially against the surface of the inner race 100 of the ball bearing 6 thus ensuring a better seal and preventing any slipping out from the bearing.

In this way the fork 2 supporting the castor 1 being integral with the outer race of the ball bearing 6, is free to rotate around the inner race 100 having as it axis the vertical axis Y, whereas device 10 for securing the bearing remains fixed, being integral with the frame of a trolley or the like.

Figures 7 and 8 show the system for securing a bearing assembly of a fork particularly for swivel castors according to further embodiment of the invention, in which the same reference numerals used in the first embodiment are use to indicate parts that are the same.

The cylindrical body 4 of the fork 2 has an annular flange 30 integral with its inner walls, which divides the cavity inside the body 4 into a top chamber 40 and a bottom chamber 41. An upper annular seat 31 and a lower annular seat 32 are provided on the upper and lower surfaces of the annular flange 30, respectively. The upper and lower annular seats 31 and 32 both have a concave shape suitable for receiving balls 38.

The device for securing the bearing assembly of the fork is denoted as a whole by reference numeral 200. A concave-shaped annular seat 31', similar to the seat 31, is made on the lower surface of the cylindrical shank 17 of the cover 11 of the device 200.

A ring-shaped plate 33 having a through hole 34 situated centrally and a concave-shaped annular seat 32'similar to the seat 32 is provided. The ring-shaped plate 33 is positioned in the bottom chamber 41 of the body 4 of the fork and the bottom pin 18 is inserted

inside the hole 34 in the ring-shaped plate 33 in such a way that the teeth or thickenings 20 abut against the lower surface of the ring-shaped plate 33. In this manner, by closing the cover 11 the balls 38 come to be in an upper race formed between the seat 31'of the cylindrical shank 17 and the seat 31 of the annular flange 30, and in a lower race formed between the seat 32 of the annular flange 30 and the seat 32'of the ring-shaped plate 33.

The fork 2 supporting the wheel 1 is free to rotate around the vertical axis Y since the annular flange 30 slides on the balls 38 exploiting the rolling friction generated thereby.

The device 200 for securing the bearing assembly of the fork, on the other hand, remains fixed since the pin 14 is fixed to the frame of a trolley or the like to which the castors 1 must be applied.

Figures 9 and 10 show a variant embodiment of the device for securing a bearing or bearing assembly of a fork. According to said variant embodiment, the top pin 14 is eliminated and the cover 11 is configured as a plate 140 for fixing to the structure to be supported. The plate 140 is substantially rectangular in shape and has through holes 141 near its four corners for fixing to the frame of a trolley or the like.