EP3753697B1

EP3753697B1 - Casting process of reinforced concrete railway ties with embedded anchor bolts

Info

Publication number: EP3753697B1
Application number: EP20174746.6A
Authority: EP
Inventors: Stefano Lucarini
Original assignee: Margaritelli Ferroviaria SpA
Current assignee: Margaritelli Ferroviaria SpA
Priority date: 2019-06-21
Filing date: 2020-05-14
Publication date: 2023-06-28
Anticipated expiration: 2040-05-14
Also published as: ES2964537T3; IT201900009840A1; EP3753697A1

Description

The present patent application relates to a casting process of reinforced concrete railway ties with embedded anchor bolts, namely at least one pair of anchor bolts, and to an apparatus for said process.
As it is known, a railway tie is suitable for being fixed to the ground in order to provide a fixing point for two rails that are supported near one end of the railway tie.
In order to perform such a fixing operation, the railway tie must be provided with a pair of anchor bolts in each point where the rails are to be supported.
The term "anchor bolt" usually refers to a threaded cylindrical stem provided with an ending portion with lower section (substantially a point) and cylindrical shape.
An attachment for rails, which consists in a drilled plate, is to be inserted on each anchor bolt from above. The drilled plate is suitable for pressing one edge of the rail in order to firmly fix the rail on the railway tie. Such a firm fixing prevents the uncontrolled movements of the rail with respect to the railway tie that may be originated by the high stress caused by the passage of trains.
After inserting the attachment of the rail on the anchor bolt, the threaded end of the anchor bolt is helically coupled with a fixing nut that fixes the attachment on the railway tie, together with the rail.
As it is known, railway ties that are made of reinforced concrete and are formed in formworks have become largely popular. Each railway tie is formed in a formwork in overturned position compared to its operating position.
In its operating position, the railway tie is provided with two surfaces for supporting the rails that are directed upwards. Therefore, also the two pairs of anchor bolts in each surface are directed upwards. On the contrary, the railway tie is arranged in an overturned position inside the formwork.
The arrangement of the railway tie in overturned position is imposed by the need to ensure the easy extraction of the railway tie from the formwork because the bottom wall of the railway tie, which must be the first one to come out of the formwork, has a higher width than the upper wall of the railway tie. To that purpose, a specific feature is implemented in order to facilitate the provision of the anchor bolts on such a reinforced concrete railway tie.
The formwork of the railway tie is provided with substantially vertical stems made of a flexible material, preferably rubber, which are disposed in its bottom wall. The number of said stems is identical to the number of anchor bolts to be provided on the railway tie.
Before casting the fluid concrete inside the formwork, a plug (which is similar to the ones that are usually known as Fischer plugs) is inserted in each one of said stems, in such a way that the opening of the plug is directed towards the bottom wall of the formwork.
After casting the fluid concrete inside the formwork, when the fluid concrete has set, the plugs are permanently embedded in the structure of the railway tie, in such a position that the opening of the plugs is flush with the upper surface of the railway tie.
After setting, the railway tie is extracted from the formwork, from up downwards, along a vertical direction. Also the plugs can be extracted from the stems along a substantially vertical direction. In view of the above, the stems are suitable for housing the anchor bolts.
In spite of its popularity, the technique of the prior art is impaired by a severe drawback that negatively affects the manufacturing process of said railway ties, both in terms of time and costs.
As a matter of fact, after extracting the railway tie, which is already provided with plugs, from the formwork, the anchor bolts must be manually mounted in the plugs by a worker.
In some instances, each one of the two surfaces that are used for supporting the rails is inclined towards the center of the railway tie. Such an inclination of each surface requires a suitable inclination of the anchor bolts of each pair, in such a way that the axis of each anchor bolt is perpendicular to the surface that is used for supporting the rail. In view of the above, the two anchor bolts of each pair must be disposed in parallel position, and moreover the two anchor bolts of the pair disposed on the surface that supports the first rail must be inclined with respect to the two anchor bolts of the pair disposed on the surface that supports the second rail. Without such a condition, the inclined position of the four anchor bolts would originate four undercuts that would prevent the downward extraction along a vertical direction of the railway tie in overturned position from the formwork.
KR100667584 , JPH0711311U and FR851197 disclose reinforced concrete railway ties. JPH0711311U further discloses a casting process of reinforced concrete railway ties, wherein a rectangular formwork is used, and an apparatus for casting a reinforced concrete railway tie according to the preamble of claim 4.
The purpose of the present invention is to disclose a casting process of reinforced concrete railway ties that is practical, versatile, reliable and capable of minimizing the use of labor.
Such a purpose is achieved according to the invention with the process of the independent claim 1 and the apparatus of the independent claim 5.
The process of the invention provides for embedding two pairs of anchor bolts, which are preferably coupled to the plugs, in the railway tie of reinforced concrete during the extraction of the railway tie from the formwork. In view of the above, the railway tie is already provided with the anchor bolts, avoiding the need for manually mounting the anchor bolts, as it occurs in the prior art.
A second purpose of the present invention is to implement a manufacturing method of a reinforced concrete railway tie that allows for extracting the railway tie from the formwork in vertical direction also when the pairs of anchor bolts are inclined with respect to the vertical extraction direction.
This purpose is achieved according to the invention with the characteristics of the dependent claim 2.
Additional characteristics of the present invention are described and claimed in the following claims.
For the sake of clarity, the description of the invention continues with reference to the appended drawings, which have a merely illustrative, not limiting value, wherein:

Figs. 1A, 1B and 1C are respectively an axonometric view, a top view and a sectional view with a longitudinal vertical plane of the formwork provided for the implementation of the process according to the invention;
Fig. 2 is an axonometric view of a railway tie obtained with the process of the invention;
Fig. 3 is an axonometric view of a railway tie that embeds two pairs of anchor bolts during the extraction from the formwork, wherein the railway tie is in overturned position;
Fig. 4 is a sectional view of the formwork and of the railway tie of Fig. 3;
Fig. 5 is a side view of the railway tie, wherein its four anchor bolts are enlarged and separated from the bushes;
Fig.6 is an enlarged detail of Fig 1C, which shows a pair of bushes in an extracted position from the seats on the bottom of the formwork;
Figs. 7A and 7B are respectively a side view and a sectional view of a conical bush with a median vertical plane;
Fig. 8 is a diagrammatic out of scale view of one of the conical seats of the formwork, which shows a conicity angle and an inclination angle with respect to a vertical direction.

With reference to Figs. 1A to 1C, the process of the invention provides for using a formwork (1) with rectangular shape. The formwork comprises a horizontal bottom wall (1a) and two longitudinal walls (1b) and two transverse walls (1c), that protrude from the bottom wall, said longitudinal walls and said transverse walls defining an internal cavity (1d) of the formwork (1);
The formwork (1) is suitable for casting a railway tie (10) made of concrete. The railway tie (10) is provided with flat surfaces (11) disposed at the ends of the railway tie. The flat surfaces (10) of the railway tie provide a surface that is used for supporting and fixing two rails (Fig. 2).
The casting of the railway tie (10) is performed while the formwork (1) is maintained in a position wherein the opening that provides access to the cavity (1d) is directed upwards. Therefore, an upper surface of the railway tie (10) will be formed on the bottom wall (1a) of the formwork. The extraction of the railway tie (10) is performed from up downwards, in vertical direction, after overturning the formwork, as shown in Figs. 3 and 4.
The formwork (1) has two pairs of vertical seats (2) in the bottom wall (1a). The vertical seats (2) have a conical shape and are preferably aligned along a median longitudinal axis Z of the bottom wall. The provision and the configuration of said vertical seats (2) can be seen in Fig. 1C, and in the partial enlarged view of Fig. 6.
With reference to Figs. 1C, 6, 7A and 7B, the seats (2) are suitable for housing bushes (3) that are inserted in the seats for the entire height of the seats.
Each bush (3) is externally provided with a conical shape that is compatible with the shape of the seat (2). The bush (3) has a threaded cylindrical conduit (internal thread) (3a), which is disposed axially and is suitable for being helically coupled with a threaded cylindrical point (external thread) (4a) of an anchor bolt (4).
In view of the above, before being inserted in the seat (2) on the bottom wall (1a) of the formwork, each bush (3) is screwed to the cylindrical point (4a) of an anchor bolt (4).
Therefore, the insertion of the bush (3) in the seat (2) obtained on the bottom wall of the formwork will produce the following consequences:

being internally screwed in the bush (3), also the point (4a) of the anchor bolt (4) is inserted in the seat (2) in the bottom wall (1a) of the formwork (1), whereas the remaining length of the anchor bolt (4) out of the bush occupies the cavity (1d) of the formwork (1), as shown in Fig. 1C; and
each bush (3) supports the anchor bolt (4) in such a way that the axis of the anchor bolt (4) coincides with an axis X of the seat (2) that houses the bush (3).

In such a condition, the fluid concrete that is cast into the cavity (1d) of the formwork will embed the four anchor bolts (4), except for their cylindrical points (4a), which are suitably inserted in the bushes (3) that are inserted in the seats (2) provided on the bottom wall (1a) of the formwork, as shown in Fig.4.
When the railway tie (10) is extracted from the formwork (1), the points (4a) of the four anchor bolts (4) are in a projecting position with respect to the two surfaces (11) provided in the railway tie (10).
During the extraction of the railway tie (10) from the formwork (1), which is performed along a vertical direction (Figs. 3 and 4), the bushes (3) are easily extracted in axial direction from the seats (2) that contained them on the bottom wall (1a) of the formwork. This is made possible by the conical shape of the bushes and of the seats.
Now, the last operation to be performed consists in unscrewing the bushes (3) from the points (4a) of the four anchor bolts (4), not only to "discover" the threads of the points of the anchor bolts, but also to use the bushes (3) in the casting process of another railway tie (1).
With reference to Fig. 7A, each bush (3) is externally provided with a pair of rectilinear facets (3b) disposed in diametrally opposite positions, in correspondence of a tapered end portion of the bush. The rectilinear facets (3b) are suitable for being tightened in anti-rotational mode between the jaws of a tool used to screw and unscrew the bush (3) to and from the point (4a) of an anchor bolt (4).
Preferably, the anchor bolts (4) that are disposed inside the formwork (1) used for casting the railway tie (10) are already provided with a plug (40), as shown in Fig. 5.
The plug (40) is provided with annular grooves and ribs to ensure that the fluid concrete can firmly embed the anchor bolt (4) because it penetrates the grooves of the plug (40).
The anchor bolts (4) can be arranged in the formwork (1) without the plugs (40) because the external thread will favor the penetration and the grip of the fluid concrete.
Each pair of seats (2) of the formwork is obtained in a removable plate (20) that is suitable for being firmly disposed on the bottom wall (1a) of the formwork (1) in correspondence of a notch. Such a provision permits to vary a center distance between the two seats (2) of each pair and therefore a center distance between two anchor bolts (4), mounting different versions of the plate (20) in the bottom wall (1a) of the formwork (1).
The process of the invention can be also used for the manufacturing of railway ties wherein the surfaces (11) that are used for supporting and fixing the rails are disposed in a symmetric, non-horizontal position, with an inclination angle towards the center of the railway tie (1), such that the pairs of anchor bolts (4) have the same inclination angle with respect to a vertical plane, as shown in Fig. 8.
In such a case, the two pairs of seats (2) are disposed at the height of two inclined sections (1a'), with respect to the horizontal bottom wall (1a) of the formwork (1), where the two surfaces (11) that are used for supporting the rails in inclined (non-horizontal) position will be formed on the railway tie (10).
With reference to Fig. 8, the four seats (2), which are obtained two by two in the inclined sections (1a') of the bottom wall of the formwork, are disposed in such a way that their axis X is perpendicular to the inclined section (1a') of the bottom wall (1a) of the formwork (1).
Because of such a provision, the axis X of each seat (2) has an inclination angle (α) relative to a vertical axis Y.
The seat (2) has such a conicity angle (β) that half of the conicity angle is higher than or equal to the inclination angle (α), according to the following condition: $β / 2 \geq α$
When such a condition between the inclination angle (α) and the conicity angle (β) is respected, during the extraction of the railway tie (1) from the formwork (10), the four bushes (3) that are screwed to the points of the anchor bolts (4) can be axially extracted from the seats (2). In fact, the inclination of the points (4a) of the anchor bolts is suitably "contained" and neutralized inside the axial conduits (3a) of the bushes (3). This prevents the formation of undercuts that would prevent the extraction of the bushes from the seats of the formwork.
It must be understood that although the process of the invention has been devised to manufacture railway ties that are provided with two surfaces for supporting and fixing two rails, the same process can be advantageously used to manufacture railway ties provided with only one surface for supporting and fixing a rail.

Claims

Casting process of reinforced concrete railway ties comprising at least one pair of anchor bolts (4), each anchor bolt being formed of a cylindrical stem with a threaded cylindrical point (4a), wherein a rectangular formwork (1) is used, which is provided with a median longitudinal axis Z and a horizontal bottom wall (1a), two longitudinal walls (1b) and two transverse walls (1c) defining an internal cavity (1d) of said formwork (1);
wherein the process comprises the following steps:
A) arranging of at least one section (1a') on the bottom wall (1a) of the formwork (1), said at least one section (1a') comprising a pair of conical seats (2) with an axis X perpendicular to the surface of the section (1a');

B) mounting of a bush (3) in said cylindrical point (4a) of each anchor bolt (4), wherein said bush (3) is internally provided with a cylindrical axial conduit (3a) suitable for receiving the cylindrical point (4a) of the anchor bolt (4); wherein said bush (3) is externally conic with a conicity angle (β) allowing a coupling in said conical seats (2) of the bottom wall of the formwork and wherein each anchor bolt (4) has a length that is lower than the height of said longitudinal and transverse walls (1b, 1c) of said formwork;

C) insertion of the bushes (3) already screwed to the points (4a) of the anchor bolts (4) inside said conical seats (2) of the bottom wall of the formwork, so that a length of the anchor bolts (4) occupies said cavity (1d) of the formwork;

D) casting of fluid concrete to fill said cavity (1d) of the formwork, embedding the anchor bolts (4);

E) extraction of said railway tie (10) from the formwork (1) according to a direction of a vertical axis Y and simultaneous extraction of said bushes (3) screwed to the points (4a) of the anchor bolts (4) from the conical seats (2) of the bottom wall (1a) of said formwork; and

F) removal of said bushes (3) from the points (4a) of the anchor bolts (4).
The process of claim 1, wherein at least one section (1a') of the bottom wall (1a) of the formwork (1) has a sloped arrangement, wherein the axis X of the conical seats (2) forms an inclination angle (α) with respect to the vertical axis Y; wherein said conicity angle (β) of the conical seat (2) is such that one half of the conicity angle (β/2) is higher than or equal to said inclination angle (α).
The process of any one of the preceding claims, wherein the two seats (3) of each pair of seats are aligned along said median longitudinal axis Z of the formwork (1).
Apparatus for casting a reinforced concrete railway tie, said apparatus comprising at least one pair of anchor bolts (4) and a rectangular formwork (1), said rectangular formwork (1) comprising a median longitudinal axis Z and a horizontal bottom wall (1a), two longitudinal walls (1b) and two transverse walls (1c) defining an internal cavity (1d) of said formwork (1); wherein said anchor bolts (4) have a length lower than the height of said longitudinal and transverse walls (1b, 1c) of said formwork (1);
wherein said horizontal bottom wall (1a) of the formwork (1) is provided with at least one section (1a') comprising a pair of conical seats (2) with an axis X perpendicular to the section (1a') of the bottom wall of the framework;

characterized in that said apparatus further comprises:
bushes (3) having a conical shape with conicity angle (β), suitable for coupling in the conical seats (2) provided on said at least one section (1a') of the bottom wall (1a) of the formwork (1), wherein each bush (3) is internally provided with a cylindrical axial conduit (3a) with threaded walls; each anchor bolt (4) being provided with a threaded cylindrical point (4a) suitable for being helically coupled with said cylindrical conduit (3a) of the bush (3).
The apparatus of claim 4, wherein said at least one section (1a') of the bottom wall (1a) of the formwork (1) has a sloped arrangement wherein the axis X of the seat forms an inclination angle (α) with respect to a vertical axis Y; wherein the conicity angle (β) of each seat (2) is such that one half of the conicity angle (β/2) is higher than or equal to said inclination angle (α).
The apparatus of claim 4 or 5, wherein the two conical seats (2) of a pair of seats are obtained in a removable plate (20) arranged in a notch on the bottom wall (1a) of the formwork (1).
The apparatus of any one of claims 4 to 6, wherein each bush (3) is externally provided with a pair of rectilinear facets (3b) in correspondence of a tapered end portion of the bush.