[0001] 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.
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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.
[0018] 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.
[0019] 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.
[0020] 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.
[0021] 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.
[0022] This purpose is achieved according to the invention with the characteristics of the
dependent claim 2.
[0023] Additional characteristics of the present invention are described and claimed in
the following claims.
[0024] 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.
[0025] 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);
[0026] 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).
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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).
[0031] 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).
[0032] 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).
[0033] 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.
[0034] 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).
[0035] 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.
[0036] 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).
[0037] 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).
[0038] 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.
[0039] 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).
[0040] 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.
[0041] 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).
[0042] 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.
[0043] 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).
[0044] 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).
[0045] Because of such a provision, the axis X of each seat (2) has an inclination angle
(α) relative to a vertical axis Y.
[0046] 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:
[0047] 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.
[0048] 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.
1. Casting process of reinforced concrete railway ties, embedding 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).
2. 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).
3. The process of any one of the preceding claims, wherein, before the execution of said
step (D), each anchor bolt (4) is coupled with a plug of Fischer type.
4. 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).
5. Apparatus for casting a reinforced concrete railway tie, embedding at least one pair
of anchor bolts (4), comprising a rectangular formwork (1), 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 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; and
each anchor bolt (4) is provided with a threaded cylindrical point (4a) suitable for
being helically coupled with said cylindrical conduit (3a) of the bush (3).
6. The apparatus of claim 5, 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).
7. The apparatus of claim 5 or 6, 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 (1 a)
of the formwork (1).
8. The apparatus of any one of claims 5 to 7, wherein each bush (3) is externally provided
with a pair of rectilinear facets (3b) in correspondence of a tapered end portion
of the bush.