EP2435645B1

EP2435645B1 - Construction prop

Info

Publication number: EP2435645B1
Application number: EP10726620.7A
Authority: EP
Inventors: Franciscus Jozef Leonardus Hubertus Brinkmann
Original assignee: Scafom International BV
Current assignee: Scafom International BV
Priority date: 2009-05-29
Filing date: 2010-05-28
Publication date: 2014-02-26
Anticipated expiration: 2030-05-28
Also published as: CN102459785A; EP2435645A1; PL2435645T3; WO2010137984A1; ES2463115T3; CN102459785B; NL2002948C2

Description

Field of the invention

The invention relates to a construction prop.

State of the art

Construction props have been known for many years. Examples of construction props are described in GB-755831 and DE6941113U . EP 0402241 already discloses a construction prop according to the preamble of claim 1. These known construction props comprise an outer pipe with a longitudinal central axis. The known outer pipe is provided with a foot at a lower end of the outer pipe and screw thread adjacent an upper end of the outer pipe. Further, two slotted holes are provided at the screw thread which extend in a direction parallel to the longitudinal central axis and which are provided diametrically relative to each other in the outer pipe. The known construction props further comprise an inner pipe which is slideably received in the outer pipe. The inner pipe is provided with a series of pairs of holes which are arranged over a part of the length of the inner pipe, while the two holes of each pair of holes are disposed diametrically relative to each other in the inner pipe. The known construction prop further comprises an adjusting nut which is provided with internal screw thread configured for cooperation with the screw thread of the outer pipe. The construction prop further comprises a supporting pin which extends, in use, through one of the pairs of holes of the inner pipe and the slotted holes in the outer pipe and which bears on a top of the adjusting nut. The inner pipe can be height-adjusted by inserting the supporting pin in another pair of holes of the inner pipe. Fine-tuning the height is obtained through rotation of the adjusting nut. In order to prevent the inner pipe from falling from the outer pipe, the inner pipe can be provided adjacent a lower end thereof with a widening and the outer pipe can be provided adjacent an upper end thereof with a reduced portion. The widening and the reduced portion should be geared to each other such that the widening cannot pass the reduced portion. With the construction prop from GB-755831 , the reduced portion is above the part provided with screw thread. With the construction prop from DE6941113U , the reduced portion is directly below the part provided with screw thread. In DE6941113U , the inside diameter of the screw thread part is also smaller than the inside diameter of the remaining part of the outer pipe, so that a better guiding of the inner pipe relative to the outer pipe is obtained and, furthermore, the risk of skewness of the inner pipe relative to the outer pipe is minimized.
GB-755831 - which has screw thread provided integrally in the outer pipe - has as a drawback that for the purpose of providing the screw thread in the outer pipe, the outer pipe should have a thickness of approximately 3.5 mm in order to have the required strength at that location too. This leads to an outer pipe with a considerable weight and hence to a construction prop with a considerable weight.
DE6941113U - which has a bush provided with screw thread connected through welding to an upper end of a pipe for forming the outer pipe - has as a drawback that a welding operation needs to be carried out for connecting the threaded bush to the pipe. After this welding operation, the outer pipe has to be re-galvanized at the location of the weld.
The object of the invention is a construction prop with which the above-described drawbacks are at least partly remedied.

Summary of the invention

Therefore, the object of the invention is a construction prop which can be of thin-walled design, wherein the screw thread portion forms an integral part of the outer pipe and which has sufficient strength for fulfilling its task.
To that end, the invention provides a construction prop which comprises:

an outer pipe with a longitudinal central axis and an outer pipe length, the outer pipe being provided with:
- ○ a foot at a lower end of the outer pipe;
- ○ screw thread adjacent an upper end of the outer pipe;
- ○ two slotted holes which are located at the screw thread and which extend in a direction parallel to the longitudinal central axis and which are provided diametrically relative to each other in the outer pipe;
an inner pipe which is slideably received in the outer pipe and which is provided with:
- ○ a series of pairs of holes which are arranged over a part of the length of the inner pipe, wherein the two holes of each pair of holes are disposed diametrically relative to each other in the inner pipe; characterized by
a reinforcing pipe part which is included adjacent an upper end of the outer pipe in the outer pipe at the screw thread, wherein the reinforcing pipe part has a reinforcing pipe part length which is smaller than the outer pipe length; and

Such a construction prop is relatively light in that the outer pipe thereof is of thin-walled design. Furthermore, the screw thread is formed through a screw thread rolling operation, which has as an advantage that the screw thread forms an integral part of the outer pipe and therefore no welding operations are required for connecting the screw thread part to the outer pipe. As a result of the presence of the reinforcing pipe part, despite the thin-walled design of the outer pipe, after the screw thread rolling operation, there is still sufficiently remaining wall thickness, also at the location of the foot of the screw thread for obtaining a screw thread with sufficient strength. Furthermore, the reinforcing pipe part provides a reduced portion of the outer pipe which, when the inner pipe is provided adjacent a lower end with a widening that cannot pass the reduced portion, forms a fall out protection for the inner pipe. Furthermore, the reduced portion provides a good guide for the inner pipe, so that the inner pipe can hardly tilt relative to the outer pipe. As no welding operation is required for providing the screw thread, furthermore, pre-galvanized pipes can be used. Pre-galvanized pipes have an excellent resistance against the formation of corrosion. Therefore, the construction prop is particularly durable and can yet be manufactured at relatively low costs.
The invention further provides a method for manufacturing a construction prop according to the invention, comprising:

providing a thin-walled outer pipe with an outer pipe length and with a wall thickness of less than 3.5 mm;
providing a reinforcing pipe part with a reinforcing pipe part length which is smaller than the outer pipe length and with an outside diameter which substantially corresponds to the inside diameter of the outer pipe, such that the reinforcing pipe part is slideably receivable in the outer pipe;
placing the reinforcing pipe part in the outer pipe and positioning the reinforcing pipe part relative to the outer pipe in an area where an outside screw thread is to be provided;
providing screw thread by means of a screw thread rolling operation on the outer pipe at the reinforcing pipe part.

Such a method is favourable because with it, a threaded, thin-walled outer pipe is obtained for which, for forming the screw thread, no welding operation is required. This may, in turn, save on finishing operations, such as re-heating and re-galvanizing. As no welding operation needs to be carried out at the location of the screw thread, pre-galvanized pipes can be used as starting material. Such pre-galvanized pipes have an excellent resistance against the forming of corrosion.
In one embodiment, the method, after placing the reinforcing pipe part and prior to the screw thread rolling operation, can further comprise folding a top edge of the outer pipe radially inwardly for forming a bevelled pipe edge in the outer pipe. Such a bevelled pipe edge is advantageous with the screw thread rolling operation as it forms a lead thereto.
The diameter of the reinforcing pipe part can be such that it is slideably receivable in a clamping manner in the outer pipe. Owing to the clamping fit, prior to the screw thread rolling operation, there is a fixation of the reinforcing pipe part relative to the outer pipe. The thus obtained fixation simplifies the handling of the outer pipe and the reinforcing pipe part prior to the screw thread rolling operation.
Further elaborations of the invention are described in the subclaims and will be further clarified in the following on the basis of an exemplary embodiment with reference to the drawing.

Brief description of the drawing

Fig. 1 shows a perspective view of an exemplary embodiment of a construction prop;
Fig. 1A shows a detail of Fig. 1;
Fig. 2 shows a top plan view and a cross-sectional view along the line A-A of the top plan view of the outer pipe after a first phase of the manufacture of the outer pipe;
Fig. 3 shows a top plan view and a cross-sectional view along the line B-B of the top plan view of the outer pipe after a second phase of the manufacture of the outer pipe;
Fig. 4 shows the detail IV of Fig. 3;
Fig. 5 shows a top plan view and a cross-sectional view along the line C-C of the top plan view of the outer pipe after a third phase of the manufacture of the outer pipe; and
Fig. 6 shows the detail VI of Fig. 5.

Detailed description

In one embodiment, of which an example is shown in Fig. 1 and of which a detail A is shown in Fig. 1A, a construction prop 10 comprises an outer pipe 12 with a longitudinal central axis L. The outer pipe 12 is provided with a foot 14 at a lower end of the outer pipe 12. Adjacent an upper end of the outer pipe 12, screw thread 16 is provided. At the screw thread, two slotted holes 18 are present which extend in a direction parallel to the longitudinal central axis L and which are provided diametrically relative to each other in the outer pipe 12. The construction prop 10 further comprises an inner pipe 20 which is slideably received in the outer pipe 12. The inner pipe 20 is provided with a series of pairs of holes 22 which are arranged over a part of the length of the inner pipe 20. The two holes of each pair of holes 22 are disposed diametrically relative to each other in the inner pipe 20. It is also possible that the inner pipe has several series of pairs of holes, for instance two series of pairs of holes, which are provided in a staggered manner over the circumference of the inner pipe 20. In one embodiment, of which an example is shown in Fig. 1, an upper end of the inner pipe 20 can be provided with an end plate 24 which has a substantially flat top surface which extends substantially perpendicularly to the longitudinal central axis L. The construction prop is in general provided with an adjusting nut 26 which is provided with inside screw thread and which is configured for cooperation with the screw thread 15 of the outer pipe 12. The construction prop further comprises in general a supporting pin 28 which, in use, is inserted through one of the pairs of holes 22 of the inner pipe 20 and the slotted holes 18 in the outer pipe 12 and which bears on a top of the adjusting nut 26. In one embodiment, of which an example is shown in Fig. 1 and 1A, the inner pipe 20 can be provided with a height marking 30. Such a height marking 30 facilitates the choice of the correct pair of holes 22 for inserting the supporting pin 28. After rough-tuning the inner pipe 20 relative to the outer pipe 12 through the choice of the correct pair of holes 22 for inserting the supporting pin 28, fine tuning of the height of the construction prop 10 can be realised with the adjusting nut 26.
In one embodiment, of which an exemplary embodiment is shown in Fig. 1, at the centre of gravity of the construction prop 10 when the inner pipe 20 is in the most slid-in condition in the outer pipe 12, the outer pipe 12 can be provided with a centre of gravity marking 32. In the exemplary embodiment of Fig. 1, the centre of gravity marking 32 is designed as a line marking which extends in tangential direction around the outer pipe 12. It is clear that also other designs of the centre of gravity marking 32 are possible. A centre of gravity marking 32 simplifies picking up the construction prop 10 by a user. The fact is that when the user picks up the construction prop 10 at the centre of gravity marking 32, the construction prop 10 will be directly in equilibrium, without the user needing to correct his point of engagement.
The height marking 30 and the centre of gravity marking 32 can be provided with the aid of, for instance, a punching operation or an etching operation. A thus provided marking 30, 32 can be made more striking by giving the marking a colour that deviates from the colour of the rest of the construction prop 10. It is also possible to provide a height marking 30 and/or centre of gravity marking 32 by applying colours only, hence without a punching or etching operation. The construction prop 10 can further be provided with a foot reinforcement 34 adjacent a lower end of the outer pipe 12. The foot reinforcement 34 can comprise a number of grooves 36 which each extend in tangential direction around the entire circumference of the outer pipe 12. Each groove 36 extends in an imaginary plane which extends perpendicularly to the longitudinal central axis L. The tangential grooves 36 do not weaken the outer pipe 12 in case of squashing as a result of a force applied to the pipe wall in a direction perpendicular to the longitudinal central axis L. On the contrary, the tangential grooves 36 reinforce the outer pipe 12 against such a load. Furthermore, the tangential grooves do offer the grooves 36 protection against denting which may occur as a result of impact of a large hammer or beam against the lower side of the outer pipe 12, which operation is carried out when construction props are removed. Dents may still be formed, however, these dents are formed in the parts of the tangential grooves 36 located radially outwardly. The parts of the tangential grooves 36 located radially inwardly remain undamaged. Therefore, sliding the inner pipe 20 inward or outward relative to the outer pipe 12 can take place unhindered, even when there is some extent of denting. The tangential grooves 36 can be provided in an area of the outer pipe 12 which extends from near the lower end of the outer pipe 12 over a length of 10 - 50 cm. In the example shown, the length of the area over which tangential grooves 36 have been provided from the foot 14 is approximately 15 cm. The tangential grooves 36 may be provided through plastic deformation of the pipe wall. The tangential grooves 36 may have a wave-shaped cross-sectional profile viewed in a cross-sectional plane in which also the longitudinal central axis L extends. The distance D between crests of two neighbouring grooves 36 can be in the range of 0.5 to 3.5 cm. With such a distance, it is sufficiently provided that hitting with a large hammer or beam does not lead to formation of dents in the parts of the foot reinforcement 34 located radially inwards. In the exemplary embodiment shown, the distance D is approximately 25 mm.
According to one aspect of the invention, the construction prop 10 is characterized by a reinforcing pipe part 38 which is included adjacent an upper end of the outer pipe 12 in the outer pipe 12 at the screw thread 16, while the reinforcing pipe part 38 has a reinforcing pipe part length L2 which is smaller than the outer pipe length L1. According to a further aspect of the invention, the outer pipe 12 is thin-walled and the screw thread 16 is provided in the outer pipe 12 through a screw thread rolling operation which is carried out after the reinforcing pipe part 38 is included in the outer pipe 12. Owing to the presence of the reinforcing pipe part 38 at the screw thread 16, in a relatively thin-walled outer pipe 12, still, screw thread 16 can be rolled. The remaining wall thickness, or the wall thickness that remains after the screw thread rolling operation, suffices even at the location of the foot of the screw thread 16 for providing sufficient sturdiness at the screw thread 16 too. Thus, as a result of the thin wall of the outer pipe 12, a relatively light construction prop 10 can be provided which can yet be obtained with few operational steps because the screw thread 16 forms an integral part of the outer pipe. For instance, there is no need for welding operations for providing the screw thread 16. As a result of the presence of the reinforcing pipe part 38, after the screw thread rolling operation for obtaining screw thread 16, a screw thread 16 remains which has a remaining wall thickness of at least 2.5 mm even in the foot of the screw thread. Therefore, the thus obtained screw thread 16 has sufficient strength. As the reinforcing pipe part 38 needs to have a more limited length L2 with respect to the length L1 of the outer pipe 38, a considerable saving in weight can be obtained.
Fig. 5 shows an example of an embodiment of the outer pipe after the screw thread rolling operation. Fig. 6 shows a detail VI of Fig. 5. The outer pipe 12 has a length in the range of, for instance, 1.4 - 2.6 m. The screw thread 16 which is provided adjacent the upper end of the outer pipe 12 extends over a length in the range of, for instance, 10 - 30 cm. Adjacent the upper end of the outer pipe 12, the reinforcing pipe part 38 is visible. It is clear that the reinforcing pipe part 38 is deformed due to the screw thread rolling operation. As a result, the reinforcing pipe part 38 and the outer pipe 12 have formed a whole, so to speak, with a great axial strength. The reinforcing pipe part 38 also forms a reduced portion of the inside diameter of the outer pipe 12, which reduced portion can serve as drop out security and as guide of the inner pipe 20. In one embodiment, the thin-walled outer pipe 12 has a wall thickness in the range of 2.0 - 3.0 mm. At the location of the screw thread 16, the outside diameter D1 can be, for instance, 63.5 mm and the inside diameter D2 for instance 52 mm. The inside diameter D3 of the remaining part of the outer pipe 12 can for instance be 58.5 mm and the outside diameter D4 of the remaining part of the outer pipe 12 can for instance also be 63.5 mm. In such a design, the wall thickness of the outer pipe 12 is 2.5 mm.
In one embodiment, prior to the screw thread rolling operation, the reinforcing pipe part 38 has an outside diameter D3 which corresponds to the inside diameter D3 of the outer pipe 12, such that the reinforcing pipe part 38 is slideably and preferably somewhat clampingly receivable in the outer pipe 12. After the screw thread rolling operation, this leads to an optimal strength of the part of the outer pipe 12 provided with screw thread 16. In unprocessed form, the reinforcing pipe part 38 can have an outside diameter D3 of, for instance, 58.5 mm or slightly less, such that the reinforcing pipe part 38 is slideably receivable in the outer pipe 12.
A sufficient strength of the part provided with screw thread 16 can be obtained when, prior to the screw thread rolling operation, the reinforcing pipe part 38 has a wall thickness S in the range of 1.0 to 2.0 mm, at least when the wall thickness of the outer pipe 12 is in the range of 2.0 to 3.0 mm. In the exemplary embodiment shown, the wall thickness S of the reinforcement pipe part is 1.5 mm.
In one embodiment, the length of the reinforcing pipe part 38 is at least as large as the length over which the screw thread 16 extends on the outer pipe 12. The length of the reinforcing pipe part 38 is preferably slightly larger than the length over which the screw thread 16 extends over the outer pipe. With a screw thread length of, for instance, 18 cm, the reinforcing pipe part 38 could be in the range of, for instance, 19 - 23 cm.
As is clearly visible in the detail IV of Fig. 3, which is shown in Fig. 4 and in the cross-sectional view of Fig. 5, in one embodiment, after placing the reinforcing pipe part 38 in the outer pipe 12 and prior to the screw thread rolling operation, a top edge of the outer pipe 12 can be folded radially inwardly for forming a bevelled pipe edge 40. Such a bevelled pipe edge 40 can form a lead for the screw thread rolling operation, so that the screw thread rolling operation can be carried out in a controlled manner.
The different steps of an embodiment of the method for manufacturing the outer pipe 12 are represented in Figs. 2 - 6.
First is provided the thin-walled outer pipe 12 with an outer pipe length L2 and with a wall thickness of less than 3.5 mm, for instance 2.5 mm. Also, the reinforcing pipe part 38 is provided with a reinforcing pipe part length L2 which is considerably smaller than the outer pipe length L1 and with an outside diameter D3 which substantially corresponds to the inside diameter of the outer pipe 12, such that the reinforcing pipe part 38 is slideably receivable in the outer pipe 12. The reinforcing pipe part 38 is placed in the outer pipe 12 and positioned relative to the outer pipe 12 in an area where an outer screw thread 16 is to be provided. This condition is shown in Fig. 2. In the exemplary embodiment shown, the top edge of the reinforcing pipe part 38 is at a distance L3 below the top edge of the outer pipe 12. L3 may be in the range of 4 - 10 mm. This provides the possibility of a next, optional operational step, viz. subsequently - that is, after placing the reinforcing pipe part 38 and, as will appear later, prior to the screw thread rolling operation - folding the top edge of the outer pipe 12 radially inwardly for forming a bevelled pipe edge 40. This condition is shown in Figs. 3 and 4. This folding radially inwardly provides a lead that facilitates the subsequent thread rolling.
After folding the top edge radially inwardly for forming the bevelled pipe edge 40, screw thread 16 can be provided on the outer pipe 12 at the reinforcing pipe part 38 by means of a screw thread rolling operation. This is shown in Figs. 5 and 6 which have been extensively elucidated hereinabove.

Claims

A construction prop comprising:
• an outer pipe (12) with a longitudinal central axis (L) and an outer pipe length (L1), the outer pipe (12) being provided with:
○ a foot (1.4) at a lower end of the outer pipe (12);

○ screw thread (16) adjacent an upper end of the outer pipe (12);

○ two slotted holes (18) which are located at the screw thread (16) and which extend in a direction parallel to the longitudinal central axis (L) and which are provided diametrically relative to each other in the outer pipe (12);

• an inner pipe (20) which is slideably received in the outer pipe (12) and which is provided with:
○ a series of pairs of holes (22) which are arranged over a part of the length of the inner pipe (20), wherein the two holes of each pair of holes (22) are disposed diametrically relative to each other in the inner pipe (12);
characterized by

• a reinforcing pipe part (38) which is included adjacent an upper end of the outer pipe (12) in the outer pipe (12) at the screw thread (16), wherein the reinforcing pipe part (38) has a reinforcing pipe part length (L2) which is smaller than the outer pipe length (L1); and
wherein the outer pipe (12) is thin-walled and the screw thread (16) is provided in the outer pipe (12) through a screw thread rolling operation which is carried out after the reinforcing pipe part (38) is included in the outer pipe (12).
A construction prop according to claim 1, wherein the length (L2) of the reinforcing pipe part (38) is at least as great as the length over which the screw thread (16) extends on the outer pipe (12).
A construction prop according to claim 1 or 2, wherein the outer pipe (12) has an outside diameter of 40 - 90 mm.
A construction prop according to any one of the preceding claims, wherein the thin-walled outer pipe (12) has a wall thickness in the range of 2.0-3.0 mm.
A construction prop according to any one of the preceding claims, wherein, prior to the screw thread rolling operation, the reinforcing pipe part (38) has an outside diameter (D3) which corresponds to the inside diameter of the outer pipe (12), such that the reinforcing pipe part (38) is slideably receivable in the outer pipe (12).
A construction prop according to any one of the preceding claims, wherein prior to the screw thread rolling operation, the reinforcing pipe part (38) has a wall thickness in the range of 1.0 to 2.0 mm.
A construction prop according to any one of the preceding claims, wherein, after placing the reinforcing pipe part (38) in the outer pipe (12) and prior to the screw thread rolling operation, a top edge of the outer pipe (12) is folded radially inwardly for forming a bevelled pipe edge (40).
A construction prop according to any one of the preceding claims, further comprising:
• an adjusting nut (26) provided with inside screw thread configured for cooperation with the screw thread (16) of the outer pipe (12).
A construction prop according to claim 8, further comprising:
• a supporting pin (28) which, in use, extends through one of the pairs of holes (22) of the inner pipe (20) and the slotted holes (18) in the outer pipe (12) and which bears on a top of the adjusting nut (26).
A construction prop according to any one of the preceding claims, comprising:
• a centre of gravity marking (32) on the outer pipe (12) at the centre of gravity of the construction prop (10) when the inner pipe (20) is in a most slid-in condition in the outer pipe (12).
A method for manufacturing a construction prop according to any one of the preceding claims, comprising:
• providing a thin-walled outer pipe (12) with an outer pipe length (L1) and with a wall thickness of less than 3.5 mm;

• providing a reinforcing pipe part (38) with a reinforcing pipe part length (L2) which is smaller than the outer pipe length and with an outside diameter (D3) which substantially corresponds to the inside diameter of the outer pipe (12), such that the reinforcing pipe part (38) is slideably receivable in the outer pipe (12);

• placing the reinforcing pipe part (38) in the outer pipe (12) and positioning the reinforcing pipe part (38) relative to the outer pipe (12) in an area where an outside screw thread (16) is to be provided;

• providing screw thread (16) by means of a screw thread rolling operation on the outer pipe (12) at the reinforcing pipe part (38).
A method according to claim 11, comprising:
• after placing the reinforcing pipe part (38) and prior to the screw thread rolling operation, folding a top edge of the outer pipe (12) radially inwardly for forming a bevelled pipe edge (40).