GB2245921A

GB2245921A - Split ferrule for rail spike

Info

Publication number: GB2245921A
Application number: GB9118491A
Authority: GB
Inventors: Hugh Richard Henry
Original assignee: Multiclip Co Ltd
Current assignee: Multiclip Co Ltd
Priority date: 1987-09-21
Filing date: 1991-08-29
Publication date: 1992-01-15
Anticipated expiration: 2007-09-21
Also published as: GB2245921B; GB2210088B; GB2210088A; GB8722191D0; GB9118491D0

Abstract

A ferrule which is transversely locatable on the shank of a screw spike comprises two thin inner half cylindrical portions which are dimensioned so as to build the shank up to the same diameter as the threaded portion of the screw spike with which the ferrule is to be used and an outer sleeve which slides axially over the threaded portion and holds the two inner half sleeves in place on the screw spike whilst the screw spike is inserted.

Description

RAIL SPIKES The present invention relates to screw rail spikes.

Screw spikes are used to attach the metal chair in which the rail of a railway line is seated to the wooden sleeper which rests in the ballast of the track.

The chair is an iron casting having a hole through which the screw spike passes, the spike having a head larger than the hole but otherwise being of smaller diameter than the hole. The space between the hole and the shank of the spike is occupied by a generally cylindrical but tapered ferrule, nowadays made of tough plastics material such as nylon or high density polyethylene. The ferrule extends out of the top of the hole in the chair and bears against the bottom of the head of the screw spike thus spacing and cushioning it from the top of the chair.

The screw spikes with which the present invention is concerned are threaded and are screwed into predrilled undersize holes in the sleeper. With time, and the passage of trains, these holes become enlarged and the screw spike becomes loose. The problem is to avoid having to replace the sleeper.

According to the present invention, a screw spike is provided with an enlarged diameter threaded portion which is preferably slightly tapered, the threaded portion having a diameter such that it can still pass through the hole in the chair and the spike has a reduced diameter with unthreaded shank around which the ferrule fits, and the ferrule is made so as to be transversely locatable on the shank of the screw spike.

More broadly, the screw spike has a shank of smaller diameter than its threaded portion.

The arrangement enables screw spikes having enlarged threaded portions (effective to take up wear in the sleeper and re-establish tight attachment of the chair to the sleeper) to be used with conventional chairs and with conventional ferrule thicknesses, ensuring adequate cushioning between the screw spike and the chair.

Since the shank has a smaller diameter than the threaded protion of the screw spike, the ferrule can no longer be simply axially slid on to the screw spike if close contact between the inside of the ferrule and the outside of the shank and the outside of the ferrule and the inside of the hole in the chair is to be achieved.

Accordingly the ferrule has to be transversely locatable on the shank. This may be achieved by making the ferrule in two half cylindrical portions, i.e.

split parallel to the longitudinal axis, which fitted together around the shank produce the desired spacing dimensions.

The invention thus extends to the screw spike, the transversely locatable ferrule system and the kit of parts consisting of the screw spike and the ferrule system.

The invention may be put into practice in various ways and one specific embodiment will be described by way of example with reference to the accompanying drawings in which: Figure 1 is a diagrammatic part cross sectional view showing a conventional screw spike and ferrule sexing a conventional chair to a wooden sleeper; the left hand half of the figure showing the conformation of the screw and the wood of the sleeper when the screw is first inserted and the right hand half, the wood retracted such to result in a loose screw; and Figure 2 is a similar view to Figure 1 showing the screw spike and split ferrule according to the present invention and the conformation of the ferrule to the chair.

Screw-spikes used in Great Britain have a square head (10) for engagement by a spanner, wrench or other driving tool, and a flange (11) which overlaps the hole (15) through the chair (16) and bears against the top surface (17) of a wood or plastics ferrule (18) which is located in the hole in the chair. Below the flange is a plain unthreaded shank (20) which passes through the chair to the threaded portion (21) of the screwspike. The threads are relatively widespread e.g. the pitch is typically 12.7 mms (0.5 inches) or 13 mms from thread crest to thread crest. The threads are assymetrical, the upper flank (nearer the head) being inclined at a greater angle (typically 700) to the longitudinal axis of the screw-spike than the lower flank (which is typically inclined at an angle of 300 to the longitudinal axis). (Different thread profiles are used in other countries).

The valley or trough region of the screw-spike between threads, which will be called the root herein, is typically flat or only very slightly curved rather than being V-shaped as in a metal screw or bolt and the length of the root between threads is typically about 6 mms.

This line joining the lowest points of the roots (the root line) may be parallel to the longitudinal axis of the screw-spike or inclined at a very small angle thereto when the screw-spike is tapered, the taper being from shank to bottom end.

Thus in the screw spike shown in Figure 1, the diameter (T), namely the line (25), of the root of the topmost full thread is 1.8 units and the diameter (B), namely the line (26) of the bottommost full thread is 1.6 units; the ratio B/T thus being 1:1.125.

In Figure 1, the left hand half of the drawing around the centre line (30) shows diagramatically the close conformation of the wood of the sleeper to the thread of the screw spike. It also shows the thickness of the ferrule (18).

In Figure 2, the screw spike in accordance with the invention has the same head (10) and flange (11) and the same thread profile as in Figure 1. However the diameter (D1), namely the line 35, of the root of the topmost full thread is 2.5 units i.e. about 40% greater than that in the conventional screw spike while the diameter (D2), namely the line 36, of the root of the bottommost full thread is 2.1 units i.e. about 30% greater than that in the conventional screw spike.

It will be noticed that the taper is also greater D2/D1 being 1:1.19. Figure 2 also shows the split ferrule (18) made in two halves 40 and 41, their abutting longitudinal faces being represented by the line (42).

The dotted lines (43) show the edge of the shank (20) which is of the same dimension as the shank (20) in Figure 1, thus enabling the same thickness of ferrule to be used.

The kit is used as follows. The old loose screw is unscrewed and a new screw as in Figure 2 has the split ferrule placed around its shank and the assembly is screwed into the hole. If desired the placement of the ferrule about the shank can be deferred until the shank is just about to enter the hole in the chair.

Another version of the ferrule has two thin inner half cylindrical portions which build the shank up to the same diameter as the threaded portion and then an outer sleeve which slides axially over the threaded portion and holds the two inner half sleeves in place whilst the screw spike is inserted. While this can be used it is less attractive than the next described arrangement since it requires two dissimilar parts and the outer sleeve limits the maximum radial dimensions of the screw thread of the spike.

Further versions modify the first arrangement of a full thickness split ferrule by providing engagement means, such as interengaging male and female formations e.g. pins and sockets, on their abutting faces so that they can be secured around the shank and will stay in place during installation of the screw spike.

Preferrably the two halves are the same shape so that a single moulding can be used.

A modification of this arrangement hinges the two split halves together and optionally provides the free abutting faces with engagement means.

The screw spike can be made in a range of diameters e.g. two, three or four to accommodate varying degrees of wear and a gauging tool used to assess the degree of wear enabling the appropriate screw spike to be selected.

The depth of the threads is limited to that which will allow the spike to pass through the hole in the chair but, in general, the clearance afforded in accommodating the ferrule will allow sufficient depth to provide adequate engagement of the wood of the sleeper.

A replacement rail spike in accordance with the present invention will have varying dimensions e.g. of root diameter (D1, D2) weight of thread, length of thread, thread spacing and length and diameter of shank, according to the specific type of rail spike it is intended to replace.

Thus as can be seen from Figures 1 and 2 the thread profile of the spike in accordance with the invention can be modified. However the same profile as a conventional screw spike could be used if desired.

Claims

CLAIMS 1. A screw spike having a shank of smaller diameter than its threaded portion. 2. The combination of a spike having an enlarged diameter threaded portion, with a diameter such that it can still pass through the hole in the chair, and a reduced diameter unthreaded shank around which the ferrule fits, and a ferrule which is transversely locatable on the shank of the screw spike. 3. A ferrule which is transversely locatable on the shank of a screw spike. 4. A ferrule which is in two half cylindrical portions, which when fitted together around the shank produce the desired spacing dimensions. AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS.

1. A ferrule which is transversely locatable on the shank of a screw spike.

2. A ferrule which is in two half cylindrical portions, which when fitted together around the shank produce the desired spacing dimensions.

3. A ferrule as claimed in Claim 1 which comprises two thin inner half cylindrical portions which are dimensioned so as to build the shank up to the same diameter as the threaded portion of the screw spike with which the ferrule is to be used and an outer sleeve which slides axially over the threaded portion and holds the two inner half sleeves in place on the screw spike whilst the screw spike is inserted.

4. A ferrule as claimed in Claim 1 which is of full thickness and is split into two portions, the two portions being provided with engagement means on their abutting faces so that they can be secured around the shank of a screw spike and will stay in place during installation of the screw spike.

5. A ferrule as claimed in Claim 1 which is split into two portions which are hinged together.

6. A ferrule as claimed in Claim 5 in which the two split portions are hinged together and the free abutting faces are provided with engagement means.

7. A ferrule as claimed in Claim 1 substantially as specifically described herein with reference to the accompanying drawings.