GB2045831A - Staircase with string-mounted step - Google Patents

Abstract

A staircase with string-mounted steps (3'), particularly a double-string wooden staircase, whose string(s) (1) each have cut-outs (2) spaced apart the distance of the steps with substantially horizontal abutment surfaces (3) corresponding in depth to abutment surfaces on the undersides of the steps, is characterised in that the steps each firmly abut the corresponding abutment surfaces (3) of each string (1) along only a narrow portion (4) along their rear lower edge to the depth of the narrow portions (4), whereas most of each step underside extends freely forward beyond the abutment surface (3) and for each intermediate step of the staircase there is a substantially vertically oriented support (8), preferably comprising one or more rods, bearing on the underside of the step near to its front edges, which support (8) rests on the tread surface on the next lower step near its rear corners on a surface portion (11) which is substantially vertically above the string abutment surface (3) of the step. <IMAGE>

Description

SPECIFICATION Staircase with string-mounted steps This invention relates to a staircase with stringmounted steps. Such staircases, preferably made of wood, may be double-string staircases having two strings running on either side of the centre of the staircase, or a single string staircase having a single relatively broad central string, or having only one side string where, for example, the other side of each step is supported on abutment surfaces provided in the wall construction or is supported by the central pillar orthe like of a spiral staircase. Such staircases, preferably made of wood, have strings with cut-outs spaced apart the distances of the steps having substantially horizontal abutment surfaces of a depth corresponding to that of the abutment surfaces of the steps on the underside of the steps.

Double string staircases of the above type are known in which the abutment surfaces of the steps extend over about 80% of the total depth of the steps and even more. This means that the steps abut cut-outs in the strings substantially over their whole depth. This has the disadvantage that the strings for such deep step abutment require relatively large string cut-outs. This however imposes the requirement the strings have a correspondingly large original breadth, so that weakening of the strings by the cut-outs is compensated for.

An object of the invention is to provide for a staircase of the type mentioned above in which the original breadth of the string of strings is substantially narrower than in known double string staircases while retaining about the same load-carrying capacity. Thereby it should be possible for the front regions of the tread surfaces of at least some steps to be free also in the region of their side edges from perforations for the passage or insertion of fastening means.

According to the invention there is provided a staircase with string-mounted steps, whose one or more strings each have cut-outs spaced apart the distance of the steps with substantially horizontal abutment surfaces corresponding in depth to abutment surfaces of the steps on the undersides of the steps, characterised in that, the steps each firmly abut the corresponding abutment surfaces of the or each string along only a narrow surface portion along the rear lower edge of their undersides to a depth corresponding to that of the narrow portionS, whereas the larger part of the underside of each of he steps extends freely forward beyond the abutment surface and for each intermediate step of the staircase there is a substantially vertically oriented support bearing on the underside of the step near to its front edges, which support rests on the tread surface of the next lower step near its rear corners on a surface portion which is substantially vertically oriented support bearing on the underside of the step near to its front edges, which support rests on the tread surface of the next lower step near its rear corners on a surface portion which is substantially vertically above the string abutment surface of the step.

Preferably the support between two neighbouring steps comprises one or more rods extending between the front portion of the underside of the upper step and the rear portion of the tread surface of the lower step, the rods having oppositely running thread portions on their ends adapted to engage in oppositely running female threads in nuts for locating the rods.

The rods can conveniently be masked by tubes of metal, wood or plastic which are located as spacer tubes between neighbouring steps and which are rotationally fast with the rods.

The nuts preferably lie fast in blind recesses formed in the underside of the upper step and in the tread surface of the lower step or in the string abutment surface of the lower step in which latter case each rod passes through a bore in the lower step.

The steps may be screwed fast to the strings in the region of their string abutment surfaces by means of screw connections, for example wood screws where the strings are of wood, from their tread surfaces.

The screw connections can conveniently be located in recesses in the steps below the nuts which the rods engage, or alternatively the screw connections are off-set to one side of the nuts which the rods engage.

In the case of a staircase with wood strings and steps the nuts may alternatively have external wood screw threads for engaging the recesses and metal female threads for engaging the rods which are suitably of metal.

In the case of a double string staircase each support preferably comprises two of the said rods extending between two opposite surface portions near the two front lower corners on the underside of the upper step and near the opposite rear upper corners on the tread surface of the lower step.

In the case of the top and bottom steps of a staircase, or of each flight of a staircase, different attachment arrangement may be adopted than is the case for intermediate steps which on at least one side will be wholly mounted on the string. The top step may have a support of the same kind as intermediate steps bearing on the next lower step, and the bottom step have such a support bearing on the lower floor or landing.

Preferred embodiments of the invention will now be described with reference to the accompanying drawings wherein: Figure 1 is a side view of a staircase according to the invention.

Figure 2 is a perspective view of a part of the staircase shown in Figure 1.

Figure 3 is a vertical section in the region of two neighbouring steps of the staircase shown in Figures 1 and 2 on a larger scale compared to Figure 1 and 2, and Figure 4 is a section corresponding to that in Figure 3 through another embodiment.

In Figures 1 and 2 the double string staircase comprises two wooden strings 1,1 with relatively small cut-outs 2. On the relatively small horizontal abutment surfaces of the cut-outs 2 in the strings 1,1, the steps 3' in each case abut only along a narrow surface portion 4 near their rear corners 5 of their undersides 6 on the corresponding abutment surfaces 3 of the strings 1,1. The larger part of the undersides 6 of the steps extends forward freely beyond the string abutment surfaces 3. Bearing on the undersides 6 of the steps near their two forward corners 7, there are in each case two substantially vertically orientated supports 8,8 which rest on the tread surface 9 of the next lower step near its two rear upper corners 10 on small surface portions 11, which are substantially vertically above the string abutment surfaces 3 of the step.

With this construction only relatively small cutouts need be made in the strings 1,1, which are thereby weakened relatively little, so that their original breadth can be relatively small compared to that of known double string staircases.

A support 8 between two neighbouring steps is shown in section in Figure 3. The support 8 preferably consists of an external tubular cladding 12, for example of wood. A rod 13, preferably made of metal, extends through and is masked by the cladding formed by wooden tube 12. Rod 13 has two oppositely running threaded portions at its two ends 14 and 15. These threaded portions engage corresponding oppositely running female threads of nuts 16 and 17 which lie fast in blind recesses 18 and 19 on the underside 6 of an upper step and the opposite tread surface 9 of the next lower step.

The nuts 16 and 17 have wood screw-like external threads which cut into the walls of recesses 18, 19 when the nuts 16, 17 are inserted and thereby give the nuts a firm~grip in the recesses. The recesses 18, 19 have a greater depth than the thickness of the nuts so that the threaded end of the rod can pass through the nut. The tubular cladding 12, which can also be made of metal, wood or plastics, is for example made rotationally fastto the rod by means of at least one radially directed pin 20. Instead of one or more pins 20 it is also possible to provide a rotationally fast coupling by having a fixed projection on the rod which enters an internal slot in the tubular cladding 12.

Other methods of obtaining a rotationally fast coupling between the rod 13 and the tubular cladding which lie within the scope of the invention will suggest themselves without difficuity to the expert.

In each of the recesses 19 below the nuts 17 there lies the head of a screw 21, which grips one of the strings 1,1 to thereby fasten the step 3' to it. This can be a wood screw, as shown in Figure 3. Instead of a wood screw a threaded boit or similar connection element can be used, the threaded end of which engages the female thread of a nut corresponding to 16 or 17 which lies fast in a recess in the string abutment surface.

In the embodiment shown in Figure 3 the nut 17 is positioned coaxially above the screw 21 which - as said - can also be replaced by a threaded bolt or the like. Clearly, if the string abutment surface 3 is of sufficient depth the nut 17 and the screw 24 can be positioned side by side offset from one another.

The double string staircase is not limited to having a top cover for the connecting forward supports 8 according to Figure 3. A number of solutions can be adopted by the expert, if the rod 13 or some corresponding support element can be inserted from above through a bore passing through a step. Also clearly, the covered top fastening of the support between two steps according to Figure 3 is not limited to a double string staircase. Similar supports can also be advantageously used for example for the steps of a spiral staircase, in which case both the upper fastening in the underside of the upper step as well as the lower fastening in the tread of the adjacent lower step are respectively masked as against the tread surface of the upper step and the underside of the lower step.

When a double string staircase as shown in Figure 3 is erected the lower step 3' is first screwed fast to the abutment surfaces 3 of the two strings 1,1, then the next higher step 3' is placed on the next higher abutment surface 3 and the threaded ends of the two rods 13 inside the tube 12 are inserted into the two nuts 16 in the upper step and the two nuts 17 in the lower step. By rotating the tubes 12 and thereby also the rods 13 which are splined to them the threaded ends of the rods are screwed into the nuts 16 and 17.

The length of the tubes 12 is such, that the two steps 3' are correctly positioned relative to each other when the tubes 12 between the steps can no longer be rotated by hand, that is when the tubes have their end faces firmly abutting the opposed surfaces of the steps. Following this the upper step is screwed to the strings. The next higher step is then erected in the same way.

The double string staircase according to Figure 4 differs from the construction shown in Figure 3 mainly in, that the rod 13 with its two oppositely threaded ends 14 and 15 extends with its lower end through a bore 19' at the rear end of the lower step 3' and into engagement with the thread of a nut 17', which is screwed into a recess 21 in the abutment surface 3 of string 1.The upper end of rod 13 engages in a nut 16, as in Figure 3, positioned in arecess 18 on the underside of the upper step near its forward end.

The embodiment according to Figure 4 has only a single threaded rod as described in Figures 3 and 4 serving both as a connecting element for connecting two steps to each other and as a fastening element for connecting a step to one or two strings. By this double function of the threaded rod a particularly simple construction is made possible, which requires a minimum of effort for connecting the steps to each other and/or for fastening the steps to the strings.

Clearly the essential features of the construction of the double string staircase according to the invention can also be used for a string staircase with only a single relatively broad central string or only one side string where on the opposite side stair supports in the wall construction are usable.

The rotationally fast coupling of tubular cladding 12 and rod 13 as shown in Figure 4can also be achieved by other means then using at least one pin, as has been expiained above with reference to Figure 3.

Claims (15)

CLAIMS:

1. A staircase with string-mounted steps, whose one or more strings each have cut-outs spaced apart the distance of the steps with substantially horizontal abutment surfaces corresponding in depth to butment surfaces of the steps on the undersides of the steps, characterised in that, the steps each firmly abut the corresponding abutment surfaces of the or each string along only a narrow surface portion along the rear lower edge of their undersides to a depth corresponding to that of the narrow portions, whereas the larger part of the underside of each of the steps extends freely forward beyong the abutment surface and for each intermediate step of the staircase there is a substantially vertically oriented support bearing on the underside of the step near to its front edges, which support rests on the tread surface of the next lower step near its rear corners on a surface portion which is substantially vertically above the string abutment surface of the step.

2. Staircase according to Claim 1 wherein the support between two neighbouring steps comprises one or more rods extending between the front portion of the underside of the upper step and the rear portion of the tread surface of the lower step, the rods having oppositely running thread portions on their ends adapted to engage in oppositely running female threads in nuts for locating the rods,

3. Staircase according to Claim 2 wherein the rods are masked by tubes of metal, wood or plastic which are located as spacer tubes between neighbouring steps and which are rotationally fast with the rods.

4. Staircase according to Claim 2 or Claim 3 wherein the nuts lie fast in blind recesses formed in the underside of the upper step and the tread surface of the lower step.

5. Staircase according to Claim 2 or Claim 3 wherein the nuts lie fast in blind recesses formed in the underside of the upper step and in the string abutment surface of the lower step while each rod passes through a bore in the lower step.

6. Staircase according to one of Claims 1 to 5, characterised in that the steps are screwed fast to the strings in the region of their string abutment surfaces by means of screw connections from their tread surfaces.

7. Staircase according to Claim 6 when dependant on Claim 4 characterised in that the screw connections are respectively located in recesses in the steps coaxially below the nuts which the rods engage.

8. Staircase according to Claim 6 when dependant on claim 3 or 4 characterised in that the screw connections are off-set to one side of the nuts which the rods engage.

9. Staircase according to Claim 6 when dependant on Claim 4 wherein the screw connections are threaded bolts which engage the female thread of the nuts which lie fast in recesses of the string abutment surface.

10. Staircase according to any preceding claim wherein the strings are made of wood.

11. Staircase according to Claim 10 when dependant on any one of Claims 6 to 9 wherein the screw connections are wood screws.

12. Staircase according to Claim 10 when dependant on Claims 7 to 9 wherein the nuts have external wood screw threads for engaging the recesses and metal female threads for engaging the rods which are of metal.

13. Staircase according to any one of the preqeding claims wherein there are double strings.

14. Staircase according to any one of Claims 2 to 12 wherein there are double strings and each support comprises two of the said rods extending between two opposite surface portions near the two front lower corners on the underside of the upper step and near the opposite rear upper corners on the tread surface of the lower step.

15. Staircase substantially as hereinbefore described with reference to Figures 1 to 3 or Figure 4 of the accompanying drawings.