GB2253874A

GB2253874A - Spring assembly for a sash window

Info

Publication number: GB2253874A
Application number: GB9200835A
Authority: GB
Inventors: Terence Hardy
Original assignee: LB Plastics Ltd
Current assignee: LB Plastics Ltd
Priority date: 1991-02-07
Filing date: 1992-01-15
Publication date: 1992-09-23
Anticipated expiration: 2012-01-15
Also published as: GB2286418B; GB9200835D0; GB9506135D0; GB2253874B; GB2286418A

Abstract

A spring assembly comprises a casing, a spring member formed from coiled strip material freely rotatably mounted within the casing, one end of the spring member projecting from the casing for attachment to a load in use, and the casing incorporating a support member to support the spring member by engaging its outer surface to transfer load from the spring member to the casing. The assembly is preferably used with a sliding sash window in which case portions of the casing are adapted for engagement with locating formations on an outer frame member in which the sash frame is slidably mounted so that the weight of the sash frame is at least partly transmitted through the spring and casing directly to the outer frame.

Description

Balance Mechanisms for Sliding Sash Windows This invention relates to spring assemblies suitable for use in balance mechanisms sliding sash windows.

Modern sliding sash window constructions incorporate spring mechanisms located within channels in the outer frame and connected to the sash frame to support the weight of the sash frame during opening and closing movement. The spring mechanisms are generally of complex construction incorporating an elongated rod member having spiral formations on its surface and surrounded by a coil spring which is both stretched or compressed and rotated as the sash frame is opened and closed. The arrangement is designed to produce essentially constant spring force at all positions of the sash frame between its fully open and fully closed positions. Spring mechanisms of this kind suffer from the disadvantage that they are complex and hence expensive constructions.

It has previously been proposed to utilize so-called constant force springs to support the sash frames of windows. Such springs generally comprise coiled spring steel strips which are free at both ends and are rotatably supported on a central support member.

The arrangement is such that the force required to uncoil the spring is the same at all positions between the fully coiled and fully uncoiled conditions. However such springs are generally suitable for supporting relatively light sash frames only and suffer from a number of other disadvantages.

According to one aspect of the invention there is provided a spring assembly comprising a casing, a spring member formed from coiled strip material freely rotatably mounted within said casing, one end of said spring member projecting from the casing for attachment to a load in use, and the casing incorporating a support member adapted to support said spring member by engagement with the outer surface thereof whereby to transfer load from said spring member to said casing.

Preferably said support member comprises an arcuate formation adapted to embrace the curved underside of the spring member. Preferably also said support member engages said spring member over an angle of between 600 and 950.

Advantageously said casing comprises separable parts movable into engagement with one another in a direction axially of said spring and incorporating complementary formations adapted to ensure correct location of said support member relative to said spring when the casing is assembled.

According to a further aspect of the invention there is provided a spring support assembly for a sliding sash window comprising a constant force spring housed within a casing from which one end of the spring projects for connection to a sash frame, portions of the casing being adapted for engagement with locating formations on an outer frame member in which the sash frame is slidably mounted whereby the weight of the sash frame is at least partly transmitted through said spring and casing directly to said outer frame member.

The invention also provides a frame assembly for a sliding sash window, comprising a frame member incorporating at least one channel adapted to face inwardly towards the sash frame when the window is assembled, and a constant force spring housed in a casing mounted in said channel and at least partly supported by direct engagement with portions of said frame member, one end of said spring extending out of said casing for connection to said sash frame, the arrangement being such that in use the weight of the sash frame is at least partly transmitted through said spring to said casing and hence directly to the frame member itself.

Preferably the mouth of said channel is restricted by lips projecting inwardly thereof to form a narrow entrance, portions of said lips being cut-away to form an opening wider than said entrance and adapted to receive and at least partially support said casing, whereby load is transmitted through the casing to said lips and hence directly to the frame member itself.

Advantageously said casing is dimensioned to form a tight fit in said channel and is provided with means enabling it to be secured to the frame member by a screw or like fastening means providing additional support.

Advantageously the inner edges of said lips are provided with inwardly directed projections in the form of flanges serving to increase the area of contact between the frame member and the portions of said casing supported thereon.

Advantageously said casing is provided with upper and lower projections adapted to locate in the entrance to said channel whereby to align the casing in the correct position relative to said frame member.

Advantageously said projections are provided with flat faces adapted to extend at right angles to the length of said channel when said casing is in position in said channel, said faces being adapted for abutment with corresponding faces of adjacent casings mounted in the same channel. This facilitates assembly of multiple spring assemblies in the one channel by enabling screw holes for use in fastening the assemblies in position to be spaced apart by a predetermined fixed distance.

The invention also provides a sliding sash window incorporating one or more assemblies according to the preceding paragraphs.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a fragmentary perspective view of a side frame member of a window incorporating spring assemblies according to the invention; Fig. 2 is an enlarged cross-section through the frame member on the line II-II in Fig. 1; Fig. 3 is a perspective view of one portion of the casing of the spring assembly shown in Fig. 2; Fig. 4 is an end elevation of the casing portion shown in Fig. 3; Fig. 5 is a cross-section through the portion of the casing shown in Figs. 3 and 4 on the line V-V in Fig. 4; Fig. 6 is an end elevation of the other portion of the easing; Fig. 7 is a cross-section through the casing portion of Fig. 6 on the line VII-VII in Fig. 6; and Fig. 8 is an enlarged view similar to Fig. 6 showing the spring in position.For reasons of clarity the spring is omitted from Figs. 2 to 7.

Referring to the drawings, Fig. 1 shows a side frame member 10 of an outer window frame consisting of identical top, bottom and side frame members interconnected at their corners. A pair of sash frame members (not shown) are adapted to be mounted in the outer frame formed from the members 10 for sliding movement relative thereto and to one another between open and closed positions, the sash frame members being supported on spring assemblies to be described hereafter.

The frame member 10 is of extruded plastics construction and incorporates a pair of side-by-side parallel channels 15A and 15B. Lips 16 project across the mouth of each channel to define a narrow entrance 17 to the channel. Inturned projections or flanges 18 are provided on each of the lips 16 and act to rigidify the structure and to provide additional load supporting surface for the spring assemblies as will be described hereafter.

Mounted within each channel 15A,15B is a sliding shoe member 20 incorporating a rotating support block 21 adapted for engagement by a pivot bar (not shown) connected to the associated sash frame. Each sash frame is supported in an upright position adjacent and parallel to the frame 10, one frame abutting against an elongated projection 22 at one edge of the frame 10 and the other being held in position by a detachable retaining member (not shown) fitted to the edge of the frame 10 opposite to the projection 22. In this way the sash frames are retained in position within the outer frame 10 for sliding movement in directions parallel to the channels 15A and 158.

A pair of spring assemblies 25 are mounted at an upper location within each of the channels 15A and 15B.

A strip steel spring member 26 extends out of each spring assembly 25 and is engaged in a slot 27 in the upper edge of the associated slide block 20. The spring assemblies support the weight of the sash frame during opening and closing sliding movement relative to the outer frame 10.

Referring now to Figs. 2 to 7 of the drawings, each of the spring assemblies 25 comprises a casing 30 formed from inner and outer complimentary parts 31 and 32. The assembled casing is of generally cylindrical form and has an outer diameter slightly less than the width of the channels 15A and 15B. The casing is fitted in position by removing portions of the projecting lips 16 to form generally circular openings at the entrances to each of the channels 15A,15B, thereby enabling the casing 30 to be inserted. A central hollow boss 33 extends through the casing and enables it to be secured to the frame member 10 by a screw 34. The width of the casing is such that when inserted in the channel 15A,15B the outer face of the casing is generally flush with the inwardly directed face of the frame member 10 whereby the casing does not interfere with sliding movement of the sash frame.

If the casing were supported on the frame member 10 solely by means of the screw 34, the whole of the load carried by the spring 26 would be transmitted to the frame member through the central boss 33 and screw 34. In order to avoid this the portion 31 of the casing is adapted to seat within and be supported by the edges of the associated opening in the frame member 10 as best seen in Fig. 2 of the drawings. The rigid nature of the lips 1 and inwardly directed flanges 18 is capable of supporting a substantial load and the weight of the sash frame is therefore primarily transmitted to the outer frame 10 through direct engagement between the casing 30 and the outer frame, the screw 34 primarily serving a locating rather than a load-supporting function.

Strengthening ribs 35 formed internally of the component 31 of the casing serve to rigidify it and increase its load-supporting capability.

The spring member 26 mounted within the casing 30 comprises a coil of spring steel strip encircling but not supported on the central boss 33. The spring is freely rotatable within the casing and is supported on an arcuate support member 40 forming part of the portion 32 of the casing 30. The support member 40 is displaced radially outwardly from the central boss 33 and is arranged to abut against and support the outer surface of the spring member over an arc which in the case of the embodiment is around 900 but which may vary from a few degrees to around 1000. Preferably the extent of the arc is between about 600 and 950. The load carried by the spring is thus transmitted directly to the casing 30 through the support member 40.

In previously proposed constant force springs the load is transmitted through a central boss similar to the boss 33 on which the spring is supported. Since the free inner end of the spring rotates around this boss, the innermost coil of the spring in effect drops off the free end of the spring each time the spring rotates around the boss. This produces a clicking action during both opening and closing movement of windows supported on constant force springs constructed in this way. By virtue of the provision of the support member 40, the load carried by the spring is transmitted through the lower portions of the coils to the support 40 instead of through the upper portions of the coils to the boss 33.

This eliminates the clicking noises experienced with constant force springs of conventional construction.

In order to support the weight of sash frames of substantial size, more than one spring assembly 25 may be required at each side of the outer frame. In the embodiment of Fig. 1 two spring mechanisms 25 are shown associated with each of the sliding sash frames, the spring members 26 from each mechanism being connected to separate slots 27 in the upper portions of the associated slide blocks 20 (only one spring is shown in Fig. 1 for clarity). Where more than one spring assembly is provided it is important that it should be correctly located and positioned relative to the other or others. It is also important that the or each spring assembly should be properly orientated relative to the associated channel 15A or 15B.

In order to facilitate location, the component 31 of the casing 30 is provided with oppositely directed projections 45 the width of which corresponds to the width of the entrance 17 of the channels 15A,15B. When the casing 30 is fitted in position, the projections 45 locate between the lips 16 and thereby ensure correct fitting of the spring assemblies. The outer ends of the projections 45 are flat and arranged to extend at right angles to the channels. Thus where two or more spring assemblies are fitted, the flat portions of the projections 45 abut one another and ensure that the spring assemblies are spaced apart by a uniform distance. This facilitates the drilling of holes for the screws 34 by maintaining a constant distance between adajcent spring assemblies fitted to the same channel of the frame 10.

To ensure correct functioning of the spring assembly the support member 40 must be located in the correct angular position below the boss 33. For this purpose a recess 46 is formed in the portion 31 of the casing in alignment with one of the projections 45. The recess 46 is equal in angular extent to the arcuate length of the support member 40 such that the two portions of the casing will only interfit if the support member 40 is engaged with the recess 46 and hence aligned with the associated projection 45. In this way provided the casing is fitted with the projecting end of the spring 26 directed downwardly towards the slide block 20, the support member 40 will necessarily be disposed below the boss 33 and in the correct angular position relative to the channel 15A or 15B.

The arrangements described are much simpler in construction and less expensive than conventional balance springs. They also improve upon previous systems incorporating constant force springs by rigidifying and improving the load carrying capacity of the spring assemblies.

Various modifications made be made without departing from the invention. For example spring casings of alternative shape may be employed provided they engage with portions of the frame member to transmit load directly between them. The frame members may be of different construction and alternative means of connecting the springs to the sliding sash frames may be employed. Constant force spring assemblies of the kind described may also be used in situations other than sliding sash windows.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. A spring assembly comprising a casing, a spring member formed from coiled strip material freely rotatably mounted within said casing, one end of said spring member projecting from the casing for attachment to a load in use, and the casing incorporating a support member adapted to support said spring member by engagement with the outer surface thereof whereby to transfer load from said spring member to said casing.

2. An assembly according to claim 1 wherein said support member comprises an arcuate formation adapted to embrace the curved underside of the spring member.

3. An assembly according to claim 2 wherein said support member engages said spring member over an angle of between 600 and 950.

4. An assembly according to claim 1, 2 or 3 wherein said casing comprises separable parts movable into engagement with one another in a direction axially of said spring and incorporating complementary formations adapted to ensure correct location of said support member relative to said spring when the casing is assembled.

5. A spring assembly substantially as hereinbefore described with reference to Figs. 3 to 8 of the accompanying drawings.

6. An assembly according to any of claims 1 to 5 for use with a sliding sash window wherein portions of said casing are adapted for engagement with locating formations on an outer frame member in which a sash frame is slidably mounted, whereby the weight of the sash frame is at least partly transmitted through said spring and said casing directly to said outer frame.

7. A spring support assembly for a sliding sash window comprising a constant force spring housed within a casing from which one end of the spring projects for connection to a sash frame, portions of the casing being adapted for engagement with locating formations on an outer frame member in which a sash frame is slidably mounted whereby the weight of the sash frame is at least partly transmitted through said spring and casing directly to said outer frame member.

8. An assembly according to claim 6 or 7 wherein said frame member incorporates at least one channel adapted to face inwardly towards the sash frame when the window is assembled, said casing being mounted in said channel and at least partly supported by engagement with portions of said frame member.

9. A frame assembly for a sliding sash window, comprising a frame member incorporating at least one channel adapted to face inwardly towards the sash frame when the window is assembled, and a constant force spring housed in a casing mounted in said channel and at least partly supported by direct engagement with portions of said frame member, one end of said spring extending out of said casing for connection to said sash frame, the arrangement being such that in use the weight of the sash frame is at least partly transmitted through said spring to said casing and hence directly to the frame member itself.

10. An assembly according to claim 8 or 9 wherein the mouth of said channel is restricted by lips projecting inwardly thereof to form a narrow entrance, portions of said lips being cut-away to form an opening wider than said entrance and adapted to receive and at least partially support said casing, whereby load is transmitted through the casing to said lips and hence directly to the frame member itself.

11. An assembly according to claim 10 wherein the inner edges of said lips are provided with inwardly directed projections serving to increase the area of contact between the frame member and the portions of said casing supported thereon.

12. An assembly according to any of claims 8 to 11 wherein said casing is dimensioned to form a tight fit in said channel and is provided with mounting means enabling it to be secured to the frame member.

13. An assembly according to claim 12 wherein said mounting means comprises a central boss within said casing and around which said spring is located, said boss being adapted for connection to said frame member by screw or like fastening means.

14. An assembly according to any of claims 8 to 13 wherein said casing is provided with upper and lower projections adapted to locate in the entrance to said channel whereby to align the casing in the correct position relative to said frame member.

15. An assembly according to claim 14 wherein said projections are provided with flat faces adapted to extend at right angles to the length of said channel when said casing is in position in said channel, said faces being adapted for abutment with corresponding faces of adjacent casings mounted in the same channel.

16. A frame assembly for a sliding sash window substantially as hereinbefore described with reference to the accompanying drawings.

17. A sliding sash window assembly incorporating one or more assemblies according to any preceding claim.