Patient support means

Patient support means comprise a net for use with a net bed having rotary shafts on to which the ends of the net are wound, so that in use the patient is supported on the net which is slung between the shafts. The net is of knitted form and manufactured from a heat-settable thermoplastics material which is heat set to provide satisfactory memory such that it does not take a substantially permanent set under normal patient loading. The knitted material of the net has a lengthwise extensibility of between 17% and 35%, a widthwise extensibility of between 4% and 12% and a ratio of lengthwise to widthwise extensibilities of between 3 and 6.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to patient support means for use with beds of the 
type in which the patient is supported on a flexible web of mesh or net 
form. A bed of this type is hereinafter referred to generally as a "net 
bed", and the web thereof as "the net". 
2. Description of the Prior Art 
The net may be slung between two shafts on to which the ends of the net are 
respectively wound, and such net beds which are in general use are 
disclosed in U.S. Pat. No. 4,270,234 provide major advantages in the 
handling of patients. The net-supporting shafts of the bed can be turned 
in the same direction to transfer the net from one shaft to the other, 
whereby the patient on the net is turned and repositioned thereon, or the 
shafts can be turned in opposite directions to raise or lower the patient 
with respect to a conventional mattress or other support surface below the 
net. Net beds in general are also particularly valuable in the prevention 
and treatment of bed sores as the net conforms to the shape of the patient 
who is thus supported with a substantially uniform pressure thereby 
eliminating high pressure loading of specific areas of the body and the 
mesh provides excellent ventilation of the skin. 
It will be appreciated from the foregoing that the material and 
construction of the net, and the mesh size thereof, must be such as to 
allow the net to conform to the shape of the patient, thereby spreading 
the load and avoiding localized high pressure areas, and also to allow 
adequate ventilation. However, the mesh apertures are desirably small 
enough to avoid the fingers of a patient being trapped therein. 
The nets at present in use, designed to satisfy these requirements, suffer 
from a number of disadvantages. A first disadvantage is that conforming of 
the net to the body shape of a patient results in excessive shortening of 
the net between the shafts, when such are employed, with the result that 
the effective length of the net available to support the patient is 
considerably reduced. Another disadvantage is that the nets tend to creep 
along the supporting shafts which, although in general more-or-less 
parallel, are often slightly inclined so as to have a narrower spacing at 
the foot end to facilitate simultaneous turning at that end by the two 
hands of a nurse. This shaft inclination increases the creepage problem. A 
further disadvantage with net beds generally is that after use the nets 
tend to retain the sag produced when supporting the patient and thus they 
do not readily, if at all, return to the original unstretched condition. 
SUMMARY OF THE INVENTION 
The principle object of the invention is to provide a net with 
characteristics which materially overcome or substantially lessen the 
foregoing problems. In particular it has been found that not only are the 
lengthwise and widthwise extensibilities of the net important, but also 
the ratio of these two parameters. 
According to the invention patient support means comprise a net, in or for 
a net bed, with a lengthwise extensibility of between 17% and 35%, a 
widthwise extensibility of between 4% and 12% and a ratio of lengthwise to 
widthwise extensibilities of between 3 and 6, the net being manufactured 
from a heat-settable thermoplastics material which is heat set to provide 
satisfactory "memory" such that it does not take a substantially permanent 
set under normal patient loading. 
The extensibility of a material, as that term is used herein and in the 
appended claims, is to be that as measured under a 3 kg longitudinal 
loading of a piece of the material concerned measuring 7.62 cm (5 ins) in 
width and 20.32 cm (8 ins) in length. 
Preferably the lengthwise extensibility lies within the range of 22% to 
30%, the widthwise extensibility lies within the range of 5% to 10%, and 
said ratio thereof lies between 3 and 6. Desirably the ratio of lengthwise 
to widthwise extensibilities lies between 4 and 5. 
The thermoplastics material used and the net formation used should be such 
that the net is launderable by normal hospital procedures and will still 
retain characteristics within the specification set. Preferably it is a 
knitted polyester fabric manufactured from 167 D/tex flat mono-filament 
polyester yarn. The knitted mesh preferably has a hole size with a 
lengthwise dimension of between 8 mm and 11 mm and a widthwise dimension 
of between 7 mm and 9 mm, the terms "length" and "width" being used herein 
with reference to the fitted bed condition, i.e. in use the patient lying 
extending in the lengthwise direction of the net. Thus, the complete net 
will normally be of greater width than length, to allow for the portions 
wound on to supporting shafts. 
Other features of the invention will be apparent from the following 
description, drawings and claims, the scope of the invention not being 
limited to the drawings themselves as the drawings are only for the 
purpose of illustrating one way in which the principles of the invention 
can be applied. Other embodiments of the invention utilizing the same or 
equivalent principles may be used and structural changes may be made by 
those skilled in the art without departing from the present invention and 
the purview of the appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The net 1 illustrated is knitted from 100% polyester flat mono-filament 
yarn of 167 D/tex. The net has an overall width of 30.48 cm (10 ft 0 ins) 
and an overall length of 25.91 cm (8 ft 6 ins). It is intended to be used 
slung between two rotatable net-supporting shafts of a net bed, which 
apart from the present net is of known form and hence is not illustrated 
in the drawings. For example, it may be as disclosed in said U.S. Pat. No. 
4,270,234. 
At each end, which is in use wound on the corresponding shaft of the net 
bed, the net 1 has two knitted-in red marker threads 2 and 3 respectively 
positioned 10.16 cm (4 ins) and 38.10 cm (15 ins) from the corresponding 
selvedge 4 of the net, the cut edges of the net thus defning the length 
dimension. Each thread 2 with the corresponding selvedge 4 defines the 
zone of the net which is to be hooked on to attachment hooks on the shaft 
to which it is fitted, and the thread 3 provides a warning that the end of 
the net is approaching as it is unwound from the corresponding shaft of 
the net bed. A central green strip 5 of 15 mm width is knitted centrally 
into the net 1 to indicate the center for initial setting up between the 
shafts of a bed. 
The knitted material of the net 1 has a weight of 226 gm plus or minus 5% 
per square meter and a minimum burst strength of 2.46 Kgm per square cm 
(35 lbs per square inch). The extensibility characteristics, as that term 
is hereinbefore defined, are a lengthwise extensibility of between 22% and 
30% and a widthwise extensibility of between 5% and 10% with an average 
ratio thereof in the range of 4 and 5. 
Referring now to the detail view of FIG. 2, the mesh is knitted with 
parallel rows of holes such as 6 having a lengthwise dimension 1 of 8 mm 
to 11 mm and a widthwise dimension w of 7 mm to 9 mm. In the widthwise 
direction adjoining holes 6 are separated by lengthwise columns of 
inter-knitted multi-filament form with the filaments of the two columns 
defining a hole 6 being inter-knitted at cross-over points such as 7 to 
define the lengthwise ends of that hole. This results in the hole shape 
and construction illustrated in which the column filaments of each four 
adjoining holes 6 cross over to leave a small hole space 8 at the centre 
of each group of four adjoining holes 6. 
The described net construction conforms satisfactorily to the shape of a 
supported patient, thereby avoiding localised high pressure zones, while 
the net does not sag in such manner as to provide undue narrowing of the 
net between the shafts. Furthermore, the hole size provides adequate skin 
ventilation without allowing the fingers of a patient to be trapped. The 
net has a good memory, and thus does not take up a permanent set under 
normal patient load, such as is not removed by simple manual tightening of 
the net between the shafts prior to re-use. The net withstands laundering 
many times by normal washing procedures, at temperatures below that at 
which the net material was heat set during manufacture, while still 
remaining within the required specification, and the problem of creepage 
along the poles of the bed which is present with prior nets is largely 
overcome or materially reduced. The material also has a satisfactory fire 
retardancy factor.