Reed valves for internal combustion engines

A reed valve for an internal combustion engine comprises an aperture closable by a resilient valve member composed of an epoxide resin laminate. The laminate preferably includes cotton.

This invention relates to reed valves for internal combustion engines, 
particularly but not exclusively for the air intakes two-stroke engines. 
A conventional reed valve comprises an aperture closed by a resilient 
flexible member composed of steel or of fibreglass. Suction upon the valve 
by the engine causes the member to deflect, opening the aperture and 
admitting air to the engine. Opening and closing of the valve occurs at a 
rate equal to the rate of revolution of the engine and creates 
considerable strain on the flexible member. Fragmentation of the member is 
regularly encountered. 
Reed valves having steel flexible members are disadvantageous in that entry 
into the engine of fragments of the member causes considerable damage. 
Fibreglass valve members are more prone to fragmentation than steel members 
although fibreglass fragments are not so damaging to the engine. 
According to the present invention there is provided an internal combustion 
engine reed valve comprising an aperture closable by a resilient valve 
member composed of an epoxide resin. 
The valve member is preferably in the form of a laminate composed of 
epoxide resin and a textile material. 
Preferred textile materials include natural fibres such as cotton or linen 
or artificial fibres such as polyethylene terephthalate, for example the 
fibre sold by ICI under the trade mark Terylene. Laminates comprising 
paper, asbestos or other fabric may also be used. Use of cotton is 
especially preferred. 
Epoxide resin valve members have a greater range of resonant frequencies 
than fibreglass members. It is important that the valve member is arranged 
to resonate at the frequencies of actuation of the valve, that is within 
the range of r.p.m at which the engine is used. 
Epoxide resin textile laminates have a lower density and greater resilience 
than fibreglass. Resistance to impact fatigue is also greater. The force 
with which the valve member impinges upon the valve seat is therefore less 
resulting in reduced fatigue of the member. Epoxide resin also has a 
superior modulus of elasticity to fibrelgass. The lower density permits 
use of thicker laminates having a wider range of mechanical properties 
e.g. resonant frequencies. A particularly preferred laminate has a Youngs 
modulus of 8.00 GNm.sup.-2, a density of 1360 kgm .sup.-3 and a tensile 
strength of 1.26.times.10.sup.7 kgm.sup.-2. 
Furthermore epoxide resin does not exhibit the tendency to disintegration 
once damage has occurred that is characteristic of fibreglass valve 
members. 
The reed valve may be spaced from the engine to reduce thermal damage to 
the epoxide. 
A particularly preferred epoxide is TUFNOL 6F/45, manufactured by Tufnol 
Limited. 
According to a preferred aspect of the present invention an internal 
combustion engine reed valve comprises a plurality of resilient valve 
members abutting in use to close the valve. 
Preferably the edges of said valve members abut to close the valve. 
The aperture of the valve is defined by the opposing surfaces of the 
resilient valve members. 
Conventional reed valves comprise a valve body having one or more 
apertures, each of which is closable by a respective resilient valve 
member. The aperture is defined by a surface of the valve member and a 
surface of the valve body. Passage of air or of a mixture of air and fuel 
through the aperture is impeded by the immovable valve body, causing 
turbulence and reducing the kinetic energy of the flow of fluid. 
Use of valves in accordance with the present invention is advantageous in 
that two surfaces of the resilient valve members which may represent the 
major proportion of the aperture, can move by flexing to allow passage of 
fluid. The turbulenece caused by a fixed obstacle is avoided. The kinetic 
energy of the fluid flow is not expended against an immovable surface. Use 
of two or more abutting resilient valve members increases the sensitivity 
of the valve to fluctuations in fluid pressure. 
The resilient valve members are preferably disposed symmetrically about the 
direction of flow of fluid through the valve. 
A valve comprising two resilient valve members may be arranged with the 
said members disposed in a prismatic configuration. The angle between the 
said members is preferably less than 90.degree., more preferably between 
35.degree. and 65.degree.. An angle of approximately 45.degree. has been 
found to be particularly appropriate. 
A valve comprising three or more resilient valve members may be arranged 
with the latter disposed in a pyramidal configuration. 
A valve may comprise a plurality of pairs of prismatically arranged 
resilient valve members. The plurality of pairs may be disposed 
side-by-side in an overall prismatic arrangement. 
Immovable side pieces are preferably provided between the resilient valve 
members. A prismatic arrangement comprising two resilient members may 
incorporate two triangular side pieces. A prismatic arrangement comprising 
a plurality of pairs of resilient members may incorporate triangular end 
pieces. Struts may be provided between adjacent resilient members to abut 
and support the side surfaces of the latter when the valve is closed. 
The side pieces and struts may be provided with flexible valve seats 
composed, for example, of rubber or other durable material.

The valve shown in the Figures is adapted for use with a two stroke engine, 
for example for an outboard motor for a boat. 
The valve body 1 contains a generally rectangular inlet 2 and supports two 
pairs of resilient valve members or reeds 3,4,5,6. The resilient members 
comprise sheets of a laminate material comprising epoxide resin and cotton 
manufactured under the Trade Mark Tufnol 6F/45. The resilient members are 
secured remote from the aperture of the valve by means of screws 7 to side 
pieces 8, 9 and struts 10. The edges of the resilient members 11 abut when 
the members are not under tension. The resilient members are arranged at 
an angle of 45.degree. although angles between 35.degree. and 65.degree. 
may be used. The resilient members cooperate with the side pieces 8,9 and 
struts 10 to seal the aperture 2. Curved plates 12 prevent excessive 
flexing of the resilient members. The curved plates 12, which may be 
replaced in alternative embodiments by the valve housings, serve to allow 
progressive curvature of the resilient members rather than hinging of the 
latter about the fixing screws. Pressure of fluid (air or a mixture of 
fuel and air) within the aperture 2, caused for example by a vacuum 
induced on the upper exterior part of the valve as shown in the Figures, 
causes the resilient members to flex towards the plates 12, allowing the 
passage of air. Release of the pressure allows the resilience of the 
members to close the valve. The characteristics of the valve may be chosen 
by selection of resilient members having an appropriate resilience and 
thickness. The resonant frequency of the valve may be chosen to match the 
rate of revolution of an engine by selection of reeds with appropriate 
dimensions. 
Use of a plurality of resilient valve members reduces the degree of flexing 
required of each member, with a consequent reduction in the stress upon 
the members. 
The following results illustrate the advantages derived from use of the 
present invention. The usual needs of a series of proprietary internal 
combustion engines whether steel, fibreglass or otherwise, were replaced 
with reeds composed of the epoxide-cotton laminate TUFNOL 6F45. 
In each case the performance of the engine was improved. The brake mean 
effective pressure, torque, brake horsepower and acceleration response 
were enhanced in each case. The effective power bands was also increased 
in each case. The high impact fatigue resistance of the laminate allowed 
larger reed members to be used, allowing a consequent reduction in the 
number of supporting struts (10 in FIG. 2) thereby increasing the area of 
the valve. 
Replacement of the 0.028 cm thick Boyesen-type steel reeds of an Outboard 
Marine Company, 3.5 h, U8 engine by 0.078 cm laminate reeds in accordance 
with the invention increased the effective power band from 6500-8500 rpm 
to 5500-9500 rpm. This engine normally incorporates a pair of arrays of 
seven reeds per cylinder. Use of the epoxide laminate enables a pair of 
arrays of three reeds to be used on each cylinder. 
Replacement of the 0.086 cm thick fibreglass reeds of a K.T.M., 500 
cm.sup.3, single cylinder motorcross motorcycle engine by 0.076 cm 
laminate reeds increased the effective power band from 3000-7000 rpm to 
2500-7500 rpm. Similar results were observed with the corresponding 125 
cm.sup.3 and 250 cm.sup.3 engines. 
The effective power band of a Cagiva, 1 cylinder, 125 cm.sup.3 engine was 
increased from 6000-11500 rpm with 0.046 cm fibreglass reeds to 5500-12000 
rpm with reeds in accordance with this engine. 
The effective power band of a Suzuki 250 cm.sup.3, single cylinder 
motorcross motorcycle engine was increased from 5000-8500 rpm with 
standard Suzuki reeds to 4000-9250 rpm using 0.073 cm epoxide laminate 
reeds. Similar results were observed with 80 cm.sup.3, 125 cm.sup.3, 250 
cm.sup.3 and 465 cm.sup.3 single cylinder Suzuki engines. 
The effective power band of a 250 cm.sup.3, single cylinder Honda 
motorcross motorcycle engine was increased from 5000-7500 rpm using 
standard steel reeds to 4250-9500 rpm with reeds in accordance with this 
invention. Similar results were observed with other Honda motorcross 
engines. 
The effective power band of a Yamaha 350 L/C YPVS, two cylinder motorcycle 
engine was increased from 7000-9500 with standard steel reeds to 
6000-10000 with 0.061 cm laminate reeds. 
The effective power band of a Yamaha 250 L/C YPVS, 2 cylinder motorcycle 
engine was similarly increased from 7000-9500 rmp to 6000-10000 rpm using 
0.063 cm laminate reeds. 
The effective power band of a 125 cm.sup.3 Kawasaki motorcross motorcycle 
engine increased from 8500-10500 rmp using standard Kawasaki fibreglass 
reeds to 8000-11500 rpm using 0.061 cm laminate reeds. 
Similar results were observed with 250 cm.sup.3 and 500 cm.sup.3 Kawasaki 
motorcross engines. 
Use of the reed valve illustrated in the drawings improves the performance 
of an engine. For example a 247 cm.sup.3 test engine was found to produce 
54 BHP at 9500 rpm using a conventional valve fitted with Tufnol 6F/45 
reed members. Replacement by a valve in accordance with the Figures fitted 
with Tufnol 6F/45 reed members produced 61.3 BHP at 9500 rpm.