[0001] The object of this invention is a dryer and a method for drying a product. The use
of this dryer and drying method is particularly advantageous for delicate garments
that have a tendency to become matted (wool for example). Inside the dryer the garments
to be dried are placed within a rotary drum. It is known that in order to minimise
the risk of garment matting, it is necessary to reduce the stress that the rotation
of the drum transfers to the garment to be dried. The rotating drum carries the garment
from the bottom to the top, where gravity forces it to drop back down again. Normally
the speeds at which the dryer drum rotates do not permit the centrifugal force to
hold the garment against the surface of the drum for the entire rotation (contrary
to what happens in a washing machine during the spinning phase).
[0002] A dryer preventing garment matting by using a moveable frame connected to the rotary
drum is known. The garment to be dried is physically held between the cylinder wall
of the drum and this frame so that it remains stable in this position. The frame comprises
a border that encloses an inlet to allow the transit of hot air from the centre of
the drum to the garment to be dried.
[0003] This dryer is not without its drawbacks.
[0004] In fact, due to the limited dimensions of the drum, the garment to be dried (a shirt
for example) folds back on itself before being positioned between the frame and the
cylinder wall of the drum. Consequently it is always the same portion of the garment
facing the centre of the drum, thereby increasing the drying time of the garment.
Furthermore, in dryers the hot air normally enters and leaves the drum via the two
opposite surface areas of the drum corresponding to the rotation axis of the drum
(2) itself.
[0005] As the garment to be dried is found along the cylindrical surface area of the drum
(therefore not along the trajectory used by the hot air), it will only be marginally
touched by the flow of hot air and as a result of this will take longer to dry.
[0006] In this context the technical basis of this invention is to propose a dryer and drying
method that overcome the drawbacks of the above-mentioned technique.
[0007] More specifically, the scope of this invention is to create a dryer that has the
capacity to improve the drying speed of delicate garments, particularly wool and other
fabrics that have a tendency to become matted.
[0008] A further aim for this invention is to improve energy efficiency when drying delicate
garments.
[0009] The technical basis indicated and the specific aims are substantially achieved by
a dryer and by a drying method designed in accordance with the technical features
expressed in one or more of the annexed claims.
[0010] Further features as well as further advantages of the present invention will become
apparent from the following description of an embodiment of a dryer and a drying method
thereof as shown in the annexed drawings, which are supplied by way of non-limiting
example, wherein:
- figure 1 shows a schematic view of a dryer according to this invention;
- figure 2 shows in detail a dryer component for this invention.
[0011] The object of this invention is a dryer for at least one product. Such dryers are
characteristically designed to dry textile garments, particularly delicate textile
garments that have the tendency to become matted (typically wool). In the annexed
drawings this dryer is identified with the reference number (1).
[0012] The dryer (1) comprises a rotary drum (2) that appropriately rotates on a primary
axis (22); advantageously the drum (2) presents substantial cylindrical symmetry,
in having as its axis of symmetry the said primary axis (22) of rotation of the drum
(2).
[0013] The dryer (1) also comprises a perforated shell (3) that may be placed inside the
drum (2) to create an inner compartment (30) suitable for holding said at least one
product to be dried. Advantageously it is free from any apparatus extending inside
the said inner compartment (30) and that acts as a support for said at least one product
to be dried. The support function for the said product to be dried is therefore exclusively
carried out by at least one wall (possibly with a reticular structure) of the shell
(3) that is used to define the outside of the said inner compartment (30).
[0014] The presence of one or more perforations (35) in the shell (3) is important in order
to permit air outside the shell (3) to enter the compartment (30) and dry said at
least one product. This previously heated external air facilitates the drying of at
least one product. The presence of at least one perforation (35) also facilitates
evacuation of moisture from the internal compartment (30).
[0015] The said perforated shell (3) comprises an outer rolling surface (31) that during
rotation of the drum (2) is free to roll along the first inner surface (32) of the
drum (2), thereby rotating the said perforated shell (3). During rotation of the drum
(2) the outer rolling surface (31), by rolling along the first inner surface (32)
of the drum (2), appropriately rotates the said perforated shell (3) on a secondary
axis of rotation (36) in a straight line with the shell (3) itself. This secondary
axis of rotation (36) essentially passes through the barycentre of the outer rolling
surface (31). The rolling can be with or without sliding (the latter is the ideal
situation that will be referenced later for further detailed considerations herein).
There is rolling between two bodies when the instantaneous axis of rotation of the
relative movement of the two bodies is in alignment with the area of contact.
[0016] In the case in question the two bodies are the shell (3) and the drum (2). Said secondary
axis of rotation (36) is different to the instantaneous axis of rotation of relative
motion indicated by reference number (5) in figure 1.
[0017] Said one or more perforations (35) pass through said outer rolling surface (31).
If there are more perforations (35) the outer rolling surface (31) has a reticular
structure with more cells, each perforation (35) being identified by a cell within
this reticular structure. The shell (3) is appropriately rigid to prevent said at
least one product to be dried being placed within the compartment (30), from being
squashed. When the shell (3) is positioned inside the drum (2) it uses gravity to
support itself against the first inner surface (32) of the drum (2).
[0018] The drum (2) is operated using a motorised means, for example an electric motor and
possibly a drive belt or cog mechanism.
[0019] The dryer (1) comprises a door that can be opened to permit the introduction and
extraction of the products to be dried inside the drum (2). The shell (3) may also
be inserted into and removed from the rotary drum (2). In particular, using this door
it is also possible to insert and remove the shell (3) into and from the drum (2).
Advantageously the shell (3) and the drum (2) are not coupled together and the shell
(3) is therefore considered to be an additional accessory to the dryer (1).
[0020] In addition to the first inner surface (32) the drum (2) also comprises a rear wall
(21) opposite the door. This rear wall (21) horizontally defines the primary axis
(22) of rotation of the drum (2). The first inner surface (32) of the drum (2) is
completely closed and expands around the primary axis of rotation (22) of the drum
(2) without intersecting it. Advantageously the first inner surface (32) of the drum
(2) follows a curved and rounded line of expansion to facilitate its movement relative
to the shell (3). This line of expansion is advantageously circular. The first inner
surface (32) expands in the area between the rear wall (21) and the door.
[0021] Under ideal operating conditions, during rotation of the drum (2), the perforated
shell (3) always remains in contact with the first inner surface (32) of the drum
(2).
[0022] Under ideal conditions, the secondary axis of rotation (36) always remains parallel
to the primary axis (22) of rotation of the drum (2).
[0023] Under ideal conditions, the perforated shell (3) rolls without sliding on the first
inner surface (32) of the drum (2).
[0024] Under ideal operating conditions, the position of the secondary axis of rotation
(36) tends to essentially remain fixed within the space, at least when the drum (2)
turns at a uniform speed.
[0025] Under ideal conditions without any sliding between the outer rolling surface (31)
of the shell (3) and the first inner surface (32) of the drum (2), the linear velocity
at one point of the outer rolling surface (31) is equal to the linear velocity of
the first inner surface (32) of the drum (2).
[0026] Advantageously the rolling surface (31) of the shell (3) has a radius r
2. Similarly the first inner surface (32) of the drum (2) has a radius r
1.
[0027] As the shell (3) can be placed inside the drum (2), the radius r
2 of the outer rolling surface (31) will be less than the radius r
1 of the first inner surface (32).
[0028] Under ideal conditions without any sliding between the outer rolling surface (31)
of the shell (3) and the first inner surface (32) of the drum (2) the modulus v of
the linear velocity at one point of the outer rolling surface (31) is equal to the
modulus v of the linear velocity of the first inner surface (32) of the drum (2).
From the equation v=ω
1r
1=ω
2r
2, it can be noted immediately that ω
2 is greater than ω
1, where ω
1 is the angular speed of rotation of the drum (2) on the primary axis (22) and ω
2 is the angular speed of rotation of the shell (3) on the secondary axis (36).
[0029] In relation to the shell (3), in order for the product to be dried when placed in
the compartment (30) to remain in its position it is necessary that the rotation speed
of the shell (3), not of the drum (2), is sufficient for the centrifugal force associated
with the rotation of the shell (3) to overcome the gravitational force acting on the
product placed in the compartment (30). This results in what is known in slang as
satellisation; the corresponding rotation speed of the shell (3) around the secondary
axis (36) is also known as satellisation speed. The Applicant has verified that the
satellisation speed of a textile garment directly and freely positioned, without the
shell (3), in a conventional dryer drum is equal to 70 rpm. The centrifugal force
acting on a garment depends on the mass m
1 of the garment, the distance of the rotation axis and the angular speed of the garment
in relation to the rotation axis.
[0030] Consequently in conditions of satellisation, it can be more or less assumed that
m
1r
170
2=m
1r
2ω
22. Combining this with the ideal condition of pure rolling motion ω
1r
1=ω
2r
2 results in the properties of the radius r
2 of the outer rolling surface (31).
[0031] This condition indicates that the appropriate radius r
2 for the outer rolling surface (31) is less than or equal to:
where:
ω1 is the rotation speed of the drum (2) expressed in rpm;
r1 is the radius of the first inner surface (32) of the drum (2) along which the shell
(3) is free to roll, expressed in the same unit of measurement as r2.
[0032] Normally ω
1 is between 45 and 65 rpm. The radius r
1 is usually between 200 and 300 millimetres.
[0033] The radius r
2 of the outer rolling surface (31) is greater than 50 millimetres, preferably greater
than 100 millimetres. This allows it to easily contain the shell (3) as well as a
product to be dried of a certain size. The radius r
2 of the outer rolling surface (31) is appropriately smaller than 150 millimetres (in
order not to excessively reduce the multiplication effect of the angular speed from
the drum (2) to the shell (3) and to allow the shell (3) to pass through the opening
door of the dryer (1)).
[0034] During actual operation, the dryer (1) may behave very differently to these ideal
conditions and may show particular evidence of transitory sliding between the rolling
surface (31) of the shell (3) and the first inner surface (32) of the drum (2). Therefore
the rolling of the shell (3) in the drum (2) could also be accompanied by some sliding.
In any event, even in the presence of sliding, it would still be possible to obtain
the benefits previously expressed in reference to the ideal circumstances (meaning
that the shell (3), having a smaller radius, would roll at a rotation speed greater
than that of the drum (2), possibly resulting in satellisation of the product to be
dried placed in the compartment (30)).
[0035] Generally when the shell (3) containing said at least one product to be dried is
placed inside the drum (2), no other products to be dried are introduced into the
said drum (2) and outside the shell (3); this in fact would hinder the motion of the
shell (3), rendering it ineffective. Furthermore, the said at least one product to
be dried placed inside the compartment (30) would benefit more from the air flow than
it would if held against the first inner surface (32) of the drum (2). As the shell
(3) rolls the product to be dried is in periodical proximity to the primary axis of
rotation (22) of the drum (2) (as previously indicated the hot air enters and leaves
via two opposite surfaces close to the primary axis of rotation (22) of the drum (2)
and therefore the said at least one product to be dried benefits more from the flow
of hot air entering the drum (2)).
[0036] The shell (3) conveniently may be opened to permit said at least one product to be
dried to be placed inside and removed from the compartment (30).
[0037] The shell (3) also conveniently comprises a first and a second portion (330, 340)
that together enclose the said inner compartment (30).
[0038] Advantageously the first and second portions (330, 340) correspond to a first and
second semi-shell (33, 34), which may be fitted together and taken apart as two halves
of the main shell (3).
[0039] The first and second portions (330, 340) can be screw-threaded onto and unscrewed
from each other. The threading allows the first and second portions (330, 340) to
be screwed and unscrewed.
[0040] This threading is made on both the first and second portions (330, 340) corresponding
to a joint (37) between them. As an alternative, another type of moveable connection
would be suitable for joining together the first and second portions (330, 340) corresponding
to a joint (37) between them. For example, elastic deformable catch-and-release mechanisms
could be used. The solution with the two portions (advantageously two semi-shells)
that can be screwed together and unscrewed is however preferable as it is less likely
that the two semi-shells will become inadvertently separated during the drying process.
The first and second portions (330, 340), advantageously the first and second semi-shells
(33, 34), when not in use can be placed one on top of the other, with the concave
sides facing towards the same plane of reference in order to reduce the amount of
space that they occupy.
[0041] The said shell (3), advantageously, is substantially spherical or ellipsoidal.
[0042] The said outer rolling surface (31), advantageously, is substantially spherical or
ellipsoidal (with perforations (35) in the outer rolling surface (31)).
[0043] It is important that the outer rolling surface (31) is rounded. This device (especially
if the outer rolling surface (31) is spherical) permits, regardless of the orientation
of the shell (3) in relation to the drum (2), rolling without the outer rolling surface
(31) becoming caught on the first inner surface (32).
[0044] Alternatively the shell (3) could be cylindrical but in this case the shell (3) could
only rotate around the axis of cylindrical symmetry.
[0045] Consequently if the secondary axis of rotation (36) and the primary axis of rotation
(22) of the drum (2) were not parallel, the operation would be adversely affected.
Amongst the possible causes of incorrect positioning of the primary and secondary
axes of rotation (22, 36) are incorrect initial positioning on the part of the user
or undesirable stress during the rotation of the drum (2), (it must be kept in mind
that in the event of satellisation the shell (3) acts as a body with eccentric mass
due to the presence of said at least one product to be dried; obviously this eccentricity
generates unwanted stresses that can result in sliding or displacement of the shell
(3) in relation to the drum (2)).
[0046] Advantageously at least one part of the rolling surface (31) of the shell (3) is
made from a material suitable for dampening the noise generated by the movement of
the shell (3) along the first inner surface (32) of the drum (2). For example, the
shell (3) can have inserts made of rubber or plastic or in a material that is slightly
deformable. It should be noted that it is usual for a large part of the shell (3)
to be made from plastic.
[0047] Advantageously the shell (3) could also have on the outer rolling surface (31) indentations
to interact (or more specifically, to mesh together with) corresponding indentations
along the first inner surface (32). This device would conveniently reduce sliding
of the shell (3) in relation to the first inner surface (32). The indentations in
the first inner surface (32) completely surround the primary axis of rotation (22)
of the drum (2). Similarly, on the shell (3) indentations on at least one plane of
the section completely encompass the said compartment (30).
[0048] An alternative solution is for the first inner surface (32) to be smooth (and therefore
lacking in any obvious irregularities). In this way there is less risk of the shell
(3) coming away from the drum (2) whilst the shell (3) is rolling along the drum (2).
[0049] Advantageously the dryer (1) comprises a housing chamber (4) for the drum (2). In
order to determine when a certain level of dryness has been attained, the dryer (1)
normally has a humidity sensor (41). This sensor (41) is indicated in figure 1 with
a dotted line to show that it has been taken out of this view so that the underlying
elements can be better seen. Advantageously this humidity sensor (41) is fixed to
the said chamber (4) and the drum (2) turns in relation to the humidity sensor (41).
Normally the humidity sensor (41) is located above the locus of points of the first
inner surface (32) that are found at the minimum distance from a fictitious horizontal
plane underlying the dryer (1). The humidity sensor (41) works on an electrical signal
and therefore it is important that it comes into electrical contact with the damp
clothes (thereby acting as electrical conductors) to be able to evaluate the level
of dampness of the clothes. If the first inner surface (32) has a cylindrical lateral
surface, this said locus of points coincides with the generatrix of the cylinder,
which is found at the minimum distance from the fictitious horizontal plane. In order
for the humidity sensor (41) to function correctly, it is necessary that the vertical
component of the distance between the humidity sensor (41) and the said locus of points
of the first inner surface (32) is less than or equal to the diameter of the outer
rolling surface (31) of the shell (3). To this regard it would also be necessary for
at least part of the shell (3) to be made from electrically conductive material. In
this way the shell (3) can function in cooperation with the humidity sensor (41).
At the moment that the humidity sensor (41) acts on an electrical signal, if at least
part of the shell (3) is made from electrically conductive material this would allow
it to connect the sensor (41) with the damp clothes, thereby acting as electrical
conductors. Advantageously the shell (3) includes an element made from electrically
conductive material that electrically connects the inside of the shell (3) to the
outside of the shell (3). This element made from electrically conductive material
runs through the thickness of the shell (3). This element made from electrically conductive
material is conveniently surrounded by (preferably enclosed in) portions of the shell
(3) that are made from electrically insulating material. This element in electrically
conductive material is designed to come into contact with the sensor (41).
[0050] The object of this invention is also a method of drying at least one product using
a dryer. This method concerns the drying of at least one delicate fabric garment (wool
for example) The method comprises the following stages:
- inserting said at least one product to be dried inside a perforated shell (3) with
an outer rolling surface (31);
- placing the said perforated shell (3) inside the drum (2);
- rotating the drum (2), first inner surface (32) of the drum (2) transferring the movement
to the rolling surface (31) of the perforated shell (3), the rolling of the shell
(3) on the first inner surface (32) of the drum (2) permitting the rotation of the
perforated shell (3) at a rotation speed greater than that of the drum (2). This permits
satellisation of the product to be dried placed in the shell (3).
[0051] During the rotation stage of the drum (2), the shell (3) is rotated by the drum (2)
at a rotation speed greater than or equal to the satellisation speed of said at least
one product to be dried placed in the shell (3). During rotation of the drum (2),
at least at its fullest potential, the product to be dried remains stable in relation
to the shell (3), therefore allowing the product to be dried without being subjected
to stresses and movements that may damage it (for this reason the method is particularly
beneficial for delicate fabric garments).
[0052] The stage of placing the said perforated shell (3) inside the drum (2) takes place
when inside the drum (2) there are no further objects (typically fabric garments)
to be dried. The stage of rotating the drum (2) takes place when there are no further
objects (typically fabric garments) to be dried placed in the drum (2) outside the
shell (3).
[0053] Advantageously the rotation speed of the drum (2) around the primary axis (22) of
rotation of the drum (2) is between 50 and 60 rpm.
[0054] Appropriately, the rotation speed of the shell (3) around the secondary axis (36)
of rotation of the shell (3) is between 75 and 100 rpm.
[0055] As previously indicated under ideal operating conditions during the rotation of the
drum (2) the perforated shell (3), particularly the outer rolling surface (31), remains
substantially in contact with the first inner surface (32) of the drum (2).
[0056] Still under ideal operating conditions, during rotation of the drum (2) the perforated
shell (3) rolls substantially without sliding on the first inner surface (32) of the
drum (2).
[0057] This method is advantageously implemented by a dryer (1) comprising one or more of
the previously described technical features.
[0058] The stage of introducing said at least one product to be dried inside the perforated
shell (3) requires opening up the said shell (3). The stage of opening up the shell
(3) is also necessary at the end of the drying process in order to remove the said
at least one product to be extracted from the shell (3). In order to advantageously
open up the said shell (3) at least two sides of a first and a second portion (330,
340) of the shell (3) - conveniently a first and a second semi-shell (33, 34) - can
be detached. The first and second portions (330, 340), like the first and second semi-shells
(33, 34), as per the other technical features detailed in reference to the method,
can be of the type described beforehand in reference to the structural and functional
features of the dryer (1). The stage of opening up the first and second semi-shells
(33, 34) can be carried out by unscrewing the first and second semi-shells (33, 34),
one from the other.
[0059] Advantageously during the rotation of the drum (2) an electrically conductive element
of the shell (3) comes into contact (periodically at least) with a humidity sensor
(41) integrated into the dryer (1). This electrically conductive element electrically
connects the inside of the shell (3) with the outside of the shell (3) (as explained
in more detail previously). In particular, this electrically conductive element puts
into contact the product to be dried inside the shell (3) and the humidity sensor
(41) to provide the dryer with a predetermined signal, upon which the drying cycle
is interrupted. Typically this signal is linked to detection by the humidity signal
(41) of an electrical current below the determined threshold.
[0060] The invention has significant benefits. First and foremost it allows the products
to be dried to attain satellisation speed, even in dryers where the drum rotation
speed would be insufficient to achieve this effect. This, as previously described,
makes this dryer particularly beneficial for use with delicate garments.
[0061] Furthermore, the invention permits optimisation of the drying times required for
fabric garments.
[0062] The idea for the invention is subject to numerous modifications and variations, all
within the scope of the inventive concept by which it is defined. Furthermore, all
the details may be substituted by other technically equivalent elements. In practice,
all the materials used, as well as the dimensions, may vary according to the requirements.
1. A dryer of at least one product comprising:
- a rotary drum (2);
- a perforated shell (3) which may be fitted inside the drum (2) and defining an inner
compartment (30) suitable for holding at least one product to be dried;
characterised in that the perforated shell (3) comprises an outer rolling surface (31) which during the
rotation of the drum (2) is free to roll spontaneously along a first inner surface
(32) of the drum (2) thereby rotating the perforated shell (3).
2. The dryer according to claim 1, characterised in that during the rotation of the drum (2) the perforated shell (3) remains substantially
always in contact with the first inner surface(32) of the drum (2).
3. The dryer according to claim 1 or 2, characterised in that during rotation of the drum (2), the perforated shell (3) rolls substantially without
sliding on the first inner surface (32) of the drum (2).
4. The dryer according to any of the foregoing claims,
characterised in that the rolling surface (31) has a radius r
2 greater than or equal to 100 millimetres and/or less than or equal to:
where:
ω1 is the angular speed of rotation of the drum (2) expressed in rpm;
r1 is the radius of the first inner surface (32) of the drum (2) along which the shell
(3) is free to roll, expressed in the same unit of measurement as r2.
5. The dryer according to any of the foregoing claims, characterised in that the shell (3) may be opened to permit the introduction and extraction of at least
one product to be dried.
6. The dryer according to any of the foregoing claims, characterised in that the shell (3) comprises, or coincides with, a first and a second portion (330, 340)
which in combination encompass the inner compartment (30) and which may be screwed
on and screwed off to and from one another.
7. The dryer according to any of the foregoing claims, characterised in that the shell (3) is substantially spherical.
8. The dryer according to any of the foregoing claims, characterised in that at least a part of the rolling surface (31) of the shell is made from a material
suitable for dampening the noise generated by the movement of the shell (3) along
the first inner surface (32) of the drum (2).
9. The dryer according to any of the foregoing claims, characterised in that the shell (3) comprises an element made from electrically conductive material which
electrically connects the inside of the shell (3) with the outside of the shell (3).
10. The dryer according to any of the foregoing claims, characterised in that it is free from any apparatus extending inside the inner compartment (30) and that
it acts as a support for at least one product to be dried.
11. A method for drying at least one product using a dryer, the method comprising the
steps of:
- introducing at least one product to be dried inside a perforated shell (3) comprising
an outer rolling surface (31);
- placing the perforated shell (3) inside the drum (2);
- rotating the drum (2), a first inner surface (32) of the drum (2) transferring the
movement to the rolling surface (31) of the perforated shell (3), the rolling of the
shell (3) on the first inner surface (32) of the drum (2) permitting the rotation
of the perforated shell (3) at a speed of rotation greater than that of the drum (2).