[0001] The present application claims the benefit of the priority of Korean Patent Application No. 10-2019-0068935, filed on June 11, 2019, which is hereby incorporated by reference in its entirety.
10 TECHNICAL FIELD
[0002] The present invention relates to a CID filter and a secondary battery comprising the CID filter, and more particularly, to a CID filter having improved safety under an abnormal high-temperature condition and a secondary battery
15 comprising the CID filter.
BACKGROUND ART
[0003] Secondary batteries that are repetitively chargeable and dischargeable may be divided into cylindrical type secondary batteries, prismatic type secondary batteries, and
20 pouch type secondary batteries according to their structures
and manufacturing methods. In general, among them, the cylindrical type secondary battery has a structure in which an electrode assembly is accommodated in a cylindrical can with an upper portion opened, and a top cap is coupled to the
25 upper portion of the cylindrical can.
[0004] In order to prevent explosion or fire that may occur when a temperature or pressure inside the cylindrical type secondary battery exceeds a certain value, generally, the cylindrical type secondary battery is provided with safety
30 devices such as a safety vent and a CID filter. According to
2

the related art, when the pressure inside the cylindrical
type secondary battery exceeds a certain value, current is
cut off by breaking the safety vent, and a gas inside the
secondary battery is discharged to the outside.
5 [0005] One of the reasons for the abnormal increase in
temperature or pressure inside the cylindrical type secondary battery is a short circuit phenomenon. When the short circuit occurs, heat is generated inside the cylindrical type secondary battery.
10 [0006] Particularly, a lot of heat is generated in a region
in which an electrode tab protruding from an electrode assembly and the CID filter are bonded to each other. According to the related art, the heat generated in the region in which the electrode tab and the CID filter are
15 bonded to each other passes through the CID filter and then
is transferred to a CID gasket disposed around the CID filter, and thus, a temperature of the CID gasket increases to cause a problem in which the CID gasket is melted. In this case, even if the safety vent is broken, since the safety vent and
20 the CID filter are reconnected to each other in the
circumferential area of the CID filter to prevent the current of the cylindrical type secondary battery from being cut off,
the cylindrical type secondary battery is impeded in safety.
DISCLOSURE OF THE INVENTION
25 TECHNICAL PROBLEM
[0007] Therefore, the problem to be solved by the present invention is to solve a problem of melting a CID gasket by minimizing heat transferred to the CID gasket through a CID filter even if a short circuit occurs in a cylindrical type
30 secondary battery.
TECHNICAL SOLUTION
3

[0008] According to one aspect of the present invention for
achieving the above object, provided is a secondary battery
comprising: an electrode assembly having a structure in which
electrodes and separators are alternately disposed; a battery
5 can configured to accommodate the electrode assembly and
having an opened upper portion; a top can coupled to the upper portion of the battery can; a CID filter provided below the top cap; a CID gasket provided in close contact with a side portion of the CID filter; and an electrode tab
10 protruding from the electrode assembly, the electrode tab
being electrically connected to the CID filter, wherein the CID filter comprises a body part defining a main body, the body part comprises: a plurality of main though-holes provided along a circumference of the body part and each of
15 which has a first width (W1); and
[0009] an auxiliary through-hole having a second width (W2) less than the first width (W1), an area (hereinafter, referred to as a ‘first connection area’) of the CID filter, which is electrically connected to the electrode tab, leans
20 toward one side with respect to a center of the CID filter,
and the auxiliary through-hole is defined between the first connection area and the CID gasket.
[0010] The auxiliary through-hole may be defined in a connection area (hereinafter, referred to as a ‘second
25 connection area’) of the body part configured to connect the
man through-holes to each other along a circumferential direction of the body part.
[0011] The auxiliary through-hole may be defined in a circular arc of a virtual circle that is centered at a center
30 of the CID filter while crossing the shortest distance
4

between the first connection area and the CID gasket, and the
second connection areas, in which the auxiliary through-hole
is not defined, among the plurality of second connection
areas may be not disposed in the circular arc.
5 [0012] The second connection areas, in which the auxiliary
through-hole is defined, among the plurality of second connection areas may be disposed adjacent to each other, and the second connection areas, in which the auxiliary through-hole is not defined, among the plurality of second connection
10 areas may be disposed adjacent to each other.
[0013] A circumference of the body part may have a circular shape, and a middle point of the circular arc may be disposed in a semi-straight line extending outward from the center of the CID filter.
15 [0014] A central angle of the circular arc may range of 90
degrees to 180 degrees.
[0015] The first connection area may be disposed at a center of the shortest distance between a center of the CID filter and the CID gasket.
20 [0016] The circular arc may cross a center of the shortest
distance between the first connection area and the CID gasket. [0017] According to another aspect of the present invention for achieving the above object, provided is a CID filter comprising: a body part defining a main body, wherein the
25 body part comprises: a plurality of main though-holes
provided along a circumference of the body part and each of which has a first width (W1); and an auxiliary through-hole having a second width (W2) less than the first width (W1), a first point is defined at an area that leans toward one side
30 with respect to a center of the body part, a second point is
5

defined at a circumference of the body part, and the
auxiliary through-hole is defined between the first point and
the second point, wherein the auxiliary through-hole is
defined in a connection area (hereinafter, referred to as a
5 ‘second connection area’) of the body part configured to
connect the main through-holes to each other along a circumferential direction of the body part.
[0018] The plurality of main through-holes may be provided at equal intervals along the circumferential direction of the
10 body part.
[0019] The auxiliary through-hole may be connected to the two main through-holes defined in both sides of the second connection area in which the auxiliary through-hole is defined.
15 [0020] The auxiliary through-hole may be spaced apart from
the two main through-holes defined in both sides of the second connection area in which the auxiliary through-hole is defined. [0021] The auxiliary through-hole may be provided in
20 plurality in the second connection area in which the
auxiliary through-hole is defined.
[0022] Since total N main through-holes are defined in the body part, total N connection areas may be provided, and the number of second connection areas, in which the auxiliary
25 through-holes are defined, among the total N second
connection areas may be N/2 or less (i) when N is an even number and is (N-1)/2 or less (ii) when N is an odd number. [0023] Total eight main through-holes may be defined, and the number of second connection areas in which the auxiliary
30 through-holes are defined may range of one to four.
6

ADVANTAGEOUS EFFECTS
[0024] According to the present invention, even if the short
circuit occurs in the cylindrical type secondary battery, the
heat transferred to the CID gasket through the CID filter may
5 be minimized to solve the problem of melting the CID gasket.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a side cross-sectional view illustrating a
structure of a secondary battery according to the present
invention.
10 [0026] FIG. 2 is a plan view illustrating an example of a
structure of a CID filter according to an embodiment of the
present invention.
[0027] FIG. 3 is a plan view illustrating another example of
the structure of the CID filter according to an embodiment of
15 the present invention.
[0028] FIG. 4 is a plan view illustrating an example of a
structure of a CID filter according to another embodiment of
the present invention.
[0029] FIG. 5 is a plan view illustrating an example of the
20 structure of the CID filter according to another embodiment
of the present invention.
MODE FOR CARRYING OUT THE INVENTION
[0030] Hereinafter, a secondary battery and a structure of a
CID filter according to the present invention will be
25 described with reference to the drawings.
[0031] Secondary battery and CID filter
[0032] FIG. 1 is a side cross-sectional view illustrating a
structure of a secondary battery according to the present
invention.
30 [0033] As illustrated in FIG. 1, a secondary battery 10
7

according to the present invention may comprise a battery can
100 having a structure with an upper portion opened. The
battery can 100 may have a cylindrical shape in a horizontal
cross-section. That is, the secondary battery according to
5 the present invention may be a cylindrical type secondary
battery.
[0034] A top cap 200 may be disposed on the upper portion of the battery can 100. In more detail, as illustrated in FIG. 1, a top cap 200 may be coupled to the upper portion of the
10 battery can 100.
[0035] A safety vent 300 may be provided below the top cap 200. When a pressure inside the secondary battery 10 exceeds a certain value, the safety vent 300 may be configured to be broken to cut off the current of the secondary battery 10 and
15 provide a path through which a gas inside the secondary
battery 10 is discharged to the outside. As illustrated in FIG. 1, a notch portion having a relatively thin thickness compared to other areas of the safety vent may be provided in the safety vent 300.
20 [0036] A CID filter 400 may also be provided below the top
cap 200. In more detail, the CID filter 400 may be provided below the safety vent 300. As illustrated in FIG. 1, a central area of the CID filter 400 and a central area of the safety vent 300 may be bonded to each other. Thus, when a
25 pressure inside the secondary battery 10 exceeds a certain
value, and thus the safety vent is broken to move upward, the CID filter 400 may also move upward to cut off the current of the secondary battery 10. [0037] A gasket 500 may be provided in close contact with an
30 inner surface of the battery can 100. As illustrated in FIG.
8

1, the gasket 500 may be provided in close contact with
circumferential areas of the top cap 200 and the safety vent
300. The gasket 500 may be configured to seal the inside the
secondary battery 10.
5 [0038] The secondary battery according to the present
invention may further comprise a CID gasket 600 that is in close contact with a side portion of the CID filter 400. The CID gasket 600 is provided to be separated from the above-described gasket 500 and may be configured to prevent the CID
10 filter 400 and the safety vent 300 from directly contacting
each other on the circumferential area of the CID filter 400. Thus, as illustrated in FIG. 1, the CID gasket 600 may be provided between the CID filter 400 and the safety vent 300 at the side portion of the CID filter 400. Each of the
15 gasket 500 and the CID gasket 600 may be made of a material
having electrical insulation properties.
[0039] An electrode assembly 700 may be accommodated in the battery can 100. The electrode assembly 700 may have a structure in which electrodes and separators are alternately
20 disposed. For example, the electrode assembly 700 may be a
jelly-roll type electrode assembly.
[0040] The electrode assembly 700 may comprise an electrode tab 700a. As illustrated in FIG. 1, the electrode tab 700a may have a structure protruding from the electrode assembly
25 700. Also, the electrode tab 700a may be electrically
connected to the CID filter 400. The electrode tab 700a and the CID filter 400 may be connected to each other, for example, through welding. In this specification, an area of the CID filter 400, which is electrically connected to the
30 electrode tab 700a will be referred to as a ‘first connection
9

area’. The first connection area C1 may lean toward one side
with respect to a center of the CID filter 400. FIG. 1
illustrates a state in which the first connection area C1
leans toward a left side with respect to the center of the
5 CID filter 400.
[0041] FIG. 2 is a plan view illustrating an example of the structure of the CID filter according to an embodiment of the present invention, and FIG. 3 is a plan view illustrating another example of the structure of the CID filter according
10 to an embodiment of the present invention.
[0042] As illustrated in FIGS. 2 and 3, the CID filter 400 according to an embodiment of the present invention may comprise a body part 400a defining a main body. A circumference of the body part 400a may have a circular shape.
15 [0043] A plurality of main through-holes 410 provided along
a circumference of the body part 400a may be defined in the body part 400a of the CID filter 400. As illustrated in FIG. 2, the main through-hole 410 may have a first width W1. The main through-hole 410 may have a circular shape. When the
20 main through-hole 410 has the circular shape, the first width
W1 may be a diameter of the main through-hole 410. Also, the main through-hole 410 may be provided at equal intervals along the circumference of the body part 400a. FIGS. 2 and 3 illustrate a case in which eight main through-holes 410 are
25 provided at equal intervals along a circumferential direction
of the body part 400a having the circular shape in the CID filter 400.
[0044] The plurality of main through-holes 410 defined in the body part 400a of the CID filter 400 may be illustrated
30 as being connected to each other by some areas of the body
10

part 400a. In more detail, the plurality of main through-
holes 410 may be connected to each other along the
circumferential direction of the body part 400a by some areas
of the body part 400a. In this specification, the area of
5 the body part 400a of the CID filter, which connects the
plurality of main through-holes 410 to each other along the circumferential direction of the body part 400a, will be referred to as a ‘second connection area’. FIGS. 2 and 3 illustrate a case in which eight second connection areas C2
10 are provided between the main through-holes 410 to correspond
to the eight main through-holes 410.
[0045] An auxiliary through-hole 420 having a second width W2 may be defined in the body part 400a of the CID filter 400 according to the present invention. Here, the second width
15 W2 may be less than the first width W1. That is, the
auxiliary through-hole 420 may have a width less than that of the main through-hole 410.
[0046] Subsequently, referring to FIG. 2, in the CID filter 400 according to the present invention, the auxiliary
20 through-hole 420 may be defined in the second connection area
C2. According to the present invention, since the auxiliary through-hole 420 is defined in the second connection area C2 connecting the main through-holes 410 to each other, the heat transfer may be minimized due to heat conduction between the
25 inside of the CID filter 400 in a central direction and the
outside of the CID filter 400 in a circumferential direction. [0047] Referring to FIG. 1 based on the above contents, in the secondary battery 10 according to the present invention, the auxiliary through-hole 420 (see FIG. 2) of the CID filter
30 400 may be provided between the first connection area C1 and
11

the CID gasket 600. Thus, according to the present invention,
transfer of heat transferred from the first connection area
C1 (that is, the area on which the CID filter and the
electrode tab are electrically connected to each other),
5 which generate a lot of heat in the secondary battery 10, to
the CID gasket 600 may be minimized to prevent a problem of melting the CID gasket 600 from occurring.
[0048] The above feature of the present invention with respect to the auxiliary through-hole 420 may be understood
10 as allowing the auxiliary through-hole 430 to block the
shortest path of the heat transfer between a first point and a second point by providing the auxiliary through-hole 420 between the virtual first point disposed on an area that leans toward one side with respect to the center of the body
15 part 400a and the virtual second point disposed around the
body part 400a.
[0049] Subsequently, referring to FIG. 2, the auxiliary through-hole 420 according to the present invention may be defined only in the second connection area C2 of a portion of
20 the plurality of second connection areas C2. FIG. 2
illustrates a case in which the auxiliary through-hole 420 is defined in each of two second connection areas C2 of the eight second connection areas C2. However, as illustrated in FIG. 3, the auxiliary through-hole 420 may be defined in each
25 of four second connection areas C2 of the eight second
connection areas C2. Alternatively, the auxiliary through-hole 420 may be defined in one or three second connection areas C2 of the eight second connection areas C2. That is, according to the present invention, when the eight main
30 through-holes 410 are defined in the CID filter 400, the
12

number of second connection areas C2 in which the auxiliary
through-holes 420 are defined may range of one to four.
[0050] As described above, the first connection area C1 may
lean toward the one side with respect to the center of the
5 CID filter 400. Here, as illustrated in FIGS. 2 and 3, the
auxiliary through-hole 420 may be defined in the second connection areas C2, which are disposed at a side to which the first connection area C1 leans, of the eight second connection areas C2.
10 [0051] The CID gasket 600 may be easily melted in the
secondary battery 10, particularly, on an area on which the first connection area C1, in which a lot of heat is generated, is relatively close to the CID gasket 600. Thus, the structure in which the second connection areas C2 are
15 disposed adjacent to the area, on which the first connection
area C1 leans, of the plurality of second connection areas C2 provided on the CID filter 400.
[0052] The number of second connection areas C2, in which the auxiliary through-holes 420 are defined, according to the
20 number of main through-holes 410 will be described as follows
by generalizing the foregoing contents.
[0053] When total N main through-holes 410 are defined in the body part 400a, total N second connection areas C2 connecting the plurality of main through-holes 410 to each
25 other may also be provided. Here, the number of second
connection areas C2, in which the auxiliary through-holes 420 are defined, among the total N second connection areas C2 is [0054] (i) N/2 or less when N is an even number and [0055] (ii) (N-1)/2 or less when N is an odd number.
30 [0056] Also, as illustrated in FIGS. 2 and 3, according to
13

the present invention, the second connection areas C2, in
which the auxiliary through-holes 420 are defined, among the
plurality of second connection areas C2 provided on the CID
filter 400 may be disposed adjacent to each other, and the
5 second connection areas C2, in which the auxiliary through-
holes 420 are not defined, among the plurality of second connection areas C2 may also be disposed adjacent to each other. This may be understood as having a structure in which the second connection areas C2, in which the auxiliary
10 through-holed 420 are defined, among the plurality of second
connection areas C2 are continuously disposed along the circumferential direction of the body part 400a, and simultaneously, the second connection areas C2, in which the auxiliary through-holes 420 are not defined, among the
15 plurality of second connection areas C2 are continuously
disposed along the circumferential direction of the body part 400a.
[0057] In the CID filter 400 according to the present invention, the area in which the auxiliary through-hole 420
20 is defined may be described by introducing the concept of a
circular arc of a virtual circle.
[0058] That is, referring to FIGS. 1 to 3, the auxiliary through-hole 420 may be provided to cross the shortest distance between the first connection area C1 and the CID
25 gasket 600. For this, the auxiliary through-hole 420 may be
defined in the circular arc A of the virtual circle that is centered at the center of the CID filter 400. Also, the second connection areas C2, in which the auxiliary through-holes 420 are not defined, among the plurality of second
30 connection areas C2 may not be provided on the circular arc A.
14

[0059] When the second connection areas C2, in which the
auxiliary through-holes 420 is defined, among the plurality
of second connection areas C2 provided on the CID filter 400
are disposed adjacent to each other, the virtual circular arc
5 A may be defined as a circular arc that is centered at the
center of the body part 400a by using centers of the two main through-holes (for example, in FIG. 2, the main through-holes respectively defined in left and right lower portions of the CID filter) defined in the outermost side among the main
10 through holes 410 adjacent to the second connection areas C2,
in which the auxiliary through-holes 420 are defined, as both ends.
[0060] As described above, since the circumference of the body part 400a has the circular shape, a middle point of the
15 virtual circular arc A may be disposed in a semi-straight
line extending outward from the center of the CID filter 400. [0061] Also, a central angle of the virtual circular arc A may range of 90 degrees to 180 degrees. FIG. 2 illustrates a case in which the central angle of the virtual circular arc A
20 is 90 degrees, and FIG. 3 illustrates a case in which the
central angle of the virtual circular arc A is 180 degrees. When the central angle of the virtual circular arc A exceeds 180 degrees, the shape of the CID filter may not be properly maintained because the auxiliary through-holes 420 are
25 provided too much, and durability of the CID filter may be
deteriorated. When the central angle of the virtual circular arc A is less than 90 degrees, the blocking of the heat transfer due to the auxiliary through-holes 420 may not effectively occur.
30 [0062] Subsequently, referring to FIGS. 1 to 3, the first
15

connection area C1 may be disposed at a center of the
shortest distance between the center of the CID filter and
the CID gasket 600, and the virtual circular arc A may cross
a center of the shortest distance between the first
5 connection area C1 and the CID gasket 600.
[0063] As illustrated in FIGS. 2 and 3, according to an embodiment of the present invention, the auxiliary through-hole 420 may be connected to two main through-holes 410 defined in both sides of the second connection area C2 in
10 which the auxiliary through-hole 420 is defined. That is,
according to an embodiment of the present invention, the auxiliary through-hole 420 and the main through-hole 410 adjacent to the auxiliary through-hole 420 may be connected to each other.
15 [0064] FIG. 4 is a plan view illustrating an example of a
structure of a CID filter according to another embodiment of the present invention, and FIG. 5 is a plan view illustrating an example of the structure of the CID filter according to another embodiment of the present invention.
20 [0065] Within a range that does not contradict each other,
the above descriptions of the structure of the CID filter according to an embodiment of the present invention may be equally applied to descriptions of a structure of a CID filter according to another embodiment of the present
25 invention. Hereinafter, the structure of the CID filter
according to another embodiment of the present invention will be described mainly based on differences from the structure of the CID filter according to an embodiment of the present invention.
30 [0066] Unlike the forgoing embodiment of the present
16

invention, according to another embodiment of the present
invention, an auxiliary through-hole 420’ may be spaced a
predetermined distance from two main through-holes 410
defined in both sides of a second connection area C2 in which
5 the auxiliary through-hole 420’ is defined. Also, according
to another embodiment of the present invention, the auxiliary through-hole 420’ may be provided in plurality in the second connection area C2 in which the auxiliary through-hole 420’ is defined.
10 [0067] According to another embodiment of the present
invention, the auxiliary through-hole 420’ may have a circular shape. When the auxiliary through-hole 420’ has the circular shape, a width of the auxiliary through-hole 420’ (that is, a second width) may be a diameter of the auxiliary
15 through-hole 420’.
[0068] FIGS. 4 and 5 illustrate a case in which two auxiliary through-holes 420’, each of which has the circular shape, are defined in the second connection area C2 in which the auxiliary through-holes 420’ is defined.
20 [0069] While the embodiments of the present invention have
been described with reference to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the
25 following claims.

CLAIMS

1.A secondary battery comprising:
an electrode assembly having a structure in which
5 electrodes and separators are alternately disposed;
a battery can configured to accommodate the electrode assembly and having an opened upper portion;
a top can coupled to the upper portion of the battery
can;
10 a CID filter provided below the top cap;
a CID gasket provided in close contact with a side portion of the CID filter; and
an electrode tab protruding from the electrode assembly,
the electrode tab being electrically connected to the CID
15 filter,
wherein the CID filter comprises a body part defining a main body,
the body part comprises:
a plurality of main though-holes provided along a
20 circumference of the body part and each of which has a first
width (W1); and
an auxiliary through-hole having a second width (W2) less than the first width (W1),
an area (hereinafter, referred to as a ‘first
25 connection area’) of the CID filter, which is electrically
connected to the electrode tab, leans toward one side with respect to a center of the CID filter, and
the auxiliary through-hole is defined between the first connection area and the CID gasket.
30
18

2. The secondary battery of claim 1, wherein the
auxiliary through-hole is defined in a connection area
(hereinafter, referred to as a ‘second connection area’) of
the body part configured to connect the man through-holes to
5 each other along a circumferential direction of the body part.
3. The secondary battery of claim 1, wherein the
auxiliary through-hole is defined in a circular arc of a
virtual circle that is centered at a center of the CID filter
10 while crossing the shortest distance between the first
connection area and the CID gasket, and
the second connection areas, in which the auxiliary
through-hole is not defined, among the plurality of second
connection areas are not disposed in the circular arc.
15
4. The secondary battery of claim 3, wherein the
second connection areas, in which the auxiliary through-hole
is defined, among the plurality of second connection areas
are disposed adjacent to each other, and
20 the second connection areas, in which the auxiliary
through-hole is not defined, among the plurality of second connection areas are disposed adjacent to each other.
5. The secondary battery of claim 4, wherein a
25 circumference of the body part has a circular shape, and
a middle point of the circular arc is disposed in a semi-straight line extending outward from the center of the CID filter.
30 6. The secondary battery of claim 5, wherein a
19

central angle of the circular arc ranges of 90 degrees to 180 degrees.
7. The secondary battery of claim 2, wherein the
5 first connection area is disposed at a center of the shortest
distance between a center of the CID filter and the CID gasket.
8. The secondary battery of claim 3, wherein the
10 circular arc crosses a center of the shortest distance
between the first connection area and the CID gasket.
9. A CID filter comprising:
a body part defining a main body,
15 wherein the body part comprises:
a plurality of main though-holes provided along a circumference of the body part and each of which has a first width (W1); and
an auxiliary through-hole having a second width (W2)
20 less than the first width (W1),
a first point is defined at an area that leans toward one side with respect to a center of the body part,
a second point is defined at a circumference of the
body part, and
25 the auxiliary through-hole is defined between the first
point and the second point, wherein the auxiliary through-
hole is defined in a connection area (hereinafter, referred
to as a ‘second connection area’) of the body part configured
to connect the main through-holes to each other along a
30 circumferential direction of the body part.
20

10. The CID filter of claim 9, wherein the plurality
of main through-holes are provided at equal intervals along
the circumferential direction of the body part.
5
11. The CID filter of claim 9, wherein the auxiliary
through-hole is connected to the two main through-holes
defined in both sides of the second connection area in which
the auxiliary through-hole is defined.
10
12. The CID filter of claim 9, wherein the auxiliary
through-hole is spaced apart from the two main through-holes
defined in both sides of the second connection area in which
the auxiliary through-hole is defined.
15
13. The CID filter of claim 12, wherein the auxiliary
through-hole is provided in plurality in the second
connection area in which the auxiliary through-hole is
defined.
20
14. The CID filter of claim 10, wherein, since total
N main through-holes are defined in the body part, total N
connection areas are provided, and
the number of second connection areas, in which the
25 auxiliary through-holes are defined, among the total N second
connection areas is N/2 or less (i) when N is an even number and is (N-1)/2 or less (ii) when N is an odd number.
15. The CID filter of claim 10, wherein total eight
30 main through-holes are defined, and
21

the number of second connection areas in which the auxiliary through-holes are defined ranges of one to four.