A battery pack case, a battery pack system, and a vehicle

Abstract

This utility model relates to a battery pack housing, a battery pack system, and a vehicle. The battery pack housing includes a base plate and a protective plate. The base plate supports the battery pack. A first buffer portion is provided at the bottom of the base plate, forming a buffer cavity between the first buffer portion and the base plate. The protective plate is disposed at the bottom of the first buffer portion. The protective plate, the first buffer portion, and the base plate together form a second buffer portion. This utility model improves the deformation resistance of the battery pack housing by providing a first and second buffer portion on the base plate, thereby improving the safety performance of the battery pack.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, and in particular to a battery pack housing, a battery pack system, and a vehicle. Background Technology

[0002] As the power source of a vehicle, the battery is one of the most important protective components in the vehicle chassis, and its reliability is closely related to vehicle safety. Battery packs often use a buffer cavity at the bottom of the pack to improve the vehicle's resistance to deformation under conditions such as scraping or bottoming out. However, current buffer cavities are all implemented through a split structure, resulting in poor resistance to deformation and thus reducing the safety performance of the battery pack. Utility Model Content

[0003] To address the aforementioned technical problems, this utility model provides a battery pack housing, a battery pack system, and a vehicle, which can improve the deformation resistance of the battery pack housing and thus enhance the safety performance of the battery pack.

[0004] On one hand, this utility model provides a battery pack housing, which includes a bottom plate and a protective plate. The bottom plate supports the battery pack, and a first buffer portion is located at the bottom of the bottom plate. A buffer cavity is formed between the first buffer portion and the bottom plate, and the first buffer portion and the bottom plate together form the buffer cavity. The protective plate is located at the bottom of the first buffer portion, and the protective plate, the first buffer portion, and the bottom plate together form a second buffer portion.

[0005] In one embodiment of the present invention, along the front-rear direction of the battery pack housing, the second buffer portion and the first buffer portion are alternately arranged at the bottom of the housing bottom plate.

[0006] In one embodiment of the present invention, the battery pack housing further includes a housing frame, a housing bottom plate is disposed at the bottom of the housing frame, a receiving cavity is formed between the housing frame and the housing bottom plate, and the battery pack is disposed in the receiving cavity.

[0007] In one embodiment of the present invention, the first buffer portion includes two side walls and a bottom wall located between the bottoms of the two side walls, and the thickness of the bottom wall gradually decreases along the direction from the front end to the rear end of the battery pack housing.

[0008] In one embodiment of the present invention, the protective plate includes a protective bottom plate, which is disposed at the bottom of the box bottom plate, and the first buffer portion is located between the box bottom plate and the protective bottom plate.

[0009] In one embodiment of the present invention, the top and / or bottom of the protective base plate are coated with a protective coating.

[0010] In one embodiment of this utility model, a smoke exhaust hole is provided on the bottom plate of the box, the smoke exhaust hole is located between two adjacent buffer cavities, and the smoke exhaust hole is aligned with the explosion-proof valve at the bottom of the battery pack.

[0011] In one embodiment of this utility model, a protective film is provided at the bottom of the box base plate, and the protective film covers the smoke exhaust hole.

[0012] On the other hand, a battery pack system is provided, including a battery pack management module, a battery pack, and a battery pack housing, wherein the battery pack management module is connected to the battery pack.

[0013] In another aspect, a vehicle is provided, including the battery pack system.

[0014] The above-mentioned technical solution of this utility model has the following advantages compared with the prior art:

[0015] The battery pack housing of this utility model absorbs impact force through the buffer cavity formed between the first buffer part and the bottom plate of the housing, and the second buffer part, thereby improving the deformation resistance of the battery pack housing and thus improving the safety performance of the battery pack. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a first structural schematic diagram of the battery pack housing of this utility model;

[0018] Figure 2 This is an exploded view of the first structure of the battery pack housing of this utility model;

[0019] Figure 3 This is a top view of the first structure of the battery pack housing of this utility model;

[0020] Figure 4 yes Figure 3 Sectional view at point AA;

[0021] Figure 5 yes Figure 4 A magnified view of a portion of point A in the middle;

[0022] Figure 6 This is a schematic diagram of the structure of the first and second buffer parts of the battery pack housing of this utility model;

[0023] Figure 7 yes Figure 6 A magnified view of a portion of point B in the middle;

[0024] Figure 8 yes Figure 3 Sectional view at point BB;

[0025] Figure 9 This is a schematic diagram of the structure of the first buffer section of the battery pack housing of this utility model, which is filled with buffer material;

[0026] Figure 10 Exploded view of the second structure of the battery pack housing of this utility model.

[0027] Explanation of reference numerals in the instruction manual:

[0028] 1. Box bottom plate; 2. First buffer section; 3. Buffer cavity; 4. Box frame; 5. Receiving cavity; 6. Energy-absorbing material; 7. Protective bottom plate; 8. Protective coating; 9. Smoke vent; 10. Protective membrane; 11. Auxiliary frame; 12. Reinforcing member; 13. Sub-cavity; 14. Side wall; 15. Bottom wall; 16. Second buffer section; 17. Protective plate. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0030] Example 1

[0031] Reference Figures 1-10 As shown, the battery pack housing of this utility model includes a bottom plate 1 and a protective plate 17. The bottom plate 1 is used to support the battery pack. A first buffer part 2 is provided at the bottom of the bottom plate 1. A buffer cavity 3 is formed between the first buffer part 2 and the bottom plate 1. The protective plate 17 is disposed at the bottom of the first buffer part 2. The protective plate 17, the first buffer part 2 and the bottom plate 1 together form a second buffer part 16.

[0032] The first buffer section 2 and the bottom plate 1 of the battery pack can be integrally formed. This application improves the deformation resistance of the battery pack housing by using an integral forming process to create a buffer cavity 3, thereby enhancing the reliability of the battery pack housing. Specifically, as shown... Figure 1As shown, the battery pack housing of this application includes a housing base plate 1, with the battery pack disposed on top of the housing base plate 1, so as to protect the battery pack through the housing base plate 1 located at the bottom of the battery pack. Further, a first buffer portion 2 is provided at the bottom of the housing base plate 1. The first buffer portion 2 is a buffer wall, and a buffer cavity 3 is formed between the buffer wall and the housing base plate 1. The buffer cavity 3 can improve the impact resistance and energy absorption capacity of the battery pack. Under conditions such as scraping or bottoming out of the vehicle, the deformation of the first buffer portion 2 can prevent the battery pack from deforming due to external forces. Furthermore, the first buffer portion 2 is integrally formed with the housing base plate 1. The deformation resistance of the integrally formed housing base plate 1 no longer depends on the strength of the connecting parts, thus improving the deformation resistance of the housing base plate 1. In addition, the integral forming process improves the modal characteristics of the housing base plate 1, thereby improving the modal characteristics and NVH performance of the battery pack housing. For example, Figure 1 , Figure 2 , Figure 4 and Figure 8 As shown, multiple first buffer sections 2 are provided along the front-rear direction of the battery pack housing. Therefore, multiple buffer cavities 3 are formed. The multiple first buffer sections 2 are evenly spaced at the bottom of the housing base plate 1 along the front-rear direction of the battery pack housing, and the multiple buffer cavities 3 are also evenly spaced at the bottom of the housing base plate 1 along the front-rear direction of the battery pack housing. The first buffer sections 2 and the housing base plate 1 can be integrally formed by welding or casting processes. In addition, the prior art generally provides two plates at the bottom of the housing frame, with a cavity between the two plates and reinforcing ribs in the cavity. This application removes the bottom plate, saving space and increasing the battery pack capacity. Furthermore, by replacing the cavity with reinforcing ribs using U-shaped buffer cavities 3, the first buffer sections 2 can ensure protective strength. Therefore, this application balances space saving and strength.

[0033] The battery pack housing also includes a protective plate 17, which is located at the bottom of the first buffer section 2. The protective plate 17, the first buffer section 2, and the bottom plate 1 of the housing together form a second buffer section 16. The second buffer section further improves the deformation resistance of the battery pack housing, thereby improving the safety performance of the battery pack.

[0034] The battery pack housing of this application absorbs the impact force through the buffer cavity 3 formed between the first buffer part 2 and the bottom plate 1 of the housing, thereby improving the deformation resistance of the battery pack housing. Furthermore, the integral molding process of the first buffer part 2 and the bottom plate 1 of the housing further improves the deformation resistance of the battery pack housing, thereby improving the safety performance of the battery pack.

[0035] In one embodiment, along the direction from the front end to the rear end of the battery pack housing, the second buffer part 16 and the first buffer part 2 are alternately arranged at the bottom of the housing bottom plate 1. By alternating the arrangement of the second buffer part 16 and the first buffer part 2, vibration can be effectively absorbed.

[0036] In one embodiment, the battery pack housing also includes a housing frame 4, a housing bottom plate 1 is disposed at the bottom of the housing frame 4, and a receiving cavity 5 is formed between the housing frame 4 and the housing bottom plate 1, and the battery pack is disposed in the receiving cavity 5.

[0037] This application uses a receiving cavity 5 to house the battery pack. Specifically, as shown... Figure 10 As shown, the battery pack enclosure also includes a frame 4, with a bottom plate 1 positioned at the bottom of the frame 4. A cavity 5 is formed between the frame 4 and the bottom plate 1 to house the battery pack. Both the frame 4 and the bottom plate 1 provide protection for the battery pack. Furthermore, the bottom plate 1 is detachably mounted at the bottom of the frame 4. If the first buffer section 2 deforms due to vehicle scraping or bottoming out, the bottom plate 1 can be replaced without replacing the entire battery pack enclosure, facilitating maintenance and reducing costs. The frame 4 is manufactured using an aluminum profile welding process. Additionally, the frame 4 integrates a liquid cooling plate and related piping to control the temperature of the battery cells, ensuring they operate at their optimal temperature.

[0038] In one embodiment, the first buffer section 2 includes two side walls 14 and a bottom wall 15 located between the bottoms of the two side walls. The tops of the two side walls 14 are disposed on the bottom surface of the box bottom plate 1, and a buffer cavity 3 is formed between the bottom wall 15, the bottom surface of the box bottom plate 1, and the two side walls 14.

[0039] This application improves the deformation resistance of the battery pack housing by forming a buffer cavity 3 through the connection of the first buffer section 2 and the bottom plate 1 of the housing. Specifically, as shown in the figure, the first buffer section 2 includes three buffer walls: two side walls 14 and a bottom wall 15. The bottom wall 15 is located between the bottoms of the two side walls 14 and is integrally formed with the side walls 14. The tops of the two side walls 14 are integrally formed with the bottom surface of the bottom plate 1 of the housing. Therefore, the two side walls 14, the bottom wall 15, and the bottom surface of the bottom plate 1 of the housing form a U-shaped structure. The U-shaped structure is integrally formed to form the buffer cavity 3. Figure 1 As shown, the U-shaped design can effectively absorb energy and deform, and the battery pack can quickly disperse after being subjected to local stress, preventing the cells from deforming under stress.

[0040] In one embodiment, the buffer cavity 3 extends in the left-right direction of the vehicle and gradually thins in the direction from the front end to the rear end of the battery pack housing.

[0041] This application improves the deformation resistance of the box base plate 1 by adjusting the wall thickness of the first buffer section 2. Specifically, as shown... Figure 6 and Figure 7As shown, the buffer cavity 3 extends along the left-right direction of the vehicle and covers the bottom plate 1 of the battery pack box along the left-right direction of the vehicle. Along the direction from the front end to the rear end of the battery pack box, the wall thickness of the bottom wall 15 gradually decreases. When the vehicle is in a state of scraping or bottoming out, the obstacle under the vehicle first contacts the thicker bottom wall 15. At this time, the obstacle exerts a larger force on the bottom wall 15, and the thicker bottom wall 15 unloads the larger force. As the vehicle continues to move forward, the force exerted by the obstacle on the bottom wall 15 decreases, and the thinner bottom wall 15 unloads the smaller force, which is equivalent to achieving graded energy absorption. This facilitates the collapse of the bottom wall 15, reducing the possibility of the battery pack box bottom plate 1 being squeezed and deformed.

[0042] In one embodiment, the buffer cavity 3 is filled with energy-absorbing material 6.

[0043] This application improves the deformation resistance of the box base plate 1 by filling the buffer cavity 3 with energy-absorbing material 6. Specifically, such as... Figure 9 As shown, the energy-absorbing material 6 inside the buffer cavity 3 can be one or more of the following: honeycomb aluminum, foamed aluminum, silicone rubber foam, polyurethane foam, and foam aerogel felt. When the vehicle is in a condition such as scraping or bottoming out, the energy-absorbing material 6 can improve the impact absorption capacity, thereby improving the deformation resistance of the box bottom plate 1 and improving the protection of the battery cell.

[0044] In one embodiment, the battery pack housing also includes a protective base plate 7, which is disposed at the bottom of the housing base plate 1, and the first buffer part 2 is located between the housing base plate 1 and the protective base plate 7.

[0045] This application improves the deformation resistance of the battery pack housing by using a protective base plate 7. Specifically, the battery pack housing also includes a protective base plate 7, which is made of DP980 hot-formed steel plate. The housing base plate 1 is located at the bottom of the housing frame 4, and the protective base plate 7 is located at the bottom of the housing base plate 1. The first buffer part 2 is located between the housing base plate 1 and the protective base plate 7, that is, the buffer cavity 3 is located between the housing base plate 1 and the protective base plate 7. When the vehicle is in a condition such as scraping or bottoming out, the impact force is first applied to the protective base plate 7. The protective base plate 7 acts as a first line of defense against deformation and absorbs energy. When the impact force is too large, the protective base plate 7 squeezes the first buffer part 2. The first buffer part 2 acts as another line of defense against deformation. Through these two lines of defense, the deformation resistance of the battery pack housing is improved, and the possibility of the battery pack being squeezed and deformed is reduced.

[0046] In one embodiment, the top and / or bottom of the protective base plate 7 is coated with a protective coating 8.

[0047] This application improves the deformation resistance of the battery pack casing through a protective coating 8. Specifically, the protective coating 8 is applied to the top and bottom of the protective base plate 7, such as... Figure 4 and Figure 5 As shown, the protective coating 8 is a polyurea coating. The polyurea coating not only provides cushioning and energy absorption, but also contributes to the lightweight design of the battery pack housing due to its low density. The protective base plate 7, made of hot-formed steel plate, possesses a certain structural strength. The polyurea coating on its top and bottom surfaces enhances the elongation at break and improves its resistance to dynamic impacts. Therefore, the polyurea coating acts as a third layer of protection against deformation, thus improving the battery pack housing's resistance to deformation through these three layers of protection, reducing the possibility of the battery pack being deformed by compression, and improving the battery pack's safety performance. Furthermore, the polyurea coating has excellent sealing properties; if the protective base plate 7 is damaged in the event of a bottom impact, the polyurea coating can ensure the battery pack's sealing performance. The polyurea coating is sprayed onto the protective base plate 7, which can be fixed to the housing base plate 1 using adhesive, mechanical fastening, or a combination of adhesive and mechanical fastening. The bottom plate 1 of the enclosure is made of aluminum profile, the protective bottom plate 7 is made of DP980 hot-formed steel plate, and the protective coating 8 is made of polyurea coating. Therefore, the bottom plate 1, the protective bottom plate 7 and the protective coating 8 are made of different materials, which can achieve complementary performance of different materials to improve the deformation resistance of the battery pack enclosure and adapt to moving or stationary spherical working conditions.

[0048] The protective coating 8 can also be applied only to the top or bottom of the protective base plate 7. The protective coating 8 is made of polyurea coating. The polyurea coating can not only play a role in buffering and absorbing energy, but also further reduce the weight of the battery pack box due to its low density.

[0049] In one embodiment, a smoke exhaust hole 9 is provided on the bottom plate 1 of the enclosure. The smoke exhaust hole 9 is located between two adjacent buffer cavities 3 and is aligned with the explosion-proof valve at the bottom of the battery pack.

[0050] This application improves the safety of the explosion-proof valve during pressure relief by using the smoke exhaust port 9. Specifically, as shown... Figure 2As shown, a smoke vent 9 is provided on the bottom plate 1 of the battery pack housing. Along the front-to-back direction of the battery pack housing, the smoke vent 9 and the buffer chamber 3 are arranged at intervals on the bottom plate 1. That is, the smoke vent 9 is positioned between any two adjacent buffer chambers 3. The smoke vent 9 is located at the top of the second buffer section 16, and the number of smoke vent 9 is consistent with the number of explosion-proof valves. One explosion-proof valve corresponds to one smoke vent 9, and the explosion-proof valves are aligned with their corresponding smoke vent 9s. This allows the explosion-proof valves on the battery pack to quickly release high-temperature gases and particulate matter inside the battery pack in extreme situations such as thermal runaway, preventing the battery pack from exploding. The high-temperature gases and particulate matter are discharged to the bottom of the battery pack through the corresponding smoke vent 9. The explosion-proof valves are located at the bottom of the battery cells, while the terminals and high-voltage electrical lines are located at the top of the battery cells, enabling separation of venting and current flow, thus improving the safety performance of the battery pack.

[0051] In one embodiment, a protective film 10 is provided at the bottom of the bottom plate 1 of the housing, and the protective film 10 covers the smoke exhaust hole 9.

[0052] This application enhances the protection of the battery pack through the protective film 10. Specifically, one smoke vent 9 is provided for each explosion-proof valve, and a protective film 10 is provided at the bottom of the casing base plate 1. The protective film is located within the second buffer section 16. Figure 4 and Figure 5 As shown, the smoke exhaust port 9 is covered by a protective film 10, which protects the normal battery cells. Furthermore, when any battery cell releases high-temperature gas and particulate matter under extreme conditions such as thermal runaway, the high-temperature gas and particulate matter are released through the explosion-proof valve on the battery cell. The high-temperature gas and particulate matter will break through the protective film 10 at the explosion-proof valve to release the pressure inside the battery cell, thus providing explosion protection. The high-temperature gas and particulate matter released from the battery cell may contain charged particles, which could potentially flow back to the explosion-proof valve of the normal battery cell. These charged particles can easily cause arcing between adjacent battery cells and the liquid cooling plate, as well as between the battery cell and the housing, leading to short circuits. Therefore, a protective film 10 is installed at the bottom of the housing base plate 1. The protective film 10 is made of mica paper, which prevents charged particles from flowing back to the normal battery cells and also provides insulation to protect them.

[0053] In one embodiment, a reinforcing member 12 is provided on the housing frame 4, which divides the receiving cavity 5 into sub-cavities 13, and the battery pack is disposed in the sub-cavities 13.

[0054] This application improves the modal characteristics of the box frame through reinforcement 12. Specifically, as... Figure 10As shown, the housing frame 4 consists of crossbeams and longitudinal beams, forming a receiving cavity 5 between them. A reinforcing member 12 is disposed inside the housing frame 4. Therefore, a sub-cavity 13 is formed between the reinforcing member 12 and the crossbeams and longitudinal beams constituting the housing frame 4. The sub-cavity 13 is used to house the battery pack. The reinforcing member 12 increases the rigidity of the housing frame 4, improves its modal characteristics, and thus enhances its NVH performance.

[0055] Example 2

[0056] A battery pack system includes a battery pack management module, a battery pack, and a battery pack housing. The battery pack management module is connected to the battery pack. The battery pack housing includes a housing base plate 1, with the battery pack disposed on top of the housing base plate 1. A first buffer section 2 is provided at the bottom of the housing base plate 1, and a buffer cavity 3 is formed between the first buffer section 2 and the housing base plate 1. A protective plate 17 is disposed at the bottom of the first buffer section 2. The protective plate 17, the first buffer section 2, and the housing base plate 1 together form a second buffer section 16.

[0057] The battery pack management module of this application is connected to the battery pack to monitor battery status, protect battery safety, and balance battery power. An auxiliary frame 11 is provided on one side of the housing frame 4, such as... Figure 10 As shown, the battery management module and wiring harness are housed within the auxiliary frame 11. This application forms a second buffer section 16 by combining the buffer cavity 3 formed by the first buffer section 2 of the base plate 1 and the protective plate 17, and by having the first buffer section 2 and the base plate 1 enclose each other. This design improves the battery pack's impact resistance and energy absorption capacity, thereby enhancing the battery pack's deformation resistance and further improving the battery pack system's deformation resistance.

[0058] Example 3

[0059] A vehicle includes a battery pack system, which includes a battery management module, a battery pack, and a battery pack housing. The battery pack management module is connected to the battery pack. The battery pack housing includes a housing base plate 1, with the battery pack disposed on top of the housing base plate 1. A first buffer portion 2 is provided at the bottom of the housing base plate 1, and a buffer cavity 3 is formed between the first buffer portion 2 and the housing base plate 1. A protective plate 17 is disposed at the bottom of the first buffer portion 2, and the protective plate 17, the first buffer portion 2, and the housing base plate 1 together form a second buffer portion 16.

[0060] The vehicle of this application includes a battery pack system. The battery pack management module of the battery pack system is connected to the battery pack to monitor the battery status, protect battery safety, and balance battery charge. This application improves the impact resistance and energy absorption capacity of the battery pack by forming a buffer cavity 3 with the first buffer part 2 set in the bottom plate of the housing, a protective plate 17, and a second buffer part 16 formed by the first buffer part 2 and the bottom plate of the housing. This, in turn, improves the deformation resistance of the battery pack housing, further improves the deformation resistance of the battery pack system, and enhances the safety performance of the vehicle.

[0061] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A battery pack housing, characterized in that: The battery pack housing includes a bottom plate (1) and a protective plate (17). The bottom plate (1) is used to support the battery pack. The bottom of the bottom plate (1) is provided with a first buffer part (2). The first buffer part (2) and the bottom plate (1) together form a buffer cavity (3). The protective plate (17) is located at the bottom of the first buffer part (2). The protective plate (17), the first buffer part (2) and the bottom plate (1) together form a second buffer part (16).

2. The battery pack housing according to claim 1, characterized in that: Along the front-rear direction of the battery pack housing, the second buffer part (16) and the first buffer part (2) are alternately arranged at the bottom of the housing bottom plate (1).

3. The battery pack housing according to claim 1, characterized in that: The battery pack housing also includes a housing frame (4), the housing bottom plate (1) is disposed at the bottom of the housing frame (4), and a receiving cavity (5) is formed between the housing frame (4) and the housing bottom plate (1), and the battery pack is disposed in the receiving cavity (5).

4. The battery pack housing according to claim 1, characterized in that: The first buffer section (2) includes two side walls (14) and a bottom wall (15) located between the bottoms of the two side walls (14). The bottom wall (15) is thinner in the direction from the front end to the rear end of the battery pack housing.

5. The battery pack housing according to claim 1, characterized in that: The protective plate (17) includes a protective base plate (7), which is disposed at the bottom of the box bottom plate (1), and the first buffer part (2) is located between the box bottom plate (1) and the protective base plate (7).

6. The battery pack housing according to claim 5, characterized in that: The top and / or bottom of the protective base plate (7) are coated with a protective coating (8).

7. The battery pack housing according to claim 1, characterized in that: The bottom plate (1) of the enclosure is provided with a smoke exhaust hole (9), which is located between two adjacent buffer cavities (3). The smoke exhaust hole (9) is aligned with the explosion-proof valve at the bottom of the battery pack.

8. The battery pack housing according to claim 7, characterized in that: A protective film (10) is provided at the bottom of the box base plate (1), and the protective film (10) covers the smoke exhaust hole (9).

9. A battery pack system, characterized in that: It includes a battery pack management module, a battery pack, and a battery pack housing as described in any one of claims 1-8, wherein the battery pack management module is connected to the battery pack.

10. A vehicle, characterized in that: Includes the battery pack system as described in claim 9.

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