Patent Publication Number: US-2021178035-A1

Title: Negative pressure pumps and related methods

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application claims the benefit under 35 U.S.C. § 119 to U.S. Provisional Patent Application No. 62/651,407 filed on Apr. 2, 2018, and U.S. Provisional Patent Application No. 62/820,912 filed on Mar. 20, 2019, the entireties of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a negative pressure pump. The pump may be used for internal or external wounds or for other medical and/or nonmedical applications. 
     INTRODUCTION 
     Circumstances can arise wherein an undesirable buildup of fluid may be removed. For example, in medical procedures, fluid may pool at the treatment site of a patient before, after, or during a procedure. Removal of the fluid may facilitate healing, e.g., at the treatment site, or otherwise promote the health of the patient. Accordingly, a desire exists for devices and methods for drawing fluids away from a site in an effective, low-cost manner. 
     SUMMARY 
     Some embodiments of the present disclosure are directed to a disposable negative pressure pump comprising a reservoir comprising an inner wall that defines a lumen along a longitudinal axis of the reservoir, a drive assembly coupled to the reservoir, the drive assembly comprising a spring, a piston forming a seal against the inner wall of the reservoir and slidable within the lumen along the longitudinal axis; and a cable extending through the lumen, the cable having a first end coupled to the drive assembly and a second end coupled to the piston, wherein sliding the piston along the reservoir via the drive assembly creates a negative pressure within the lumen. The reservoir may have a constant cross-sectional dimension along an entire length of the reservoir and the cable may be coupled to the drive assembly at a cable attachment point. Further, the drive assembly may comprise a first drum and a second drum, where the cable attachment point may be on the second drum. The spring may be coupled to the second drum, or coupled to each of the first drum and the second drum. In at least one embodiment, winding of the spring onto the first drum may cause winding of the cable onto the second drum, and winding of the cable onto the second drum may move the piston along the longitudinal axis of the reservoir. A medical system for removing fluid from a target site may comprise a patient therapy unit comprising a manifold and the above-described negative pressure pump. 
     Embodiments of the present disclosure also are directed to a method of removing fluid from a target site, the method comprising: placing a first end of a manifold at the target site, wherein a second end of the manifold is coupled to a negative pressure pump comprising: a reservoir comprising an inner wall that defines a lumen along a longitudinal axis of the reservoir, the manifold being in communication with the reservoir; a drive assembly coupled to the reservoir and comprising a spring; and a piston coupled to the drive assembly, the piston having a cross-sectional dimension corresponding to a cross-sectional dimension of the reservoir; and initiating the drive assembly of the negative pressure pump, wherein motion of the spring moves the piston within the lumen to create a negative pressure within the reservoir. The target site may be an internal wound, an external wound, any location on a patient, or any location related to a patient. A location on a patient may include a location within the patient&#39;s body, a location on a patient&#39;s skin, a patient treatment site (which may not necessarily be a wound), a surgical site, etc. A location related to a patient may include an apparatus or device used in patient treatment, a surgical site, a clinical study site, etc. The spring may be comprised of a torsion spring. 
     The piston may be spaced from the drive assembly along the longitudinal axis of the reservoir before initiating the drive assembly and the piston may be adjacent to the drive assembly after initiating the drive assembly. In at least one embodiment, the drive assembly may be coupled to the piston by a cable extending along the longitudinal axis, and the drive assembly may further comprise a first drum and a second drum. The cable may be coupled to the second drum, and the spring may engage each of the first drum and the second drum when the drive assembly is initialized. 
     Embodiments of the present disclosure also include a method of manufacturing a negative pressure pump, the method comprising: biasing a spring of the drive assembly to wind from a first drum to a second drum, wherein the reservoir of the negative pressure pump comprises an inner wall that defines a lumen along a longitudinal axis of the reservoir, the drive assembly being coupled to the reservoir, and wherein the drive assembly is coupled to the piston by a cable extending through the lumen of the reservoir. The biasing may include winding the spring on the second drum and locking the spring into a biased position. Alternatively or in addition, the biasing may include accessing a spring winding gear of the drive assembly via a gear access hole, and possibly sealing the gear access hole after biasing the spring. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated into and constitute a part of this specification, illustrate various exemplary embodiments and, together with the description, serve to explain the principles of the present disclosure. The drawings show different aspects of the present disclosure and, where appropriate, reference numerals illustrating like structures, components, materials and/or elements in different figures are labeled similarly. It is understood that various combinations and/or omissions of the structures, components, and/or elements, other than those specifically shown, are contemplated and are within the scope of the present disclosure. 
       There are many inventions described and illustrated herein. The described inventions are neither limited to any single aspect nor embodiment thereof, nor to any combinations and/or permutations of such aspects and/or embodiments. Moreover, each of the aspects of the described inventions, and/or embodiments thereof, may be employed alone or in combination with one or more of the other aspects of the described inventions and/or embodiments thereof. For the sake of brevity, certain permutations and combinations are not discussed and/or illustrated separately herein. Notably, an embodiment or implementation described herein as “exemplary” is not to be construed as preferred or advantageous, for example, over other embodiments or implementations; rather, it is intended to reflect or indicate that the embodiment(s) is/are “example” embodiment(s). 
         FIG. 1  provides an exploded view of an exemplary negative pressure pump&#39;s reusable drive unit and a disposable reservoir, according to one embodiment of the present disclosure. 
         FIGS. 2A-2D  provide various views of a mechanical drive mechanism of the reusable drive units of  FIG. 1 , according to one embodiment of the present disclosure. 
         FIGS. 3A-3C  provide various views of an exemplary locking mechanism that may secure a reusable drive unit to a disposable reservoir, according to one embodiment of the present disclosure. 
         FIGS. 4A-4G  provide an exemplary method of using an exemplary negative pressure pump comprised of a reusable drive unit and a disposable reservoir, according to one embodiment of the present disclosure. 
         FIG. 5  provides a view of an exemplary disposable negative pressure pump, according to a second embodiment of the present disclosure. 
         FIGS. 6A-6C  provide various views of a mechanical drive assembly of a disposable negative pressure pump, according to the second embodiment of the present disclosure. 
         FIGS. 7A-7C  depict exemplary operation of a drive assembly, according to the second embodiment of the present disclosure. 
         FIGS. 8A-8D  provide an exemplary method of using a disposable negative pressure pump, according to an embodiment of the present disclosure. 
         FIGS. 9A-9B, 10A-10C, 11A-11B, and 12  show various alternative embodiments of a drive assembly of a negative pressure pump, according to embodiments of the present disclosure. 
         FIGS. 13A-13F  provide various views of an exemplary pressure-actuated negative pressure pump, according to an embodiment of the present disclosure. 
         FIGS. 14A and 14B  provide cross-sectional, perspective views of exemplary constant torque spring driven negative pressure pumps, according to one embodiment of the present disclosure. 
         FIGS. 14C and 14D  provide exploded views of an exemplary drive assembly of the negative pressure pumps of  FIGS. 14A and 14B , according to one embodiment of the present disclosure. 
         FIGS. 14E and 14F  provide views of exemplary drive assembly locks of the negative pressure pumps of  FIGS. 14A and 14B , according to one embodiment of the present disclosure. 
         FIGS. 14G - FIG. 141  provide views of exemplary mechanisms for energizing the respective constant torque springs of the negative pressure pumps of  FIGS. 14A and 14B , according to one embodiment of the present disclosure. 
         FIG. 14J  provides views of various sizes of the constant torque spring driven negative pressure pumps of  FIGS. 14A and 14B , according to embodiments of the present disclosure. 
     
    
    
     As used herein, the terms “comprises,” “comprising,” “includes,” “including,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. The term “exemplary” is used in the sense of “example,” rather than “ideal.” In addition, the terms “first,” “second,” and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish an element or a structure from another. Moreover, the terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of one or more of the referenced items. 
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure relate to a pump, e.g., a negative pressure pump, which may be used to remove fluids from a target site. The pump may include a drive mechanism and a reservoir. In use, a tubing manifold may be connected to the reservoir and the pump may be used by a to provide negative pressure at the target site to promote. For example, a medical professional may use the pump to remove fluids from a patient, e.g., to promoting healing. The drive mechanism may create a negative pressure chamber in the reservoir, thus drawing fluids into the reservoir. The present disclosure describes various embodiments, including spring-actuated and pressure-actuated negative pressure pump devices. 
     A first embodiment of the spring-actuated mechanical negative pressure pump may include a reusable mechanical drive mechanism coupled to a disposable reservoir. A second embodiment of the spring-actuated mechanical negative pressure pump may include an entirely disposable negative pressure pump (where both a mechanical drive mechanism and reservoir may be disposable). The pressure-actuated negative pressure pump of a further embodiment may include a gas/pressure-based drive mechanism. For example, this embodiment may use a change in gas pressure to move a plunger through a reservoir to generate negative pressure (e.g., a pressure range from 100 mmHg to 760 mmHg in a chamber or reservoir of the pump), rather than using mechanical energy. At least a portion of the pressure-actuated negative pressure pump may be disposable. These and other aspects of the present disclosure are described in greater detail below. 
     As shown in  FIG. 1 , a first embodiment of a negative pressure pump  10  with a disposable reservoir may include a reusable drive unit  11  and a reservoir  20  arranged along a central, longitudinal axis x. The reusable drive unit  11  may include a drive housing  12  and a carrier  13 . Drive housing  12  may be of any suitable cross-sectional configuration, including, but not limited to, rectangular, circular, elliptical, triangular, or oval. Drive housing  12  may be comprised of suitable material, including, but not limited to, glass, plastic, metal, rubber, silicone, or a combination thereof. At least a portion of drive housing  12  may be opaque, transparent, or translucent. For example, drive housing  12  may include one or more transparent/translucent openings or windows that permit visualization of the contents of drive housing  12  (described in detail in  FIGS. 2A-2D ). 
     Drive housing  12  may include a first end  12   a  and a second end  12   b , joined by an elongate surface  12   c . The first end  12   a , second end  12   b , and elongate surface  12   c  may form the outer surface of drive housing  12 . In one embodiment, the first end  12   a  or elongate surface  12   c  may include an activation mechanism for reusable drive unit  11  (e.g., a button or switch). In one embodiment, second end  12   b  of the drive housing  12  may include a rim that may receive carrier  13 . 
     Drive housing  12  may be coupled to carrier  13 . In one embodiment, a spring or wire (not shown) may extend from drive housing  12  to carrier  13 . For example, the spring or wire may extend through at least a portion of the length of carrier  13  such that carrier  13  may be disposed at the end of the spring or wire (as described at  FIG. 2D ). 
     In one embodiment, the cross-section of carrier  13  may have the same shape as drive housing  12  (e.g., rectangular, circular, elliptical, triangular, oval, etc.). Carrier  13  may include a first portion  13   a  and a second portion  13   b . In one embodiment, carrier  13  may be shaped so that the first portion  13   a  is concentric with the second end  12   b  of drive housing  12 . For example, drive housing  12  may include a rim that extends past the first portion  13   a  of carrier  13 , towards the second portion  13   b  of carrier  13 . In this way, drive housing  12  may at least partially encase carrier  13 . 
     In one embodiment, the first portion  13   a  of the carrier  13  may form a seal against drive housing  12 &#39;s second end  12   b . For example, the first portion  13   a  of carrier  13  may be at a default (e.g., storage) position flush against second end  12   b  of drive housing  12 . In one embodiment, drive housing  12  and carrier  13  may include interlocking features that may secure carrier  13  to drive housing  12 . In one embodiment, the first portion  13   a  may also be sized to fit inside reservoir  20 . 
     In one embodiment, at least a portion of the second portion  13   b  may have the same cross-sectional shape as drive housing  12  and first portion  13   a . The second portion  13   b  may be sized to fit inside a plunger  25 . In one embodiment, the first portion  13   a  may be larger than second portion  13   b . For example, ledge  13   c  may exist between first portion  13   a  and second portion  13   b , due to the first portion  13   a  being larger than second portion  13   b . The drive mechanisms of drive unit  11  are further described in  FIGS. 2A-2D . 
     In one embodiment, fluid reservoir  20  may be joined to reusable drive unit  11 . For example, at least a portion of drive housing  12  may be attached to reservoir  20 , and carrier  13  may be disposed inside a lumen of reservoir  20 . Reservoir  20  may be a hollow receptacle of any suitable cross-sectional configuration, including, but not limited to, rectangular, circular, elliptical, triangular, or oval. In one embodiment, the cross-sectional shape of reservoir  20  may correspond to the cross-sectional shape of drive housing  12 . The cross-sectional size and shape of reservoir  20  may be consistent throughout the length of reservoir  20  (with the exception of manifold connector  24 , as explained in further detail below). For example, the reservoir  20  may have or be arranged along a longitudinal axis, and the reservoir  20  may have a consistent cross-sectional shape along the length of the longitudinal axis. For example, the reservoir  20  may be cylindrical with a consistent diameter along the longitudinal axis of the reservoir  20 . Other shapes of the reservoir  20  are contemplated and encompassed herein, e.g., other polygonal shapes such as rectangular, triangular, etc. Reservoir  20  may be comprised of disposable material, including, but not limited to, glass, plastic, metal, rubber, silicone, or a combination thereof. At least a portion of reservoir  20  may be opaque, transparent (to see contents therein), or translucent. In one embodiment, the outer surface of reservoir  20  may further include markings or indicators, for instance, indicating volume. Reservoir  20  may further include anti-slip coatings, ridges, protrusions, adhesives, or a combination thereof for ease of handling. 
     Reservoir  20  may include a housing  21 , a manifold connector  24 , and a plunger  25 . In one embodiment, housing  21  may include a first end  23   a  and a second end  23   b , joined by a wall  23   c . First end  23   a  may include an opening to reservoir  20 . In at least one embodiment, the first end  23   a  may abut the second end  12   b  of drive housing  12 . The first end  23   a  of reservoir  20  may be secured to the second end  12   b  of drive housing  12 . For example, first end  23   a  and second end  12   b  may include interlocking parts, threads, or surfaces that align against or within each other. The first end  23   a  and second end  12   b  may form a seal (e.g., using an o-ring) so that contents of reservoir  20  cannot escape or leak out of reservoir  20  when the first end  23   a  and second end  12   b  are in contact. 
     In at least one embodiment, the second end  23   b  may close off reservoir  20 . First end  23   a  may include a hollow or open cross-section of reservoir  20 , and second end  23   b  may include a solid surface in the shape of the cross-section of reservoir  20 . In at least one embodiment, the first end  23   a  and second end  23   b  may share the same cross-sectional shape and/or size. 
     In at least one embodiment, the second end  23   b  may include manifold connector  24 . Manifold connector  24  may comprise a lumen that contains a valve, e.g., a one-way valve. During use of the negative pressure pump  10 , a manifold may be attached to manifold connector  24 . The attachment may connect (e.g., provide fluid communication between) the target site, e.g., inside of a patient, and the inner chamber of reservoir  20  (formed by the first end  23   a , second end  23   b , and wall  23   c ). 
     In at least one embodiment, wall  23   c  may form a lumen of housing  21 . Wall  23   c  may include an outer surface  23   d  and inner surface  23   e . Anti-slip coatings, ridges, protrusions, and adhesives may be disposed on outer surface  23   d . Inner surface  23   e  may form the lumen or inner chamber of reservoir  20 . The inner surface  23   e  may have a cross-section that corresponds to or matches the cross-section of outer surface  23   d . In at least one embodiment, inner surface  23   e  may include a smooth surface. 
     In at least one embodiment, reservoir  20  may further contain plunger  25 . Plunger  25  may include a wall  27   a  aligned with axis x, and a base  27   b  transverse to axis x. Plunger wall  27   a  may have a cross-section corresponding to the reservoir inner surface  23   e  and/or the second portion  13   b  of carrier  13 . Plunger wall  27   a  may be attached to plunger base  27   b . Plunger base  27   b  may seal the lumen formed by plunger wall  27   a  from an area of reservoir  20  beneath plunger  25  (as viewed in  FIGS. 4E-4G ). 
     In at least one embodiment, reservoir second end  23   b  and reservoir inner surface  23   e  may contain plunger  25  within the lumen of reservoir  20 . In particular, plunger base  27   b  may contact a reservoir base located at reservoir second end  23   b  when the reservoir is in an unused, storage, or default position. When the reservoir is in use, plunger  25  may slide along the reservoir inner surface  23   e . In at least one embodiment, plunger wall  27   a  may be in direct contact, e.g., constant contact, with reservoir inner surface  23   e , for instance, the outer surface of plunger wall  27   a  may lie against the reservoir inner surface  23   e . Alternatively, plunger wall  27   a  may have an O-ring or other seal around it to ride against the reservoir wall  23   c.    
     In at least one embodiment, plunger  25  may move along reservoir inner surface  23   e  by interlocking with carrier  13  (as described in more detail in  FIGS. 3A and 3B ). In some cases, plunger wall  27   a  may receive or contain at least the carrier second portion  13   b  within its lumen. Further, in some cases, plunger wall  27   a  may further receive at least a portion, or all, of the first portion  13   a  of carrier  13 . In at least one embodiment, a bottom face of the second portion  13   b  of carrier  13  may abut the base  25   b  of plunger  25 . A top edge of plunger wall  27   a  may also contact the ledge  13   c  of carrier  13 . In at least one embodiment, base  25   b  of plunger  25  may include a locking mechanism that engages, e.g., captures, a corresponding lock feature of carrier  13 . An exemplary locking mechanism is described in more detail in connection to  FIGS. 3A and 3B . 
       FIGS. 2A-2D  show an exemplary drive mechanism  30  that may initiate usage of the negative pressure pump  10 . For example, drive mechanism  30  may be used to extend spring  40  (and carrier  13 ) towards plunger  25 . Drive mechanism  30  may be disposed inside drive housing  12 . In at least one embodiment, drive mechanism  30  may include an actuator, e.g., button  31 , battery (not shown), motor  35 , spring  40 , gear system  39 , and clutch  44 . Spring  40  may be comprised of a wound drive spring, constant torque spring, mainspring, or any type of torsion spring. 
     As shown in  FIG. 2A , drive mechanism  30  may be activated by an actuator, illustrated as button  31 . Button  31  may include any nub, protrusion, release, or actuation mechanism extending from the drive housing  12 . For example, button  31  may extend from the top of first end  12   a  or radially outwards from elongate surface  12   c . Once button  31  engages drive mechanism  30 , drive mechanism  30  may push a drive spring  40  and carrier  13  through the lumen of the reservoir housing  21 . It is noted that other types of actuators, such as switches, may be used to engage drive mechanism  30 . Once spring  40 /carrier  13  receives plunger  25 , plunger  25  may connect to spring  40 /carrier  13 . 
       FIGS. 2B-2D  provide views of exemplary drive mechanism  30 , including motor  35 , gear system  39 , spring  40 , lock gearing  41  (shown in  FIGS. 2C and 2D ), contact wheels  43 , and mount  45 . In at least one embodiment, button  31  (of  FIG. 2A ) may activate motor  35  of drive mechanism  30 . Motor  35  may include any type of electrical, battery-operated, single-use, or rechargeable motor. In one embodiment, motor  35  may stop running when carrier  13  contacts or otherwise engages plunger  25 . Motor  35  of drive mechanism  30  may cause movement of the gear system  39 . 
     Gear system  39  may include a torque-reducing series of gears that translate power provided by the motor  35  to spring  40 . For example, motor  35  may be connected to a gear  39   a  of gear system  39  (e.g., as shown in  FIG. 2B ). As shown in  FIG. 2C , gear  39   a  may be adjacent to a second gear, e.g., gear  39   b . Motor  35  may move gear  39   a , which may then translate motion to a gear  39   b . Gear  39   b  may include gear shaft  39   c . Gear shaft  39   c  may be in contact with spring  40 . In at least one embodiment, gear shaft  29   c  may include teeth or protrusions that may interlock with other gears (e.g., lock gearing  41 , as explained in further detail below). 
     In at least one embodiment, drive mechanism includes two or more springs, which may be wound drive springs and/or constant torque springs. For example, spring  40  may include two wound drive springs. Further, gear shaft  39   c  may be positioned between the two drive springs (e.g., as shown in  FIG. 2C ). In at least one embodiment, both of the two wound drive springs of spring  40  may be biased to be retracted in the drive housing  12 . Exemplary springs may include constant torque springs. Spring(s)  40  may be retracted and wound inside drive housing  12  while at an exemplary default position. Motor  35  may cause the gear system  39  to unwind the spring  40  and uncoil the spring  40  out against the biased position of spring  40 . 
     In at least one embodiment, gear system  39  may further include lock gearing  41  (e.g., as shown in  FIGS. 2C and 2D ). In an exemplary configuration, lock gearing  41  may be disposed on one side of spring  40 , while gear  39   a  and gear  39   b  may be disposed on another side, e.g., an opposite side, of spring  40 . Lock gearing  41  may include protrusions that interlock with a corresponding member of gear system  39  (e.g., protrusions of gear shaft  39   c  as shown in  FIG. 2C ). The interlocking of lock gearing  41  with gear shaft  39   c  may provide a one-way clutch  44  (as shown in  FIG. 2C ), which may stop the motion of gear system  39  in lowering the spring  40  (and carrier  13 ) into the lumen of the reservoir  20 . One-way clutch  44  may be used to disengage motor  35  from spring  40 . The clutch  44  may allow connection of an optional external winding handle/key to be used (as an alternative to the motor  35  extending spring  40  to move carrier  13 ). If the side of the clutch  44  (with gear  41  in  FIG. 2C ) is turned clockwise, gear  39   c  may slide axially so that the teeth mating with gear  41  disengage due to the angle of the teeth. A separate clutch/mechanism may be used to disengage motor  35  when the spring(s)  40  retract so the spring(s)  40  do not need to provide torque necessary to drive the motor backwards. Alternatives could include allowing friction wheels to separate or gears to disengage due to spring force, or an additional interface could be added which transmits force only when the motor applies torque to the gears. 
     In operation, motor  35  may engage gear system  39  to extend spring  40  through reservoir  20  until carrier  13  attaches to plunger  25  (at plunger  25 &#39;s default position at the bottom of reservoir  20 ). In particular, contact wheels  43  may be positioned under the gear system  39 . Contact wheels  43  may include two circular wheels that contact one or more drive springs  40  that translate motion to springs  40 . Alternatively, one or more contact wheels  43  may contact a single spring  40 . The contact wheels  43  may be driven by the gear train. Contact wheels  43  may include a high friction, compliant surface (e.g., rubber). The wheels  43  may be spaced such that they pinch the spring(s)  40  between them, advancing the spring(s)  40  by friction as they turn. The wheels  43  may be made of rubber or any non-slip material. In at least one embodiment, contact wheels  43  may further secure the position of spring  40  and maintain friction with spring  40  so that spring  40  is fed into the lumen of reservoir  20 , rather than unraveling into the drive unit  11  or gear system  39 . For example, if spring  40  includes two springs, each of the springs  40  may feed through a contact point  43   a  between the two contact wheels  43  (e.g., as shown in  FIG. 2D ). As an alternate embodiment, spring  40  may be a single spring  40 . 
     In one embodiment, carrier  13  may include a mount  45  (e.g., as shown in  FIGS. 2B and 2D ). In one embodiment, mount  45  may include a block or protrusion positioned between carrier  13  and the components of drive mechanism  30 . In at least one embodiment, mount  45  may secure spring  40  to carrier  13 , so that as spring  40  is driven by drive mechanism  30 , carrier  13  moves as well. 
       FIG. 3A  shows an exemplary locking mechanism for securing carrier  13  to plunger  25 , prior to filling reservoir  20 .  FIG. 3B  shows an exemplary embodiment of disengaging carrier  13  from plunger  25 , e.g., once reservoir  20  is filled. 
     In at least one embodiment, the locking shown in  FIG. 3A  may take place when the plunger  25  is at the bottom of reservoir  20  (e.g., when plunger base  27   b  lies against the base at reservoir second end  23   b ). In at least one embodiment, carrier  13  may be lowered through the lumen of reservoir  20  (using drive mechanism  30  and spring  40 ), until carrier  13  contacts plunger  25 . Spring  40  may be fastened to carrier  13  using mount  45 . In the embodiment of  FIG. 3A , spring  40  may connect permanently, in any suitable fashion, to carrier  13 . This connection may involve a separate component or features integral to the spring  40  and carrier  13  which connect. In one embodiment, mount  45  may include a portion  45   a  that is secured to spring  40 , as well as a portion  45   b  that extends into and connects to at least a portion of the carrier first portion  13   a . As previously described, at least a portion of carrier  13  may be received inside a cavity of plunger  25 , and a surface (e.g., a rim or ledge) of carrier  13  may contact an outer surface of plunger  25 . In at least one embodiment, carrier  13  may include one or more pivoting barbs  50 . In at least one embodiment, barbs  50  may extend from the first portion  13   a  of carrier  13  to the second portion  13   b  of carrier  13 . Barbs  50  may include two barbs  50 , each of the two barbs  50  including a rounded head  53  at one end and a hook  55  at the opposite end. The rounded head  53  may be biased towards a closed position where each of the hooks  55  substantially points radially inward towards the plunger base  27   b.    
     In at least one embodiment, plunger  25  may include an interlocking member  60 . Interlocking member  60  may include at least two surfaces that correspond to and engage one or more surfaces of hooks  55 . Carrier  13  may engage plunger  25  when barbs  50  of carrier  13  lock against interlocking member  60  of plunger  25 . 
       FIG. 3B  shows carrier  13  releasing plunger  25 . The action of  FIG. 3B  may occur once spring  40  is fully retracted and the carrier first portion  13   a  is in contact with second end  12   b  of drive housing  12 . In at least one embodiment, the contact between the carrier  13  and drive housing  12  may cause barbs  50  to rotate and release interlocking member  60 . In some embodiments, barbs  50  may release interlocking member  60  upon activation by a user (e.g., pressing a release button or other actuator).  FIG. 3C  shows a cross section including one of the barbs  50 . Barbs  50  may be spring loaded (spring not shown) towards the center axis of pump  10  and reservoir  20  to capture the interlocking member  60  on the plunger  25 . When the carrier  13  (pulled by spring  40 ) reaches the end of its travel, protrusions  900  on the drive housing  12  contact an arm  51  of each of the barbs  50  and pivot them so they disengage from the interlocking member  60 . Alternate locking mechanisms may include any configuration of magnets, latches, catches, fastenings, interlocking members, snaps, etc. 
       FIGS. 4A-4D  illustrate an exemplary method of preparing the negative pressure pump  10  for use. First, reusable drive unit  11  may be secured to reservoir  20 . As shown in  FIG. 4A , at their initial positions, carrier  13  may be at the base of reusable drive unit  11  and plunger  25  may at the base of reservoir  20 .  FIG. 4B  depicts a step of securing a tube to manifold connector  24  at the base of reservoir  20 . (This step may occur at any point prior to the steps of  FIGS. 4E-4G .) An opposite end of the tube may be in fluid communication with a target site, such as an internal or external wound of a patient, including prior to the step shown in  FIG. 4A . 
       FIG. 4C  shows a step in which interaction with button  31  may activate a motor  35  (see  FIGS. 2A-2D ) in the reusable drive unit  11 . The reusable drive unit  11  may prompt spring  40  to extend from reusable drive unit  11 , into reservoir  20 . For example, the motor  35  may cause spring  40  to unwind from drive housing  12 . Drive unit  11  may include a carrier  13  attached to the end of a spring  40 . As drive unit  11  lowers spring  40  into reservoir  20 , the movement of spring  40  may also push carrier  13  towards the base of reservoir  20 . 
       FIG. 4D  illustrates an exemplary step where spring  40  may be extended through the length of the lumen of reservoir  20 , and carrier  13  may contact plunger  25 . At this step, carrier  13  may lock with plunger  25 . In at least one embodiment, carrier  13  may automatically attach to the plunger  25  upon contact. For example, carrier  13  may attach to plunger  25  by engaging a molded barb feature (e.g., as depicted in  FIG. 3A ). 
       FIGS. 4E-4G  show an exemplary embodiment of using negative pressure pump  10 . For example, the motor  35 /drive mechanism  30  (see  FIGS. 2A-2D ) may disengage (e.g., turn off) once carrier  13  contacts and locks with plunger  25 . In at least one embodiment, spring  40  may be biased to retract inside drive housing  12 . When the negative pressure pump  10  is in use (and drive mechanism  30  is turned off), spring  40  may automatically return to its retracted position inside drive housing  12 . This motion of plunger  25  may generate negative pressure inside the lumen of reservoir  20 . 
       FIG. 4E  depicts a step of using a spring powered mechanism for moving a plunger to generate negative pressure, e.g., constant negative pressure, to draw fluid into a reservoir. In particular,  FIG. 4E  depicts an exemplary step in which spring  40  may automatically retract, towards and into drive unit  11 . Since spring  40  may be connected to plunger  25  (by way of carrier  13 ), the upwards motion of spring  40  may also pull plunger  25  upwards through the reservoir lumen. This negative pressure may cause fluid to be drawn from the connected tubing, into reservoir  20 . In other words, fluids from a tube (fastened to manifold connector  24 ) may flow into the lumen of reservoir  20  as the carrier  13  and plunger  25  travel up through the reservoir lumen. Such fluids may comprise body fluids from a target site of a patient, e.g., an internal or external wound or other location of a patient, wherein collection and removal of fluid may be desired. 
     Once the reservoir is full, the tube optionally may be unfastened from manifold connector  24  (e.g., as shown in  FIG. 4F ). The drive unit  11  optionally may also be disconnected from reservoir  20 . In at least one embodiment, plunger  25  may stay in the reservoir  20  to provide a seal (via an O-ring between plunger  25  and reservoir wall  23   c , for example) and prevent the reservoir contents from spilling. For example, removing reservoir  20  from drive unit  11  may involve disengaging the carrier  13  from plunger  25  (e.g., as shown in  FIG. 4G ). The step illustrated in  FIG. 4G  may include unlocking mechanisms illustrated in  FIG. 3B , or any other form of releasing plunger  25  from carrier  13 , including an automatic disengagement at the top of the stroke of plunger  25 . Reservoir  20  may be discarded, e.g., the used reservoir  20  being disposable, while drive unit  11  may be reused with another reservoir  20 . Manifold  24  may include a one-way valve so that contents of reservoir  20  are sealed in reservoir  20 . In some embodiments, drive unit  11  does not contact bodily fluids, and therefore does not require cleaning. 
     In summary, once a reservoir is filled, the plunger may seal the full reservoir so that the reservoir may be removed from the reusable drive unit. In at least one embodiment, the reusable drive unit may automatically disconnect from the plunger (e.g., as shown in the example of  FIG. 3B ). In some embodiments, the reusable drive unit and plunger may be joined in a connection, and a user may unlock the connection to release the reservoir from the drive unit. In at least one scenario, releasing the plunger from the drive unit may involve the carrier disengaging the plunger. In at least one case, the carrier may automatically release the plunger and the plunger may seal the reservoir. A user may then manually remove the drive unit (and carrier) from the reservoir (and plunger). For example, a latch may hold the drive unit to the reservoir, or the drive unit may engage the reservoir via a friction fit. A user may disconnect the drive unit from the reservoir once the internal components of the drive unit and reservoir (e.g., the carrier and plunger, respectively) are disengaged. 
     In at least one embodiment, a new, empty reservoir may be attached to the drive unit (e.g., reusable drive unit) once the reservoir filled with collected fluid is removed/released from the drive unit. The process may then restart (e.g., with the steps of  FIGS. 4A-4D  and a new reservoir/plunger), where a user may engage an actuator, e.g., press a button, to activate the motor drive mechanism to lower the spring into the lumen of the new reservoir. The carrier may attach to the plunger of the new reservoir and allow fluid to fill the new reservoir. In short, a full reservoir may be detached from the reusable drive unit, a new empty reservoir may be secured to the reusable drive unit, a user may reset the spring to initiate usage of the new reservoir, and collection of fluid can continue. In embodiments therefore, a system, or kit, may include a single reusable drive and a plurality of disposable reservoirs, and optionally tubing and/or a tubing manifold. The system or kit may include a charger for charging a power supply of the drive unit, such as a rechargeable battery. 
       FIG. 5  depicts a second exemplary embodiment of a negative pressure pump  100 . In particular, the example shown in  FIG. 5  may be intended for single use, e.g., fully disposable. Disposable negative pressure pump  100  comprise material or materials suitable for single-use, including, but not limited to, plastic, glass, metal, silicone, or a combination thereof. At least a portion of negative pressure pump  100  may be opaque, transparent, or translucent. Negative pressure pump  100  may be of any suitable cross-sectional configuration, including, but not limited to, rectangular, circular, elliptical, triangular, or oval. 
     In at least one embodiment, negative pressure pump  100  may include a first end  100   a , a wall  100   b , and a second end  100   c . The first end  100   a  may be a solid form of the cross-section of negative pressure pump  100 . For example, if negative pressure pump  100  comprises a plastic structure with an elliptical cross-section, first end  100   a  may be a plastic ellipses. In at least one embodiment, first end  100   a  may include an opening for activation button  101 . The activation button  101  may be in any shape that may extend from first end  100   a . For example, activation button  101  may be a protrusion, a latch, a switch, or any combination thereof. 
     In at least one embodiment, wall  100   b  may have an outer surface and an inner surface. In at least one embodiment, the outer surface of wall  100   b  may include markings or other indicators, for instance, indicating volume. The outer surface of wall  100   b  may further include anti-slip coatings, ridges, protrusions, adhesives, or a combination thereof for ease of handling. In at least one embodiment, the inner surface of wall  100   b  may form a lumen  112 . Drive housing  103 , spring  105 , and plunger  107  may all be contained inside lumen  112 . At least a portion of lumen  112  may serve as reservoir  109 . In one embodiment, the inner (or lumen) surface of wall  100   b  may be smooth. 
     In at least one embodiment, drive housing  103  may be disposed adjacent the first end  100   a , at a top portion of lumen  112 . Drive housing  103  may contain a drive mechanism that is activated by activation button  101 . Drive housing  103  may comprise any material or materials suitable for single-use, including, but not limited to, plastic, glass, metal, silicone, or a combination thereof. The drive housing  103  and a drive mechanism contained therein are described in more detail in connection to  FIGS. 6A-7C . 
     Spring  105  may include any suitable type of spring, e.g., a coil spring, torsion spring, clock spring, etc. In the device of  FIG. 5 , spring  105  may be biased to retract into drive housing  103 . In some embodiments, spring  105  may include a wire or cable that does not store energy. In at least one embodiment, spring  105  may retract into the drive housing  103  upon actuation of the activation button  101 . One end of spring  105  may be secured inside drive housing  103 , and another end of spring  105  may be attached to or otherwise coupled to plunger  107 . At a default position prior to the use of negative pressure pump  100 , plunger  107  may lie at second end  100   c  of negative pressure pump  100 . This may mean that, at a default position, spring  105  may extend through the length of lumen  112 , e.g., spring  105  may stretch from drive housing  103  (adjacent first end  100   a ) to plunger  107  (at the second end  100   c ). Spring  105  may include one or more springs and/or a cable attached to a member of the drive mechanism. In at least one embodiment, spring  105  may include a spring portion and a cable or wire portion. 
     In at least one embodiment, plunger  107  may have substantially the same cross-section as lumen  112 . Plunger  107  may include a top  107   a , a side wall  107   b , and a bottom  107   c . In at least one embodiment, top  107   a  may be fixedly attached to spring  105 . Plunger side wall  107   b  may be flush against the inner surface of wall  100   b . For example, plunger side wall  107   b  may directly contact the inner surface of wall  100   b , or a seal, such as an O-ring, may be between, and directly contact each of, wall  100   b  and the inner surface of wall  100   b . Plunger bottom  107   c  may be positioned at the pump second end  110   c  when the negative pressure pump  100  is at a default position. When the negative pressure pump  100  is in use, plunger  107  may move along lumen  112  (e.g., plunger  107  being slidable along the inner surface of wall  100   b ), towards the drive housing  103 . 
     In one embodiment, pump second end  100   c  may include a base  111  and manifold connector  113 . In at least one embodiment, base  111  may close the lumen formed by pump wall  100   c . In at least one embodiment, the default position of plunger bottom  107   c  may be inside lumen  112  and adjacent to, e.g., on top of, base  111 . Base  111  may include an opening comprising manifold connector  113 . The opening may provide access to the lumen formed by wall  100   b . Manifold connector  113  may include a valve, e.g., a one-way valve, that may be attached to tubing that extends to the target site, e.g., on or within a patient&#39;s body, permitting fluid to enter reservoir  109  but preventing fluid from escaping reservoir  109 . 
       FIGS. 6A-6C  include various views of drive housing  103  and an exemplary drive assembly  200 . Because pump  100  may be built for one-time use and disposable, drive assembly  200  of pump  100  may include fewer components and/or employ a different mechanism than the drive mechanism  30  of reusable drive unit  11 . Further, for example, drive assembly  200  may release and store a spring (as described further herein), whereas drive mechanism  30  may actively move a spring against its biased position.  FIGS. 6A-6C  describe an exemplary drive assembly  200  and related components in more detail. 
     As shown in  FIG. 6A , drive housing  103  may include a wall  130 . In at least one embodiment, wall  130  may have a cross-section that corresponds to lumen  112 . Wall  130  may define its own lumen  131 . In at least one embodiment, wall  130  may include a cutout  150 . Cutout  150  may include a portion of wall  130  that is at a different height from another portion of wall  130 . Cutout  150  may be of any appropriate shape or size. In at least one embodiment, cutout  150  may provide access to the drive assembly  200 . For example, drive assembly  200  may be positioned inside lumen  131 . A wall  130  that is the same height for the entire perimeter of lumen  131  may block access to drive assembly  200 . Cutout  150  may expose at least a portion of drive assembly  200 . 
     As shown in  FIGS. 6A-6C , drive assembly  200  may include activation button  101 , spring  105 , hub  210 , wedge  230 , and latch  250 .  FIGS. 6B and 6C , in particular, show exemplary configurations of activation button  101 , wedge  230 , and latch  250 . In at least one embodiment, activation button  101  may include a protrusion  300 , mount  301 , and arms  303  (e.g., as shown in  FIGS. 6A and 6B ). The activation button arms  303  may further include notches  305  (shown in  FIG. 6C  and explained in more detail below). In at least one embodiment, protrusion  300  may be a portion of activation button  101  that extends from the top of pump  100 . A user may activate pump  100  by pushing protrusion  300 . Protrusion  300  may be of any shape, including but not limited to rectangular (as shown in  FIGS. 6A-6C ), circular, square, star-shaped, or elliptical, etc. Protrusion  300  optionally may include grooves or anti-slip surface(s) to facilitate handling. 
     In at least one embodiment, protrusion  300  may be disposed on top of mount  301 . Mount  301  may include a surface that joins protrusion  300  to arms  303 . In at least one embodiment, arms  303  may extend on either side of spring  105 . For example as shown in  FIG. 6B , spring  105  may be disposed between arm  303   a  and arm  303   b  (“arms  303 ”). In at least one embodiment, arms  303  may also fit over wedge  230  and hold wedge  230  against spring  105  (while at a default position before usage of pump  100 ). In at least one embodiment, each of arms  303  may include a notch  305  at one side. For example,  FIG. 6C  shows arm  303   a  with a notch  305   a . Latch  250  may be positioned at the same side as the notches  305  of arms  303 . 
     In at least one embodiment, spring  105  may comprise a wound drive spring disposed on hub  210 . Spring  105  may unwind and/or wind onto hub  210 . In at least one embodiment, hub  210  may include a wheel, a casing, a rubber roller, or any component that can capture spring  105  so that spring  105  remains untangled. Hub  210  may be secured via an axle extending across the pump  100  (as shown in  FIG. 6C ), so that hub  210  rotates about the axle. 
     In at least one embodiment, wedge  230  may comprise a pivotable arm  400  with a stopper  450  disposed at one end of the arm  400 . At a default position, stopper  450  may be held against spring  105  by arms  303  of activation button  101  (e.g., as shown in  FIGS. 6C and 7A ). 
     Latch  250  may include bar  500 , which joins locking arm  500   a  to locking arm  500   b  (“locking arms  500 ”), as shown in  FIG. 6B . In at least one embodiment, bar  500  may be positioned alongside arms  303  of activation button  101 . Bar  500  may hold locking arms  500  adjacent to notches  305  (as shown in  FIG. 6C ). In at least one embodiment, at least a portion of each of the locking arms  500  may extend into at least a portion of each of the notches  305 . For example, locking arm  500   a  may fit into notch  305   a .  FIGS. 7A-7C  illustrate the interaction of locking arms  500  with notches  305  in more detail. 
       FIGS. 7A-7C  depict exemplary operation of drive assembly  200 . At one exemplary default position shown in  FIG. 7A , activation button  101  is not depressed. Protrusion  300  may extend fully upward from the first end  100   a  of pump  100  and the internal components of drive assembly  200  may be at rest (e.g., not in motion) including spring  105  fully extended to a bottom of reservoir  109 . In at least one embodiment, stopper  450  of wedge  230  may abut spring  105 . Hub  210  and spring  105  therefore are fixed and stationary. Further, locking arms  500  of latch  250  may each abut a surface of activation button arms  303 , below and adjacent to notches  305  (see  FIG. 6C ). 
     Upon depression of activation button  101  (as shown in  FIG. 7B ), protrusion  300  may extend into the first end  100   a  of pump  100 . Mount  301  (see  FIGS. 6A and 6B ) may translate the downward motion to arms  303 . Because wedge  230  may be coupled to arms  303 , the downward motion of arms  303  may force a downward motion of stopper  450  (and/or) a pivoting of elongate arm  400 . The motion of wedge  230  may release spring  105 , and spring  105  may begin to wind onto hub  210 . In other words, depression of the button  101  may release spring  105 , which may cause spring  105  to retract onto hub  210  due to its bias to retract. 
     By completing a stroke of protrusion  300 , arms  303  may lower sufficiently to allow locking arms  500  to pivot and enter their corresponding notches  305  (as shown in  FIG. 7C ). Latch  250  may permanently catch the activation button  101  and wedge  230 . 
       FIGS. 8A-8D  illustrate an exemplary method of using the negative pressure pump  100 , where the entire pump device may be single-use. Pump  100  may include a spring-powered negative pressure drive assembly  200  with an attached fluid reservoir  109 . In particular, pump  100  may include an extended spring  105  attached to a plunger  107  positioned at the bottom of reservoir  109  (e.g., as shown in  FIG. 8A ). One end of a tube may be connected to manifold connection  113 , with the other tube end in fluid communication with a wound cavity, or other portion of a patient&#39;s body or target site, requiring fluid collection. Pressing a button (e.g., activation button  101 ) may release a wedge stopper in the drive assembly  200  (not shown). The spring may be charged to store energy prior to usage (e.g., during manufacturing). Accordingly, the release of the wedge stopper may cause the spring  105  to retract (e.g., as shown in  FIG. 8B ). Since spring  105  is connected to plunger  107 , the winding of spring  105  may pull plunger  107  through reservoir lumen  112  and generate negative pressure in the reservoir  109 . In at least one embodiment, one end of spring  105  may be connected to plunger  107 . In some embodiments, spring  105  may be coupled to, e.g., attached to, the plunger  107  via a cable, so that release of the spring  105  pulls a cable, and pulling of the cable attached to plunger  107  generates negative pressure in reservoir  109 . The negative pressure in reservoir  109  may permit reservoir  109  to draw and collect fluid from the target site, e.g., of a patient (e.g., as shown in  FIG. 8C ). When the reservoir  109  is full and/or the desired amount of fluid drawn into the reservoir  109 , the tubing optionally may be disconnected from manifold connection  113  (e.g., as shown in  FIG. 8D ). The entire device (pump  100 ) may then be discarded. 
       FIGS. 9A and 9B  show another exemplary device that includes a torsion spring. The torque produced by a torsion spring may increase as the spring is wound and decrease as it is unwound. However, a substantially constant force (and substantially constant negative pressure) on the piston may be desired. The tension in a wire or other type of cable may be calculated as the spring torque divided by the radius of the sheave. The wire may be captured in the grooves in the sheaves. As the spring unwinds and torque decreases, the radius of the sheave where the wire leaves the sheave may decrease. A constant force can be maintained if the ratio of spring torque to sheave diameter (where the wire exits) is maintained. 
       FIGS. 10A-10B  show arrangements using principles similar to  FIGS. 9A and 9B . Again, the figures are not exhaustive as to the mechanisms involved in how the springs may be wound or released. The figures show methods to achieve constant force from clock springs (e.g., a wound multicore ribbon cable), which may provide oscillating or fluctuating torque.  FIGS. 10A-10C  show two pulleys attached to the clock spring so that the pulleys may spin as the clock spring unwinds. A drive belt may be wrapped around the pulleys and each of two pulleys attached to variable pitch lead screws, so that the torque and motion of the clock spring may be transmitted to the two lead screws. Wires may be connected from the nuts on the lead screws to the piston, so that the force on the nuts may be applied to the piston, creating negative pressure. The force on the nuts may be proportional to the torque on the screws divided by the screw lead, and the torque on the screws may be proportional to the torque in the spring. Therefore, even in cases in which the spring torque is not constant, a constant or substantially constant force can be maintained if the ratio of the spring torque to screw lead is constant. 
       FIGS. 11A and 11B  may be similar in concept to the embodiments of  FIGS. 9A and 9B , except a clock spring may be used in place of the wire torsion spring (e.g., a helical spring), and two wires may be wrapped on the same tapered sheave. A constant force can be maintained if the ratio of spring torque to sheave diameter (where the wire exits) is maintained. 
       FIG. 12  shows an arrangement where a “knob” on the top of the device could be twisted to energize a spring or cable in the gear drive. In this concept, the plunger may start at the bottom of the reservoir, and a cable attached to the plunger may be wrapped around a pulley at the top of the reservoir. For example, the cable may be attached or fixed to a cable attachment on the pulley. As the knob is wound, the cable may wrap around the pulley. (In at least one embodiment, the cable is nearly straight rather than slack.) In this configuration, the gear drive can be separated from the reservoir. Engaging the gear drive with the pulley may wind up the cable and move the plunger. 
       FIGS. 13A-13F  show an exemplary pressure-actuated negative pressure pump, according to some embodiments of the present disclosure. In at least one embodiment, for every 1 mL of fluid, 260 mL of vapor may be generated resulting in a potential collected fluid volume of 260 mL. The fluid can be a single fluid or a mixture of different fluids that have a vapor pressure that is at or proximate atmospheric pressure (760 mmHg) plus the desired device vacuum pressure (e.g., 125 mmHg) plus mechanical losses in the system (e.g., 700 mmHg). Thus, an approximate 1585 mmHg vapor pressure may be used at 20° C. An exemplary fluid mixture that can produce this vapor pressure is n-pentane and n-butane. Many other fluids and fluid mixtures are possible too. 
     In at least one embodiment, 1 mL of the n-pentane/n-butane mixture may be placed in the positive pressure compartment  1550  of the device during manufacturing. The plunger  1560  of this compartment may be locked into place until user activation of the device. The device may be designed to handle the pressure of the mixture during the storage period, much like a hand-held cigarette lighter. At activation, the plunger  1560  in the positive pressure compartment  1550  may be pushed, increasing the volume of that compartment, and also increasing the volume of the negative pressure compartment  1555 , thus creating the desired vacuum pressure. The fluid mixture may increase in volume, e.g., 260 times (1 mL to 260 mL) as it transitions from a liquid to a vapor, all while maintaining the same vapor pressure. In such embodiments of a 250 mL reservoir vacuum device, less than 1 mL of fluid could be used to actuate the device. The device  1600  of  FIGS. 13A-13F  may include two compartments (one positive pressure  1550 , and one negative pressure  1555 ) each with a plunger  1560  connected by a rigid structure. The positive pressure compartment  1550  may contain a mixture of fluids that generate a vapor pressure causing positive pressure. The plunger  1560  may initially be locked in position at the bottom of the reservoir, as shown by  FIG. 13E . When the locking mechanism is released, the plunger  1560  moves, thus generating negative pressure in the negative pressure compartment  1555 . The plunger  1560  may move through the pressure compartments  1550  and  1555 , to a final position as shown in  FIG. 13F . Slot  1603  on device top  1601  may be a vent to atmospheric pressure. This entire device  1600  may be a disposable or reusable device. 
       FIGS. 14A and 14B  show embodiments of another exemplary negative pressure pump  1700  that includes a torque spring. Negative pressure pump  1700  may be of any suitable cross-sectional configuration, including, but not limited to, rectangular, circular, elliptical, triangular, or oval. Negative pressure pump  1700  may comprise any suitable material or materials, including, but not limited to, glass, plastic, metal, rubber, silicone, or a combination thereof. At least a portion of negative pressure pump  1700  may be opaque, transparent, or translucent. 
     Negative pressure pump  1700  may include a drive assembly housing  1701  and a reservoir  1703 . Housing  1701  and reservoir  1703  may be joined at an interface  1702 . Interface  1702  may include an overlap in a portion of housing  1701  and a portion of reservoir  1703 , as shown in  FIGS. 14A and 14B . For example, the portion of housing  1701  may be configured to fit inside and against an inner surface of the portion of reservoir  1703 . As an alternate embodiment, a portion of reservoir  1703  may be configured to fit inside and against an inner surface of housing  1701 . The concentric circumferences of housing  1701  and reservoir  1703  may form interface  1702 . 
     In at least one embodiment, housing  1701  and reservoir  1703  may be fixedly coupled so that interface  1702  is permanent. For example, housing  1701  and reservoir  1703  may be adhered together at interface  1702  via glue, other adhesive, or another method of permanent fixation. In some embodiments, pump  1700  may comprise one single integrated unit. In such a case, housing  1701  and reservoir  1703  may be formed during manufacturing as a single integral unit (e.g., from one material), rather than formed from the joining together of housing reservoir  1701  and reservoir  1703 . In some embodiments, housing  1701  and reservoir  1703  may be removably coupled so that housing  1701  may be released or separated from reservoir  1703  at interface  1702 . For example, housing  1701  and reservoir  1703  may be connected at interface  1702  via a snap-fit, friction-fit, or other releasable engagement. In such a case, housing  1701  may be released from reservoir  1703  (e.g., after reservoir  1703  is full). Then, housing  1701  may be coupled to a second reservoir and reused. 
     The drive assembly housing  1701  may include a drive assembly  1705 . The drive assembly  1705  may be activated by an actuator, e.g., button  1707 , having a lock mechanism (shown in more detail at  FIGS. 14E and 14F ). The drive assembly  1705  may include a spring storage drum  1709 , a spring  1711 , e.g., constant torque spring, and an output drum  1713  having a cable attachment point  1715 . In at least one embodiment, button  1707  may releasably lock the output drum  1713  and storage drum  1709  in a fixed position. Spring storage drum  1709  and output drum  1713  may each comprise cylindrical storage units configured and sized to contain spring  1711 . Spring  1711  may have a flat or ribbon-like structure and be made from metal, alloys, plastic, elastomers, electroactive polymers, etc., or a combination thereof. Spring  1711  may be made of a flexible material and have a thickness that allows it to unwind from output drum  1713  and onto spring storage drum  1709 . Spring  1711  may be contained on the output drum  1713  while in a default position, during manufacturing. Also during manufacturing, spring  1711  may be biased and energized by winding the spring  1711  onto the output drum  1713 . During use, spring  1711  may wind from the output drum  1713  onto the storage drum  1709  when the drums are released from their fixed position via button  1707 . 
     The drive assembly  1705  may drive the motion of a piston. For example the cable attachment point  1715  of output drum  1713  may be a connection point for cable  1717 . Cable  1717  may be any suitable flexible elongate member. For example, cable  1717  may comprise a wire, rope, cord, string, etc. Cable  1717  may extend through reservoir  1703  while at a default position. One end of cable  1717  may be attached to the cable attachment point  1715  and the second end of cable  1717  may be connected to a piston  1719 . Piston  1719  may form a seal against an inner surface of reservoir  1703 , e.g., via O-rings  1721  as shown in  FIGS. 14A and 14B , or other suitable annular seal. Piston  1719  may have a default position at the base  1723  of reservoir  1703 . For example, a bottom surface of piston  1719  may be in contact with a surface of base  1723  when piston  1719  is at its default position. Accordingly, at a default position from manufacturing, cable  1717  may extend through reservoir  1703 : one end of cable  1717  may be connected to the output drum  1713  at the drive assembly  1705  and the other end may be connected to piston  1719  at the base  1723  of reservoir  1703 . During pump usage, rotation of the output drum  1713  may cause cable  1717  to wind onto an axle of output drum  1713  and draw piston  1719  through the length of reservoir  1703 . In other words, cable  1717  may retract and cause piston  1719  to move from the base  1723  of reservoir  1703  towards the drive assembly  1705 . The piston  1719  may move through a lumen of reservoir  1703 , along a longitudinal axis defined by reservoir  1703  (e.g., where the longitudinal axis may be analogous to axis x of  FIG. 1 ). 
     The base  1723  of reservoir  1703  may include a connector  1725  configured to receive a manifold, e.g., a manifold of a patient therapy unit. Connector  1725  may include a valve to control pressure, e.g., so that pump  1700  does not immediately “lose” pressure, even if a manifold is not yet attached to the connector. The valve may include a one-way valve, configured to permit fluid into (but not out of) reservoir  1703 . When the piston  1719  moves through the reservoir  1703 , fluid may be drawn from the patient therapy unit into the reservoir  1703 . Piston  1719  may form a barrier between the fluid of the reservoir  1703 , and the drive assembly  1705 . 
     Pump  1700  may be assembled during manufacturing such that spring  1711  is energized and piston  1719  is at the base  1723  of reservoir  1703 . The spring output drum  1713  may be locked in position (described in connection to  FIGS. 14E and 14F ) such that cable  1717  is slack. When the pump  1700  is ready for use, a user may attach a manifold to the connector  1725  and press button  1707 . Pressing button  1707  may unlock drive assembly  1705 , causing torque on the output drum  1713  to create tension in cable  1717 . The tension in cable  1717  may cause an upward force on the piston  1719 , drawing the piston  1719  through the reservoir  1703 . The force may remain constant as the spring  1711  unwinds and the cable  1717  winds onto output drum  1713 . The motion of the piston  1719  may create a constant negative pressure and draw fluid from the manifold through the valve in connector  1725  into the reservoir  1703 . When the reservoir  1703  is full and/or the desired amount of fluid removed from the target site, a user may disconnect the manifold from connector  1725 . 
       FIGS. 14C and 14D  provide exploded views of an exemplary drive assembly of the negative pressure pump of  FIGS. 14A and 14B . As shown in  FIGS. 14C and 14D , drive assembly housing  1701  may include two discrete halves, each half having an outer surface  1800  and an edge surface  1802 . The halves of drive assembly housing  1701  may be joined together at their edge surfaces  1802  by mating housing fixtures  1803   a  in each half, or via any other suitable method of permanent or releasable engagement. Drive assembly housing  1701  may also include a discrete, compressible member  1801 . An outer surface of member  1801  may be accessible to a user. Meanwhile, an inner surface of member  1801  may abut button  1707 , e.g., inaccessible to a user. Drive assembly housing  1701  may include fixtures  1803   a ,  1803   b , and  1803   c  inside the inner surface of drive assembly housing  1701 . Fixtures  1803   a  may align the two halves of drive assembly housing  1701  and assist in securing the two halves to one another. Fixtures  1803   b  may further position the two halves of drive assembly housing  1701 , position storage drum  1709  and output drum  1713 , and/or provide structural support to drive assembly housing  1701 . Fixtures  1803   c  (shown in  FIG. 14C ) may contain spindles  1805  of storage drum  1709  and output drum  1713 . The fixtures  1803   b  and  1803   c  may be configured to permit the spindles  1805  to rotate, such that storage drum  1709  and output drum  1713  may spin freely once button  1707  is activated. Button  1707  may include a head portion  1807  abutting the inner surface of member  1801 , and a tail portion  1809  extending, at least, the length of output drum  1713 . In at least one embodiment, tail portion  1809  may comprise an elongate member with one or more fins or ribs extending from a central, longitudinal axis of the tail portion  1809 . 
       FIGS. 14E and 14F  provide views of exemplary drive assembly locks of the negative pressure pump of  FIGS. 14A and 14B . In the illustrated embodiments, tail portion  1809  of button  1707  includes a button lock tab  1811 . The button lock tab  1811  may extend perpendicular to the longitudinal axis of the tail portion  1809  and contact the output drum  1713 .  FIG. 14E  further provides an embodiment where the tail portion  1809  of button  1707  may include a button position detent  1813 , which may extend along the longitudinal axis of the tail portion  1809  and extend into a cavity formed by a fixture  1803   a  of drive assembly housing  1701 .  FIG. 14F  provides an embodiment including button position detents  1813  at a head portion  1807  of button  1707 . Button position detent(s)  1813  may steady or maintain the position of button  1707 . For example as shown in  FIG. 14E , button  1707  may be positioned inside drive assembly housing  1701  via member  1801  engaging head portion  1807  of button  1707 , and the fixture  1803   c  of the drive assembly housing  1701  interior containing button position detent  1813  at the tail portion  1809  of button  1707 . 
     In at least one embodiment, output drum  1713  may include lock rib(s)  1815  which may overlap and abut button lock tab  1811 . For example, output drum  1713  may comprise a cylinder with a base  1817 . The base  1817  may be positioned perpendicular to the longitudinal axis of the cylinder. The base  1817  may contain rib(s), fins, or protrusion(s) which may form lock rib(s)  1815 . In at least one scenario, the lock ribs  1815  may be positioned such that they are not on surface(s) of the output drum  1713  that contact the spring  1711 . The lock ribs  1815  may be at equal intervals extending from the center of output drum  1713  (as shown in  FIG. 14E ) or along the perimeter of base  1817  (as shown in  FIG. 14F ). At a default position, the button lock tab  1811  may maintain the position of output drum  1713  by abutting output drum lock ribs  1815 . A user may operate pump  1700  by pressing member  1801  (of  FIG. 14C  or  FIG. 14D ), thus shifting tail portion  1809  of button  1707  in the direction of housing fixture  1803   c . The movement of tail portion  1809  towards housing fixture  1803   c  may shift button lock tab  1811  such that button lock tab  1811  no longer abuts output drum lock rib  1815 . This motion may release output drum  1713  to rotate due to the pre-set bias of spring  1711 . Rotation of output drum  1713  retracts cable  1717  and piston  1719  (of  FIGS. 14A and 14B ), allowing fluid to be drawn into reservoir  1703 . 
     In at least one embodiment, output drum  1713  may include a single lock rib  1815 . In some embodiments, output drum  1713  may include a plurality of lock ribs  1815 , for example eight equally spaced ribs about output drum  1713  (as shown in  FIG. 14E  or  FIG. 14F ). The plurality of lock ribs  1815  may provide manufacturing tolerance during manufacturing of pump  1700 . For example, multiple lock ribs  1815  permit output drum  1713  to rotate only until button lock tab  1811  abuts at least one drum lock rib  1815 . The more lock ribs  1815  on output drum  1713 , the less output drum  1713  is able to rotate before button lock tab  1811  contacts a lock rib  1815 . 
     In at least one embodiment, pump  1700  is configured to be activated only once. For example, pump  1700  may be structured such that button  1707  does not re-engage surface  1801  and button lock tab  1811  does not re-engage rib  1815 . In some embodiments, pump  1700  may be activated intermittently. For example, button  1707  may be biased to contact surface  1801 , for instance, using a spring positioned at tail portion  1809 . In one such scenario, pump  1700  may draw fluid into reservoir  1703  only when button  1707  is pressed. For instance, while button  1707  is pressed, button lock tab  1811  may release output drum  1713  to rotate, unwinding spring  1711  and retracting cable  1717 . When button  1707  is not pressed, button lock tab  1811  may again abut an output drum lock rib  1815  and stop the rotation of output drum  1713  because button  1707  may be biased to contact surface  1801 . Multiple drum lock ribs  1815  on output drum  1713  may ensure that output drum  1713  does not turn a full rotation when button  1707  is not pressed. This embodiment provides the capability for a user to start, stop, and restart fluid withdrawal into reservoir  1703 , rather than only providing control regarding when to start fluid withdrawal. In at least one embodiment, the rate of rotation of output drum  1713  may be controlled, e.g., by a graded button lock tab  1811  that may vary the rotation rate of output drum  1713 , depending on how far button  1707  is pressed. Such a case provides the user with the ability to control the rate of retraction of fluid into the lumen of the reservoir. In some embodiments, the retraction of cable  1717  may occur at a constant rate, such that fluid may be drawn into the reservoir at a constant rate. 
     As shown in  FIGS. 14F and 14G , pump  1700  may include a spring winding gear  1819  and gear access hole  1821 . The spring winding gear  1819  and gear access hole  1821  may permit initial activation of pump  1700 , intermittent fluid withdrawal, or re-use of pump  1700 . For example, spring winding gear  1819  and gear access hole  1821  may be used to wind the spring  1711  to the output drum  1713  and thus energize spring  1711 . As context, spring  1711  may be wound on storage drum  1709  at a default state, prior to manufacture. The spring  1711  may be un-energized when it is on the storage drum  1709 . The spring  1711  may be energized when it is wound from the storage drum  1709  to the output drum  1713  during manufacture, e.g., by using spring winding gear  1819  engaged with a pinion  1823  through gear access hole  1821 , as described further below. 
       FIG. 14F  illustrates an exemplary embodiment where spring winding gear  1819  may be positioned on the base  1817  of output drum  1713 . In at least one embodiment, the spring winding gear  1819  may be coaxial with the output drum  1713  and have a smaller radius than output drum  1713 . Spring winding gear  1819  may include teeth  1820  along its outer circumference. 
     Gear access hole  1821  may be an opening in drive assembly housing  1701  (as shown in  FIGS. 14F and 14G ). The gear access hole  1821  may be offset from the central axis and a majority of the spring winding gear  1819  (as shown in  FIG. 14G ), such that a pinion  1823  inserted through the gear access hole  1821  may engage spring winding gear  1819 . In particular, as shown in  FIGS. 14H and 141 , pinion  1823  may comprise a cylindrical rod with interlocking teeth  1825  along at least a portion of its outer circumference. The interlocking teeth  1825  of pinion  1823  may engage teeth  1820  of the spring winding gear  1819 . In at least one embodiment, turning the pinion  1823  clockwise while its interlocking teeth  1825  are engaged with teeth  1820  may wind the spring  1711  from the storage drum  1709  to the output drum  1713 . 
     As shown in  FIG. 141 , a fixture  1831  may be used to guide the pinion  1823  into gear access hole  1821 , maintain the position of pinion  1823 , and keep the position of pinion  1823  square with spring winding gear  1819 . While  FIG. 141  shows the pinion  1823  being turned by hand, any variety of winding methods may be used, including motorized winding mechanisms. 
     In at least one embodiment, the gear access hole  1821  may be accessible only during factory assembly of pump  1700  (e.g., inaccessible during operation by a user to remove fluid). For instance, gear access hole  1821  may be accessible only before the drive assembly housing  1701  is assembled with the reservoir  1703 . In this way, the spring  1711  may only be wound during factory assembly, rather than by an end user before, during, or after user of the pump  1700 . In one scenario, gear access hole  1821  may be sealed before pump  1700  leaves the factory site. 
     As shown in  FIG. 14J  (which depicts front and rear views of three pumps), negative pressure pump  1700  may be any variety of sizes, e.g., a 500 mL size illustrated by pump  2000   a  and pump  2000   b , a 300 mL size illustrated by pump  2100   a  and pump  2100   b , and a 150 mL size illustrated by pump  2200   a  and pump  2200   b.    
     The description above and examples are illustrative, and are not intended to be restrictive. One of ordinary skill in the art may make numerous modifications and/or changes without departing from the general scope of the invention. For example, and as has been described, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. Additionally, portions of the above-described embodiments may be removed without departing from the scope of the invention. In addition, modifications may be made to adapt a particular situation or aspect to the teachings of the various embodiments without departing from their scope. Many other embodiments will also be apparent to those of skill in the art upon reviewing the above description. 
     Additionally, while a number of objects and advantages of the embodiments disclosed herein (and variations thereof) are described, not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the systems and techniques described herein may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.