CA2129174C

CA2129174C - Break-away safety shield for needle cannula

Info

Publication number: CA2129174C
Application number: CA002129174A
Authority: CA
Inventors: Lawrence Partika
Original assignee: Becton Dickinson and Co
Current assignee: Becton Dickinson and Co
Priority date: 1993-08-06
Filing date: 1994-07-29
Publication date: 1998-08-25
Anticipated expiration: 2014-07-29
Also published as: US5344408A; JPH07148176A; DE69410185T2; ES2116536T3; DE69410185D1; EP0638326B1; EP0638326A1; CA2129174A1; JP2709270B2

Abstract

A safety shield assembly is provided for safely enclosing a needle cannula. The safety shield assembly includes an inner shield that is slidably movable along the needle cannula. The inner shield includes a locking structure which locks the inner shield with respect to the distal end of the needle cannula. The safety shield assembly alsoincludes an outer shield that is in releasable engagememt with the inner shield. The outer shield will separate from the inner shield in response to excessive force exerted thereon, and hence avoids failure of the structure locking the inner shield to the needle cannula.

Description

-~ ~ 2 ~ 1 7 4 BREAK-AWAY SAFETY S~TF~In FOR NEEDLE CANNULA

1. Field of the Invention. The subject invention relates to safety shields that are axially movable along a needle cannula ~om a proxlmal position where the tip of the needle cannula is exposed to a distal position where the tip of the needle cannula is protectively enclosed.

2. Descril~tion of the Prior Art. The prior art hypodermic syringe in~ des an elongate barrel having an open proxilllal end, a distal end and a fluid receiving chamber therebetween. The distal end of the prior art syringe barrel defines a tip having a fluid passage ~Ytçndin~ thel~llllough and commllnic~tin~ with the cl-~llber.
A plunger may be slidably disposed in the open pro~ilnal end of the syringe barrel for urging fluid through the passage in the tip.
A needle cannula can be mounted to the distal end of the prior art syringe barrel. The needle cannula has a ploxilllal end, a sharp distal end and a lumen eYtçndin~ therebetween. The plo~ilnal end of the needle cannula is secured to a mounting hub that can be engaged on the distal end of the syringe barrel such that the passage through the distal end of the syringe barrel collllllulficates with the lumen through the needle c~nnlll~
The prior art needle cannula is prepackaged in a needle shield to prevent aceidçnt~l needle sticks prior to the first intçntled use of the needle c~nnlll~ The shield can be removed a~er the needle cannula has been mounted to the syringe barrel and immediately prior to use. A health care worker then uses the unshielded needle cannula and hypodermic syringe to either inject medication into a patient or to withdraw bodily fluid for subsequent diagnostic evaluation.
Needle sticks that occur before the hypodermic syringe is used create less risk of infection because the needle is sterile. However, needle sticks occurring a~er the hypodermic syringe has been used pose a greater risk of infection or disease tr~nsmi~ion. As a result, the prior art incllldes shields for protectively enclosing at least the tip of the used needle c~nnlll~

-2- ~ g17~

Some prior art shields define a separate cap that can be telescoped in a prox~lllal direction over the used needle sanmll~ However, separate caps often are lost or misplaced in the hectic en~irc,nlllt;.ll of a medical facility. Additionally, the movelllenl of the used needle cannula and the separate cap toward one another creates the potential for an accid~nt~l needle stick.
The prior art also inc1~des needle shields that cannot be misplaced and that areint.on-lec~ to avoid the movement of one hand toward the other during a shielding operation. Needle shields of this type typically are releasably relained near the ploxilllal end of the needle cannlll~ The distal end of the needle cannula is exposed and can be used in the .,l~dald manner. A~er use, however, the prior art needle shield can be slid distally along the needle cannula and into a shielding position.
The prior art needle shield of this type typically in~ des means for lockingly ing the needle cannula when the distal tip has been reached. The locking is intçntlec~ to prevent further movement of the prior art shield in either a distal direction or a plo~-lllal direction. Distally directed movement of the locked prior art needle shield in some prior art devices is prevented by frictional or spring biased engagement of the shield with the smooth outer cylindrical surface of the needle c~nn~ Prior art shields of this general type are shown, for example, in: U.S. Patent No. 4,929,241;
U.S. Patent No. 5,053,017 and WIPO Publication PCT/CA90/00031. Other prior art needle shields lockingly engage a discontinuity along the length of the needle cannula as shown in U.S. Patent No. 4,846,811.
Prior art needle shields of the type described above can be designed to exert significant locking forces against the exterior surface of the needle cann--l~ However, all such prior art needle shields will have some limit to their locking force. The locking force will be limited by the design and will vary with the dimensional tolerances of the shield components. Thus, separation of the needle shield from the needle cannula can occur if the forces exceed the ~ .X;Il~ l locking force between the prior art needle shield and the needle c~nn-ll~ Needle shields desirably should be as small as possible. However, smaller needle shields will exert lower gripping forces, and hence are more easily separated from the needle c~nn~
Separation of a prior art needle shield from a needle cannula may not require abusive use of the hypodermic syringe. Rather, separation can occur inadvertently if a health care worker exerts too much force in an effort to shield the needle cannlll~
Separation of the needle shield is accolllpal-ied by a sudden recognizable reduction in engagement forces between the shield and the needle cann~ . The automatic reaction -3~ 1 7 4 ~

by the health care worker who inadvertently caused the separation is to attempt an immediate re-shielding by urging the shield back in a pro~inlal direction. This is precisely the movement that shields of this type are intçnrled to avoid. Under these circl.m.et~nces, the re-shielding attempt will be an abrupt reactionary movement that can easily generate an accidental needle stick with a potentially co~ ted needle.

SUMMARY OF THE INVENTION
The subject invention is directed to a safety shield assembly. The safety shieldassembly in~ des a rigid inner shield that slidably moves in response to a force Fs from a proxilllal position on a needle cannula to a distal position where the tip of the needle cannula is safely shielded. The inner shield may include means for sensing the distal end of the needle cannula and means for securely gripping the needle cannula when the distal tip of the needle cannula has been ehielded The locked inner shield may be prevented from a return or pro~ al mov~lllelll along the needle c~nn~ , and will move further distally only in response to a relatively great failure force Ff.
The safety shield assembly also in(~ludes an outer shield ~ub~ lly surrounding the inner shield. The outer shield is releasable engaged with the inner shield, and can be separated or broken from the inner shield in response to a breakaway force Fb The inner and outer shields are designed such that the breakaway force, Fb, is greater than the force Fs required to slide the inner safety shield along the needle c~nmll~ but less than the force Ff required to separate the inner shield from the needle c~nnlll~
In most instances the health care worker will never know that the safety shield assembly in~ ldes two colllponelll~. More particularly, the health care worker will merely grasp the outer shield in a standard manner, and will exert a force equal or slightly greater than Fs to slide the inner shield distally along the needle c~nnul~ This force exerted by the health care worker typically will be less than the breakaway force Fb required to separate the outer shield from the inner shield. However, if the health care worker inadvertently or incolle~illy exerts an excessive force on the safety shield assembly, the outer shield will separate from the inner shield when the breakaway force Fb is reached and well prior to the time when the failure force Ff is reached.
Thus, such excessive force will merely separate the outer shield from the inner shield after locking has been achieved. The inner shield will remain safely in place insurrounding relationship to the distal tip of the needle c~nnlll~

BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of a hypodermic syringe and a safety shield in accordance with the subject invention.
Fig. 2 is a cross-sectional view taken along line 2-2 in Fig. 1.
Fig. 3 is a cross-sectional view similar to Fig. 2, but showing the needle cannula and safety shield assembly in a fully shielded condition.
Fig. 4 is a cross-sectional view similar to Figs. 2 and 3, but showing the outershield partly cli~eng~ged from the inner shield.
Fig. 5 is a perspective view similar to Fig. I but showing the outer shield fully sep~ated from the inner shield.
Fig. 6 is a cross-sectional view similar to Fig. 2, but showing a second embodiment of an inner shield.
Fig. 7 is a cross-sectional view showing the inner shield of Fig. 6 shielding the cannula tip of the outer shield partially ~ er~ged from the inner shield.
Fig. 8 is a perspective view, partly in section, showing a third embodiment of inner and outer shields disposed in the retracted needle tip exposing position on a needle c7~nn~
Fig. 9 is a cross-sectional view showing a fifth embodiment of the inner shield and outer shields.
Fig. 10 is a cross-sectional view similar to Fig. 2, but showing an ~lt~rll~te engagement between the inner and outer shields.
Fig. 11 is a cross-sectional view similar to Fig. 10, but showing another alternate ~ng~ment between the inner and outer shield.
Fig. 12 is a cross-sectional view subst~nti~lly similar to the embodiment of Fig.
10 with frangible links connecting the inner shield and the outer shield.
Fig. 13 is a cross-sectional view ~ubslalllially similar to the embodiment of Fig.
10 with frangible sheet material com eclillg the inner shield and the outer shield.
Fig. 14 is a cross-sectional view subst~nti~lly similar to the embodiment of Fig.
10 with the addition of a flexible link connecting the inner shield and the hub.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A safety shield assembly in accordance with the subject invention is identified generally by the numeral 10 in Figs. 1-5. Safety shield assembly 10 is slidably disposed on a needle cannula 12 having a pr~,x.",al end 14, a sharp distal tip 16 and a lumen 5- ~ 7 ~

~.xt~n-lin~ thelebc;lweel-. Plu~mal end 14 of needle cannula 12 is securely mounted to a hub 18 which is threadedly engageable with a hypodermic syringe 20.
Safety assembly 10 initially is releasably engaged or positioned near proxilllalend 14 of needle cannula 12. However, safety shield asse l-bly 10 can be slid distally in response to force Fs exerted thereon by a thumb and forefinger as shown in Fig. 1.
Safety shield assembly 10 inchldes an inner shield 22 and an outer shield 24 releasably engaged over the inner shield 22. The inner shield may take any of several di~relll forms. As shown in Figs. 2-4, inner shield 22 is ~ubs~ lly similar to the shield depicted in the above-referenced U.S. Patent No. 4,929,241. More particularly, the pro~illlal end of inner shield 22 defines a base 26 slidably mounted over needle cannula 12. Lever arms 28 and 30 project distally from base 26 and include inwardly directed ends 32 and 34 respectively. As shown in Fig. 2, ends 32 and 34 are in sliding engagement with the outer cylindrical surface of needle cannula 12. In this condition lever arms 28 and 30 les~ec~ively are preloaded away from needle cannula 12. Lever arms 28 and 30 further include locking teeth 36 and 38 respe~iLively which project inwardly toward needle cannula 12 from locations intermediate the les~ec~ive lengths of lever arms 28 and 30. Locking teeth 36 and 38 are dimensioned to be spaced from needle cannula 12 when ends 32 and 34 of leverarms 28 and 30 are in sliding engagement with needle cannula 12.
Outer shield 24 is pl~r~l~bly a generally cylindrical structure having opposed plu~llal and distal ends 40 and 42 respectively. Outer shield 24 prere ~hly defines an axial length greater than the collesl)ol1dil-g axial length of inner shield 22. Thus, inner shield 22 is subst~nti~lly in~cces~ihle, and outer shield assembly 24 will define the region of all manual contact with shield assembly 10.
Pluxi~al end 40 of outer shield 24 incll1des a radially inwardly P.~t~n~ling flange 44 which is dimen~ioned to releasably engage radial outer portions of base 26 at the proxilllal end of inner shield 22. Flange 44 will separate from inner shield 22 if relative forces be~ween inner and outer shields 22 and 24 approach the breakawayforce, Fb.
Distally directed forces of Fs exerted on outer shield 24 will cause an initial sliding movement of the entire shield assembly 10 distally indicated as direction "A" in Fig. 1, without sepalating outer shield 24 from inner shield 22. Sufficient distal movement of shield assembly 10 will cause ends 32 and 34 of lever arms 28 and 30 to pass beyond distal end 16 of needle cannula 12. The preload referred to above will cause arms 28 and 30 to resiliently return toward an undeflected condition, such that ~ ~ ~ 9 ~ ~ ~

ends 32 and 34, protectively enclose distal tip 16 of needle cannula 12 to prevent pru~ al movement of the needle shield, and such that teeth 36 and 38 glippingly engage the outer circull~lelllial surface of needle cannula 12 to help prevent further distal movement of the needle shield.
Most health care workers will detect the locking of shield assembly 10 to needle cannula 12 and will stop their exertion of axial forces thereon. However,inexperienced health care workers or workers distracted by exigencies of a medical facility may continue to exert axial forces on shield assembly 10 after the Fig. 3 locked engagement has been achieved. Inner shield 22 will resist distally directed force up to a force Ff beyond which failure of the locked eng~gem~nt to needle cannula 12 will occur. However, the breakaway force Fb between inner and outer shields 22 and 24 is less than failure force Ff. Hence, continued exertion of distally directed axial force on outer shield 24 after the locked Fig. 3 position has been achieved will merely cause fiange 44 to (li~çn~ge from inner shield 22 as shown in Fig. 4. Continued force will cause the complete separation of outer shield 24 from inner shield 22 as shown in Fig.
5. However, inner shield 22 will remain protectively engaged in shielding relationship to distal point 16 of needle cannula 12 subst~nti~lly as shown in Figs. 3 and 4. Thus, even if the health care worker appreciates his or her error and a~ell~ls to re-shield needle cannula 12, an accidental needle stick will be positively prevented by the continued glipping engagement of inner shield 22 with needle cannula 12.
The inner shield can take many other optional configurations for protectively enclosing distal tip 16 of needle cannula 12. For example, in Fig. 6, a shield assembly 45 having an inner shield 46 subst~nti~lly as shown in WIPO Publication No.
PCT/CA90/0031. More particularly, inner shield 46 in Figs. 6 and 7 incl~ldes an inner shield housing 48 which colllains a wedge actuator 50 in clipping engagement over needle cannula 12. A biased actuator 52 also is slidably mounted to needle cannula 12 in a position distally of wedge actuator 50. Clamp 54 is in sliding engagement with needle cannula 12 at a first location intermediate wedge actuator 50 and biased actuator 52, and at a second position distally of biased actuator 52. Clamp 54 also is engaged by wedge actuator 50. A coil spring 56 extends belween biased actuator 52 and clamp 54. Spring 56 will cause clamp 54 to rotate counter clockwise as shown in Fig. 7. This rotation will cause the distal end of clamp 54 to protectively enclose distal tip 16 of syringe barrel 12, and will ~imlllt~neously cause proximal portions of clamp 54 inside aperture 55 in the clamp to grippingly engage needle cannula 12.Wedge actuator 50 will drive clamp 54 into tighter clamping engagement in response 7 ~ P-2800 to distally directed axially forces exerted on inner shield 46. As noted above, some force Ff will exist beyond which failure of inner shield 46 will occur. Outer shield 58 prt;venls such failure from occurring. More particularly, outer shield 58 subst~nti~lly completely encloses inner shield 46 to prevent direct manual contact with any portion of inner shield 46. Outer shield 58 also inrll~des a ridge 60 for releasably griping the prox""al end of inner shield 46. Outer shield 58 will separate from inner shield 46 in response to a breakaway force Fb which exceeds the force required to slidably move the entire shield assembly along needle cannula 123, but which is less than the failure force Ff. Thus, the shield assenlbly shown in Figs. 6 and 7 will function subst~nti~lly the same as the shield assembly of Figs. 2-4 despite the significantly dirrerentconstruction of the inner shield.
A third safety shield assembly that will pe~m similarly to the shield assemblies of Figs. 1-7, is shown in Fig. 8, and is identified generally by the numeral 61.
Shield assembly 61 incl~ldes an inner shield 62 subsl~,lially as disclosed in U.S. Patent No. 5,053,017. More particularly, inner shield 62 is ~"ped and formed from a unitary strip of spring metal and incl~ldes a proxi",ally disposed base 64 having an ape,lu,e 65 for slidably en~gin~ needle cannula 12. Arms 66 and 68 extend from base 64 and include ends which are in sliding contact with the needle c~nn~ Arm 66 is preloaded and biased away from needle cannula 12. Then, when the end of arm 66 aligns with distal tip 16 of needle cannula 12, arm 66 will resiliently return toward an undeflected condition, such that the end thereof protectively encloses distal tip 16 of needle cannula 12. Sim.llt~neously, needle cannula 12 will be securely gripped by base 64 in the area of aperture 65. Shield assembly 61 further inrl~ldes an outer shield 70 having inwardly facing cantilever members 71 capable of releasably ~ng~gin~ the inner shield 62. Outer shield 70 will separate from inner shield 62 in response to a breakaway force Fb which is greater than the force Fs required to slide inner shield 62 along needle cannula 12. In this embodiment the breakaway force is the force required to deflect the cantilevers 71 as they pass over the largest portion of the inner shield.
However, as in the previous embodiment, breakaway force Fb to separate outer shield 70 from inner shield 62 is less than the force Ff that will cause failure of inner shield 62 on needle cannula 12.
The embodiments of the subject invention described and illustrated above all rely upon an inner shield 22, 46, 62 grippingly ç~ing a needle c~nn..l~ Some prior art safety shields attempt to enhance shielding effecliveness by providing physical structure to help prevent further distal motion of the shield, such as a disconli"uily along the length of the needle c~nn.ll~ or a notch may be formed in a needle cannula for gripping engagement by locking means on a shield. Also, a flexible link of plastic may connect the shield and the hub, as illustrated in Fig. 14. Similarly, a bead of material may be disposed at a selected axial position along the needle cannula for engagement by the shield. These structures on the needle cannula are intçn-led to prevent complete separation of the shield thelerl~lll. However, as noted above, all such shields will fail in response to some application of excess force even if the shield does not move from the needle the needle may be pulled out of the needle hub or the needle hub may be pulled out of the syringe barrel. The colllbinalion of inner and outer shields as desclil,ed above can be applied to a needle cannula having engagement disco~ ies thereon. For example, a needle shield assembly 75 is shown in Fig. 9,and includes an inner shield 76 subst~nti~lly similar to the shield shown in U.S. Patent No. 4,8456,811. Inner shield 76 inr,h~des an annular engagement groove 78 for ~gin~ a bead 80 on the needle cannula 12. Shield assembly lOc further inrl~ldes an outer shield 82 releasably engaged with inner shield 76. As in the previous embodimrnt~, outer shield 82 will separate from inner shield 76 in response to abreakaway force Fb which is greater than the force Fs required to slide inner shield 76 along needle cannula 12, but less than the failure force Ff required to separate inner shield 76 from annular bead 80 on needle cannula 12.
The embodiments described and illustrated above all inr,hlded engagement means on the ploxilllal end ofthe outer shield for releasably en~ing the plo~illlal end of the inner shield. Variations of this engagement are possible, and are shown sçhrm~tically in Figs. 10 and 11. More particularly, Fig. 10 shows a shield assembly 83 having an inner shield 84 with an annular groove 86 intermediate its length. Inner shield 84 may include locking means as shown in some of the above described embodiments. Shield assembly 83 further includes an outer shield 88 having an inwardly extçndin~ annular bead 90, or separate inwardly directed projections, releasably engaged in annular groove 86 of inner shield 84. As in the previous emborlim~nts, outer shield 88 will separate from inner shield 84 in response to a breakaway force Fb which is greater than the force Fs le4-1iled to slide the inner shield 84 along the needle cannula 12, but less than the failure force Ff at which the locking structure of the inner shield 84 to the needle cannula fails.
Fig. 11 shows a shield assembly 91 where an inner shield 92 inrhldes an annular locking groove 94 on an inwardly facing surface 96 near distal end 98. An outer shield 100 has a proximally projecting sleeve 102 with a locking bead 104 for 9 ~$~4 releasable engagement in groove 94 of inner shield 92. As in the previous embodiments7 outer shield 100 will separate from inner shield 92 in response to a breakaway force Fb which is greater than the force Fs required to slide inner shield 92 axially along needle cannula 12, but less than the force Ff at which the lockingmer~ni~m of inner shield 92 fails.
It is also within the purview of the instant invention to include connecting theinner shield and the outer shield by a frangible link or a plurality of frangible links, as illustrated in Fig. 12. Fig. 12 shows shield assembly 106 consis~ g of inner shield 108 connected to outer shield 110 through integrally molded frangible links 112 and 114.
The links may be formed by integrally molding the inner and outer shields at the same time. The frangible connection may be provided by connecting the inner and outershields with adhesive-backed l~min~ted sheet m~t~.ri~l, such as paper label stock or plastic sheet, dç~igned to fracture at a preselected Fb. Fig. 13 illustrates such an embodiment. In Fig. 13 shield assembly 120 consists of inner shield 122 and outer shield 124 connected by l~min~ted adhesive-backed paper strips 126 and 128. Flexible links may also be molded on one of the shields and attached to the other shield using adhesive, me~ n;c~l joining, ultrasonic welding or the like. Fig. 14 illustrates shield assembly 134 which is identical in all respects to shield assembly 83 of Fig. 10, except that in the shield assembly of Fig. 14 inner shield 84 is connected to needle hub 36 through a flexible link 138. In this embodiment flexible link 138 is made of plastic and is connected to inner shield 84 at 140 and to needle hub 136 at 142. Flexible link 138 is long enough to allow the inner shield to extend distally to cover needle tip 16 but not far enough to allow inner shield 84 to move distally past distal tip 16 of needle 12.

Claims

1. A safety shield assembly comprising:
a needle cannula having a proximal end, a distal end and a lumen therethrough;
an inner shield slidably movable along said needle cannula from a proximal position where said distal end of said needle cannula is exposed to a distal position where said proximal end of said needle cannula is shielded;
locking means for helping to prevent said inner shield from moving distally with respect to said needle cannula when said inner shield is in said distal position on said needle cannula;
an outer shield disposed in surrounding relationship to said inner shield; and means for selectively disengaging said outer shield from said inner shield in response to a distally directed force of a selected magnitude exerted thereon, said distally directed force being less than the force to move said inner shield distally of the needle cannula, after said inner shield is in said distal position.

2. The safety shield assembly of Claim 1, wherein said inner and outer shields each include opposed proximal and distal ends, said outer shield including deflectable locking means adjacent said proximal end for releasably engaging said proximal end of said inner shield.

3. The safety shield assembly of Claim 1, wherein said inner shield includes opposed proximal and distal ends and an engagement deformation therebetween, said outer shield including an engagement deformation releasably engageable with said engagement deformation of said inner shield.

4. The safety shield assembly of Claim 3, wherein said engagement deformation of said inner shield comprises a recessed annular deformation therein, and wherein said engagement deformation of said outer shield is a projection releasably engageable with said recessed annular deformation of the inner shield.

5. The safety shield assembly of Claim 1, wherein the inner shield includes opposed proximal and distal ends and opposed inner and outer surfaces, said inner shield including an engagement deformation on portions of said inner surface adjacent said distal end, said outer shield including opposed proximal and distal ends, said outer shield further comprising engagement means projecting proximally from said distal end for engagement with said engagement deformation of said inner shield.

6. The safety shield assembly of Claim 5, wherein the engagement deformation of said inner shield comprises an annular groove, the engagement means of said outer shield comprising a deflectable engagement sleeve projecting proximally from said distal end of said outer shield for releasably engaging the engagementgroove of said inner shield.

7. The safety shield assembly of Claim 1, wherein said needle cannula includes a locking deformation intermediate said proximal and distal ends thereof, said locking means of said inner shield being lockingly engageable with said locking deformation on said needle cannula.

8. The safety shield assembly of Claim 1 wherein said means for selectively disengaging said outer shield from inner shield includes a frangible link connecting said outer shield to said inner shield.

9. The safety shield assembly of Claim 8 wherein said frangible link is integrally molded to one of said shields.

10. The safety shield assembly of Claim 8 wherein said frangible link comprises an adhesive backed sheet connected by said adhesive to said inner shield and said outer shield.

11. The safety shield assembly of Claim 1 wherein said locking means is disposed in said inner shield for locking said inner shield to said cannula.

12. The safety shield assembly of Claim 11 wherein said locking means includes a deformation on said cannula.

13. The safety shield assembly of Claim 12 wherein said deformation is an outwardly extending projection.

14. The safety shield assembly of Claim 1 wherein said needle cannula includes a needle hub having a passageway therethrough at said proximal end of said cannula, said lumen and said passageway being in fluid communication.

15. The safety shield assembly of Claim 14 wherein said locking means includes a flexible link between said needle hub and said inner shield.

16. The safety shield assembly of Claim 1, wherein locking means includes sensing means for sensing said distal end of said needle cannula and for locking said inner shield to said needle cannula upon said sensing of said end of said needle cannula by said sensing means.

17. The needle shield assembly of Claim 16, further comprising biasing means for moving said locking means relative to said needle cannula upon sensing of the end of said needle cannula by said sensing means.