turning now to the drawings , fig1 shows a hotpack , generally designated as 11 , which is utilized to apply moist heat to a body , such as , for example , a human body 12 . hotpack 11 is formed by adjacent sheets 14 and 15 , as best shown in fig4 of porous , or liquid permeable , material , such as cotton duct , for example , which sheets are joined , as by sewing , for example , at the outer edges 16 ( the sheets may also be folded to avoid the need for sewing the edges whenever possible ) to form an outer cover 18 . in addition , as shown in fig1 the sheets forming the outer cover 18 may be joined along juncture lines 20 and 21 ( normal to one another and extending from side to side of the sheet ) to form pockets 23 , which pockets are essentially enclosed spaces for receiving heat retaining material 25 therein , as best shown in fig4 . the outer cover 18 is chosen so that when the hotpack is immersed in a hot liquid , such as water , the liquid passes through the cover and into contact with the heat retaining material , which may be , for example , clay , and preferably bentonite . the heat retaining material is chosen so as to be raised in temperature when subjected to a heated medium , such as hot water , and then slowly release the heat when brought to a medium of lower temperature , as is well known . a temperature monitor , or dot , 27 is mounted on cover 18 by means of a collar securing portion 29 having shoulders 31 and 32 engaging opposite sides of sheet 14 . as shown , monitor 27 includes an externally visible indicating portion , or face , 34 and a sensing portion 36 which extends away from the surface and well into the heat retaining material 25 , as again best shown in fig4 . a plurality of loops 38 are attached to each of the corners of cover 18 for facilitating handling of the hotpack , particularly when heated . while only one temperature monitor 27 is shown , it is to be appreciated that a plurality could be utilized , if desired . referring to fig2 face 34 of the thermometer monitoring unit 27 is shown , for illustration purposes , having a changeable background area 40 , a constant background area 41 , and a constant foreground area 42 . these areas may be different colors , so as to portray a &# 34 ; not hot &# 34 ; condition ( fig2 ) or a &# 34 ; hot &# 34 ; condition ( fig3 ). the indicia and / or particular scheme for indicating a particular condition may , of course , be varied as desired so long as the condition correctly portrays the condition being sensed by sensing portion 36 of the temperature monitoring unit . for the illustration of fig2 and 3 , sensing portion 36 of the monitor is preferably a two condition sensor with a rapid change at a predetermined temperature , which sensors are well known to the art . temperature monitor 27 may include a metal casing , and preferably has a plastic face for indicating the then prevailing condition of the heat retaining material externally of the cover . referring to fig1 hotpack 11 may be placed on a human body 12 after the hotpack has been heated sufficiently so that the heat retaining material 25 in enclosed spaces 23 has been heated to a predetermined temperature sufficient to cause the temperature monitor to indicate that the hotpack is ready for use . this indication takes the form of the word &# 34 ; hot &# 34 ; clearly visible on face 34 in the illustration of fig3 . until the hotpack is ready for use , the not ready indication of the hotpack is indicated on face 34 of the thermometer monitor unit . as shown in the illustration of fig2 the &# 34 ; not hot &# 34 ; condition is shown by the word hot circled with a slanted line thru the word which is achieved by background areas 40 and 41 being of different colors with the foreground area 42 ( i . e ., hot ) being of yet another color ( or white ) as shown in fig1 and 3 . when the temperature of the heat retaining material reaches the predetermined temperature , background area 40 changes color so that it is the same color as background area 41 . the word &# 34 ; hot &# 34 ; has not changed color , however , and is now clearly visible indicating to the user that the temperature of the heat retaining material has attained the predetermined temperature . of course , other designs may be utilized for face 34 of the thermometer monitoring unit such as , for example , background areas 40 and 41 could remain the same color and the word &# 34 ; hot &# 34 ; could change color upon reaching the predetermined temperature . additionally , other words and / or different indicia other than &# 34 ; hot &# 34 ;, such as &# 34 ; go &# 34 ; or &# 34 ; ready &# 34 ;, could also be used on face 34 . as shown best in fig4 thermometer unit 27 is attached to sheet 14 of cover 18 by means of collar 29 so that the sensor 36 is located near the center of enclosed space 23 in thermal contact with the clay 25 therein . thermometer unit 27 may be attached , however , in any conventional fashion to cover 18 . for use as a two condition indicator , sensor unit 36 has a rapid change so that the indicating face , or dot , is reversible such that when the temperature of the heat retaining material drops below the predetermined temperature , the face will change state and indicate the &# 34 ; not hot &# 34 ; condition ( as illustrated in fig2 ), and when the heat retaining material is again raised to a temperature above the predetermined temperature , the face will change state and indicate a &# 34 ; hot &# 34 ; condition ( as illustrated in fig3 ). the predetermined temperature found best suited for use with hotpacks is about 70 ° c . as is known in the art , when the hotpack is immersed in hot water until ready for use , the heat retaining material ( bentonite ) absorbs water and swells to fill the pockets formed by cover 18 . when sufficiently hot , as shown by temperature monitor 27 , the hotpack is brought to a position adjacent to the body to apply moist heat to the body with the heat of the hotpack being slowly dissipated during this period until it is no longer effective ( at which time the condition &# 34 ; not hot &# 34 ; is shown by temperature monitor 27 ). while not specifically shown in fig1 it is to be understood that conventional hotpack treatment recommends that the hotpack not be applied directly to a human body . instead a layer of towels or other such materials are normally placed between the hotpack and the human body , and , in addition , the hotpack may be wrapped in towels to help insulate the hotpack so that it will retain heat for a longer period of time . as can be appreciated from the foregoing , this invention provides an improved hotpack that includes temperature indications to facilitate safe and effective use .
a temperature indicative hotpack is disclosed . a temperature monitoring unit has an indicating portion and a sensing portion with the monitoring unit being mounted on one liquid permeable wall enclosing a heat retaining material so that the temperature of the heat retaining material is accurately determined by the sensing portion within the enclosure and displayed externally of the enclosure by means of the indicating portion so that the hotpack can be safely and effectively utilized .